SE467627B - SET ON PAPER MAKING - Google Patents

Abstract

A method for the production of paper by forming and dewatering a suspension of cellulose containing fibres on a wire. The forming and dewatering takes place in the presence of an anionic, inorganic colloid, an aluminate and a cationic synthetic polymer. The process gives improved dewatering and improved retention of fines and optional fillers.

Description

The irrigation takes place in the presence of an anionic inorganic colloid, an aluminate and a cationic synthetic polymer.

The three components can be charged to the fiber stock in any order. The best effect is obtained if the aluminate is added to the stock first, after which the cationic synthetic polymer and then the anionic inorganic colloid are added. Significant improvement over prior art is obtained even if the anionic inorganic colloid is added to the stock first, followed by the cationic polymer and the aluminate in any order. Separate addition of the three respective components is preferred even if it is possible to premix two of the components before the addition.

Suitable cationic synthetic polymers according to the invention are those cationic, organic nitrogen-containing polymers which are used in papermaking as retention aids and / or wet strength agents. Particularly suitable are cationic polyacrylamides, polyethyleneimines, polyamine and polyamidoamine resins, etc. Polyamine resins and polyamidoamine resins are suitably used in epichlorohydrin modified form. Other cationic synthetic polymers that can be used are the cationic melamine-formaldehyde and urea-formaldehyde wet strength resins. The amount of cationic synthetic polymer should be in the range of from 0.01 to 3% by weight, preferably from 0.03 to 2% by weight, based on dry fibers and, if necessary, film medium. The anionic inorganic colloids used are previously known for use in papermaking. Examples of normal ones are titanyl sulphate sols, silica sols or montmorillonite, bentonite, aluminum-modified aluminum silicate sols. silica sols, As the terms colloidal and colloidal indicate, refers to very small particles of The particles should have a specific surface area exceeding about 50m2 / g and preferably above 100m2 / g. Silica-based colloids are preferred as the anionic inorganic colloid. the anionic inorganic agents. silica-based colloids are the silica sols with dense colloidal particles described in Particularly suitable 10 which is incorporated as 3 41056, and the aluminum-containing European patent reference in this application a specific surface area of so-looo m2 / g and even more preferably ce ioo-1ooo m2 / g, the best results being observed when it is 300-700 m2 / g. It has been established that the colloidal silica particles should have a medium included in the European patent application for reference. The specific surface area of these sols should be about particle size below 20 nm and preferably of from about 10 down to about 1 nm (a colloidal silica particle having a specific surface area of about 550 m 2 / g corresponds to an average particle size of about 5 nm). Good results are obtained when using the indicated silica sols in the form of an alkali-stabilized sol, which contains about 2-60% by weight of SiO2, preferably about 4-30% by weight of SiO2. The silica sol can be stabilized with an alkali in a SiO 2: M 2 O molar ratio of from 10: 1 to 300: 1, preferably 1s = 1 to 100 = 1 (M is K, Li and NH 4). above, very good results are obtained when using colloidal particles which have at least one surface layer of aluminum silicate or aluminum-modified surface groups containing silicon and aluminum atoms in a ratio of from 9.5: 0.5 to 7.5: 2.5 sizes a ion from the group Na, As mentioned silica sol, so that the surfaces and particles of the particles and specified also refer to these silica sols. Silica sols that meet the above specifications are commercially available, for example from Eka Nobel AB.

The amount of anionic colloid added to the stock should be in the range <from 0.005 to 2% by weight, preferably from 0.01 to 0.4% by weight, based on dry cellulosic fibers and any fillers. The concentration of colloid, preferably colloidal silica, in the sol fed to the stock is not critical. From a practical point of view, it is appropriate that the sols, when dosed to the stock, have a concentration of from 0.05 to 5.0% by weight.

By aluminate is meant alkali metal aluminate as is well known for hydrophobing with pine resin. is use in papermaking, especially Preferably, sodium aluminate (Na 2 Al 2 O 4) is used, but of course potassium aluminate can also be used even if it is less advantageous in terms of cost. The amount of aluminate can vary within wide limits. The addition of aluminate to the stock is suitably made in the form of aqueous solutions where the concentration is not critical but is adjusted with regard to practical reasons. According to the invention, it has been found that even very small amounts of aluminate, in relation to the amount of anionic inorganic colloid, give significant improvements in the dewatering effect.

Improvement is obtained at a weight ratio of aluminate, calculated as Al 2 O 3, to inorganic colloid of 0.01: 1. The upper limit is not critical. However, no significant improvements are obtained when the ratio of aluminate to inorganic colloid exceeds 3: 1. Suitably the ratio is from 0.02: 1 to 1.5: 1, preferably from 0.05: 1 to 0.7: 1.

Indicated ratios all the weight ratio between aluminate, calculated as AIZO3, and the inorganic colloid.

The improved retention and dewatering effect with the system according to the invention is obtained over a wide pH range of the stock. The pH can be in the range from about 4 to about 10. The pH is suitably above 5 and preferably in the range from 6 to 9. If the desired pH is not achieved by the addition of the aluminate solution, which is itself alkaline, the pH of the stock can be adjusted by adding e.g. sodium hydroxide. If alkaline buffering fillers are used, such as chalk, the appropriate pH is normally reached without adjustments. Fillers other than chalk can of course be used, but then you have to make sure that the pH limits.

In papermaking according to the invention, mineral fillers aVSeI 'may be included in the stock kept within the above of the usual types, for example kaolin, titanium dioxide, gypsum, chalk and talc. The term "mineral filler" is used herein to include, in addition to these fillers, also wollastonite and glass fibers and also low density mineral fillers. The mineral filler is usually added to water slurry at the usual concentrations used as fillers. Optionally, the filler may be treated as expanded perlite. before such addition to the stock with components of the dewatering and retention system of the invention, for example by treatment with the cationic synthetic polymer and the aluminate or the inorganic anionic colloid, after which it the remaining component is added to the stock.

The three-component system according to the invention can be used in the production of paper from different types of cellulose-containing stock. The stock should contain weight percent cellulose-containing fibers. The three-component system can, for example, be used for stockings of fibers from chemical pulp, sulphite pulp, thermomechanical refiner pulp or abrasive pulp from both hardwood and softwood. It can of course also be used for stockings of recycled fibers.

The process according to the invention can be carried out in a manner known per se and with other known additives to the fiber stock, such as hydrophobing agents, etc.

The invention is further elucidated in fibers. at least 50 such as sulphate and pulp, the following examples, where parts and percentages refer to parts by weight and percentages by weight, unless otherwise indicated.

Example 1 In the following experiments, the dewatering effect has been investigated by means of any of the dewatering ability "Canadian Freeness is the Tester", common method of characterization according to SCAN-C 21:65.

The stock was based on bleached birch / pine sulphate pulp (60:40) and contained 30% by weight of chalk. 8.5 and its CSF was 300 ml.

In the table, the chemical additives refer to tonnes of dry stock system (fibers + fillers). The anionic colloid consisted of an alkali-stabilized silica sol with a surface area of 500 m2 / g. The cationic synthetic polymer was a cationic polyacrylamide sold by Allied Colloids under the name Percol 292. The sodium aluminate was added in the form of stock. to the chemical additives, 1 liter of diluted 467 627 10 15 20 25 30 '35 6 was made (about 0.3%) at intervals of 15 seconds with stirring in the order of aluminate, cationic polymer, organic colloid. The flocculated stock was transferred to the freeness apparatus and measurements were made 15 seconds after the last addition. The water collected is a measure of dewatering capacity and in ml Canadian Standard Freeness (CSE). The water obtained in the experiments using the three components was very clear and stated this shows that also a good retention effect of fine fiber material to the flocks is obtained.

Try Al2O3 Katj. polymer Anj. colloid CSF nr kg / t kg / t 'kg / t m1 1 - - - 300 2 - 0.3 S - 370 3 - 0.6 - 305 4 - 0.9 - 390 5 0.15 -' - 290 6 0.15 0.3 - 350 1 - _ 1.0 295 s 0.15 - 1.0 290 9 - 0.3 0.5 420 10 - 0.3 1.0 430 11 - 0.3 1.5 440 12 0.015 0.3 0.5 495 13 0.15 0.3 1.0 520 14 0.225 0.3 1.5 515 15 - 0.6 0.5 425 16 - 0.6 1.0 490 11 - 0.6 1.5 510 10 0.075 0.6 0.5 495 19 0.15 0.6 1.0 570 20 0.225 0.6 1.5 505 As can be seen, the use of even very small amounts of aluminate gives a significantly improved dewatering ability of the system cationic polymer and anionic colloid. The corresponding effect of aluminate does not occur if it is used in combination with, only cationic polymer or only anionic colloid. 467 627 Example 2 This example was in complete agreement with Example 1 with the only difference that other cationic synthetic polymers were used. These consisted of A) an epichlorohydrin modified polyamidoamine resin sold by Hercules Inc. under the name Kymene 557 H and B) a modified polyamine resin sold by Hercules Inc. under the name Delfloc-50.

Try A1203 Katj. polymer Anj. colloid CSF No. kg / h type; kg / t kg / t ml 1 - - - 300 2 - A; 0.6 - 305 3 - A; 1,2 - 315 4 - A; I - 315 5 - A; 1.2 0.5 325 6 - A; ,, 330 7 - A; ,, 310 8 0.075 A; , 2, 360 9 0.15 A; , 2, 390 10 0.225 A; , 2, 410 ll 0.30 A; 1,2 2, 395 12 - B; 1,2 - 290 13 - B; ,, 280 14 0.225 B; 1.2 1.5 335 Example 3 In this experiment an abrasive stock was used which did not contain fillers. The stock had been added with 0.5 g / l of Na 2 SO 4 .10H 2 O to give ionic strength corresponding to that which occurs in practice. The cationic polymer was the same polyacrylamide as in the colloid Example 1. The anionic 15% alkali stabilized silica sol where the surface of the colloidal particles was modified with 9% Al atoms and the surface of the particles was 500 m 2 / g. The order of addition was sodium aluminate, cationic polymer followed by anionic colloid. Experiments were performed partly at a measured pH of 6 and partly at a pH of 7.5 where the pH was adjusted with dilute H 2 SO 4 and dilute NaOH, respectively. of aluminum modified, 467 627 10 15 20 25 30 35 8 Try Al203 Cat. polymer Anj. colloid CSF no kg / t kg / t kg / t ml bra 6.0 ¶ 1 - - - 120 2 - 0.3 - 190 3 - 0.6 - 220 4 - 0 0.9 _ 245 5 -, - 250 6 - 0.6 0.5 275 7 - 0.6 1.0 0 305 8 - 0.6 1.5 300 9 0.075 0.6 0.5 325 10 0.15 0.6 1.0 _ 345 ll 0.225 0.6 1.5 350 EH 7.5 12 - 0.6 - 220 13 _ 0.6 0.5 245 14 - 0.6 1.0 210 15 - 0.6 1.5 275 16 0.075 0, 6 0.5 295 17 0.15 0.6 1.0 325 18 0.225 0.6 1.5 340 19 - 0.9 1.5 310 20 0.225 0.9 1.5 370 Example gel 4 In these experiments, as well as in Example 3 an abrasive stock with the addition of 0.5 g / l Na 2 SO 4 .10 H 2 O.

The pH of the stock was 6.5 and the chemicals added were sodium aluminate, a cationic polyethyleneimine sold by BASF under the name Polymin SK and an anionic colloid consisting of a bentonite colloid which had a specific surface area in water of about 400 to 800 m2 / g.

Try Al203 Katj. polymer Anj. colloid CSE no kg / h kg / h kg / h} ml 1 _ _ - 120 2 - 0.3 _ 175 3 - 0.6 _ 230 4 - 0.9 - _ 300 467 627 9 Try Al203 Cat. polymer Anj. koll-eid CSF nr kg / t kg / t kg / t ml 5 - 1.2 - 310 6 - 0.6, 260 7 - 0.6, 280 8 - 0.9, 340 9 0.075 0.6 0, 295 10 0.15 0.6 l, 335 ll 0.15 0.9 l, 390

Claims (8)

467 627 10 15 20 25 30 35 10 Patent claim A method of making paper by forming and dewatering a cellulose-containing suspension characterized by forming and dewatering fibers on a wire, thereof, taking place in the presence of an anionic inorganic colloid consisting of montmorillonite, bentonite, a titanyl sulfate sol, a modified silica sol, an aluminum-aluminum silicate sol, with anionic inorganic colloid consisting of a polymeric silicic acid with a specific surface area of not less than 1050 m2 / g, an aluminate and a cationic, nitrogen-containing, synthetic polymeric retention and / or wet strength agent. A method according to claim 1, wherein the colloid is a silica particle silica sol or an exception of the known sol, a silica sol with at least one surface layer of aluminum silicate or an aluminum modified silica sol. 3. Assume that the particle size of the colloid is at most 20 nm. 4. A method according to claim 1, wherein the cationic, which have claim 2, characterized in the nitrogen-containing, synthetic polymeric retention or wet strength agent is a cationic polyacrylamide, polyethyleneimine, polyamine or polyamidoamine. 5. A method according to any one of the preceding claims, characterized in that the aluminate is added to the fiber suspension before the anionic inorganic colloid and the cationic polymeric retention or wet strength agent. 6. A method according to any one of them, gane colloid is within the weight percent, calculated on dry matter. of claim 1, 2 or 3, that the amount of anionic ear range from 0.005 to 2 fibers and any filler 7. A method of retention according to any one of claims 1 or 4, characterized in that the amount of cationic polymeric wet strength agent is in the range from 0.01 to 3% by weight, based on dry fibers and any fillers. or 467 627 ll 8. A method according to claim 1, characterized in that the weight ratio of aluminate, calculated as Al 2 O 3, to anionic inorganic colloid is in the range from 0.01: 1 to 3: 1.