JP5088775B2 - Paper additive and paper making method using the same - Google Patents

Description

The present invention relates to a papermaking additive used in a papermaking process. More specifically, the present invention relates to a papermaking additive capable of improving the strength of paper by being used in a papermaking process and a papermaking method using the same.

Usually, anionicity and amphotericity are used as the paper strength enhancer. Of these, amphoteric paper strength enhancers are conventionally copolymers of acrylamide and N, N-dialkylamino (meth) acrylate or N, N-dialkylamino (meth) acrylamide and (meth) acrylic acid. Have been used. In addition, N, N-methylenebisacrylamide and the like are copolymerized as a cross-linking agent, and more recently, a paper strength enhancer composed of a polymer exhibiting unique solution properties has been developed by copolymerizing N, N-dimethylacrylamide. (Patent Document 1 or Patent Document 2).
In addition, an additive for papermaking of a graft type in which the main chain and the side chain have an ionic bias (Patent Documents 3 and 4), an additive for papermaking related to an ionic polyacrylamide mixture containing N-substituted acrylamide (Patent Document 5) ), An ionic polyacrylamide mixture containing a polyfunctional monomer (Patent Document 6) is disclosed, but in each case, the cationic group portion is mainly composed of (meth) acrylamide, and the spatial density of the cationic group is It was low and the fixability to pulp was not sufficient. In addition, an additive for papermaking comprising a mixture of an amphoteric acrylamide polymer and a non-acrylamide polymer comprising a cationic vinyl monomer as essential components (Patent Document 7), an anionic monomer in the presence of a dispersing agent comprising a cationic polymer The paper strength enhancer (Patent Document 8) obtained by copolymerizing the product and (meth) acrylamide etc. is disclosed, both of which utilize an ion complex, and make paper such as salt and other contaminants. There were problems such as being easily affected by the environment and not being effective.

The paper strength enhancing effect is due to the hydrogen bonding strength between the hydroxyl group in the cellulose molecule and the side chain having hydrogen bonding strength in the paper strength enhancing agent. The molecular weight of the polymer used as a paper strength enhancer also affects the effect. That is, the effect as a paper strength enhancer is not remarkable unless there is a certain molecular weight or more, that is, a molecular weight of several hundred thousand or more. The molecular weight of the paper strength enhancer added to the wet end that has been conventionally used is about several hundred thousand to one million, and the type in which the crosslinkable monomer is copolymerized with this has two million to 500 million. Ten thousand. Since the crosslinkable polymer can reduce the apparent solution viscosity, it can barely maintain a product form of 15-20% by weight as the concentration. However, when the molecular weight is so high, the product concentration is already predicted to be 20% by weight. The product concentration cannot be increased any more in the form of a simple aqueous solution. Therefore, a paper strength enhancer in a form different from the current situation is required. In order to solve this problem, a dispersion polymerization type in an aqueous salt solution has been developed (Patent Document 9).

On the other hand, looking at the current state of the papermaking process, starch-based paper strength enhancers are used in many papermaking sites due to cost and other advantages, but there are problems such as a large amount of use and poor fixability.
Japanese Patent Laid-Open No. 5-140893 JP-A-7-97790 JP 05-195485 JP 07-090797 Japanese Patent Laid-Open No. 10-131085 JP 10-131086 JP 2005-023434 A JP2002-294593 JP 2002-227095 A

An object of the present invention is to provide an additive for papermaking that has a high paper strength enhancing effect when pulp with a high content of used paper is used, or when there are many fine fibers, and as a result can improve paper quality. is there.

The present inventors have intensively studied, in the presence of a cationic polymer having a polymerizable double bond, a nonionic monomer having (meth) acrylamide as a main component and, if necessary, an ionic monomer. It has been found that a complex formed by copolymerizing a body can solve the above problems. Furthermore, it has been found that a particularly remarkable effect is exhibited when the amount of anionic groups and the amount of cationic groups in the composite are in a specific ratio.

The invention of claim 1 is an anionic monomer in the presence of a cationic polymer having a polymerizable double bond formed by polymerizing a monomer having two or more polymerizable double bonds and a cationic monomer. Polymerize 0 to 10 mol% of ionic monomer of 0 to 10 mol% of the body and 0 to 10 mol% of cationic monomer and 80 to 100 mol% of copolymerizable nonionic monomer mainly composed of (meth) acrylamide A paper strength enhancer comprising a composite obtained by performing the process, wherein the amount of the anionic group and the amount of the cationic group in the composite satisfy the following formulas (1) and (2): It relates to a potentiator .
(1) (Amount of cationic group derived from cationic monomer) / (Amount of anionic group derived from anionic monomer) <1 (molar ratio)
(2) (amount of anionic group derived from anionic monomer) / (amount of cationic group derived from cationic polymer + amount of cationic group derived from cationic monomer) <1 (molar ratio) is there.

In the invention of claim 2, the amount of the cationic polymer having a polymerizable double bond is 5 to 30% by weight with respect to the sum of the total amount of monomers and the amount of the cationic polymer. The present invention relates to a paper strength enhancer .

The invention of claim 3 is characterized in that the ionic monomer is only an anionic monomer and the ratio of the amount of anionic group to the amount of cationic group satisfies the following formula (3). It relates to the paper strength enhancer described.
(3) (Amount of anionic group derived from anionic monomer) / (Amount of cationic group in cationic polymer) <1 (molar ratio)

The invention according to claim 4 is characterized in that the monomer polymerized in the presence of a cationic polymer having a polymerizable double bond is a nonionic monomer having (meth) acrylamide as a main component. Or it relates to the paper strength enhancer of 2.

In the invention of claim 5, the cationic polymer having a polymerizable double bond is a copolymer of a monomer having a tertiary amino group and a monomer having two or more polymerizable double bonds. It relates to the paper strength enhancer in any one of Claims 1-4 characterized by the above-mentioned.

The invention according to claim 6 relates to the paper strength enhancer according to any one of claims 1 to 5 , wherein the polymerization method is dispersion polymerization in which a salt is allowed to coexist during polymerization.

The paper additive of the present invention is a composite composed of a polymer in which a polymer portion that expresses paper strength is grafted to a cationic polymer portion having a high cationic group density, and therefore has a fixability to pulp. It is good, and therefore exhibits a high paper strength enhancing effect. In addition, it exerts a high paper strength enhancing effect without being affected by the quality of the papermaking raw material. That is, by using the papermaking additive of the present invention, a high paper strength enhancing effect can be expected even in raw pulp having a high content of used paper, raw pulp having a large amount of fine components, raw pulp having a high salt concentration, and the like.

The papermaking additive of the present invention can be obtained by any method of solution polymerization, emulsion polymerization, and dispersion polymerization. Dispersion polymerization is particularly preferred from the viewpoint of polymer concentration, good dissolution, etc. of the obtained product, but is not limited thereto. Hereinafter, the dispersion polymerization type papermaking additive will be described. This papermaking additive comprises a monomer mixture comprising a nonionic monomer comprising (meth) acrylamide as a main component and an anionic monomer and a cationic monomer as necessary. In particular, a polymer composite produced by a dispersion polymerization method in the presence of a dispersant composed of a cationic polymer having a polymerizable double bond. A water-soluble polymer comprising a polymer fine particle dispersion dispersed in an aqueous salt solution can be produced according to Japanese Patent Application Laid-Open No. 62-15251. In this method, an ionic monomer or an ionic monomer and a nonionic monomer are stirred in a salt aqueous solution in the presence of a dispersant composed of an ionic polymer soluble in the salt aqueous solution. A dispersion of polymer fine particles having a particle diameter of 100 μm or less can be produced.

Next, a specific manufacturing method will be described. The inorganic salts constituting the aqueous salt solution are more preferably polyvalent anion salts, and sulfates or phosphates are suitable. Specifically, ammonium sulfate, sodium sulfate, magnesium sulfate, aluminum sulfate, ammonium hydrogen phosphate, sodium hydrogen phosphate And potassium hydrogen phosphate. These salts are preferably used as an aqueous solution having a concentration of 15% or more. In this, the monomers are dissolved, and further, a dispersing agent composed of a cationic polymer having a polymerizable double bond is allowed to coexist, and after adjusting the pH to 2 to 5, after substitution with nitrogen, a polymerization initiator is used. Start the polymerization.

The polymerization concentration is 15% to 35% by weight as the monomer concentration, but preferably 20% to 30% by weight. As the monomer supply method, polymerization may be started or batched, or may be divided and supplied as appropriate.

Examples of the anionic monomer include (meth) acrylic acid, itaconic acid, maleic acid, styrene sulfonic acid, acrylamide 2-methylpropane sulfonic acid and the like. Examples of tertiary amino group-containing cationic monomers among the cationic monomers include dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylamide, diethylamino And propyl (meth) acrylamide. Examples of the quaternary ammonium base-containing cationic monomer include (meth) acryloyloxyethyltrimethylammonium chloride, (meth) acryloyloxyethyldimethylbenzylammonium chloride, (meth) acryloylaminopropylacryloyloxyethyltrimethylammonium chloride, (Meth) acryloylaminopropylacryloyloxyethyldimethylbenzylammonium chloride, (meth) acryloyloxy 2-hydroxypropyltrimethylammonium chloride and the like can be mentioned. Further, diallylmethylamine, diallylbenzylamine, diallyldimethylammonium chloride, diallylmethylbenzylammonium chloride and the like can be mentioned.

It is also a useful method to modify the polymer by appropriately copolymerizing other copolymerizable nonionic monomers. Examples of such monomers include N, N-dimethylacrylamide, vinyl acetate, acrylonitrile, methyl acrylate, 2-hydroxyethyl (meth) acrylate, diacetone acrylamide, N-vinylpyrrolidone, N-vinylformamide. N-vinylacetamide and the like.

A cationic polymer having a double bond that coexists at the time of polymerization is obtained by copolymerizing a cationic monomer and a monomer having two or more polymerizable double bonds. It is considered that the polymerizable double bond incorporated into the polymer is less reactive and partly remains even after the completion of copolymerization. Examples of such cationic monomers include (meth) acryloyloxyethyltrimethylammonium chloride, (meth) acryloylaminopropyltrimethylammonium chloride, dimethyldiallylammonium chloride, dimethylaminoethyl (meth) acrylate, diethylaminoethyl. (Meth) acrylate, dimethylaminopropyl (meth) acrylamide, diethylaminopropyl (meth) acrylamide and the like. From the viewpoint of paper strength, a cationic monomer having a tertiary amino group is preferred. Examples of monomers having two or more polymerizable double bonds include bis (meth) acrylamides such as methylene bis (meth) acrylamide and ethylene bis (meth) acrylamide, ethylene glycol di (meth) acrylate, diethylene glycol di Examples include (meth) acrylates, di (methacrylates) such as triethylene glycol di (meth) acrylate, divinylbenzene, triallyl isocyanurate, trimethylolpropane tri (meth) acrylate, and pentaerythritol tetraacrylate. Among these monomers having two or more polymerizable double bonds, the most preferable one is
Methylenebisacrylamide.

The content of the monomer having two or more polymerizable double bonds is preferably 0.005% by weight to 0.5% by weight with respect to the amount of the cationic monomer. More preferably, it is 0.01 wt%-0.3 wt%. When the amount is 0.005% by weight or less, the formation of the composite is insufficient and the effect of increasing paper strength is reduced. If it exceeds 0.5% by weight, gelation occurs during polymerization, and the effect of increasing paper strength decreases.

The addition amount of the compound is preferably 0.005% by weight to 0.5% by weight with respect to the cationic polymer having a tertiary amino group. More preferably, it is 0.01 weight%-0.3 weight%. If it is 0.001% by weight or less, the formation of the composite becomes insufficient and the effect of increasing paper strength is reduced. If it exceeds 0.5% by weight, gelation occurs during polymerization, and the effect of increasing paper strength decreases. The reaction between the cationic polymer and the functional group having reactivity with the cationic polymer and the compound having a polymerizable double bond is carried out under ordinary conditions.

The molecular weight of the cationic polymer is preferably 10 to 5 million. In the case of dispersion polymerization in salt water, if the molecular weight is high, the viscosity of the dispersion becomes high, which is not preferable. Accordingly, the molecular weight is preferably from 100,000 to 1,000,000, more preferably from 100,000 to 500,000. Moreover, when carrying out aqueous solution polymerization, since the problem of a viscosity is not so related, 10-5 million are preferable, More preferably, it is 10-5 million.

The addition amount of these cationic polymers is 2 to 35% by weight, preferably 5 to 30% by weight, based on the sum of the total amount of monomers and the cationic polymer weight. If it is 2% or less, there is no effect as an additive for papermaking, and if it is 35% or more, it is disadvantageous in terms of cost.

The effect of the papermaking additive of the present invention is that the positively charged composite as a whole is fixed to the pulp by the interaction with the negatively charged pulp, and exhibits an effect of increasing paper strength.
Therefore,
(Amount of anionic group derived from anionic monomer) / (Amount of cationic group derived from cationic polymer + Amount of cationic group derived from cationic monomer) <1 (molar ratio)
It is preferable that In addition, when the amount of anionic group derived from an anionic monomer at the time of polymerization is less than the amount of cationic group derived from a cationic monomer, not only the cationic polymer portion but also the entire complex is adsorbed to the pulp. Therefore, the sufficient paper strength increasing effect is not exhibited. Therefore, more preferably, at the time of polymerization, a composite is obtained by polymerizing a nonionic monomer having an acrylamide as a main component and an anionic monomer, or by polymerizing only a nonionic monomer having an acrylamide as a main component. It is preferable to obtain

It is preferable that the content of (meth) acrylamide, which has a large contribution to increasing paper strength, is preferable, but some polymers that could not form a graft structure with a cationic polymer having a double bond contribute to increasing paper strength. For this purpose, an ionic monomer may be added. The amount of (meth) acrylamide is preferably 80 to 100 mol% of the whole monomer. When adding an anionic monomer and a cationic monomer, 0-10 mol% is respectively preferable.

The polymerization conditions are usually appropriately determined according to the monomer used and the copolymerization mol%, and the temperature is in the range of 0 to 100 ° C. For the initiation of polymerization, a radical polymerization initiator is used. These initiators may be either oil-soluble or water-soluble, and can be polymerized by any of azo, peroxide, and redox systems. Examples of oil-soluble azo initiators are 2,2′-azobisisobutyronitrile, 1,1′-azobis (cyclohexanecarbonitrile), 2,2′-azobis (2-methylbutyronitrile), 2,2′-azobis (2-methylpropionate), 4,4-azobis (4-methoxy-2,4dimethyl) valeronitrile and the like are mentioned and dissolved in a water-miscible solvent and added.

Examples of water-soluble azo initiators include 2,2′-azobis (amidinopropane) dichloride, 2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] And dihydrochloride, 4,4′-azobis (4-cyanovaleric acid), and the like. Examples of redox systems include a combination of ammonium peroxodisulfate and sodium sulfite, sodium hydrogen sulfite, trimethylamine, tetramethylethylenediamine, and the like. Further examples of peroxides include ammonium or potassium peroxodisulfate, hydrogen peroxide, benzoyl peroxide, lauroyl peroxide, octanoyl peroxide, succinic peroxide, t-butylperoxy 2-ethylhexanoate, and the like. I can give you. Most preferred among these initiators are 2,2′-azobis (amidinopropane) dihydrochloride, 2,2′-azobis [2- (5-methyl-2-imidazoline), which is a water-soluble azo initiator. -2-yl) propane] dihydrochloride.

The paper additive of the present invention exhibits excellent effects such as an increase in paper strength by itself, but the effect of the cationic starch can be further improved by using it together with the cationic starch.

The papermaking additive used in the present invention is generally diluted with water to form a uniform aqueous solution and then added to the papermaking raw material before papermaking. Usually, the polymer concentration is diluted to 0.1 to 2% by weight. When used in combination with cationic starch, the order of addition may be the addition of the cationic starch-based paper strength enhancer followed by the addition of the paper additive of the present invention, or in advance with the cationic starch-based paper strength enhancer. The dissolved paper additive of the present invention may be added after mixing. The amount of addition is 0.03 to 0.5% by weight with respect to the dry solid content of the papermaking raw material.

(Examples) Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist.

(Production Example 1 of Cationic Polymer) 217.6 g of deionized water, 60.0 g of dimethylaminoethyl methacrylate, 95% in a four-necked 500 ml separable flask equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen introduction tube 19.7 g of sulfuric acid, 0.15 g of sodium hypophosphite, and 0.03 g of methylenebisacrylamide were added to obtain a uniform mixed solution. Thereafter, nitrogen is introduced from the nitrogen introduction tube while stirring to remove dissolved oxygen. During this time, the internal temperature is adjusted to 33 to 35 ° C. using a constant temperature water bath. 30 minutes after introduction of nitrogen, 0.048 g of 2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride (based on monomer, 800 ppm) was added to initiate polymerization. I let you. Polymerization was continued for 7 hours to complete the reaction. This is a 20% cationic polymer 1 aqueous solution.

(Cationic polymer production example 2) Production was carried out in the same manner as in Cationic polymer production example 1 except that 0.01 g of methylenebisacrylamide was used. This is designated as 20% cationic polymer 2 aqueous solution.

(Production Example 3 of Cationic Polymer) 216.8 g of deionized water, 60.0 g of dimethylaminoethyl methacrylate, 95% in a four-necked 500 ml separable flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen introduction tube 19.7 g of sulfuric acid, 0.54 g of methallylsulfonic acid, and 0.06 g of methylenebisacrylamide were added to obtain a uniform mixed solution. Thereafter, nitrogen is introduced from the nitrogen introduction tube while stirring to remove dissolved oxygen. During this time, the internal temperature is adjusted to 33 to 35 ° C. using a constant temperature water bath. 30 minutes after the introduction of nitrogen, 0.048 g of 2,2′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride (based on monomer, 800 ppm) was added for polymerization. Started. Polymerization was continued for 7 hours to complete the reaction. This is 20% cationic polymer 3 aqueous solution.

(Cationic polymer production example 5) Production was performed in the same manner as in Cationic polymer production example 3 except that 0.3 g of methallylsulfonic acid and 0.03 g of methylenebisacrylamide were used. This is designated as 20% cationic polymer 5 aqueous solution.

(Cationic polymer production example 6) Production was carried out in the same manner as in Cationic polymer production example 1 except that sodium hypophosphite was 0.24 g and methylenebisacrylamide was 0.18 g. This is a 20% cationic polymer 6 aqueous solution.

(Comparative Production Example 1 of Cationic Polymer)
Production was carried out in the same manner as in Cationic Polymer Production Example 1 except that methylenebisacrylamide was not used. This is a 20% comparative cationic polymer 1 aqueous solution.

(Comparative Production Example 2 of Cationic Polymer) A cationic polymer was produced in the same manner as in Cationic Polymer Production Example 3 except that methylenebisacrylamide was not added. This is designated as a 20% comparative cationic polymer 2 aqueous solution.

In a four-necked 500 ml separable flask equipped with a stirrer, reflux condenser, thermometer and nitrogen inlet tube, 48.4 g of deionized water, 69.6 g of ammonium sulfate, 2.4 g of sodium chloride, 5.07 g of 60% acrylic acid, 50 % Acrylamide (113.9 g) was added to obtain a uniform mixed solution, 60 g of 20% cationic polymer 1 aqueous solution (20% by weight of monomer), and sodium hypophosphite (0.06 g) as a polymerization degree regulator Body 0.1% by weight) was added and completely dissolved. Thereafter, nitrogen is introduced from the nitrogen introduction tube while stirring to remove dissolved oxygen. During this time, the internal temperature is adjusted to 33 to 35 ° C. using a constant temperature water bath. 30 minutes after nitrogen introduction, 2,48'-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride 0.0048 g (with respect to monomer, 80 ppm) was added for polymerization. Started. After 5 hours from the start of polymerization, 0.012 g of the initiator was added, and the polymerization was continued for 15 hours to complete the reaction. This is referred to as Production Example 1. The viscosity was measured to obtain a measure for the molecular weight of the polymer composite. When this Production Example 1 was dissolved so that the polymer composite was 2%, the viscosity was 98 mPas.

Production was carried out in the same manner as in Production Example 1, except that 20% cationic polymer 2 aqueous solution was used instead of 20% cationic polymer 1 aqueous solution. This is referred to as Production Example 2. When this Production Example 2 was dissolved so that the polymer composite was 2%, the viscosity was 111 mPas.

Production was carried out in the same manner as in Production Example 1, except that 48.8 g of deionized water, 7.09 g of 60% acrylic acid and 111.5 g of 50% acrylamide were used. This is referred to as Production Example 3. When this Production Example 3 was dissolved so that the polymer composite was 2%, the viscosity was 68 mPas.

In a four-neck 500 ml separable flask equipped with a stirrer, reflux condenser, thermometer and nitrogen inlet tube, deionized water: 48.6 g, ammonium sulfate 69.6 g, sodium chloride 2.4 g, 60% acrylic acid 5.07 g, Add 113.9 g of 50% acrylamide to make a homogeneous mixed solution, 60 g of 20% cationic polymer 3 aqueous solution (20% by weight of monomer), 0.12 g of sodium hypophosphite as a polymerization degree regulator 0.2% by weight of the monomer and 0.3 g of methallylsulfonic acid (0.5% by weight of the monomer) were added and completely dissolved. Thereafter, nitrogen is introduced from the nitrogen introduction tube while stirring to remove dissolved oxygen. During this time, the internal temperature is adjusted to 33 to 35 ° C. using a constant temperature water bath. 30 minutes after nitrogen introduction, 2,48'-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride 0.0048 g (with respect to monomer, 80 ppm) was added for polymerization. Started. After 5 hours from the start of polymerization, 0.012 g of the initiator was added, and the polymerization was continued for 15 hours to complete the reaction. This is referred to as Production Example 4. When this Production Example 4 was dissolved so that the polymer composite was 2%, the viscosity was 36 mPas.

In a four-neck 500 ml separable flask equipped with a stirrer, reflux condenser, thermometer and nitrogen inlet tube, deionized water: 48.3 g, ammonium sulfate 69.6 g, sodium chloride 2.4 g, 60% acrylic acid 3.04 g, Add 116.4 g of 50% acrylamide to make a uniform mixed solution, 60 g of 20% cationic polymer 5 aqueous solution (20% by weight of monomer), 0.06 g of sodium hypophosphite as a polymerization degree regulator (per unit amount) Body 0.1% by weight) and methallylsulfonic acid 0.3g (0.5% by weight monomer) were added and completely dissolved. Thereafter, nitrogen is introduced from the nitrogen introduction tube while stirring to remove dissolved oxygen. During this time, the internal temperature is adjusted to 33 to 35 ° C. using a constant temperature water bath. 30 minutes after nitrogen introduction, 2,48'-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride 0.0048 g (with respect to monomer, 80 ppm) was added for polymerization. Started. After 5 hours from the start of polymerization, 0.012 g of the initiator was added, and the polymerization was continued for 15 hours to complete the reaction. This is referred to as Production Example 6. When this Production Example 6 was dissolved so that the polymer composite was 2%, the viscosity was 63 mPas.

Production was carried out in the same manner as in Production Example 6 except that 47.8 g of deionized water, 1.01 g of 60% acrylic acid, and 118.8 g of 50% acrylamide were used. This is designated as Production Example 7. When this Production Example 7 was dissolved so that the polymer composite was 2%, the viscosity was 58 mPas.

Production was carried out in the same manner as in Production Example 6 except that 47.6 g of deionized water, 120.0 g of 50% acrylamide, and acrylic acid were not used. This is designated as Production Example 8. When this Production Example 8 was dissolved so that the polymer composite was 2%, the viscosity was 64 mPas.

Deionized water: 76.00 g, 60% acrylic acid 3.38 g, 50% acrylamide 79.95 g was added to a four-necked 500 ml separable flask equipped with a stirrer, reflux condenser, thermometer and nitrogen inlet tube. As a mixed solution, 40 g of 20% cationic polymer 3 aqueous solution (20% by weight of monomer) and 1.6 g of methallylsulfonic acid (4.0% by weight of monomer) as a polymerization degree regulator were added, It was completely dissolved. Thereafter, nitrogen is introduced from the nitrogen introduction tube while stirring to remove dissolved oxygen. During this time, the internal temperature is adjusted to 33 to 35 ° C. using a constant temperature water bath. 30 minutes after nitrogen introduction, 2,32′-azobis [2- (5-methyl-2-imidazolin-2-yl) propane] dihydrochloride 0.0032 g (against monomer, 80 ppm) was added for polymerization. Started. After 5 hours from the start of polymerization, 0.008 g of the initiator was added, and the polymerization was further continued for 15 hours to complete the reaction. This is referred to as Production Example 9. When this Production Example 9 was dissolved so that the polymer composite was 2%, the viscosity was 7 mPas.

Production was performed in the same manner as in Production Example 1, except that 20% cationic polymer 6 aqueous solution was used instead of 20% cationic polymer 1 aqueous solution. This is designated as Production Example 10. When this Production Example 10 was dissolved so that the polymer composite was 2%, the viscosity was 122 mPas.

(Comparative Production Example 1) Production was carried out in the same manner as in Production Example 1, except that 20% cationic polymer 1 aqueous solution was used instead of 20% cationic polymer 1 aqueous solution. This is referred to as Comparative Production Example 1. When this comparative production example 1 was dissolved so that the polymer composite was 2%, the viscosity was 83 mPas.

(Comparative Production Example 2) Production was performed in the same manner as in Production Example 4 except that 20% cationic cationic polymer 2 aqueous solution was used instead of 20% cationic polymer 3 aqueous solution. This is referred to as Comparative Production Example 2. When this comparative production example 2 was dissolved so that the polymer composite was 2%, the viscosity was 17 mPas. Table 1 shows the main conditions of the production examples and comparative production examples.

( Table 1 )
DMM: dimethylaminoethyl methacrylate (mol% in the complex)
MBAA: Methylenebisacrylamide (vs. DMM wt%)
AAC: Acrylic acid (mol% in complex)
AAM: Acrylamide (mol% in complex)
A / C: molar ratio of the amount of anionic groups to the amount of cationic groups in the composite 2% Solution viscosity: mPas

Using LBKP beaten to 400 ml Canadian Standard Freeness, a papermaking test was conducted using the papermaking additive of the present invention. After adjusting LBKP to a concentration of 1.0%, the pH was adjusted to 7.5 with sulfuric acid. To this papermaking raw material, the additive for papermaking of Production Examples 1 to 3 diluted to 1% and the additive for papermaking of Comparative Production Example 1 were added so as to be 0.5% based on the pulp, and stirred for 30 seconds. After that, paper is made with a tappi standard sheet machine so that the basis weight is 80 g / m 2, and the obtained wet paper is pressed at 4 kg / cm 2 for 3 minutes and then dried with a 105 ° C. rotary dryer for 3 minutes to obtain hand-made paper. It was. The hand-made paper was conditioned at 20 ° C. and 65% HR for 24 hours, and then the specific burst strength was measured according to JIS: P8112. The results are shown in Table 2. The paper additive produced using a cationic polymer having a polymerizable double bond showed higher strength than that produced using a cationic polymer having no double bond.

Using LBKP beaten to 400 ml Canadian Standard Freeness, a papermaking test was conducted using the papermaking additive of the present invention. After adjusting LBKP to a concentration of 1.0%, commercial calcium carbonate is added to the pulp at 15%, aluminum sulfate (8.0% as Al2O3) to pulp at 1.2%, and sulfuric acid is adjusted to pH 7.5. It was adjusted. 30 seconds after adding the papermaking additive of Production Example 4 and 6 to 10 diluted to 1% to this papermaking raw material and the papermaking additive of Comparative Production Example 2 to 0.1% with respect to the pulp The mixture was stirred, and a commercial yield agent (ND200C manufactured by Hymo Co., Ltd.) was added to 200 ppm with respect to the pulp, followed by stirring for 30 seconds. After that, paper is made with a tappi standard sheet machine so that the basis weight is 80 g / m 2, and the obtained wet paper is pressed at 4 kg / cm 2 for 3 minutes and then dried with a 105 ° C. rotary dryer for 3 minutes to obtain hand-made paper. It was. The hand-made paper was conditioned at 20 ° C. and 65% HR for 24 hours, and then the specific burst strength was measured according to JIS: P8112. The results are shown in Table 3. The paper additive produced using a cationic polymer having a polymerizable double bond showed higher strength than that produced using a cationic polymer having no double bond.

Table 2 (Example 11)

Table 3 (Example 12)

Claims (6)

In the presence of a cationic polymer having a polymerizable double bond formed by polymerizing a monomer having two or more polymerizable double bonds and a cationic monomer, 0 to 10 mol% of an anionic monomer It is obtained by polymerizing a monomer mixture having a composition consisting of 0 to 10 mol% of a cationic monomer and 80 to 100 mol% of a copolymerizable nonionic monomer mainly composed of (meth) acrylamide. A paper strength enhancer comprising a composite , wherein the amount of anionic groups and the amount of cationic groups in the composite satisfy the following formulas (1) and (2) .
(1) (Amount of cationic group derived from cationic monomer) / (Amount of anionic group derived from anionic monomer) <1 (molar ratio)
(2) (Amount of anionic group derived from anionic monomer) / (Amount of cationic group derived from cationic polymer + Amount of cationic group derived from cationic monomer) <1 (molar ratio) The paper strength enhancer according to claim 1, wherein the amount of the cationic polymer having a polymerizable double bond is 5 to 30% by weight based on the sum of the total amount of the monomer and the amount of the cationic polymer. The paper strength enhancement according to claim 1 or 2, wherein the ionic monomer is only an anionic monomer, and the ratio of the anionic group amount to the cationic group amount satisfies the following formula (3): Agent .
(3) Anionic group amount derived from anionic monomer) / (Cation group amount in cationic polymer) <1 (molar ratio) The paper strength according to claim 1 or 2, wherein the monomer that is polymerized in the presence of a cationic polymer having a polymerizable double bond is a nonionic monomer having (meth) acrylamide as a main component. Enhancer . The cationic polymer having a polymerizable double bond is a copolymer of a monomer having a tertiary amino group and a monomer having two or more polymerizable double bonds. Item 5. The paper strength enhancer according to any one of Items 1 to 4 . The paper strength enhancer according to any one of claims 1 to 5 , wherein the polymerization method is dispersion polymerization in which a salt is allowed to coexist during polymerization.