JP5645246B2 - Copolymer latex, composition for paper coating and coated paper - Google Patents

Description

  The present invention relates to a copolymer latex and the like preferably used for pigment binders, carpet backing agents, adhesives, pressure-sensitive adhesives, fiber binders and paints in paper coating. More specifically, for example, a copolymer latex capable of giving a coated paper having good coating workability and excellent suppression of printing gloss and stickiness of the coated paper surface, a paper coating composition and a coating Regarding paper.

  For the purpose of improving the printability of paper and improving the optical properties such as gloss, coated paper has pigments such as kaolin clay, calcium carbonate, satin white, talc, and titanium oxide, and pigments on the surface of the base paper. A paper coating composition (paper coating agent) comprising, as main components, a copolymer latex as a binder and a water-soluble polymer (starch, polyvinyl alcohol, carboxymethyl cellulose, etc.) as a viscosity modifier or an auxiliary binder ) Is formed by coating.

  As the copolymer latex, styrene-butadiene copolymer latex obtained by emulsion polymerization of styrene and butadiene as main monomer components and so-called SB latex is widely used.

  In order to increase the commercial value of coated paper, there are a wide variety of required items. Among them, printing gloss is an important item that determines the final commercial value of printed coated paper. Conventionally, in order to increase the printing gloss of coated paper, a method of reducing the particle size of the copolymer latex and a method of using a conjugated diene monomer such as butadiene in a specific amount or more are known. However, these methods certainly increase the printing gloss, but the fluidity at low shear rate decreases (the coating solution viscosity increases), causing problems in the transfer of the coating solution, etc. In order to increase the stickiness of the paper surface, problems such as backing roll stains and supercalendar stains occur, which is not preferable.

  As an improved prior application technique, the amount of potassium in the alkali metal and alkali metal in the copolymer latex film is adjusted within a certain range, thereby having excellent printing gloss, dry pick strength, and wet pick strength. It has been proposed that a coated paper can be obtained (see Patent Document 1). Even with this method, the printing gloss is improved, but the viscosity of the copolymer latex and the stickiness of the coated paper surface are not achieved.

  In addition, by coexisting a (co) polymer having a low glass transition point and a (co) polymer having a high glass transition point in the same copolymer latex, a coating excellent in printing gloss, surface strength and rigidity is applied. It has been proposed to obtain paper (see Patent Document 2). This method also improves the printing gloss, but does not achieve an improvement in the viscosity of the copolymer latex and the stickiness of the coated paper surface.

  On the other hand, by suppressing the concentration of 4-vinylcyclohexene remaining in the copolymer latex to 100 ppm or less with respect to the solid content of the copolymer latex, there is less odor, printing gloss, coating operability, blank paper gloss, etc. It has been proposed that a coated paper having excellent printability can be obtained (see Patent Document 3). In this method, the printing gloss and the stickiness of the copolymer latex film are improved, but the viscosity of the copolymer latex and the stickiness of the coated paper surface are not achieved.

JP 2009-91669 A JP 2006-176696 A JP 2003-277546 A

  From the above situation, the present invention is excellent in coating workability by using it as a coated paper for printing, exhibiting high printing gloss, and lowering the viscosity of the copolymer latex and good coated paper. It is an object of the present invention to provide a paper coating binder that can simultaneously satisfy the surface stickiness.

  As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention first determined the composition of the monomer mixture used for producing the copolymer in a specific range with respect to the copolymer latex, Secondly, when the copolymer latex is produced, it is found that the above problem may be solved by what is obtained by emulsion polymerization of the monomer mixture in the presence of a specific component. As a result of research, it has been found that the above problems can be solved, and the present invention has been made.

That is, the present invention provides the following copolymer latex and the like.
[1] Component (a): Conjugated diene monomer 20 to 80% by mass, Component (b): Ethylene unsaturated carboxylic acid monomer 0.5 to 7% by mass, and Component (c): Other Copolymerizable monomers (excluding those corresponding to the following component (a)) 13 to 79.5% by mass (however, the sum of the component (a), the component (b), and the component (c)) Is a polymer derived from a linear or branched olefin having 3 to 6 carbon atoms, with respect to 100 parts by mass of the monomer mixture. Copolymer latex obtained by emulsion polymerization in the presence of 0.0002 to 0.045 parts by mass of component (b) which is an oligomer having a degree of 2 to 10.
[2] The copolymer latex according to the above [1], wherein the component (a) is a propylene oligomer or butene oligomer having 6 to 20 carbon atoms.
[3] The emulsion polymerization is the copolymer latex according to the above [1] or [2], wherein the temperature is lowered by 5 ° C. or more during the polymerization step with respect to the polymerization temperature.
[4] The copolymer latex according to any one of [1] to [3], wherein the rate of decrease in the polymerization temperature in the range of 1 to 10 ° C./hr.
[5] A paper coating composition comprising the copolymer latex according to any one of [1] to [4].
[6] A coated paper produced using the paper coating composition described in [5] above.

  According to the copolymer latex of the present invention, the coating workability is excellent, a high printing gloss is exhibited on the coated paper, and an increase in the viscosity of the copolymer latex is suppressed. Moreover, the coated paper using the composition for paper coating containing the copolymer latex of this invention has the effect that the stickiness of the coated paper surface is favorable (a stickiness is suppressed).

  Hereinafter, modes for carrying out the present invention (hereinafter, embodiments of the present invention) will be described in detail. In addition, this invention is not limited to the following embodiment, It can implement variously within the range of the summary.

  The copolymer latex of the present invention is suitably used as a pigment binder for coated paper and coated paperboard.

  The copolymer latex of the present invention comprises (a) component: 20-80% by mass of conjugated diene monomer, (b) component: 0.5-7% by mass of ethylenically unsaturated carboxylic acid monomer, and ( c) Component: Other copolymerizable monomers (excluding those corresponding to the following component (a)) 13 to 79.5% by mass (provided that component (a), component (b), and component (c)) Is obtained by emulsion polymerization of a monomer mixture consisting of 100% by mass. Hereinafter, these will be sequentially described.

  By using this component (a), the flexibility of the resulting copolymer latex can be improved, and the adhesive force and impact absorption can be improved.

  The amount of the component (a) used is the total amount of raw material monomers (the component (a), the component (b), and the component (c)) used when the copolymer latex of the present invention is produced. (Hereinafter sometimes abbreviated as “total amount of raw material monomers”) is 100 parts by mass, 20 to 80 parts by mass, preferably 25 to 70 parts by mass, and more preferably 28 to 60 parts by mass. It is. By making the amount used 20 parts by mass or more, it is possible to give the copolymer good impact resistance and good adhesive strength. Moreover, by setting it as 80 mass parts or less, it can prevent that a copolymer becomes too soft and adhesive force falls or coating operativity falls.

  Examples of the component (a) include 1,3-butadiene, isoprene, 2-chloro-1,3-butadiene, and the like. These may be used alone or in combination of two or more. it can.

  By using the component (b), the dispersion stability of the obtained copolymer latex can be improved, and the adhesive force can be increased.

  The amount of component (b) used is 0.5 to 7 parts by weight, preferably 0.8 to 5.5 parts by weight, more preferably 1 when the total amount of raw material monomers is 100 parts by weight. -5 parts by mass. By setting the amount used to 0.5 parts by mass or more, it is possible to maintain the dispersion stability required at the time of pigment mixing and in the coating process. Moreover, by setting it as 7 mass parts or less, the viscosity of copolymer latex can be suppressed and water resistance can also be improved.

  As said (b) component, acrylic acid, methacrylic acid, crotonic acid etc. are mentioned, for example, These can be used individually by 1 type or in combination of 2 or more types. In particular, it is preferable that the component (b) contains acrylic acid. Moreover, it is preferable to use together dibasic ethylenically unsaturated carboxylic acid monomers, such as itaconic acid, fumaric acid, and maleic acid, and acrylic acid. By using a dibasic ethylenically unsaturated carboxylic acid monomer and acrylic acid in combination, the coating workability can be improved while maintaining the required pick strength.

  The component (c) can impart various properties to the obtained copolymer latex.

  The amount of component (c) used is 13 to 79.5 parts by mass, preferably 20 to 70 parts by mass, when the total amount of raw material monomers is 100 parts by mass.

Examples of the component (c) include aromatic vinyl monomers such as styrene, α-methylstyrene, vinyltoluene, and p-methylstyrene;
Vinyl cyanide monomers such as acrylonitrile, methacrylonitrile, α-chloroacrylonitrile;
Alkyl acrylates such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate;
Alkyl methacrylates such as methyl methacrylate and butyl methacrylate;
Hydroxyalkyl esters such as 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate;
Aminoalkyl esters such as aminoethyl acrylate, dimethylaminoethyl acrylate, diethylaminoethyl acrylate;
Pyridines such as 2-vinylpyridine and 4-vinylpyridine;
Glycidyl esters such as glycidyl acrylate and glycidyl methacrylate;
Amides such as acrylamide, methacrylamide, N-methylolacrylamide, N-methylacrylamide, N-methylmethacrylamide, glycidylmethacrylamide, N, N-butoxymethylacrylamide;
Carboxylic acid vinyl esters such as vinyl acetate;
Examples include vinyl halides such as vinyl chloride, but those corresponding to the following component (a) are excluded. These are used alone or in combination of two or more.

In addition, the copolymer latex of the present embodiment is a monomer mixture composed of the above components (a) to (c), or one or two or more linear or branched olefins having 3 to 6 carbon atoms. (I) component which is an oligomer having a polymerization degree of 2 to 10 derived from
Is obtained by emulsion polymerization in the presence of.

  The amount of the component (a) used is 0.0002 to 0.045 parts by mass, preferably 0.0002 to 0.03 parts by mass, more preferably 0 to 100 parts by mass of the total amount of the raw material monomers. 0002 to 0.015 parts by mass. By using 0.0002 parts by mass or more, the latex viscosity can be reduced and good printing gloss and stickiness can be realized, and when the amount used is 0.045 parts by mass or less, the printing gloss can be improved.

  Examples of the component (a) include oligomers such as propylene and butene, and the carbon number is preferably 6-20. Moreover, a C6-C50 propylene oligomer, (iso) butene oligomer, and (iso) pentene oligomer can also be used preferably. These can be used alone or in combination of two or more.

  The oligomer referred to as the component (a) means that it is at least a dimer or more. Among them, the use of a tetramer gives excellent printed gloss to the resulting coated paper. From the viewpoint of The most preferable compound as the component (a) is propylene tetramer.

In the present embodiment, the method for adding the component (a) during the emulsion polymerization is not particularly limited, and various methods can be used. As such a method, for example,
(I) A method in which the component (a) is added directly to water used for emulsion polymerization or added after being emulsified and dispersed.
(Ii) a method of carrying out emulsion polymerization by dissolving the component (a) in one or more of the raw material monomers (a) to (c);
(Iii) A method in which the component (a) is previously dissolved in various solvents, added to the polymerization system, and emulsion polymerization is performed together with the raw material monomer,
(Iv) A method in which the component (a) is dissolved in a raw material component other than the raw material monomers (a) to (c) and added to the polymerization site. In addition, these methods can also use 1 type or multiple types together.
However, it is desirable to employ the method (iv) from the viewpoint that the obtained copolymer latex imparts excellent printing gloss to the coated paper. Furthermore, the component (a) is most preferably added after being dissolved in a chain transfer agent used during emulsion polymerization.

  In the emulsion polymerization in the present embodiment, in addition to the above components, an emulsifier, a radical initiator, a chain transfer agent, various polymerization regulators and the like can be appropriately blended.

  As such an emulsifier, an anionic, cationic, amphoteric or nonionic surfactant, or a reactive emulsifier can be used. These can be used alone or in combination of two or more.

Examples of preferred surfactants include anionic surfactants such as aliphatic soaps, rosin acid soaps, alkyl sulfosuccinates, polyoxyethylene alkyl sulfates;
Nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl allyl ether, polyoxyethyleneoxypropylene block copolymer, and the like.

  Examples of the emulsifying dispersant for emulsifying and dispersing include water-soluble polymers such as polyvinyl alcohol, nonionic surfactants, anionic surfactants, cationic surfactants, other surfactants, and amphoteric surfactants. Is mentioned. Such various emulsifiable dispersants can be used singly or in combination.

  As the radical initiator, for example, a radical initiator that initiates addition polymerization of monomers by radical decomposition in the presence of heat or a reducing agent can be used. As the radical initiator, either an inorganic initiator or an organic initiator can be used.

  Specific examples of such radical initiators include peroxodisulfates, peroxides, azobis compounds, and the like. More specifically, for example, potassium peroxodisulfate, sodium peroxodisulfate, ammonium peroxodisulfate, hydrogen peroxide, t-butyl hydroperoxide, benzoyl peroxide, 2,2-azobisbutyronitrile, cumene hydroperoxide Etc. These can be used alone or in combination of two or more.

  In addition, what is called a redox type | system | group initiator which uses reducing agents, such as sodium hydrogen sulfite, ascorbic acid, its salt, erythorbic acid, its salt, and Rongalite in combination with a polymerization initiator can also be used.

As the chain transfer agent, it is possible to use a known chain transfer agent usually used in radical polymerization. Preferable examples include mercaptans such as n-butyl mercaptan, t-butyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-lauryl mercaptan;
Disulfides such as tetramethylthiudium disulfide, tetraethylthiudium disulfide;
Halogenated derivatives such as carbon tetrachloride and carbon tetrabromide;
2-ethylhexyl thioglycolate etc. are mention | raise | lifted and these can be used individually or in combination of 2 or more types.
In addition, the addition method of a chain transfer agent can use well-known addition methods, such as lump addition, batch addition, and continuous addition suitably.

  Examples of the polymerization regulator include a pH regulator and a chelating agent. Preferable examples of the pH adjuster include sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium hydrogen carbonate, disodium hydrogen phosphate and the like, and preferable examples of the chelating agent include sodium ethylenediaminetetraacetate and the like. .

  The polymerization temperature at the time of performing the emulsion polymerization is usually 0 to 100 ° C., but the range of 40 to 95 ° C. is preferable from the viewpoint of production efficiency and quality such as adhesive strength of the obtained copolymer latex. . Furthermore, from the viewpoint of achieving better adhesive strength, the polymerization temperature is preferably lowered by 5 ° C. or more during the polymerization step. In addition, it is preferable that the rate of decrease in the temperature of the polymerization temperature falls within a range of 1 to 10 ° C./hr.

  The method for adding the raw material monomer in the emulsion polymerization is not particularly limited, and any method such as batch addition (collective polymerization), continuous addition (continuous polymerization), or divided addition (sequential polymerization) may be used.

  In the emulsion polymerization, a seed polymerization method can be used, and any method such as an external seed method or an internal seed method can be adopted.

  The copolymer latex of the present invention preferably contains acrylic acid as a monomer. The content thereof is preferably 50 to 3500 ppm (mass ratio when the total mass of the solid content of the copolymer latex is 100 mass%) in the copolymer latex, and more preferably 100 to 3300 ppm. More preferably, it is 200 to 3000 ppm. By setting within this range, the pick strength, the stickiness when wet of the latex film, and the inking property can be raised to good levels.

  The copolymer latex of the present invention is prepared, for example, by diluting or concentrating in a range of usually 30 to 60% by mass as a solid content concentration as a final product.

  The copolymer latex of the present invention has a solids glass transition temperature (Tg) of −60 ° C. to + 50 ° C. from the viewpoint of achieving both adhesive strength in coated paper and stickiness when latex film is wet. Generally, it is in the range of ° C. Preferably it is -40 to +45 degreeC, More preferably, it is the range of -30 to +40 degreeC. Tg may have not only one point but also a plurality of Tg in one type of copolymer latex.

  The number average particle size of the copolymer latex of the present embodiment is usually 50 nm to 150 nm, preferably 55 nm to 140 nm, more preferably 60 nm to 130 nm, from the viewpoint of achieving both pick strength and polymerization stability. .

  It is possible to add various additives to the copolymer latex of the present invention, if necessary, or to mix other latexes. Examples of such additives include dispersants, antifoaming agents, anti-aging agents, water-proofing agents, bactericides, and printability improvers. In addition, alkali-sensitive latex, plastic pigment, and the like can be mixed and used.

  The composition for paper coating of this invention contains the copolymer latex mentioned above. In the paper coating composition, the copolymer latex of the present invention can be used as a pigment binder.

  When the copolymer latex in the form of the present invention is used as a binder for a paper coating composition, for example, in a water in which a dispersant is dissolved, the copolymer latex is added together with the following various additives and mixed. And a uniform dispersion can be obtained. Examples of such various additives include inorganic pigments (kaolin clay, calcium carbonate, titanium dioxide, aluminum hydroxide, satin white, talc, etc.), organic pigments known as plastic pigments and binder pigments, water-soluble polymers ( Starch, casein, polyvinyl alcohol, carboxymethyl cellulose, etc.), thickeners, dyes, antifoaming agents, preservatives, water resistance agents, lubricants, printability improvers, water retention agents, and the like.

  Here, the pigment constituting the composition for paper coating is preferable when a pigment having a small number average particle diameter is mainly used because particularly remarkable pick strength and wet pick strength can be expressed. That is, for kaolin clay, it is preferable to use a pigment having a particle size of 2 μm or less of 84% by mass or more, and for calcium carbonate, a pigment having a particle size of 2 μm or less of 90% by mass or more.

  As the usage-amount of the copolymer latex contained in the composition for paper coating, it is 3-30 mass parts (solid content conversion) normally as a compounding quantity with respect to 100 mass parts of pigments.

  The paper coating composition of the present invention can be applied to a base paper by a conventional method using, for example, various blade coaters, roll coaters, air knife coaters, bar coaters and the like. There is no particular limitation on the coating form, and it can be applied to the base paper on one side or both the front and back sides, and the number of coatings per side is not particularly limited. It can also use for what is called double coating which performs two coating processes. In this case, the copolymer latex of the present invention can be used for both a pigment composition (paper coating agent) for undercoating and a pigment composition (paper coating agent) for top coating. , It may be used for only one of them.

  The paper coating composition of the present invention can be used for various types of paper without any particular limitation, and various printings such as offset sheet-fed printing paper, offset rotary printing paper, gravure printing paper, letterpress printing paper, etc. It is preferably used for paper and paperboard, cardboard paper, wrapping paper, etc., but is particularly preferably used for offset sheet-fed printing paper and offset rotary printing paper.

  Furthermore, the copolymer latex of the present invention can also be used in paper coating agents, carpet backing agents, other adhesives, and various paints.

[Evaluation method of each physical property]
(1) Pick strength:
Using an RI printing tester (manufactured by Meisei Seisakusho), 0.4 cc of printing ink (Printing Ink, manufactured by Toyo Ink Manufacturing Co., Ltd.) (trade name) was printed once on a coated paper sample, and picking appeared on a rubber roll The state was backed on another mount and the state was observed. The evaluation was a relative 10-point evaluation method, and the higher the score, the smaller the picking phenomenon.
(2) Print gloss:
Using an RI printing tester (manufactured by Meisei Seisakusho), 0.5 cc of offset rotary printing ink was printed twice on a coated paper sample at an interval of 15 sec, and printed gloss using a gloss meter after 24 hours. The value of was measured. The larger the value, the better the print gloss.
(3) Coated paper surface stickiness:
The coated paper sample was placed with the coated surface facing upward, five coated paper samples were overlaid, and a 15 kg weight was placed thereon and allowed to stand for one week. Thereafter, the coated papers that were superposed were peeled off, and the picking state on the coated paper surface was observed. The evaluation was a relative 10-point evaluation method, and the higher the score, the smaller the picking phenomenon.
(4) Viscosity of copolymer latex:
The copolymer latex was adjusted to 25 ° C., pH 8, and solid content concentration 50%, and the viscosity was measured using a B-type viscometer (Tokyo Keiki). When the viscosity is 400 mP · s or more, it becomes difficult to transfer the latex, and the transfer efficiency decreases.
(5) Particle diameter of copolymer latex:
The copolymer latex was observed with a transmission electron microscope, and the average particle size was calculated using an image processing apparatus.
[Example 1]

Production of copolymer latex A A pressure reactor equipped with a stirrer, a hot water jacket for adjusting the internal temperature, and quantitative addition equipment for various raw materials, 78 parts by mass of water as a raw material at the initial stage of polymerization, 0.1% sodium dodecylbenzenesulfonate Polymerization initial raw materials consisting of 1 part by mass, 0.1 part by mass of sodium dodecyl diphenyl ether disulfonate, and 0.3 part by mass of α-methylstyrene dimer were charged together and stirred sufficiently at 78 ° C. Next, 2.5 parts by mass of itaconic acid, 0.2 parts by mass of fumaric acid, 6.8 parts by mass of styrene, 0.06 parts by mass of methyl methacrylate, and 2.4% of acrylonitrile prepared for the first polymerization step. Parts by weight, 0.3 parts by weight of hydroxyethyl acrylate, 0.3 parts by weight of acrylic acid, 0.45 parts by weight of α-methylstyrene dimer, 0.02 parts by weight of t-dodecyl mercaptan and 0.0003 parts by weight of propylene tetramer A monomer for the first polymerization step and a chain transfer agent mixture comprising the chain transfer agent composition are charged all at once into this pressure-resistant reaction vessel, and after stirring and mixing, an aqueous solution of sodium peroxodisulfate having a concentration of 30% by mass 0.2 parts by mass (in terms of solid content) was added to the pressure resistant vessel over 5 minutes to initiate the polymerization reaction.

  90 minutes after the end of the addition of the aqueous sodium peroxodisulfate solution, 27.2 parts by mass of styrene, 48 parts by mass of butadiene, 0.24 parts by mass of methyl methacrylate, 9.6 acrylonitrile, prepared for the second polymerization step. Parts by weight, 1.2 parts by weight of hydroxyethyl acrylate, 1.2 parts by weight of acrylic acid, 1.8 parts by weight of α-methylstyrene dimer, 0.1 parts by weight of t-dodecyl mercaptan and 0.001 parts by weight of propylene tetramer The addition of the monomer and the chain transfer agent mixture for the second polymerization step, which consisted of the chain transfer agent composition, was started in this pressure-resistant reaction vessel, and the entire amount was continuously added over 5.25 hr. An aqueous mixture comprising 17 parts by weight of water, 0.2 parts by weight of sodium dodecyl diphenyl ether disulfonate, and 0.75 parts by weight of sodium peroxodisulfate at the start of addition of the monomer and chain transfer agent mixture for the second polymerization step Was added continuously until the addition of the monomer and chain transfer agent mixture for the second polymerization step was completed, and the polymerization reaction was accelerated. From the start of continuous addition of the monomer and chain transfer agent mixture for the second polymerization step, the polymerization temperature, that is, the internal temperature of the pressure-resistant reactor is started at a rate of 2.9 ° C / hr, and the polymerization temperature is 70 ° C. When it became, temperature reduction was finished. That is, the temperature was lowered by 8 ° C. Thereafter, the reaction was continued at the temperature after completion of the temperature decrease until the continuous addition of the monomer and chain transfer agent mixture for the second polymerization step was completed. Thereafter, the polymerization temperature was raised to 95 ° C. over 60 minutes and maintained at 95 ° C. for 15 minutes to obtain a copolymer latex.

  To this copolymer latex, potassium hydroxide and sodium hydroxide were added to adjust the pH to 5.0 or more, and unreacted monomers were removed by a steam stripping method, and then sodium hydroxide was used. The pH was adjusted to 8.0 and the solid content concentration was adjusted to 50% by mass. These production conditions are summarized in Table 1.

  Next, the viscosity and particle size of the copolymer latex A thus obtained were measured. As a result, excellent results were obtained in the viscosity of the copolymer latex (Table 1).

Preparation of paper coating composition and preparation of coated paper Next, the obtained copolymer latex and the following constituent materials were used and mixed uniformly to prepare a paper coating composition. In addition, the following mixing | blendings (mass part) are the values converted into solid content altogether except water.
Kaolin clay 40 parts by weight Heavy calcium carbonate 60 parts by weight Sodium polyacrylate 0.05 parts by weight Sodium hydroxide 0.06 parts by weight Oxidized starch 3.0 parts by weight Copolymer latex A 8 parts by weight Water (coating liquid) Added so that the total solid content is 66% by mass)
As kaolin clay, Amazon Plus (ratio of particle diameter 2 μm or less = 97 mass% or more) (trade name), as heavy calcium carbonate, Carbital 90 (ratio of particle diameter 2 μm or less = 90 mass% or more) (product) Name), Aron T-50 (manufactured by Toagosei Co., Ltd.) (trade name) as the sodium polyacrylate, and Oji Corn Starch B (made by Oji Corn Starch Co., Ltd.) (trade name) as the oxidized starch, respectively.

Next, the paper coating composition obtained in this way was applied to a coated base paper having a basis weight of 74 g / m ² with a blade coater so that the coating amount was 10 g / m ² on one side. After drying, a super calender treatment was performed at a roll temperature of 50 ° C. and a linear pressure of 147,000 N / m to obtain a coated paper. The obtained coated paper was evaluated by a printing test. The pick strength, printing gloss, and surface stickiness of this coated paper were measured, and the results are shown in Table 1. In any case, excellent results were obtained.

[Examples 2 to 7]
As shown in Table 1, copolymer latexes B to G were obtained in the same manner as in Example 1 except that the raw material composition of the copolymer latex, the polymerization temperature, and the temperature lowering conditions were changed. The viscosity and particle size of the obtained copolymer latex were measured. In addition, Table 1 shows the results of evaluating the physical properties of the coated paper prepared using the respective copolymer latexes under the same conditions as in Example 1. Excellent results were obtained for both the viscosity of the copolymer latex and the physical properties of the coated paper.

[Example 8]
As shown in Table 1, a copolymer latex was produced without lowering the polymerization temperature during the polymerization. A copolymer latex H was obtained in the same manner as in Example 1 except that the polymerization temperature was changed. The viscosity and particle size of the obtained copolymer latex H were measured. Table 1 shows the results of evaluating the physical properties of the coated paper prepared using the copolymer latex H under the same conditions as in Example 1. Excellent results were obtained in the viscosity of the copolymer latex and the printed gloss and surface stickiness of the physical properties of the coated paper.

[Comparative Examples 1-4]
As shown in Table 1, copolymer latexes a to d were obtained in the same manner as in Example 1 except that the raw material composition of the copolymer latex, the polymerization temperature, and the temperature lowering conditions were changed. Table 1 shows the results of evaluating the physical properties of the coated paper prepared under the same conditions as in Example 1 using each of the obtained copolymer latexes.

In Comparative Examples 1 to 4, the proportion of the monomer component constituting the copolymer latex or the proportion of the component (a) is out of the scope of the present invention, and the printed gloss and surface stickiness of the coated paper The physical properties of either the viscosity or the viscosity of the copolymer latex were inferior.
(Production conditions and evaluation results of copolymer latex)

According to the present invention, a copolymer latex that is excellent in coating operability, exhibits high printing gloss, reduces the viscosity of the copolymer latex, and simultaneously satisfies the suppression of stickiness on the coated paper surface. Can be provided. Therefore, the present invention has high utility value particularly in the coated paper manufacturing industry and related industries.

Claims (6)

  (A) Component: 20-80% by mass of conjugated diene monomer, (b) Component: 0.5-7% by mass of ethylenically unsaturated carboxylic acid monomer, and (c) Component: other copolymerizable 13-79.5% by mass (excluding those corresponding to the following component (a)) (provided that the total of component (a), component (b), and component (c) is 100 The polymerization degree derived from a linear or branched olefin having 3 to 6 carbon atoms, with respect to 100 parts by mass of the monomer mixture. A copolymer latex obtained by emulsion polymerization in the presence of 0.0002 to 0.045 parts by mass of component (b) which is an oligomer of No. 10.   The copolymer latex according to claim 1, wherein the component (a) is a propylene oligomer or butene oligomer having 6 to 20 carbon atoms.   The copolymer latex according to claim 1 or 2, wherein the emulsion polymerization is performed at a temperature drop of 5 ° C or more during the polymerization step with respect to the polymerization temperature. The copolymer latex according to claim 3, wherein the rate of decrease in the temperature of the polymerization temperature falls within a range of 1 to 10 ° C / hr.   The composition for paper coating containing the copolymer latex as described in any one of Claims 1-4. Coated paper produced using the paper coating composition according to claim 5.