JP5331363B2 - Method for producing cationic surface sizing agent, sizing agent obtained by the method, and paper coated with the sizing agent - Google Patents

Description

  In the present invention, a copolymer (A) containing a tertiary amino group-containing monomer, a (meth) acrylic ester monomer, and a styrene monomer as constituent units and one or more hydrophobic monomers in the presence of a surfactant. A method of producing a cationic surface sizing agent, characterized in that the tertiary amino group of the copolymer (A) is converted into a quaternary ammonium base after polymerization, and a cationic surface sizing agent produced by the production method; The present invention relates to a paper coated with the sizing agent.

  Recent trends in papermaking technology include the improvement of operability during papermaking, or the increase in papermaking pH due to neutralization and the reduction of dirt in the papermaking system when calcium carbonate is internally added as a filler. The amount of the sizing agent is reduced, or the coating amount of the surface sizing agent is increased after paper making without internal addition, so that the water resistance of paper and paperboard is improved. Under such circumstances, cases where anionic surface sizing agents are not effective are increasing, and in particular, a neutral surface sizing agent is coated with a cationic surface sizing agent.

  However, when it is used for paper and paperboard, which has been increasing in recent years, with extremely low sizing properties, or paper made without the addition of a sizing agent, it diffuses into the paper layer even if a conventional cationic copolymer is applied. The effect cannot be fully demonstrated. Therefore, a large amount of coating is required to ensure practical sizing properties, and problems are likely to occur in terms of operation and cost. In particular, this problem is significant with high ash neutral paper.

  Conventional cationic surface sizing agents generally include a copolymer having a tertiary amino group mainly composed of styrenes and a tertiary amino group-containing monomer (that is, a cationic monomer) or a quaternary modified by quaternization thereof. It consists of the aqueous solution of the copolymer which has an ammonium base (refer patent documents 1-2). The polymer performs solution polymerization using an oil-soluble polymerization initiator in an organic solvent or a mixed solvent of an organic solvent and water, or emulsion polymerization using a water-soluble polymerization initiator in a water-based solvent. It is synthesized by the technique of performing. Cationic surface sizing agent that polymerizes in solution is a polymerization mainly composed of styrenic monomer and cationic monomer. In order to improve copolymerization and increase the effect of imparting size, a large amount of organic solvent is used in the production process. Solution polymerization had to be performed. Further, when the organic solvent contained in a large amount is distilled after water-solubilization or in the case of a water-soluble organic solvent, if it is a small amount, it is contained in the product water as it is.

  On the other hand, a cationic surface sizing agent obtained by emulsion polymerization of a styrene monomer and a cationic monomer in an aqueous medium without using an organic solvent, or emulsion polymerization of a hydrophobic monomer in a cationic polymer aqueous solution of the above solution polymerization (Patent Document 3) 10)), the conventional cationic polymerization of the solution polymerization described above, even when applied to neutral paper using an internally added sizing agent as well as paper and newspaper made without using the internally added sizing agent. Compared with the sizing agent, the effect of imparting sizing is inferior.

  Furthermore, these cationic surface sizing agents have strong adhesion to an anionic surface due to their properties, and the dry film is hardly soluble in water. For this reason, when the sizing agent is dried during the production of the product or in the coating solution, the coating does not re-dissolve, which may lead to operational troubles such as scale adhesion.

  Also, with newsprint paper coated with a conventional cationic surface sizing agent, the sizing agent adheres to the PS plate via a dampening solution during printing on the offset printing press, and after the offset printing press stops, When it is raised, the sizing agent adhering to the PS plate is difficult to fall off, so that the non-image area is sensitized and printing troubles due to plate stains are likely to occur. In particular, this problem is likely to occur at present when the neutralization of newsprint tends to increase the size of newsprint by applying a large amount of cationic surface sizing agent.

  In addition, offset printing inks have recently been replaced by AF inks using vegetable oils that do not contain aromatic components as solvents for environmental reasons. However, newspapers using conventional cationic surface sizing agents have been used. The paper was not sufficiently printable for AF ink.

JP 2006-161259 A JP 2006-320993 A Japanese Patent Laid-Open No. 11-256696 JP-A-11-279983 JP 54-006902 A JP 59-076966 JP 2001-262495 A JP 2006-016712 A JP 2002-129494 A Special table 2008-501830 gazette

  In the present invention, a neutral paper having a sizing degree of 2 seconds or less, in which no internal sizing agent is used, the internal sizing agent and the external sizing agent are used together only by coating the external sizing agent. It is an object of the present invention to provide a cationic surface sizing agent that gives the same high sizing properties as sometimes.

  In addition, the present invention improves the stability of the product in the coating liquid and the re-dissolvability of the dry resin, and compared with conventional cationic surface sizing agents, troubles caused by adhesion of the dry film during production and use are reduced. It is an object of the present invention to provide a cationic surface sizing agent that can suppress generation.

  In addition, the present invention is also applicable to a case where the elution substance due to the penetration of dampening water adheres to the non-image area of the PS plate for offset printing and becomes sensitized during offset set printing. It is an object of the present invention to provide a cationic surface sizing agent that is excellent in the detergency of the oil-repellent part and hardly causes scumming on the newspaper printing surface.

  It is another object of the present invention to provide a cationic surface sizing agent that is excellent in ink deposition on the printing surface of paper printed with offset ink, particularly newsprint paper, and can suppress the occurrence of printing unevenness.

The present invention provides the following method for producing a cationic surface sizing agent, the sizing agent obtained by the method, a surface treatment method using the sizing agent, and a paper coated with the sizing agent.
(1) (a) 20-50% by weight of a tertiary amino group-containing monomer,
(B) 10 to 80% by weight of a C _{4 to} C ₁₈ alkyl ester of (meth) acrylic acid,
(C) a first step of obtaining a copolymer (A) by solution polymerization of a monomer mixture containing 0 to 70% by weight of styrenes in the presence of a chain transfer agent;
A step of obtaining a copolymer (B) by polymerizing one or more hydrophobic monomers in the presence of the copolymer (A) and a surfactant, wherein 3 in the copolymer (B) The second step in which the constituent ratio of the secondary amino group-containing monomer (a) is 10 to 20% by weight and the constituent ratio of the copolymer (A) is 90 to 10% by weight, and the copolymer (B) A method for producing a cationic surface sizing agent, comprising a third step in which a tertiary amino group is a quaternary ammonium base.
(2) In the first step, the copolymer (A) obtained by solution polymerization is neutralized with respect to the tertiary amino group-containing monomer (a) of the copolymer (A). The production method according to item (1), wherein the acid is used to form an aqueous solution.
(3) The production method according to (1) or (2) above, wherein the average particle size of the copolymer (A) in the form of an aqueous solution in the first step is 50 nm or less.
(4) The production method according to any one of (1) to (3), wherein an average particle size of the cationic surface sizing agent obtained in the third step is 150 nm or less.
(5) In the third step, any one of the above items (1) to (4), wherein 50 to 100 mol% of the tertiary amino group contained in the copolymer (B) is converted to a quaternary ammonium salt with epichlorohydrin. The manufacturing method as described in.
(6) The tertiary amino group-containing monomer (a) is any one of the above (1) to (5), wherein the dialkylaminoalkyl (meth) acrylate and / or dialkylaminoalkyl (meth) acrylamide is used. Production method.
(7) The production method according to any one of (1) to (6), wherein the surfactant is cationic.
(8) A cationic surface sizing agent produced by the production method according to any one of (1) to (7).
(9) A paper surface treatment method comprising coating the surface of paper with the cationic surface sizing agent according to (8) or a mixture of the sizing agent and a water-soluble polymer compound.
(10) A paper characterized in that the cationic surface sizing agent according to (8) or a mixture of the sizing agent and a water-soluble polymer compound is applied to the surface of the paper.
(11) The paper according to item (10), wherein the paper before applying the surface sizing agent is paper containing no internal sizing agent and / or neutral paper having a Steecht sizing degree of 2 seconds or less. .

  In the present invention, at least one hydrophobic monomer in the presence of a copolymer (A) containing a tertiary amino group-containing monomer, a (meth) acrylic ester monomer, and a styrene monomer as constituent units and a surfactant. After the polymerization, the compatibility of the copolymer (A) with the copolymer (A) during polymerization of the hydrophobic monomer can be improved by changing the tertiary amino group of the copolymer (A) to a quaternary ammonium base. Further, by finally converting the tertiary amino group of the copolymer (A) to a quaternary ammonium base, it is excellent in molecular spreading without being dispersed as an aggregated molecule when diluted to a coating solution concentration. For this reason, even when coated on highly water-absorbed paper made without using an internal sizing agent, the amount of surface sizing agent distributed on the paper surface without being dispersed by aggregated molecules throughout the paper Therefore, it is considered that the hydrophobicity of the surface sizing agent is sufficiently exhibited on the paper surface.

  That is, one or more hydrophobic monomers in the presence of the tertiary amino group-containing monomer of the present invention, a copolymer (A) containing a (meth) acrylic ester monomer and a styrene monomer as constituent units and a surfactant. After cationic polymerization, the cationic surface sizing agent obtained by converting the tertiary amino group of the copolymer (A) to a quaternary ammonium base is used as an aqueous tertiary amine salt solution or quaternary ammonium of the cationic copolymer. Compared to conventional cationic surface sizing agents in which a hydrophobic monomer is emulsion-polymerized in the presence of an aqueous salt solution or an emulsifier, it provides superior sizing properties, stability of the product in the coating liquid, and Compared to conventional cationic surface sizing agents that can improve re-solubility, have strong adhesion, and have a dry film that is hardly soluble in water, it is less likely to cause problems during production and use. . Furthermore, when offset printing causes the elution substance due to the penetration of dampening water to adhere to the non-image area of the PS plate for offset printing and make it oil-sensitive, the oil-sensitive part is then washed when the offset printing is restarted. Excellent in resistance to stains on the newspaper printing surface.

  Further, the ink is excellent in ink setting property for an offset ink, particularly an AF ink not containing an aromatic component, and the occurrence of printing unevenness can be suppressed.

The cationic surface sizing agent of the present invention is
(A) a tertiary amino group-containing monomer 20 to 50% by weight;
(B) 10 to 80% by weight of a C _{4 to} C ₁₈ alkyl ester of (meth) acrylic acid,
(C) a first step of obtaining a copolymer (A) by solution polymerization of a monomer mixture containing 0 to 70% by weight of styrenes in the presence of a chain transfer agent;
After polymerizing one or more hydrophobic monomers in the presence of the copolymer (A) and a surfactant, the copolymer (B) is converted into a copolymer (B) using the tertiary amino group of the copolymer (A) as a quaternary ammonium base. ) In which the constituent ratio of the tertiary amino group-containing monomer (a) in the copolymer (B) is 10 to 20% by weight and the constituent ratio of the copolymer (A) is 90%. It is produced by a production method comprising a second step of 10% by weight and a third step in which the tertiary amino group of the copolymer (B) is a quaternary ammonium base. Preferably, in the first step, the copolymer (A) obtained by solution polymerization is neutralized with respect to the tertiary amino group-containing monomer (a) of the copolymer (A). The above acids are used to form an aqueous solution.

  Hereinafter, the first step, the second step, and the third step will be described.

[First step]
Preferred examples of the tertiary amino group-containing monomer (a) that is a constituent component of the copolymer (A) include dialkylaminoalkyl (meth) acrylate and dialkylaminoalkyl (meth) acrylamide.
Specific examples of the dialkylaminoalkyl (meth) acrylate include dimethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminopropyl (meth) acrylate, diethylaminopropyl (meth) An acrylate etc. are mentioned.

  Specific examples of the dialkylaminoalkyl (meth) acrylamide include dimethylaminoethyl (meth) acrylamide, diethylaminoethyl (meth) acrylamide, dimethylaminopropyl (meth) acrylamide, and diethylaminopropyl (meth) acrylamide.

The C _{4 to} C ₁₈ alkyl ester (b) of (meth) acrylic acid, which is a constituent of the copolymer (A), includes n-butyl (meth) acrylate, isobutyl (meth) acrylate, and ethylhexyl (meth) acrylate. And cyclic or acyclic hydrocarbon esters such as lauryl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, and benzyl (meth) acrylate. Thus, the (meth) acrylic acid ester of component (b) includes an alkyl (meth) acrylate having a C _{4 to} C ₁₈ alkyl group, and an aromatic or alicyclic hydrocarbon group in the ester portion. It may be.

  Examples of styrenes (c) that are constituent components of the copolymer (A) include styrene, α-methylstyrene, vinyltoluene, ethylvinyltoluene, chloromethylstyrene, and the like.

  As a constituent component of the copolymer (A), in addition to the components (a) to (c), other copolymerizable vinyl monomers (d) can be used as necessary.

Examples of the other monomer (d) include C ₁ -C ₃ short chain alkyl (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, and the like. , Hydroxyl-containing (meth) acrylates such as hydroxypropyl (meth) acrylate and 2-hydroxyethyl (meth) acrylate, (meth) acrylamide, acrylonitrile and the like.

  The ratio of each monomer constituting the copolymer (A) (weight% of each monomer with respect to 100% by weight of the total amount of monomers) will be described. First, the tertiary amino group-containing monomer (a) is 20 to 50% by weight. Yes, preferably 20 to 40% by weight. When the ratio of the monomer (a) is less than the above range, the solubility when water-solubilized is lowered. On the other hand, when it exceeds the above range, the hydrophobicity of the resulting sizing agent is lowered and the size effect is reduced.

The content of the C ₄ -C ₁₈ alkyl ester (b) of (meth) acrylic acid is 10 to 80% by weight, preferably 10 to 75% by weight. When the ratio of the monomer (b) is less than the above range, the hydrophobicity is lowered, the solubility is lowered during solution polymerization, and the copolymerizability is deteriorated. On the other hand, when the above range is exceeded, the ratio of the tertiary amino group-containing monomer becomes too low.

Moreover, content of styrene (c) is 0 to 70 weight%, Preferably it is 3 to 65 weight%.
When the ratio of styrenes (c) exceeds the above range, the copolymerizability deteriorates during solution polymerization. When the copolymerizability is lowered, the active ingredient of the surface sizing agent is agglomerated microparticles and scattered on the paper surface, and only a non-uniform coating can be achieved, so the size effect is reduced.

Further, the other monomer (d) is used as necessary, but its content is 0 to 30% by weight, preferably 0 to 20% by weight.
The copolymer (A) is produced by solution polymerization in an organic solvent using the monomer components (a) to (c) or the monomer component (d) as a constituent monomer.

  Examples of the organic solvent include isopropyl alcohol, n-butanol, isobutanol, t-butanol, sec-butanol, acetone, methyl ethyl ketone, methyl-n-propyl ketone, 3-methyl-2-butanol, diethyl ketone, methyl isopropyl ketone, Examples thereof include methyl isobutyl ketone, diisopropyl ketone, ethylbenzene, toluene and the like, and these can be used alone or in admixture of two or more.

  The amount of the organic solvent used relative to all monomers is 55% by weight or less, preferably 35% by weight or less.

  In the present invention, in solution polymerization of the copolymer (A), it is necessary to perform polymerization in the presence of a chain transfer agent from the viewpoint of preventing a viscosity increase and smoothly performing a polymerization reaction. As the chain transfer agent, an oil-soluble and water-soluble chain transfer agent can be arbitrarily used. However, when polymerizing in an oleophilic organic solvent, an oil-soluble chain transfer agent is used, and conversely, a hydrophilic organic solvent is used. When used, water-soluble chain transfer agents are relatively preferred.

  Examples of the oil-soluble chain transfer agent include mercaptans such as t-dodecyl mercaptan, n-dodecyl mercaptan, n-octyl mercaptan, mercaptopropionic acid dodecyl ester, cumene, carbon tetrachloride, 痾 -methylstyrene dimer, terpinolene, etc. Is mentioned.

Examples of the water-soluble chain transfer agent include mercaptoethanol, thioglycolic acid and salts thereof.
The amount of the chain transfer agent used relative to the monomer is preferably about 1 to 5% by weight, but is not limited to this range.

  Moreover, as the polymerization initiator used in the solution polymerization, various commonly used polymerization initiators can be used without particular limitation, and for example, azo polymerization initiators, peroxide polymerization initiators, and the like can be used as appropriate. Examples of the azo polymerization initiator include azobismethylbutyronitrile, dimethylazobisisobutyrate, azobisdimethylvaleronitrile, azobisisobutyronitrile, and the like. Examples of the peroxide-based polymerization initiator include benzoyl persulfate, t-butyl peroxybenzoate, t-butyl peroxyisopropyl monocarbonate, t-butyl peroxy-2-ethylhexanoate, cumene hydroperoxide, and the like. It is done.

  In the first step, the copolymer (A) obtained by solution polymerization is converted to a tertiary amino group-containing monomer (a) of the copolymer (A) with an acid having a neutralization amount of tertiary amino group or more. The aqueous copolymer (A) is preferably used as an emulsifier in the emulsion polymerization in the second step.

  Usually, water and acids are added to the reaction solution obtained by the above solution polymerization, and then the solvent is removed by distillation or the like to obtain an aqueous solution of the copolymer (A).

The acids are not particularly limited, and for example, acetic acid, formic acid, propionic acid and the like can be used as appropriate.
In the aqueous solution of the obtained copolymer (A), the copolymer (A) is preferably in a dissolved state, but even if it is present in the form of particles, the average particle diameter is 50 nm or less. Preferably there is. If the average particle size of the copolymer (A) exceeds 50 nm, the particle size of the copolymer (B) obtained in the second step tends to be large, and the size tends to decrease.

[Second step]
In the second step, one or more hydrophobic monomers are polymerized in the presence of the copolymer (A) and a surfactant to obtain a copolymer (B). The constituent ratio of the tertiary amino group-containing monomer (a) in the copolymer (B) is 10 to 20% by weight, and the constituent ratio of the copolymer (A) is 90 to 10% by weight.

As the hydrophobic monomer, various hydrophobic monomers can be used singly or in appropriate combination of two or more, but one or more (meth) acrylic acid C _{1 to} C ₁₈ alkyl ester (d) and one or more can be used. Those containing styrenes (c) are preferred in that they are excellent in size effect.

The alkyl group in (meth) alkyl esters of C ₁ -C ₁₈ acrylic acid (d), for example, a methyl group, an ethyl group, n- propyl group, an isopropyl group, n- butyl group, isobutyl group, s- butyl And cyclic or acyclic hydrocarbon groups such as a group, t-butyl group, pentyl group, hexyl group, 2-ethylhexyl group, lauryl group, cetyl group, stearyl group, cyclohexyl group and benzyl group. Thus, the (meth) acrylic acid ester of component (d) includes an alkyl (meth) acrylate having a C _{1 to} C ₁₈ alkyl group, and an aromatic or alicyclic hydrocarbon group in the ester portion. It may be. Examples of the styrenes (c) include styrenes used for the production of the copolymer (A).

  When the hydrophobic monomer contains (meth) acrylic acid ester (d) and styrenes (c), the proportion of styrenes (c) used is preferably about 10 to 70% by weight, more preferably 20 to 60% by weight. It is. Moreover, the usage-amount of (meth) acrylic acid ester (d) is about 30 to 90 weight%, Preferably it is 40 to 80 weight%. When the composition ratio of the hydrophobic monomer is out of the above range, a sufficient size effect tends not to be obtained.

  The proportion of the copolymer (A) and the hydrophobic monomer used is such that the constituent ratio of the tertiary amino group-containing monomer (a) in the copolymer (B) is 10 to 20% by weight, and the copolymer The composition ratio of (A) is adjusted to be 90 to 10% by weight (preferably 75 to 25% by weight). Here, the constituent ratio of the tertiary amino group-containing monomer (a) in the copolymer (B) is the solid content of the aqueous solution of the copolymer (A) and the total amount of the hydrophobic monomers. It means the proportion of the secondary amino group-containing monomer (a). The composition ratio of the copolymer (A) in the copolymer (B) is the copolymer (A) that occupies the total amount of the solid content of the aqueous solution of the copolymer (A) and the hydrophobic monomer. ) Of the solid content of the aqueous solution. When the composition ratio of the tertiary amino group-containing monomer (a) is less than the above range, the water solubility of the copolymer (A) tends to be inferior and the size property tends to decrease. There is a tendency for the size to decrease too much. When the constituent ratio of the constituent ratio of the copolymer (A) is less than the above range, there is a tendency to reduce the size, while when it exceeds the above range, there is a tendency to reduce the redissolvability of the dry film and the printability.

  The copolymer (B) can be easily produced by emulsion polymerization in the presence of a suitable polymerization initiator in an aqueous medium containing the copolymer (A) and a surfactant. As the surfactant, a normal cation, anion, or nonionic surfactant can be used without particular limitation, but a cationic surfactant is particularly preferable from the viewpoint of compatibility with the copolymer (A). Examples of the cationic surfactant include a quaternary ammonium salt of a long-chain alkylamine. The type of the polymerization initiator is not particularly limited, and for example, any of persulfates such as potassium persulfate and ammonium persulfate, water-soluble azo compounds, and other redox catalyst systems can be used.

[Third step]
In the third step, the cationic surface sizing agent of the present invention is obtained using the tertiary amino group of the copolymer (B) as a quaternary ammonium base.

Various commonly used quaternizing agents to be reacted with the copolymer (B) can be used. Typical examples include dimethyl sulfate, methyl chloride, allyl chloride, ethylene chlorohydrin, benzyl chloride, epichlorohydrin and the like. Epichlorohydrin is particularly preferred from the viewpoint of reactivity. The amount of the quaternizing agent used is preferably an amount that quaternizes 50 to 100 mol% of the tertiary amino group contained in the copolymer (B), more preferably quaternizes 50 to 90 mol%. Amount. When the amount of the quaternizing agent used is less than the above range, there is a tendency for the size to decrease due to a decrease in dissociation of the cationic group. The reaction with the quaternizing agent can be carried out according to a known and usual method.
The cationic sizing agent thus obtained preferably has an average particle size of 150 nm or less, more preferably 50 to 100 nm. When the average particle diameter of the sizing agent exceeds the above range, there is a tendency for the size property to decrease. The thickness is more preferably 50 nm or more from the viewpoint of re-solubility of the dry film.

[Application of cationic surface sizing agent]
The surface sizing agent of the present invention can be widely applied regardless of acidic paper using aluminum sulfate as a fixing agent and neutral paper using calcium carbonate as a filler.

  Specific examples of the base paper include newsprint paper, inkjet paper, thermal recording base paper, pressure-sensitive recording base paper, high-quality paper, paperboard, and other papers. The surface sizing agent of the present invention is a combination with an internal sizing agent. Basically, the base paper is a paper that does not contain an internal sizing agent (whether acidic paper or neutral paper), and the neutrality of the Steecht sizing is 2 seconds or less. Paper is preferred. However, application of the surface sizing agent of the present invention to paper containing the internally added sizing agent is not excluded. In addition, the surface sizing agent of the present invention hardly causes scumming during newspaper printing, and is particularly suitable for neutral newsprint paper.

When applying the surface sizing agent of the present invention, the amount of the sizing agent varies depending on the type of paper, and a thick coating solution is applied thinly or a low concentration coating solution is applied thickly to change the adhesion mode. It can also be changed. Furthermore, it does not ask | require single-sided coating and double-sided coating. Accordingly, the amount of surface sizing agent cannot be generally specified, but the solid content is generally about 0.01 to 0.2 g / m ² , preferably about 0.02 to 0.1 g / m ^2. .

  Moreover, when coating, the water-soluble polymer compound which is a binder can be used together with the surface sizing agent of the present invention. Especially for newsprint applications, water-soluble polymer compounds are effective in increasing the surface strength and suppressing the generation of paper dust during printing. Examples of the water-soluble polymer compound include starch, enzyme-modified starch, thermochemically modified starch, oxidized starch, esterified starch, etherified starch (for example, hydroxyethylated starch), starch such as cationized starch, polyvinyl alcohol, and the like. , Fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, carboxyl modified polyvinyl alcohol, silanol modified polyvinyl alcohol, cationic modified polyvinyl alcohol, polyvinyl alcohols such as terminal alkyl modified polyvinyl alcohol, polyacrylamide, cationic polyacrylamide, anionic poly Polyacrylamides such as acrylamide and amphoteric polyacrylamide, cellulose derivatives such as carboxymethylcellulose, hydroxyethylcellulose, and methylcellulose Use or can be used in combination. Among these, at least one selected from starches, polyvinyl alcohols, and polyacrylamides is preferable.

  When used in combination with a water-soluble polymer compound, the compounding ratio with the cationic surface sizing agent is not particularly specified. However, it is usually appropriate to add 1 to 50 parts by weight of the cationic surface sizing agent to 100 parts by weight of the water-soluble polymer compound, preferably 5 to 40 parts by weight, more preferably 5 to 30 parts. Parts by weight.

  In addition to the water-soluble polymer compound, the coating liquid containing the cationic surface sizing agent of the present invention has an anti-Nepari agent, an antiseptic, an antifoaming agent, a lubricant, and an anti-slip agent as long as the desired effect is not adversely affected. , An auxiliary agent such as an ultraviolet ray inhibitor, a fading inhibitor, a fluorescent brightening agent, and a viscosity stabilizer may be contained.

  The coating method may be applied with a normal paper coating apparatus. Examples thereof include apparatuses such as a two-roll size press, a blade metering size press, a rod metalling size press, a gate roll coater, a bar coater, an air knife coater, and a spray coating machine. Among these apparatuses, a film transfer type coater typified by a gate roll coater is desirable, and in particular, when coating on newsprint base paper, a gate roll coater (GRC) is common, and the present invention is also most suitable. Used for.

  The coating speed is not particularly limited as long as it is about the same as that of a paper machine capable of producing various kinds of normal paper. In the case of newspaper, it is usually in the range of 800-2500 m / min. By coating at a high speed of 800 m / min or more, the coating liquid is dried before it sufficiently penetrates into the paper layer. Therefore, the paper when the coating liquid exists near the surface layer and water is absorbed. Swelling of fibers existing in the surface layer can be more effectively suppressed.

  In the present invention, it is preferable to apply a calendar treatment in order to obtain a paper thickness and smoothness suitable for offset printing after coating and drying a surface sizing agent. Examples of the calendar include a normal hard nip calender and a high temperature soft nip calender. In the case of newsprint, a high temperature soft nip calender is preferable because it is suitable for weight reduction.

  The above-mentioned various base papers include MP such as ground valve (GP), thermomechanical / pulp (TMP), chemithermomechanical pulp (CTMP), semi-chemical pulp (SCP), kraft pulp (KP), sulfite pulp (SP). Chemical pulp represented by (CP), deinked pulp (DIP) obtained by deinking waste paper containing these pulps, recovered pulp obtained by disaggregating waste paper from the papermaking process, etc. , Alone or mixed at an arbitrary ratio, and paper is made by a publicly known paper machine. Newspaper paper has a strong demand for higher DIP content due to recent interest in environmental protection, so the DIP content is preferably 50 to 100% by weight.

  For base paper, as necessary, white carbon, clay, silica, talc, titanium oxide, calcium carbonate, calcium carbonate-silica composite, synthetic resin filler (vinyl chloride resin, polystyrene resin, urea formalin resin, melamine) Resin, styrene / butadiene copolymer resin, etc.). Of these, calcium carbonate is preferred. Also, polyacrylamide polymer, polyvinyl alcohol polymer, cationic starch, urea / formalin resin, melamine / formalin resin and other internal paper strength enhancers, acrylamide and aminomethylacrylamide copolymer salts, cationic Internal additives such as starch, polyethyleneimine, polyethylene oxide, drainage and / or yield improver such as acrylamide and sodium acrylate copolymer, rosin sizing agent, AKD, ASA, petroleum sizing agent, neutral rosin sizing agent You may contain adjuvants, such as a sizing agent, a ultraviolet-ray inhibitor, and a fading prevention agent.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these Examples. In the following description, parts and% mean parts by weight and% by weight unless otherwise specified.

Moreover, the average particle diameter of the copolymer (A) and the cationic surface sizing agent was measured as follows.
Measurement was performed by a dynamic light scattering method using a dynamic light scattering photometer DLS-700 manufactured by Otsuka Electronics Co., Ltd.

  In Tables 1, 3, and 4, “not measurable” means that the measurement is below the measurement limit of the above measurement method and the measurement was not possible.

[Synthesis Example of Copolymer (A)]
<Synthesis Example 1>
40 parts of dimethylaminoethyl methacrylate, 20 parts of 2-ethylhexyl methacrylate, 40 parts of styrene, 1.5 parts of chain transfer agent t-dodecyl mercaptan and 32.5 parts of isopropyl alcohol are placed in a four-necked flask and heated to 85 ° C. Then, 2 parts of 2,2′-azobisisobutyronitrile was added as an initiator and polymerized at 90 ° C. for 3 hours. Next, as neutralization of dimethylaminoethyl methacrylate, 17.0 parts of 90% acetic acid and 250 parts of water were added to make it water-soluble, followed by distillation by heating to distill off isopropyl alcohol and diluting with water to achieve a solid content of 25%. A polymer aqueous solution was obtained.

<Synthesis Example 2>
30 parts of dimethylaminopropylacrylamide, 10 parts of n-butyl methacrylate, 60 parts of styrene, 2.0 parts of chain transfer agent n-dodecyl mercaptan and 32.5 parts of toluene are placed in a four-necked flask and heated to 105 ° C. Then, 2.0 parts of t-butyl peroxyisopropyl monocarbonate was added as an initiator, and the mixture was polymerized at 110 ° C. for 3 hours. Next, as a neutralization of dimethylaminopropylacrylamide, 12.8 parts of 90% acetic acid and 250 parts of water were added to make it water-soluble, followed by distillation by heating to distill off toluene, dilute with water, and have a solid content of 25% solids. A combined aqueous solution was obtained.

<Synthesis Example 3>
25 parts of dimethylaminoethyl methacrylate, 55 parts of n-butyl methacrylate, 20 parts of 2-ethylhexyl methacrylate, 1.5 parts of chain transfer agent n-dodecyl mercaptan and 32.5 parts of isopropyl alcohol are placed in a four-necked flask. The mixture was heated to 0 ° C. and 2 parts of 2,2′-azobis (2-methylbutyronitrile) was added as an initiator, followed by polymerization at 90 ° C. for 3 hours. Next, as a neutralization of dimethylaminoethyl methacrylate, 10.6 parts of 90% acetic acid and 250 parts of water were added to make water-soluble, followed by distillation by heating to distill off isopropyl alcohol and diluting with water to achieve a solid content of 25%. A polymer aqueous solution was obtained.

<Synthesis Examples 4-8>
Synthesis Example 3 except that the type and amount of tertiary amino group-containing monomer used, the type and amount of (meth) acrylic acid alkyl ester, the amount of styrene used, and the amount of 90% acetic acid used are shown in Table 1. In the same manner, a copolymer aqueous solution having a solid content of 25% was obtained. In Table 1, “DM neutralization rate” in the item showing the amount of 90% acetic acid used (parts by weight) is the amount of neutralization of tertiary amino group-containing monomers including DM (dimethylaminoethyl methacrylate). This means (the same applies to Tables 3 and 4).

[Examples relating to the production of cationic surface sizing agents]
<Example 1>
In a four-necked flask, 200 parts of the aqueous cationic copolymer solution obtained in Synthesis Example 1 as a copolymer (A) (50 parts as a solid content), 175 parts of water, and surfactant 2.3 described in Table 2 were used. Methyl methacrylate 7.5 parts, n-butyl methacrylate 15 parts, 2-ethylhexyl acrylate 15 parts, and styrene 37.5 parts were added as hydrophobic monomers, heated to 75 ° C., and the initiator 0.38 shown in Table 2 was added. Part was added and polymerized at 85 ° C. for 3 hours. Next, 8.2 parts of epichlorohydrin was added at 85 ° C., reacted for 3 hours, cooled and diluted with water to obtain a cationic surface sizing agent having a solid content of 25%.

<Examples 2 to 6>
Table 2 shows the type and amount of copolymer (A) used, the amount of water, the type and amount of surfactant, the type and amount of hydrophobic monomer, the type and amount of initiator, and the amount of epichlorohydrin. Except for the above, a cationic surface sizing agent having a solid content of 25% was obtained in the same manner as in Example 1. In Table 2, “DM excess” in the item showing the amount of 90% acetic acid used (parts by weight) means the excess of the tertiary amino group-containing monomer including DM (dimethylaminoethyl methacrylate). (The same applies to Table 5).

<Example 7>
In a four-necked flask, 7.5 parts of 90% acetic acid, 400 parts of the copolymer obtained in Synthesis Example 7 as a copolymer (A) (100 parts as a solid content), 58 parts of water, the interface described in Table 2 0.8 parts of an activator, 2.5 parts of methyl methacrylate as a hydrophobic monomer, 10 parts of n-butyl methacrylate, 5 parts of isobutyl acrylate, and 7.5 parts of styrene are added and heated to 75 ° C. 0.13 part was added and polymerized at 85 ° C. for 3 hours. Next, 11.7 parts of epichlorohydrin was added at 85 ° C., reacted for 3 hours, cooled and diluted with water to obtain a cationic surface sizing agent having a solid content of 25%.

<Example 8>
In a four-necked flask, 8.0 parts of 90% acetic acid, 375 parts of the copolymer obtained in Synthesis Example 8 as a copolymer (A) (93.8 parts as a solid content), 73 parts of water, Table 2 0.9 parts of surfactant, 3.1 parts of methyl methacrylate, 9.4 parts of n-butyl methacrylate, 6.3 parts of n-butyl acrylate, and 12.5 parts of styrene as a hydrophobic monomer are heated to 75 ° C. Then, 0.16 part of the initiator listed in Table 2 was added and polymerized at 85 ° C. for 3 hours. Next, 12.4 parts of epichlorohydrin was added at 85 ° C., reacted for 3 hours, cooled and diluted with water to obtain a cationic surface sizing agent having a solid content of 25%.

[Synthesis Example of Copolymer (A)]
<Synthesis Example 9>
30 parts of dimethylaminoethyl methacrylate, 10 parts of n-butyl methacrylate, 60 parts of styrene, 1.5 parts of chain transfer agent n-dodecyl mercaptan and 32.5 parts of isopropyl alcohol are placed in a four-necked flask and heated to 85 ° C. Then, 2 parts of 2,2′-azobis (2-methylbutyronitrile) was added as an initiator and polymerized at 90 ° C. for 3 hours. Next, as a neutralization of dimethylaminoethyl methacrylate, 12.7 parts of 90% acetic acid and 250 parts of water were added to make it water-soluble, followed by distillation by heating to distill off isopropyl alcohol and dilute with water to achieve a solid content of 25%. A polymer aqueous solution was obtained.

<Synthesis Examples 10-18>
Synthetic Example 9 except that the type and amount of tertiary amino group-containing monomer used, the type and amount of (meth) acrylic acid alkyl ester, the amount of styrene used, and the amount of 90% acetic acid used are shown in Table 3. In the same manner, a copolymer aqueous solution having a solid content of 25 was obtained.

<Synthesis Example 19 (using quaternary amino group-containing monomer)>
Methacryloyloxyethyltrimethylammonium chloride 37.5 parts (80% aqueous solution, solid 30 parts / water 7.5 parts), n-butyl methacrylate 20 parts, styrene 50 parts, chain transfer agent n-dodecyl mercaptan 1.5 And 32.5 parts of isopropyl alcohol were placed in a four-necked flask, heated to 85 ° C., added with 2 parts of 2,2′-azobis (2-methylbutyronitrile) as an initiator, and polymerized at 90 ° C. for 3 hours. . Subsequently, 90% acetic acid 9.6 and 250 parts of water were added to make it water-soluble, but an insolubilized product that could not be solubilized remained. In addition, an attempt was made to filter the component in liquid form with a wire mesh (# 150), but it could not be filtered due to clogging. For this reason, it was not used for performance evaluation.

[Comparative Example for Production of Cationic Surface Sizing Agent]
<Comparative Example 1>
30 parts of dimethylaminoethyl methacrylate, 70 parts of styrene, 2.0 parts of chain transfer agent n-dodecyl mercaptan and 32.5 parts of toluene are placed in a four-necked flask and heated to 105 ° C. to give t-butyl as an initiator. 2.0 parts of peroxyisopropyl monocarbonate was added and polymerized at 110 ° C. for 3 hours. Next, as a neutralization of dimethylaminoethyl methacrylate, 12.7 parts of 90% acetic acid and 250 parts of water were added for water solubilization, and then toluene was distilled off by heating distillation. Next, 12.4 parts of epichlorohydrin was added at 85 ° C., reacted for 3 hours, cooled and diluted with water to obtain a cationic surface sizing agent having a solid content of 25%.

<Comparative example 2>
25 parts of dimethylaminoethyl methacrylate, 55 parts of n-butyl methacrylate, 20 parts of styrene, 1.5 parts of chain transfer agent n-dodecyl mercaptan and 32.5 parts of isopropyl alcohol are placed in a four-necked flask and heated to 85 ° C. Then, 2 parts of 2,2′-azobis (2-methylbutyronitrile) was added as an initiator and polymerized at 90 ° C. for 3 hours. Next, as a neutralization of dimethylaminoethyl methacrylate, 10.6 parts of 90% acetic acid and 250 parts of water were added to make it water-soluble, followed by distillation by heating to distill off isopropyl alcohol. Next, 11.8 parts of epichlorohydrin was added at 85 ° C., reacted for 3 hours, cooled and diluted with water to obtain a cationic surface sizing agent having a solid content of 25%.

<Comparative Example 3>
Four parts of 20 parts of dimethylaminoethyl methacrylate, 15 parts of methyl methacrylate, 50 parts of 2-ethylhexyl methacrylate, 15 parts of 2-ethylhexyl acrylate, 1.5 parts of chain transfer agent n-dodecyl mercaptan and 32.5 parts of isopropyl alcohol The flask was placed in a flask, heated to 85 ° C., 2 parts of 2,2′-azobis (2-methylbutyronitrile) was added as an initiator, and polymerization was performed at 90 ° C. for 3 hours. Next, as a neutralization of dimethylaminoethyl methacrylate, 8.5 parts of 90% acetic acid and 250 parts of water were added to make it water-soluble, and then distilled by heating to distill off isopropyl alcohol. Next, 10.6 parts of epichlorohydrin was added at 85 ° C., reacted for 3 hours, cooled and diluted with water to obtain a cationic surface sizing agent having a solid content of 25%.

<Comparative Example 4>
In a four-necked flask, 350 parts of the aqueous copolymer solution obtained in Synthesis Example 9 as the copolymer (A) (87.5 parts as a solid content), 88 parts of water, and the surfactant 1.1 described in Table 5 were used. Part, 7.5 parts of methyl methacrylate, 15 parts of n-butyl acrylate and 15 parts of styrene as a hydrophobic monomer were added, heated to 75 ° C., 0.19 part of the initiator shown in Table 5 was added, and polymerization was carried out at 85 ° C. for 3 hours. did. Next, 10.8 parts of epichlorohydrin was added at 85 ° C., reacted for 3 hours, cooled and diluted with water to obtain a cationic surface sizing agent having a solid content of 25%.

<Comparative Examples 5-10>
Table 5 shows the type and amount of copolymer (A) used, the amount of water, the type and amount of surfactant, the type and amount of hydrophobic monomer, the type and amount of initiator, and the amount of epichlorohydrin. Otherwise, a cationic surface sizing agent having a solid content of 25% was obtained in the same manner as in Comparative Example 4.

<Comparative Example 11>
In a four-necked flask, 300 parts of the copolymer obtained in Synthesis Example 16 as a copolymer (A) (75 parts as a solid content), 117 parts of water, 1.5 parts of a surfactant described in Table 5, hydrophobic 5 parts of methyl methacrylate, 20 parts of n-butyl methacrylate, 10 parts of isobutyl acrylate and 15 parts of styrene are added as heat-sensitive monomers, heated to 75 ° C., added with 0.25 part of the initiator shown in Table 5, and polymerized at 85 ° C. for 3 hours After cooling, it was diluted with water to obtain a cationic surface sizing agent having a solid content of 25%.

<Comparative Example 12>
In a four-necked flask, 6.4 parts of 90% acetic acid, 300 parts of the aqueous copolymer solution obtained in Synthesis Example 17 as a copolymer (A) (75 parts as a solid content), 117 parts of water, and Table 5 1.5 parts of a surfactant, 5 parts of methyl methacrylate as a hydrophobic monomer, 20 parts of n-butyl methacrylate, 10 parts of isobutyl acrylate, and 15 parts of styrene were added and heated to 75 ° C. Then, the mixture was polymerized at 85 ° C. for 3 hours, then cooled and diluted with water to obtain a cationic surface sizing agent having a solid content of 25%.

<Comparative Example 13>
In a four-necked flask, 350 parts of the aqueous copolymer solution obtained in Synthesis Example 18 as a copolymer (A) (87.5 parts as a solid content) was placed, heated to 85 ° C., and 9.1 parts of epichlorohydrin was added. The reaction was continued for 3 hours. Next, 88 parts of water, 1.1 parts of the surfactant described in Table 5, 15 parts of n-butyl methacrylate, 11.3 parts of 2-ethylhexyl methacrylate, 3.8 parts of 2-ethylhexyl acrylate, 7 parts of styrene .5 parts, heated to 75 ° C., added 0.19 part of the initiator listed in Table 5, polymerized at 85 ° C. for 3 hours, cooled and diluted with water to obtain a cationic surface size of 25% solids An agent was obtained.

[Evaluation of neutral newsprint for offset printing]
<Test Example 1>
To a pulp slurry prepared by mixing and disaggregating 80 parts of DIP (freeness 180 ml), 15 parts of TMP (freezing degree 100 ml), and 5 parts of softwood bleached kraft pulp (NBKP, freeness 600 ml), As a standard, 5.0% calcium carbonate was added, and neutral paper making was performed with a twin wire type paper machine so that the basis weight was 42 g / m ² , thereby obtaining newsprint base paper. The obtained newsprint base paper had a paper surface pH of 6.5 and an ash content of 12.2% (content of calcium carbonate in the paper was 10.3%). Further, the obtained base paper had a sizing degree of less than 1 second. Using a gate roll coater on this base paper, a surface treatment agent comprising hydroxyethylated starch and the surface sizing agent obtained in Example 1 (solid content concentration of hydroxyethylated starch 6.0%, solid content concentration of surface sizing agent) 0.45%) was coated evenly on both the felt surface and the wire surface to obtain newspaper for offset printing. The coating amounts of hydroxyethylated starch and surface sizing agent were 0.40 g / m ² (single side) and 0.03 g / m ² (single side), respectively. About the obtained newspaper paper, 1 microliter drip water absorbency and ink deposit property were evaluated by the following method. The results are shown in Table 6.

<Test Examples 2-8, Comparative Test Examples 1-13>
Instead of the surface sizing agent obtained in Example 1, coating and evaluation were performed in the same manner as in Test Example 1, except that the surface sizing agents of Examples 2 to 8 and Comparative Examples 1 to 13 were used.

<Evaluation of 1 μL drip water absorption>
For each newspaper (Test Examples 1-8, Comparative Test Examples 1-13), the JAPAN TAPPI paper pulp test method No. In accordance with 32-2 (paper-water absorption test method-part 2: dropping method), a water absorption test was performed with 1 μL of water, and the time required for water absorption was measured.

<Evaluation of ink fillability>
About each newspaper paper (Test Examples 1-8, Comparative Test Examples 1-13), an offset rotary press was used, and 10,000 copies were printed using high-viscosity AF ink, which is eco-ink for offset manufactured by Toyo Ink Manufacturing Co., Ltd. . The inking property (printing unevenness) of the printed sample was visually evaluated according to the following criteria.
A: The printing surface is not uneven and a very uniform image is obtained;
○: There is almost no unevenness on the printed surface, and a uniform image is obtained;
Δ: There is some unevenness on the printed surface, and the image is uneven;
X: The printed surface is uneven and the image is very uneven.

[Resolubility of surface sizing agent]
<Test Example 9>
The surface sizing agent of Example 1 was diluted to 5% solids, and 10 g of the diluted solution was impregnated into filter paper (No. 2, 90 mm). The filter paper impregnated with the sizing agent in a dryer at 40 ° C. was dried for 3 hours to obtain a sizing agent dry resin.

<Test Examples 10-16, Comparative Test Examples 14-26>
A sizing dry resin was obtained in the same manner as in Test Example 9 except that the surface sizing agents of Examples 2 to 8 and Comparative Examples 1 to 13 were used instead of the surface sizing agent of Example 1.

<Evaluation of re-solubility of surface sizing agent>
For the surface sizing agent dry resin (Test Examples 9 to 16 and Comparative Test Examples 14 to 26), the weight of the filter paper containing the surface sizing agent dry resin was measured and then immersed in warm water at 50 ° C. for 2 minutes. After 2 minutes, the filter paper was pulled up and dried overnight in a dryer at 40 ° C. The re-dissolution rate of the sizing agent dry resin was measured by measuring the weight of the dried product before and after being immersed in warm water. The results are shown in Table 7.

[Thermal stability of surface sizing agent]
<Test Example 17>
The surface sizing agent stock solution of Example 1 was sealed in a SUS pipe to obtain a sample for thermal stability evaluation.

<Test Examples 18-24, Comparative Test Examples 27-39>
A sample for thermal stability evaluation was obtained in the same manner as in Test Example 17 except that the surface sizing agents of Examples 2 to 8 and Comparative Examples 1 to 13 were used instead of the surface sizing agent of Example 1.

<Evaluation of thermal stability of surface sizing agent>
Samples for thermal stability evaluation (Test Examples 17 to 24, Comparative Test Examples 27 to 39) were stored in a dryer at 70 ° C. for 24 hours. As the thermal stability, the product viscosity of the surface sizing agent before and after the test was measured and compared. The results are shown in Table 8.

The abbreviations shown in Tables 1 to 5 represent the following.
(monomer)
DM: dimethylaminoethyl methacrylate St: styrene DMAPAA: dimethylaminopropyl acrylamide 2EHMA: 2-ethylhexyl methacrylate 2EHA: 2-ethylhexyl acrylate MMA: methyl methacrylate LMA: lauryl methacrylate
nBMA: n-butyl methacrylate
nBA: n-butyl acrylate
iBMA: Isobutyl methacrylate
iBA: isobutyl acrylate DMC: methacryloyloxyethyl trimethyl ammonium chloride (surfactant)
E-1: Octadecyltrimethylammonium chloride
E-2: Dodecyltrimethylammonium chloride E-3: Hexadecyltrimethylammonium chloride
(Initiator)
I-1: 2,2′-azobis (2-methylpropiondiamine) dihydrochloride
I-2: 2,2′-azobis [N- (2-carboxyethyl) -2-methylpropiondiamine
I-3: 2,2′-azobis [2- (3,4,5,6-tetrahydropyrimidinpropan-2-yl) propane] dihydrochloride

Claims (11)

(A) a tertiary amino group-containing monomer 20 to 50% by weight;
(B) 10 to 80% by weight of a C _{4 to} C ₁₈ alkyl ester of (meth) acrylic acid;
(C) a first step of obtaining a copolymer (A) by solution polymerization of a monomer mixture containing 0 to 70% by weight of styrenes in the presence of a chain transfer agent;
A step of obtaining a copolymer (B) by polymerizing one or more kinds of hydrophobic monomers in the presence of the copolymer (A) and a surfactant, wherein 3 in the copolymer (B) The constituent ratio of the secondary amino group-containing monomer (a) is 10 to 20% by weight, the constituent ratio of the copolymer (A) is 90 to 10% by weight , and the hydrophobic monomer is (meth) acrylic acid. A cationic surface size comprising a second step which is a C _{1 to} C ₁₈ alkyl ester or a styrene, and a third step in which the tertiary amino group of the copolymer (B) is a quaternary ammonium base. Manufacturing method.   In the first step, the copolymer (A) obtained by solution polymerization is converted to a tertiary amino group-containing monomer (a) of the copolymer (A) with an acid having a neutralization amount of tertiary amino group or more. The manufacturing method of Claim 1 made into the form of an aqueous solution using. The production method according to claim 2 , wherein the average particle size of the copolymer (A) in the form of an aqueous solution in the first step is 50 nm or less.   The production method according to any one of claims 1 to 3, wherein an average particle size of the cationic surface sizing agent obtained in the third step is 150 nm or less.   The production method according to any one of claims 1 to 4, wherein in the third step, 50 to 100 mol% of the tertiary amino group contained in the copolymer (B) is converted to quaternary ammonium salt with epichlorohydrin.   The production method according to any one of claims 1 to 5, wherein the tertiary amino group-containing monomer (a) is dialkylaminoalkyl (meth) acrylate and / or dialkylaminoalkyl (meth) acrylamide.   The production method according to claim 1, wherein the surfactant is cationic.   A cationic surface sizing agent produced by the production method according to claim 1.   9. A paper surface treatment method comprising applying the cationic surface sizing agent according to claim 8 or a mixture of the sizing agent and a water-soluble polymer compound to the paper surface.   A paper, characterized in that the cationic surface sizing agent according to claim 8 or a mixture of the sizing agent and a water-soluble polymer compound is coated on the surface of the paper.   The paper according to claim 10, wherein the paper before the surface sizing agent is applied is paper containing no internal sizing agent and / or neutral paper having a Steecht sizing degree of 2 seconds or less.