Compositions and methods for increasing wet and dry paper strength

Abstract

The present invention discloses a composition for increasing paper strength, the composition comprising: a dialdehyde-modified polyacrylamide enhancer, a water-soluble compound, and water, where the water-soluble compound is soluble in water at about 5 wt% or more at about 25 DEG C. The water soluble compound is typically present in a weight greater than the weight of the enhancer. The composition is formed by combining the enhancer and the water-soluble compound in an aqueous medium to form a composition wherein the water-soluble compound is typically present in an amount greater than the enhancer on a dry basis, the composition is dried to form a powder or paste that has a water content of less than about 10% by weight and is stable after storage at about room temperature for about six months, and the powder or paste is reconstituted by adding water thereto. The reconstituted composition may then be used in papermaking.

Description

[0001] This application is a divisional application of an invention patent application with an application date of February 27, 2020, application number 202080023407.X (PCT / US2020 / 020012), and titled “Compositions and methods for increasing wet paper strength and dry paper strength”.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims the benefit of U.S. Application No. 16 / 288,477, filed on February 28, 2019. Technical Field

[0004] In general, the present disclosure relates to compositions and methods for increasing wet and dry paper strength. In particular, the present disclosure relates to forming a composition, drying the composition so that it is storage stable, reconstituting the composition, and then using the reconstituted composition to make paper. Background Art

[0005] Glyoxalated polyacrylamides (GPAM) resins have been widely used in aqueous solutions of the paper industry. These GPAM resins are usually added to the wet end of the papermaking process and improve the papermaking process and paper properties. The performance of these GPAM resins can be improved by increasing the molecular weight, changing the polymer structure and / or by controlling the reactive glyoxal functionality level. However, the low solids, temperature and pH sensitivity and relatively short shelf life of GPAM resins are major commercial issues. It is necessary to have a GPAM resin with a longer shelf life, stability during transportation and high concentration during transportation. However, this problem has not been solved so far.

[0006] Several options for improving the stability of GPAM resin are known in the art. These options include using stabilizer (US2011 / 0146925 A1), using low-molecular-weight acrylamide-based polymers to carry out glyoxalation (US 4,605,702) or using the microparticles (US 4,954,538) of glyoxalated polyacrylamide prepared by inverse emulsion polymerization technology. Recently, BASF (US 8703847 B2, US 9879381B2) discloses the transportation of high solid polyacrylamide solution and carries out glyoxalation at factory site. This process needs to accurately control pH value and temperature to produce reproducible material.

[0007] However, none of these approaches solves the problem to be addressed.

[0008] GPAM resins cannot dissolve back into water when they dry on their own and the aldehyde functional groups are no longer available to impart paper strength properties. In addition, highly concentrated GPAM solutions have an even shorter shelf life than less concentrated solutions. Products used in industry are typically only about 10% solids when stored and sold.

[0009] Therefore, there still exists an opportunity to improve and develop compositions and methods that meet the current industry needs.Furthermore, other desirable features and characteristics of the present disclosure will become apparent from the subsequent detailed description of the disclosure and the appended claims, taken in conjunction with this background of the disclosure. Summary of the invention

[0010] The present disclosure provides a composition for increasing the strength of paper. The composition includes a dialdehyde-modified polyacrylamide strengthening agent, a water-soluble compound, and water, wherein the water-soluble compound contains one or more hydroxyl or amide moieties and is soluble in water at about 5% by weight or more at about 25° C. In addition, the water-soluble compound is generally present in a weight greater than the weight of the dialdehyde-modified polyacrylamide strengthening agent.

[0011] The present disclosure also provides a method for forming a composition. The method includes the step of combining a dialdehyde-modified polyacrylamide strengthening agent and a water-soluble compound in an aqueous medium to form a composition, wherein the water-soluble compound is generally present in an amount greater than the dialdehyde-modified polyacrylamide strengthening agent on a dry basis. The method also includes the step of drying the composition to form a powder or paste having a water content of less than about 10% by weight and being stable after storage at about room temperature for about six months, and the step of adding water thereto to reconstitute the powder or paste.

[0012] The present disclosure also provides a method for improving the wet strength and / or dry strength of paper. The method includes the steps of combining a dialdehyde-modified polyacrylamide strengthening agent and a water-soluble compound in an aqueous medium to form a composition, wherein the water-soluble compound is present in an amount greater than the dialdehyde-modified polyacrylamide strengthening agent on a dry basis. The method also includes the steps of drying the composition to form a powder or paste having a water content of less than about 10% by weight and being stable after storage for about six months at about room temperature, reconstructing the powder or paste by adding water thereto, providing an aqueous slurry of cellulose fibers, mixing the reconstructed composition with the aqueous slurry of cellulose fibers, and forming paper from the combination of the reconstructed composition and the aqueous slurry of cellulose fibers, wherein the paper has increased wet strength and / or dry strength compared to paper formed without the reconstructed composition. DETAILED DESCRIPTION

[0013] The following detailed description is merely exemplary in nature and is not intended to limit the composition for increasing paper strength. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description.

[0014] In summary, embodiments of the present disclosure relate to compositions for increasing paper strength and methods for forming the compositions. For the sake of brevity, conventional techniques associated with preparing such compositions may not be described in detail herein. In addition, the various tasks and process steps described herein may be incorporated into a more comprehensive process or technique having additional steps or functions not described in detail herein. In particular, the various steps in forming such compositions may be well known, and therefore, for the sake of brevity, many conventional steps will only be briefly mentioned herein or will be omitted entirely without providing well-known process details.

[0015] As used herein and unless otherwise indicated: (1) all percentages, parts, ratios, etc. are by weight; (2) when an amount, concentration, or other value or parameter is given as a preferred upper limit and a preferred lower limit, this should be understood as specifically disclosing all ranges formed by any pair of typical upper limits and typical lower limits, whether or not such ranges are disclosed individually; (3) the term "total solids" refers to the solids remaining after volatiles (e.g., solvents) have been removed; (4) the term "active solids" refers to the at least one GPAM resin portion of the total solids remaining after subtracting the water-soluble compounds used in the feed.

[0016] Composition

[0017] The present disclosure provides a composition for increasing the strength of paper. The composition can be a liquid, a powder or a paste. Alternatively, the composition can change from a liquid to a powder and / or a paste or from a powder to a paste, or vice versa, at different time points during the manufacturing method and / or use.

[0018] Paper strength is typically measured based on dry strength or wet strength. In various embodiments, the compositions of the present disclosure provide at least about 80, 85, 90, 95% or greater increase in dry strength of paper formed using the compositions, compared to paper formed without the compositions of the present invention. In other embodiments, the compositions of the present disclosure provide at least about 80, 85, 90, 95% or greater increase in wet strength of paper formed using the compositions, compared to paper formed without the compositions of the present invention. Typically, wet strength is determined using TAPPI method T456 using a Finch Cup. Typically, dry strength is determined using TAPPI test method T494.

[0019] In other embodiments, the composition provides about 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95% or even 100% of the wet strength and / or dry strength of paper formed using GPAM alone without drying and subsequent reconstruction. In fact, in other embodiments, the composition provides about 5, 10, 15, 20% or even greater improvement in the wet strength and / or dry strength of paper formed using GPAM alone without drying and subsequent reconstruction. This performance is very important because it allows the composition of the present disclosure to be transported and storage-stable in the absence of water. This greatly reduces transportation costs and complexity and solves the above problems.

[0020] In another embodiment, the above composition imparts wet strength and / or temporary wet strength and / or dry strength to paper formed or treated with the reconstituted composition. For example, in one embodiment, the composition is in powder form and has a shelf life of at least six months, such that after six months, the wet strength and / or dry strength properties of the paper are at least about 80% of the wet strength and / or dry strength properties of the paper measured within one month of the manufacture of the composition. In other embodiments, after six months, the wet strength and / or dry strength properties of the paper are at least about 85, 90, 95% or more of the wet strength and / or dry strength properties of the paper measured within one month of the manufacture of the composition.

[0021] In various embodiments, the composition comprises, consists essentially of, or consists of a dialdehyde-modified polyacrylamide strengthening agent, a water-soluble compound comprising one or more hydroxyl or amide moieties and soluble in water at about 5% by weight or more at about 25° C., and water. In various embodiments, the composition may or may not include any one or more of the additives or other compounds described below.

[0022] In various embodiments, the composition has less than about 5, 10, 15, 20, 25 or 30% by weight solids. In other embodiments, the composition has a solid content of about 10% to about 30% by weight. In other embodiments, the composition has a solid content greater than about 30% by weight. The solid content is generally formed by any compound that is not volatile after extraction of the water-soluble compound.

[0023] In other embodiments, the composition is soluble in an aqueous solution of about 1% by weight at about 25°C. In other embodiments, the composition is soluble in an aqueous solution of about 1 to 5% by weight at about 25°C. The composition itself can be completely soluble in water, for example, with a solubility of up to about 100%. However, this is different from the amount of the composition actually used. For example, the composition can be used in an amount of up to about 5% by weight in water.

[0024] In one embodiment, the composition imparts both wet strength and better chemical retention during the papermaking process.As known and understood by those skilled in the art, chemical retention may describe the retention of fines and other similar artifacts.

[0025] Dialdehyde modified polyacrylamide enhancer

[0026] There is no particular limitation on the dialdehyde-modified polyacrylamide strengthening agent, which can be any dialdehyde-modified polyacrylamide in the art. For example, the dialdehyde-modified polyacrylamide can be further defined as a glyoxalated polyacrylamide including an aldehyde group, also referred to as GPAM or GPAM resin. Other non-limiting examples of suitable dialdehyde-modified polyacrylamide include cationic polyacrylamide, acrylamide DADMAC (polydiallyl dimethyl ammonium chloride) copolymers, and the like, and combinations thereof.

[0027] In other embodiments, the dialdehyde modified polyacrylamide strengthening agent can be cationic and can be a copolymer that is the reaction product of an acrylamide monomer and a cationic monomer or includes the reaction product of an acrylamide monomer and a cationic monomer. As will be appreciated by those skilled in the art, examples of suitable cationic monomers include polydiallyldimethylammonium chloride monomers and the like.

[0028] In other embodiments, the dialdehyde modified polyacrylamide strengthening agent is further defined as a polyacrylamide resin having an aldehyde-based reactive group. In another embodiment, a prepolymer is used to form a GPAM resin, wherein the prepolymer can be cationic, anionic or amphoteric in nature. There is no particular limitation on the various ionic monomers that can be incorporated into the GPAM prepolymer and thus into the GPAM resin and can be selected by those skilled in the art. In various embodiments, monomers such as diallyldimethylammonium chloride or acrylamide-methylpropane sulfonic acid can be used.

[0029] In other embodiments, the dialdehyde modified polyacrylamide strengthening agent is the reaction product of glyoxal and a prepolymer, which is the reaction product of a polyacrylamide monomer and diallyldimethylammonium chloride monomer, wherein the molar ratio of acrylamide to diallylmethylammonium chloride is from about 99:1 to about 50:50, respectively, and wherein about 40 mole % of the acrylamide groups of the polyacrylamide monomer are reacted and about 15 mole % of the acrylamide groups have active aldehyde functional groups.

[0030] There is no particular restriction on the amount of the dialdehyde-modified polyacrylamide strengthening agent in the composition. In various embodiments, the amount of the dialdehyde-modified polyacrylamide strengthening agent is described in more detail below as a ratio to the water-soluble compound. For example, the water-soluble compound may be present in a dry weight ratio greater than about 1:1, about 1.5:1, about 2:1, about 2.5:1, about 3:1, about 3.5:1, about 4:1, about 4.5:1 or about 5:1 or even greater than the dialdehyde-modified polyacrylamide strengthening agent. Typically, the water-soluble compound is present in a weight greater than the weight of the dialdehyde-modified polyacrylamide strengthening agent. Relative to weight percentage, the dialdehyde-modified polyacrylamide strengthening agent can be present in an amount of about 1 to about 20, about 2 to about 10, about 2 to about 8, about 5 to about 10 or about 5 to about 8 pounds (lbs) / ton of dry paper. In other embodiments, the dialdehyde modified polyacrylamide strengthening agent can be present in an amount of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, etc. to 20 pounds (lbs) per ton of dry paper. In various non-limiting embodiments, all values ​​and ranges of values ​​including and between the above values ​​are expressly contemplated for use herein.

[0031] In various embodiments, a dialdehyde modified polyacrylamide strengthening agent is formed using a vinylamide polymer and a reactant as described below. The main chain vinylamide polymer that can be subsequently glyoxalized can be synthesized by free radical or redox catalytic polymerization of vinylamide monomer and optional one or more ionic comonomers or nonionic comonomers. A cross-linking agent with multiple polymerizable vinyl functional groups can also be included to give the main chain polymer structure. Chain transfer agents (such as sodium hypophosphite) can be used to control the molecular weight of the polymer molecule and introduce branches.

[0032] The vinylamide polymer can be formed by any suitable polymerization process. The polymer can be prepared by solution polymerization, water-in-oil suspension polymerization or water-in-oil emulsion polymerization. The polymer can be produced in the form of beads by suspension polymerization or in the form of water-in-oil emulsion or dispersion by water-in-oil emulsion polymerization. Alternatively, the vinylamide polymer can be provided as a dispersion in an aqueous medium. For example, this can be a dispersion of at least 20 microns of vinylamide particles in an aqueous medium containing a leveling agent. This can for example also be included in an aqueous dispersion of vinylamide particles prepared by the polymerization of aqueous monomers in the presence of a low intrinsic viscosity polymer such as polydiallyldimethylammonium chloride and optional other dissolved substances such as electrolytes and / or polyhydroxy compounds such as polyalkylene glycols.

[0033] The vinylamide polymers that can be glyoxalated can have any molecular weight that can be obtained by polymer synthesis methods known to those skilled in the art. The vinylamide polymers can be nonionic, cationic, anionic or amphoteric. The vinylamide polymers can be crosslinked or structured. The average molecular weight of the vinylamide polymers can be 500 to about 5,000,000 or even 10,000,000 daltons.

[0034] The starting vinylamide polymer generally has a mean molecular weight of at least 500, but more generally at least about 10,000 to about 5,000,000. For example, mean molecular weights of 50,000 to 2,000,000, 70,000 to 1,000,000 are contemplated. In various non-limiting embodiments, the disclosed method allows the glyoxalation of vinylamide polymers of about 50,000 or greater, about 70,000 or greater and even about 85,000 or 100,000 or greater. Typical mean molecular weight ranges are, for example, between 5,000 to about 150,000, 10,000 to about 150,000 or 25,000 to about 150,000.

[0035] Suitable vinylamide monomers are (meth)acrylamide, C1-C4 monosubstituted (meth)acrylamide such as N-methyl (meth)acrylamide, N-ethyl (meth)acrylamide. The most typical vinyl monomers are acrylamide and methacrylamide. The term (meth)acrylamide includes both acrylamide and methacrylamide.

[0036] The vinylamide content provides the site to which the reactant or glyoxal substituent is connected. The minimum ratio of the vinylamide units that can be present can be sufficient to make the glyoxalated polymer thermosetting, so that the glyoxalated polymer forms a water-insoluble film when laid on a glass plate from an aqueous solution and heated at about 105° C. for 5 minutes. Therefore, the vinylamide polymer (before glyoxalation) can be formed by at least about 10% by weight of vinylamide monomers. Usually, the vinylamide polymer is formed by at least about 20 to about 100% by weight of vinylamide monomers. For example, the vinylamide polymer is formed by at least about 20 to about 99% by weight, at least about 25 to about 90% by weight of vinylamide monomers, or at least about 50% by weight and most usually at least about 70% by weight of vinylamide monomers. Weight % is based on the total weight of monomers added to form the vinylamide polymer. Once the monomers are polymerized, they become binding units in the polymer. Therefore, there may be units that can give polymer ionic properties in the polymer of the present disclosure, or those units that serve as diluents or spacers, or units that give special properties such as water-soluble units that increase or decrease.

[0037] Ionic comonomers that can be used in conjunction with the vinylamide monomers can be cationic, potentially cationic, anionic, potentially anionic, or amphoteric. When a cationic comonomer is used, one or more cationic monomers can be used and the total amount of cationic monomers can be such that the glyoxal adduct of the vinylamide copolymer is self-supporting (self-substantive) to the cellulose fibers in the aqueous suspension. Cationic comonomers can also be used.

[0038] Suitable cationic monomers or potential cationic monomers include diallyldialkylamine, 2-vinylpyridine, 2-(dialkylamino)alkyl (meth)acrylate, dialkylaminoalkyl (meth)acrylamide, including acid addition salts and quaternary ammonium salts thereof. Specific examples of such cationic monomers or potential cationic monomers are diallyldimethylammonium chloride, (meth)acryloyloxyethyltrimethylammonium chloride (dimethylaminoethyl (meth)acrylate, methyl chloride quaternary salt), 2-vinyl-N-methylpyridinium chloride, (p-vinylphenyl)-trimethylammonium chloride, (meth)acrylate 2-ethyltrimethylammonium chloride, 1-methacryloyl-4-methylpiperazine, Mannich polyacrylamide (i.e., polyacrylamide reacted with dimethylamine formaldehyde adduct to obtain N-(dimethylaminomethyl) and (meth)acrylamidopropyltrimethylammonium chloride). Potential cationic monomers can be, for example, monomers that provide cationic charge under acidic conditions, such as when the amine functional group on the potential cationic monomer is protonated.

[0039] The amount of cationic comonomer can be from about 0% to about 90% by weight, from about 0.1 to about 50% by weight, from about 0.1 to about 40% by weight, from about 0.1 to about 30% by weight, from about 0.1 to about 25% by weight, or from about 0.1 to about 15 or about 10% by weight. The weight % is based on the total weight of the monomers added to form the vinylamide polymer.

[0040] Suitable anionic monomers can be selected from vinyl acidic materials such as acrylic acid, methacrylic acid, maleic acid, allyl sulfonic acid, vinyl sulfonic acid, itaconic acid, fumaric acid, potential anionic monomers such as maleic anhydride and itaconic anhydride and their alkali metal salts and ammonium salts, 2-acrylamido-2-methyl-propanesulfonic acid and its salt, sodium styrene sulfonate, etc. Alternatively, if the starting vinylamide polymer is polyacrylamide, it can be partially hydrolyzed to obtain some anionic characteristics and then functionalized with a reactant. Potential anionic monomers can be, for example, acrylamide, which forms an acid when partially hydrolyzed, and the acid can impart anionic characteristics to the polymer under alkaline conditions. Alternatively, potential anionic monomers can be, for example, anhydride monomers, such as maleic anhydride or itaconic anhydride, which can be hydrolyzed to form the corresponding acid.

[0041] The vinylamide polymer can be amphoteric; that is, the polymer can include both anionic and cationic functional groups. Amphoteric vinylamide polymers can be formed from both anionic and cationic monomers, or from zwitterionic monomers. The various monomers (anionic, cationic and / or zwitterionic monomers) can be reacted in any weight ratio to form the amphoteric vinylamide polymer. Preferably, the predominant charge on the amphoteric vinylamide polymer formed is cationic. Thus, the mole % of cationic monomer predominates relative to the mole % of anionic monomer incorporated into the amphoteric vinylamide polymer.

[0042] Suitable nonionic monomers other than vinylamides may be selected from (meth)acrylates such as octadecyl (meth)acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, hydroxyethyl (meth)acrylate and 2-ethylhexyl acrylate; N-alkylacrylamides, N-octyl (meth)acrylamide, N-tert-butylacrylamide, N-vinylpyrrolidone, N,N-dialkyl (meth)acrylamides such as N,N'-dimethylacrylamide; styrene, vinyl acetate, hydroxyalkyl acrylates and hydroxyalkyl methacrylates such as 2-hydroxyethyl acrylate and acrylonitrile.

[0043] The starting vinylamide polymer or the resulting vinylamide polymer adduct may be cross-linked, branched or otherwise structured or linear. For example, the starting vinylamide polymer or the resulting vinylamide polymer adduct may be linear, cross-linked, chain-transferred, or cross-linked and chain-transferred (structured).

[0044] The crosslinking agent is typically a polyethylenically unsaturated crosslinking agent. Examples are methylenebis(meth)acrylamide, triallyl ammonium chloride; tetraallyl ammonium chloride, polyethylene glycol diacrylate; polyethylene glycol dimethacrylate; N-vinyl acrylamide; divinylbenzene; tetra(ethylene glycol) diacrylate; acryloyloxyethyl dimethylallylammonium chloride; diallyloxyacetic acid sodium salt; diallyl octylamide; trimethylpropane ethoxylate triacrylate; N-allyl acrylamide, N-methylallyl acrylamide, pentaerythritol triacrylate and combinations thereof. Alternatively or additionally, other systems for crosslinking may be used. For example, covalent crosslinking via side groups may be achieved, for example by using ethylenically unsaturated epoxy or silane monomers, or by using multifunctional crosslinking agents such as silanes, epoxides, polyvalent metal compounds or other known crosslinking systems.

[0045] Chain transfer agents can be used to synthesize the starting vinylamide polymer. Suitable chain transfer agents are 2-mercaptoethanol; low molecular weight organic acids such as lactic acid, formic acid, malic acid or butyric acid; isopropanol; thioacids and hypophosphites.

[0046] Now, let's look at the reactants, which typically include more than one aldehyde moiety. The reactants can be selected from glyoxal, glutaraldehyde, furan dialdehyde, 2-hydroxyadipaldehyde, succinaldehyde, dialdehyde starch, diepoxides, and combinations thereof. Glyoxal is a typical reactant. The molar ratio of amide (on the vinylamide polymer) to the reactants is typically from about 12:1 to about 2:1, such as from about 10:1 to about 2.5:1, from about 6:1 to about 2.5:1, and from about 6:1 to about 3:1. The molar content of amide on the vinylamide polymer can be determined experimentally by methods known in the art or calculated from known monomer compositions.

[0047] Adding alkali or changing the pH value to above 7 is the most commonly used method for catalyzing the glyoxalation reaction. Generally, it is generally believed that the pH range of 7 to 13 is the catalytic environment of the reaction. For example, the pH range of 8 to 12 is particularly suitable. Alternatively, a concentrated pH buffer solution can be added to maintain the pH.

[0048] Water soluble compounds

[0049] Turning now to water-soluble compounds, the compounds are soluble in water at about 5% by weight or more at about 25°C. Solubility (or being soluble) is generally defined as the analytical composition of a saturated solution, expressed as the proportion of a specified solute in a specified solvent. In this case, the water-soluble compound, when present, is soluble in water at about 25°C at 5% or more. In other embodiments, the water-soluble compound is soluble in water at about 10, 15, 20 or 25% by weight or more, such as up to 90, 95 or more weight percent at about 25°C.

[0050] The water soluble compound may be polymeric or may be a separate compound. In other embodiments, a mixture of polymers and separate compounds may be used. In one embodiment, the water soluble compound has the ability to impart beneficial properties to paper.

[0051] In various embodiments, the water soluble compound comprises a plurality of hydroxyl and / or amide and / or urea groups. In one embodiment, the water soluble compound comprises one or more than one hydroxyl group.

[0052] In various embodiments, the water-soluble compound is selected from carbohydrates, polyvinyl alcohol (PVA polymer), acrylamide-containing polymers or combinations thereof. For example, carbohydrates can be further defined as monosaccharides, disaccharides, polysaccharides and combinations thereof. Therefore, the water-soluble compound can be selected from monosaccharides, disaccharides, polysaccharides and combinations thereof. In various embodiments, the water-soluble compound is maltodextrin. However, any saccharide can be used.

[0053] In other embodiments, the water-soluble compound is a polymer containing acrylamide. Suitable non-limiting examples include amphoteric polyacrylamide, amphoteric polyacrylamide copolymers with water-soluble monomers, and combinations thereof. The selection of water-soluble compounds can be carried out by those skilled in the art according to whether dry strength or wet strength is the target for improvement.

[0054] In one embodiment, the water-soluble compound is a small molecule, or a macromolecule derived from a natural material, or prepared by modification of a natural material, or chemically synthesized.

[0055] In one embodiment, the water-soluble compound comprises a small molecule, an oligomer or a polymer, or is a small molecule, an oligomer or a polymer. In one embodiment, the water-soluble compound has three or more hydroxyls, or each repeating unit of the oligomer or polymer has three or more hydroxyls. In one embodiment, the water-soluble compound is a carbohydrate. In one embodiment, the water-soluble compound comprises an oligo- or polysaccharide. In one embodiment, the water-soluble compound is glycerol.

[0056] In one embodiment, the water-soluble compound comprises a polymer having repeating units of acrylamide. In one embodiment, acrylamide is polymerized with a monomer containing a cationic functional group or an anionic functional group or a combination of both. In one embodiment, the acrylamide-containing polymer may be functionalized.

[0057] In one embodiment, the water-soluble compound is further defined as a copolymer formed by the reaction of organic monomers. The monomers are not particularly limited and may be selected from acrylamide monomers, sugars, hydroxyl-containing monomers, amide-containing monomers, carboxyl-containing monomers, aldehyde-containing monomers, and the like, and combinations thereof. Alternatively, the monomer may be any polar or hydrophilic monomer, as will be appreciated by those skilled in the art.

[0058] When the dialdehyde-modified polyacrylamide strengthening agent and the water-soluble compound are combined, the dialdehyde-modified polyacrylamide strengthening agent is usually reacted with the water-soluble compound so that most of the available aldehyde groups (hemiacetal) of the dialdehyde-modified polyacrylamide strengthening agent are reacted with the hydroxyl groups of the water-soluble compound. In one embodiment, there are excess hydroxyl groups compared to the reactive aldehyde groups. For example, the amount of hydroxyl groups present can be 1.5, 2, 3 or even more times compared to the reactive aldehyde groups.

[0059] In one embodiment, the present disclosure provides a composition comprising a glyoxalated polyacrylamide resin mixed with a water-soluble compound at a molecular level. The entire mixture of GPAM and the water-soluble compound does not exist in the form of an aqueous solution, and when the GPAM mixture is placed in water, a solution containing GPAM will be generated, so that the GPAM can impart wet strength and / or dry strength properties to paper.

[0060] In one embodiment, the final reactive GPAM resin is produced by dissolving the above composition in water to reconstitute the aldehyde groups. In another embodiment, the hydroxyl groups are replaced with other chemical groups that form reversible bonds when reacting with the reactive aldehyde groups of the GPAM resin.

[0061] As described above, the water-soluble compound may be present in a dry weight ratio of greater than about 1:1, about 1.5:1, about 2:1, about 2.5:1, about 3:1, about 3.5:1, about 4:1, about 4.5:1, or about 5:1, or even greater, respectively, to the dialdehyde-modified polyacrylamide strengthening agent. Typically, the water-soluble compound is present in a weight greater than the weight of the dialdehyde-modified polyacrylamide strengthening agent. With respect to weight percentage, the water-soluble compound may be present in an amount of about 1 to about 100 pounds (lbs) per ton of dry paper or any weight percentage corresponding to the above weight percentages and ratios of the water-soluble compound and the dialdehyde-modified polyacrylamide strengthening agent. The water-soluble compound is typically present in a weight greater than the dialdehyde-modified polyacrylamide strengthening agent. However, if based on a molar ratio, the water-soluble compound and the dialdehyde-modified polyacrylamide strengthening agent are typically present in a molar amount such that there are more hydroxyl groups than aldehyde groups. The molar ratio of hydroxyl groups to aldehyde groups can be, for example, greater than about 1:1, about 1.5:1, about 2:1, about 2.5:1, about 3:1, about 3.5:1, about 4:1, about 4.5:1, or about 5:1, or even greater. In some embodiments, it should be considered that even if the molar amount of hydroxyl groups is greater than the molar amount of aldehyde groups, the weight of the compound containing aldehyde groups (i.e., the dialdehyde-modified polyacrylamide strengthening agent) may be greater than the weight of the compound including hydroxyl groups (i.e., the water-soluble compound). Therefore, as long as the molar amount of hydroxyl groups is equal to or greater than the molar amount of aldehyde groups, the amount of water-soluble compound present is not always greater than the weight of the dialdehyde-modified polyacrylamide strengthening agent. In various non-limiting embodiments, all values ​​and value ranges (including endpoints and values ​​between those values) are explicitly considered for use herein.

[0062] water

[0063] The composition also includes water. Water can exist in almost any amount. Typically, based on the gross weight of the composition, water is present in an amount of at least about 95, 95.5, 95, 96.5, 97, 97.5, 98, 98.5, 99, 99.5 % by weight or the like. Typically, the remainder that makes the gross weight total 100 % by weight is a combination of dialdehyde-modified polyacrylamide strengthening agent and a water-soluble compound. In various non-limiting embodiments, all values ​​and value ranges (including endpoints and values ​​between those values) are explicitly contemplated for use herein.

[0064] Other Implementations

[0065] In various embodiments, the present disclosure provides a method for producing dry aldehyde cross-linked polyacrylamide to improve papermaking process and paper strength properties. The method includes: a) mixing aldehyde functionalized polyacrylamide resin with water and certain water-soluble compounds, b) removing water by air or vacuum drying, c) storing and transporting the composition and d) reconstructing or re-dissolving the composition in water to regain the efficacy of GPAM resin as a strength additive for paper. The present disclosure produces GPAM resin with low water content or essentially no water content, which can be transported in dry form with little or no reduction in strength properties, and can be dissolved in water and used in papermaking or paper processing processes. Therefore, the method of the present disclosure further improves product shelf life, reduces transportation costs and is easy to handle. In another embodiment, the present disclosure provides a method for producing soluble dry GPAM, which is stable and can be transported at high solids content, made without pH or temperature treatment and used to improve papermaking process and paper strength properties.

[0066] In one embodiment, the present disclosure is a composition comprising a glyoxalated polyacrylamide resin reacted with a compound having a plurality of hydroxyl groups, wherein a majority of the aldehyde groups (hemiacetal) of the glyoxalated resin react with the hydroxyl groups or hydroxyl compounds, and such a composition is formed by mixing the GPAM with the hydroxyl compound and then drying the mixture.

[0067] In one embodiment, the starting GPAM resin is water soluble. On the other hand, the starting hydroxy compound is water soluble. In another aspect, both compounds are water soluble and the composition mixture is in the form of an aqueous solution before drying. In one embodiment, the above composition is formed by reacting an aldehyde with a hydroxyl group when the composition is dried.

[0068] Method of forming a composition for increasing paper strength:

[0069] The present disclosure also provides a method for forming a composition. The method includes the step of mixing a dialdehyde-modified polyacrylamide strengthening agent with a water-soluble compound in an aqueous medium to form a composition. The dialdehyde-modified polyacrylamide strengthening agent can be added to the water-soluble compound, or vice versa, to form the composition. In addition, water can be added to the dialdehyde-modified polyacrylamide strengthening agent, the water-soluble compound, and / or a combination thereof in any order and amount. In other words, all orders of addition of the above components are contemplated herein.

[0070] Without wishing to be bound by theory, in some embodiments, the hydroxyl groups of the water-soluble compound react with the aldehyde groups of the dialdehyde-modified polyacrylamide strengthening agent to form a reversible covalent bond. Also without wishing to be bound by theory, the hydroxyl groups, amides or other similar groups of the water-soluble compound may form hemiacetal bonds with the glyoxal-based functional groups of the dialdehyde-modified polyacrylamide strengthening agent during drying. Also without wishing to be bound by theory, the hydroxyl groups, amides or other water-soluble groups of the water-soluble compound may form associations with the dialdehyde-modified polyacrylamide strengthening agent to prevent the composition from self-crosslinking to the extent that the composition is no longer water soluble. In one embodiment, excess hydroxyl groups may be part of the composition.

[0071] The method also includes the step of drying the composition to form a powder or paste having a water content of less than about 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 or 0.5% by weight and being stable after storage at about room temperature for about six months. The powder is not particularly limited and may include particles of the composition of any size. It is also contemplated that the powder may be further processed, sieved or pulverized to form a powder having a specific average size characteristic.

[0072] The term "stable after storage" means that the product retains its properties after storage, for example the percentages described in detail above.

[0073] Because the composition in relatively dry form is substantially no longer self-crosslinking, the composition is dried to form a powder or paste so that the composition can be redissolved or reconstituted by dissolving in water and subsequently added during papermaking to impart strength to paper.

[0074] The drying step can be selected by those skilled in the art. For example, drying may include or not include applying heat, airflow, vacuum, tumbling, stirring, etc. In other words, any drying equipment can be selected, including but not limited to oven, flash dryer, column dryer, freeze dryer, spray dryer, fluidized bed dryer, ring dryer, rotary dryer, air dryer, vacuum dryer and combination thereof. In one embodiment, the composition is dried at room temperature. In another embodiment, the composition is dried at a temperature lower than about 50° C. In another embodiment, the composition is dried at a temperature between about 50° C. and about 100° C. In another embodiment, the composition is dried at a temperature higher than about 100° C.

[0075] This step can also be described as drying to remove most of the water so that the composition is no longer able to react with itself during a period that would prevent it from being stored for 3 months and then re-dissolved or reconstituted to form a functional GPAM solution for papermaking.

[0076] The method further comprises reconstituting the powder or paste by adding water thereto. The step of reconstituting can be further described as adding water to the powder or paste so as to re-form the aqueous composition. The aqueous composition can be a solution, emulsion or dispersion of the composition particles in water.

[0077] The above compositions, methods and articles can all be based on compositions that also contain or do not contain other materials commonly used in papermaking or aqueous solution preparation. The compositions may contain or do not contain additives such as defoamers, biocides, pigments and fillers. Various methods of preparing solutions known in the art can be used. Various methods of pumping, drying, redissolving and reconstructing materials known in the art can be used. Dry and wet strength tests of paper can be performed according to methods known in the paper field.

[0078] Example

[0079] Example 1

[0080] GPAM resin was prepared from a combination of poly(acrylamide-diallyldimethylammonium chloride) (95:5 molar ratio) and glyoxal. The level of glyoxalation was such that 40% of the acrylamide groups of poly(acrylamide-diallyldimethylammonium chloride) were reacted and 15% remained with active aldehyde functional groups.

[0081] GPAM resin (as a dialdehyde modified polyacrylamide strengthening agent) was thoroughly mixed with 30 wt% maltodextrin (as a solution of a water-soluble compound). More specifically, GPAM resin was a 10 wt% aqueous solution and mixed with an equal amount of a 30 wt% aqueous solution of maltodextrin to form a 3:1 mixture by weight. A first sample of the mixture was air-dried to form Inventive Composition 1. A second sample of the mixture was dried at 50°C to form Inventive Composition 2. If desired, these materials can be ground into powders, but this is not in these examples.

[0082] After several days, each of Inventive Composition 1 and Inventive Composition 2 was redissolved / reconstituted in water to form a 5 wt% solution.

[0083] Samples of inventive compositions 1 and 2 were used to make handsheets and compared to handsheets made using virgin GPAM resin without water soluble compounds (ie, maltodextrin) to determine paper strength. The virgin GPAM without water soluble compounds was comparative composition 1.

[0084] The pulp used to form the handsheets was a mixture of hardwood and softwood in a 50:50 weight ratio. The paper was made with tap water at a pH of about 6.

[0085] For evaluation of Comparative Composition 1, paper containing 0.3 wt. % of the comparative composition (on a dry basis) was soaked in water for 3 seconds, 30 seconds and 30 minutes to produce wet strength values ​​of 10.34, 8.68 and 6.28 Newtons per inch of width, respectively. This was considered a comparative example.

[0086] For evaluation of Inventive Composition 1, 0.3 wt. % of Inventive Composition 1 was used to make paper and soaked in water for 3 seconds, 30 seconds and 30 minutes to produce wet strength values ​​of 3.58, 2.82 and 2.34 Newtons per inch of width, respectively.

[0087] For evaluation of Inventive Composition 2, 0.3% of Inventive Composition 2 was used to make paper and soaked in water for 3 seconds, 30 seconds and 30 minutes to produce wet strength values ​​of 3.36, 2.84 and 2.38 N / inch respectively.

[0088] Papers formed with inventive compositions 1 and 2 contained only about 25% of the GPAM present, yet still exhibited significant wet strength compared to paper formed using comparative composition 1. These results indicate that the aldehyde functionality of the GPAM is regenerated when the solid composition is reconstituted with water.

[0089] Example 2

[0090] Inventive Composition 2, comprising the above mixture dried at 50°C, was used to produce additional handsheets which were evaluated to determine temporary wet strength. More specifically, a 0.3 wt% GPAM solution was compared to 0.6 wt% and 1.2 wt% solutions of the inventive composition, such that 0.15 wt% and 0.3 wt% GPAM were added at the time of use. The temporary wet strength results are listed in Table 1 below.

[0091] Table 1

[0092] GPAM% in paper 3 seconds wet strength 30 seconds wet strength Comparative composition 1 0.3 3.83 3.64 Composition 2 of the present invention 0.15 2.62 2.40 Composition 2 of the present invention 0.3 3.60 3.43

[0093] Based on the level of GPAM added to the paper, in view of the above results, it is apparent that the inventive composition performs almost as well as Comparative Composition 1. These results must be further considered in view of the surprising and unexpected benefit associated with the inventive composition, namely the ability to be dried and stored. When the above results are considered in conjunction with this unexpected benefit, one skilled in the art will appreciate the uniqueness of the present invention.

[0094] Other embodiments

[0095] The following examples further demonstrate that the properties of the glyoxalated polyacrylamide can be maintained after drying and dissolving in an aqueous medium. In these examples, the reconstituted compositions help improve paper properties when the solutions are used in a papermaking process.

[0096] The examples in Table 2 below were formed by mixing solutions of various water-soluble compounds into GPAM solutions at the dry weight ratios listed below. The mixtures thus formed were then air-dried overnight. The solubility of the air-dried compositions was tested by preparing 1% solutions in aqueous media. In some cases, the solubility of the material can be increased by increasing the pH of the solution.

[0097] Table 2

[0098]

[0099] GPAM 1 is a glyoxalated polyacrylamide made by glyoxalating a polymer of acrylamide and DADMAC (95:5 mole percent) with about 8 mole % reactive aldehyde.

[0100] GPAM 2 is a glyoxalated polyacrylamide made by glyoxalating a polymer of acrylamide and DADMAC (95:5 mole percent) with about 15 mole percent reactive aldehyde.

[0101] GPAM 3 is a glyoxalated polyacrylamide made by glyoxalating a polymer of acrylamide and DADMAC (90:10 mole percent) with about 15 mole percent reactive aldehyde.

[0102] The amphoteric polymer is an amphoteric polyacrylamide formed from acrylamide / acrylic acid / itaconic acid and dimethylaminoethyl methacrylate monomers.

[0103] The term "insoluble" means that solubility is assessed visually at 25° C. and a significant amount of the compound is not soluble in water. For example, less than 10% by weight of the compound is soluble in water.

[0104] The term "soluble" means that solubility is assessed visually at 25°C and no compound is visible, thereby indicating that a clear solution has resulted and complete or nearly complete dissolution has been achieved. For example, greater than 95% by weight of the compound is dissolved.

[0105] The term "partially soluble" means that solubility is assessed visually at 25°C and some of the compound is visible, indicating a turbid solution. For example, about 10 to about 95% by weight of the compound is dissolved.

[0106] ACM-DADMAC copolymer (95:5) is a cationic polyacrylamide, wherein the molar ratio of DADMAC to polyacrylamide is 95:5.

[0107] ACM-DADMAC copolymer (90:10) is a cationic polyacrylamide, wherein the molar ratio of DADMAC to polyacrylamide is 90:10.

[0108] Further examples:

[0109] Further examples demonstrate the improvement in dry strength properties of handsheets made from 100% recycled media having a hardness of 50 ppm, an alkalinity of 25 ppm, 2.5% GPC D15F oxidized starch, and a conductivity of 2000 μS / cm.

[0110] The pH of the system was 7.0 and the pulp freeness was 35-420 Canadian Standard Freeness (CSF).Handsheets were made on a Noble and Wood handsheet machine with a basis weight of 100 lbs / 3000 ft2.

[0111] Various compositions, the same as those described above, were added at a level of 0.4% composition by weight on an active ingredient basis relative to dry pulp after re-dissolution. The handsheets were wet pressed and dried on a drum dryer at 240°F for 1 minute to a moisture content of 3% to 5%. Subsequently, dry tensile (TAPPI Test Method T494, om-01), Ring Crush Index (TAPPI Test Method T822 om-02), and Mullen Burst (TAPPI Test Method T403) were determined. The results are listed in Table 3 below.

[0112] Table 3

[0113]

[0114] This data demonstrates that even after reconfiguration, GPAMs retain their performance with respect to the above-mentioned physical properties.

[0115] Although at least one exemplary embodiment has been presented in the foregoing detailed description, it should be understood that there are a large number of variations. It should also be understood that the one or more exemplary embodiments are merely examples and are not intended to limit the scope, applicability, or configuration in any way. On the contrary, the foregoing detailed description will provide a convenient roadmap for implementing the exemplary embodiments for those skilled in the art. It should be understood that various changes may be made to the functions and arrangements of the elements described in the exemplary embodiments without departing from the scope set forth in the appended claims.

Claims

1. A composition for increasing the strength of paper, the composition comprising: A. dialdehyde modified polyacrylamide enhancer; and B. a water-soluble compound containing one or more hydroxyl or amide moieties and soluble in water at about 5% by weight or more at 25°C, and C. Water The water-soluble compound is present in a weight greater than the weight of the dialdehyde-modified polyacrylamide strengthening agent.

2. The composition according to claim 1, wherein the dialdehyde-modified polyacrylamide strengthening agent is a glyoxalated polyacrylamide containing an aldehyde group.

3. The composition of claim 1, wherein the water-soluble compound is selected from carbohydrates, polyvinyl alcohol, acrylamide-containing polymers, or combinations thereof.

4. The composition of claim 1, wherein the dialdehyde-modified polyacrylamide strengthening agent is cationic and is a copolymer comprising the reaction product of an acrylamide monomer and a cationic monomer.

5. The composition of any one of claims 1 to 4, wherein the water-soluble compound is present in a dry weight ratio with the dialdehyde-modified polyacrylamide strengthening agent of greater than about 1:1, preferably greater than about 3:

1.

6. The composition of claim 1 wherein the water soluble compound is further defined as a copolymer formed by reacting organic monomers.

7. The composition of claim 1, wherein the water-soluble compound is selected from the group consisting of monosaccharides, disaccharides, polysaccharides, and combinations thereof; acrylamide-containing polymers having a cationic or anionic charge; or amphoteric polyacrylamides.

8. The composition of claim 1, wherein the dialdehyde-modified polyacrylamide strengthening agent is the reaction product of: Glyoxal; and A prepolymer which is the reaction product of polyacrylamide monomers and diallyldimethylammonium chloride monomers, wherein the molar ratio of acrylamide to diallylmethylammonium chloride is about 99:1 to about 50:50, respectively, and Wherein about 40 mol % of the acrylamide groups of the polyacrylamide monomers are reacted and about 15 mol % of the acrylamide groups have reactive aldehyde functional groups.

9. The composition of claim 1, wherein the composition is in powder form and has a shelf life of at least six months, such that after six months the wet strength and / or dry strength properties of the paper are at least 80% of the wet strength and / or dry strength properties of the paper measured within one month of manufacture of the composition.

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