Aqueous glyoxalated polyacrylamide composition
An aqueous composition includes water and a cationic polymeric resin having at least one reactive aldehyde group and formed from the reaction of glyoxal and a polymer. The polymer comprises at least one acrylamide repeating unit and at least one cationic repeating unit wherein a number of reactive aldehyde equivalents divided by a number of equivalents of residual glyoxal based on the total weight of the polymer is greater than about 1.2, wherein prior to reaction the polymer has greater than about 50 mole % acrylamide repeat units and from about 2 to about 30 mole % cationic repeating units, wherein greater than about 5 mole % of the acrylamide repeating units are converted to reactive aldehyde groups in the cationic polymer resin; and wherein the composition exhibits a viscosity gain of less than about 200%.
1. An aqueous composition comprising:
water; and
a cationic glyoxalated polyacrylamide having at least one reactive aldehyde group and formed from the reaction of glyoxal and a polymer;
wherein the polymer comprises at least one acrylamide repeating unit and at least one cationic repeating unit;
wherein the extent of reaction of glyoxal with acrylamide groups of the polymer is such that at least 40 mole % of the acrylamide groups are converted to reactive aldehyde functionality;
the at least one cationic repeating unit is formed from one or more of the following: diallyldimethylammonium chloride (DADMAC), 2-(acryloyloxyethyl)-trimethylammonium chloride, 2-(dimethylamino)ethyl acrylate, 3-acrylamidopropyl-trimethylammonium chloride, dimethylaminopropyl acrylamide, or combinations thereof;
greater than about 60 mole % of the acrylamide repeating units of the polymer react with glyoxal;
a mole ratio of equivalents of reactive aldehyde groups in the composition versus equivalents of glyoxal in the composition is greater than about 1.5; and wherein
when the composition comprises about 10 wt % of the cationic glyoxalated polyacrylamide at a pH of about 3.2, the composition exhibits less than about 10 mole % loss of equivalents of reactive aldehyde groups after ageing at about 40° C. for about 30 days;
when the composition comprises about 10 wt % of the cationic glyoxalated polyacrylamide at a pH of about 3.2, the composition exhibits less than about 50% increase in viscosity after ageing at about 40° C. for about 30 days;
when the composition comprises about 10 wt % of the cationic glyoxalated polyacrylamide at a pH of about 3.2, the composition exhibits less than about a 30% increase in free glyoxal equivalents after ageing at about 40° C. for about 30 days; and
the composition has a solids content of at least about 14%.
2. The aqueous composition of claim 1 wherein the mole ratio of equivalents of reactive aldehyde groups in the composition versus equivalents of glyoxal in the composition is greater than about 2.
3. A process of forming the aqueous composition of claim 1 wherein the process has a reaction window that is less than about 0.14 and that is defined as at a time during the step of reacting as (polymer RSV)×(polymer RSV)×(solids of the polymer as defined in the reaction window) divided by the ratio of moles of glyoxal to moles of acrylamide groups of the polymer before glyoxalation occurs.
4. The process of claim 3 wherein a ratio of the RSV of the cationic glyoxalated polyacrylamide resin to the RSV of the polymer is less than 1.5.
5. A process for preparing the aqueous composition of claim 1 , the method comprising the steps of:
polymerizing two or more monomers via free radical polymerization to form a polymer comprising at least one acrylamide repeating unit and at least one cationic repeating unit;
reacting the acrylamide groups of the polymer with glyoxal to form cationic glyoxalated polyacrylamide resin and optionally removing excess glyoxal, to form the aqueous composition;
wherein the step of reacting the polymer and the glyoxal occurs by the addition of a water mixture of the polymer to a solution of the glyoxal such that greater than 50 mole % of the polymer-glyoxal reaction that occurs does so before about 100% of the polymer in the polymer mixture is added to the glyoxal in the solution; wherein a percentage of polymer-glyoxal reaction is defined as about the maximum percentage of acrylamide groups that react after about 8 hours of reaction time with glyoxal at about 22° C. and a pH of about 8.9, and
wherein the reaction of the polymer and the glyoxal is continued after about 100% of the polymer in the solution is added to reach a level of glyoxalation such that at least about 40 mole % of the acrylamide repeating units of the polymer are converted to reactive aldehyde groups and wherein less viscosity increase occurs during the polymer-glyoxal reaction than if the solution of the glyoxal was added to the solution of the polymer.
6. The process of claim 5 wherein the step of reacting the polymer and the glyoxal occurs by the addition of a water mixture of the polymer to a solution of the glyoxal such that greater than about 65 mole % of the final polymer-glyoxal reaction occurs before about 100% of the polymer in the solution is added to the glyoxal mixture.
7. A process of forming paper, the process comprising the steps of:
providing an aqueous suspension of cellulosic fibers;
adding the aqueous composition of claim 1 to the suspension,
forming the cellulosic fibers into a sheet; and
drying the sheet to produce a paper having an initial wet tensile strength that is at least about 10% greater than a comparative paper.
8. The process of claim 7 wherein drying the sheet produces a paper having an initial wet tensile strength that is at least about 30% greater than a comparative paper.