JP2017210701A - Additive for paper and manufacturing method of paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an additive for paper adding high dry paper durability strength and a manufacturing method of the paper.SOLUTION: There is provided a paper durability agent for paper containing a crosslinking agent containing (a) (meth)acrylamide, (b) a monomer having a keto group and (c) an anionic monomer as essential components and capable of reacting with (d) (meth)acrylamide-based polymer and (e) the monomer having the keto group. Preferably the content of a skeleton derived from the (b) monomer having the keto group contained in the (d) (meth)acrylamide-based polymer is 1 to 30 mol%.SELECTED DRAWING: None

Description

  The present invention relates to a paper paper strength agent and a paper manufacturing method containing a (meth) acrylamide polymer and a crosslinking agent, and more particularly to a paper paper strength material and a paper manufacturing method that impart high dry paper strength strength.

  Various polyacrylamide-based paper strength agents are used in the papermaking process in order to improve the productivity accompanying the increase in the speed of the paper machine or the quality of the paper. Polyacrylamide-based paper strength agents have been improved to improve paper quality and productivity as internal paper strength agents added to pulp slurry and surface paper strength agents applied to the paper surface.

  For example, an anionic acrylamide system obtained by reacting at least acrylamides (a), unsaturated dicarboxylic acids (b), (meth) allylsulfonic acid and / or a salt thereof (c) in order to improve surface strength. There is a method of applying a surface coating agent composition containing the resin [A] to a liner (see Patent Document 1). Further, the surface paper strength enhancer for polyacrylamide paperboard having a solubility parameter of 13 to 17 obtained by copolymerizing a monomer group comprising a carboxyl group-containing unsaturated monomer and (meth) acrylamide in the presence of an ionic chain transfer agent. Has also been proposed (Patent Document 2).

However, these inventions are inadequate as a method for improving the strength, and in particular, due to the improvement of the recycling rate of used paper and the deterioration of the quality of used paper, the paper strength improvement effect of paper types that require higher strength. Was not fully satisfactory.

On the other hand, it is known that polyvinyl alcohol having a keto group is used for paper. For example, surface-sized paper on which a surface sizing agent having a specific ratio of diacetone acrylamide copolymer-modified polyvinyl alcohol and a water-soluble hydrazide compound is applied. Manufacturing method (Patent Document 3), and an inkjet recording paper (Patent Document 4) that uses acetoacetyl group-modified polyvinyl alcohol and a crosslinking agent for the porous ink water-absorbing layer.

However, these inventions are based on polyvinyl alcohol and are not fully satisfactory as a strength improver for paper.

Further, a thermal recording material (Patent Document 5) using a (meth) acrylamide copolymer having a core-shell structure and having a diacetone group in the side chain as a protective layer is disclosed. It aims at water resistance and barrier properties, and there is no description about improving paper strength.

JP 2007-23422 A JP 2014-205938 A Japanese Patent Laid-Open No. 10-298896 JP 2005-35007 A JP 2010-36419 A

  The present invention relates to a paper paper strength agent containing a (meth) acrylamide polymer and a cross-linking agent, and a method for producing paper, and includes a (meth) acrylamide polymer and a cross-linking agent that are excellent in the paper strength enhancing effect of paper. It is an object of the present invention to provide a paper sheet strength agent and a paper manufacturing method using the paper strength agent.

  As a result of intensive studies, the present inventors have found a paper paper strength agent having a high paper strength enhancing effect and have completed the present invention.

That is, the present invention, which is a means for solving the above problems,
(Invention 1)
(D) a (meth) acrylamide polymer obtained by copolymerizing (a) (meth) acrylamide, (b) a monomer having a keto group, (c) a monomer having an anionic monomer as an essential component, and (e) a keto A paper strength agent comprising a monomer having a group and a cross-linking agent capable of reacting.
(Invention 2)
The content of the skeleton derived from the monomer having (b) keto group contained in the (d) (meth) acrylamide polymer described in (Invention 1) is 1 to 30 mol% (Invention 1). ) Paper paper strength agent.
(Invention 3)
(B) A molar ratio of a skeleton derived from a monomer having a keto group and a crosslinking agent capable of reacting with the monomer having (e) a keto group is from 100: 10 to 200 (invention 1) or (invention) Paper additive as described in 2).
(Invention 4)
(B) The paper strength agent according to any one of (Invention 1) to (Invention 3), wherein the keto group of the monomer having a keto group is a diacetone group and / or an acetoacetyl group.
(Invention 5)
(D) The content of the skeleton derived from the (c) anionic monomer contained in the (meth) acrylamide polymer is 10 to 80 mol%, and any one of (Invention 1) to (Invention 4) Paper strength agent according to item.
(Invention 6)
(Invention 1) to (Invention 5) A method for producing paper, comprising applying the paper strength agent according to any one of (Invention 5) to paper.
It is.

  According to the present invention, it is possible to provide a polyacrylamide type paper strength agent that is excellent in the paper strength enhancement effect of paper and a method for producing paper using the polyacrylamide type paper strength agent.

The present invention
(A) (meth) acrylamide,
(B) a monomer having a keto group,
(C) a (meth) acrylamide polymer having an anionic monomer as an essential component;
(E) A paper strength agent comprising a crosslinking agent capable of reacting with a monomer having a keto group.
It is.

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

  Examples of the monomer (b) having a keto group include acrolein, diacetone acrylamide, diacetone methacrylate, acetoacetoxyethyl methacrylate, 4-vinylacetoacetanilide, acetoacetylallylamide, and the like, either alone or Two or more types can be used in combination.

  Among the monomers having the keto group (b), diacetone acrylamide and acetoacetoxyethyl methacrylate are particularly preferable from the viewpoint of improving paper strength and economy.

  Examples of the (c) anionic monomer include unsaturated monocarboxylic acids, unsaturated dicarboxylic acids, unsaturated tricarboxylic acids, unsaturated tetracarboxylic acids, unsaturated sulfonic acids, unsaturated phosphonic acids, and salts thereof. One of 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, 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 such as sodium and potassium salts thereof, ammonium salts and the like.

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

  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, acrylic acid, itaconic acid, (meth) allylsulfonic acid and salts thereof are particularly preferable, and acrylic acid is more preferable from the viewpoint of improving paper strength and economy.

The content of the skeleton derived from the monomer (b) having a keto group contained in the (d) (meth) acrylamide polymer is preferably 1 to 30 mol%. When the content is less than 1 mol%, a sufficient paper strength improvement effect may not be obtained, and when it exceeds 30 mol%, a sufficient paper strength improvement effect may not be obtained.

The content of the skeleton derived from the (c) anionic monomer contained in the (d) (meth) acrylamide polymer is preferably 10 to 80 mol%. If the amount is less than 10 mol%, a sufficient paper strength improvement effect may not be obtained, and if it exceeds 80 mol%, a sufficient paper strength improvement effect may not be obtained.

Polymerization can also be carried out by adding other monomers to the polymerization components (a) to (c). It can superpose | polymerize by adding another monomer in the ratio of 10 mol% or less with respect to the total 100 mol% of said polymerization component (a)-(c). Examples of the monomer other than the polymerization components (a) to (c) include a cationic monomer, a nonionic monomer, a chain transfer agent, and a crosslinking agent.

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

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

  Moreover, as a monomer which has the said quaternary ammonium salt, the monomer obtained by reaction of the monomer which has the said tertiary amino group, and a quaternizing agent is mentioned. 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 nonionic monomer include (meth) acrylic acid ester, (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.

  Examples of the chain transfer agent include alkyl mercaptans, thioglycolic acid and esters thereof, isopropyl alcohol, and monomers having an allyl group such as allyl alcohol and allylamine.

  Examples of the cross-linking agent include polyfunctional monomers such as N-substituted (meth) acrylamide, di (meth) acrylates, bis (meth) acrylamides, divinyl esters, and the like. These may be used, and these may be used alone or in combination of two or more. Examples of the crosslinking agent include a water-soluble aziridinyl compound, a water-soluble polyfunctional epoxy compound, a silicon compound and the like in addition to the polyfunctional monomer, and 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.

The polymerization initiator used in the polymerizations (a) to (c) 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 Examples thereof include perphosphates such as sodium perphosphate, potassium perphosphate, and ammonium perphosphate. In this case, it can be used alone, but can also be used as a redox polymerization initiator in combination with a reducing agent.

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

Examples of the polymerization initiator used in the present invention include azobisisobutyronitrile, 2,2′-azobis-2-amidinopropane hydrochloride, 2,2′-azobis-2,4-dimethylvaleronitrile, Azo compounds such as 4′-azobis-4-cyanovaleric acid and its salts can also be used. These polymerization initiators may be used alone or in combination of two or more.

  There is no restriction | limiting in particular as a manufacturing method by superposition | polymerization of said (a)-(c), A conventionally well-known various method is employable. For example, in an inert gas atmosphere such as nitrogen gas, in a reaction vessel equipped with a stirrer and a thermometer, monomers (a) to (c) as polymerization components described above and water as a solvent (an organic solvent as necessary) And a chain transfer agent and / or a cross-linking agent as necessary. Further, an acid such as sulfuric acid or hydrochloric acid or sodium hydroxide, potassium hydroxide, ammonia, etc. The pH is adjusted with a pH adjusting agent such as alkali. Thereafter, a polymerization initiator is added and reacted at a reaction temperature of 20 to 90 ° C. for 1 to 5 hours to obtain an aqueous solution of (d) (meth) acrylamide polymer. 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.

The crosslinking agent capable of reacting with the monomer having the (e) keto group is not particularly limited as long as it has reactivity with the monomer having a keto group. For example, an aldehyde group-containing compound, a primary amino group in the molecule Examples thereof include compounds containing two or more compounds and isocyanate compounds. These may be used alone or in combination of two or more.

Examples of the aldehyde group-containing compound include glyoxylate, formaldehyde, acetaldehyde, propionaldehyde, crotonaldehyde, monoaldehydes such as benzaldehyde, glyoxal, glutaraldehyde, malondialdehyde, terephthalaldehyde, and dialdehyde starch. Of these, glyoxylate and glyoxal are preferably used. Examples of glyoxylate include metal salts and amine salts of glyoxylic acid. Examples of metal salts include alkali metals such as lithium, sodium, and potassium, alkaline earth metals such as magnesium and calcium, titanium, zirconium, chromium, Transition metals such as manganese, iron, cobalt, nickel and copper, other metals such as zinc and aluminum and metal salts of glyoxylic acid, and amine salts include amines such as ammonia, monomethylamine, dimethylamine and trimethylamine Examples include glyoxylic acid salts.

In the compound containing two or more primary amino groups in the molecule, the primary amino group is a primary amino group bonded to a carbon atom of an aliphatic group, aromatic group or heterocyclic group, and a primary amino group bonded to a nitrogen atom. An amino group (that is, a terminal amino group of hydrazine). From the viewpoint of the paper strength enhancing effect, a hydrazine-type amino group is preferable, and a hydrazide, semicarbazide, or carbohydrazide structure is particularly preferable. Specific examples of the compound having two or more primary amino groups bonded to a carbon atom include ethylenediamine, diethylenetriamine, triethylenediamine, metaxylenediamine, norbornanediamine, 1,3-bisaminomethylcyclohexane, and the like. Specific examples of the compound having two or more amino groups include hydrazine and salts thereof, carbohydrazide, succinic acid dihydrazide, adipic acid dihydrazide, citric acid trihydrazide, sebacic acid dihydrazide, isophthalic acid dihydrazide, and the like, Examples include a reaction product of polyisocyanate and hydrazine such as 4,4′-ethylene disemicarbazide and 4,4′-hexamethylene disemicarbazide, and a polymer hydrazide such as polyacrylic acid hydrazide. Adipic acid dihydrazide is particularly preferable in view of water solubility and reactivity.

The molar ratio of (b) the skeleton derived from the monomer having a keto group and (e) the crosslinking agent capable of reacting with the monomer having a keto group in the paper strength agent of the present invention is preferably 100: 10 to 200 ( b) When the molar ratio of the crosslinker capable of reacting with the monomer having a keto group is less than 10 with respect to the skeleton 100 derived from the monomer having a keto group, a sufficient paper strength improving effect cannot be obtained. When the molar ratio is more than 200, the effect of improving paper strength may reach its peak, which is economically disadvantageous.

  (D) A (meth) acrylamide polymer and (e) a monomer having a keto group can be mixed with a crosslinking agent capable of reacting to form a paper paper strength agent. The crosslinker capable of reacting with (d) the (meth) acrylamide polymer and (e) the monomer having a keto group is excellent in compatibility with each other, but has a high viscosity when the total solid content concentration is higher than 30%. It may become too much and the handling property may deteriorate. Further, the temperature when mixing the (d) (meth) acrylamide polymer and the crosslinking agent capable of reacting with the monomer having (e) a keto group is not particularly specified, but is 100 ° C. or lower because it is an aqueous solution, In order to suppress an increase in viscosity, generation of precipitates, etc., mixing at a temperature of 5 ° C. or higher is preferable.

Examples of the method of using the paper strength agent of the present invention include a method of coating on various base papers and a method of adding to a pulp slurry.

When the paper paper strength agent of the present invention is applied to various base papers, other chemicals can be mixed as necessary within the range where the effects of the present invention are not impaired. Various additives include surface paper strength agents such as polyvinyl alcohols and starches, surface sizing agents, anti-slip agents, mold release agents, preservatives, antifoaming agents, viscosity modifiers, dyes, water repellents, and the like. Can do. Moreover, the density | concentration at the time of the coating of the paper paper strength agent of this invention is 0.1-15 mass% as solid content, Preferably it is 1-10 mass%. The coating temperature is preferably 20 to 80 ° C. The coating amount of the paper paper strength agent can be appropriately set in consideration of the sizing degree of the base paper and other factors. Usually, the solid content is 0.05 to 10 g / m ² , preferably 0. .1 to 5 g / m ² .

  When the paper strength agent of the present invention is applied to various base papers, it can be applied to paper by a known method, for example, size press, film press, gate roll coater, blade coater, calendar, bar coater. Coating can be performed using a knife coater or an air knife coater. Moreover, spray coating can also be performed.

When the paper strength agent of the present invention is added to various pulp slurries, the pulp slurry is obtained by diluting the pulp with water to form a slurry, and as the pulp, bleaching of kraft pulp, sulfite pulp or the like, or Unbleached chemical pulp, groundwood pulp, mechanical pulp, bleached unbleached high-yield pulp, etc., and waste paper pulp such as newspaper waste paper, magazine waste paper, corrugated waste paper and deinked waste paper, etc. The paper paper strength agent of the present invention can be used in any of these pulp slurries.

  The paper paper strength agent of the present invention is used by adding 0.01 to 5.0 solids by mass, preferably 0.1 to 3.0 solids by mass, per dry mass of pulp to the pulp slurry. Can do. When adding an aluminum compound such as a sulfuric acid band or polyaninium chloride (PAC), it is preferable to add 0.5 to 3.0 solid mass%. Further, as a method of adding the paper paper strength agent of the present invention to the pulp slurry, for example, a method of adding the paper paper strength agent of the present invention without using any aluminum compound, the paper of the present invention after adding the aluminum compound A method of adding a paper strength agent, a method of adding an aluminum compound after adding the paper strength agent of the present invention, a method of simultaneously adding an aluminum compound and the paper strength agent of the present invention, and the like. It 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. 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. Moreover, the paper to be manufactured usually has a basis weight of about 10 to 400 g / m ² .

  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.

  The paper produced by applying the paper paper strength agent of the present invention or the paper produced by adding the paper strength material of the present invention to the pulp slurry includes PPC paper, photosensitive paper base paper, and thermal paper base paper. Information paper, art paper, cast coated paper, coated base paper such as high-quality coated paper, tissue paper, towel paper, sanitary paper such as napkin base paper, fruit tree bag base paper, cleaning tag base paper, decorative board base paper / wall paper base paper, printing Paper paper, laminated base paper, processed base paper such as food container base paper, packaging paper such as double-packed kraft paper and single gloss kraft paper for heavy bags, electrical insulating paper, liner, core, paper tube base paper, gypsum board base paper, Newspaper paper, paperboard board, etc. can be mentioned, and in any papermaking process, useful paper strength improvement effect can be given to the papermaking. Among these, it is particularly preferable to use it for paper that requires paper strength. The paper referred to in the present invention includes paperboard.

  Hereinafter, the present invention will be described by way of examples. In the examples, “%” means “% 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, 545.0 g of water, (a) 220.4 g of 50% acrylamide aqueous solution as (meth) acrylamide, (b) As a monomer having a keto group, 52.5 g of diacetone acrylamide and (c) 109.2 g of 80% acrylic acid and 4.4 g of sodium methallylsulfonate were charged as an anionic monomer. Next, the temperature was raised to 45 ° C. in a nitrogen gas atmosphere, and 0.44 g of ammonium persulfate was added as a polymerization initiator. Next, 0.11 g of sodium metabisulfite was added to initiate the polymerization. After raising the reaction temperature to 90 ° C, the reaction was carried out for 2 hours while maintaining 85 ° C. Thereafter, 65.0 g of water was added to obtain a polyacrylamide polymer having a solid content of 25.2% and a viscosity of 2,600 mPa · s (25 ° C., using Brookfield rotary viscometer). The polymer is diluted with water so that the concentration in terms of solid content is 3%, and (e) adipic acid dihydrazide is used as a crosslinking agent capable of reacting with a monomer having a keto group (b): mol of (e). In addition, a paper strength agent was obtained so that the ratio was 100: 50. This paper paper strength agent was applied to both sides of a core raw paper (basis weight 120 g / m ² ) using a wire bar so as to give a coating amount of 4 g to obtain a coating core. The obtained coating core was conditioned at a temperature of 23 ° C. and a humidity of 50% for 12 hours or more, and then a short span compression test (SCT): ISO 9895 was measured. The results are shown in Table 1.

Examples 2-24
The ratio of (a) (meth) acrylamide, (b) a monomer having a keto group, (c) an anionic monomer, and (e) a monomer having a keto group can be changed as shown in Table 1. Except for the above, a paper strength agent was obtained in the same manner as in Example 1. The same operation as in Example 1 was performed to create a coating core, and the same evaluation as in Example 1 was performed. The results are shown in Table 1.

Comparative Example 1
(E) A paper strength agent was obtained in the same manner as in Example 1 except that a crosslinking agent capable of reacting with a monomer having a keto group was not used. The same operation as in Example 1 was performed to create a coating core, and the same evaluation as in Example 1 was performed. The results are shown in Table 2.

Comparative Examples 2-16
A paper strength agent was prepared in the same manner as in Comparative Example 1 except that the ratio of (a) (meth) acrylamide, (b) monomer having a keto group, and (c) anionic monomer was changed as shown in Table 2. Obtained. The same operation as in Example 1 was performed to create a coating core, and the same evaluation as in Example 1 was performed. The results are shown in Table 2.

Comparative Example 17
A paper strength agent was prepared in the same manner as in Comparative Example 1 except that the ratio of (a) (meth) acrylamide, (b) monomer having a keto group, and (c) anionic monomer was changed as shown in Table 2. Obtained. A paper sheet having a weight ratio of acrylamide / acrylic acid / sodium methallylsulfonate of 35/65/2 and having the same composition as the polyacrylamide copolymer (C) used in Example 1 of Japanese Patent Application Laid-Open No. 2014-205938 Become a power agent. The same operation as in Example 1 was performed to create a coating core, and the same evaluation as in Example 1 was performed. The results are shown in Table 2.

Comparative Example 18
A four-necked flask equipped with a stirrer, thermometer, reflux condenser, dropping funnel and nitrogen gas inlet tube was charged with 462.0 g of water, 163.1 g of 50% acrylamide aqueous solution, and 21.6 g of diacetone acrylamide.
Next, the temperature was raised to 60 ° C. in a nitrogen gas atmosphere, and 0.19 g of ammonium persulfate was added as a polymerization initiator.
Then 0.29 g of sodium metabisulfite was added to initiate the polymerization. After confirming the exotherm, 111.0 g of water, 163.1 g of 50% acrylamide aqueous solution, 21.6 g of diacetone acrylamide, and 0.48 g of ammonium persulfate were added. Subsequently, 0.36 g of sodium metabisulfite was added, and the reaction temperature was raised to 90 ° C. When the reaction was performed for 2 hours, 56.3 g of water was added to obtain a polyacrylamide polymer having a solid content of 20.8% and a viscosity of 8,500 mPa · s (25 ° C., using Brookfield rotary viscometer). The polymer is diluted with water so that the concentration in terms of solid content is 3%, and (e) adipic acid dihydrazide is used as a crosslinking agent capable of reacting with a monomer having a keto group (b): mol of (e). In addition, a paper strength agent was obtained so that the ratio was 100: 50. This paper paper strength agent was applied to both sides of a core raw paper (basis weight 120 g / m ² ) using a wire bar so as to give a coating amount of 4 g to obtain a coating core. The obtained coating core was conditioned at a temperature of 23 ° C. and a humidity of 50% for 12 hours or more, and then a short span compression test (SCT): ISO 9895 was measured. The results are shown in Table 2.

Comparative Example 19
(E) A paper strength agent was obtained in the same manner as in Comparative Example 18 except that a crosslinking agent capable of reacting with a monomer having a keto group was not used. The same operation as in Comparative Example 18 was performed to prepare a coating core, and the same evaluation as in Comparative Example 18 was performed. The results are shown in Table 2.

Comparative Example 20
In a 1 liter four-necked flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube, 607.8 g of water, (a) 249.6 g of 50% acrylamide aqueous solution as (meth) acrylamide, (b) 37.3 g of diacetone acrylamide as a monomer having a keto group, 54.9 g of a 65% aqueous solution of diallyldimethylammonium chloride as a cationic monomer, and 75% 2-propene-1-aminium, N-hydroxyethyl-N, as a chain transfer agent N, 2-trimethyl and 2.1 g of chloride aqueous solution were charged. Next, the temperature was raised to 50 ° C. in a nitrogen gas atmosphere, and 0.5 g of ammonium persulfate was added as a polymerization initiator. Next, 0.1 g of sodium metabisulfite was added to initiate the polymerization. After raising the reaction temperature to 90 ° C, the reaction was carried out for 2 hours while maintaining 85 ° C. Thereafter, 47.6 g of water was added to obtain a polyacrylamide polymer having a solid content of 20.2% and a viscosity of 4,200 mPa · s (25 ° C., using Brookfield rotary viscometer). The polymer is diluted with water so that the concentration in terms of solid content is 3%, and (e) adipic acid dihydrazide is used as a crosslinking agent capable of reacting with a monomer having a keto group (b): mol of (e). In addition, a paper strength agent was obtained so that the ratio was 100: 50. This paper paper strength agent was applied to both sides of a core raw paper (basis weight 120 g / m ² ) using a wire bar so as to give a coating amount of 4 g to obtain a coating core. The obtained coating core was conditioned at a temperature of 23 ° C. and a humidity of 50% for 12 hours or more, and then a short span compression test (SCT): ISO 9895 was measured. The results are shown in Table 2.

Comparative Example 21
(E) A paper strength agent was obtained in the same manner as in Comparative Example 20 except that a crosslinking agent capable of reacting with a monomer having a keto group was not used. The same operation as in Comparative Example 20 was performed to prepare a coating core, and the same evaluation as in Comparative Example 20 was performed. The results are shown in Table 2.

Comparative Example 22
NIPPON GOHSEI GOSEFIMER Z100 (acetoacetyl group-containing polyvinyl alcohol) was diluted with water to a solid content equivalent concentration of 3%, and adipic acid dihydrazide was added to the solid content equivalent to 0.3%. A coating solution was obtained. This coating solution was applied to both sides of a core base paper (basis weight 120 g / m ² ) using a wire bar so that the coating amount was 4 g, to obtain a coating core. The obtained coating core was conditioned at a temperature of 23 ° C. and a humidity of 50% for 12 hours or more, and then a short span compression test (SCT): ISO 9895 was measured. The results are shown in Table 2.

Abbreviations in Tables 1 and 2 are as follows.
AAm: acrylamide,
DAAM: diacetone acrylamide,
AAEM: 2-acetoacetoxyethyl methacrylate AAc: acrylic acid,
IA: Itaconic acid,

AMPS: 2-acrylamido-2-methylpropanesulfonic acid SMAS: sodium methallylsulfonate DADMAC: diallyldimethylammonium chloride
ADH: adipic acid dihydrazide GOA: calcium salt of glyoxylic acid,
Gly: Glioquizal,
DETA: Diethylenetriamine

Example 25
In a four-necked flask equipped with a stirrer, thermometer, reflux condenser, dropping funnel, nitrogen gas inlet tube, water 510.0 g, 50% acrylamide aqueous solution 120.1 g, 30% sulfuric acid aqueous solution 24.2 g, dimethylaminoethyl methacrylate 23.0 g, itaconic acid 1.5 g, diacetone acrylamide 19.0 g, N, N-dimethylacrylamide 0.45 g and sodium methallylsulfonate 0.89 g were charged. Next, the temperature was raised to 60 ° C. in a nitrogen gas atmosphere, 0.15 g of ammonium persulfate was added as a polymerization initiator, polymerization was started, and the reaction temperature was raised to 90 ° C. Thereafter, a monomer comprising 80.0 g of water, 132.9 g of 50% aqueous acrylamide solution, 0.9 g of dimethylaminoethyl methacrylate, 7.3 g of itaconic acid, 0.45 g of N, N-dimethylacrylamide, and 0.89 g of sodium methallylsulfonate. When the mixed solution was added and 0.56 g of ammonium persulfate was further added and reacted for 2 hours, 58.7 g of water was added to obtain a polyacrylamide polymer having a solid content of 20.8%. The composition of this polyacrylamide polymer is shown in Table 3.
The polymer is diluted with water so that the concentration in terms of solid content is 1%, and (e) adipic acid dihydrazide is used as a crosslinking agent capable of reacting with a monomer having a keto group (b): mol of (e). In addition, a paper strength agent was obtained so that the ratio was 100: 50.
A sulfuric acid band is added to 1.5% by weight of alumina in terms of alumina with respect to the pulp solid content to a corrugated waste paper pulp slurry having a concentration of 2.4%, beating degree (Canadian Standard Freeness) 340, electric conductivity 200 mS / m, The obtained paper additive was added in an amount of 0.5 solid mass% based on the pulp solid content. After stirring the pulp slurry, the pulp concentration was diluted to 0.8% with water at pH 6.5, paper was made with a square sheet machine, and after pressing, dried at 100 ° C. for 120 seconds with a drum dryer. A paper with an amount of 120 g / m ² was obtained. For the obtained paper, the paper was conditioned at a temperature of 23 ° C. and a humidity of 50% for 12 hours or more, and then a short span compression test (SCT): ISO 9895 was measured. The results are shown in Table 3.

Examples 26-29
The ratio of (a) (meth) acrylamide, (b) a monomer having a keto group, (c) an anionic monomer, (e) a crosslinker capable of reacting with a monomer having a keto group was changed as shown in Table 3. Otherwise, a paper strength agent was obtained in the same manner as in Example 25. The same operation as in Example 25 was performed to create paper, and the same evaluation as in Example 25 was performed. The results are shown in Table 3.

Comparative Example 23
(E) A paper strength agent was obtained in the same manner as in Example 25 except that a crosslinking agent capable of reacting with a monomer having a keto group was not used. The same operation as in Example 25 was performed to create paper, and the same evaluation as in Example 25 was performed. The results are shown in Table 3.

Comparative Example 24
A paper strength agent was prepared in the same manner as in Comparative Example 23 except that the ratio of (a) (meth) acrylamide, (b) monomer having a keto group, and (c) anionic monomer was changed as shown in Table 3. Obtained. The same operation as in Example 25 was performed to create paper, and the same evaluation as in Example 25 was performed. The results are shown in Table 3.

Abbreviations in Table 3 are as follows.
AAm: acrylamide,
DAAM: diacetone acrylamide,
IA: Itaconic acid,
SMAS: sodium methallyl sulfonate,
DM: dimethylaminoethyl methacrylate,
DMAA: N, N-dimethylacrylamide ADH: adipic acid dihydrazide

From the results of Tables 1 and 2, Examples 1 to 24 produced by applying the paper paper strength agent of the present invention were compared with Comparative Examples 1 to 16 in which no crosslinker capable of reacting with a keto group was used. And Comparative Example 17 that did not use a monomer having a keto group, and Comparative Examples 18 to 21 that did not use an anionic monomer, and Comparative Example 22 that used an acetoacetyl group-containing polyvinyl alcohol. It can be seen that the paper strength of the obtained paper is high.
Moreover, from the result of Table 3, Examples 25-29 manufactured by adding the paper strength agent of this invention to a pulp slurry were compared with Comparative Examples 23 and 24 which did not use the crosslinking agent which can react with a keto group. It can be seen that the paper strength of the obtained paper is high.

Claims (6)

(D) a (meth) acrylamide polymer obtained by copolymerizing (a) (meth) acrylamide, (b) a monomer having a keto group, (c) a monomer having an anionic monomer as an essential component, and (e) a keto A paper strength agent comprising a monomer having a group and a cross-linking agent capable of reacting. The content of the skeleton derived from the monomer (b) having a keto group contained in the (d) (meth) acrylamide polymer according to claim 1 is 1 to 30 mol%. Paper paper strength agent as described. The molar ratio of (b) a skeleton derived from a monomer having a keto group and (e) a crosslinking agent capable of reacting with the monomer having a keto group is 100: 10 to 200. Paper additive. (B) The paper sheet strength agent according to any one of claims 1 to 3, wherein the keto group of the monomer having a keto group is a diacetone group and / or an acetoacetyl group. (D) The content of the skeleton derived from the (c) anionic monomer contained in the (meth) acrylamide-based polymer is 10 to 80 mol%, according to any one of claims 1 to 4. Paper paper strength agent. A paper manufacturing method comprising applying the paper strength agent according to any one of claims 1 to 5 to paper.