Thermoplastic Vulcanizate Gasket for Use in an Electrolyzer

Abstract

An electrolyzer comprising an electrolyzer cell is disclosed. The electrolyzer cell comprises a first spacer frame, a second spacer frame, and a first gasket having a first surface contacting the first spacer frame and a second and opposing surface contacting the second spacer frame. The first gasket comprises a thermoplastic vulcanizate comprising a thermoplastic resin and an at least partially cured elastomer. The thermoplastic vulcanizate exhibits a Shore A hardness (ISO 868-85) of from 35 to 100.

Description

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims filing benefit of U.S. Provisional Patent Application No. 63/435,842 having a filing date of Dec. 29, 2022 and U.S. Provisional Patent Application No. 63/496,990 having a filing date of Apr. 19, 2023, both of which are hereby incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

Electrolyzers utilize electrical energy to drive a chemical reaction. The fuel, e.g., alkaline water, is supplied to an electrochemical cell within the electrolyzer and product, hydrogen gas and oxygen gas, is removed from the electrochemical cell. An electrolyzer system generally includes a stack of individual cells that are in electrical and fluid communication with one another. Each cell includes several components, such as electrodes, separators, frames, gaskets, etc., which are retained in a particular orientation with one another to allow for the necessary fluid flow and electrical communication. To maintain the desired orientations, spacers in the form of spacer plates or frames surrounding active components are utilized. In addition, gaskets are utilized for sealing purposes to prevent the leakage of any liquid or gas. Conventional gaskets are formed from rubbers, such as silicone rubber, or fluoropolymer materials. While such materials can be formed in the desired shapes, they may be relatively difficult and costly to form into high precision shapes necessary to meet desired specifications and may not necessarily provide the desired balance of properties.

As such, a need currently exists for gaskets that can be more readily incorporated into an electrolyzer.

SUMMARY OF THE INVENTION

In accordance with one embodiment of the present disclosure, an electrolyzer comprising an electrolyzer cell is disclosed. The electrolyzer cell comprises a first spacer frame, a second spacer frame, and a first gasket having a first surface contacting the first spacer frame and a second and opposing surface contacting the second spacer frame. The first gasket comprises a thermoplastic vulcanizate comprising a thermoplastic resin and an at least partially cured elastomer. The thermoplastic vulcanizate exhibits a Shore A hardness (ISO 868-85) of from 35 to 100.

Other features and aspects of the present disclosure are set forth in greater detail below.

BRIEF DESCRIPTION OF THE FIGURES

A full and enabling disclosure of the present disclosure, including the best mode thereof to one skilled in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures, in which:

FIG. 1 is a schematic view of one embodiment of an electrolyzer cell; and

FIG. 2 is a schematic view of one embodiment of an electrolyzer system.

DETAILED DESCRIPTION

It is to be understood by one of ordinary skill in the art that the present discussion is a description of exemplary embodiments only, and is not intended as limiting the broader aspects of the present disclosure.

Generally speaking, the present disclosure is directed to an electrolyzer that includes a first spacer frame, a second spacer frame, and a gasket separating the first spacer frame and the second spacer frame wherein the gasket is formed from a thermoplastic vulcanizate (“TPV”) comprising a thermoplastic resin and an at least partially cured elastomer. In general, the gasket is disposed between the spacer frames, which can be pressed against each other. As a result, the gasket comprising the thermoplastic vulcanizate can be utilized to provide an adequate seal to prevent leakage, for instance of a gas or liquid, into other parts of the electrolyzer.

The present inventors have discovered that a thermoplastic vulcanizate can provide the desired properties necessary to function as a gasket of an electrolyzer. For instance, in order to function as a seal, the thermoplastic vulcanizate may exhibit a particular hardness. In particular, the thermoplastic vulcanizate may exhibit a particular Shore A hardness (ISO 868-85; 15 seconds), which is utilized to measure the hardness of the thermoplastic vulcanizate and provide an indication of the resistance to indentation. In this regard, the thermoplastic vulcanizate may have a Shore A hardness of from 35 to 100. For instance, the thermoplastic vulcanizate may have a Shore A hardness of 35 or more, such as 40 or more, such as 45 or more, such as 50 or more, such as 55 or more. The thermoplastic vulcanizate may have a Shore A hardness of 100 or less, such as 95 or less, such as 90 or less, such as 80 or less, such as 70 or less, such as 65 or less, such as 60 or less, such as 55 or less, such as 50 or less. Such hardness may allow for the gasket to provide the compliance necessary to effectively function as a seal and conform to the desired shape between the spacer frames.

In addition, the thermoplastic vulcanizate may exhibit a certain strength as indicated by certain mechanical properties. For instance, the thermoplastic vulcanizate may exhibit a 100% modulus (ASTM D412-16), also referred to as the modulus at 100% elongation, of at least 0.3 MPa, such as from 0.5 to 5 MPa. For instance, the 100% modulus may be 0.3 MPa or more, such as 0.4 MPa or more, such as 0.5 MPa or more, such as 0.8 MPa or more, such as 1 MPa or more, such as 1.1 MPa or more, such as 1.2 MPa or more, such as 1.3 MPa or more, such as 1.4 MPa or more, such as 1.5 MPa or more, such as 2 MPa or more, such as 2.5 MPa or more, such as 3 MPa or more, such as 4 MPa or more, such as 5 MPa or more, such as 6 MPa or more, such as 10 MPa or more, such as 20 MPa or more, such as 30 MPa or more. The 100% modulus may be 50 MPa or less, such as 40 MPa or less, such as 30 MPa or less, such as 25 MPa or less, such as 20 MPa or less, such as 15 MPa or less, such as 10 MPa or less, such as 8 MPa or less, such as 6 MPa or less, such as 5 MPa or less, such as 4.5 MPa or less, such as 4 MPa or less, such as 3.8 MPa or less, such as 3.5 MPa or less, such as 3.3 MPa or less, such as 3 MPa or less, such as 2.8 MPa or less, such as 2.5 MPa or less, such as 2.3 MPa or less, such as 2 MPa or less, such as 1.9 MPa or less, such as 1.8 MPa or less, such as 1.5 MPa or less, such as 1.3 MPa or less, such as 1.1 MPa or less, such as 0.8 MPa or less.

The thermoplastic vulcanizate may also exhibit a tensile stress at break (i.e., strength) of from 0.5 to 50 MPa, such as from 1 to 20 MPa, such as from 2 to 10 MPa. For instance, the thermoplastic vulcanizate may exhibit a tensile stress of 0.5 MPa or more, such as 1 MPa or more, such as 1.5 MPa or more, such as 2 MPa or more, such as 2.5 MPa or more, such as 3 MPa or more, such as 3.5 MPa or more, such as 4 MPa or more, such as 5 MPa or more, such as 6 MPa or more, such as 7 MPa or more, such as 10 MPa or more, such as 15 MPa or more, such as 20 MPa or more, such as 30 MPa or more, such as 40 MPa or more, such as 50 MPa or more, such as 60 MPa or more, such as 70 MPa or more. The tensile stress may be 100 MPa or less, such as 80 MPa or less, such as 60 MPa or less, such as 50 MPa or less, such as 40 MPa or less, such as 30 MPa or less, such as 25 MPa or less, such as 20 MPa or less, such as 18 MPa or less, such as 15 MPa or less, such as 13 MPa or less, such as 11 MPa or less, such as 10 MPa or less, such as 9 MPa or less, such as 8 MPa or less, such as 7 MPa or less, such as 6.5 MPa or less, such as 6 MPa or less, such as 5.5 MPa or less, such as 5 MPa or less, such as 4.5 MPa or less, such as 4 MPa or less, such as 3.5 MPa or less, such as 3 MPa or less, such as 2.5 MPa or less. The tensile stress may be determined in accordance with ASTM D412-16 at a temperature of 23° C.

The thermoplastic vulcanizate may also exhibit a desired elongation at break. For instance, the elongation al break may be 20% or more, such as 40% or more, such as 60% or more, such as 80% or more, such as 100% or more, such as 200% or more, such as 300% or more, such as 400% or more, such as 500% or more, such as 550% or more, such as 600% or more, such as 650% or more, such as 700% or more, such as 750% or more, such as 900% or more. The elongation at break may be 1500% or less, such as 1300% or less, such as 1000% or less, such as 800% or less, such as 600% or less, such as 500% or less, such as 450% or less, such as 400% or less, such as 350% or less, such as 300% or less. The elongation at break may be determined in accordance with ASTM D412-16 at a temperature of 23° C.

The thermoplastic vulcanizate may also exhibit a desired ultimate tear strength. For instance, the ultimate tear strength may be 1.5 MPa or more, such as 2 MPA or more, such as 2.5 MPa or more, such as 2.7 MPa or more, such as 2.8 MPa or more. The ultimate tear strength may be 10 MPa or less, such as 8 MPa or less, such as 6 MPa or less, such as 5 MPa or less, such as 4 MPa or less, such as 3.5 MPa or less, such as 3.3 MPa or less, such as 3.1 MPa or less, such as 3 MPa or less, such as 2.9 MPa or less, such as 2.8 MPa or less, such as 2.7 MPa or less. The ultimate tear strength may be determined in accordance with ASTM D624-00 at a temperature of 23° C.

The thermoplastic vulcanizate may also be characterized by an advantageously low compression set. For instance, the compression set may be 60% or less, such as 55% or less, such as 50% or less, such as 45% or less, such as 40% or less, such as 35% or less, such as 30% or less, such as 25% or less, such as 20% or less. The compression set may be 5% or more, such as 8% or more, such as 10% or more, such as 13% or more, such as 15% or more, such as 18% or more, such as 20% or more, such as 25% or more, such as 30% or more, such as 35% or more. The compression set may be determined in accordance with ASTM D395B-18. Such aforementioned compression set may be at 70° C. after 22 hours. In another embodiment, such aforementioned compression set may be at 125° C. after 70 hours.

Also, the thermoplastic vulcanizate may exhibit a relatively low coefficient of friction. For instance, the coefficient of friction may be 3 or less, such as 2.8 or less, such as 2.5 or less, such as 2.2 or less, such as 2 or less, such as 1.8 or less, such as 1.5 or less. The coefficient of friction may be more than 1, such as 1.2 or more, such as 1.5 or more, such as 1.7 or more, such as 1.9 or more, such as 2 or more, such as 2.2 or more. The coefficient of friction may be determined by pulling a weighted sled sample over a glass surface with a test distance of 200 mm and a test weight of 350 grams wherein the coefficient of friction is the force required to pull the sled with the sample of material thereunder.

Various embodiments of the present disclosure will now be described in more detail.

I. Thermoplastic Vulcanizate

A. Thermoplastic Resin

As indicated above, the thermoplastic vulcanizate contains one or more thermoplastic resins. In one embodiment, one thermoplastic resin may be utilized as the thermoplastic resin. In other embodiments, the thermoplastic resin may include a mixture of thermoplastic resins. For instance, more than one thermoplastic resin, such as two or three thermoplastic resins, may be utilized in the thermoplastic vulcanizate. Furthermore, the thermoplastic resin may be a homopolymer or a copolymer. In one embodiment, the thermoplastic resin may be a homopolymer. In another embodiment, the thermoplastic resin may be a copolymer.

In general, any thermoplastic resin suitable for use in the manufacture of a thermoplastic vulcanizate can be employed as the thermoplastic resin. For instance, the thermoplastic resin may include a polyolefin, a polyimide, a polyester, a polyamide, poly(phenylene ether), a polycarbonate, a styrene-acrylonitrile copolymer, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polystyrene derivatives, polyphenylene oxide, polyoxymethylene, fluorine-containing thermoplastic resins, or a mixture thereof.

In one embodiment, the thermoplastic resin may include at least a polyolefin. The polyolefin can be formed by polymerizing one or more alpha-olefins such as ethylene, propylene, 1-butene, 1-hexene, 1-octene, 2-methyl-1-propene, 3-methyl-1-pentene, 4-methyl-1-pentene, 5-methyl-1-hexene, and mixtures thereof. Copolymers of ethylene and propylene or ethylene or propylene with another alpha-olefin such as 1-butene, 1-hexene, 1-octene, 2-methyl-1-propene, 3-methyl-1-pentene, 4-methyl-1-pentene, 5-methyl-1-hexene or mixtures thereof may be also utilized in accordance with the present disclosure. In one embodiment, when the primary monomer is ethylene, the copolymer may be propylene or another C₄-C₈ alpha-olefin monomer. In one embodiment, the comonomer may be propylene. In another embodiment, the comonomer may be a C₄-C₈ alpha-olefin monomer. When the primary monomer is propylene, the copolymer may be ethylene or another C₄-C₈ alpha-olefin monomer. In one embodiment, the comonomer may be ethylene. In another embodiment, the comonomer may be a C₄-C₈ alpha-olefin monomer.

Other suitable polyolefin copolymers may include copolymers of olefins with styrene such as styrene-ethylene copolymer or polymers of olefins with α,β-unsaturated acids, α,β-unsaturated esters such as polyethylene-acrylate copolymers. Non-olefin thermoplastic resins may include polymers and copolymers of styrene, α,β-unsaturated acids, α,β-unsaturated esters, and mixtures thereof. For example, polystyrene, polyacrylate, and polymethacrylate may be used.

When the thermoplastic resin includes a polyolefin copolymer formed of ethylene or propylene as the primary monomer, the corresponding comonomer may be present in an amount of 0.1 wt. % or more, such as 0.5 wt. % or more, such as 1 wt. % or more, such as 2 wt. % or more, such as 5 wt. % or more, such as 10 wt. % or more, such as 15 wt. % or more, such as 20 wt. % or more. The comonomer may be present in an amount of 40 wt. % or less, such as 30 wt. % or less, such as 25 wt. % or less, such as 20 wt. % or less, such as 15 wt. % or less, such as 10 wt. % or less, such as 8 wt. % or less, such as 6 wt. % or less, such as 5 wt. % or less. Similarly, the corresponding comonomer may be present in an amount of 0.1 mol. % or more, such as 0.5 mol. % or more, such as 1 mol. % or more, such as 2 mol. % or more, such as 5 mol. % or more, such as 10 mol. % or more, such as 15 mol. % or more, such as 20 mol. % or more. The comonomer may be present in an amount of 40 mol. % or less, such as 30 mol. % or less, such as 25 mol. % or less, such as 20 mol. % or less, such as 15 mol. % or less, such as 10 mol. % or less, such as 8 mol. % or less, such as 6 mol. % or less, such as 5 mol. % or less.

In one embodiment, the polyolefin may be an ethylene polymer, a propylene polymer, or a mixture thereof. For instance, the ethylene polymer may be a polyethylene homopolymer in one embodiment. In another embodiment, the ethylene polymer may be a polyethylene copolymer. The propylene polymer may be a polypropylene homopolymer in one embodiment. In another embodiment, the propylene polymer may be a polypropylene copolymer. Furthermore, the polypropylene polymer may be isotactic or syndiotactic polypropylene. For instance, the polypropylene polymer may be isotactic polypropylene in one embodiment. In another embodiment, the polypropylene polymer may be syndiotactic polypropylene.

These homopolymers and copolymers may be synthesized using any polymerization technique known in the art such as, but not limited to, the Phillips catalyzed reactions, conventional Ziegler-Natta type polymerizations, and metallocene catalysis including, but not limited to, metallocene-alumoxane and metallocene-ionic activator catalysis. Suitable catalyst systems thus include chiral metallocene catalyst systems, see, e.g., U.S. Pat. No. 5,441,920, and transition metal-centered, heteroaryl ligand catalyst systems, see, e.g., U.S. Pat. No. 6,960,635.

In one embodiment, the thermoplastic resin may also include a functionalized thermoplastic resin. The functionalized thermoplastic resin in one embodiment may be present as the primary thermoplastic resin. In another embodiment, the functionalized thermoplastic resin may be present as a secondary thermoplastic resin, for instance in an amount less than another thermoplastic resin within the thermoplastic vulcanizate.

The functionalized thermoplastic resin may include a polymer including at least one functional group. The functional group, which may also be referred to as a functional substituent or functional moiety, includes a hetero atom. In one or more embodiments, the functional group includes a polar group. Examples of polar groups include hydroxy, carbonyl, ether, halide, amine, imine, nitrile, silyl, epoxide, or isocyanate groups. Exemplary groups containing a carbonyl moiety include carboxylic acid, anhydride, ketone, acid halide, ester, amide, or imide groups, and derivatives thereof. In one embodiment, the functional group includes a succinic anhydride group, or the corresponding acid, which may derive from a reaction (e.g., polymerization or grafting reaction) with maleic anhydride, or a B-alkyl substituted propanoic acid group or derivative thereof.

In general, the thermoplastic resin can include a solid, generally high molecular weight polymeric material. The thermoplastic resin may have a Mw of about 50,000 g/mol or more, such as 75,000 g/mol or more, such as 100,000 g/mol or more, such as 200,000 g/mol or more, such as 300,000 g/mol or more, such as 400,000 g/mol or more, such as 500,000 g/mol or more, such as 750,000 g/mol or more, such as 1,000,000 g/mol or more, such as 2,000,000 g/mol or more, such as 3,000,000 g/mol or more. The Mw may be about 6,000,000 g/mol or less, such as about 5,000,000 g/mol or less, such as 4,000,000 g/mol or less, such as 3,000,000 g/mol or less, such as 2,000,000 g/mol or less, such as 1,500,000 g/mol or less, such as 1,000,000 g/mol or less, such as 900,000 g/mol or less, such as 800,000 g/mol or less, such as 700,000 g/mol or less. Furthermore, the thermoplastic resin may have a Mn of about 50,000 g/mol or more, such as 75,000 g/mol or more, such as 100,000 g/mol or more, such as 200,000 g/mol or more, such as 300,000 g/mol or more, such as 400,000 g/mol or more, such as 500,000 g/mol or more, such as 750,000 g/mol or more, such as 1,000,000 g/mol or more, such as 2,000,000 g/mol or more, such as 3,000,000 g/mol or more. The Mn may be about 6,000,000 g/mol or less, such as about 5,000,000 g/mol or less, such as 4,000,000 g/mol or less, such as 3,000,000 g/mol or less, such as 2,000,000 g/mol or less, such as 1,500,000 g/mol or less, such as 1,000,000 g/mol or less, such as 900,000 g/mol or less, such as 800,000 g/mol or less, such as 700,000 g/mol or less. In general, the molecular weight may be characterized by GPC (gel permeation chromatography) using polystyrene standards.

The thermoplastic resin may be a crystalline polymer in one embodiment or a semi-crystalline polymer in another embodiment. For instance, the crystallinity may be at least 25%, such as at least 35%, such as at least 45%, such as at least 55%, such as at least 65%, such as at least 70% by weight. The crystallinity may be determined by differential scanning calorimetry. For instance, crystallinity may be determined by dividing the heat of fusion of a sample by the heat of fusion of a 100% crystalline polymer.

The thermoplastic resin may also have a particular glass transition temperature (“Tg”). For instance, the glass transition temperature may be relatively high. In this regard, the Tg may be about −120° C. or more, such as −110° C. or more, such as −100° C. or more, such as −90° C. or more, such as −70° C. or more, such as −50° C. or more, such as −30° C. or more, such as −25° C. or more, such as −20° C. or more, such as −15° C. or more, such as −10° C. or more, such as −5° C. or more, such as 0° C. or more, such as 5° C. or more, such as 10° C. or more, such as 20° C. or more, such as 30° C. or more, such as 50° C. or more, such as 80° C. or more, such as 100° C. or more, such as 120° C. or more, such as 140° C. or more, such as 160° C. or more, such as 180° C. or more, such as 200° C. or more. The Tg may be about 300° C. or less, such as 260° C. or less, such as 220° C. or less, such as 180° C. or less, such as 140° C. or less, such as 100° C. or less, such as 80° C. or less, such as 60° C. or less, such as 40° C. or less, such as 30° C. or less, such as 20° C. or less, such as 10° C. or less, such as 5° C. or less, such as 0° C. or less, such as −5° C. or less.

In addition, the thermoplastic resin may have a particular melt temperature (“Tm”). For instance, the melt temperature of the thermoplastic resin may be relatively high. Furthermore, the melt temperature of the thermoplastic resin may be lower than the decomposition temperature of the elastomer in the thermoplastic vulcanizate, such decomposition temperature generally characterized as when the molecular bonds begin to break or scission such that the molecular weight of the elastomer begins to decrease. In this regard, the Tm may be about 100° C. or more, such as 120° C. or more, such as 140° C. or more, such as 150° C. or more, such as 160° C. or more, such as 170° C. or more, such as 180° C. or more, such as 190° C. or more, such as 200° C. or more, such as 240° C. or more, such as 280° C. or more. The Tm may be about 400° C. or less, such as 360° C. or less, such as 320° C. or less, such as 300° C. or less, such as 280° C. or less, such as 250° C. or less, such as 220° C. or less, such as 200° C. or less, such as 180° C. or less, such as 160° C. or less.

The thermoplastic resin may also be characterized as having a particular heat of fusion. For instance, the heat of fusion may be about 0.1 J/g or more, such as about 1 J/g or more, such as about 2 J/g or more, such as about 5 J/g or more, such as about 10 J/g or more, such as about 10 J/g or more, such as about 30 J/g or more, such as 40 J/g or more, such as 50 J/g or more, such as 60 J/g or more, such as 70 J/g or more, such as 100 J/g or more, such as 120 J/g or more, such as 140 J/g or more, such as 160 J/g or more, such as 180 J/g or more, such as 200 J/g or more. The heat of fusion may be about 300 J/g or less, such as about 260 J/g or less, such as about 240 J/g or less, such as about 200 J/g or less, such as about 180 J/g or less, such as about 150 J/g or less, such as about 120 J/g or less, such as about 100 J/g or less, such as about 80 J/g or less, such as about 60 J/g or less, such as about 50 J/g or less, such as about 40 J/g or less, such as about 30 J/g or less, such as about 20 J/g or less.

The thermoplastic resin may have a melt flow rate of up to 400 g/10 min. In general, the thermoplastic resin may have better properties where the melt flow rate is less than about 30 g/10 min., preferably less than 10 g/10 min, such as less than about 2 g/10 min, such as less than about 1 g/10 min, such as less than about 0.8 g/10 min. In general, the melt flow rate may be 0.1 g/10 min or more, such as 0.2 g/10 min or more, such as 0.3 g/10 min or more, such as 0.4 g/10 min or more, such as 0.5 g/10 min or more. Melt flow rate is a measure of how easily a polymer flows under standard pressure and is measured by using ASTM D-1238 at 190° C. and 2.16 kg load.

The thermoplastic vulcanizate may generally comprise about 10 wt. % or more, such as about 15 wt. % or more, such as about 20 wt. % or more, such as about 25 wt. % or more, such as about 30 wt. % or more, such as about 35 wt. % or more, such as about 40 wt. % or more, such as about 50 wt. % or more, such as about 60 wt. % or more of the thermoplastic resin. The thermoplastic vulcanizate may comprise about 90 wt. % or less, such as about 80 wt. % or less, such as about 70 wt. % or less, such as about 60 wt. % or less, such as about 50 wt. % or less, such as about 40 wt. % or less of the thermoplastic resin. In another embodiment, such aforementioned weight percentages may be based on the combined weight of the thermoplastic resin and the elastomer combined within the thermoplastic vulcanizate.

B. Elastomer

As indicated above, the thermoplastic vulcanizate contains an elastomer. In general, any elastomer suitable for use in the manufacture of TPVs can be utilized in accordance with the present disclosure. In one embodiment, one elastomer may be utilized as the elastomer. In other embodiments, the elastomer may include a mixture of elastomers. For instance, more than one elastomer, such as two or three elastomers, may be utilized in the thermoplastic vulcanizate.

Any elastomer or mixture thereof that is capable of being vulcanized (that is crosslinked or cured) can be used as the elastomer (also referred to herein sometimes as the rubber). Reference to a rubber or elastomer may include mixtures of more than one. Useful elastomers typically contain a degree of unsaturation in their polymeric main chain. Some non-limiting examples of these rubbers include polyolefin copolymer elastomers, butyl rubber, natural rubber, styrene-butadiene copolymer rubber (e.g., styrene/ethylene-butadiene/styrene), butadiene rubber, acrylonitrile rubber, halogenated rubber such as brominated and chlorinated isobutylene-isoprene copolymer rubber, butadiene-styrene-vinyl pyridine rubber, urethane rubber, polyisoprene rubber, epichlolorohydrin terpolymer rubber, and polychloroprene.

Vulcanizable elastomers includes polyolefin copolymer elastomers. These copolymers are made from one or more of ethylene and higher alpha-olefins, which may include, but are not limited to propylene, 1-butene, 1-hexene, 4-methyl-1 pentene, 1-octene, 1-decene, or combinations thereof, and may include one or more copolymerizable, multiply unsaturated comonomer, such as diolefins, or diene monomers. The alpha-olefins can be propylene, 1-hexene, 1-octene, or combinations thereof. These rubbers may lack substantial crystallinity and can be suitably amorphous copolymers.

The diene monomers may include, but are not limited to, 5-ethylidene-2-norbornene; 1,4-hexadiene; 5-methylene-2-norbornene; 1,6-octadiene; 5-methyl-1,4-hexadiene; 3,7-dimethyl-1,6-octadiene; 1,3-cyclopentadiene; 1,4-cyclohexadiene; dicyclopentadiene; 5-vinyl-2-norbornene, divinyl benzene, and the like, or a combination thereof. The diene monomers can be 5-ethylidene-2-norbornene and/or 5-vinyl-2-norbornene. If the copolymer is prepared from ethylene, alpha-olefin, and diene monomers, the copolymer may be referred to as a terpolymer (EPDM rubber), or a tetrapolymer in the event that multiple alpha-olefins or dienes, or both, are used (EAODM rubber).

In one embodiment, the polyolefin elastomer copolymer may include an ethylene acrylic copolymer (also referred to as an ethylene-acrylate copolymer). The ethylene acrylic copolymer comprises (i) copolymerized units of a monomer having the structure represented by formula (A):

wherein R¹ is hydrogen or a C₁-C₁₂ alkyl and R² is a C₁-C₁₂ alkyl, a C₁-C₂₀ alkoxyalkyl, a C₁-C₁₂ cyanoalkyl, or a C₁-C₁₂ haloalkyl (e.g., fluoroalkyl or bromoalkyl) and (ii) copolymerized units of ethylene. The ethylene acrylic copolymer may also optionally comprise (iii) copolymerized units of an unsaturated carboxylic acid or an anhydride thereof.

The ethylene acrylic copolymer may be amorphous. The term “amorphous” generally refers to a copolymer that exhibits little or no crystalline structure at room temperature in the unstressed state. Alternatively, an amorphous material may have a heat of fusion of less than 4 J/g, as determined according to ASTM D3418-08.

As indicated above, the ethylene acrylic copolymer comprises copolymerized units (i) of the monomer of formula (A). Such monomer may be an alkyl ester or alkoxyalkyl ester of propenoic acid. In this regard, the ethylene acrylic copolymer may comprise an alkyl ester or alkoxyalkyl ester of propenoic acid together with a cure site monomer and an ethylene monomer. Examples of suitable alkyl and alkoxyalkyl esters of propenoic acid include alkyl acrylates and alkoxyalkyl acrylates as well as monomers in which the propenoic acid is substituted with a C₁-C₁₂ alkyl group. Examples include an alkyl methacrylate, an alkyl ethacrylate, an alkyl propacrylate, an alkyl hexacrylate, an alkoxyalkyl methacrylate, an alkoxyalkyl ethacryate, an alkoxyalkyl propacrylate, an alkoxyalkyl hexacrylate, and any combination thereof.

The alkyl and alkoxyalkyl esters of propenoic acid and substituted propenoic acids can be C₁-C₁₂ alkyl esters of acrylic or methacrylic acid or C₁-C₂₀ alkoxyalkyl esters of acrylic or methacrylic acid. Examples include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2 methoxyethylacrylate, 2-ethoxyethylacrylate, 2-(n-propoxy)ethylacrylate, 2 (n-butoxy)ethylacrylate, 3-methoxypropylacrylate, 3-ethoxypropyl-acrylate, and mixtures thereof. The ester group can comprise branched or unbranched C₁-C₈ alkyl groups or unbranched C₁-C₄ alkyl groups. Specific examples include alkyl (meth)acrylate esters such as methyl acrylate, methyl methacrylate, ethyl acrylate, butyl acrylate, and mixtures thereof.

The polymerized units of the monomer of formula (A) can be present in an amount ranging from about 20% or more, such as about 30% or more, such as about 40% or more, such as about 45% or more, such as about 50% or more, to about 75% or less, such as about 70% or less, such as about 65% or less by weight of the ethylene acrylic copolymer. For example, polymerized units of the monomer of formula (A), such as a propenoic acid ester comonomer, can be present in an amount ranging from about 45% or from about 50% to about 70% by weight of the ethylene acrylic copolymer. In some examples, the concentration of polymerized units of the monomer of formula (A), such as a propenoic acid ester comonomer, can range from about 55% to about 70% by weight of the ethylene acrylic copolymer. Also, as generally understood, the polymerized units of the monomer of formula (A) may include a first monomer of formula (A) and a second monomer of (A) wherein the combination of the monomers is present in the aforementioned weight percentages.

In addition to comprising the polymerized units of a monomer of formula (A), the ethylene acrylic copolymer comprises copolymerized units of ethylene. The copolymerized units of ethylene can constitute the remainder of the weight % of the ethylene acrylic copolymer, after accounting for the copolymerized units of the monomer of formula (A) and any other monomers, such as the optional copolymerized units of the unsaturated carboxylic acid or an anhydride thereof. For example, the copolymerized units of ethylene can be present in an amount ranging from about 10% or more, such as about 15% or more, such as about 20% or more, such as about 25% or more, such as about 28% or more, such as about 30% or more, such as about 35% or more, such as about 40% or more to about 65% or less, such as about 60% or less, such as about 58% or less, such as about 55% or less, such as about 50% or less, such as about 45% or less, such as about 40% or less by weight of the ethylene acrylic copolymer. The copolymerized units of ethylene can constitute the balance of the weight percent being attributed to the copolymerized units of the monomer of formula (A) and if present, the copolymerized units of the unsaturated carboxylic acid or an anhydride thereof.

In addition to comprising the polymerized units of a monomer of formula (A) and the copolymerized units of ethylene, the ethylene acrylic copolymer may further comprise a copolymerized cure site monomer such as a carboxylic acid, an anhydride thereof, or any mixture of the acid and anhydride of the acid. Suitable unsaturated carboxylic acids include acrylic acid, methacrylic acid, 1,4-butenedioic acids, citraconic acid, monoalkyl esters of 1,4-butenedioic acids, and mixtures thereof. The 1,4-butenedioic acids may exist in cis- or trans-form or both (e.g., maleic acid or fumaric acid) prior to polymerization. Suitable cure site comonomers also include anhydrides of unsaturated carboxylic acids, such as maleic anhydride, citraconic anhydride, itaconic anhydride, and mixtures thereof. Cure site monomers can include maleic acid and any of its half acid esters (monoesters) or diesters, such as the methyl or ethyl half acid esters (e.g., monoethyl maleate); fumaric acid and any of its half acid esters or diesters, such as the methyl, ethyl or butyl half acid esters; and monoalkyl and monoarylalkyl esters of itaconic acid. The cure site monomer can be present in some examples in an amount ranging from about 0.5% or more, such as about 1% or more, such as about 1.5% or more, such as about 2% or more to about 10% or less, such as about 8% or less, such as about 6% or less, such as about 5% or less, such as about 4% or less, such as about 3% or less by weight of the ethylene acrylic copolymer, such as from about 2% to about 5% by weight, such as from about 2% to about 4% by weight of the ethylene acrylic copolymer.

The ethylene acrylic copolymer may consist essentially of or consist of the copolymerized units of the monomer of formula (A), the copolymerized units of ethylene, and the optional copolymerized units of an unsaturated carboxylic acid or an anhydride thereof. In another embodiment, the ethylene acrylic copolymer may consist essentially of or consist of the copolymerized units of the monomer of formula (A), the copolymerized units of ethylene, and the copolymerized units of an unsaturated carboxylic acid or an anhydride thereof. “Consist essentially of” in this context refers an ethylene acrylic copolymer that does not materially diminish the elastomeric properties of the ethylene acrylic copolymer if the copolymer consisted solely of the copolymerized units.

One specific example of the ethylene acrylic copolymer includes a copolymer of (i) methyl acrylate, butyl acrylate, or any combination thereof, present in an amount ranging from about 50% to about 70% by weight of the ethylene acrylic copolymer; (ii) ethylene, which constitutes the remainder of the weight % of the ethylene acrylic copolymer; and (iii) a cure site monomer having carboxylic acid functionality, present in an amount ranging from about 2% to about 5% by weight of the ethylene acrylic copolymer (e.g., 2% to 4%).

Elastomers that are polyolefin elastomer copolymers can contain, unless specified otherwise herein, from about 15 to about 90 mole percent ethylene units deriving from ethylene monomer, from about 40 to about 85 mole percent, or from about 50 to about 80 mole percent ethylene units. The copolymer may contain from about 10 to about 85 mole percent, or from about 15 to about 50 mole percent, or from about 20 to about 40 mole percent, alpha-olefin units deriving from alpha-olefin monomers. The foregoing mole percentages are based upon the total moles of the mer units of the polymer. Where the copolymer contains diene units, the copolymers may contain from 0.1 to about 14 weight percent, from about 0.2 to about 13 weight percent, or from about 1 to about 12 weight percent units deriving from diene monomer. The weight percent diene units deriving from diene may be determined according to ASTM D-6047. In some occurrences, the copolymers contain less than 5.5 weight percent, such as less than 5.0 weight percent, such as less than 4.5 weight percent, such as less than 4.0 weight percent units deriving from diene monomer. In yet other cases, the copolymers contain greater than 6.0 weight percent, such as greater than 6.2 weight percent, such as greater than 6.5 weight percent, such as greater than 7.0 weight percent units, such as greater than 8.0 weight percent deriving from diene monomer.

The polyolefin elastomer copolymer may be obtained using polymerization techniques known in the art such as traditional solution or slurry polymerization processes. For instance, the catalyst employed to polymerize the ethylene, alpha-olefin, and diene monomers into elastomeric copolymers can include both traditional Ziegler-Natta type catalyst systems, especially those including titanium and vanadium compounds, as well as metallocene catalysts for Group 3-6 (titanium, zirconium and hafnium) metallocene catalysts, particularly the bridged mono- or biscyclopentadienyl metallocene catalysts. Other catalyst systems such as Brookhart catalyst systems may also be employed.

In one embodiment, the elastomer may include a butyl rubber. For instance, the butyl rubber includes copolymers and terpolymers of isobutylene and at least one other comonomer. Useful comonomers include isoprene, divinyl aromatic monomers, alkyl substituted vinyl aromatic monomers, and mixtures thereof. Exemplary divinyl aromatic monomers include vinyl styrene. Exemplary alkyl substituted vinyl aromatic monomers include a-methyl styrene and paramethyl styrene. These copolymers and terpolymers may also be halogenated such as in the case of chlorinated and brominated butyl rubber. In one or more embodiments, these halogenated polymers may derive from monomers such as parabromomethylstyrene.

In one or more embodiments, the butyl rubber includes copolymers of isobutylene and isoprene, copolymers of isobutylene and paramethyl styrene, terpolymers of isobutylene, isoprene, and divinyl styrene, branched butyl rubber, and brominated copolymers of isobutene and paramethylstyrene (yielding copolymers with parabromomethylstyrenyl mer units). These copolymers and terpolymers may be halogenated. Furthermore, butyl rubbers may be prepared by polymerization, using techniques known in the art such as at a low temperature in the presence of a Friedel-Crafts catalyst.

In one embodiment, where the butyl rubber includes the isobutylene-isoprene copolymer, the copolymer may include from about 0.5 to about 30, or from about 0.8 to about 5, percent by weight isoprene based on the entire weight of the copolymer with the remainder being isobutylene.

In another embodiment, where the butyl rubber includes isobutylene-paramethyl styrene copolymer, the copolymer may include from about 0.5 to about 25, and from about 2 to about 20, percent by weight paramethyl styrene based on the entire weight of the copolymer with the remainder being isobutylene. In one embodiment, isobutylene-paramethyl styrene copolymers can be halogenated, such as with bromine, and these halogenated copolymers can contain from about 0 to about 10 percent by weight, or from about 0.3 to about 7 percent by weight halogenation.

In other embodiments, where the butyl rubber includes isobutylene-isoprene-divinyl styrene, the terpolymer may include from about 95 to about 99, or from about 96 to about 98.5, percent by weight isobutylene, and from about 0.5 to about 5, or from about 0.8 to about 2.5, percent by weight isoprene based on the entire weight of the terpolymer, with the balance being divinyl styrene.

In the case of halogenated butyl rubbers, the butyl rubber may include from about 0.1 to about 10, or from about 0.3 to about 7, or from about 0.5 to about 3 percent by weight halogen based upon the entire weight of the copolymer or terpolymer.

In one or more embodiments, the glass transition temperature (Tg) of the butyl rubber can be less than about −55° C., or less than about −58° C., or less than about −60° C., or less than about −63° C. Also, the Mooney viscosity (ML₁₊₈@125° C.) of the butyl rubber can be from about 25 to about 75, or from about 30 to about 60, or from about 40 to about 55.

In general, the elastomer, in particular the polyolefin elastomer copolymer, may have a Mw of about 50,000 g/mol or more, such as 75,000 g/mol or more, such as 100,000 g/mol or more, such as 200,000 g/mol or more, such as 300,000 g/mol or more, such as 400,000 g/mol or more, such as 500,000 g/mol or more, such as 750,000 g/mol or more, such as 1,000,000 g/mol or more. The Mw may be about 3,000,000 g/mol or less, such as 2,000,000 g/mol or less, such as 1,500,000 g/mol or less, such as 1,000,000 g/mol or less, such as 900,000 g/mol or less, such as 800,000 g/mol or less, such as 700,000 g/mol or less, such as 600,000 g/mol or less, such as 500,000 g/mol or less, such as 400,000 g/mol or less, such as 300,000 g/mol or less. Furthermore, the elastomer, in particular the polyolefin elastomer copolymer, may have a Mn of about 50,000 g/mol or more, such as 75,000 g/mol or more, such as 100,000 g/mol or more, such as 200,000 g/mol or more, such as 300,000 g/mol or more, such as 400,000 g/mol or more, such as 500,000 g/mol or more, such as 750,000 g/mol or more, such as 1,000,000 g/mol or more. The Mn may be about 3,000,000 g/mol or less, such as 2,000,000 g/mol or less, such as 1,500,000 g/mol or less, such as 1,000,000 g/mol or less, such as 900,000 g/mol or less, such as 800,000 g/mol or less, such as 700,000 g/mol or less, such as 600,000 g/mol or less, such as 500,000 g/mol or less, such as 400,000 g/mol or less, such as 300,000 g/mol or less. In general, the molecular weight may be characterized by GPC (gel permeation chromatography) using polystyrene standards.

The thermoplastic vulcanizate can generally comprise about 2 wt. % or more, such as about 5 wt. % or more, such as about 10 wt. % or more, such as about 15 wt. % or more, such as about 20 wt. % or more, such as about 25 wt. % or more, such as about 30 wt. % or more, such as about 40 wt. % or more, such as about 50 wt. % or more of the elastomer. The thermoplastic vulcanizate may comprise about 90 wt. % or less, such as about 80 wt. % or less, such as about 70 wt. % or less, such as about 60 wt. % or less, such as about 50 wt. % or less, such as about 40 wt. % or less, such as about 35 wt. % or less, such as about 30 wt. % or less, such as about 25 wt. % or less, such as about 20 wt. % or less, such as about 15 wt. % or less of the elastomer. In another embodiment, such aforementioned weight percentages may be based on the combined weight of the thermoplastic resin and the elastomer combined in the thermoplastic vulcanizate.

Furthermore, when a mixture of elastomers is present, the primary elastomer may be present in an amount of about 60 wt. % or more, such as about 70 wt. % or more, such as about 80 wt. % or more, such as about 90 wt. % or more to less than 100 wt. % based on the weight of the elastomer. The secondary elastomer may be present in an amount of 40 wt. % or less, such as 30 wt. % or less, such as 20 wt. % or less, such as 15 wt. % or less, such as 10 wt. % or less, such as 5 wt. % or more to more than 0 wt. % of the elastomer.

C. Curing Composition

As indicated herein, the TPV formulation, in particular the elastomer within the formulation, may undergo dynamic vulcanization wherein the elastomer is at least partially cured. In general, any curing agent that is capable of curing or crosslinking the elastomer may be used. Some non-limiting examples of these curing agents include phenolic resins, peroxides, maleimides, and silicon-containing curing agents. The curing agents may be used with one or more coagents that serve as initiators, catalysts, etc. for purposes of improving the overall cure state of the elastomer. For instance, the curing composition of some embodiments includes one or both of zinc oxide (ZnO) and stannous chloride (SnCl₂).

In general, the phenolic resins may not necessarily be limited. For instance, these may include resole resins made by the condensation of alkyl substituted phenols or unsubstituted phenols with aldehydes, which can be formaldehydes, in an alkaline medium or by condensation of bi-functional phenoldialcohols. The alkyl substituents of the alkyl substituted phenols typically contain 1 to about 10 carbon atoms. Dimethylol phenols or phenolic resins, substituted in para-positions with alkyl groups containing 1 to about 10 carbon atoms can be used. These phenolic curing agents may be thermosetting resins and may be referred to as phenolic resin curing agents or phenolic resins. These phenolic resins may be ideally used in conjunction with a catalyst system. For example, non-halogenated phenol curing resins are used in conjunction with halogen donors and, optionally, a hydrogen halide scavenger. Where the phenolic curing resin is halogenated, a halogen donor is not required but the use of a hydrogen halide scavenger, such as ZnO, can be used.

Peroxide curing agents are generally selected from organic peroxides. Examples of organic peroxides include, but are not limited to, di-tert-butyl peroxide, dicumyl peroxide, t-butylcumyl peroxide, alpha, alpha-bis(tert-butylperoxy)diisopropyl benzene, 2,5 dimethyl 2,5-di(t-butylperoxy)hexane, 1,1-di(t-butylperoxy)-3,3,5-trimethyl cyclohexane, benzoyl peroxide, lauroyl peroxide, dilauroyl peroxide, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexyne-3, and mixtures thereof. Also, diaryl peroxides, ketone peroxides, peroxydicarbonates, peroxyesters, dialkyl peroxides, hydroperoxides, peroxyketals and mixtures thereof may be used.

The silicon-containing curing agents generally include silicon hydride compounds having at least two SiH groups. These compounds react with carbon-carbon double bonds of unsaturated polymers in the presence of a hydrosilylation catalyst. Silicon hydride compounds include, but are not limited to, methylhydrogen polysiloxanes, methylhydrogen dimethyl-siloxane copolymers, alkyl methyl polysiloxanes, bis(dimethylsilyl)alkanes, bis(dimethylsilyl)benzene, and mixtures thereof.

As noted above, hydrosilylation curing may be conducted in the presence of a catalyst. These catalysts can include, but are not limited to, peroxide catalysts and catalysts including transition metals of Group VIII. These metals include, but are not limited to, palladium, rhodium, and platinum, as well as complexes of these metals.

In certain embodiments, the curing composition also includes one or both of ZnO and SnCl₂. In one embodiment, the curing composition may include zinc oxide. In another embodiment, the curing composition may include stannous chloride. In a further embodiment, the curing composition may include zinc oxide and stannous chloride.

Coagents may also be employed with the curing agents, such as the phenolic resin and/or peroxides. The coagent may include a multi-functional acrylate ester, a multi-functional methacrylate ester, or combination thereof. In other words, the coagents include two or more organic acrylate or methacrylate substituents. Examples of multi-functional acrylates include diethylene glycol diacrylate, trimethylolpropane triacrylate (TMPTA), ethoxylated trimethylolpropane triacrylate, propoxylated trimethylolpropane triacrylate, propoxylated glycerol triacrylate, pentaerythritol triacrylate, bistrimethylolpropane tetraacrylate, pentaerythritol tetraacrylate, ethoxylated pentaerythritol tetraacrylate, ethoxylated pentaerythritol triacrylate, cyclohexane dimethanol diacrylate, ditrimethylolpropane tetraacrylate, or combinations thereof. Examples of multi-functional methacrylates include trimethylol propane trimethacrylate (TMPTMA), ethylene glycol dimethacrylate, butanediol dimethacrylate, butylene glycol dimethacrylate, diethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, allyl methacrylate, or combinations thereof. The coagent may also include triallylcyanurate, triallyl isocyanurate, triallyl phosphate, sulfur, N-phenyl-bis-maleamide, zinc diacrylate, zinc dimethacrylate, divinyl benzene, 1,2-polybutadiene, trimethylol propane trimethacrylate, tetramethylene glycol diacrylate, trifunctional acrylic ester, dipentaerythritolpentacrylate, polyfunctional acrylate, retarded cyclohexane dimethanol diacrylate ester, polyfunctional methacrylates, acrylate and methacrylate metal salts, oximer for e.g., quinone dioxime, and the like.

Furthermore, an oil can be employed in the cure system. The oil may also be referred to as a process oil, an extender oil, or plasticizer. Useful oils include mineral oils, synthetic processing oils, or combinations thereof and may act as plasticizers. The plasticizers include, but are not limited to, aromatic, naphthenic, and extender oils. Exemplary synthetic processing oils include low molecular weight polylinear alpha-olefins, and polybranched alpha-olefins. Suitable esters include monomeric and oligomeric materials having an average molecular weight below about 2,000 g/mole, or below about 600 g/mole. Specific examples include aliphatic mono- or diesters or alternatively oligomeric aliphatic esters or alkyl ether esters.

The curing composition may be added in one or more locations, including the feed hopper of a melt mixing extruder. In some embodiments, the curing agent and any additional coagents may be added to the TPV formulation together; in other embodiments, one or more coagents may be added to the TPV formulation at different times from any one or more of the curing agents, as the TPV formulation is undergoing processing to form a TPV.

In general, the amount of curing agent present should be sufficient to at least partially vulcanize the elastomer and in some embodiments, to completely vulcanize the elastomer.

D. Other Additives

The thermoplastic vulcanizate formulations of some embodiments may optionally further comprise one or more additives. Suitable additional TPV additives include, but are not limited to, plasticizers, process oils, fillers, processing aids, acid scavengers, antioxidants, stabilizers, lubricants, antiblocking agents, anti-static agents, waxes, foaming agents, colorants/pigments, flame retardants and other processing aids and/or the like. In this regard, the resulting thermoplastic vulcanizate may also comprise one or more of such additives.

Any suitable process oil may be included in some embodiments. In particular embodiments, process oils may be selected from: (i) extension oil, that is, oil present in an oil-extended rubber (such as oil present with the elastomer); (ii) free oil, that is, oil that is added during the vulcanization process (separately from any other TPV formulation component such as the elastomer and thermoplastic vulcanizate); (iii) curative oil, that is, oil that is used to dissolve/disperse the curing agents, for example, a curative-in-oil dispersion such as a phenolic resin-in-oil (and in such embodiments, the curing composition may therefore be present in the TPV formulation as the curative-in-oil additive); and (iv) any combination of the foregoing oils from (i)-(iii). Thus, process oil may be present in a TPV formulation as part of another component (e.g., as part of the elastomer when the process oil is an extension oil, such that the elastomer comprises elastomer and extension oil; or as part of the curing composition when the process oil is the carrier of a curative-in-oil, such that the curing composition comprises the curative oil and a curing agent). On the other hand, process oil may be added to the TPV separately from other components, i.e., as free oil.

The extension oil, free oil, and/or curative oil may be the same or different oils in various embodiments. Process oils may include one or more of (i) “refined” or “mineral” oils, and (ii) synthetic oils. As used herein, mineral oils refer to any hydrocarbon liquid of lubricating viscosity (i.e., a kinematic viscosity at 100° C. of 1 mm²/sec or more) derived from petroleum crude oil and subjected to one or more refining and/or hydroprocessing steps (such as fractionation, hydrocracking, dewaxing, isomerization, and hydrofinishing) to purify and chemically modify the components to achieve a final set of properties. Such “refined” oils are in contrast to “synthetic” oils, which are manufactured by combining monomer units into larger molecules using catalysts, initiators, and/or heat.

In general, either refined or synthetic process oils according to some embodiments may include, but are not limited to, any one or more of aromatic, naphthenic, and paraffinic oils. Exemplary synthetic processing oils are polylinear alpha-olefins, polybranched alpha-olefins, and hydrogenated polyalphaolefins. The compositions of some embodiments of this invention may include organic esters, alkyl ethers, or combinations thereof.

In certain embodiments, at least a portion of the process oil (e.g., all or a portion of any one or more of extension oil, free oil, and/or curative oil) is a low aromatic/sulfur content oil and has (i) an aromatic content of less than 5 wt. %, or less than 3.5 wt. %, or less than 1.5 wt. %, based on the weight of that portion of the process oil; and (ii) a sulfur content of less than 0.3 wt. %, or less than 0.003 wt. %, based on the weight of that portion of the process oil. Aromatic content may be determined in a manner consistent with method ASTM D2007. The percentage of aromatic carbon in the process oil of some embodiments is preferably less than 2, 1, or 0.5%. In certain embodiments, there are no aromatic carbons in the process oil. The proportion of aromatic carbon (%) as used herein is the proportion (percentage) of the number of aromatic carbon atoms to the number of all carbon atoms determined by the method in accordance with ASTM D2140.

Suitable process oils of particular embodiments may include API Group I, II, III, IV, and V base oils. See API 1509, Engine Oil Licensing and Certification System, 17th Ed., September 2012, Appx. E, incorporated herein by reference.

A TPV formulation of some embodiments may also or instead include a polymeric processing additive. The processing additive employed in such embodiments is a polymeric resin that has a very high melt flow index. These polymeric resins include both linear and branched molecules that have a melt flow rate that is greater than about 500 dg/min, more preferably greater than about 750 dg/min, even more preferably greater than about 1000 dg/min, still more preferably greater than about 1200 dg/min, and still more preferably greater than about 1500 dg/min. The thermoplastic elastomers of the present disclosure may include mixtures of various branched or various linear polymeric processing additives, as well as mixtures of both linear and branched polymeric processing additives. Reference to polymeric processing additives will include both linear and branched additives unless otherwise specified. The preferred linear polymeric processing additives are polypropylene homopolymers. The preferred branched polymeric processing additives include diene-modified polypropylene polymers.

In addition, the formulation may also include reinforcing and/or non-reinforcing fillers. Fillers and extenders that can be utilized include conventional inorganics such as calcium carbonate, clays, silica, talc, titanium dioxide, as well as organic, such as carbon block, graphene, and organic and inorganic nanoscopic fillers. In one embodiment, the filler may include graphene. The graphene may be a monolayer or a multilayer (i.e., graphite). For instance, the graphene may be multilayer, such as bilayer graphene, trilayer graphene, or a mixture thereof. The graphene may be pristine graphene or CVD graphene. The graphene may also include graphene nanoplatelets, such as those having a thickness of from 1 nm to 3 nm and/or a lateral dimension of from 100 nm to 100 μm. Furthermore, the graphene may be modified. For instance, the graphene may be oxidized (graphene oxide), reduced graphene oxide, or functionalized graphene oxide. The aforementioned denominations are further defined per ISO/TS 8004-13:2017. In addition, the manner in which the graphene my be provided is also not limited. For instance, the graphene may be added in a powder form, pre-compacted, and/or via master-batch.

In certain embodiments, the TPV formulation may include acid scavengers. These acid scavengers may be added to the thermoplastic vulcanizate after the desired level of cure has been achieved. Preferably, the acid scavengers are added after dynamic vulcanization. Useful acid scavengers include hydrotalcites. Both synthetic and natural hydrotalcites can be used. An exemplary natural hydrotalcite can be represented by the formula Mg₆Al₂(OH)₁₆CO₃·4H₂O. Synthetic hydrotalcite compounds may have formula Mg_4.3Al₂(OH)₁₂·6CO₃·mH₂O or Mg_4.5Al₂(OH)₁₃CO₃·3.5H₂O.

These additives can be utilized in an amount to provide the desired effect. In this regard, the additives may be present in an amount of up to about 50 weight percent of the total TPV formulation or TPV. In this regard, a respective additive and/or combination of additives may be present in an amount of 0.001 wt. % or more, such as 0.01 wt. % or more, such as 0.05 wt. % or more, such as 0.1 wt. % or more, such as 0.2 wt. % or more, such as 0.3 wt. % or more, such as 0.5 wt. % or more, such as 1 wt. % or more, such as 2 wt. % or more, such as 3 wt. % or more, such as 5 wt. % or more, such as 8 wt. % or more, such as 10 wt. % or more, such as 12 wt. % or more, such as 15 wt. % or more, such as 20 wt. % or more, such as 25 wt. % or more, such as 30 wt. % or more. They may be present in an amount of 50 wt. % or less, such as 40 wt. % or less, such as 30 wt. % or less, such as 25 wt. % or less, such as 20 wt. % or less, such as 18 wt. % or less, such as 15 wt. % or less, such as 13 wt. % or less, such as 10 wt. % or less, such as 8 wt. % or less, such as 6 wt. % or less, such as 4 wt. % or less, such as 3 wt. % or less, such as 2 wt. % or less, such as 1 wt. % or less, such as 0.5 wt. % or less. In another embodiment, such aforementioned percentages may be based on the weight of the thermoplastic resin. In a further embodiment, such aforementioned percentages may be based on the weight of the elastomer. In an even further embodiment, such aforementioned percentages may be based on the combined weight of the thermoplastic resin and elastomer.

E. TPV Formulation

In general, as used herein, a “TPV formulation” refers to the mixture of ingredients blended or otherwise compiled before or during processing of the TPV formulation in order to form a TPV. This is in recognition of the fact that the ingredients that are mixed together and then processed may or may not be present in the final TPV in the same amounts added to the formulation, depending upon the reactions that take place among some or all of the ingredients during processing of the mixed ingredients.

In general, a TPV formulation according to various embodiments includes the elastomer, thermoplastic resin, and curing agent (or curing composition) along with any other optional additives. As will be discussed in more detail below, the TPV formulation undergoes processing, including dynamic vulcanization, to form a TPV. In certain embodiments, any other additives may be added to the TPV formulation during processing, either before or after dynamic vulcanization.

Relative amounts of the various components in TPV formulations are conveniently characterized based upon the amount of elastomer in the formulation, in particular in parts by weight per hundred parts by weight of rubber (phr). In embodiments wherein the elastomer comprises both elastomer with an extension oil, as is common for much commercially available elastomers such as EPDM, the phr amounts are based only upon the amount of elastomer, exclusive of extension oil present with the elastomer. Thus, as an example, an elastomer containing 100 parts EPDM (rubber) and 75 parts extension oil would in fact be considered present in a TPV formulation at 175 phr (i.e., on the basis of the 100 parts EPDM rubber). If such a TPV formulation were further characterized as containing 50 phr thermoplastic resin, the formulation would include 50 parts by weight of thermoplastic resin in addition to the 100 parts by weight elastomer and 75 parts by weight extension oil.

TPV formulations of some embodiments may include the thermoplastic resin in an amount from about 20 to about 300 parts per hundred parts by weight of the elastomer or rubber (phr). In various embodiments, the thermoplastic resin is included in a TPV formulation in an amount ranging from a low of any one of about 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 165, 170, and 175 phr, to a high of any one of about 100, 125, 150, 175, 200, 225, 250, 275, and 300 phr. The thermoplastic resin may be included in an amount ranging from any of the aforementioned lows to any of the aforementioned highs, provided that the high value is greater than or equal to the low value. In particular embodiments, increasing amounts of thermoplastic resin correspond to increasing hardness of the dynamically vulcanized TPV.

When the elastomer consists of elastomer only, it is by definition present at 100 phr (since it is the basis of the phr notation). However, in embodiments wherein the elastomer component comprises a constituent other than an elastomer, such as an extender oil, the elastomer may be included in a TPV formulation in an amount ranging from a low of any one of about 100.05, 100.1, 100.15, 100.2, 105, 110, 115, and 120 phr to a high of any one of about 110, 120, 125, 150, 175, 200, 225, and 250 phr.

As previously noted, TPV formulations of certain embodiments may optionally include additional TPV additives. Amounts of additional additive are separate and in addition to those additives already included in another component of a TPV formulation. For instance, any additive such as extension oil included with the elastomer has already been accounted for as part of the amount of elastomer added to the formulation; recited amounts of additional additives therefore are exclusive of additives already included with the elastomer. Additional additives may be present in a TPV formulation in the aggregate in an amount ranging from about 0 phr to about 300 phr. In certain embodiments, additional additives may in the aggregate be present in the TPV in an amount ranging from a low of any one of about 0, 5, 10, 15, 25, 30, 40, 50, 60, 70, 80, 90, and 100 phr, to a high of any one of about 25, 30, 40, 50, 60, 80, 100, 125, 150, 175, 200, 225, 250, 275, and 300 phr. The additional additives may be included in an aggregate amount ranging from any one of the aforementioned lows to any one of the aforementioned highs, provided that the high value is greater than or equal to the low value. In one embodiment, such aforementioned phr may refer to the additional additives individually rather than the aggregate.

For convenience, components of TPV formulations of various embodiments may alternatively be characterized based upon their weight percentages in the TPV formulation according to the following:

The thermoplastic resin(s) may be present in a TPV formulation in amounts ranging from a low of any one of about 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, and 25 wt. % to a high of any one of about 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, and 60 wt. %, provided that the high is greater than or equal to the low.

The elastomer(s) may be present in a TPV formulation in amounts ranging from a low of any one of about 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, and 35 wt. % to a high of any one of about 35, 40, 45, 50, 55, 60, 65, 70, 75, and 80 wt. %, provided that the high is greater than or equal to the low, and that the elastomeric(s) are present in the TPV formulation within the range of about 20 to about 300 phr.

The optional additional TPV additive(s) may be present in a TPV formulation in aggregate amounts ranging from a low of any one of about 0, 5, 10, 15, 20, 25, 30, 35, and 40 wt. % to a high of any one of about 30, 35, 40, 45, 50, 55, 60, and 65 wt. %, provided that the high is greater than or equal to the low, and that the additive(s) are present in the TPV formulation within the range of about 0 to about 300 phr.

F. Processing TPV Formulations

The thermoplastic vulcanizate of the present disclosure is prepared by dynamic vulcanization techniques. The term “dynamic vulcanization” refers to a vulcanization or curing process for a TPV formulation comprising an elastomer, wherein the elastomer is vulcanized under conditions of high shear mixing at a temperature above the melting point of the thermoplastic resin to produce a thermoplastic vulcanizate. In dynamic vulcanization, an elastomer is simultaneously crosslinked and dispersed as fine particles within the thermoplastic resin or matrix, although other morphologies, such as co-continuous morphologies, may exist depending on the degree of cure, the elastomer to resin viscosity ratio, the intensity of mixing, the residence time, and the temperature.

In some embodiments, processing may include melt blending, in a chamber, a TPV formulation comprising the elastomer, thermoplastic resin, and curing agent. The chamber may be any vessel that is suitable for blending the selected composition under temperature and shearing force conditions necessary to form a thermoplastic vulcanizate. In this respect, the chamber may be a mixer, such as Banbury™ mixers or Brabender™ mixers, and certain mixing extruders such as co-rotating, counter-rotating, and twin-screw extruders, as well as co-kneaders, such as Buss® kneaders. According to one embodiment, the chamber is an extruder, which may be a single or multi-screw extruder. The term “multi-screw extruder” means an extruder having two or more screws; with two and three screw extruders being exemplary, and two or twin screw extruders being preferred in some embodiments. The screws of the extruder may have a plurality of lobes; two and three lobe screws being preferred. It will readily be understood that other screw designs may be selected in accordance with the methods of embodiments of the present disclosure. In some embodiments, dynamic vulcanization may occur during and/or as a result of extrusion. After discharging from the mixer, the blend containing the vulcanized rubber and the thermoplastic can be milled, chopped, extruded, pelletized, injection-molded, or processed by any other desirable technique.

The dynamic vulcanization of the elastomer may be carried out to achieve relatively high shear. In particular embodiments, the blending may be performed at a temperature not exceeding about 400° C., preferably not exceeding about 300° C., and more preferably not exceeding about 250° C. The minimum temperature at which the melt blending is performed is generally higher than or equal to about 130° C., preferably higher than or equal to about 150° C. and more particularly higher than about 180° C. The blending time is chosen by taking into account the nature of the compounds used in the TPV formulation and the blending temperature. The time generally varies from about 5 seconds to about 120 minutes, and in most cases from about 10 seconds to about 30 minutes.

Dynamic vulcanization in some embodiments may include phase inversion. As those skilled in the art appreciate, dynamic vulcanization may begin by including a greater volume fraction of rubber than thermoplastic resin. As such, the thermoplastic resin may be present as the discontinuous phase when the rubber volume fraction is greater than that of the volume fraction of the thermoplastic resin. As dynamic vulcanization proceeds, the viscosity of the rubber increases and phase inversion occurs under dynamic mixing. In other words, upon phase inversion, the thermoplastic resin phase becomes the continuous phase.

Other additive(s) are preferably present within the TPV formulation when dynamic vulcanization is carried out, although in some embodiments, one or more other additives (if any) may be added to the composition after the curing and/or phase inversion (e.g., after the dynamic vulcanization portion of processing). The additional additives may be included after dynamic vulcanization by employing a variety of techniques. In one embodiment, they can be added while the thermoplastic vulcanizate remains in its molten state from the dynamic vulcanization process. For example, the additional additives can be added downstream of the location of dynamic vulcanization within a process that employs continuous processing equipment, such as a single or twin screw extruder. In other embodiments, the thermoplastic vulcanizate can be “worked-up” or pelletized, subsequently melted, and the additional additives can be added to the molten thermoplastic vulcanizate product. This latter process may be referred to as a “second pass” addition of the ingredients.

Despite the fact that the elastomer may be partially or fully cured, the thermoplastic vulcanizate can be processed and reprocessed by conventional plastic processing techniques such as extrusion, injection molding, and compression molding. The elastomer within these thermoplastic elastomers is usually in the form of finely-divided and well-dispersed particles of vulcanized or cured rubber within a continuous thermoplastic phase or matrix, although a co-continuous morphology or a phase inversion is also possible. In those embodiments where the cured rubber is in the form of finely-divided and well-dispersed particles within the thermoplastic medium, the rubber particles may have an average diameter that is less than 50 μm, such as less than 30 μm, such as less than 10 μm, such as less than 5 μm, such as less than 1 μm. In preferred embodiments, at least 50%, such as at least 60%, such as at least 75% of the rubber particles may have an average diameter of less than 5 μm, such as less than 2 μm, such as less than 1 μm.

The degree of cure can be measured by determining the amount of rubber that is extractable from the thermoplastic vulcanizate by using cyclohexane or boiling xylene as an extractant. Preferably, the rubber may have a degree of cure where not more than 15 weight percent, such as not more than 10 weight percent, such as not more than 5 weight percent, such as not more than 3 weight percent is extractable by cyclohexane at 23° C. as described in U.S. Pat. Nos. 4,311,628, 5,100,947 and 5,157,081, all of which are incorporated herein by reference. Alternatively, the rubber may have a degree of cure such that the crosslink density is at least 4×10⁻⁵, such as at least 7×10⁻⁵, such as at least 10×10−5 moles per milliliter of rubber. See Crosslink Densities and Phase Morphologies in Dynamically Vulcanized TPEs, by Ellul et al., Rubber Chemistry and Technology, Vol. 68, pp. 573-584 (1995).

The resulting thermoplastic vulcanizate may have the desired density that allows it to be utilized for a molded part as described herein. In this regard, the density may be 0.3 g/cm³ or more, such as 0.4 g/cm³ or more, such as 0.5 g/cm³ or more, such as 0.6 g/cm³ or more, such as 0.65 g/cm³ or more, such as 0.7 g/cm³ or more, such as 0.75 g/cm³ or more, such as 0.8 g/cm³ or more, such as 0.85 g/cm³ or more, such as 0.9 g/cm³ or more, such as 0.95 g/cm³ or more, such as 1 g/cm³ or more, such as 1.05 g/cm³ or more, such as 1.1 g/cm³ or more, such as 1.15 g/cm³ or more, such as 1.2 g/cm³ or more. The density may be 2 g/cm³ or less, such as 1.8 g/cm³ or less, such as 1.6 g/cm³ or less, such as 1.4 g/cm³ or less, such as 1.3 g/cm³ or less, such as 1.2 g/cm³ or less, such as 1.1 g/cm³ or less, such as 1.0 g/cm³ or less, such as 0.95 g/cm³ or less, such 0.90 g/cm³ or less, such as 0.7 g/cm³ or less, such as 0.6 g/cm³ or less, such as 0.55 g/cm³ or less.

G. Formation of Gasket

Once formed, the thermoplastic vulcanizate may be shaped into the form of a molded part, in particular a gasket as described herein for use in an electrolyzer, using any of a variety of techniques as is known in the art. For instance, the thermoplastic vulcanizate can advantageously be fabricated by employing typical molding processes, such as injection molding, extrusion molding, compression molding, blow molding, rotational molding, overmolding, etc. In general, these processes include heating the thermoplastic vulcanizate to a temperature that is equal to or in excess of the melt temperature of the thermoplastic resin to form a pre-form for a mold cavity to then form the molded part, cooling the molded part to a temperature at or below the crystallization temperature of the thermoplastic vulcanizate, and releasing the molded part from a mold. The mold cavity defines the shape of the molded part, such as the gasket. The molded part is cooled within the mold at a temperature at or below the crystallization temperature of the thermoplastic vulcanizate and the molded part can subsequently be released from the mold. The process may also utilize extrusion molding to form the gasket. In this regard, the thermoplastic vulcanizate may be extruded as described herein. Upon exiting the extruder, the thermoplastic vulcanizate may be formed or shaped to form the gasket. Such gasket may be formed by using a particular die to shape the thermoplastic vulcanizate as it exits the extruder. Such shaping/forming process, such as the extrusion process, may be an automated or robotic process.

II. Electrolyzer

As indicated above, the gasket formed from the thermoplastic vulcanizate as disclosed herein can be utilized in an electrolyzer. In general, the electrolyzer may not necessarily be limited. For instance, the electrolyzer may be an alkaline electrolyzer, such as an anion exchange electrolyzer. In this regard, the electrolyzer may be utilized to produce hydrogen gas and oxygen gas from a liquid wherein the gases can be provided in a separated state. In general, the liquid may be pure water or may be a solution. For instance, the solution may be an electrolytic solution containing an electrolyte, such as sodium hydroxide or potassium hydroxide, to generate hydrogen gas and oxygen gas. To produce the gases, the electrolyzer utilizes an electrolytic cell. Although there may be some structural differences, an electrolytic cell generally comprises a gasket, a diaphragm/separator, and electrodes, such as a cathode and an anode at both ends thereof.

In general, the components, such as the electrodes may be contained within a spacer frame. In particular, such spacer frames may surround the components in order to maintain the desired orientation. As an example, the spacer frame may surround an electrode, such as a cathode. Similarly, the spacer frame may surround a second electrode, such as an anode. In addition, in some embodiments, the spacer frame may surround a diaphragm, such as an ion-permeable diaphragm. Nevertheless, a first spacer frame may be separated from a second spacer frame by a gasket comprising the thermoplastic vulcanizate as defined herein. In this regard, a first surface of the gasket may contact the first spacer frame while the second and opposing surface of the gasket may contact the second spacer frame. Furthermore, in one embodiment, such contact may be adjacent an edge of the respective spacer frames.

Even though the above mentions the use of a spacer frame for surrounding and holding a diaphragm, in one embodiment, the diaphragm may be contained in the gasket. For instance, the gasket can include a slit portion in the inner periphery, in particular along the entire inner periphery. This slit may be presented in which the ion-permeable diaphragm can be held. Furthermore, such slit may not extend through the entire width of the gasket such that the outer edge of the diaphragm is contained within the gasket.

As just one potential configuration, the electrolytic cell can include a first spacer frame including a first electrode, such as a positive electrode, followed by a gasket. The gasket may be followed by a second spacer frame holding a diaphragm. Such spacer frame may be followed by a gasket and a third spacer frame including a second electrode, such as a negative electrode. When the diaphragm is held within the gasket, the electrolytic cell may include a first spacer frame including a first electrode, such as a positive electrode, followed by a gasket. The gasket may be followed by a second spacer frame including a second electrode, such as a negative electrode.

By disposing a diaphragm behind each electrode constituting a cell, oxygen gas and hydrogen gas generated from each surface of the electrode can be discharged to the outside in a separated state, and high purity can be obtained. The ion-permeable diaphragm may generally have low gas permeability, small conductivity, and strong strength. The diaphragm may be a pore size on the order of micrometers, e.g., from about 0.1 micrometers to about 100 micrometers, or from about 1 micrometer to about 50 micrometers in some embodiments. Typical diaphragms may include, for instance, microporous ceramics, microporous polymeric films (e.g., porous polyvinyl chloride (PVC), polyolefins, and PTFE). The diaphragm may also include an anion exchange membrane to prevent convection and diffusion, while permitting anion movement across the membrane. One example of such a membrane is a polymer electrolyte membrane that allows passage of anions (e.g., hydroxide anions) created at one side of a bipolar electrode to the associated side of an adjacent bipolar electrode. Such an anion exchange membrane may include, for instance, a composite of zirconia and polysulfone available under the trade designation Zirfon®. Combinations of macroporous separators, microporous separators, and/or anion exchange members may also be employed in the diaphragm.

In addition, the shape of the gasket is not necessarily limited. For instance, the gasket may be circular, rectangular, oval, etc. in shape. Regardless, the shape of the gasket may correspond to the outer peripheral portion of the electrode. In particular, the diameter or cross section of the gasket may be the same as that of the electrode/spacer frame. Furthermore, the thickness may not be limited. For instance, the thickness may be 0.1 mm or more, such as 0.2 mm or more, such as 0.3 mm or more, such as 0.5 mm or more 2 5 mm or less, such as 4 mm or less, such as 3 mm or less, such as 2.5 mm or less, such as 2 mm or less, such as 1.5 mm or less, such as 1 mm or less, such as 0.8 mm or less, such as 0.6 mm or less, such as 0.5 mm or less, such as 0.4 mm or less.

As indicated herein, a liquid may be provided in order to generate a gas, such as hydrogen gas and oxygen gas. In this regard, the gasket may include first and second passage holes on one side or end (or upper portion or lower portion) of the gasket and/or electrode for the passage of a first gas and a second gas, respectively. In addition, the gasket may include third and fourth passage holes on the opposing end or side (or other of the lower portion or upper portion) of the gasket and/or electrode for passage of the liquid/electrolyte. Particularly, the gasket may include a passage hole which can communicate with an anolyte inlet, a passage hole which can communicate with a catholyte inlet, a passage hole which can communicate with an anolyte/gas outlet, and a passage hole which can communicated with a catholyte/gas outlet. Generally, these inlet passage holes may be formed on one side or end of the gasket and/or electrode while the outlet passage holes may be formed on the opposing end or side of the gasket and/or electrode. Although the above mentions two passage holes for the liquid/electrolyte, in some embodiments, it should be understood that there may only be one passage hole for the liquid/electrolyte.

Meanwhile, when a voltage is applied to the anode electrode and the cathode electrode, for example, and the anode electrode is charged with an electric charge of the opposite polarity compared to the cathode, the electrolytic solution existing between the electrodes is electrolyzed to generate oxygen gas and hydrogen gas. The diaphragm can prevent mixing of the oxygen gas generated from the surface charged with the anode (+) of one electrode and hydrogen gas generated from the surface charged with the cathode (−) of the facing electrode.

While the above may generally reference a cell including two electrodes, it should be understood that the electrolyzer may include a cell stack. For instance, the cell stack may be formed by a plurality of cells including electrodes with spacer frames and gaskets for sealing purposes. The respective cells may be in fluid and electric communication with one another. In addition, the individual cells can be joined to one another, for instance by adhesion, welding, bolting, etc. or by use of a case or shell that holds the individual components of the stack together with pressure seals.

FIG. 1 illustrates one embodiment of an electrolyzer cell for use in an electrolyzer. Such cell can include spacer frames 208, 210, 212. The spacer frames 210 and 212 include an electrode while spacer frame 208 includes a diaphragm. Between the spacer frames is included a gasket 102 formed of the thermoplastic vulcanizate as described herein. The spacer frames 208, 210, and 212 can also define a seal channel in the surface that can retain the gasket for sealing to prevent leakage from the assembled cell. It will be understood that while illustrated with a generally circular shape, the spacer frames 208, 210, 212 and gaskets 202 can have any suitable shape (e.g., square, oval, rectangular, etc.).

In general, the first spacer frame 210 can hold a bipolar electrode. The electrolyzer cell can also include a second spacer frame 208 that can hold a diaphragm. The third spacer frame 212 can also hold a bipolar electrode. Within such frames, they may include passage holes that align with passage holes of other spacer frames within the cell and if more than one cell, within the cell stack. Such alignment can assist with the transfer of liquid/electrolyte and gas produced via the electrolysis.

Aside from the above, additional electrolyzer spacer frames and gaskets that include a thermoplastic vulcanizate as described can be incorporated in a cell. For instance, in some embodiments, an electrolyzer cell can include a gas diffusion layer, which is generally located between a bipolar plate and an electrode. A gas diffusion layer can be retained by an electrolyzer spacer frame as described herein. A gasket as defined herein may be utilized to separate such spacer frame from an adjacent spacer frame. Of course, the electrolyzer can also include gaskets made from materials other than the thermoplastic vulcanizate of the present disclosure if so desired.

Furthermore, the electrolyzer may be utilized within an electrolyzer system. For instance, referring to FIG. 2, one embodiment of an electrolyzer system is illustrated that contains an electrolyzer stack 35 that incorporates a plurality of bipolar electrode electrolyzer cells 10 as described above. Of course, any electrolyzer cell or stack thereof that includes a spacer frame and gasket that in turn includes the thermoplastic vulcanizate could be incorporated in an electrolyzer system. In the illustrated embodiment, feed can be supplied to both sides of the electrolyzer cell stack 35 via a cathode inlet 30 to the cathode side of the cell and an anode inlet 32 to the anode side of the cell. In some embodiments, feed may be fed only one side of the cells of the stack 35. In those embodiments in which the cells include an exchange membrane separator, feed may be fed to both sides of the cell in order to maintain hydration of the membrane. Product outlets 31, 33, can deliver the electrolysis products (e.g., oxygen and hydrogen) from the cell stack 35. The feed can be an alkaline aqueous solution, e.g., an aqueous solution of a suitable alkaline, including without limitation, potassium hydroxide, sodium hydroxide, lithium hydroxide, or mixtures thereof. For instance, the feed can include from about 20 wt. % to about 40 wt. % alkaline in an aqueous solution.

Feed can be provided to inlets 30, 32 via a common feed line 121 as well as a recycle hose 122. In embodiments, feed to the cell can be pretreated, such as by initial feed 120 to a heat exchanger 108 to heat the feed to a suitable temperature (e.g., about 80° C.). Outlets 31, 33 can carry the oxygen and hydrogen products to additional system components such as product separators 112, 114, demisters 128 and dryers 129. Separated hydrogen and oxygen product of the cell stack 35 can be delivered from the system 125, 130. For instance, hydrogen product can be delivered directly to a system for utilization, e.g., to a fuel cell as a fuel, to a storage facility, or to a secondary system for further processing, e.g., chemical formation.

To operate the alkaline electrolyzer cell stack 35, a water pump 134 is operated to introduce feed 120 into any preprocessing procedures, e.g., heating via heat exchanger 108, and then into one or both sides of the electrochemical cell stack via inlets 32, 33. In some embodiments, the feed can be fed to both sides of the cell stack 35 in order to provide the cell components (e.g., anion exchange membranes) with moisture high enough to allow the performance of the cell stack 35.

At the cathode (or cathode side of a bipolar electrode) of an electrolyzer, water is reacted according to the half reaction:

2H₂O+2e⁻→H₂+2OH⁻

The hydroxide ions thus formed at the cathode are transported to the anode, where reaction occurs according to the half reaction:

2OH″→½O₂+H₂O+2e⁻

The oxygen and hydrogen are then discharged from the cell stack 35 via outlets 31, 33. In general, the products can be discharged with feed so far as feed has been supplied in an amount great enough to purge products from the cell stack 35. Thereafter, the oxygen and hydrogen products can be separated from the remaining feed, e.g., via product separators 112, 114, demister 128, dryer 129, to provide purified hydrogen product 130 and oxygen product 125. The separated feed can be recycled to the cell stack 35 via recycle hose 122.

The following test methods may be employed to determine the properties referenced herein.

Test Methods

Melting Temperature, Glass Transition Temperature, Heat of Fusion: The melting temperature (“Tm”), glass transition temperature (“Tg”), and the heat of fusion (“Hf”) may be determined by differential scanning calorimetry (“DSC”) as is known in the art using commercially available equipment such as a TA Instruments Model Q100. Typically, 6 to 10 mg of the sample, that has been stored at room temperature (about 23° C.) for at least 48 hours, is sealed in an aluminum pan and loaded into the instrument at room temperature (about 23° C.). The sample is equilibrated at 25° C. and then it is cooled at a cooling rate of 10° C./min to −80° C. The sample is held at −80° C. for 5 min and then heated at a heating rate of 10° C./min to 25° C. The glass transition temperature is measured from this heating cycle (“first heat”). For samples displaying multiple peaks, the melting point (or melting temperature) is defined to be the peak melting temperature associated with the largest endothermic calorimetric response in that range of temperatures from the DSC melting trace. The Tg was measured by again heating the sample from −80° C. to 80° C. at a rate of 20° C./min (“second heat”). The glass transition temperature reported is the midpoint of step change when heated during the second heating cycle. Areas under the DSC curve are used to determine the heat of transition (heat of fusion, Hf, upon melting or heat of crystallization, Hc, upon crystallization, if the HI value from the melting is different from the Hc value obtained for the heat of crystallization, then the value from the melting (Tm) shall be used), which can be used to calculate the degree of crystallinity (also called the percent crystallinity). The percent crystallinity (X %) is calculated using the formula: [area under the curve (in J/g)/H^∘ (in J/g)]*100, where H^∘ is the heat of fusion for the homopolymer of the major monomer component. These values for H^∘ are to be obtained from the Polymer Handbook, Fourth Edition, published by John Wiley and Sons, New York 1999, except that a value of 290 J/g is used as the equilibrium heat of fusion (H^∘) for 100% crystalline polyethylene, a value of 140 J/g is used as the equilibrium heat of fusion (H^∘) for 100% crystalline polybutene, and a value of 207 J/g (H^∘) is used as the heat of fusion for a 100% crystalline polypropylene.

These and other modifications and variations of the present disclosure may be practiced by those of ordinary skill in the art, without departing from the spirit and scope of the present disclosure. In addition, it should be understood that aspects of the various embodiments may be interchanged both in whole or in part. Furthermore, those of ordinary skill in the art will appreciate that the foregoing description is by way of example only, and is not intended to limit the invention so further described in such appended claims.

Claims

1. An electrolyzer comprising:

an electrolyzer cell comprising a first spacer frame, a second spacer frame, and a first gasket having a first surface contacting the first spacer frame and a second and opposing surface contacting the second spacer frame,

wherein the first gasket comprises a thermoplastic vulcanizate comprising a thermoplastic resin and an at least partially cured elastomer, and

wherein the thermoplastic vulcanizate exhibits a Shore A hardness (ISO 868-85) of from 35 to 100.

2. The electrolyzer of claim 1, wherein the thermoplastic vulcanizate exhibits a Shore A hardness (ISO 868-85) of from 40 to 70.

3. The electrolyzer of claim 1, wherein the thermoplastic vulcanizate exhibits a 100% modulus of at least 1 MPa.

4. The electrolyzer of claim 1, wherein the thermoplastic vulcanizate exhibits a coefficient of friction of 3 or less.

5. The electrolyzer of claim 1, wherein the thermoplastic vulcanizate exhibits a tensile stress at break of 0.5 MPa to 20 MPa.

6. The electrolyzer of claim 1, wherein the thermoplastic vulcanizate exhibits an elongation at break of 200% or more to 1000% or less.

7. The electrolyzer of claim 1, wherein the thermoplastic resin comprises a polyimide, a polyester, a polyamide, a poly(phenylene ether), a polycarbonate, a styrene-acrylonitrile copolymer, a polyethylene terephthalate, a polybutylene terephthalate, a polystyrene or a derivative thereof, a polyphenylene oxide, a polyoxymethylene, a fluorine-containing thermoplastic resin, or a mixture thereof.

8. The electrolyzer of claim 1, wherein the thermoplastic resin comprises a polyolefin.

9. The electrolyzer of claim 8, wherein the polyolefin comprises polypropylene.

10. The electrolyzer of claim 1, wherein the elastomer comprises natural rubber, styrene-butadiene copolymer rubber, butadiene rubber, acrylonitrile rubber, halogenated rubber, butadiene-styrene-vinyl pyridine rubber, urethane rubber, polyisoprene rubber, epichlolorohydrin terpolymer rubber, polychloroprene, or a mixture thereof.

11. The electrolyzer of claim 1, wherein the elastomer comprises a polyolefin elastomer copolymer.

12. The electrolyzer of claim 1, wherein the elastomer comprises an ethylene/propylene/non-conjugated diene copolymer rubber (EPDM).

13. The electrolyzer of claim 1, wherein the elastomer comprises an ethylene acrylic copolymer.

14. The electrolyzer of claim 1, wherein the elastomer comprises a butyl rubber.

15. The electrolyzer of claim 1, wherein the thermoplastic vulcanizate comprises from about 10 wt. % to about 90 wt. % of the elastomer and from about 10 wt. % to about 90 wt. % of the thermoplastic resin wherein the wt. % is based on the weight of the thermoplastic vulcanizate.

16. The electrolyzer of claim 1, wherein the gasket defines a first passage hole and a second passage hole for passage of a first gas and a second gas, respectively, and a third passage hole for passage of a liquid.

17. The electrolyzer of claim 1, wherein the first spacer frame surrounds a first electrode and the second spacer frame surrounds a second electrode.

18. The electrolyzer of claim 1, wherein the first spacer frame surrounds a first electrode and the second spacer frame surrounds a diaphragm.

19. The electrolyzer of claim 18, further comprising a third spacer frame and a gasket comprising a second thermoplastic vulcanizate wherein the gasket has a first surface contacting the second spacer frame and a second and opposing surface contacting the third spacer frame.

20. The electrolyzer of claim 19, wherein the third spacer frame surrounds a second electrode.