Strengthening agents and processes for making and using same

Abstract

In some embodiments, a process can include combining a plurality of fibers and water to produce a slurry, forming the slurry into a wet paper web, pressing and draining the wet paper web to produce a wet paper sheet, and drying the wet paper sheet to produce a paper product. A strengthening agent can be combined with the fibers and water to produce the slurry, applied to the wet paper web, and/or applied to the wet paper sheet. The strengthening agent can include a polyamidoamine-epihalohydrin resin and an additive. The additive can include a tannin and/or a compound having a chemical formula (I) of:where: R1, R2, and R3 can independently be a hydroxyl group or a methoxy group, and R4, R5, and R6 can independently be H, an alkyl group, an aldehyde group, a carboxylic acid group, or a —C═C—COOH group.

What is claimed is: 
     
         1 . A process for making a paper product, comprising:
 combining a plurality of fibers and water to produce a slurry;   forming the slurry into a wet paper web;   pressing and draining the wet paper web to produce a wet paper sheet, wherein a strengthening agent is (i) combined with the plurality of fibers and water to produce the slurry, (ii) applied to the wet paper web, (iii) applied to the wet paper sheet, or (iv) a combination of at least two of (i), (ii), and (iii), and wherein the strengthening agent comprises a polyamidoamine-epihalohydrin resin and an additive, wherein the additive comprises at least one of a tannin and a compound having a chemical formula (I) comprising:   
       
         
           
           
               
               
           
         
         wherein: R 1 , R 2 , and R 3  are independently a hydroxyl group or a methoxy group, and R 4 , R 5 , and R 6  are independently H, an alkyl group, an aldehyde group, a carboxylic acid group, or a —C═C—COOH group; and 
         drying the wet paper sheet to produce the paper product. 
       
     
     
         2 . The process of  claim 1 , wherein the strengthening agent is in the form of a contact product produced by mixing the polyamidoamine-epihalohydrin resin and the additive such that the contact product is (i) combined with the plurality of fibers and water to produce the slurry, (ii) applied to the wet paper web, (iii) applied to the wet paper sheet, or (iv) a combination of at least two of (i), (ii), and (iii). 
     
     
         3 . The process of  claim 2 , wherein the polyamidoamine-epihalohydrin resin and the additive are mixed with one another for at least 1 minute to prepare the contact product. 
     
     
         4 . The process of  claim 2 , wherein the polyamidoamine-epihalohydrin resin and the additive are mixed with one another at a temperature of from about 0° C. to about 35° C. 
     
     
         5 . The process of  claim 1 , wherein the polyamidoamine-epihalohydrin resin and the additive are separately: (i) combined with the plurality of fibers and water to produce the slurry, (ii) applied to the wet paper web, (iii) applied to the wet paper sheet, or (iv) a combination of at least two of (i), (ii), and (iii). 
     
     
         6 . The process of  claim 1 , wherein at least a portion of the polyamidoamine-epihalohydrin resin is combined with the plurality of fibers and water to produce the slurry, and wherein at least a portion of the additive is applied to the wet paper web, applied to the wet paper sheet, or a combination thereof. 
     
     
         7 . The process of  claim 1 , wherein the additive comprises the tannin, and wherein the tannin comprises a condensed tannin, a hydrolyzable tannin, or a mixture thereof. 
     
     
         8 . The process of  claim 7 , wherein the additive comprises the hydrolysable tannin, and wherein the hydrolyzable tannin comprises tannic acid. 
     
     
         9 . The process of  claim 7 , wherein the additive comprises the condensed tannin, wherein the condensed tannin is extracted from one or more components of a plant, and wherein the plant comprises  mimosa , wattle,  quebracho , pine,  gambier , oak, chestnut,  eucalyptus , birch, willow, maple, or a mixture thereof. 
     
     
         10 . The process of  claim 1 , wherein the additive comprises gallic acid, syringic acid, syringol, pyrogallol, quercetin, methoxycatechol, sinapic acid, or a mixture thereof. 
     
     
         11 . The process of  claim 1 , wherein the polyamidoamine-epihalohydrin resin, the additive, or each of the polyamidoamine-epihalohydrin resin and the additive further comprises a liquid medium. 
     
     
         12 . The process of  claim 11 , wherein the liquid medium comprises water, an alkylene glycol, a polyalkylene glycol, or a mixture thereof. 
     
     
         13 . The process of  claim 11 , wherein the polyamidoamine-epihalohydrin resin and the additive each comprise the liquid medium, and wherein the polyamidoamine-epihalohydrin resin and the additive independently have a solids content of from about 5 wt % to about 55 wt %. 
     
     
         14 . The process of  claim 1 , wherein a weight ratio of the additive to the polyamidoamine-epihalohydrin resin, on a solids basis, is from about 0.01:1 to about 0.3:1, based on a combined weight of the additive and the polyamidoamine-epihalohydrin resin. 
     
     
         15 . The process of  claim 1 , wherein an amount of the strengthening agent in the paper product, on a solids basis, is from about 0.1 kg to about 40 kg per 1,000 kg of the plurality of fibers, on dry basis, in the paper product. 
     
     
         16 . A paper product, comprising:
 a paper substrate comprising a plurality of fibers; and   a strengthening agent disposed on the fibers, wherein the strengthening agent comprises a polyamidoamine-epihalohydrin resin and an additive, wherein the additive comprises at least one of a tannin and a compound having a chemical formula (I), comprising:   
       
         
           
           
               
               
           
         
         wherein: R 1 , R 2 , and R 3  are independently a hydroxyl group or a methoxy group, and R 4 , R 5 , and R 6  are independently H, an alkyl group, an aldehyde group, a carboxylic acid group, or a —C═C—COOH group. 
       
     
     
         17 . The paper product of  claim 16 , wherein an amount of the strengthening agent in the paper product, on a solids basis, is from about 0.1 kg to about 40 kg per 1,000 kg of the plurality of fibers, on a dry basis, in the paper product. 
     
     
         18 . The paper product of  claim 16 , wherein a weight ratio of the additive to the polyamidoamine-epihalohydrin resin in the strengthening agent is from about 0.01:1 to about 0.3:1. 
     
     
         19 . The paper product of  claim 16 , wherein the additive comprises the tannin, and wherein the tannin comprises tannic acid. 
     
     
         20 . The paper product of  claim 16 , wherein the additive comprises gallic acid, syringic acid, syringol, pyrogallol, quercetin, methoxycatechol, sinapic acid, or a mixture thereof.