WO2012164909A1

WO2012164909A1 - Polyacrylamide-based dry paper-strengthening agent, and paper manufacturing method

Info

Publication number: WO2012164909A1
Application number: PCT/JP2012/003498
Authority: WO
Inventors: 英夫茨木; 隆之西; 佐藤　健
Original assignee: 星光Pmc株式会社
Priority date: 2011-05-31
Filing date: 2012-05-29
Publication date: 2012-12-06
Also published as: CN102808353B; JP5618213B2; JP2012251252A; CN102808353A

Abstract

The present invention is: a polyacrylamide-based dry paper-strengthening agent containing amphoteric polyacrylamide, the polyacrylamide-based dry paper-strengthening agent being characterized in that the amphoteric polyacrylamide is obtained by polymerizing (a) 70-99.8 mol% of (meth)acrylamide, (b) 0.1-15 mol% of a cationic vinyl polymer, and (c) 0.1-15 mol% of an anionic vinyl polymer, the weight-average molecular mass (A) of the polyacrylamide-based dry paper-strengthening agent is 2,000,000-10,000,000, the ratio [(A)/(B)] between the weight-average molecular mass (A) and the B-type viscosity (B)(mPa∙s) of a 20 mass% aqueous solution obtained by adjusting the polyacrylamide-based dry paper-strengthening agent so that the solids concentration in the polyacrylamide-based dry paper-strengthening agent is 20 mass% at 25°C is equal to or greater than 500, and the thread length in a 20-mass% aqueous solution at 25°C is 5-60 mm; and a method for manufacturing paper-in which the polyacrylamide-based dry paper-strengthening agent is used.

Description

Polyacrylamide internal paper strength agent and paper manufacturing method

The present invention relates to a polyacrylamide internal paper strength agent and a method for producing paper. Specifically, the paper has a good texture, a paper strength enhancement effect, and a polyacrylamide internal paper strength with excellent drainage. The present invention relates to a paper and a method for producing paper using the polyacrylamide internal paper strength agent.

Paper strength enhancers including various polyacrylamide internal paper strength agents are used in the paper making process in order to improve productivity associated with the speeding up of the paper machine or improve paper quality. In particular, polyacrylamide internal paper strength agents are being improved in order to improve paper quality and productivity.

For example, an aqueous acrylamide polymer solution having a high concentration and a high molecular weight but a low viscosity, a paper strength such as a specific burst strength and a Z-axis strength, or a weight average molecular weight as a paper strength enhancer excellent in freeness, A paper strength enhancer has been proposed in which the weight average inertia radius and the weight average molecular weight as an index indicating the average degree of crosslinking are in a specific range (see, for example, Patent Document 1). In addition, a paper strength enhancer having a specific molecular weight distribution for further improving and stabilizing the paper strength enhancing performance of the amphoteric acrylamide-based paper strength enhancing agent having a branched structure has been proposed (see, for example, Patent Document 2). .

However, in these inventions, a papermaking system and a paper strength enhancer that are not added to the pulp slurry are not added to the pulp slurry, such as sulfate band and polyaluminum chloride (PAC), which are fixing aids for the paper strength enhancer. However, when used in a papermaking system where the paper strength enhancing effect reaches its peak, it is not sufficiently satisfactory with respect to the good texture of the paper, the paper strength enhancing effect, and the drainage improving effect.

Japanese Patent Application Laid-Open No. 08-067715 JP 2010-196192 A

The present invention provides a polyacrylamide internal paper strength agent having good paper texture, excellent paper strength enhancement and excellent drainage, and a method for producing paper using the polyacrylamide internal paper strength agent. Is an issue.

As a result of intensive studies to solve the above problems, the present inventor has a specific amphoteric polyacrylamide, and the polyacrylamide internal paper strength agent having specific physical properties has a good paper texture, The present inventors have found that it is excellent in paper strength enhancing effect, drainage, and yield improving effect, and that it is preferable to use the polyacrylamide internal paper strength agent under specific paper making conditions.

That is, the means for solving the problem is as follows:
<1> A polyacrylamide internal paper strength agent containing amphoteric polyacrylamide, wherein the amphoteric polyacrylamide comprises (a) (meth) acrylamide 70 to 99.8 mol%, (b) cationic vinyl monomer. Obtained by polymerizing 1 to 15 mol% and (c) 0.1 to 15 mol% of an anionic vinyl monomer,
The weight average molecular weight (A) of the polymer in the polyacrylamide internal paper strength agent is 2 million to 10 million, and the solid content concentration in the weight average molecular weight (A) and the polyacrylamide internal paper strength agent The ratio of the 20% by mass aqueous solution obtained by preparing the polyacrylamide-based internally added paper strength agent to 25% at 25 ° C. with the B-type viscosity (B) (mPa · s) [(A) / (B)] is 500 or more, and the yarn length at 25 ° C. of the 20% by mass aqueous solution is 5 to 60 mm,
<2> The polyacrylamide internal paper strength agent according to <1>, wherein the weight average molecular weight (A) is 4 million to 7 million, and the string length is 10 to 40 mm.
<3> (d) a (meth) allyl group as a chain transfer agent with respect to a total of 100 mol% of the (a) (meth) acrylamide, the (b) cationic vinyl monomer, and the (c) anionic vinyl monomer The polyacrylamide according to <1> or <2> above, wherein 0.01 to 2.0 mol% of a monomer having a hydrogen atom and (e) 0.01 to 2.0 mol% of an N-substituted (meth) acrylamide monomer as a crosslinking agent are used as polymerization components Internal paper strength agent,
<4> A method for producing paper, wherein the polyacrylamide internal paper additive is added to a pulp slurry according to any one of the above items <1> to <3>.
<5> The polyacrylamide internal paper additive according to any one of the above items <1> to <3> is added to the pulp slurry, and the papermaking pH of the pulp slurry after the addition is 5.0 to 8.5. A method for producing paper for producing pulp slurry;
<6> A paper slurry characterized by not adding an aluminum compound to the pulp slurry but adding the polyacrylamide internal paper strength agent according to any one of the above <1> to <3>. Production method,
<7> An aluminum compound is added to the pulp slurry, and the polyacrylamide internal paper strength agent according to any one of the above <1> to <3> is added to the pulp solid content in an amount of 0.5 to 3 A method for producing paper, characterized by adding 0.0% by mass in solid content,
It is.

It is possible to provide a polyacrylamide internal paper strength agent having good paper texture and excellent paper strength enhancement and drainage, and a method for producing paper using the polyacrylamide internal strength paper strength agent.

The polyacrylamide internal paper strength agent of the present invention contains amphoteric polyacrylamide obtained by polymerizing a specific monomer, thereby having a paper strength enhancing effect, and the polymer in the polyacrylamide internal paper strength agent Has a specific weight average molecular weight, (the weight average molecular weight) / (B-type viscosity of a 20% by weight aqueous solution of polyacrylamide internal paper strength agent) is within a specific range, and the polyacrylamide internal paper strength is Due to the delicate balance that the string length of the 20% by weight aqueous solution of the agent is in a specific range, it is presumed that a good paper strength enhancing effect and drainage can be obtained without deteriorating the paper texture.

The amphoteric polyacrylamide contained in the polyacrylamide internal paper strength agent of the present invention is a main component of the polyacrylamide internal paper strength agent, and the proportion of the total amount of solids is 90% by mass or more and less than 100% by mass. It is preferable to use amphoteric polyacrylamide obtained by completing the polymerization reaction of a specific monomer described later.

The amphoteric polyacrylamide contained in the polyacrylamide internal paper strength agent of the present invention can be obtained by polymerizing by a usual method. It is preferable to carry out the treatment because it becomes easy to obtain the amphoteric polyacrylamide used in the polyacrylamide internal paper strength agent of the present invention.

The amphoteric polyacrylamide contained in the polyacrylamide internal paper strength agent of the present invention comprises (a) (meth) acrylamide 70 to 99.8 mol%, (b) cationic vinyl monomer 0.1 to 15 mol% and (c ) Obtained by polymerizing 0.1 to 15 mol% of an anionic vinyl monomer. The polyacrylamide internal paper strength agent of the present invention has a paper strength enhancing effect by containing the polyacrylamide. The polymerization proportions of the polymerization components (a) to (c) are preferably (a) (meth) acrylamide 80 to 99.8 mol%, (b) cationic vinyl monomer 0.1 to 10 mol%, and (c) anion. The vinyl monomer content is 0.1 to 10 mol%.

The (a) (meth) acrylamide is acrylamide or methacrylamide, and can be used in a powder or an aqueous solution.

Examples of the (b) cationic vinyl monomer include a vinyl monomer having a tertiary amino group or a quaternary ammonium salt.

Examples of the vinyl monomer having a tertiary amino group include dialkylaminoalkyl (meth) acrylate such as dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, and diethylaminopropyl (meth) acrylate. ) Diacrylate aminoalkyl (meth) acrylamides such as acrylates, dimethylaminopropyl (meth) acrylamide, and diethylaminopropyl (meth) acrylamide, hydrochlorides of vinyl monomers having the tertiary amino group, and inorganic acids such as sulfates Examples thereof include salts and organic acid salts such as formate and acetate of vinyl monomers having a tertiary amino group.

The vinyl monomer having the quaternary ammonium salt includes a vinyl monomer obtained by a reaction between the vinyl monomer having a tertiary amino group and a quaternizing agent. Examples of the quaternizing agent include alkyl halides such as methyl chloride and methyl bromide, aralkyl halides such as benzyl chloride and benzyl bromide, dimethyl sulfate, diethyl sulfate, epichlorohydrin, 3-chloro-2-hydroxypropyltrimethyl. Ammonium chloride, glycidyl trialkyl ammonium chloride, etc. are mentioned. These vinyl monomers having a tertiary amino group or a quaternary ammonium salt may be used alone or in combination of two or more.

Examples of the (c) anionic vinyl monomer include unsaturated monocarboxylic acid, unsaturated dicarboxylic acid, unsaturated tricarboxylic acid, unsaturated tetracarboxylic acid, unsaturated sulfonic acid, unsaturated phosphonic acid, and salts thereof. These can be used alone or in combination of two or more.

Among these, unsaturated monocarboxylic acids and salts thereof include acrylic acid, methacrylic acid, 2- (meth) acrylamide-N-glycolic acid, N-acryloylglycine, 3-acrylamidopropanoic acid, 4-acrylamidobutanoic acid and Examples thereof include alkali metals such as sodium and potassium salts or ammonium salts.

Examples of the unsaturated dicarboxylic acid and salts thereof include maleic acid, fumaric acid, itaconic acid, citraconic acid and alkali metal salts such as sodium and potassium salts thereof, ammonium salts, and the like.

Examples of the unsaturated tricarboxylic acids and salts thereof include aconitic acid, 3-butene-1,2,3-tricarboxylic acid, 4-pentene-1,2,4-tricarboxylic acid and their sodium and potassium salts. Examples include alkali metal salts or ammonium salts.

Examples of the unsaturated tetracarboxylic acid and salts thereof include 1-pentene-1,1,4,4-tetracarboxylic acid, 4-pentene-1,2,3,4-tetracarboxylic acid, and 3-hexene. -1,1,6,6-tetracarboxylic acid and alkali metal salts or ammonium salts thereof such as sodium and potassium salts thereof.

Examples of the unsaturated sulfonic acid include vinyl sulfonic acid, styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, and alkali metal salts or ammonium salts thereof such as sodium and potassium.

Examples of the unsaturated phosphonic acid include vinylphosphonic acid, α-phenylvinylphosphonic acid, and alkali metal salts such as sodium and potassium salts, ammonium salts, and the like.

Among the above anionic vinyl monomers, unsaturated monocarboxylic acid, unsaturated dicarboxylic acid, specifically acrylic acid, 2-acrylamide-N-glycolic acid, itaconic acid and Their salts are particularly preferred.

In the present invention, it is preferable to use a chain transfer agent in combination when producing the amphoteric polyacrylamide, and (d) a chain transfer agent of 0.1% in total with respect to 100 mol% of the polymerization components (a) to (c). It is preferable to use 01 to 2.0 mol%. Examples of the (d) chain transfer agent include alkyl mercaptans, thioglycolic acid and esters thereof, isopropyl alcohol, and monomers having an allyl group such as allyl alcohol, allylamine, and (meth) allylsulfonic acid. Among these, alkali metal salts such as sodium salt and potassium salt of (meth) allylsulfonic acid and (meth) allylsulfonic acid or ammonium salts are preferable.

In the present invention, it is preferable that a crosslinking agent is used in combination when the amphoteric polyacrylamide is produced, and (e) the crosslinking agent is used in an amount of 0.01 to 100 mol% of the total of the polymerization components (a) to (c). It is preferable to use 2.0 mol%. (E) As the crosslinking agent, for example, a polyfunctional monomer such as N-substituted (meth) acrylamide, di (meth) acrylates, bis (meth) acrylamides, divinyl esters, etc. These may be used alone or in combination of two or more. Examples of the crosslinking agent (e) include a water-soluble aziridinyl compound, a water-soluble polyfunctional epoxy compound, a silicon compound, and the like in addition to the polyfunctional monomer. Among these, N-substituted (meth) acrylamide is preferable. These may be used individually by 1 type and may use 2 or more types together.

Examples of the N-substituted (meth) acrylamide include N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N- Examples thereof include isopropyl (meth) acrylamide and Nt-octyl (meth) acrylamide.

Examples of the di (meth) acrylates include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, and glycerin di (meth). An acrylate etc. can be mentioned, These may be used individually by 1 type and may use 2 or more types together. Examples of the bis (meth) acrylamides include N, N′-methylenebis (meth) acrylamide, ethylenebis (meth) acrylamide, hexamethylenebis (meth) acrylamide, N, N′-bisacrylamideacetic acid, N, N Examples include '-bisacrylamide methyl acetate, N, N-benzylidenebisacrylamide, and N, N'-bis (acrylamidemethylene) urea. These may be used alone or in combination of two or more. You may use together. Examples of the divinyl esters include divinyl adipate, divinyl sebacate, diallyl phthalate, diallyl malate, and diallyl succinate. These may be used alone or in combination. You may use the above together. Examples of other bifunctional monomers include allyl (meth) acrylate, divinylbenzene, diisopropenylbenzene, N-methylolacrylamide, diallyldimethylammonium salt, diallylamine, diallylchlorendate, glycidyl (meth) acrylate, and A silicon compound etc. can be mentioned, These may be used individually by 1 type and may use 2 or more types together.

Examples of the trifunctional monomer include triacryl formal, triallyl isocyanurate, N, N-diallylacrylamide, N, N-diallylmethacrylamide, triallylamine, and triallyl trimellitate. These may be used alone or in combination of two or more.

Examples of the tetrafunctional monomer include tetramethylol methane tetraacrylate, tetraallyl pyromellitate, N, N, N ′, N′-tetraallyl-1,4-diaminobutane, tetraallylamine salt, and tetraallyloxyethane. These may be used alone or in combination of two or more.

Examples of the water-soluble aziridinyl compound include tetramethylolmethane-tri-β-aziridinylpropionate, trimethylolpropane-tri-β-aziridinylpropionate, and 4,4′-bis (ethyleneimine). And carbonylamino) diphenylmethane. These may be used alone or in combination of two or more. Examples of the water-soluble polyfunctional epoxy compound include (poly) ethylene glycol diglycidyl ether, (poly) propylene glycol diglycidyl ether, (poly) glycerin diglycidyl ether, and (poly) glycerin triglycidyl ether. These may be used alone or in combination of two or more. Examples of the silicon compound include 3- (meth) acryloxypropyltrimethoxysilane, 3- (meth) acryloxypropyldimethoxymethylsilane, 3- (meth) acryloxypropyltrimethoxysilane, and 3- (meth). Examples include acryloxypropylmethyldichlorosilane, 3- (meth) acryloxyoctadecyltriacetoxysilane, 3- (meth) acryloxy-2,5-dimethylhexyldiacetoxymethylsilane, and vinyldimethylacetoxysilane. May be used alone or in combination of two or more.

In the present invention, when producing the amphoteric polyacrylamide, the polymerization components (a) to (e) may be polymerized by adding other monomers to the polymerization components (a) to (c). )) In a proportion of 10 mol% or less, preferably 5 mol% or less, with respect to the total 100 mol%, it is possible to polymerize by adding other monomers, and it is more preferable not to add the other monomers. Examples of other monomers other than the polymerization components (a) to (e) include nonionic vinyl monomers. Examples of nonionic vinyl monomers include (meth) acrylic acid esters, (meth) acrylonitrile, styrene, styrene derivatives, vinyl acetate, vinyl propionate, and methyl vinyl ether. These may be used alone or in combination of two or more.

The polymerization initiator used in the present invention is not particularly limited, and known ones can be used. For example, persulfates such as sodium persulfate, potassium persulfate and ammonium persulfate, peroxides such as hydrogen peroxide, benzoyl peroxide, tert-butyl hydroperoxide, di-tert-butyl peroxide, sodium bromate And bromates such as potassium bromate, perborates such as sodium perborate, potassium perborate and ammonium perborate, percarbonates such as sodium percarbonate, potassium percarbonate and ammonium percarbonate , Sodium perphosphate, potassium perphosphate, and perphosphates such as ammonium perphosphate, and the like can be used singly or in combination of two or more. The agent can be used alone, but can also be used as a redox polymerization initiator in combination with a reducing agent. Examples of the polymerization initiator include azobisisobutyronitrile, 2,2′-azobis-2-amidinopropane hydrochloride, 2,2′-azobis-2,4-dimethylvaleronitrile, 4,4′- Azo compounds such as azobis-4-cyanovaleric acid and its salts can also be used, and may be used alone or in combination of two or more.

Examples of the reducing agent include sulfites, bisulfites, organic amines such as N, N, N ′, N′-tetramethylethylenediamine, azo compounds such as 2,2′-azobis-2-amidinopropane hydrochloride, aldose, etc. Examples of such reducing sugars. These reducing agents may be used alone or in combination of two or more.

The method for producing amphoteric polyacrylamide is not particularly limited, and various conventionally known methods can be employed. For example, in a reaction vessel equipped with a stirrer and a thermometer in an inert gas atmosphere such as nitrogen gas, the monomers (a) to (c) as polymerization components described above and water as a solvent (if necessary, an organic solvent And (d) a chain transfer agent and / or (e) a cross-linking agent, if necessary, an acid such as sulfuric acid and hydrochloric acid, or sodium hydroxide, hydroxylation The pH is adjusted with a pH adjuster such as an alkali such as potassium or ammonia. Thereafter, a polymerization initiator is added and the reaction is carried out at a reaction temperature of 20 to 90 ° C. for 1 to 5 hours to obtain the target amphoteric polyacrylamide. Moreover, it can also superpose | polymerize, dripping a monomer, water, a chain transfer agent, a crosslinking agent, a pH adjuster, and one part or all part of a polymerization initiator to a reaction container as needed.

Amphoteric polyacrylamide is usually supplied in the form of an aqueous solution. The concentration is not particularly limited, but from the viewpoint of transportation cost and handling, the solid content concentration in the polyacrylamide internal paper strength agent is preferably 10 to 40% by mass.

In the polyacrylamide internal paper strength agent of the present invention, the weight average molecular weight (A) of the polymer in the polyacrylamide internal paper strength agent is 2 million to 10 million, preferably 4 million to 7 million. . If the weight average molecular weight (A) is less than 2 million, the paper strength enhancing effect cannot be sufficiently obtained, and if it is greater than 10 million, aggregation tends to occur, resulting in poor texture.

The weight average molecular weight (A) is obtained by GPC-MALS method in which a multi-angle light scattering detector is connected to GPC, and the measurement conditions are as follows.
GPC body: LC1100 series column manufactured by Agilent Technologies, Inc .: SHODEX SB806MHQ manufactured by Showa Denko KK
Eluent: N / 10 phosphate buffer (pH 3) containing N / 10 sodium nitrate
Flow rate: 1.0 ml / min Detector 1: Multi-angle light scattering detector DAWN manufactured by Wyatt Technology
Detector 2: Suggested refractive index detector RI-101 manufactured by Showa Denko KK

20 masses obtained by preparing the polyacrylamide internal paper strength agent so that the weight average molecular weight (A) and the solid content concentration in the polyacrylamide internal strength paper strength agent are 20 mass% at 25 ° C. The ratio [(A) / (B)] to the B-type viscosity (B) (mPa · s) of the% aqueous solution is 500 or more, preferably 500 or more and 1500 or less. When the ratio [(A) / (B)] is less than 500, a sufficient paper strength enhancing effect cannot be obtained. Here, the B type viscosity (B) is diluted or concentrated so that the solid content concentration in the polyacrylamide internal paper strength agent is 20.0% by mass at 25 ° C. This is a B-type viscosity at 25 ° C. of a 20% by mass aqueous solution adjusted with sulfuric acid or sodium hydroxide so that the pH of the polyacrylamide internal paper strength agent becomes 3.0, No. as a rotor of the B-type viscometer. No. 4 was used, and the rotation speed of the rotor was appropriately adjusted from 12 to 60 rpm according to the viscosity. The unit is mPa · s.

When the B-type viscosity (B) is 3,000 to 10,000 mPa · s, the ratio of the weight-average molecular weight (A) to the B-type viscosity (B) (mPa · s) [(A) / (B )] Is preferably 500 or more.

The yarn length at 25 ° C. of the 20% by mass aqueous solution of the polyacrylamide internal paper strength agent is 5 to 60 mm, preferably 10 to 40 mm. If the string length is less than 5 mm, a sufficient paper strength enhancing effect cannot be obtained, and if it exceeds 60 mm, overcoagulation occurs, resulting in poor texture.
In the present invention, the yarn length of the polyacrylamide internal paper strength agent is determined by using a universal testing machine manufactured by Sagawa Seisakusho Co., Ltd. in a glass 100 ml container having an inner diameter of 4 cm. Put 100g of 20% by weight aqueous solution, keep it at 25 ° C, use a stainless steel rod with a sphere with a diameter of 10mm at the tip of a rod with a length of 140mm and a diameter of 2mm. When the thread extending from the liquid surface when the stainless steel rod is pulled up at a speed of 1 mm / second using a universal testing machine is broken into the 20% by weight aqueous solution of the paper strength agent from the liquid surface. This is a value obtained by measuring the length.
The said thread length is adjusted by adjusting the balance of the usage-amount of a chain transfer agent and a crosslinking agent.

Examples of the method of using the polyacrylamide internal paper strength agent of the present invention include a method of adding the polyacrylamide internal paper strength agent to the pulp slurry (hereinafter sometimes abbreviated as “internal addition”). .

Pulp slurry is obtained by diluting pulp with water to form a slurry, and as pulp, bleaching of kraft pulp, sulfite pulp, etc., or bleaching of unbleached chemical pulp, groundwood pulp, mechanical pulp, thermomechanical pulp, etc. Or unbleached high-yield pulp, and used paper pulp such as used newspaper, magazine used paper, cardboard used paper and deinked used paper, and the polyacrylamide-based internal paper strength agent of the present invention is used for these pulp slurries. It can be used for both.

The polyacrylamide-based internal paper strength agent of the present invention is usually 0.01 to 5.0% by mass, preferably 0.05 to 3.0% by mass, more preferably 0.05% by mass, based on the dry mass of the pulp in the pulp slurry. Can be used by adding 0.5 to 3.0% by mass of solid content. When an aluminum compound such as a sulfuric acid band or polyaluminum chloride (PAC) is added, it is preferable to add 0.5 to 3.0% by mass of solid content. Examples of the method of adding the polyacrylamide internal paper strength agent to the pulp slurry include a method of adding a polyacrylamide internal paper strength agent without using any aluminum compound, and a polyacrylamide after adding the aluminum compound. Examples include a method of adding an internal paper strength agent, a method of adding an aluminum compound after adding a polyacrylamide internal strength paper, and a method of simultaneously adding an aluminum compound and a polyacrylamide internal strength agent. Any method may be used.

In the production of the paper of the present invention, either an acidic pulp slurry using aluminum sulfate or a neutral pulp slurry using no or a small amount of aluminum sulfate may be used. Further, an acidic rosin sizing agent, a neutral rosin sizing agent, an alkyl ketene dimer sizing agent, an alkenyl or alkyl succinic anhydride sizing agent, and the like may be added to the pulp slurry. Examples of the method for adding these sizing agents include, for example, a method of adding a polyacrylamide internal paper strength agent after adding a sizing agent to a pulp slurry, and a method of adding a polyacrylamide type internal paper strength agent, Examples thereof include a method of adding, and a method of adding the sizing agent after the polyacrylamide internal paper strength agent is diluted and mixed in advance. Besides, size fixing agent for pulp slurry, internal paper strength agent other than the present invention, antifoaming agent, clay, kaolin, calcium carbonate, barium sulfate, titanium oxide and other fillers, pH adjuster, dye, fluorescent You may make it contain a brightener etc. suitably. The paper to be produced usually has a basis weight of about 10 to 400 g / m ² .
In the present invention, it is preferable not to add an aluminum compound such as a sulfate band or polyaluminum chloride (PAC) to the pulp slurry. When an aluminum compound is added, the polyacrylamide internal paper strength agent is added to the pulp slurry. It is preferable to add 0.5 to 3.0% by mass of the solid content in the pulp.

In addition, additives other than the above sizing agents such as fillers, dyes, internal paper strength agents other than the present invention, wet paper strength enhancers, and yield improvers are also used as needed in the pulp slurry comprising the raw material pulp. You may do it. Furthermore, with a size press, gate roll coater, bill blade coater, calendar, etc., surface paper strength enhancer such as starch, polyvinyl alcohol, acrylamide polymer, surface sizing agent, dye, coating color, anti-slip agent, etc. as required It may be applied.

As described above, the papermaking pH of the pulp slurry obtained by adding the polyacrylamide internal paper strength agent of the present invention to the pulp slurry and adding other additives as necessary is 5.0 to 8.5. Is preferable from the viewpoint of the paper strength enhancing effect, and is more preferably 6.5 to 8.5. The papermaking pH in the present invention is the pH of the pulp slurry immediately before dewatering with the papermaking machine, and the pH of the pulp slurry immediately before dewatering with the papermaking machine generally corresponds to the pH at the inlet in the actual machine. .

Paper manufactured using the polyacrylamide internal paper strength agent of the present invention includes information paper such as PPC paper, photosensitive paper base paper, and thermal paper base paper, art paper, cast coated paper, high quality coated paper, etc. Sanitary paper such as base paper, tissue paper, towel paper, napkin base paper, fruit tree bag base paper, cleaning tag base paper, decorative board base paper / wallpaper base paper, photographic paper base, processed base paper such as laminated base paper, food container base paper, heavy bag Wrapping paper such as double craft paper and single gloss kraft paper, electrical insulation paper, liner, core, paper tube base paper, gypsum board base paper, newsprint paper, paperboard board, etc., in any papermaking process Also, it is possible to give a useful paper strength enhancing effect to the paper made. Of these, it is particularly preferable to use paper that requires paper strength or paper that restricts the use of sulfuric acid bands. The paper referred to in the present invention includes paperboard.

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples. However, the present invention is not limited to the following examples unless it exceeds the gist. Hereinafter, “%” indicates “% by mass” unless otherwise specified.

Example 1
In a 1 liter four-necked flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube, 547.80 g of water, 201.70 g of 50% acrylamide aqueous solution as monomers (1), dimethylaminoethyl methacrylate 12.26 g, itaconic acid 5.07 g, N, N-dimethylacrylamide 1.16 g and sodium methallylsulfonate 1.97 g were charged and adjusted to pH 3.0 with 12.02 g of 30% aqueous sulfuric acid. Next, the temperature was raised to 60 ° C. in a nitrogen gas atmosphere, 0.24 g of ammonium persulfate was added as a polymerization initiator, polymerization was started, and the reaction temperature was raised to 90 ° C. Thereafter, 49.20 g of water, 8.60 g of 30% aqueous sulfuric acid solution, 136.68 g of 50% aqueous acrylamide solution, 8.17 g of dimethylaminoethyl methacrylate, 1.69 g of itaconic acid, 0.77 g of N, N-dimethylacrylamide, methallylsulfone Monomer (2) consisting of 0.90 g of sodium acid is added, 0.48 g of ammonium persulfate is further added, and when the estimated B-type viscosity at 25 ° C. reaches 3000 mPa · s, 49.45 g of water is added, A polyacrylamide internal paper strength agent with a content of 20.2% was obtained. The string length, B-type viscosity of 20% aqueous solution obtained by adjusting the solid content concentration in the resulting polyacrylamide internal paper strength agent to 20.0% at 25 ° C. and pH 3.0 ( 25 ° C.) (B), the results of measuring the weight average molecular weight (A) of the polymer in the polyacrylamide internal paper strength agent, and the weight average molecular weight (A) calculated from the measurement results and the B type viscosity (B) The ratio [(A) / (B)] is shown in Table 2.

The string length of the 20% aqueous solution was measured using a universal testing machine manufactured by Sagawa Seisakusho. 100 g of the 20% aqueous solution was placed in a glass 100 ml container having an inner diameter of 4 cm and kept at 25 ° C. Then, using a stainless steel rod with a sphere with a diameter of 10 mm at the tip of a rod with a length of 140 mm and a diameter of 2 mm, the one with the sphere is placed in the 20% aqueous solution 20 mm from the liquid surface, and from there a universal test The stainless steel rod was pulled up at a speed of 1 mm / second using a machine. At that time, the length of the yarn extending from the liquid surface was taken as the value of the kite yarn length.

The weight average molecular weight (A) of the polymer in the polyacrylamide internal paper strength agent was measured by a GPC-MALS method in which a multi-angle light scattering detector was connected to GPC. The measurement conditions are as follows.
GPC body: LC1100 series column manufactured by Agilent Technologies, Inc .: SHODEX SB806MHQ manufactured by Showa Denko KK
Eluent: N / 10 phosphate buffer (pH 3) containing N / 10 sodium nitrate
Flow rate: 1.0 ml / min Detector 1: Multi-angle light scattering detector DAWN manufactured by Wyatt Technology
Detector 2: Suggested refractive index detector RI-101 manufactured by Showa Denko KK

Examples 2 to 9, Comparative Examples 1 to 7
The composition of monomers (1) and monomers (2) was changed as shown in Table 1, and the polyacrylamide system was the same as in Example 1, except that the viscosity of the polyacrylamide internal paper strength agent was changed. An internal paper strength agent was obtained. The obtained polyacrylamide internal paper strength agent was adjusted in the same manner as in Example 1 so that the solid content concentration in the polyacrylamide internal paper strength agent was 20.0% at 25 ° C. and pH 3.0. To obtain a 20% aqueous solution, and the results of measuring the string length, B-type viscosity (25 ° C.) (B) of the obtained 20% aqueous solution, and the weight average molecular weight of the polymer in the polyacrylamide internal paper strength agent and Table 2 shows the ratio [(A) / (B)] of the weight average molecular weight (A) and the B-type viscosity (B) calculated from the measurement results.

Abbreviations in Table 1 are as follows.
AAm: acrylamide,
DM: dimethylaminoethyl methacrylate,
DMBz: dimethylaminoethyl methacrylate benzyl chloride quaternized product,
DABz: dimethylaminoethyl acrylate benzyl chloride quaternized product,
IA: Itaconic acid,
AGA: 2-acrylamide-N-glycolic acid,
AA: acrylic acid,
SMAS: sodium methallyl sulfonate,
DMAA: N, N-dimethylacrylamide

The numerical values in parentheses of Comparative Example 7 in Table 2 indicate the physical properties of a 15% aqueous solution obtained by adjusting the solid content concentration in the polyacrylamide internal paper strength agent to 15% at 25 ° C. ing.

Application Example 1
Corrugated waste paper pulp slurry having a concentration of 2.4%, beating degree (Canadian Standard Freeness) 350, conductivity of 300 mS / m, and the polyacrylamide internal paper strength agent obtained in Example 1 with respect to the pulp solids. 0.5% by weight solids was added. After stirring this pulp slurry, the pulp concentration was diluted to 0.8% with water of pH 7.0, and then paper was made with a sheet machine made by The Noble & Wood, and after pressing, a drum dryer was used. It was dried at 100 ° C. for 120 seconds to obtain a paper having a basis weight of 120 g / m ² . About the obtained paper, it evaluated by the texture, specific burst strength, and internal bond which are described below. The results are shown in Table 3. Further, drainage was evaluated (DDT) after adjusting the pulp slurry in the same manner as described above until the pulp concentration was 0.8%. The results are shown in Table 3.

Texture: Light was applied from the bottom of a 20 cm square paper, and those whose density could be clearly confirmed were visually evaluated as the paper texture was poor.
Specific burst strength: Performed according to JIS P8112.
Internal bond: Performed according to JAPAN TAPPI 18-2.

DDT: Tappi, Volume 56, No. 10 (1973), page 46, “Drainage Jar”, using the same equipment as the diluted pulp slurry (concentration) (0.8%) By pouring 500 mL into a 7.5 cm diameter jar, opening the lower cock while stirring at 600 rpm, filtering through a 100 mesh wire mesh, and measuring the time to reach a certain filtrate volume The drainage can be evaluated. The time until the filtrate amount reached 100 g was measured. The smaller the value, the better the drainage.

Application Examples 2-9, Application Comparison Examples 1-7
In Application Example 1, the same operation as in Application Example 1 was carried out except that the type of polyacrylamide internal paper strength agent was changed as shown in Table 3, and a paper having a basis weight of 120 g / m ² was obtained. . The obtained paper was evaluated in the same manner as in Application Example 1. The results are shown in Table 3. In addition, the drainage evaluation (DDT) was performed in the same manner as in Application Example 1. The results are shown in Table 3. In addition, since the problem to be solved by the present invention is to provide a paper additive with good paper texture and excellent paper strength enhancing effect, when the texture of handmade paper is poor, Subsequent evaluations, specific burst strength, internal bond and DDT were not measured. Items that were not measured in Table 3 were marked with “-”.

Application Example 10
A sulfuric acid band of 0.1% by mass in terms of alumina was added to the pulp solid content of corrugated waste paper pulp slurry having a concentration of 2.4%, beating degree (Canadian Standard Freeness) 350, and conductivity of 300 mS / m, The polyacrylamide internal paper strength agent obtained in Example 1 was added in an amount of 0.5% by mass relative to the pulp solids. After stirring this pulp slurry, the pulp concentration was diluted to 0.8% with water at pH 6.5, and then paper was made with a sheet machine made by The Noble & Wood, and after pressing, a drum dryer was used. It was dried at 100 ° C. for 120 seconds to obtain a paper having a basis weight of 120 g / m ² . The obtained paper was evaluated in the same manner as in Application Example 1. The results are shown in Table 4. In addition, the drainage evaluation (DDT) was performed in the same manner as in Application Example 1. The results are shown in Table 4.

Application Examples 11-18, Application Comparison Examples 8-14
In Application Example 10, the same operation as in Application Example 10 was performed except that the type of the polyacrylamide internal paper strength agent was changed as shown in Table 4, and a paper having a basis weight of 120 g / m ² was obtained. . The obtained paper was evaluated in the same manner as in Application Example 1. The results are shown in Table 4. In addition, the drainage evaluation (DDT) was performed in the same manner as in Application Example 1. The results are shown in Table 4. It is to be noted that the problem to be solved by the present invention is to provide an additive for paper making that has a good paper texture and excellent paper strength enhancing effect. Some specific burst strength, internal bond and DDT measurements were not made. Items not measured in Table 4 are indicated as “−”.

Application Examples 19 to 27, Application Comparative Examples 15 to 21
In Application Example 10, a paper having a basis weight of 120 g / m ^{2 was} obtained by performing the same operation as in Application Example 10 except that the type and addition rate of the polyacrylamide internal paper strength agent were changed as shown in Table 5. Got. The obtained paper was evaluated in the same manner as in Application Example 1. The results are shown in Table 5. In addition, the drainage evaluation (DDT) was performed in the same manner as in Application Example 1. The results are shown in Table 5. It is to be noted that the problem to be solved by the present invention is to provide an additive for paper making that has a good paper texture and excellent paper strength enhancing effect. Some specific burst strength, internal bond and DDT measurements were not made. Items not measured in Table 5 are indicated as “−”.

Application Examples 28 to 36, Application Comparison Examples 22 to 28
In Application Example 10, a paper having a basis weight of 120 g / m ^{2 was} obtained by performing the same operation as in Application Example 10 except that the type and addition rate of the polyacrylamide internal paper strength agent were changed as shown in Table 6. Got. The obtained paper was evaluated in the same manner as in Application Example 1. The results are shown in Table 6. In addition, the drainage evaluation (DDT) was performed in the same manner as in Application Example 1. The results are shown in Table 6. It is to be noted that the problem to be solved by the present invention is to provide an additive for paper making that has a good paper texture and excellent paper strength enhancing effect. Some specific burst strength, internal bond and DDT measurements were not made. Items not measured in Table 6 are indicated as “−”.

Application Example 37
Add a sulfuric acid band of 0.3% by mass in terms of alumina to the pulp solid content of corrugated waste paper pulp slurry with a concentration of 2.4%, beating degree (Canadian Standard Freeness) 330, conductivity 500 mS / m, The polyacrylamide internal paper strength agent obtained in Example 1 was added in an amount of 3.0% by mass relative to the pulp solids. After stirring this pulp slurry, the pulp concentration is diluted to 0.8% with water at pH 5.5, and then paper is made with a sheet machine made by The Noble & Wood, and after pressing, a drum dryer is used. It was dried at 100 ° C. for 120 seconds to obtain a paper having a basis weight of 120 g / m ² . The obtained paper was evaluated in the same manner as in Application Example 1. The results are shown in Table 7. In addition, the drainage evaluation (DDT) was performed in the same manner as in Application Example 1. The results are shown in Table 7.

Application Examples 38 to 45, Application Comparative Examples 29 to 35
In application example 37, except having changed the kind of polyacrylamide type internal paper strength agent as shown in Table 7, operation similar to application example 37 was performed, and the paper of basic weight 120g / m < ² > was obtained. . The obtained paper was evaluated in the same manner as in Application Example 1. The results are shown in Table 7. In addition, the drainage evaluation (DDT) was performed in the same manner as in Application Example 1. The results are shown in Table 7. It is to be noted that the problem to be solved by the present invention is to provide an additive for paper making that has a good paper texture and excellent paper strength enhancing effect. Some specific burst strength, internal bond and DDT measurements were not made. Items that were not measured in Table 7 were marked with “-”.

Application Example 46
Obtained in Example 1 to a mixed pulp slurry of hardwood bleached kraft pulp (LBKP) / coat broke (CB) = 8/2 having a concentration of 2.4%, beating degree (Canadian Standard Freeness) 400, conductivity 100 mS / m the polyacrylamide in paper strength agent which is to pulp solids, was added 0.25 wt-% solids. After stirring this pulp slurry, the pulp concentration is diluted to 0.8% with water at pH 8.0, and further 10% calcium carbonate (Tama Pearl 121: manufactured by Okutama Kogyo Co., Ltd.) is added with stirring. Paper was made with a sheet machine made by Wood (The Noble & Wood), pressed, and then dried with a drum dryer at 100 ° C. for 100 seconds to obtain paper with a basis weight of 60 g / m ² . The obtained paper was evaluated for texture and internal bond in the same manner as in Application Example 1, and further, the ash content was measured according to JIS P 8128 as an evaluation of the filler yield. The results are shown in Table 8. In addition, the drainage evaluation (DDT) was performed in the same manner as in Application Example 1. The results are shown in Table 8.

Application Examples 47 to 54, Application Comparative Examples 36 to 42
In application example 46, except having changed the kind of polyacrylamide type internal paper strength agent as shown in Table 8, the same operation as application example 46 was performed, and the paper of basic weight 60g / m < ² > was obtained. . The obtained paper was evaluated in the same manner as in Application Example 46. The results are shown in Table 8. In addition, the drainage evaluation (DDT) was performed in the same manner as in Application Example 46. The results are shown in Table 8. It is to be noted that the problem to be solved by the present invention is to provide an additive for paper making that has a good paper texture and excellent paper strength enhancing effect. Some internal bonds, ash and DDT measurements were not performed. In Table 8, items that were not measured were indicated as “−”.

Application Examples 55 to 63, Application Comparative Examples 43 to 49
In Application Example 46, the same operation as in Application Example 46 was performed except that the type and addition rate of the polyacrylamide internal paper strength agent were changed as shown in Table 9, and a paper having a basis weight of 60 g / m ² . Got. The obtained paper was evaluated in the same manner as in Application Example 46. The results are shown in Table 9. In addition, the drainage evaluation (DDT) was performed in the same manner as in Application Example 46. The results are shown in Table 9. It is to be noted that the problem to be solved by the present invention is to provide an additive for paper making that has a good paper texture and excellent paper strength enhancing effect. Some internal bonds, ash and DDT measurements were not performed. Items that were not measured in Table 9 were marked with “-”.

Application Example 64
In mixed pulp slurry of hardwood bleached kraft pulp (LBKP) / coat broke (CB) = 8/2 with a concentration of 2.4%, beating degree (Canadian Standard Freeness) 410, conductivity 100 mS / m, based on pulp solids Then, 0.1% by mass of a sulfate band was added in terms of alumina, and then 0.25% by mass of the polyacrylamide internal paper strength agent obtained in Example 1 was added. After stirring this pulp slurry, the pulp concentration is diluted to 0.8% with water at pH 7.5, and 10% of calcium carbonate (Tama Pearl 121: manufactured by Okutama Kogyo Co., Ltd.) is further added with stirring. Paper was made with a sheet machine made by Wood (The Noble & Wood), pressed, and then dried with a drum dryer at 100 ° C. for 100 seconds to obtain paper with a basis weight of 60 g / m ² . The obtained paper was evaluated in the same manner as in Application Example 46. The results are shown in Table 10. In addition, the drainage evaluation (DDT) was performed in the same manner as in Application Example 1. The results are shown in Table 10.

Application Examples 65 to 72, Application Comparative Examples 50 to 56
In Application Example 64, except that the type of polyacrylamide internal paper strength agent was changed as shown in Table 10, the same operation as in Application Example 64 was performed to obtain a paper having a basis weight of 60 g / m ² . . The obtained paper was evaluated in the same manner as in Application Example 64. The results are shown in Table 10. Further, drainage evaluation (DDT) was performed in the same manner as in Application Example 64. The results are shown in Table 10. It is to be noted that the problem to be solved by the present invention is to provide an additive for paper making that has a good paper texture and excellent paper strength enhancing effect. Some internal bonds, ash and DDT measurements were not performed. Items that were not measured in Table 10 were marked with “−”.

Application Examples 73 to 81, Application Comparative Examples 57 to 63
In Application Example 64, except that the type and addition rate of the polyacrylamide internal paper strength agent were changed as shown in Table 11, the same operation as in Example 64 was performed, and a paper having a basis weight of 60 g / m ² was obtained. Obtained. The obtained paper was evaluated in the same manner as in Application Example 64. The results are shown in Table 11. Further, drainage evaluation (DDT) was performed in the same manner as in Application Example 64. The results are shown in Table 11. It is to be noted that the problem to be solved by the present invention is to provide an additive for paper making that has a good paper texture and excellent paper strength enhancing effect. Some internal bonds, ash and DDT measurements were not performed. Items that were not measured in Table 11 were marked with “−”.

From the results of the polyacrylamide type internal paper strength agent of the example and the application example using the polyacrylamide type internal strength paper strength agent of Comparative Example 1, the polyacrylamide type internal strength paper strength agent of the present invention is the texture of paper, Although the paper strength, yield, and drainage are excellent in balance, a polyacrylamide internal paper strength agent in which the amount of (b) cationic vinyl monomer and (c) anionic vinyl monomer used is more than 15 mol% is an important effect. It can be seen that the paper strength enhancing effect is not sufficiently obtained.

From the results of the application examples using the polyacrylamide internal paper strength agent of the example and the polyacrylamide internal paper strength agent of Comparative Example 2, the polyacrylamide internal paper strength agent of the present invention has a string length of 5 It can be seen that the paper strength enhancing effect, the yield, and the drainage are excellent as compared with the polyacrylamide internal paper strength agent which is small and has a weight average molecular weight (A) of less than 2 million.

From the results of application examples using the polyacrylamide internal paper strength agent of the example and the polyacrylamide internal paper strength agent of Comparative Example 3, the polyacrylamide internal paper strength agent of the present invention has a good texture, It can be seen that the polyacrylamide internal paper strength agent having a string length greater than 60 mm and a weight average molecular weight greater than 10 million is not suitable for evaluation because of poor paper texture.

From the results of the application examples using the polyacrylamide internal paper strength agent of Example and the polyacrylamide internal paper strength force of Comparative Example 4, the polyacrylamide internal paper strength agent of the present invention has a weight average molecular weight (A). Compared with the conventional polyacrylamide internal paper strength agent with a ratio [(A) / (B)] of 500 to B type viscosity (B), it is superior in paper strength enhancing effect, yield and drainage. I understand.

From the results of application examples using the polyacrylamide internal paper strength agent of the example and the polyacrylamide internal paper strength agent of Comparative Example 5, the polyacrylamide internal paper strength agent of the present invention has a good texture, It can be seen that polyacrylamide-based internally added paper strength agents having a string length of more than 60 mm have poor paper texture and are not suitable for evaluation.

From the results of the application examples using the polyacrylamide internal paper strength agent of the examples and the polyacrylamide internal strength paper strength agents of Comparative Examples 6 and 7, the polyacrylamide internal paper strength agent of the present invention has a paper texture. Polyacrylamide-based internal paper strength, which is good, the string length is larger than 60 mm, and the ratio [(A) / (B)] of weight average molecular weight (A) to B-type viscosity (B) is smaller than 500 It can be seen that the agent is not suitable for evaluation due to poor paper texture.

Moreover, from the result of the application example using the polyacrylamide internal paper strength agent of Comparative Example 7, the ratio of the string length and weight average molecular weight (A) to the B-type viscosity (B) in the 15% aqueous solution [( The value of A) / (B)] is within the range of the string length and ratio [(A) / (B)] to the 20% aqueous solution specified in the present invention and satisfies the other requirements of the present invention. Even if the value of the ratio [(A) / (B)] of the string length and the weight average molecular weight (A) to the B-type viscosity (B) in the 20% aqueous solution does not satisfy the requirements of the present invention It turns out that the texture of the paper is poor and is not suitable for evaluation.

From the results of application examples using the polyacrylamide internal paper strength agent of Example 1 and Example 8 and the polyacrylamide internal strength paper strength agent of the other examples, the polyacrylamide internal paper strength agent of the present invention was obtained. It can be seen that the string length is preferably 10 to 40 mm.

From the results of application examples using the polyacrylamide internal paper strength agent of Example 1 and the polyacrylamide internal strength paper strength agents of Examples 2 and 3, the polyacrylamide internal paper strength agent of the present invention has a molecular weight. Is 4 to 7 million.

From the results of Application Example 10 to Application Example 36 and the results of Application Comparison Example 8 to Application Comparison Example 28, the polyacrylamide-based internally added paper strength agent of the present invention increases as the addition ratio increases. It can be seen that the difference in the paper strength enhancing effect with the internally added paper strength agent becomes large.

From the results of Application Example 64 to Application Example 72 and Application Comparison Example 50 to Application Comparison Example 56 and the results of Application Example 73 to Application Example 81 and Application Comparison Example 57 to Application Comparison Example 63, the polyacrylamide of the present invention is obtained. It can be seen that the internal paper strength agent has a greater difference in paper strength enhancement effect than the polyacrylamide internal paper strength agent of Comparative Example when the addition rate is 0.5% rather than 0.25%.

Claims

A polyacrylamide-based internal paper strength agent containing amphoteric polyacrylamide, wherein the amphoteric polyacrylamide comprises (a) (meth) acrylamide 70 to 99.8 mol%, (b) cationic vinyl monomer 0.1 to 15 mol % And (c) 0.1-15 mol% of anionic vinyl monomer is polymerized,
The weight average molecular weight (A) of the polymer in the polyacrylamide internal paper strength agent is 2 million to 10 million, and the solid content concentration in the weight average molecular weight (A) and the polyacrylamide internal paper strength agent The ratio of the 20% by mass aqueous solution obtained by preparing the polyacrylamide-based internally added paper strength agent to 25% at 25 ° C. with the B-type viscosity (B) (mPa · s) [(A) / (B)] is 500 or more, and the yarn length at 25 ° C. of the 20% by mass aqueous solution of the polyacrylamide internal paper strength agent is 5 to 60 mm, Agent.
2. The polyacrylamide internal paper strength agent according to claim 1, wherein the weight average molecular weight (A) is 4 million to 7 million and the string length is 10 to 40 mm.
(D) Monomer having (meth) allyl group as a chain transfer agent with respect to a total of 100 mol% of (a) (meth) acrylamide, (b) cationic vinyl monomer and (c) anionic vinyl monomer 3. The poly according to claim 1, wherein 0.01 to 2.0 mol% and (e) N-substituted (meth) acrylamide monomer as a crosslinking agent and 0.01 to 2.0 mol% are used as polymerization components. Acrylamide internal paper strength agent.
A method for producing paper, characterized in that the polyacrylamide internal paper strength agent according to any one of claims 1 to 3 is added to a pulp slurry.
A polyacrylamide-based internal paper strength agent according to any one of claims 1 to 3 is added to a pulp slurry, and a pulp slurry having a papermaking pH of 5.0 to 8.5 after the addition is added to the papermaking. A method for producing paper, characterized in that:
A method for producing paper, characterized in that the polyacrylamide-based internal paper strength agent according to any one of claims 1 to 3 is added to the pulp slurry without adding an aluminum compound.
An aluminum compound is added to the pulp slurry, and the polyacrylamide internal paper strength agent according to any one of claims 1 to 3 is added in an amount of 0.5 to 3.0 solids by mass based on the pulp solids. A method for producing paper, characterized by comprising adding.