Sizing agent for paper, method of producing sizing agent for paper, and method of producing paper

Abstract

To provide a novel sizing agent for paper, more specifically a surface sizing agent that imparts excellent sizing performance when applied to a surface of base paper.SOLUTION: The sizing agent for paper comprises a copolymer (A) having a structure of a monomer (a) unit that includes one or more non-conjugated C=C double bonds within an alicyclic carbon skeleton.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a papermaking sizing agent, and more particularly to a surface sizing agent that imparts excellent sizing performance to base paper by being coated on the surface of the base paper. [Background technology]

[0002] There are various types of surface sizing agents, but when focusing on the form of the sizing component in the sizing agent product, they can be broadly classified into solution types, which are in the form of a solution, and emulsion types, which are in the form of an emulsion.

[0003] Of these, solution-type polymers use water-soluble polymers in which styrene, unsaturated hydrocarbons, (meth)acrylic acid esters, etc. serve as the hydrophobic moiety and (meth)acrylic acid and its salts, etc. serve as the hydrophilic moiety. Although recent improvements have been reported using 2,4,4-trimethyl-1-pentene and α-olefins (terminal non-conjugated double bonds, see Patent Document 1), further improvements in sizing performance have been required.

[0004] On the other hand, emulsion-type surface sizing agents are obtained by emulsion polymerization of hydrophobic monomers in an emulsion made with a hydrophobic polymer, synthetic polymers, starch dispersants, and other low-molecular-weight emulsifiers. Compared to solution-type surface sizing agents, these products have a lower viscosity and less foaming, leading to their active development and use in recent years. The ionic nature of the emulsion can be controlled by imparting ionicity to emulsifiers or surfactant polymers, leading to the development of cationic and anionic types. Hydrophobic monomers include styrene, acrylates, unsaturated carboxylic acids, and α-olefins. In recent years, patents have been reported that further improve the sizing effect by using unique materials in addition to hydrophobic monomers. Examples include shellac (see Patent Document 2), epichlorohydrin-modified polyaminopolyamide resins (see Patent Document 3), polysaccharides incorporating reactive groups (see Patent Document 4), and surface sizing agents containing rosins (see Patent Document 5). These unique materials have been shown to significantly affect the performance of surface sizing agents.

[0005] Similarly, the investigation and use of new materials is expected to contribute to solving various problems and improving the performance of surface sizing agents. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent application 2004-200878 [Patent Document 2] Patent application 2001-017600 [Patent Document 3] Patent application 2015-139056 [Patent Document 4] Patent application 2019-037134 [Patent Document 5] Patent application 2019-006666 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0007] The problem to be solved by the present invention is to provide a novel papermaking sizing agent which exhibits superior sizing performance by using a monomer that is distinct from conventional types. [Means for solving the problem]

[0008] As a result of extensive investigations aimed at solving the above problems, the present inventors have found that a surface sizing agent obtained by polymerization in the presence of a monomer having one or more non-conjugated C=C double bonds in an alicyclic carbon skeleton has excellent sizing effect, and have completed the present invention.

[0009] That is, the present invention, which is a means for solving the above problems, <1> a papermaking sizing agent containing a copolymer (A) having a structure of a monomer (a) unit having one or more non-conjugated C=C double bonds in an alicyclic carbon skeleton; <2> The copolymer (A) further has a structure of a hydrophobic monomer (b) unit and a structure of a hydrophilic monomer (c) unit. <1> Paper sizing agents, <3> The copolymer (A) is characterized in that the content of monomer (a) units having one or more non-conjugated C=C double bonds in an alicyclic carbon skeleton is 0.1 to 40 mass %, the content of other hydrophobic monomer (b) units is 20 to 99.8 mass %, and the content of hydrophilic monomer (c) units is 0.1 to 40 mass %. <2> Paper sizing agents, <4> a method for producing a papermaking sizing agent, comprising copolymerizing a monomer containing a monomer (a) having one or more non-conjugated C=C double bonds in an alicyclic carbon skeleton; <5> A method for producing a papermaking sizing agent, comprising copolymerizing a monomer (a) having one or more non-conjugated C=C double bonds in an alicyclic carbon skeleton, another hydrophobic monomer (b), and a hydrophilic monomer (c); <6> The copolymerization method according to claim 1, wherein the content of the monomer (a) having one or more non-conjugated C=C double bonds in the alicyclic carbon skeleton is 0.1 to 40 mass %, the content of the other hydrophobic monomer (b) is 20 to 99.8 mass %, and the content of the hydrophilic monomer (c) is 0.1 to 40 mass % based on the total amount of the copolymerized monomers. <5> A method for producing the papermaking sizing agent according to the present invention <7> The aforementioned <1> ~ <3> 0.01 to 5 g / m 2 A method for producing paper, characterized by coating the paper. is. [Effects of the Invention]

[0010] By using the papermaking sizing agent of the present invention, paper with excellent sizing performance can be obtained, and the sizing performance of fine paper in particular can be improved. BEST MODE FOR CARRYING OUT THE INVENTION

[0011] The present invention relates to a papermaking sizing agent containing a copolymer (A) having a structure of monomer (a) units having one or more non-conjugated C=C double bonds in an alicyclic carbon skeleton. The present invention will be specifically described below.

[0012] Sizing agents containing the copolymer (A) are available in the form of emulsion type and solution type.

[0013] Monomers used to obtain the structure of the monomer (a) unit having one or more non-conjugated C=C double bonds in the alicyclic carbon skeleton include commonly available dicyclopentenyloxyethyl methacrylate, dicyclopentenyloxyethyl acrylate, dicyclopentenyl acrylate, vinylcyclohexene, 5-vinyl-2-norbornene, and limonene. Other examples include monomers with conjugated C=C double bonds and non-conjugated C=C double bonds obtained by Diels-Alder reaction of alkyne dienophiles such as dimethyl acetylenedicarboxylate and diethyl acetylenedicarboxylate with enophiles such as butadiene and cyclopentabutadiene; monomers with reactive functional groups such as dicyclopentenyl alcohol, dicyclopentenyloxyethyl alcohol, 3-cyclohexene-1-carboxylic acid, and 5-norbornene-2-methylamine bonded via epoxide cleavage or isocyanate in the side chains of glycidyl methacrylate and methacrylic acid isocyanate; olefin-containing ketones such as 2-cyclopenten-1-one, olefin-containing aldehydes such as 3-cyclohexene-1-carboxaldehyde, and olefin-containing esters such as methyl 5-norbornene-2-carboxylate; and non-conjugated olefin-based monomers obtained by nucleophilic attack of Grignard reagents such as vinyl magnesium bromide and allyl magnesium bromide on non-conjugated olefin-based monomers. More preferred are dicyclopentenyloxyethyl methacrylate, dicyclopentenyloxyethyl acrylate, and dicyclopentenyl acrylate. These monomers may be used alone or in combination of two or more.

[0014] The reason why the copolymer having the structure of the monomer (a) unit having one or more non-conjugated C=C double bonds in the alicyclic carbon skeleton of this patent improves sizing performance is unclear, but if the copolymer does not contain non-conjugated C=C double bonds, no improvement in sizing performance is observed.

[0015] The copolymer (A) contained in the papermaking sizing agent of the present invention preferably has a structure of a hydrophobic monomer (b) unit and a structure of a hydrophilic monomer (c) unit in addition to the structure of the monomer (a) unit, from the viewpoints of sizing properties, product stability, and dispersibility in solvents.

[0016] Other examples of the monomers used to obtain the structure of the hydrophobic monomer (b) unit include styrenes such as styrene, α-methylstyrene, vinyltoluene, and divinylbenzene; methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, normal butyl (meth)acrylate, isobutyl (meth)acrylate, tertiary butyl (meth)acrylate, octyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, and alkyl (meth)acrylates such as benzyl (meth)acrylate; dialkyl diesters of maleic acid and fumaric acid; vinyl esters such as vinyl acetate and vinyl propionate; nitriles such as acrylonitrile and methacrylonitrile; linear α-olefins such as diisobutylene, 1-dodecene, 1-tetradecene, 1-hexadecene, and 1-octadecene; N-alkyl (meth)acrylamides; and alkyl vinyl ethers such as methyl vinyl ether. One of these monomers can be used alone, or two or more can be mixed and used. Among these, styrenes and / or alkyl (meth)acrylates are preferred, and styrene and / or butyl (meth)acrylate and 2-ethylhexyl (meth)acrylate are more preferred.

[0017] The monomer used to obtain the structure of the hydrophilic monomer (c) unit in the present invention is an anionic monomer and / or a nonionic monomer, and one or more of these hydrophilic monomers can be used.

[0018] Examples of anionic monomers include carboxyl group-containing monomers, sulfonic acid group-containing monomers, phosphate ester group-containing monomers, and salts thereof. These anionic monomers can be used alone or in combination. The anionic monomers are preferably converted into salts at any time during the production process using alkalis such as alkali metal hydroxides (e.g., sodium hydroxide, potassium hydroxide), ammonia, amine bases (e.g., methylamine, dimethylamine) as neutralizing agents, since this can impart hydrophilicity to the anionic monomers.

[0019] Examples of carboxyl group-containing monomers include α,β-unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, and citraconic acid; their acid anhydrides, neutralized salts, and half esters; examples of sulfonic acid group-containing monomers include vinyl sulfonic acid, (meth)allyl sulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, and sulfonated styrene; examples of phosphate group-containing monomers include phosphate esters of hydroxyalkyl (meth)acrylates; and among these, carboxyl group-containing monomers are preferred. These anionic monomers can be used alone or in combination.

[0020] Examples of the nonionic monomer include (meth)acrylamide, and hydroxyl group-containing (meth)acrylates such as hydroxyethyl acrylate, hydroxyethyl methacrylate, etc. These nonionic monomers can be used alone or in combination of two or more.

[0021] When copolymer (A) has a structure of monomer (a) units having one or more non-conjugated C=C double bonds in an alicyclic carbon skeleton, other hydrophobic monomer (b) units, and hydrophilic monomer (c) units, the mass ratio of (a):(b):(c) is preferably 0.1-40:20-99.8:0.1-40 in terms of sizing performance, more preferably 1-30:40-98:1-30, and even more preferably 1-20:60-98:1-20. Note that when the papermaking sizing agent is a solution-type sizing agent, a mass ratio of 1-20:40-79:20-40 is more preferable.

[0022] The papermaking sizing agent of the present invention is preferably produced by the following polymerization method using the above-mentioned monomers.

[0023] In the method for producing a paper sizing agent of the present invention, emulsion polymerization and solution polymerization can be employed, and an emulsion-type paper sizing agent can be obtained by emulsion polymerization, and a solution-type paper sizing agent can be obtained by solution polymerization. Of these, emulsion-type paper sizing agents are preferred, and are preferably used as surface sizing agents.

[0024] Examples of the emulsion polymerization and solution polymerization methods that can be used include a batch addition polymerization method in which all of the monomers are charged into a reaction vessel at once and polymerized; a divided addition polymerization method in which some or all of the monomers are dividedly added to a reaction vessel and polymerized; and a continuous dropping polymerization method in which some or all of the monomers are continuously dropped into a reaction vessel and polymerized.

[0025] Examples of radical polymerization initiators used in the polymerization of the present invention include oil-soluble azo catalysts such as 2,2'-azobisisobutyronitrile and dimethyl 2,2'-azobis(2-methylpropionate); oil-soluble organic peroxides such as benzyl peroxide, tert-butyl peroxybenzoate, and tert-butylperoxy-2-ethylhexanoate; persulfates such as ammonium persulfate, potassium persulfate, and sodium persulfate; water-soluble peroxides such as hydrogen peroxide; redox polymerization catalysts formed by combining these persulfates and peroxides with a reducing agent; water-soluble azo catalysts such as 2,2'-azobis(2-amidinopropane) dihydrochloride; and water-soluble organic peroxides such as tert-butyl hydroperoxide. However, the initiators are not limited to these, and other known and commonly used polymerization initiators can also be used. Two or more of these polymerization initiators may be used in combination.

[0026] The amount of the polymerization initiator used is usually 0.1 to 10% by mass based on the total amount of the monomers used in the present invention. The polymerization initiator may be added to the reaction vessel together with the monomers at any timing before or after the reaction, or may be added dropwise continuously.

[0027] In addition, known chain transfer agents can be used in the polymerization of the present invention, and examples thereof include α-methylstyrene dimer; alkyl mercaptan compounds such as normal octyl mercaptan, tertiary dodecyl mercaptan, and normal dodecyl mercaptan; mercaptan derivatives such as thioglycolic acid derivatives, mercaptopropionic acid derivatives, mercaptoethanol, thiomalic acid, and thiosalicylic acid; and alcohols such as ethanol and isopropyl alcohol.

[0028] These chain transfer agents may be charged together with the monomers into a reaction vessel all at once or may be added dropwise continuously. Two or more of these chain transfer agents may be used in combination. The amount of the chain transfer agent used varies depending on the type of chain transfer agent used, but is preferably in the range of 0 to 5% by mass based on the total amount of the monomers used in the present invention.

[0029] The emulsion-type papermaking sizing agent can be obtained by copolymerizing the monomers constituting the copolymer (A) by emulsion polymerization in the presence of a copolymer (B) consisting of a hydrophobic monomer (d) and a hydrophilic monomer (e), starches (C), and at least one selected from a low-molecular-weight emulsifier.

[0030] In any of the polymerization steps using the emulsifiers described above, a monomer is emulsion-polymerized in a solvent using a radical polymerization initiator, and any conventionally known polymerization method that can be used in emulsion polymerization can be applied as the polymerization method.

[0031] The copolymer (B), starch (C), and / or low-molecular-weight emulsifier described in the preceding paragraph may be charged into a reaction vessel together with the monomers all at once, or may be added in portions or dropwise, or may be added at any timing during the production.

[0032] In the present invention, the copolymer (B) is a copolymer of a hydrophobic monomer (d) and a hydrophilic monomer (e), and plays the role of a dispersant in emulsion polymerization.

[0033] As the hydrophobic monomer (d) used in the polymerization of the copolymer (B), any of the monomers shown as the monomer (a) having one or more non-conjugated C=C double bonds in the alicyclic carbon skeleton and the other hydrophobic monomers (b) can be used, and these monomers may be used alone or in combination of two or more.

[0034] As the hydrophilic monomer (e) used in the polymerization of the copolymer (B), any of the monomers shown as the hydrophilic monomer (c) above can be used, and these monomers may be used alone or in combination of two or more.

[0035] As a polymerization method for the copolymer (B), a conventionally known polymerization method, polymerization initiator, and chain transfer agent that can be applied to solution polymerization can be used.

[0036] The obtained copolymer (B) solution can be used as a solution-type surface sizing agent as it is, but can also be used as a dispersing agent for emulsion polymerization to obtain copolymer (A).

[0037] When copolymer (A) is produced by emulsion polymerization in the presence of copolymer (B), the mass ratio of copolymer (B) to other hydrophobic monomer (b) is preferably 5 to 50:100, and more preferably 10 to 40:100, from the viewpoint of the stability and sizing performance of the obtained copolymer.

[0038] In the present invention, the copolymer (A) can be obtained even in the presence of starch (C), and this dispersant (C) contributes to the dispersion stability and mechanical stability of the emulsion in the coating liquid.

[0039] The starch used as the raw material for starch (C) is not particularly limited, and various known starches can be used. Examples include starches obtained from corn, potato, tapioca, wheat, rice, sago palm, and waxy maize, as well as modified starches obtained by processing such starches. Examples of modified starches include oxidized starch, cationized starch, phosphate-modified starch, carboxymethylated starch, hydroxyethylated starch, carbamylethylated starch, dialdehyde-modified starch, and esterified starch with acetic acid or the like. These may be used alone or in combination of two or more. Commercially available products may also be used. Among these, modified starch is preferred.

[0040] The above-mentioned starches also include starches obtained by chemical and / or physical treatment and decomposition. Preferably, the starches and modified starches are further chemically and / or physically treated and decomposed to obtain starches. The decomposition is preferably carried out before the start of polymerization of the monomers (a) to (c), but may also be carried out during the monomer polymerization. The decomposition method can be one or more selected from oxidation treatment, heat treatment, acid decomposition treatment, and enzyme treatment.

[0041] The mass ratio of the starch (C) to the other hydrophobic monomer (b) is preferably 20 to 400:100, more preferably 40 to 300:100, from the viewpoint of the mechanical stability and sizing performance of the resulting emulsion.

[0042] In the present invention, the copolymer (A) can be obtained even in the presence of a low molecular weight emulsifier.

[0043] In the present invention, the low molecular weight emulsifier refers to a known low molecular weight surfactant, and examples thereof include cationic, nonionic, amphoteric or anionic surfactants and radically polymerizable surfactants, and at least one selected from these groups can be used.

[0044] Examples of cationic surfactants include acetates and epichlorohydrin-modified products of primary and secondary amines, tetraalkylammonium chloride, trialkylbenzylammonium chloride, acetates of rosin amine, epichlorohydrin-modified products, monooxyethylene alkylamines, and polyoxyethylene alkylamines.

[0045] Examples of anionic surfactants include alkyl sulfates, alkyl ether sulfates, alkylbenzene sulfonates, and alkali salts of naphthalene sulfonate-formalin condensates.

[0046] Examples of nonionic surfactants include polyoxyalkylene alkyl ethers, polyoxyalkylene alkylphenyl ethers, polyoxyalkylene fatty acid esters, sorbitan fatty acid esters, and polyethylene glycol fatty acid esters.

[0047] Further, examples of radically polymerizable surfactants include polyoxyalkylene alkyl ethers, polyoxyalkylene phenyl ethers, and polyoxyalkylene mono- or distyryl phenyl ethers, each having one or more functional groups with a C=C double bond in the molecule, such as a (meth)allyl group, a 1-propenyl group, a 2-methyl-1-propenyl group, an isopropenyl group, a vinyl group, and a (meth)acryloyl group, as well as sulfonates and sulfate ester salts derived therefrom.

[0048] The amount of the low molecular weight emulsifier used is usually 0 to 10% by mass based on the total amount of the other hydrophobic monomer (b) used in the present invention.

[0049] In the solution polymerization of the present invention, it is preferable to copolymerize the monomers constituting the copolymer (A) in a solvent.

[0050] Examples of solvents that can be used in the solution polymerization of the present invention include water; lower alcohol organic solvents such as methyl alcohol, ethyl alcohol, and isopropyl alcohol; aromatic organic solvents such as benzene, toluene, and xylene; ketone organic solvents such as acetone and methyl ethyl ketone; and acetic acid organic solvents such as acetic anhydride and glacial acetic acid. These can be used alone or in combination of two or more, but it is preferable that no organic solvent, which is a hazardous material for papermaking sizing, remains. Therefore, when an organic solvent other than water is used, lower alcohol solvents or ketone organic solvents with a boiling point of less than 100°C that can be easily distilled off after polymerization, or toluene that can be distilled off by azeotropy with water, are preferably used.

[0051] Examples of polymerization methods that can be used include a batch addition polymerization method in which the monomers are charged into a reaction vessel all at once and polymerized, a divided addition polymerization method in which some or all of the monomers are dividedly added to a reaction vessel and polymerized, and a continuous dropping polymerization method in which some or all of the monomers are continuously dropped into a reaction vessel and polymerized.

[0052] The paper sizing agent obtained by the method for producing a paper sizing agent of the present invention may contain additives such as antioxidants, antifoaming agents, preservatives, chelating agents, and water-soluble aluminum compounds, if necessary.

[0053] The papermaking sizing agent can be used as a surface sizing agent or an internal sizing agent for papermaking, but is preferably used as a surface sizing agent.

[0054] Surface sizing agents are applied to base paper to exert a sizing effect mainly on the surface of the paper, while internal sizing agents are added to the pulp slurry when paper is manufactured to exert a sizing effect throughout the paper.

[0055] Pulps used in the base paper to which the surface sizing agent of the present invention is applied include bleached or unbleached chemical pulps such as kraft pulp or sulfite pulp, bleached or unbleached high-yield pulps such as groundwood pulp, mechanical pulp or thermomechanical pulp, and waste paper pulp such as recycled newspaper, recycled magazine, recycled corrugated cardboard or deinked recycled paper.

[0056] To the slurry prepared by dispersing the pulp in water, additives such as fillers, dyes, rosin-based sizing agents for acidic papermaking, alkyl ketene dimer and alkenyl succinic anhydride-based sizing agents for neutral papermaking, and rosin-based sizing agents for neutral papermaking, as well as dry strength agents, wet strength agents, retention aids, drainage aids, and antifoaming agents may be added as necessary to obtain base paper or paper in order to achieve the physical properties required for each type of paper. When used as an internal sizing agent, these are added to the pulp slurry. Examples of fillers include clay, talc, titanium oxide, and heavy and light calcium carbonate. These may be used alone or in combination.

[0057] When applied as a surface sizing agent, the sizing agent may be used as is or diluted with water, or may be mixed with at least one selected from the group consisting of starches such as oxidized starch, phosphate-esterified starch, enzyme-modified starch, ammonium persulfate-modified starch, cationic starch, and amphoteric starch, celluloses such as carboxymethyl cellulose, polyvinyl alcohols, polyacrylamides, and water-soluble polymers such as sodium alginate. Furthermore, additives such as other surface sizing agents, pH adjusters such as aluminum sulfate, conductive agents such as sodium chloride and sodium sulfate, antislip agents, preservatives, rust inhibitors, antifoaming agents, viscosity modifiers, dyes, and pigments may also be used in combination.

[0058] The concentration of the coating solution when applied as an emulsion surface sizing agent is usually 0.1 to 5% by mass, preferably 0.2 to 2% by mass. A concentration of 0.1% by mass or more can achieve the desired sizing effect, and a concentration of 2% by mass or less is preferred from the viewpoint of cost.

[0059] Usually, the coating amount is 0.01 to 5 g / m 2 , preferably 0.02 to 0.3 g / m 2 Within the above range, the sizing effect is particularly well exhibited.

[0060] When used as a surface sizing agent, the coating machine that can be used includes a size press, a film press, a gate roll coater, a rod metering coater, a blade coater, a calendar, a bar coater, a knife coater, an air knife coater, a curtain coater, etc. It can also be applied to the surface of base paper using a spray coater.

[0061] Examples of sized papers that can be obtained using a papermaking sizing agent include various types of paper and paperboard, such as recording paper, inkjet recording paper, laser printer paper, form paper, thermal transfer paper, and thermal recording paper, coated paper, such as art paper, cast coated paper, and wood-free coated paper, packaging paper, such as kraft paper and pure white roll paper, western paper, such as notebook paper, book paper, and printing paper, paperboard for paper containers, such as newsprint, manila cardboard, white cardboard, and chipboard, and paperboard, such as liner and medium. [Example]

[0062] The present invention will be described in more detail below with reference to Production Examples, Examples, and Comparative Examples, but the present invention is not limited to these Examples. In the following, "parts" and "%" mean parts by mass and % by mass, respectively, unless otherwise specified. In the following, "NV" means the solids concentration in a sample calculated from the sample weight before and after measurement at 150°C for 20 minutes.

[0063] 1-1. Preparation of copolymer (B) aqueous solution [Manufacturing Example 1] In a 1-liter four-neck flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet tube, 600 parts of water, 150 parts of styrene, and 80 parts of 80% aqueous methacrylic acid solution were mixed, and 40 parts of 30% aqueous potassium persulfate solution was added, followed by polymerization for 2 hours. Then, 110 parts of 25% aqueous caustic soda solution was added, and the mixture was diluted with ion-exchanged water to an NV of 25%, yielding an aqueous copolymer (B-1) solution.

[0064] [Manufacturing Example 2] A 25% aqueous solution of copolymer (B-2) was obtained in the same manner as in Production Example 1, except that 150 parts of styrene, 43 parts of acrylic acid, and 21 parts of maleic anhydride were used as monomers.

[0065] [Manufacturing Example 3] An aqueous solution of copolymer (B-3) was obtained in the same manner as in Production Example 1, except that 75 parts of isobutyl methacrylate, 75 parts of ethylhexyl acrylate, and 80 parts of an 80% aqueous methacrylic acid solution were used as monomers.

[0066] 1-2. Preparation of emulsion-type paper sizing agent (in the presence of copolymer (B)) Example 1 A 1-liter four-neck flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet tube was charged with 565 parts of water, 204 parts of 25% copolymer (B-1) aqueous solution, 3.4 parts of dicyclopentenyloxyethyl methacrylate as a monomer (a) having one or more non-conjugated C=C double bonds in an alicyclic carbon skeleton, 85 parts of normal butyl acrylate and 85 parts of isobutyl methacrylate as other hydrophobic monomers (b), 51 parts of 50% acrylamide aqueous solution as a hydrophilic monomer (c), and 0.1 parts of ammonium persulfate aqueous solution. The mixture was heated to 90°C while stirring under a nitrogen stream, and maintained at 90°C for 3 hours to complete the emulsion polymerization reaction, yielding an emulsion-type surface sizing agent with an NV of 24.8%.

[0067] (Examples 2 to 16) Emulsion-type surface sizing agents were obtained according to the polymerization method of Example 1, while varying the types and amounts of the monomer (a) having one or more non-conjugated C=C double bonds in the alicyclic carbon skeleton, other hydrophobic monomer (b), hydrophilic monomer (c), and aqueous solution of copolymer (B) as shown in Table 1.

[0068] (Comparative Example 1) A 1-liter four-neck flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube was charged with 569 parts of water, 204 parts of a 25% aqueous solution of copolymer (B-1), 85 parts of normal butyl acrylate and 85 parts of isobutyl methacrylate as other hydrophobic monomers (b), 51 parts of a 50% aqueous solution of acrylamide as hydrophilic monomers (c), and 0.1 parts of a 4% aqueous solution of ammonium persulfate. The mixture was heated to 90°C while stirring under a nitrogen stream, and maintained at 90°C for 3 hours to complete the emulsion polymerization reaction, yielding an emulsion-type surface sizing agent with an NV of 24.3%.

[0069] (Comparative Example 2) A 1-liter four-neck flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet tube was charged with 565 parts of water, 204 parts of 25% copolymer (B-1) solution, 17 parts of dicyclopentanyl methacrylate having no non-conjugated double bonds instead of (a), 85 parts of normal butyl acrylate and 85 parts of isobutyl methacrylate as other hydrophobic monomers (b), 51 parts of 50% aqueous acrylamide solution as hydrophilic monomers (c), and 0.1 parts of 4% aqueous ammonium persulfate solution, and the mixture was heated to 90°C while stirring under a nitrogen stream. The temperature was then maintained at 90°C for 3 hours to complete the emulsion polymerization reaction, yielding an emulsion-type surface sizing agent with an NV of 24.6%.

[0070] [Table 1]

[0071] Explanation of terms in the table α: Dicyclopentenyloxyethyl methacrylate β: Dicyclopentenyloxyethyl acrylate γ: Dicyclopentenyl acrylate ξ: Cyclopentanyl methacrylate BA: n-butyl acrylate IBMA: Isobutyl methacrylate St: styrene EHA: Ethylhexyl acrylate AAm: acrylamide MAA: methacrylic acid AA: acrylic acid Man: Maleic anhydride The same applies to the following tables

[0072] Table 2 shows the physical properties of the samples prepared in the examples and comparative examples.

[0073] [Table 2]

[0074] Evaluation test of papermaking sizing agents as surface sizing agents (Test Example 1) Evaluation of sizing performance on fine paper (1) Production of neutral woodfree base paper Pulp (a 9:1 hardwood to softwood pulp mixture) beaten to 380 ml Canadian Standard Freeness was prepared into a 2.5% slurry, to which 2% calcium carbonate (TP121S, Okutama Kogyo Co., Ltd.) was added (bone-dry weight basis). Aluminum sulfate (0.5% bone-dry weight basis), cationic starch (Cato304, National Starch Co., Ltd.), and alkyl ketene dimer sizing agent (AD1602, Seiko PMC Co., Ltd.) were then added sequentially. The slurry was then diluted to a consistency of 0.25% with dilution water at pH 7.5. Then, 15% (bone dry weight basis) calcium carbonate (Okutama Kogyo Co., Ltd.; TP121S) and 0.01% (bone dry weight basis) retention aid (Hymo Co., Ltd.; NR12MLS) were added to the diluted pulp slurry, and the mixture was pulped using a Noble & Wood paper machine at a basis weight of 65 g / m 2 The paper was made so that the pH of the paper was 7.5. The wet paper was dried using a drum dryer at 100°C for 80 seconds.

[0075] (2) Preparation of coating liquid Corn starch (Corn Starch Y, manufactured by Nippon Shokuhin Kako Co., Ltd.) was diluted with water to a concentration of 10%, and 0.3% ammonium persulfate based on the solid content of the starch was added. The mixture was gelatinized at 95°C for 30 minutes and adjusted to pH 8.5 using sodium hydroxide. The paper sizing agents obtained in Examples 1 to 16 and Comparative Examples 1 and 2 were then added to the mixture so as to achieve the following NV to prepare a coating solution. NV of coating liquid: Ammonium persulfate modified starch...6%, paper sizing agent...0.3%

[0076] (3) Production of fine paper and evaluation of sizing performance The coating solution prepared in (2) above was applied to the base paper prepared in (1) above using a size press. The amount of surface sizing agent applied to this coated paper was 0.06 g / m 2 After coating, the coating was dried using a drum dryer at 100°C for 80 seconds. The obtained test paper was conditioned for 24 hours in a constant temperature and humidity environment (23°C, 50% relative humidity), and the Stockigt size (based on JISP8122) was measured.

[0077] The results of the sizing degree evaluation are shown in Table 3. The larger the Stockigt sizing degree value, the better the sizing performance.

[0078] [Table 3]

[0079] The evaluation results show that the papers in Evaluation Examples 1 to 16 in Table 3, which were produced using the papermaking sizing agent of the present invention, have superior sizing performance (Stöckigt degree) compared to the papers in Comparative Evaluation Examples 1 and 2, which were produced using a papermaking sizing agent different from the papermaking sizing agent of the present invention.

[0080] 2-1. Manufacturing of solution-type paper sizing agents Example 17 A 1-liter four-neck flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet tube was charged with 23 parts of dicyclopentenyloxyethyl methacrylate as a monomer (a) having one or more non-conjugated C=C double bonds in an alicyclic carbon skeleton, 131 parts of styrene as another hydrophobic monomer (b), 66 parts of acrylic acid as a hydrophilic monomer (c), 2 parts of azobisisobutyronitrile, and 90 parts of isopropyl alcohol. The mixture was then heated to 80 ° C for 7 hours, followed by 2.5 parts of azobisisobutyronitrile, and the mixture was further heated at the same temperature for 3 hours. Next, 90 parts of 48% potassium hydroxide was added as a neutralizer, followed by 300 parts of water, and the temperature was raised to 100%. The isopropyl alcohol was then removed by distillation. Water was added to obtain a solution-type paper sizing agent with a NV of 27.3%.

[0081] (Examples 18 to 24) The types and amounts of the monomer (a) having one or more non-conjugated C=C double bonds in the alicyclic carbon skeleton, other hydrophobic monomer (b), and hydrophilic monomer (c) were changed as shown in Table 4, and a solution-type paper sizing agent was obtained according to the polymerization method of Example 17.

[0082] (Comparative Example 3) A 1-liter four-neck flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet tube was charged with 154 parts of styrene as the hydrophobic monomer (b), 66 parts of acrylic acid as the hydrophilic monomer (c), 2.5 parts of azobisisobutyronitrile, and 90 parts of isopropyl alcohol, and the mixture was maintained at 80°C for 7 hours. 2.5 parts of azobisisobutyronitrile were then added and the mixture was maintained at the same temperature for another 3 hours. Next, 90 parts of 48% potassium hydroxide was added as a neutralizer, followed by 300 parts of water. The mixture was further heated and the isopropyl alcohol was distilled off. Water was added to obtain a solution-type paper sizing agent with a NV of 26.9%.

[0083] Comparative Example 4 A 1-liter four-neck flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet tube was charged with 23 parts of dicyclopentanyl methacrylate, 131 parts of styrene as the hydrophobic monomer (b), 66 parts of acrylic acid as the hydrophilic monomer (c), 2.5 parts of azobisisobutyronitrile, and 90 parts of isopropyl alcohol. The mixture was then heated to 80°C for 7 hours, followed by 2.5 parts of azobisisobutyronitrile, and the mixture was further heated at the same temperature for 3 hours. Next, 90 parts of 48% potassium hydroxide was added as a neutralizer, followed by 300 parts of water. The mixture was then heated and the isopropyl alcohol was distilled off. Water was then added to obtain a solution-type paper sizing agent with a NV of 26.4%.

[0084] [Table 4]

[0085] Explanation of terms in the table IPA: Isopropyl alcohol

[0086] Table 5 shows the physical properties of the samples prepared in the examples and comparative examples.

[0087] [Table 5]

[0088] Evaluation test of papermaking sizing agents as surface sizing agents The evaluation method for the solution-type surface sizing agent was carried out in accordance with Test Example 1 described above.

[0089] The results of the sizing degree evaluation are shown in Table 6. The larger the Stockigt sizing degree value, the better the sizing performance.

[0090] [Table 6]

[0091] The evaluation results show that the papers in Evaluation Examples 17 to 24 in Table 6, which were produced using the papermaking sizing agent of the present invention, have superior sizing performance (Stöckigt degree) compared to the papers in Comparative Evaluation Examples 3 and 4, which were produced using papermaking sizing agents different from the papermaking sizing agent of the present invention.

[0092] 3. Production of emulsion-type paper sizing agents (in the presence of low-molecular-weight emulsifiers) Example 25 In a 1-liter four-neck flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet tube, 700 parts of water, a low-molecular emulsifier (Dowfax TM10 parts of 2A1 (DOW Chemical Co.) active ingredient, 10 parts of dicyclopentenyloxyethyl methacrylate as a monomer (a) having one or more non-conjugated C=C double bonds in an alicyclic carbon skeleton, 100 parts of normal butyl acrylate and 100 parts of isobutyl methacrylate as other hydrophobic monomers (b), 60 parts of 50% aqueous acrylamide solution as a hydrophilic monomer (c), and 0.8 parts of ammonium persulfate were charged, heated to 90°C, and stirred. The emulsion polymerization was completed by stirring at 90°C for 3 hours, and then cooled to 40°C. Water was added so that the NV became 25%, and a paper surface sizing agent was obtained.

[0093] Example 26 In a 1-liter four-neck flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet tube, 700 parts of water, a low-molecular emulsifier (Dowfax TM 10 parts of 2A1 (DOW Chemical Co.) (active ingredient), 20 parts of dicyclopentenyloxyethyl methacrylate as a monomer (a) having one or more non-conjugated C=C double bonds in an alicyclic carbon skeleton, 95 parts of normal butyl acrylate and 95 parts of isobutyl methacrylate as other hydrophobic monomers (b), 60 parts of a 50% aqueous acrylamide solution as a hydrophilic monomer (c), and 0.8 parts of ammonium persulfate were charged, heated to 90°C, and stirred. The mixture was stirred at 90°C for 3 hours to complete the emulsion polymerization, cooled to 40°C, and water was added to adjust the NV to 25%, to obtain a papermaking surface sizing agent.

[0094] (Comparative Example 5) A 1-liter four-neck flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet tube was charged with 700 parts of water, 10 parts of a low-molecular-weight emulsifier, 110 parts of normal butyl acrylate and 110 parts of isobutyl methacrylate as other hydrophobic monomers (b), 60 parts of a 50% aqueous acrylamide solution as hydrophilic monomers (c), and 0.8 parts of ammonium persulfate, and the mixture was heated to 90°C and stirred. The mixture was stirred at 90°C for 3 hours to complete the emulsion polymerization, cooled to 40°C, and water was added so that the NV became 25%, yielding a surface sizing agent for papermaking.

[0095] 4. Preparation of emulsion-type paper sizing agent (in the presence of starch (C)) 4-1 Production of starches (C) [Manufacturing Example 4] A reaction vessel equipped with a stirrer, a thermometer, and a reflux condenser was charged with 100 parts of cationized starch, 550 parts of water, and 4 parts of ammonium persulfate, and the mixture was heated to gelatinize. Water and sodium hydroxide were then added to adjust the NV and pH, yielding an aqueous modified cationized starch solution with an NV of 14% and a pH of 4.

[0096] 4-2. Emulsion polymerization using starches (C) Example 27 A 1-liter four-neck flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet tube was charged with 674.7 parts of the 14% modified cationized starch aqueous solution from [Production Example 4] as starch (C), 70 parts of water, and 0.1 parts of iron (II) oxide heptahydrate, and the mixture was heated to 80°C and stirred. A dropping funnel (I) was charged with 18.7 parts of dicyclopentenyloxyethyl methacrylate as monomer (a) having one or more non-conjugated C=C double bonds in an alicyclic carbon skeleton, and 93.7 parts of normal butyl acrylate and 93.7 parts of styrene as other hydrophobic monomers (b). A dropping funnel (II) was charged with 5.7 parts of a 35% aqueous hydrogen peroxide solution and 50 parts of water, and each was added dropwise over 2 hours at 80°C using the dropping funnel. After the dropwise addition, the mixture was stirred at 80°C for 2 hours to complete the emulsion polymerization, cooled to 40°C, and water was added to give a NV of 30.1%, to obtain a surface sizing agent for papermaking.

[0097] (Comparative Example 6) A 1-liter four-neck flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen inlet tube was charged with 674.7 parts of the 14% modified cationized starch aqueous solution from [Production Example 4] as starch (C), 70 parts of water, and 0.1 parts of iron (II) oxide heptahydrate, and the mixture was heated to 80°C and stirred. A dropping funnel (I) was charged with 103 parts of normal butyl acrylate and 103 parts of styrene as other hydrophobic monomers (b), and a dropping funnel (II) was charged with 5.7 parts of a 35% aqueous hydrogen peroxide solution and 50 parts of water, which were then added dropwise over 2 hours at 80°C using the dropping funnel. After the dropwise addition, the mixture was stirred at 80°C for 2 hours to complete the emulsion polymerization, cooled to 40°C, and water was added so that the NV was 29.9%, yielding a papermaking surface sizing agent.

[0098] [Table 7]

[0099] Table 8 shows the physical properties of the samples prepared in the examples and comparative examples.

[0100] [Table 8]

[0101] (Test Example 2) Evaluation of sizing performance on paperboard (1) Paperboard manufacturing 380 ml of recycled corrugated cardboard pulp with Canadian Standard Freeness, 10.0% ash content, and pH 7.0 was added to 1.0% aluminum sulfate (based on bone dry mass) of the pulp, 0.3% polyacrylamide-based strength agent (manufactured by Seiko PMC Corporation; DS4433) as a paper strength agent, and 0.1% rosin-based sizing agent (manufactured by Seiko PMC Corporation; CC1401) as a sizing agent, in this order, and diluted to 0.8% with water having an electrical conductivity of 170 mS / m. The pulp slurry was used in a Noble & Wood paper machine to prepare a 120 g / m2 paper. 2 The paper was made so that the pH of the paper was 7.3. The wet paper was dried using a drum dryer at 100°C for 160 seconds.

[0102] (2) Preparation of coating liquid The paper sizing agents obtained in Examples 25 to 27 and Comparative Examples 5 and 6 were diluted with water and kept at 50° C. before coating. A coating solution was prepared so as to have the following NV. NV of coating liquid: 1.5% Paper sizing agent...1.5%

[0103] (3) Paperboard manufacturing and sizing performance evaluation The coating solution prepared in (2) above was applied to the base paper using a size press. The amount of the paper surface sizing agent applied to the coated paper was 0.15 g / m 2 The obtained test paper was conditioned for 24 hours in a constant temperature and humidity environment (23°C, 50% relative humidity), and the Cobb water absorbency (120 seconds) (based on JISP8140) was measured. The smaller the Cobb water absorbency value, the better the sizing performance. The evaluation results are shown in Table 9.

[0104] [Table 9]

[0105] It can be seen that the papers of Evaluation Examples 25 to 27 in Table 9, which were produced using the papermaking sizing agent of the present invention, have superior sizing performance (Cobb water absorption sizing degree) compared to the papers of Comparative Examples 5 to 6, which were produced using papermaking sizing agents different from the papermaking sizing agent of the present invention.

Claims

1. A papermaking sizing agent comprising a copolymer (A) having a structure of a monomer (a) unit having one or more non-conjugated C═C double bonds in an alicyclic carbon skeleton.

2. 2. The papermaking sizing agent according to claim 1, wherein the copolymer (A) further comprises a structure of other hydrophobic monomer (b) units and a structure of hydrophilic monomer (c) units.

3. The papermaking sizing agent according to claim 2, characterized in that the copolymer (A) contains 0.1 to 40 mass% of monomer (a) units having one or more non-conjugated C═C double bonds in an alicyclic carbon skeleton, 20 to 99.8 mass% of other hydrophobic monomer (b) units, and 0.1 to 40 mass% of hydrophilic monomer (c) units.

4. A method for producing a papermaking sizing agent, comprising copolymerizing a monomer containing a monomer (a) having one or more non-conjugated C═C double bonds in an alicyclic carbon skeleton.

5. A method for producing a papermaking sizing agent, comprising copolymerizing monomers including a monomer (a) having one or more non-conjugated C═C double bonds in an alicyclic carbon skeleton, another hydrophobic monomer (b), and a hydrophilic monomer (c).

6. 6. The method for producing a papermaking sizing agent according to claim 5, wherein the amount of the monomer (a) having one or more non-conjugated C═C double bonds in an alicyclic carbon skeleton is 0.1 to 40% by mass, the amount of the other hydrophobic monomer (b) is 20 to 99.8% by mass, and the amount of the hydrophilic monomer (c) is 0.1 to 40% by mass, based on all the monomers to be copolymerized.

7. The papermaking sizing agent according to any one of claims 1 to 3 is used in an amount of 0.01 to 5 g / m ２ A method for producing paper, characterized by coating.

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