Method for manufacturing paper or cardboard

Abstract

A method for the production of paper or cardboard is provide comprising the following steps: (A) Adding a water soluble polymer P to a first aqueous pulp suspension, wherein polymer P is obtainable by Polymerizing to a polymer V of (i) 33 to 83 mol % of a monomer of formula I ##STR00001## in which R.sup.1═H or C.sub.1-C.sub.6 alkyl, (ii) 6 to 56 mol % of diallyl dimethyl ammonium chloride, diallyl diethyl ammonium chloride or a salt form of a monoethylenically unsaturated monomer, (iii) 11 to 61 mol % of a monoethylenically unsaturated carboxylic acid, sulfonic acid or phosphonic acid, or salt forms thereof, (iv) 0 to 50 mol % of one or more ethylenically unsaturated monomers, and hydrolyzing the N—C(═O)R.sup.1 groups to form primary amino or amidine groups, (B) dehydrating the second aqueous pulp suspension to a wet paper structure, (C) dehydrating the wet paper structure.

Claims

1. Method for the production of paper or cardboard comprising the following steps: (A) Adding a water-soluble polymer P to a first aqueous pulp suspension having a dry content between 0.1% by weight and 6% by weight, thereby forming a second aqueous pulp suspension containing polymer P, wherein polymer P is obtainable by radical polymerization to a polymer V of (i) 33 to 83 mol % of a monomer of formula I ##STR00024## in which R.sup.1═H or C.sub.1-C.sub.6 alkyl, (ii) 6 to 56 mol % of diallyl dimethyl ammonium chloride, diallyl diethyl ammonium chloride or a salt form of a monoethylenically unsaturated monomer with a quaternized nitrogen as the sole charge-bearing group at a pH value of 7, (iii) 11 to 61 mol % of a monoethylenically unsaturated carboxylic acid, a monoethylenically unsaturated sulfonic acid or a monoethylenically unsaturated phosphonic acid, or salt forms thereof, (iv) 0 to 50 mol % of one or more ethylenically unsaturated monomers other than monomer (i), (ii) and (iii), wherein the total amount of all monomers (i), (ii), (iii) and (iv) is 100 mol %, and hydrolyzing the N—C(═O)R.sup.1 groups of the units of the monomers of formula (I) polymerized into polymer V to form primary amino or amidine groups to polymer P, wherein at least 87% of the units of the monomers of formula (I) polymerized into polymer V are hydrolyzed, based on the number of all units of the monomers of formula I polymerized into polymer V, (B) dehydrating the second aqueous pulp suspension containing polymer P on a water-permeable substrate to a wet paper structure having a dry content between 18.5% by weight and 25% by weight, (C) dehydrating the wet paper structure, resulting in the paper or cardboard.

2. Method according to claim 1, wherein the water-permeable substrate is a sieve.

3. Method according to claim 1, wherein the amount of monomer (i) is 33 to 65 mol %.

4. Method according to claim 1, wherein the amount of monomer (ii) is 6 to 45 mol %.

5. Method according to claim 1, wherein the amount of monomer (iii) is 11 to 40 mol %.

6. Method according to claim 1, wherein the amount of monomer (iv) is 0 to 30 mol %.

7. Method according to claim 1, wherein for monomer (i) R.sup.1═H.

8. Method according to claim 1, wherein monomer (ii) is diallyl dimethyl ammonium chloride, diallyl diethyl ammonium chloride, a salt form of an N-alkyl-N′-vinylimidazolium, a salt form of an N-alkylated vinylpyridinium, a salt form of an acrylic amidoalkyl trialkylammonium or a salt form of a methacrylamidoalkyl trialkylammonium.

9. Method according to claim 8, wherein monomer (ii) is diallyl dimethyl ammonium chloride.

10. Method according to claim 1, wherein monomer (iii) is a mono-ethylenically unsaturated C.sub.3-C.sub.8 mono- or dicarboxylic acid, acrylamido-2-methylpropane sulfonic acid, or salt forms thereof.

11. Method according to claim 10, wherein monomer (iii) is acrylic acid, methacrylic acid, acrylamido-2-methylpropanesulfonic acid or salt forms thereof.

12. Method according to claim 11, wherein monomer (iii) is acrylic acid or methacrylic acid or its sodium salt or potassium salt.

13. Method according to claim 1, wherein monomer (iv) is acrylonitrile, vinyl acetate, N-vinylpyrrolidone or N-vinylimidazole.

14. Method according to claim 1, wherein polymer P is amphoteric-cationic.

15. Method according to claim 1, wherein in step (C) the dehydration comprises the following steps: (C-1) dehydrating the wet paper structure by pressing, resulting in a moist paper sheet, (C-2) dehydrating the moist paper sheet by heat input, resulting in the paper or card board.

16. Method according to claim 1, wherein the amount of added polymer P is 0.01% by weight to 6.0% by weight based on the dry content of the first aqueous pulp suspension.

17. Method according to claim 1, wherein in step (A) polymer P is added to a first pulp suspension, the dry content of which is greater than 1.5% by weight and up to 6.0% by weight, and the second pulp suspension containing polymer P is diluted to a dry content between 0.1% by weight and up to 1.5% by weight.

18. Method according to claim 1, wherein in step (A) a further organic polymer other than polymer P is added to the first pulp suspension or the second pulp suspension containing polymer P.

19. Method according to claim 1, wherein in step (A) a filler is added to the first pulp suspension or the second pulp suspension containing polymer P.

20. A water-soluble polymer P obtainable by radical polymerization to a polymer V of (i) 33 to 83 mol % of a monomer of formula I ##STR00025## in which R.sup.1═H or C.sub.1-C.sub.6 alkyl, (ii) 6 to 56 mol % of diallyl dimethyl ammonium chloride, diallyl diethyl ammonium chloride or a salt form of a monoethylenically unsaturated monomer with a quatemized nitrogen as the sole charge-bearing group at a pH value of 7, (iii) 11 to 61 mol % of a monoethylenically unsaturated carboxylic acid, a monoethylenically unsaturated sulfonic acid or a monoethylenically unsaturated phosphonic acid, or salt forms thereof, (iv) 0 to 50 mol % of one or more ethylenically unsaturated monomers other than monomer (i), (ii) and (iii), wherein the total amount of all monomers (i), (ii), (iii) and (iv) is 100 mol %, and hydrolyzing the N—C(═O)R.sup.1 groups of the units of the monomers of formula (I) polymerized into polymer V to form primary amino or amidine groups to polymer P, wherein at least 87% of the units of the monomers of formula (I) polymerized into polymer V are hydrolyzed, based on the number of all units of the monomers of formula I polymerized into polymer V.

Description

EXAMPLES

(1) The percentages in the examples are percentages by weight, unless stated otherwise.

(2) A) Additives

(3) A-1) Methods for the characterization of polymers

(4) The solid content is determined by spreading 0.5 to 1.5 g of the polymer solution in a metal lid 4 cm in diameter and then drying in a convection dryer at 140° C. for 120 minutes. The ratio of the mass of the sample after drying under the above conditions to the weighed sample mass multiplied by 100 gives the solid content of the polymer solution in % by weight. Drying is carried out at ambient pressure, possibly 101.32 kPa, without correction for deviation due to weather and sea level.

(5) The degree of hydrolysis is the percentage of hydrolyzed N—CHO groups of the N-vinylformamide monomers used in the polymerization in relation to the total amount of N-vinylformamide used in the polymerization. The degree of hydrolysis of homopolymers or copolymers in which N-vinylformamide is used in the polymerization and which are subjected to hydrolysis is determined by enzymatic analysis of the formic acid or formates released during hydrolysis (test set from Boehringer Mannheim).

(6) The polymer content indicates the content of polymer without counterions in the aqueous solution in percentage by weight, i.e. counterions are not considered. The polymer content is the sum of the weight percentages of all structural units of the polymer in g, which are present in 100 g of the aqueous solution. It is determined by calculation. For this purpose, potentially charge-bearing structural units in the charged form are included, i.e., for example, amino groups in the protonated form and acid groups in the deprotonated form. Counterions of the charged structural units such as a sodium cation, chloride, phosphate, formate, acetate, etc. are not taken into account. The calculation may be carried out in such a way that, for a batch, starting from the quantities of monomers used, optionally a degree of hydrolysis of certain monomers and optionally a proportion of reactants which is reacted in a polymer-analogous manner by reaction with the polymer to form a covalent bond, the molar quantities of the structural units of the polymer present at the end of the reaction are determined and these are converted into proportions by weight using the molar masses of the structural units. For this purpose, a complete, i.e. 100% conversion of all monomers or reactants in general is assumed. The sum of the weight fractions gives the total amount of polymer in this approach. The polymer content results from the ratio of the total amount of polymer to the total mass of the batch. In addition to the total amount of polymer mentioned above, the total mass of the batch thus contains reaction medium, possibly cations or anions and everything added to the reaction batch which is not assumed to be incorporated in the polymer. Substances removed from the reaction mixture (e.g. water distilled off, if necessary, etc.) are deducted.

(7) The total content of primary amino groups and/or amidine groups may be determined in the same way as described above for the polymer content. Starting from the quantities of monomers used, the analytically determined degree of hydrolysis, the ratio of amidine groups to primary amino groups determined by .sup.13C-NMR spectroscopy and, if appropriate, the proportion which has been reacted in a polymer-analogous manner by reaction with the polymer with formation of a covalent bond, the molar composition of the structural units of the polymer present at the end of the reaction is determined. With the aid of the molar mass of the individual structural units, the molar proportion of primary amino groups and/or amidine units in meq which is present in 1 g of polymer may be calculated therefrom. For the determination by .sup.13C-NMR spectroscopy, the area of the formate group HCOO— (173 [ppm]) may be related to the area of the amidine group —N═CH—N— (152 ppm).

(8) The K-values are measured according to H. Fikentscher, Cellulose Chemistry, Volume 13, 48-64 and 71-74 under the conditions indicated in each case. The values in brackets indicate the concentration of the polymer solution based on the polymer content as well as the solvent. The measurements were carried out at 25° C. and a pH value of 7.5.

(9) Unless otherwise specified, only completely desalinated water was used in the production of the additives.

(10) A-2) Polymerizations and Hydrolysis

Example P-P1

Additive 1

(11) ((hydrolyzed terpolymer VFA/DADMAC/Na-acrylate=40 mol %/30 mol %/30 mol %, K-value 95)

(12) a) Polymerization Precursor V1

(13) As feed 1, a mixture of 209.8 g aqueous 32% by weight Na-acrylate solution adjusted to a pH value of 6.4 and 68.3 g N-vinylformamide was provided.

(14) As feed 2, 1.5 g 2,2′-azobis(2-methylpropionamidine) dihydrochloride was dissolved in 74.5 g water at room temperature.

(15) As feed 3, 1.6 g of 2,2′-azobis(2-methylpropionamidine) dihydrochloride was dissolved in 80.4 g of water at room temperature.

(16) As feed 4, 200 g water and as feed 5, 340 g water was provided.

(17) In a 2-L-glass apparatus with anchor stirrer, descending condenser, internal thermometer and nitrogen introduction tube, 200 g water and 2.2 g 75% by weight phosphoric acid were prepared. At a speed of 100 rpm, approx. 3.0 g of a 25% by weight caustic soda lye was added so that a pH value of 6.5 was achieved. Subsequently, 177.3 g of a 65% by weight aqueous DADMAC (=diallyl dimethyl ammonium chloride) solution was mixed in. The receiver was heated to 63° C. and the pressure in the apparatus was reduced to approx. 210 mbar, so that the reaction mixture just started boiling at 63° C. Then feeds 1 and 2 were started simultaneously and dosed synchronously in 4 h at a constant 63° C. 1.5 h after starting feed 1, water feed 4 was started and dosed in 2.5 h. After the end of feeds 1, 2 and 4, feed 3 was added within 2 h. 30 min after starting feed 3 (=4.5 h after starting feed 1) the pressure was set to 500 mbar and the internal temperature was increased to 85° C. After the end of feed 3, the batch was kept at 85° C. for another hour and then feed 5 was mixed in as quickly as possible. The batch was cooled down to room temperature and the vacuum was released by venting with normal air. Water was constantly distilled off during the entire polymerization time (7 h), so that a total of 108 g was distilled off.

(18) The result was a yellow, highly viscous solution with a solids content of 20.5% by weight. The K-value of the copolymer was 95 (0.5% by weight in 5% by weight aqueous NaCl solution).

(19) b) Hydrolysis to Final Product Additive 1

(20) 190.0 g of the polymer solution V1 obtained above were mixed with 0.8 g of a 40% by weight aqueous sodium bisulfite solution in a 500 ml four-necked flask with leaf stirrer, internal thermometer, dropping funnel and reflux condenser at a stirrer speed of 80 rpm and then heated to 80° C. Then 28.0 g of a 25% by weight aqueous sodium hydroxide solution was added. The mixture was kept at 80° C. for 7 hours. The product obtained was cooled to room temperature and adjusted to a pH value of 6.8 by the addition of 15.9 g of 37% by weight hydrochloric acid.

(21) A slightly yellow, viscous polymer solution was obtained with a solid content of 20.6% by weight and a polymer content of 12.0% by weight. The degree of hydrolysis of the vinylformamide units was 94 mol %.

Example P-P2

Additive 2

(22) (hydrolyzed terpolymer VFA/DADMAC/Na-acrylate=35 mol %/35 mol %/30 mol %, K-value 79)

(23) a) Polymerization Precursor V2

(24) As feed 1, a mixture of 209.8 g aqueous 32% by weight Na-acrylate solution adjusted to a pH value of 6.4 and 59.8 g N-vinylformamide was provided.

(25) As feed 2, 1.6 g of 2,2′-azobis(2-methylpropionamidine) dihydrochloride was dissolved in 78.4 g of water at room temperature.

(26) As feed 3, 1.7 g of 2,2′-azobis(2-methylpropionamidine) dihydrochloride was dissolved in 84.3 g of water at room temperature.

(27) As feed 4, 200 g water and as feed 5, 340 g water was provided.

(28) In a 2-L-glass apparatus with anchor stirrer, descending cooler, internal thermometer and nitrogen introduction tube, 200 g water and 2.2 g 75% by weight phosphoric acid were added. At a speed of 100 rpm, approx. 3.0 g of a 25% by weight caustic soda lye was added so that a pH value of 6.5 was achieved. Subsequently, 206.8 g of a 65% by weight aqueous DADMAC solution were mixed in. The receiver was heated to 63° C. and the pressure in the apparatus was reduced to about 210 mbar, so that the reaction mixture just started boiling at 63° C. Then feeds 1 and 2 were started simultaneously and added synchronously in 4 h at constant 63° C. 1.5 h after starting feed 1, water feed 4 was started and added in 2.5 h. After the end of feeds 1, 2 and 4, feed 3 was added within 2 h. 30 min after starting feed 3 (=4.5 h after starting feed 1) the pressure was set to 500 mbar and the internal temperature was increased to 85° C. After the end of feed 3, the batch was kept at 85° C. for another hour and then mixed into feed 5 as quickly as possible. The batch was cooled down to room temperature and the vacuum was released by aeration with normal air. Water was constantly distilled off during the entire polymerization time (7 h), so that a total of 96 g was distilled off.

(29) The result was a yellow, viscous solution with a solid content of 20.6% by weight. The K-value of the copolymer was 79 (0.5% by weight in 5% by weight aqueous NaCl solution).

(30) b) Hydrolysis to Final Product

(31) 190.0 g of the polymer solution V2 obtained above were mixed with 0.6 g of a 40% by weight aqueous sodium bisulfite solution in a 500 ml four-necked flask with leaf stirrer, internal thermometer, dropping funnel and reflux condenser at a stirrer speed of 80 rpm and then heated to 80° C. Then 25.0 g of a 25% by weight aqueous sodium hydroxide solution was added. The mixture was kept at 80° C. for 8 hours. The product obtained was cooled to room temperature and adjusted to a pH value of 6.7 by the addition of 13.1 g of 37% by weight hydrochloric acid.

(32) A slightly yellow, viscous polymer solution with a solid content of 20.6% and a polymer content of 12.7% was obtained. The degree of hydrolysis of the vinylformamide units was 95 mol %.

Example P-P3

Additive 3

(33) (hydrolyzed terpolymer VFA/DADMAC/Na-acrylate=40 mol %/40 mol %/20 mol %, K-value 71)

(34) a) Polymerization Precursor V3

(35) As feed 1, a mixture of 134.2 g aqueous 32% by weight Na-acrylate solution adjusted to a pH value of 6.4 and 65.5 g N-vinylformamide was provided.

(36) As feed 2, 1.6 g of 2,2′-azobis(2-methylpropionamidine) dihydrochloride was dissolved in 78.4 g of water at room temperature.

(37) As feed 3, 1.4 g of 2,2′-azobis(2-methylpropionamidine) dihydrochloride was dissolved in 70.6 g of water at room temperature.

(38) As feed 4, 200 g water and as feed 5, 540 g water was provided.

(39) In a 2-L-glass apparatus with anchor stirrer, descending cooler, internal thermometer and nitrogen introduction tube, 200 g water and 2.2 g 75% by weight phosphoric acid were added. At a speed of 100 rpm, approx. 3.0 g of a 25% by weight caustic soda lye was added so that a pH value of 6.5 was achieved. Subsequently, 226.8 g of a 65% by weight aqueous DADMAC solution were mixed in. The receiver is heated to 63° C. and the pressure in the apparatus is reduced to approx. 210 mbar, so that the reaction mixture just started boiling at 63° C. Then feeds 1 and 2 were started simultaneously and dosed synchronously in 4 h at a constant 63° C. 1.5 h after starting feed 1, water feed 4 was started and dosed in 2.5 h. After the end of feeds 1, 2 and 4, feed 3 was added within 2 h. 30 min after starting feed 3 (=4.5 h after starting feed 1) the pressure was set to 500 mbar and the internal temperature was increased to 85° C. After the end of feed 3, the batch was kept at 85° C. for another hour and then mixed into feed 5 as quickly as possible. The batch was cooled down to room temperature and the vacuum was released by aeration with normal air. Water was constantly distilled off during the entire polymerization time (7 h), so that a total of 207 g was distilled off.

(40) The result was a slightly yellow, viscous solution with a solids content of 20.8% by weight. The K-value of the copolymer was 71 (0.5% by weight in 5% by weight aqueous NaCl solution).

(41) b) Hydrolysis to Final Product

(42) 210.0 g of the polymer solution V3 obtained above were mixed with 0.8 g of a 40% by weight aqueous sodium bisulfite solution in a 500 ml four-necked flask with leaf stirrer, internal thermometer, dropping funnel and reflux condenser at a stirrer speed of 80 rpm and then heated to 80° C. Then 26.8 g of a 25% by weight aqueous sodium hydroxide solution were added. The mixture was kept at 80° C. for 5.5 h. The product obtained was cooled to room temperature and adjusted to a pH value of 7.0 by the addition of 13.7 g of 37% by weight hydrochloric acid.

(43) A slightly yellow, viscous polymer solution with a solid content of 20.5% by weight and a polymer content of 12.7% by weight was obtained. The degree of hydrolysis of the vinylformamide units was 97 mol %.

Example P-P4

Additive 4

(44) (hydrolyzed terpolymer VFA/DADMAC/Na-acrylate=50 mol %/20 mol %/30 mol %, K-value 97)

(45) a) Polymerization Precursor V4

(46) As feed 1, a mixture of 284.1 g aqueous 32% by weight Na-acrylate solution adjusted to a pH value of 6.4 and 115.6 g N-vinylformamide (99%) was provided.

(47) As feed 2, 0.9 g 2,2′-azobis(2-methylpropionamidine) dihydrochloride was dissolved in 45.4 g water at room temperature.

(48) As feed 3, 1.7 g of 2,2′-azobis(2-methylpropionamidine) dihydrochloride was dissolved in 84.2 g of water at room temperature.

(49) As feed 4, 200 g water and as feed 5, 228 g water was provided.

(50) In a 2-L-glass apparatus with anchor stirrer, descending cooler, internal thermometer and nitrogen introduction tube, 200 g water and 3.0 g 75% by weight phosphoric acid were added. At a speed of 100 rpm, approx. 4.7 g of a 25% by weight caustic soda lye were added so that a pH of 6.6 was achieved. Subsequently, 160.0 g of a 65% by weight aqueous DADMAC solution was mixed in. The receiver was heated to 66° C. and the pressure in the apparatus was reduced to about 250 mbar, so that the reaction mixture just started boiling at 66° C. Then feeds 1 and 2 were started simultaneously and dosed synchronously in 4 h at constant 66° C. 1.5 h after starting feed 1, water feed 4 was started and dosed in 2.5 h. After the end of feeds 1, 2 and 4, feed 3 was added within 2 h. 1 h after starting feed 3 (=5 h after starting feed 1) the pressure was set to 650 mbar and the internal temperature was increased to 90° C. After the end of feed 3, the batch was kept at 85° C. for another hour and then mixed into feed 5 as quickly as possible. The batch was cooled down to room temperature and the vacuum was released by aeration with normal air. Water was constantly distilled off during the entire polymerization time (7 h), so that a total of 78 g was distilled off.

(51) The result was a slightly yellow, highly viscous solution with a solids content of 26.7% by weight. The K-value of the copolymer was 97 (0.5% by weight in 5% by weight aqueous NaCl solution).

(52) b) Hydrolysis to Final Product

(53) 180.0 g of the polymer solution V4 obtained above were mixed with 1.3 g of a 40% by weight aqueous sodium bisulfite solution in a 500 ml four-necked flask with leaf stirrer, internal thermometer, dropping funnel and reflux condenser at a stirrer speed of 80 rpm and then heated to 80° C. Then 43.1 g of a 25% by weight aqueous sodium hydroxide solution was added. The mixture was kept at 80° C. for 6 h. The product obtained was cooled to room temperature and adjusted to a pH value of 7.8 by the addition of 21.2 g 37% by weight hydrochloric acid by weight.

(54) The result was a slightly yellow, viscous polymer solution with a solid content of 24.8% by weight and a polymer content of 13.8% by weight. The degree of hydrolysis of the vinylformamide units was 95 mol %.

Example P-P5

Additive 5

(55) (hydrolyzed terpolymer VFA/DADMAC/Na-acrylate=60 mol %/10 mol %/30 mol %, K-value 100)

(56) a) Polymerization Precursor V5

(57) As feed 1, a mixture of 313.6 g aqueous 32% by weight Na acrylate solution adjusted to a pH value of 6.4 and 153.2 g N-vinylformamide was provided.

(58) As feed 2, 1.8 g of 2,2′-azobis(2-methylpropionamidine) dihydrochloride was dissolved in 86.7 g of water at room temperature.

(59) As feed 3, 1.0 g of 2,2′-azobis(2-methylpropionamidine) dihydrochloride was dissolved in 47.6 g of water at room temperature.

(60) As feed 4, 200 g water and as feed 5, 265 g water was provided.

(61) In a 2-L-glass apparatus with anchor stirrer, descending cooler, internal thermometer and nitrogen introduction tube, 200 g water and 3.0 g 75% by weight phosphoric acid were added. At a speed of 100 rpm, approx. 4.7 g of a 25% by weight caustic soda lye were added so that a pH value of 6.5 was achieved. Subsequently, 88.3 g of a 65% by weight aqueous DADMAC solution were mixed in. The receiver was heated to 63° C. and the pressure in the apparatus was reduced to about 210 mbar, so that the reaction mixture just started boiling at 63° C. Then feeds 1 and 2 were started simultaneously and dosed synchronously in 4 h at constant 63° C. 1.5 h after starting feed 1, water feed 4 was started and dosed in 2.5 h. After the end of feeds 1, 2 and 4, feed 3 was added within 2 h. 1 h after starting feed 3 (=5 h after starting feed 1) the pressure was set to 380 mbar and the internal temperature was increased to 75° C. After the end of feed 3, the preparation was kept at 75° C. for another hour and then mixed into feed 5 as quickly as possible. The preparation was cooled down to room temperature and the vacuum was released by aeration with normal air. Water was constantly distilled off during the entire polymerization time (7 h), so that a total of 114 g was distilled off.

(62) The result was a yellow, highly viscous solution with a solids content of 24.5% by weight. The K-value of the copolymer was 100 (0.5% by weight in 5% by weight aqueous NaCl solution).

(63) b) Hydrolysis to Final Product

(64) 170.0 g of the polymer solution V5 obtained above were mixed with 1.5 g of a 40% by weight aqueous sodium bisulfite solution in a 500 mL four-necked flask with leaf stirrer, internal thermometer, dropping funnel and reflux condenser at a stirrer speed of 80 rpm and then heated to 80° C. Then 49.5 g of a 25% by weight aqueous sodium hydroxide solution were added. The mixture was kept at 80° C. for 7 h. The product obtained was cooled to room temperature and adjusted to a pH value of 8.1 by the addition of 22.2 g of 37% by weight hydrochloric acid.

(65) A slightly yellow, viscous polymer solution was obtained with a solid content of 22.9% by weight and a polymer content of 11.8% by weight. The degree of hydrolysis of the vinylformamide units was 96 mol %.

Example P-P6

Additive 6

(66) (hydrolyzed copolymer VFA/DADMAC/Na-acrylate/TAACl=39.99 mol %/30.02 mol %/29.97 mol %/0.02 mol %, simplified description: crosslinked hydrolyzed terpolymer VFA/DADMAC/Na-acrylate/=40 mol %/30 mol %/30 mol % and 0.02 mol % TAACl as crosslinker, K-value 86)

(67) a) Polymerization Precursor V6

(68) As feed 1, a mixture of 209.8 g aqueous 32% by weight Na-acrylate solution adjusted to a pH value of 6.4, 68.3 g N-vinylformamide and 0.1 g N,N,N-tetraallylammonium chloride was provided.

(69) As feed 2, 1.5 g 2,2′-azobis(2-methylpropionamidine) dihydrochloride was dissolved in 74.5 g water at room temperature.

(70) As feed 3, 1.6 g of 2,2′-azobis(2-methylpropionamidine) dihydrochloride was dissolved in 80.4 g of water at room temperature.

(71) As feed 4, 200 g water and as feed 5, 340 g water was provided

(72) In a 2-L-glass apparatus with anchor stirrer, descending cooler, internal thermometer and nitrogen introduction tube, 200 g water and 2.2 g 75% by weight phosphoric acid were added. At a speed of 100 rpm, approx. 3.0 g of a 25% by weight caustic soda lye was added so that a pH value of 6.5 was achieved. Subsequently, 177.3 g of a 65% by weight aqueous DADMAC solution were mixed in. The receiver was heated to 63° C. and the pressure in the apparatus was reduced to about 210 mbar, so that the reaction mixture just started boiling at 63° C. Then feeds 1 and 2 were started simultaneously and dosed synchronously in 4 h at constant 63° C. 1.5 h after starting feed 1, water feed 4 was started and dosed in 2.5 h. After the end of feeds 1, 2 and 4, feed 3 was added within 2 h. 30 min after starting feed 3 (=4.5 h after starting feed 1) the pressure was set to 500 mbar and the internal temperature was increased to 85° C. After the end of feed 3, the batch was kept at 85° C. for another hour and then mixed into feed 5 as quickly as possible. The batch was cooled down to room temperature and the vacuum was released by aeration with normal air. Water was constantly distilled off during the entire polymerization time (7 h), so that a total of 109 g was distilled off.

(73) The result was a yellow, viscous solution with a solid content of 20.4% by weight. The K-value of the copolymer was 86 (0.5% by weight in 5% by weight aqueous NaCl solution).

(74) b) Hydrolysis to Final Product

(75) 190.0 g of the polymer solution V6 obtained above were mixed with 0.8 g of a 40% by weight aqueous sodium bisulfite solution in a 500 ml four-necked flask with leaf stirrer, internal thermometer, dropping funnel and reflux condenser at a stirrer speed of 80 rpm and then heated to 80° C. Then 25.3 g of a 25% by weight aqueous sodium hydroxide solution were added. The mixture was kept at 80° C. for 7 h. The product obtained was cooled to room temperature and adjusted to a pH value of 6.8 by adding 13.8 g of 37% by weight hydrochloric acid.

(76) A slightly yellow, viscous polymer solution was obtained with a solid content of 20.1% by weight and a polymer content of 12.2% by weight. The degree of hydrolysis of the vinylformamide units was 93 mol %.

Example P-P7

Additive 7

(77) (hydrolyzed terpolymer VFA/DADMAC/Na methacrylate=40 mol %/30 mol %/30 mol %, K-value 74)

(78) a) Polymerization Precursor V7

(79) As feed 1, a mixture of 257.1 g aqueous 30% by weight Na-methacrylate solution adjusted to a pH value of 6.4 and 68.3 g N-vinylformamide was provided.

(80) As feed 2, 1.6 g of 2,2′-azobis(2-methylpropionamidine) dihydrochloride was dissolved in 77.4 g of water at room temperature.

(81) As feed 3, 1.7 g of 2,2′-azobis(2-methylpropionamidine) dihydrochloride was dissolved in 84.3 g of water at room temperature.

(82) As feed 4, 340 g water was provided.

(83) In a 2-L-glass apparatus with anchor stirrer, descending cooler, internal thermometer and nitrogen introduction tube 200 g water and 2.2 g 75% by weight phosphoric acid were provided. At a speed of 100 rpm, approx. 3.0 g of a 25% by weight caustic soda lye was added so that a pH value of 6.5 was achieved. Then 177.3 g of a 65% by weight aqueous DADMAC solution was mixed in. The receiver was heated to 63° C. and the pressure in the apparatus was reduced to approx. 210 mbar, so that the reaction mixture just started boiling at 63° C. Then feeds 1 and 2 were started simultaneously and dosed synchronously in 4 h at constant 63° C. After the end of feeds 1 and 2, feed 3 was added within 2 h. 30 min after starting feed 3 (=4.5 h after starting feed 1) the pressure was set to 500 mbar and the internal temperature was increased to 85° C. After the end of feed 3, the batch was kept at 85° C. for another hour and then mixed into feed 4 as quickly as possible. The preparation was cooled down to room temperature and the vacuum was released by aeration with normal air. Water was constantly distilled off during the entire polymerization time (7 h), so that a total of 138 g was distilled off.

(84) The result was a yellow, highly viscous solution with a solids content of 24.8% by weight. The K-value of the copolymer was 74 (0.5% by weight in 5% by weight aqueous NaCl solution).

(85) b) Hydrolysis to Final Product

(86) 180.0 g of the polymer solution V7 obtained above were mixed with 0.8 g of a 40% by weight aqueous sodium bisulfite solution in a 500 ml four-necked flask with leaf stirrer, internal thermometer, dropping funnel and reflux condenser at a stirrer speed of 80 rpm and then heated to 80° C. Then 30.6 g of a 25% by weight aqueous sodium hydroxide solution were added. The mixture was kept at 80° C. for 8 h. The product obtained was cooled to room temperature and adjusted to a pH value of 6.8 by adding 17.0 g 37% by weight hydrochloric acid.

(87) The result was a slightly yellow, viscous polymer solution with a solid content of 25.0% by weight and a polymer content of 14.4% by weight. The degree of hydrolysis of the vinylformamide units was 90 mol %.

Example P-P8

Additive 8

(88) (hydrolyzed terpolymer VFA/DADMAC/Na-acrylate=40 mol %/30 mol %/30 mol %, K-value 97)

(89) a) Polymerization Precursor V8

(90) As feed 1, a mixture of 209.8 g aqueous 32% by weight Na-acrylate solution adjusted to a pH value of 6.4 and 68.3 g N-vinylformamide was provided.

(91) As feed 2, 1.5 g of 2,2′-azobis(2-methylpropionamidine) dihydrochloride was dissolved in 74.5 g of water at room temperature.

(92) As feed 3, 1.6 g of 2,2′-azobis(2-methylpropionamidine) dihydrochloride was dissolved in 80.4 g of water at room temperature.

(93) As feed 4, 200 g water and as feed 5, 390 g water was provided.

(94) In a 2-L-glass apparatus with anchor stirrer, descending cooler, internal thermometer and nitrogen introduction tube 200 g water and 2.2 g 75% by weight phosphoric acid were provided. At a speed of 100 rpm, approx. 3.0 g of a 25% by weight caustic soda lye was added so that a pH value of 6.5 was achieved. Afterwards 177.3 g of a 65% by weight aqueous DADMAC solution were mixed in. The receiver was heated to 63° C. and the pressure in the apparatus was reduced to approx. 210 mbar, so that the reaction mixture just started boiling at 63° C. Then feeds 1 and 2 were started simultaneously and dosed synchronously in 4 h at constant 63° C. 1.5 h after starting feed 1, water feed 4 was started and dosed in 2.5 h. After the end of feeds 1, 2 and 4, feed 3 was added within 2 h. 30 min after starting feed 3 (=4.5 h after starting feed 1) the pressure was set to 500 mbar and the internal temperature was increased to 85° C. After the end of feed 3, the batch was kept at 85° C. for another hour and then mixed into feed 5 as quickly as possible. The preparation was cooled down to room temperature and the vacuum was released by aeration with normal air. Water was constantly distilled off during the entire polymerization time (7 h), so that a total of 150 g was distilled off.

(95) The result was a yellow, highly viscous solution with a solid content of 20.5% by weight. The K-value of the copolymer was 97 (0.5% by weight in 5% by weight aqueous NaCl solution).

(96) b) Hydrolysis to Final Product

(97) 170.0 g of the polymer solution V8 obtained above were mixed with 0.7 g of a 40% by weight aqueous sodium bisulfite solution in a 500 ml four-necked flask with leaf stirrer, internal thermometer, dropping funnel and reflux condenser at a stirrer speed of 80 rpm and then heated to 80° C. Then 21.8 g of a 25% by weight aqueous sodium hydroxide solution were added. The mixture was kept at 80° C. for 8 h. The product obtained was cooled to room temperature and adjusted to a pH value of 7.0 by adding 11.9 g 37% by weight hydrochloric acid.

(98) A slightly yellow, viscous polymer solution with a solid content of 20.7% by weight and a polymer content of 12.5% by weight was obtained. The degree of hydrolysis of the vinylformamide units was 88 mol %.

Example P-P9

Additive 9

(99) (hydrolyzed terpolymer VFA/DADMAC/Na-acrylate=40 mol %/30 mol %/30 mol %, K-value 97)

(100) a) Polymerization Precursor V9

(101) As feed 1, a mixture of 209.8 g aqueous 32% by weight Na-acrylate solution adjusted to a pH value of 6.4 and 68.3 g N-vinylformamide was provided.

(102) As feed 2, 1.5 g of 2,2′-azobis(2-methylpropionamidine) dihydrochloride was dissolved in 74.5 g of water at room temperature.

(103) As feed 3, 1.6 g of 2,2′-azobis(2-methylpropionamidine) dihydrochloride was dissolved in 80.4 g of water at room temperature.

(104) As feed 4, 200 g water and as feed 5, 390 g water was provided.

(105) In a 2-L-glass apparatus with anchor stirrer, descending cooler, internal thermometer and nitrogen introduction tube 200 g water and 2.2 g 75% by weight phosphoric acid were provided. At a speed of 100 rpm, approx. 3.0 g of a 25% by weight caustic soda lye was added so that a pH value of 6.5 was achieved. Afterwards 177.3 g of a 65% by weight aqueous DADMAC solution were mixed in. The receiver was heated to 63° C. and the pressure in the apparatus was reduced to approx. 210 mbar, so that the reaction mixture just started boiling at 63° C. Then feeds 1 and 2 were started simultaneously and dosed synchronously at constant 63° C. in 4 h. 1.5 h after starting feed 1, water feed 4 was started and dosed in 2.5 h. After the end of feeds 1, 2 and 4, feed 3 was added within 2 h. 30 min after starting feed 3 (=4.5 h after starting feed 1) the pressure was set to 500 mbar and the internal temperature was increased to 85° C. After the end of feed 3, the preparation was kept at 85° C. for another hour and then mixed into feed 5 as quickly as possible. The preparation was cooled down to room temperature and the vacuum was released by aeration with normal air. Water was constantly distilled off during the entire polymerization time (7 h), so that a total of 150 g was distilled off.

(106) The result was a yellow, highly viscous solution with a solid content of 20.5% by weight. The K-value of the copolymer was 95 (0.5% by weight in 5% by weight aqueous NaCl solution).

(107) b) Hydrolysis to Final Product

(108) 190.0 g of the polymer solution V9 obtained above were mixed with 0.8 g of a 40% by weight aqueous sodium bisulfite solution in a 500 ml four-necked flask with leaf stirrer, internal thermometer, dropping funnel and reflux condenser at a stirrer speed of 80 rpm and then heated to 80° C. Then 20.7 g of a 25% by weight aqueous sodium hydroxide solution were added. The mixture was kept at 80° C. for 8 h. The product obtained was cooled to room temperature and adjusted to a pH value of 7.1 by adding 11.3 g 37% by weight hydrochloric acid.

(109) A slightly yellow, viscous polymer solution with a solid content of 20.3% by weight and a polymer content of 12.6% by weight was obtained. The degree of hydrolysis of the vinylformamide units was 85 mol %.

Example P-P10

Additive 10

(110) (hydrolyzed copolymer VFA/Na-acrylate=70 mol %/30 mol %, K-value 90)

(111) a) Polymerization Precursor V10

(112) As feed 1, a mixture of 100.0 g water, 224.6 g aqueous 32% by weight Na-acrylate solution adjusted to a pH value of 6.4 and 128.0 g N-vinylformamide was provided.

(113) As feed 2, 0.9 g of 2,2′-azobis(2-methylpropionamidine) dihydrochloride was dissolved in 125.8 g of water at room temperature.

(114) In a 2-L-glass apparatus with anchor stirrer, descending condenser, internal thermometer and nitrogen introduction tube, 407 g water and 1.9 g 85% by weight phosphoric acid were provided. At a speed of 100 rpm approx. 3.7 g of a 25% by weight caustic soda lye were added, so that a pH of 6.6 was achieved. The receiver was heated to 80° C. and the pressure in the apparatus was reduced to about 450 mbar, so that the reaction mixture just started boiling at 80° C. Then feeds 1 and 2 were started simultaneously. At constant 80° C. feed 1 was added in 1.5 h and feed 2 in 2.5 h. After the addition of feed 2 was completed, the reaction mixture was postpolymerized for another 2.5 h at 80° C. During the entire polymerization and post-polymerization, approx. 143 g of water were distilled off. The batch was then cooled to room temperature under normal pressure.

(115) The result was a yellow, viscous solution with a solid content of 23.8% by weight. The K-value of the copolymer was 90 (0.5% by weight in 5% by weight aqueous NaCl solution).

(116) b) Hydrolysis to Final Product

(117) 847.2 g of the polymer solution V10 obtained above were mixed with 9.3 g of a 40% by weight aqueous sodium bisulfite solution in a 2 L four-neck flask with leaf stirrer, internal thermometer, dropping funnel and reflux condenser at a stirrer speed of 80 rpm and then heated to 80° C. Then 313.7 g of a 25% by weight aqueous sodium hydroxide solution were added. The mixture was kept at 80° C. for 7 h. The product obtained was cooled to room temperature and adjusted to a pH value of 8.5 by adding 117.0 g 37% by weight hydrochloric acid.

(118) A slightly yellow, viscous polymer solution with a solid content of 23.0% by weight and a polymer content of 9.9% by weight was obtained. The degree of hydrolysis of the vinylformamide units was 98 mol %.

Example P-P11

Additive 11

(119) (hydrolyzed terpolymer VFA/DADMAC/Na-acrylate=30 mol %/30 mol %/40 mol %, K-value 92)

(120) a) Polymerization Precursor V11

(121) As feed 1, a mixture of 273.8 g aqueous 32% by weight Na-acrylate solution adjusted to a pH value of 6.4 and 50.1 g N-vinylformamide was provided.

(122) As feed 2, 1.6 g of 2,2′-azobis(2-methylpropionamidine) dihydrochloride was dissolved in 65.0 g of water at room temperature.

(123) As feed 3, 0.9 g 2,2′-azobis(2-methylpropionamidine) dihydrochloride was dissolved in 35.0 g water at room temperature.

(124) As feed 4 200 g water and as feed 5 350 g water was provided

(125) In a 2-L-glass apparatus with anchor stirrer, descending cooler, internal thermometer and nitrogen introduction tube 200 g water and 2.2 g 75% by weight phosphoric acid were added. At a speed of 100 rpm, approx. 3.0 g of a 25% by weight caustic soda lye was added so that a pH value of 6.5 was achieved. Then 173.5 g of a 65% by weight aqueous DADMAC solution was mixed in. The receiver was heated to 63° C. and the pressure in the apparatus was reduced to approx. 210 mbar, so that the reaction mixture just started boiling at 63° C. Then feeds 1 and 2 were started simultaneously and dosed synchronously at constant 63° C. in 4 h. 1.5 h after starting feed 1, water feed 4 was started and dosed in 2.5 h. After the end of feeds 1, 2 and 4, feed 3 was added within 2 h. 30 min after starting Feed 3 (=4.5 h after starting feed 1) the pressure was set to 500 mbar and the internal temperature was increased to 85° C. After the end of feed 3, the batch was kept at 85° C. for another hour and then mixed into feed 5 as quickly as possible. The preparation was cooled down to room temperature and the vacuum was released by aeration with normal air. Water was constantly distilled off during the entire polymerization time (7 h), so that a total of 85 g was distilled off. The result was a yellow, viscous solution with a solid content of 20.4% by weight. The K-value of the copolymer was 95 (0.5% by weight in 5% by weight aqueous NaCl solution).

(126) b) Hydrolysis to Final Product

(127) 200.0 g of the polymer solution V11 obtained above were mixed with 0.6 g of a 40% by weight aqueous sodium bisulfite solution in a 500 ml four-necked flask with leaf stirrer, internal thermometer, dropping funnel and reflux condenser at a stirrer speed of 80 rpm and then heated to 80° C. Then 19.7 g of a 25% by weight aqueous sodium hydroxide solution were added. The mixture was kept at 80° C. for 8 h. The product obtained was cooled to room temperature and adjusted to a pH value of 6.3 by adding 11.8 g 37% by weight hydrochloric acid.

(128) The result was a slightly yellow, viscous polymer solution with a solid content of 20.8% by weight and a polymer content of 12.9% by weight. The degree of hydrolysis of the vinylformamide units was 92 mol %.

(129) A-3) Overview of the Polymers Produced

(130) Table TabA1 shows the monomers used for the polymerization of the non-hydrolyzed precursors and the K-value obtained for the polymer. Table TabA2 shows the calculated contents of polymerized functionalities of the hydrolyzed copolymers. The calculation is based on the experimentally determined degree of hydrolysis of the N-vinylformamide used for polymerization.

(131) TABLE-US-00001 TABLE TabA1 N-vinyl Sodium formamide DADMAC.sup.d) Sodium acrylate methacrylate TAAC.sup.c) Polymer [mol %].sup.a) [mol %].sup.a) [mol %].sup.a) [mol %].sup.a) [mol %].sup.a) K-value V1 40 30 30 — — 95 V2 35 35 30 — — 79 V3 40 40 20 — — 71 V4 50 20 30 — — 97 V5 60 10 30 — — 100 V6 40 30 30 — 0.02.sup.d) 86 V7 40 30 — 30 — 74 V8 40 30 30 — — 97 V9 40 30 30 — — 95 V10 70 — 30 — — 90 V11 30 30 40 — — 95 Footnotes: .sup.a)Molar quantity used in percent of all monomers used .sup.b)DADMAC = diallyl dimethyl ammonium chloride .sup.c)TAAC = N,N,N,N-Tetraallylammonium chloride .sup.d)Due to the very small percentage content of 0.02 mol % no percentage deduction for one of the other three monomers

(132) TABLE-US-00002 TABLE TabA2 Non- hydrolyzed Cationic N—CHO of Hydrolyzed Primary Quaternized Carboxylate groups the original N—CHO of amine nitrogen groups of minus Degree of N-vinyl the original or From acrylate or anionic hydrolysis formamide.sup.e) formamide.sup.f) amidin.sup.g) DADMAC.sup.h) methacrylate.sup.i) groups.sup.j) Polymer [%].sup.c) [mol %].sup.d) [mol %].sup.d) [mol %].sup.d) [mol %].sup.d) [mol %].sup.d) [mol %].sup.d) 1 .sup.b) 94 2.4 37.6 37.6 30 30 37.6 2 .sup.b) 95 1.7 33.3 33.3 35 30 38.3 3 .sup.b) 97 1.2 38.8 38.8 40 20 58.8 4 .sup.b) 95 2.5 47.5 47.5 20 30 37.5 5 .sup.b) 96 2.4 57.6 57.6 10 30 37.6 6 .sup.b) 93 2.8 37.2 37.2 30.sup.k) 30 37.2.sup.k) 7 .sup.b) 90 4.0 36.0 36.0 30 30 .sup.l) 36.0 8 .sup.b) 88 4.8 35.2 35.2 30 30 35.2 9 .sup.a) 85 6.0 34.0 34.0 30 30 34.0 10 .sup.a)  98 1.4 68.6 68.6 — 30 38.6 11 .sup.a)  92 2.4 27.6 27.6 30 40 17.6 Footnotes: .sup.a) Comparative .sup.b) According to invention .sup.c)Percentage of the number of hydrolyzed N—CHO groups relative to the number of all N-vinylformamides used in the polymerization .sup.d)Molar amount in percent based on all monomers of the non-hydrolyzed polymer used .sup.e)Non-hydrolyzed N—CHO groups of the N-vinyl formamide used in the polymerization calculated on the basis of the amount of N-vinyl formamide used in the polymerization minus hydrolyzed N—CHO groups of the N-vinyl formamide used in the polymerization .sup.f)Hydrolyzed N—CHO groups of the N-vinylformamide used in the polymerization calculated on the basis of the amount of N-vinylformamide used in the polymerization and a certain degree of hydrolysis .sup.g)Primary amine or amidine (if primary amine cyclized with adjacent remaining N—CHO group) .sup.h)DADMAC = diallyl dimethyl ammonium chloride .sup.i)Carboxylate groups calculated on the basis of sodium acrylate or sodium methacrylate used for polymerization .sup.j)Primary amine, amidine and quaternized nitrogen as cationic groups .sup.k)Plus a small amount of 0.02 mol % of quaternized nitrogen from N,N,N,N-tetraallylammonium chloride .sup.l) Here sodium methyl acrylate instead of sodium acrylate during polymerization

(133) B) Papers

(134) B-1) Physical Characterizations

(135) Determination of Dry Content

(136) For the determination of the dry content (TG), the mass of the moist sample (MF) is determined from a moist paper sample on a calibrated top-pan dial balance, which can be weighed to 0.01 g. Preferably, the wet paper sample has an area of at least 10 cm×10 cm. The moist paper sample is then placed in a calibrated drying cabinet, which can maintain a set temperature to within ±2° C. deviation, and dried at a set temperature of 105° C. until the mass is constant. This is typically achieved after 90 minutes. The still warm dried paper sample is then transferred to a desiccator containing a suitable drying agent such as silica gel. After cooling to room temperature, the mass of the dried paper sample (MT) is determined on the above-mentioned balance. The dry content of the paper sample is calculated according to TG=100.Math.MT/MF and is given in % by weight. The percentage value is often given with one decimal place. If this percentage does not change with the rounded first decimal place, this is the indication that mass constancy has been reached for dry contents from 1 to 100% by weight. For dry contents from 0 to less than 1% by weight, the rounded second decimal place of the percentage value is the corresponding indication. Drying takes place at ambient pressure, possibly 101.32 kPa, without correction for any deviation caused by weather and sea level. Drying shall be carried out at ambient pressure, 101.32 kPa if necessary. No correction is made for a slightly different air pressure due to weather and sea level. In the case of a moist sample which does not yet have a sheet consistency, e.g. a pulp suspension or a pulp, the moist sample is dried in an appropriate tray with a large surface area.

(137) Internal Strength of a Dried Paper Sheet Obtained

(138) A dried paper sheet obtained is examined after storage in a climatic room at constant 23° C. and 50% humidity for 12 hours. The internal strength is carried out according to a procedure that complies with Tappi regulation T833 pm-94. This involves cutting 10 strips of paper 2.5 cm wide and 12.7 cm long from two sheets of A4 paper previously obtained from the dried paper web of the test machine. Each individual paper sample is attached with double-sided adhesive tape to a separate base plate and a metal bracket. The metal angle is knocked out with a pendulum, splitting the paper sample to be tested in a plane parallel to the paper surface. The energy required for this process is measured. The device used for the measurement is an Internal Bond Test Station from TMI (Testing Machines Inc. Islandia, N.Y. USA). The double-sided adhesive tape is a product of 3M (width 25.4 mm type Scotch no. 140). The measuring instrument supplies the energy required for the splitting process, based on a standardized area in J/m2. The average value of 10 individual measurements is calculated.

(139) B-2) Production of the Paper Raw Material

(140) The raw material for paper production is a pulp, which is produced by beating paper webs in a pulper. The pulp is obtained by dissolving it in drinking water and mechanically processing the paper webs in the pulper at a dry content of approx. 3.5% by weight. The pulp then typically has a fineness around 50° Schopper Riegler. The paper webs are packaging raw papers of the specification “Testliner 2” with a grammage of 120 g/m.sup.2, which come from Thurpapier in Weinfelden (Switzerland).

(141) B-3) Treatment of the Paper Raw Material with Additives

(142) The paper raw material is treated with additives either in “thick stock” at a dry content of 3.5% by weight or in “thin stock” at a dry content of 0.8% by weight.

(143) In case of “thick stock treatment” 500 g pulp with a dry content of 3.5% by weight is placed in a large glass beaker. The additive is then added with stirring as a 2% by weight solution based on polymer content. Substances are treated with 1.315 g 2% by weight additive solution based on polymer content or with 2.63 g 2% by weight additive solution based on polymer content. This corresponds to a treatment with 0.15% or 0.3% polymer content based on dry pulp.

(144) Subsequently, 100 g of the treated pulp is transferred into another glass vessel and then diluted with drinking water to a concentration of 0.8% by weight dry content.

(145) In the case of thin stock treatment, 114.3 g of pulp with a dry content of 3.5% by weight is placed in a large glass beaker. The pulp is then diluted with drinking water to a concentration of 0.8% by weight dry content. The additive is added with stirring as a 2% by weight solution based on polymer content. Pulp is treated with 0.3 g additive solution based on polymer content or 0.6 g additive solution based on polymer content. This corresponds to a treatment with 0.15% and 0.3% polymer content based on dry pulp.

(146) B-4) Papers Production

(147) The aim is to produce paper sheets with a grammage of 120 g/m2 starting from a pulp treated with an additive which has a dry content of 0.8% by weight before the additive treatment or a pulp which has a dry content of 0.8% by weight but is not treated with an additive (=reference). The paper sheets are produced on a dynamic sheet former by TechPap (France). A paper stock suspension, here the treated or untreated pulp, is sprayed onto a wire. The wire is clamped in a vertical, rapidly rotating drum. The dehydration and sheet formation in this system is determined not only by the sheet structure, but above all by the centrifugal forces within the rotating drum. By varying the speed of rotation of the drum, the centrifugal force acting on the resulting sheet structure may also be varied. The result is a variation of the dehydration of the wet paper structure, which leads to a variation of the dry content in the wet paper structure. What is meant here is the dry content of the wet paper structure immediately after removal from the water-permeable substrate (wire), which is clamped in the drum of the dynamic sheet former. The wet paper structure may also be referred to herein as a wet paper sheet, but this does not expressly refer to a re-wetted, previously dried paper sheet.

(148) The number of drum revolutions is varied in 5 steps between 600 and 1100 revolutions per minute, whereby dry contents in the range between 15% by weight and 21% by weight may be adjusted. A small part of the still wet paper structure is used for the immediate determination of the dry content after the removal of the wet paper structure from the wire of the dynamic sheet former. For each setting, wet paper structures with two different dry contents between 17% by weight and 21% by weight are produced.

(149) After removal of the wet paper structure from the drum of the dynamic sheet former, the wet paper sheets are covered on both sides with blotting paper and pressed in a static press at 6 bar for 30 seconds. Moist paper sheets are obtained, whose dry content after pressing is typically between 41% by weight and 43% by weight. If the dry content falls significantly below the lower value, the thickness of the blotting paper or the number of sheets applied may be increased to reach the above range.

(150) The resulting moist paper sheet is then covered again on both sides with fresh blotting paper and then clamped in a drying cylinder for 10 minutes. The surface temperature of the drying cylinder is approx. 100° C. After drying, the dry paper sheets obtained are placed in an air-conditioned room for conditioning.

(151) B-5) Papers Produced

(152) As reference examples, three wet paper structures or wet paper sheets with dry contents of 15.3% by weight, 17.6% by weight and 20.2% by weight respectively are produced. The wet paper structure or wet paper sheets are then pressed and the resulting moist paper sheets are then dried.

(153) As comparative examples, wet paper structures or wet paper sheets are prepared with one of the additives 1 to 8 in two dosage quantities (1.5 g and 3 g polymer content relative to 1 kg dry pulp) and one dosage of the corresponding dosage quantity in the thick stock and one dosage quantity in the thin stock. The dry content of the produced wet paper structure or wet paper sheets is below 18.5% by weight. The wet paper structure or wet paper sheets are then pressed and the resulting moist paper sheets are then dried.

(154) As comparative examples IIa, wet paper structures or wet paper sheets are produced with one of the additives 9 to 11 each with two dosage quantities each (1.5 g and 3 g polymer content based on 1 kg dry pulp) and one dosage of the corresponding dosage quantity in the thick stock and in the thin stock. The dry content of the produced wet paper structure or wet paper sheets is below 18.5% by weight. The wet paper structure or wet paper sheets are then pressed and the resulting moist paper sheets are then dried.

(155) As comparative examples IIb, wet paper structures or wet paper sheets are produced with one of the additives 9 to 11 each with two dosage quantities each (1.5 g and 3 g polymer content based on 1 kg dry pulp) and one dosage of the corresponding dosage quantity in the thick stock and in the thin stock. The dry content of the produced wet paper structure or wet paper sheets is above 18.5% by weight. The wet paper structure or wet paper sheets are then pressed and the resulting moist paper sheets are then dried.

(156) As examples of the invention, wet paper structures or wet paper sheets are produced with one of the additives 1 to 8 each with two dosage quantities each (1.5 g and 3 g polymer content based on 1 kg dry pulp) and one dosage of the corresponding dosage quantity each in the thick stock and in the thin stock. The dry content of the produced wet paper structure or wet paper sheets is above 18.5% by weight. The wet paper structure or wet paper sheets are then pressed and the resulting moist paper sheets are then dried.

(157) B-6) Internal Strength of the Dry Paper Sheets Produced

(158) Tables TabB1 and TabB2 show the internal strengths of the papers produced when additives are added to the thin stock, and Tables TabB3 and TabB4 show those when additives are added to the thick stock.

(159) TABLE-US-00003 TABLE TabB1 1.5 g polymer content per 1 kg paper stock when added to thin stock Dry content Internal Dry content Internal [% by strength [% by strength Example no. Additive weight] [J/m.sup.2] weight] [J/m.sup.2] 1.sup.a) — 15.3 144 2.sup.a) — 17.6 148 3.sup.a) — 20.2 141 B1-1.sup.a) 9 15.3 171 B1-2.sup.a) 9 18.9 174 B1-3.sup.a) 10 17.6 155 B1-4.sup.a) 10 19.2 156 B1-5.sup.a) 11 17.2 164 B1-6.sup.a) 11 19.3 163 B1-7.sup.a) 1 17.6 161 B1-8.sup.b) 1 19.5 229 B1-9.sup.a) 2 17.8 157 B1-10.sup.b) 2 19.4 223 B1-11.sup.a) 3 17.6 164 B1-12.sup.b) 3 19.7 216 B1-13.sup.a) 4 16.9 167 B1-14.sup.b) 4 19.5 221 B1-15.sup.a) 5 17.3 157 B1-16.sup.b) 5 20 224 B1-17.sup.a) 6 17.4 168 B1-18.sup.b) 6 20.1 220 B1-19.sup.a) 7 17.3 163 B1-20.sup.b) 7 19.4 213 B1-21.sup.a) 8 17.6 161 B1-22.sup.b) 8 19.1 207 Footnotes: .sup.a)Comparative .sup.b)According to invention

(160) TABLE-US-00004 TABLE TabB2 3.0 g polymer content per 1 kg paper stock when added to thin stock Dry content Internal Dry content Internal [% by strength [% by strength Example no. Additive weight] [J/m.sup.2] weight] [J/m.sup.2] 1.sup.a) — 15.3 144 2.sup.a) — 17.6 148 3.sup.a) — 20.2 141 B2-1.sup.a) 9 17.9 185 B2-2.sup.a) 9 19.4 189 B2-3.sup.a) 10 17.4 176 B2-4.sup.a) 10 19 180 B2-5.sup.a) 11 17.6 181 B2-6.sup.a) 11 19.4 181 B2-7.sup.a) 1 17.9 177 B2-8.sup.b) 1 19.7 267 B2-9.sup.a) 2 18.2 174 B2-10.sup.b) 2 19.8 276 B2-11.sup.a) 3 17.7 183 B2-12.sup.b) 3 20.0 271 B2-13.sup.a) 4 17.5 180 B2-14.sup.b) 4 19.9 262 B2-15.sup.a) 5 17.3 188 B2-16.sup.b) 5 19.8 275 B2-17.sup.a) 6 17.6 174 B2-18.sup.b) 6 20.0 261 B2-19.sup.a) 7 17.7 179 B2-20.sup.b) 7 19.9 271 B2-21.sup.a) 8 17.9 171 B2-22.sup.b) 8 19.4 262 Footnotes: .sup.a)Comparative .sup.b)According to invention

(161) TABLE-US-00005 TABLE TabB3 1.5 g polymer content per 1 kg paper stock when added to thick stock Dry content Internal Dry content Internal [% by strength [% by strength Example no. Additive weight] [J/m.sup.2] weight] [J/m.sup.2] 1.sup.a) — 15.3 144 2.sup.a) — 17.6 148 3.sup.a) — 20.2 141 B3-1.sup.a) 9 18.1 166 B3-2.sup.a) 9 19.2 159 B3-3.sup.a) 10 17.3 169 B3-4.sup.a) 10 19.3 162 B3-5.sup.a) 11 16.9 159 B3-6.sup.a) 11 19.1 155 B3-7.sup.a) 1 17.3 156 B3-8.sup.b) 1 19.3 231 B3-9.sup.a) 2 17.4 164 B3-10.sup.b) 2 19.2 226 B3-11.sup.a) 3 17.1 154 B3-12.sup.b) 3 20.4 218 B3-13.sup.a) 4 17.2 156 B3-14.sup.b) 4 19.7 237 B3-15.sup.a) 5 17.0 163 B3-16.sup.b) 5 19.6 223 B3-17.sup.a) 6 17.9 155 B3-18.sup.b) 6 19.7 218 B3-19.sup.a) 7 16.8 155 B3-20.sup.b) 7 19.7 225 B3-21.sup.a) 8 17.2 157 B3-22.sup.b) 8 18.9 221 Footnotes: .sup.a)Comparative .sup.b)According to invention

(162) TABLE-US-00006 TABLE TabB4 3.0 g polymer content per 1 kg paper stock when added to thick stock Dry content Internal Dry content Internal [% by strength [% by strength Example no. Additive weight] [J/m.sup.2] weight] [J/m.sup.2] 1.sup.a) — 15.3 144 2.sup.a) — 17.6 148 3.sup.a) — 20.2 141 B4-1.sup.a) 9 17.8 178 B4-2.sup.a) 9 19.5 172 B4-3.sup.a) 10 17.8 179 B4-4.sup.a) 10 19.9 185 B4-5.sup.a) 11 17.3 175 B4-6.sup.a) 11 18.9 176 B4-7.sup.a) 1 16.9 175 B4-8.sup.b) 1 19.1 284 B4-9.sup.a) 2 18.1 177 B4-10.sup.b) 2 20.1 274 B4-11.sup.a) 3 17.4 169 B4-12.sup.b) 3 20.6 282 B4-13.sup.a) 4 17.9 169 B4-14.sup.b) 4 20.2 295 B4-15.sup.a) 5 17.5 179 B4-16.sup.b) 5 20.3 279 B4-17.sup.a) 6 18.0 176 B4-18.sup.b) 6 19.9 283 B4-19.sup.a) 7 17.4 176 B4-20.sup.b) 7 19.7 265 B4-21.sup.a) 8 17.5 173 B4-22.sup.b) 8 19.3 276 Footnotes: .sup.a)Comparative .sup.b)According to invention

(163) Tables TabB1 to TabB4 show for the produced dry paper sheets that (i.sub.B) a dry content of the wet paper structure or wet paper sheet of between 15.3% by weight and 20.2% by weight does not cause a difference in the internal strength of the dry paper sheet in the reference examples without additive 1 to 11, (ii.sub.B) a dry content of the wet paper structure or wet paper sheet between 15.3% by weight and 19.9% by weight does not cause a difference in the internal strength of the dry paper sheet in comparative examples Ila and Ilb with an additive 9 to 11, (iii.sub.B) a dry content of the wet paper structure or wet paper sheet above 18.5% by weight causes a significant increase in the internal strength of the dry paper sheet examples according to invention with an additive 1 to 8, this increase being related to the internal strengths of the dry paper sheets in the comparison examples I with an additive 1 to 8, the difference in a dry content of the wet paper structure or wet paper sheet being below 18.5% by weight, (iv.sub.B) the addition of an additive 1 to 8 to a pulp with a dry content of 3.5% by weight and subsequent dilution to 0.8% by weight tends to give higher internal strength compared with the addition of the same additive to a pulp with a dry content of 0.8% by weight, especially when 3.0 g of additive is added instead of 1.5 g of additive.

(164) Tables TabA1 and TabA2 show for the additives 1 to 11: (i.sub.A) a content of polymerized 10 mol % DADMAC is a difference between additive 5 according to the invention and the comparative additive 10, in which instead of DADMAC more N-vinylformamide is used in the polymerization of its precursor V10, (ii.sub.A) a content of polymerized 35 mol % N-vinylformamide is a difference for the precursor V2 of additive 2 according to the invention compared to additive 11, in whose precursor V11 5 mol % less N-vinylformamide is polymerized and instead 5 mol % more DADAMAC is polymerized, (iii.sub.A) a degree of hydrolysis of 88% of all N-vinylformamide monomers polymerized in its precursor V8 is a difference of additive 8 according to the invention compared to additive 9, which has a degree of hydrolysis of 85% of all N-vinylformamide monomers polymerized in its precursor V9.