JP3453613B2 - Water retention agent for paper coating paint - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-retaining agent for a paper coating paint, which mainly contains a pigment and a binder, and is used for producing a coated paper.

[0002]

2. Description of the Related Art In recent years, the productivity and quality of coated paper have improved.
From the viewpoints of cost reduction, energy saving, etc., high-concentration and high-speed coating of paper coating paint has been actively promoted. As a method of increasing the solid content of a paper coating paint for high concentration and high speed coating, for example, a method of using calcium carbonate as a pigment, which gives a lower viscosity than clay, and a binder, only in a low solid content aqueous solution. A method is used in which a large amount of latex is used by reducing a natural binder such as unretainable starch, or a method in which only latex is used without using starch at all. In such a high-concentration paper coating paint, water retention and fluidity are poor, so in order to improve this, a method of adding sodium alginate, polyacrylate, carboxymethylcellulose (hereinafter referred to as CMC), Styrene-maleate copolymer (Japanese Unexamined Patent Publication No. 56-101996) or an alkali thickening type copolymer having a specific composition and a polyol compound (Japanese Unexamined Patent Publication No. 2-5
3996) has been proposed.

[0003]

However, these conventional water-retaining agents have a large tendency to thicken the paper coating paint, and therefore, if the water-retaining agent in an amount necessary for imparting the required water retention is added, the paper-retaining agent cannot be used. Viscosity of coating material, especially shear rate applied to paper coating material in coating with blade coater 10
It had a drawback that the high shear viscosity at ⁶ / sec or higher was high and blade coating could not be performed. That is, the conventional water retention agent cannot achieve high concentration of the paper coating paint, which is an obstacle to high speed coating. Further, conventional water retention agents have a drawback that the water retention effect is still insufficient and it is difficult to exert the effect unless a large amount is added. Poor flow characteristics or insufficient water retention of these paper coating paints causes problems such as streaking, uneven coating and binder migration during coating, white paper and uneven print gloss of coated paper, and water-ink imperfections. It was a serious problem in producing high quality coated paper.

[0004]

DISCLOSURE OF THE INVENTION The present inventors have a high water-retaining effect and suppress an increase in viscosity of a paper coating paint at a low shear rate, and a high shear rate, particularly a shear rate of 10 ⁶ /
The present invention has been achieved as a result of earnest studies on a novel water retention agent for paper coating paints that can lower the viscosity of not less than a second.

That is, the present invention relates to (1) 25 to 90 parts by weight of methacrylic acid, and (2) the following general formula [Chemical Formula 3] in 100 parts by weight of total monomers.

[Chemical 3] (In the formula, R ₁ is H or CH ₃ , and R ₂ has 6 to 6 carbon atoms.
22 is an alkyl group of 22) A10-7
5 parts by weight as an essential constituent component and 0 to 50 parts by weight of another ethylenically unsaturated monomer B (excluding vinyl acetate) copolymerizable with these, monomer B / monomer A The monomer mixture having a weight ratio of 5 or less is 10 in total.
From 0 to 25 parts by weight of polyoxyethylene alkylphenyl ether sulfate salt, polyoxyethylene alkyl ether sulfate salt, polyoxyethylene alkylphenyl ether phosphate ester salt, or polyoxyethylene alkyl ether phosphate ester salt The relative viscosity at 25 ° C. of a 1% aqueous solution neutralized with sodium hydroxide obtained by emulsion polymerization using a radical polymerization catalyst in the presence of one or more selected anionic emulsifiers is 2.5 to A water-retaining agent for a paper-coating paint consisting of 500 alkali-sensitive emulsions (claim 1), and a paper-coating paint containing the water-holding agent mainly as a pigment and a binder in an amount of 0.001 per 100 parts by weight of the pigment.
To 10 parts by weight are contained in the paper coating composition (Claim 3).

As a specific example of the monomer A used in the present invention, hexyl (meth) acrylate [hexyl (meth) acrylate means hexyl acrylate or hexyl methacrylic acid]. The same applies hereinafter], heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate,
N-octyl (meth) acrylate, decyl (meth) acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate,
Hexadecyl (meth) acrylate, stearyl (meth) acrylate, behenyl (meth) acrylate, and the like (meth) acrylic acid alkyl ester having an alkyl group having 6 to 22 carbon atoms, and these may be used alone or in combination with 2
More than one species can be used. Among these, preferred are hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, decyl (meth) acrylate, lauryl (meth) acrylate, and (meth) acrylate. Tridecyl acrylate and (meth)
Stearyl acrylate, more preferred are 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, decyl (meth) acrylate and lauryl (meth) acrylate.

Specific examples of the other copolymerizable ethylenically unsaturated monomer B include methyl (meth) acrylate,
1 carbon atom consisting of ethyl (meth) acrylate, propyl (meth) acrylate, and butyl (meth) acrylate
Examples of the (meth) acrylic acid alkyl ester having an alkyl group of 4 to 4, acrylonitrile, styrene and the like can be used alone or in combination of two or more. Among these, preferred are (meth) acrylic acid alkyl ester having an alkyl group having 2 to 4 carbon atoms and consisting of ethyl (meth) acrylate, propyl (meth) acrylate and butyl (meth) acrylate, and acrylonitrile. More preferred is an alkyl (meth) acrylate ester having an alkyl group having 2 to 4 carbon atoms and consisting of ethyl (meth) acrylate, propyl (meth) acrylate and butyl (meth) acrylate.

In the water retention agent for paper coating paint of the present invention, the ratio of methacrylic acid to monomer A and monomer B is 25 to 90 parts by weight of methacrylic acid in 100 parts by weight of total monomers. The monomer A comprises 10 to 75 parts by weight as an essential constituent component, and the other ethylenically unsaturated monomer B copolymerizable with them is contained in a proportion of 0 to 50 parts by weight. The weight ratio of the monomer A is 5 or less, preferably 27 to 85 parts by weight of methacrylic acid, 15 to 73 parts by weight of the monomer A, 0 to 45 parts by weight of the monomer B, and the monomer B. The weight ratio of / monomer A is 3 or less, more preferably 30 to 80 parts by weight of methacrylic acid, 20 to 70 parts by weight of monomer A and 0 to 40 parts by weight of monomer B, In addition, the weight ratio of monomer B / monomer A is 2 or less. When the amount of methacrylic acid is less than 25 parts by weight, the water retention property is lowered, and when it exceeds 90 parts by weight, the viscosity of the paper coating composition, especially the shear rate of 10 ⁶ /
The viscosity becomes too high under high shear for more than a second, which is not preferable. When the amount of the monomer A is less than 10 parts by weight, the viscosity of the paper coating composition becomes high, especially under high shearing at a shear rate of 10 ⁶ / sec or more, and when it exceeds 75 parts by weight, the water retention property becomes high. It is not preferable because it decreases. When the amount of the monomer B exceeds 50 parts by weight, the viscosity of the coating composition for paper is increased, especially under high shearing at a shearing rate of 10 ⁶ / sec or more, and the water retention is also lowered, which is not preferable. On the other hand, when the weight ratio of monomer B / monomer A exceeds 5, the viscosity of the coating material for paper coating, especially the viscosity under high shearing at a shearing rate of 10 ⁶ / sec or higher, is not preferable.

Examples of the anionic emulsifier used in the present invention include polyoxyethylene alkylphenyl ether sulfates, alkali metal salts, ammonium salts or amine salts of polyoxyethylene alkylphenyl ether sulfates, polyoxyethylene alkylphenyl ether phosphates and polyoxys. It is an alkali metal salt, ammonium salt or amine salt of ethylene alkyl ether phosphate. Of these, preferred is polyoxyethylene (ethylene oxide addition mole number 2 to 100) octyl phenyl ether sulfate,
Polyoxyethylene (ethylene oxide addition mole number 2
100) Nonyl phenyl ether sulfate, polyoxyethylene (ethylene oxide addition mole number 2-10)
0) alkyl (6 to 22 carbon atoms) ether sulfate, polyoxyethylene (ethylene oxide addition mole number 2 to 100) octyl phenyl ether phosphate monoester, polyoxyethylene (ethylene oxide addition mole number 2 to 100) octyl phenyl ether phosphate Diester, polyoxyethylene (ethylene oxide addition mole number 2 to 100) nonylphenyl ether phosphate monoester, polyoxyethylene (ethylene oxide addition mole number 2 to 100) nonylphenyl ether phosphate diester, polyoxyethylene (ethylene oxide addition mole number 2 To 100) alkyl (C6 to C22) ether phosphate monoester, and polyoxyethylene (ethylene oxide addition mole number 2 to 100) alkyl (C6 to C6)
22) Alkali metal, ammonium or amine salts of ether phosphate diesters, more preferably polyoxyethylene (ethylene oxide addition mole number 2-50).
Octyl phenyl ether sulfate, polyoxyethylene (ethylene oxide addition mole number 2 to 50) nonyl phenyl ether sulfate, polyoxyethylene (ethylene oxide addition mole number 2 to 50) alkyl (carbon number 6 to 18) ether sulfate, polyoxyethylene (ethylene oxide Addition mole number 2 to 50) Octyl phenyl ether phosphate monoester, polyoxyethylene (ethylene oxide addition mole number 2 to 50) octyl phenyl ether phosphate diester, polyoxyethylene (ethylene oxide addition mole number 2 to 50) nonyl phenyl ether phosphorus Acid monoester, polyoxyethylene (ethylene oxide addition mole number 2-50) Nonylphenyl ether phosphate diester, polyoxyethylene (ethylene oxide addition Le number 2-50) alkyl (number 8-18) ether phosphoric acid monoester carbon, and polyoxyethylene (ethylene oxide addition molar number 2 to 50)
Alkali metal, ammonium or amine salts of alkyl (C8-18) ether phosphate diesters. These anionic emulsifiers may be used alone or in combination of two or more, and if necessary, a nonionic emulsifier may be used in combination, for example, polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether,
Polyoxyethylene type nonionic emulsifiers such as fatty acid polyethylene glycol ester, ethylene oxide adduct of partial fatty acid ester of polyhydric alcohol, fatty acid amide ethylene oxide adduct and ethylene oxide / propylene oxide copolymer, and fatty acid ester of glycerin, fatty acid of sorbitol Examples include polyhydric alcohol type nonionic emulsifiers such as esters, sorbitan fatty acid esters, polyhydric alcohol alkyl ethers, and alkanolamines fatty acid amides.

The amount of the anionic emulsifier used is 1 to 25 parts by weight, preferably 3 to 2 parts by weight, based on 100 parts by weight of the total amount of the monomers.
The amount is 0 parts by weight, more preferably 5 to 15 parts by weight. When the amount of the anionic emulsifier used is less than 1 part by weight, aggregates are generated in the emulsion polymerization, and the stability of the obtained aqueous dispersion of the emulsion polymer is lowered. On the other hand, if it exceeds 25 parts by weight, the water resistance of the emulsion polymer is lowered, the wet pick of the coated paper is apt to be lowered, and foaming of the paper coating paint is apt to occur, which is not preferable.

The emulsion polymerization method of the water retention agent for paper coating paint of the present invention is carried out by adding and dispersing methacrylic acid, a monomer mixture of monomer A and monomer B, and an anionic emulsifier in water.
Persulfates such as ammonium persulfate and potassium persulfate, or radical polymerization catalysts such as azobisisobutyronitrile and benzoyl peroxide may be added dropwise, and emulsion polymerization may be performed at 40 to 120 ° C. The radical polymerization catalyst may be added in such an amount that the relative viscosity becomes 2.5 to 500. In emulsion polymerization, a mixture of a monomer mixture and an anionic emulsifier is added dropwise to an aqueous dispersion of a radical polymerization catalyst, or a monomer mixture, an anionic emulsifier and an aqueous dispersion of a radical polymerization catalyst are added to water. It is also possible to drop the solution at the same time in a separate line to carry out emulsion polymerization, and the emulsion polymerization method is not particularly limited.

The water-retaining agent for the paper coating paint of the present invention has a relative viscosity of 2.5 to 500 measured with an Ubbelohde viscometer at 25 ° C. in a 1% aqueous solution neutralized with sodium hydroxide.
And preferably 3.0 to 350, and more preferably 4.0 to 200. If the relative viscosity is less than 2.5, the water retention becomes low, and if it exceeds 500, the viscosity of the paper coating composition becomes high, the viscosity under high shear does not decrease, and the desired flow characteristics cannot be obtained.

The water-retaining agent for a paper coating composition of the present invention is an alkali-sensitive emulsion, and contains water of amines such as ammonia and monoethanolamine, alkali metals such as sodium and potassium, or alkaline earth metals such as magnesium and calcium. The oxides are usually adjusted to pH 7 to 13 and used before use. pH
The method of adjustment may be such that the water retention agent for paper coating paint of the present invention is adjusted to a target pH with an alkali in advance and then added to the paper coating paint, or the paper coating paint is adjusted to a target pH in advance. The necessary amount of alkali may be added to the above, and the water retention agent for the paper coating paint of the present invention may be added thereto with stirring.

The water retention agent for paper coating paint of the present invention may contain or be mixed with an antioxidant, an ultraviolet absorber, a water resistant agent, an antiseptic / antifungal agent, an antifoaming agent, a dye and a pigment. .

The water retention agent for paper coating paints of the present invention is used to improve the water retention and fluidity characteristics by adding it to a paper coating paint mainly containing a pigment and a binder. Particularly, it is most suitable for high-speed coating by increasing the concentration of paper coating paint.

Examples of pigments include clay, calcium carbonate, titanium oxide, satin white, barium sulfate,
Examples thereof include inorganic pigments such as talc and zinc oxide, and organic pigments such as polystyrene plastic pigments, which may be used alone or in combination.

Examples of the binder include natural binders such as starch, modified starch, casein and modified soybean protein, and styrene butadiene latex, carboxyl modified styrene butadiene latex, acrylic resin emulsion, vinyl acetate resin emulsion, vinyl chloride resin emulsion and the like. Examples include synthetic binders.

The amount (in terms of solid content) of the water-retaining agent for a paper coating paint of the present invention is usually 0.001 to 10 parts by weight, preferably 0 to 100 parts by weight of the pigment in the paper coating paint. ．
The amount is 01 to 5 parts by weight, more preferably 0.05 to 3 parts by weight. If it is less than 0.001 part by weight, the effect of imparting water retention and the effect of improving the flow characteristics are insufficient, and even if it is used in an amount of more than 10 parts by weight, the effect of improving the water retention and the effect of improving the flow characteristics is not improved so much, and the water resistance is lowered. Absent.

The paper coating paint using the water-retaining agent for paper coating paint of the present invention is usually used in the form of an aqueous dispersion, and if necessary, other additives such as a dispersant such as sodium polyacrylate. A defoaming agent such as fatty acid ester, a lubricant such as calcium stearate, a water resistant agent such as glyoxal or a urea resin or a polyamide polyamine resin, an antiseptic agent, a fluorescent dye and the like are added. Further, a water retention agent other than the present invention, such as CMC and sodium alginate, can be used in combination, but it is preferable to use them in an amount of 50% by weight or less of the water retention agent for the paper coating paint of the present invention. If it is more than 50% by weight, the effect of improving the fluidity and water retention is lowered.

The paper coating composition can be coated on the paper by a known method, for example, with an air knife coater, a blade coater, a roll coater, a rod coater or the like. After coating, dry and calendering or super calendering finish if necessary. The coating temperature is usually 1
0 to 60 ° C, the drying temperature is usually 90 to 150 ° C, and the temperature of the calender ring, super calender ring or soft nip calender ring is usually 30 to 200 ° C.

[0021]

EXAMPLES The present invention will be further described below with reference to examples, but the present invention is not limited thereto. In the following examples, "parts" means "parts by weight" and "%" means "% by weight".

Example 1 In a glass reaction vessel equipped with a dropping funnel, a reflux condenser, a stirrer and a thermometer, 600 parts of water, 165.
8 parts, 76.3 parts of decyl acrylate, 21.1 parts of hexyl methacrylate and 36.8 parts of sodium salt of polyoxyethylene (25 mol of ethylene oxide adduct) stearyl ether sulfate were added, and potassium persulfate of 0. 100 parts of a 5% aqueous solution was added dropwise from a dropping funnel for 3 hours to cause a reaction. The reaction temperature was kept at 80 to 100 ° C. After maintaining the same temperature for 3 hours after completion of dropping (hereinafter referred to as aging), cooled to 30 ° C. and taken out, a water retention agent A for paper coating paint (hereinafter referred to as water retention) which is a white emulsion having a concentration of 30% and a viscosity of 11 mPa · S. (Abbreviated as Agent A) was obtained.

Example 2 In the same manner as in Example 1, water 6 was added to a glass reaction vessel.
00 parts, methacrylic acid 112.8 parts, 2-ethylhexyl acrylate 118.3 parts, hexyl acrylate 5.5
Parts, ethyl acrylate 30.3 parts, isobutyl acrylate 8.3 parts, polyoxyethylene (ethylene oxide 1
5 mol of adduct) 22.0 parts of nonylphenyl ether phosphate monoester disodium salt and 2.8 parts of polyoxyethylene (25 mol of ethylene oxide adduct) lauryl ether sulfate sodium salt were added, and potassium persulfate of 0. 100 parts of 4% aqueous solution was added dropwise to the reaction,
After aging and cooling, a water retention agent B for paper coating paint (hereinafter abbreviated as water retention agent B), which is a white emulsion having a concentration of 30% and a viscosity of 10 mPa · S, was obtained.

Example 3 In the same manner as in Example 1, water 6 was added to a glass reaction vessel.
00 parts, methacrylic acid 117.8 parts, lauryl acrylate 28.0 parts, 2-ethylhexyl acrylate 28.1
Parts, ethyl acrylate 78.5 parts, ethyl methacrylate 28.0 parts, polyoxyethylene (ethylene oxide 1
8 mol adduct) nonylphenyl ether sulfate potassium salt 16.8 parts and polyoxyethylene (ethylene oxide 25 mol adduct) octylphenyl ether phosphate diester potassium salt 2.8 parts were added, and potassium persulfate 0.6 was added with stirring. % Aqueous solution 100 parts dropwise, reaction,
A water-retaining agent for paper coating paint C (hereinafter water-retaining agent C) which is a white emulsion having a concentration of 30% and a viscosity of 10 mPa · S after aging and cooling.
Abbreviated).

Example 4 In the same manner as in Example 1, water 6 was added to a glass reaction vessel.
00 parts, methacrylic acid 87.0 parts, 2-ethylhexyl acrylate 81.6 parts, decyl acrylate 95.2 parts,
Propyl acrylate 5.4 parts, ethyl acrylate 2.7
Parts, and 28.0 parts of polyoxyethylene (9 mol of ethylene oxide adduct) nonylphenyl ether phosphate monoester disodium salt were added, and 100 parts of a 0.1% ammonium persulfate aqueous solution was added dropwise with stirring to carry out reaction and aging.
Upon cooling, a water retaining agent D for paper coating paint (hereinafter abbreviated as water retaining agent D) was obtained as a white emulsion having a concentration of 30% and a viscosity of 15 mPa · S.

Example 5 In the same manner as in Example 1, water 6 was added to a glass reaction container.
00 parts, methacrylic acid 198.8 parts, decyl acrylate 31.8 parts, 2-ethylhexyl methacrylate 26.5
Parts, ethyl acrylate 8.0 parts, polyoxyethylene (ethylene oxide 22 mol adduct) octyl ether sulfate sodium salt 14.0 parts and polyoxyethylene (ethylene oxide 9 mol adduct) phosphoric acid diester monosodium salt 21.0 parts Is added, 100 parts of 0.5% aqueous solution of potassium persulfate is added dropwise with stirring, reacted, aged, and cooled to obtain a water retaining agent E for paper coating paint (hereinafter referred to as water retaining agent E, which is a white emulsion having a concentration of 30% and a viscosity of 12 mPa · S). (Abbreviated as agent E) was obtained.

Example 6 In the same manner as in Example 1, water 6 was added to a glass reaction vessel.
00 parts, 82.9 parts of methacrylic acid, 203.1 parts of n-octyl acrylate and 14.0 parts of polyoxyethylene (ethylene oxide 22 mol adduct) octyl ether sulfate sodium salt were added, and ammonium persulfate 0.11 was added with stirring. A 100% aqueous solution was added dropwise, reacted, aged, and cooled to obtain a water retention agent F for paper coating paint (hereinafter abbreviated as water retention agent F) which was a white emulsion having a concentration of 30% and a viscosity of 12 mPa · S.

Example 7 In the same manner as in Example 1, water 6 was added to a glass reaction vessel.
20 parts, 197.4 parts of methacrylic acid, 37.6 parts of stearyl acrylate and 45.0 parts of polyoxyethylene (22 mol of ethylene oxide adduct) octylphenyl ether sulfate sodium salt were added, and ammonium persulfate 0.4% was added with stirring. 100 parts of aqueous solution was added dropwise to the reaction,
A water-retaining agent G for paper coating paint (hereinafter, water-retaining agent G) which is a white emulsion having a concentration of 28% and a viscosity of 13 mPa · S after aging and cooling.
Abbreviated).

Example 8 In the same manner as in Example 1, water 6 was added to a glass reaction vessel.
00 parts, 106.3 parts methacrylic acid, 16.4 parts decyl acrylate, 27.3 parts lauryl acrylate, 68.1 parts ethyl acrylate, 54.5 parts n-butyl acrylate and polyoxyethylene (ethylene oxide 18 Molar adduct) lauryl ether sulfate sodium salt 2
7.5 parts was added, 100 parts of 0.6% potassium persulfate aqueous solution was added dropwise with stirring, and the reaction, aging, and cooling were carried out to a concentration of 30%,
A water retention agent H for paper coating paint (hereinafter abbreviated as water retention agent H), which is a white emulsion having a viscosity of 10 mPa · S, was obtained.

Comparative Example 1 In the same manner as in Example 1, water 6 was added to a glass reaction vessel.
00 parts, methacrylic acid 56.3 parts, hexyl acrylate 169.0 parts, decyl methacrylate 56.3 parts and polyoxyethylene (ethylene oxide 25 mol adduct)
Stearyl ether sulfate sodium salt 18.4
10 parts of a 0.5% aqueous solution of potassium persulfate with stirring.
0 part was dropped, reacted, aged and cooled to give a concentration of 30% and a viscosity of 9
A water retention agent I which was a white emulsion of mPa · S was obtained.

Comparative Example 2 In the same manner as in Example 1, water 7 was placed in a glass reaction container.
50 parts, methacrylic acid 254.5 parts, lauryl acrylate 13.4 parts and polyoxyethylene (ethylene oxide 18 mol adduct) lauryl ether sulfate sodium salt 32.1 parts were added, and potassium persulfate 0.6% was added with stirring. 100 parts of the aqueous solution was dropped, reacted, aged, and cooled to obtain a water retention agent J which was a white emulsion having a concentration of 15% and a viscosity of 8 mPa · S.

Comparative Example 3 In the same manner as in Example 1, water 6 was added to a glass reaction container.
00 parts, methacrylic acid 112.8 parts, ethyl acrylate 162.4 parts, polyoxyethylene (ethylene oxide 15 mol adduct) nonylphenyl ether phosphate monoester disodium salt 22.0 parts and polyoxyethylene (ethylene oxide 25 mol) Addition product: 2.8 parts of sodium lauryl ether sulfate salt was added, and 100 parts of 0.3% ammonium persulfate aqueous solution was added dropwise with stirring.
After the reaction, aging and cooling, a water retaining agent K which is a white emulsion having a concentration of 30% and a viscosity of 13 mPa · S was obtained.

Comparative Example 4 In the same manner as in Example 1, water 6 was added to a glass reaction container.
00 parts, methacrylic acid 112.8 parts, 2-ethylhexyl acrylate 19.8 parts ethyl acrylate 142.6
Parts, 22.0 parts of polyoxyethylene (15 mol of ethylene oxide adduct) nonylphenyl ether phosphate monoester disodium salt and 2.8 parts of sodium salt of polyoxyethylene (25 mol of ethylene oxide adduct) lauryl ether sulfate, 100 parts of an aqueous solution of 0.3% ammonium persulfate was added dropwise with stirring, reacted, aged, and cooled to obtain a water retention agent L which was a white emulsion having a concentration of 30% and a viscosity of 12 mPa · S.

Comparative Example 5 In the same manner as in Example 1, water 3
00 parts, isopropyl alcohol 300 parts, methacrylic acid 165.8 parts, hexyl acrylate 76.3 parts, decyl methacrylate 21.1 parts and polyoxyethylene (ethylene oxide 25 mol adduct) stearyl ether sulfate sodium salt 36.8 parts Was added, and 100 parts of an 8.1% ammonium persulfate aqueous solution was added dropwise with stirring.
After the reaction and aging, isopropyl alcohol was distilled off, the concentration was adjusted, and the mixture was cooled to obtain a water retention agent M which was a white emulsion having a concentration of 30% and a viscosity of 11 mPa · S.

Comparative Example 6 In the same manner as in Example 1, water 8 was added to a glass reaction container.
00 parts, methacrylic acid 28.5 parts, hexyl acrylate 29.5 parts, ethyl acrylate 31.2 parts and polyoxyethylene (ethylene oxide 13 mol adduct) nonylphenyl ether sulfate sodium salt 34.0.
90 parts of an aqueous solution of ammonium persulfate 0.14% and 10 parts of an aqueous solution of copper sulfate 0.001% are added dropwise at 60 to 100 ° C. over 15 hours under stirring, and the reaction, aging and cooling are performed to obtain a concentration of 10%, A water retention agent N which is a white emulsion having a viscosity of 8 mPa · S was obtained.

Comparative Example 7 The polyoxyethylene of Example 1 (ethylene oxide 25
Emulsion polymerization was carried out in the same manner as in Example 1 except that the amount of stearyl ether sulfate sodium salt was changed to 2.6 parts, but aggregates were generated, and mechanical stability of the obtained emulsion was obtained. It was bad and could not be used.

Comparative Example 8 In the same manner as in Example 1, water 6 was added to a glass reaction vessel.
00 parts, 126.0 parts methacrylic acid, 58.0 parts hexyl acrylate, 16.0 parts decyl methacrylate and polyoxyethylene (ethylene oxide 25 mol adduct)
Stearyl ether sulfate sodium salt 100.
0 parts was added and 0.5% aqueous solution of potassium persulfate with stirring 1
The water retaining agent O, which is a white emulsion having a concentration of 30% and a viscosity of 15 mPa · s, was obtained by dropping 00 parts, reacting, aging and cooling.

Comparative Example 9 A water retaining agent P was obtained by preparing a 5% aqueous solution of carboxymethyl cellulose [Cerogen PR manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.].

Comparative Example 10 Sodium alginate [Kimitsu Algin L manufactured by Kimitsu Kasei Co., Ltd.
-2] 5% aqueous solution was prepared to obtain a water retention agent Q.

Comparative Example 11 In the same manner as in Example 1, water 6 was added to a glass reaction container.
00 parts, 194.4 parts of methacrylic acid, 83.3 parts of ethyl acrylate and 22.2 parts of polyoxyethylene (15 mol of ethylene oxide adduct) lauryl ether sulphate sodium salt were added, and a 0.32% ammonium persulfate aqueous solution was added with stirring. After dropping 100 parts of the mixture, reacting, aging and cooling, a white emulsion R-1 having a concentration of 30% and a viscosity of 12 mPa · S was obtained. This average molecular weight is 720,00 by GPC.
It was 0. R-1 to 1,000 parts glycerin 3
Add 0 parts and 70 parts of water, concentration 30%, viscosity 11mPa
A water retention agent R which is a white emulsion of S was obtained. (This water retention agent is produced according to the invention of JP-A-2-53996)

Comparative Example 12 In the same manner as in Example 1, 500 parts of isopropyl alcohol and 105 parts of methacrylic acid were placed in a glass reaction container.
195 parts of 2-ethylhexyl acrylate, 50 parts of 2-mercaptoethanol, 15 azobisisobutyronitrile
1 part of the mixture was reacted at the reflux temperature of isopropyl alcohol, isopropyl alcohol was distilled off, and water and ammonia water were added to obtain a copolymer S having a pH of 9 and a concentration of 30%. The relative viscosity of this 1% aqueous solution at 20 ° C. was 2.0, and the K value by the Fikentscher method was 60. (This water retention agent is produced according to the invention of JP-A-61-207700)

The water retention agents of Examples 1-8, Comparative Examples 1-6 and Comparative Example 8 were adjusted to pH 9 with sodium hydroxide, and 1
% Relative aqueous solution at 25 ° C. was measured using an Ubbelohde viscometer and shown in Table 1.

[0043]

[Table 1]

The performance of the water retention agents of Examples 1-8 and Comparative Examples 1-12 was evaluated by the following method. The results are shown in Table 2.

(1) Formulation of coating composition for paper (part: means solid content, means parts by weight) No. 1 Pre-dispersed Toclay [ENGEL HARD MINERA
L & CHEMICALS, UW-90] 70 parts, heavy calcium carbonate [Pharmatech Co., Ltd., FMT-90] 15
Part, light calcium carbonate [Okutama Kogyo KK, Tamapearl TP-222-HS] 15 parts, dispersant [San Nopco KK, SN Dispersant 5040] 0.2 part,
0.1 to 0.3 parts of sodium hydroxide, 3 parts of phosphoric acid-modified starch [MS-4600 manufactured by Japan Food Processing Co., Ltd.], SB
R latex [manufactured by Japan Synthetic Rubber Co., Ltd., JSR069
6] 12 parts, lubricant [San Nopco Ltd., Nopcoat C-104-HS] 1 part and water retention agent 0.2 parts to prepare a paper coating paint with pH 9.0, paint concentration 63 and 65% did.

(2) Physical properties of paper coating paint Low shear viscosity: BM type viscometer manufactured by Tokyo Keiki Co., Ltd., 60 rp
m, measured at 25 ° C. It is preferable that the viscosity is low. High shear viscosity: Measured at 25 ° C. at a shear rate of 2 × 10 ⁶ / sec, capillary viscometer manufactured by Anton Paar. It is preferable that the viscosity is low. Water retention: Measured by Sdi Warren's ring cell method. The larger the value, the better. Coating suitability: Waferuser CLC-6000 at a coating speed of 1,500 m / min and coating concentrations of a63% and b6
A 5% paper coating paint was applied and dried. It is preferable that the amount of coating does not increase as much as possible even when the concentration of the coating composition on paper increases. That is, the smaller the coating amount ratio of b / a, the better. In this case, since coating can be performed without increasing the blade pressure, there is no paper breakage, and a bulky coating layer can be obtained, and white paper gloss, smoothness, printing gloss, and water absorbing ink after supercalendering The meat is improved. Coating unevenness: The coating unevenness of the paper coated with a coating density b of 65% was visually determined. ◯: No coating unevenness, Δ: Some coating unevenness occurred, ×: White paper with a lot of coating unevenness Gloss: Coated paper with a coating amount of 10 gr / m ² at 60 ° C and a linear pressure of 80 kg / cm 2 using a super calender After passing twice,
The humidity was adjusted and measured. Printing gloss, dry pick, wet pick, water-absorption ink inking property: Printed by Aki Seisakusho RI-1 type printability tester. Dry pick, wet pick, and water-absorbent ink inking property were evaluated by a 5-point method. The larger the number, the better. Smoothness: Measured with the Oken smoothness tester. The larger the value, the higher the smoothness and the better.

[0047]

[Table 2]

[0048]

EFFECT OF THE INVENTION The water-retaining agent for paper coating paints of the present invention has a very small increase in viscosity of the paper coating paint under low shear, and a shear rate of 1
Under the high shear of 0 ⁶ / sec or more, the paper-coated paint exhibits a viscosity-reducing property, and has a very high water-retaining effect which has not been heretofore known. The water-retaining agent of the present invention can easily increase the concentration of a paper coating paint and is excellent in coating suitability,
It has an effect that a paper coating paint having physical properties suitable for high speed coating can be prepared. Furthermore, the water retention agent of the present invention is used to suppress migration of binders and the like based on high water retention, decrease in blade pressure based on viscosity reduction under high shear, or immobilization of coating paint by increasing the concentration of paper coating paint. It has an effect and can form a uniform and bulky coating layer with no coating unevenness, and it is possible to obtain a smooth coated paper with excellent white paper gloss, printing gloss and water-absorption ink inking. . The water retention agent for paper-coating paints of the present invention is suitable for the production of coated papers because it exhibits the above effects.

Continuation of front page (56) References JP-A-61-43607 (JP, A) JP-A-61-55289 (JP, A) JP-A-57-149594 (JP, A) JP-A-63-59497 (JP , A) JP-A-8-158296 (JP, A) JP-A-56-115630 (JP, A) JP-A-60-28597 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB) Name) D21H 11/00-27/42 C08F 2/00-2/60 C08L 1/00-101/14 C09D 101/00-201/10

Claims (3)

(57) [Claims] 1. A total of 100 parts by weight of monomers, (1) 25 to 90 parts by weight of methacrylic acid, and (2) the following general formula [Chemical formula 1] (In the formula, R ₁ is H or CH ₃ , and R ₂ has 6 to 6 carbon atoms.
22 is an alkyl group of 22) A10-7
5 parts by weight as an essential constituent component and 0 to 50 parts by weight of another ethylenically unsaturated monomer B (excluding vinyl acetate) copolymerizable with these, monomer B / monomer A The monomer mixture having a weight ratio of 5 or less is 10 in total.
From 0 to 25 parts by weight of polyoxyethylene alkylphenyl ether sulfate salt, polyoxyethylene alkyl ether sulfate salt, polyoxyethylene alkylphenyl ether phosphate ester salt, or polyoxyethylene alkyl ether phosphate ester salt The relative viscosity at 25 ° C. of a 1% aqueous solution neutralized with sodium hydroxide obtained by emulsion polymerization using a radical polymerization catalyst in the presence of one or more selected anionic emulsifiers is 2.5 to A water retention agent for paper coating paints, which is composed of 500 alkali-sensitive emulsions. 2. The water retention agent for paper coating paint according to claim 1, wherein the pH thereof is adjusted to 7 to 13. 3. A total of 100 parts by weight of monomers, (1) 25 to 90 parts by weight of methacrylic acid, and (2) the following general formula [Chemical Formula 2] (In the formula, R ₁ is H or CH ₃ , and R ₂ has 6 to 6 carbon atoms.
22 is an alkyl group of 22) A10-7
5 parts by weight as an essential constituent component and 0 to 50 parts by weight of another ethylenically unsaturated monomer B (excluding vinyl acetate) copolymerizable with these, monomer B / monomer A The monomer mixture having a weight ratio of 5 or less is 10 in total.
From 0 to 25 parts by weight of polyoxyethylene alkylphenyl ether sulfate salt, polyoxyethylene alkyl ether sulfate salt, polyoxyethylene alkylphenyl ether phosphate ester salt, or polyoxyethylene alkyl ether phosphate ester salt The relative viscosity at 25 ° C. of a 1% aqueous solution neutralized with sodium hydroxide obtained by emulsion polymerization using a radical polymerization catalyst in the presence of one or more selected anionic emulsifiers is 2.5 to The present invention is characterized in that 0.001 to 10 parts by weight of a water-retaining agent for a paper-coating paint consisting of 500 alkali-sensitive emulsions is added to a paper-coating paint mainly containing a pigment and a binder per 100 parts by weight of the pigment. A coating composition for paper.