JP7453648B2 - New paper strength agent - Google Patents

Description

The present invention relates to a paper strength agent used in the manufacture of paper.

Polyacrylamide-based paper strength agents have conventionally been used as paper strength agents that impart strength to paper. Polyacrylamide paper strength agents are classified into anionic types, cationic types, and amphoteric types depending on their ionicity. Currently, from the viewpoint of performance, amphoteric paper strength agents are the mainstream. Amphoteric type polyacrylamide paper strength agents are made of amphoteric acrylamide water-soluble polymers obtained by copolymerizing acrylamide with various polymerization components such as cationic monomers and anionic monomers (Patent Document 1). The amphoteric acrylamide water-soluble polymer forms a polyion complex. Polyion complexes are formed by electrostatic interactions between cationic and anionic groups. It is known that amphoteric acrylamide water-soluble polymers exhibit paper strength enhancing effects by forming polyion complexes.

In recent years, as waste paper has become more recycled and closed, fine fibers and dissolved electrolyte substances have accumulated within the papermaking system, and the electrical conductivity of the papermaking system has been on the rise. For this reason, particularly with amphoteric paper strength agents, the formation of ionic complexes is inhibited, resulting in a situation where sufficient effects cannot be exhibited.

On the other hand, it is known that water-soluble polymers having hydrophobic groups in their molecules form aggregates in water (Non-Patent Document 1). Since hydrophobic aggregates are formed by hydrophobic interactions, their formation is not inhibited by the presence of dissolved electrolytes.

Reactive surfactants are examples of polymerizable monomers having hydrophobic groups. Techniques (Patent Documents 2 and 3) have been disclosed in which a reactive surfactant is added in order to suppress the wrapping phenomenon of an aqueous polymer solution around a stirring shaft during the production of a paper strength agent. This technology is intended to suppress the wrapping phenomenon of an aqueous polymer solution around a stirring shaft during polymerization, and does not involve adding a reactive surfactant to improve the performance of polymerized polymers. In addition, an aqueous polymer composition consisting of a mixture of an aqueous polymer copolymerized with a reactive surfactant and a polymerizable monomer and polymer fine particles has excellent mechanical, chemical, and storage stability, and is suitable for coated paper. It has been disclosed that when used, surface strength, internal strength, printability, etc. are improved (Patent Document 4). This technology requires polymer fine particles and is aimed at surface coating agents. Furthermore, an internally added papermaking additive containing a (meth)acrylamide-based copolymer having a synthetic resin emulsion and a reactive surfactant as copolymerization components is disclosed (Patent Document 5). The purpose of this technique is to improve the dispersibility of synthetic resin emulsions and the fixability to fibers.

JP2012-251252A Japanese Unexamined Patent Publication No. 2-8207 Japanese Unexamined Patent Publication No. 2-104796 Japanese Patent Application Publication No. 10-120711 Japanese Patent Application Publication No. 11-189988 Kobunshi Vol. 46, March issue (1997), paragraphs 128-131

The purpose of the present invention is to solve the problems of commonly used amphoteric paper strength agents and to provide a new type of paper strength agent that is less susceptible to the effects of ionic impurities and has an excellent paper strength enhancement effect. It is in.

As a result of extensive studies, the present inventor found that a reactive surfactant, (meth)acrylamide, and a cationic monomer are essential components, and a monomer that is obtained by polymerizing a monomer that does not contain a hydrophobic monomer. We have discovered that polymers exhibit excellent paper strength enhancement effects.

According to the present invention, it is possible to obtain a paper strength agent that has an excellent paper strength increasing effect and has a novel structure that has not been seen before.

The present invention will be explained in detail below.

The polymer of the present invention contains a reactive surfactant, (meth)acrylamide, and a cationic monomer as essential components, and is obtained by polymerizing monomers that do not contain hydrophobic monomers. Polymerization can be carried out by conventionally known methods such as aqueous solution polymerization, suspension polymerization, and dispersion polymerization in salt water. For example, the desired polymer can be obtained by adding a monomer mixture, water, and a radical polymerization initiator to a predetermined reaction vessel, stirring and heating the mixture in an inert gas atmosphere such as nitrogen gas.

式（１）
ここで、ｍは１～３の整数、ｎは１０～１０００の整数

式（２）
ここで、ｍは１～３の整数、ｎは３～１０００の整数、Ｋはアルカリ金属、アルカリ土類金属、アンモニウム基またはアルカノールアミン基

式（３）
ここで、ｎは３～１０００の整数、Ｋはアルカリ金属、アルカリ土類金属、アンモニウム基またはアルカノールアミン基 Here, the reactive surfactant is a monomer that has a substituent having a radically polymerizable ethylenic double bond in one molecule and functions as a surfactant. Examples of the reactive surfactant include polyoxyethylene styrenated propenyl phenyl ether represented by the following formula (1) (Daiichi Kogyo Seiyaku Co., Ltd., Aqualon AN-10 (average value of n: 10), AN-20 ( n average value 20), AN-30 (n average value 30), etc.), polyoxyethylene styrenated propenyl phenyl ether sulfate salt represented by the following formula (2) (Aqualon AR manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) -10 (average value of n: 10), AR-20 (average value of n: 20), etc.), polyoxyethylene nonylpropenyl phenyl ether sulfate salt represented by the following formula (3) (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) Aqualon BC-10 (average value of n: 10), BC-20 (average value of n: 20), etc.), octoxypolyethylene glycol polypropylene glycol mono(meth)acrylate, lauroxypolyethylene glycol mono(meth)acrylate, stearoxypolyethylene Examples include glycol mono(meth)acrylate, polyoxyalkylene alkenyl ether ammonium sulfate, and the like. It is also possible to combine two or more of these. The amount of the reactive surfactant is 0.5% by mass to 15% by mass or less, based on the total monomers, preferably more than 1% by mass to 15% by mass or less, and more preferably 5 to 10% by mass. be. A polymer obtained by copolymerizing a reactive surfactant, acrylamide, and a cationic monomer forms a hydrophobic aggregate in water, improving the paper strength enhancement effect. If the amount of the reactive surfactant is small, the copolymerization with acrylamide and the cationic monomer will be insufficient, resulting in insufficient formation of hydrophobic aggregates, and the paper strength enhancing effect will be reduced. Moreover, when the amount of reactive surfactant is large, the amount of acrylamide is reduced, and the bonding force due to hydrogen bonding with pulp is reduced, resulting in a reduction in paper strength enhancement effect.

Formula (1)
Here, m is an integer from 1 to 3, and n is an integer from 10 to 1000.

Formula (2)
Here, m is an integer of 1 to 3, n is an integer of 3 to 1000, and K is an alkali metal, an alkaline earth metal, an ammonium group, or an alkanolamine group.

Formula (3)
Here, n is an integer from 3 to 1000, K is an alkali metal, an alkaline earth metal, an ammonium group, or an alkanolamine group.

Examples of the cationic monomer include salts of inorganic or organic acids such as dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylamide, diethylaminopropyl (meth)acrylamide, or salts of these acids. Examples include monomers having quaternary ammonium salts obtained by reacting a tertiary amino group-containing monomer with a quaternizing agent such as methyl chloride, benzyl chloride, dimethyl sulfate, or epichlorohydrin. Among these, monomers having a quaternary ammonium salt include (meth)acryloyloxyethyltrimethylammonium chloride, (meth)acryloyloxyethyldimethylbenzylammonium chloride, and the like. The amount of the cationic monomer is preferably 3 to 30% by weight, more preferably 5 to 25% by weight based on the total monomers. If the amount of the cationic monomer is small, the adsorption to the pulp will decrease and the paper strength enhancement effect will decrease. Furthermore, if the amount of the cationic monomer is too large, the amount of acrylamide will decrease, the bonding strength due to hydrogen bonding with the pulp will decrease, and the paper strength enhancement effect will decrease.

The copolymer related to the paper strength agent of the present invention can further contain nonionic monomers other than acrylamide, anionic monomers, crosslinkable monomers, etc. as polymerization components. The total amount of these is preferably 20% by mass or less of the total monomers. The polymer used in the paper strength agent of the present invention does not contain a hydrophobic monomer as a polymerization component. Here, the hydrophobic monomer means a monomer having a solubility in water at 20° C. of 2% by mass or less. Examples of hydrophobic monomers include butyl (meth)acrylate, octyl (meth)acrylate, stearyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, dodecyl (meth)acrylate, octadecyl (meth)acrylate, Examples include styrene.

Examples of nonionic monomers other than acrylamide include dimethylacrylamide, vinylformamide, and hydroxyethyl (meth)acrylate. It is also possible to combine two or more of these.

Examples of anionic monomers include monocarboxylic acid monomers such as (meth)acrylic acid and crotonic acid, dicarboxylic acid monomers such as maleic acid and itaconic acid, and 2-acrylamido-2-methylpropanesulfonic acid. Examples include organic sulfonic acid monomers, alkali metal salts such as sodium salts, ammonium salts, and the like. It is also possible to combine two or more of these.

Examples of the crosslinkable monomer include methylene bisacrylamide, ethylene glycol di(meth)acrylate, N-methylolacrylamide, triallylisocyanate, divinylbenzene, and the like. The addition rate of the crosslinking monomer is preferably 1% by mass or less based on the total monomers.

In the present invention, it is preferred to use a chain transfer agent. Examples of the chain transfer agent include alkylmercaptans, thioglycolic acid and its esters, isopropyl alcohol, allyl alcohol, allylamine, sodium diphosphite, and the like. Further, monomers such as methallyl sulfonates such as sodium methallyl sulfonate, potassium methallyl sulfonate, and ammonium methallyl sulfonate may be mentioned.

Examples of the polymerization initiator include persulfates such as sodium persulfate, potassium persulfate, and ammonium persulfate, and peroxides such as hydrogen peroxide and benzoyl peroxide. Although these can be used alone, they can also be used as redox polymerization initiators in combination with reducing agents such as sulfites and hydrogen sulfites. 2,2'-azobis[2-(5-methyl-imidazolin-2-yl)propane] hydrochloride, 2,2'-azobis[2-(5-methyl-imidazolin-2-yl)propane] hydrochloride, Azo polymerization initiators such as 2,2'-azobis-2-amidinopropane hydrochloride can also be used. The amount of polymerization initiator is 0.05% to 2% by weight, preferably 0.1 to 1% by weight based on the total monomers.

The polymerization reaction is usually carried out at a temperature of 30°C to 100°C and for a period of 0.5 to 20 hours. The concentration of the resulting polymer is usually 5 to 50% by weight.

The obtained polymer preferably has a viscosity of 5 to 50 mPa·s as a 1% by mass aqueous solution of the polymer. The viscosity was measured using a B-type viscometer at a rotation speed of 60 rpm and 25°C. If the viscosity is lower than this, the paper strength enhancing effect will be insufficient. Moreover, if the viscosity is higher than this, the solubility will decrease and handling will become difficult. As the B-type viscometer, general-purpose products such as B8M model and TVB-10M model manufactured by Toki Sangyo Co., Ltd. are used as appropriate. If the viscosity is 100 mPa·s or less, use a No. 1 rotor.

The types of paper for which the paper strength agent of the present invention is used include newsprint, wood-free printing paper, medium-quality printing paper, gravure printing paper, PPC paper, coated base paper, lightly coated paper, packaging paper, liner and core base paper board, etc. The agent is added to the pulp slurry or to the wet end, such as on the wet paper, during the papermaking process. The addition rate is 0.05 to 10% by mass, preferably 0.1 to 5% by mass, in terms of solids, based on the dry solids content of the pulp. The agent can also be used in combination with other paper strength agents, sizing agents, aluminum sulfate, coagulants, retention aids, drainage aids, and other papermaking chemicals.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. The viscosity was measured using a B-type viscometer at a rotation speed of 60 rpm and 25°C.

(Example 1)
In a 500 mL four-necked flask, 1.0 g of reactive surfactant octoxypolyethylene glycol polypropylene glycol monomethacrylate (Blenmar 50 POEP-800B, manufactured by NOF Corporation), 3.1 g of 80% by mass acryloyloxyethyldimethylbenzyl ammonium chloride, 50 % acrylamide, 152.0 g of demineralized water, 0.10 g of sodium diphosphite, and 0.1 g of VA-044 (manufactured by Wako Pure Chemical Industries, Ltd.) were charged, and nitrogen gas was passed through the mixture while stirring at 200 rpm. After 30 minutes, the temperature was raised to 50°C and maintained for 3 hours. Thereafter, it was held at 70°C for 2 hours. Thereafter, it was cooled to obtain an aqueous polymer solution. The viscosity of the obtained 1% by mass aqueous solution of the polymer was 20.5 mPa·s. The results are shown in Table 1.

(Example 2)
In a 500 mL four-necked flask, 1.0 g of reactive surfactant octoxypolyethylene glycol polypropylene glycol monomethacrylate (Blenmar 50 POEP-800B, manufactured by NOF Corporation), 11.3 g of 80% by mass acryloyloxyethyldimethylbenzyl ammonium chloride, 50 % acrylamide, 142.9 g of demineralized water, 0.10 g of sodium diphosphite, and 0.1 g of VA-044 (manufactured by Wako Pure Chemical Industries, Ltd.) and nitrogen gas was passed through the mixture while stirring at 200 rpm. After 30 minutes, the temperature was raised to 50°C and maintained for 3 hours. Thereafter, it was held at 70°C for 2 hours. Thereafter, it was cooled to obtain an aqueous polymer solution. The viscosity of the obtained 1% by mass aqueous solution of the polymer was 17.5 mPa·s. The results are shown in Table 1.

(Example 3)
In a 500 mL four-necked flask, 1.0 g of the reactive surfactant Aquaron AN-10 (manufactured by Daiichi Kogyo Seiyaku), 9.4 g of 80% by mass acryloyloxyethyltrimethylammonium chloride, 83.2 g of 50% by mass acrylamide, and 151.6 g of brine, 0.30 g of sodium methallylsulfonate, and 0.1 g of VA-044 (manufactured by Wako Pure Chemical Industries, Ltd.) were charged, and nitrogen gas was passed through the mixture while stirring at 200 rpm. After 30 minutes, the temperature was raised to 50°C and maintained for 3 hours. Thereafter, it was held at 70°C for 2 hours. Thereafter, it was cooled to obtain an aqueous polymer solution. The viscosity of the obtained 1% by mass aqueous solution of the polymer was 23.5 mPa·s. The results are shown in Table 1.

( Reference example 4)
In a 500 mL four-necked flask, 0.25 g of the reactive surfactant Aquaron AN-10 (manufactured by Daiichi Kogyo Seiyaku), 9.4 g of 80% by mass acryloyloxyethyltrimethylammonium chloride, 84.6 g of 50% by mass acrylamide, and 151.0 g of brine, 0.30 g of sodium methallylsulfonate, and 0.1 g of VA-044 (manufactured by Wako Pure Chemical Industries, Ltd.) were charged, and nitrogen gas was passed through the mixture while stirring at 200 rpm. After 30 minutes, the temperature was raised to 50°C and maintained for 3 hours. Thereafter, it was held at 70°C for 2 hours. Thereafter, it was cooled to obtain an aqueous polymer solution. The viscosity of the obtained 1% by mass aqueous solution of the polymer was 18.5 mPa·s. The results are shown in Table 1.

(Example 5)
In a 500 mL four-necked flask, 5.0 g of the reactive surfactant Aquaron AN-10 (manufactured by Daiichi Kogyo Seiyaku), 9.4 g of 80% by mass acryloyloxyethyltrimethylammonium chloride, 75.1 g of 50% by mass acrylamide, and 155.4 g of brine, 0.30 g of sodium methallylsulfonate, and 0.1 g of VA-044 (manufactured by Wako Pure Chemical Industries, Ltd.) were charged, and nitrogen gas was passed through the mixture while stirring at 200 rpm. After 30 minutes, the temperature was raised to 50°C and maintained for 3 hours. Thereafter, it was held at 70°C for 2 hours. Thereafter, it was cooled to obtain an aqueous polymer solution. The viscosity of the obtained 1% by mass aqueous solution of the polymer was 27.0 mPa·s. The results are shown in Table 1.

(Example 6)
In a 500 mL four-necked flask, 2.5 g of the reactive surfactant Aqualon AN-10 (manufactured by Daiichi Kogyo Seiyaku), 9.4 g of 80% by mass acryloyloxyethyltrimethylammonium chloride, 80.1 g of 50% by mass acrylamide, and 153.1 g of brine, 0.30 g of sodium methallylsulfonate, and 0.1 g of VA-044 (manufactured by Wako Pure Chemical Industries, Ltd.) were charged, and nitrogen gas was passed through the mixture while stirring at 200 rpm. After 30 minutes, the temperature was raised to 50°C and maintained for 3 hours. Thereafter, it was held at 70°C for 2 hours. Thereafter, it was cooled to obtain an aqueous polymer solution. The viscosity of the obtained 1% by mass aqueous solution of the polymer was 32.5 mPa·s. The results are shown in Table 1.

(Example 7)
In a 500 mL four-necked flask, 0.50 g of reactive surfactant Aquaron AN-10 (manufactured by Daiichi Kogyo Seiyaku), 7.5 g of dimethylaminoethyl methacrylate, 5.0 g of 35% hydrochloric acid, and 84.2 g of 50% by mass acrylamide. , 152.1 g of demineralized water, 0.30 g of sodium methallylsulfonate, and 0.1 g of VA-044 (manufactured by Wako Pure Chemical Industries, Ltd.) were charged, and nitrogen gas was passed through the mixture while stirring at 200 rpm. After 30 minutes, the temperature was raised to 50°C and maintained for 3 hours. Thereafter, it was held at 70°C for 2 hours. Thereafter, it was cooled to obtain an aqueous polymer solution. The viscosity of the obtained 1% by mass aqueous solution of the polymer was 23.5 mPa·s. The results are shown in Table 1.

(Example 8)
In a 500 mL four-necked flask, 5.0 g of reactive surfactant Aquaron AR-10 (manufactured by Daiichi Kogyo Seiyaku), 7.5 g of dimethylaminoethyl methacrylate, 5.0 g of 35% hydrochloric acid, and 75.1 g of 50% by mass acrylamide. , 157.8 g of demineralized water, 0.30 g of sodium methallylsulfonate, and 0.1 g of VA-044 (manufactured by Wako Pure Chemical Industries, Ltd.) were charged, and nitrogen gas was passed through the mixture while stirring at 200 rpm. After 30 minutes, the temperature was raised to 50°C and maintained for 3 hours. Thereafter, it was held at 70°C for 2 hours. Thereafter, it was cooled to obtain an aqueous polymer solution. The viscosity of the obtained 1% by mass aqueous solution of the polymer was 22.0 mPa·s. The results are shown in Table 1.

(Example 9)
In a 500 mL four-neck flask, 2.5 g of reactive surfactant Aqualon AR-10 (manufactured by Daiichi Kogyo Seiyaku), 7.5 g of dimethylaminoethyl methacrylate, 5.0 g of 35% hydrochloric acid, and 80.0 g of 50% by mass acrylamide. , 155.1 g of demineralized water, 0.30 g of sodium methallylsulfonate, and 0.1 g of VA-044 (manufactured by Wako Pure Chemical Industries, Ltd.) were charged, and nitrogen gas was passed through the mixture while stirring at 200 rpm. After 30 minutes, the temperature was raised to 50°C and maintained for 3 hours. Thereafter, it was held at 70°C for 2 hours. Thereafter, it was cooled to obtain an aqueous polymer solution. The viscosity of the obtained 1% by mass aqueous solution of the polymer was 29.2 mPa·s. The results are shown in Table 1.

( Reference example 10)
In a 500 mL four-necked flask, 0.25 g of reactive surfactant Aquaron AR-10 (manufactured by Daiichi Kogyo Seiyaku), 7.5 g of dimethylaminoethyl methacrylate, 5.0 g of 35% hydrochloric acid, and 84.5 g of 50% by mass acrylamide. , 152.8 g of demineralized water, 0.30 g of sodium methallylsulfonate, and 0.1 g of VA-044 (manufactured by Wako Pure Chemical Industries, Ltd.) were charged, and nitrogen gas was passed through the mixture while stirring at 200 rpm. After 30 minutes, the temperature was raised to 50°C and maintained for 3 hours. Thereafter, it was held at 70°C for 2 hours. Thereafter, it was cooled to obtain an aqueous polymer solution. The viscosity of the obtained 1% by mass aqueous solution of the polymer was 20.2 mPa·s. The results are shown in Table 1.

(Example 11)
In a 500 mL four-necked flask, 1.0 g of reactive surfactant Aquaron AR-10 (manufactured by Daiichi Kogyo Seiyaku), 7.5 g of dimethylaminoethyl methacrylate, 5.2 g of 35% hydrochloric acid, and 83.1 g of 50% by mass acrylamide. , 153.5 g of demineralized water, 0.35 g of sodium methallylsulfonate, and 0.1 g of VA-044 (manufactured by Wako Pure Chemical Industries, Ltd.) were charged, and nitrogen gas was passed through the mixture while stirring at 200 rpm. After 30 minutes, the temperature was raised to 50°C and maintained for 3 hours. Thereafter, it was held at 70°C for 2 hours. Thereafter, it was cooled to obtain an aqueous polymer solution. The viscosity of the obtained 1% by mass aqueous solution of the polymer was 27.5 mPa·s. The results are shown in Table 1.

(Example 12)
In a 500 mL four-necked flask, 1.0 g of the reactive surfactant Aquaron AR-10 (manufactured by Daiichi Kogyo Seiyaku), 7.5 g of dimethylaminoethyl methacrylate, 5.0 g of 35% hydrochloric acid, and 1.0 g of 80% by mass acrylic acid. 3g of 50% by mass acrylamide, 83.2g of demineralized water, 153.5g of demineralized water, 0.35g of sodium methallylsulfonate, and 0.1g of VA-044 (manufactured by Wako Pure Chemical Industries, Ltd.) were charged, and nitrogen gas was passed through the mixture while stirring at 200 rpm. After 30 minutes, the temperature was raised to 50°C and maintained for 3 hours. Thereafter, it was held at 70°C for 2 hours. Thereafter, it was cooled to obtain an aqueous polymer solution. The viscosity of the obtained 1% by mass aqueous solution of the polymer was 20.5 mPa·s. The results are shown in Table 1.

(Example 13)
In a 500 mL four-necked flask, 1.0 g of reactive surfactant Aquaron AR-10 (manufactured by Daiichi Kogyo Seiyaku), 7.5 g of dimethylaminoethyl methacrylate, 5.0 g of 35% hydrochloric acid, and 83.1 g of 50% by mass acrylamide. , 153.5 g of demineralized water, 0.05 g of methylenebisacrylamide, 0.90 g of sodium methallylsulfonate, and 0.1 g of VA-044 (manufactured by Wako Pure Chemical Industries, Ltd.) were charged, and nitrogen gas was passed through the mixture while stirring at 200 rpm. After 30 minutes, the temperature was raised to 50°C and maintained for 3 hours. Thereafter, it was held at 70°C for 2 hours. Thereafter, it was cooled to obtain an aqueous polymer solution. The viscosity of the obtained 1% by mass aqueous solution of the polymer was 19.7 mPa·s. The results are shown in Table 1.

(Example 14)
In a 500 mL four-neck flask, 2.5 g of reactive surfactant Aqualon AR-10 (manufactured by Daiichi Kogyo Seiyaku), 7.5 g of dimethylaminoethyl methacrylate, 5.0 g of 35% hydrochloric acid, and 80.0 g of 50% by mass acrylamide. , 155.0 g of demineralized water, 0.05 g of methylenebisacrylamide, 0.90 g of sodium methallylsulfonate, and 0.1 g of VA-044 (manufactured by Wako Pure Chemical Industries, Ltd.) were charged, and nitrogen gas was passed through the mixture while stirring at 200 rpm. After 30 minutes, the temperature was raised to 50°C and maintained for 3 hours. Thereafter, it was held at 70°C for 2 hours. Thereafter, it was cooled to obtain an aqueous polymer solution. The viscosity of the obtained 1% by mass aqueous solution of the polymer was 16.2 mPa·s. The results are shown in Table 1.

(Comparative example 1)
In a 500 mL four-neck flask, add 3.1 g of 80% by mass acryloyloxyethyldimethylbenzyl ammonium chloride, 96.4 g of 50% by mass acrylamide, 150.9 g of demineralized water, 0.10 g of sodium diphosphite, VA-044 (Japanese). 0.1 g of Hikari Pure Chemical Industries, Ltd.) was added, and nitrogen gas was passed through the mixture while stirring at 200 rpm. After 30 minutes, the temperature was raised to 50°C and maintained for 3 hours. Thereafter, it was held at 70°C for 2 hours. Thereafter, it was cooled to obtain an aqueous polymer solution. The viscosity of the obtained 1% by mass aqueous solution of the polymer was 18.5 mPa·s. The results are shown in Table 1.

(Comparative example 2)
In a 500 mL four-necked flask, 9.4 g of 80 mass% acryloyloxyethyltrimethylammonium chloride, 85.6 g of 50 mass% acrylamide, 155.6 g of demineralized water, 0.30 g of sodium methallylsulfonate, VA-044 (Wako Pure) Nitrogen gas was passed through the mixture while stirring at 200 rpm. After 30 minutes, the temperature was raised to 50°C and maintained for 3 hours. Thereafter, it was held at 70°C for 2 hours. Thereafter, it was cooled to obtain an aqueous polymer solution. The viscosity of the obtained 1% by mass aqueous solution of the polymer was 18.5 mPa·s. The results are shown in Table 1.

(Comparative example 3)
In a 500 mL four-necked flask, add 7.5 g of dimethylaminoethyl methacrylate, 5.0 g of 35% hydrochloric acid, 85.0 g of 50% by mass acrylamide, 152.5 g of demineralized water, 0.25 g of sodium methallylsulfonate, VA-044 ( 0.1 g (manufactured by Wako Pure Chemical Industries, Ltd.) was added, and nitrogen gas was passed through the mixture while stirring at 200 rpm. After 30 minutes, the temperature was raised to 50°C and maintained for 3 hours. Thereafter, it was held at 70°C for 2 hours. Thereafter, it was cooled to obtain an aqueous polymer solution. The viscosity of the resulting 1% by mass aqueous solution of the polymer was 22.5 mPa·s. The results are shown in Table 1.

反応性界面活性剤；
５０ＰＯＥＰ－８００Ｂ：オクトキシポリエチレングリコールポリプロピレングリコールモノメタクリレート（日油株式会社製ブレンマー５０ＰＯＥＰ－８００Ｂ）
ＡＮ－１０：ポリオキシエチレンスチレン化プロペニルフェニルエーテル（第一工業製薬株式会社製アクアロンＡＮ－１０）
ＡＲ－１０：ポリオキシエチレンスチレン化プロペニルフェニルエーテル硫酸エステル塩（第一工業製薬株式会社製アクアロンＡＲ－１０）
カチオン性単量体；
ＤＭＢＺ：アクリロイルオキシエチルジメチルベンジルアンモニウムクロライド
ＤＭＭ：ジメチルアミノエチルメタクリレート
ＤＭＱ：アクリロイルオキシエチルトリメチルアンモニウムクロライド
その他の単量体；ＡＡＣ：アクリル酸、ＭＢＡＡ：メチレンビスアクリルアミド ( Table 1 )

reactive surfactant;
50POEP-800B: Octoxypolyethylene glycol polypropylene glycol monomethacrylate (Blenmar 50POEP-800B manufactured by NOF Corporation)
AN-10: Polyoxyethylene styrenated propenyl phenyl ether (Aqualon AN-10 manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
AR-10: Polyoxyethylene styrenated propenyl phenyl ether sulfate salt (Aqualon AR-10 manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
Cationic monomer;
DMBZ: Acryloyloxyethyldimethylbenzylammonium chloride DMM: Dimethylaminoethyl methacrylate DMQ: Acryloyloxyethyltrimethylammonium chloride Other monomers; AAC: Acrylic acid, MBAA: Methylenebisacrylamide

(Test example 1)
A paper quality measurement test of the paper strength agent in the present invention was conducted. First, LBKP was beaten with a Niagara beater and adjusted to Canadian standard freeness (beating degree) of 355 mL. For 500 mL of slurry with a pulp concentration of 1% by mass (pH 6.4, electrical conductivity 17.1mS/m), the height of the example in Table 1 was adjusted so that the pulp solid content was 0.5% by mass and 1% by mass. A molecular sample or a comparative polymer sample was added, and after stirring at 800 rpm for 1 minute, paper was made using a Tappi sheet machine (80 mesh wire was used), followed by pressing at a pressure of 410 kPa for 5 minutes, and then a rotary dryer. It was used and dried at 105°C. The paper was conditioned for 24 hours at a temperature of 23° C. and a humidity of 50% to obtain paper with a basis weight of 80 g/cm ² . The tensile strength of the obtained paper (TENSILON RTC-1210A manufactured by Orientec) and bursting strength were measured according to JIS P8112, and the results shown in Table 2 were obtained. The practical test example showed an improvement in paper strength compared to the paper of the comparative test example.

(Table 2)

(Test example 2)
To 500 mL of slurry with a pulp concentration of 1 mass % prepared in the same manner as in Test Example 1 (freeness: 320 mL), the polymers of the examples shown in Table 1 were added so that the concentrations were 0.5 mass % and 1 mass % based on the pulp solid content. Add the sample or comparative polymer sample, stir for 1 minute at 800 rpm, then make paper using a Tappi sheet machine (using 80 mesh wire), press for 5 minutes at a pressure of 410 kPa, and then use a rotary dryer. and dried at 105°C. The paper was conditioned for 24 hours at a temperature of 23° C. and a humidity of 50% to obtain paper with a basis weight of 80 g/cm ² . The internal bond strength (internal bond tester manufactured by Kumagai Riki Kogyo) and bursting strength of the obtained paper were measured according to JIS P8112, and the results shown in Table 3 were obtained. The practical test example showed an improvement in paper strength compared to the paper of the comparative test example.

( Table 3 )

(Test example 3)
To 500 mL of a slurry with a pulp concentration of 1 mass % prepared in the same manner as in Test Example 1 (beating degree 355 mL), the polymers of the examples shown in Table 1 were added so that the concentrations were 0.5 mass % and 1 mass % based on the pulp solid content. Add the sample or comparative polymer sample, stir for 1 minute at 800 rpm, then make paper using a Tappi sheet machine (using 80 mesh wire), press for 5 minutes at a pressure of 410 kPa, and then use a rotary dryer. and dried at 105°C. The paper was conditioned for 24 hours at a temperature of 23° C. and a humidity of 50% to obtain paper with a basis weight of 80 g/cm ² . The internal bond strength of the obtained paper (internal bond tester manufactured by Kumagai Riki Kogyo) and bursting strength were measured according to JIS P8112, and the results shown in Table 4 were obtained. The practical test example showed an improvement in paper strength compared to the paper of the comparative test example.

(Table 4)

(Test example 4)
To 500 mL of a slurry with a pulp concentration of 1 mass % prepared in the same manner as in Test Example 1 (freeness: 355 mL), the polymers of the examples shown in Table 1 were added so that the concentrations were 0.5 mass % and 1 mass % based on the pulp solid content. Adding a sample or a comparative polymer sample or a commercially available amphoteric polyacrylamide paper strength agent (solid content 20% by mass, pH 7 cation equivalent value 1.33 meq/g, anion equivalent value 1.06 meq/g), After stirring at 800 rpm for 1 minute, paper was made using a Tappi sheet machine (80 mesh wire was used), followed by pressing at a pressure of 410 kPa for 5 minutes, and further drying at 105° C. using a rotary dryer. The paper was conditioned for 24 hours at a temperature of 23° C. and a humidity of 50% to obtain paper with a basis weight of 80 g/cm ² . The internal bond strength (internal bond tester manufactured by Kumagai Riki Kogyo) and bursting strength of the obtained paper were measured according to JIS P8112, and the results shown in Table 5 were obtained. The practical test example showed an improvement in paper strength compared to the paper of the comparative test example.

(Table 5)

Claims (2)

As a reactive surfactant, one or more selected from polyoxyethylene styrenated propenyl phenyl ether, polyoxyethylene styrenated propenyl phenyl ether sulfate salt, octoxypolyethylene glycol polypropylene glycol mono(meth)acrylate, (meth)acrylamide , is a polymer obtained by polymerizing monomer components that contain a cationic monomer as an essential component and does not contain a hydrophobic monomer, and the polymer has a reactive surface activity with respect to all monomers. A paper strength agent characterized in that the agent is made of a polymer obtained by polymerizing monomer components in an amount of more than 1% by mass and not more than 15% by mass . The paper strength agent according to claim 1, wherein the viscosity of the 1% by mass aqueous solution of the polymer measured by a B-type viscometer at a rotation speed of 60 rpm and a temperature of 25° C. is 5 to 50 mPa·s.