MXPA00000801A

MXPA00000801A - Polyamidoamine/epichlorohydrin resins bearing polyol sidechains as dry strength agents

Info

Publication number: MXPA00000801A
Application number: MXPA/A/2000/000801A
Authority: MX
Inventors: Barton K Bower
Original assignee: Hercules Incorporated
Priority date: 1997-07-29
Filing date: 2000-01-24
Publication date: 2001-03-05

Abstract

Compositions suitable for use as dry strength additives comprising water soluble polyamidoamine/epichlorohydrin resin bearing polyol sidechains wherein the weight fraction of the polyol in the resin is less than 50 percent by weight and the polyol sidechain is attached to the polyamidoamine/epichlorohydrin resin by carbon-nitrogen bond, such as amide bond or secondary or tertiary amine bonds.

Description

POLYAMIDOAMINE / EPICLOROHIDRINE RESINS CARRIER SIDE CHAINS AS AGENTS FOR DRY RESISTANCE BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to additives for dry strength for paper and, more specifically, to polyamidoamine / epichlorohydrin resins bearing polyol side chains.

Description of the prior art Resistance is a very important property in paper products. At constant base weight, the use of additives for dry strength increases strength. Agents for dry strength allow papermakers to use less pulp, less expensive pulp and / or more filler materials while making paper products strong enough, stiff and opaque. The benefits for users of paper products include stronger packaging and lower postage and postage costs. Conventional dry strength agents include starch, urea / formaldehyde resins, melamine / formaldehyde resins, acrylamide copolymers and polyamidoamine / epichlorohydrin resins.

USP 3,962,159 (Ray-Chaudhuri, et al.) Describes the polymerization of dispersible starches in water, polyamidoanes and epichlorohydrin. The weight ratio of starch to polyamidoamine is between 1: 9 and 9: 1. Although Ray-Chaudhuri uses the term "grafted copolymer" he is in fact making block copolymers of the condensing agent. All preparations of USP 3,962,159 form carbon-oxygen bonds between the starch and the polyamidoamine, except for that of Example 19 where a quaternary ammonium bond is formed. USP 3,314,897 (Gaertner) describes the treatment of polysaccharide substrates (starch, textiles, such as starch, linen, rayon and cellulose paper products) with a minor amount of a prepolymer composed of aliphatic amine addition products / epichlorohydrin in reaction with an amine having at least 2 amino hydrogens. In other words, Gaertner uses a smaller amount of this prepolymer to modify the polysaccharide substrates instead of modifying a polyamidoamine / epichlorohydrin resin including the polyol side chains and obtaining a water soluble product. USP 3,320,066 (Garth) discloses the separate addition of the polyamide epichlorohydrin resin, dialdehyde carbohydrate and optionally carboxymethylcellulose and / or cationic starch to the paper pulp, i.e. to the diluted slurry of the pulp of paper obtained after the refining operation. South African Patent 695018 discloses starch / polymeric polyamine compositions wherein the polyamine is formed by a reaction of an alkylene dihalide, for example, ethylene dichloride, and an amine, for example diethylenetriamine. The preparation of a polyamphenamide or a polyaminoamide / epichlorohydrin resin [sic] is not described. French Patent 1,488,141 (which corresponds to Canadian Patent 797,130) describes the improvement of the strength of the cellulosic material by: (a) treating an aqueous suspension of cellulose fibers with a cationic resin for wet strength (as can be the cationic urea-formaldehyde resin, and cationic polyamides, obtained from the reaction of polyalkylene polyamine and dicarboxylic acid which are entangled with epichlorohydrin), (b) adjusting the pH of the suspension to 4.0-5.5, (c) the treatment of the suspension with a dialdehyde polysaccharide, (d) adjusting the pH of the suspension to 4.0-5.5 and (e) forming a continuous material of the treated cellulose fibers. USP 4,097,427 (Ait en) describes the interaction of the polyalkylene polyamine / epichlorohydrin resins with starch for improved wet strength. The polyamidoamine / epichlorohydrin resins are not described.

USP 3,763,060 (Hamerstrand et al.) Discloses the interaction of sodium xanthate starch with polyamide polyamine-epichlorohydrin (PAE) resin wherein the bond between the xanthate starch and the PAE resin is a carbon-sulfur bond.

USP 4,940,514 (Stange, et al.) Describes the interaction of vinyl polymers with starch digested by enzymes. There is no description of polyamidoamine / epichlorohydrin resins. USP 4,818,341 (Degen, et al.) Describes the interaction of vinyl polymers with starch digested with enzymes. There is no description of polyamidoamine / epichlorohydrin resins. USP 5,334,287 (Hartmann, et al.) Describes the use of N-vinylcarboxamide free radical grafted copolymers of mono-, oligo- or polysaccharides. There is no description of polyamidoamine / epichlorohydrin resins.

SUMMARY OF THE INVENTION In accordance with the present invention there are provided compositions for improving the dry strength of paper containing polyamidoamine / epichlorohydrin resins with a content of azetidinium ion, water soluble, carriers of polyol side chains, wherein the fraction in The weight of the polyol in the resin is less than 50% by weight and the polyol side chain is linked to the polyamidoamine / epichlorohydrin resin by a carbon-nitrogen bond.

According to the present invention there are provided the processes for the preparation of the water-soluble polyamidoamine / epichlorohydrin resins, carriers of polyol side chains. In accordance with the present invention, a paper with better dry strength characteristics is provided, which contain water soluble polyamidoamine / epichlorohydrin resins, carriers of polyol side chains. In accordance with the present invention, there is further provided the process for improving the dry strength of the paper by adding water-soluble polyamidoamine / epichlorohydrin resins, carriers of polyol side chains, to the aqueous pulp.

DETAILED DESCRIPTION OF THE INVENTION It has been described that the polyamidoamine / epichlorohydrin resins containing azetidinium ion, carriers of polyol side chains, wherein the weight fraction of the polyol in the resin is less than 50% by weight and the side chain polyol is bound to the polyamidoamine / epichlorohydrin resin by carbon-nitrogen amide, secondary amine or tertiary amine bonds, will improve the dry strength of the paper and as such will have an economic benefit for the paper manufacturers and the paper user.

The polyamidoamines are prepared by the method described in US 2,926,116 and EPA 488,767. The polyamidoamine / epichlorohydrin resins having amino-chlorohydrin, azetidinium and / or epoxide functionality can be prepared as described in US 2,926,116; US 5,171,795; EPA 408,767; GB 865,727; US 4,605,709; and US 4,537,657. The description of these patents is incorporated herein by reference. The polyol side chains are defined as organic residues containing two or more hydroxyl groups, wherein at least half of the carbon atoms in the polyol side chain carry hydroxyl groups. To be useful as starting materials for the compositions of the present invention, the precursor molecule of a polyol side chain must also have one, and only one functional group, selected from the group consisting of carboxylic acid, lactone, amine and aldehyde. Carbohydrates, which include the monosaccharides, disaccharides, oligosaccharides and polysaccharides, glycerol, glyceraldehyde, 3-amino-1, 2-propanediol, 3-alkylamino-1, 2-propanediol, 3-hydroxyethylamino-1,2-propanediol, threose, erythrose, xylose, arabinose, ribose, fructose, glucose, galactose, mannose, sucrose, maltobiose, maltotriose, lactose, cellobiose, helicellulose, cellulose, starch, dextrins, pyrodextrin, alginate, glycogen, inulin, furcelar * an, agar, carrageenan , locust bean gum, fucoidan, guar, laminaran, gum arabic, ghatti gum, karaya gum, tragacanth gum, gum okra, tamarind gum, xanthan, scleroglucan, psyllium gum, pectin, dextran, methylcellulose, ethylcellulose, hydroxyethylcellulose, Hydroxypropylcellulose and chitin are precursors of the polyol side chains or can be converted into polyol side chain precursors. If it is not already present, a functional group carboxylic acid, lactone, amine or aldehyde can be provided to the structure of the initial material using conventional synthetic methods. For example, chitin can be depolymerized and deacetylated to form glucosamine or the alginate can be completely decarboxylated to obtain a terminal monoaldehyde. Preferred polyol residues are threrythyl, erythrityl, xylythyl, arabinityl, ribityl, fructityl, glucityl, galactityl, manityl, maltobiotyl, maltotriotyl, lactobiotyl, cellobiotyl and prirodextrinityl [sic]. For example, the term "glycolyl polyol residue" refers to the 6-carbon polyol side chain attached via the precursors 1-amino-1-deoxy-sorbitol, 1-methylamino-1-deoxysorbitol, glucosamine, gluconic acid, gluconolactone or N -aminoethylgluonamide. The most preferred polyol residues are glucithyl, maltobiotyl, lactobiotyl and prirodextrinityl.

The novel compositions of the present invention can be prepared by reacting the polyols having carboxylic acid functionality or lactone with polyamidoamines (PAA) to form amide bonds followed by the reaction with epichlorohydrin. These can also be prepared by reacting the polyol amines with azetidinium or epoxide groups of the polyamidoamine / epichlorohydrin resins (PA / E). In addition, these can be prepared by reductive amination of reducing sugars with polyamidoamines followed by the reaction with epichlorohydrin. Accordingly, the compositions of the present invention can be prepared by: (a) reacting a polyol having carboxylic acid functionality or lactone with less than about 95 mol% of the amino groups of a polyamidoamine to form amide bonds. This is followed by: (b) the reaction of the amine groups of the polyamidoamine which has not been used to form the amide bonds with epichlorohydrin to provide at least one amino-chlorohydrin, epoxide or azetidinium chloride functionality. The reaction of the functional groups carboxylic acid and lactone with amines, as well as the reaction of the amines with epichlorohydrin are procedures well known in the art [eg, G. Ziegast, B. Pfannemuller, Makromol. Chem. Rap. Comm., 5, 373 (1984)] and they can be done in a conventional way. An alternative process for preparing the polyamidoamine / epichlorohydrin resins with a water-soluble azetidinium ion content, carriers of polyol side chains of the present invention is by reaction of a polyol having amino functionality with less than about 95 mol% of functional groups azetidinium or epoxide of the polyamidoamine / epichlorohydrin resin to form secondary or tertiary amino bonds. The reaction of the amines with azetidinium or epoxide functional groups is well known in the art [for example N. Chapman et al., J. Chem. Soc, 1925 (1959) and V. R. Gaertner, J. Org. Cnern. 33, 523 (1968)] and can be performed by conventional methods. Another method for the preparation of the compositions of the present invention, the polyol groups can be attached to the polyamidoamine / epichlorohydrin resin by reductive amination of the aldehyde groups of the sugars reducers for less than about 95 mol% of the amino groups of the polyaroi oamine to form tertiary non-linkages. Then, the polyaraidoamine unsaturated groups that have not been used to form the tertiary amino bonds are reacted with epichlorohydrin to provide at least one amino chlorohydrin, epoxide or azetidinium chloride functionality. Reductive amination of groups aldehyde by the amino groups to form amino bonds is well known in the art (for example, J.J. Scheibel et al., U.S. 5,500,150, 3/19/96) and can be performed by conventional methods. The novel compositions of this invention retain the ability of polyamidoamine / epichlorohydrin polymers to be substantive for paper pulp, which is anionic, at neutral dibasic pH in papermaking. The permanent cationic charge due to the azetidinium group is conserved given that at least 5 mol% of the azetidinium group that would be present in the absence of the polyol side chains is present in the new compositions. The polyol side chains will also have an attraction for the hemicelluloses on the surfaces of the pulp. A fundamental problem of the PA / E paper strength agents of the prior art is that the polyamidoamine / epichlorohydrin polymers do not mix optimally with the amorphous cellulose since a certain type of polymer solves itself better than it would be solvated by a different type of polymer, and since the polyamidoamine / epichlorohydrin polymers are very different in structure compared to the amorphous cellulose polymers naturally found on the surface of paper pulp fibers. The new compositions of the present invention overcome this deficiency providing polyamidoamine / epichlorohydrin polymers with polyol substituents which are highly compatible with amorphous cellulose and improve the mixing of the reinforcing additives and the amorphous cellulose. The polyol side chains attached to the polyamidoamine / epichlorohydrin polymers will be attracted to the surfaces of the cellulose pulp and will contribute to reinforcing by forming hydrogen bonds with the surfaces of the cellulose pulp. To facilitate the appearance of the fiber-fiber bridge formation of the paper reinforcement mechanism, the novel compositions of the invention retain the self-crosslinking property of the polyamidoamine / epichlorohydrin resins having at least 5 mol% of the reactive functional groups (aminoclorohydrin, azetidinium and epoxides) of those that would be present in the absence of the polyol side chains. Resins with polyol side chains can increase their viscosity and molecular weight during paper drying and storage due to the crosslinking or crosslinking reactions of azetidinium and epoxide. The azetidinium and epoxide groups also form bonds with the paper pulp by reaction with the nucleophiles of the amorphous cellulose on the surface of the paper pulp. The following examples are provided for purposes of illustration of the present invention. All parts and percentages are by weight unless otherwise specified.

EXAMPLE 1 Preparation of lactobionic polyamidoamine amide: lactobionic acid (26.86 g, 75 mmol) and a polyamidoamine (Polymer 567 resin for dry strength available from Hercules Incorporated) prepared from adipic acid and diethylenetriamine (57.18 g, 300 mmol amine ) in ethylene glycol (84 g) were heated at 130 ° C for 80 minutes. The titration of the amine indicated that 24% of the initial amine had been converted to the amide carbohydrate.

Conversion of lactobionic amide polyamidoamine to resin: Lactobionic amide polyamidoamine (50% solids in ethylene glycol, 132.36 g, 176 mmol of amine), water (88.16 g) and epichlorohydrin (21.29 g, 230 mmol) were stirred at 25 ° C. C for 18 hours and then stirred and heated at 65 ° C for 60 minutes. Water (417.7 g) and concentrated sulfuric acid (4.52 g) were added and the reaction mixture was heated to room temperature obtaining the product with 13.1% solids, pH 2.89, viscosity 46 cP Brookfield, 4520 ppm, 1,3-dichloro-2-propanol, 2320 ppm 3-chloropropanediol and 24% by weight of polyol in the final product based on the dried organic solids.

EXAMPLE 2 Reaction of polyamidoamine / epichlorohydrin resin with glucosamine: Polyamidoamine / epichlorohydrin resin (Kymene® 557H, resin for wet strength available from Hercules Incorporated, 12.3% solids, 63 cP Brookfield viscosity, 8200 ppm, 1,3-dichloro -2-propanediol, 2200 ppm, 3-chloropropanediol, 499.98 g, 300 mmol of azetidinium plus aminoclorohydrin) and glucosamine hydrochloride (19.07, 88 mmol) were mixed and the pH was adjusted to 10 with sodium hydroxide (6 molar). After stirring and heating at 65 ° C for 50 minutes keeping the pH at 10, the reaction mixture was cooled to room temperature and acidified with concentrated sulfuric acid (10.89 g) giving the product with 17.3% solids, pH 2.95 and viscosity Brookfield of 39 cP. HPLC (high performance liquid chromatography) indicated that 39% of the loaded glucosamine had reacted. The weight fraction of the polyol in the final product was 20% based on the dried organic solids.

EXAMPLE 3 Reaction of polyamidoamine / epichlorohydrin resin with pyrodextrin N-aminoethyl amide: Polyamidoamine / epichlorohydrin resin (Kymene® 557LX for wet strength, available from Hercules Incorporated, 12.4% solids, 42 cP Brookfield viscosity, 780 ppm 1, 3 -dichloro-2-propanol, 190 ppm 3-chloropropanediol, 720.89 g, 360 mmoles of azetidinium plus aminoclorohydrin) and pyrodextrin N-aminoethylamide (ICN Biomedicals INC. pyrodextrin or Sigma Chemical Company pyrodextrin oxidized pro bromo, dehydrated, reacted with ethylene diamine, 50% solids in ethylene glycol, 59.63 g, 32 mmol of amine) was stirred at 25 ° C maintaining the pH at 9 with sodium hydroxide (6 molar, 109 g) until Gardner viscosity -Holdt was "DE" in 5 hours. The concentrated sulfuric acid (9.5 g) was added giving the product with 12.7% solids, pH 2.91, Brookfield viscosity of 78 cP, 350 ppm of 1,3-dichloro-2-propanol, 220 ppm of 3-chloropropanediol and 24% by weight of polyol in the final product on the basis of the dried organic solids.

EXAMPLE 4 Papermaking and dry strength testing: In Table 1, the dry strengths of the papers prepared from the new agents for the Dry strength is compared to the dry strengths of the paper prepared without the strength additive (white). The papers 1-7 contain resins prepared by the procedure of Example 1, the papers 8-15 resins prepared by the procedure of Example 2, and the papers 16-28 resins prepared by the procedure of Example 3. The paper pulp was a 70:30 mixture of cellulose sulphate, hardwood, bleached James River Burgess: cellulose sulphate, softwood, bleached Rayonier; the hardness of water was 50 ppm, the alkalinity was 25 ppm and the pH was 7.6. After refining with a 12 inch double disc refiner, Jones, the pulp refining was 430-435 CSF. The dry strength agents of the present invention were added to the wet end of the papermaking machine at the level of 1% by weight as compared to the dry paper pulp. The paper was dried at 4.0-4.8% by weight moisture using a 45 lb./in. Linear press and 7 drying rolls at 150-190 ° F. The basis weight of the paper was 40 lbs / ream. The oven was cured at 80 ° C for 0.5 hours. The tensile strength in the Z direction (perpendicular to the plane of the paper) was used as the measure of the dry strength effect. The tensile strength in the Z direction was measured by holding the blade against two plates with double-sided tape and moving the plates away from each other with the tester CS-163D digital ZDT until the paper separated.

Table 1 Increase in tensile strength in the dimension Z, dry, in comparison with the white Paper # Precursor polyol PAA or Carbohydrate Inc. ZDT PAA / E% by weight against white 1 Gluconolactone P657 26% 19.8% 2 Lactobionic lactone P657 43 25.0 3 Lactobionic lactone P657 41 40.0 4 Gluconolactone P657 13 27.4 Maltobionic lactone P657 22 33.0 6 Maltobionic lactone P657 38 36.0 7 Lactobionic Lactone P657 24 39.5 8 Glucosamine * HCl K557H 34 21.8 9 Meglumine K557H 36 30.2 Meglumine K557H 28 37.5 11 Aminosorbitol K557H 20 28.8 12 Glucosamine * HCl K557H 34 29.9 13 Glucosamine * HCl K557H 34 32.0 14 Aminosorbitol K557H 20 35.5 Glucosamine »HCl K557H 20 34.3 16 N-aminoethyl ICN II K557LX 38 50.4 17 N-aminoethyl ICN I K557LX 39 50.4 18 N-aminoethyl Sigma III K557LX 37 53.1 19 N-aminoethyl Sigma III K557LX 25 58.1 N-aminoethyl Sigma I K557LX 25 57.8 Table 1 (continued) Paper i t Polyol precursor P Ó Carbohydrate Inc. ZDT PAA / E% by weight against white 21 N-aminoethyl maltobionic K557LX 19 47.5 22 N-aminoethyl lactobionic K557LX 27 43.5 23 N-aminoethyl Sigma I K557LX 39 57.6 24 N-aminoethyl lactobionic K557LX 15 44.1 N-aminoethyl ICN I K557LX 24 60.2 26 N-aminoethyl lactobionic K557LX 15 47.5 27 N-aminoethyl ICN II K557LX 24 54.7 28 N-aminoethyl maltobionic K557LX 25 48.2

Claims

1. A composition consisting of polyamidoamine / epichlorohydrin resin with a content of azetidinium ions, soluble in water, carrier of polyol side chains, wherein the weight fraction of the polyol in the resin is less than 50% by weight and the side chain polyol is bound to the polyamidoamine / epichlorohydrin resin by carbon-nitrogen bond. The composition of claim 1, wherein the polyol side chain is attached to the polyamidoamine / epichlorohydrin resin by amide bond. The composition of claim 1, wherein the polyol side chain is attached to the polyamidoamine / epichlorohydrin resin by secondary or tertiary amino bond. The composition of claim 1, wherein the polyol side chain is selected from the group consisting of polyol-residues in monosaccharides, oligosaccharide disaccharides and polysaccharides. The composition of claim 1, wherein the polyol side chain is selected from the group consisting of polyol residues in monosaccharides, disaccharides, oligosaccharides and polysaccharides, glycerol, glyceraldehyde, 3-amino-1,2-propanediol, 3- alkylamino-l, 2-propanediol, 3- hydroxyethylamino-1,2-propanediol, threose, erythrose, xylose, arabinose, ribose, fructose, glucose, galactose, mannose, sucrose, maltose, maltotriose, lactose, cellobiose, hemicellulose, cellulose, starch, dextrin, pyrodextrin, alginate, glycogen, inulin, furcellaran, agar, carrageenan, microbial gum, locust bean gum, fucoidan, guar, laminaran, gum arabic, ghatti gum, karaya gum, tragacanth gum, okra gum, tamarind gum, xanthan, scleroguan, gum psyllium, pectin, dextran, methylcellulose, ethylcellulose, hydroethylcellulose, hydroxypropylcellulose and chitin. The composition of claim 5, wherein the polyol side chain is selected from the group consisting of thretyl, erythrityl, xylythyl, arabinityl, ribityl, fructityl, glucityl, galactityl, manityl, maltobiotyl, maltotriotyl, maltobiotyl, cellobiotyl, and prirodextrimityl. The composition of claim 5, wherein the polyol side chain is derived from the initial polyol material having, in the natural product or provided by synthetic method, functional groups selected from the group consisting of carboxylic acid, lactone, amine and aldehyde groups . The composition of claim 7, wherein the side chain polyol is obtained from the group consisting of gluconolactone, lactobionic acid, lactobionic lactone, maltobionic acid, maltobionic lactone, glucosamine, 1-amino-1-deoxysorbitol or 1-N-methylamino-l-deoxysorbitol (meglumine), glucose, maltose and pyrodextrin N-aminoethyl amide. The composition of claim 6, wherein the polyol side chain is selected from the group consisting of glucithyl, maltobiotyl, lactobiotyl and prirodextrinityl. The composition of claim 5, 8 or 9, wherein the weight fraction of the polyol in the resin is less than about 40% by weight. The composition of claim 5, 8 or 9, wherein the weight fraction of the polyol in the resin is less than about 30% by weight. The composition of claim 5, 8 or 9, wherein the weight fraction of the polyol in the resin is at least about 5% by weight. The composition of claim 5, 8 or 9, wherein the weight fraction of the polyol in the resin is at least about 10% by weight. 14. A process for the preparation of polyamidoamine / water-soluble epichlorohydrin resin bearing polyol side chains, consists of: (a) the reaction of the polyol having a functional group carboxylic acid or lactone with less than about 95 mol% of the amino groups of the polyamidoamine by the formation of amide bonds; and (b) the reaction of the amine groups of the polyamidoamine that have not been used to form the amide bonds with epichlorohydrin to provide at least aminoclorohydrin functionalities, epoxide or azetidinium chloride. 15. A process for preparing water-soluble polyamidoamine / epichlorohydrin resin bearing polyol side chains consists of: reacting the polyol having amino functional group with less than about 95 mol% of azetidinium or epoxide functional groups of the polyamidoamine / epichlorohydrin resin. 16. A process for preparing polyamidoamine / water-soluble epichlorohydrin resin, bearing polyol side chains, consists of: (a) reductive amination of the aldehyde groups of the reducing sugars for less than about 95 mol% of the amine groups of the polyamidoamine to form tertiary amino bonds; and (b) the reaction of the amino groups of the polyamidoamine that have not been used to form the tertiary amino bonds with epichlorohydrin for provide at least functionalities aminocohydrin, epoxide or azetidinium chloride. 17. Paper containing the composition of claim 1. 18. Paper containing the composition of claim 5. 19. Paper containing the composition of claim 6. 20. Paper containing the composition of claim 9. 21. A process for making paper to improve the dry strength of the paper produced consists in adding to the finished aqueous pulp at the wet end of the papermaking machine the composition of claim 1, and forming the paper of the aqueous finish. 2

2. A papermaking process for improving the dry strength of the paper produced consists in adding the composition of claim 5 to the wet pulp end of the papermaking machine at the wet end of the papermaking machine and forming the paper from the finish. aqueous. 2

3. A process for making paper, to improve the dry strength of the paper produced, consists in adding to the finish of the aqueous pulp at the wet end of the paper-forming machine the composition of the paper. Claim 6, and form the role of the aqueous finish. 2

4. A process for making paper, to improve the dry strength of the paper produced, consists in adding to the finish of the aqueous pulp at the wet end of the papermaking machine the composition of claim 9, and forming the paper from of the aqueous finish. 2

5. The process of claims 21, 22, 23 or 24, wherein the amount of water-soluble polyamidoamine / epichlorohydrin resin carrying polyol side chains is from about 0.1 to about 10%, based on the dried pulp.