SE460730B - PROCEDURES FOR MANUFACTURING PAPER WITH FORBETTRAD TORRHAALL FASTENCE - Google Patents

Description

The speed of the 460 750 machines has risen, the effect of the alumina has not been sufficient, and synthetic polymers, especially polyacrylamides, have been used. In recent times, on the one hand, due to cost reasons and on the other hand, in order to achieve better printing results, increasing amounts of fillers have been used. In this case, problems have been encountered in some factories with regard to the strength of the paper, and therefore the mass of strength additives has been added. This known joint use has not led to any astonishing increase in strength. The probable reason is that the filler has more strongly than the other pulp components adsorbed the added retention aid.

A co-use of cationic starch and anionic retention aid of the polyacrylamide type is also known from the manufacture of so-called super-filled paper grades. Such paper grades that contain two or three times more fillers than usual are proposed to be manufactured with the aid of the said additive combination (STFI contact no. 3, 1982, pp. 3-4). In the manufacture of paper containing e.g. 50% kaolin can use 5% cationic starch and 0.3% anionic polyacrylamide. According to the publication, such use of cationic starch together with an anionic polymer is based on the fact that the cationic and anionic components are dosed according to the charge in the same ratio, whereby the starch is forced to settle and stick to the paper in larger amounts than the mass. adsorption capacity. The improvement at a filler content of 0% is surprisingly small. Corresponding results should be obtained by dosing only starch about 2%.

In laboratory studies (TAPPI åâ (l976); 6, 120-122), cationic starch and anionic polyacrylamide have also been shown to function as a two-component retention aid composition. In the experiments, the strength effect has not been investigated. Fillers were also used in these experiments. 5-10% TiO2, and the dosing of additives was based on reservation optimization.

Acrylamide, whose molecular weight is optimally 100,000 - 500,000, can be used in paper as a dry hard glue. A composition of such anionic acrylamide and cationic starch has been tested as a dry hard glue without significant positive results (J.P. Casey: Pulp and Paper Chemistry and Chemical Technology, 3rd ed., Vol. III, Wiley et Sons 1981, p. 1456). One reason for the poor result is probably that the circumstances could not be chosen correctly.

It has now surprisingly been found that the use of polysaccharide type additives and synthetic polymeric retention aids can be arranged so as to achieve a surprising improvement over the foregoing in terms of the dry strength properties of the paper or board with less additional amounts than before. The main features of the invention appear from the appended claims.

By polysaccharide type additives is meant here polysaccharides or their derivatives or compounds which are intended to be added to the pulp, which are mainly known as dry strength additives and which have been previously described in said works (J.P.

Casey sid. 1475-1514). With these means, in addition to the dry strength, one can also influence the separation of water from the web of the paper machine, an optimal formation of the paper web, and especially in the case of derivatives on the retention and also on the wet strength. Said agent has an ability to form hydrogen bonds with cellulose and thus increase the strength of the paper. Due to price factors, the most commonly used of these polysaccharide-type additives are starches and their derivatives. Due to good retention properties, cationized starches can be used to advantage. Other additives of the polysaccharide type according to the invention are plant adhesives (eg guar gum with its derivatives), alginate and cellulose derivatives, such as e.g. carboxymethylcellulose, methylcellulose and hydroxyethylcellulose. 460 730 The synthetic retention aids of the invention have high molecular weight, are long chain polymers, such as polyethylene oxide or polyacrylamide, the latter either as such or partially or completely hydrolysed or substituted or copolymerized.

Polyethylene oxide is nonionic and its molecular weight is suitably over 1,000,000. The latter may be anionic, cationic or nonionic and their molecular weight is over 200,000, suitably over 1,000,000. The use of the agents as compositions or mixtures is also possible.

Substantially filler-free paper or board qualities refer here to those in the manufacture of which no filler has been used at all or only in small quantities, a maximum of 10% and generally below 5%.

The retention of cationic starch in amounts of use according to the invention is 90-100% (Casey, pp. 1492, 1495). Thus, the increase in starch provided by the invention cannot be based on the fact that by means of the retention agent the retention of the polysaccharide additive would obtain substantially improved strength properties (in contrast to known methods in which the strength is increased by depositing a polysaccharide additive and a polymer having the opposite charge so that the strength thereby increases). On the other hand, the retention additive according to the invention does not in itself have any appreciable increasing effect on the strength when the amount of use remains at a level according to the invention, ie at the order of magnitude corresponding to normal use of retention aids. Thus, the surprising effect according to the invention should be due to a strong synergistic effect of the agents used. In the method according to the invention, the retention aid is selected from case to case by using known methods, such as e.g. retention test with laboratory scale so that an optimal retention result is obtained. The conditions (mass, water, bonding, etc. effect) determine whether the best result is achieved with anionic, cationic or nonionic retention aids. Deviations from known methods are thus such that the charges of the polysaccharide-type additive and the retention aid do not have to cancel each other out, and do not even have to be of the opposite sign.

The method according to the invention can suitably be applied in the manufacture of paper and board grades which are completely or partially free of mineral fillers, such as kraft paper, newsprint or board. However, the use of the invention is not limited to the manufacture thereof. In the manufacture of grades with filler contents, however, the aim of retention aids to be adsorbed should generally be taken into account primarily in the surfaces of the filler particles. When increasing the retention dose dosage over the amount that the fillers adsorb so that the retention agent can function in a manner that the invention presupposes and is attached to the fibers, it is often necessary to use economically large amounts of increase. Therefore, it is advantageous to carry out a manufacture of filler-containing paper according to the invention so that the filler is treated separately with a retention aid which has been found to be suitable therefor (which may be the same as the retention aid according to the invention), and then the filler according to the invention is added to the treated pulp. . Another way is to pretreat the filler according to a method known per se (eg according to the method in the previously mentioned STFI contact publication: on the filler surface cationic starch is obtained when the filler is first dispersed anionically). In this way, the character of the filler surface changes completely, whereby it is possible to mix it into the mass even before the retention agent, without losing the strength advantage obtained with the polymer system according to the invention. The pretreatment of the filler can of course be arranged to take place in the presence of the pulp. 460 730 Some embodiments of the invention are described in the following examples.

Example 1 The pulp mixture was 50% chemical pulp, 50% mechanical pulp. The pulp was removed from a machine and 0.7% cationic starch "Posamyl B" (Avebe, Holland) was added to a machine pile and 0.125% resin glue "T-glue" (Hercules, USA) and to achieve the desired degree of gluing and 0.4% alum. Various amounts of anionic polyacrylamide were added to the pulp, which were found to be most suitable for the pulp, and in the second series of tests first 0.4% cationic starch and then different amounts of polymer. 60 g / m sheets were made from the pulp and these were tested. The results were as follows: Polyacrylic Pulp (contains 0.7% Pulp (contains 0.7% amide cat. Starch) cat. Starch) + 0.4 cat. starch% Cleavage- Tensile strength- Cleavage- Tensile strength- strength strength strength kN / m strength kN / m Y / MJ / m 0 (known) 185 2.55 190 2.80 0.01 185 2.80 265 3 .05 0.02 230 3.0 300 3.05 0.03 240 3.0 360 _ 3.3 0.04 _ 250 3.0 530 3.32 From the results it can be seen that even an addition of 0 .01% polyacrylamide improved sheet strength. According to the state of the art, such small additions of polyacrylamide should not significantly affect the strength of the pulp. 460 730 Example 2 As example 1, with the difference that the pulp was taken before the machine purchase, ie it had no additives. The adhesives were added to the pulp first, then polyacrylamide and finally 0.4% cationic starch.

The results were: Polyacrylamide,% 0 0.01 0.02 0.03 2.

Cleavage strength, Y / m 110 125 125 135 The cleavage strength was less than in Example 1 because cationic starch was 0.7% less. However, the results show that the addition of polyacrylamide improves the strength.

Example 3 As Example 2, but starch was added before polyacrylamide and its amount was varied. The results were as follows: Cationic starch,% Éâíššåäšålï 8: 3 amide,% Cleavage Tensile strength, kN / m Y / m 0 105 1.48 0.01 120 1.70 0.02 135 1.98 0.03 155 2130 Q - «---- -_-__.__.__. _..__.______ _ _ __ ____ __ ___ ___ 460 730 Cationic starch,% Polyacrylic- 0.6 amide,% Cleavage- Tensile strength- strength, kN / m J / m 0 105- 1.70 0.01 120 1.82 0.02 135 2.10 0.03 '220 2.35 Cationic starch,% Polyacrylic 0.8 amide,% Cleavage Tensile strength strength, kN / m Y / m 0 115 1.65 0, 01 120 1.85 0.02 140 2.20 0.03 (test completed) In several tests in the paper industry, promising results obtained on a laboratory scale have not been true at all when these were transferred to the production machine. Therefore, the chemical system according to the invention has been tested on a cardboard machine. The machine is of so-called.

Inverform type. The surface and back layer are made of pure chemical pulp and about 50% mechanical pulp is used for the middle layer.

A greater use of mechanical pulp is limited by the peeling strength of the finished board. It is normally 85-90 J / m and 0.8% cationic starch is added to the mass of the intermediate layer. Even larger quantities, even 2% have been tried, but without results. 460 730 Example 4 Factory test run was performed. Cationic starch was constantly dosed in the machine bin. Its amount varied from 0.6 to 1.2%. The cleavage strength was about 90 J / m: the polyacrylamide was added after the filters and its dosage was gradually increased. When the dosage increased by 0.042%, the cleavage strength increased to 120 J / m.

Example 5 Another factory test run was performed. In this test, 1.2% cationic starch was constantly dosed into the machine bowl. The dosage amount and location of the polyacrylamide was varied, and at some test sites an extra amount of starch was dosed after the polyacrylamide. In each case, the best results and the required amounts of polyacrylamide were as follows: Additive dosage Cleavage strength Y / m - 85-90 0.045% polyacrylamide after filters 125 0.025% polyacrylamide before filters + 0.6% cationic starch after filters 170 0} O25% polyacrylamide before the mixing pumps + 0.6% cationic starch after the filters 150 Example 6 By performing the laboratory sheet tests, the effect of various polyacrylamide type retention aids on the dry strength of the paper was examined. The pulp contained 45% cellulose and 55% abrasive pulp.

The pulp was taken from an equalization container and it contained 1.2% cationic starch. 60 g / m of sheet with a circulation water sheet form was made from the pulp and 0.02% polyacrylamide was added to the pulp just before the pulp was poured into the sheet mold. The results were: \ Ion content of the retention aid Desalination strength, of polyacrylamide type J / m (without retention agent) 332 cationic 389 nonionic 357 anionic 388 It is noted that the best result was obtained by using either cationic or anionic retention aid, i.e. both cationic and anionic polyacrylamide strength together with cationic starch.

Example 7 A sample according to Example 6 was repeated with the difference that as pulp a pulp was used which contained 23% waste cellulose and 77% abrasive pulp, the amount of cationic starch was 0.7% and the polyacrylamide dosage was 0.03% and the sheets were made as 100 Y / m without circulating water. The results were: Ion content of retention Cleavage tensile index, average of polyacrylamide void strength, Nm / g type J / m (without retention agent) 102 17.5 cationic ~ 133 18.5 weakly anionic 124 18.7 strongly anionic 137 18.0 460 730 Éll It is again noticed that an advantageous interaction is obtained with cationic starch with both anionic and cationic polyacrylamide.

Example gel 8 With laboratory sheet form was made of pulp that contained 25% abrasive pulp and 75% folding cardboard waste 60 j / m the sheet of circulating water. To the pulp was added in good time (at least 0.5 h) before sheet preparation either native guar gum plant glue or amphoteric guar gum plant glue. The amount of both was 1.2%. Just before the pulp is poured into the sheet form, this 0.03% different retention agent of polyacrylamide type was added. The results were: Desalination strength, Y / m zero sample (= no plant adhesive and no retention aid) 177 Guamgum, native _ 270 Guamgum, amphoteric 248 It is noted that a similar beneficial interaction obtained with cationic starch retention agent compositions can also be obtained with plant adhesive retention compositions.

Claims (6)

460 730 PATENT CLAIMS 1. a process for the manufacture of paper or paperboard by adding a fibrous pulp suspension additive of polysaccharide type and synthetic retention aids to improve the dry strength of the paper or paperboard and the possibility of adding to the filler, characterized in the fibrous pulp suspension, based on the dry mass of the pulp. 0.2-3% synthetic retention aid. substance weight, polysaccharide type additive and 0.005-0.1% A) the additive is carried out to the fibrous pulp suspension, is substantially free of filler, B) at least a part of the retention aid is added to the fibrous pulp slurry before the filler additive, or SOTD C) to the fibrous pulp is pre-added. Process according to Claim 1, characterized in that 0.8 to 1.5% of polysaccharide-type additive is added to the fibrous pulp suspension, calculated on the dry matter weight of the pulp. Process according to Claim T or 2, in that starch or its derivatives, preferably cationic starch, are used as polysaccharide-type additives. A method according to any one of the preceding claims, of a suspension added to fibrous pulp, based on the dry matter weight of the pulp, 0.02-0.05% synthetic retention aid. 5. A process according to any one of the preceding claims, characterized in that polyacrylamide or its derivatives or copolymers or polyethylene oxide or compositions thereof are used as synthetic retention aids. 6. A method according to any one of the preceding claims, characterized in that at least a part of the polysaccharide-type additives is added to the fibrous pulp suspension before the synthetic retention aids.