Method for manufacture of paper and cardboard

FIELD: pulp-and-paper industry.

SUBSTANCE: method involves preparing cellulose suspension; providing flocculation and draining of suspension on netted surface; molding and drying of resultant sheet. Flocculation of suspension is provided by introducing of water-soluble polymer selected from the group consisted of polysaccharide and synthetic polymer with characteristic viscosity of at least 4 deciliter/g. Repeated flocculation procedure is provided by adding of system including silicon-containing material and water-soluble polymer. According to one of versions, silicon-containing material is added before or simultaneously with water-soluble polymer. According to other version, water-soluble polymer is of anionic kind of polymers, which is added before introduction of silicon-containing material.

EFFECT: improved draining and holding procedures facilitating adequate conditions for paper and cardboard molding procedure.

18 cl, 2 tbl, 4 ex

 

The present invention relates to a method of manufacture of paper and paperboard from pulp of fibrous masses using the new floculants system.

During the manufacture of paper and cardboard pulp and liquid fibrous mass drain on a movable grid (often called grid paper machine for casting sheet, which is then dried. It is well known adding to the pulp slurry a water-soluble polymer to cause the effect flocculation of the pulp solids and improve drainage on a movable grid.

To produce more paper many modern paper machines operate with higher speeds. Due to the higher speed machines pay much attention to the drainage systems and retention, which provide enhanced drainage. However, it is known that increasing the molecular weight polymer additives that promote the retention, which is injected directly before drainage, accompanied by a tendency to increase the rate of drainage, but does harm to the molding. Achieving an optimal balance of retention, drainage, drying and molding by adding a single polymer additives that promote the retention, involves problems of a technological nature, so common practice is the fast sequential addition of two separate materials.

In EP-A 235893 is proposed a method in which at the stage of exposure to shear stress in the fiber for making paper introduced almost linear water-soluble cationic polymer, and then after this stage, the impact of shear force carried out for the second flocculation by the addition of bentonite. The implementation of this method provides the possibility of improved drainage, and good molding and retention. This method, which has found industrial embodiment of the firm Ciba Specialty Chemicals in the form of technology under the trademark Hydrocol®, has confirmed its effectiveness for more than a decade.

Were later made various attempts to develop variants of this method by making small modifications in one or more components.

In the US 5393381 described a method of manufacturing paper or cardboard, in which a suspension of the fibers of the fibrous mass of the added water-soluble branched cationic polyacrylamide and bentonite. This branched cationic polyacrylamide is prepared by polymerization in solution of a mixture of acrylamide, cationic monomer, agent education branches and regulator polymerization degree.

In the US 5882525 described method in which a dispersion of suspended solids, for example in the fibrous mass is for the manufacture of paper, to release water type cationic branched water-soluble polymer, the solubility of which is greater than about 30%. This cationic branched water-soluble polymer prepared from the same components as those described in US 5393381, i.e. by polymerization of a mixture of acrylamide, cationic monomer, agent education branches and regulator polymerization degree.

According to EP-A 17353 on raw fibrous mass, characterized by a high cationic demand, treated with bentonite, followed almost nonionic additive that promotes retention. Although the suspension in the implementation of this method is essentially a suspension containing no filler, AU-And 63977/86 described modification, according to which this suspension may include a filler and according to which the bentonite is injected into a dense fibrous mass, then this thick fibrous mass is diluted to form a liquid fibrous mass in a liquid fibrous mass is added a relatively low molecular weight cationic polyelectrolyte, and then add a nonionic high-molecular additive that promotes retention. Thus, this method is used coagulants polymer and injected into a dense fibrous mass after bentonite.

Such HVL of the ordinary, as those described in EP-A 17353 and AU 63977/86, from the point of view of a manufacturer of paper from a suspension which has a high cationic demand and relatively low filler contents are satisfactory, but are rather unsatisfactory, taking into account the retention of the filler, when the suspension contains substantial amounts of filler.

In the application EP-A 608986 described a method of manufacturing paper filled with the introduction of the original suspension of cationic coagulant for flocculation relatively concentrated suspension of fibers and filler, the addition of bentonite or other anionic powder material in the pulp liquid fibrous mass or dense fibrous mass and then add in the liquid fibrous mass of polymer additives that promote the retention, before draining this liquid fibrous mass for casting sheet. The application States that the presence of the coagulant in a concentrated suspension of fibers and filler improves the retention of these last.

In EP-A 308752 described method of making paper, in which the composition of the paper add low molecular weight cationic organic polymer, and then the colloidal silica and high molecular weight charged acrylamide copolymer with molecular the weight of at least 500000. From the description it appears indicating that the highest range of molecular masses, which reach when receiving low molecular weight cationic polymer added to the composition of the first paper is from 1000 to 500000. Such low molecular weight polymers expect an indispensable manifestation of the characteristic viscosity of up to about 2 DL/g

In the work of the TM Gallager 1990 TAPPI Press, Atlanta, S. 141 Short Course entitled Neutral/Alkaline Paper making is described, it is claimed, are technically accessible system kremmidiotis microparticles, in which the use of cationic coagulants polymer, high molecular weight anionic polyacrylamide and colloidal solution of silicic acid with 5-nanometer particles. Such coagulant polymers have, apparently, a low molecular weight and high charge density. Said, that although there is the potential for high retention, molding, after all, is a consequence of the high concentration of polyacrylamide. In this system usually uses the addition of small amounts of silicon dioxide (less than 0.10%).

However, there is still a need for further improvement of the methods of manufacturing paper with further improvement of drainage and retention without compromising the molding process. Moreover, there is also a need to create more effective f is oculentis system for making paper with high filler contents.

In accordance with the first object of the present invention proposes a method of making paper or paperboard comprising preparing a pulp suspension, flocculation of the suspension, draining the suspension on the grid casting sheet and the subsequent drying of the sheet, in which the pulp suspension localroot the introduction of essentially water-soluble polymer selected from the

a) polysaccharide and

b) a synthetic polymer with a characteristic viscosity at least 4 DL/g,

and then localroot followed by the addition system for the re-flocculation, where the system for re-flocculation includes I) a silicon-containing material and (II) essentially water-soluble polymer, characterized in that either the silicon-containing material and a water-soluble polymer added to the suspension at the same time, or silicon-containing material is injected before adding the water-soluble polymer.

In accordance with the second object of the present invention proposes a method of making paper or paperboard comprising preparing a pulp suspension, flocculation of the suspension, draining the suspension on the grid casting sheet and the subsequent drying of the sheet, in which the pulp suspension localroot the introduction of essentially water-soluble polymer selected from the

a) poly is Farida and

b) a synthetic polymer with a characteristic viscosity at least 4 DL/g,

and then localroot followed by the addition system for the re-flocculation, where the system for re-flocculation includes I) a silicon-containing material and (II) essentially water-soluble anionic polymer, characterized in that the water-soluble anionic polymer is introduced into the cellulosic suspension before adding the silicon-containing material.

It was found that the flocculation of pulp suspensions using floculants system, which includes the introduction in the pulp suspension multi-component system that includes a water-soluble polymer with a characteristic viscosity above 4 DL/g, followed by the system to re-flocculation according to the invention provides improved retention and drainage without any appreciable deterioration of the molding in comparison with the results of the implementation of other known methods.

Silicon-containing material may be any of the materials selected from the group comprising particles on kremmidiotis basis, kremmidiotis the microgels, colloidal silica, colloidal solution of silicic acid, silica gels, polysilicates, cationic silica, aluminosilicates, polyaluminosilicate, borosilicate, polibar ilicate, zeolites and swelling clays. This silicon-containing material can be in the form of anionic material of the microparticles. When silicon-containing material is a swellable clay, as it usually can be used clay bentonite compounds, preventing type. The preferred clay is able to swell in water, these include clay, which in the water are exposed to the natural swelling and clay, which can be modified, for example by ion exchange, to give them swelling in water. Suitable swelling in water of clay include, though not limited to, clay, often referred to as hectorite, smectites, montmorillonite, nontronite, saponite, sekonic, gormiti, attapulgite and sepiolites. Floculants material may be bentonite, which is described in EP-A 235893 and EP-A 335575.

Thus, the first component floculants system in accordance with the invention is a water-soluble polymer which is introduced into the cellulosic suspension before the system to re-flocculation. Water-soluble polymer must have sufficient molecular weight to cause bridging flocculation in the whole pulp suspensions. A water-soluble polymer may be any suitable natural or synthetic polymer. They may be a natural polymer, such as polishuri is, in particular, such as starch, such as anionic, nonionic, amphoteric, preferably cationic starch. This natural polymer may have any molecular weight, but the preferred high molecular weight, and may be, for example, the characteristic viscosity above 4 DL/g, the Preferred polymer is a high molecular weight synthetic water-soluble polymer. Therefore, the polymer can be any water-soluble polymer with a characteristic viscosity at least 4 DL/g are Preferred such polymers have characteristic viscosity of at least 7 DL/g, for example up to 16 or 18 DL/g, but is usually in the range from 7 or 8 to 14 or 15 DL/g, This water-soluble polymer can be anionic, nonionic, amphoteric, but preferred cationic. Water-soluble polymer can be obtained from any water soluble monomer or monomer mixture. Under vodorastvorimostew is meant that the solubility of the monomer in water is at least 5 g/100 tubes

As the water-soluble polymer of the first component floculants system is necessary and can be used nonionic polymer or, in other words, the ionic polymer. When the polymer is ionic, in the preferred embodiment, the ion content is in predlahat low to medium. For example, the charge density of the ionic polymer may be below 5 mEq./g, preferably below 4, mostly below 3 mEq./, As a rule, ionic polymer may comprise up to 50 wt.% links-ionic monomer. When the polymer is ionic, it may be anionic, cationic or amphoteric. When the polymer anionactive, it can be derived from a water soluble monomer or monomer mixture in which at least one monomer is anionic or potentially anionic. The anionic monomer may be polymerized alone or copolymerization with any other acceptable monomer, for example, any water-soluble nonionic monomer. Typical anionic monomer may be any ethylene-unsaturated carboxylic acid or sulfonic acid. Preferred anionic polymers derived from acrylic acid or 2-acrylamide-2-methylpropanesulfonic acid. When a water-soluble polymer is anionic, in the preferred embodiment, it is a copolymer of acrylic acid (or its salts) with acrylamide. When the polymer is nonionic, it can be any polyalkylene or vinyl polymer obtained stepwise polymerization, which are synthesized from any water soluble neyo ogandaga monomer or mixture of monomers. Typical water-soluble nonionic polymer is polietilenoksidnoy or acrylamides a homopolymer.

When the first component floculants system is nonionic or anionic, may require pre-treatment of pulp suspensions of cationic agent, such as alum, polyaluminium, aluminiumhydride or, in other words, cationic essentially water-soluble polymer. Such pre-treatment cationic agent can be directly pulp suspension or any of the components of this pulp suspension.

The preferred first component floculants system is a cationic or potentially cationic water-soluble polymer. Preferred cationic water-soluble polymers have a cationic or potentially cationic functional groups. For example, the cationic polymer may contain free amino groups, which, after introduction into the pulp slurry with a relatively low pH value for the protonation of the free amino groups become cationic. However, in the preferred embodiment, the cationic polymers have a permanent cationic charge, in particular a Quaternary ammonium group. The polymer should and can be obtained from in rastvorimogo ethylene-unsaturated cationic monomer or mixture of monomers, in which at least one of the monomers is cationic. Preferred cationic monomer is selected from diallyldimethylammoniumchloride, acid additive salts and Quaternary ammonium salts or dialkylaminoalkyl(meth)acrylate, or dialkylaminoalkyl(meth)acrylamides. The cationic monomer may be polymerized alone or copolymerization with water-soluble nonionic, cationic or anionic monomers. Especially preferred cationic polymers include copolymers methylchloride Quaternary ammonium salts dimethylaminoethylacrylate or methacrylate.

The first component may be an amphoteric polymer and, therefore, to include, apparently, as anionic or potentially anionic and cationic or potentially cationic functional groups. Thus, the amphoteric polymer can be obtained from a mixture of monomers, at least one of which is cationic or potentially cationic, at least one monomer is anionic or potentially anionic and optionally contains at least one nonionic monomer. Acceptable monomers certainly include any of cationic, anionic and nonionic monomers described in the present description. Pre is respectful amphoteric polymer is apparently, a polymer of acrylic acid with methylchloride stereoselectivity by dimethylaminoethylacrylate and acrylamide.

As the first component may be used water-soluble polymer with a rheological oscillation value of tan Delta at 0.005 Hz more than 1.1 (determined in the present description of the method), such as proposed in co-pending application for patent with priority based on patent application US room 60/164231 (the reference number PP/W-21916/P1/AC 526), filed with the same priority date as this application. This water-soluble polymer may also have a slightly branched structure, which is achieved, for example, the introduction of small quantities of agent education branches, in particular up to 20 miscast./million To typical agents of education branches are any agents of education branches, which in the present description is presented as acceptable for obtaining a branched anionic polymer. Such branched polymers can also be obtained by the inclusion in the monomer mixture control degree of polymerization. Control degree of polymerization can be included in the amount of at least 2 miscast./million and can be used up to 200 miscast./million As a rule, the content controller polymerization degree is away in the interval from 10 to 50 miscast./million As the regulator of the degree of polymerization can be used any acceptable chemical substance, such as hypophosphite sodium, 2-mercaptoethanol, malic acid or thioglycolate acid.

Branched polymers can be obtained by using a controller of the degree of polymerization and using more substantial quantities of agent education branches, for example up to 100 or 200 miscast./million, assuming the number of control degrees of polymerization are sufficient to guarantee that the resulting polymer has solubility. Branched water-soluble polymer can generally be obtained from water-soluble monomer mixture comprising at least one cationic monomer, at least 10 molar ppm million regulator polymerization degree and less than 20 molar ppm million agent education branches. Preferred branched water-soluble polymer has a rheological oscillation value of tan Delta at 0.005 Hz 0,7 more (determined in the present description of the method).

Water-soluble polymers can also be obtained by any convenient method, for example by polymerization in solution, the polymerization in suspension of water in the oil or by polymerization in emulsion of water in oil. As a result, the polymerase is Itachi in solution form aqueous polymer gels, you can cut, dry and grind with cooking powdered product. The polymers can be obtained in the form of a bead suspension polymerization or emulsion or dispersion of water in oil by polymerization in emulsion of water in oil, for example in accordance with the method described in EP-A 150933, EP-A 102760 or EP-A 126528.

In accordance with the invention, water-soluble polymers are added to the pulp suspension before you system to re-flocculation, you can enter at any reasonable point. Such a polymer can be introduced at a very early stage of the process, for example in a dense fibrous mass, but it is preferable to add a liquid fibrous mass. The polymer can be added in any effective way to achieve flocculation quantity. Usually the concentration of the cationic polymer will certainly exceed 20 miscast./million, calculated on the dry weight of the suspension. In the preferred embodiment, it is added in the amount of at least 50 miscast./million, for example from 100 to 2000 miscast./million Concentration of this polymer as a rule exceed 150 ppm million, may exceed 200 ppm million and may even exceed 300 ppm million

Often, the concentration may be in the range from 150 to 600 ppm million, mainly in the range from 200 to 400 ppm million

Silicon-containing material and water-soluble floor is measures as components of the system to re-flocculation can be entered in the pulp suspension at the same time. For example, both components can be added to the pulp suspension separately, but at the same stage or at the same point add. When the components of the system to re-flocculation injected simultaneously, the silicon-containing material and a water-soluble polymer can be added to the mixture. This mixture can be prepared in situ by combining silicon-containing material and a water-soluble polymer according to the place of addition or in the supply line leading to the insertion point. In a preferred embodiment, the system for re-flocculation is a pre-prepared mixture of siliceous material and water-soluble polymer.

According to another preferred variant implementation of the invention the two components of the system to re-flocculation administered sequentially, with silicon-containing material is added before the introduction of the water-soluble polymer system to re-flocculation.

Silicon-containing material may be any of the materials selected from the group comprising particles on kremmidiotis basis, kremmidiotis the microgels, colloidal silica, colloidal solution of silicic acid, silica gels, polysilicates, aluminosilicates, polyaluminosilicate, borosilicate, polymorbidity and zeolites. Silicon-containing material can be in the form of anionic mater the Ala of the microparticles. Alternatively silicon-containing material may be cationic silicon dioxide.

According to one preferred variant implementation of the invention, the silicon-containing material selected from silica and polysilicates. This silica can be any colloidal silica, such as that described in WO 86/00100. The polysilicate may be colloidal silicic acid, which is described in US 4388150.

Polysilicate according to the invention can be obtained by acidification of an aqueous solution of alkali metal silicate. For example, partial acidification of the alkali metal silicate to a pH of about 8-9 using mineral acids or acidic ion-exchange resins, acidic salts and acidic gases can be obtained polysilicon microgels, otherwise known as active silica. It may be necessary sufficient aging freshly polysilicon acid to provide the opportunity for the formation of three-dimensional structures. Typically, the time of aging is insufficient to move the polysilicon acid in the gel. Especially preferred silicon-containing materials include polyaluminosilicate. Polyaluminosilicate can be, for example, aluminized polysilicon acid is prepared by first obtaining microparticles polik is annieway acid, and then followed by treatment with aluminum salts, for example as set forth US 5176891. Such polyaluminosilicate consist of silicon microparticles with aluminum, are mainly located in the surface area.

In another embodiment, polyaluminosilicate can be polyparticulate the microgels with a specific surface area greater than 1000 m2/g, prepared by the reaction of alkali metal silicate with an acid and a water-soluble aluminum salts, for example as described in US 5482693. The molar ratio of the aluminum oxide/silicon dioxide in polyaluminosilicate, as a rule, can be in the range from 1:10 to 1:1500.

Polyaluminosilicate can be obtained by acidification of an aqueous solution of alkali metal silicate to a pH of 9 or 10 using concentrated sulfuric acid, containing from 1.5 to 2.0 wt.% water-soluble aluminum salts such as aluminum sulfate. This aqueous solution can be subjected to sufficient aging for the formation of three-dimensional structure of the microgel. As a rule, polyaluminosilicate subjected to aging for up to about two and a half hours before dilution with aqueous polysilicate until the content of silicon dioxide of 0.5 wt.%.

Silicon isomerases material may be colloidal borosilicate, for example such as described in WO 99/16708. Colloidal borosilicate can be prepared by introduction of R is zbowling aqueous solution of alkali metal silicate in contact with the cation exchange resin to obtain silicic acid, and then obtaining the target product by mixing a dilute aqueous solution of a borate of an alkali metal hydroxide alkali metal, resulting in an aqueous solution containing from 0.01 to 30% In2About3the pH value of which ranges from 7 to 10.5. One preferred object of the silicon-containing material is a silicon dioxide.

When the silicon-containing material using silicon dioxide or a silicate material type, the size of its particles greater than 10 nm. The preferred particle size of the silica or silicate material is in the range from 20 to 250 nm, mostly in the range of from 40 to 100 nm.

In a more preferred embodiment, a silicon-containing material is a swellable clay. As swelling clays typically can be used clay bentonite compounds, preventing type. Preferred swelling in water of clay, these include clay, which in the water are exposed to the natural swelling and clay, which can be modified, for example by ion exchange, to give them swelling in water. Suitable swelling in water of clay include, though not limited to, clay, often referred to as hectorite, smectites, montmorillonite, nontronite, saponite, sekonic, gormiti, attapulgite and with policy. Typical anionic swelling clay is described in EP-A 235893 and EP-A 335575.

The most preferred clay is a clay bentonite compounds, preventing type. Bentonite can be prepared in the form of bentonite alkali metal. Bentonites occur in nature or as alkaline bentonites, such as sodium bentonite, or as a salt of alkaline-earth metal, usually calcium or magnesium salt. Usually bentonites alkaline-earth metal activated by treatment with sodium carbonate or sodium bicarbonate. Activated swelling bentonite is often put on paper mill in the form of a dry powder. Alternatively bentonite can be prepared in the form of a fluid slurry of activated bentonite with a high dry matter content, for example at least 15 or 20% of dry matter, in particular as described in EP-A 485124, WO-A 97/33040 and WO-A 97/33041.

In the manufacture of paper bentonite can be added to the pulp suspension in the form of aqueous bentonite compounds, preventing sludge. As a rule, bentonite compounds, preventing the slurry comprises up to 10 wt.% bentonite. Usually bentonite compounds, preventing the slurry includes at least 3% of bentonite, typically about 5 wt.% bentonite. When it is delivered to a paper mill in the form of a fluid slurry with a high content of dry matter, this sludge is usually diluted to the appropriate concentration. In some cases, the fluid is Lam bentonite with a high dry matter content can be entered directly into the fibre pulp for making paper.

Silicon-containing material should be added in quantities of at least 100 miscast./million, calculated on the dry weight of the suspension. The required concentration of silicon-containing material can reach 10000 miscast./million or more. One preferred object of the invention effective concentration is found from 100 to 500 miscast./million another option may be preferred higher concentrations of silicon-containing material, for example from 1000 to 2000 miscast./million

It may be desirable to obtain a water-soluble polymer system to re-flocculation of the water-soluble monomer or mixture of water-soluble monomers. Under the water-solubility is meant that the solubility of the monomer in water is at least 5 g/100 tubes According to another variant of the polymer system to re-flocculation using a natural polymer such as a polysaccharide. As the polysaccharide should be applied starch. Such polymers may be nonionic, cationic, amphoteric, but preferred anionic. The polymers of the system to re-flocculation may be the same or different polymers floculants system.

Water-soluble polymer system to re-flocculation may have any molecular weight, but usually the n shows the characteristic viscosity of at least 1.5 DL/g Water-soluble polymer agent to re-flocculation should be relatively high molecular weight and possess a characteristic viscosity of at least 3 or 4 DL/g, and often its characteristic viscosity is at least 7 or 10 DL/g Characteristic viscosity polymer agent to re-flocculation can reach 25 or 30 DL/g, but usually its characteristic viscosity not greater than 20 DL/g Characteristic viscosity preferred polymeric agent to re-flocculation is typically between 7 and 16 or 17 DL/g, mainly from 8 to 11 or 12 DL/g, This polymer can to be branched, for example in the application of agent education branches, which in the present description were discussed above in regard to the first polymer component floculants system. However, the preferred florulenta system is almost linear, i.e. the polymer is produced essentially in the absence of the agent, the formation of branches.

One object of the invention is a water-soluble polymer agent to re-flocculation is an anionic polymer. This anionic polymer may bear the potential to ionize group, which when introduced into the cellulosic suspension become ionized. However, the preferred polymer is obtained from (m is Nisha least one water-soluble anionic monomer. Preferred anionic polymer is produced from a water soluble monomer or mixture of water-soluble monomers. The mixture of water-soluble monomers may include one or more water-soluble anionic monomers optionally with one or more water-soluble nonionic monomers. Anionic monomers may include ethylene-unsaturated carboxylic acid (including its salt) and the ethylene-unsaturated sulfonic acids (including their salts).

Anionic monomers typically may be selected from acrylic acid, methacrylic acid, 2-acrylamide-2-methylpropanesulfonic acids and their alkali metal salts. Nonionic monomers, optionally mixed with anionic monomers include any water-soluble nonionic monomers which are compatible with anionic monomers. For example, suitable nonionic monomers include acrylamide, methacrylamide, 2-hydroxyethylacrylate and N-vinyl pyrrolidone. Particularly preferred anionic polymers include copolymers of acrylic acid or sodium acrylate with acrylamide. The anionic polymer may include 100% of the links of the anionic monomer or a relatively small number of links anionic monomer, such as 1 wt.% or less. However, it is usually acceptable anionic p is the materials include at least 5% of the links anionic monomer, and often at least 10 wt.% links anionic monomer. Often anionic polymers can include up to 90 or 95 wt.% links anionic monomer. Preferred anionic polymers include the links of anionactive monomer in the range from 20 to 80 wt.%, more preferably contain from 40 to 60 wt.% links anionic monomer.

In another variant implementation of the invention water-soluble polymer agent to re-flocculation is a cationic polymer. This cationic polymer may bear the potential to ionize group, which when introduced into the cellulosic suspension become ionized, such as monomer units, side bearing free amino groups. However, the preferred polymer is obtained from at least one water-soluble cationic monomer. The preferred cationic polymer is produced from a water soluble monomer or mixture of water-soluble monomers. The mixture of water-soluble monomers may include one or more water-soluble cationic monomers optionally with one or more water-soluble nonionic monomers. Cationic monomers include Quaternary ammonium salt aminoalkyl(meth)acrylate, aminoalkyl(meth)acrylamides, diallyldimethylammonium is chloride etc. When the cationic polymer is prepared from a mixture of cationic monomer with a nonionic monomers, suitable nonionic monomers can be any water-soluble nonionic monomers which are compatible with cationic monomers, such as nonionic monomers mentioned above in respect of anionic polymers.

Particularly preferred polymers include copolymers methylchloride stereoselectivity dimethylaminoethylacrylate with acrylamide. The cationic polymer may include only cationactive monomer units or, in other words, may contain a relatively small number of links of the cationic monomer, such as 1 wt.% or less. Typically, the cationic polymer comprises at least 5% of the links of the cationic monomer, and often at least 10 wt.% links cationic monomer. Often cationic polymers can include up to 90 or 95 wt.% links cationic monomer. Preferred cationic polymers include links cationic monomer in the range from 20 to 80 wt.%, and more preferably contain from 40 to 60 wt.% links cationic monomer.

However, according to another variant implementation of the invention water-soluble polymer agent to re-flocculation is an amphoteric floor the measures. This amphoteric polymer may bear the potential to ionize group, which when introduced into the cellulosic suspension become ionized, for example, monomer units bearing side free amino group and/or is able to ionize the acid group. However, the preferred polymer is obtained from at least one water-soluble cationic monomer and at least one anionic monomer. Preferred amphoteric polymer is produced from a water soluble monomer or mixture of water-soluble monomers. The mixture of water-soluble monomers may include one or more water-soluble cationic monomers and one or more water-soluble anionic monomers optionally with one or more water-soluble nonionic monomers.

Cationic monomers include Quaternary ammonium salt aminoalkyl(meth)acrylate, aminoalkyl(meth)acrylamides, diallyldimethylammoniumchloride etc. Anionic monomers may include ethylene-unsaturated carboxylic acid (including its salt) and the ethylene-unsaturated sulfonic acids (including their salts). Anionic monomers typically may be selected from acrylic acid, methacrylic acid, 2-acrylamide-2-methylpropanesulfonic acids and their salts of alkaline metal is. When the amphoteric polymers prepared from a mixture of cationic monomer, an anionic monomer and a nonionic monomer, suitable nonionic monomers can be any water-soluble nonionic monomers which are compatible with anionactive and cationic monomers, such as nonionic monomers mentioned above in respect of anionic polymers. Particularly preferred polymer is a copolymer methylchloride stereoselectivity of dimethylaminoethylacrylate, acrylic acid and acrylamide.

Amphoteric polymer may include a relatively small number of links of the anionic and cationic monomers, such as 1 wt.% or less each. However, usually amphoteric polymer comprises at least 5% of the links anionic monomer and at least 5% of the links of the cationic monomer. In some cases it may be necessary to have more than two links one ionic monomer than the other. So, for example, may require a larger number of links cationic monomer than anionic monomer. Usually amphoteric polymer comprises at least 10 wt.% links cationic monomer, and often more than 20 or 30% cationic links. Preferred amphoteric polymer includes C is Enya cationic monomer in the range from 20 to 80 wt.%, and more preferably contains from 40 to 60 wt.% links cationic monomer. Amphoteric polymer may include at least 20 or 30% anionic monomer unit. It may be necessary presence of the amphoteric polymer of at least 40 or 50 wt.% anionic links. Water-soluble amphoteric polymer may be linear or, in other words, branched, which is achieved, for example, the introduction of the monomer of small quantities of agent education branches, as set forth above in the present description.

Still another variant implementation of the invention water-soluble polymer agent to re-flocculation is a nonionic polymer. As the nonionic polymer may be used any water-soluble polymer with a characteristic viscosity of at least 1.5 DL/g, which is essentially nonionic properties. Nonionic polymer may be polyalkylene, such as polyethylene oxide or polypropyleneoxide, or may be a vinyl polymer obtained stepwise polymerization, which are synthesized from ethylene-unsaturated nonionic monomer or a mixture of ethylene-unsaturated nonionic monomers. Acceptable monomers include acrylamide, methacrylamide, 2-hydroxyethylacrylate and N-vinyl pyrrolidone. Preferred is a nonionic polymers include polyethylene oxide and acrylamide a homopolymer. Water-soluble nonionic polymer may be linear or, in other words, branched, which is achieved, for example, the introduction of the monomer of small quantities of agent education branches, as set forth above in the present description.

Water-soluble polymeric agents to re-flocculation can also be obtained by any convenient method, for example by polymerization in solution, the polymerization in suspension of water in the oil or by polymerization in emulsion of water in oil. The polymers can be obtained in the form of a bead suspension polymerization or emulsion or dispersion of water in oil by polymerization in emulsion of water in oil, for example in accordance with the method described in EP-A 150933, EP-A 102760 or EP-A 126528.

Water-soluble polymer component of the system to re-flocculation add enough to achieve flocculation quantity. The concentration of polymer to re-flocculation, as a rule, certainly more than 20 miscast./million, calculated on the dry weight of the suspension, although it can reach 2000 miscast./million However, in the preferred embodiment, the polymeric agent to re-flocculation enter in the amount of at least 50 miscast./million, for example from 150 to 600 ppm million, mainly in the range from 200 to 400 ppm million

One preferred object of the invention before the add is the group of silicon-containing material flocculated pulp suspension is subjected to mechanical treatment of the shear force. Therefore, before adding a silicon-containing material flocculated slurry can pass through one or more means of shear force, selected from the means for pumping, mixing and cleaning. Therefore, when a liquid suspension of pulp at first localroot adding a cationic polymer, the slurry can pass through at least one of the tools such as a centrifugal pump and centrifugal sorting, and then re-flocculation of silica-containing material. The influence of shear stress leads to mechanical destruction of the flocculated material is a liquid suspension of fibrous masses, resulting in the formation of the flakes smaller. Mechanical destruction of flakes there is also a tendency to acquisition of newly formed surfaces on which the silicon-containing material capable of easily associated, thus enhancing and improving the re-flocculation.

Another preferred object of the invention before adding the water-soluble polymer agent to re-flocculation re-flocculated suspension prepared by adding a silicon-containing material is subjected to mechanical treatment of the shear force. Thus, this re-flocculated suspension m which should pass through one or more of the above-mentioned means of shear force. Mechanical destruction of cereals re-flocculated liquid suspension of fibrous masses tend to decrease their size and due to the acquisition of the newly formed surfaces can be achieved more effectively further flocculation using a water-soluble polymer agent to re-flocculation. Thus, one particularly preferred variant of the liquid suspension of fibrous mass localroot using cationic water-soluble polymer with a characteristic viscosity above 4 DL/g and flocculated suspension is passed through one or more presented in the present description means of shear force, and then processed shear force re-flocculated suspension is treated silicon-containing material with the subsequent machining of the shear force, and then processed shear force re-flocculated liquid suspension of pulp additionally localroot adding a water-soluble polymer agent to re-flocculation with a characteristic viscosity of at least 1.5 DL/g

When implementing this method, a water-soluble polymer agent to re-flocculation usually added as a means of last clicks the processing, whereupon it is added to the system last and often closer to the stage drainage. Thus, the polymer agent to re-flocculation enter after the last point of impact wysokosciowe force, a means which may, for example, to serve centrifugal sorting. Therefore, in a particularly preferred variant of the method of the water-soluble polymer agent to re-flocculation add after centrifugal sorting.

According to another preferred object of the invention between the points of addition of silicon-containing material to achieve the re-flocculation and adding a water-soluble polymer agent to re-flocculation no machining shear force is not carried out. Although machining shear force flocculated suspensions after addition of the water-soluble polymer agent to re-flocculation may be desirable, in this embodiment, after adding the polymer agent to re-flocculation is no significant influence of the shear force is preferable not to perform. Thus, in this preferred object of the invention as silicon-containing material and a water-soluble polymer agent to re-flocculation add after the centrifugal is chiroki.

In all preferred embodiments of carrying out the invention a water-soluble polymer agent to re-flocculation added at the final stage of the process, for example between centrifugal sorting and drainage. Because in accordance with generally accepted point of view of strengthening the structure of the flakes is accompanied by deterioration of the molding process, the surprise was that in the process according to the invention, when the last of the polymeric additive, enabling re-flocculation, injected near the stage drainage of any appreciable deterioration of the molding process however does not happen and meanwhile greatly improve the characteristics of the drainage and retention in comparison with achievable with the implementation of other methods known in the art.

In addition, when performing the invention may need additional floculant or coagulant materials. For example, florulenta system may optionally include a water-soluble organic polymers or inorganic materials, such as alum, polyaluminium, the trihydrate of aluminofluoride and alamoflorida. Water-soluble organic polymers can serve as natural polymers, such as cationic starch, anionic collapse of the al and amphoteric starch. Alternatively a water-soluble polymer may be a synthetic polymer, which could be amphoteric, anionic, nonionic or preferably cationic. As the water-soluble polymer can be used any water-soluble polymer, preferably exhibiting ionic properties. Preferred ionic water-soluble polymers have a cationic or potentially cationic functional groups.

It may be necessary to use in the composition of the cellulose dense fibrous mass or components of a dense fibrous mass addition of cationic coagulant. As such a cationic water-soluble polymer can be used relatively low molecular weight polymer with a relatively high cationactive. For example, this polymer can serve as a homopolymer of any suitable ethylene-unsaturated cationic monomer that is polymerized to obtain a polymer with a characteristic viscosity of up to 3 DL/g Preferred homopolymers of diallyldimethylammoniumchloride. Low molecular weight polymer with high cationactive may be a polymer obtained stepwise polymerization, formed by the polycondensation of amines with other acceptable di - or trifunctional mother who Lamy. For example, this polymer can be obtained by reaction of one or more amines selected from dimethylamine, trimethylamine, Ethylenediamine, etc. with epichlohydrin, and preferred epichlorohydrin. Purpose of the use of such an additional component may be the neutralization of the charge, for example in cases where the fibrous mass has a relatively high cationic demand, in particular in the case of manufacturing newsprint. Alternatively cationic coagulant can promote the curing of the resin and/or adhesive to fix pitch and/or stickles).

Although the inclusion of these additional materials, such as organic cationic coagulants, alum and other inorganic materials, it is possible, they usually need not, therefore, preferred variants of the method is carried out, apparently, in the absence of cationic coagulants.

In one preferred embodiment, after adding at least one of the components floculants system pulp suspension is subjected to mechanical treatment of the shear force. Thus, in this preferred embodiment, at least one component floculants system mix in the pulp suspension, causing flocculation, and then flocculated suspension is subjected to fur the technical processing of the shear force. This stage is the impact of shear stress that can be carried out by passing the flocculated slurry through one or more processing tools shear force, selected from the means for pumping, cleaning and blending. For example, such funds shear processing include centrifugal pumps and centrifugal sorting, but they could be any other tools used in the process, in which the influence of the shear force.

Requires machining of the shear force acting on flocculated suspension in such a way as to destroy the flakes. At the stage of exposure to shear stress, you can add all the components floculants system, although in the preferred embodiment, at least the last component floculants system is introduced into the pulp slurry at the point of the technological process, after which the drainage from the casting sheet significant impact shear force was absent. Therefore, in a preferred embodiment, the pulp suspension add at least one component floculants system, and then flocculated suspension is subjected to mechanical processing shear force, during which the flakes are mechanically destroy, then add at least one component FL is culantro system for re-flocculation of the suspension before drainage.

According to one preferred variant implementation of the present invention proposes a method of making paper from slurry pulp of fibrous mass comprising a filler. The filler may be any of conventionally used filling materials. For example, the filler may be a clay, such as kaolin, or the filler may be calcium carbonate, which you could use powdered calcium carbonate or you may prefer the use of titanium dioxide as a filling material. Examples of other filling materials include synthetic polymeric fillers.

Usually cellulosic fibrous mass comprising substantial amounts of filler, harder flocculating. This is especially true in cases fillers of particles of very small size, such as precipitated calcium carbonate. Thus, in accordance with the preferred object of the present invention proposes a method of manufacturing paper filled with. Fibrous material for the manufacture of paper may include any suitable amount of filler. Usually the pulp suspension comprises at least 5 wt.% filling material. The pulp suspension typically includes up to 40% filler, preferably the number of filler is in the range from 10 to 40%. The required content of the filler in the finished sheet of paper or cardboard up to 40 wt.%. Therefore, in accordance with this preferred object of the present invention proposes a method of manufacturing paper or cardboard, which first proposed the use of pulp suspensions, comprising a filler, and in this suspension of solid particles localroot introduction to suspension floculants system, including a water-soluble polymer with a characteristic viscosity at least 4 DL/g, a silicon-containing material, and then a water-soluble polymer with a characteristic viscosity of at least 1.5 DL/g, as represented in the present description. In another variant implementation of the invention features a method of making paper or paperboard of a suspension of cellulosic fibrous pulp, which contains almost no filler.

The invention is illustrated by the following examples.

Example 1 (comparative)

Drainage properties is determined using an instrument Shopper-Rigler (Schopper-Riegler) with the locked rear hole, resulting in drainage water exits through the front hole. Used cellulosic fibrous mass is a suspension of the pulp of hardwood/softwood 50/50 containing 40 wt.%(in terms of total weight of dry matter) of precipitated calcium carbonate. Before adding the filler suspension of the fibrous mass is crushed to the consistency of grind 55° (determined by the method of Shopper-Rigler). This suspension is injected 5 kg/t (based on the total weight of dry matter) of cationic starch [the degree of substitution (Sz): 0,045].

This fibrous mass is mixed copolymer of acrylamide and methylchloride Quaternary ammonium salts dimethylaminoethylacrylate (mass ratio of 75/25) with a characteristic viscosity greater of 11.0 DL/g (product A), and then after exposure to shear stress using a mechanical stirrer add bentonite. The drainage time in seconds at each concentration of the product and bentonite are given in table 1.

Table 1
Product a (g/t)Bentonite (g/t)
  05001000
 0102--
 500-3427
 1000--14

Example 2

Drainage tests of example 1 is repeated using the product And at a concentration of 500 g/t and bentonite in which concentratie 500 g/t, except that after adding bentonite carry out phase additional exposure to shear stress, followed by the addition of a linear water-soluble anionic copolymer of acrylamide and sodium acrylate (product B) (mass ratio 62,9/37.1) with a characteristic viscosity of 16 DL/g Time drainage are shown in table 2.

Table 2
The concentration of product B (g/g)The drainage time (s)
034
12517
25013
50010

It is obvious that even at a concentration of 125 g/t product B significantly improves drainage.

Example 3

Example 2 is repeated, except that bentonite and product B (anionic polymer) is added simultaneously with achieving similar results.

Example 4

Example 2 is repeated, except that the product B (anionic polymer) is added before the bentonite. The results are better than in the process carried out without product B.

1. Method of making paper or paperboard comprising preparing a pulp suspension, flocculation of the suspension, draining the suspension on the grid casting sheet and following the eyelet of this sheet, in which the pulp suspension localroot the introduction of water-soluble cationic synthetic polymer with a characteristic viscosity at least 4 DL/g, and the flocculated pulp suspension is subjected to mechanical processing shear force and then re-localroot followed by the addition system for the re-flocculation, where the system for re-flocculation includes I) a silicon-containing material and (II) a water-soluble anionic polymer with a characteristic viscosity at least 4 DL/g, characterized in that either the silicon-containing material and water-soluble anionic polymer added to the suspension at the same time, or silicon-containing material is added before or after the introduction of the water-soluble anionic polymer, and silicon-containing material (I) and water-soluble anionic polymer (II) is introduced into the cellulosic suspension after centrifugal sorting and water-soluble cationic synthetic polymer is injected into the diluted pulp suspension.

2. The method according to claim 1, wherein the silicon-containing material is an anionic material in the form of microparticles.

3. The method according to claim 1 or 2, wherein a material comprising silicon-containing material is chosen from the group comprising particles on kremmidiotis basis, credit is medicine the microgels, colloidal silica, a colloidal solution of silicic acid, silica gels, polysilicates, cationic silica, aluminosilicates, polyaluminosilicate, borosilicate, polymorbidity and zeolites.

4. The method according to claim 1 or 2, in which the silicon-containing material is a swellable clay.

5. The method according to claim 4, in which the swellable clay is a clay bentonite compounds, preventing type.

6. The method according to claim 4, in which the swelling clay is chosen from the group comprising hectorite, smectites, montmorillonite, nontronite, saponite, sekonic, gormiti, attapulgite and sepiolites.

7. The method according to any of the preceding paragraphs, in which the water-soluble cationic polymer exhibits a charge density of less than 5 mEq./g, preferably less than 3 mEq./he

8. The method according to any of the preceding paragraphs, in which the water-soluble cationic polymer obtained from water-soluble ethylene-unsaturated monomer or a water-soluble mixture of the ethylene-unsaturated monomers comprising at least one cationic monomer.

9. The method according to any of the preceding paragraphs, in which the water-soluble cationic polymer comprises up to 50 wt.% cationic Monomeric units.

10. The method according to claim 1, in which the water-soluble polymer added to the pulp suspension before you system to re-floccules and, represents a branched water-soluble polymer, which has a characteristic viscosity above 4 DL/g and exhibits a rheological oscillation value of tan Delta at 0.005 Hz 0,7 more (calculated at 1.5 wt.% an aqueous solution of the polymer).

11. The method according to any of the preceding paragraphs, in which the water-soluble cationic polymer has a characteristic viscosity of at least 7 DL/g

12. The method according to any of the preceding paragraphs, in which the water-soluble anionic polymer is an essentially linear water-soluble polymer.

13. The method according to any of the preceding paragraphs, in which the water-soluble anionic polymer has a characteristic viscosity of at least 7 DL/g

14. The method according to any of the preceding paragraphs, in which the water-soluble anionic polymer is produced from water-soluble anionic monomer or a mixture of water-soluble monomers containing one or more water-soluble anionic monomers.

15. The method according to any of the preceding paragraphs, in which the pulp suspension includes a filler.

16. The method according to item 15, in which a sheet of paper or paperboard comprises up to 40 wt.% the filler.

17. The method according to item 15 or 16, in which the filler material is chosen from the group comprising precipitated CT is eat calcium, powdered calcium carbonate, clay (mainly kaolin and titanium dioxide.

18. The method according to any one of claims 1 to 14, in which the pulp suspension contains almost no filler.



 

Same patents:

FIELD: mining industry and mechanical engineering.

SUBSTANCE: the invention is dealt with methods of production of a paper, in particular, with its smoothing. The water suspension containing cellulose fibers and optional fillers (i) add the sizing dispersion containing a sizing agent and a polymer including one or several aromatic groups and (ii) a sizing promoter containing a polymer intercalating one or several aromatic groups. Mould and dry the produced suspension. The sizing dispersion and sizing promoter are added to the water suspension separately. The invention ensures improvement of the process of sizing the cellulose fibers having a high conductivity.

EFFECT: the invention ensures improvement of the process of sizing the cellulose fibers having a high conductivity.

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FIELD: paper industry.

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20 cl, 10 tbl, 8 ex

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11 cl, 4 dwg, 5 tbl, 3 ex

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2 cl, 5 ex, 1 tbl

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