Use of melt plasticizers to enhance processability and mechanical properties of polyolefin articles

The present invention relates to plasticized polyolefin compositions comprising a polyolefin and plasticizer comprising certain types or grades of poly-esterified sucrose. The poly-esterified sucrose has a weight average molecular weight of between 1,800 grams/mole and 3,500 grams/mole, and is present at levels of about 0.01% to 80% by weight in the polyolefin and more preferably 0.10 to 1.25% by weight in the polyolefin. The polyolefin may be a polypropylene homopolymer, copolymer, or impact copolymer, or a high density polyethylene, low density polyethylene, or linear low density polyethylene, or blends thereof. The compositions of the present invention exhibit significant increases in both axial and biaxial elongations, significant increases in the tenacity, significant reductions in the achievable linear density or reductions in the achievable gauge or thickness, significant improvements in throughputs and processing efficiencies and/or significant increases in the overall “toughness” of the extruded poly-esterified sucrose modified polyolefins.

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Description
BACKGROUND OF THE INVENTION

Polyolefins are important and widely used polymers. The use of polyolefin resins to produce fibers, tapes, films, sheeting, molded articles and related products has been a rapidly growing and increasingly competitive market. Polyolefins can be grouped into several broad categories, in particular their industrial grades include high density polyethylene, low density polyethylene, linear low density polyethylene, co-polymers of polyethylene, iso-tactic, and syndiotactic polypropylene homopolymer and polypropylene copolymers.

When polyolefins are extruded into fiber, films, tapes, monofilaments, or molded parts they are used extensively in but not limited to the following markets:

1. Carpets and Floor Coverings

2. Wall coverings and Sound Insulation materials

3. Baby Diapers and Hygenics Applications

4. Commercial & Residential Upholstery

5. Some Apparel Applications

6. Geotextiles

7. Building Materials

8. Automotive

9. Wire, Cable and electrical housings

10. Curtains Drapes and Window Dressings

11. Industrial Fabrics and belting

12. Mattress ticking and bedding fabrics

13. Outdoor furniture and leisure products

14. Ropes and Cordage

15. Decorative Fabrics

There are many advantages in using polyolefin polymers. These include:

1. Low specific gravity.

2. Low coefficient of thermal conductivity.

3. Polyolefins are easily extruded and processed.

4. Polyolefins continue to be the fastest commercially growing and available thermoplastic polymers in the world.

5. Polyolefins are inherently resistant to mold, mildews and fungus.

7. Polyolefins are very chemically resistant, in fact, considered to be almost 100% chemically inert.

8. Polyolefins are very economical. It is one of the lowest costing thermoplastics per pound in the world.

9. Polyolefins are somewhat easily modified by the addition of commercially available pigments and additives.

Because of these advantages, there has always been a market driven need for property process modifier chemical additives yielding novel or unique processing enhancements with improved processing efficiencies. Since there is a direct relationship between the process used to produce a polyolefin article, the resultant polymer morphology and the final mechanical/physiochemical properties obtained, more desirable mechanical properties can be achieved through exploitation of the imparted improved processing efficiency of the polyolefin article.

Economically and commercially available property modifiers for polyolefin products will only continue to fuel this already rapidly growing market demand.

Historically, prior art recognizes the use of other internal lubricants and plasticizers such as amide waxes, certain grades of oxidized waxes, and the metallic soaps (calcium stearate, zinc stearate, etc) being used to improve extrusion processing, post processing, such as printing or futher conversion, and/or to improve the dispersion of other additives such as pigments and fillers that are being incorporated into the polyolfin thermoplastic. Unfortunately, these other plasticizing additives impart inherent problems associated with their use. For example, amide waxes have excellent cost economics and a very high degree of chemical efficiency when used as “slip agents” during the extrusion processing of polyolefin blown films. However, their use in color critical applications is limited due to the fact that these additives have a tendency to discolor upon long term heat aging, they have poor processing thermal stability which can lead to immediate discoloration, and they are very migratory. Discoloration and a high degree of migration of the plasticizing additive precludes their use, for example, in many fiber and fibrillated or slit film applications where color and frictional properties are such critical factors. The plasticizers described in this invention have similar economics and chemical efficiency which lends their use as plasticizing agents in polyolefins resulting in new and novel processing properties and physical properties of the polyolefin articles in which they are properly used.

Use of one such class of chemical additive plasticizers includes what the inventor terms “melt plasticizers”. A melt plasticizer needs to meet the following criteria to be an effective polymer and processing modifier to enhance processing of the polyolefin and results in improved or more desirable mechanical properties:

    • 1. It must be very chemically compatible with the polyolefin when the polyolefin is in its molten state.
    • 2. It must be sufficiently thermally stable.
    • 3. It must impart no coloration.
    • 4. It must have low odor, non-toxic or no odor during processing and impart no odor to the final polyolefin article.
    • 5. It must have acceptable and optimal migratory characteristics in the polymer matrix upon cooling.
    • 6. It must be chemically non-interacting with other pigments or other chemical additives present in the polymer matrix.
    • 7. It must be economical.
    • 8. It must be available in a form or processed into a form as to allow easy processing by the polymer converter.

In particular, there is one chemical family of melt plasticizers composed of partially to completely esterified sucrose (Sucrose Esters of Fatty Acids—SEFA) that meet all of the above criteria. When certain SEFA compositions are combined with polyolefin resin in relatively low concentrations to produce fibers, films, and tapes, the resultant articles yield novel and unexpected processing enhancements during their formation and/or mechanical properties in the final article.

SUMMARY OF INVENTION

This invention is the use of melt plasticizers, in particular certain types or grades of poly-esterified sucrose (Sucrose Esters of Fatty Acids—SEFA Chemistries), used in the composition of polyolefins yielding certain novel and unexpected extrusion processing and post extrusion processing conditions that result in:

    • 1. Significant increases in both axial and biaxial elongations of the extruded melt plasticized polyolefin article.
    • 2. Significant increases in the “tenacity” or breaking strength of the extruded melt plasticized polyolefin article.
    • 3. Significant reductions in the achievable linear density or reductions in the gauge/thickness of melt plasticized polyolefin articles.
    • 4. Significant improvements in throughputs and processing efficiencies of extruded melt plasticized polyolefin articles.
    • 5. Significant increases in the overall “toughness” of the extruded melt plasticized polyolefin articles.

DETAILED DESCRIPTION OF THE INVENTION

As used herein the term “yarn” means fibers formed by extruding a molten thermoplastic material through a plurality of fine, usually circular, die capillaries as molten threads or filaments which are then subsequently quenched with water or air. Thereafter, the filaments are then taken up by a winder and traversed into a continuous package of filaments. This yarn is referred to as “partially oriented yarn (POY) continuous filament yarn”. In some instances the filaments may be oriented through stretching the plurality of filaments over steam heated, hot oil heated or electrically heated “draw” rolls before the filaments are traversed onto a package by the winder. This type of yarn is referred to as “fully oriented continuous (FOY) continuous filament yarn”. There are occasions where the filaments may be texturized (given a three dimensional crimped effect) in the process before or after winding through the use of hot air jet texturing or stuffer box method. This yarn is referred to as “bulked continuous filament yarn (BCF)”. If the yarn is to be either drawn and/or textured after take-up winding, the plurality of filaments are first extruded, quenched and taken up via winding onto a continuous package and stored as partially oriented yarn (POY). This is step 1. The stored yarn packages are then placed on a draw texturing machine where the plurality of filaments are then either combined with one another or processed as individual yarns, drawn and/or textured through a hot air jet texturizer or heated stuffer box texturizer and then re-wound onto another continuous package to form a final package of continuous texturized yarn. This is step 2. This type of 2 step process for producing a textured yarn is often referred to as a “2 step textured yarn”.

In some cases, where the plurality of filaments are round cylindrical filaments and are such that the individual filaments are very much larger in diameter than in BCF or POY yarn. In this process the filaments are extruded, quenched, draw oriented and the individual filaments are taken up on a traversing winder, the yarn is referred to as “monofilament” yarn. There are occasions where the yarn may be specially heat treated over heated draw rolls or passed through an annealing oven where the filaments are heat set annealed before winder take up.

As used herein the term “staple fibers” means fibers formed by extruding a molten thermoplastic material through a plurality of fine, usually circular, die capillaries as molten threads or filaments which are then subsequently quenched with water or air. Thereafter, the filaments are bundled together to form a “tow” which is then pulled over heated rolls which stretch or draw the towed fibers resulting in higher degrees of orientation yielding the desirable mechanical properties. The tow is then pulled into a texturizing unit where three dimensional crimp is imparted to the towed fiber bundle. The tow of fibers is then pulled further into a cutting unit that then cuts or chops the towed filaments into specific lengths. The fiber is then transported, usually pneumatically, to a collection and baling unit where it is consolidated and secured as a storable or shippable bale of staple fiber. This entire process is referred to as the “short spin process”. In some case, the older process of long spin, or two step spinning is still preferred to produce staple fibers. In this process, the fibers are extruded as per in short spinning, but quenching of the fibers followed by very low levels of orientation occur followed by filament fiber take up. The packages of partially oriented filament fibers are referred to as a “tow” and this completes the first step of the long spin process. The packages of filament fibers or “tow” are then accumulated and placed on a “creeling frame”. This frame is designed to hold a plurality of these packages of filament fibers and the filaments are combined and pulled over heated orientation rolls that spin at increasingly higher rates of speed. This action on the towed filaments stretches the filaments imparting a desired degree of orientation thereby imparting the required mechanical properties. Steam or other forms of heat may be applied via passing the filament tow through a dry or steam heated oven before or after the orientation step to impart higher levels pliability to the slightly softened polymer. The filament tow is then pulled into a stuffer box machine that imparts three dimensional crimp to the towed filaments. The crimped towed filaments are then fed into a “cutter” where the filament fiber tow is then cut or chopped into lengths of fiber. The fiber is then transported, usually pneumatically, to a collection and baling unit where it is consolidated and secured as a storable or shippable bale of staple fiber. This fibers is referred to as “long spin” or “two step” staple fibers.

As used herein the term “tape yarn” means fibers formed by extruding a molten thermoplastic material through a plurality of slits, usually rectilinear in shape, as molten tapes which are then subsequently quenched in a water bath. Thereafter, the tapes are oriented through stretching the plurality of tapes over steam heated, hot oil heated or electrically heated “draw” rolls before the filaments are traversed onto a package by the winder. This type of yarn is referred to as “tape yarn” or “profile tape yarn”.

As used herein the term “slit tape yarn” means fibers formed by extruding a molten thermoplastic material through a slot or slit type profile die usually rectilinear in shape, as a continuous film which is then subsequently quenched in a water bath. Thereafter, the film is cut by a row of industrial razor knives forming a width of individual tapes and these slit tapes are continuously pulled through a either a heated oven, over a heated plate, or over steam heated, hot oil heated or electrically heated “draw” rolls before the oriented slit tapes are traversed onto a package by the winder. This type of yarn is referred to as “slit tape yarn”. There are occasions where the process may have a heated annealing oven where the yarns are exposed to imparted heat and therefore heat set to reduce shrinkage before winder take up. Additionally, there are occasions where the slit tapes may be pulled over a fibrillation device where the individual slit tape yarns are subjected to a mechanical shear force resulting in the formation of a connected networked plurality of smaller tape fibers. These individual “fibrillated tape yarns” are then taken up on a traverse winder for yarn package formation.

As used herein the term molded articles means the formation of a thermoplastic article that is the result of injecting a molten thermoplastic into a closed mold that is subsequently chilled and then opened thereby ejecting the formed, cooled thermoplastic part from the mold. The part is then collected either manually or through automation, inspected, quality controlled and then packaged for further use. In particular there are two primary processes used to produce molded articles or parts. These two processes are described as “injection molding” and “blow molding”. Injection molding indicates that the molten polymer is injected into a mold and fills the mold via the positive pressure obtained from the extrusion process. Blow molding indicates that the extruder melts and delivers the molten thermoplastic to a hollow mold and the molten thermoplastic fills the mold via positive pressure from air or some other gas source near the exit nozzle at the end of the extrusion die tip.

As used herein the term “extruded sheets” means sheets are formed by extruding molten thermoplastic material through a slot shaped die that is configured in such a way that the thickness of the sheet is maintained by pulling it through a quenching bath or over chill roll(s). The sheet is then trimmed while it is being taken up onto a roll where it is doffed from the machine and stored. In some cases post processing of the sheet may include flame ionization treatment followed by printing.

As used herein the term “blown film” means films formed by extruding a molten thermoplastic material through a circular type profile die as a continuous film which is then subsequently filled with positive pressure air resulting in the quenching of the molten thermoplastic film. The positive pressure quenching air not only quenches the film but also bi-axially orients the film resulting in more desirable mechanical properties such as improved bursting strength, tear strength or elongations. The resultant vertical continuous bubble formed is then pulled upward into a containment cage with rollers that guide the film bubble and flatten it geometrically until the bubble is collapsed into a bi-layered continuous film product. This film is often redirected downward to the based of the machine where it is taken up on a continuous roll. In some cases the film may be slit or have its edges trimmed before take up. There are instances where the blown film process is configured in such a way to allow the extrusion processing of multiple layers produced from multiple types of thermoplastic polymers. These “multi layered blown films” have many applications where enhanced mechanical properties and air permeability properties are highly engineered for a particular purpose. The semi-finished rolls of film may then be post processed to include pre-treatment for printing, printed and/or cutting and conversion into the finished film product.

As used herein the term “cast film” means films formed by extruding a molten thermoplastic material through a slot type profile die as a continuous film which is then subsequently pulled over a chill roll or into a water quench bath. Orientation of the cast film product may occur before or after quenching. If after quenching, the film must be re-heated by pulling through a heated oven or pulling the film over heated rolls. If orientation of the film occurs before the quench, it may be accomplished by pulling and forming the film from the die at such a rate of speed that the film becomes elongated sufficiently to induce orientation in the film in the direction that it is being pulled. The film can also be oriented in the cross machine direction through the use of a tentering frame that grabs the outer edges of the film as the film is pulled through a heated oven. After film formation, orientation and quenching, the film can then be trimmed or taken up onto a continuous roll for storage and inspection. Also, multiple layered films can be extruded via this process where the “layers” of film are often fused together via inherent adhesion properties to form a multi-layer film construction.

As used herein, the term “polymer” generally includes but is not limited to homopolymers, copolymers, such as for example, block, graft, random and alternating copolymers, terpolymers, etc. and blends thereof. Furthermore, unless otherwise specifically limited, the term polymer shall include all possible geometrical configurations of the polymeric chemistry. These geometric isomer configurations include but are not limited to isotactic, syndiotactic, and random symmetries.

The term “polyolefin” includes polypropylene homopolymers and copolymers with other alpha olefins such as ethylene, butene-1, pentene-1, hexene-1, etc., and various types of polyethylene including high density polyethylene, low density polyethylene, linear low density polyethylene and its copolymers with other alpha olefins. Commodity polyethylenes are commercially produced in a variety of different types and grades. Homopolymerisation of ethylene with transition metal based catalysts leads to the production of so-called “high density” grades of polyethylene. These polymers have relatively high stiffness and are useful for making articles where inherent rigidity is required. Copolymerisation of ethylene with higher 1-olefins (e.g. butene, hexene or octene) is employed commercially to provide a wide variety of copolymers differing in density and in other important physical properties. Particularly important copolymers made by copolymerising ethylene with higher 1-olefins using transition metal based catalysts are the copolymers having a density in the range of 0.91 to 0.93. These copolymers which are generally referred to in the art as “linear low density polyethylene” are in many respects similar to the so called “low density” polyethylene produced by the high pressure free radical catalysed polymerisation of ethylene. Such polymers and copolymers are used extensively in the manufacture of flexible blown film.

The monomers from which the polyolefins of the present invention is derived and used in preparing the present invention are preferably C2 to C20 olefins. Examples of the C2 to C20 alpha-olefins include ethylene, propylene, 1-butene, 2-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-dodecene, 1-hexadodecene, 4-methyl-1-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 3,3-dimethyl-1-butene, diethyl-1-butene, trimethyl-1-butene, 3-methyl-1-pentene, ethyl-1-pentene, propyl-1-pentene, dimethyl-1-pentene, methylethyl-1-pentene, diethyl-1-hexene, trimethyl-1-pentene, 3-methyl-1-hexene, dimethyl-1-hexene, 3,5,5-trimethyl-1-hexene, methylethyl-1-heptene, trimethyl-1-heptene, dimethyloctene, ethyl-1-octene, methyl-1-nonene, vinylcyclopentene, vinylcyclohexene, vinylnorbornene, cyclooctadiene, dicyclooctadiene, methylenenorbornene, 5-methylene-2-norbornene, 5-methyl-1,4-hexadiene, and 7-methyl-1,6-octadiene.

As used herein, the term “melt plasticizer” is a chemical class of polymeric additives to that relative to the polymer in which they are used meets the following criteria:

    • 1. It must be very chemically compatible with the polyolefin when the polyolefin is in its molten state.
    • 2. It must be sufficiently thermally stable.
    • 3. It must impart no coloration.
    • 4. It must have low odor, non-toxic or no odor during processing and impart no odor to the final polyolefin article.
    • 5. It must have acceptable and optimal migratory characteristics in the polymer matrix upon cooling.
    • 6. It must be chemically non-interacting with other pigments or other chemical additives present in the polymer matrix.
    • 7. It must be economical.
    • 8. It must be available in a form or processed into a form as to allow easy processing by the polymer converter or formulator.

In particular there is a chemical family of melt plasticizers of which certain grades of poly-esterified sucrose have been identified that meet all of the above criteria and when combined in small concentrations with polyolefin resins to fibers, films, tapes, and thick gauge parts yield novel and unexpected processing enhancements and/or mechanical properties to the final article.

As used herein, the term poly-esterified sucrose represents a commercially distinct chemical class (chemical compound) known as sucrose esters of fatty acids (SEFA). SEFA compounds are high molecular weight compounds formed by esterifying fatty acids to a sucrose molecule backbone, which contains eight potential esterification sites. The fatty acids used to form these esters include those containing about eight or more carbon atoms, and preferably containing from 8 to about 22 carbon atoms, and mixtures of such esters. Suitable esters can be prepared by the reaction of diazoalkanes and fatty acids, or derived by alcoholysis from the fatty acids naturally occurring in fats and oils. Fatty acid esters suitable for use herein may be derived from either saturated or unsaturated fatty acids. Suitable preferred saturated fatty acids include, for example, capric, lauric, palmitic, stearic, behenic, isomyristic, isomargaric, myristic, caprylic, and anteisoarachadic. Suitable preferred unsaturated fatty acids include, for example, maleic, linoleic, licanic, oleic, linolenic, and erydiogenic acids. Mixtures of fatty acids derived from soybean oil, palm oil, coconut oil, cottonseed and fatty hydrogenated rapeseed oil are especially preferred for use herein. Methyl esters are the preferred fatty acid esters for use herein, since their use in the processes herein tends to result in high yields of polyol fatty acid poly-esterified reaction products.

As used herein, the term “polyol” is intended to include any aliphatic or aromatic compound containing at least two free hydroxyl groups. In practicing the processes disclosed herein, the selection of a suitable polyol is simply a matter of choice. For example, suitable polyols may be selected from the following classes: saturated and unsaturated straight and branched chain linear aliphatic; saturated and unsaturated cyclic aliphatic, including heterocyclic aliphatic; or mononuclear or polynuclear aromatics, including heterocyclic aromatics. Carbohydrates and non-toxic glycols are preferred polyols. Monosaccharides suitable for use herein include, for example, mannose, galactose, arabinose, xylose, ribose, apiose, rhamnose, psicose, fructose, sorbose, tagitose, ribulose, xylulose, and erythrulose. Oligosaccharides suitable for use herein include, for example, maltose, kojibiose, nigerose, cellobiose, lactose, melibiose, gentiobiose, turanose, rutinose, trehalose, sucrose and raffinose. Polysaccharides suitable for use herein include, for example, amylose, glycogen, cellulose, chitin, inulin, agarose, zylans, mannan and galactans. Although sugar alcohols are not carbohydrates in a strict sense, the naturally occurring sugar alcohols are so closely related to the carbohydrates that they are also preferred for use herein. The sugar alcohols most widely distributed in nature and suitable for use herein are sorbitol, mannitol and galactitol.

Particularly preferred classes of materials suitable for use herein include the monosaccharides, the disaccharides and sugar alcohols. Preferred carbohydrates and sugar alcohols include xylitol, sorbitol and sucrose. Sugar ethers and alkoxylated polyols, such as polyethoxy glycerol can also be used herein.

A preferred solid material is poly-esterified sucrose in which the degree of esterification is 7-8, and in which the fatty acid moieties are C18 mono- and/or di-unsaturated and behenic, in a molar ratio of unsaturates:belienic of 1:7 to 3:5. A particularly preferred solid poly-esterified sugar is the octaester of sucrose in which there are about 7 behenic fatty acid moieties and about 1 oleic acid moiety in the molecule. Other materials include cottonseed oil or soybean oil fatty acid esters of sucrose. The ester materials are further described in, U.S. Pat. No. 2,831,854, U.S. Pat. No. 4,005,196, to Jandacek, issued Jan. 25, 1977; U.S. Pat. No. 4,005,195, to Jandacek, issued Jan. 25, 1977, U.S. Pat. No. 5,306,516, to Letton et al., issued Apr. 26, 1994; U.S. Pat. No. 5,306,515, to Letton et al., issued Apr. 26, 1994; U.S. Pat. No. 5,305,514, to Letton et al., issued Apr. 26, 1994; U.S. Pat. No. 4,797,300, to Jandacek et al., issued Jan. 10, 1989; U.S. Pat. No. 3,963,699, to Rizzi et al, issued Jun. 15, 1976; U.S. Pat. No. 4,518,772, to Volpenhein, issued May 21, 1985; and U.S. Pat. No. 4,517,360, to Volpenhein, issued May 21, 1985.

It has been found that certain colorless, odorless, tasteless and thermally stable grades of poly-esterified sucrose may be used as melt plasticizers as part of the composition of polyolefin fibers, films, tapes and thick gauge parts yielding novel processing conditions and subsequent improvements in desirable physical properties. In particular there are, “clean grades” of partially to fully saturated poly-esterified sucrose which have a weight average molecular weight of approximately 1,800 to 3,500 grams/mole which are suitable for use in the polyolefin compositions outlined herein.

Typically, 0.10% to 1.25% of poly-esterfied sucrose based on total weight of the composition is used to impart the desired processing conditions and impart the subsequent mechanical enhancements and properties to the final modified polyolefin composition. However, direct addition of the poly-esterified sucrose chemistry is not convenient nor practical as the poly-esterified sucrose will normally take the form of a liquid or soft solid making its ease of handling and incorporation into the polymer matrix impossible using standard single screw extrusion processing. Therefore, it is important that the poly-esterified sucrose be melted and thoroughly incorporated into an appropriate polyolefin carrier resin and melt extrusion compounded and chipped or pelletized masterbatch (concentrate) form prior to its use by the end use processor. It has been found that additive masterbatches of up to 80% active poly-esterified sucrose and 20% polyolefin carrier resin can be produced using this method. More so, certain grades of solid, wax-like poly-esterified sucrose are easily flaked into free flowing powders and are thereby pre-mixed with polyolefin carrier resins resulting in easily processed masterbatch pre-mixes.

Normally polyolefin fibers, tapes, films and thick gauge molded parts are produced using the following polyolefins:

    • 1. Polypropylene Homopolymers and Copolymers, including block or random copolymers of propylene having up to 10 wt % of another comonomer or mixtures of comonomers such as ethylene or an alpha-olefin of 4 to 8 carbon atoms
    • 2. High density polyethylenes
    • 3. Low Density Polyethylenes
    • 4. Linear Low Density polyethylene and its copolymers, containing mixtures of comonomers such as propylene or an alpha-olefin of 4 to 8 carbon atoms

In addition to the use of poly-esterified sucrose, other additives may be used to chemically or physically modify the polyolefin compositions in which poly-esterified sucrose is used. These other additives include organic and inorganic pigments or dyes, anti-oxidants, acid scavengers, nucleating agents, slip agents, antistatic agents, other plastisizers or lubricants besides poly-esterified sucrose, ultra-violet light stablizers, ultra-violet absorbers, metal deactivators, flame retardants, conductive fillers, other homopolymers or non-elastomeric co-polymers.

Polyolefins produced using poly-esterified sucrose has several advantages due to imparted improvements in the extrusion processing and post processing used to manufacture them.

Polyolefins produced using and containing poly-esterified sucrose yield the following enhancements:

    • 1. At levels between 0.1% to 1.25% by weight in the final polyolefin article, poly-esterified sucrose modified polyolefin articles (fibers, monofilaments, films and coatings) can be produced that exhibit a much higher imparted elongation. Elongations increase significantly under standard processing conditions. This can be beneficial when producing polyolefin articles where a higher degree of elongation is desired with maximum extrusion processing speeds.
    • 2. At levels between 0.1% to 1.25% in the final polyolefin article, poly-esterified sucrose modified polyolefin articles (fibers, monofilaments, films and coatings) can be produced that exhibit a much higher elongation under standard processing conditions. When the processing conditions are adjusted to eliminate the high elongation using high orientation levels, higher imparted breaking strengths (tenacities) can be obtained. In fiber applications, these higher breaking strengths are typically measured as tenacity and are assigned a value expressed in grams per denier (g/den.). In other geometries such as thicker films or thick gauge parts the force is applied until the polyolefin article fails. For example, in polypropylene fibers, typically the highest tenacity achieved for standard industry bulked continuous filament or continuous filament yarns made from polypropylene homopolymer and other polyolefinic resins is approximately 4.0 g/den. When 0.1% to 1.25% by weight of poly-esterified sucrose is used in the composition of the polymeric blend and the processing conditions adjusted accordingly, increased levels of elongation are imparted resulting in better processing efficiencies and allowing for imparting higher levels of orientation through increasing the draw ratio of the filament yarns. Higher tenacities of poly-esterified sucrose modified polyolefin fibers can therefore be obtained at high efficiencies, produced using a wide range of existing standard fiber extrusion equipment, and at higher than nominal production rates.
    • 3. At levels between 0.1% to 1.25% by weight in the final polyolefin, poly-esterified sucrose modified polyolefin articles (fibers, monofilaments, films and coatings) can be produced that exhibit a much higher elongation under standard processing conditions. This much higher elongation can be further exploited through the production of very fine fibers or very thin films. Under appropriate processing conditions and a high degree of uniaxial (for fibers) or biaxial (for films) orientation very fine “denier” fibers or very thin films can be produced far smaller than what is normally achievable using polyolefin resins without the use of pol-esterified sucrose in the production of fiber and film articles. Typically, with out the use of poly-esterified sucrose, polyolefin filament and staple fibers can be produced with a lower linear density of 1.2 denier/filament. Poly-esterified sucrose modified polyolefin fibers allow the production of polyolefin fibers with linear densities in the “micro-denier” range (less than 1.0 denier/filament) at higher rates of production and high processing efficiencies.
    • 4. At levels between 0.1% and 1.25% of poly-esterified sucrose used in the composition of the final polyolefin article (fibers, monofilaments, films and coatings), a rheological phenomenon occurs whereby improved internal and external lubricity leads to improved processing of polyolefins resins. This is particularly important for the production of polyolefin fibers, films and similar structures where this processing benefit can allow production increases (throughputs) of 25% or more. In effect the polymer flows more readily, exits the die more readily, and is drawn and oriented more easily downstream, allowing much higher rates of production to be achieved.
    • 5. At levels between 0.1% and 1.25% by weight of poly-esterified sucrose in the composition of the final polyolefin article (fibers, monofilaments, films and coatings), highly oriented fibers and films can be produced resulting in an overall increase in “toughness”. Specifically, “toughness” is the area integrated under a typical stress-strain (x,y) curve as is achieved through mechanical stress testing of a fiber or film. As breaking tenacities increase other mechanical properties can be affected in such a way that the overall toughness can be enhanced. Improving the toughness of poly-esterified sucrose modified polyolefin articles (fibers, monofilaments, films and coatings) is a very desirable mechanical enhancement that up until recently has only been achievable through less economical means.
    • 6. At levels between 0.1% and 1.25% by weight in the final polyolefin article (in thick gauge parts), flow of the polymer in the injection molding or blow molding process is enhanced allowing for the following process and resultant property benefits:
      • a. Shorter cycle times can be achieved due to lower extrusion head pressures and cooler nozzle temperatures. These lower head pressures and cooler nozzle temperatures imparted to the polyolefin from the poly-esterified sucrose additive keeps the shear stresses on the polymer to a minimum and frictional heat is reduced during the injection or blow molding portion of the process. Since reduced cycle times are typically induced via higher temperature settings to achieve lower viscosities of the polymer, the temperature settings can be reduced with the use of these two classes of melt plasticizers. More desirable and more predictable mechanical properties of the final parts produced can be achieved.
      • b. Thinner parts are achieved much more evenly and uniformly.

EXAMPLE(S)

The poly-esterified sucrose may be dry blended with flake polyolefin carrier polymer at an optimal concentration level of 5% to as much as 80% by weight. Other co-additives may be incorporated into this masterbatch formulation as well, including, but not limited to, anti-oxidants, ultra violet light stabilizers, and pigments. The mix is then extruded, quenched and pelletized using a twin screw extruder, quench bath and face cut or strand cut pelletizer. Other methods for incorporating the additive into the carrier resin may also be employed to anyone skilled in the art of thermoplastic compounding. The resultant additive pellet produced is then referred to as “masterbatch” pellets. These additive masterbatch pellets are then blended with neat polyolefin resin and extruded into the finished fiber, film or thick gauge part. Processing of this blended polymeric mix results in novel processing properties that can be adjusted to achieve unexpected and surprising results not achievable without the poly-esterified sucrose additive masterbatch.

The following examples illustrate the effect on processability and subsequent achievable mechanical properties of the poly-esterified sucrose modified polyolefin articles.

General Recipe—Poly-Esterified Sucrose Masterbatch Recipe

A 100 lbs polyolefin/additive blend is prepared by weighing and physically mixing the following components and feeding them into a twin screw extruder using of the following melt plasticizer recipe:

Poly-Esterified Sucrose Melt Plasticizer Masterbatch Recipe

71.0% Isotactic Polypropylene Homopolymer (Melt Flow Index=12 gram/10 mins.)

4.0% Secondary or Tertiary Hindered Amine Ultra-violet Light Stabilizer

25.0% Of a Clean Grade Poly-esterified Sucrose containing greater than or equal to 97% octa-, hepta-, and hexa-ester groups with a molecular weight of about 2,400 grams/mole and a fluid viscosity of about 17 centapoise at 250 degrees Celsius.

Example 1

The materials in the above “general recipe” were combined and thoroughly and homogenously mixed, fed into a twin screw extruder, extruded, quenched and pelletized. The resultant melt plasticizer masterbatch pellets are then thoroughly mixed at 3.0% by weight with 97.0% of 12 MFR polypropylene homopolymer and then fed into a single screw extruder melted, mixed and extruded. The extrudate was then forced through a spinnerette and continuous filament fibers were spun, quenched, drawn or oriented over dry heat godet rolls and taken up by a traversing winder as a continuous package of untexturized yarn at 1300 meters/minute. The package of yarn was then physically tested and its mechanical properties were determined and compared to yarn extruded exactly as above but not containing the poly-esterified sucrose additive masterbatch (melt plasticizer masterbatch). The table below lists the physical properties of the melt plasticized modified yarn verses yarn extruded with no additive modifications and processed under the same processing conditions:

Property Modified Yarn Unmodified Yarn % Melt Plasticizer Masterbatch 3.0% 3.0% Denier (grams/9000 meters) 1100 denier 1100 denier Draw Ratio (1 stage draw) 3 to 1 3 to 1 Tenacity 3.0 gram/denier 3.0 grams/denier Elongation (at Break) 75% 60%

As can be seen in the above table, addition of 3.0% (by weight) of the melt plasticizer masterbatch outlined in the general recipes above were blended into the resin to produce the continuous filament polypropylene yarns and processed under identical extrusion conditions results in a yarn that has 25% higher levels of elongation.

Example 2

The materials in the above “general recipe” were combined and thoroughly and homogenously mixed, fed into a twin screw extruder, extruded, quenched and pelletized. The resultant melt plasticizer masterbatch pellets are then thoroughly mixed at 3.0% by weight with 97.0% of 12 MFR polypropylene homopolymer and then fed into a single screw extruder melted, mixed and extruded. The extrudate was then forced through a spinnerette and continuous filament fibers were spun, quenched, drawn or oriented over dry heated godet rolls and taken up by a traversing winder as a continuous package of untexturized yarn at 1300 meters/minute. The package of yarn was then physically tested and its mechanical properties were determined and compared to yarn extruded exactly as above but at a much higher draw ratio via increasing the speed of the second heated godet role. Also, the amount of polymer through put was increased by increasing the speed of the melt pump and extruder to compensate for the higher degree of draw so that the linear density (denier) of the yarn would not change when compared to the melt plasticized modified yarn. The table below lists the physical properties of the melt plasticized modified yarn verses yarn extruded with no melt plasticizer additive modifications:

Property Modified Yarn Unmodified Yarn % Melt Plasticizer Masterbatch 3.0% 3.0% Denier (grams/9000 meters) 1100 denier 1100 denier Draw Ratio (1 stage draw) 4.6 to 1 3 to 1 Tenacity (Max. Break Strength) 4.5 grams/denier 3.0 grams/denier Elongation (at Break) 55% 60%

As can be seen in the above table, addition of 3.0% (by weight) of the melt plasticizer masterbatch blended into the resin to produce the continuous filament polypropylene yarn (modified yarn) resulted in a yarn that has approximately the same degree of elongation but a significantly higher achievable tenacity. In fact, this higher tenacity yarn has a 50% higher tenacity than what would optimally be achieved without the melt plasticizer masterbatch additive. Additionally, the higher tenacity yarn above is obtained at the same degree of processing efficiency as the lower tenacity yarn.

Example 3

The polypropylene in the above mentioned “general recipe” was replaced with a 12 melt flow indexed linear low density polyethylene homopolymer (film or fiber grade). The melt plasticizer masterbatch pellets are then thoroughly mixed at 3.0% by weight with 97.0% by weight with 12 melt flow linear low density polyethylene and then fed into a single screw extruder and melted, mixed and extruded. The extrudate was then forced through a spinnerette, extruded and was oriented using standard draw ratios of about 2.5 to 1. When the elongation of the polyethylene fibers was determined it was noted as being 25% higher than would be expected if no melt plasticizer masterbatch were used. The trial was then run again to achieve higher throughputs and the take up speeds were increased by 25%. The fiber processed very well even at these higher processing speeds. The filament fibers were then mechanically tested to determine their elongation and it was found that the elongations were acceptable for this partially oriented yarn. The higher through puts achieved at exceptional processing efficiency was considered a surprising discovery on the part of the experimenters.

Example 4

3% (by weight) of the melt plasticizer masterbatches detailed in the above “general recipe” were mixed with 97% of 12 melt flow rate polypropylene homopolymer and then fed into a single screw extruder and melted, mixed and extruded. The extrudate was then forced through a spinnerette and fibers were spun and taken up at approximately 1300 meters/minute. The package of partially oriented filament yarn was then taken to a separate drawing process and highly oriented until the elongation was reduced to approximately 30%. The fiber produced was uniform and had excellent physical properties. However, it was found that the fiber had a significantly reduced linear density, meaning that the fibers were much finer than would be expected if no melt plasticizer masterbatch were used in their manufacture. The experiment was repeated again to assess whether or not the filament fibers could be further drawn and processed reducing the linear density even lower. Surprisingly, it was found that filaments having a denier of less than 1.0 gram/denier (“micro-denier” filaments) could be extruded and processed efficiently for commercially production.

Example 5

3% (by weight) of the melt plasticizer masterbatches in the above “general recipe” for the melt plasticizer masterbatch once combined and thoroughly and homogenously mixed with 97% of 12 melt flow rate polypropylene homopolymer were fed into a single screw extruder mounted on an injection molding machine and the mix was melted, mixed and extruded. The extrudate was then forced through heated channels into a mold and the mold was cooled thereby cooling the molded part. The mold was then separated through automated means and the molded part was ejected from the mold. The part was observed to have very smooth surface features, excellent thin part definition and no geometric distortions of any kind. It was then decided to measure the optimal cycle time improvement that such a recipe mix and injection molding machine could achieve to said parts if the molding machine were run continuously. Typically without the additive the cycle times for this unmodified polypropylene part would be on the order of 25 seconds. After use of 2.5% of the melt plasticizer masterbatch, nozzle temperatures were kept to an optimal temperature level even though the cycle times were reduced by 25%. After use of the melt plasticizer masterbatch, the cycle times were reduced to approximately 18 seconds and a high quality comparable part was produced.

Claims

1. A polyolefin article comprised of 0.01% to 80.00% by weight of a poly-esterified sucrose having a weight average molecular weight of 1,800 grams per mole to 3,500 grams per mole.

2. The polyolefin article of claim 1 wherein the polyolefin portion of the article is comprised of a balance of polypropylene homopolymer.

3. The polyolefin article of claim 1 wherein the polyolefin portion of the article is comprised of a balance of iso-tactic polypropylene homopolymer.

4. The polyolefin article of claim 1 wherein the polyolefin portion of the article is comprised of a balance of polypropylene co-polymer derived from any of the following co-monomers including ethylene, propylene, 1-butene, 2-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-dodecene, 1-hexadodecene, 4-methyl-1-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 3,3-dimethyl-1-butene, diethyl-1-butene, trimethyl-1-butene, 3-methyl-1-pentene, ethyl-1-pentene, propyl-1-pentene, dimethyl-1-pentene, methylethyl-1-pentene, diethyl-1-hexene, trimethyl-1-pentene, 3-methyl-1-hexene, dimethyl-1-hexene, 3,5,5-trimethyl-1-hexene, methylethyl-1-heptene, trimethyl-1-heptene, dimethyloctene, ethyl-1-octene, methyl-1-nonene, vinylcyclopentene, vinylcyclohexene, vinyinorbornene, cyclooctadiene, dicyclooctadiene, methylenenorbornene, 5-methylene-2-norbornene, 5-methyl-1,4-hexadiene, and 7-methyl-1,6-octadiene.

5. The polyolefin article of claim 1 wherein the polyolefin portion of the article is comprised of a balance of linear low density polyethylene.

6. The polyolefin article of claim 1 wherein the polyolefin portion of the article is comprised of a balance of low density polyethylene.

7. The polyolefin article of claim 1 wherein the polyolefin portion of the article is comprised of a balance of high density polyethylene.

8. The polyolefin article of claim 1 wherein the article is a continuous filament (CF) yarn.

9. The polyolefin continuous filament yarn of claim 8 wherein the continuous filament tape is a bulked continuous filament (BCF) yarn.

10. The polyolefin article of claim 1 wherein the article is a staple fiber.

11. The continuous filament yarn of claim 8 wherein the continuous filament yarn is a partially oriented yarn.

12. The polyolefin article of claim 1 wherein the article is a slit tape yarn.

13. The polyolefin slit tape of claim 12 wherein the slit tape is a fibrillated slit tape yarn.

14. The polyolefin article of claim 1 wherein the article is a film produced from the blown film process.

15. The polyolefin article of claim 1 wherein the article is a cast film produced from the cast die film process.

16. The polyolefin article of claim 1 wherein the article is a blow molded part.

17. The polyolefin article of claim 1 wherein the article is an injection molded part.

18. The polyolefin article of claim 1 wherein the article is an extruded sheet.

19. The polyolefin article of claim 1 wherein the article is an extruded profile.

20. The polyolefin article of claim 1 wherein the article is an extruded masterbatch composition.

Patent History
Publication number: 20060182963
Type: Application
Filed: Sep 12, 2005
Publication Date: Aug 17, 2006
Inventor: Howard Bradshaw (Marietta, GA)
Application Number: 11/224,357
Classifications
Current U.S. Class: 428/364.000
International Classification: D02G 3/00 (20060101);