SOLIDIFYING COMPOSITION FOR PAPER AND CARDBOARD

Abstract

The invention relates to an aqueous composition comprising (a) polymers having primary amino groups and/or amidine groups to a combined content for these groups of ≧1.5 meq/g of polymer, and (b) 0.01 to 50 mol % of 1,4-cyclohexanedione (b) based on the combined amount of primary amino groups and amidine groups of the polymers,
wherein the pH of the aqueous composition is ≦6,
and further to its use as strength enhancer and to a method of producing paper and board, employment of the aqueous composition and also the paper and board thus obtained.

Claims

1. An aqueous composition comprising (a) a polymer having primary amino groups and/or amidine groups in a combined content for these groups of ≧1.5 meq/g of polymer, and (b) 0.01 to 50 mol % of 1,4-cyclohexanedione based on the combined content of primary amino groups and amidine groups of the polymer, wherein the pH of the aqueous composition is ≦6.

2. The aqueous composition according to claim 1 comprising ≧50 wt % of water based on the aqueous composition.

3. The aqueous composition according to claim 1 wherein the pH of the aqueous composition is in the range from 2 to 6.

4. The aqueous composition according to claim 1, wherein the polymer having primary amino groups and/or amidine groups is selected from the group consisting of hydrolyzed homopolymers of N-vinylcarboxamide, hydrolyzed copolymers of N-vinylcarboxamide with further neutral monoethylenically unsaturated monomers, hydrolyzed copolymers of N-vinylcarboxamide with anionic monoethylenically unsaturated monomers, hydrolyzed copolymers of N-vinylcarboxamide with cationic monoethylenically unsaturated monomers, hydrolyzed homopolymers of N-vinylcarboxamide which have been converted in a polymer-analogous manner, Hofmann degradation products of homo- or copolymers of (meth)acrylamide, and polymers comprising ethyleneimine units.

5. The aqueous composition according to claim 1 wherein the polymer having primary amino groups and/or amidine groups is selected from the group consisting of hydrolyzed copolymers of N-vinylcarboxamide with further neutral monoethylenically unsaturated monomers, hydrolyzed copolymers of N-vinylcarboxamide with anionic monoethylenically unsaturated monomers, and hydrolyzed copolymers of N-vinylcarboxamide with cationic monoethylenically unsaturated monomers, wherein the degree of hydrolysis is ≧10 mol %.

6. The aqueous composition according to claim 1, wherein the polymer having primary amino groups and/or amidine groups is a partially or fully hydrolyzed copolymer obtained by polymerization of 30-99 mol % of at least one monomer of the formula ##STR00010## where R.sup.1 is H or C.sub.1-C.sub.6 alkyl, 0-70 mol % of one or more further neutral monoethylenically unsaturated monomers (iia), 0-70 mol % of one or more monomers (iib) selected from the group consisting of monoethylenically unsaturated sulfonic acids, monoethylenically unsaturated phosphonic acids, monounsaturated esters of phosphoric acid, monoethylenically unsaturated carboxylic acids having 3 to 8 carbon atoms in the molecule and/or their alkali metal, alkaline earth metal or ammonium salts, 0-70 mol % of one or more monomers (iic) selected from the group consisting of monoethylenically unsaturated monomers bearing protonatable secondary or tertiary amino groups and quaternized monoethylenically unsaturated monomers, all based on the overall monomer composition and optionally one or more compounds having at least two ethylenically unsaturated double bonds in the molecule, with the proviso that the sum total for the fractions of monomers (iia), (iib) and (iic) is altogether in the range from 1 to 70 mol %, and subsequent partial or complete hydrolysis of the polymerized units of monomers (I) in the polymer to form amino groups.

7. The aqueous composition according to claim 1 wherein the polymer having primary amino groups and/or amidine groups is a partially or fully hydrolyzed copolymer of N-vinylcarboxamide with further neutral, anionic and/or cationic monoethylenically unsaturated monomers, wherein this monomer is selected from the group consisting of acrylonitrile, vinyl acetate, sodium acrylate, diallyldimethyl ammonium chloride, [3-(dimethylamino)propyl]acrylamide, N-[3-(dimethylamino)propyl]methacrylamide, [3-(trimethylammonio)propyl]acrylamide chloride and N-[3-(trimethylammonio)propyl]methacrylamide chloride.

8. The aqueous composition according to claim 1, wherein the polymer having primary amino groups and/or amidine groups is a partially or fully hydrolyzed copolymer of N-vinylcarboxamide with sodium acrylate, and a degree of hydrolysis ≧30 mol %.

9. The aqueous composition according to claim 1 wherein the polymer having primary amino groups and/or amidine groups is a partially or fully hydrolyzed homopolymer of N-vinylcarboxamide and a degree of hydrolysis ≧30 mol %.

10. The aqueous composition according to claim 1, wherein the aqueous composition comprises (a) 5 to 40 wt %, based on the aqueous composition, of a polymer having primary amino groups and/or amidine groups with a combined content for these groups of ≧1.5 meq/g of polymer, and (b) 0.1 to 30 mol % of 1,4-cyclohexanedione based on the combined content of primary amino groups and/or amidine groups of the polymers.

11. A method of enhancing strength of a fibrous material during papermaking, comprising raising the pH of the aqueous composition of claim 1 by at least one point.

12. A method of producing paper or board, said method comprising a step of adding the aqueous composition according to claim 10 to a paper stock with a pH in the range from 6 to 8 and then dewatering the paper stock by sheet formation and drying.

13. The method according to claim 11, wherein the aqueous composition is present in an amount comprising from 0.01 to 6 wt % of the polymer having primary amino groups and/or amidine groups, based on fibrous material.

14. The method according to claim 13, wherein wastepaper is used as fibrous material.

15. The method according to claim 13, wherein from 20 to 30 wt % of filler based on the paper is used.

16. Paper or board obtained according to the method of claim 12.

Description

EXAMPLES

[0183] The examples which follow further elucidate the present invention. The percentages in the examples are weight percent, unless otherwise stated.

[0184] The following abbreviations are used hereinbelow:

VFA: vinylformamide
NaAS: sodium acrylate
VAc: vinyl acetate
AN: acrylonitrile
DADMAC: diallyldimethylammonium chloride
PVFA: polyvinylformamide
Copo VFA/NaAS: copolymer of vinylformamide and sodium acrylate
Copo VFA/VAc: copolymer of vinylformamide and vinyl acetate
Copo VFA/AN/Na-Itaconat: copolymer of vinylformamide, acrylonitrile, sodium itaconate
Copo VFA/NaAS/AN: copolymer of vinylformamide, sodium acrylate and acrylonitrile
Copo VFA/DADMAC: copolymer of vinylformamide and DADMAC

[0185] K values were measured as described in H. Fikentscher, Cellulosechemie, volume 13, 48-64 and 71-74 under the particular conditions specified. The particulars between parentheses indicate the concentration of the polymer solution and the solvent.

[0186] The percentages in the examples are percent by weight, unless otherwise stated.

[0187] Solids contents of polymers were quantified by 0.5 to 1.5 g of the polymer solution being distributed in a 4 cm diameter tin lid and then dried at 140° C. in a circulating air drying cabinet for two hours. The ratio of the mass of the sample after drying under the above conditions to the mass at sample taking is the solids content of the polymer.

[0188] The water used in the examples was completely ion-free.

[0189] Preparation of polymers having primary amino groups and/or amidine groups

[0190] The preparation was carried out in two or three steps:

1) polymerization
2) hydrolysis of polymers, and optionally
3) polymer-analogous reaction

1) Polymerizations

[0191]

TABLE-US-00001 TABLE 1 Overview of polymerizations Monomer composition in mol % Solids Na content Example VFA Na acrylate Vinyl acetate Acrylonitrile DADMAC itaconate K value wt % P1 100 — — — — — .sup.  45.sup.3) 36.4 P2 100 — — — — — .sup.  90.sup.3) 19.7 P3 100 — — — — — 120  12.6 P4 80 20 — — — — 86 21.5 P5 70 30 — — — — 55 24.0 P6 70 30 — — — — 85 16.0 P7 70 30 — — — — 90 23.8 P8 70 30 — — — — 122  15.9 P9 60 40 — — — — 92 25.0 P10 70 — 30 — — — .sup.  84.sup.1) 15.5 P11 60 — 40 — — — .sup.  74.sup.1) 15.7 P12 50 — 50 — — — .sup.  68.sup.1) 16.5 P13 49.5 — — 49.5 — 1 .sup. 175.sup.2) 16.3 P14 50 30 — 20   — — 90 25.6 P15 70 — — — 30 — 80 20.0 .sup.1)K value quantified in formamide .sup.2)K value quantified in DMSO .sup.3)K value quantified in water

Example P1 (VFA Homopolymer, K 45)

[0192] Feed 1 was provided by providing 423.1 g of N-vinylformamide (BASF).

[0193] Feed 2 was provided by dissolving 9.7 g of 2,2′-azobis(2-methylpropionamidine)dihydrochloride (Wako) in 112.0 g of water at room temperature.

[0194] A 2 l glass apparatus fitted with anchor stirrer, descending condenser, internal thermometer and nitrogen inlet tube was initially charged with 585.2 g of water and 4.6 g of 75 wt % phosphoric acid. About 8.2 g of 25 wt % aqueous sodium hydroxide solution were admixed at a speed of 100 rpm, attaining pH 6.6. The initial charge was heated to 80° C. and the pressure in the apparatus was reduced sufficiently for the reaction mixture to just start to boil at 80° C. (about 460 mbar). Feeds 1 and 2 were then started at the same time and admixed concurrently over a period of 3 hours at a constant 80° C. On completion of the admixture the reaction mixture was postpolymerized at 80° C. for a further three hours. During the entire polymerization and postpolymerization, about 100 g of water were distilled off. The batch was subsequently cooled down to room temperature under atmospheric pressure.

[0195] The product obtained was a slightly yellow, viscous solution having a solids content of 36.4 wt %. The K value of the polymer was 45 (1.0 wt % in water).

Example P2 (VFA Homopolymer, K 90)

[0196] Feed 1 was provided by providing 234 g of N-vinylformamide.

[0197] Feed 2 was provided by dissolving 1.2 g of 2,2′-azobis(2-methylpropionamidine)dihydrochloride in 56.8 g of water at room temperature.

[0198] A 2 l glass apparatus fitted with anchor stirrer, descending condenser, internal thermometer and nitrogen inlet tube was initially charged with 1080.0 g of water and 2.5 g of 75 wt % phosphoric acid. 2.1 g of 25 wt % aqueous sodium hydroxide solution were admixed at a speed of 100 rpm, attaining pH 6.6. The initial charge was heated to 73° C. and the pressure in the apparatus was reduced sufficiently for the reaction mixture to just start to boil at 73° C. (about 350 mbar). Feeds 1 and 2 were then started at the same time. At a constant 73° C., feeds 1 and 2 were added, respectively, over one hour and 15 minutes and over 2 hours. On completion of the admixture of feed 2, the reaction mixture was postpolymerized at 73° C. for a further three hours. During the entire polymerization and postpolymerization, about 190 g of water were distilled off. The batch was subsequently cooled down to room temperature under atmospheric pressure.

[0199] The product obtained was a slightly yellow, viscous solution having a solids content of 19.7 wt %. The K value of the polymer was 90 (0.5 wt % in water)

Example P3 (VFA Homopolymer, K 120)

[0200] Feed 1 was provided by dissolving 1.1 g of 2,2′-azobis(2-methylpropionamidine)dihydrochloride in 108.9 g of water at room temperature.

[0201] A 2 l glass apparatus fitted with anchor stirrer, descending condenser, internal thermometer and nitrogen inlet tube was initially charged with 961.0 g of water and 2.4 g of 75 wt % phosphoric acid. About 3.7 g of 25 wt % aqueous sodium hydroxide solution were admixed at a speed of 100 rpm, attaining pH 6.6. Subsequently, 222.2 g of N-vinylformamide were admixed. The initial charge was heated to 62° C. and the pressure in the apparatus was reduced sufficiently for the reaction mixture to just start to boil at 62° C. (about 220 mbar). Feed 1 was added over four hours at a constant 62° C. The reaction mixture was subsequently postpolymerized at 62° C. for two hours. During the entire polymerization and postpolymerization, about 200 g of water were distilled off. The batch was subsequently diluted with 670 g of water and cooled down to room temperature under atmospheric pressure.

[0202] The product obtained was a slightly yellow, viscous solution having a solids content of 12.6 wt %. The K value of the polymer was 120 (0.1 wt % in 5 wt % aqueous NaCl solution).

Example P4 (VFA/Na Acrylate Copolymer 80 mol %/20 mol %, K 86)

[0203] Feed 1 was provided by providing a mixture of 293.7 g of water, 242.96 g of aqueous 32 wt % sodium acrylate solution adjusted to pH 6.4 and 237.2 g of N-vinylformamide.

[0204] Feed 2 was provided by dissolving 1.4 g of 2,2′-azobis(2-methylpropionamidine)dihydrochloride in 203.6 g of water at room temperature.

[0205] A 2 l glass apparatus fitted with anchor stirrer, descending condenser, internal thermometer and nitrogen inlet tube was initially charged with 659.4 g of water and 3.5 g of 75 wt % phosphoric acid. 6.0 g of 25 wt % aqueous sodium hydroxide solution were admixed at a speed of 100 rpm, attaining pH 6.6. The initial charge was heated to 80° C. and the pressure in the apparatus was reduced sufficiently for the reaction mixture to just start to boil at 80° C. (about 460 mbar). Feeds 1 and 2 were then started at the same time. At a constant 80° C., feeds 1 and 2 were added, respectively, over two hours and over 2.5 hours. On completion of the admixture of feed 2, the reaction mixture was postpolymerized at 80° C. for a further 2.5 hours. During the entire polymerization and postpolymerization, about 170 g of water were distilled off. The batch was subsequently cooled down to room temperature under atmospheric pressure.

[0206] The product obtained was a slightly yellow, viscous solution having a solids content of 21.5 wt %. The K value of the copolymer was 86 (0.5 wt % in 5 wt % aqueous NaCl solution).

Example P5 (VFA/Na Acrylate Copolymer=70 mol %/30 mol %, K 55)

[0207] Feed 1 was provided by providing a mixture of 147.3 g of water, 317.6 g of aqueous 32 wt % sodium acrylate solution adjusted to pH 6.4 and 181.0 g of N-vinylformamide.

[0208] Feed 2 was provided by dissolving 5.1 g of 2,2′-azobis(2-methylpropionamidine)dihydrochloride in 165.9 g of water at room temperature.

[0209] A 2 l glass apparatus fitted with anchor stirrer, descending condenser, internal thermometer and nitrogen inlet tube was initially charged with 573.4 g of water and 3.0 g of 75 wt % phosphoric acid. 5.2 g of 25 wt % aqueous sodium hydroxide solution were admixed at a speed of 100 rpm, attaining pH 6.6. The initial charge was heated to 80° C. and the pressure in the apparatus was reduced sufficiently for the reaction mixture to just start to boil at 80° C. (about 460 mbar). Feeds 1 and 2 were then started at the same time. At a constant 80° C., feeds 1 and 2 were added, respectively, over two hours and over 2.5 hours. On completion of the admixture of feed 2, the reaction mixture was postpolymerized at 80° C. for a further 2.5 hours. During the entire polymerization and postpolymerization, about 170 g of water were distilled off. The batch was subsequently cooled down to room temperature under atmospheric pressure.

[0210] The product obtained was a slightly yellow, viscous solution having a solids content of 24.0 wt %. The K value of the copolymer was 55 (0.5 wt % in 5 wt % aqueous NaCl solution).

Example P6 (VFA/Na Acrylate Copolymer=70 mol %/30 mol %)

[0211] Feed 1 was provided by providing a mixture of 340.0 g of water, 176.5 g of aqueous 32 wt % sodium acrylate solution adjusted to pH 6.4 and 100.6 g of N-vinylformamide.

[0212] Feed 2 was provided by dissolving 5.8 g of 2,2′-azobis(2-methylpropionamidine)dihydrochloride in 164.2 g of water at room temperature.

[0213] Feed 3 was provided by dissolving 5.8 g of 2,2′-azobis(2-methylpropionamidine)dihydrochloride in 164.2 g of water at room temperature.

[0214] A 2 l glass apparatus fitted with anchor stirrer, descending condenser, internal thermometer and nitrogen inlet tube was initially charged with 380 g of water and 1.2 g of 85 wt % phosphoric acid. 4.2 g of 25 wt % aqueous sodium hydroxide solution were admixed at a speed of 100 rpm, attaining pH 6.6. The initial charge was heated to 80° C. and the pressure in the apparatus was reduced sufficiently for the reaction mixture to just start to boil at 80° C. (about 450 mbar). Feeds 1 and 2 were then started at the same time and added concurrently over 2 h. The reaction mixture was subsequently postpolymerized at 80° C. for a further hour. Feed 3 was then admixed over 5 min, followed by a further two hours of postpolymerization 80° C. During the entire polymerization and postpolymerization, about 100 g of water were distilled off. The batch was subsequently cooled down to room temperature under atmospheric pressure.

[0215] The product obtained was a slightly yellow, viscous solution having a solids content of 16.0 wt %. The K value of the copolymer was 85 (determined at 0.5 wt % in 5 wt % aqueous NaCl).

Example P7 (VFA/Na Acrylate Copolymer=70 mol %/30 mol %, K 90)

[0216] Feed 1 was provided by providing a mixture of 100.0 g of water, 224.6 g of aqueous 32 wt % sodium acrylate solution adjusted to pH 6.4 and 128.0 g of N-vinylformamide.

[0217] Feed 2 was provided by dissolving 0.9 g of 2,2′-azobis(2-methylpropionamidine)dihydrochloride in 125.8 g of water at room temperature.

[0218] A 2 l glass apparatus fitted with anchor stirrer, descending condenser, internal thermometer and nitrogen inlet tube was initially charged with 407 g of water and 1.9 g of 85 wt % phosphoric acid. About 3.7 g of 25 wt % aqueous sodium hydroxide solution were admixed at a speed of 100 rpm, attaining pH 6.6. The initial charge was heated to 80° C. and the pressure in the apparatus was reduced sufficiently for the reaction mixture to just start to boil at 80° C. (about 450 mbar). Feeds 1 and 2 were then started at the same time. At a constant 80° C., feeds 1 and 2 were added, respectively, over 1.5 h and over 2.5 hours. On completion of the admixture of feed 2, the reaction mixture was postpolymerized at 80° C. for a further 2.5 hours. During the entire polymerization and postpolymerization, about 143 g of water were distilled off. The batch was subsequently cooled down to room temperature under atmospheric pressure.

[0219] The product obtained was a slightly yellow, viscous solution having a solids content of 23.8 wt %. The K value of the copolymer was 90 (0.5 wt % in 5 wt % aqueous NaCl solution).

Example P8 (VFA/Na Acrylate Copolymer=70 mol %/30 mol %)

[0220] Feed 1 was provided by providing a mixture of 330.0 g of water, 217.8 g of aqueous 32 wt % sodium acrylate solution adjusted to pH 6.4 and 124.2 g of N-vinylformamide.

[0221] Feed 2 was provided by dissolving 0.3 g of 2,2′-azobis(2-methylpropionamidine)dihydrochloride in 66.8 g of water at room temperature.

[0222] Feed 3 was provided by dissolving 0.2 g of 2,2′-azobis(2-methylpropionamidine)dihydrochloride in 17.4 g of water at room temperature.

[0223] A 2 l glass apparatus fitted with anchor stirrer, descending condenser, internal thermometer and nitrogen inlet tube was initially charged with 668.3 g of water and 1.9 g of 75 wt % phosphoric acid. 3.1 g of 25 wt % aqueous sodium hydroxide solution were admixed at a speed of 100 rpm, attaining pH 6.6. The initial charge was heated to 73° C. and the pressure in the apparatus was reduced sufficiently for the reaction mixture to just start to boil at 73° C. (about 340 mbar). Feeds 1 and 2 were then started at the same time. At a constant 3° C., Feeds 1 and 2 were added, respectively, over 2 hours and over 3 hours. On completion of the admixture of feed 2, the reaction mixture was postpolymerized at 73° C. for a further 2.5 hours. Feed 3 was then admixed over 5 min, followed by a further two hours of postpolymerization at 73° C. During the entire polymerization and postpolymerization, about 190 g of water were distilled off. The batch was subsequently cooled down to room temperature under atmospheric pressure.

[0224] The product obtained was a slightly yellow, viscous solution having a solids content of 15.9 wt %. The K value of the copolymer was 122 (0.1 wt % in 5 wt % aqueous NaCl solution).

Example P9 (VFA/Na Acrylate Copolymer=60 mol %/40 mol %, K 92)

[0225] Feed 1 was provided by providing a mixture of 423.5 g aqueous 32 wt % sodium acrylate solution adjusted to pH 6.4 and 155.1 g of N-vinylformamide.

[0226] Feed 2 was provided by dissolving 2.1 g of 2,2′-azobis(2-methylpropionamidine)dihydrochloride in 227.9 g of water at room temperature.

[0227] A 2 l glass apparatus fitted with anchor stirrer, descending condenser, internal thermometer and nitrogen inlet tube was initially charged with 573.4 g of water and 3.0 g of 85 wt % phosphoric acid. 5.2 g of 25 wt % aqueous sodium hydroxide solution were admixed at a speed of 100 rpm, attaining pH 6.6. The initial charge was heated to 77° C. and the pressure in the apparatus was reduced sufficiently for the reaction mixture to just start to boil at 77° C. (about 450 mbar). Feeds 1 and 2 were then started at the same time. At a constant 77° C., feeds 1 and 2 were added, respectively, over 1.5 h and over 2.5 hours. On completion of the admixture of feed 2, the reaction mixture was postpolymerized at 80° C. for a further 2.5 hours. During the entire polymerization and postpolymerization, about 200 g of water were distilled off. The batch was subsequently cooled down to room temperature under atmospheric pressure.

[0228] The product obtained was a slightly yellow, viscous solution having a solids content of 25.0 wt %. The K value of the copolymer was 92 (0.5 wt % in 5 wt % aqueous NaCl solution).

Example P10 (VFA/VAc Copolymer=70 mol %/30 mol %, K 84)

[0229] Feed 1 was provided by providing 76.5 g of vinyl acetate.

[0230] Feed 2 was provided by dissolving 0.4 g of 2,2′-azobis(2-methylpropionamidine)dihydrochloride in 98.2 g of water at room temperature.

[0231] Feed 3 was provided by dissolving 0.1 g of 2,2′-azobis(2-methylpropionamidine)dihydrochloride in 44.7 g of water at room temperature.

[0232] Feed 4 was provided by providing 750 g of water.

[0233] A 2 l glass apparatus fitted with anchor stirrer, reflux condenser, internal thermometer and nitrogen inlet tube was initially charged with 352.5 g of water, 2.2 g of 85 wt % phosphoric acid and 22.4 g of a 10 wt % aqueous Mowiol 44-88 solution. 4.0 g of 25 wt % aqueous sodium hydroxide solution were admixed at a speed of 100 rpm such that a pH of 6.5 was attained. The initial charge was admixed with 149.0 g of N-vinylformamide and subjected to the introduction of nitrogen at 3 l/h for half an hour to remove oxygen present. In the meantime, the initial charge was heated to 65° C. Feed 1 was then admixed over 5 minutes, followed by feed 2 over 5 h. 1.0 h after feed 2 was started, feed 4 is additionally started and admixed over 2.5 hours. On completion of feed 2, the reaction mixture was postpolymerized at 65° C. for one hour, then admixed with feed 3 over 5 minutes and heated to 70° C. Postpolymerization was continued at 70° C. for a further 2 hours. Thereafter, the reflux condenser is replaced by a descending condenser. The pressure in the apparatus was reduced to 580 mbar and about 68 g of water were distilled off at 80° C. The product was cooled down to room temperature under atmospheric pressure.

[0234] The product obtained was a finely divided white suspension having a solids content of 15.5 wt %. The K value of the copolymer was 84 (0.5 wt % in formamide).

Example P11 (VFA/VAc Copolymer=60 mol %/40 mol %, K 74)

[0235] Feed 1 was provided by providing 100.1 g of vinyl acetate.

[0236] Feed 2 was provided by dissolving 0.4 g of 2,2′-azobis(2-methylpropionamidine)dihydrochloride in 98.2 g of water at room temperature.

[0237] Feed 3 was provided by dissolving 0.1 g of 2,2′-azobis(2-methylpropionamidine)dihydrochloride in 44.7 g of water at room temperature.

[0238] Feed 4 was provided by providing 750 g of water.

[0239] A 2 l glass apparatus fitted with anchor stirrer, reflux condenser, internal thermometer and nitrogen inlet tube was initially charged with 352.8 g of water, 2.2 g of 85 wt % phosphoric acid and 22.4 g of a 10 wt % aqueous Mowiol 44-88 solution. 4.0 g of 25 wt % aqueous sodium hydroxide solution were admixed at a speed of 100 rpm to obtain a pH of 6.5. The initial charge was admixed with 125.2 g of N-vinylformamide and subjected to the introduction of nitrogen at 3 l/h for half an hour to remove oxygen present. In the meantime, the initial charge was heated to 65° C. Feed 1 was then admixed over 5 minutes, followed by feed 2 over 5 h. 1.5 h after feed 2 was started, feed 4 is additionally started and admixed over 2.5 hours. On completion of feed 2, the reaction mixture was postpolymerized at 65° C. for one hour, then admixed with feed 3 over 5 minutes and heated to 70° C. Postpolymerization was continued at 70° C. for a further 2 hours. Thereafter, the reflux condenser is replaced by a descending condenser. The pressure in the apparatus was reduced to 540 mbar and about 102 g of water were distilled off at 80° C. The product was cooled down to room temperature under atmospheric pressure.

[0240] The product obtained was a finely divided white suspension having a solids content of 15.7 wt %. The K value of the copolymer was 74 (0.5 wt % in formamide).

Example P12 (VFA/VAc Copolymer=50 mol %/50 mol %, K 68)

[0241] Feed 1 was provided by providing 127.3 g of vinyl acetate.

[0242] Feed 2 was provided by dissolving 0.5 g of 2,2′-azobis(2-methylpropionamidine)dihydrochloride in 101.8 g of water at room temperature.

[0243] Feed 3 was provided by dissolving 0.1 g of 2,2′-azobis(2-methylpropionamidine)dihydrochloride in 46.4 g of water at room temperature.

[0244] Feed 4 was provided by providing 750 g of water.

[0245] A 2 l glass apparatus fitted with anchor stirrer, reflux condenser, internal thermometer and nitrogen inlet tube was initially charged with 338.4 g of water, 2.2 g of 85 wt % phosphoric acid and 23.2 g of a 10 wt % aqueous Mowiol 44-88 solution. 4.0 g of 25 wt % aqueous sodium hydroxide solution were admixed at a speed of 100 rpm such that a pH of 6.5 was attained. The initial charge was admixed with 106.2 g of N-vinylformamide and subjected to the introduction of nitrogen at 3 l/h for half an hour to remove oxygen present. In the meantime, the initial charge was heated to 65° C. Feed 1 was then admixed over 5 minutes, followed by feed 2 over 5 h. 2 h after feed 2 was started, feed 4 was additionally started and admixed over 2.5 hours. On completion of feed 2, the reaction mixture was postpolymerized at 65° C. for 1 hour, then admixed with feed 3 over 5 minutes and heated to 70° C. Postpolymerization was continued at 70° C. for a further 2 hours. Thereafter, the reflux condenser is replaced by a descending condenser. The pressure in the apparatus was reduced to 540 mbar and about 200 g of water were distilled off at 80° C. The vacuum was broken and the product was cooled down to room temperature.

[0246] The product obtained was a finely divided white suspension having a solids content of 16.5 wt %. The K value of the copolymer was 68 (0.5 wt % in formamide).

Example P13 (VFA/AN/Na itaconate copolymer=49.5 mol %/49.5 mol %/1.0 mol %, K 175)

[0247] Feed 1 was provided by providing 221.3 g of acrylonitrile.

[0248] Feed 2 was provided by providing 299.3 g of N-vinylformamide.

[0249] Feed 3 was provided by dissolving 0.7 g of 2,2′-azobis(2-methylpropionamidine)dihydrochloride in 128.8 g of water at room temperature.

[0250] A 2 l glass apparatus fitted with anchor stirrer, reflux condenser, internal thermometer and nitrogen inlet tube was initially charged with 1600.0 g of water, 5.2 g of 75 wt % phosphoric acid, 26.0 g of Luviskol K90 polyvinylpyrrolidone (BASF) and 154.7 g of 7 wt % aqueous itaconic acid solution. 37.4 g of 25 wt % aqueous sodium hydroxide solution were admixed at a speed of 100 rpm such that a pH of 6.8 was attained. Nitrogen was introduced into the initial charge at 10 l/h for half an hour to remove existing oxygen. In the meantime, the initial charge was heated to 60° C. Feeds 1 to 3 were then started at the same time. The addition at a constant 60° C. took 3.5 hours for feed 1, three hours for feed 2 and 4 h for feed 3. The reaction mixture was then postpolymerized at 60° C. for a further 2.5 hours.

[0251] Then, 546 g of water were admixed and the reflux condenser was replaced by a descending condenser. The pressure in the apparatus was reduced to 220 mbar and 552 g of water were distilled off at 64° C. The product was cooled down to room temperature under atmospheric pressure.

[0252] The product obtained was a finely divided white suspension having a solids content of 16.3 wt %. The K value of the copolymer was 175 (0.1 wt % in DMSO).

Example P14 (VFA/Na Acrylate/AN Copolymer=50 mol %/30 mol %/20 mol %, K 90)

[0253] Feed 1 was provided by providing 342.7 g of 32 wt % aqueous sodium acrylate solution.

[0254] Feed 2 was provided by providing 139.5 g of N-vinylformamide.

[0255] Feed 3 was provided by providing 41.2 g of acrylonitrile.

[0256] Feed 4 was provided by dissolving 1.0 g of 2,2′-azobis(2-methylpropionamidine)dihydrochloride in 114.8 g of water at room temperature.

[0257] A 2 l glass apparatus fitted with anchor stirrer, reflux condenser, internal thermometer and nitrogen inlet tube was initially charged with 540.0 g of water and 2.7 g of 75 wt % phosphoric acid. 4.0 g of 25 wt % aqueous sodium hydroxide solution were admixed at a speed of 100 rpm such that a pH of 6.7 was attained. Nitrogen was introduced into the initial charge at 10 l/h for half an hour to remove the oxygen present. In the meantime, the initial charge was heated to 72° C. Feeds 1 to 4 were then started at the same time. The addition at a constant 72° C. took two hours for feed 1, 1.3 h for feed 2, 2.0 h for feed 3 and three hours for feed 4. The reaction mixture was then postpolymerized at 72° C. for a further 2.5 h.

[0258] Then, 121 g of water were admixed and the reflux condenser was replaced by a descending condenser. The pressure in the apparatus was reduced to 320 mbar and 121 g of water were distilled off at 72° C. The product was cooled down to room temperature under atmospheric pressure.

[0259] The product obtained was a slightly cloudy, viscous solution having a solids content of 25.6 wt %. The K value of the copolymer was 90 (0.5 wt % in 5 wt % aqueous NaCl solution).

Example P15 (VFA/DADMAC Copolymer=70 mol %/30 mol %, K 80)

[0260] Feed 1 was provided by providing 119.1 g of N-vinylformamide.

[0261] Feed 2 was provided by dissolving 2.1 g of 2,2′-azobis(2-methylpropionamidine)dihydrochloride in 88.2 g of water at room temperature.

[0262] A 2 l glass apparatus fitted with anchor stirrer, descending condenser, internal thermometer and nitrogen inlet tube was initially charged with 202.2 g of water and 2.2 g of 85 wt % phosphoric acid. 3.0 g of 25 wt % aqueous sodium hydroxide solution were admixed at a speed of 100 rpm to obtain a pH of 6.5. Then, 176.8 g of a 65 wt % aqueous solution of diallyldimethylammonium chloride (Aldrich) were mixed in. Nitrogen was passed into the initial charge at 10 l/h for half an hour to remove the oxygen present. In the meantime, the initial charge was heated to 66° C. The pressure in the apparatus was reduced to about 240 mbar, so the reaction mixture just began to boil at 66° C. Feeds 1 and 2 were then started at the same time. The addition at a constant 66° C. took two hours for feed 1 and 4 hours for feed 2. On completion of the admixture of feed 2, the reaction mixture was postpolymerized at 66° C. for a further hour. Pressure and internal temperature were then raised to 360 mbar and 75° C. respectively and the mixture was subjected to a postpolymerization at 74° C. for a further two hours. The reaction mixture was still boiling under these conditions. About 90 g of water were distilled off during the entire polymerizationd and postpolymerization. Then, 690 g of water were admixed and the batch was cooled down to room temperature under atmospheric pressure.

[0263] The product obtained was a slightly yellow viscous solution having a solids content of 20%. The K value of the copolymer was 80 (1 wt % in 5 wt % aqueous NaCl solution).

[0264] 2. Hydrolyses

[0265] The hydrolyses described hereinbelow in Examples H1 to H24 are collated in table 2.

TABLE-US-00002 TABLE 2 Reaction conditions and polymer used for hydrolysis Content of prim. Degree of amine + Starting Hydrolysis Amount.sup.5) hydrolysis PG amidine Ex. polymer agent [mol %] [mol %] [wt %] [meq/g].sup.6) Comments H1 P1 NaOH 75 70 11.4 13.4 H2 P2 NaOH 120 100  7.8 22.7 H3 P2 NaOH 73 70 9.5 13.4 H4 P2 NaOH 50 50 11.8 8.7 H5 P2 NaOH 40 40 10.3 6.6 H6 P2 NaOH 36 35 10.6 5.7 H7 P3 NaOH 50 48 7.9 8.3 H8 P4 NaOH 50 52 13.1 7.0 H9 P4 NaOH 110 100  9.8 16.2 H10 P5 NaOH 120 100  10.9 12.4 H11 P5 NaOH 50 52 14.5 6.0 H12 P6 NaOH 120 100  13.4 H13 P7 NaOH 110 100  10.1 13.4 H14 P7 NaOH 45 50 10.9 5.7 H15 P8 HCl 43 50 10.6 5.7 .sup.2) H16 P8 NaOH 110 100  5.9 13.4 H17 P8 NaOH 51 50 7.0 5.7 H18 P9 NaOH 110 100  12.6 11.0 H19 P10 NaOH 120 .sup. 100.sup.1) 6.4 15.9 .sup.3) H20 P11 NaOH 120 .sup. 100.sup.1) 6.4 13.6 .sup.3) H21 P12 NaOH 120 .sup. 100.sup.1) 6.6 11.4 .sup.3) H22 P13 HCl 100 98 5.6 9.8 .sup.4) H23 P14 HCl 120 100  13.9 9.3 .sup.2) H24 P15 NaOH 100 99 11.0 10.3 PG: polymer content without counter-ion .sup.1)The degree of hydrolysis of the vinyl acetate was >95%. .sup.2)The required amount of acid was chosen such that the sodium acrylate units in the polymer were additionally protonated. .sup.3)The required amount of aqueous sodium hydroxide solution was chosen such that the vinyl acetate units in the molecule were completedly hydrolyzed. .sup.4)The required amount of acid was chosen such that the sodium itaconate units in the polymer were additionally protonated. .sup.5)Amount of hydrolysis agent in mol % based on the molar vinylformamide quantity used for the starting polymer. .sup.6)Combined content of primary amino groups and/or amidine units in 1 g of polymer without counter-ion.

[0266] The degree of hydrolysis is the mol % fraction of hydrolyzed VFA units, based on the VFA units originally present in the polymer.

[0267] The degree of hydrolysis of the hydrolyzed homopolymers/copolymers of N-vinylformamide was quantified by enzymatic analysis of the formates/formic acid released in the hydrolysis (test kit from Boehringer Mannheim).

[0268] The degree of hydrolysis of hydrolyzed polymers bearing vinyl acetate units was quantified in a similar manner by using an analogous test kit from Boehringer Mannheim for the released acetic acid/acetates.

[0269] The polymer content without counter-ions indicates the wt % of polymer in the aqueous solution without inclusion of counter-ions. The polymer content without counter-ions represents the sum total of the proportional parts by weight of all structural units of the polymer in g which are present in 100 g of the solution. The polymer content without counter-ions is determined arithmetically. Potentially charge-bearing structural units are included in the charged form, i.e., for instance amino groups in the protonated form and acid groups in the deprotonated form. Counter-ions to charged structural units such as Na, chloride, phosphate, formate, acetate, etc. are not included. The calculation can be performed for any one batch by using the usage amounts of monomers, the degree of hydrolysis and any fraction which has been converted in a polymer-analogous manner to determine the molar amounts of the polymer's structural units present at the end of the reaction and convert them arithmetically, by means of the molar masses of the structural units, into the proportional parts by weight. The sum total of the proportional parts by weight represents the overall amount of polymer in this batch. The polymer content without counter-ion follows from the ratio of the overall amount of polymer to the overall mass of the batch.

[0270] The combined content of primary amino groups and/or amidine groups is obtainable in a manner similar to the procedure described above for the polymer content. The usage amounts of monomers, the analytically quantified degree of hydrolysis, the ratio of amidine groups to primary amino groups which is quantified by .sup.13C NMR spectroscopy and, where appropriate, the fraction which was converted in a polymer-analogous manner are used to determine the molar composition of the polymer's structural units present at the end of the reaction. The molar mass of the individual structural units can be used to calculate therefrom the molar fraction of primary amino groups and/or amidine units in meq which are present in 1 g of polymer.

Example H1

[0271] 250.0 g of the polymer solution obtained by P1 were placed in a 500 ml four-neck flask fitted with blade stirrer, internal thermometer, dropping funnel and reflux condenser, admixed with 6.4 g of 40 wt % aqueous sodium bisulfite solution, and then heated to 80° C., at a stirrer speed of 80 rpm. Then, 147.8 g of 25 wt % aqueous sodium hydroxide solution were admixed. The mixture was maintained at 80° C. for three hours. The product obtained was cooled down to room temperature and adjusted to pH 2.0 with 163.1 g of 37 wt % hydrochloric acid.

[0272] A slightly yellow polymer solution was obtained. The degree of hydrolysis of the vinylformamide units was 70 mol %.

Example H2

[0273] 300.0 g of the polymer solution obtained by P2 were placed in a 1 l four-neck flask fitted with blade stirrer, internal thermometer, dropping funnel and reflux condenser and heated to 80° C. at a stirrer speed of 80 rpm. Then, 157.3 g of 25 wt % aqueous sodium hydroxide solution were admixed. The mixture was maintained at 80° C. for three hours. The product obtained was cooled down to room temperature.

[0274] A slightly yellow polymer solution was obtained. The degree of hydrolysis of the vinylformamide units was 100 mol %.

Example H 3

[0275] 700.0 g of the polymer solution obtained by P2 were placed in a 2 l three-neck flask fitted with blade stirrer, internal thermometer, dropping funnel and reflux condenser, admixed with 9.8 g of 40 wt % aqueous sodium bisulfite solution, and then heated to 80° C., at a stirrer speed of 80 rpm. Then, 219.3 g of 25 wt % aqueous sodium hydroxide solution were admixed. The mixture was maintained at 80° C. for three hours. The product obtained was cooled down to room temperature and adjusted to pH 7.0 with 102.1 g of 37 wt % hydrochloric acid.

[0276] A slightly yellow polymer solution was obtained. The degree of hydrolysis of the vinylformamide units was 70 mol %.

Example H 4

[0277] 400.0 g of the polymer solution obtained by P2 were placed in a 1 l four-neck flask fitted with blade stirrer, internal thermometer, dropping funnel and reflux condenser and heated to 80° C. at a stirrer speed of 80 rpm. Then, 87.4 g of 25 wt % aqueous sodium hydroxide solution were admixed. The mixture was maintained at 80° C. for three hours. The product obtained was cooled down to room temperature and adjusted to pH 7.0 with 39.8 g of 37 wt % hydrochloric acid.

[0278] A slightly yellow polymer solution was obtained. The degree of hydrolysis of the vinylformamide units was 50 mol %.

Example H 5

[0279] 136.1 g of the polymer solution obtained by P2 were placed in a 500 ml four-neck flask fitted with blade stirrer, internal thermometer, dropping funnel and reflux condenser, admixed with 1.9 g of 40 wt % aqueous sodium bisulfite solution, and then heated to 80° C., at a stirrer speed of 80 rpm. Then, 23.8 g of 25 wt % aqueous sodium hydroxide solution were admixed. The mixture was maintained at 80° C. for 4 hours. The product obtained was cooled down to room temperature and adjusted to pH 3.0 with 24.7 g of 37 wt % hydrochloric acid.

[0280] A slightly yellow polymer solution was obtained. The degree of hydrolysis of the vinylformamide units was 40 mol %.

Example H 6

[0281] 603.3 g of the polymer solution obtained by P2 were placed in a 1 l four-neck flask fitted with blade stirrer, internal thermometer, dropping funnel and reflux condenser, admixed with 8.6 g of 40 wt % aqueous sodium bisulfite solution, and then heated to 80° C., at a stirrer speed of 80 rpm. Then, 94.9 g of 25% aqueous sodium hydroxide solution were admixed. The mixture was maintained at 80° C. for 4 hours. The product obtained was cooled down to room temperature and adjusted to pH 3.0 with 31.7 g of 37 wt % hydrochloric acid.

[0282] A slightly yellow polymer solution was obtained. The degree of hydrolysis of the polymerized vinylformamide units was 35 mol %.

Example H 7

[0283] 250.0 g of the polymer solution obtained by P3 were placed in a 500 ml four-neck flask fitted with blade stirrer, internal thermometer, dropping funnel and reflux condenser, admixed with 2.3 g of 40 wt % aqueous sodium bisulfite solution, and then heated to 80° C., at a stirrer speed of 80 rpm. Then, 34.7 g of 25 wt % aqueous sodium hydroxide solution were admixed. The mixture was maintained at 80° C. for three hours. The product obtained was cooled down to room temperature and adjusted to pH 3.0 with 31.7 g of 37 wt % hydrochloric acid.

[0284] A slightly yellow polymer solution was obtained. The degree of hydrolysis of the vinylformamide units was 48 mol %.

Example H 8

[0285] 300.0 g of the polymer solution obtained by P4 were placed in a 500 ml four-neck flask fitted with blade stirrer, internal thermometer, dropping funnel and reflux condenser, admixed with 3.5 g of 40 wt % aqueous sodium bisulfite solution, and then heated to 80° C., at a stirrer speed of 80 rpm. Then, 53.6 g of 25 wt % aqueous sodium hydroxide solution were admixed. The mixture was maintained at 80° C. for three hours. The product obtained was cooled down to room temperature and adjusted to pH 7.5 with 24.1 g of 37 wt % hydrochloric acid.

[0286] A slightly yellow polymer solution was obtained. The degree of hydrolysis of the vinylformamide units was 52 mol %.

Example H 9

[0287] 1006.0 g of the polymer solution obtained by P4 were placed in a 2 l four-neck flask fitted with blade stirrer, internal thermometer, dropping funnel and reflux condenser, admixed with 11.7 g of 40 wt % aqueous sodium bisulfite solution, and then heated to 80° C., at a stirrer speed of 80 rpm. Then, 395.4 g of 25 wt % aqueous sodium hydroxide solution were admixed. The mixture was maintained at 80° C. for 7 hours. The product obtained was cooled down to room temperature.

[0288] A slightly yellow polymer solution was obtained. The degree of hydrolysis of the vinylformamide units was 100 mol %.

Example H10

[0289] 300.0 g of the polymer solution obtained by P5 were placed in a 500 ml four-neck flask fitted with blade stirrer, internal thermometer, dropping funnel and reflux condenser, admixed with 3.3 g of 40 wt % aqueous sodium bisulfite solution, and then heated to 80° C., at a stirrer speed of 80 rpm. Then, 120.4 g of 25 wt % aqueous sodium hydroxide solution were admixed. The mixture was maintained at 80° C. for three hours. The product obtained was cooled down to room temperature.

[0290] A slightly yellow polymer solution was obtained. The degree of hydrolysis of the vinylformamide units was 100 mol %.

Example H11

[0291] 300.0 g of the polymer solution obtained by P5 were placed in a 500 ml four-neck flask fitted with blade stirrer, internal thermometer, dropping funnel and reflux condenser, admixed with 3.3 g of 40 wt % aqueous sodium bisulfite solution, and then heated to 80° C., at a stirrer speed of 80 rpm. Then, 50.2 g of 25 wt % aqueous sodium hydroxide solution were admixed. The mixture was maintained at 80° C. for three hours. The product obtained was cooled down to room temperature and adjusted to pH 7.5 with 22.6 g of 37 wt % hydrochloric acid.

[0292] A slightly yellow polymer solution was obtained. The degree of hydrolysis of the vinylformamide units was 52 mol %.

Example H12

[0293] 600.0 g of the polymer solution obtained by P6 were placed in a 2 l four-neck flask fitted with blade stirrer, internal thermometer, dropping funnel and reflux condenser, admixed with 4.5 g of 40 wt % aqueous sodium bisulfite solution, and then heated to 80° C., at a stirrer speed of 80 rpm. Then, 150.0 g of 25% aqueous sodium hydroxide solution were admixed. The mixture was maintained at 80° C. for 7 hours. The product obtained was cooled down to room temperature. A slightly yellow polymer solution was obtained. The degree of hydrolysis of the vinylformamide units was 100 mol %.

Example H13

[0294] 847.2 g of the polymer solution obtained by P7 were placed in a 2 l four-neck flask fitted with blade stirrer, internal thermometer, dropping funnel and reflux condenser, admixed with 9.3 g of 40 wt % aqueous sodium bisulfite solution, and then heated to 80° C., at a stirrer speed of 80 rpm. Then, 313.7 g of 25% aqueous sodium hydroxide solution were admixed. The mixture was maintained at 80° C. for 7 hours. The product obtained was cooled down to room temperature and adjusted to pH 8.5 with 117.0 kg of 37 wt % hydrochloric acid.

[0295] A slightly yellow polymer solution was obtained. The degree of hydrolysis of the vinylformamide units was 100 mol %.

Example H14

[0296] 846.5 g of the polymer solution obtained by P7 were placed in a 2 l four-neck flask fitted with blade stirrer, internal thermometer, dropping funnel and reflux condenser, admixed with 236.3 g of completely ion-free water and 9.3 g of 40 wt % aqueous sodium bisulfite solution, and then heated to 80° C., at a stirrer speed of 80 rpm. Then, 128.3 g of 25% aqueous sodium hydroxide solution were admixed. The mixture was maintained at 80° C. for 5 hours. The product obtained was cooled down to room temperature and adjusted to pH 8.3 with 52.0 kg of 37 wt % hydrochloric acid.

[0297] A slightly yellow polymer solution was obtained. The degree of hydrolysis of the vinylformamide units was 50 mol %.

Example H15

[0298] 360.0 g of the polymer solution obtained by P8 were placed in a 500 ml four-neck flask fitted with blade stirrer, internal thermometer, dropping funnel and reflux condenser, admixed with 2.5 g of 40 wt % aqueous sodium bisulfite solution, and heated to 80° C. at a stirrer speed of 80 rpm. Then, 41.3 g of 37% hydrochloric acid were admixed. The mixture was maintained at 80° C. for three hours. The product obtained was cooled down to room temperature.

[0299] A slightly yellow polymer solution was obtained. The degree of hydrolysis of the vinylformamide units was 50 mol %.

Example H16

[0300] 638.4 g of the polymer solution obtained by P8 were placed in a 1 l four-neck flask fitted with blade stirrer, internal thermometer, dropping funnel and reflux condenser, admixed with 4.7 g of 40 wt % aqueous sodium bisulfite solution, and then heated to 80° C., at a stirrer speed of 80 rpm. Then, 158.3 g of 25 wt % aqueous sodium hydroxide solution were admixed. The mixture was maintained at 80° C. for 6 hours. The product obtained was cooled down to room temperature.

[0301] A slightly yellow polymer solution was obtained. The degree of hydrolysis of the vinylformamide units was 100 mol %.

Example H17

[0302] 1224.3 g of the polymer solution obtained by P8 were placed in a 2 l four-neck flask fitted with blade stirrer, internal thermometer, dropping funnel and reflux condenser, admixed with 704.4 g of completely ion-free water and 8.9 g of 40 wt % aqueous sodium bisulfite solution, and then heated to 80° C., at a stirrer speed of 80 rpm. Then, 140.4 g of 25 wt % aqueous sodium hydroxide solution were admixed. The mixture was maintained at 80° C. for 5 hours. And then cooled down to room temperature.

[0303] A slightly yellow polymer solution was obtained. The degree of hydrolysis of the vinylformamide units was 50 mol %.

Example H18

[0304] 1102.9 g of the polymer solution obtained by P9 were placed in a four-neck flask fitted with blade stirrer, internal thermometer, dropping funnel and reflux condenser, admixed with 10.5 g of 40 wt % aqueous sodium bisulfite solution, and then heated to 80° C., at a stirrer speed of 80 rpm. Then, 355.6 g of 25 wt % aqueous sodium hydroxide solution were admixed. The mixture was maintained at 80° C. for 7 hours and then cooled down to room temperature.

[0305] A slightly cloudy polymer solution was obtained. The degree of hydrolysis of the vinylformamide units was 100 mol %.

Example H19

[0306] 200.0 g of the polymer solution obtained by P10 were placed in a 500 ml four-neck flask fitted with blade stirrer, internal thermometer, dropping funnel and reflux condenser, admixed with 1.5 g of 40 wt % aqueous sodium bisulfite solution, and then heated to 80° C., at a stirrer speed of 80 rpm. Then, 73.4 g of 25 wt % aqueous sodium hydroxide solution were admixed. The mixture was maintained at 80° C. for three hours, and the suspension formed a solution. The product obtained was cooled down to room temperature.

[0307] A slightly cloudy polymer solution was obtained. The degree of hydrolysis of the vinylformamide units and of the vinyl acetate units was 100 mol % in both cases.

Example H20

[0308] 200.0 g of the polymer solution obtained by P10 were placed in a 500 ml four-neck flask fitted with blade stirrer, internal thermometer, dropping funnel and reflux condenser, admixed with 1.3 g of 40 wt % aqueous sodium bisulfite solution, and then heated to 80° C., at a stirrer speed of 80 rpm. Then, 72.0 g of 25 wt % aqueous sodium hydroxide solution were admixed. The mixture was maintained at 80° C. for three hours, and the suspension formed a solution. The product obtained was cooled down to room temperature.

[0309] A slightly cloudy polymer solution was obtained. The degree of hydrolysis of the vinylformamide units and of the vinyl acetate units was 100 mol % in both cases.

Example H21

[0310] 200.0 g of the polymer solution obtained by P12 were placed in a 500 ml four-neck flask fitted with blade stirrer, internal thermometer, dropping funnel and reflux condenser, admixed with 1.1 g of 40 wt % aqueous sodium bisulfite solution, and then heated to 80° C., at a stirrer speed of 80 rpm. Then, 72.8 g of 25 wt % aqueous sodium hydroxide solution were admixed. The mixture was maintained at 80° C. for three hours, and the suspension formed a solution. The product obtained was cooled down to room temperature.

[0311] A slightly cloudy polymer solution was obtained. The degree of hydrolysis of the vinylformamide units and of the vinyl acetate units was 100 mol % in both cases.

Example H22

[0312] 450.0 g of the polymer solution obtained by P13 were placed in a 1 l four-neck flask fitted with blade stirrer, internal thermometer, dropping funnel and reflux condenser and admixed at a stirrer speed of 80 rpm with 450 g of water and 2.8 g of 40 wt % aqueous sodium bisulfite solution and then with 54.6 g of 37% hydrochloric acid. The mixture was heated to the boil and refluxed for 4 hours. The product obtained was cooled down to room temperature.

[0313] A yellowish polymer solution having a solids content of 8.6 wt % was obtained. The degree of hydrolysis of the vinylformamide units was 98 mol %.

Example H23

[0314] 180.0 g of the polymer solution obtained by P14 were placed in a 500 ml four-neck flask fitted with blade stirrer, internal thermometer, dropping funnel and reflux condenser and admixed with 1.5 g of 40 wt % aqueous sodium bisulfite solution, and then heated to reflux, at a stirrer speed of 80 rpm. The mixture was admixed with 53.9 g of 37 wt % hydrochloric acid and refluxed for 8 hours. The product obtained was cooled down to room temperature.

[0315] A viscous, slightly cloudy polymer solution having a solids content of 22.5 wt % was obtained. The degree of hydrolysis of the vinylformamide units was 100 mol %.

Example H24

[0316] 200.0 g of the polymer solution obtained by P15 were placed in a 500 ml four-neck flask fitted with blade stirrer, internal thermometer, dropping funnel and reflux condenser and heated to 80° C. at a stirrer speed of 80 rpm. Once 80° C. had been reached, first 1.4 g of 25 wt % aqueous sodium bisulfite solution and then 44.6 g of 25 wt % aqueous sodium hydroxide solution were added such that that they became mixed in efficiently. The reaction mixture was maintained at 80° C. for 3 hours and then cooled down to room temperature. A viscous, slightly yellow polymer solution having a solids content of 22.7 wt % was obtained. The degree of hydrolysis of the vinylformamide units was 99 mol %.

3. Polymer-Analogous Conversions

[0317] The hereinbelow detailed polymer-analogous reactions are summarized in table 3. The polymer-analogous reactions were all carried out with starting polymer H2, i.e., a fully hydrolyzed homopolymer of vinylformamide (polyvinylamine having a 100 mol % degree of hydrolysis).

TABLE-US-00003 TABLE 3 Polymer-analogous conversions Content of prim. amine + Starting Reagent.sup.2) Conversion amidine Example polymer Reagent [mol %] [mol %] PG [wt %] [meq/g].sup.3) PA1 H2 acrylamide 40 >99 5.4 8.3 PA2 H2 acrylamide 66 >99 13.3 3.7 PA3 H2 benzyl 10 >99 8.2 17.0 chloride PA4 H2 acrylonitrile 30 >99 5.3 11.7 PA5 H2 acrylonitrile 60 >98 6.6 5.3 PA6 H2 QUAB 432.sup.1) 1 >99 4.5 21.2 .sup.1)QUAB 342 alkylating agent (from SKW, Germany) .sup.2)Amount of reagent used [mol %] based on prim. amino groups .sup.3)Combined content of primary amino groups and/or amidine units in 1 g of polymer without counter-ion PG: polymer content without counter-ion

[0318] The degree of conversion in the reactions hereinbelow was quantified by quantifying the residual reagent content of the end product. The methods used are specified in the respective examples.

Example PA 1

[0319] 250 g of the polymer solution obtained by H2 were initially charged to a 500 ml four-neck flask fitted with blade stirrer, internal thermometer, dropping funnel and reflux condenser. Under agitation (stirrer speed 80 rpm), the solution was diluted with 250 g of water and adjusted to pH 10 by admixture of about 17 g of 37 wt % hydrochloric acid. 18.9 g of 50 wt % aqueous acrylamide solution were added dropwise at room temperature and the solution obtained was gradually heated to 70° C. The solution was left at 70° C. for 6 hours and the established pH was maintained by admixture of 25 wt % aqueous sodium hydroxide solution. The solution was then cooled down to room temperature and adjusted to pH 8.3 by admixture of 10.2 g of 37 wt % hydrochloric acid.

[0320] The viscous solution obtained had a residual acrylamide content of 20 ppm (HPLC) and a 5.4 wt % polymer content without counter-ion.

Example PA 2

[0321] 850 g of the polymer solution obtained by H2 were initially charged to a 1 l four-neck flask fitted with blade stirrer, internal thermometer, dropping funnel and reflux condenser. Under agitation (stirrer speed 80 rpm), the solution was adjusted to pH 9 by admixture of about 79 g of 37 wt % hydrochloric acid. 148.9 g of 50 wt % aqueous acrylamide solution were added dropwise at room temperature and the reaction mixture obtained was gradually heated to 70° C. The solution was maintained at 70° C. for 6 hours and then cooled down to room temperature. Then the pH was adjusted to pH 8.4 by admixture of 3.7 g of 37 wt % hydrochloric acid.

[0322] The viscous solution obtained had a residual acrylamide content of 40 ppm (HPLC) and a 13.3 wt % polymer content without counter-ion.

Example PA 3

[0323] 200.0 g of the polymer solution obtained by H2 were initially charged to a 500 ml four-neck flask fitted with blade stirrer, internal thermometer, dropping funnel and reflux condenser. Under agitation (stirrer speed 80 rpm), 4.6 g of benzyl chloride were admixed. The dispersion obtained was heated to 65° C. and maintained at that temperature for three hours to form a clear, viscous solution having an 8.2 wt % polymer content without counter-ion. The residual benzyl chloride content (HPLC) was below the 10 ppm limit of detection.

Example PA 4

[0324] 200.0 g of the polymer solution obtained by H2 were initially charged to a 500 ml three-neck flask fitted with blade stirrer, internal thermometer, dropping funnel and reflux condenser. Under agitation (stirrer speed 80 rpm), 200 g of water were admixed first. Using 12.6 g of 37% hydrochloric acid, the pH was adjusted to 10 and then 5.9 g of acrylonitrile were admixed. The solution obtained was heated to 75° C., maintained at that temperature for 5 hours and then cooled down to room temperature. The viscous solution obtained had a residual acrylonitrile content (headspace GC) of 130 ppm. The polymer content without counter-ion was 5.3 wt %.

Example PA 5

[0325] 200.0 g of the polymer solution obtained by H2 were initially charged to a 500 ml four-neck flask fitted with blade stirrer, internal thermometer, dropping funnel and reflux condenser. Under agitation (stirrer speed 80 rpm), 200 g of water were admixed first. Using 12.6 g of 37 wt % hydrochloric acid, the pH was adjusted to 10 and then 11.8 g of acrylonitrile were admixed. The solution obtained was heated to 75° C., maintained at that temperature for 5 hours and then cooled down to room temperature. The viscous solution obtained had a residual acrylonitrile content (headspace GC) of 300 ppm. The polymer content without counter-ion was 6.6 wt %.

Example PA 6

[0326] 200.0 g of the polymer solution obtained by H2 were initially charged to a 500 ml four-neck flask fitted with blade stirrer, internal thermometer, dropping funnel and reflux condenser. Under agitation (stirrer speed 80 rpm), 120 g of water were first admixed, followed by 3.2 g of QUAB 342 (3-chloro-2-hydroxypropyllauryldimethylammonium chloride, alkylating agent from SKW, Germany). The solution obtained was heated to 66° C. and maintained at that temperature for 5 hours. Following this reaction time, complete conversion of the alkylating agent was detected using the Preuβmann test. This was followed by cooling down to room temperature. The viscous solution obtained had a 4.5 wt % polymer content without counter-ion.

[0327] A description of the Preuβmann test procedure is found, for example, in EP 1651699 page 4 line 50 to page 5 line 20.

Example SP 1

[0328] The polymer used was identical to the Hofmann degradation product referred to as C8 béta 2 in the table on page 13 of WO 2006/075115. It was prepared by reacting polyacrylamide with sodium hypochlorite in a molar ratio of 1:1 and aqueous sodium hydroxide solution, while the molar ratio of sodium hydroxide to sodium hypochlorite was 2:1.

[0329] The polymer content without counter-ion was 4.5% and the primary amino group content was 9.8 meq/g.

Preparation of Inventive Aqueous Compositions

Examples EF1 to EF44

[0330] The general procedure for this was as follows:

[0331] 250 g of the particular solution obtained for the polymer having primary amino groups and/or amidine groups (see table 4) was initially charged at room temperature to a 500 ml three-neck flask fitted with blade stirrer, pH electrode and dropping funnel. The pH reported in the table was then established by the admixture of 37 wt % hydrochloric acid or of 25 wt % sodium hydroxide solution. 1,4-Cyclohexanedione (from Aldrich) was then admixed in solid form. The amount of cyclohexanedione used is shown in table 4. The mixture was stirred at room temperature for two hours to completely dissolve the cyclohexanedione. The solution thus obtained was used for performance testing.

TABLE-US-00004 TABLE 4 Examples of inventive compositions 1,4- CHD.sup.3) PG.sup.4) Ex. Starting polymer pH [mol %] [wt %] EF1 H1 PVFA, K 45; HG 70% 2.0 15 13.3 EF2 H2 PVFA, K 90; HG >95% 1.0 8 6.2 EF3 H2 PVFA, K 90; HG >95% 1.0 5 6.0 EF4 H3 PVFA, K 90; HG70% 1.0 8 8.9 EF5 H4 PVFA, K 90; HG50% 3.0 2 10.0 EF6 H4 PVFA, K 90; HG50% 3.0 5 5.5 EF7 H4 PVFA, K 90; HG50% 3.0 8 9.8 EF8 H5 PVFA, K 90; HG40% 3.0 8 10.8 EF9 H6 PVFA, K 90; HG35% 3.0 8 11.1 EF10 H7 PVFA, K 120; HG50% 3.0 8 8.1 EF11 H8 Copo VFA/NaAS = 80/20, 3.0 8 12.5 K 90, HG 50% EF12 H9 Copo VFA/NaAS = 80/20, 1.4 5 7.9 K 90, HG >95% EF13 H10 Copo VFA/NaAS = 70/30, 3.0 15 9.9 K 55, HG >95% EF14 H11 Copo VFA/NaAS = 70/30, 3.0 15 15.5 K 55, HG 52% EF15 H12 Copo VFA/NaAS = 70/30, 3.0 5 11.5 K 85, HG >95% EF16 H13 Copo VFA/NaAS = 70/30, 2.0 2 8.4 K 90, HG >95% EF17 H13 Copo VFA/NaAS = 70/30, 2.0 5 8.4 K 90, HG >95% EF18 H13 Copo VFA/NaAS = 70/30, 2.0 8 8.5 K 90, HG >95% EF19 H14 Copo VFA/NaAS = 70/30, 4 1 10.5 K 90, HG 50% EF20 H14 Copo VFA/NaAS = 70/30, 4 2 10.6 K 90, HG 50% EF21 H14 Copo VFA/NaAS = 70/30, 4 5 10.7 K 90, HG 50% EF22 H14 Copo VFA/NaAS = 70/30, 4 8 11.0 K 90, HG 50% EF23 .sup.1) H15 Copo VFA/NaAS = 70/30, 4 5 10.2 K 120, HG 50% EF24 H16 Copo VFA/NaAS = 70/30, 2.5 2 5.5 K 122, HG >95% EF25 H16 Copo VFA/NaAS = 70/30, 2.5 5 5.6 K 122, HG >95% EF26 H16 Copo VFA/NaAS = 70/30, 2.5 8 5.7 K 122, HG >95% EF27 H17 Copo VFA/NaAS = 70/30, 3 2 6.7 K 122, HG 50% EF28 H17 Copo VFA/NaAS = 70/30, 3 5 6.7 K 122, HG 50% EF29 H17 Copo VFA/NaAS = 70/30, 3 8 6.8 K 122, HG 50% EF30 H18 Copo VFA/NaAS = 60/40, 2.3 5 10.1 K 90, HG >95% EF31 .sup.2) H19 Copo VFA/VAc = 70/30, 1.0 5 5.4 K 84, HG >95% EF32 .sup.2) H20 Copo VFA/VAc = 60/40, 1.0 5 5.4 K 74, HG >95% EF33 .sup.2) H21 Copo VFA/VAc = 50/50, 1.0 5 5.4 K 684, HG >95% EF34 .sup.1) H22 Copo VFA/AN/Na itaconate = 1.5 5 5.6 49.5/49.5/1.0, K 174, HG >95% EF35 .sup.1) H22 Copo VFA/AN/Na itaconate = 1.5 8 5.8 49.5/49.5/1.0, K 174, HG >95% EF36 .sup.1) H23 Copo VFA/NaAS/AN = 1.5 5 11.9 50/30/20, K 90, HG >95% EF37 H24 Copo VFA/DADMAC = 70/30, 2 5 9.8 K 80, HG >95% EF38 PA1 2 5 9.6 EF39 PA2 2 5 10.1 EF40 PA3 2 5 8.2 EF41 PA4 2 5 4.1 EF42 PA5 2 5 4.2 EF43 PA6 2 5 3.2 EF44 SP1 Hofmann degradation product 1 5 2.3 HG: degree of hydrolysis .sup.1) HCl hydrolysis .sup.2) VAc fully hydrolyzed .sup.3)1,4-CHD: amount of 1,4-cyclohexanedione admixed in mol % based on the polymer's combined amount of primary amino groups and amidine groups .sup.4)PG: polymer content without counter-ion

PERFORMANCE EXAMPLES

General Procedure for Producing Wood-Free Papers

[0332] A 70/30 mixture of bleached birch sulfate and bleached spruce sulfite was beaten in a laboratory pulper at a solids concentration of 4% until free of fiber bundles and a 30-35 freeness was obtained. The beaten pulp was then admixed with an optical brightener (Blankophor® PSG, Bayer AG) and a cationic starch (HiCat® 5163 A). The cationic starch was digested as a 10 wt % starch slurry in a jet cooker at 130° C. and 1 minute residence time. The optical brightener was added at 0.5 wt % of the commercial product, based on the dry content of the paper stock suspension. The cationic starch was added at 0.5 wt % of starch, based on the dry content of the paper stock suspension. The pH of the stock was in the range between 7 and 8. The beaten stock was subsequently diluted with water to a solids concentration of 0.35 wt %. In the next step, an aqueous composition of Examples EF11-EF33 and EF36 was added to the paper stock. The amount admixed varied according to the examples.

[0333] Then, 500 ml of the particular treated paper stock suspension were mixed with a 15 wt % filler slurry consisting of precipitated calcium carbonate (PCC). Finally, a cationic retention aid (Polymin® KE 540, BASF SE) was also added to the paper stock. The amount of retention aid added was in each case 0.01 wt % of polymer (solids), based on the dry content of the entire paper stock suspension.

[0334] The paper stock suspensions thus obtained were used to fabricate 80 g/m.sup.2 sheets of paper on a Rapid-Köthen sheet-former to ISO 5269/2. The moist sheets of paper were subsequently dried at 90° C. for 7 minutes. By trying out various filler quantities for mixing the filler with the treated fibrous material and adjusting the particular slurry quantity accordingly, an approximately 25 wt % filler content can be established for every example and in relation to the references.

REFERENCE

[0335] For comparison, the general procedure for producing wood-free paper was followed to prepare a paper stock suspension—and sheets of paper therefrom—without adding an aqueous composition. The filler content of the reference sheet was likewise established at 25 wt %.

Examples 1-24

[0336] The inventive aqueous compositions of Examples EF11-EF33 and EF 36 were used to produce sheets of paper in accordance with the procedure for producing wood-free papers. The aqueous composition was admixed at 0.12 wt % of polymer having primary amino groups and/or amidine groups (solids) based on fibrous material (solids).

Comparative Example 1 (Comp. 1)

[0337] Sheets of paper were produced according to the general procedure for producing wood-free papers except that a 7 wt % aqueous solution of H17 (70/30 VFA/NaAS copolymer having a 50% degree of hydrolysis and a 122 K value for the unhydrolyzed polymer) was used instead of the inventive aqueous composition. The aqueous composition was admixed at 0.12 wt % of polymer having primary amino groups and/or amidine groups (solids) based on fibrous material (solids).

Examples 25-48

[0338] The inventive aqueous compositions of Examples EF11-EF33 and EF 36 were used to produce sheets of paper in accordance with the procedure for producing wood-free papers. The aqueous composition was admixed at 0.24 wt % of polymer having primary amino groups and/or amidine groups (solids) based on fibrous material (solids).

Comparative Example 2 (Comp. 2)

[0339] Sheets of paper were produced according to the general procedure for producing wood-free papers except that a 7 wt % aqueous solution of H17 (70/30 VFA/NaAS copolymer having a 50% degree of hydrolysis and a 122 K value for the unhydrolyzed polymer) was used instead of the inventive aqueous composition. The aqueous composition was admixed at 0.24 wt % of polymer having primary amino groups and/or amidine groups (solids) based on fibrous material (solids).

Testing of Wood-Free Sheets of Paper

[0340] Following a 12 hour storage period in a conditioning chamber at a constant 23° C. and 50% relative humidity, the sheets were tested for dry breaking length to DIN 54540, inner strength to DIN 54516 and flexural stiffness to DIN 53121. The results are shown in table 5 (0.12% admixture) and table 6 (0.24% admixture).

TABLE-US-00005 TABLE 5 Testing of wood-free sheets of paper admixed with the aqueous composition at 0.12 wt % of polymer having primary amino groups and/or amidine groups (solids) based on fibrous material (solids). Dry breaking Inner Flexural Aqueous Filler content length strength stiffness Example composition [%] [m] [N] [mN] reference — 24.5 3614 127 47.2 Comp. 1 — 24.5 4481 195 58.7 1 EF11 24.9 4698 232 59.1 2 EF12 25.1 4892 245 65.2 3 EF13 25.5 4256 188 56.9 4 EF14 24.8 4434 202 56.4 5 EF15 25.5 5187 288 69.2 6 EF16 24.9 4998 274 66.5 7 EF17 25.3 4912 281 67.3 8 EF18 24.7 4745 264 63.7 9 EF19 25.4 4691 231 59.3 10 EF20 25.3 4812 256 58.2 11 EF21 24.8 4790 261 60.1 12 EF22 25.1 4412 239 55.7 13 EF23 24.8 4789 258 56.9 14 EF24 24.7 5378 306 71.4 15 EF25 25.4 5511 339 70.1 16 EF26 25.1 5088 299 68.6 17 EF27 25.3 5290 311 72.3 18 EF28 25.5 5589 341 74.9 19 EF29 24.9 5134 302 68.4 20 EF30 24.5 4734 265 62.9 21 EF31 24.8 4911 287 65.3 22 EF32 24.7 4845 288 67.1 23 EF33 25.3 4723 276 65.9 24 EF36 25.0 4845 267 74.3

[0341] The performance test data reveal that in each case the use of inventive composition EF27, EF28 or EF29, which comprises polymer H17 and 1,4-cyclohexanedione (Examples 17, 18 and 19), leads to distinctly enhanced strengths for the papers compared with papers obtained using polymer H17 only (Comp. 1).

TABLE-US-00006 TABLE 6 Testing of wood-free sheets of paper admixed with the aqueous composition at 0.24 wt % of polymer having primary amino groups and/or amidine groups (solids) based on fibrous material (solids). Dry breaking Inner Flexural Aqueous Filler content length strength stiffness Example composition [wt %] [m] [N] [mN] reference — 25.1 3614 127 47.2 Comp. 2 25.3 4255 161 54.1 25 EF11 24.7 4378 188 55.4 26 EF12 25.4 4456 185 56.9 27 EF13 25.1 4199 164 57.4 28 EF14 25.2 4244 178 52.5 29 EF15 25.4 4819 212 59.6 30 EF16 24.6 4765 204 56.8 31 EF17 24.8 4734 209 58.4 32 EF18 24.8 4512 194 58.9 33 EF19 25.2 4434 181 55.8 34 EF20 25.0 4687 193 56.6 35 EF21 25.3 4538 206 58.6 36 EF22 24.6 4227 189 53.2 37 EF23 24.7 4511 211 54.4 38 EF24 25.1 5017 234 64.2 39 EF25 25.3 4945 241 63.2 40 EF26 24.5 4845 229 61.9 41 EF27 25.4 5023 214 68.2 42 EF28 25.3 5123 281 69.9 43 EF29 24.7 4840 254 65.6 44 EF30 24.5 4478 223 58.9 45 EF31 24.6 4411 221 61.7 46 EF32 24.9 4528 218 63.7 47 EF33 25.1 4498 244 62.9 48 EF36 25.2 4634 217 69.6

[0342] The performance test data reveal that in each case the use of inventive composition EF27, EF28 or EF29, which comprises polymer H17 and 1,4-cyclohexanedione (Examples 41, 42 and 43), leads to distinctly enhanced strengths for the papers compared with papers obtained using polymer H17 only (Comp. 2).

General Procedure for Producing Test Liner Examples A1 to A44

[0343] Further compounds used as auxiliaries: [0344] retention aid: Percol 540 polyacrylamide emulsion having a solids content of 43%, a cationic charge density of 1.7 mmol/100 g and a K value of 240.

Pretreatment of Paper Stock:

[0345] A 100% wastepaper stock (a mixture of the varieties 1.02, 1.04, 4.01) was beaten with tap water in a pulper at a consistency of 4 wt % until free of fiber bundles and ground in a refiner to a freeness of 40° SR. This stuff was subsequently diluted with tap water to a consistency of 0.8 wt %.

[0346] The paper stock gave a Schopper-Riegler value of SR 40 in the drainage test.

[0347] The wastepaper-based paper stock thus pretreated was admixed under agitation with the table 7 inventive compositions of Examples EF1-EF44. The aqueous composition was admixed at 0.3 wt % of polymer having primary amino groups and/or amidine groups (solids) based on fibrous wastepaper material (solids).

[0348] The retention aid (Percol 540) was then added to the paper stock in the form of a 1 wt % aqueous solution meaning that 0.04 wt % of polymer (solids) based on fibrous wastepaper material (solids) was used. The pH of the paper stock was maintained at a constant pH 7 (by means of 5 wt % sulfuric acid).

[0349] Test papers were then produced using a dynamic sheet-former from Tech Pap, France. The paper was subsequently dried, with contact dryers, to a paper moisture content of 5 wt %.

Reference (not in Accordance with the Present Invention)

[0350] For reference, the general procedure for producing test liners was followed to produce a paper stock suspension, and sheets of paper therefrom, without adding an inventive aqueous composition.

Comparative Example A1 (not in Accordance with the Present Invention)

[0351] For comparison, the general procedure for producing test liners was followed to produce a paper stock suspension, and sheets of paper therefrom, by using polymer H4 instead of the inventive composition.

[0352] The amount of polymer H4 admixed was chosen such that 0.3 wt % of polymer having primary amino groups based on fibrous wastepaper material (solids) was used.

Drainage Test

[0353] One (1) liter of the paper stock described above was used in each example and was in each case admixed in succession under agitation with the particular aqueous composition specified in the table and thereafter drained using a Schopper-Riegler drainage tester by measuring the time in seconds for a quantity (filtrate) of 600 ml to pass through. The concentration of polymers having primary amino groups and/or amidine groups (solids) was 1 wt % in each case. The results of the measurements are reported in the table.

[0354] The papers collated in table 7 were subsequently produced.

Performance Testing of Test Papers

[0355] The paper was conditioned at 50% relative humidity for 24 hours and then subjected to the following strength tests: [0356] bursting pressure as per DIN ISO 2758 (up to 600 kPa) and DIN ISO 2759 (above 600 kPa) [0357] SCT shortspan compression test as per DIN 54518 (quantification of strip crush resistance) [0358] CMT corona medium test as per DIN EN 23035 (quantification of flat crush resistance)

[0359] As is apparent from the results in table 7, using the inventive aqueous compositions comprising polymers having primary amino groups and/or amidine groups and 1,4-cyclohexanedione provides a significant increase in paper strengths.

TABLE-US-00007 TABLE 7 Performance test results Parts by Aqueous weight Basis weight Drainage time CMT CMT SCT SCT Burst Burst Example composition (solids).sup.1) [g/m.sup.2] [sec] [N .Math. m.sup.2/g] [%] [kN .Math. m.sup.2/g] [%] [kPa .Math. m.sup.2/g] [%] reference — — 120 60 1.61 0 1.24 0 2.56 0 Comp. polymer H4 0.3 121 40 1.77 10 1.38 12 2.86 12 A1 A1 EF1 0.3 121 70 1.93 20 1.50 21 3.04 19 A2 EF2 0.3 120 35 1.96 22 1.47 19 3.09 21 A3 EF3 0.3 121 38 1.91 19 1.51 22 3.09 21 A4 EF4 0.3 122 37 1.93 20 1.47 19 3.04 19 A5 EF5 0.3 121 35 1.99 24 1.51 22 3.17 24 A6 EF6 0.3 120 35 1.93 20 1.50 21 3.04 19 A7 EF7 0.3 121 35 1.96 22 1.47 19 3.16 23 A8 EF8 0.3 120 34 1.97 23 1.45 18 3.0 17 A9 EF9 0.3 120 39 1.78 11 1.38 12 2.85 11 A10 EF10 0.3 121 28 1.97 23 1.47 19 3.06 20 A11 EF11 0.3 121 45 1.99 24 1.51 22 3.16 23 A12 EF12 0.3 120 41 1.93 20 1.47 19 3.09 21 A13 EF13 0.3 120 42 1.95 22 1.50 21 3.05 20 A14 EF14 0.3 120 45 1.90 18 1.46 19 3.01 17 A16 EF16 0.3 120 44 1.97 23 1.47 19 3.01 17 A17 EF17 0.3 120 47 1.91 19 1.51 22 3.0 17 A18 EF18 0.3 120 41 1.93 20 1.47 19 3.17 24 A24 EF24 0.3 121 44 1.93 20 1.50 20 3.02 18 A25 EF25 0.3 120 49 1.89 17 1.45 18 3.09 21 A26 EF26 0.3 121 45 1.93 20 1.50 21 3.15 23 A27 EF27 0.3 120 41 1.95 22 1.45 18 3.0 17 A28 EF28 0.3 120 41 2.01 25 1.51 22 3.16 23 A31 EF31 0.3 120 32 1.81 13 1.42 15 2.89 13 A32 EF32 0.3 121 41 1.83 14 1.40 13 2.91 14 A33 EF33 0.3 120 41 1.8 12 1.40 13 2.89 13 A34 EF34 0.3 120 43 2.01 25 1.50 20 3.16 23 A35 EF35 0.3 120 45 2.0 24 1.5 20 2.14 22 A37 EF37 0.3 121 50 1.77 10 1.36 11 2.84 11 A39 EF39 0.3 120 47 1.95 21 1.50 21 3.04 19 A40 EF40 0.3 120 41 1.78 10 1.38 12 2.85 12 A41 EF41 0.3 120 43 2.0 24 1.5 20 3.12 22 A42 EF42 0.3 121 45 1.96 22 1.51 22 3.07 20 A43 EF43 0.3 120 48 1.78 11 1.36 11 2.86 12 A44 EF44 0.3 120 80 1.93 20 1.50 20 3.02 18 .sup.1)amount of polymer with primary amino groups and/or amidine groups (solids) used in the form of the aqueous composition of the present invention.

[0360] The % age for CMT, SCT and Burst indicates in each case the % increase versus reference.

[0361] The performance test data reveal that in each case the use of inventive composition EF5, EF6 or EF7, each comprising polymer H4 and 1,4-cyclohexanedione (Examples A5, A6 and A7), leads to distinctly enhanced strengths for the papers compared with paper obtained using polymer H4 only (Comp. A1).