Additive compositions and methods for papermaking with high-kappa furnishes

Abstract

A strength additive composition for papermaking processes using high-kappa furnish is disclosed. The composition comprises an aqueous media and a glyoxalated polyacrylamide (gPAM) resin having a weight average molecular weight (Mw) of at least about 5 MDa, a radius of gyration (Rg) of at least about 150 nm, and a structural density (Rg/Mw) of less than about 15 nm/Mda. A method of preparing the composition is also disclosed, and may be carried out in situ during a papermaking process (i.e., as an on-site method). A process of forming paper with the composition is also disclosed, and comprises combining the composition with an aqueous suspension of cellulosic fibers, forming the cellulosic fibers into a sheet, and drying the sheet to produce a paper.

1 . An additive composition for papermaking, comprising:
 an aqueous media; and   a glyoxalated polyacrylamide (gPAM) resin having a weight average molecular weight (Mw) of at least about 5 MDa, a radius of gyration (Rg) of at least about 150 nm, and a structural density (Rg/Mw) of less than about 15 nm/Mda.   
     
     
         2 . The additive composition of  claim 1 , wherein the glyoxalated polyacrylamide resin comprises the reaction product of (A) a cationic acrylamide (cAM) prepolymer and (B) glyoxal in an aqueous media, and wherein:
 (i) the cAM prepolymer (A) is present in the aqueous media at an initial concentration of from about 0.5 to about 4 wt. %;   (ii) the cAM prepolymer (A) and the glyoxal (B) are reacted in a dry weight (w/w) ratio of from about 75:25 to about 95:5 (A):(B); or   (iii) both (i) and (ii).   
     
     
         3 . The additive composition of  claim 2 , wherein the glyoxalated polyacrylamide (gPAM) resin has a weight average molecular weight (Mw) of at least about 6 MDa, wherein the cAM prepolymer (A) is present in the aqueous media at an initial concentration of from about 1 to about 2.5 wt. %, and wherein the cAM prepolymer (A) and the glyoxal (B) are reacted in a dry weight (w/w) ratio of from about 80:20 to about 90:10 (A):(B). 
     
     
         4 . The additive composition of  claim 2 , wherein the cAM prepolymer (A) comprises the reaction product of:
 (A1) an acrylamide (AM) monomer;   (A2) a cationic monomer; and   optionally, (A3) one or more additional ethylenically unsaturated monomer(s);   
       wherein the cAM prepolymer (A) comprises from about 0.5 to about 3.5 mol %, alternatively from about 1 to about 3 mol % of cationic monomer units derived from the cationic monomer (A2). 
     
     
         5 . The additive composition of  claim 4 , wherein the cAM prepolymer (A):(i) comprises from about 1 to about 3 mol % of cationic monomer units derived from the cationic monomer (A2); (ii) has a reduced solution viscosity (RSV) of from about 0.6 to about 1.6 dL/g; or (iii) both (i) and (ii). 
     
     
         6 . The additive composition of  claim 4 , wherein the AM monomer (A1), the cationic monomer (A2), and optionally the additional ethylenically unsaturated monomer(s) (A3) are reacted in the presence of a chain transfer agent. 
     
     
         7 . The additive composition of  claim 4 , wherein:
 (i) the AM monomer (A1) comprises acrylamide;   (ii) the cationic monomer (A2) comprises diallyldimethylammonium chloride (DADMAC);   (iii) the one or more additional ethylenically unsaturated monomer(s) (A3), when present, are selected from styrenes, alkyl acrylates, vinyl acetates, and vinyl carboxylic acids, esters, or salts thereof; or   (iv) any combination of (i)-(iii).   
     
     
         8 . The additive composition of  claim 2 , wherein the cAM prepolymer (A) has a reduced solution viscosity (RSV) of from about 0.5 to about 1.8 dL/g. 
     
     
         9 . A method of preparing an additive composition for papermaking, comprising:
 I) preparing a cationic acrylamide (cAM) prepolymer having a cationic monomer content of less than about 3.5 mol %; and   II) selectively glyoxalating the cAM prepolymer by controlling the concentration of the cAM prepolymer in an aqueous media during glyoxalation to give a glyoxalated polyacrylamide (gPAM) resin having a weight average molecular weight (Mw) of at least about 5 MDa, a radius of gyration (Rg) of at least about 150 nm, and a structural density (Rg/Mw) of less than about 15 nm/Mda.   
     
     
         10 . The method of  claim 9 , wherein the weight average molecular weight (Mw) of the glyoxalated polyacrylamide (gPAM) resin is at least about 6 MDa. 
     
     
         11 . The method of  claim 9 , wherein the cAM prepolymer (A) comprises: (i) a cationic monomer content of from about 1 to about 3 mol %; (ii) a reduced solution viscosity (RSV) of from about 0.5 to about 1.8 dL/g; or (iii) both (i) and (ii). 
     
     
         12 . The method of  claim 9 , wherein (II) selectively glyoxalating the cAM prepolymer comprises reacting the cAM prepolymer (A) and glyoxal (B) in an aqueous media, and wherein:
 (i) the cAM prepolymer (A) is present in the aqueous media at an initial concentration of from about 0.5 to about 2.5%;   (ii) the cAM prepolymer (A) and the glyoxal (B) are reacted in a dry weight (w/w) ratio of from about 80:20 to about 90:10 (A):(B); or   (iii) both (i) and (ii).   
     
     
         13 . The method of  claim 9 , further comprising preparing the cAM prepolymer (A), wherein preparing the cAM prepolymer (A) comprises reacting (A1) an acrylamide (AM) monomer, (A2) a cationic monomer, and optionally (A3) one or more additional ethylenically unsaturated monomer(s) in the presence of a chain transfer agent, and wherein the cAM prepolymer (A) comprises from about 0.5 to about 3.5 mol % of cationic monomer units derived from the cationic monomer (A2). 
     
     
         14 . The method of  claim 13 , wherein the cAM prepolymer (A) comprises from about 1 to about 3 mol % of cationic monomer units derived from the cationic monomer (A2). 
     
     
         15 . The method of  claim 13 , wherein:
 (i) the AM monomer (A1) comprises acrylamide;   (ii) the cationic monomer (A2) comprises diallyldimethylammonium chloride (DADMAC);   (iii) the one or more additional ethylenically unsaturated monomer(s) (A3), when present, are selected from styrenes, alkyl acrylates, vinyl acetates, and vinyl carboxylic acids, esters, or salts thereof; or   (iv) any combination of (i)-(iii).   
     
     
         16 . The method of  claim 15 , wherein the one or more additional ethylenically unsaturated monomer(s) (A3) are present in the reaction of the AM monomer (A1), the cationic monomer (A2), and the chain transfer agent, and wherein the one or more additional ethylenically unsaturated monomer(s) (A3) is selected from styrenes, alkyl acrylates, vinyl acetates, and combinations thereof. 
     
     
         17 . A process of forming paper, said process comprising:
 (1) providing an aqueous suspension of cellulosic fibers;   (2) combining the additive composition of  claim 1  with the aqueous suspension;   (3) forming the cellulosic fibers into a sheet; and   (4) drying the sheet to produce a paper.   
     
     
         18 . The process of  claim 17 , wherein the aqueous suspension of cellulosic fibers: (i) comprises a kappa number of at least about 30; (ii) comprises unbleached kraft (UBK) virgin fiber; (iii) comprises recycled fibers; (iv) is substantially free from polyamidoepichlorohydrins (PAE); or (V) any combination of (i)-(iv). 
     
     
         19 . The process of  claim 18 , wherein the aqueous suspension of cellulosic fibers comprises a mixture of virgin fibers and recycled fibers. 
     
     
         20 . The process of  claim 17 , wherein the gPAM resin is prepared in-situ within about 5 hours of combining the additive composition with the aqueous suspension.