Flushable tissue products

Abstract

Flushable paper products and methods of improving the temporary wet strength of flushable paper, flushable tissue, and flushable crepe paper are provided. More specifically, the invention relates to adding cationic GPAM and colloidal silica to a cellulosic fiber stock to decrease the zeta potential or to render the zeta potential more negative, to increase paper machine runnability, and to form a flushable paper product with increased initial wet strength and increased wet strength decay.

Description

FLUSHABLE TISSUE PRODUCTSRELATED APPLICATIONS

[0001] The present invention relates to and claims benefit of priority to U.S. Provisional Application Number 63 / 670,281, filed on July 12, 2024, and Finnish Application Number Fl 20245992, filed on August 8, 2024, the contents of both are which are incorporated by reference in their entirety herein.FIELD OF THE INVENTION

[0002] The present invention generally relates to improving the temporary wet strength of flushable paper, flushable tissue, and flushable crepe paper. More specifically, the invention relates to adding cationic GPAM + colloidal silica or GPAM + bentonite to a cellulosic fiber stock to increase paper machine runnability and to form a flushable paper product with increased initial wet strength and increased wet strength decayBACKGROUND OF THE INVENTION

[0003] Temporary wet strength is critical for flushable paper grades that come in contact with water or moist skin. Wet tensile strength is a measure of the resistance of a paper to breaking or tearing under force after being immersed in water. Temporary wet strength is measured by the percentage of wet tensile strength decay over a set period of time.

[0004] In papermaking, a temporary wet strength aid, such as glyoxylated polyacrylamide (GPAM), is often employed to increase the initial wet strength of flushable paper products. For example, GPAM increases the initial wet strength of bathroom tissues, facial tissues, napkins, and wipes, a useful property since these products often come into contact with water during their use. This initial wet strength should significantly decay over a set period of time so that, once discarded in water, the paper product will break apart easily and become flushable.

[0005] GPAM is typically prepared through the reaction between glyoxal and a cationic polyacrylamide (CPAM) base-polymer as first reported in U.S. Pat. No. 3556932 and as discussed in U.S. Pat. Nos. 4,605,702, and 7,828,934. GPAM wet strength is temporary since it decreases over time. GPAM increases paper strength through covalent bond formation between its aldehyde groups and cellulose hydroxyl groups. This covalent bond is reversible in water, resulting in rapid wet strength decay over time. This rapid decrease in wet strength is desirable for flushed paper products, which must disintegrate rapidly after use.

[0006] Flushable paper products, such premium bath tissue, are often produced using pulp suspensions with low anionic charge densities. GPAM is often highly cationic. Therefore, GPAM may only applied at low dosage levels. Excess GPAM saturates a fiber surface and delivers no additional strength benefits. Furthermore, un-retained GPAM molecules can convert pulp zeta potential from net anionic to net cationic, causing paper machine runnability issues. Zeta potential is a parameter that characterizes the electrical repulsion between particles in a papermaking furnish.

[0007] As a result, anionic polymers such as anionic polyacrylamide (APAM) may be added to neutralize excess GPAM. Unfortunately, the introduction of anionic polyacrylamide also leads to a significant decrease of paper wet strength decay percentage. U.S. Pat. No. 9328462 claims the combination of GPAM and an anionic polyacrylamide (APAM) as papermaking additives to increase dewatering rate and dry strength of paper. However, the combination of APAM and GPAM led to a worse wet strength decay percentage than GPAM alone.

[0008] Other anionic particles, such as silica and bentonite, have been used along with GPAM for papermaking. U.S. Pat. App. No. 20100326615 claims addition of silica to GPAM containing furnish for increasing fiber retention and dewatering rate. However, no improvement in wet strength decay was observed. Furthermore, tissue products are light weight and water drains relatively fast during tissue sheet formation. Since colloidal silica and bentonite products are conventional papermaking dewatering aids, they are not applied during flushable tissue making processes.

[0009] Accordingly, an object of this invention is to provide flushable paper products with initial wet strength and wet strength decay properties that are similar to or improved compared to GPAM treated products. Another object of this invention is to provide flushable paper products with wet strength decay properties that are improved compared to GPAM and APAM treated products. An additional object of this invention is to provide methods for decreasing the zeta potential of a GPAM treated fiber stock, thereby improving runnability on a paper machine.SUMMARY OF THE INVENTION

[0010] The present disclosure generally encompasses improving the temporary wet strength of flushable paper, flushable tissue, and flushable crepe paper. More specifically, the invention relates to adding cationic GPAM +colloidal silica or GPAM + bentonite to a cellulosic fiber stock to render the zeta potential of the stock less positive or more negative (compared to GPAM-treated stock), thereby increasing paper machine runnability. The present invention also encompasses flushable paper products with initial wet strength and wet strength decay properties that are similar to or improved compared to GPAM treated products. The present invention also encompasses flushablepaper products with wet strength decay properties that are improved compared to GPAM and APAM treated products.

[0011] In one aspect, the present invention provides a flushable paper composition comprising:

[0012] (a) cellulosic fibers; (b) at least one glyoxalated polyacrylamide (GPAM); and (c) one or more silicon-containing particles.

[0013] In some exemplary embodiments, the flushable paper composition comprises:

[0014] (a) a tissue paper, a lightweight paper, a light crepe paper, a paper for sanitary use, a bathroom tissue, a facial tissue, a napkin, a wipe, or a special sanitary paper for medical applications;(b) a single ply grammage of less than 35 g / m2, 5-35 g / m2, 5-30, 5-25 g / m2, 5-20 g / m2, 5-15 g / m2, or 5-10 g / m2; (c) an increased GPAM content compared to an equivalent flushable paper composition without said silicon-containing particles; (d) an increased initial wet tensile strength compared to an equivalent flushable paper composition without said silicon-containing particles; (e) an increased wet strength decay compared to an equivalent flushable paper composition comprising an anionic polymer or anionic polyacrylamide (APAM) in place of said silicon-containing particles; or (f) any combination of (a)-(e).

[0015] In some exemplary embodiments, said cellulosic fibers:

[0016] (a) comprise virgin fibers, recycled fibers, or a mixture of virgin and recycled fibers; (b) comprise cellulosic or lignocellulosic fibers selected from the group consisting of softwood fibers, hardwood fibers, recycled fibers, refined fibers, mill broke fibers, coated broke fibers, non-wood fibers, or any combination thereof; (c) originate from pulp, Kraft pulp, unbleached Kraft pulp, bleached pulp, unbleached pulp, process water from pulp, paper, and / or board production, neutral sulfite semi chemical (NSSC) pulp, mechanical pulp, non-wood pulp, straw pulp, wheat pulp, or any combination thereof; (d) comprise a mixture of a softwood virgin Kraft pulp and a hardwood virgin bleached Kraft pulp, optionally comprising a ratio by weight of hardwood pulp to softwood pulp of (100:0; 95:5-5:95, 90:10-10:90, 80:20-20:80, 60:40-40:60; 50:50; 40:60; 30:70; 20:80; 10:90, 5:95, or 0:100; (e) when formulated as an aqueous fiber slurry, comprise a zeta potential ranging from -350 to 0 mV, -300 to O mV, -250 to 0 mV, -200 to 0 mV, -150 to 0 mV, -100 to 0 mV, -80 to 0 mV, -60 to 0 mV, -40 to 0 mV, -20 to 0 mV, -12 to 0 mV, -10 to 0 mV, or -5 to 0 mV; or (f) any combination of (a)- (e).

[0017] In some exemplary embodiments, said glyoxalated polyacrylamide (GPAM):

[0018] (a) comprises a net cationic charge; (b) comprises a cationic charge density of at least +0.5 mEq / g, 0.5-5 mEq / g, 0.5-4 mEq / g, 0.5-3 mEq / g, 0.5-2 mEq / g, or 0.5-1 mEq / g at pH 7.0; (c) comprisesat least one base-polymer, which is glyoxalated, wherein said base-polymer comprises one or more acrylamide based co-polymers comprising one or more neutral monomers, one or more cationic monomers, and optionally one or more anionic monomers, wherein:

[0019] (i) said one or more neutral monomers are selected from the group consisting of primary amide-containing monomers, acrylamide, methacrylamide, ethyl acrylamide, crotonamide, N-methyl acrylamide, N-butyl acrylamide, N-ethyl methacrylamide, and any combination thereof; (ii) said one or more cationic monomers are selected from the group consisting of acryloyloxyethyltrimethyl ammonium chloride (Q.9), methacryloyloxyethyltrimethylammonium chloride (MAETAC), methacrylamidopropyltrimethylammonium chloride (MAPTAC), acrylamidopropyltrimethylammonium chloride (APTAC), methacryloyloxyethyldimethylammonium sulfate, diallyldialkylammonium halides diallyldimethylammonium chloride (DADMAC), diallyldiethylammonium chloride; dialkylaminoalkyl acrylates, dialkylaminoalkyl methacrylates and their quaternary or acid salts; dimethylaminoethyl acrylate (DMAEA), dimethylaminoethyl methacrylate (DMAEMA), dimethylaminoethyl acrylate methyl chloride quaternary salt, dimethylaminoethyl acrylate methyl sulfate quaternary salt, dimethylaminoethyl acrylate benzyl chloride quaternary salt, dimethylaminoethyl acrylate sulfuric acid salt, dimethylaminoethyl acrylate hydrochloric acid salt, diethylaminoethyl acrylate methyl chloride quaternary salt, dimethylaminoethyl methacrylate methyl chloride quaternary salt, dimethylaminoethyl methacrylate methyl sulfate quaternary salt, dimethylaminoethyl methacrylate benzyl chloride quaternary salt, dimethylaminoethyl methacrylate sulfuric acid salt, dimethylaminoethyl methacrylate hydrochloric acid salt, dimethylaminoethyl methacryloyl hydrochloric acid salt; dialkylaminoalkylacrylamides, methacrylamides and their quaternary or acid salts; acryloylamidopropyltrimethylammonium chloride, dimethylaminopropyl acrylamide, dimethylaminopropyl acrylamide methyl sulfate quaternary salt, dimethylaminopropyl acrylamide sulfuric acid salt, dimethylaminopropyl acrylamide hydrochloric acid salt, dimethylaminopropyl methacrylamide, dimethylaminopropyl methacrylamide methyl sulfate quaternary salt, dimethylaminopropyl methacrylamide sulfuric acid salt, dimethylaminopropyl methacrylamide hydrochloric acid salt, diethylaminoethylacrylate, and diethylaminoethylmethacrylate; and any combination thereof; and (iii) optionally, said one or more anionic monomers contain functional groups selected from the group consisting of carboxylic acids, sulfonic acids, a phosphonic acids, their corresponding water soluble salts, their corresponding water dispersible salts, and any combination thereof; or said one or more anionic monomers comprise acrylic acid, methacrylic acid, maleic acid, itaconic acid, vinyl sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid (AMPS), acrylamido methanesulfonic acid, acrylamido ethanesulfonic acid, 2-hydroxy-3-acrylamide propanesulfonic acid, styrene sulfonic acid, and vinyl phosphonic acid, their corresponding alkali metal, alkaline earth metal, and ammonium salts, or any combination thereof;

[0020] (iv) said at least one base-polymer comprises a neutral monomer content or an acrylamide content ranging from 1-99 wt-%, 10-90 wt-%, 20-80 wt-%, 30-80 wt-%, 40-80 wt-%, 40-60 wt-%, 40- 50 wt-%, or 50-70 wt-%; (v) said at least one base-polymer comprises a cationic monomer content ranging from 1-99 wt-%, 10-90 wt-%, 20-80 wt-%, 30-80 wt-%, 40-80 wt-%, 50-80 wt-%, 60-80 wt-%, or 50-70 wt-%; (vi) said at least one base-polymer optionally comprises an anionic monomer content ranging from 0-50% by weight; (vii) said at least one base-polymer comprises a net cationic charge ranging from 1-99 wt-%, 10-90 wt-%, 20-80 wt-%, 30-80 wt-%, 40-80 wt-%, 40-60 wt-%, 40-50 wt-%, or 50-70 wt-% , at pH 7; (viii) said at least one base-polymer comprises a weight average molecular weight ranging from 5-1000 kDa, 5-500 kDa, 5-400 kDa, 5-300 kDa, 5-250 kDa, 5-200 kDa, 5-150 kDa, 5-100 kDa, 5-80 kDa, 5-60 kDa, 5-40 kDa, 5-20 kDa, or 5-10 kDa; or (ix) any combination of (i)-(viii);

[0021] (d) comprises a glyoxakbase-polymer weight ratio of 1:99-20:80, 1:99-15:85, or 5:95-10:90 ; or (e) any combination of (a)-(d).

[0022] In some exemplary embodiments, said silicon-containing particles:

[0023] (a) comprise microparticles and / or nanoparticles; (b) are selected from the group consisting of silica; colloidal silica; aluminum modified silica, aluminum modified colloidal silica, aluminum phyllosilicates, bentonite, sodium bentonite, calcium bentonite, and montmorillonite; (c) comprise a surface area of 300-1200 m2 / g, 400-1200 m2 / g, 600-1200 m2 / g, 800-1200 m2 / g, 900-1200 m2 / g, 1000-1200 m2 / g, or 1100-1200 m2 / g; (d) act as a zeta potential modifier which decreases, renders negative, or renders more negative the zeta potential of said cellulosic fibers; or (e) any combination of (a)-(d).

[0024] In some exemplary embodiments of the flushable paper composition:

[0025] (a) said silicon-containing particles comprise aluminum modified colloidal silica; (b) said base- polymer comprises (i) acrylamide and any combination DADMAC, Q9, and / or MAPTAC; or (ii) acrylamide and DADMAC; (c) the flushable paper composition comprises a GPAM dosage of 0.1-40 Ib / t, 0.1-30 Ib / t, 0.1-20 Ib / t, 0.1-15 Ib / t, 0.1-10 Ib / t, 0.1-8 Ib / t, 0.1-6 Ib / t, 0.1-5 Ib / t, 0.1-4 Ib / t, 0.1-3 Ib / t, 0.1-2 Ib / t, 0.1-1 Ib / t, or 0.1-0.5 Ib / t; (d) the flushable paper composition comprises a ratio-by weight of said silicon-containing particles:GPAM. of 30:1-1:30, 25:1-1:25, 1:20-20:1, 1:15-15:1, 1:10- 10:1, 1:8-8:1, 1:6-6:1, 1:4-4:1, 1:3-3:1 or 1:2-2:1, which is calculated as a dry weight of silicon- containing particles to dry weight of active GPAM; or (e) any combination of (a)-(d).

[0026] In another aspect, the present invention provides a method for producing a flushable paper, the method comprising

[0027] (a) contacting an aqueous fiber slurry with a glyoxalated polyacrylamide (GPAM) composition, and a silicon-containing particle composition, thereby forming a fiber stock; and (b) adding said fiber stock to the wet end of a paper machine.

[0028] In some exemplary embodiments of the method:

[0029] (i) said GPAM composition and silicon-containing particle composition are added to said aqueous fiber slurry simultaneously or sequentially in any order; and / or (ii) the method further comprises after step (b), removing sufficient water from the fiber stock to form a wet fibrous web and then pressing and drying the wet fibrous web to obtain said flushable paper.

[0030] In some exemplary embodiments of the method:

[0031] (a) said aqueous fiber slurry comprises a 1stzeta potential ranging from -350 to 0 mV, -300 to 0 mV, -250 to 0 mV, -200 to 0 mV, -150 to 0 mV, -100 to 0 mV, -80 to 0 mV, -60 to 0 mV, -40 to 0 mV, -20 to 0 mV, -12 to 0 mV, -10 to 0 mV, or -5 to 0 mV; (b) contacting said aqueous fiber slurry with said GPAM composition results in a 2ndzeta potential which (i) is increased or less negative compared to said 1stzeta potential; and / or (ii) is positive; (c) contacting said aqueous fiber slurry with said GPAM composition and said silicon-containing particle composition results in said fiber stock comprising a 3rdzeta potential which (i) is negative; (ii) is decreased or more negative compared to said 2ndzeta potential; (iii) is equal to said 1stzeta potential; and / or (iv) ranges from - 200 to +20 mV, -200 to +10 mV, -200 to +5 mV, -200 to +0.5 mV, -200 to +0.1 mV, -200 to 0 mV, -150 to 0 mV, -100 to 0 mV, -80 to 0 mV, -60 to 0 mV, -40 to 0 mV, -20 to 0 mV, -12 to 0 mV, -10 to 0 mV, or -5 to 0 mV; or (d) any combination of (a)-(c).

[0032] In some exemplary embodiments of the method said flushable paper comprises:

[0033] (a) a tissue paper, a lightweight paper, a light crepe paper, a paper for sanitary use, a bathroom tissue, a facial tissue, a napkin, a wipe, or a special sanitary paper for medical applications; (b) a single ply grammage of less than 35 g / m2, 5-35 g / m2, 5-30, 5-25 g / m2, 5-20 g / m2, 5-15 g / m2, or 5-10 g / m2; (c) an increased GPAM content compared to an equivalent flushable paper composition without said silicon-containing particles; (d) an increased initial wet tensile strength compared to an equivalent flushable paper composition without said silicon-containing particles; (e) an increased wet strength decay compared to an equivalent flushable paper composition comprising an anionic polymer or anionic polyacrylamide (APAM) in place of said silicon-containing particles; or (f) any combination of (a)-(e).

[0034] In some exemplary embodiments of the method said aqueous fiber slurry:

[0035] (a) comprises virgin fibers, recycled fibers, of a mixture of virgin and recycled fibers; (b) comprises cellulosic or lignocellulosic fibers selected from the group consisting of softwood fibers, hardwood fibers, recycled fibers, refined fibers, mill broke fibers, coated broke fibers, non-wood fibers, or any combination thereof; (c) comprises pulp, Kraft pulp, unbleached Kraft pulp, bleached pulp, unbleached pulp, process water from pulp, paper, and / or board production, neutral sulfite semi chemical (NSSC) pulp, mechanical pulp, non-wood pulp, straw pulp, wheat pulp, or any combination thereof; (d) comprises a mixture of a softwood virgin Kraft pulp and a hardwood virgin bleached Kraft pulp, optionally comprising a ratio by weight of hardwood pulp to softwood pulp of 100:0; 95:5-5:95, 90:10-10:90, 80:20-20:80, 60:40-40:60; 50:50; 40:60; 30:70; 20:80; 10:90, 5:95, or 0:100; (e) optionally comprises a thick stock, which is diluted to form a thin stock; (f) comprises a freeness of 400-600 CSF, 450-550 CSF, or 450-500 CSF; (g) comprises a consistency of 0.3-0.8 wt%, 0.4-0.7 wt%, or 0.45-0.62 wt%, wherein consistency is defined as weight % of total solids in the fiber slurry; (h) comprises a pH of 5-8, 5.5-7.5, or 6-7; (i) comprises a net anionic charge; or (j) any combination of (a)-(i).

[0036] In some exemplary embodiments of the method said GPAM composition:

[0037] (a) comprises an aqueous solution or emulsion comprising a wt% of GPAM solids ranging from 1-20 wt%, 1-15 wt%, 1-12 wt%, 1-11 wt%, 1-10 wt%, or 2-5 wt%; (b) comprises a viscosity of 10-100 cPs, 10-80 cPs, 10-60 cPs, 10-40 cPs, 10-20 cPs, or 10-15 cPs as measured by a Brookfield LV viscometer using a #1 spindle at 60 rpm and 25 °C; (c) comprises a net cationic charge; (d) comprises a cationic charge density of at least +0.5 mEq / g, 0.5-5 mEq / g, 0.5-4 mEq / g, 0.5-3 mEq / g, 0.5-2 mEq / g, or 0.5-1 mEq / g at pH 7.0; (e) comprises at least one base-polymer, which is glyoxalated, wherein said base-polymer comprises one or more acrylamide based co-polymers comprising one or more neutral monomers, one or more cationic monomers, and optionally one or more anionic monomers, wherein:

[0038] (i) said one or more neutral monomers are selected from the group consisting of primary amide-containing monomers, acrylamide, methacrylamide, ethyl acrylamide, crotonamide, N-methyl acrylamide, N-butyl acrylamide, N-ethyl methacrylamide, and any combination thereof; (ii) said one or more cationic monomers are selected from the group consisting of acryloyloxyethyltrimethyl ammonium chloride (Q9), methacryloyloxyethyltrimethylammonium chloride (MAETAC), methacrylamidopropyltrimethylammonium chloride (MAPTAC), acrylamidopropyltrimethylammonium chloride (APTAC), methacryloyloxyethyldimethylammonium sulfate, diallyldialkylammonium halides diallyldimethylammonium chloride (DADMAC),diallyldiethylammonium chloride; dialkylaminoalkyl acrylates, dialkylaminoalkyl methacrylates and their quaternary or acid salts; dimethylaminoethyl acrylate (DMAEA), dimethylaminoethyl methacrylate (DMAEMA), dimethylaminoethyl acrylate methyl chloride quaternary salt, dimethylaminoethyl acrylate methyl sulfate quaternary salt, dimethylaminoethyl acrylate benzyl chloride quaternary salt, dimethylaminoethyl acrylate sulfuric acid salt, dimethylaminoethyl acrylate hydrochloric acid salt, diethylaminoethyl acrylate methyl chloride quaternary salt, dimethylaminoethyl methacrylate methyl chloride quaternary salt, dimethylaminoethyl methacrylate methyl sulfate quaternary salt, dimethylaminoethyl methacrylate benzyl chloride quaternary salt, dimethylaminoethyl methacrylate sulfuric acid salt, dimethylaminoethyl methacrylate hydrochloric acid salt, dimethylaminoethyl methacryloyl hydrochloric acid salt; dialkylaminoalkylacrylamides, methacrylamides and their quaternary or acid salts; acryloylamidopropyltrimethylammonium chloride, dimethylaminopropyl acrylamide, dimethylaminopropyl acrylamide methyl sulfate quaternary salt, dimethylaminopropyl acrylamide sulfuric acid salt, dimethylaminopropyl acrylamide hydrochloric acid salt, dimethylaminopropyl methacrylamide, dimethylaminopropyl methacrylamide methyl sulfate quaternary salt, dimethylaminopropyl methacrylamide sulfuric acid salt, dimethylaminopropyl methacrylamide hydrochloric acid salt, diethylaminoethylacrylate, and diethylaminoethylmethacrylate; and any combination thereof; (iii) optionally, said one or more anionic monomers contain functional groups selected from the group consisting of carboxylic acids, sulfonic acids, a phosphonic acids, their corresponding water soluble salts, their corresponding water dispersible salts, and any combination thereof; or said one or more anionic monomers comprise acrylic acid, methacrylic acid, maleic acid, itaconic acid, vinyl sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid (AMPS), acrylamido methanesulfonic acid, acrylamido ethanesulfonic acid, 2-hydroxy-3-acrylamide propane sulfonic acid, styrene sulfonic acid, and vinyl phosphonic acid, their corresponding alkali metal, alkaline earth metal, and ammonium salts, or any combination thereof; (iv) said at least one base-polymer comprises a neutral monomer content or an acrylamide content ranging from 1-99 wt-%, 10-90 wt-%, 20-80 wt-%, 30-80 wt-%, 40-80 wt-%, 40-60 wt-%, 40-50 wt-%, or 50-70 wt-%; (v) said at least one base-polymer comprises a cationic monomer content ranging from 1-99 wt-%, 10-90 wt-%, 20- 80 wt-%, 30-80 wt-%, 40-80 wt-%, 50-80 wt-%, 60-80 wt-%, or 50-70 wt-%; (vi) said at least one base- polymer optionally comprises an anionic monomer content ranging from 0-50% by weight; (vii) said at least one base-polymer comprises a net cationic charge ranging from 1-99 wt-%, 10-90 wt-%, 20- 80 wt-%, 30-80 wt-%, 40-80 wt-%, 40-60 wt-%, 40-50 wt-%, or 50-70 wt-% , at pH 7; (viii) said at least one base-polymer comprises a weight average molecular weight ranging from 5-1000 kDa, 5-500kDa, 5-400 kDa, 5-300 kDa, 5-250 kDa, 5-200 kDa, 5-150 kDa, 5-100 kDa, 5-80 kDa, 5-60 kDa, 5-40 kDa, 5-20 kDa, or 5-10 kDa; or (ix) any combination of (i)-(viii);

[0039] (f) comprises a glyoxakbase-polymer weight ratio of 1:99-20:80, 1:99-15:85, or 5:95-10:90; or (g) any combination of (a)-(f).

[0040] In some exemplary embodiments of the method said silicon-containing particle composition:

[0041] (a) comprises one or more silicon-containing particles selected from the group consisting of silica; colloidal silica; aluminum modified silica, aluminum modified colloidal silica, aluminum phyllosilicates, bentonite, sodium bentonite, calcium bentonite, and montmorillonite, wherein said silicon-containing particles comprise microparticles and / or nanoparticles; (b) comprises a liquid dispersion comprising a dispersed phase comprising said one or more silicon-containing particles dispersed in water and further comprising a total solid content of 5-25 wt%, 5-20 wt%, 5-15 wt%, 5- 10 wt%, 5-8 wt% or 5-7 wt%; (c) comprises a surface area of 300-1200 m2 / g, 400-1200 m2 / g, 600- 1200 m2 / g, 800-1200 m2 / g, 900-1200 m2 / g, 1000-1200 m2 / g, or 1100-1200 m2 / g; (d) comprises an S-value of 8-80%, 8-60%, 8-40%, 8-20%, 8-16%, 8-14%, 8-12%, or 8-10%, wherein S-value is the wt-% of SiO2 in the dispersed phase of said liquid dispersion; (e) acts as a zeta potential modifier which decreases, renders negative, or renders more negative the zeta potential of said cellulosic fibers; or (f) any combination of (a)-(e).

[0042] In some exemplary embodiments of the method:

[0043] (a) said aqueous fiber slurry comprises a dosage of said GPAM composition ranging from 0.1- 40 Ib / t, 0.1-30 Ib / t, 0.1-20 Ib / t, 0.1-15 Ib / t, 0.1-10 Ib / t, 0.1-8 Ib / t, 0.1-6 Ib / t, 0.1-5 Ib / t, 0.1-4 Ib / t, 0.1- 3 Ib / t, 0.1-2 Ib / t, 0.1-1 Ib / t, or 0.1-0.5 Ib / t; (b) said fiber stock comprises a dosage of said silicon- containing particle composition that (i) is sufficient to form a ratio by weight of said silicon- containing particles:GPAM of 30:1-1:30, 25:1-1:25, 1:20-20:1, 1:15-15:1, 1:10-10:1, 1:8-8:1, 1:6-6:1, 1:4-4:1, 1:3-3:1 or 1:2-2:1, calculated as a dry weight of silicon-containing particles to dry weight of active GPAM; and (ii) is sufficient to form said 3rd zeta potential in the fiber stock; (c) the method further comprises increasing the dosage of said silicon-containing particle composition until said 3rd zeta potential is observed in the fiber stock; (d) said base-polymer of said GPAM comprises (i) acrylamide and any combination DADMAC, Q9, and / or MAPTAC; or (ii) acrylamide and DADMAC; (e) said silicon-containing particles comprise aluminum modified colloidal silica; or (f) any combination of (a)-(e).

[0044] In another aspect, the present invention provides a fiber stock composition comprising:

[0045] (a) an aqueous suspension comprising cellulosic fibers, at least one glyoxalated polyacrylamide (GPAM), and one or more silicon-containing particles according to any of the foregoing; or (b) an aqueous suspension comprising an aqueous fiber slurry, a glyoxalated polyacrylamide (GPAM) composition, and a silicon-containing particle composition obtainable by a method according to any of the foregoing.DETAILED DESCRIPTION OF THE INVENTION

[0046] Before describing the invention, the following definitions are provided. Unless stated otherwise all terms are to be construed as they would be by a person skilled in the art.DEFINITIONS

[0047] As used herein, the singular forms "a," "an," and "the" may mean "one" but also include plural referents such as "one or more" and "at least one" unless the context clearly dictates otherwise. All technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this invention belongs unless clearly indicated otherwise.

[0048] As used herein, the term "or" in the claims is used to mean "and / or" unless explicitly indicated to refer to alternatives only or the alternatives are mutually exclusive, although the disclosure supports a definition that refers to only alternatives and "and / or."

[0049] As used herein the term "or combinations thereof' as used herein refers to all permutations and combinations of the listed items preceding the term unless stated otherwise.PAPERMAKING

[0050] As used herein, the term "aqueous suspension", "aqueous slurry", or "slurry" generally refer to a heterogeneous mixture of a fluid that contains insoluble or sparingly soluble solid particles sufficiently large for sedimentation. Suspensions and slurries of the present invention may also comprise some amount of solid particles, often termed colloidal particles, which do not completely settle or take a long time to settle completely.

[0051] As used herein, the terms "broke" or "mill broke" refer to paper, which during the paper making process becomes suitable only for repulping. Broke may contain trimmings or paper that is out of specification. Broke is re-used material which never left the mill is not regarded as recycled or recovered. Broke is a valuable source of fiber and is recycled internally at the mill. As used herein, the term "coated broke" refers to broke that contains coatings that are applied to the base sheet of paper as it is being manufactured. When the broke contains these coatings, it presents special problems in recycling to recover fiber values because the coatings introduce materials which wouldnot normally be present in the original stock of fiber used to manufacture the base paper sheet. The coated broke may also contain dyes and / or other additives.

[0052] The term "cellulosic" refers to a substance made from cellulose or a derivative of cellulose. The term "lignocellulosic" refers to a substance derived from plant dry matter or biomass, which comprises at least cellulose and hemicellulose, which are carbohydrate polymers, and lignin, an aromatic-rich polymer. All pulp and fiber products, including molded pulp and molded fiber products described herein may be cellulosic and / or lignocellulosic. In general, as used herein, the terms cellulosic and lignocellulosic are used interchangeably with identical meaning.

[0053] As used herein, the term "fiber" or "cellulosic fiber" refers to the basic structural unit of paper or board.

[0054] As used herein, the term "consistency" generally refers to percent oven dry mass in the stock, slurry, or furnish (i.e., 100% * oven dry mass / total mass).

[0055] As used herein, the terms "fiber suspension", "fiber slurry", and "aqueous suspension of cellulosic fibers" generally refer to a suspension of cellulosic fibers and pulp from which tissue, paper, or board is made. The cellulosic fibers and pulp may contain virgin fibers and / or recycled fibers. The suspension may also contain, optional fillers, dyes, process water, and / or white water. The suspension may contain a mixture of water, dissolved paper pulp, and optionally other soluble or insoluble components produced or added during the stock preparation phase of papermaking.

[0056] The terms "fiber stock" and "furnish" generally refer to a fiber suspension of cellulosic fibers, optional fillers, optional dyes, optional chemical and / or polymeric additives, and optionally other soluble or insoluble components used to manufacture tissue, paper, or board. A papermaking furnish or fiber stock is added to the wet end of a paper machine and then drained and dried to form a cellulosic product comprising tissue, paper, or board.

[0057] A fiber stock may be a "thick stock" or a "thin stock". As used herein, the term "thick stock" generally refers to an aqueous suspension of papermaking pulp and other materials with a consistency of about 1 to 5%. As used herein, the term "thin stock" generally refers to an aqueous suspension of papermaking pulp and other materials, after having been diluted to a consistency below 1% with water, synthetic water, whitewater, or other process water at a fan pump.

[0058] As used herein, the terms "fixation", "fixing" and "fix" means that a substance is associated or attached onto the fibers at least temporarily or permanently.

[0059] The terms "flushable", "flushable product", or "flushable paper" refers to a tissue or paper product formed from plant dry matter from any source, virgin or recycled, that is able to be disposedof through sanitation fixtures , such as toilets, without clogging or otherwise interfering with the disposal process. A flushable product may include a tissue paper, a lightweight paper, a light crepe paper, a paper for sanitary use, a bathroom tissue, a facial tissue, a napkin, a wipe, or a special sanitary paper for medical applications. The current measure of flushability is set by the 4th edition of the INDA / EDANA Flushability Guidelines (Guidelines for Assessing the Fl usha bility of Disposable Nonwoven Products (May 2018)). As used herein, flushable also refers to tissue or paper products with rapid wet strength decay, such as greater than 50%, 55%, 58%, 60%, 62%, or 64% percent wet strength decay or higher, which break up easily in after immersing for 1-30 min water and / or after flushing.

[0060] The term "grammage refers to the mass in grams of a tissue or paper per square meter (g / m2, GSM). The term "basis weight" refers to the weight of a sheet of tissue or paper based on standard size.

[0061] As used herein, the terms "papermaking process" and "papermaking application" generally refers to any process by which tissue, paper, and / or paperboard may be produced. For example, such processes include making paper products from pulp, such as methods comprising forming an aqueous fiber stock / furnish, adding the stock / furnish to the wet end of a paper machine, draining on a wire to form a sheet, and drying the sheet. The steps of forming the papermaking furnish, draining and drying may be carried out in any conventional manner generally known in the art.

[0062] As used herein, the terms "recycled fiber" and "recovered fiber", refer to paper, paperboard, and fibrous wastes from retail stores, office buildings, homes, manufacturing plants, and so forth, after they have passed through their end-usage as a consumer item. Manufacturing wastes include: dry paper and paperboard waste generated after completion of the papermaking process including by way of example: envelope cuttings, bindery trimmings, and other paper and paperboard waste resulting from printing, cutting, forming, and other converting operations; bag, box, and carton manufacturing wastes; mill wrappers, and rejected unused stock; and repulped finished paper and paperboard from obsolete inventories of paper and paperboard manufacturers, merchants, wholesalers, dealers, printers, converters, or others. In particular the term "recycled fibers" includes recycled fibers derived by processing of paper and other consumer cellulosic materials, e.g., paper, old corrugated containerboard (OCC), mixed office waste (MOW), old magazine (OMG), unbleached kraft pulp, neutral sulphite semi chemical (NCCS) pulp and / or mechanical pulp. Source materials for recycled fibers may be selected from old corrugated containerboard, mixed office waste, old newsprint, old magazines, double liner kraft, and any mixtures thereof. Mixed waste (MXW) denotes recycled mixture of recycled board, such as OCC, white lined chipboard and / or folding boxboard, and recycled paper, such as old newsprint, old magazines and / or office waste papers. Mixed office wastedenotes recycled fiber material mainly containing copying papers, printer papers and offset papers. Double lined kraft denotes recycled fiber material comprising clean sorted unprinted corrugated cardboard cartons, boxes, sheet or trimmings, e.g., of kraft or jute liner. White lined chipboard (WLC) denotes multiply board comprising deinked fiber material and / or un-deinked recycled fiber material originating e.g., from OCC, mixed office waste or old newspapers (ONP) in or more of the layers.

[0063] The term "vyhite water" generally refers to process water within a paper machine system, especially referring to water that is drained from paper as the sheet is being formed.

[0064] The terms "wet end of a paper machine" or "wet end" generally refer to the parts of a papermaking process between pulping (or bleaching) and wet-pressing of the paper.

[0065] The terms "wet strength" or "wet tensile strength" refer to a measure of the resistance of a paper to breaking or tearing under force after being immersed in water. "Initial wet strength" refers to the tensile strength of a paper immediately after be immersed in or coated with water. "Permanent wet strength" refers to the tensile strength after soaking in water for an amount of time (e.g., 30 min). Temporary wet strength is measured by the percentage of wet tensile strength decay over a set period of time (e.g., 30 min). As used herein, IWT refers to Initial Wet Tensile Strength; PWT refers to Permanent Wet Tensile Strength; and Wet Strength Decay = 100*(l-PWT / IWT).

[0066] The term "zeta potential" refers to the average electrical potential at a hydrodynamic slip plane adjacent to a solid surface exposed to a liquid. Zeta potential data provide the papermaker with a way to predict how a furnish is likely to respond to the addition of cationic or anionic additives. The zeta potential is a good predictor of the magnitude of electrical repulsive forces between particles of known size and shape as a function of distance. Slurries of fibers that have high absolute values of zeta potentials (greater than plus or minus 20 mV) are likely to remain in stable dispersion during storage. For flushable paper products and methods of the present invention, a thick stock having a zeta potential that is approximately equal to the natural zeta potential of unmodified fibers (e.g., about -200 to -0 mV, -100 to -5 mV, or -40 to -10 mV), is desirable for paper machine runnability.ADDITIVES AND POLYMERS

[0067] As used herein "acrylamide" refers to a neutral monomer of molecular formula: C3H5NO and a molecular weight of 71.08 g / mol.

[0068] As used herein, the term "anionic polyacrylamide (APAM)" refers to a copolymer of acrylamide and anionic monomers, such as acrylic acid or ATBS, and also encompasses acrylamidepolymers which are partially or completely hydrolyzed following polymerization to form acrylate or acrylic acid side chains.

[0069] As used herein, "anionic monomer" refers to a monomer which possesses a negative charge in aqueous solution at a pH above a certain threshold depending on the pKa values of acidic protons contained therein. The "anionic monomers" may be neutral at low pH (e.g., from a pH of about 0-1, 0-2, or 0-3) and become anionic as the pH of solution is increased. Non-limiting representative anionic monomers include acrylic acid, sodium acrylate, ammonium acrylate, methacrylic acid, 2- acrylamido-2-methylpropanesulfonic acid (AMPS), vinyl sulfonic acid, styrene sulfonic acid, maleic acid, sulfopropyl acrylate or methacrylate or other water-soluble forms of these or other polymerizable carboxylic or sulphonic acids, sulfomethylated acrylamide, ally sulfonate, itaconic acid, acrylamidomethylbutanoic acid, fumaric acid, vinylphosphonic acid, allylphosphonic acid, phosphonomethylated acrylamide, methacrylate, itaconate, 2-acrylamido 2-methyl propane sulphonate, sulfoalkyl(meth)acrylic acids, sulfonated styrenes, unsaturated dicarboxylic acids, sulfoalkyl(meth)acrylamides, vinyl acetate, n-vinylformamide, n-vinylacetamide, n-vinylcaprolactam, n-vinylimidazole, n-vinylpyridine, n-vinylpyrolidone, acrylamidopropyltrimonium chloride, salts of said acids and the like, or another anionic ethylenically unsaturated compound.

[0070] As used herein, the term "cationic monomer" generally refers to a monomer that possesses a positive charge. Examples thereof include acryloyloxy ethyl trimethylammonium chloride (Q9) monomers. Cationic monomers may also be selected from 2-(acryloyloxy)ethyl trimethylammonium chloride ("AETAC" or "Q9"), methacryloyloxyethyltrimethylammonium chloride ("MAETAC"), methacrylamidopropyltrimethylammonium chloride ("MAPTAC"), acrylamidopropyltrimethylammonium chloride ("APTAC"), methacryloyloxyethyldimethylammonium sulfate, diallyldimethylammonium chloride ("DADMAC"); dialkylaminoalkyl acrylates and dialkylaminoalkyl methacrylates and their quaternary or acid salts, including but not limited to, dimethylaminoethyl acrylate ("DMAEA"), dimethylaminoethyl methacrylate ("DMAEA"), dimethylaminoethyl acrylate methyl chloride quaternary salt, dimethylaminoethyl acrylate methyl sulfate quaternary salt, dimethylaminoethyl acrylate benzyl chloride quaternary salt, dimethylaminoethyl acrylate sulfuric acid salt, dimethylaminoethyl acrylate hydrochloric acid salt, diethylaminoethyl acrylate methyl chloride quaternary salt, dimethylaminoethyl methacrylate methyl chloride quaternary salt, dimethylaminoethyl methacrylate methyl sulfate quaternary salt, dimethylaminoethyl methacrylate benzyl chloride quaternary salt, dimethylaminoethyl methacrylate sulfuric acid salt, dimethylaminoethyl methacrylate hydrochloric acid salt, dimethylaminoethyl methacryloyl hydrochloric acid salt; dialkylaminoalkylacrylamides and methacrylamides and their quaternary or acid salts, including but not limited to, acryloylamidopropyltrimethylammoniumchloride, dimethylaminopropyl acrylamide, dimethylaminopropyl acrylamide methyl sulfate quaternary salt, dimethylaminopropyl acrylamide sulfuric acid salt, dimethylaminopropyl acrylamide hydrochloric acid salt, methacrylamidopropyltrimethylammonium chloride, dimethylaminopropyl methacrylamide, dimethylaminopropyl methacrylamide methyl sulfate quaternary salt, dimethylaminopropyl methacrylamide sulfuric acid salt, dimethylaminopropyl methacrylamide hydrochloric acid salt, diethylaminoethylacrylate, diethylaminoethylmethacrylate; and diallyldialkylammonium halides, including but not limited to, diallyldiethylammonium chloride and diallyldimethylammonium chloride ("DADMAC"), and any combination thereof.

[0071] As used herein, the term "glyoxalated polyacrylamide (GPAM)" or "GPAM" generally refers to a polymer obtained by reacting glyoxal and a polyacrylamide "base polymer" to form a glyoxalated polymer backbone (see e.g., U.S. Pat. No. 3,556,932 which first disclosed the synthesis of a GPAM composition prepared by reacting glyoxal with a cationic polyacrylamide). Cationic charge on the polyacrylamide backbone of the GPAM renders the polymer self-retaining on fibers. In general, GPAM comprises a reactive polymer that can covalently bond with cellulose upon dehydration.Exemplary GPAMS are reactive cationic polymers containing reactive aldehydes, which react with carboxylate and -OH moieties on cellulosic and lignocellulosic fibers to form covalent bonds.Exemplary GPAMS are used as wet and / or dry strength additives and as retention aids and drainage aids in papermaking. GPAM wet strength is temporary since it decreases over time. GPAM increases paper strength through covalent bond formation between its aldehyde groups and cellulose hydroxyl groups. This covalent bond is reversible in water, resulting in rapid wet strength decay over time. This rapid decrease in wet strength is desirable for flushed paper products, which must disintegrate rapidly after use.

[0072] As used herein, "nonionic monomer" refers to a monomer which possesses a net charge of zero in aqueous solution. Non-limiting examples of nonionic monomers include, acrylamide, N- alkylacrylamides, N,N-dialkylacrylamides, methacrylamide, N-vinylmethylacetamide or formamide, vinyl acetate, vinyl pyrrolidone, alkyl methacrylates, acrylonitrile, N-vinylpyrrolidone other acrylic (or other ethylenically unsaturated) ester or other water insoluble vinyl monomers such as styrene or acrylonitrile.

[0073] As used herein, the terms "polyacrylamide" or "PAM" generally refer to polymers and copolymers comprising acrylamide moieties, and the terms encompass any polymers or copolymers, including terpolymers, comprising acrylamide moieties, e.g., one or more acrylamide (co)polymers of acrylamide and additional monomers capable of copolymerizing with acrylamide. PAMs described herein may be produced in one of various forms, including, for example, dry (powder ) form (e.g., DPAM), emulsion polyacrylamide (EPAM), or liquid polyacrylamide (aqueous solution). Amphotericpolyacrylamides (AmPAM) may be formulated in dry (powder ) form (e.g., AmDPAM), or emulsion form (AmEPAM).

[0074] As used herein, the terms "polymer" or "polymeric additives" and similar terms are used in their ordinary sense as understood by one skilled in the art, and thus may be used herein to refer to or describe a large molecule (or group of such molecules) that may comprise recurring units. Polymers may be formed in various ways, including by polymerizing monomers and / or by chemically modifying one or more recurring units of a precursor polymer. Unless otherwise specified, a polymer may comprise a "homopolymer" that may comprise substantially identical recurring units that may be formed by, for example, polymerizing a particular monomer. Unless otherwise specified, a polymer may also comprise a "copolymer" that may comprise two or more different recurring units that may be formed by, for example, copolymerizing, two or more different monomers, and / or by chemically modifying one or more recurring units of a precursor polymer. Unless otherwise specified, a polymer or copolymer may also comprise a "terpolymer" or a "tetrapolymer" which generally refer to polymers that comprise three, four, or more different recurring monomer units. The term "polymer" as used herein is intended to include both the acid form of the polymer as well as its various salts. Polymers may be amphoteric in nature, that is, containing both anionic and cationic substituents, although not necessarily in the same proportions. Polymer molecular weights may be measured by various methods known to persons of skill in the art. For example, weight average molecular weight may be measured using gel permeation chromatography (GPC). Polymer molecular weights may be measured by various methods known to persons of skill in the art. For example, weight average molecular weight may be measured using gel permeation chromatography (GPC). Additionally, polymer molecular weights may be measured by GPC / Light Scattering / Viscometry also known as Triple Detection GPC which employs Refractive Index Detector (with or without UV Detector), Dilute Solution Viscometry and Light Scattering all in series to determine molecular weights, distribution and related solution parameters.

[0075] The term "silicon-containing particles" refers to silica-based particles, finely ground minerals, or clay particles containing various forms of silicon including oxides of silicon, silicon dioxide (e.g., silica), silicates, silicate minerals and optionally aluminum, aluminum oxides, silicon, silanes, and other elements. "Silicon-containing particles" refers to silica-based particles, silica; colloidal silica; aluminum modified silica, aluminum modified colloidal silica, clay minerals, aluminum phyllosilicates, bentonite, sodium bentonite, calcium bentonite, montmorillonite, and other clay minerals, including kaolin clays Al2Si2O5(OH)4), smectite clays, illite clays, and chlorite clays.

[0076] "Silicon-containing particles" may comprise colloidal particles, microparticles and / or nanoparticles, and / or may comprise a surface area of 300-1200 m2 / g, 400-1200 m2 / g, 600-1200m2 / g, 800-1200 m2 / g, 900-1200 m2 / g, 1000-1200 m2 / g, or 1100-1200 m2 / g. For the present invention, silicon-containing particles may be formulated as a slurry or dispersion and may be added to a mixture of cellulosic fibers and GPAM, and act as a zeta potential modifier which decreases, renders less positive, renders negative, or renders more negative the zeta potential of the mixture. For the present invention, silicon-containing particles also act to increase the initial wet strength and to increase the wet strength decay of flushable paper products.

[0077] In certain embodiments of the present invention, "silicon-containing particles" are selected from the group of silica-based particles consisting of silica, colloidal silica, silicon oxides, aluminum modified silica, aluminum modified colloidal silica, or silicon dioxides. These particles comprise an average particle size ranging from 1 nm - 100 pm, 10 nm - 10 pm, or 100 nm - 1 pm.

[0078] In other embodiments of the present invention, "silicon-containing particles" are selected from clay minerals, aluminum phyllosilicates, bentonite, sodium bentonite, calcium bentonite, montmorillonite, and other clay minerals, including kaolin clays AI2Si2O5(OH)4), smectite clays, illite clays, and chlorite clays. These materials may have an average particle size ranging from 0.1-2000 pm, 0.5-1500 pm, 1-1000 pm, 10-900 pm, 20-800 pm, 30-700 pm, 40-600 pm, or 50-500 pm.

[0079] As used herein, "bentonite" can be any of the materials commercially referred to as bentonites or as bentonite-type clays, i.e., anionic swelling clays such as sepiolite, attapulgite or, montmorillonite. The montmorillonites are preferred. Bentonites broadly as described in U.S. Pat. No. 4,305,781 are suitable. Raw bentonite has a broad distribution of particle sizes ranging from 0.8 pm to 2000 pm. Suitable montmorillonite clays include Wyoming bentonite or Fullers Earth. The clays may or may not be chemically modified, e.g., by alkali treatment to convert calcium bentonite to alkali metal bentonite. The swelling clays are usually metal silicates wherein the metal comprises a metal selected from aluminum and magnesium, and optionally other metals, and the ratio silicon atoms:metal atoms in the surface of the clay particles, and generally throughout their structure, is from about 5:1 to 1:1. Bentonite particles

[0080] The term "aluminum modified silica" refers to a modified silica prepared by reacting colloidal silica with sodium aluminate according to U.S. Pat. No. 5643414. During this process, aluminum molecules are incorporated into the surface of the colloidal silica, thereby rendering the surface of the particle more anionic. Modification of the silica surface with sodium aluminate gives a fixed negative surface charge that is not pH dependent and gives the surface a higher charge (at pH range 3-9) relative to nonmodified silica.

[0081] The term "s-value" refers to a parameter that characterizes the degree of aggregation in structured or aggregated silica dispersions. S-value is a measure of the silica (as per cent) in thedispersed phase and can be obtained from viscosity measurements. A high S-value indicates lower density, well-dispersed, non-aggregated colloidal particles, whereas a low S-value suggests that the primary particles have formed higher density micro-aggregate structures containing multiple primary particles. The S-value may be measured and calculated according to the formulas given in J. Phys. Chem. 60 (1956), 955-957 by Iler, R. K. & Dalton, R. L. The S-value depends on the silica content, the viscosity, and the density of the silica sol. A high S-value indicates a low microgel content. Generally, as used herein, the S-value represents the amount of SiO2 in % by weight that is present in the dispersed phase of a silica dispersion.UNITS

[0082] As used herein, the terms "Ibs / t" refers to pounds of dry mass of added material (e.g., additive, solute, and / or particle) per ton of suspended and dissolved solids.

[0083] As used herein, the phrases "wt %" denotes pounds of dry mass of additive per dry mass of solids in the formulation, solution, or slurry, multiplied by 100%.DESCRIPTION OF THE INVENTION

[0084] This invention provides a flushable tissue product comprising GPAM and silicon-containing microparticles being added to the pulp suspension. In certain embodiments, the tissue paper is a lightweight paper or, light crepe paper made both from virgin and recycled paper pulp with a grammage below 35 g / m2(GSM). In certain embodiments, the GPAM sample has a net cationic charge density of at least +0.5 meq / g. In certain embodiments, the silicon containing microparticles comprise colloidal silica comprising a surface area from 300 m2 / g to 1200 m2 / g and an S-value of from 80% to 8%. In certain embodiments, the silicon containing microparticles comprise bentonite.

[0085] Tissue paper products include those for sanitary use, such as bathroom and facial tissue, napkins, paper towels and wipes, and special sanitary papers used in sterile medical procedures. Some key properties of tissue products are softness, dry and wet strength, and wet strength decay. Furthermore, tissue products are light weight and water drains relatively fast during tissue sheet forming process. Common tissue paper grades include bath tissue (toilet paper), facial tissue, napkin, and paper towel. Some of those products, such as bath tissue, and are required to be flushable after use. Therefore, high wet strength decay is a critical product attribute. Conventional paper towel products are designed to retain high permanent wet strength. However, there has been growing interest to design flushable away-from-home towel products.

[0086] GPAM products are widely used in the paper industry to increase temporary wet strength of paper products. GPAM is typically added to the pulp suspension before paper sheet formation.Upon drying of the treated paper sheet, GPAM forms covalent bonds with paper cellulose to increase dry strength. Since the covalent bond between GPAM and cellulose is reversible in water, this wet strength may decrease rapidly over time.

[0087] However, GPAM products can only be applied at low dosage levels since excess GPAM can convert pulp zeta potential from net anionic to net cationic, causing a series of paper machine runnability issues. As a result, anionic polymers such as anionic polyacrylamide (APAM) are sometimes added to neutralize excess GPAM. Unfortunately, the introduction of anionic polyacrylamide also leads to a significant decrease of paper wet strength decay percentage.

[0088] Colloidal silica also bears a negative charge. Modifying the surface of silica with aluminum increases the permanent negative charge of a given particle. Since colloidal silica products are conventional papermaking dewatering aids, they are not applied during tissue making processes.

[0089] The objective of adding silica + GPAM or GPAM + bentonite in this invention is to provide flushable paper products with initial wet strength and wet strength decay properties that are similar to or improved compared to GPAM treated products. Another object is to provide flushable paper products with wet strength decay properties that are improved compared to GPAM and APAM treated products. An additional object is to provide methods for decreasing the zeta potential (i.e., rendering less positive or rendering more negative) of a GPAM treated fiber stock, thereby improving runnability on a paper machine.

[0090] In one aspect, the present invention provides a flushable paper composition comprising:

[0091] (a) cellulosic fibers; (b) at least one glyoxalated polyacrylamide (GPAM); and (c) one or more silicon-containing particles.

[0092] In some exemplary embodiments, the flushable paper composition comprises:

[0093] (a) a tissue paper, a lightweight paper, a light crepe paper, a paper for sanitary use, a bathroom tissue, a facial tissue, a napkin, a wipe, or a special sanitary paper for medical applications; (b) a single ply grammage of less than 35 g / m2, 5-35 g / m2, 5-30, 5-25 g / m2, 5-20 g / m2, 5-15 g / m2, or 5-10 g / m2; (c) an increased GPAM content compared to an equivalent flushable paper composition without said silicon-containing particles; (d) an increased initial wet tensile strength compared to an equivalent flushable paper composition without said silicon-containing particles; (e) an increased wet strength decay compared to an equivalent flushable paper composition comprising an anionic polymer or anionic polyacrylamide (APAM) in place of said silicon-containing particles; or (f) any combination of (a)-(e).

[0094] In some exemplary embodiments, said cellulosic fibers:

[0095] (a) comprise virgin fibers, recycled fibers, or a mixture of virgin and recycled fibers; (b) comprise cellulosic or lignocellulosic fibers selected from the group consisting of softwood fibers, hardwood fibers, recycled fibers, refined fibers, mill broke fibers, coated broke fibers, non-wood fibers, or any combination thereof; (c) originate from pulp, Kraft pulp, unbleached Kraft pulp, bleached pulp, unbleached pulp, process water from pulp, paper, and / or board production, neutral sulfite semi chemical (NSSC) pulp, mechanical pulp, non-wood pulp, straw pulp, wheat pulp, or any combination thereof; (d) comprise a mixture of a softwood virgin Kraft pulp and a hardwood virgin bleached Kraft pulp, optionally comprising a ratio by weight of hardwood pulp to softwood pulp of 100:0; 95:5-5:95, 90:10-10:90, 80:20-20:80, 60:40-40:60; 50:50; 40:60; 30:70; 20:80; 10:90, 5:95, or 0:100; (e) when formulated as an aqueous fiber slurry, comprise a zeta potential ranging from -350 to 0 mV, -300 to 0 mV, -250 to 0 mV, -200 to O mV, -150 to 0 mV, -100 to 0 mV, -80 to 0 mV, -60 to 0 mV, -40 to 0 mV, -20 to 0 mV, -12 to 0 mV, -10 to 0 mV, or -5 to 0 mV, which zeta potential ranges are typically observed for unmodified fiber slurries for use in papermaking; or (f) any combination of (a)-(e).

[0096] In some exemplary embodiments, said glyoxalated polyacrylamide (GPAM):

[0097] (a) comprises a net cationic charge; (b) comprises a cationic charge density of at least +0.5 mEq / g, 0.5-5 mEq / g, 0.5-4 mEq / g, 0.5-3 mEq / g, 0.5-2 mEq / g, or 0.5-1 mEq / g at pH 7.0; (c) comprises at least one base-polymer, which is glyoxalated, wherein said base-polymer comprises one or more acrylamide based co-polymers comprising one or more neutral monomers, one or more cationic monomers, and optionally one or more anionic monomers, wherein:

[0098] (i) said one or more neutral monomers are selected from the group consisting of primary amide-containing monomers, acrylamide, methacrylamide, ethyl acrylamide, crotonamide, N-methyl acrylamide, N-butyl acrylamide, N-ethyl methacrylamide, and any combination thereof; (ii) said one or more cationic monomers are selected from the group consisting of acryloyloxyethyltrimethyl ammonium chloride (09), methacryloyloxyethyltrimethylammonium chloride (MAETAC), methacrylamidopropyltrimethylammonium chloride (MAPTAC), acrylamidopropyltrimethylammonium chloride (APTAC), methacryloyloxyethyldimethylammonium sulfate, diallyldialkylammonium halides diallyldimethylammonium chloride (DADMAC), diallyldiethylammonium chloride; dialkylaminoalkyl acrylates, dialkylaminoalkyl methacrylates and their quaternary or acid salts; dimethylaminoethyl acrylate (DMAEA), dimethylaminoethyl methacrylate (DMAEMA), dimethylaminoethyl acrylate methyl chloride quaternary salt, dimethylaminoethyl acrylate methyl sulfate quaternary salt, dimethylaminoethyl acrylate benzyl chloride quaternary salt, dimethylaminoethyl acrylate sulfuric acid salt, dimethylaminoethyl acrylate hydrochloric acid salt, diethylaminoethyl acrylate methyl chloride quaternary salt,dimethylaminoethyl methacrylate methyl chloride quaternary salt, dimethylaminoethyl methacrylate methyl sulfate quaternary salt, dimethylaminoethyl methacrylate benzyl chloride quaternary salt, dimethylaminoethyl methacrylate sulfuric acid salt, dimethylaminoethyl methacrylate hydrochloric acid salt, dimethylaminoethyl methacryloyl hydrochloric acid salt; dialkylaminoalkylacrylamides, methacrylamides and their quaternary or acid salts; acryloylamidopropyltrimethylammonium chloride, dimethylaminopropyl acrylamide, dimethylaminopropyl acrylamide methyl sulfate quaternary salt, dimethylaminopropyl acrylamide sulfuric acid salt, dimethylaminopropyl acrylamide hydrochloric acid salt, dimethylaminopropyl methacrylamide, dimethylaminopropyl methacrylamide methyl sulfate quaternary salt, dimethylaminopropyl methacrylamide sulfuric acid salt, dimethylaminopropyl methacrylamide hydrochloric acid salt, diethylaminoethylacrylate, and diethylaminoethylmethacrylate; and any combination thereof; and (iii) optionally, said one or more anionic monomers contain functional groups selected from the group consisting of carboxylic acids, sulfonic acids, a phosphonic acids, their corresponding water soluble salts, their corresponding water dispersible salts, and any combination thereof; or said one or more anionic monomers comprise acrylic acid, methacrylic acid, maleic acid, itaconic acid, vinyl sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid (AMPS), acrylamido methanesulfonic acid, acrylamido ethanesulfonic acid, 2-hydroxy-3-acrylamide propane sulfonic acid, styrene sulfonic acid, and vinyl phosphonic acid, their corresponding alkali metal, alkaline earth metal, and ammonium salts, or any combination thereof;

[0099] (iv) said at least one base-polymer comprises a neutral monomer content or an acrylamide content ranging from 1-99 wt-%, 10-90 wt-%, 20-80 wt-%, 30-80 wt-%, 40-80 wt-%, 40-60 wt-%, 40- 50 wt-%, or 50-70 wt-%; (v) said at least one base-polymer comprises a cationic monomer content ranging from 1-99 wt-%, 10-90 wt-%, 20-80 wt-%, 30-80 wt-%, 40-80 wt-%, 50-80 wt-%, 60-80 wt-%, or 50-70 wt-%; (vi) said at least one base-polymer optionally comprises an anionic monomer content ranging from 0-50% by weight; (vii) said at least one base-polymer comprises a net cationic charge ranging from 1-99 wt-%, 10-90 wt-%, 20-80 wt-%, 30-80 wt-%, 40-80 wt-%, 40-60 wt-%, 40-50 wt-%, or 50-70 wt-% , at pH 7; (viii) said at least one base-polymer comprises a weight average molecular weight ranging from 5-1000 kDa, 5-500 kDa, 5-400 kDa, 5-300 kDa, 5-250 kDa, 5-200 kDa, 5-150 kDa, 5-100 kDa, 5-80 kDa, 5-60 kDa, 5-40 kDa, 5-20 kDa, or 5-10 kDa; or (ix) any combination of (i)-(viii);

[0100] (d) comprises a glyoxakbase-polymer weight ratio of 1:99-20:80, 1:99-15:85, or 5:95-10:90 ; or (e) any combination of (a)-(d).

[0101] In some exemplary embodiments, said silicon-containing particles:

[0102] (a) comprise microparticles and / or nanoparticles; (b) are selected from the group consisting of silica; colloidal silica; aluminum modified silica, aluminum modified colloidal silica, aluminum phyllosilicates, bentonite, sodium bentonite, calcium bentonite, and montmorillonite; (c) comprise a surface area of 300-1200 m2 / g, 400-1200 m2 / g, 600-1200 m2 / g, 800-1200 m2 / g, 900-1200 m2 / g, 1000-1200 m2 / g, or 1100-1200 m2 / g; (d) act as a zeta potential modifier which decreases, renders less positive, renders negative, or renders more negative the zeta potential of said cellulosic fibers; or (e) any combination of (a)-(d).

[0103] In some exemplary embodiments of the flushable paper composition:

[0104] (a) said silicon-containing particles comprise aluminum modified colloidal silica; (b) said basepolymer comprises (i) acrylamide and any combination DADMAC, Q9, and / or MAPTAC; or (ii) acrylamide and DADMAC; (c) the flushable paper composition comprises a GPAM dosage of 0.1-40 Ib / t, 0.1-30 Ib / t, 0.1-20 Ib / t, 0.1-15 Ib / t, 0.1-10 ib / t, 0.1-8 Ib / t, 0.1-6 Ib / t, 0.1-5 Ib / t, 0.1-4 Ib / t, 0.1-3 Ib / t, 0.1-2 Ib / t, 0.1-1 Ib / t, or 0.1-0.5 Ib / t; (d) the flushable paper composition comprises a ratio by weight of said silicon-containing particles:GPAM of 30:1-1:30, 25:1-1:25, 1:20-20:1, 1:15-15:1, 1:10- 10:1, 1:8-8:1, 1:6-6:1, 1:4-4:1, 1:3-3:1 or 1:2-2:1, which is calculated as a dry weight of silicon- containing particles to dry weight of active GPAM; or (e) any combination of (a)-(d).

[0105] In another aspect, the present invention provides a method for producing a flushable paper, the method comprising

[0106] (a) contacting an aqueous fiber slurry with a glyoxalated polyacrylamide (GPAM) composition, and a silicon-containing particle composition, thereby forming a fiber stock; and (b) adding said fiber stock to the wet end of a paper machine.

[0107] In some exemplary embodiments of the method:

[0108] (i) said GPAM composition and silicon-containing particle composition are added to said aqueous fiber slurry simultaneously or sequentially in any order; and / or (ii) the method further comprises after step (b), removing sufficient water from the fiber stock to form a wet fibrous web and then pressing and drying the wet fibrous web to obtain said flushable paper.

[0109] In some exemplary embodiments of the method: (a) said aqueous fiber slurry comprises a 1stzeta potential ranging from -350 to 0 mV, -300 to 0 mV, -250 to 0 mV, -200 to 0 mV, -150 to 0 mV, - 100 to 0 mV, -80 to 0 mV, -60 to 0 mV, -40 to 0 mV, -20 to 0 mV, -12 to 0 mV, -10 to 0 mV, or -5 to 0 mV, which zeta potential ranges are typically observed for unmodified fiber slurries for use in papermaking.

[0110] In some exemplary embodiments of the method: (b) contacting said aqueous fiber slurry with said GPAM composition results in a 2ndzeta potential which (i) is increased or less negative compared to said 1stzeta potential; and / or (ii) is positive. In certain embodiments the 2ndzeta potential (i .e., after addition of GPAM) is increased by 1-500 mV, 1-400 mv, 1-300 mv, 1-200 mv, 1- 100 mv, 1-90 mv, 1-80 mv, 1-70 mv, 1-60 mv, 1-50 mv, 1-40 mv, 1-30 mv, 1-20 mv, 1-10 mv, 1-5 mv, or 1-2 mv, compared to the 1stzeta potential (i.e., the unmodified fiber slurry prior to addition of GPAM) .

[0111] In some exemplary embodiments of the method: (c) contacting said aqueous fiber slurry with said GPAM composition and said silicon-containing particle composition results in said fiber stock comprising a 3rdzeta potential which (i) is negative; (ii) is decreased, less positive, or more negative compared to said 2ndzeta potential; (iii) is equal to said 1stzeta potential; and / or (iv) ranges from - 200 to +20 mV, -200 to +10 r V, -200 to +5 mV, -200 to +0.5 mV, -200 to +0.1 mV, -200 to 0 mV, -150 to 0 mV, -100 to 0 mV, -80 to 0 mV, -60 to 0 mV, -40 to 0 mV, -20 to 0 mV, -12 to 0 mV, -10 to 0 mV, or -5 to 0 mV; or (d) any combination of (a)-(c).

[0112] In some exemplary embodiments of the method said flushable paper comprises:

[0113] (a) a tissue paper, a lightweight paper, a light crepe paper, a paper for sanitary use, a bathroom tissue, a facial tissue, a napkin, a wipe, or a special sanitary paper for medical applications; (b) a single ply grammage of less than 35 g / m2, 5-35 g / m2, 5-30, 5-25 g / m2, 5-20 g / m2, 5-15 g / m2, or 5-10 g / m2; (c) an increased GPAM content compared to an equivalent flushable paper composition without said silicon-containing particles; (d) an increased initial wet tensile strength compared to an equivalent flushable paper composition without said silicon-containing particles; (e) an increased wet strength decay compared to an equivalent flushable paper composition comprising an anionic polymer or anionic polyacrylamide (APAM) in place of said silicon-containing particles; or (f) any combination of (a)-(e).

[0114] In some exemplary embodiments of the method said aqueous fiber slurry:

[0115] (a) comprises virgin fibers, recycled fibers, or a mixture of virgin and recycled fibers; (b) comprises cellulosic or lignocellulosic fibers selected from the group consisting of softwood fibers, hardwood fibers, recycled fibers, refined fibers, mill broke fibers, coated broke fibers, non-wood fibers, or any combination thereof; (c) comprises pulp, Kraft pulp, unbleached Kraft pulp, bleached pulp, unbleached pulp, process water from pulp, paper, and / or board production, neutral sulfite semi chemical (NSSC) pulp, mechanical pulp, non-wood pulp, straw pulp, wheat pulp, or any combination thereof; (d) comprises a mixture of a softwood virgin Kraft pulp and a hardwood virgin bleached Kraft pulp, optionally comprising a ratio by weight of hardwood pulp to softwood pulp of100:0; 95:5-5:95, 90:10-10:90, 80:20-20:80, 60:40-40:60; 50:50; 40:60; 30:70; 20:80; 10:90, 5:95, or 0:100; (e) optionally comprises a thick stock, which is diluted to form a thin stock; (f) comprises a freeness of 400-600 CSF, 450-550 CSF, or 450-500 CSF; (g) comprises a consistency of 0.3-0.8 wt%, 0.4-0.7 wt%, or 0.45-0.62 wt%, wherein consistency is defined as weight % of total solids in the fiber slurry; (h) comprises a pH of 5-8, 5.5-7.5, or 6-7; (I) comprises a net anionic charge; or (j) any combination of (a)-(i).

[0116] In some exemplary embodiments of the method said GPAM composition:

[0117] (a) comprises an aqueous solution or emulsion comprising a wt% of GPAM solids ranging from 1-20 wt%, 1-15 wt%, 1-12 wt%, 1-11 wt%, 1-10 wt%, or 2-5 wt%; (b) comprises a viscosity of 10-100 cPs, 10-80 cPs, 10-60 cPs, 10-40 cPs, 10-20 cPs, or 10-15 cPs as measured by a Brookfield LV viscometer using a #1 spindle at 60 rpm and 25 °C; (c) comprises a net cationic charge; (d) comprises a cationic charge density of at least +0.5 mEq / g, 0.5-5 mEq / g, 0.5-4 mEq / g, 0.5-3 mEq / g, 0.5-2 mEq / g, or 0.5-1 mEq / g at pH 7.0; (e) comprises at least one base-polymer, which is glyoxalated, wherein said base-polymer comprises one or more acrylamide based co-polymers comprising one or more neutral monomers, one or more cationic monomers, and optionally one or more anionic monomers, wherein:

[0118] (i) said one or more neutral monomers are selected from the group consisting of primary amide-containing monomers, acrylamide, methacrylamide, ethyl acrylamide, crotonamide, N-methyl acrylamide, N-butyl acrylamide, N-ethyl methacrylamide, and any combination thereof; (ii) said one or more cationic monomers are selected from the group consisting of acryloyloxyethyltrimethyl ammonium chloride (Q.9), methacryloyloxyethyltrimethylammonium chloride (MAETAC), methacrylamidopropyltrimethylammonium chloride (MAPTAC), acrylamidopropyltrimethylammonium chloride (APTAC), methacryloyloxyethyldimethylammonium sulfate, diallyldialkylammonium halides diallyldimethylammonium chloride (DADMAC), diallyldiethylammonium chloride; dialkylaminoalkyl acrylates, dialkylaminoalkyl methacrylates and their quaternary or acid salts; dimethylaminoethyl acrylate (DMAEA), dimethylaminoethyl methacrylate (DMAEMA), dimethylaminoethyl acrylate methyl chloride quaternary salt, dimethylaminoethyl acrylate methyl sulfate quaternary salt, dimethylaminoethyl acrylate benzyl chloride quaternary salt, dimethylaminoethyl acrylate sulfuric acid salt, dimethylaminoethyl acrylate hydrochloric acid salt, diethylaminoethyl acrylate methyl chloride quaternary salt, dimethylaminoethyl methacrylate methyl chloride quaternary salt, dimethylaminoethyl methacrylate methyl sulfate quaternary salt, dimethylaminoethyl methacrylate benzyl chloride quaternary salt, dimethylaminoethyl methacrylate sulfuric acid salt, dimethylaminoethyl methacrylate hydrochloric acid salt, dimethylaminoethyl methacryloyl hydrochloric acid salt;dialkylaminoalkylacrylamides, methacrylamides and their quaternary or acid salts; acryloylamidopropyltrimethylammonium chloride, dimethylaminopropyl acrylamide, dimethylaminopropyl acrylamide methyl sulfate quaternary salt, dimethylaminopropyl acrylamide sulfuric acid salt, dimethylaminopropyl acrylamide hydrochloric acid salt, dimethylaminopropyl methacrylamide, dimethylaminopropyl methacrylamide methyl sulfate quaternary salt, dimethylaminopropyl methacrylamide sulfuric acid salt, dimethylaminopropyl methacrylamide hydrochloric acid salt, diethylaminoethylacrylate, and diethylaminoethylmethacrylate; and any combination thereof; (ill) optionally, said one or more anionic monomers contain functional groups selected from the group consisting of carboxylic acids, sulfonic acids, a phosphonic acids, their corresponding water soluble salts, their corresponding water dispersible salts, and any combination thereof; or said one or more anionic monomers comprise acrylic acid, methacrylic acid, maleic acid, itaconic acid, vinyl sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid (AMPS), acrylamido methanesulfonic acid, acrylamido ethanesulfonic acid, 2-hydroxy-3-acrylamide propane sulfonic acid, styrene sulfonic acid, and vinyl phosphonic acid, their corresponding alkali metal, alkaline earth metal, and ammonium salts, or any combination thereof; (iv) said at least one base-polymer comprises a neutral monomer content or an acrylamide content ranging from 1-99 wt-%, 10-90 wt-%, 20-80 wt-%, 30-80 wt-%, 40-80 wt-%, 40-60 wt-%, 40-50 wt-%, or 50-70 wt-%; (v) said at least one base-polymer comprises a cationic monomer content ranging from 1-99 wt-%, 10-90 wt-%, 20- 80 wt-%, 30-80 wt-%, 40-80 wt-%, 50-80 wt-%, 60-80 wt-%, or 50-70 wt-%; (vi) said at least one base- polymer optionally comprises an anionic monomer content ranging from 0-50% by weight; (vii) said at least one base-polymer comprises a net cationic charge ranging from 1-99 wt-%, 10-90 wt-%, 20- 80 wt-%, 30-80 wt-%, 40-80 wt-%, 40-60 wt-%, 40-50 wt-%, or 50-70 wt-% , at pH 7; (viii) said at least one base-polymer comprises a weight average molecular weight ranging from 5-1000 kDa, 5-500 kDa, 5-400 kDa, 5-300 kDa, 5-250 kDa, 5-200 kDa, 5-150 kDa, 5-100 kDa, 5-80 kDa, 5-60 kDa, 5-40 kDa, 5-20 kDa, or 5-10 kDa; or (ix) any combination of (i)-(viii);

[0119] (f) comprises a glyoxal.base-polymer weight ratio of 1:99-20:80, 1:99-15:85, or 5:95-10:90; or (g) any combination of (a)-(f).

[0120] In some exemplary embodiments of the method said silicon-containing particle composition:

[0121] (a) comprises one or more silicon-containing particles selected from the group consisting of silica; colloidal silica; aluminum modified silica, aluminum modified colloidal silica, aluminum phyllosilicates, bentonite, sodium bentonite, calcium bentonite, and montmorillonite, wherein said silicon-containing particles comprise microparticles and / or nanoparticles; (b) comprises a liquid dispersion comprising a dispersed phase comprising said one or more silicon-containing particles dispersed in water and further comprising a total solid content of 5-25 wt%, 5-20 wt%, 5-15 wt%, 5-10 wt%, 5-8 wt% or 5-7 wt%; (c) comprises a surface area of 300-1200 m2 / g, 400-1200 m2 / g, 600- 1200 m2 / g, 800-1200 m2 / g, 900-1200 m2 / g, 1000-1200 m2 / g, or 1100-1200 m2 / g; (d) comprises an S-value of 8-80%, 8-60%, 8-40%, 8-20%, 8-16%, 8-14%, 8-12%, or 8-10%, wherein S-value is the wt-% of SiO2 in the dispersed phase of said liquid dispersion; (e) acts as a zeta potential modifier which decreases, renders less positive, renders negative, or renders more negative the zeta potential of said cellulosic fibers; or (f) any combination of (a)-(e).

[0122] In some exemplary embodiments of the method:

[0123] (a) said aqueous fiber slurry comprises a dosage of said GPAM composition ranging from 0.1- 40 Ib / t, 0.1-30 Ib / t, 0.1-20 Ib / t, 0.1-15 Ib / t, 0.1-10 Ib / t, 0.1-8 Ib / t, 0.1-6 Ib / t, 0.1-5 Ib / t, 0.1-4 Ib / t, 0.1- 3 Ib / t, 0.1-2 Ib / t, 0.1-1 Ib / t, or 0.1-0.5 Ib / t; (b) said fiber stock comprises a dosage of said silicon- containing particle composition that (i) is sufficient to form a ratio by weight of said silicon- containing partides:GPAM of 30:1-1:30, 25:1-1:25, 1:20-20:1, 1:15-15:1, 1:10-10:1, 1:8-8:1, 1:6-6:1, 1:4-4:1, 1:3-3:1 or 1:2-2:1, calculated as a dry weight of silicon-containing particles to dry weight of active GPAM; and (ii) is sufficient to form said 3rd zeta potential in the fiber stock; (c) the method further comprises increasing the dosage of said silicon-containing particle composition until said 3rd zeta potential is observed in the fiber stock; (d) said base-polymer of said GPAM comprises (i) acrylamide and any combination DADMAC, Q9, and / or MAPTAC; or (ii) acrylamide and DADMAC; (e) said silicon-containing particles comprise aluminum modified colloidal silica; or (f) any combination of (a)-(e).

[0124] In another aspect, the present invention provides a fiber stock composition comprising:

[0125] (a) an aqueous suspension comprising cellulosic fibers, at least one glyoxalated polyacrylamide (GPAM), and one or more silicon-containing particles according to any of the foregoing; or (b) an aqueous suspension comprising an aqueous fiber slurry, a glyoxalated polyacrylamide (GPAM) composition, and a silicon-containing particle composition obtainable by a method according to any of the foregoing.

[0126] Having described the invention in detail the invention is further described in the following examples.EXAMPLES

[0127] The examples provided herein are for illustrative purposes so that the invention may be more fully understood. These examples should not be construed as limiting the invention in any way.Example 1: Evaluation of GPAM and Silica as Temporary Wet Strength Aids

[0128] Handsheets containing the inventive temporary wet strength aids (GPAM + silica) were prepared and evaluated against handsheets containing GPAM and a conventionally used anionic polymer.

[0129] Preparation of Handsheets Containing Temporary Wet Strength Aids

[0130] GPAM Composition

[0131] A GPAM composition was prepared by reacting glyoxal and a cationic polyacrylamide base polymer with a weight average molecular weight of 10 kDa. The GPAM composition was prepared according to U.S. Pat. Nos. 3556932 and 8435382, which are hereby incorporated by reference in their entirety. The finished GPAM composition had a charge density of +1.8 meq / g, a solid content of 11 %, and a viscosity value of 20 cPs as measured by a Brookfield LV viscometer using spindle #1 at 60 rpm at 25 °C.

[0132] Aluminum Modified Silica Composition

[0133] An aluminum modified silica composition was prepared by reacting colloidal silica with sodium aluminate according to U.S. Pat. No. 5643414, which is hereby incorporated by reference in its entirety. The aluminum modified silica composition was formulated as a colloidal dispersion in water with a solid content of 7.4 wt%, an S-value of 14%, and a surface area of 1100 m2 / g.

[0134] Bentonite Clay

[0135] Bentonite clay was applied with cationic GPAM to study their effect on paper wet strength. The commercial bentonite clay product, FennoSol BP GT, was from Kemira Chemicals. The bentonite can be any of the materials commercially referred to as bentonites or as bentonite-type clays, i.e., anionic swelling clays such as sepiolite, attapulgite or, preferably, montmorillonite. The montmorillonites are preferred.

[0136] Anionic Polymer

[0137] A conventionally used anionic polymer (e.g., an anionic polyacrylamide (APAM)) was prepared by copolymerizing acrylamide and sodium acrylate according to U.S. Pat. No. 6939443, which is hereby incorporated by reference in its entirety. The finished APAM had an anionic charge density of -2.9 mEq / g and a weight average molecular weight of 250 kDa. Polymer weight average molecular weight was determined using gel permeation chromatography. Molecular weight calculation was carried out using a calibration based on polyethylene oxide standards.

[0138] Handsheet Preparation

[0139] Handsheets were prepared with different dosages of GPAM, GPAM + APAM, or GPAM + aluminum modified silica to evaluate their effectiveness of the inventive temporary wet strength aid (GPAM + silica) for flushable paper products. For the present invention, a high initial wet strength and a high wet strength decay percentage is desirable.

[0140] Flushable tissue paper is typically lightweight paper or lightweight crepe paper. For testing purposes, the prepared handsheets were not creped and contained higher grammages (grams per square meter, g / m2, GSM) than is typical for flushable tissue.

[0141] For handsheet preparation, a thick stock containing 50% softwood virgin bleached Kraft pulp and 50% hardwood virgin bleached Kraft pulp was prepared. Both the hardwood pulp and the softwood pulp were refined to between 450-550 CSF before being blended together. The final freeness of the combined pulp was 450-500 CSF.

[0142] The thick stock was diluted with synthetic water, which contained 150 ppm of sulfate ions, 35 ppm of calcium ions, and a conductivity of 550 to 600 pS / cm. Synthetic water was added to the thick stock to form a thin stock with a consistency (i.e., wt-% dry solids in the stock) of 0.45-0.62 wt%. The pH of the thin stock was adjusted to 6.0.

[0143] Handsheets (approximately 80 GSM) were prepared according to the standard handsheet protocol of the Dynamic Sheet Former (DSF). GPAM composition (3 Ib / t or 6 Ib / t) was first added to the thin stock under agitation. After 30 seconds of mixing, either aluminum modified silica composition (0.5 Ib / t, 1 Ib / t, or 2 Ib / t) or APAM (0.5 Ib / t, 1 Ib / t, or 2 Ib / t) was added to the thin stock.

[0144] Zeta potential of untreated and treated thin stock samples was measured using a fiber potential analyzer (FPA Touch from AFG ANALYTIC GMBH). Dosages and zeta potential results are shown in Table 1.After another 30 seconds of mixing, the treated thin stock was added to the DSF to prepare 80 GSM sheets. The formed sheet was then pressed with a pneumatic roll press (15 psi) and dried with a rotary drum dryer (60-sec drying time at 240 °F). Dried sheets were then cured in a forced air oven at 105 °C for 5 minutes.

[0145] Table 1: Effects of colloidal silica on zeta potential and temporary wet strength of GPAM treated handsheets.*IWT-lnitial Wet Tensile Strength; PWT-Permanent Wet Tensile Strength; Wet Strength Decay = 100*(l- PWT / IWT)

[0146] Evaluation of Handsheets

[0147] Initial Wet Tensile (IWT) Strength Testing

[0148] Initial wet tensile strength (IWT) of Handsheets 1-10 was determined immediately after deionized water was brushed onto both sides of a handsheet sample. Wet tensile breaking strength was determined according to TAPPI TEST Method T456. Eight measurements were taken per condition on cross directions using a Thwing-Albert QC3A tensile tester. Results were normalized to 80 GSM basis weight. IWT is useful for evaluating the performance characteristics of tissue products, paper towels, bags and other papers subjected to stress or used while wet. IWT results are shown in Table 1.

[0149] Permanent Wet Tensile (PWT) Strength Testing (After 30 Minute Soak)

[0150] Permanent wet tensile (PWT) strength of Handsheets 1-10 was measured by wetting a sample handsheet strip in deionized water for 30 minutes, removing excess water from the specimen, and then applying a constant rate of elongation to the specimen and recording the force per unit width required to break the specimen. The maximum cross-directional tensile stress developed in the test specimen before rupture is recorded as tensile strength. This procedure references TAPPI Test Method T576. Eight measurements were taken per condition using Thwing-Albert QC3A tensile tester. Results were normalized to 80 GSM basis weight. PWT results are shown in Table 1.

[0151] Wet Strength Decay

[0152] Wet strength decay of Handsheets 1-10 was calculated using the following equation: Wet Strength Decay = 100*(l-PWT / IWT). Wet strength decay results are shown in Table 1.

[0153] Results

[0154] For the present invention, a thick stock having a zeta potential that is approximately equal to the natural zeta potential of unmodified fibers (e.g., about -200 to -10 mV), is desirable for paper machine runnability. Handsheets having a high initial wet strength and a high wet strength decay percentage is also desirable. These strength properties indicate that the added temporary wet strength aid is suitable for flushable paper products.

[0155] Results from Table 1 indicate that addition of GPAM to the thin stock increased the zeta potential of the stock in a dose dependent manner. The zeta potential of untreated thin stock was - 40 mV. Addition of 3 I b / t GPAM rendered the zeta potential less negative, which is undesirable. Addition of 6 Ib / t of GPAM changed pulp zeta potential from -40 mV to +5.6 mV, resulting in a very undesirable positive zeta potential. These results provide proof that excess GPAM can convert pulp zeta potential from net anionic to net cationic, which is known to cause paper machine runnability issues.

[0156] Results further indicate that addition of APAM to the GPAM-treated thin stock effectively lowered (i.e., rendered more negative) the zeta potential and increased the IWT of handsheets. However, addition of APAM also considerably lowered wet strength decay percentage of the handsheets, which is undesirable for flushable products. These results provide proof of the negative impact of anionic polyacrylamide (APAM) on wet strength decay percentage of lab prepared handsheets treated with GPAM.

[0157] Results further indicate that addition of colloidal silica or bentonite clay to the GPAM treated thin stock effectively lowered (i.e., rendered more negative) the zeta potential and increased the IWT of handsheets.

[0158] It was surprisingly found that handsheets treated with aluminum modified colloidal silica + GPAM or bentonite + GPAM displayed increased wet strength decay compared to the APAM + GPAM treated handsheets. Handsheets treated with GPAM + silica or GPAM + bentonite, displayed wet strength decays that were nearly equivalent to the GPAM treated control Handsheets 1 and 6.

[0159] Silica and bentonite were surprisingly effective at neutralizing the positive charge of GPAM- modified fibers without increasing the PWT of the resulting handsheets. Without being bound to theory, it can be rationalized that colloidal silica or bentonite outperformed APAM due to the presence of silanol (SiOH) groups on the silica and bentonite, which can be deprotonated to bear negative charge (SiOj. It is postulated that this SiO" group can participate in a bonding arrangement with cationic GPAM, lowering the overall zeta potential of GPAM treated cellulosic suspension. This bonding arrangement also seems to be more readily hydrolyzed in the presence of water, allowing for increased wet strength decay of aluminum modified colloidal silica + GPAM and bentonite + GPAM treated handsheets compared to the APAM + GPAM treated handsheets. This phenomena allows colloidal silica and bentonite to effectively improve charge balance of the GPAM treated thin stock without increasing the PWT of the resulting handsheets.

[0160] These results demonstrate the surprising benefits of adding colloidal silica or bentonite for lowering both thin stock zeta potential and improving handsheet wet strength decay. These results provide proof of the benefits of adding colloidal silica or bentonite in place of APAM for increasing wet strength decay percentage of lab prepared handsheets treated with GPAM.

[0161] These results further provide proof of concept that the inventive temporary wet strength aids (e.g., GPAM + silica) are suitable for improving the zeta potential of fiber stock and for use as temporary wet strength aids for production of flushable paper products.

Claims

1. CLAIMSWhat is claimed is:

1. A flushable paper composition comprising:(a) cellulosic fibers;(b) at least one glyoxalated polyacrylamide (GPAM); and(c) one or more silicon-containing particles.

2. The flushable paper composition of claim 1, which comprises:(a) a tissue paper, a lightweight paper, a light crepe paper, a paper for sanitary use, a bathroom tissue, a facial tissue, a napkin, a wipe, or a special sanitary paper for medical applications;(b) a single ply grammage of less than 35 g / m2, 5-35 g / m2, 5-30, 5-25 g / m2, 5-20 g / m2, 5-15 g / m2, or 5-10 g / m2;(c) an increased GPAM content compared to an equivalent flushable paper composition without said silicon-containing particles;(d) an increased initial wet tensile strength compared to an equivalent flushable paper composition without said silicon-containing particles;(e) an increased wet strength decay compared to an equivalent flushable paper composition comprising an anionic polymer or anionic polyacrylamide (APAM) in place of said silicon- containing particles; or(f) any combination of (a)-(e).

3. The flushable paper composition of claim 1 or 2, wherein said cellulosic fibers:(a) comprise virgin fibers, recycled fibers, or a mixture of virgin and recycled fibers;(b) comprise cellulosic or lignocellulosic fibers selected from the group consisting of softwood fibers, hardwood fibers, recycled fibers, refined fibers, mill broke fibers, coated broke fibers, non-wood fibers, or any combination thereof;(c) originate from pulp, Kraft pulp, unbleached Kraft pulp, bleached pulp, unbleached pulp, process water from pulp, paper, and / or board production, neutral sulfite semi chemical (NSSC) pulp, mechanical pulp, non-wood pulp, straw pulp, wheat pulp, or any combination thereof;(d) comprise a mixture of a softwood virgin Kraft pulp and a hardwood virgin bleached Kraftpulp, optionally comprising a ratio by weight of hardwood pulp to softwood pulp of 100:0; 95:5-5:95, 90:10-10:90, 80:20-20:80, 60:40-40:60; 50:50; 40:60; 30:70; 20:80;10:90, 5:95, or 0:100;(e) when formulated as an aqueous fiber slurry, comprise a zeta potential ranging from -350 to 0 mV, -300 to 0 mV, -250 to 0 mV, -200 to 0 mV, -150 to 0 mV, -100 to 0 mV, -80 to 0 mV, -60 to 0 mV, -40 to 0 mV, -20 to 0 mV, -12 to 0 mV, -10 to 0 mV, or -5 to 0 mV; or(f) any combination of (a)-(e).

4. The flushable paper composition of claim 1, 2, or 3, wherein said glyoxalated polyacrylamide (GPAM):(a) comprises a net cationic charge;(b) comprises a cationic charge density of at least +0.5 mEq / g, 0.5-5 mEq / g, 0.5-4 mEq / g, 0.5-3 mEq / g, 0.5-2 mEq / g, or 0.5-1 mEq / g at pH 7.0;(c) comprises at least one base-polymer, which is glyoxalated, wherein said base-polymer comprises one or more acrylamide based co-polymers comprising one or more neutral monomers, one or more cationic monomers, and optionally one or more anionic monomers, wherein:(i) said one or more neutral monomers are selected from the group consisting of primary amide-containing monomers, acrylamide, methacrylamide, ethyl acrylamide, crotonamide, N-methyl acrylamide, N-butyl acrylamide, N-ethyl methacrylamide, and any combination thereof;(ii) said one or more cationic monomers are selected from the group consisting of acryloyloxyethyltrimethyl ammonium chloride (Q.9), methacryloyloxyethyltrimethylammonium chloride (MAETAC), methacrylamidopropyltrimethylammonium chloride (MAPTAC), acrylamidopropyltrimethylammonium chloride (APTAC), methacryloyloxyethyldimethylammonium sulfate, diallyldialkylammonium halides diallyldimethylammonium chloride (DADMAC), diallyldiethylammonium chloride; dialkylaminoalkyl acrylates, dialkylaminoalkyl methacrylates and their quaternary or acid salts; dimethylaminoethyl acrylate (DMAEA), dimethylaminoethyl methacrylate (DMAEMA), dimethylaminoethyl acrylate methyl chloride quaternary salt, dimethylaminoethyl acrylate methyl sulfate quaternary salt, dimethylaminoethyl acrylate benzyl chloride quaternary salt, dimethylaminoethylacrylate sulfuric acid salt, dimethylaminoethyl acrylate hydrochloric acid salt, diethylaminoethyl acrylate methyl chloride quaternary salt, dimethylaminoethyl methacrylate methyl chloride quaternary salt, dimethylaminoethyl methacrylate methyl sulfate quaternary salt, dimethylaminoethyl methacrylate benzyl chloride quaternary salt, dimethylaminoethyl methacrylate sulfuric acid salt, dimethylaminoethyl methacrylate hydrochloric acid salt, dimethylaminoethyl methacryloyl hydrochloric acid salt; dialkylaminoalkylacrylamides, methacrylamides and their quaternary or acid salts; acryloylamidopropyltrimethylammonium chloride, dimethylaminopropyl acrylamide, dimethylaminopropyl acrylamide methyl sulfate quaternary salt, dimethylaminopropyl acrylamide sulfuric acid salt, dimethylaminopropyl acrylamide hydrochloric acid salt, dimethylaminopropyl methacrylamide, dimethylaminopropyl methacrylamide methyl sulfate quaternary salt, dimethylaminopropyl methacrylamide sulfuric acid salt, dimethylaminopropyl methacrylamide hydrochloric acid salt, diethylaminoethylacrylate, and diethylaminoethylmethacrylate; and any combination thereof;(iii) optionally, said one or more anionic monomers contain functional groups selected from the group consisting of carboxylic acids, sulfonic acids, a phosphonic acids, their corresponding water soluble salts, their corresponding water dispersible salts, and any combination thereof; or said one or more anionic monomers comprise acrylic acid, methacrylic acid, maleic acid, itaconic acid, vinyl sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid (AMPS), acrylamido methanesulfonic acid, acrylamido ethanesulfonic acid, 2-hydroxy-3-acrylamide propane sulfonic acid, styrene sulfonic acid, and vinyl phosphonic acid, their corresponding alkali metal, alkaline earth metal, and ammonium salts, or any combination thereof;(iv) said at least one base-polymer comprises a neutral monomer content or an acrylamide content ranging from 1-99 wt-%, 10-90 wt-%, 20-80 wt-%, 30-80 wt-%, 40-80 wt-%, 40-60 wt-%, 40-50 wt-%, or 50-70 wt-%;(v) said at least one base-polymer comprises a cationic monomer content ranging from 1-99 wt-%, 10-90 wt-%, 20-80 wt-%, 30-80 wt-%, 40-80 wt-%, 50-80 wt-%, 60- 80 wt-%, or 50-70 wt-%;(vi) said at least one base-polymer optionally comprises an anionic monomer contentranging from 0-50% by weight;(vii) said at least one base-polymer comprises a net cationic charge ranging from 1-99 wt-%, 10-90 wt-%, 20-80 Wt-%, 30-80 wt-%, 40-80 wt-%, 40-60 wt-%, 40-50 wt-%, or 50-70 wt-%, at pH 7;(viii) said at least one base-polymer comprises a weight average molecular weight ranging from 5-1000 kDa, 5-500 kDa, 5-400 kDa, 5-300 kDa, 5-250 kDa, 5-200 kDa, 5-150 kDa, 5-100 kDa, 5-80 kDa, 5-60 kDa, 5-40 kDa, 5-20 kDa, or 5-10 kDa; or(ix) any combination of (i)-(viii);(d) comprises a glyoxakbase-polymer weight ratio of 1:99-20:80, 1:99-15:85, or 5:95-10:90; or(e) any combination of (a)-(d).

5. The flushable paper composition of any one of the foregoing claims, wherein said silicon- containing particles:(a) comprise microparticles and / or nanoparticles;(b) are selected from the group consisting of silica, colloidal silica, aluminum modified silica, aluminum modified colloidal silica, aluminum phyllosilicates, bentonite, sodium bentonite, calcium bentonite, and montmorillonite;(c) comprise a surface area of 300-1200 m2 / g, 400-1200 m2 / g, 600-1200 m2 / g, 800-1200 m2 / g, 900-1200 m2 / g, 1000-1200 m2 / g, or 1100-1200 m2 / g;(d) act as a zeta potential modifier which decreases, renders negative, or renders more negative the zeta potential of said cellulosic fibers; or(e) any combination of (a)-(d).

6. The flushable paper composition of any one of the foregoing claims, wherein:(a) said silicon-containing particles comprise aluminum modified colloidal silica;(b) said base-polymer comprises (i) acrylamide and any combination DADMAC, Q9, and / or MAPTAC; or (ii) acrylamide and DADMAC;(c) the flushable paper composition comprises a GPAM dosage of 0.1-40 Ib / t, 0.1-30 Ib / t, 0.1-20 Ib / t, 0.1-15 Ib / t, 0.1-10 Ib / t, 0.1-8 Ib / t, 0.1-6 Ib / t, 0.1-5 Ib / t, 0.1-4 Ib / t, 0.1-3 Ib / t, 0.1-2 Ib / t, 0.1-1 Ib / t, or 0.1-0.5 Ib / t;(d) the flushable paper composition comprises a ratio by weight of said silicon-containingparticles:GPAM of 30:1-1:30, 25:1-1:25, 1:20-20:1, 1:15-15:1, 1:10-10:1, 1:8-8:1, 1:6-6:1, 1:4-4:1, 1:3-3:1 or 1:2-2:1, which is calculated as a dry weight of silicon-containing particles to dry weight of active GPAM; or(e) any combination of (a)-(d).

7. A method for producing a flushable paper, the method comprising(a) contacting an aqueous fiber slurry with a glyoxalated polyacrylamide (GPAM) composition, and a silicon-containing particle composition, thereby forming a fiber stock; and(b) adding said fiber stock to the wet end of a paper machine.

8. The method of claim 7, wherein:(i) said GPAM composition and silicon-containing particle composition are added to said aqueous fiber slurry simultaneously or sequentially in any order; and / or(ii) the method further comprises after step (b), removing sufficient water from the fiber stock to form a wet fibrous web and then pressing and drying the wet fibrous web to obtain said flushable paper.

9. The method of claim 7 or 8, wherein:(a) said aqueous fiber slurry comprises a 1stzeta potential ranging from -350 to 0 mV, -300 to 0 mV, -250 to 0 mV, -200 to 0 mV, -150 to 0 mV, -100 to 0 mV, -80 to 0 mV, -60 to 0 mV, -40 to 0 mV, -20 to 0 mV, -12 to 0 mV, -10 to 0 mV, or -5 to 0 mV;(b) contacting said aqueous fiber slurry with said GPAM composition results in a 2ndzeta potential which (i) is increased or less negative compared to said 1stzeta potential; and / or (ii) is positive;(c) contacting said aqueous fiber slurry with said GPAM composition and said silicon- containing particle composition results in said fiber stock comprising a 3rdzeta potential which (i) is negative; (ii) is decreased or more negative compared to said 2ndzeta potential; (Hi) is equal to said 1stzeta potential; and / or (iv) ranges from -200 to +20 mV, - 200 to +10 mV, -200 to +5 mV, -200 to +0.5 mV, -200 to +0.1 mV, -200 to 0 mV, -150 to 0 mV, -100 to 0 mV, -80 to 0 mV, -60 to 0 mV, -40 to 0 mV, -20 to 0 mV, -12 to 0 mV, -10 to 0 mV, or -5 to 0 mV; or(d) any combination of (a)-(c).

10. The method of claim 7, 8, or 9, wherein said flushable paper comprises:(a) a tissue paper, a lightweight paper, a light crepe paper, a paper for sanitary use, a bathroom tissue, a facial tissue, a napkin, a wipe, or a special sanitary paper for medical applications;(b) a single ply grammage of less than 35 g / m2, 5-35 g / m2, 5-30, 5-25 g / m2, 5-20 g / m2, 5-15 g / m2, or 5-10 g / m2;(c) an increased GPAM content compared to an equivalent flushable paper composition without said silicon-containing particles;(d) an increased initial wet tensile strength compared to an equivalent flushable paper composition without said silicon-containing particles;(e) an increased wet strength decay compared to an equivalent flushable paper composition comprising an anionic polymer or anionic polyacrylamide (APAM) in place of said silicon- containing particles; or(f) any combination of (a)-(e).

11. The method of any one of claims 7-10, wherein said aqueous fiber slurry:(a) comprises virgin fibers, recycled fibers, or a mixture of virgin and recycled fibers;(b) comprises cellulosic or lignocellulosic fibers selected from the group consisting of softwood fibers, hardwood fibers, recycled fibers, refined fibers, mill broke fibers, coated broke fibers, non-wood fibers, or any combination thereof;(c) comprises pulp, Kraft pulp, unbleached Kraft pulp, bleached pulp, unbleached pulp, process water from pulp, paper, and / or board production, neutral sulfite semi chemical (NSSC) pulp, mechanical pulp, non-wood pulp, straw pulp, wheat pulp, or any combination thereof;(d) comprises a mixture of a softwood virgin Kraft pulp and a hardwood virgin bleached Kraft pulp, optionally comprising a ratio by weight of hardwood pulp to softwood pulp of 100:0; 95:5-5:95, 90:10-10:90, 80:20-20:80, 60:40-40:60; 50:50; 40:60; 30:70; 20:80; 10:90, 5:95, or 0:100;(e) optionally comprises a thick stock, which is diluted to form a thin stock;(f) comprises a freeness of 400-600 CSF, 450-550 CSF, or 450-500 CSF;(g) comprises a consistency of 0.3-0.8 wt%, 0.4-0.7 wt%, or 0.45-0.62 wt%, wherein consistency is defined as weight % of total solids in the fiber slurry;(h) comprises a pH of 5-8, 5.5-7.5, or 6-7;(i) comprises a net anionic charge; or(j) any combination of (a)-(i).

12. The method of any one of claims 7-11, wherein said GPAM composition:(a) comprises an aqueous solution or emulsion comprising a wt% of GPAM solids ranging from 1-20 wt%, 1-15 wt%, 1-12 wt%, 1-11 wt%, 1-10 wt%, or 2-5 wt%;(b) comprises a viscosity of 10-100 cPs, 10-80 cPs, 10-60 cPs, 10-40 cPs, 10-20 cPs, or 10-15 cPs as measured by a Brookfield LV viscometer using a #1 spindle at 60 rprri and 25 °C;(c) comprises a net cationic charge;(d) comprises a cationic charge density of at least +0.5 mEq / g, 0.5-5 mEq / g, 0.5-4 mEq / g, 0.5-3 mEq / g, 0.5-2 mEq / g, or 0.5-1 mEq / g at pH 7.0;(e) comprises at least one base-polymer, which is glyoxalated, wherein said base-polymer comprises one or more acrylamide based co-polymers comprising one or more neutral monomers, one or more cationic monomers, and optionally one or more anionic monomers, wherein:(i) said one or more neutral monomers are selected from the group consisting of primary amide-containing monomers, acrylamide, methacrylamide, ethyl acrylamide, crotonamide, N-methyl acrylamide, N-butyl acrylamide, N-ethyl methacrylamide, and any combination thereof;(ii) said one or more cationic monomers are selected from the group consisting of acryloyloxyethyltrimethyl ammonium chloride (Q9), methacryloyloxyethyltrimethylammonium chloride (MAETAC), methacrylamidopropyltrimethylammonium chloride (MAPTAC), acrylamidopropyltrimethylammonium chloride (APTAC), methacryloyloxyethyldimethylammonium sulfate, diallyldialkylammonium halides diallyldimethylammonium chloride (DADMAC), diallyldiethylammonium chloride; dialkylaminoalkyl acrylates, dialkylaminoalkyl methacrylates and their quaternary or acid salts; dimethylaminoethyl acrylate (DMAEA), dimethylaminoethyl methacrylate (DMAEMA), dimethylaminoethyl acrylate methyl chloride quaternary salt, dimethylaminoethyl acrylate methyl sulfate quaternary salt, dimethylaminoethyl acrylate benzyl chloride quaternary salt, dimethylaminoethyl acrylate sulfuric acid salt, dimethylaminoethyl acrylate hydrochloric acid salt,diethylaminoethyl acrylate methyl chloride quaternary salt, dimethylaminoethyl methacrylate methyl chloride quaternary salt, dimethylaminoethyl methacrylate methyl sulfate quaternary salt, dimethylaminoethyl methacrylate benzyl chloride quaternary salt, dimethylaminoethyl methacrylate sulfuric acid salt, dimethylaminoethyl methacrylate hydrochloric acid salt, dimethylaminoethyl methacryloyl hydrochloric acid salt; dialkylaminoalkylacrylamides, methacrylamides and their quaternary or acid salts; acryloylamidopropyltrimethylammonium chloride, dimethylaminopropyl acrylamide, dimethylaminopropyl acrylamide methyl sulfate quaternary salt, dimethylaminopropyl acrylamide sulfuric acid salt, dimethylaminopropyl acrylamide hydrochloric acid salt, dimethylaminopropyl methacrylamide, dimethylaminopropyl methacrylamide methyl sulfate quaternary salt, dimethylaminopropyl methacrylamide sulfuric acid salt, dimethylaminopropyl methacrylamide hydrochloric acid salt, diethylaminoethylacrylate, and diethylaminoethylmethacrylate; and any combination thereof;(iii) optionally, said one or more anionic monomers contain functional groups selected from the group consisting of carboxylic acids, sulfonic acids, a phosphonic acids, their corresponding water soluble salts, their corresponding water dispersible salts, and any combination thereof; or said one or more anionic monomers comprise acrylic acid, methacrylic acid, maleic acid, itaconic acid, vinyl sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid (AMPS), acrylamido methanesulfonic acid, acrylamido ethanesulfonic acid, 2-hydroxy-3-acrylamide propane sulfonic acid, styrene sulfonic acid, and vinyl phosphonic acid, their corresponding alkali metal, alkaline earth metal, and ammonium salts, or any combination thereof;(iv) said at least one base-polymer comprises a neutral monomer content or an acrylamide content ranging from 1-99 wt-%, 10-90 wt-%, 20-80 wt-%, 30-80 wt-%, 40-80 wt-%, 40-60 wt-%, 40-50 wt-%, or 50-70 wt-%;(v) said at least one base-polymer comprises a cationic monomer content ranging from 1-99 wt-%, 10-90 wt-%, 20-80 wt-%, 30-80 wt-%, 40-80 wt-%, 50-80 wt-%, 60- 80 wt-%, or 50-70 wt-%;(vi) said at least one base-polymer optionally comprises an anionic monomer content ranging from 0-50% by weight;(vii) said at least one base-polymer comprises a net cationic charge ranging from 1-99 wt-%, 10-90 wt-%, 20-80 wt-%, 30-80 wt-%, 40-80 wt-%, 40-60 wt-%, 40-50 wt-%, or 50-70 wt-%, at pH 7;(viii) said at least one base-polymer comprises a weight average molecular weight ranging from 5-1000 kDa, 5-500 kDa, 5-400 kDa, 5-300 kDa, 5-250 kDa, 5-200 kDa, 5-150 kDa, 5-100 kDa, 5-80 kDa, 5-60 kDa, 5-40 kDa, 5-20 kDa, or 5-10 kDa; or(ix) any combination of (i)-(viii);(f) comprises a glyoxakbase-polymer weight ratio of 1:99-20:80, 1:99-15:85, or 5:95-10:90; or(g) any combination of (a)-(f).

13. The method of any one of claims 7-12, wherein said silicon-containing particle composition:(a) comprises one or more silicon-containing particles selected from the group consisting of silica; colloidal silica; aluminum modified silica, aluminum modified colloidal silica, aluminum phyllosilicates, bentonite, sodium bentonite, calcium bentonite, and montmorillonite, wherein said silicon-containing particles comprise microparticles and / or nanoparticles;(b) comprises a liquid dispersion comprising a dispersed phase comprising said one or more silicon-containing particles dispersed in water and further comprising a total solid content of 5-25 wt%, 5-20 wt%, 5-15 wt%, 5-10 wt%, 5-8 wt% or 5-7 wt%;(c) comprises a surface area of 300-1200 m2 / g, 400-1200 m2 / g, 600-1200 m2 / g, 800-1200 m2 / g, 900-1200 mz / g, 1000-1200 m2 / g, or 1100-1200 m2 / g;(d) comprises an S-value of 8-80%, 8-60%, 8-40%, 8-20%, 8-16%, 8-14%, 8-12%, or 8-10%, wherein S-value is the wt-% of SiO2 in the dispersed phase of said liquid dispersion;(e) acts as a zeta potential modifier which decreases, renders negative, or renders more negative the zeta potential of said cellulosic fibers; or(f) any combination of (a)-(e).

14. The method of any one of claims 7-13, wherein:(a) said aqueous fiber slurry comprises a dosage of said GPAM composition ranging from 0.1-40 Ib / t, 0.1-30 Ib / t, 0.1-20 Ib / t, 0.1-15 Ib / t, 0.1-10 Ib / t, 0.1-8 Ib / t, 0.1-6 Ib / t, 0.1-5 Ib / t, 0.1-4 Ib / t, 0.1-3 Ib / t, 0.1-2 Ib / t, 0.1-1 Ib / t, or 0.1-0.5 Ib / t;(b) said fiber stock comprises a dosage of said silicon-containing particle composition that (i) is sufficient to form a ratio by weight of said silicon-containing particles:GPAM of 30:1- 1:30, 25:1-1:25, 1:20-20:1, 1:15-15:1, 1:10-10:1, 1:8-8:1, 1:6-6:1, 1:4-4:1, 1:3-3:1 or 1:2- 2:1, calculated as a dry weight of silicon-containing particles to dry weight of active GPAM; and (ii) is sufficient to form said 3rdzeta potential in the fiber stock;(c) the method further comprises increasing the dosage of said silicon-containing particle composition until said 3rdzeta potential is observed in the fiber stock;(d) said base-polymer of said GPAM comprises (i) acrylamide and any combination DADMAC, Q.9, and / or MAPTAC; or (ii) acrylamide and DADMAC;(e) said silicon-containing particles comprise aluminum modified colloidal silica; or(f) any combination of (a)-(e).

15. A fiber stock composition comprising:(a) an aqueous suspension comprising cellulosic fibers, at least one glyoxalated polyacrylamide (GPAM), and one or more silicon-containing particles according to any one of claims 1-6; or(b) an aqueous suspension comprising an aqueous fiber slurry, a glyoxalated polyacrylamide (GPAM) composition, and a silicon-containing particle composition obtainable by a method according to any one of claims 7-14.

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