NO164852B - PROCEDURE FOR MANUFACTURING PAPER, CARTON AND PAPER WITH HIGH-DRY, WATER- AND LOT-FASTNESS. - Google Patents

Abstract

1. A process for the production of paper, cardboard and board having high dry strength, wet strength and alkali resistance by adding an aqueous polymer solution to the paper stock in an amount of from 0.1 to 5% by weight, based in each case on the solids, and draining the paper stock on a screen to form sheets, wherein the aqueous polymer solution used is a reaction product obtained by reacting (1) a homopolymer of a vinylimidazole of the formula I see diagramm : EP0146000,P6,F1 where R**1 , R**2 and R**3 are each H or CH3 , and R**1 may furthermore be C2 H5 , C3 H7 or C4 H9 , or (2) a water-soluble copolymer of a) at least 5% by weight of a vinylimidazole of the formula I, b) up to 95% by weight of acrylamide and/or methacrylamide and, if desired, c) up to 30% by weight of acrylonitrile, methylenically unsaturated C3 -C5 - carboxylic acid or one of its esters, with epichlorhydrin in a ratio of from 0.02 to 2.9 moles of epichlorhydrin per molar equivalent of basic nitrogen in the homopolymer or copolymer, in the absence of a polyalkyleneimine.

Description

For the production of wet-fast paper, it becomes the paper starting material in the neutral or slightly alkaline pH

area in practice almost exclusively added to resins produced by reacting epichlorohydrin with long-chain basic polyamidoamines, cf. U.S. patent 2 926 116. As the polyamide chain which forms the basis of the resins is relatively easily split hydrolytically, these resins have the disadvantage that they only exhibit a relatively poor storage stability. The alkali resistance of paper treated with these resins needs to be improved.

From the U.S. patent 3 700 623 resins are known which are produced by reacting epichlorohydrin with polymers of diallylamines. Such products enable the production of paper with high dry, wet and alkali resistance. However, the resins are very expensive and have thus far not found any application in practice. A disadvantage of these resins is that they must first be activated with lye liquids in the paper mill to achieve an optimal effect. The resins also have the disadvantage that they lead to a strong darkening of the whiteness of the paper thus treated.

The invention is based on the task of providing resins which, when added to the paper starting material in the neutral to slightly alkaline pH range, increase the dry, wet and alkali resistance of the paper thus produced. The resins must be usable directly without activation and, furthermore, must not lead to a darkening of the whiteness of the paper.

The invention relates to a method for producing paper, cardboard and cardboard with high dry, wet and lye resistance by adding aqueous polymer solutions to the paper pulp in an amount of 0.1-5% by weight, in each case calculated on the solids, and dewatering of the paper pulp on a wire during web formation, characterized by the use as aqueous polymer solutions of reaction products that are obtained from the conversion of

(1) homopolymers of vinylimidazole of the formula I

where R 1 , R 2 , R 3 =H, CH 3 ; and R 1 further means C 2 H 5 , C 3 H 7 ,

C4Hg; or off

(2) water-soluble copolymers of

a) at least 5% by weight of a vinyl imidazole with the formula I,

b) up to 95% by weight of acrylamide and/or methacrylamide, and optionally c) up to 30% by weight of acrylonitrile, methacrylonitrile, vinyl acetate, vinylpyrrolidone, an ethylenically unsaturated C3- to

C5-carboxylic acid or ester thereof

with epichlorohydrin in a ratio of 0.02 to 2.9 mol epichlorohydrin per moles of basic nitrogen equivalent in the homo- or copolymer, in the absence of polyalkylenimines.

Homo- and copolymers of vinylimidazole are known. They are produced, for example, by polymerization of vinylimidazoles with the formula I

where R 1 , R 2 , R 3 =H, CH 3 ; and R1 also means C2H5, C3H7, C4Hg, in aqueous solution in the presence of radical polymerization initiators at temperatures of 50-100, preferably 60-100°C. R<1>can in the case of. C3-alkyl be n- or isopropyl and in the case of C4-alkyl n-, iso- or tert.-butyl.

For the production of copolymers of vinylimidazole, at least 5% by weight of a vinylimidazole with the formula I is used as component (a), while up to 95% by weight of acrylamide and/or methacrylamide is used as component (b) in the copolymer. Copolymers of (a) 15 - 30% by weight of a vinyl imidazole with the formula I are preferably used, where R<1>, R<2> and R<3> mean hydrogen or R<2> and R<3> hydrogen and R<1 >methyl, or a mixture of the monomers, and (b) 85 - 70% by weight acrylamide as starting polymer for the production of the wet-set resins.

The copolymers can e.g. be modified in that they polymerized as component (c) contain up to 30% by weight of acrylonitrile, methacrylonitrile, vinyl acetate, vinyl pyrrolidone, an ethylenically unsaturated C3 to C5 carboxylic acid or ester thereof. The monomers for component (c) are used in such an amount that the polymers formed are still water-soluble. Therefore, for example, long-chain esters of ethylenically unsaturated C3- to C5-carboxylic acids are polymerized only in an amount of up to approx. 5% by weight, while acrylic acid methyl ester or acrylonitrile can constitute up to 30% by weight in the construction of the copolymers. For modifying the copolymers, several of the monomers mentioned under (c) can also be used simultaneously during the polymerization, e.g. acrylonitrile and acrylic acid, acrylonitrile, vinyl acetate and vinylpyrrolidone or acrylic acid and acrylic acid ester.

The homo- and copolymers of vinylimidazole have K values from 30 to 150, preferably 60 - 120 (determined according to H. Fikentscher with 0.1% polymer solutions in 5% aqueous sodium bicarbonate solution at 20°C). They are converted in an aqueous medium with epichlorohydrin to resins. Per mol of basic nitrogen equivalent in the polymer, 0.02 - 2.9, preferably 1.0 - 2.5 mol of epichlorohydrin is used. The resins are preferably prepared by adding epichlorohydrin to an aqueous solution of the homo- or copolymer of a compound with the formula I and allowing the mixture to react until epoxide can no longer be detected. In order to be able to control the reaction in a fully satisfactory manner, the epichlorohydrin addition is carried out continuously or in stages. The reaction temperature is between 0 and 100, preferably between 20 and 80°C. Reaction times are approx. 2-6 hours. Condensation occurs at pH values from 5 to 10. To obtain stable resin solutions, the pH value of the aqueous solution before or after the end of condensation is set to a value in the range 2-4. For this adjustment of the pH value, sulfuric acid or formic acid is preferably used. Ready-to-use aqueous resin solutions have a solids content of 10 - 20

% by weight and a viscosity of 100 - 5000 m.Pas. (measured in 10% solution according to Brookfield, 20 rpm, 20°C).

The aqueous resin solutions can be used directly or possibly after a further dilution with water - they can be diluted with water in all conditions - in the production of. paper. They are then added to the paper pulp before web formation in an amount, calculated on the solids, of 0.1 - 5, preferably 0.25 - 1% by weight. If the aqueous resin solutions are added to the paper pulp just before the pulp inlet in an amount of 0.005 - 0.1%, calculated on dry fiber material and 100% resin, then these resins are excellent creping aids, e.g. for toilet paper.

The resin solutions used according to the invention are added to the fiber slurry under the usual conditions for paper manufacture. The resins are effective for all known paper, cardboard and cardboard qualities, e.g. in the production of writing paper, printing paper and packaging paper. The paper, respectively the cardboard and the cardboard, can be made from many fiber materials, for example from sulphite or sulphate pulp (bleached or unbleached, sanding pulp or recycled paper or mixtures of the aforementioned fiber types). The pulp suspension's pH value is 4-9, preferably 6-8. It is also possible to apply the resin solutions to the surface of the already formed paper, e.g. in the glue press.

The parts specified in the following examples are parts by weight,

and the percentages are based on the weight of the substances.

The sheets were produced in a Rapid-Kothen laboratory sheet former. The dry wear length was measured according to DIN 53 112, Blatt 1 and the wet wear length according to DIN 53 112, Blatt 2.

The lye strength (lye resistance) was determined in the same way

as the wet strength, as a 1% sodium hydroxide solution was used instead of water to rewet the paper (5 min. at 50°C).

The whiteness of the paper sheets was determined using a ref-lex ion photometer (Elrefo equipment) according to DIN 53 145.

The K value of the polymers was determined according to H. Fikentscher, Cellulosechemie 13, 58-64 and 71-74 (1932), at a temperature of 20°C in a 5% aqueous sodium chloride solution; thereby means K =

k. 10<3>.

Preparation of the resin solutions

Resin 1

a) Preparation of an aqueous solution of a homopolymer of N-vinylimidazole

In a polymerization vessel, 500 parts of vinylimidazole and 450 parts of water were mixed, and while passing through nitrogen at a temperature of 100°C, 8 parts of tert were added in the course of one hour. -butyl perethylhexanoate in 40 parts methanol.. After the addition of the polymerization initiator was finished, the reaction mixture was post-polymerized for 7 hours at a temperature of 91°C and then diluted to a solids content of 30.3% by adding water. A brown, slightly cloudy, highly viscous polymer solution is formed. The K-value of the homopolymer is 86.

b) Reaction of the homopolymer with epichlorohydrin 878 g of a 30.3% aqueous solution of it according to a)

obtained poly-N-vinylimidazole (corresponding to 2.7 equivalents of basic nitrogen) was diluted with 1630 g of water and 677 g (7.3 mol) of epichlorohydrin were added at room temperature and stirred. Below this, the viscosity of the solution rose slowly. After 30 minutes, 193 g of sulfuric acid (2 mol) were added, which resulted in a pH value of 2. The reaction mixture was heated to 80°C and stirred at this temperature for 4 hours, during which 2100 g of water was added in portions. An aqueous solution of the resin 1 was obtained, which had a solids content of 17.2% and a pH value of 1.7. The viscosity of the aqueous solution was 380 mPas.

Resin 2

a) Preparation of an aqueous copolymer solution

In a polymerization vessel containing 250 parts water

additions I and II were added under stirring and passage of nitrogen from two separate supply containers

set simultaneously at a temperature of 90°C during one hour. Addition I consisted of 150 parts of acrylamide, 150 parts of vinylimidazole and 150 parts of water; while addition II was a solution of 3 parts of 2,2'-azobis(2- amidinopropane)

-dihydrochloride in 47 parts water. The reaction mixture was then post-polymerized at a temperature of 90°C for 4 hours and adjusted to a solids content of 30.3% at

addition of water. The K value of the copolymer was 68.

b) Reaction of the copolymer with epichlorohydrin 233 g (corresponding to 0.4 equivalent basic nitrogen) of a

A 30.3% aqueous solution of the copolymer according to a) was diluted with 286.5 g of water and 41.6 g (0.45 mol) of epichlorohydrin was added at room temperature. The reaction mixture was then slowly heated to 75°C. After 60 minutes, the viscosity of the reaction mixture had clearly increased. It was then adjusted to a pH value of 2.0 with 44 g (0.8 mol) under 85% formic acid and stirred for a further 2 hours at a temperature of 75°C. After this time, the reaction was complete. The reaction mixture was adjusted to a solids content of 15% by adding 200 g of water. The aqueous solution of resin 2 had a viscosity of 230 mPas. and a pH value of 3.0.

Resin 3

a) Preparation of an aqueous copolymer solution

A polymerization vessel was filled with 125 parts of water and

heated to a temperature of 80°C with stirring and passage of nitrogen. When the temperature of 80°C was reached, 2 different additions were added continuously over the course of an hour. Addition I consisted of a solution of 225 parts of acrylamide and 75 parts of N-vinylimidazole in 225 parts of water, while addition II was a solution of 3 parts of 2,2'-azobis(2-amidinopropane)-dihydrochloride in 4 7 parts of water . After the addition of the monomers and initiator was finished, the reaction mixture was post-polymerized for 4 hours at a temperature of 80°C and then adjusted to a solids content of 10.1% by adding water. The K value of the copolymer was 84.

b) Reaction of the copolymer a) with epichlorohydrin 297.6 g (equivalent to 0.1 equivalent basic nitrogen) of

a 10.1% aqueous solution of the copolymer a) was added to 150 g of water, 16.7 g (0.18 mol) of epichlorohydrin and 9.7 g (0.18 mol) of 85% formic acid and heated to a temperature at 75°C. After a reaction time of 4 hours at 75°C

an 8.4% aqueous solution of the resin 3 is obtained, which had a viscosity of 3800 mPas. and a pH value of 3.6.

Resin 4

a) Preparation of an aqueous copolymer solution

A polymerization vessel was filled with 145 parts of water and

heated to a temperature of 80°C with stirring and passage of nitrogen. After the water had reached a temperature of 80°C, additions I and II were added at the same time within an hour. Addition I consisted of a solution of 255 parts acrylamide, 45 parts N-vinylimidazole in 255

parts of water, while addition II was a solution of 1.5 g of 2,2'-azobis(s-amidinopropane) dihydrochloride in 48.5 parts of water. After addition of the monomers and the initiator, the reaction mixture was post-polymerized for 4 hours at 80°C and then diluted to a solids content of 5% by adding water. The K value of the copolymer was 113.

b) Reaction of the copolymer a) with epichlorohydrin 894.6 g (corresponding to 0.08 equivalent basic nitrogen) of

6.9 g (0.13 mol) of 85% formic acid and 11.8 g (0.13 mol) of epichlorohydrin were added to the above-described 5% aqueous solution of copolymer a) at room temperature. The reaction mixture was heated to a temperature of 80°C and stirred for 5 hours at this temperature. An aqueous solution of resin 4 was obtained, which had a solids content of 6.0% and a pH value of 3.6. The viscosity was 600 mPas.

Example 1

A 0.5% pulp suspension in water was prepared from 100% spruce sulphite pulp. The pH value of the suspension was 7.5, and the degree of grinding was 35°SR. The mass suspension was divided into 3 equal parts, and each part was prepared under the following conditions into sheets with a basis weight of 80g/m 2:

a) Nothing was added to the pulp suspension.

b) To the pulp suspension, 1%, calculated on the solids, of an aqueous solution of a commercial neutral-wet-fast resin based on a reaction product of epichlorohydrin and a polyamidoamine of diethylenetriamine and adipic acid was added. The neutral wet-fast resin was prepared according to Example 1 of U.S. Pat. patent 2 926 116. c) 1%, calculated on the solids, of the resin 3 described above was added to the pulp suspension.

The 3 sheets produced according to a) to c) were tested with regard to dry wear length, wet wear length, alkali resistance and whiteness. The results are summarized in table 1.

Example 2

A 0.5% aqueous pulp suspension was produced from 100% mixed recycled paper. The pH value of the suspension was 7.2 and the grinding degree 50°SR. The mass suspension was then divided into 5 equal parts, and each of these was prepared under the following conditions into sheets with a surface mass of 80 g/m 2:

a) No further addition to the pulp suspension was made. b) Addition of 0.5%, calculated on dry fiber mass, of the neutral-wet-fast resin described in example 1b). c) Addition of 1.0%, calculated on dry fiber mass, of the neutral-wet-fast resin described in example 1b). d) Addition of 0.5%, calculated on the solids, of resin 4 and e) Addition of 1.0%, calculated on the solids, of resin 4.

All the paper sheets produced in this way were examined with regard to dry and wet wear length. The results are shown in table 2.

Example 3

Using a trial paper machine with a working width

of 75 cm, at a speed of 65 m/minute, a paper of 80% bleached spruce sulphite pulp and 20% bleached beech sulphite pulp was produced with a basis weight of 80 g/m 2. The pH value of the pulp suspension was 7.5 and the mixing grade 35°SR. Under the conditions a) to g) stated below, paper was produced from this pulp suspension:

a) No addition made.

b) Addition of 0.25% of the neutral wet-fast resin specified in example 1b).

c) Addition of 0.5% of the resin according to b).

d) Addition of 1.0% of the resin according to b).

e) Addition of 0.25% of resin 4.

f) Addition of 0.5% of resin 4.

g) Addition of 1.0% of resin 4.

The percentages are in all cases based on them

solids, i.e. the pulp suspension and the resin solutions. The addition of the resin solutions according to a) to g) was carried out in the thick mass area. The wet wear length and alkali resistance of the paper samples produced in this way were determined. The measurements are mean values of the longitudinal and transverse directions of the paper referred to

the paper machine. The following values were found:

Claims (2)

1. Process for the production of paper, cardboard and cardboard with high dry, wet and lye strength by adding aqueous polymer solutions to the paper pulp in an amount of 0.1 - 5% by weight, in each case calculated on the solids, and dewatering of the paper pulp on a wire during web formation, characterized by the use as aqueous polymer solutions of reaction products that are obtained from the conversion of (1) homopolymers of vinylimidazole of the formula I where R 1 , R 2 , R 3 =H, CH 3 ; and R 1 further means C 2 H 5 , C 3 H 7 , C 4 H 9 ; or off (2) water-soluble copolymers of a) at least 5% by weight of a vinyl imidazole with the formula I, b) up to 95% by weight of acrylamide and/or methacrylamide, and optionally c) up to 30% by weight of acrylonitrile, methacrylonitrile, vinyl acetate, vinylpyrrolidone, an ethylenically unsaturated C3 to C5 carboxylic acid or ester thereof with epichlorohydrin in a ratio of 0.02 to 2.9 mol epichlorohydrin per moles of basic nitrogen equivalent in the homo- or copolymer, in the absence of polyalkylenimines. 2. Method according to claim 1, characterized by the use of reaction products which are obtained by reacting water-soluble copolymers of a) 15 12 "> ■» 70 know"l;^11^™ and