JP4400202B2 - Surface sizing agent for papermaking - Google Patents

Description

The present invention relates to an emulsion-type surface sizing agent for papermaking. Specifically, the present invention relates to an emulsion-type surface sizing agent for papermaking that is excellent in size effect during gate roll coating and size press coating, and has less foaming of the system. Furthermore, the present invention relates to a surface sizing agent for papermaking that is excellent in feathering suitability and bleeding suitability in ink jet printing.

In the papermaking process, an internal sizing method is widely used in which an internal sizing agent is added to pulp slurry in order to impart sizing properties to the finished paper. According to this, since the sizing agent can be almost 100% retained on the paper surface, normal size performance such as printability, writing property, water resistance, oil resistance (barrier property), and printability in the ink jet recording method. It is possible to obtain various effects such as (feathering suitability and bleeding suitability) that are difficult to obtain by the internally added size method. Various surface sizing agents are known, and in recent years, an anionic styrene in an aqueous solution of an alkyl or alkenyl-substituted succinate as a surface sizing agent for neutral paper that exhibits an excellent sizing effect on neutral paper. 2. Description of the Related Art A surface sizing agent (for example, see Patent Document 1) containing a composition formed by blending a polymer as an active ingredient is known.

  Surface sizing agent is applied in various ways such as size press coating, gate roll coating, dove sizing coating, shim size press coating, calendar coating and blade coating in the middle of the wet paper drying process (dryer part). Although it is applied to the paper surface by a method, gate roll coating that can cope with size press coating using two applicator rolls and high-speed papermaking is generally used. Size press coating is a method in which the paper is immersed in a relatively low concentration liquid stored between applicator rolls and then squeezed with the roll. The size liquid penetrates deep into the paper. The size effect is manifested by binding to the pulp fiber. On the other hand, gate roll coating is a system in which a film of size liquid is transferred to the paper surface from a roll in which a relatively high concentration of size liquid is stored via an applicator roll in contact with the roll. Since it can be fixed 100%, the paper surface can be greatly modified.

  As described above, there are various surface sizing agent coating methods. However, there are few surface sizing agents that can be applied to all methods, and there are some cases where it is difficult to realize the size effect when the coating apparatus is switched. Therefore, with the change of the coating method, there is a trouble that the composition of the surface sizing agent has to be changed in consideration of the desired paper quality effect (size property, printability, writing property, inkjet property, etc.). It was.

JP 9-228293 A

The problem to be solved by the present invention is the use of an alkyl or alkenyl-substituted succinate that has been widely used as a raw material for neutral sizing agents in recent years, and the current mainstream size press coating method and gate roll coating method. An object of the present invention is to provide an emulsion-type surface sizing agent for papermaking, which can exhibit a good sizing effect in both systems. Furthermore, it is providing the surface sizing agent for paper manufacture which is excellent also in the feathering and bleeding ability in inkjet printing.

  As a result of intensive studies to solve the above problems, the present applicant has found that a specific amount of various vinyl monomers in the presence of a specific amount of an alkali salt of alkyl or alkenyl-substituted succinic anhydride having 8 to 36 carbon atoms. It has been found that according to the paper sizing agent using an aqueous emulsion composition obtained by emulsion polymerization, the above problems can be solved.

That is, the present invention is 100 wt % of a vinyl monomer mixture comprising 80 to 98 wt% of a hydrophobic unsaturated monomer, 1 to 15 wt% of (meth) acrylic acid and 1 to 10 wt% of an acrylamide monomer. And an aqueous emulsion composition obtained by emulsion polymerization of an alkyl or alkenyl-substituted succinic anhydride alkali salt having 16 to 20 carbon atoms, which is 2 to 8 parts by weight (in terms of solid content). Paper-making surface sizing agent; paper-making surface sizing agent, and a water-soluble polymer obtained by further polymerizing a hydrophobic unsaturated monomer and a carboxyl group-containing unsaturated monomer to the paper-making surface sizing agent Agent.

According to the surface sizing agent for papermaking according to the present invention, a certain size effect can be obtained regardless of the coating method. In particular, a well-balanced size effect can be obtained during gate roll and size press coating. Moreover, there is also a feature that the foaming of the system is small. Furthermore, it is also characterized by excellent feathering and bleeding suitability in ink jet printing.

First, the aqueous emulsion composition which is an active ingredient of the paper sizing agent according to the present invention will be described. The basic polymer of the emulsion is a vinyl polymer having various known vinyl monomers, particularly hydrophobic unsaturated monomers, (meth) acrylic acid and acrylamide monomers as constituent components.

Examples of the hydrophobic unsaturated monomer include styrenes such as styrene, α-methylstyrene, vinyltoluene, α-olefins whose alkyl group is a straight chain or branched chain having 6 to 22 carbon atoms, and carbon number of the alkyl group. 1 to 18 (meth) acrylic acid alkyl ester, the ester substituent is a hydroxyalkyl group such as 2-hydroxyethyl group and 2-hydroxypropyl group, various (meth) acrylic acid esters such as benzyl group and allyl group, ( Examples thereof include vinyl esters such as (meth) acrylonitrile, vinyl acetate and vinyl propionate, and alkyl vinyl ethers having 1 to 22 carbon atoms. These hydrophobic unsaturated monomers can be used alone or in combination of two or more. Among them, styrenes and / or (meth) acrylic acid alkyl esters are preferable. Among the above (meth) acrylic acid esters, (meth) acrylic acid alkyl esters having 1 to 18 carbon atoms in the alkyl group are preferable. In particular, the case where the alkyl group has 1 to 12 carbon atoms is preferable. Examples of the alkyl group having 1 to 18 carbon atoms include straight chain, branched chain and cyclic groups, such as methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i- Examples thereof include a butyl group, a t-butyl group, a neopentyl group, an n-hexyl group, a cyclohexyl group, a 2-ethylhexyl group, a decyl group, a palmityl group, and a stearyl group.

Only (meth) acrylic acid, and with the carboxyl-containing monomers, maleic acid, maleic half esters, itaconic acid, itaconic Sanhan ester, citraconic acid, fumaric acid, Ru crotonic acid and the like. Particularly preferred is (meth) acrylic acid and / or a salt thereof.

  Examples of the acrylamide monomers include acrylamide, methacrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N-isopropyl (meth) acrylamide, and N-tertiary. N-substituted monoalkyl (meth) acrylamides such as butyl (meth) acrylamide, N-lauryl (meth) acrylamide, and N-cyclohexyl substituted alkyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N -Diisopropyl (meth) acrylamide, N, N-ditertiary butyl (meth) acrylamide, N, N-dilauryl (meth) acrylamide, N, N-ditertiary octyl (meth) acrylamide, and N, N-dicyclohexyl ( Data) acrylamide, N- substituted dialkyl (meth) acrylamide, diacetone acrylamide, and the like. Among these, (meth) acrylamide is preferable.

In addition to the above-mentioned vinyl monomers, nonionic unsaturated monomers such as vinyl pyrrolidone, and sulfonic acid-containing anionic impurities such as vinyl sulfonic acid and 2-acrylamido-2-methylpropane sulfonic acid as necessary. A saturated monomer or an alkali salt thereof can also be used. The amount used is in a range that does not reduce the size performance of the resulting emulsion-type paper surface sizing agent according to the present invention, and is usually 10% by weight or less of the total weight of the basic polymer.

The amount of each of the hydrophobic unsaturated monomer, (meth) acrylic acid and acrylamides used in the basic polymer is 80 to 98% by weight , preferably 84 to 96% by weight, (meth). Acrylic acid is about 1 to 15% by weight , preferably 2 to 8% by weight, and acrylamides are about 1 to 10% by weight , preferably 1 to 6% by weight. When the amount of the hydrophobic unsaturated monomer used is less than 80% by weight, it tends to be difficult to obtain a good size effect, and when it exceeds 98% by weight, the stability of the emulsion tends to be lowered. Further, when the amount of (meth) acrylic acid used is less than 1% by weight, the storage stability of the emulsion tends to be lowered, and when it exceeds 10% by weight, the size effect is lowered and the emulsion is constituted. Since the particles contain a relatively large amount of anionic functional groups, the viscosity of the emulsion tends to increase and workability tends to decrease. Further, when the amount of acrylamide used is less than 1% by weight, the storage stability and mechanical stability at the time of dilution in a hard water system tend to decrease, and when the amount exceeds 10% by weight, the size effect decreases. It tends to be.

  In order to disperse the basic polymer in water, at least 50% or more, more preferably 80 to 100%, of the carboxyl groups contained in the basic polymer needs to be neutralized. Such neutralization can be performed at the stage of the carboxyl group-containing unsaturated monomer as well as after the production of the basic polymer. As the neutralized salt, alkali metal salts such as sodium hydroxide and potassium hydroxide, and ammonium salts and / or volatile amine salts are preferable.

  As for the ammonium salt, an ammonium salt such as ammonium carbonate can be used in addition to ammonia. Examples of the volatile amine include aliphatic, alicyclic or aromatic amine salts having about 1 to 12 carbon atoms, similar arylamine salts, alkanolamine salts and the like. Specifically, for example, aliphatic amines such as monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine and monobutylamine, alicyclic amines such as cyclohexylamine, aromatic amines such as aniline, arylamines, alkanolamines, etc. And primary amines and secondary amines. Among these neutralized salts, an ammonium salt with ammonia is particularly preferable.

Next, an alkali salt of an alkyl or alkenyl substituted succinic anhydride having 16 to 20 carbon atoms will be described. This material is intended in the present invention exhibits an emulsifier (protective colloid) effects of the backbone polymer, the alkali salts include salts of alkali metals, ammonia or organic amines. By using this, the size effect at the time of gate roll coating and size press coating is improved, and foaming of the system can be suppressed. However, since the size effect at the time of size press tends to decrease if this amount is used more than necessary, the amount used is 100 parts by weight of the vinyl monomer mixture constituting the basic polymer described above. 2 to 8 parts by weight , particularly preferably 3 to 6 parts by weight. If the amount used is too small, a satisfactory size effect cannot be obtained at the time of gate roll coating, and if it is 8 parts by weight or more, the size effect at the time of size pressing tends to be difficult to obtain as described above.

Below, the manufacturing method of the emulsion which comprises the surface sizing agent for paper manufacture which concerns on this invention is demonstrated. The emulsion may be produced by known means. For example, an aqueous solution in which the alkyl salt having 16 to 20 carbon atoms or the alkenyl-substituted succinic anhydride is dissolved is charged into a reaction vessel equipped with a suitable heating device and a stirrer. The vinyl monomer mixture and a known radical polymerization initiator are added to the container, and then water, an organic solvent and various known emulsifiers are charged into the container, and the mixture is heated with stirring to start polymerization. The method of neutralizing is mentioned. In addition, the charging method of the vinyl monomer may be either batch charging or divided dropping, or may be a dropping method together with a radical polymerization initiator. The polymerization temperature is usually about 40 to 150 ° C., and the reaction time is about 2 to 12 hours.

The type of the polymerization initiator is not particularly limited, inorganic peroxides such as hydrogen peroxide, ammonium persulfate, potassium persulfate, organic peroxides such as benzoyl peroxide, dicumyl peroxide, lauryl peroxide, 2, Known substances such as azo compounds such as 2′-azobisisobutyronitrile and dimethyl-2,2′-azobisisobutyrate can be appropriately selected and used. The amount used is usually about 0.01 to 5 parts by weight per 100 parts by weight of the vinyl monomer. In the case of a radical polymerization initiator, the reaction system may be a redox system by using a reducing agent such as sodium bisulfite or sodium thiosulfate in combination. In addition, a chain transfer agent such as dodecyl mercaptan, 2-mercaptobenzothiazole, bromotrichloromethane and the like can be used to adjust the degree of polymerization to a desired viscosity during polymerization, The amount is usually about 0.01 to 5 parts by weight per 100 parts by weight (solid content) of the body mixture.

  Examples of the organic solvent used in the emulsion polymerization include alcohols such as ethyl alcohol and propyl alcohol, lower ketones such as acetone and methyl ethyl ketone, aromatic hydrocarbons such as toluene and benzene, ethyl acetate, chloroform and dimethylformamide. They can be used alone or in appropriate combination. However, these organic solvents are preferably distilled off by steam distillation or vacuum distillation.

    In the emulsion polymerization, various known anionic or nonionic surfactants can be used alone or in admixture as long as the object of the present invention is not impaired. The amount of the surfactant used is 10% by weight or less, more preferably 5% by weight or less, based on the total weight of all monomers constituting the basic polymer. When it exceeds 10% by weight, the foamability of the obtained emulsion becomes strong, and troubles due to foam may be caused when it is used as a coating solution. Examples of the nonionic surfactant include polyethylene glycol, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene styryl phenyl ether, polyoxyethylene sorbitan fatty acid ester and the like. Examples of the anionic surfactant include alkyl sulfates, alkyl benzene sulfonates, polyoxyethylene alkyl ether sulfates, polyoxyethylene alkyl phenyl ether sulfates, dialkyl sulfosuccinates, alkyl sulfonates, polyoxyethylene alkyls. Ether sulfosuccinate, polyoxyethylene styryl phenyl ether sulfosuccinate ester salt, polyoxyethylene alkyl ether phosphate ester, α-olefin sulfonate, naphthalene sulfonate formalin condensate, polyoxyethylene alkyl phenyl ether sulfate ester, etc. Etc. Moreover, you may use the nonionic or anionic surfactant etc. which have a reactive functional group in a molecule | numerator (refer Unexamined-Japanese-Patent No. 2003-293288) as shown by the following general formula. A cationic surfactant cannot be used because aggregates are generated during polymerization.

(Wherein R ₁ and R ₂ are a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms; X is a copolymerizable functional group containing a carbon-carbon double bond; A in (AO) is carbon N is an integer of 1 to 100; B is at least one selected from hydrogen, sulfonic acid group, phosphoric acid group, sulfosuccinic acid group and salts thereof, and sulfosuccinic acid group ester Is shown.)

(In the formula, R ₃ is a hydrocarbon group having 1 to 20 carbon atoms or an aromatic ring substituted with at least one hydrocarbon group having 1 to 20 carbon atoms; X is a common group containing a carbon-carbon double bond; A polymerizable functional group; in (AO), A is an alkylene group having 2 to 4 carbon atoms or a substituted alkylene group; n is an integer of 1 to 100; B is hydrogen, a sulfonic acid group, a phosphoric acid group, a sulfosuccinic acid group, and (At least one selected from these salts and sulfosuccinic acid group esters; l represents an integer of 0 or 1)

  The emulsion composition thus obtained has a yellowish cloudy appearance, and has a pH of 7.5 to 8.5, a viscosity of 5 to 30 mPa · s (25 ° C.), and a particle size of 60 to 200 nm at a concentration of 25% by weight. is there.

In the surface sizing agent for emulsion type papermaking of the present invention, starches such as oxidized starch, phosphate esterified starch, enzyme-modified starch, and cationized starch that are usually used in combination as a paper strength enhancer; celluloses such as carboxymethylcellulose Polyvinyl alcohols, polyacrylamides, and water-soluble polymers such as sodium alginate can be added and used. In addition, if necessary, various other known sizing agents, emulsion type sizing agents, anti-slip agents, antiseptics, rust inhibitors, pH adjusters, antifoaming agents, thickeners, fillers, antioxidants, water resistance Agents, film-forming aids, pigments, dyes and the like can be added.

  In addition, as an additive for the paper sizing surface sizing agent according to the present invention, a gate roll coating is prepared by blending a water-soluble polymer obtained by polymerizing a hydrophobic unsaturated monomer and a carboxyl group-containing unsaturated monomer. It is possible to improve the sizing property at the time of processing, and in addition, it is possible to obtain good color ink jet aptitude, specifically, the effect of balanced feathering aptitude and bleeding aptitude. The water-soluble polymer is a polymer aqueous solution (solution) obtained by polymerizing the above-described hydrophobic unsaturated monomer and the above-described carboxyl group-containing unsaturated monomer according to various known polymerization methods. As the combination of the bodies, for example, styrene-maleic acid, styrene- (meth) acrylic acid and the like are preferable. The amount of the hydrophobic unsaturated monomer and the carboxyl group-containing unsaturated monomer is not particularly limited, but in the basic polymer, the former is usually about 20 to 80% by weight and the latter is usually about 80 to 20% by weight. is there. The water-soluble polymer thus obtained usually has a molecular weight (polystyrene conversion value by gel permeation chromatography) of about 1,000 to 1,000,000, preferably 2,000 to 100,000, and usually has a solid content of about 10 to 30% by weight. It has physical properties such that the viscosity in the partial concentration range is about 10 to 10000 mPa · s (25 ° C.), the pH is about 8.0 to 9.5, and the acid value is usually about 150 to 600. In the present invention, the water-soluble polymer is usually less than 300 parts by weight (solid content), preferably 20 to 250 parts by weight (solid) with respect to 100 parts by weight (solid content) of the paper sizing surface sizing agent according to the present invention. Minutes). The means for mixing is not particularly limited. If it exceeds 300 parts by weight, the feathering for ink jetting tends to be rather lowered.

The surface sizing agent for papermaking of the present invention can be applied to various papers and paperboards without any particular limitation. The types of paper include foam paper, PPC paper, thermal recording base paper, pressure sensitive recording base paper, etc., and base paper for coated paper such as base paper, art paper, cast coated paper, high quality coated paper, kraft paper, pure white Examples include wrapping paper such as roll paper, various papers (Western paper) such as notebook paper, book paper, printing paper, and newsprint paper; paperboard paperboard such as Manila ball, white ball, and chipball, and paperboard such as liner.

Further, the surface sizing agent for papermaking of the present invention includes the effects of raw materials such as pulp, filler, internal sizing agent, internal paper strength enhancer, yield improver, and internal chemicals, and papermaking pH, papermaking temperature, papermaking machine. This is almost unaffected by papermaking conditions such as the type of paper. The surface sizing agent for papermaking of the present invention is applied to the above-mentioned various papers by a conventionally known coating method, for example, an impregnation method, a size press method, a gate roll method, a gate roll method, a calendar method, or a spray method. However, the size effect in the size press method and the gate roll method is particularly good. The coating amount of the paper is usually 0.001~2g / m ² (solid content), preferably from 0.005 to 0.5 / m ^2.

  Hereinafter, the present invention will be specifically described with reference examples and comparative examples, but the present invention is not limited to these examples. In each example, all parts and% are based on weight unless otherwise specified.

Synthesis example 1
While introducing nitrogen into a reactor equipped with a stirrer, a reflux condenser, and a nitrogen introduction tube, 100 parts of soft water and 75 parts of isopropyl alcohol were charged, and the system was heated to 80 ° C. while stirring. Next, a monomer mixed solution in which 45 parts of styrene and 55 parts of acrylic acid were mixed into the system, and an aqueous polymerization initiator solution in which 5 parts of potassium persulfate was dissolved in 120 parts of water were dropped into the system over about 3 hours. The system was incubated for 2 hours to complete the reaction. Thereafter, isopropyl alcohol was distilled off, and after cooling, 46.4 parts of 28% aqueous ammonia solution (100 mol% relative to acrylic acid) was added and diluted with water to adjust the concentration of the copolymer to 20%. A copolymer aqueous solution (hereinafter referred to as polymer (A)) having a viscosity at 25 ° C. of 1100 mPa · s was obtained.

Synthesis example 2
While introducing nitrogen into a reactor equipped with a stirrer, a reflux condenser, and a nitrogen introduction tube, 60 parts of isopropyl alcohol was charged, and the system was heated to the reflux temperature while stirring. Next, a monomer mixed solution prepared by mixing 50 parts of styrene, 15 parts of methyl methacrylate, 30 parts of acrylic acid, 5 parts of acrylamide and 1.5 parts of azobisisobutyronitrile was added to the system over about 2 hours. Then, the system was kept warm for 4 hours to complete the reaction. Thereafter, the mixture was cooled to 75 ° C., and 24 parts of a 48% sodium hydroxide aqueous solution and 360 parts of water were added. After completion of the addition, isopropyl alcohol is distilled off, and after cooling, 9 parts of 28% aqueous ammonia solution is added and diluted with water to adjust the concentration of the copolymer to 20%, and the viscosity at 25 ° C. is 300 mPa · s. An aqueous copolymer solution (hereinafter referred to as polymer (B)) was obtained.

Production Example 1 (Production of aqueous emulsion composition)
In a 1 liter four-necked flask (reaction vessel) equipped with a stirrer, thermometer, reflux condenser and nitrogen inlet tube, 300 parts of water and 5.0 parts of alkenyl succinic anhydride having 18 carbon atoms as protective colloid 12.5 parts of an aqueous solution having a non-volatile content of 40% and a pH of 13.0 consisting of 2.38 parts of a 48% sodium hydroxide aqueous solution (100 mol% neutralized with respect to the alkenyl succinic anhydride). 5 parts by weight based on the total weight of the monomer, α-methylstyrene 8 parts, butyl methacrylate 84 parts, methacrylic acid 6 parts, acrylamide 2 parts, N-dodecyl mercaptan 0.5 parts, 48% caustic soda 5.8 parts (methacrylic) 100 mol% neutralization with respect to the acid) and an anionic surfactant (Neohaitenol S-70: manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 4 parts were charged. After sufficiently replacing oxygen in the reaction system with nitrogen, the temperature of the mixture was raised to 70 ° C., and then a radical polymerization initiator (an aqueous solution in which 2.5 parts of ammonium persulfate was dissolved in 8 g of water) was added to the reaction vessel. did. Next, after emulsion polymerization for 20 minutes, the temperature was raised to 80 ° C., and the polymerization reaction was allowed to proceed in the temperature range of 80 to 85 ° C. for 2 hours. Thus, an emulsion composition (surface sizing agent for papermaking) having a pH of 8.2, a solid content concentration of 25.5%, and a viscosity of 10 mPa · s / 25 ° C. was obtained.

Production Examples 2-11
An emulsion composition (surface sizing agent for papermaking) was obtained in the same manner except that the raw materials shown in Table 1 were used.

In the table, αSt means α-methylstyrene, BMA means butyl acrylate, MAA means methacrylic acid, and AM means acrylamide.

In the table,
* 1: Indicates the weight percentage of emulsifier used relative to the total amount (parts) of monomer.
* 2: This means the neutralization rate (mol%) of carboxyl groups in the backbone polymer that forms the emulsion.
* 3: Means the solid content concentration (% by weight) of the emulsion composition.
* 4: Indicates a value (mPa · s) measured with a Brookfield viscometer at 25 ° C.

In the table,
C _18-36 ASA: An alkyl or alkenyl substituted succinic anhydride alkali salt having 8 to 36 carbon atoms.
ODSA: means succinic anhydride substituted with an alkenyl group having 18 carbon atoms (octadecenyl group).
DDSA: means succinic anhydride substituted with an alkenyl group having 12 carbon atoms (dodecenyl group).
HDSA: means succinic anhydride substituted with an alkenyl group having 16 carbon atoms (hexadecenyl group).
S-70; sodium half-ester sulfosuccinate (trade name “Neohaitenol S-70” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)

<Preparation of surface sizing solution: for size press coating>
The emulsion composition of Production Example 1 described in Table 1 contains 0.15% in solid concentration, and oxidized starch (trade name “Oji Ace”: manufactured by Oji Corn Starch Co., Ltd.) contains 5% in solid concentration. The balance was a surface sizing solution consisting of water. Surface sizes 2 to 11 were similarly prepared for Production Examples 2 to 11.

In addition, the polymer (A) obtained in Synthesis Example 1 was mixed with the emulsion composition according to Production Example 1 so that the solid content ratio was 1/1, and the solid content concentration was 0.15% with water. A surface sizing solution 12 containing 5% of the oxidized starch in solid content and the balance comprising water was prepared.

An aqueous sodium salt solution of an alkenyl succinic anhydride having 18 carbon atoms is mixed with the polymer (A) obtained in Synthesis Example 1 so that the solid content ratio is 5/5, and the solid content concentration is 0.15 with water. %, A surface sizing solution 13 containing 5% of the above-mentioned oxidized starch in solid content and the balance comprising water was prepared.

  An aqueous sodium salt solution of an alkenyl succinic anhydride having 18 carbon atoms is mixed with the polymer (B) obtained in Synthesis Example 2 so that the solid content ratio is 95/5, and the solid content concentration is 0.15 with water. %, And the oxidized starch was contained in a solid content of 5%, and the balance was prepared as a surface sizing solution 14 consisting of water.

  Only the polymer (A) obtained in Synthesis Example 1 was prepared with a surface concentration solution 15 containing a solid content concentration of 0.15% in water and the oxidized starch in a solid content of 5%, with the balance being water. .

<Preparation of surface sizing solution: for gate roll>
The composition concentration of the surface size liquids 1 to 11, 12, 13, 14, and 15 for the size press is such that the solid content concentration of oxidized starch is 8% and the concentration of solid content components other than oxidized starch is 3%. The changed ones were designated as surface size liquids 16 to 26, 27, 28, 29, and 30, respectively.

<Test paper preparation: size press method>
Neutral high-quality paper (weighing 70 g / m ² , Steecht size degree 0 second) is used as a base paper, and each of the above surface size liquids 1 to 15 is used for a laboratory size press coating machine (size press for testing, Riki Kumagai). Coating was carried out by Kogyo Co., Ltd. Next, each coated paper was dried at 105 ° C. for 1 minute with a rotary drum dryer to obtain a target test paper.

<Test paper preparation: gate roll method>
The neutral high-quality paper was used as a base paper, and coating was performed using a lab gate roll coating machine (manufactured by SMT Co., Ltd.) using each of the surface size liquids 16 to 30. Next, each coated paper was dried at 105 ° C. for 1 minute with a rotary drum dryer to obtain a target test paper.

Examples, comparative examples (measurement of squeecht size)
Using each coated paper obtained by the above-mentioned method, the Steecht sizing degree was measured in accordance with JIS P8122. The results are shown in Table 2.

(Drop size measurement)
Using each coated paper obtained by the above method, 0.5 μL of deionized water was dropped on the paper surface, and the time until gloss was lost was measured. The results are shown in Table 2.

(Measurement of foamability)
The height of foaming (mm) was measured when each of the surface sizing liquids 1 to 16 was heated to 50 ° C. and treated with a household mixer for 1 minute. The results are shown in Table 2.

(Evaluation of inkjet suitability (print density measurement))
Each coated paper obtained by the size press method was printed in monochrome color (dye) using an inkjet printer (trade name “BJC-420J” manufactured by Canon Inc.). Subsequently, the density measurement of the printing site | part obtained using the reflection densitometer (Brand name "Gretag D186": Gretag Macbeth Co., Ltd. product) was performed. The larger the value, the higher the print density. The results are shown in Table 2.

(Evaluation of ink jet aptitude (feathering test))
Straight lines and characters with a constant line width that go straight in monochrome color (dye) using an inkjet printer (trade name “BJC-420J” manufactured by Canon Inc.) on each coated paper obtained by the size press method. This was done by visually observing blurring of straight lines and outer edges of characters. The case where there was no feathering was set to 6, and the case where ink could not be recognized due to ink bleeding was set to 0. The results are shown in Table 2.

(Evaluation of inkjet suitability (bleeding test))
On each coated paper obtained by the size press method, printing is performed so that yellow and black are adjacent to each other using an inkjet printer (trade name “BJC-420J” manufactured by Canon Inc.). This was performed by visually evaluating the bleeding of the black ink. The case where there was no feathering was set to 6, and the case where ink was blurred and the character could not be identified was set to 0. The results are shown in Table 2.

As is apparent from the results shown in Table 2, Examples 1 to 3 exhibit a high size effect even in the size press method and the gate roll method. That is, a good size effect can be expressed in both the size press coating method and the gate roll coating method, and foaming in the system is very small. In Comparative Examples 1 to 3 , and 10 , since the alkenyl-substituted succinic anhydride alkali salt as the protective colloid is used in excess of 8 % by weight of the total amount of the vinyl monomer, the size effect in the gate roll method is relatively high. However, the size press method has a low degree of steecht size. Comparative Example 5 is a blend of an alkali salt of alkenyl succinic anhydride and a polymer comprising a hydrophobic unsaturated monomer, methacrylic acid and an acrylamide monomer, but the alkenyl succinic anhydride is added in the same amount. Compared with Example 1 etc. which are these, it turns out that size is hard to express in a gate roll method.

Further, from Example 4 in Table 2, a water-soluble polymer obtained by polymerizing a hydrophobic unsaturated monomer and a carboxyl group-containing unsaturated monomer as an additive to the paper sizing agent according to the present invention. By blending, it is possible to obtain good color ink jet aptitude, specifically, an effect of balancing the feathering and bleeding.

Claims (7)

Hydrophobic unsaturated monomer 80-98 wt%, and (meth) vinyl monomer mixture 100 parts by weight consisting of 1 to 15% by weight of acrylic acid and acrylamide monomer 1 to 10% by weight, whereas A surface sizing agent for papermaking comprising an aqueous emulsion composition obtained by emulsion polymerization of an alkyl or alkenyl-substituted succinic anhydride alkali salt having 16 to 20 carbon atoms , which is 2 to 8 parts by weight (in terms of solid content) . The surface sizing agent for papermaking according to claim 1, wherein the hydrophobic unsaturated monomer is styrene and / or (meth) acrylic acid alkyl ester. The surface sizing agent for papermaking according to claim 1 or 2, wherein the acrylamide monomer is (meth) acrylamide. Papermaking surface sizing agent according to any one of claims 1 to 3, further mixing a hydrophobic unsaturated monomers and carboxyl group-containing unsaturated monomer is polymerized obtained water-soluble polymer Surface sizing agent for papermaking. The said water-soluble copolymer which becomes less than 300 weight part (solid content) with respect to 100 weight part (solid content) of the paper-made surface sizing agent in any one of Claims 1-4 is mixed. The surface sizing agent for papermaking described in 1. A paper sizing method, wherein the paper surface is sized using the paper surface sizing agent according to any one of claims 1 to 5 . Paper which coats the surface sizing agent for papermaking in any one of Claims 1-5 on the surface.