JP2018012909A - Paper durability promoter, method for producing paper durability promoter, paper and method for producing paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a paper durability promoter having excellent storage stability though having a high molecular weight, also, unreacted (meth)acrylamide is reduced, and further, upon addition to raw material pulp, the tone of paper is not disturbed by over-flocculation while being fixed to the pulp, and exhibiting an excellent paper durability effect as well, a method for producing the paper durability promoter, paper containing the paper durability promoter, and a method for producing the paper.SOLUTION: There is provided a paper durability promoter containing, as polymerization components (A), (meth)acrylamide (a1), a cationic vinyl monomer (a2), an anionic vinyl monomer (a3) and a crosslinking vinyl monomer (a4), and containing a copolymer (B) in which the weight average molecular weight (Mw) is 1,000,000 to 8000,000 and a molecular weight distribution (Mw/Mn) is 1.5 to 3.0, also provided is a method for producing the paper durability promoter, also provided is paper containing the paper durability promoter, and also provided is a method for producing the paper.SELECTED DRAWING: None

Description

  The present invention relates to a paper strength enhancer, a method for producing a paper strength enhancer, paper, and a method for producing paper.

Conventionally, anionic, cationic or amphoteric acrylamide polymers have been widely used as paper strength agents for imparting strength to paper.
In recent years, paper pulp mills have been using raw pulp with low paper strength containing short fibers derived from used paper due to an increase in the ratio of used paper. In addition, the use of waste paper makes it difficult for metal ions contained in white paper water to increase the electrical conductivity in the papermaking system and to exert the effect of the paper strength enhancer added to the raw material pulp to supplement the paper strength. doing. Under such circumstances, in the manufacture of paperboard that requires a higher paper strength effect, it is necessary to add a large amount of paper strength enhancer, but the water quality tends to be further deteriorated, which is not environmentally preferable.

  In order to maintain the paper strength effect of these papermaking environments, a method for increasing the molecular weight of a paper strength enhancer is known (Patent Document 1). However, when the paper strength enhancer is simply made to have a high molecular weight, the product viscosity increases, handling properties deteriorate, the viscosity increases during long-term storage, and the product may not be usable. Furthermore, if a large amount of a paper strength enhancer with a high molecular weight is added to the raw material pulp, even if the paper strength enhancer settles on the pulp, overcoagulation will occur and the formation of the resulting paper will deteriorate, reducing the paper strength effect. The problem of doing also occurs. Examples of a technique for suppressing an increase in the viscosity of the paper strength enhancer include, for example, at least one monomer selected from N, N-dimethylacrylamide and N, N-dimethacrylamide, a cationic vinyl monomer Body, an anionic vinyl monomer, and at least one monomer mixture selected from acrylamide and methacrylamide are polymerized in an aqueous medium in the presence of a radical polymerization initiator to obtain a weight average molecular weight. A method for producing an additive for papermaking, comprising forming a prepolymer of 500,000 to 1,500,000, then adding a persulfate, and further carrying out polymerization until the weight average molecular weight is at least 1.1 times Is also known (Patent Document 2). However, the production method requires a step of causing a cross-linking reaction between polymers. In this step, the degree of branching varies, and there is a concern that a paper strength enhancer having a wide molecular weight distribution is generated.

  As a technique for controlling the molecular weight distribution, water-soluble cationic monomers and / or their salts, α, β-unsaturated carboxylic acids and / or their salts, acrylamide and / or methacrylamide are essential constituent monomer components. An amphoteric paper strength enhancer characterized by being polymerized, having a specific cation equivalent value, an anion equivalent value, a weight average molecular weight of 1,000,000 to 6,000,000, and a degree of multi-branch representing a width of molecular weight distribution of 10 or less Is known (Patent Document 3). However, the molecular weight distribution of the paper strength-enhancing agent has a wide range, and an excellent paper strength effect has been a problem.

Japanese Patent Laid-Open No. 2-611197 JP-A-5-287663 JP 7-189177 A

  The object of the present invention is to have excellent storage stability while having a high molecular weight, and to reduce unreacted (meth) acrylamide, and further to overcoagulation while fixing to the pulp when added to the raw material pulp. An object of the present invention is to provide a paper strength enhancer that exhibits an excellent paper strength effect without disturbing the formation of the paper, a method for producing the paper strength enhancer, a paper containing the paper strength enhancer, and a method for producing the paper. .

  As a result of intensive studies, the present inventor has found that a paper strength enhancer containing a copolymer having a weight average molecular weight and a molecular weight distribution controlled in a specific range can solve the above-mentioned problems. In particular, it has also been found that the effect of the present invention becomes remarkable by applying a method for producing a paper strength enhancer comprising three steps of separately adding a polymerization initiator. That is, the present invention relates to the following paper strength enhancer, paper strength enhancer manufacturing method, paper and paper manufacturing method.

1. The polymerization component (A) includes (meth) acrylamide (a1), cationic vinyl monomer (a2), anionic vinyl monomer (a3) and crosslinkable vinyl monomer (a4), and has a weight average molecular weight (Mw). A paper strength enhancer comprising a copolymer (B) having 1 to 8 million and a molecular weight distribution (Mw / Mn) of 1.5 to 3.0.

2. The paper strength enhancer according to Item 1, wherein the unreacted component (a1) contained in the copolymer (B) is 50 ppm or less.

3. In the polymerization component (A), the component (a1) is 55 to 97.95 mol%, the component (a2) is 1 to 20 mol%, the component (a3) is 1 to 20 mol%, and the component (a4) is 0.05. Item 5. The paper strength enhancer according to Item 1 or 2 which is contained in an amount of 5 mol%.

4). 4. The paper strength enhancer according to any one of Items 1 to 3, wherein the gel strength of the paper strength enhancer is 0.05% by weight or less in terms of solid content.

5. Item 5. The paper strength enhancer according to any one of Items 1 to 4, wherein the polymerization component (A) further contains a chain transfer agent (a5).

6). The paper strength enhancer according to any one of Items 1 to 5, wherein the component (a2) contains a tertiary amino group-containing vinyl monomer and / or a quaternized salt of the vinyl monomer.

7). (A3) The paper strength enhancer according to any one of Items 1 to 6, wherein the component contains a vinyl monomer having a carboxyl group.

8). (A4) The paper strength enhancer according to any one of Items 1 to 7, wherein the component contains a crosslinkable vinyl monomer having an N, N-substituted amide group.

9. Item 9. The paper strength enhancer according to any one of Items 1 to 8, wherein the solid content concentration is 20% by weight and the viscosity at a temperature of 25 ° C is 2,500 to 80,000 mPa · s.

10. Step (I): a step of obtaining a reaction product (1) by reacting the polymerization component (A) in the presence of a polymerization initiator,
Step (II): a step of obtaining a reaction product (2) by reacting the reaction product (1) with a persulfate as a polymerization initiator,
And step (III): the above-mentioned item comprising a step of obtaining a copolymer (B) by reacting the reaction product (2) with an azo polymerization initiator and / or a redox initiator as a polymerization initiator. The manufacturing method of the paper strength enhancer in any one of 1-9.

11. A paper containing the paper strength enhancer according to any one of Items 1 to 9.

12 A method for producing paper using the paper strength enhancer according to claim 1.

  Since the paper strength enhancer of the present invention is made high molecular weight while controlling the production of excessively branched high molecular weight substances by controlling the weight average molecular weight and molecular weight distribution, when added to the raw material pulp, The formation was not disturbed by over-aggregation while fixing to the pulp, and the resulting formed paper also exhibited excellent paper strength effects. In particular, in the paper strength enhancer obtained from the above-described production method, those effects are remarkable, the residual amount of unreacted acrylamide is small, and the storage stability is excellent.

  The paper strength enhancer of the present invention comprises, as polymerization component (A), (meth) acrylamide (a1) (hereinafter referred to as (a1) component), cationic vinyl monomer (a2) (hereinafter referred to as (a2) component), A copolymer (B) containing an anionic vinyl monomer (a3) (hereinafter referred to as component (a3)) and a crosslinkable vinyl monomer (a4) (hereinafter referred to as component (a4)) and having the weight average molecular weight and molecular weight distribution; ).

  The component (a1) means acrylamide or methacrylamide.

  As the content ratio of the component (a1), the total content ratio of the polymerization components (A) is 100 mol%, usually about 55-97.95 mol%, preferably about 60-95 mol%, more preferably 70- About 90 mol%.

  The component (a2) is not particularly limited, and various known ones can be used. However, from the viewpoint that the paper strength enhancer is well fixed on the raw material pulp and exhibits an excellent paper strength effect. It is preferable to contain a quaternary amino group-containing vinyl monomer and / or a quaternized salt of the vinyl monomer. Specific examples of the vinyl monomer include, for example, N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylamide, N, N- Examples include tertiary amino group-containing vinyl monomers such as diethylaminopropyl (meth) acrylamide; quaternized salts of the vinyl monomers obtained by reacting these tertiary amino group-containing vinyl monomers with a quaternizing agent. The vinyl monomer salt may be an inorganic acid salt such as hydrochloride or sulfate, or an organic acid salt such as acetate. Examples of the quaternizing agent to be reacted include methyl chloride, benzyl chloride, dimethyl sulfate, epichlorohydrin and the like. Among these, N, N-dimethylaminoethyl (meth) acrylate and / or benzyl chloride quaternized salt of N, N-dimethylaminoethyl (meth) acrylate are more preferable from the viewpoint of availability and the same points as described above. These can be used alone or in combination of two or more.

  The content ratio of the component (a2) is usually set so that the total content ratio of the polymerization components (A) is 100 mol% from the viewpoint that the paper strength enhancer is well fixed to the raw material pulp and exhibits an excellent paper strength effect. Is about 1 to 20 mol%, preferably about 2 to 17 mol%, more preferably about 2 to 12 mol%.

  The component (a3) is not particularly limited, and various known ones can be used. From the viewpoint that the paper strength enhancer is well fixed on the raw material pulp and exhibits an excellent paper strength effect. It is preferable to include a vinyl monomer having a group. Specific examples of the vinyl monomer include α, β-unsaturated monocarboxylic acids such as (meth) acrylic acid and crotonic acid; α, β such as maleic acid, fumaric acid, itaconic acid, muconic acid and citraconic acid. -Unsaturated dicarboxylic acid; Organic sulfonic acids such as vinyl sulfonic acid and styrene sulfonic acid, or sodium salts and potassium salts of the above various organic acids. Among these, acrylic acid and / or itaconic acid are preferable from the viewpoint of availability and the same points as described above. These can be used alone or in combination of two or more.

  The content ratio of the component (a3) is usually set so that the total content ratio of the polymerization components (A) is 100 mol% from the viewpoint that the paper strength enhancer is well fixed to the raw material pulp and exhibits an excellent paper strength effect. Is about 1 to 20 mol%, preferably about 2 to 17 mol%, more preferably about 2 to 12 mol%.

  (A4) It does not specifically limit as a component, Various well-known things can be used. Specific examples of the component (a4) include, for example, crosslinkable vinyl monomers having an allyl group such as allyl (meth) acrylate, N-allyl (meth) acrylamide, and N, N-diallyl (meth) acrylamide; ) Acrylate, triethylene glycol mono (meth) acrylate, polyethylene glycol mono (meth) acrylate such as tetraethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, methoxypolyethylene glycol mono (meth) acrylate, polytrimethylene Poly alcohols such as glycol mono (meth) acrylate, polytetramethylene glycol mono (meth) acrylate, polyethylene glycol propylene glycol mono (meth) acrylate A crosslinkable vinyl monomer having a lenglycol group; a crosslinkable vinyl monomer having an N-substituted amide group such as diacetone acrylamide, N-isopropylacrylamide, 2-acrylamido-2-methylpropanesulfonic acid and salts thereof; N, N- Crosslinkable vinyl monomers having N, N-substituted amide groups such as dimethylacrylamide and N, N-diethylacrylamide; divinylbenzene, 1,3,5-triacryloylhexahydro-1,3,5-triazine, triallyl isocyan Examples thereof include aromatic polyvinyl crosslinkable monomers such as nurate, triallyl trimellitate, triallylamine, tetramethylolmethane tetraacrylate, and tetraallyl pyromellilate. Among these, from the viewpoint of improving the weight average molecular weight of the copolymer (B), a crosslinkable vinyl monomer having an N, N-substituted amide group is preferable, and N, N-dimethylacrylamide is more preferable. These can be used alone or in combination of two or more.

  The content ratio of the component (a4) is usually 0.05 to 5 with the total content ratio of the polymerization components (A) being 100 mol% from the viewpoint of controlling the weight average molecular weight and molecular weight distribution of the copolymer (B). About mol%, preferably about 0.07 to 2.5 mol%, more preferably about 0.1 to 1 mol%.

  Furthermore, the polymerization component (A) can also contain a chain transfer agent (a5) (hereinafter referred to as component (a5)) as necessary. When the component (a5) is used, the polymer chain before the crosslinking reaction becomes shorter, and a copolymer having a low viscosity and a higher molecular weight can be obtained. Specific examples of the component (a5) include, for example, mercaptans such as 2-mercaptoethanol and n-dodecyl mercaptan, α-methylstyrene dimer, sodium methallylsulfonate, potassium methallylsulfonate and ammonium methallylsulfonate. Methallylsulfonate, ethanol, alcohols having no allyl group such as isopropyl alcohol and pentanol, carbon tetrachloride, ethylbenzene, isopropylbenzene, cumene, 2,4-diphenyl-4-methyl-1-pentene, etc. Is mentioned. Among these, methallyl sulfonate is preferable and sodium methallyl sulfonate is more preferable from the viewpoint of adjusting the weight average molecular weight and viscosity of the paper strength enhancer. These can be used alone or in combination of two or more.

  The content ratio of the component (a5) is generally 0.05 because the total content ratio of the polymerization components (A) is 100 mol% from the viewpoint of obtaining a relatively low viscosity copolymer (B) while increasing the molecular weight. About 5 mol%, preferably about 0.1-3 mol%, more preferably about 0.2-2 mol%.

  In addition, the polymerization component (A) may contain a component (a6) other than the components (a1) to (a5) (hereinafter referred to as the component (a6)) as long as the effects of the present invention are not impaired. Specific examples of the component (a6) include, for example, bis (meth) acrylamides such as methylolacrylamide, methylenebis (meth) acrylamide, and ethylenebis (meth) acrylamide; ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate , Di (meth) acrylates such as polyethylene glycol di (meth) acrylate; divinyl esters such as divinyl adipate and divinyl sebacate; epoxy acrylates and urethane acrylates; aroma such as styrene, α-methylstyrene and vinyltoluene Group vinyl monomer; methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, (meth) acrylate-2-ethylhexyl, (meth) a Alkyl (meth) acrylates such as cyclohexyl acrylate; vinyl carboxylic acid esters such as vinyl acetate and vinyl propionate; cumene, α-methylstyrene dimer, 2,4-diphenyl-4-methyl-1-pentene and the like It can be illustrated. These may be used alone or in combination of two or more.

  The content ratio of the component (a6) is not particularly limited, but is usually 5 mol% or less, preferably 2.5 mol% or less, where the total content of the polymerization components (A) is 100 mol%.

  The method for producing the paper strength enhancer of the present invention is not particularly limited, but any method capable of producing a copolymer having a weight average molecular weight and a molecular weight distribution within the specific range described above, simultaneous polymerization, drop polymerization, and multistage polymerization. Various known polymerization methods such as these can be employed. For example, the manufacturing method etc. which contain process (I)-(III) mentioned later are mentioned. Hereinafter, it demonstrates for every process.

<About step (I)>
Step (I) in the production method of the present invention is a step of obtaining a reaction product (1) by reacting the polymerization component (A) in the presence of a polymerization initiator.

  The polymerization component (A) can also be used as a solution. As the solvent, water is usually preferable because it sufficiently dissolves or disperses the polymerization component (A) and does not adversely affect the polymerization reaction. However, a hydrophilic organic solvent such as ethanol or isopropanol may be used in combination as a cosolvent. good. Further, when the polymerization component (A) contains a component that is easily hydrolyzed, sulfuric acid or the like may be added.

  Although it does not specifically limit as superposition | polymerization conditions in process (I), For example, superposition | polymerization temperature is about 35-100 degreeC and superposition | polymerization time is about 1 to 10 hours.

  It does not specifically limit as a polymerization initiator used for process (I), A various well-known thing can be used. Specific examples of the polymerization initiator include persulfates such as ammonium persulfate, potassium persulfate, and sodium persulfate, and azo polymerization initiators such as 2,2′-azobis (2-amidinopropane) hydrochloride. Can be mentioned. Among these, it is preferable to use ammonium persulfate, potassium persulfate and / or 2,2'-azobis (2-amidinopropane) hydrochloride from the viewpoint of sufficiently proceeding the polymerization reaction of the polymerization component (A). These may be used alone or in combination of two or more. Moreover, although it is arbitrary, you may use a reducing agent together at the point which makes radical generation | occurrence | production of an organic peroxide easy. Examples of the reducing agent include sulfites such as sodium sulfite, bisulfites such as sodium bisulfite, triethanolamine, and cuprous sulfate.

  Although the usage-amount of the polymerization initiator in process (I) is not specifically limited, From the point which advances the polymerization reaction of a polymerization component (A) fully, it is usually 0.1 with respect to 100 weight part of polymerization components (A). About 0.5 to 2.0 parts by weight, preferably about 0.1 to 0.5 parts by weight.

  The reaction product (1) when the step (I) is completed preferably has a polymerization rate of about 95 to 98%. By setting it as this polymerization rate, in process (II), since there are few remaining polymerization components (A), generation | occurrence | production of the gel by rapid heat_generation | fever becomes easy to be suppressed, for example. Further, a product having a high molecular weight and a relatively low viscosity is easily obtained. In addition, the polymerization rate here shows what was consumed by the polymerization reaction among the polymerization components (A).

<About step (II)>
Step (II) in the production method of the present invention is a step of obtaining the reaction product (2) by reacting the reaction product (1) with a persulfate as a polymerization initiator.

  Although it does not specifically limit as superposition | polymerization conditions in process (II), For example, superposition | polymerization temperature is about 50-100 degreeC and superposition | polymerization time is about 0.5 to 5 hours.

  As the polymerization initiator used in the step (II), a persulfate is used because the reaction product (1) obtained in the step (I) is crosslinked while controlling the molecular weight distribution while increasing the molecular weight. Among these, ammonium persulfate is preferable. On the other hand, the use of an azo polymerization initiator is not preferable because the crosslinking reaction hardly proceeds and the molecular weight of the reaction product (2) does not increase.

  Although the usage-amount of the polymerization initiator in process (II) is not specifically limited, From the same point as the above, about 0.05-2 weight part normally with respect to 100 weight part of polymerization components (A), Preferably it is 0. About 1 to 0.5 parts by weight.

  The reaction product (2) when the step (II) is completed preferably has a polymerization rate of 99.8% or more. By setting the polymerization rate, since the remaining polymerization component (A) is small in the step (III), for example, the generation of gel due to rapid heat generation is easily suppressed. In addition, the final paper strength enhancer also tends to exert a good formation and paper strength effect.

<About Step (III)>
In step (III) in the production method of the present invention, the reaction product (2) is reacted using an azo polymerization initiator and / or a redox initiator as a polymerization initiator, whereby the copolymer (B) is reacted. It is a process to obtain.

  Although it does not specifically limit as superposition | polymerization conditions in process (III), For example, superposition | polymerization temperature is about 50-100 degreeC and superposition | polymerization time is about 0.5 to 5 hours.

  As the polymerization initiator used in step (III), an azo polymerization initiator and / or a redox initiator is used from the viewpoint of obtaining a high molecular weight copolymer (B) having a controlled molecular weight distribution. Here, the redox initiator means an initiator obtained by combining a persulfate with a reducing agent.

  Although the usage-amount of the polymerization initiator in process (III) is not specifically limited, From the same point as the above-mentioned, normally about 0.05-2 weight part with respect to 100 weight part of polymerization components (A), Preferably it is 0. About 1 to 1 part by weight, more preferably about 0.2 to 0.5 part by weight. In addition, when using a redox initiator, the use ratio of a polymerization initiator and a reducing agent is normally a polymerization initiator / reducing agent = about 90/10 to 40/60, preferably 80/20 in terms of solid weight ratio. About 50/50.

  The copolymer (B) obtained by the production method of the present invention has little unreacted component (a1) because it suppresses the generation of gel and is excellent in the storage stability of the paper strength enhancer. preferable. In addition, the method etc. which measure the content of an unreacted (a1) component by a liquid chromatography are mentioned. The content of the unreacted component (a1) contained in the paper strength enhancer is usually 50 ppm or less, preferably 20 ppm or less in terms of solid content from the same point as described above.

  The weight average molecular weight of the copolymer (B) of the present invention is 1 million to 8 million, preferably 1.5 million to 8 million, more preferably 1.8 million to 7 million, and particularly preferably 2.5 million to 8 million. 6 million. When the weight average molecular weight is less than 1,000,000, the fixing rate of the paper strength enhancer to the raw material pulp is lowered, and the paper strength effect is lowered when the paper is made. On the other hand, when it exceeds 8 million, it becomes difficult to control the molecular weight distribution, and the paper strength enhancer causes over-aggregation, and the formation of the paper tends to be disturbed.

  The molecular weight distribution (Mw / Mn) of the copolymer (B) is 1.5 to 3.0, preferably 2.0 to 3.0, more preferably 2.2 to 2.9. It is. When the molecular weight distribution (Mw / Mn) exceeds 3.0, the pulp slurry tends to be excessively agglomerated, the formation is disturbed, and the paper strength enhancing effect and storage stability of the paper strength enhancer are likely to be poor. If the molecular weight distribution (Mw / Mn) is less than 1.5, it is presumed that the paper is easily affected by fluctuations in the papermaking system, and it is difficult to exert a stable paper strength effect. Here, Mw is an abbreviation for weight average molecular weight, and Mn is an abbreviation for number average molecular weight.

The paper strength enhancer of the present invention has reduced insoluble matter in order to exhibit excellent storage stability and paper strength effect, and the content ratio is represented by “gelation rate”. The gelation rate is the ratio of gel (solid content) contained in the total solid content of the paper strength enhancer, and “gel” is a copolymer insolubilized in water during the production of the paper strength enhancer. Insoluble matter. The gelation rate in the present invention is 0.05% by weight or less, preferably 0.03% by weight or less, more preferably, in terms of solid content, since the paper strength enhancer exhibits excellent storage stability and paper strength effect. Is 0.02% by weight or less. The gelation rate of the present invention is calculated using (Equation 1).
(Formula 1) Gelation rate (%) = (Amount of gel (solid content) (g)) / (Amount of total solid content in paper strength enhancer (g)) × 100

  The measurement of the gelation rate is not particularly limited, and examples thereof include a method in which a paper strength enhancer is subjected to natural filtration using a mesh (metal mesh) or the like as it is or diluted with deionized water. In addition, when the paper strength enhancer is naturally filtered, the residue (gel) after filtration contains moisture, so that it is preferably dried under heating. As drying conditions, for example, the temperature is about 100 to 160 ° C. (preferably about 105 to 140 ° C.), and the time is about 0.5 to 5 hours (preferably about 1 to 4 hours).

  The paper strength enhancer has problems such as being unable to be used due to aggregation and gelation due to the influence of temperature, climate, etc. during long-term storage. In the present invention, the gelation rate is also adopted as an index of storage stability, and the lower the value, the better the evaluation.

  From the viewpoint of storage stability in the present invention, for example, the gelation rate of the paper strength enhancer after storage at 40 ° C. for 2 weeks is 0.05% by weight or less, preferably 0.03% by weight or less. Preferably it is 0.02 weight% or less.

  Further, as other physical properties of the paper strength enhancer of the present invention, the viscosity at a solid content concentration of 20% by weight and a temperature of 25 ° C. is usually 2, from the point that the formation of the paper is not disturbed and the paper strength effect is excellent. It is about 500 to 80,000 mPa · s, preferably about 5,000 to 60,000 mPa · s.

  The paper strength enhancer of the present invention can be prepared by blending various additives as required. Examples of the additive include antifoaming agents, preservatives, chelating agents, water-soluble aluminum compounds, bow glass, urea, polysaccharides and the like.

  The method for using the paper strength enhancer is not particularly limited, and examples thereof include a method of internally adding into the raw material pulp slurry, and a method of coating on the surface of the raw paper.

  When internally added to the raw material pulp slurry, the paper strength enhancer of the present invention is added to the pulp slurry to make paper. Although the usage-amount of a paper strength enhancer is not specifically limited, It is about 0.01 to 4.0 weight% with respect to the dry weight of a pulp. The kind of the pulp is not particularly limited, and examples thereof include chemical pulps such as LBKP and NBKP, mechanical pulps such as GP and TMP, and waste paper pulp. When internally adding the paper strength enhancer, in addition, as a fixing agent, sulfate band, aluminum hydroxide, etc., pH adjuster, sulfuric acid, sodium hydroxide, etc., sizing agent, wet paper strength agent, filler, talc, Clay, kaolin, titanium dioxide, calcium carbonate and the like can be added.

When coating on the surface of the base paper, the paper strength enhancer of the present invention is used in a solution diluted with water or the like, and applied to the base paper surface by various known means. The viscosity of the diluted solution is usually 1 to 40 mPa · s at 50 ° C. at a solid content concentration of 5% by weight. As the type of base paper, uncoated paper made from wood cellulose fibers can be used, and the coating means is not particularly limited. For example, a bar coater, knife coater, air knife coater, calendar, gate Examples thereof include a roll coater, a blade coater, a 2-roll size press, and a rod metal ring. The coating amount (solid content) of the paper strength enhancer is not particularly limited, but is usually about 0.001 to ² g / m ² , preferably about 0.005 to 1.0 g / m ² .

  The paper of the present invention is less susceptible to over-aggregation of the paper strength enhancer, so that it does not disturb the formation and exhibits an excellent paper strength effect.

  The paper of the present invention is used in various products, such as coated base paper, newsprint paper, liner, core, paper tube, printing writing paper, foam paper, PPC paper, cup base paper, inkjet paper, thermal paper, etc. Is mentioned.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. All parts and% are based on weight. For convenience, monomers and the like are abbreviated as follows.

The following compounds are abbreviated.
AM: Acrylamide DM: Dimethylaminoethyl methacrylate DML: Benzyl chloride quaternized salt of dimethylaminoethyl methacrylate DMAEA-BQ: Benzyl chloride quaternized salt of dimethylaminoethyl acrylate DMAEA-Q: Methyl chloride quaternary salt of dimethylaminoethyl acrylate Salt IA: Itaconic acid AA: Acrylic acid DMAA: N, N-dimethylacrylamide TAF: 1,3,5-triacroylhexahydro-1,3,5-triazine SMAS: Sodium methallylsulfonate APS: Ammonium persulfate NPS: sodium persulfate KPS: potassium persulfate SPS: sodium bisulfite V-50: 2,2'-azobis (2-amidinopropane) hydrochloride

(viscosity)
The viscosity of the sample adjusted to 25 ° C. was measured using a Brookfield viscometer (manufactured by Toki Sangyo Co., Ltd.).

(Weight average molecular weight, molecular weight distribution)
The weight average molecular weight and molecular weight distribution were measured by gel permeation chromatography (GPC) method under the following measurement conditions.
GPC body: Tosoh Co., Ltd. column: Tosoh Co., Ltd. guard column PWXL 1 and GMPWXL 2 (temperature 40 ° C.)
Eluent: 0.5 mol / l acetate buffer (0.5 mol / l acetic acid (manufactured by Wako Pure Chemical Industries, Ltd.) + 0.5 mol / l sodium acetate (manufactured by Kishida Chemical Co., Ltd.), aqueous solution, pH about 4.2 )
Flow rate: 0.8 ml / min Detector:
Viscotech's TDA MODEL 301 (concentration detector, 90 ° light scattering detector and viscosity detector (temperature 40 ° C.)) RALLS method measurement sample: solid content concentration of copolymer (B) is 0.5% After diluting with deionized water, an aqueous sodium hydroxide solution was added until the pH reached 10-12. After immersing in a hot water bath at 80 ° C. or higher for 1 hour, the pH was adjusted to 6-8 with sulfuric acid. It was diluted to 025% and measured.

Example 1
<Process (I)>
In a reactor equipped with a stirrer, thermometer, reflux condenser, nitrogen gas inlet tube and three dropping funnels, 276.2 parts of ion-exchanged water was added and oxygen in the reaction system was removed through nitrogen gas. Heated to ° C. In the dropping funnel (1), 106.7 parts (29.0 mol%) of AM, 32.5 parts (4.0 mol%) of DM, 0.3 part (0.05 mol%) of DMAA, SMAS 2.0 parts (0.25 mol%), 62.5% sulfuric acid 15.9 parts, and ion-exchanged water 319 parts, and the pH was adjusted to around 3.0 with sulfuric acid (mixture (a) ). In addition, 229.3 parts (62.4 mol%) of AM, 26.9 parts (4.0 mol%) of IA, 0.3 part (0.05 mol%) of DMAA in the dropping funnel (2), 2.0 parts (0.25 mol%) of SMAS and 408.2 parts of ion-exchanged water were charged, and the pH was adjusted to around 3.0 with sulfuric acid (mixed solution (I)). To the dropping funnel (3), 0.6 part of APS and 180 parts of ion-exchanged water were charged (initiator liquid (c)). Next, the initiator liquid (c) was dropped from the dropping funnel (3) over 3 hours. In parallel, the mixed solution (a) in the dropping funnel (1) is dropped over about 1.5 hours, and immediately after the dropping is finished, the mixed solution (a) in the dropping funnel (2) is added over about 1.5 hours. It was dripped.
<Process (II)>
After completion of dropping, 0.4 part of APS and 10 parts of ion-exchanged water were added and kept warm for 1 hour.
<Step (III)>
Further, 0.8 part of V-50 and 10 parts of ion exchange water were added and the temperature was kept for 1 hour, and then 400 parts of ion exchange water was added. The solid content concentration was 20.0% and the viscosity (25 ° C.) was 8,000 mPa. -The copolymer (B-1) of s was obtained. The physical properties of the copolymer (B-1) are shown in Table 1 (the same applies hereinafter).

Example 2
The monomer composition shown in Table 1 was synthesized by charging 0.6 part of V-50 and 180 parts of ion-exchanged water into the dropping funnel (3) in the step (I) of Example 1 to obtain a copolymer (B -2) was obtained.

Example 3
In step (I) of Example 1, 0.6 part of APS and 90 parts of ion-exchanged water (initiator liquid (c)) were added to the dropping funnel (3), and SPS was 0 to the dropping funnel (4). .5 parts and 90 parts of ion-exchanged water (initiator liquid (D)) were respectively added dropwise to the system over 3 hours and synthesized to obtain a copolymer (B-3).

Example 4
In step (III) of Example 1, 0.8 parts of APS, 0.67 parts of SPS, and 10 parts of ion exchange water were added and synthesized to obtain a copolymer (B-4).

Example 5
In Step (II) of Example 1, 0.4 part of NPS and 10 parts of ion-exchanged water were added and synthesized to obtain a copolymer (B-5).

Example 6
With the monomer composition shown in Table 1, 0.6 part of KPS and 180 parts of ion-exchanged water were charged in the dropping funnel (3) in Step I of Example 1, and KPS was 0 in Step II of Example 1. .4 parts and 10 parts of ion exchange water were added and synthesized to obtain a copolymer (B-6).

Example 7
In the monomer composition shown in Table 1 and in Step I of Example 4, the dropping funnel (3) was charged with 0.6 part of V-50 and 180 parts of ion-exchanged water, synthesized, and copolymer (B- 7) was obtained.

Examples 8 and 9
The monomer compositions shown in Table 1 were synthesized in the same manner as in Example 4 to obtain copolymers (B-8) and (B-9).

Examples 10-23
The monomer compositions shown in Table 1 were synthesized in the same manner as in Example 1 to obtain copolymers (B-10) to (B-23).

Comparative Examples 1-3, Comparative Examples 5-7
The monomer compositions and polymerization initiators shown in Table 1 were synthesized in the same manner as in Example 1, and copolymers (B-24) to (B-26) and (B-28) to (B-30) were synthesized. Obtained.

Comparative Example 4
In step (II) of Example 1, 0.4 part of APS, 0.33 part of SPS and 10 parts of ion exchange water were added and synthesized to obtain a copolymer (B-27).

(Content of unreacted component (a1))
Copolymers (B-1) to (B-30) were subjected to HPLC using the following eluent, and the content of the unreacted component (a1) was calculated.
(Measurement condition)
Column: manufactured by Shiseido CAPCELL PAC C18 MG II S5; 1.5 mmI. D. × 250mm
Eluent: Water / acetonitrile = 95/5 solution containing N / 100 sodium dodecyl sulfate (adjusted to pH 2.3 with phosphoric acid)
Detector: NANOSPACE SI-2 UV-VIS detector 3002 manufactured by Shiseido
Detection wavelength: 205 nm

  For the copolymers (B-1) to (B-30), the following physical properties and papermaking evaluation were performed. In addition, evaluation using (B-1) to (B-30) was expressed as Evaluation Examples 1 to 23 and Comparative Evaluation Examples 1 to 7, respectively (composite order).

(Gelation rate)
Copolymers (B-1) to (B-30) were each diluted with deionized water so that the solid content concentration was 1.0%, and then 100 g of the diluted solution was added to a 350 mesh wire mesh (previously weighed). Filtered. The amount of gel (solid) after drying for 3 hours with a circulating drier at a temperature of 105 ° C. was measured and calculated according to (Equation 1). It shows that it is so favorable that a gelatinization rate is low. The results are shown in Table 2 (the same applies hereinafter).
(Formula 1) Gelation rate (%) = (Amount of gel (solid content) (g)) / (Amount of total solid content in paper strength enhancer (g)) × 100

(Storage stability)
After allowing the copolymers (B-1) to (B-30) to stand in a constant temperature bath at 40 ° C. for 2 weeks, the gelation rate was measured by the same method as described above. The lower the gelation rate, the better the storage stability.

(Paper evaluation)
Add 1.5% sulfuric acid band to pulp adjusted to 370 ml of Canadian Standard Freeness (C.S.F.) by beating used corrugated paper with a Niagara-type beater. An aqueous solution was added to adjust the pH to 6.7. Next, 1.0% of the paper strength enhancer (B-1) obtained in each of the above Examples and Comparative Examples was added to the pulp and stirred, and then the basis weight was 180 g / m using a tapi sheet machine. ^The paper was made to be ² and press dehydrated at 5 kg / cm ² for 2 minutes. Next, it was dried for 3 minutes at 105 ° C. with a rotary drier, and conditioned for 24 hours under the conditions of a temperature of 23 ° C. and a humidity of 50%, thereby obtaining an adult paper 1. Paper strength enhancers (B-2) to (B-30) were also made in the same manner. In addition, it made paper by the same method, without adding paper strength enhancer, and obtained the paper 2.

(Fixing rate)
Using a nitrogen analyzer (manufactured by Mitsubishi Chemical Corporation), the nitrogen content of the formed paper 1 and the formed paper 2 was measured and then calculated from the following formula.
Fixing rate (%) = (Nitrogen content of paper 1−Nitrogen content of paper 2) ÷ (Theoretical nitrogen content of used paper strength enhancer × Addition rate of used paper strength enhancer) × 100
The theoretical nitrogen content means the molar use ratio of the components (a1) to (a6) of the paper strength enhancer and the weight ratio of nitrogen in the paper strength enhancer calculated from the composition formula of each of these components. To do.
(Form)
The passing light (brightness) from each synthetic paper obtained by the above method was taken into a commercially available measuring instrument (trade name “Personal Image Processing System Hyper-700”, manufactured by OBS), and the luminance distribution was obtained by statistical analysis. The obtained value was used as the coefficient of variation of formation. The formation variation coefficient indicates that the smaller the value, the better the formation. The results are shown in Table 2 (the same applies hereinafter).
(Specific burst strength)
The specific burst strength (kPa · m ² / g) was measured in accordance with JIS P 8131 using each of the resultant paper obtained by the above method.
(Specific tensile strength)
The specific tensile strength (N · m / g) was measured in accordance with JIS P 8113 using each of the formed papers obtained by the above method.
(Specific compression strength)
The specific compressive strength (N · m ² / g) was measured in accordance with JIS P 8126 using each of the formed papers obtained by the above method.

Claims (12)

  The polymerization component (A) includes (meth) acrylamide (a1), cationic vinyl monomer (a2), anionic vinyl monomer (a3) and crosslinkable vinyl monomer (a4), and has a weight average molecular weight (Mw). A paper strength enhancer comprising a copolymer (B) having 1 to 8 million and a molecular weight distribution (Mw / Mn) of 1.5 to 3.0.   The paper strength enhancer according to claim 1, wherein the unreacted (meth) acrylamide (a1) contained in the copolymer (B) is 50 ppm or less.   Polymerization component (A) is (a1) component 55-97.95 mol%, (a2) component 1-20 mol%, (a3) component 1-20 mol%, and (a4) component 0.05-5 mol%. The paper strength enhancer according to claim 1 or 2 which is contained.   The paper strength enhancer according to any one of claims 1 to 3, wherein the gel strength of the paper strength enhancer is 0.05% by weight or less in terms of solid content.   The paper strength enhancer according to any one of claims 1 to 4, wherein the polymerization component (A) further contains a chain transfer agent (a5).   The paper strength enhancer according to any one of claims 1 to 5, wherein the component (a2) contains a tertiary amino group-containing vinyl monomer and / or a quaternized salt of the vinyl monomer.   The paper strength enhancer according to any one of claims 1 to 6, wherein the component (a3) contains a vinyl monomer having a carboxyl group.   The paper strength enhancer according to any one of claims 1 to 7, wherein the component (a4) contains a crosslinkable vinyl monomer having an N, N-substituted amide group.   The paper strength enhancer according to any one of claims 1 to 8, which has a solid content concentration of 20 wt% and a viscosity at a temperature of 25 ° C of 2,500 to 80,000 mPa · s. Step (I): a step of obtaining a reaction product (1) by reacting the polymerization component (A) in the presence of a polymerization initiator,
Step (II): a step of obtaining a reaction product (2) by reacting the reaction product (1) with a persulfate as a polymerization initiator,
And step (III): a step of obtaining a copolymer (B) by reacting the reaction product (2) with an azo polymerization initiator and / or a redox initiator as a polymerization initiator. The manufacturing method of the paper strength enhancer in any one of 1-9.   A paper containing the paper strength enhancer according to claim 1. A method for producing paper using the paper strength enhancer according to claim 1.