RU2347029C1 - Method of manufacturing paper - Google Patents

Abstract

FIELD: textiles; paper.

SUBSTANCE: method (versions) concerns manufacture of paper and can be used in the paper and pulp industry. Method includes (i) providing a water suspension, which contains cellulose fibres; (ii) adding to the suspension after all the stages of strong shearing action of the first polymer, which is a cationic polymer; a second polymer and a third polymer, which is an organic or inorganic anionic polymer; and (iii) dehydration of the obtained suspension for forming paper.

EFFECT: improvement in the drainage and retention for all types of paper stock, increasing the speed of the papermaking machine, using low doses of polymers, improving the method of paper manufacturing and increasing the economic efficiency of the process.

16 cl, 7 tbl, 7 ex

Description

Field of use of the invention

The present invention relates to a method for making paper. More specifically, the invention relates to a method of making paper, which comprises adding the first, second, and third polymers to an aqueous cellulosic suspension after all stages of strong shear and dewatering the resulting paper-forming suspension.

BACKGROUND OF THE INVENTION

In the manufacture of paper, an aqueous suspension containing cellulosic fiber and, optionally, fillers and additives, called “paper pulp”, is fed by pumps, sieves and cleaners in which it is subjected to strong shear, into the headbox from which the paper pulp let on the forming mesh conveyor. Water from the pulp is discharged through the forming mesh conveyor in such a way that a wet paper web is formed on the mesh conveyor, and this web is further dehydrated and dried in the drying section of the paper machine. Additives that aid in drainage and retention are typically introduced into the pulp stream at various points to improve drainage and increase the adsorption of finely divided inclusions, such as fine fibers, fillers and additives, cellulose fibers so that they are held by the fibers on the mesh conveyor. An example of commonly used additives by which they promote drainage and retention are organic polymers, inorganic substances, and combinations thereof.

US Pat. No. 6,103,065 discloses a method for improving retention and drainage of a paper-making composition, comprising the steps of adding at least one cationic polymer with a high charge density and a molecular weight of 100,000-2000000 to the composition after the last strong shear; adding at least one polymer having a molecular weight of more than 2,000,000; and adding a bentonite clay having a swellability.

European Patent EP No. 1238161 B1 discloses a method of making paper or paperboard in which the cellulosic suspension is flocculation by adding a substantially water-soluble cationic synthetic polymer with an intrinsic viscosity of at least 4 dl / g to a thin pulp stream of pulp. wherein the flocculated cellulosic suspension is subjected to mechanical shear, and then subjected to refloculation by adding, following the centrifugal cleaner, a reflocculating composition, in which includes: (i) a silicon-containing material; and (ii) a substantially water-soluble anionic polymer with a characteristic viscosity of at least 4 dl / g. The method is said to improve retention and drainage.

International application WO 2004/015200 discloses a method for manufacturing paper and paperboard by shearing a material for making paper; adding a composition of microparticles consisting of cationic polymers and an inorganic component consisting of small particles to the paper making material, following the last stage of shear, before agglomeration of the material; dewatering the paper-making material so as to form a sheet; and drying said sheet. It is claimed that the method improves retention and drainage.

The authors believe that it would be advisable to create a method of manufacturing paper, with which it would be possible to further improve drainage, retention and molding.

SUMMARY OF THE INVENTION

The present invention is directed to a method for manufacturing paper, including:

(i) providing an aqueous suspension containing cellulosic fiber;

(ii) adding to the suspension after all stages of strong shear:

- the first polymer, which is a cationic polymer having a charge density of more than 4.0 meq / g;

- a second polymer having a molecular weight of more than 500,000; and

- a third polymer, which is an anionic polymer; and

(iii) dewatering the resulting suspension to form paper.

The present invention also aims to provide a method of manufacturing paper, including:

(i) providing an aqueous suspension containing cellulosic fiber;

(ii) adding to the suspension after all stages of strong shear:

- the first polymer, which is an acrylamide-based cationic polymer having a charge density of more than 2.5 meq / g;

- the second polymer, which is an acrylamide-based polymer having a molecular weight of more than 500,000; and

- a third polymer, which is an anionic polymer; and

(iii) dewatering the resulting suspension to form paper.

The present invention is additionally directed to the creation of a method of manufacturing paper, including:

(i) providing an aqueous suspension containing cellulosic fiber;

(ii) adding to the suspension after all stages of strong shear:

- the first polymer, which is a cationic polymer having a charge density of more than 2.5 meq. / g;

- the second polymer, which is a water-dispersible polymer; and

- a third polymer, which is an anionic polymer; and

(iii) dewatering the resulting suspension to form paper.

DETAILED DESCRIPTION OF THE INVENTION

According to the present invention, it was found that drainage and retention can be improved without any significant deterioration, or even improvement, of the paper forming process, by using a method including the introduction of additives to improve drainage and retention containing the first, second and third polymers, into the cellulosic suspension after all stages of strong shear and subsequent dewatering of the resulting suspension for forming paper. The present invention provides improved drainage and retention in the manufacture of paper from all types of paper pulp, in particular paper pulp containing mechanical or reusable pulp, and paper pulp with a high content of salts (highly conductive) and colloidal substances, as well as in the manufacture of paper methods with a large consumption of circulating water, i.e. large reuse of recycled water and limited consumption of fresh water. Thus, the present invention makes it possible to increase the speed of the paper machine and to use lower dosages of polymers to achieve appropriate drainage and / or retention efficiency, which thus leads to an improvement in the paper manufacturing process and an increase in economic efficiency.

The term "additives to improve drainage and retention", which is used in this description, refers to two or more components with which, when introduced into an aqueous cellulosic suspension, improve drainage and retention compared to the conditions under which the above two or more components.

The first polymer of the present invention is a cationic polymer having a charge density of at least 2.5 meq / g, a value of at least 3.0 meq / g is preferred, at least at least least 4.0 meq / g. A suitable charge density value is in the range of 2.5 to 10.0 meq / g, preferably in the range of 3.0 to 8.5 meq / g.

The first polymer may be selected from inorganic and organic cationic polymers. Preferably, the first polymer is water soluble. Examples of suitable first polymers are: polyaluminium compounds, for example polyaluminium chlorides, polyaluminium sulfates, polyaluminium compounds containing both chloride ions and sulfate ions, polyaluminium silicate sulfates and mixtures thereof.

Further suitable first polymers include cationic organic polymers, for example acrylamide-based cationic polymers, polydiallyldialkylammonium halides, for example polydiallyldimethylammonium chloride; polyethyleneimines; polyamidoamines; polyamines and polymers based on vinylamine. For example, suitable cationic organic polymers include polymers obtained by the polymerization of a water-soluble cationic ethylenically unsaturated monomer or preferably a mixture of monomers containing one or more water-soluble cationic ethylenically unsaturated monomers and, optionally, one or more other water-soluble ethylenically unsaturated monomers. Examples of suitable water-soluble cationic ethylenically unsaturated monomers are diallyldialkylammonium halides, for example diallyldimethylammonium chloride, and cationic monomers represented by the general structural formula (I):

where R ₁ represents H or CH ₃ ; R ₂ and R ₃ represent (each) H or preferably a hydrocarbon group; a suitable group is alkyl containing from 1 to 3 carbon atoms, preferably from 1 to 2 carbon atoms; A represents O or NH; B represents an alkyl or alkylene group containing from 2 to 8 carbon atoms; a value of from 2 to 4 carbon atoms is suitable; or a hydroxypropylene group; R ₄ represents H or preferably a hydrocarbon group; a suitable group is an alkyl group containing from 1 to 4 carbon atoms, preferably from 1 to 2 carbon atoms, or a substituted group containing an aromatic group; suitable is a phenyl or substituted phenyl group which can be attached to nitrogen by an alkylene group, usually containing from 1 to 3 carbon atoms; a value of from 1 to 2 carbon atoms is suitable; suitable R ₄ includes a benzyl group (—CH ₂ —C ₆ H ₅ ); X ^- represents an anionic counterion, usually it is a chloride-like halogen.

Examples of suitable monomers represented by the general structural formula (I) are quaternary monomers obtained by treating dialkylaminoalkyl (meth) acrylates, for example dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminohydroxypropyl (meth) acrylate, and (dialkylaminoalkyl) for example dimethylaminoethyl (meth) acrylamide, diethylaminoethyl (meth) acrylamide, dimethylaminopropyl (meth) acrylamide, and diethylaminopropyl (meth) acrylamide, methyl chloride or benzyl chloride. Preferred cationic monomers according to the general formula (I) include dimethylaminoethyl acrylate methyl chloride quaternary salt, dimethylaminoethyl methacrylate methyl chloride quaternary salt, dimethylaminoethyl acrylate benzyl chloride quaternary salt and dimethylaminoethyl methacrylate benzyl quaternary salt.

The monomer mixture may contain one or more water soluble nonionic ethylenically unsaturated monomers. Examples of suitable copolymerizable nonionic monomers are acrylamide monomer and acrylamide-based monomers, for example methacrylamide, N-alkyl (meth) acrylamides, for example N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, Nn-propyl (meth) acrylamide N-isopropyl (meth) acrylamide, Nn-butyl (meth) acrylamide, Nt-butyl (meth) acrylamide and N-isobutyl (meth) acrylamide; N-alkoxyalkyl (meth) acrylamides, for example Nn-butoxymethyl (meth) acrylamide and N-isobutoxymethyl (meth) acrylamide; N, N-dialkyl (meth) acrylamides, for example N, N-dimethyl (meth) acrylamide; dialkylaminoalkyl (meth) acrylamides; acrylate-based monomers like dialkylaminoalkyl (meth) acrylates; and vinylamines. The monomer mixture may also contain one or more water-soluble anionic or potentially anionic ethylenically unsaturated monomers, preferably in small amounts. The term "potentially anionic monomer", as used herein, is understood to mean that it includes a monomer containing a group potentially suitable for ionization that becomes anionic when incorporated into the polymer when used in a cellulosic suspension. An example of suitable anionic and potentially anionic monomers for copolymerization are ethylenically unsaturated carboxylic acids and their salts, for example (meth) acrylic acid and its salts; suitable are (meth) sodium acrylate, ethylenically unsaturated sulfonic acids and their salts, for example 2-acrylamido-2-methylpropanesulfonate _, sulfoethyl (meth) acrylate, vinyl sulfonic acid and its salts, styrene sulfonate and paravinylphenol (hydroxy styrene) and their salts. Examples of preferred monomers suitable for copolymerization are acrylamide and methacrylamide, i.e. (meth) acrylamide; and examples of preferred cationic organic polymers are acrylamide-based cationic polymer, i.e. a cationic polymer obtained from a mixture of monomers containing one or more acrylamide monomers and acrylamide-based monomers.

The first polymer in the form of a cationic organic polymer may have a weight average molecular weight of at least 10,000, often at least 50,000. More often, the molecular weight is at least 100,000, and usually at least about 500,000, a value of at least about 1 million is suitable, and more than about 2 million is preferred. The upper limit is not limited; it can be about 30 million, usually 20 million.

The second polymer according to the present invention is preferably an organic polymer, which may be selected from nonionic, cationic, anionic and amphoteric polymers. The second polymer may be a water soluble or water dispersible polymer. Suitable is a second polymer made by polymerizing one or more ethylenically unsaturated monomers, preferably one or more ethylenically unsaturated water-soluble monomers. For example, preferred second polymers are acrylamide based polymers.

For example, suitable second polymers are water-soluble and water-dispersed non-ionic organic polymers obtained by polymerization of one or more water-soluble non-ionic ethylenically unsaturated monomers. For example, suitable non-ionic monomers are acrylamide and the aforementioned non-ionic monomers based on acrylamide, and monomers based on acrylate, and vinyl amines. For example, preferred nonionic monomers are acrylamide and methacrylamide, i.e. (meth) acrylamide; and preferred second polymers include a non-ionic acrylamide-based polymer.

In addition, suitable second polymers include cationic organic polymers obtained by polymerization of a water-soluble cationic ethylenically unsaturated monomer or preferably a mixture of monomers containing one or more water-soluble cationic ethylenically unsaturated monomers and, optionally, one or more other water-soluble ethylenically unsaturated monomers. Among the suitable cationic monomers include the monomers represented by the above general structural formula (I), wherein R _1, R _2, R _3, R _4, A, B and X ^- have the meanings as defined above; and diallyldialkylammonium halides, for example diallyldimethylammonium chloride. The monomer mixture may contain one or more water soluble nonionic ethylenically unsaturated monomers. For example, nonionic monomers suitable for copolymerization are acrylamide and the aforementioned nonionic acrylamide-based monomers, and acrylate-based monomers, and vinylamines. The monomer mixture may also contain one or more water-soluble anionic or potentially anionic ethylenically unsaturated monomers, preferably in small amounts. For example, suitable for copolymerization of anionic and potentially anionic monomers are ethylenically unsaturated carboxylic acids and their salts and sulfonic ethylenically unsaturated acids and their salts, for example, any one of the substances mentioned above. Preferred monomers for copolymerization are acrylamide and methacrylamide, i.e. (meth) acrylamide, and preferred second polymers include a cationic acrylamide-based polymer.

An additional example of suitable second polymers is anionic organic polymers obtained by polymerizing a water-soluble anionic or potentially anionic ethylenically unsaturated monomer or preferably a mixture of monomers containing one or more water-soluble anionic or potentially anionic ethylenically unsaturated monomers and, optionally, one or more other water-soluble ethylenically unsaturated monomers. Examples of suitable anionic and potentially anionic monomers include ethylenically unsaturated carboxylic acids and their salts and sulfonic ethylenically unsaturated acids and their salts, for example any one of the substances mentioned above. The monomer mixture may contain one or more water soluble nonionic ethylenically unsaturated monomers. For example, non-ionic monomers suitable for copolymerization are acrylamide and the aforementioned non-ionic acrylamide-based monomers, and acrylate-based monomers, and vinyl amines. The monomer mixture may also contain one or more water-soluble cationic and potentially cationic ethylenically unsaturated monomers, preferably in small amounts. The term "potentially cationic monomer", as used herein, is understood to mean that it encompasses a monomer containing a group potentially suitable for ionization that becomes cationic when it is incorporated into the polymer when it is introduced into the cellulosic suspension. For example, cationic and potentially cationic monomers suitable for copolymerization are those represented by the general structural formula (I) above and diallyldialkylammonium halides, for example diallyldimethylammonium chloride. Preferred monomers for copolymerization are (meth) acrylamide, and the preferred second polymer is an anionic acrylamide based polymer.

In addition, suitable second polymers are amphoteric organic polymers obtained by polymerizing a mixture of monomers containing one or more water-soluble anionic or potentially anionic ethylenically unsaturated monomers and one or more water-soluble cationic or potentially cationic ethylenically unsaturated monomers and, optionally, one or more other water-soluble ethylenically unsaturated . Examples of suitable anionic and potentially anionic monomers are ethylenically unsaturated carboxylic acids and their salts and sulfonic ethylenically unsaturated acids and their salts, for example any one of the substances mentioned above. Examples of suitable cationic and potentially cationic monomers are monomers represented by the general structural formula (I) above and diallyldialkylammonium halides, for example diallyldimethylammonium chloride. The monomer mixture may contain one or more water soluble nonionic ethylenically unsaturated monomers. Examples of suitable non-ionic monomers for copolymerization are acrylamide and the aforementioned non-ionic monomers based on acrylamide, and monomers based on acrylate, and vinyl amines. An example of preferred monomers suitable for copolymerization is (meth) acrylamide, and examples of preferred second polymers are amphoteric acrylamide based polymers.

In preparing suitable second polymers, the monomer mixture, in addition to the aforementioned ethylenically unsaturated monomers, may also contain one or more multifunctional crosslinking agents. The presence of multifunctional cross-linking agents in the mixture of monomers contributes to the possibility of obtaining second polymers, which are water-dispersion polymers. Multifunctional crosslinking agents may be nonionic, cationic, anionic or amphoteric. Examples of suitable multifunctional crosslinking agents are compounds containing at least two ethylenically unsaturated bonds, for example N, N-methylene bis (meth) acrylamide, polyethylene glycol (meth) acrylate, N-vinyl (meth) acrylamide, divinylbenzene, triallylammonium salts and N-methylallyl (meth) acrylamide; compounds containing an ethylenically unsaturated bond with and a reactive group, for example glycidyl (meth) acrylate, acrolein and methylol (meth) acrylamide; and compounds containing at least two reactive groups, for example dialdehydes, for example glyoxal, diepoxide compounds and epichlorohydrin. A suitable aqueous dispersion second polymer can be obtained using at least 4 mol. ppm multifunctional crosslinking agent based on the monomer present in the mixture of monomers, or based on the monomer units present in the polymer, preferably from about 4 mol. ppm to about 6000 mol. ppm, most preferably from 20 mol. ppm up to 4000 mol. ppm Examples of suitable in-dispersion organic polymers are those disclosed in US Pat. No. 5,167,766, which is hereby incorporated by reference. Further examples of suitable second polymers are water-dispersed anionic, cationic and amphoteric organic polymers, and preferred second polymers include water-dispersed anionic organic polymers, preferably water-dispersed anionic polymers based on acrylamide.

The second polymers according to the invention are preferably water soluble and can have a weight average molecular weight of at least about 500,000. Usually, the weight average molecular weight is at least about 1 million, a value of at least about 2 million is suitable. and preferably at least about 5 million. The upper value is not limiting; it can be about 50 million, usually 30 million.

The second polymer according to the invention may have a charge density of less than about 10 meq / g, a value of less than about 6 meq / g is suitable, less than about 4 meq / g is preferred, more preferred is less than 2 meq / g. Suitable the charge density is in the range from 0.5 meq / g to 10.0 meq / g, preferably from 1.0 meq / g to 4.0 meq / g. Examples of suitable second polymers are anionic organic polymers having a charge density of less than 10.0 meq / g, a value of less than 6.0 meq / g is suitable, less than 4.0 meq / g is preferred. Suitable second polymers further include cationic organic polymers having a charge density of less than 6.0 meq / g, a value of less than 4.0 meq / g is suitable, less than 2.0 meq / g is preferred.

The third polymer according to the present invention is an anionic polymer, which may be selected from inorganic and organic anionic polymers. Examples of suitable third polymers are water soluble and water dispersible inorganic and organic anionic polymers.

Examples of suitable third polymers are inorganic anionic polymers based on silicic acid and silicate (silicic acid salts), i.e. silicon-based anionic polymers. Suitable silicon-based anionic polymers can be prepared by condensation polymerization of silicon-containing compounds, for example silicic acids and silicates, which can be homopolymerized or copolymerized. Preferably, the silicon-based anionic polymers comprise silicon-based anionic particles whose size is within the size of the colloidal particles. Silicon-based anionic particles are usually supplied in the form of aqueous colloidal dispersions, so-called “sols”. Silicon-based sols can be modified and may contain other elements, for example aluminum, boron, nitrogen, zirconium, gallium and titanium, which can be in the aqueous phase and / or in the form of particles based on silicon. Examples of suitable silicon-based anionic particles are polysilicic acids, polysilicon microgels, polysilicates, polysilicon microgels, colloidal silica, colloidal modified silica, polyaluminosilicates, polyaluminosilicate microgels, polyborosilicates, etc. Examples of suitable silicon-based anionic particles are those disclosed in US Pat. which are hereby incorporated by reference.

Examples of suitable silicon-based anionic particles are those having an average size of less than about 100 nm, preferably less than about 20 nm, and more preferably in the range of about 1 nm to about 10 nm. As is customary in silicon chemistry, particle size is understood to mean the average size of primary particles, which may or may not be aggregated. Preferably, the silicon-based anionic polymer contains aggregated silicon-based anionic particles. Specific surface area silica-based particles is at least 50 m ² / g, and preferably - at least 100m ² /g.Obychno specific surface area can be up to about 1700 m ² / g, and preferably - up to 1000 m ² / g. The specific surface area is measured by titration using NaOH, as described in the book GW Sears Analytical Chemistry ("Analytical Chemistry") 28 (1956): 12, 1981-1983, and in US patent No. 5176891, after appropriate removal or regulation of the content of any compounds present in the sample that could interfere with titration, for example, aluminum and boron compounds. This area, therefore, represents the average specific surface area of the particles.

In a preferred embodiment, the silicon-based anion particles have a specific surface area ranging from 50 m ² / g to 1000 m ² / g, more preferably from 100 m ² / g to 950 m ² / g. Preferably, the silicon-based particles are present in the ash having an S-parameter in the range from 8% to 50%, preferably from 10% to 40%, containing silicon-based particles with a specific surface in the range from 300 m ² / g to 1000 m ² / g, a value of from 500 m ² / g to 950 m ^z / g is suitable, and it is preferable from 750 m ² / g to 950 m ² / g, and these sols can be modified, as mentioned above. The S parameter is measured and calculated according to the procedure described by Iler and Dalton in Phys. Chem. (“Physical Chemistry”) 60 (1956), 955-957. The degree of aggregation or microgel formation is determined by the S-parameter, and a lower value of the S-parameter is an indicator of a greater degree of aggregation.

In another preferred embodiment of the invention, the silicon-based particles have a large specific surface area, a value of more than about 1000 m ² / g is suitable. The specific surface can be in the range from 1000 m ² / g to 1700 m ² / g, and preferably from 1050 m ² / g to 1600 m ² / g.

In addition, examples of suitable third polymers are water-soluble and water-dispersed organic anionic polymers obtained by polymerizing an anionic or potentially anionic ethylenically unsaturated monomer or, preferably, a mixture of monomers containing one or more anionic or potentially anionic ethylenically unsaturated monomers, and, optionally, one or more than other ethylenically unsaturated monomers. Preferably, ethylenically unsaturated monomers are water soluble. Examples of suitable anionic and potentially anionic monomers are carboxylic ethylenically unsaturated acids and their salts, sulfonic ethylenically unsaturated acids and their salts, for example any of the substances mentioned above. The monomer mixture may contain one or more water soluble nonionic ethylenically unsaturated monomers. Examples of suitable non-ionic monomers for copolymerization are acrylamide and the aforementioned non-ionic monomers based on acrylamide, and monomers based on acrylate, and vinyl amines. The monomer mixture may also contain one or more water-soluble cationic and potentially cationic ethylenically unsaturated monomers, preferably in small amounts. Examples of cationic monomers suitable for copolymerization are the monomers represented by the general structural formula (I) above and diallyldialkylammonium halides, for example diallyldimethylammonium chloride. The monomer mixture may also contain one or more multifunctional crosslinking agents. The presence of multifunctional cross-linking agents in the mixture of monomers contributes to the possibility of obtaining third polymers, which are water-dispersion polymers. Examples of suitable multifunctional crosslinking agents are the aforementioned multifunctional crosslinking agents. These agents can be used in the above amounts. Examples of suitable inlet-dispersion organic anionic polymers are those disclosed in US Pat. No. 5,167,766, which is incorporated herein by reference. An example of preferred monomers suitable for copolymerization is (meth) acrylamide, and an example of preferred third polymers are water-soluble and water-dispersed acrylamide-based anionic polymers.

The third polymer according to the invention, which is an organic anionic polymer, preferably an organic anionic polymer, which is water soluble, has a weight average molecular weight of at least about 500,000. Typically, its weight average molecular weight is at least about 1 million, suitable is a value of at least about 2 million, and preferably at least about 5 million. The upper value is not limiting; it can be about 50 million, usually 30 million.

The third polymer, which is an organic anionic polymer, can have a charge density of less than about 14 meq / g, a value of less than about 10 meq / g is suitable, less than about 4 meq / g is preferred. A suitable charge density value is in the range from 1.0 meq / g to 14.0 meq / g, and preferably from 2.0 meq / g to 10.0 meq / g.

Examples of preferred additives for improving drainage and retention according to the invention are:

(i) a first polymer, which is an acrylamide-based cationic polymer; a second polymer, which is an acrylamide-based cationic polymer; and a third polymer, which is silicon-based anionic particles;

(ii) a first polymer being a cationic polyaluminium compound; a second polymer, which is an acrylamide-based cationic polymer; and a third polymer, which is silicon-based anionic particles;

(iii) a first polymer, which is an acrylamide-based cationic polymer; a second polymer, which is a water-soluble or water-dispersed anionic acrylamide-based polymer; and a third polymer, which is silicon-based anionic particles;

(iv) a first polymer being a cationic polyaluminium compound; a second polymer, which is a water-soluble or water-dispersed anionic acrylamide-based polymer; and a third polymer, which is silicon-based anionic particles;

(v) a first polymer, which is an acrylamide-based cationic polymer; a second polymer, which is an acrylamide-based cationic polymer; and a third polymer, which is a water-soluble or water-dispersed anionic acrylamide-based polymer;

(vi) a first polymer being a cationic polyaluminium compound; a second polymer, which is an acrylamide-based cationic polymer; and a third polymer, which is a water-soluble or water-dispersed anionic acrylamide-based polymer.

According to the present invention, the first, second and third polymers are added to the aqueous cellulosic suspension after it passes through all stages of strong mechanical shear and before drainage. Examples of stages of severe shear include the stages of injection and cleaning. For example, such shear stages occur when the cellulosic suspension is passed through mixing pumps, pressure screens, and centrifugal cleaners. Suitable conditions are those under which the centrifugal cleaner is the last stage of strong shear and, therefore, the first, second and third polymers are suitably introduced after the centrifugal cleaner. Preferably, after the introduction of the first, second and third polymers, the cellulosic suspension is fed into a headbox, from which the suspension is introduced onto a forming mesh conveyor for drainage.

It may be desirable to further add additives during the execution of the process according to the present invention. Preferably, these additives are introduced into the cellulosic suspension before it passes through the last stage of strong shear. Examples of such additives are starches, for example cationic, anionic and amphoteric starches, preferably cationic starch; water-soluble organic polymer coagulants, for example cationic polyamines, polyamidamines, polyethyleneimines, condensation polydicyandiamides and polymers with the addition of low molecular weight vinyl with a high cationic charge; inorganic coagulants, for example aluminum compounds, for example aluminum and polyaluminium compounds.

The first, second and third polymers can be introduced separately into the cellulosic suspension. It is suitable to introduce the first polymer into the cellulosic suspension before introducing the second and third polymers. The second polymer can be introduced before, simultaneously with or after the introduction of the third polymer. In an alternative embodiment, the first polymer is preferably introduced into the cellulosic suspension simultaneously with the second polymer, and then the third polymer is introduced.

The first, second and third polymers according to the invention can be introduced into the cellulosic suspension to be dehydrated in quantities that can vary widely. In general, the first, second, and third polymers are introduced in amounts under which drainage and retention are improved compared to conditions under which the polymers are not added. The first polymer is usually added in an amount of at least about 0.001 wt.%, Often at least about 0.005 wt.%, Based on the weight of the dry polymer from the weight of the dry pulp of the suspension, and the upper limit is usually about 2 , 0 wt.%; suitable is a value of about 1.5 wt.%. Similarly, the second polymer is usually added in an amount of at least about 0.001 wt.%, Often at least about 0.005 wt.%, Based on the weight of the dry polymer from the weight of the dry cellulose suspension, and the upper limit is usually is about 2.0 wt.%; suitable is a value of about 1.5 wt.%. Similarly, the third polymer is usually added in an amount of at least about 0.001 wt.%, Often at least about 0.005 wt.%, Based on the weight of the dry polymer or dry SiO ₂ from the weight of the dry cellulose suspension, and the upper limit is usually about 2.0 wt.%; suitable is a value of about 1.5 wt.%.

When starch and / or cationic coagulant is used in the process, such additives can be added in amounts of at least about 0.001% by weight, based on the weight of the dry additive based on the weight of the dry cellulose suspension. Suitable amounts range from about 0.05 wt.% To about 3.0 wt.%, Preferably from about 0.1 wt.% To about 2.0 wt.%.

The method according to the present invention is applicable in all papermaking processes and using any cellulosic suspensions, and it is especially useful in the manufacture of paper from pulp having a high electrical conductivity. In such cases, the electrical conductivity of the paper pulp, which is dehydrated on a mesh conveyor, is usually at least about 1.5 mS / cm, preferably at least 3.5 mS / cm, and more preferably at least 5.0 mS / cm. Conductivity can be measured with standard instruments, such as the WTW LF 539 instrument supplied by Christian Berner.

The present invention further encompasses paper making methods in which recycled water is reused extensively, i.e. Recycling of recycled water is used to a large extent, for example, from 0 tons to 30 tons of fresh water per 1 ton of dry paper is used, usually less than 20 tons, preferably less than 15 tons, more preferably less than 10 tons and especially less than 5 tons. Fresh water can be served at any stage of the process; for example, fresh water can be mixed with cellulosic fiber to form a cellulosic suspension; fresh water can be mixed with a thick cellulosic suspension to dilute it so as to obtain a liquid cellulosic suspension into which the first, second and third polymers are added.

The method according to the invention is used for the manufacture of paper. The term "paper" used in this description, of course, means not only paper and its manufacture, but also other products in the form of a canvas, such as cardboard and its manufacture. The method can be used to make paper from various types of suspensions of cellulose fiber, and the suspension should preferably contain at least 25 wt.%, And more preferably at least 50 wt.% Of such fiber, based on the dry matter. Suspensions can be formed using chemical pulp, for example, sulfate and sulfite pulp, thermomechanical pulp (TMBM), chemical-thermomechanical pulp, pulp in the form of an organosol, refiner pulp or wood pulp from both hardwood and and from coniferous wood; or from fiber obtained from annual plants, for example from red pennisetum, bagasse, flax, straw, etc .; recycled fiber suspensions may also be processed. The invention is preferably applicable to methods for making paper from suspensions containing wood fiber.

The suspension also contains conventional types of mineral fillers, for example kaolin, clay, titanium dioxide, gypsum, talc and both natural and synthetic calcium carbonate, for example chalk, marble chips, calcium carbonate chips and precipitated calcium carbonate. The paper pulp may, of course, also contain conventional types of additives used for making paper, for example wet strength agents, sizing agents, for example rosin-based agents, ketendimers, keten multimers, succinic alkenyls, etc.

Preferably, the invention is applicable to paper machines that produce paper containing wood fiber and paper based on recycled fiber, for example paper of types SC, LWC and various types of book and newsprint; and paper machines that produce printing and writing paper that does not contain wood fiber (the term "paper that does not contain wood fiber" means paper containing about 15 wt.% wood fiber). An example of a preferred application of the invention is the manufacture of paper and multilayer paper from cellulosic suspensions containing at least 50 wt.% Mechanical and / or reusable fiber. Preferably, the invention is applicable to papermaking machines operating at a speed of from 300 m / min to 3000 m / min, and more preferably from 500 m / min to 2500 m / min.

The invention is further illustrated by the following examples, which, however, do not limit the scope of the invention. Parts and percentages are expressed in mass parts and mass percentages, respectively, unless otherwise indicated.

Examples

The following additives were used in the examples:

C-PAM 1: Acrylamide-based cationic polymer made by polymerization of acrylamide (40 mol%) and acryloxyethyltrimethylammonium chloride (60 mol%); the polymer had a weight average molecular weight of about 3 million and a cationic charge density of about 4.2 meq / g.

C-PAM 2: Acrylamide-based cationic polymer made by polymerization of acrylamide (60 mol%) and acryloxyethyltrimethylammonium chloride (40 mol%); the polymer had a weight average molecular weight of about 3 million and a cationic charge density of about 3.3 meq / g.

C-PAM 3: Acrylamide-based cationic polymer made by polymerization of acrylamide (88 mol%), acryloxyethyltrimethylammonium chloride (10 mol%) and dimethyl acrylamide (2 mol%); the polymer had a weight average molecular weight of about 6 million and a cationic charge density of about 1.2 meq / g.

C-PAM 4: Acrylamide-based cationic polymer made by polymerization of acrylamide (90 mol%) and acryloxyethyltrimethylammonium chloride (10 mol%); the polymer had a weight average molecular weight of about 6 million and a cationic charge density of about 1.2 meq / g.

PAC: Cationic polyaluminium chloride with a cationic charge density of about 8.0 meq / g.

C-PAl 1: A cationic polyamine having a weight average molecular weight of about 200,000 and a cationic charge density of about 7 meq / g.

C-PAl 2: A cationic polyamine having a weight average molecular weight of about 400,000 and a cationic charge density of about 7 meq / g.

A-PAM: Anionic acrylamide-based polymer made by polymerization of acrylamide (80 mol%) and acrylic acid (20 mol%); the polymer had a weight average molecular weight of about 12 million and an anion charge density of about 2.6 meq / g.

A-X-PAM: Anionic crosslinked acrylamide-based polymer made by polymerization of acrylamide (30 mol%) and acrylic acid (70 mol%); the polymer had a weight average molecular weight of about 100,000 and an anion charge density of about 8.0 meq / g.

Silicon Compound: An anionic inorganic condensation polymer of silicic acid in the form of a colloidal solution of silicic acid modified with aluminum, having an S parameter of about 21 and containing silicon-based particles with a specific surface of about 800 m ² / g.

Bentonite: Bentonite.

Example 1

Drainage (dewatering) was evaluated using a dynamic drainage analyzer (DBP) supplied by Akribi, Sweden, which measures the dewatering time of a given volume of paper pulp (by draining liquid) through a mesh conveyor while removing the plug and applying vacuum from the mesh conveyor side opposite the side on which the paper pulp is placed.

The paper pulp used in the tests was based on 75 wt.% TMBM and 25 wt.% DIP fiber material and precipitated recycled water from the newsprint production line. The concentration of paper pulp was 0.78%. The electrical conductivity of the pulp was 1.5 mS / cm and the pH was 6.8.

To simulate the additions after all stages of strong shear, the paper pulp was mixed in a divided bulkhead with different mixing speeds. Mixing and adding was performed as follows:

stirred at a speed of 1000 rpm for 20 s;

stirred at a speed of 2000 rpm for 10 s;

stirred at a speed of 1000 rpm for 15 s, while adding;

dehydrated paper pulp, at the same time automatically recording the duration of dehydration.

Additions to the pulp were made as follows.

The first addition (dosage 5 kg / t) was made 15 s before dehydration; the second addition (dosage 0.8 kg / t) was made 10 s before dehydration; the third addition (dosage 0.5 kg / t) was made 5 s before dehydration.

Table 1 presents the duration of dehydration for various modes of addition. Dosages of polymer and bentonite were determined from the calculation of the mass of dry product from the mass of dry cellulose suspension, and the sol based on silica particles from the calculation of the mass of SiO ₂ from the mass of dry paper pulp.

Test No. 1 illustrates the results obtained without the use of any additives. Tests No. 2-4 illustrate the methods used for comparison, and Test No. 5-7 illustrate the methods according to the invention.

Table 1 Test No. First add Second Addendum Third addition Dehydration duration one - - - 60.6 2 C-PAl 1 C-PAM 4 Bentonite 24.5 3 C-PAl 1
C-PAl 2
(1: 1) C-PAM 4 Bentonite 24.4 four - C-PAM 4 Bentonite 32,4 5 C-PAM 1 C-PAM 3 Silica 22.4 6 C-PAM 2 C-PAM 4 Silica 21,2 7 C-PAM 2 C-PAM 3 Silica 19.0

The data in table 1 show that the application of the method according to the present invention can improve dehydration.

Example 2

Drainage was evaluated using a dynamic drainage analyzer (DBP), as in example 1.

The pulp used in the tests was based on 75% by weight of TMBM, 25% by weight of DIP fiber material and bleaching water from papermaking. The concentration of paper pulp was 0.77%. The electrical conductivity of the pulp was 1.6 mS / cm and the pH was 7.2.

To simulate the additions before and after all stages of strong shear, the paper pulp was mixed in a divided bulkhead with different mixing speeds. Mixing and adding was performed as follows:

mixed at a speed of 1000 rpm for 25 s, at the same time performing from 0 to 2 additions;

stirred at a speed of 2000 rpm for 10 s;

mixed at a speed of 1000 rpm for 15 s, while at the same time performing from 0 to 3 additions;

dehydrated paper pulp, at the same time automatically recording the duration of dehydration.

Additions to the pulp were made as follows.

The first addition, if performed, was done 45 seconds or 15 seconds before dehydration, the second addition, if performed, was performed 25 seconds or 10 seconds before dehydration, and the third addition, if performed, was made 5 seconds before dehydration .

Table 2 presents the duration of dehydration for various modes of addition. The time for the addition before dehydration is shown in seconds, and the dosages of the first, second and third additions are respectively shown in kg / t. The dosage of the polymer was determined from the calculation of the mass of dry product from the mass of dry cellulose suspension, and the sol based on silica particles from the calculation of the mass of SiO ₂ from the mass of dry paper pulp.

Test No. 1 illustrates the results obtained without the use of any additives. Tests No. 2-7 illustrate the methods used for comparison, and tests No. 8-10 illustrate the methods according to the invention.

table 2 Test
No. First
added The second added. Third add The time to complete the addition before dehydration, s 1st; 2nd; 3rd Dosage, kg / t; 1st; 2nd; 3rd Will continue.
dehydrated., with one - - - - 84.0 2 C-RAM 2 C-RAM 4 Silica 45/25/5 0, / 0.2 / 0.5 61.8 3 C-RAM 2 C-RAM 4 Silica 45/25/5 0.2 / 0.2 / 0.5 50,2 four C-RAM 2 C-RAM 4 Silica 45/25/5 0.1 / 0.5 / 0.5 39.0 5 C-RAM 2 C-RAM 4 Silica 45/10/5 0.1 / 0.2 / 0.5 56.0 6 C-RAM 2 C-RAM 4 Silica 45/10/5 0.2 / 0.2 / 0.5 46.0 7 C-RAM 2 C-RAM 4 Silica 45/10/5 0.1 / 0.5 / 0.5 32.1 8 C-RAM 2 C-RAM 4 Silica 10/15/5 0.1 / 0.2 / 0.5 48,2 9 C-RAM 2 C-RAM 4 Silica 10/15/5 0.2 / 0.2 / 0.5 43.8 10 C-RAM 2 C-RAM 24 Silica 10/15/5 0.1 / 0.5 / 0.5 31,0

The data in table 2 clearly show that the application of the method according to the present invention can improve dehydration.

Example 3

Drainage was evaluated according to the methodology used in example 2.

Retention was assessed using a nephelometer supplied by Novasina, Switzerland, by measuring the turbidity of the filtrate, recycled water obtained by draining the pulp. Turbidity was measured in NTU (NTU - nephelometric turbidity unit).

In this example, paper pulp was used and the mixing and addition modes are the same as in example 2.

The data in table 3 illustrate the effect of dehydration under various modes of addition. Test No. 1 illustrates the results obtained without the use of any additives. Tests No. 2 and 3 illustrate the methods used for comparison, and test No. 4 illustrates the method according to the invention.

Table 3 Test No. The first added. The second added. Third add Execution time added before dehydration, s; 1st; 2nd; 3rd Dosage, kg / t; 1st; 2nd; 3rd Will continue. dehydration., with Turbidity, NTU one - - - - - 84.0 one hundred 2 C-RAM 2 A-RAM Silica 45/25/5 0.8 / 0.2 / 0.5 66.0 31 3 C-RAM 2 A-RAM Silica 45/10/5 0.8 / 0.2 / 0.5 61.9 32 four C-RAM 2 A-RAM Silica 10/15/5 0.8 / 0.2 / 0.5 53,2 26

The data in table 3 show that the application of the method according to the present invention improves the dehydration process.

Example 4

Drainage and retention were evaluated according to the methods used in example 3. In this example, paper pulp was used and the mixing and addition modes were the same as in example 2.

Table 4 presents data characterizing the effect of dehydration under various modes of additions. Test No. 1 illustrates the results obtained without the use of any additives. Tests No. 2-7 illustrate the methods used for comparison, and tests No. 8-9 illustrate the methods according to the invention.

Table 4 Test No. The first added. The second added. Third add Execution time added before dehydration, s; 1st; 2nd; 3rd Dosage, kg / t; 1st; 2nd; 3rd Will continue. dehydration., with Turbidity, NTU one - - - - - 84.0 one hundred 2 C-RAM 2 - A-RAM 45 / - / 5 0.2 / - / 0.3 148.0 76 3 C-RAM 2 - A-RAM 15 / - / 5 0.2 / - / 0.3 132.4 58 four - C-RAM 4 A-RAM - / 25/5 - / 0.8 / 0.3 101.0 eighteen 5 - C-RAM 4 A-RAM - / 10/5 - / 0.80 / 0.3 82,2 26 6 C-RAM 2 C-RAM 4 A-RAM 45/25/5 0.2 / 0.8 / 0.2 77.4 twenty 7 C-RAM 2 C-RAM 4 A-RAM 45/25/5 0.2 / 0.8 / 0.3 60.0 22 8 C-RAM 2 C-RAM 4 A-RAM 10/15/5 0.2 / 0.8 / 0.2 49.0 17 9 C-RAM 2 C-RAM 4 A-RAM 10/15/5 0.2 / 0.8 / 0.3 52,5 twenty

The data in table 4 show that the application of the method according to the present invention improves drainage (dehydration) and retention processes.

Example 5

Drainage and retention were evaluated according to the methods used in example 3. In this example, the mixing and addition modes used were the same as in example 2.

The paper pulp used in this example was based on 75 wt.% TMBM, 25 wt.% DIP fibrous material and bleaching water from a newsprint production line. The concentration of paper pulp was 0.82%. The electrical conductivity of the pulp was 1.7 mS / cm, and the pH was 7.2.

Table 5 presents data characterizing the effect of dehydration under various modes of additions. Test No. 1 illustrates the results obtained without the use of any additives. Tests No. 2-8 illustrate the methods used for comparison, and test No. 9 illustrates the method according to the invention.

Table 5 Test No. The first added. The second added. Third add Execution time added before dehydration, s; 1st; 2nd; 3rd Dosage, kg / t; 1st; 2nd; 3rd Will continue. dehydration., with Turbidity, NTU one - - - - - 93.9 82 2 - C-RAM 4 Silica - / 25/5 - / 0.2 / 0.5 67.7 58 3 - C-RAM 4 Silica - / 10/5 - / 0.2 / 0.5 60.7 68 four RAS - Silica 45 / - / 5 2 / - / 0.5 88.5 62 5 RAS - Silica 15 / - / 5 2 / - / 0.5 83.5 73 6 RAS C-RAM 4 - 45/25 / - 2 / 0.2 / - 51.8 52 7 RAS C-RAM 4 - 45/10 / - 2 / 0.2 / - 54.5 56 8 RAS C-RAM 4 Silica 45/10/5 2 / 0.2 / 0.5 54.6 51 9 RAS C-RAM 4 Silica 10/15/5 2 / 0.2 / 0.5 51,2 48

The data in table 5 show that the application of the method according to the present invention improves drainage (dehydration) and retention processes.

Example 6

Drainage was evaluated according to the methodology used in example 2. In this example, paper pulp was used and the mixing and addition modes were the same as in example 5.

Table 6 presents data characterizing the effect of dehydration under various modes of additions. Test No. 1 illustrates the results obtained without the use of any additives. Tests No. 2-6 illustrate the methods in which additives used for comparison (reference) were used, and test No. 7 illustrates the method according to the invention.

Table 6 Test
No. First
added The second added. Third add The time to complete the addition before dehydration, s 1st; 2nd; 3rd Dosage, kg / t; 1st; 2nd; 3rd Will continue. dehydrated., with one - - - - - 93.9 2 RAS C-RAM 4 - 45/25 / - 2 / 0.2 / - 51.8 3 RAS C-RAM 4 - 45/10 / - 2 / 0.2 / - 54.5 four RAS C-RAM 4 - 15/10 / - 2 / 0.2 / - 48.7 5 RAS C-RAM 4 A-X-RAM 45/25/5 2 / 0.2 / 0.1 44.8 6 RAS C-RAM 4 A-X-RAM 45/10/5 2 / 0.2 / 0.1 43.9 7 RAS C-RAM 4 A-X-RAM 10/15/5 2 / 0.2 / 0.1 42.9

The data in table 6 show that the application of the method according to the present invention improves the drainage process.

Example 7

Drainage was evaluated according to the methodology used in example 2. In this example, paper pulp was used and the mixing and addition modes were the same as in example 5.

Table 7 presents data characterizing the effect of dehydration under various modes of additions. Test No. 1 illustrates the results obtained without the use of any additives. Tests No. 2-7 illustrate the methods used for comparison, and test No. 8 illustrates the method according to the invention.

Test
No. First
added The second added. Third add The time to complete the addition before dehydration, s 1st; 2nd; 3rd Dosage, kg / t; 1st; 2nd; 3rd Will continue. Dehydrated., With one - - - - - 93.9 2 RAS - A-RAM 45 / - / 5 0.2 / - / 0.1 185.0 3 RAS - A-RAM 15 / - / 5 0.2 / - / 0.1 96.8 four - C-RAM 4 A-RAM - / 25/5 - / 0.8 / 0.1 76.5 5 - C-RAM 4 A-RAM - / 10/5 - / 0.8 / 0.1 55.1 6 RAS C-RAM 4 A-RAM 45/25/5 0.2 / 0.8 / 0.1 107.0 7 RAS C-RAM 4 A-RAM 45/10/5 0.2 / 0.8 / 0.1 61.5 8 RAS C-RAM 4 A-RAM 10/15/5 0.2 / 0.8 / 0.1 39.8

The data in table 7 show that the application of the method according to the present invention improves the dehydration process.

Claims (16)

1. A method of manufacturing paper, including:
(i) providing an aqueous suspension containing cellulosic fiber;
(ii) adding to the suspension after all stages of strong shear:
a first polymer, which is a cationic polymer, having a charge density of more than 4.0 meq / g;
a second polymer having a molecular weight of more than 500,000; and
a third polymer, which is an anionic polymer; and
(iii) dewatering the resulting suspension to form paper. 2. A method of manufacturing paper, including:
(i) providing an aqueous suspension containing cellulosic fiber;
(ii) adding to the suspension after all stages of strong shear:
the first polymer, which is an acrylamide-based cationic polymer having a charge density of more than 2.5 meq / g;
a second polymer, which is an acrylamide-based polymer having a molecular weight of more than 500,000; and
a third polymer, which is an anionic polymer; and
(iii) dewatering the resulting suspension to form paper. 3. A method of manufacturing paper, including:
(i) providing an aqueous suspension containing cellulosic fiber;
(ii) adding to the suspension after all stages of strong shear:
a first polymer, which is a cationic polymer, having a charge density of more than 2.5 meq / g;
a second polymer, which is a water dispersible polymer; and
a third polymer, which is an anionic polymer; and
(iii) dewatering the resulting suspension to form paper. 4. The method according to claim 1 or 3, in which the first polymer is an organic polymer. 5. The method according to claim 4, in which the first polymer is a cationic polymer based on acrylamide. 6. The method according to claims 1, 2 or 3, in which the first polymer has a molecular weight of at least 500,000. 7. The method according to claim 1, in which the first polymer is an inorganic polymer. 8. The method according to claims 1, 3 or 7, in which the first polymer is polyaluminium chloride. 9. The method according to claims 1 or 2, in which the second polymer has a molecular weight of more than 1,000,000. 10. The method according to claims 1, 2 or 3, in which the second polymer is cationic. 11. The method according to claims 1, 2 or 3, in which the second polymer is anionic. 12. The method according to claims 1, 2 or 3, in which the third polymer is an inorganic polymer. 13. The method of claim 12, wherein the third polymer is silicic acid or a silicate-based polymer. 14. The method according to item 13, in which the third polymer contains colloidal particles based on silicon. 15. The method according to any one of claims 1, 2 or 3, in which the third polymer is an organic polymer. 16. The method according to clause 15, in which the third polymer is an acrylamide-based polymer.