JP5347216B2 - Copolymer latex and process for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a copolymer latex excellent in printing aptitude, etc., and especially, even if the printing velocity range is over a wide range, forming coated paper excellent in the printing aptitude. <P>SOLUTION: This copolymer latex is provided by containing (B) a copolymer obtained by the emulsion polymerization of a second monomer component consisting of prescribed amounts of (d) an aliphatic conjugated diene-based monomer, (e) a vinyl cyanide monomer, (f) an ethylenically unsaturated carboxylic acid monomer and (g) another monomer copolymerizable with the (d) through (f) [provided that, (d)+(e)+(f)+(g)=100 mass%] in the presence of a polymer (A) obtained by emulsion-polymerizing prescribed amounts of (a) an aliphatic group diene-based monomer, (b) an ethylenically unsaturated carboxylic acid monomer and (c) another monomer copolymerizable with the (a) and (b) [provided that (a)+(b)+(c)=100 mass%], and having 50 to 120 nm number-average particle diameter of the copolymer (B). <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a copolymer latex and a method for producing the same, and more specifically, for example, excellent in coating operability (particularly high-speed coating operability) such as fluidity (viscosity) and water retention, and, for example, surface The present invention relates to a copolymer latex that is excellent in printability such as strength, white paper gloss, and print gloss, and that can form a coated paper with excellent printability even when the printing speed range is wide, and a method for producing the same. .

  In recent years, catalogs, posters, magazines and art journals have been formed by applying a paper coating composition containing pigment and binder to paper (coating base paper) in order to improve the appearance and printability. Has been. The binder contained in the paper coating composition includes, for example, starch and latex. When a latex is contained in the binder, a coated paper having excellent coating operability and excellent printing suitability such as printing gloss, ink drying property, and surface strength can be obtained.

  By the way, with the recent increase in the quality of coated paper and the increase in production speed, there has been a problem that operability is lowered and production efficiency is lowered. In particular, the occurrence of so-called streak defects called streaks is a problem. For such a problem, it is known to use a predetermined latex in the binder contained in the paper coating composition. Examples of the predetermined latex include latex obtained by using latex particles having a small particle diameter, latex obtained by reducing the content of ethylenically unsaturated carboxylic acid monomer, or in the presence of a water-soluble polymer. Latex obtained by polymerizing latex particles has been proposed (see Patent Document 1).

JP 2006-152528 A

  However, the coating liquid (composition for paper coating) disclosed in Patent Document 1 suppresses the occurrence of coating defects such as streaks, and coating operability such as water retention (especially high-speed coating operability). ), But there is still room for improvement. That is, the fluidity (viscosity) to suppress the occurrence of coating defects such as streak and the coating operability such as water retention (especially high-speed coating operability) and the surface strength, for example, Excellent in printability such as white paper gloss and print gloss, especially in the point that it is possible to form coated paper with excellent printability even when the printing speed range is wide, there is still room for improvement. It was something to leave.

  The present invention has been made in view of such problems of the prior art, and the problem is, for example, coating operability such as fluidity (viscosity) and water retention (especially high-speed coating). Excellent operability) and excellent printability such as surface strength, white paper gloss, print gloss, etc. Especially, it is possible to form coated paper with excellent printability even when the printing speed range is wide. It is providing the copolymer latex which is these, and its manufacturing method.

  As a result of diligent studies to achieve the above-mentioned problems, the present inventors obtained a polymer by polymerizing a monomer component containing a predetermined amount of monomer, and in the presence of the predetermined amount of the obtained polymer. The copolymer component is obtained by emulsion polymerization of a monomer component containing a predetermined amount of monomer, and the copolymer latex in which the number average particle diameter of the obtained copolymer is within a predetermined range, The present inventors have found that the above problems can be achieved and have completed the present invention.

  That is, according to the present invention, the following copolymer latex and the production method thereof are provided.

[1] (a) Aliphatic conjugated diene monomer 30 to 75 % by mass, (b) Ethylenically unsaturated carboxylic acid monomer 25 to 65% by mass, and (c) Aromatic vinyl monomer, alkyl (Meth) acrylate, vinyl acetate, monomer having a hydroxyl group, or other monomer 0-20% by mass which is a vinyl cyanide monomer (provided that (a) + (b) + (c) = 100 mass%) of the first monomer component obtained by emulsion polymerization (a) in the presence of 0.1 to 10 parts by mass, (d) an aliphatic conjugated diene monomer 30 -70 mass%, (e) 5-40 mass% vinyl cyanide monomer, (f) 0.1-10 mass% ethylenically unsaturated carboxylic acid monomer, and (g) aromatic vinyl monomer , Alkyl (meth) acrylate, vinyl acetate, or other monomer having a hydroxyl group A total of 100 parts by mass of the second monomer component consisting of 5% by mass (provided that (d) + (e) + (f) + (g) = 100% by mass)) was emulsion-polymerized (provided that When the emulsion polymerization is performed a plurality of times, it contains a copolymer (b) obtained) so that the total of the second monomer components used in the plurality of emulsion polymerizations is 100 parts by mass, And copolymer latex whose number average particle diameter of the said copolymer (b) is 50-120 nm.

[2] The copolymer latex according to the above [1], wherein the polymer (A) has a number average particle diameter of 30 to 80 nm.

[3] The glass transition temperature of the copolymer (b) is at least one point in the range of −100 to 60 ° C., and the copolymer (b) has the lowest transition region in the differential calorimetric curve. The copolymer latex according to the above [1] or [2], wherein the difference (ΔT) between the temperature T1 and the maximum temperature T2 is 30 ° C. or more.
[4] The copolymer according to any one of [1] to [3], wherein (c) the other monomer is acrylonitrile, and (g) the other monomer is styrene or methyl methacrylate. Polymer latex.
[5] The copolymer latex according to any one of [1] to [4], which is for paper coating.

[6] (a) Aliphatic conjugated diene monomer 30 to 75 % by mass, (b) Ethylenically unsaturated carboxylic acid monomer 25 to 65% by mass, and (c) Aromatic vinyl monomer, alkyl (Meth) acrylate, vinyl acetate, monomer having a hydroxyl group, or other monomer 0-20% by mass which is a vinyl cyanide monomer (provided that (a) + (b) + (c) = 100 mass%) is emulsion polymerized to obtain a polymer (I), and in the presence of 0.1 to 10 parts by mass of the obtained polymer (I), (d) 30-70% by weight of an aliphatic conjugated diene monomer, (e) 5-40% by weight of vinyl cyanide monomer, (f) 0.1-10% by weight of ethylenically unsaturated carboxylic acid monomer, and (G) Aromatic vinyl monomer, alkyl (meth) acrylate, vinyl acetate, or monomer having a hydroxyl group A total of 100 parts by mass of the second monomer component consisting of 0 to 55% by mass of other monomers (provided that (d) + (e) + (f) + (g) = 100% by mass) Emulsion polymerization (however, when the emulsion polymerization is performed a plurality of times, the total of the second monomer components used for the plurality of emulsion polymerizations is 100 parts by mass) A method for producing a copolymer latex, which obtains a copolymer latex containing a copolymer (b) having a particle diameter of 50 to 120 nm.

[ 7 ] The method for producing a copolymer latex according to [ 6 ] above, wherein the polymer (A) has a number average particle diameter of 30 to 80 nm.

[ 8 ] The glass transition temperature of the copolymer (b) is at least one point in the range of −100 to 60 ° C., and the difference between the lowest temperature T1 and the highest temperature T2 of the transition region in the differential calorimetric curve. The method for producing a copolymer latex according to the above [ 6 ] or [ 7 ], wherein (ΔT) is 30 ° C or higher.

  The copolymer latex of the present invention has excellent coating operability such as fluidity (viscosity) and water retention (particularly high-speed coating operability), and has, for example, surface strength, white paper gloss, printing gloss, etc. The printability is excellent, and in particular, there is an effect that a coated paper having excellent printability can be formed even when the printing speed range is wide.

  BEST MODE FOR CARRYING OUT THE INVENTION The best mode for carrying out the present invention will be described below, but the present invention is not limited to the following embodiment, and is based on the ordinary knowledge of those skilled in the art without departing from the gist of the present invention. It should be understood that modifications and improvements as appropriate to the following embodiments also fall within the scope of the present invention.

[1] Copolymer latex and production method thereof:
The copolymer latex of the present invention comprises (a) an aliphatic conjugated diene monomer (hereinafter sometimes referred to as “(a) monomer”) 30 to 75 % by mass, (b) ethylenically unsaturated. 25 to 65% by mass of a carboxylic acid monomer (hereinafter sometimes referred to as “(b) monomer”), and (c) an aromatic vinyl monomer, alkyl (meth) acrylate, vinyl acetate, hydroxyl group. Or 20 to 20% by mass of another monomer that is a vinyl cyanide monomer (hereinafter sometimes referred to as “(c) monomer”) (provided that (a) + In the presence of 0.1 to 10 parts by mass of the polymer (b) obtained by emulsion polymerization of the first monomer component (b) + (c) = 100% by mass), (d) aliphatic 30 to 70% by mass of a conjugated diene monomer (hereinafter sometimes referred to as “(d) monomer”), (e) a vinyl cyanide monomer ( Hereinafter, 5-40% by mass (sometimes referred to as “(e) monomer”), (f) ethylenically unsaturated carboxylic acid monomer (hereinafter, referred to as “(f) monomer”). ) 0.1 to 10% by mass, and (g) an aromatic vinyl monomer, alkyl (meth) acrylate, vinyl acetate, or other monomer having a hydroxyl group (hereinafter referred to as “(g) The total of the second monomer component consisting of 0 to 55% by mass (sometimes referred to as “monomer”), provided that (d) + (e) + (f) + (g) = 100% by mass) 100 parts by mass of emulsion polymerization (however, when the emulsion polymerization is performed a plurality of times, the total of the second monomer components used for the plurality of emulsion polymerizations is 100 parts by mass) The resulting copolymer (b) is contained, and the copolymer (b) has a number average particle diameter of 50 to 120 nm. Such a copolymer latex is excellent in coating operability such as fluidity (viscosity) and water retention (especially high-speed coating operability) and, for example, surface strength, blank paper gloss, printing gloss, etc. It is excellent in printability, and in particular, even when the printing speed range is wide, a coated paper having excellent printability can be formed. The details will be described below.

[1-1] Polymer (A):
In order to produce the copolymer latex of the present invention, first, (a) monomer 30 to 80% by mass, (b) monomer 20 to 70% by mass, and (c) monomer 0 to 20%. A polymer (A) is obtained by emulsion polymerization of a first monomer component consisting of mass% (however, (a) + (b) + (c) = 100 mass%).

  The first monomer component is composed of the monomers (a) to (c). Examples of the monomer (a) include 1,3-butadiene, isoprene, 2-chloro-1,3-butadiene, chloroprene, 2-methyl-1,3-butadiene, and 2,3-dimethyl-1,3. -Butadiene etc. can be mentioned. Among these, 1,3-butadiene is preferable. In addition, these (a) monomers can be used individually by 1 type or in combination of 2 or more types.

  (A) Content of a monomer is 30-80 mass% with respect to the whole 1st monomer component. (A) It is preferable that content of a monomer is 35-75 mass%, and it is still more preferable that it is 40-70 mass%. (A) There exists a possibility that superposition | polymerization stability may fall that content of a monomer is less than 30 mass%. On the other hand, if it exceeds 80% by mass, the polymerization stability may be lowered.

  (B) As an ethylenically unsaturated carboxylic acid monomer, acrylic acid, methacrylic acid, fumaric acid, maleic acid, itaconic acid etc. can be mentioned, for example. In addition, these (b) monomers can also be used individually by 1 type or in combination of 2 or more types.

  (B) Content of a monomer is 20-70 mass% with respect to the whole 1st monomer component. (B) It is preferable that content of a monomer is 25-65 mass%, and it is still more preferable that it is 30-60 mass%. (B) There exists a possibility that superposition | polymerization stability may fall that content of a monomer is less than 20 mass%. On the other hand, when it is more than 70% by mass, the polymerization stability at the time of emulsion polymerization of the polymer (I) is lowered, and it may be difficult to control the particle size. Moreover, there exists a possibility that an aggregate may increase in copolymer latex.

  (C) Examples of the monomer (a) and other monomer copolymerizable with the monomer (b) include aromatic vinyl monomers, alkyl (meth) acrylates, vinyl acetate, and hydroxyl groups. And the like, and vinyl cyanide monomers. Among these, examples of the aromatic vinyl monomer include styrene, α-methylstyrene, p-methylstyrene, vinyltoluene, chlorostyrene, and the like. In particular, styrene is preferable. Examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, benzyl ( Examples include meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, isobornyl (meth) acrylate, and 2-cyanoethyl (meth) acrylate. In particular, methyl methacrylate is preferable. Examples of the monomer having a hydroxyl group include hydroxyethyl acrylate and hydroxyethyl methacrylate. Examples of the vinyl cyanide monomer include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, vinylidene cyanide, and the like. The above monomers may be used alone or in combination of two or more.

  (C) Content of a monomer is 0-20 mass% with respect to the whole 1st monomer component. (C) It is preferable that content of a monomer is 0-15 mass%, and it is still more preferable that it is 0-10 mass%. (C) There exists a possibility that sufficient water retention may not be obtained as content of a monomer exceeds 20 mass%. In addition, when (c) monomer is not contained as a 1st monomer component, that is, the content of (c) monomer may be zero.

  As described above, the copolymer latex of the present invention is produced by emulsion polymerization of the first monomer component to produce a polymer (A). Emulsion polymerization when producing the polymer (I) can be carried out in an aqueous medium using an emulsifier, a polymerization initiator, a molecular weight regulator and the like. The polymerization temperature is preferably 20 to 100 ° C, more preferably 40 to 90 ° C, and particularly preferably 50 to 80 ° C. The polymerization time is preferably 1 to 15 hours, and more preferably 2 to 10 hours.

  Examples of the emulsifier include anionic surfactants, nonionic surfactants, and amphoteric surfactants. In addition, these are independent or can use 2 or more types together. Examples of the anionic surfactant include higher alcohol sulfates, alkylbenzene sulfonates, aliphatic sulfonates, and polyethylene glycol alkyl ether sulfates. As the nonionic surfactant, an ordinary polyethylene glycol alkyl ester type, alkyl ether type, alkylphenyl ether type, or the like is used. Examples of amphoteric surfactants include those having a carboxylate, sulfate, sulfonate, and phosphate ester salt as the anion moiety, and an amine salt and quaternary ammonium salt as the cation moiety. Betaines such as lauryl betaine and stearyl betaine, amino acid types such as lauryl-β-alanine, stearyl-β-alanine, lauryl di (aminoethyl) glycine, and octyldi (aminoethyl) glycine can be used.

  Examples of the polymerization initiator include water-soluble polymerization initiators such as sodium persulfate, potassium persulfate, and ammonium persulfate, and oil-soluble polymerization initiators such as benzoyl peroxide, lauryl peroxide, and 2,2′-azobisisobutyronitrile. And redox polymerization initiators in combination with a reducing agent, and the like. These can be used alone or in combination of two or more.

  Known molecular weight regulators, chelating agents, inorganic electrolytes, and the like can be used. Examples of molecular weight regulators include halogenated hydrocarbons such as chloroform and carbon tetrabromide, mercaptans such as n-hexyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, and thioglycolic acid, dimethylxanthogen Xanthogens such as disulfide and diisopropylxanthogen disulfide, terpinolene, α-methylstyrene dimer, 1,1-diphenylethylene and the like which can be used in usual emulsion polymerization can be used. Of these, it is preferable to use a mercaptan-based molecular weight regulator.

  The compounding quantity of the said polymer (I) is 0.1-10 mass parts with respect to 100 mass parts of copolymers (b) mentioned later. It is preferable that the said compounding quantity is 0.3-8 mass parts, More preferably, it is 0.5-6 mass parts. Especially preferably, it is 1-5. If the blending amount is less than 0.1 parts by mass, the water retention effect tends to be insufficient. On the other hand, if it exceeds 10 parts by mass, the polymerization stability of the emulsion polymerization in the presence of the polymer (I) tends to be low, and the particle size control tends to be difficult. In addition, aggregates tend to increase in the copolymer latex.

  Moreover, it is preferable that the number average particle diameter of a polymer (I) is 30-80 nm. The number average particle size is more preferably 40 to 70, and particularly preferably 45 to 65. When the number average particle size of the polymer (a) is less than 30 nm, the particle size of (b) may be small. On the other hand, if it exceeds 80 nm, the particle size of (b) may increase. Here, in this specification, the “number average particle diameter” is a number average particle diameter measured by a light scattering analysis method. The number average particle diameter can be measured by, for example, a particle diameter measuring device “FPRA-1000 (trade name)” manufactured by Otsuka Electronics Co., Ltd.

[1-2] Copolymer (b):
Next, in order to produce the copolymer latex of the present invention, in the presence of 0.1 to 10 parts by mass of the polymer (ii), (d) an aliphatic conjugated diene monomer 30 to 70 parts by mass. %, (E) 5 to 40% by weight of vinyl cyanide monomer, (f) 0.1 to 10% by weight of ethylenically unsaturated carboxylic acid monomer, and (g) aromatic vinyl monomer, alkyl ( 0 to 55% by mass of other monomer which is a monomer having a meth) acrylate, vinyl acetate or a hydroxyl group (provided that (d) + (e) + (f) + (g) = 100% by mass) A total of 100 parts by mass of the second monomer component consisting of is emulsion-polymerized to obtain a copolymer (b). That is, the copolymer latex of the present invention contains a copolymer (b).

  As the (d) aliphatic conjugated diene monomer of the second monomer component, those similar to the monomer (a) described above can be used.

  (D) The monomer content is 30 to 70% by mass with respect to the entire second monomer component. (D) It is preferable that content of a monomer is 33-60 mass%, and it is still more preferable that it is 35-55 mass%. (D) When content of a monomer is less than 30 mass%, since a copolymer (b) becomes too hard, there exists a tendency for adhesive strength to become inadequate. On the other hand, when the content of the monomer (d) is more than 70% by mass, the paper coating layer formed from the paper coating composition becomes too soft, so that the anti-sticking property becomes insufficient. Tend.

  Examples of the second monomer component (e) vinyl cyanide monomer include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, vinylidene cyanide, and the like. Among these, acrylonitrile is preferable.

  (E) Content of monomer is 5-40 mass% with respect to the whole 2nd monomer component. (D) It is preferable that content of a monomer is 10-35 mass%, and it is still more preferable that it is 15-33 mass%. When the content of the monomer (d) is less than 5% by mass, the ink solvent resistance is lowered, so that the print gloss may be lowered. On the other hand, if the content of the monomer (d) is more than 40% by mass, the copolymer (b) becomes too hard and the adhesive strength may be insufficient.

  As the (f) ethylenically unsaturated carboxylic acid monomer of the second monomer component, those similar to the monomer (b) described above can be used. (F) Content of monomer is 0.1-10 mass% with respect to the whole 2nd monomer component. (F) It is preferable that content of a monomer is 0.7-7 mass%, and it is still more preferable that it is 1-5 mass%. (F) When the monomer content is less than 0.1% by mass, the polymerization stability and dispersion stability of emulsion polymerization in the presence of the polymer (A) tend to be lowered. On the other hand, if the content of the monomer (f) is more than 10% by mass, the viscosity of the copolymer latex becomes too high, and the coating workability tends to be lowered.

  (G) As another monomer copolymerizable with said (d)-said (f), the thing similar to the already mentioned (c) monomer can be used. (G) Content of a monomer is 0-55 mass% with respect to the whole 2nd monomer component. (G) It is preferable that content of a monomer is 0-40 mass%, and it is still more preferable that it is 0-30 mass%. (G) If the monomer content exceeds 55% by mass, the copolymer may become too hard and the adhesive strength may decrease. In the case where (g) monomer is not contained in the second monomer component, that is, the content of (g) monomer may be zero.

  The copolymer latex of the present invention contains a copolymer (b) obtained by emulsion polymerization of the second monomer component in the presence of the polymer (a). The emulsion polymerization for obtaining the copolymer (b) can be carried out in the same manner as the above-described method (emulsion polymerization).

  The number average particle size of the copolymer (b) needs to be 50 to 120 nm. The number average particle diameter is preferably 55 to 110 nm, and more preferably 55 to 95 nm. If the number average particle size of the copolymer (b) is less than 50 nm, the viscosity of the copolymer latex becomes too high, and the coating workability tends to be lowered. On the other hand, when the number average particle size of the copolymer (b) is more than 120 nm, water retention and adhesive strength tend to decrease.

  The glass transition temperature of the copolymer (b) is preferably at least one point in the range of −100 to 60 ° C., more preferably at least one point in the range of −80 to 55 ° C., −70 It is particularly preferable that at least one point exists in the range of ˜50 ° C. If it is lower than -100 ° C, the paper coating layer formed from the paper coating composition becomes too soft, and there is a risk that the anti-sticking property will be insufficient. On the other hand, when it exceeds 60 ° C., the copolymer (b) becomes too hard, and the adhesive strength may be insufficient.

  Furthermore, the glass transition temperature of the copolymer (b) is preferably such that the difference (ΔT) between the lowest temperature T1 and the highest temperature T2 of the transition region is 30 ° C. or higher in the differential calorimetric curve, and 35 ° C. or higher. More preferably, it is particularly preferably 40 ° C. or higher. If ΔT is less than 30 ° C., it is difficult to maintain a high printing suitability at a high level in a wide printing speed range, and thus there is a possibility that a sufficient printing speed range cannot be secured. In addition, the surface strength and impact resistance of the coated paper are lowered, and there is a possibility that the coated paper cannot withstand impact deformation with a high deformation speed in high-speed printing. That is, the strength of the coated paper may be reduced.

  Here, in this specification, the “transition region of the differential calorimetric curve” is a differential calorimetric curve obtained when the glass transition temperature is measured with a differential scanning calorimeter using the copolymer latex of the present invention as a sample. It is a glass transition region, and particularly refers to a temperature region when it is in a wide spread state over a certain temperature region. In this transition region, the peak portion (tip portion) of the transition region is shaped like a triangular apex portion in the above temperature region of the differential curve ([temperature]-[power / time] curve) of the differential calorific value curve. Instead, it has a broad peak shape like a trapezoidal top and bottom. Thus, when the transition region is in a wide spread state, one or more glass transition temperatures cannot be observed, and the entire region showing the glass transition in the differential calorimetric curve is the glass transition region (transition region). ). The range of the transition region is the range from the temperature at which the value of [Power] starts to change to the temperature at which the series of changes in the value of [Power] ends in the above differential calorific value curve ([temperature]-[power] curve). is there. The copolymer latex from which such a differential calorimetric curve is obtained is such that the copolymer constituting it is composed of a plurality of polymers having different glass transition temperatures, and the respective glass transition temperatures are continuously arranged. It is thought that it is composed.

[2] Composition for paper coating:
A paper coating composition (hereinafter sometimes referred to as “the present paper coating composition”) can be produced using the copolymer latex of the present invention as a binder. Since the present paper coating composition contains the copolymer latex of the present invention, the fluidity (viscosity) of the coating liquid, the coating operability such as water retention (especially high-speed coating operability). It is possible to obtain a coated paper having excellent printability such as excellent surface strength, white paper gloss, print gloss, etc., and having the above-mentioned excellent printability over a wider printing speed range.

  The copolymer latex of the present invention contained in the paper coating composition functions as a binder. In addition to the copolymer latex, the binder latex includes starch, casein, soybean protein, and the like. You may contain. Of these, starch is preferred. As the starch, processed starch such as phosphate esterified starch, hydroxyethyl etherified starch, oxidized starch, and enzyme-modified starch can be used. These can be used alone or in combination of two or more.

  In addition to the binder, the present paper coating composition may optionally contain various commonly used additives such as pigments, water resistance improvers, pigment dispersants, viscosity modifiers, color pigments, fluorescent dyes and pH modifiers. Can be blended. Examples of pigments that can be used include kaolin, heavy calcium carbonate, light calcium carbonate, titanium dioxide, aluminum hydroxide, and satin white. Among these, heavy calcium carbonate is preferable, and it is also preferable to use kaolin and heavy calcium carbonate. These can be used alone or in combination of two or more.

  Further, in the present paper coating composition, the content of the copolymer latex is 1 to 30 parts by mass, preferably 3 to 25 parts by mass, and 5 to 20 parts by mass with respect to 100 parts by mass of the pigment. More preferably, it is part. If it is less than 1 part by mass, it may be difficult to exhibit a sufficient adhesion function as a binder. When it exceeds 30 parts by mass, the whiteness of the coated paper is impaired, and it causes operational troubles in the coated paper manufacturing process and the coated paper printing process due to excessive adhesiveness. Here, the content of the copolymer latex is the content of the solid content of the copolymer latex, and the solid content of the copolymer latex is a dispersion medium or a solvent from the copolymer latex. Ingredient excluding water.

  The total amount of pigment and copolymer latex contained in the paper coating composition is preferably 90% by mass or more, and 95% by mass with respect to the total solid content of the paper coating composition. It is still more preferable that it is above.

  The coated paper produced by applying the present paper coating composition to the coating base paper is particularly excellent in printability such as surface strength, white paper gloss, and print gloss, and this excellent printability over a wide printing speed range. It is what has. Hereinafter, a coated paper produced by applying the present paper coating composition to a coated base paper (hereinafter sometimes referred to as “the present coated paper”) will be described.

  The present coated paper is obtained by applying the above-described composition for coating a present paper to a coating base paper as a coating liquid, and the coating base paper and a coating layer obtained by coating the coating base paper with the coating liquid. Are provided.

  The coating base paper constituting the present coated paper is not particularly limited as long as it exhibits excellent printability as the present coated paper by coating the present paper coating composition. The kind of the raw material pulp of the coating base paper is not particularly limited, and examples thereof include mechanical pulp, chemical pulp, and waste paper pulp (DIP). In addition, the coated base paper includes, as internal additives, pigments such as calcium carbonate, clay and talc, sizing agents such as alkyl ketene dimers, rosin acid soaps and sulfuric acid bands, paper strength enhancers such as cationic starch and polyacrylamide, and A bulking agent or the like can also be used. Furthermore, a surface sizing agent such as acrylamide or acrylic-styrene polymer can be applied to the surface of the coated base paper using a size press, a gate roll coater, a metered size press or the like.

As for the coating layer which comprises this coated paper, it is preferable that the coating amount of the composition for paper coating is 1-50 g / m < ² >. If it is less than 1 g / m ² , blank paper gloss and printing gloss may be lowered, and if it is more than 50 g / m ² , the improvement in quality may be reduced for the cost.

  The manufacturing method of this coated paper is to apply the above-described composition for coating paper (coating liquid) to a coating base paper by the following coating method. As a coating method for coating the paper coating composition (coating liquid) on the coating base paper, a method used in a general method for producing coated paper can be employed. For example, the coating can be performed using a blade coater, an air knife coater, a bar coater, a gate roll coater, a chanplex coater, a size press coater, a gravure coater, a curtain coater, or the like.

  As a method for producing the coated paper, in addition to the coating process of coating the coating liquid on the coating base paper, after preparing the undried coated paper by applying the paper coating composition, It is preferable to have a drying step of drying the undried coated paper. Moreover, you may provide a calendar process further after the said drying process. By performing the calendar process, it is possible to sufficiently bring out the blank gloss and print gloss of the coated paper obtained. Furthermore, you may have a desired process suitably other than the above-mentioned process.

  The coated paper can be particularly suitably used for sheet-fed offset printing and rotary offset printing. It can also be used for other lithographic printing, intaglio printing such as gravure printing, and letterpress printing. And since this coated paper is coated with the present paper coating composition, it has excellent printability such as surface strength, white paper gloss, and print gloss, and has this excellent printability over a wider printing speed range. Is.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples. In the examples and comparative examples, “parts” and “%” are based on mass unless otherwise specified.

(Synthesis Example 1)
In a pressure-resistant reaction vessel equipped with a stirrer and a temperature controller, 100 parts of water, 1.2 parts of sodium dodecylbenzenesulfonate, (a) 0.35 parts of butadiene as an aliphatic conjugated diene monomer, (b) ethylene Methacrylic acid 0.35 parts, potassium persulfate 0.3 parts, sodium hydrogen sulfite 0.04 parts, ferrous sulfate heptahydrate 0.0012 parts, and t-dodecyl mercaptan 0 .6 parts were charged and the inside of the polymerization system was replaced with nitrogen. Thereafter, the temperature in the polymerization system was raised to 40 ° C., and emulsion polymerization was carried out at this temperature for 2 hours. The polymerization conversion rate was 95%. It was 46 nm when the number average particle diameter was measured about the polymer (I) in the obtained polymer aqueous solution.

(Number average particle size)
The number average particle size of the polymer (A) and the copolymer (B) was measured using a particle size measuring device (FPAR-1000: manufactured by Otsuka Electronics Co., Ltd.).

(Synthesis Examples 2-9)
Except having set it as the mixing | blending prescription shown in Table 1, it carried out similarly to the synthesis example 1, and prepared the polymer (I) of the synthesis examples 2-9. The number average particle diameter of the obtained polymers (a) of Synthesis Examples 2 to 9 was measured. The measurement results are shown in Table 1.

(Synthesis Example 10)
The emulsion polymerization in the presence of the polymer (A) was performed as follows. First, as the first-stage monomer component, sodium dodecylbenzenesulfonate 0.3 part, potassium persulfate 1.0, sodium hydrogen sulfite 0.1 part, ferrous sulfate heptahydrate 0.003 part, (d ) 5.4 parts of butadiene as an aliphatic conjugated diene monomer, (g) 1.35 parts of styrene as another monomer copolymerizable with (d) to (f), (e) cyanide 2.5 parts of acrylonitrile as a vinyl monomer and 0.2 parts of acrylic acid as an (f) ethylenically unsaturated carboxylic acid monomer were charged, and the inside of the polymerization system was replaced with nitrogen. Thereafter, the temperature in the polymerization system was raised to 40 ° C., and polymerization was carried out at this temperature for 1.5 hours.

  Next, as the second-stage monomer component, 28.0 parts of butadiene, 7.25 parts of styrene, 10.5 parts of acrylonitrile, 0.255 parts of acrylic acid, 0.6 parts of α-methylstyrene dimer, t-dodecyl mercaptan 0.16 part and 0.01 part of sodium hydrogen sulfite were continuously added into the polymerization system over 7 hours to carry out polymerization.

  Further, as the third-stage monomer component, 3.7 parts of butadiene, 15.315 parts of styrene, 6 parts of acrylonitrile, 0.125 part of acrylic acid, 0.22 part of itaconic acid, 0.1 part of t-dodecyl mercaptan, And 0.035 part of sodium hydrogen sulfite was continuously added into the polymerization system over 2 hours. Thereafter, the temperature in the polymerization system was raised to 55 ° C.

  Thereafter, 4.15 parts of butadiene, 8.0 parts of acrylonitrile as the fourth-stage monomer component, and (g) methyl methacrylate as another monomer copolymerizable with (d) to (f) above. 0 parts, 1.255 parts acrylic acid, 0.78 parts itaconic acid, 0.1 part α-methylstyrene dimer, and 0.223 parts t-dodecyl mercaptan over 2 hours, 0.3 parts sodium bisulfite It was continuously added to the polymerization system over 3.5 hours. In the first to fourth stage monomer components, (d) an aliphatic conjugated diene monomer, (e) a vinyl cyanide monomer, (f) an ethylenically unsaturated carboxylic acid monomer, and ( g) The total amount of the other monomers copolymerizable with (d) to (f) (the total of the second monomer components) is 100 parts.

(Synthesis Examples 11 and 12)
In Synthesis Examples 11 and 12, emulsion polymerization was performed in the same manner as in Synthesis Example 10 except that the blending amounts shown in Tables 2 and 3 were used. In Examples and Comparative Examples shown below, emulsion polymerization is performed according to any one of Synthesis Examples 10 to 12 in the presence of any one polymer (A) of Synthesis Examples 1 to 9. To obtain a copolymer latex.

Example 1
In a pressure-resistant reaction vessel equipped with a stirrer and a temperature controller, 0.7 part of the polymer (A) obtained in Synthesis Example 1 was added, and the emulsion polymerization method (Synthesis of the second monomer component) of Synthesis Example 10 was performed. 100 parts in total) gave a copolymer latex. The final polymerization conversion was 98%. The obtained copolymer latex was adjusted to pH 7.5 using sodium hydroxide, and then unreacted monomers were removed by blowing water vapor, followed by heating and steam distillation to obtain a copolymer having a solid content concentration of 50%. A polymer latex was obtained. The copolymer latex was evaluated as follows.

(Toluene insoluble matter (%))
The copolymer latex was adjusted to pH 8.0 and then coagulated with isopropanol to obtain a coagulated product. After washing and drying the solidified product, a predetermined amount (about 0.03 g) of the sample was immersed in a predetermined amount (100 ml) of toluene for 20 hours. Thereafter, the mixture was filtered through a 120-mesh wire mesh, and the amount (mass%) of the remaining solid content relative to the total solid content of the sample was measured.

(Glass transition temperature (Tg))
The copolymer latex was vacuum dried at 100 ° C. for 20 hours to produce a film. The dried film was measured for the glass transition temperature (° C.) of the copolymer (b) contained in the copolymer latex according to the ASTM method using a differential scanning calorimeter (DSC6100: manufactured by Seiko Instruments Inc.). It was measured.

(Differential calorific curve)
Using a differential scanning calorimeter (DSC6100: manufactured by Seiko Instruments Inc.), a differential calorimetric curve was measured according to the ASTM method. The difference (ΔT) (° C.) between the lowest temperature T1 and the highest temperature T2 in the transition region of the copolymer (b) was calculated from this differential calorimetric curve. In Tables 4 and 5, “(ΔT) (° C.)” is shown.

  The copolymer latex of this example has a copolymer (b) number average particle size of 58 nm, toluene insoluble content of 94.4%, glass transition temperature of −20 ° C., the lowest transition region in the differential calorimetric curve / The difference in maximum temperature (ΔT) was 65 ° C.

(Preparation of composition for paper coating)
50.0 parts of kaolin clay, 50.0 parts of calcium carbonate, 0.025 part of sodium polyacrylate as a dispersant, 0.05 part of sodium hydroxide, 3.0 parts of starch, and the co-polymer obtained as described above. An appropriate amount of water is added to 10.0 parts of the polymer latex (as solid content) to adjust the total solid content to 65%, and mixed uniformly using a mixer (manufactured by Shimazaki Co., Ltd.). A working composition was prepared. This paper coating composition was evaluated as follows.

(Color viscosity)
The color viscosity was measured using a BM viscometer (model number “DVM-BII”, manufactured by TOKIMEC, INC.) For the paper coating composition immediately after preparation. The rotor used was # 4. When the value of the color viscosity is low, it indicates that the coating liquid (paper coating composition) has good fluidity and is excellent in coating operability.

(High shear viscosity)
The high shear viscosity was measured by using a Hercules high shear viscometer (model number “HR-801C”, manufactured by Kumagai Riki Kogyo Co., Ltd.). The measurement conditions were Bob type F, rotational speed 6600 rpm, and sweep time 10 seconds. When the value of the high shear viscosity is low, it indicates that the coating liquid (composition for paper coating) at the time of high-speed coating has good fluidity and is excellent in coating operability.

(Water retention)
The water retention was measured using the AA-GWR water retention measuring device “M-250” (manufactured by Kaltec Scientific, Inc.) after preparing the paper coating composition. The measurement conditions were as follows: MEMBRAN FILTER of 0.45 μm was used at a measurement pressure of 1.75 kg / cm ² and a measurement time of 360 seconds. In addition, when a measured value is low, it shows that it is a coating liquid (composition for paper coating) with high water retention and excellent coating operability.

The composition for paper coating of this example had a color viscosity of 1120 mPa · s, a high shear viscosity of 34.4 mPa · s, and a water retention of 36.8 g / m ² . The pH was 8.1.

(Manufacture of coated paper)
The above-mentioned composition for paper coating is coated on a base paper to be coated with an electric blade coater (manufactured by Kumagaya Rikyu Kogyo Co., Ltd.) so that the coating amount is 12.0 ± 0.5 g / m ^{2 on} one side Then, the coated base paper which dried by processing for 5 second with a 180 degreeC electric hot air dryer was obtained. The obtained coated base paper is left in a constant temperature and humidity chamber at a temperature of 23 ° C. and a humidity of 60% for one day, and then super calender treatment is performed twice under the conditions of a linear pressure of 140 kg / cm and a roll temperature of 50 ° C. Paper was manufactured. The coated paper was evaluated as follows.

(Dry pick strength)
The degree of picking when printed by an RI printing machine (manufactured by Meisei Seisakusho) was visually judged and evaluated in five stages. As the evaluation criteria, the smaller the picking phenomenon, the higher the score (5 points). Specifically, there are 5 points when there is no picking, 4 points when there is a little picking, 3 points when there is partial picking, 2 points when there is picking as a whole, and overall picking is intense One case was given as one point. In addition, the numerical value was shown by the average value of the frequency | count of a measurement (6 times).

(Wet pick strength)
The surface of the coated paper was moistened with a water-absorbing roll using an RI printer (manufactured by Meisei Co., Ltd.), and then the degree of picking when printed with the RI printer was visually determined and evaluated in five stages. . As the evaluation criteria, the smaller the picking phenomenon, the higher the score (5 points). Specifically, there are 5 points when there is no picking, 4 points when there is a little picking, 3 points when there is partial picking, 2 points when there is picking as a whole, and overall picking is intense One case was given as one point. In addition, the numerical value was shown by the average value of the frequency | count of a measurement (6 times).

(White paper gloss)
Using a Murakami gloss meter (Murakami Color Research Laboratory Co., Ltd.), the white paper gloss of the coated paper at an angle of 75 degrees was measured. In addition, it shows that white paper gloss is so high that a measured value is large.

(Print gloss)
Using a RI printing machine (Meiji Seisakusho Co., Ltd.), a commercially available black ink for offset printing (trade name “SMX Tack Grade 15”, Toyo Ink Co., Ltd.) was applied once and then Murakami gloss meter (Murakami) The printing gloss of the coated paper at an angle of 60 degrees was measured using Color Technology Laboratory. The larger the measured value, the higher the print gloss.

  The coated paper of this example had a dry pick strength of 4.0, a wet pick strength of 3.9, a blank paper gloss of 66.1, and a print gloss of 65.9.

(Examples 2-5, Comparative Examples 3-5)
A copolymer latex, a paper coating composition, and a coated paper were obtained in the same manner as in Example 1 except that the formulations shown in Tables 4 and 5 were used. Tables 4 and 5 show the evaluation results of the obtained copolymer latex, the composition for paper coating, and the coated paper.

(Comparative Example 1)
The “first-stage monomer component” shown in Table 2 was charged into a pressure-resistant reaction vessel equipped with a stirrer and a temperature controller, and the inside of the polymerization system was replaced with nitrogen. Thereafter, the temperature in the polymerization system was raised to 40 ° C., and polymerization was carried out at this temperature for 1.5 hours. Next, the “second-stage monomer component” shown in Table 2 was continuously added to the polymerization system over 7 hours. Furthermore, the “third stage monomer component” shown in Table 2 was continuously added into the polymerization system over 2 hours. Thereafter, the temperature in the polymerization system was raised to 50 ° C., and each component of the “fourth stage monomer component” shown in Table 2 excluding sodium bisulfite was taken over 2 hours. It was continuously added into the polymerization system over time. The final polymerization conversion rate was 98%. The copolymer latex thus obtained was adjusted to pH 7.5 using sodium hydroxide, and then unreacted monomers were removed by blowing water vapor, and further a solid content concentration of 50 by heating steam distillation. % Copolymer latex was obtained. Thereafter, in the same manner as in Example 1 described above, a paper coating composition and coated paper were obtained. Table 5 shows the evaluation results of the obtained copolymer latex, the paper coating composition, and the coated paper.

(Comparative Example 2)
The “first-stage monomer component” shown in Table 2 was charged into a pressure-resistant reaction vessel equipped with a stirrer and a temperature controller, and the inside of the polymerization system was replaced with nitrogen. Thereafter, the temperature in the polymerization system was raised to 45 ° C., and polymerization was carried out at this temperature for 4 hours. Next, the temperature in the polymerization system was raised to 55 ° C., and among the “second-stage monomer components” shown in Table 2, each component excluding sodium bisulfite was taken for 5 hours, and sodium bisulfite was taken for 9 hours. Added continuously to the polymerization system. The final polymerization conversion rate was 98%. The copolymer latex thus obtained was adjusted to pH 7.5 using sodium hydroxide, and then unreacted monomers were removed by blowing water vapor, and further a solid content concentration of 50 by heating steam distillation. % Copolymer latex was obtained. Thereafter, in the same manner as in Example 1 described above, a paper coating composition and coated paper were obtained. Table 5 shows the evaluation results of the obtained copolymer latex, the paper coating composition, and the coated paper.

  As shown in Tables 4 and 5, when the copolymer latex of Examples 1 to 6 is used, the fluidity (viscosity) and water retention are compared with the case where the copolymer latex of Comparative Examples 1 to 5 is used. Paper coating compositions with excellent coating operability (especially high-speed coating operability), etc., and excellent printability such as surface strength, white paper gloss, and print gloss, and printing. Even when the speed range is wide, it is clear that a coated paper having excellent printability can be formed.

  Among the copolymer latexes of Examples 1 to 4, since the copolymer latexes of Examples 2 and 3 are in the range of 1 to 5 (1.5 and 3), water retention It was confirmed that the property, the dry pick strength, and the wet pick strength were good.

  Among the copolymer latexes of Examples 3, 5, and 6, the copolymer latex of Example 3 is the (b) ethylenically unsaturated carboxylic acid monomer (methacrylic acid) in the first monomer component. Since the content was large, it was confirmed that the water retention was good.

  The copolymer latex of the present invention can produce, for example, a paper coating composition excellent in coating operability (particularly high-speed coating operability) such as fluidity (viscosity) and water retention, and For example, a composition for paper coating that has excellent printability such as surface strength, white paper gloss, and print gloss, and can form a coated paper with excellent printability even when the printing speed range is wide. It can be suitably used as a product (binder).

Claims (8)

(A) Aliphatic conjugated diene monomer 30 to 75 % by mass,
(B) 25 to 65% by mass of an ethylenically unsaturated carboxylic acid monomer, and (c) an aromatic vinyl monomer, alkyl (meth) acrylate, vinyl acetate, a monomer having a hydroxyl group, or vinyl cyanide 0 to 20% by mass of other monomers that are monomers,
(However, (a) + (b) + (c) = 100 mass%)
In the presence of 0.1 to 10 parts by mass of the polymer (ii) obtained by emulsion polymerization of the first monomer component comprising:
(D) 30 to 70% by mass of an aliphatic conjugated diene monomer
(E) 5 to 40% by mass of vinyl cyanide monomer,
(F) 0.1 to 10% by mass of an ethylenically unsaturated carboxylic acid monomer, and (g) an aromatic vinyl monomer, an alkyl (meth) acrylate, vinyl acetate, or a monomer having a hydroxyl group 0 to 55% by weight of a monomer,
(However, (d) + (e) + (f) + (g) = 100 mass%)
100 parts by mass in total of the second monomer component consisting of the above (e.g., when the emulsion polymerization is performed a plurality of times, the second monomer component used in the plurality of emulsion polymerizations) A copolymer latex containing the copolymer (b) obtained), and having a number average particle diameter of 50 to 120 nm.   2. The copolymer latex according to claim 1, wherein the polymer (A) has a number average particle diameter of 30 to 80 nm.   The glass transition temperature of the copolymer (b) is at least one point in the range of −100 to 60 ° C., and the copolymer (b) has a minimum temperature T1 in the transition region in the differential calorimetric curve. The copolymer latex according to claim 1 or 2, wherein a difference (ΔT) from the maximum temperature T2 is 30 ° C or more.   The copolymer latex according to any one of claims 1 to 3, wherein (c) the other monomer is acrylonitrile, and (g) the other monomer is styrene or methyl methacrylate.   The copolymer latex according to any one of claims 1 to 4, which is used for paper coating. (A) Aliphatic conjugated diene monomer 30 to 75 % by mass,
(B) 25 to 65% by mass of an ethylenically unsaturated carboxylic acid monomer, and (c) an aromatic vinyl monomer, alkyl (meth) acrylate, vinyl acetate, a monomer having a hydroxyl group, or vinyl cyanide 0 to 20% by mass of other monomers that are monomers,
(However, (a) + (b) + (c) = 100 mass%)
The first monomer consisting of is emulsion polymerized to obtain a polymer (I),
In the presence of 0.1 to 10 parts by mass of the obtained polymer (I),
(D) 30 to 70% by mass of an aliphatic conjugated diene monomer
(E) 5 to 40% by mass of vinyl cyanide monomer,
(F) 0.1 to 10% by mass of an ethylenically unsaturated carboxylic acid monomer, and (g) an aromatic vinyl monomer, an alkyl (meth) acrylate, vinyl acetate, or a monomer having a hydroxyl group 0 to 55% by weight of a monomer,
(However, (d) + (e) + (f) + (g) = 100 mass%)
100 parts by mass of the total of the second monomer component consisting of the above (e.g., when the emulsion polymerization is performed a plurality of times, the total of the second monomer components used for the plurality of emulsion polymerizations) Is 100 parts by mass), whereby a copolymer latex containing a copolymer (B) having a number average particle size of 50 to 120 nm is obtained.   The method for producing a copolymer latex according to claim 6, wherein the number average particle diameter of the polymer (A) is 30 to 80 nm.   The glass transition temperature of the copolymer (b) is at least one point in the range of −100 to 60 ° C., and the difference (ΔT) between the lowest temperature T1 and the highest temperature T2 in the transition region in the differential calorimetric curve. The method for producing a copolymer latex according to claim 6 or 7, wherein the temperature is 30 ° C or higher.