A method of manufacturing paper

 

Method for manufacturing paper and can be used in the pulp and paper industry. The method includes obtaining a fine suspension of cellulose fibers. Then it added a water-soluble polymer binder and a water-soluble cationic substances. The last chosen from water-soluble organic polymeric coagulants with a characteristic viscosity of not more than 3 DL/g and inorganic coagulants. The technical result is improved flocculation of the suspension and increase the speed of dehydration, as well as increasing uderzhivaemoi fibers and small particles. 8 C.p. f-crystals, 4 PL.

The invention relates to methods of making paper (including cardboard) and, in particular, to methods of making paper, reinforced with starch.

In normal practice, the paper is made using a process comprising fokusirovanie (flocculation) of the pulp suspension by adding restraint polymer of high molecular weight substances; dehydration flocculating suspension through a wire mesh with getting wet sheet and drying the sheet.

A special type of ways of making paper from the confirmed destruction of cereal when shaken with repeated flocculonodular with the addition of microcorpuscular substances, for example, bentonite.

It is well known, the introduction of low molecular weight cationic polymer in the slurry, or by adding it to the stage gross mass, or subsequently in a variety of papermaking processes for different purposes. Well known is also the introduction of inorganic coagulants, such as semi-aluminum chloride or alum, for a variety of purposes. You can refer to, for example, in U.S. patent 4913775 with a description of the various processes and, in particular, microcorpuscular process, sold under the brand name "Hydrocol".

You know the addition of cationic starch in the pulp suspension in a papermaking processes as a means of hardening, and some processes and as a means of facilitating retention. Also described ways, including adding raw, raw starch in the pulp suspension. In General, the processes in which the starch is added to the pulp suspension, have certain disadvantages, and therefore special attention has to be paid to ensure good retention of the starch, so that no significant quantities of dissolved or undissolved starch bleaching water in the dehydration of the pulp through the wire roximately or other polymeric binder, able to supply hydrogen to the cellulose are added to the finely ground raw material together with a cationic polymer having a molecular weight in excess of 150,000, and preferably 1 000 000 and more, and makes insoluble anionic binder. Can also be added cationic starch.

In patent WO 93/01353 described the ways in which anionic retention contribute: starch, cellulose derivative or guar gum powder, free from cationic groups, and to the suspension is added a compound of aluminum. Another way in which the anionic compound and a low molecular weight cationic polymer added to the suspension described in Japanese patent A-03193996.

Although various known processes can be optimized to obtain a desired strength of the dry sheet and to obtain a satisfactorily short time of dehydration and/or good retention of fibers and/or binder, it would be desirable to be able to carry out the process, giving optimal use of the binder in the sheet (and, hence, optimum strength together with good retention binder, fibers and small particles in the pulp suspension, and good drainage properties (assaileth).

It would seem that these goals can achieve the th of uderzhivaemoi high molecular weight cationic polymer compound, but we found that it does not give any significant or useful enhancements.

According to the invention, characterized by the signs on items 1-9 formula of the invention, a method of manufacturing paper (including cardboard) has the following stages: - production of fine suspension of cellulose fibers; mixing this suspension (a) water-soluble anionic or non-ionic polymeric binder and (b) water-soluble cationic substance selected from water-soluble organic polymeric coagulants with a characteristic viscosity of not more than 3 DL/g and inorganic coagulants; - then fokusirovanie suspension by mixing in her anionic retention of the substance (which may be microecosystem anionic conducive to the holding substance); - dehydration flocculating suspension to obtain a wet sheet; drying the wet sheet.

Surprisingly, we found that the addition of anionic retention of the substance instead of the traditional cationic polymer flocculants after addition of a binder and a cationic polymer coagulant gives good fokusirovanie suspension and as a result significantly improves the speed of dehydration and gives one the urge binder, leaving it at a good level.

The pulp slurry may be normal fine obtained from any conventional cellulose raw materials, including re-supplied to the processing of the material. Fine raw materials can be completely devoid of filler (i.e. without special add significant quantities of filler) or can have filler.

The binder is a water-soluble substance that is able to substantially bind the hydrogen from cellulose, i.e., capable of binding the cellulose fibers in the paper raw material, for example, to the level of at least 1-2% (dry binder based on the dry material), often with retention of binding to the level of at least 60-70% or even 80%. Almost binder need not be non-ionic or anionic, as if it is cationic, the linking of the binder and cellulose fibers will be mainly due to cationic groups, and not due to binding by hydrogen. For the predominance of hydrogen bonding as a nonionic or anionic binder is usually applied polyhydraminos substance. So it was acting as a binder in the final sheet, increasing its strength, it is the Dol is 50000 and above, in General it can be and above 100000.

Almost polymeric binder is typically cellulose composition, natural rubber or starch, but it can be a synthetic polymer, e.g. polyvinyl alcohol. Natural and modified natural polymers include cellulose, resins and starches, for example, carboxymethylcellulose, xanthan rubber, guar gum, manoharachary and, preferably, anionic starch. Preferably the binder is more of an ionisable group, which in General, sulfate, carboxylate or phosphate. Suitable starches include oxidized starch, phosphate starch and karboksimetilirovaniya starch.

The amount of binder is generally at least 1% (dry weight of the binder relative to the dry weight of the suspension) and can be raised, for example, up to 10%. As a rule, it is in the range 1-8%, preferably 3%, may be, for example, 3-5% (i.e. from 30 to 50 kg/t).

The cationic substance is preferably a cationic polymer coagulant, characteristic viscosity of not more than 3 DL/g In this description of the characteristic viscosity was measured by a viscometer suspended level at 25oWith B2 DL/g, for example, 1.5 DL/g or lower. It is usually at least 0.1 to 0.5 DL/g is Preferred cationic polymeric coagulants have a high charge density, for example, above 3 mEq/g, typically above 4 mEq/g

Inorganic coagulant, for example from aluminum compounds, in particular semi-aluminum chloride, can be used separately as a water-soluble cationic material or in combination with a polymer coagulant.

Preferred cationic polymeric coagulants are substances type polyethylenimine or polyamines (preferably completely stereoselectivity), the polymers dicyandiamide condensation (usually fully or stereoselectivity in the form of salts) and water-soluble polymers ethylenedeamine monomer or Monomeric mixture formed from 50 to 100 mol.% cationic monomer and 0-50 mol.% another monomer. The amount of cationic monomer is usually at least 80 to 90 mol.%, and often the preferred homopolymers. Ethylenedeamine cationic monomers that can be used include: dialkylaminoalkyl (meta)acrylate and acrylamide (usually stereoselectivity in the form or in the form of salts) and diallyldimethylammoniumchloride ("DADMAC"). On the polymer, the co monomer is usually acrylamide or other water-soluble non-ionic ethylenedeamine monomer.

Cationic polymer coagulant may be a linear polymer. Alternatively the coagulant can be obtained in the presence of multifunctional additives, which give the structure, for example, polyethyleneimine monomers such as: tetralology ammonium chloride, double-methylene acrylamide and a multifunctional monomer incorporated into the polymer chain. The amount of these additives when used is generally 10 ppm and 50 ppm. It can reach 200 ppm or 500 ppm.

Generally, the amount of the cationic substance exceeds the amount required to provide a noticeable retention of adding anionic substance that promotes retention. The quantity should be sufficient to give a suspension of z-potential, which is close to zero or positive, but satisfactory retention often you can get even a few negative z-potential. In practice, the number of cationic substances are best determined by the formation of fine raw material containing the desired quantity of binder (with Viggo retention of the substance after the addition of different amounts of cationic substances.

Usually it is not desirable that the cationic substance included a significant number or even many high molecular weight cationic polymeric substances (for example, having a characteristic viscosity above 4 DL/g), as the use of such substances usually did not improve the properties, provided that it was used a sufficient amount of the cationic substance is inorganic and/or has a low molecular weight. However, if desired, you can add other substances together with a cationic polymer or inorganic coagulants mentioned above, or after them, provided that these additives do not interfere with the process.

The amount of cationic polymer coagulant is usually 0.25 to 10.0 pounds of active polymer per ton of dry cellulosic suspension, and preferably 1-3 kg/so

Binder in the process, you can add before the introduction of cationic coagulant or after him. Binder and the coagulant can be added and at the same time. The coagulant can be added in a single dose or parts, for example, before and after binding. The order of adding the binder and cationic coagulant may vary without affecting significantly the results.

After obrabotannoi contributing to the retention of the substance. This mixing can be carried out with average or high shear force, but is usually done only with the application of a force sufficient for mixing of anionic substances in suspension, for example, in the pressure box or to him.

The number of anionic substances that contribute to retention, is usually 0.5 to 10.0 kg per ton of dry cellulosic suspension, preferably 1-4 kg/so

Anionic substance that promotes retention, is a material that causes fokusirovanie processed fine suspension and thus improves its dehydration with relatively suspension deflocculating.

This can be a water-soluble anionic polymeric substance, such as described in patent WO 98/29604.

However, preferably it microchromosome anionic conducive to holding a substance, which may be inorganic or organic. For example, it may be organic anionic microchromosome contributing to the retention of the substance, described in U.S. patent 5167766, 5274055. Preferably is an inorganic substance. Such substances are well known and include swelling clays, in General called bentonites, colloidal silica, the further mixture, for example, organic and inorganic microparticles.

Preferably the pulp suspension after processing binder and cationic coagulant and before adding anionic contributing to the retention of substances no components are not introduced. After processing anionic conducive to the holding substance flokulirovannym suspension is drained through the wire mesh to obtain a wet sheet. Then the wet sheet is dried in the usual manner to obtain a dry paper (including cardboard).

In the process of holding the binder in the sheet is preferably at least about 60-70%, and more preferably at least 80% and even 85-90% or more.

In the invention we provide the use of anionic facilitate retention of the substances mentioned above, to enhance dewatering the pulp suspension is treated with a binder and a cationic polymer coagulant to the above types.

In the process, we often find that the time of dehydration for a given volume of return water can be reduced to 70-60% of the time dehydration in the same conditions, but without addition of anionic retaining means and may even be reduced to 50 or 40% of this is For each test took 1 liter of pulp with a concentration of solids of 0.5%. For each method in a binder was added to the anionic starch at 3%, and then the polymer in the dosage given in the table below. Some tests were added and other substances, doses of which are indicated in the tables.

The polymer As represented homopolymer DD the characteristic viscosity of about 1 DL/g

Test was performed on dehydration and measured the time of collecting 600 ml of return water. This is the time of dehydration. The results are presented in tables 1-3.

It is seen that good results are obtained by dehydration using only polymer a, And further various additives flocculosa substances noticeable improvement is not shown. However, when sodium bentonite is added after the polymer And the free dehydration is significantly increased, reaching values much lower than expected.

Example 2.

These tests show good fixation of starch, obtained by the system of the invention. In these tests used the same raw materials as in example 1. To it is added anionic starch at the level of 3% of dry starch to dry the fiber. Next, you add the cationic coagulant. Then, according to some systems of this invention, is added to the thought 4.

The polymer is a homopolymer of DADMAC with a characteristic viscosity of about 2 DL/g

Claims

1. Method of making paper, which receive a fine suspension of cellulose fibers, mixed into the suspension a water-soluble anionic or non-ionic polymer binder and a water-soluble cationic substance selected from water-soluble organic polymeric coagulants with a characteristic viscosity of not more than 3 DL/g and inorganic coagulants, then localroot suspension by stirring in her anionic retaining substances and dewatered flocculated slurry for forming a wet sheet with subsequent drying.

2. The method according to p. 1 in which the anionic or nonionic polymer binder can significantly associate hydrogen with cellulose and cationic substance is a cationic polymer coagulant with a characteristic viscosity of not more than 3 DL/g

3. The method according to p. 1 or 2 in which the polymeric binder selected from cellulose compounds, natural rubber, starch and polyvinyl alcohol.

4. The method according to p. 1 or 2 in which the polymeric binder is chosen from anionic starch and carbon is polietileniminov, polyamines, dicyandiamide polymers and water-soluble polymers ethyleneamines monomer or Monomeric mixture comprising 50-100 mol. % cationic monomer and 0-50 mol.% another monomer.

6. The method according to p. 5, in which the cationic polymer is a polymer of monomers comprising water-soluble polyethyleneimine monomer.

7. The method according to any of the preceding paragraphs, in which the water-soluble cationic substance is a polymer consisting of 80-100% of diallyldimethylammoniumchloride and 0-20% of acrylamide and having a characteristic viscosity below 3 DL/g

8. The method according to any of the preceding paragraphs, in which the anionic retention substance selected from inorganic swelling clays, colloidal silica or polysilicon acid and silica microgels, modified alumina, colloidal silica or polysilicon acid, or polysilicate microgels and organic microparticles.

9. The method according to any of the preceding paragraphs, in which the binder is chosen from anionic starch and carboxymethylcellulose, cationic substance is a polymer diallyldimethylammoniumchloride having a characteristic viscosity below 3 DL/g, and anionic retention substance one

 

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