STRENGTHENING AGENTS AND PROCESSES FOR MAKING AND USING SAME

- ECOLAB USA INC.

In some embodiments, a process can include combining a plurality of fibers and water to produce a slurry, forming the slurry into a wet paper web, pressing and draining the wet paper web to produce a wet paper sheet, and drying the wet paper sheet to produce a paper product. A strengthening agent can be combined with the fibers and water to produce the slurry, applied to the wet paper web, and/or applied to the wet paper sheet. The strengthening agent can include a polyamidoamine-epihalohydrin resin and an additive. The additive can include a tannin and/or a compound having a chemical formula (I) of: where: R1, R2, and R3 can independently be a hydroxyl group or a methoxy group, and R4, R5, and R6 can independently be H, an alkyl group, an aldehyde group, a carboxylic acid group, or a —C═C—COOH group.

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Description
CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Patent Application No. 63/535,701, filed on Aug. 31, 2023, which is incorporated by reference herein.

FIELD

Embodiments described generally relate to strengthening agents and process for making and using same. More particularly, such embodiments relate to strengthening agents for imparting wet strength to paper products that include one or more polyamidoamine-epihalohydrin resins and one or more certain additives and processes for making and using same.

BACKGROUND

Paper is sheet material containing interconnected small, discrete fibers. The fibers are usually formed into a sheet on a fine screen from a dilute water suspension or slurry. Typically paper is made from cellulose fibers, although occasionally synthetic fibers are used. The wet strength of paper is defined (U.S. Pat. No. 5,585,456) as the resistance of the paper to rupture or disintegration when it is wetted with water. Paper products made from untreated cellulose fibers lose their strength rapidly when they become wet, i.e., they have very little wet strength. Wet strength of ordinary paper is only about 5% of its dry strength. Various processes of treating paper products have been employed to overcome this disadvantage.

Wet strength resins applied to paper are either of the “permanent” or “temporary” type, which are defined by how long the paper retains its wet strength after immersion in water. While permanent wet strength is a desirable characteristic in packaging materials, it presents a disposal problem. Paper products having permanent wet strength are typically degradable only under undesirably severe conditions. While some resins are known to impart temporary wet strength (temporary wet strength resins) and would be suitable for sanitary or disposable paper uses, they often suffer from one or more drawbacks. For example, the temporary wet strength resins generally do not provide an optimal combination of dry and wet strength or softness properties to the sanitary or disposable paper products. There is a need, therefore, for improved processes for imparting appropriate levels of wet strength and/or repulpability to paper products.

SUMMARY

Strengthening resins and processes for making and using same are provided. In some embodiments, a process for making a paper product can include combining a plurality of fibers and water to produce a slurry. The slurry can be formed into a wet paper web. The wet paper web can be pressed and drained to produce a wet paper sheet. A strengthening agent can be (i) combined with the plurality of fibers and water to produce the slurry, (ii) applied to the wet paper web, (iii) applied to the wet paper sheet, or (iv) a combination of at least two of (i), (ii), and (iii). The strengthening agent can include a polyamidoamine-epihalohydrin resin and an additive. The additive can be or can include at least one of a tannin and a compound having a chemical formula (I):

where: R1, R2, and R3 are independently a hydroxyl group or a methoxy group, and R4, R5, and R6 are independently H, an alkyl group, an aldehyde group, a carboxylic acid group, or a —C═C—COOH group. The process can also include drying the wet paper sheet to produce the paper product.

In some embodiments, a paper product can include a paper substrate that can be or can include a plurality of fibers and a strengthening agent disposed on the fibers. The strengthening agent can be or can include a polyamidoamine-epihalohydrin resin and an additive. The additive can be or can include at least one of a tannin and a compound having a chemical formula (I):

where: R1, R2, and R3 are independently a hydroxyl group or a methoxy group, and R4, R5, and R6 are independently H, an alkyl group, an aldehyde group, a carboxylic acid group, or a —C═C—COOH group.

DETAILED DESCRIPTION

Polyamidoamine-epichlorohydrin (PAE) resins have long been used to impart permanent wet strength to a wide range of paper products, e.g., tissue, paper towel, and paperboard. It has been surprisingly and unexpectedly discovered that the addition of an additive to a polyamidoamine-epihalohydrin resin can significantly increase the dry strength and/or the wet strength of paper products. The common feature across the suitable additives is that the chemical structure of the additive includes a six carbon atom aromatic ring that includes three functional groups on adjacent carbon atoms of the aromatic ring, where the functional groups are independently a hydroxyl (—OH) group or a methoxy (—OCH3) group. In some embodiments, the additive can be or can include a tannin. In other embodiments, the additive can be or can include one or more compounds having a chemical formula (I):

where R1, R2, and R3 can independently be a hydroxyl group or a methoxy group, and R4, R5, and R6 can independently be H, an alkyl group, an aldehyde group, a carboxylic acid group, a —C═C—COOH group, a hydroxyl group, or a methoxy group. In some embodiments, R1, R2, and R3 can independently be a hydroxyl group or a methoxy group, and R4, R5, and R6 can independently be H, an alkyl group, an aldehyde group, a carboxylic acid group, or a —C═C—COOH group. In some embodiments, if one or more of R4, R5, and R6 include the alkyl group, the alkyl group can include from 1 carbon atom to 10 carbon atoms. Suitable additives that have the chemical formula (I) can be or can include, but are not limited to, gallic acid, syringic acid, syringol, pyrogallol, quercetin, methoxycatechol, sinapic acid, or any mixture thereof. In some embodiments, the additive can be or can include a tannin and one or more compounds having the chemical formula (I).

In some embodiments, the PAE resin and/or the additive can include one or more liquid mediums and can be in the form of a suspension, dispersion, or solution. Illustrative liquid mediums can be or can include, but are not limited to, water, an alkylene glycol, a polyalkylene glycol, or a mixture thereof. As further described below, during the process of making a paper product, the PAE resin and the additive can be separately applied or otherwise contacted with the plurality of fibers during one or more steps used to make the paper product and/or the PAE resin and the additive can be applied together as a contact product. The contact product between the PAE resin and the additive can be made by pre-blending or otherwise mixing the PAE resin and the additive prior to use in making the paper product, as further described below.

In some embodiments, when the PAE resin and/or the additive includes a liquid medium, the PAE resin and the additive can independently have a solids content (PAE resin solids and additive solids, respectively) in an amount of about 5 wt %, about 8 wt %, about 10 wt %, about 12 wt %, about 15 wt %, about 20 wt %, about 23 wt %, about 25 wt %, about 27 wt %, or about 30 wt % to about 33 wt %, about 35 wt %, about 37 wt %, about 40 wt %, about 43 wt %, about 45 wt %, about 47 wt %, about 50 wt %, about 53 wt %, about 55 wt %, about 57 wt %, about 60 wt %, about 63 wt %, about 65 wt %, about 67 wt %, or about 70 wt %. In some embodiments, the PAE resin can have a greater solids content than the additive. In other embodiments, the additive can have a greater solids content than the PAE resin. In still other embodiments, the PAE resin and the additive can have substantially the same solids content as compared to one another. In some embodiments, the strengthening agent, when in the form of a contact product, can have a solids content (a combined amount of PAE resin solids and additive solids) in an amount of about 5 wt %, about 8 wt %, about 10 wt %, about 12 wt %, about 15 wt %, about 20 wt %, about 23 wt %, about 25 wt %, about 27 wt %, or about 30 wt % to about 33 wt %, about 35 wt %, about 37 wt %, about 40 wt %, about 43 wt %, about 45 wt %, about 47 wt %, about 50 wt %, about 53 wt %, about 55 wt %, about 57 wt %, about 60 wt %, about 63 wt %, about 65 wt %, about 67 wt %, or about 70 wt %. For example, in some embodiments, the strengthening agent in the form of a contact product can be in the form of an aqueous dispersion, suspension, solution, or other mixture and can have a solids concentration of 10 wt % to 60 wt %, 30 wt % to 60 wt %, 30 wt % to 50 wt %, 10 wt % to 30 wt %, 12 wt % to 27 wt %, 15 wt % to 25 wt %, or 17 wt % to 23 wt %.

The solids weight, solids concentration, or solids content of a dispersion, suspension, solution, or other solid/liquid mixture, e.g., the PAE resin, the additive, or the contact product produced by contacting the PAE resin and the additive with one another, as understood by those skilled in the art, can be measured by determining the weight loss upon heating a small sample, e.g., about 5 grams to about 8 grams of the mixture, to a suitable temperature, e.g., about 105° C., and for a period of time sufficient to remove the liquid therefrom. By measuring the weight of the sample before and after heating, the percent solids in the sample can be directly calculated or otherwise estimated.

Process for Making Paper Products

The process for making the paper product can include combining a plurality of fibers and water to produce a slurry; forming the slurry into a wet paper web; pressing and draining the wet paper web to produce a wet paper sheet; and drying the wet paper sheet to produce a dried paper sheet. In some embodiments, the process for making the paper product can include taking an aqueous slurry that includes about 0.1 wt %, about 0.5 wt %, about 1 wt %, or about 1.5 wt % to about 2.5 wt %, about 3 wt %, about 4 wt %, or about 5 wt % of the plurality of fibers, based on the weight of the aqueous slurry, and dewatering the slurry to form a wet paper web that can include about 8 wt %, about 10 wt %, about 12 wt %, or about 15 wt % to about 17 wt %, about 21 wt %, about 23 wt %, or about 25 wt % of the plurality of fibers, based on the weight of the wet paper web. For example, the papermaking fibers can be deposited onto a foraminate surface to form the wet paper web. The wet paper web can be pressed and drained to produce a wet paper sheet that includes about 40 wt %, about 45 wt %, about 50 wt %, or about 55 wt % to about 60 wt %, about 65 wt %, about 70 wt %, about 75 wt %, about 80 wt %, or about 90 wt % of the plurality of fibers, based on the weight of the wet paper sheet. The wet paper sheet can then be dried to produce a dried paper sheet that can have a moisture content of about 0.1 wt %, about 0.5 wt %, about 1 wt %, about 2 wt %, about 3 wt % or about 4 wt % to about 6 wt %, about 8 wt %, about 10 wt %, or about 12 wt %, based on the weight of the dried paper sheet. In some embodiments, the dried paper sheet can be free of any moisture.

Accordingly, transforming the slurry into the dried paper sheet can be accomplished via a series of steps that can include, but are not limited to, inertial dewatering (early forming section of the machine), press dewatering (press section of the machine), and/or thermally evaporating the water (dryer section of the machine). In some paper making machines, through-air drying cylinders can be located after the forming section and before the dryer section. The PAE resin and the additive can be incorporated separately and/or together as a preblended mixture or contact product during the papermaking process by: (i) combining with the plurality of fibers and water to produce the slurry, (ii) applying to the wet paper web, (iii) applying to the wet paper sheet, or a combination of at least two of (i), (ii), and (iii).

In some embodiments, the PAE resin and the additive can be co-applied or co-dosed, i.e., separately applied, during any one or more of (i), (ii), and/or (iii). In some embodiments, the PAE resin can be combined with the plurality of fibers and water to produce the slurry and the additive can be applied to the wet paper web and/or applied to the wet paper sheet. In other embodiments, the PAE resin and the additive can each be combined with the plurality of fibers and water to produce the slurry, can each be applied to the wet paper sheet, and/or can each be applied to the wet paper web. When the PAE resin and the additive are combined or applied during the same step of the process, the PAE resin can be added before the additive, the additive can be added before the PAE resin, or added at the same time with respect to one another. In still other embodiments, a first quantity of the PAE resin or a first quantity of the additive can be added during a given step followed by the other component and then a second quantity of the PAE resin or a second quantity of the additive can be added. Any number of alternating additions of the PAE resin and the additive can be used during the production of the paper product.

As noted above, in some embodiments the PAE resin and the additive can be mixed, blended, stirred, combined, or otherwise contacted with one another to produce the strengthening agent in the form of a preblended mixture or contact product. As such, in some embodiments, the strengthening agent can be a contact product produced by contacting the PAE resin and the additive prior to contact with the plurality of fibers in the slurry, the wet paper web, or the wet paper sheet in the paper making process.

The PAE resin and additive can be combined with one another in any order or sequence. For example, the PAE resin can be added to the additive, the additive can be added to the PAE resin, the PAE resin and the additive can be simultaneously combined with one another, or any combination thereof. In one embodiment, the PAE resin can be added to a mixing vessel first and the additive can be subsequently added to the mixing vessel. In another embodiment, the additive can be added to the mixing vessel first and the PAE resin can be subsequently added. In yet another embodiment, the PAE resin and the additive can be simultaneously added to the mixing vessel. In yet another embodiment, a first portion of the PAE resin can be added to the mixing vessel first and the additive can be subsequently added to the mixing vessel, and then a second portion of the PAE resin can be added to the mixing vessel or vice versa. In some embodiments, the PAE resin can include a liquid medium and the additive (without a liquid medium) can be combined with the PAE resin to produce the contact product. In other embodiments, the PAE resin and the additive can each include a liquid medium when combined with one another to produce the contact product.

In some embodiments, when the strengthening agent includes the PAE resin and the additive in the form of the contact product, the PAE resin and the additive can be combined with one another at a temperature of about 0° C., about 5° C., about 10° C., about 15° C., or about 20° C. to about 25° C., about 30° C., about 35° C., about 40° C., or about 45° C. In some embodiments, the PAE resin and the additive can be combined with one another at room temperature. The PAE resin and additive can be mixed for a period of time of about 0.5 minutes, about 1 minute, about 10 minutes, about 30 minutes, about 45 minutes or about 1 hour to about 2 hours, about 3 hours, about 4 hours, about 5 hours, about 10 hours, or more under active stirring or other agitation. In some embodiments, the PAE resin can be added to the mixing vessel first and the additive can be added slowly over a period of time. In some embodiments, the slow addition of the additive can reduce the total time the PAE resin and the additive need to be stirred to produce the strengthening agent in the form of the contact product.

In some embodiments, when the strengthening agent is in the form of a contact product, the strengthening agent can be stored at room temperature, e.g., about 22° C., until the strengthening agent is used to make the paper product. In other embodiments, when the strengthening agent is in the form of a contact product, the strengthening agent can be stored at a temperature less than room temperature until the strengthening agent is used to make the paper product. In such embodiment, the strengthening agent in the form of a contact product can be stored at a temperature of less than 20° C., less than 15° C., less than 10° C., or less than 5° C., e.g., about 2° C. to about 4° C.

In some embodiments, the strengthening agent can also be used in conjunction with and/or serially with other additional ingredients conventionally used in the production of paper products and other cellulosic products. Such additional ingredients conventionally used can include, but are not limited to, sizing agents, colorants, inorganic pigments, fillers, anti-curl agents, surfactants, plasticizers, humectants, defoamers, UV absorbers, light fastness enhancers, polymeric dispersants, dye mordants, optical brighteners, leveling agents, and the like. All types of pigments and fillers can be added to the paper product. Such materials include, but are not limited to, clay, talc, titanium dioxide, calcium carbonate, calcium sulfate, and diatomaceous earths. Other additives, including, for example, alum, can also be used in the manufacture of paper products.

In some embodiments, a weight ratio of the additive to the PAE resin, on a solids basis, in the strengthening agent used to make the paper product can be from 0.01:1, 0.05:1, 0.1:1, 0.15:1, 0.2:1, 0.25:1, or 0.3:1 to 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, or 1:1. In other embodiments, the weight ratio of the additive to the PAE resin, on a solids basis, in the strengthening agent used to make the paper product can be from 0.01:1, 0.03:1, 0.05:1, 0.07:1, or 0.09:1 to 0.1:1, 0.105:1, 0.15:1, 0.2:1, 0.25:1, or 0.3:1. In some embodiments, the optimal weight ratio of the additive to the PAE resin can be based, at least in part, on the particular additive or combination of additives and the particular PAE resin or combination of PAE resins used to produce the strengthening agent.

In some embodiments, the amount of the strengthening agent, on a solids basis, that can be used to make the paper product can be from about 0.1 kg, about 0.25 kg, about 0.5 kg, about 0.7 kg, about 1 kg, about 3 kg, or about 5 kg to about 7 kg, about 10 kg, about 13 kg, about 15 kg, about 17 kg, about 20 kg, about 25 kg, about 30 kg, about 35 kg, or about 40 kg per 1,000 kg (tonne) of the plurality of fibers, on a dry basis. In some embodiments, the paper product can have a basis weight, based on a dry weight of the paper product, of about 10 g/m2 or gsm, about 20 g/m2, about 30 g/m2, about 35 g/m2, about 40 g/m2, about 45 g/m2, about 50 g/m2, or about 55 g/m2 to about 60 g/m2, about 65 g/m2, about 70 g/m2, about 75 g/m2, about 80 g/m2, about 85 g/m2, about 80 g/m2, about 95 g/m2, about 100 g/m2, about 105 g/m2, about 110 g/m2, about 115 g/m2, about 120 g/m2, about 125 g/m2, about 130 g/m2, or greater.

In some embodiments, the paper product made with the strengthening agent can have a dry tensile strength that can be greater than a dry tensile strength of a comparative paper product. In some embodiments, the paper product made with the strengthening agent can have a wet tensile strength that can be greater than a wet tensile strength of a comparative paper product. The comparative paper product refers to a paper product made under the same conditions except the additive is not used and the amount of the PAE resin used is equal to the amount of the strengthening agent, i.e., the combined amount of the PAE resin and the additive, with the amounts based on the solids weight of the strengthening agent used to make the paper product and the PAE resin used to make the comparative paper product. For example, if the strengthening agent had a weight ratio of the additive to the PAE resin of 0.1:1 and the strengthening agent was applied, on a solids basis, in an amount of 10 kg per 1,000 kg of fibers on a dry basis, then the amount of PAE resin used to make the comparative paper product, on a solids basis, would be 10 kg per 1,000 kg of fibers on a dry basis. Accordingly, the amount of PAE resin used to make the comparative paper product is greater than the amount of PAE resin used in the strengthening agent by an amount equal to the amount of the additive (on a solids basis).

In some embodiments, the dry tensile strength of the paper product contacted with the strengthening agent can be greater that the dry tensile strength of a comparative paper product made only with the PAE resin in an amount of about 1%, about 3%, about 5%, or about 10% to about 15%, about 20%, about 23%, about 25% or more. In some embodiments, the wet tensile strength of the paper product contacted with the strengthening agent can be greater that the wet tensile strength of a comparative paper product made only with the PAE resin in an amount of about 1%, about 3%, about 5%, or about 10% to about 15%, about 20%, about 23%, about 25% or more. In some embodiments, the wet tensile strength divided by the dry tensile strength (wet/dry (%)) of the paper product contacted with the strengthening agent can be greater that the wet/dry (%) of a comparative paper product made with the PAE resin and not the additive in an amount of about 1%, about 3%, about 5%, or about 10% to about 15%, about 20%, about 23%, about 25% or more.

The plurality of fibers used to make the paper product can be or can include any type of cellulosic fibers, any type of non-cellulosic fibers, and combinations of cellulosic and non-cellulosic fibers. The cellulosic fibers that can be used can be or can include, but are not limited to, sulfate (Kraft) fibers, sulfite fibers, soda fibers, neutral sulfite semi-chemical (NSSC) fibers, thermomechanical (TMP) fibers, chemi-thermomechanical (CTMP) fibers, groundwood (GWD) fibers, and any combination of these fibers. Any of the foregoing cellulosic fibers may be bleached or unbleached. These designations refer to wood pulp fibers that have been prepared by any of a variety of processes that are typically used in the pulp and paper industry. The non-cellulosic fibers can be or can include, but are not limited to, viscose rayon or regenerated cellulose fibers.

In some embodiments, the fibers can be derived from bleached furnish, softwood, hardwood, paper pulp, mechanical pulp, or any mixture thereof. In some embodiments, the fibers can include non-wood fibers, such as cotton fibers or cotton derivatives, abaca, kenaf, sabai grass, flax, esparto grass, straw, jute, hemp, bagasse, milkweed floss fibers, and pineapple leaf fibers; and wood fibers such as those obtained from deciduous and coniferous trees, including softwood fibers, such as northern and southern softwood kraft fibers, hardwood fibers, such as maple, birch, aspen, or any mixture thereof. In some embodiments, the fibers can be or can include fibers recovered from previously manufactured fiber products. In other words, the fibers can be or can include recycled fibers. In some embodiments, the plurality of fibers can be a mixture of softwood and hardwood fibers. In such embodiments, the mixture of softwood and hardwood fibers can include about 1 wt %, about 10 wt %, about 20 wt %, about 30 wt %, about 40 wt %, or about 50 wt % to about 60 wt %, about 70 wt %, about 80 wt %, about 90 wt %, or about 99 wt % of softwood fibers, on a dry basis, based on a combined weight of the softwood fibers and the hardwood fibers.

Tannins

There are a wide variety of tannins. As used herein, “tannin” refers to both hydrolyzable tannins and condensed tannins. Illustrative genera of shrubs and/or trees from which suitable tannins can be derived can be or can include, but are not limited to, Acacia, Castanea, Vachellia, Senegalia, Terminalia, Phyllanthus, Caesalpinia, Quercus, Schinopsis, Tsuga, Rhus, Juglans, Carya, and Pinus, or any combination thereof. In some embodiments, genera from which suitable tannins can be derived can be or can include, but are not limited to, Schinopsis, Acacia, or a combination thereof. In other embodiments, genera from which suitable tannins can be derived can include, but are not limited to, Pinus, Carya, or a combination thereof. In some embodiments, suitable condensed and/or hydrolyzable tannins can be synthetically derived. In some embodiments, suitable synthetically derived condensed tannins can include synthetic oligo-proanthocyanidins (OPC) such as those described in S. Quideau et al., Plant Polyphenols: Chemical Properties, Biological Activities, and Synthesis, Angewandte Chemie International Edition 50(3), pp. 586-621 (2011). In some embodiments, the tannin can include a mixture of one or more bio-sourced tannins and one or more synthetic tannins.

Hydrolyzable tannins are decomposable in water with which the hydrolyzable tannins can react with to form other compounds. The hydrolyzable tannins can be or can include, but are not limited to, tannic acid, pyrogallol, ellagic acid, epigallocatechin gallate, epicatechin gallate, epigallocatechin, of esters of a sugar, e.g., glucose, with gallic and/or digallic acids, or any mixture thereof. Illustrative hydrolyzable tannins can be or can include, but are not limited to, extracts recovered from Castanea sativa, e.g., chestnut, Terminalia and Phyllantus, e.g., myrabalans tree species, Caesalpinia coriaria, e.g., divi-divi, Caesalpinia spinosa, e.g., tara, algarobilla, valonea, and Quercus, e.g., oak. Condensed tannins are polymers formed by the condensation of flavans. Condensed tannins can be linear or branched molecules. Illustrative condensed tannins can be or can include, but are not limited to, Acacia mearnsii, e.g., wattle or mimosa bark extract, Schinopsis, e.g., quebracho wood extract, Tsuga, e.g., hemlock bark extract, Rhus, e.g., sumac extract, Juglans, e.g., walnut, Carya illinoinensis, e.g., pecan, and Pinus, e.g., Radiata pine, Maritime pine, bark extract species.

The condensed tannins typically include about 70 wt % to about 80 wt % active phenolic ingredients (the “tannin fraction”) and the remaining ingredients (the “non-tannin fraction”) typically include, but are not limited to, carbohydrates, hydrocolloid gums, and amino and/or imino acid fractions. The condensed tannins can be used as recovered or extracted from the organic matter or the condensed tannins can be purified, e.g., to about 95 wt % or greater of active phenolic ingredients. Hydrolyzable tannins and condensed tannins can be extracted from the starting material, e.g., trees and/or shrubs, using well established processes. A more detailed discussion of tannins is discussed and described in the Handbook of Adhesive Technology, Second Edition, CRC Press, 2003, chapter 27, “Natural Phenolic Adhesives I: Tannin,” and in Monomers, Polymers and Composites from Renewable Resources, Elsevier, 2008, chapter 8, “Tannins: Major Sources, Properties and Applications.”

The condensed tannins can be classified or grouped into one of two main categories, namely, those containing a resorcinol unit and those containing a phloroglucinol unit. Illustrative tannins that include the resorcinol unit can be or can include, but are not limited to, black wattle tannins and quebracho tannins. The resorcinol unit can be represented by Formula (II) below.

The resorcinol group is shown within the box overlaying the unit structure of black wattle and quebracho tannins in Formula (III) below. For simplicity, the structure of black wattle and quebracho tannins is represented by their flavonoid unit structure.

Illustrative tannins that include the phloroglucinol unit can be or can include, but are not limited to, pecan tannins and pine tannins. The phloroglucinol unit can be represented by Formula (IV) below.

The phloroglucinol unit is shown within the box overlaying the unit structure of pecan and pine tannins in Formula (V) below. For simplicity, the structure of pecan and pine tannins is represented by their flavonoid unit structure.

Phloroglucinol is known for higher reactivity than resorcinol. As such, tannins that include the phloroglucinol unit exhibit a greater reactivity than tannins that include the resorcinol unit.

If the additive includes a mixture of hydrolyzable tannins and condensed tannins, such mixture can include any ratio of the hydrolyzable tannins to the condensed tannins with respect to one another can be used. In some embodiments, if the additive includes both hydrolyzable tannins and condensed tannins, the additive can include about 1 wt % to about 99 wt % of the condensed tannins, based on the combined weight of the hydrolyzable tannins and the condensed tannins. In other embodiments, if the additive includes both hydrolyzable tannins and condensed tannins, the additive can include at least 50 wt %, at least 55 wt %, at least 60 wt %, at least 70 wt %, at least 75 wt %, at least 80 wt %, at least 85 wt %, at least 90 wt %, at least 95 wt %, or at least 97 wt % of the condensed tannins, based on the combined weight of the hydrolyzable tannins and the condensed tannins.

If the additive includes two or more different condensed tannins, the two or more condensed tannins can include a resorcinol unit and/or a phloroglucinol unit. In some embodiments, the additive can include two or more different condensed tannins that each can include resorcinol units, e.g., quebracho tannins and black wattle tannins. In other embodiments, the additive can include two or more different condensed tannins, where a first condensed tannin can include a resorcinol unit, e.g., black wattle tannin, and a second condensed tannin can include a phloroglucinol unit, e.g., pine tannin. In another embodiment, the additive can include two or more different condensed tannins that can each include a phloroglucinol unit, e.g., pine tannins and pecan tannins.

The tannins can have an acidic pH. For example, the pH of the tannins can be about 3, about 3.5, or about 4 to about 5, about 5.5, about 6, or about 6.5. Suitable, commercially available tannins can be or can include, but are not limited to, black wattle tannin or wattle bark tannin, quebracho tannin, hemlock tannin, sumac tannins, pecan tannin, mimosa tannin, pine tannins, or any mixture thereof.

PAE Resins

PAE resins are well-known in the art. A variety of techniques are known in the art for making polyamidoamine-epichlorohydrin (PAE) resins that can be employed to produce suitable PAE resins that can be used to produce the strengthening agent. In some embodiments, suitable PAE resins can be produced by modifying a polyamidoamine polymer or prepolymer by reaction with one or more epihalohydrins, e.g., epichlorohydrin, to produce the PAE resin. The epihalohydrin is a difunctional compound having different, hence “asymmetric”, chemical functionalities, epoxy and chlorine groups. This asymmetric functionality allows the epichlorohydrin ring to open upon reaction with the epoxy group with secondary amines, followed by the pendant chlorohydrin moieties used for both: (1) intramolecular cyclization to generate a cationic azetidinium functionality; or 2) intermolecular cross-linking the polymer to increase molecular weight.

In other embodiments, another process that utilizes one or more functionally-symmetric (“symmetrical”) cross-linkers, an epihalohydrin, and, optionally, mono-functional modifiers that separates the process into at least two discrete steps can be used to produce a suitable PAE resin. The first step can form an intermediate molecular weight, cross-linked prepolymer, prepared upon reacting the PAE prepolymer with a functionally-symmetric cross-linker. Unlike the function of the asymmetric cross-linker epihalohydrin, the symmetric cross-linker utilizes the same moiety for reaction with both prepolymer secondary amine groups to effect cross-linking. If desired, the optional monofunctional groups can be used before, after, or during the cross-linking step to impart additional functionality to a prepolymer without the cross-linking function. The second step utilizes the epihalohydrin to impart cationic functionality without it being required for any cross-linking function, by using a reduced amount of epihalohydrin to maximize azetidinium ion formation on the polymer.

Illustrative processes for making the PAE resin can include, but are not limited to, the processes described in U.S. Pat. Nos. 2,926,154; 3,086,961; 3,700,623; 3,772,076; 4,233,417; 4,298,639; 4,298,715; 4,341,887; 4,853,431; 5,019,606; 5,510,004; 5,567,798; 5,585,456; 5,644,021; 6,429,267; 7,868,071; 8,785,593; 8,999,110; 9,828,302; 10,077,217; 10,633,798; 10,301,777; 10,190,261; and 10,711,401. Many commercially available PAE resin are known and can be used to make the strengthening agent described herein. Suitable commercially available PAE resins can include, but are not limited to, KYMENE® resins available from Solenis Technologies L.P., FENNOSTRENGTH® resins available from Kemira, and Maresin wet strength resins available from Mare.

EXAMPLES

In order to provide a better understanding of the foregoing discussion, the following non-limiting examples are offered. Although the examples can be directed to specific embodiments, they are not to be viewed as limiting the invention in any specific respect. All parts, proportions, and percentages are by weight unless otherwise indicated.

Hand sheets were made and tested. The hand sheets used in all examples were prepared according to the following procedure. The paper furnishes used to make the hand sheets that were tested was a mixture that included about 60 wt % of hardwood and about 40 wt % of softwood Kraft pulp mixture. The furnish was prepared by slushing dry lap, bleached hardwood, and softwood Kraft pulps. The final pulp mixture was diluted with tap water to a final consistency of about 0.6% and brought to a pH of about 6 with sulfuric acid before use. Hand sheets were prepared by mixing about 450 ml of an about 0.6 wt % consistency furnish at 1000 RPM in a Dynamic Drainage Jar. The furnish aliquot was designed to produce a base sheet that had a basis weight of about 60 gram per square meter (gsm).

Hand sheets experiments were carried out to evaluate how the dry tensile strength, the wet tensile strength, and the wet/dry (%) were affected via the use of various additives in combination with PAE resins. For the additives used to make the strengthening agents in the Examples below, an appropriate amount of water and the additive were added to a mixing jar and stirred with a magnetic mixing bar to make aqueous solutions. The mixtures were stirred for a time period of about 30 minutes to produce the aqueous solutions. The aqueous additive solutions in the examples below had a concentration of solids in an amount from about 0.1 wt % to 0.5 wt %, depending on the particular example.

When the strengthening agent was preblended to produce a contact product that included the PAE resin and the additive, the following procedure was used. An appropriate amount of the PAE resin was added to a mixing jar and stirred with a cage stirrer at about 800 rpm. An appropriate amount of the aqueous additive solution was added to the PAE resin and stirred for a sufficient amount of time, generally between 30 min and 2 hours, depending on the example. Some of the conditions used to preblend the PAE resin and the additive used in each set of examples varied, e.g., the mixing time, but for each particular set of examples the conditions used to prepare the preblended strengthening agent were the same.

Example I

The PAE resin (Resin A) used in CEx. 2 and Ex. 1-3 had a backbone polymer composed of adipic acid/diethylenetriamine, a solids content of about 20 wt %, a weight average molecular weight of at least 300,000 Da, an azetidinium content of at least 40%, and a residual CPD/DCP content of <1,000 ppm. The tannic acid and gallic acid were obtained from Acros Organics. The pyrogallol was obtained from TCI. The PAE resin and the strengthening agents in Table 1 were all applied in the wet end to the furnish blend before the sheet was formed.

TABLE 1 Weight Wet Ratio End PAE: Dose BW Dry Tensile Wet Tensile Wet/Dry Example Description Additive (lb/ton) (gsm) (Nm/g) STDEV (Nm/g) STDEV (%) CEx. 1 Blank n/a 0 110.6 29.3 1.2 0.38 0.0 1.3 CEx. 2A PAE Only n/a 10 111.1 39.9 1.1 8.99 0.4 22.3 Ex. 1A Preblended 1:0.1 10 115.4 42.8 2.2 10.07 0.3 23.5 PAE/Tannic Acid Ex. 2A Preblended 1:0.1 10 111.4 41.6 2.6 10.20 0.9 24.5 PAE/Gallic Acid Ex. 3A Preblended 1:0.1 10 110.5 40.7 0.7 10.04 0.3 24.7 PAE/Pyrogallol CEx. 2B PAE Only 15 113.3 38.9 1.5 9.35 0.4 24.0 Ex. 1B Preblended 1:0.1 15 112.6 47.9 1.3 12.02 0.5 25.1 PAE/Tannic Acid Ex. 2B Preblended 1:0.1 15 117.8 44.3 0.7 12.08 0.3 27.3 PAE/Gallic Acid Ex. 3B Preblended 1:0.1 15 113.0 42.6 2.2 12.07 0.8 28.4 PAE/Pyrogallol

As shown in Table 1, all inventive examples that preblended the additive with the PAE resin exhibited a similar increase in the wet/dry (%) and were all greater than the wet/dry (%) exhibited by CEx. 2A and CEx. 2B. More particularly, the increase for Ex. 1-3 ranged from about 4.6% (Ex. 1B) all the weight up to about 18.3% (Ex. 3B).

Example II

The PAE resin (Resin B) used in CEx. 4 and Exs. 4 and 5 had a backbone polymer composed of gluterate/diethylenetriamine, a solids content of about 25 wt %, a weight average molecular weight of at least 400,000 Da, an azetidinium content of at least 50%, and a residual CPD/DCP content of >1,000 ppm. The gallic acid used was the same as in Example I. Ex. 4 used a preblended strengthening agent whereas Ex. 5 co-dosed, i.e., applied separately. The preblended strengthening agent used in Ex. 4 was applied in the wet end to the furnish blend before the sheet was formed. In Ex. 5, the PAE resin was applied in the wet end to the furnish blend before the sheet was formed and the aqueous solution of gallic acid was applied to in the wet end to the furnish blend before the sheet was formed, i.e., the PAE resin and the gallic acid were co-dosed by applying with separate syringes simultaneously.

TABLE 2 Weight Wet Ratio End PAE: Dose BW Dry Tensile Wet Tensile Wet/Dry Example Description Additive (lb/ton) (gsm) (Nm/g) STDEV (Nm/g) STDEV (%) CEx. 3 Blank n/a 0 70.4 26.1 0.9 0.33 0.0 1.2 CEx. 4 PAE n/a 15 70.0 38.2 0.7 10.15 0.2 26.6 Ex. 4 Preblended 1:0.1 15 70.9 41.6 0.9 11.55 0.7 27.9 PAE/Gallic Acid Ex. 5 Co-dosed 1:01  15 70.6 41.1 0.6 11.53 0.8 28.0 PAE/Gallic Acid

Table 2 shows that the combination of PAE and gallic acid in Ex. 4 and Ex. 5 had a wet/dry (%) greater than CEx. 4 that included only PAE. Table 2 further shows that Ex. 4 and Ex. 5 exhibited a similar increase in wet/dry (%), which indicates that preblending the PAE and the gallic acid is not necessary and the two can be co-dosed without needing to be preblended with one another to achieve the increased wet/dry (%) over CEx. 4.

Example III

The PAE resin (Resin C) used in CEx. 6 and Exs. 6-8 had a backbone polymer composed of adipic acid/diethylenetriamine, a solids content of about 25 wt %, a weight average molecular weight of at least 400,000 Da, an azetidinium content of at least 50%, and a residual DCP/CPD content of >1,000 ppm. The gallic acid used was the same as in Example I. The syringol was obtained from Thermo Scientific. The syringic acid was obtained from TCI. The PAE resin and the strengthening agents in Table 3 were all applied in the wet end to the furnish blend before the sheet was formed.

TABLE 3 Weight Wet Ratio End PAE: Dose BW Dry Tensile Wet Tensile Wet/Dry Example Description Additive (lb/ton) (gsm) (Nm/g) STDEV (Nm/g) STDEV (%) CEx. 5 Blank n/a 0 65.3 26.6 1.2 0.31 0.0 1.2 CEx. 6 PAE n/a 15 64.2 40.2 3.3 10.09 0.3 25.7 Ex. 6 Preblended 1:0.1 15 64.5 42.1 3.0 11.54 0.5 26.8 PAE/Gallic Acid Ex. 7 Preblended 1:0.1 15 64.6 39.5 1.9 11.19 0.6 27.7 PAE/Syringol Ex. 8 Preblended 1:0.1 15 64.1 39.7 0.9 11.13 0.5 27.6 PAE/Syringic Acid

As shown in Table 3, the gallic acid, syringol, and syringic acid all led to similar increases in the wet/dry (%) as compared to CEx. 6.

Example IV

The PAE resin (Resin A) used in CExs. 8 and 9 and Exs. 9-11 was the same PAE resin used in Example I. The tannic acid used in Examples 9-11 was the same as in Example I. The PAE resins and the strengthening agents in Table 4 were all applied in the wet end to the furnish blend before the sheet was formed.

TABLE 4 Weight Wet Ratio End PAE: Dose BW Dry Tensile Wet Tensile Wet/Dry Example Description Additive (lb/ton) (gsm) (Nm/g) STDEV (Nm/g) STDEV (%) CEx. 7 Blank n/a 0 112.1 25.0 1.4 0.3 0.0 1.3 CEx. 8 PAE n/a 6 109.4 33.3 2.4 8.1 0.5 24.2 CEx. 9 PAE n/a 8 109.2 33.5 0.7 8.2 0.7 24.5 Ex. 9 Preblended 1:0.1 8 110.4 37.8 1.1 10.1 0.2 26.7 PAE/Tannic Acid Ex. 10 Preblended  1:0.12 8 110.8 36.9 1.5 8.5 0.5 23.1 PAE/Tannic Acid Ex. 11 Preblended 1:0.3 8 107.5 33.6 0.7 6.9 0.2 20.5 PAE/Tannic Acid

As shown in Table 4, when a weight ratio of tannic acid to the PAE resin exceeded 0.1:1, the tannic acid did not lead to an increase in the wet/dry (%) as compared to CExs. 8 and 9. When the weight ratio of the tannic acid to the PAE resin was 0.1:1, however, a significant increase in the wet/dry (%) was obtained. More particularly, Ex. 9 exhibited about a 9% increase in the wet/dry (%) as compared to CEx. 9.

Example V

The PAE resin (Resin A) used in CExs. 11 and 12 and Exs. 12-16 was the same PAE resin used in Example I. The tannic acid used in Examples 13-16 was the same as in Example I. The PAE resin and the strengthening agents in Table 5 were all applied in the wet end to the furnish blend before the sheet was formed.

TABLE 5 Weight Wet Ratio End PAE: Dose BW Dry Tensile Wet Tensile Wet/Dry Example Description Additive (lb/ton) (gsm) (Nm/g) STDEV (Nm/g) STDEV (%) CEx. 10 Blank 0 119.1 26.9 0.3 0.4 0.0 1.4 CEx. 11 PAE 4 120.4 34.7 2.9 7.6 0.5 22.7 Ex. 12 Preblended 1:0.1  4 119.8 39.9 2.5 9.7 1.6 24.2 PAE/Tannic Acid CEx. 12 PAE 8 119.9 38.1 2.7 9.4 0.8 24.6 Ex. 13 Preblended 1:0.1  8 120.0 42.0 1.6 11.2 0.5 26.7 PAE/Tannic Acid Ex. 14 Preblended 1:0.05  8 119.0 40.4 2.8 10.3 0.7 25.6 PAE/Tannic Acid Ex. 15 Preblended 1:0.075 8 120.6 41.3 2.5 10.9 0.7 26.3 PAE/Tannic Acid Ex. 16 Preblended 1:0.125 8 120.2 40.9 2.7 10.3 0.8 25.1 PAE/Tannic Acid

As shown in Table 5, Exs. 12-16 that had weight ratio of tannic acid to the PAE resin all exhibited a greater wet/dry (%) value and all performed similarly. Table 5 illustrates a roughly 1 unit drop in wet tensile strength from Ex. 13 to Ex. 16 (11.2 to 10.3), while Table 4 illustrates a roughly 1.5 unit drop (10.1 to 8.5) as the weight ratio of the PAE resin to the additive increased above 1:0.1.

Example VI

The PAE resin (Resin A) used in CExs. 13 and 14 and Exs. 17-21 was the same as that used in Example I. The tannic acid used in Example 17 was the same as in Example I. The wattle bark tannin used in Examples 18-20 was obtained from Supertan W&C and had a CAS No. of 1401-55-4. The gallic acid used in Ex. 21 was the same as in Example I. The PAE resin and the strengthening agents in Table 6 were all applied in the wet end to the furnish blend before the sheet was formed.

TABLE 6 Weight Wet Ratio End PAE: Dose BW Dry Tensile Wet Tensile Wet/Dry Example Description Additive (lb/ton) (gsm) (Nm/g) STDEV (Nm/g) STDEV (%) CEx. 13 Blank n/a 0 115.7 25.9 1.3 0.3 0.0 1.3 CEx. 14 PAE n/a 6 115.0 35.4 1.5 7.6 0.3 21.6 Ex. 17 Preblended 1:0.1 6 116.4 38.2 0.2 8.5 0.2 22.3 PAE/Tannic Acid Ex. 18 Preblended  1:0.05 6 116.9 37.4 1.9 8.4 0.4 22.4 PAE/Wattle Bark Tannin Ex. 19 Preblended 1:0.1 6 113.2 38.1 1.4 8.6 0.2 22.5 PAE/Wattle Bark Tannin Ex. 20 Preblended 1:02  6 116.9 39.4 2.6 8.6 0.1 22.0 PAE/Wattle Bark Tannin Ex. 21 Preblended 1:0.1 6 116.9 36.8 1.9 8.6 0.3 23.3 PAE/Gallic Acid

As shown in Table 6, Exs. 17-21 all exhibited a slightly greater wet/dry (%) value and all performed similar to one another.

Example VII

The PAE resin (Resin A) used in CExs. 15 and 16 and Exs. 22-24 was the same as that used in Example I. The tannic acid used in Example 22 was the same as used in in Example I. The wattle bark tannin used in Example 23 was the same as used in Example VI. The gallic acid used in Ex. 24 was the same as used in Example I. The PAE resin and the strengthening agents in Table 7 were all applied in the wet end to the furnish blend before the sheet was formed.

The hand sheets made in this example were tested for repulpability according to the following procedure. Sheets that contained the wet strengthening agent were soaked in hot tap water (about 30° C. to about 50° C.) at a consistency of about 1% for about 30 minutes and then disintegrated for about 20 minutes in a Lorentzen & Wettre 260 pulp disintegrator. The furnish was then used to form new handsheets using the same process (but no additional chemistry) in order to measure and compare the formation of the sheets.

TABLE 7 Relative Formation Weight Ratio BW of Repulped Sheets Example Description PAE:Additive (gsm) Average STD CEx. 15 Blank n/a 78.94 23.20 1.47 CEx. 16 PAE n/a 75.56 12.51 0.63 Ex. 22 PAE/Tannic 1:0.1 78.94 11.29 0.79 Acid Preblended Ex. 23 PAE/Wattle 1.:0.1  80.01 11.06 0.63 Bark Tannin Preblended Ex. 24 PAE/Gallic 1:0.1 78.53 10.97 0.26 Acid Preblended

As shown in Table 7, the strengthening agents in Exs. 22-24 that included tannic acid, wattle bark tannin, and gallic acid, respectively, did not have a significant affect on the repulpability of the hand sheets.

Example VIII

The PAE resin (Resin A) used in CExs. 17 and 18 and Exs. 25-27 was the same as that used in Example I. The tannic acid used in Example 25 and the gallic acid used in Example 27 were the same as used in Example I. The wattle bark tannin used in Example 26 was the same as used in Example VI. The gallic acid used in Ex. 24 was the same as in Example I. The PAE resins and the strengthening agents in Table 8 were all applied in the wet end to the furnish blend before the sheet was formed. In addition to measuring the dry and wet tensile strength (Table 8), the brightness of the hand sheets was also measured (Table 9).

TABLE 8 Weight Wet Ratio End PAE: Dose BW Dry Tensile Wet Tensile Wet/Dry Example Description Additive (lb/ton) (gsm) (Nm/g) STDEV (Nm/g) STDEV (%) CEx. 17 Blank n/a 0 110.4 27.1 2.3 0.3 0.0 1.1 CEx. 18A PAE n/a 2 110.7 34.0 1.6 5.4 0.3 15.9 CEx. 18B PAE n/a 4 109.4 36.0 2.4 7.3 0.9 20.1 CEx. 18C PAE n/a 8 109.3 38.8 1.8 9.2 0.5 23.7 Ex. 25A PAE/Tannic 1:0.1 2 109.2 34.8 1.1 5.9 0.3 17.0 Ex. 25B Acid 1:0.1 4 107.9 40.6 1.9 9.0 0.4 22.2 Ex. 25C Preblended 1:0.1 8 108.7 43.1 3.6 10.5 0.9 24.4 Ex. 26A PAE/Wattle 1:0.1 2 108.5 35.3 0.8 6.1 0.3 19.1 Bark Ex. 26B Tannin 1:0.1 4 108.9 39.3 1.1 8.4 0.4 21.3 Ex. 26C Preblended 1:0.1 8 110.8 42.2 2.4 10.4 1.1 24.7 Ex. 27A PAE/Gallic 1:0.1 2 108.7 34.3 0.9 6.1 0.1 17.8 Ex. 27B Acid 1:0.1 4 108.2 37.1 2.1 7.8 0.3 20.9 Ex. 27C Preblended 1:0.1 8 107.0 41.9 1.7 10.0 0.8 24.0

As shown in Table 8, Exs. 25-27 all exhibited a slightly greater wet/dry (9%) value and all performed similar to one another.

TABLE 9 Example L* a* b* Br CEx. 17 96.94 −1.10 4.09 86.95 CEx. 18A 96.67 −1.13 4.36 85.98 CEx. 18B 96.48 −1.14 4.42 85.46 CEx. 18C 96.51 −1.25 4.55 85.34 Ex. 25A 96.03 −1.03 5.02 83.65 Ex. 25B 95.51 −0.99 5.42 81.99 Ex. 25C 94.71 −0.89 5.95 79.53 Ex. 26A 95.82 −0.66 4.72 83.51 Ex. 26B 95.01 −0.39 5.12 81.15 Ex. 26C 93.93 −0.07 5.29 78.55 Ex. 27A 96.62 −1.12 4.42 85.79 Ex. 27B 96.52 −1.14 4.50 85.44 Ex. 27C 96.37 −1.21 4.64 84.90

The L*, a*, and b* values are the way color or shade is measured and were measured according to TAPPI Test Method T452 (brightness) and T524 (color). The L*, a*, and b* are specific to the particular instrument used to measure the values. The “L*” value is a measure of “lightness” along a black/white axis. The “a*” value is a measure of red/green. The “b*” value is a measurement of blue/yellow. The instrument used in measure the L*, a*, and b* values was a Technidyne ColorTouch X.

As shown in Table 9, Exs. 25-27 all exhibited a slightly reduced brightness value (Br) as compared to the corresponding comparative example. However, the decrease in brightness was generally very minimal. Also, as shown in Table 9, the strengthening agent that included gallic acid as the additive (Ex. 27) exhibited the lowest impact on brightness and color as compared to when the strengthening agent included tannic acid or wattle bark tannin as the additive.

Example IX

The PAE resin (Resin A) used in CExs. 19 and 20 and Exs. 28-33 was the same as that used in Example I. The tannic acid used in Ex. 28 and the gallic acid used in Ex. 29 were the same as used in in Example I. The dihydroxybenzoic acid used in Ex. 30 was obtained from Aldrich. The caffeic acid used in Ex. 31 was obtained from TCI. The pyrogallol used in Ex. 32 was the same as used in Example I. The polyvinyl alcohol used in Ex. 33 was obtained from Sekisui. The PAE resin and the strengthening agents in Table 10 were all applied in the wet end to the furnish blend before the sheet was formed.

TABLE 10 Weight Wet Ratio End PAE: Dose BW Dry Tensile Wet Tensile Wet/Dry Example Description Additive (lb/ton) (gsm) (Nm/g) STDEV (Nm/g) STDEV (%) CEx. 19 Blank n/a 0 119.4 28.6 1.6 0.2 0.0 0.9 CEx. 20 PAE n/a 8 117.8 38.6 1.2 7.6 0.7 19.8 Ex. 28 Preblended 1:0.1 8 119.4 44.1 2.9 9.5 0.8 21.9 PAE/Tannic Acid Ex. 29 Preblended 1:0.1 8 119.3 40.6 1.9 9.3 0.2 22.8 PAE/Gallic Acid Ex. 30 Preblended 1:0.1 8 120.1 39.0 2.1 7.7 0.4 19.7 PAE/ Dihydroxybenzoic Acid Ex. 31 Preblended 1:0.1 8 120.2 40.3 2.0 8.2 0.4 22.8 PAE/Caffeic Acid Ex. 32 Preblended 1:0.1 8 120.8 39.6 1.6 8.6 0.7 21.9 PAE/Pyrogallol Ex. 33 Preblended 1:0.1 8 122.7 38.1 2.4 8.5 0.5 22.3 PAE/Polyvinyl Alcohol

As shown in Table 10, Exs. 28, 29, 31, 32, and 33 that included the tannic acid, gallic acid, caffeic acid, pyrogallol, and polyvinyl alcohol, respectively, as the additive, all had a greater wet/dry (%) than the CEx. 20. Ex. 30 that included dihydroxybenzoic acid as the additive however, did not exhibit any increase in the wet/dry (%).

Example X

The PAE resin (Resin A) used in CExs. 21 and 22 and Exs. 34-39 was the same as that used in Example I. The tannic acid used in Ex. 34, the gallic acid used in Ex. 35, and the pyrogallol used in Ex. 36 were the same as used in in Example I. The catechol used in Ex. 37 and the hydroquinone used in Ex. 38 were obtained from Solvay. The glycerol used in Ex. 39 was the same as used in Example I. The PAE resin and the strengthening agents in Table 11 were all applied in the wet end to the furnish blend before the sheet was formed.

TABLE 11 Weight Wet Ratio End PAE: Dose BW Dry Tensile Wet Tensile Wet/Dry Example Description Additive (lb/ton) (gsm) (Nm/g) STDEV (Nm/g) STDEV (%) CEx. 21 Blank n/a 0 110.6 29.3 1.2 0.38 0.0 1.3 CEx. 22A PAE n/a 10 111.1 39.9 1.1 8.99 0.4 22.3 CEx 22B n/a 15 113.3 38.9 1.5 9.35 0.4 24.0 Ex. 34A Preblended 1:0.1 10 115.4 42.8 2.2 10.07 0.3 23.5 Ex. 34B PAE/Tannic Acid 1:0.1 15 112.6 47.9 1.3 12.02 0.5 25.1 Ex. 35A Preblended 1:0.1 10 111.4 41.6 2.6 10.20 0.9 24.5 Ex. 35B PAE/Gallic Acid 1:0.1 15 117.8 44.3 0.7 12.08 0.3 27.3 Ex. 36A Preblended 1:0.1 10 110.5 40.7 0.7 10.04 0.3 24.7 Ex. 36B PAE/Pyrogallol 1:0.1 15 113.0 42.6 2.2 12.07 0.8 28.4 Ex. 37A Preblended 1:0.1 10 109.9 39.5 1.6 9.20 0.3 23.3 Ex. 37B PAE/Catechol 1:0.1 15 114.7 40.1 1.4 9.74 0.4 24.4 Ex. 38A Preblended 1:0.1 10 114.7 38.5 0.8 9.04 0.5 23.5 Ex. 38B PAE/Hydroquinone 1:0.1 15 115.3 40.7 1.7 9.86 0.5 24.3 Ex. 39A Preblended 1:0.1 10 113.1 40.3 2.4 8.93 0.6 22.2 Ex. 39B PAE/Glycerol 1:0.1 15 113.2 39.7 1.1 9.63 0.2 24.3

The data shown in Table 11 appears to suggest that hydrogen bonding alone is not sufficient to explain the increase in the wet/dry (%) value. More particularly, glycerol (Ex. 39) that includes three hydroxyl functional groups, like tannic acid, gallic acid, and pyrogallol (Ex. 34-36), did not show any increase in the wet/dry (%).

Certain embodiments and features have been described using a set of numerical upper limits and a set of numerical lower limits. It should be appreciated that ranges including the combination of any two values, e.g., the combination of any lower value with any upper value, the combination of any two lower values, and/or the combination of any two upper values are contemplated unless otherwise indicated. Certain lower limits, upper limits and ranges appear in one or more claims below. All numerical values are “about” or “approximately” the indicated value, and take into account experimental error and variations that would be expected by a person having ordinary skill in the art. As such, unless otherwise indicated, all numbers indicating quantities in this disclosure are to be understood as being modified by the term “about” in all instances.

Various terms have been defined above. To the extent a term used in a claim is not defined above, it should be given the broadest definition persons in the pertinent art have given that term as reflected in at least one printed publication or issued patent. Furthermore, all patents, test procedures, and other documents cited in this application are fully incorporated by reference to the extent such disclosure is not inconsistent with this application and for all jurisdictions in which such incorporation is permitted.

While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

1. A process for making a paper product, comprising:

combining a plurality of fibers and water to produce a slurry;
forming the slurry into a wet paper web;
pressing and draining the wet paper web to produce a wet paper sheet, wherein a strengthening agent is (i) combined with the plurality of fibers and water to produce the slurry, (ii) applied to the wet paper web, (iii) applied to the wet paper sheet, or (iv) a combination of at least two of (i), (ii), and (iii), and wherein the strengthening agent comprises a polyamidoamine-epihalohydrin resin and an additive, wherein the additive comprises at least one of a tannin and a compound having a chemical formula (I) comprising:
wherein: R1, R2, and R3 are independently a hydroxyl group or a methoxy group, and R4, R5, and R6 are independently H, an alkyl group, an aldehyde group, a carboxylic acid group, or a —C═C—COOH group; and
drying the wet paper sheet to produce the paper product.

2. The process of claim 1, wherein the strengthening agent is in the form of a contact product produced by mixing the polyamidoamine-epihalohydrin resin and the additive such that the contact product is (i) combined with the plurality of fibers and water to produce the slurry, (ii) applied to the wet paper web, (iii) applied to the wet paper sheet, or (iv) a combination of at least two of (i), (ii), and (iii).

3. The process of claim 2, wherein the polyamidoamine-epihalohydrin resin and the additive are mixed with one another for at least 1 minute to prepare the contact product.

4. The process of claim 2, wherein the polyamidoamine-epihalohydrin resin and the additive are mixed with one another at a temperature of from about 0° C. to about 35° C.

5. The process of claim 1, wherein the polyamidoamine-epihalohydrin resin and the additive are separately: (i) combined with the plurality of fibers and water to produce the slurry, (ii) applied to the wet paper web, (iii) applied to the wet paper sheet, or (iv) a combination of at least two of (i), (ii), and (iii).

6. The process of claim 1, wherein at least a portion of the polyamidoamine-epihalohydrin resin is combined with the plurality of fibers and water to produce the slurry, and wherein at least a portion of the additive is applied to the wet paper web, applied to the wet paper sheet, or a combination thereof.

7. The process of claim 1, wherein the additive comprises the tannin, and wherein the tannin comprises a condensed tannin, a hydrolyzable tannin, or a mixture thereof.

8. The process of claim 7, wherein the additive comprises the hydrolysable tannin, and wherein the hydrolyzable tannin comprises tannic acid.

9. The process of claim 7, wherein the additive comprises the condensed tannin, wherein the condensed tannin is extracted from one or more components of a plant, and wherein the plant comprises mimosa, wattle, quebracho, pine, gambier, oak, chestnut, eucalyptus, birch, willow, maple, or a mixture thereof.

10. The process of claim 1, wherein the additive comprises gallic acid, syringic acid, syringol, pyrogallol, quercetin, methoxycatechol, sinapic acid, or a mixture thereof.

11. The process of claim 1, wherein the polyamidoamine-epihalohydrin resin, the additive, or each of the polyamidoamine-epihalohydrin resin and the additive further comprises a liquid medium.

12. The process of claim 11, wherein the liquid medium comprises water, an alkylene glycol, a polyalkylene glycol, or a mixture thereof.

13. The process of claim 11, wherein the polyamidoamine-epihalohydrin resin and the additive each comprise the liquid medium, and wherein the polyamidoamine-epihalohydrin resin and the additive independently have a solids content of from about 5 wt % to about 55 wt %.

14. The process of claim 1, wherein a weight ratio of the additive to the polyamidoamine-epihalohydrin resin, on a solids basis, is from about 0.01:1 to about 0.3:1, based on a combined weight of the additive and the polyamidoamine-epihalohydrin resin.

15. The process of claim 1, wherein an amount of the strengthening agent in the paper product, on a solids basis, is from about 0.1 kg to about 40 kg per 1,000 kg of the plurality of fibers, on dry basis, in the paper product.

16. A paper product, comprising:

a paper substrate comprising a plurality of fibers; and
a strengthening agent disposed on the fibers, wherein the strengthening agent comprises a polyamidoamine-epihalohydrin resin and an additive, wherein the additive comprises at least one of a tannin and a compound having a chemical formula (I), comprising:
wherein: R1, R2, and R3 are independently a hydroxyl group or a methoxy group, and R4, R5, and R6 are independently H, an alkyl group, an aldehyde group, a carboxylic acid group, or a —C═C—COOH group.

17. The paper product of claim 16, wherein an amount of the strengthening agent in the paper product, on a solids basis, is from about 0.1 kg to about 40 kg per 1,000 kg of the plurality of fibers, on a dry basis, in the paper product.

18. The paper product of claim 16, wherein a weight ratio of the additive to the polyamidoamine-epihalohydrin resin in the strengthening agent is from about 0.01:1 to about 0.3:1.

19. The paper product of claim 16, wherein the additive comprises the tannin, and wherein the tannin comprises tannic acid.

20. The paper product of claim 16, wherein the additive comprises gallic acid, syringic acid, syringol, pyrogallol, quercetin, methoxycatechol, sinapic acid, or a mixture thereof.

Patent History
Publication number: 20250075432
Type: Application
Filed: Aug 30, 2024
Publication Date: Mar 6, 2025
Applicant: ECOLAB USA INC. (ST. PAUL, MN)
Inventors: En-Wei Lin (Taichung City), Stephen Raye Marrou (Mount Prospect, IL), Gary Samuel Furman, JR. (St. Charles, IL)
Application Number: 18/820,354
Classifications
International Classification: D21H 21/20 (20060101); D21H 17/02 (20060101); D21H 17/06 (20060101); D21H 17/55 (20060101); D21H 23/14 (20060101);