HIGH MOLECULAR WEIGHT TEMPORARY WET STRENGTH RESIN FOR PAPER

Abstract

The present disclosure provides cellulose reactive glyoxalated vinylamide polymers which impart improved wet strength decay properties, as well as high efficiency of wet strength build in paper products. A method of preparing a cellulose reactive glyoxalated vinylamide polymer composition, and methods of its use in maunfacturing paper products, as well as the resulting paper products, are also provided.

Claims

1. A cellulose reactive glyoxalated copolymer composition comprising an aqueous medium and about 0.1 to about 4 weight % of a cellulose reactive glyoxalated vinylamide copolymer, based total weight of the aqueous medium, wherein the glyoxalated vinylamide copolymer is obtained by reaction in an aqueous reaction medium of glyoxal and a cationic vinylamide copolymer, a dry weight of glyoxal:cationic copolymer in the aqueous reaction medium ranging from about 5 to about 40 glyoxal to about 95 to about 60 cationic vinylamide copolymer, the aqueous reaction medium having a total solids concentration of from about 0.3 to about 3.0%, the cationic vinylamide copolymer having a weight average molecular weight of about 15,000 Daltons to about 80,000 Daltons based on total weight of the cationic vinylamide copolymer before reaction with glyoxal, and comprised of about 5 to about 95 weight % diallyldimethyl ammonium halide monomer and about 95 to about 5 weight % acrylamide monomer, based on the total weight of the cationic copolymer before glyoxalation.

2. The cellulose reactive glyoxalated copolymer composition according to claim 1, wherein the cationic vinylamide copolymer has a weight average molecular weight of greater than 20,000 Daltons to about 80,000 Daltons, based on total weight of the cationic vinylamide copolymer before reaction with glyoxal.

3. The cellulose reactive glyoxalated copolymer composition according to claim 1, wherein the cationic vinylamide copolymer has a weight average molecular weight of about 20,500 Daltons, based on total weight of the cationic vinylamide copolymer before reaction with glyoxal.

4. The cellulose reactive glyoxalated copolymer composition according to claim 1, wherein the total solids concentration in the aqueous reaction medium is from about 0.5 to about 2.5%.

5. The cellulose reactive glyoxalated copolymer composition according to claim 1, wherein the dry weight of glyoxal:cationic copolymer in the aqueous reaction medium ranges from about 23 glyoxal to about 77 cationic vinylamide copolymer.

6. The cellulose reactive glyoxalated copolymer composition according to claim 1, obtained by reaction carried out at a reaction pH of 8.5 to 12.

7. The cellulose reactive glyoxalated copolymer composition according to claim 1, obtained by reaction carried out for 10 to 300 minutes.

8. The cellulose reactive glyoxalated copolymer composition according to claim 1, obtained by reaction carried out at a temperature from 15 to 35 C.

9. A method for preparing a cellulose reactive glyoxalated copolymer composition comprising: reacting a substantially aqueous reaction mixture of a cationic vinylamide copolymer and glyoxal at a dry weight of glyoxal:cationic copolymer in the aqueous reaction medium ranging from about 5 to about 40 glyoxal to about 95 to about 60 cationic vinylamide copolymer, the aqueous reaction medium having a total solids concentration of from about 0.3 to about 3.0%, the cationic vinylamide copolymer having a weight average molecular weight of about 15,000 Daltons to about 80,000 Daltons based on total weight of the cationic vinylamide copolymer before reaction with glyoxal and comprising about 5 to about 95 weight % diallyldimethyl ammonium halide monomer and about 95 to about 5 weight % acrylamide monomer, based on the total weight of the cationic copolymer before glyoxalation and at a reaction pH of 8.5 to 12.

10. The method for preparing a cellulose reactive glyoxalated copolymer composition according to claim 9, wherein the cationic vinylamide copolymer has a weight average molecular weight of greater than 20,000 Daltons to about 80,000 Daltons based on total weight of the cationic vinylamide copolymer before reaction with glyoxal.

11. The method for preparing a cellulose reactive glyoxalated copolymer composition according to claim 9, wherein the cationic vinylamide copolymer has a weight average molecular weight of about 20,500 Daltons.

12. The method for preparing a cellulose reactive glyoxalated copolymer composition according to claim 9, wherein the total solids concentration in the aqueous reaction medium is from about 0.5 to about 2.5%.

13. The method for preparing a cellulose reactive glyoxalated copolymer composition according to claim 9, wherein the dry weight of glyoxal:cationic copolymer in the aqueous reaction medium ranges from about 10 to about 30 glyoxal to about 90 to about 70 cationic vinylamide copolymer, from about 23 glyoxal to about 77 cationic vinylamide copolymer.

14. The method for preparing a cellulose reactive glyoxalated copolymer composition according to claim 9, wherein the reaction is carried out at a reaction pH of 9.5 to 10.5.

15. The method for preparing a cellulose reactive glyoxalated copolymer composition according to claim 9, wherein the reaction is carried out for 10 to 300 minutes.

16. The method for preparing a cellulose reactive glyoxalated copolymer composition according to claim 9, wherein the reaction is carried out at a temperature from 15 to 35 C.

17. (canceled)

18. (canceled)

19. (canceled)

20. A paper coated with or comprising the glyoxalated copolymer composition of claim 1.

21. The cellulose reactive glyoxalated copolymer composition according to claim 1, wherein the cationic vinylamide copolymer has a weight average molecular weight of greater than 20,000 Daltons to 25,000 Daltons, based on total weight of the cationic vinylamide copolymer before reaction with glyoxal.

22. The cellulose reactive glyoxalated copolymer composition according to claim 1, obtained by reaction carried out at a reaction pH of 9.5 to 10.5.

23. The cellulose reactive glyoxalated copolymer composition according to claim 1, obtained by reaction carried out for 100 to 150 minutes.

Description

DETAILED DESCRIPTION

[0043] The present disclosure provides a cellulose reactive glyoxalated vinylamide copolymer, as well as a composition comprising an aqueous medium containing the glyoxalated vinylamide copolymer. Disclosed herein is a process for glyoxalating acrylamide copolymers found unexpectedly to enable the use of relatively high molecular weight (molecular weight measured prior to glyoxalation) copolymers in paper product, while still providing a high rate of wet strength decay over time in the paper product. A combination of: 1) starting vinylamide copolymer molecular weight; 2) vinylamide copolymer concentration in a reaction solution; 3) ratio of cationic acrylamide polymer to dialdehyde cross-linker; and 4) reaction pH, have been found to provide this unique combination of properties of high wet strength efficiency and high wet strength decay over time. Features of the disclosed process include using starting acrylamide copolymers with molecular weight in the range of 15,000 to 80,000 Daltons, reacting the starting vinylamide copolymers with glyoxal at a total solids concentration (weight % of starting copolymer and glyoxal in reaction mixture) between 0.3 and 3.0%, a dry weight range of 95:5 to 60:40 (copolymer:glyoxal), and running the glyoxalation reaction at a pH between 8.5 and 12. The reaction can be run for a time of from 10 to 300 minutes.

Starting Copolymer

[0044] The starting vinylamide copolymers that are used in adduct formation (such as glyoxalation) can be obtained by methods of polymer synthesis known to those skilled in the art, such as free radical or redox catalysis polymerization of a vinylamide monomer, and one or more co-monomers. The vinylamide copolymer is cationic. Cross-linking agents with multiple polymerizable vinyl functionalities can also be included in the formulations to impart structure to the backbone polymer. A chain transfer agent, such as sodium hypophosphite, can be used to control the molecular weight of the polymer molecules, as well as to introduce branching.

[0045] The cationic copolymer before glyoxalation has a weight average molecular weight of about 15,000 to about 80,000 Daltons, including about 15,000 to about 75,000 Daltons, about 15,000 to about 70,000 Daltons, including about 15,000 to about 65,000 Daltons, including about 15,000 to about 60,000 Daltons, about 15,000 to about 55,000 Daltons, about 15,000 to about 50,000 Daltons, about 15,000 to about 47,500 Daltons, about 15,000 to about 40,000 Daltons, about 15,000 to about 35,000 Daltons, about 15,000 to about 30,000 Daltons, about 15,000 to about 25,000 Daltons; about 20,000 to about 80,000 Daltons, including about 20,000 to about 75,000 Daltons, about 20,000 to about 70,000 Daltons, about 20,000 to about 65,000 Daltons, about 20,000 to about 60,000 Daltons, about 20,000 to about 55,000 Daltons, about 20,000 to about 50,000 Daltons, about 20,000 to about 47,500 Daltons, about 20,000 to about 40,000 Daltons, about 20,000 to about 35,000 Daltons, about 20,000 to about 30,000 Daltons, about 20,000 to about 25,000 Daltons; or greater than 20,000 to about 80,000 Daltons, including greater than 20,000 to about 75,000 Daltons, greater than 20,000 to about 70,000 Daltons, greater than 20,000 to about 65,000 Daltons, greater than 20,000 to about 60,000 Daltons, greater than 20,000 to about 55,000 Daltons, greater than 20,000 to about 50,000 Daltons, greater than 20,000 to about 47,500 Daltons, greater than 20,000 to about 40,000 Daltons, greater than 20,000 to about 35,000 Daltons, greater than 20,000 to about 30,000 Daltons, or greater than 20,000 to about 25,000 Daltons. An exemplary cationic copolymer has a molecular weight before glyoxalation of greater than 20,000 to about 80,000 Daltons, about 20,500 Daltons, about 46,100 Daltons or about 79,500 Daltons.

[0046] The cationic copolymer for glyoxalation is a cationic copolymer comprising at least two different monomer units: vinylamide, e.g., acrylamide monomer, and a diallyldimethylammonium halide monomer. An exemplary cationic copolymer comprises vinylamide monomer and diallyldimethylammonium halide monomer, or contains only vinylamide monomer and diallyldimethylammonium halide monomer. The halide of the diallyldimethylammonium halide monomer can include bromine (Br), chlorine (CO, iodine (I), or fluorine (F). An exemplary diallyldimethylammonium halide monomer is diallyldimethylammonium chloride (DADMAC).

[0047] The cationic copolymer comprises about 5 to about 95 weight % diallyldimethylammonium halide monomer and about 95 to about 5 weight % acrylamide monomer, about 7.5 to about 92.5 weight % diallyldimethylammonium halide monomer and about 92.5 to about 7.5 weight % acrylamide monomer, about 10 to about 90 weight % diallyldimethylammonium halide monomer and about 90 to about 10 weight % acrylamide monomer, about 15 to about 85 weight % diallyldimethylammonium halide monomer and about 85 to about 15 weight % acrylamide monomer, about 20 to about 60 weight % diallyldimethylammonium halide monomer and about 80 to about 40 weight % acrylamide monomer, or about 20 to about 40 weight % diallyldimethylammonium halide monomer and about 80 to about 60 weight % acrylamide monomer, based on total weight of the cationic copolymer before glyoxalation. An exemplary cationic copolymer comprises about 5 to about 25 weight % diallyldimethylammonium halide monomer and about 95 to about 75 weight % acrylamide monomer, or about 5 to about 15 weight % diallyldimethylammonium halide monomer and about 95 to about 55 weight % acrylamide monomer.

[0048] The cationic copolymer can include one, two, three, or more cationic, non-cationic, or anionic monomer units. Cationic copolymers can include nonionic and anionic monomer provided the aggregate charge of the copolymer is cationic.

[0049] Suitable cationic monomers or potentially cationic monomers include diallyldialkyl amines, 2-vinylpyridine, 2-(dialkylamino)alkyl(meth)acrylates, dialkylamino alkyl(meth) acrylamides, including acid addition and quaternary ammonium salts thereof. Specific examples of such cationic monomers or potentially cationic monomers are (meth)acryloyloxy ethyl trimethylammonium chloride (dimethyl amino ethyl(meth)acrylate, methyl chloride quaternary salt), 2-vinyl-N-methylpyridinium chloride, (p-vinylphenyl)-trimethylammonium chloride, (meth)acrylate 2-ethyltrimethylammonium chloride, 1-methacryloyl-4-methyl piperazine, Mannich polyacrylamides i.e., polyacrylamide reacted with dimethylamine formaldehyde adduct to give the N-(dimethyl amino methyl) and (meth)acrylamido propyltrimethyl ammonium chloride.

[0050] Suitable anionic monomers can be selected from vinyl acidic material such as acrylic acid, methacrylic acid, maleic acid, allyl sulfonic acid, vinyl sulfonic acid, itaconic acid, fumaric acid, potentially anionic monomers such as maleic anhydride and itaconic anhydride and their alkali metal and ammonium salts, 2-acrylamido-2-methyl-propanesulfonic acid and its salts, sodium styrene sulfonate and the like.

[0051] Suitable non-ionic monomers other than the vinylamide can be selected from the group consisting of (meth) acrylic esters such as octadecyl(meth)acrylate, ethyl acrylate, butyl acrylate, methylmethacrylate, hydroxyethyl(meth)acrylate and 2-ethylhexylacrylate; N-alkyl acrylamides, N-octyl(meth)acrylamide, N-tert-butyl acrylamide, N-vinylpyrrolidone, N,N-dialkyl(meth)acrylamides such as N,N-dimethyl acrylamide; styrene, vinyl acetate, hydroxy alkyl acrylates and methacrylate such as 2-hydroxy ethyl acrylate and acrylonitrile.

[0052] The cationic copolymer can be crosslinked, branched or otherwise structured or linear. For example, the cationic copolymer can be linear, crosslinked, chain-transferred, or crosslinked & chain-transferred (structured).

[0053] Crosslinking agents are usually polyethylenically unsaturated crosslinking agents. Examples are methylene bis(meth)acrylamide, triallylammonium chloride; tetraallyl ammonium chloride, poly(ethylene glycol) diacrylate; poly(ethylene glycol) dimethacrylate; N-vinyl acrylamide; divinylbenzene; tetra(ethylene glycol) diacrylate; dimethylallylaminoethylacrylate ammonium chloride; diallyloxyacetic acid, Na salt; diallyloctylamide; trimethyllpropane ethoxylate triacryalte; N-allylacrylamide N-methylallylacrylamide, pentaerythritol triacrylate and combinations thereof. Other systems for crosslinking can be used instead of or in addition to these. For instance, covalent crosslinking through pendant groups can be achieved by the use of ethylenically unsaturated epoxy or silane monomers, or by the use of polyfunctional crosslinking agents such as silanes, epoxies, polyvalent metal compounds or other known crosslinking systems.

Total Solids Concentration in Reaction Solution

[0054] The glyoxalation reaction of the polyvinylamide is carried out at concentrations of the polyvinylamide where gelation is prevented. Moreover, in the method of the disclosure, the total solids concentration (total solids being weight of starting vinylamide copolymer and glyoxal) of the reaction solution is about 0.3 to about 3% by weight total solids, at about 0.5 to about 2.5% by weight total solids, at about 0.65 to about 2% by weight total solids, at about 0.75 to about 2% by weight total solids, at about 0.75 to about 1.5% by weight total solids, or at about 0.75 to about 1% by weight total solids. An exemplary total solids concentration in the glyoxalation reaction solution is about 1%.

Ratio of Cationic Starting Acrylamide Polymer to Dialdehyde Cross-Linker

[0055] The glyoxalated copolymer is obtained by reaction in an aqueous reaction medium of a dry weight ratio of glyoxal:cationic copolymer ranging from about 5 to about 40 glyoxal to about 95 to about 60 cationic copolymer (i.e., about 5:95 to about 40:60), including from about 10 to about 30 glyoxal to about 90 to about 70 cationic copolymer (i.e., about 10:90 to about 30:70), including from about 20 to about 25 glyoxal to about 80 to about 75 cationic copolymer (i.e., about 20:80 to about 25:75). The weight percent of glyoxal and cationic polymer is based on the total weight of the dry reactants before the glyoxalation step.

[0056] An exemplary aqueous reaction medium contains 0.77% by weight copolymer solids, 0.23% by weight glyoxal on a dry basis, and 99% deionized water, corresponding to a dry weight ratio of glyoxal:cationic copolymer of 23:77.

Reaction pH

[0057] Base addition or changing the pH to above 7 is the most common method of catalyzing the glyoxalation reaction. In the method of the disclosure, the reaction pH is a pH of 8.5 to 12, a pH 9 to 11.5, a pH of 9.5 to 11, or a pH of 9.5 to 10.5. An exemplary pH for the reaction is 10.5.

[0058] The duration of the reaction necessary to obtain the desired product (e.g., 0.1 to 4 wt. glyoxalated copolymer or 0.25 to 4 wt. glyoxalated copolymer in the aqueous composition) will vary depending on concentration, temperature and pH, as well as other factors known in the art to affect the rate of glyoxalation. The glyoxalation reaction of the present disclosure is run for 10 to 300 minutes, 25 to 250 minutes, 50 to 200 minutes, 100 to 200 minutes, or 100 to 150 minutes. An exemplary reaction time is 120 minutes.

[0059] The glyoxalation reaction is carried out at a temperature ranging from 15 to 35 C., from 20 to 30 C., or from 20 to 25 C. An exemplary reaction temperature is 20 C.

[0060] The glyoxalation reaction can be carried out in batch or continuous mode. For instance, the reaction can be carried out in a in a continuous reactor with pH measurement capability at the papermaking site.

[0061] Conventional additives which can be added to the glyoxalation reaction are chelating agents to remove polymerization inhibitors, pH adjusters, initiators, buffers, surfactants or combinations thereof. The disclosed process can be practiced without any one or all of such conventional additives.

Monitoring of Glyoxalated Copolymer Formation

[0062] Viscosity is typically measured during the reaction using the UL adapter for a BROOKFIELD LV series viscometer. The UL adapter has no spindle number. Only one setting is possible. The base of the adapter cup is removed and the assembly is placed directly into the reaction mixture. Viscosity measurements are automatically recorded every second during the length of the catalyzed reaction. The viscometer is set to a speed of 60 rpm and the temperature of the reaction mixture is maintained at 25 C.

[0063] The glyoxalated copolymer formation may also be monitored by monitoring the consumption of glyoxal using methods known in the art. For example, one such method may include the method disclosed by Mitchel, R. E. J, et al. The use of Girard-T reagent in a rapid and sensitive method for measuring glyoxal and certain other odicarbonyl compounds, Analytical Biochemistry, Volume 81, Issue 1, July 1977, Pages 47-56. The percent residual glyoxal can be determined from 2 wt. % aqueous solutions of the glyoxalated polyvinylamides. Residual glyoxal is removed from the glyoxalated polymer by dialysis through a 3500 MWCO membrane tubing. Ten milliliters (ml) of dialyzed sample is derivatized by adding 2.0 ml of o-(2,3,4,5,6 Pentafluorobenzyl)-hydroxyamine hydrochloride (6.6 mg/ml) for approximately 2 hours. The glyoxal is then extracted from the dialysis solution using 1:1 hexane-diethyl ether. Analysis of the extract can be completed by gas chromatography on an HP 5890 Gas Chromatograph (GC) #6 instrument using a DB-5 15 m, 0.53 mm i.d., 1.5 m df (column length, internal diameter, and film thickness, respectively) column. Once the residual glyoxal is determined and the amount of pre-reaction glyoxal is known, the percent glyoxal consumed can be calculated.

Glyoxalated Copolymer Composition

[0064] The glyoxalated copolymer composition of the disclosure contains the glyoxalated copolymer in an amount of about 0.1 to about 4 weight %, including about 0.25 to about 4 weight %, about 1 to about 3 weight %, or about 1.5 to 2.5 weight %, based on total weight of the aqueous medium. When the amount of glyoxalated copolymer in the glyoxalated copolymer composition exceeds about 4 weight %, then gelation becomes a problem.

[0065] The glyoxalated copolymer composition of the disclosure is a thermosetting resin. The glyoxalated copolymer composition can comprise more than one type of glyoxalated vinylamide copolymer or one or more other glyoxalated polymers useful for temporary wet strength paper applications. Alternatively, the glyoxalated copolymer composition of the disclosure contains substantially only the glyoxalated copolymer of the disclosure as the polymeric thermosetting resin component.

[0066] The glyoxalated copolymer composition has a viscosity of equal to or less than 100 centipoise (cP), a viscosity from about 5 to about 100 cP, a viscosity less than or equal to 30 cP, a viscosity from about 30 to about 5 cP, a viscosity from about 25 to about 10 cP, a viscosity less than or equal to 25 cP, or a viscosity less than 25 to about 5 cP, as measured using a Brookfield viscometer.

[0067] The disclosure provides a cellulose reactive glyoxalated copolymer composition comprising an aqueous medium and about 0.1 to about 4 weight %, about 0.25 to about 4 weight %, about 1 to about 3 weight %, or about 1.5 to 2.5 weight % of a cellulose reactive glyoxalated vinylamide copolymer, based total weight of the aqueous medium, wherein: the glyoxalated vinylamide copolymer is obtained by reaction in an aqueous reaction medium of glyoxal and a cationic vinylamide copolymer; a dry weight of glyoxal:cationic copolymer in the aqueous reaction medium ranging from about 5 to about 40 glyoxal to about 95 to about 60 cationic vinylamide copolymer, about 10 to about 30 glyoxal to about 90 to about 70 cationic vinylamide copolymer, from about 20 to about 25 glyoxal to about 80 to about 75 cationic vinylamide copolymer, or about 23 glyoxal to about 77 cationic vinylamide copolymer; the aqueous reaction medium having a total solids concentration of from 0.3 to 3.0%, from 0.5 to 2.5%, from 0.65% to 2%, from 0.75% to 2%, 0.75 to 1.5%, or from 0.75 to 1%; the cationic vinylamide copolymer having a weight average molecular weight of about 15,000 Daltons to about 80,000 Daltons, greater than 20,000 Daltons to about 80,000 Daltons, greater than 20,000 Daltons to about 60,000 Daltons, greater than 20,000 Daltons to about 50,000 Daltons, greater than 20,000 Daltons to about 25,000 Daltons, about 20,500 Daltons, about 47,500 Daltons, or about 79,500 Daltons, based on total weight of the cationic vinylamide copolymer before reaction with glyoxal, and comprised of about 5 to about 95 weight % diallyldimethyl ammonium halide monomer and about 95 to about 5 weight % acrylamide monomer, about 5 to about 25 weight % diallyldimethylammonium halide monomer and about 95 to about 75 weight % acrylamide monomer, about 5 to about 15 weight % diallyldimethylammonium halide monomer and about 95 to about 55 weight % acrylamide monomer, about 7.5 to about 92.5 weight % diallyldimethylammonium halide monomer and about 92.5 to about 7.5 weight % acrylamide monomer, about 10 to about 90 weight % diallyldimethylammonium halide monomer and about 90 to about 10 weight % acrylamide monomer, about 15 to about 85 weight % diallyldimethylammonium halide monomer and about 85 to about 15 weight % acrylamide monomer, about 20 to about 60 weight % diallyldimethylammonium halide monomer and about 80 to about 40 weight % acrylamide monomer, or about 20 to about 40 weight % diallyldimethylammonium halide monomer and about 80 to about 60 weight % acrylamide monomer, based on the total weight of the cationic copolymer before glyoxalation, wherein the acrylamide monomer is acrylamide, methacrylamide, N-methyl acrylamide, or a substituted acrylamide

Use of Glyoxalated Copolymer Composition

[0068] The glyoxalated copolymer composition of the disclosure is useful as a high molecular weight temporary wet strength resin additive for paper. Accordingly, the present disclosure further provides a method of making paper, which includes a step of combining a glyoxalated copolymer composition of the disclosure and cellulosic fiber slurry or applying a glyoxalated copolymer composition to a wet/dry web paper. In the method of making paper, the sequence in which the cellulose fibers are combined with the glyoxalated copolymer composition is not particularly limited. For example, the method can include adding the glyoxalated copolymer composition to an aqueous suspension of cellulose fibers; adding cellulose fibers to the glyoxalated copolymer composition; adding the glyoxalated copolymer composition and cellulose fibers to an aqueous solution; and/or reacting in an aqueous reaction medium comprising cellulose fibers a dry weight ratio of glyoxal:cationic copolymer ranging from about 5:95 to about 40:60 to form the glyoxalated copolymer, wherein the glyoxalated copolymer is about 0.1 to about 4 weight % based on total weight of the aqueous reaction medium. Thus, the disclosure provides a method for preparing paper with improved wet strength properties comprising the steps of: a) providing an aqueous slurry of cellulosic fibers; b) adding the glyoxalated copolymer composition of the disclosure to the aqueous slurry; c) forming a web from the aqueous slurry formed in step b); and d) drying the web, to form a paper product having improved efficiency of initial wet strength development as well as increased wet strength decay over time.

[0069] The glyoxalated copolymer composition can be added to the thick or thin stock. When added to the thin stock, it may be added before the fan pump. A substantial amount of wet strength is imparted when as little as about 0.10 wt. % of the glyoxalated copolymer, based on dry fiber weight of the glyoxalated copolymer is added to the furnish. For example, suitable dosages include about 0.10 to about 40 (0.05-20 kg/metric ton) pounds dry polymer per ton of dry furnish, about 1 to about 20, (0.5-10 kg/metric ton), about 1 to about 10 (0.5-5 kg/metric ton), about 1 to about 8 (0.5-4 kg/metric ton) pounds, or 1.5 to about 6 (1.0-3 kg/metric ton) pounds dry polymer per ton of dry furnish.

[0070] Application of the glyoxalated copolymer composition to wet/dry paper may be accomplished by any conventional means. Examples include but are not limited to size press, padding, spraying, immersing, printing or curtain coating. Accordingly, the disclosure also provides a method for providing paper with improved wet strength properties comprising the steps of: a) spraying, immersing, coating or otherwise applying glyoxalated copolymer composition of the disclosure onto a wet web or wet paper; and b) drying the coated wet web or wet paper, to form a paper product having improved efficiency of initial wet strength development as well as increased wet strength decay over time.

[0071] The disclosure includes a paper product containing a cellulose reactive glyoxalated copolymer composition comprising an aqueous medium and about 0.1 to about 4 weight %, about 0.25 to about 4 weight %, about 1 to about 3 weight %, or about 1.5 to 2.5 weight % of a cellulose reactive glyoxalated vinylamide copolymer, based total weight of the aqueous medium, wherein: the glyoxalated vinylamide copolymer is obtained by reaction in an aqueous reaction medium of glyoxal and a cationic vinylamide copolymer; a dry weight of glyoxal:cationic copolymer in the aqueous reaction medium ranging from about 5 to about 40 glyoxal to about 95 to about 60 cationic vinylamide copolymer, about 10 to about 30 glyoxal to about 90 to about 70 cationic vinylamide copolymer, from about 20 to about 25 glyoxal to about 80 to about 75 cationic vinylamide copolymer, or about 23 glyoxal to about 77 cationic vinylamide copolymer; the aqueous reaction medium having a total solids concentration of from 0.3 to 3.0%, from 0.5 to 2.5%, from 0.65% to 2%, from 0.75% to 2%, 0.75 to 1.5%, or from 0.75 to 1%; the cationic vinylamide copolymer having a weight average molecular weight of about 15,000 Daltons to about 80,000 Daltons, greater than 20,000 Daltons to about 80,000 Daltons, greater than 20,000 Daltons to about 60,000 Daltons, greater than 20,000 Daltons to about 50,000 Daltons, greater than 20,000 Daltons to about 25,000 Daltons, about 20,500 Daltons, about 47,500 Daltons, or about 79,500 Daltons, based on total weight of the cationic vinylamide copolymer before reaction with glyoxal, and comprised of about 5 to about 95 weight % diallyldimethyl ammonium halide monomer and about 95 to about 5 weight % acrylamide monomer, about 5 to about 25 weight % diallyldimethylammonium halide monomer and about 95 to about 75 weight % acrylamide monomer, about 5 to about 15 weight % diallyldimethylammonium halide monomer and about 95 to about 55 weight % acrylamide monomer, about 7.5 to about 92.5 weight % diallyldimethylammonium halide monomer and about 92.5 to about 7.5 weight % acrylamide monomer, about 10 to about 90 weight % diallyldimethylammonium halide monomer and about 90 to about 10 weight % acrylamide monomer, about 15 to about 85 weight % diallyldimethylammonium halide monomer and about 85 to about 15 weight % acrylamide monomer, about 20 to about 60 weight % diallyldimethylammonium halide monomer and about 80 to about 40 weight % acrylamide monomer, or about 20 to about 40 weight % diallyldimethylammonium halide monomer and about 80 to about 60 weight % acrylamide monomer, based on the total weight of the cationic copolymer before glyoxalation, wherein the acrylamide monomer is acrylamide, methacrylamide, N-methyl acrylamide, or a substituted acrylamide.

[0072] The disclosure includes a paper product containing the glyoxalated copolymer composition, wherein the glyoxylated copolymer is the reaction product form by reacting a substantially aqueous reaction mixture of a cationic vinylamide copolymer and glyoxal at a dry weight of glyoxal:cationic copolymer in the aqueous reaction medium ranging from about 5 to about 40 glyoxal to about 95 to about 60 cationic vinylamide copolymer, the aqueous reaction medium having a total solids concentration of from 0.3 to 3.0%, the cationic vinylamide copolymer having a weight average molecular weight of about 15,000 Daltons to about 80,000 Daltons based on total weight of the cationic vinylamide copolymer before reaction with glyoxal and comprising about 15 to about 85 weight % diallyldimethyl ammonium halide monomer and about 85 to about 15 weight % acrylamide monomer, based on the total weight of the cationic copolymer before glyoxalation and at a reaction pH of 8.5 to 12.

EXAMPLES

[0073] The products, compositions, and methods of making and using are further described in detail by reference to the following experimental examples. These examples are provided for purposes of illustration only, and are not intended to be limiting unless otherwise specified. Thus, the products, compositions, and methods of the disclosure should in no way be construed as being limited to the following examples, but rather, should be construed to encompass any and all variations which become evident as a result of the teaching provided herein.

Example 1 Synthesis and Glyoxalation of Starting Copolymer Backbones

[0074] A cationic copolymer containing 8.6 weight % diallyldimethylammonium chloride monomer and 91.4 weight % acrylamide were prepared as follows.

[0075] A suitable one liter reaction vessel, equipped with a reflux condenser, overhead stirrer, thermocouple, and nitrogen sparge, was charged with 253.4 parts of water, 21.8 parts of 63.5% diallyldimethylammonium chloride, 0.91 parts adipic acid, 1.75 parts sodium hypophosphite, and 2.1 parts ammonium persulfate. The reactor contents were heated to 30 C. and sparged with nitrogen for 30 minutes. Next, two continuous feedsFeed One and Feed Twowere started simultaneously, each lasting for 120 minutes. Feed One contained a mixture of 276.5 parts of 53% acrylamide, 77 parts of deionized water, 0.32 parts of potassium bromate, and 2.17 parts of CHEL DPTA-41 (BASF Corporation, New Jersey; aqueous solution of pentasodium diethylenetriamine-pentaacetate). Feed Two contained 1.4 parts of sodium bisulfate, 15 parts deionized water, and 1.75 parts of sodium hypophosphite. Once the two feeds were started, an exotherm ensued, and the temperature of the reactor contents rose to 75 C., and was maintained at this temperature for the remainder of the reaction by applying cooling or heating to the system as needed. After 120 minutes, and the feeds were complete, the temperature of the reaction mass was raised to 85 C., and 2 parts of ammonium persulfate dissolved in 47 parts of deionized water was added to the reactor contents over a two minute period, which was followed by a 120 minute hold at 85 C. Finally, the polymer was cooled and collected. The resultant copolymer had a molecular weight of 20,500 Daltons (Copolymer A).

[0076] The procedure followed to produce Copolymer A was repeated two additional times, with the only change being the quantity of sodium hypophosphite added to the initial reactor charge and to the Feed Two.

[0077] When the sodium hypophosphite charge was 0.49 parts added separately to both the initial reactor charge and the Feed Two, then the resultant copolymer had a molecular weight of 46,100 Daltons (Copolymer B).

[0078] When the sodium hypophosphite charge was 0.26 parts added separately to both the initial reactor charge and the Feed Two, then the resultant copolymer had a molecular weight of 79,400 Daltons (Copolymer C).

[0079] The copolymer backbones were then glyoxalated. A homogeneous glyoxalation reaction solution as made from deionized water, Copolymer A and 40% glyoxal, such that the reaction solution was 0.77% by weight copolymer solids, 0.23% by weight glyoxal on a dry basis and 99.0% deionized water. The total solids concentration of the reaction solution was 1%. Dropwise addition of a 5% sodium hydroxide solution was made to the glyoxalation solution, which was under continuous mixing, to raise the pH of the solution to 10.5, and the pH was held at 10.5 and temperature was held at 20 C. for 120 minutes. At the end of 120 minutes, the pH was lowered to a solution pH of 3.5 by the dropwise addition of sulfuric acid. The final glyoxalated copolymer sample (g-pam 1) was collected.

[0080] The same glyoxalation procedure as described above was followed to produce glyoxalated copolymers from Copolymer B and Copolymer C, which final products were collected and designated g-pam 2 and g-pam 3, respectively

Example 2 Comparative Glyoxalated Copolymer 1

[0081] A sample of comparative prior art glyoxalated polyacrylamide was produced according to the method described in Example 1 of U.S. Pat. No. 4,605,702. The molecular weight (Mw) of this initial copolymer was 3,070 Daltons. The sample is designated herein as Comparative g-pam 1.

Example 3 Comparative Glyoxalated Copolymer 2

[0082] A second sample of comparative prior art g-pam is produced according to the method described in Example 1 of U.S. Pat. No. 3,556,932. The molecular weight (Mw) of this initial copolymer was 12,080 Daltons. The sample is designated herein as Comparative g-pam 2.

Example 4 Comparative Glyoxalated Copolymer 3

[0083] A third comparative g-pam was produced by glyoxalating a sample of Copolymer A (20,500 Daltons) from Example 1. Copolymer A was glyoxalated by the method set forth in Example 1 of U.S. Pat. No. 3,556,932. The final glyoxalated material was collected and is designated herein as Comparative g-pam 3.

Example 5 Paper Products

[0084] An aqueous, pulp slurry was synthesized from a 70:30 ratio of hardwood to softwood fibers, beaten to 380 Canadian Standard Freeness (CSF) and diluted to 0.5% consistency, with pH of 6.9. Aliquots of the pulp slurry were collected, placed under overhead stirring, and glyoxalated copolymer solutions were added to the pulp slurry to achieve final addition levels of 5, 10 and 20 pounds of g-pam (dry weight) per ton of oven dry pulp. Once addition of the g-pam to the pulp slurry was completed, the mixture was then stirred for 30 seconds to permit absorption of the g-pam onto the fiber in the aqueous pulp slurry. Each aliquot of pulp slurry with g-pam additive produced a 200 square centimeter round handsheet with a basis weight of 60 grams per square meter. The formed web was then pressed between paper blotters, and dried on a steam-heated rotary drum dryer at a temperature of 240 F. to produce a handsheet.

[0085] Wet tensile strength of the finished paper was measured according to TAPPI Test Method T456. Each tensile strength value is the average of 3 measurements and reported in pounds per inch (lbf/in). The 5 minute Wet Tensile Strength was determined by soaking the treated paper in water at pH 7.0 for 5 minutes and then measuring the wet tensile strength. The % Decay is calculated as (initial wet tensile strength5 minute wet tensile strength)/initial wet tensile strength. The results are set forth in Table 1.

TABLE-US-00001 TABLE 1 5 minute Initial Wet Wet Wet Tensile Tensile Tensile Strength Strength Decay Dosage (lbf/in) (lbf/in) (%) g-pam 1 5 lb/ton 0.89 0.46 48.93% 10 lb/ton 1.39 0.87 37.66% 20 lb/ton 2.20 1.08 50.86% Comparative 5 lb/ton 0.49 0.26 47.36% g-pam 1 10 lb/ton 0.49 0.25 49.51% 20 lb/ton 0.68 0.37 46.02% Comparative 5 lb/ton 0.87 0.51 41.34% g-pam 2 10 lb/ton 1.11 0.63 43.23% 20 lb/ton 1.21 0.84 30.48% Comparative 5 lb/ton 1.32 0.91 31.13% g-pam 3 10 lb/ton 1.94 1.52 21.77% 20 lb/ton 3.10 2.24 27.7%

[0086] The data for Comparative g-pam 2 illustrates the good initial wet strength imparted by the polymer of U.S. Pat. No. 3,556,932, as well as the poor wet tensile strength decay. The data for Comparative g-pam 1 illustrates the improved wet tensile strength decay for a lower molecular weight starting polymer (relative to U.S. Pat. No. 3,556,932), as well as the poor initial wet strength imparted by a polymer of U.S. Pat. No. 4,605,702.

[0087] In notable contrast, the data for g-paml illustrates an initial wet strength as good, or better, than that of a polymer according to U.S. Pat. No. 3,556,932, while also having wet tensile strength decay as good, or better, than that of a polymer according to U.S. Pat. No. 4,605,702. Thus, the glyoxalated vinylamide copolymer of the present disclosure unexpectedly possesses both efficient initial wet strength build and a high rate of wet tensile strength decay.

[0088] Comparative g-pam 3 illustrates that glyoxalating Copolymer A with the glyoxalation method of U.S. Pat. No. 3,556,932, improved the initial wet tensile strength of the paper, relative to the Comparative g-pam 2, however, the paper has markedly poorer wet tensile strength decay relative to both Comparative g-pam 2 and g-pam 1. Thus, compared to prior art methods of glyoxalation, the glyoxalation method of the present disclosure unexpectedly provides glyoxalated copolymers imparting superior wet strength properties to paper.

[0089] Mullen Burst Strength of the finished paper was measured according to TAPPI Test Method T403. The 30 minute Wet Burst Strength was determined by soaking the treated paper in water at pH 7.0 for 30 minutes and then measuring the wet burst strength. The % Decay is calculated as (initial wet burst strength30 minute wet burst strength)/initial wet burst strength. The results are set forth in Table 2.

TABLE-US-00002 TABLE 2 Initial Wet 30 minute Wet Burst Strength Burst Strength Wet Burst Dosage (Kpa * m.sup.2/g) (Kpa * m.sup.2/g) Decay (%) Comparative g- 5 lb/ton 0.5987 0.2259 62% pam 1 10 lb/ton 0.8590 0.3209 63% 20 lb/ton 1.9569 0.9706 50% g-pam 1 5 lb/ton 0.6646 0.2675 60% 10 lb/ton 1.3702 0.5037 63% 20 lb/ton 2.2255 1.0959 51% g-pam 2 5 lb/ton 0.7545 0.3424 55% 10 lb/ton 1.6364 0.8440 48% 20 lb/ton 2.6607 1.5849 40% g-pam 3 5 lb/ton 0.9733 0.4919 49% 10 lb/ton 1.6115 0.9166 43% 20 lb/ton 2.9817 2.0527 31%

[0090] The data for Comparative g-pam 1 illustrates a good wet burst strength decay for this additive, however it also shows that poor initial wet strength is imparted by the polymer of U.S. Pat. No. 4,605,702. The data for g-pam 1 shows equal performance in wet burst decay to Comparative g-pam 1, while advantageously demonstrating a notably higher initial wet burst strength result. The data for g-pam 2 and g-pam 3 shows the impact of using higher molecular weight polymers in the process of the disclosure, specifically that additives made from higher Mw polymers show a higher initial wet burst strength result, and a lower level of wet burst strength decay.

[0091] The disclosures of each and every patent, patent application, and publication cited herein are hereby incorporated herein by reference in their entirety for all purposes.

[0092] While the products, compositions, methods of making them, and their methods of use have been disclosed with reference to specific embodiments, it is apparent that other embodiments and variations may be devised by others skilled in the art without departing from the true spirit and scope of the described products and methods. The appended claims are intended to be construed to include all such embodiments and equivalent variations.