JPH0977913A - Copolymer latex and composition containing the same and used for coated paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a copolymer latex reduced in viscosity and improved in stability, flowability and water retentivity by mixing two specified copolymer latices with each other. SOLUTION: One hundred (100) pts.wt. monomer mixture containing 15-55 pts.wt. aliphatic conjugated diene monomer, 0.5-5 pts.wt. ethylenically unsaturated monomer and other comonomers is emulsion-copolymerized in the presence of a polymerization initiator to obtain a copolymer latex (A) having a mean particle diameter (DA) of 60-200nm. One hundred (100) pts.wt. monomer mixture containing 15-55 pts.wt. aliphatic conjugated diene monomer, 4-20 pts.wt. ethylenically unsaturated monomer and 4-20 pts.wt. ethylenically unsaturated amide monomer is emulsion-copolymerized in the presence of a polymerization initiator to obtain a copolymer latex (B) having a mean particle diameter (DB) of 30-100nm and satisfying the formula: DB<DA-10. Components A and B are mixed with each other in an A/B weight ratio of 98/2 to 65/35 (in terms of the solid matter).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copolymer latex which itself has a reduced viscosity and excellent stability, and further has fluidity and water retention containing the copolymer latex. The present invention relates to a composition for coated paper which is excellent in

[0002]

2. Description of the Related Art In recent years, high-speed coating has been required in the production of coated paper. In high-speed coating, if the coating liquid comprising the composition for coated paper has high fluidity, that is, if the viscosity is too high at a high shear rate, streaks and the like are likely to occur, leading to deterioration in operability and quality of the coated paper. Further, it is necessary that the viscosity is not too high even at a low shear rate in view of handling the coating liquid. On the other hand,
Water retention of the coating liquid is also important. If the water retention of the coating liquid is low, the water content of the coating liquid will rapidly permeate into the base paper and the components of the coating liquid will become non-uniform due to evaporation toward the surface during forced drying, which will deteriorate the quality of the coated paper. .

In order to improve water retention, it is widely used to add water-soluble polymer compounds such as starch, casein, carboxymethyl cellulose, alginic acid, polyacrylic acid salt and styrene-maleic anhydride copolymer to the composition for coated paper. Although being carried out, the addition of a water-soluble polymer compound remarkably increases the viscosity of the composition for coated paper and, at the same time, lowers gloss and the like in terms of quality of coated paper.

As a means for solving these problems, a method of blending an alkali-soluble latex and an alkali-insoluble latex has been attempted. For example, JP-A-63-3031 is used.
Japanese Unexamined Patent Publication No. 96 and Japanese Unexamined Patent Publication No. 1-229894 are known. However, according to the studies by the present inventors, the relationship between the fluidity and the water retention of the coated paper composition containing these latexes was not always satisfactory.

[0005]

The object of the present invention is to provide a copolymer latex which itself has reduced viscosity and excellent stability, and to improve the fluidity and the fluidity of the copolymer latex containing the copolymer latex. It is intended to provide a composition for coated paper which is excellent in water retention.

[0006]

Means for Solving the Problems As a result of intensive studies to solve these problems, the present inventors have found that a monomer containing an aliphatic conjugated diene monomer and an ethylenically unsaturated acid monomer is selected. Obtained by emulsion polymerization of a copolymer latex obtained by emulsion polymerization and a monomer containing an aliphatic conjugated diene monomer, an ethylenically unsaturated acid monomer and an ethylenically unsaturated amide monomer. By mixing the former and the latter of which the average particle size of the copolymer latex is in a specific range in a specific ratio, it was found that a copolymer latex having reduced viscosity and excellent stability can be obtained. Furthermore, they have found that the balance of fluidity and water retention is improved in a composition for coated paper containing the copolymer latex, and have completed the present invention.

That is, in the present invention, the following copolymer latex (A) and copolymer latex (B) are used in a solid content weight ratio of (A) / (B) = 98 / 2-65 / 35. It is a copolymerized latex obtained by mixing, and a composition for coated paper characterized by containing the copolymer latex. Copolymer latex (A): 15-55 parts by weight of aliphatic conjugated diene-based monomer, ethylenically unsaturated acid monomer 0.5-
Average particle size (DA (nm)) 60-200 obtained by emulsion copolymerization of 100 parts by weight of a monomer mixture containing 5 parts by weight.
nm copolymer latex, copolymer latex (B): 15-55 parts by weight of aliphatic conjugated diene monomer, ethylenically unsaturated acid monomer 4-20
By weight, 100 parts by weight of a monomer mixture containing 4 to 20 parts by weight of an ethylenically unsaturated amide monomer is obtained by emulsion copolymerization and has an average particle diameter (DB (nm)) of 30 to 100 nm and DB < A copolymer latex that is DA-10.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
Examples of the aliphatic conjugated diene-based monomer used in the copolymer latex (A) and (B) include 1,3-butadiene, 2-methyl-1,3-butadiene, and 2-chloro-.
Mention may be made of 1,3-butadiene, especially 1,3-
Butadiene is preferably used. The amount of the monomer is 15-55 parts by weight based on all the monomers. When the amount used is less than the above range, sufficient adhesive strength cannot be obtained, and when the amount is too large, water resistance and adhesive strength decrease, which is not preferable.

Examples of ethylenically unsaturated acid monomers include:
Monocarboxylic acids such as acrylic acid, methacrylic acid and crotonic acid, dicarboxylic acids such as maleic acid, fumaric acid and itaconic acid and anhydrides thereof, half esters, styrenesulfonic acid, 2-sulfoethyl acrylate, acrylamidopropanesulfonic acid And a sulfonic acid group-containing unsaturated monomer and salts thereof. The amount of these used is 0.5-5 parts by weight in the copolymer latex (A) and 4-20 parts by weight in the (B) with respect to all the monomers. If the amount used is outside the above range, the stability of the copolymerized latex and the composition for coated paper containing the same, the water retention,
The adhesive strength may be insufficient, or the viscosity or high shear viscosity may become too high, resulting in poor workability.

Further, examples of the ethylenically unsaturated amide type monomer in the copolymer latex (B) include amides such as (meth) acrylamide, N-methylol (meth) acrylamide and N, N-methylenebisacrylamide. Examples include a group-containing unsaturated monomer and an N-substituted compound thereof, and the amount of these used is 4 to 20 parts by weight based on all monomers. If the amount used is outside the above range, the stability, water retention and adhesive strength of the copolymerized latex and the composition for coated paper containing the copolymer latex are insufficient, or the viscosity or high shear viscosity becomes too high, resulting in workability. It may be inferior.

In the copolymer latexes (A) and (B), other copolymerizable monomers are further used.
Examples thereof include aromatic vinyl monomers such as styrene, α-methylstyrene, vinyltoluene and p-methylstyrene, and (meth) acrylic acid esters such as ethyl (meth) acrylate and butyl (meth) acrylate. , Vinyl cyanides, and the like. Particularly, styrene is preferably used as the aromatic vinyl monomer, methyl methacrylate is preferably used as the (meth) acrylic acid ester, and acrylonitrile is preferably used as the vinyl cyanides. Furthermore, examples of other copolymerizable monomers include hydroxyl group-containing unsaturated monomers such as (meth) acrylic acid-2-hydroxyethyl, epoxy group-containing unsaturated monomers such as glycidyl methacrylate, vinyl acetate, Examples thereof include vinyl esters such as vinyl propionate. The ethylenically unsaturated amide monomer used in the above-mentioned copolymer latex (B) can be mentioned as a copolymerizable monomer in the copolymer latex (A).

Examples of the polymerization initiator used in the emulsion copolymerization of the present invention include persulfates such as potassium persulfate, ammonium persulfate and sodium persulfate; water-soluble initiators such as hydrogen peroxide; Redox initiators in combination with reducing agents such as sodium and amines are suitable, and water-soluble azo initiators and oil-soluble initiators such as benzoyl peroxide and azobisisobutyronitrile can also be used.

Further, as an example of an emulsifier used for controlling the particle size of the copolymer latex produced during emulsion copolymerization and imparting sufficient stability to the copolymer latex, a high-grade emulsifier is used. Sulfate ester of alcohol,
Alkyl benzene sulfonate, aliphatic sulfonate,
Anionic surfactant such as alkyl diphenyl ether (di) sulfonate, nonionic surfactant such as alkyl ester type of polyethylene glycol, alkyl phenyl ether type, alkyl ether type, and amphoteric surfactant such as betaine type are independent. Alternatively, they may be used in combination of two or more. Examples of the chain transfer agent used for the production of the copolymer latex of the present invention include t-dodecyl mercaptan, n-dodecyl mercaptan, n-octyl mercaptan, mercaptoethanol, mercaptopropionic acid and its sulfur-containing compounds such as esters, Disulfides such as tetraethylthiuram disulfide, alkyl halides such as carbon tetrachloride, terpenoids such as terpinolene, α-methylstyrene dimer and the like, and a chain transfer agent generally used for controlling the molecular weight in the emulsion copolymerization reaction alone or 2 Can be used in combination of more than one type.
The method for producing the copolymer latex of the present invention is not particularly limited as long as the conditions of the present invention are satisfied, and a conventionally known emulsion polymerization method may be used.

Average particle diameters DA (nm) and DB (nm) of the copolymer latexes (A) and (B) of the present invention
Must satisfy the relationship of 60 ≦ DA ≦ 200 and 30 ≦ DB ≦ 100. When the particle size of the latex is too small, the latex viscosity may be too high, or the stability of the latex and the composition for coated paper may be insufficient, which may cause problems in handling workability, coating workability and the like. If the particle size of the latex is too large, problems such as high high shear viscosity of the coated paper composition may occur. Further, the average particle diameter DA of the copolymer latex (A) and (B)
(Nm) and DB (nm) need to satisfy the relationship of DA-10> DB. Outside of this range, the fluidity of the latex and the coated paper composition may be insufficient, or the water retention of the coated paper composition may be insufficient. The particle size of the latex can be controlled by a known method such as changing the amount and type of the emulsifier.

The mixing ratio of the copolymer latexes (A) and (B) of the present invention is (A) / (B) = 9 in terms of solid content weight ratio.
It must be in the range of 8 / 2-65 / 35. Outside this range, the fluidity of the latex mixture and the coated paper composition containing the latex mixture may be insufficient, or the water retention of the coated paper composition may be insufficient.

In the composition for coated paper of the present invention, as a pigment, kaolin clay, calcium carbonate, satin white, titanium oxide, aluminum hydroxide, barium sulfate,
Inorganic pigments such as zinc oxide, organic pigments such as polystyrene, SBR and phenol resin are used alone or in combination of two or more kinds, and also dispersants, water resistance agents, viscosity modifiers, defoamers, water retention agents, dyes. Lubricants, pH adjusters, surfactants, antiseptics, other auxiliaries and additives can be used as required.

As the binder, in addition to the copolymer latex of the present invention, if necessary, a water-soluble polymer such as starch, casein, polyvinyl alcohol, etc., a latex such as polyvinyl acetate, an acrylate copolymer, etc. Can be used together. The copolymer latex of the present invention is usually used in the range of 5 to 30 parts by weight (solid content) with respect to the pigment (solid content).

[0018]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited to these examples. In addition, all parts and% in the examples represent parts by weight and% by weight, unless otherwise specified.

Example 1 [Production Example of Copolymer Latex (A1, A2)] 100 parts by weight of water and a necessary amount of sodium lauryl sulfate were charged in an autoclave equipped with a stirrer, thoroughly stirred and mixed, and deoxidized by nitrogen substitution. I went. Then, the temperature was raised to 65 ° C., 1.8 parts by weight of potassium persulfate was added, and then 1
A mixture of 00 parts of monomer, chain transfer agent, 40 parts of water and 0.2 parts of sodium lauryl sulfate was added into the autoclave over about 6 hours. After the monomer addition is complete, 10 more
After reacting for a time, the mixture was cooled and 0.1 part of N, N-diethylhydroxyamine was added to terminate the polymerization. After completion of the polymerization, the pH was adjusted to 8.0 with sodium hydroxide, and then unreacted monomers and volatile residual organic substances were removed by steam stripping, and the solid content was concentrated to 50% to obtain a copolymer latex. (A) was obtained.

Example 2 [Production Example of Copolymer Latex (B1, B2) and Comparative Production Example (RA, RB)] 200 parts by weight of water and a necessary amount of sodium lauryl sulfate were charged in an autoclave equipped with a stirrer and sufficiently stirred. The mixture was mixed and deoxidized by nitrogen substitution. Then, the temperature was raised to 65 ° C., 1.8 parts by weight of potassium persulfate was added, and then 100 parts of the monomer shown in Table 1, the chain transfer agent, 40 parts of water and 0.2 part of sodium lauryl sulfate were added. The mixture was added into the autoclave over about 6 hours. After the addition of the monomer is completed, the reaction is further performed for 10 hours, then cooled, and N, N-diethylhydroxyamine 0.1
Parts were added to complete the polymerization. After completion of the polymerization, the pH was adjusted to 8.0 with sodium hydroxide, and then unreacted monomers and volatile residual organic substances were removed by steam stripping, and the solid content was concentrated to 50% to obtain a copolymer latex. (B) and a comparative copolymer latex were obtained. However, B2 and RB were used as latex having a large increase in latex viscosity and a solid content concentration of 40%.

Example 3 [Production Examples of Copolymer Latex Compositions and Comparative Production Examples] The copolymer latexes before steam stripping were combined with the copolymer latexes shown in Experimental Examples and Comparative Experimental Examples in Table 2, After mixing at a solid content ratio, unreacted monomers and volatile residual organic substances were removed by steam stripping, and the solid content concentration was concentrated to 50%.

Evaluation Example 1 [Properties of Copolymer Latex] A) Gel Content of Copolymer Latex The copolymer latex was uniformly cast on a polypropylene plate, dried at room temperature for 1 week, and dried with hot air at 80 ° C. Dry in a circulating dryer for 1 hour to form a film. After precisely weighing about 1 g with an analytical balance and immersing in 100 cc of toluene for 2 days, 10 ml of a toluene solution is sampled, the solid content after drying is weighed, and the gel content is calculated by the following method.

[0023]

[Equation 1] B) Particle size measurement of copolymer latex The copolymer latex was diluted with pure water to a predetermined concentration and then measured with a submicron particle size measuring instrument manufactured by Coulter Electronics. C) Viscosity measurement of copolymer latex It was calculated from the value after 60 seconds at 60 rpm using a rotating rotor type B viscometer. D) Mechanical stability Latex 1 adjusted to a solid content concentration of 30% and pH 8.0
50 g was treated with a Marlon tester under a load of 15 kg for 30 minutes, and the weight of aggregates that did not pass through a 300-mesh wire net was measured and expressed in ppm with respect to the latex solid content.

Example 4 [Production of Coated Paper Composition] First grade kaolin clay (UW-
90, manufactured by Engelhard Co., Ltd., 50 parts by weight, heavy calcium carbonate (Carbital 90, manufactured by Shiraishi Industry Co., Ltd.), 50 parts by weight, dispersant (Aron T-40, manufactured by Toagosei Co., Ltd.).
0.2 parts by weight and 0.09 parts by weight of sodium hydroxide were dispersed in water using a Cowles disperser to prepare a pigment slurry. 0.3 parts by weight of calcium stearate (Nopcoat C-104, manufactured by San Nopco Ltd.) as a lubricant, and oxidized starch (Corn Ace C, Ltd.) as an adhesive were added.
1 part by weight of Oji Corn Starch Co., Ltd.) and 10 parts by weight of the copolymer latex shown in the experimental examples and comparative experimental examples of Table 2 in terms of solid content are added to adjust the solid content concentration to 65%. I got a thing.

Evaluation Example 2 [Properties of Coated Paper Composition] A) Mechanical Stability 150 g of coated paper composition having solid content concentration adjusted to 50%
Was treated with a Marlon tester for 20 minutes under a load of 15 kg, and the weight of the agglomerates that did not pass through the 300 mesh wire net was measured, and indicated in ppm with respect to the solid content of the coated paper composition. B) High shear viscosity It was measured with a Hercules type high shear viscometer (4400 rpm, F Bob) manufactured by Kumagai Riki Kogyo Co., Ltd. C) Water retention test Water Retenti at 20 ° C and 60% relative humidity
on Meter.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

[Table 3]

[0029]

As described above, the copolymer latex of the present invention itself has a reduced viscosity and excellent stability,
It is clear that the composition for coated papers containing the copolymer latex has excellent fluidity and water retention and is unprecedentedly useful.

(72) Inventor Goro Kuwamura 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Mitsui Toatsu Chemical Co., Ltd. (72) Kenichi Nakane 1190 Kasama-cho, Sakae-ku, Yokohama, Kanagawa Mitsui Toatsu Chemical Co., Ltd.

Claims (2)

[Claims] 1. A copolymer latex (A) and a copolymer latex (B) described below in a solid content weight ratio of (A) / (B).
= 98 / 2-65 / 35 mixed latex. Copolymer latex (A): 15-55 parts by weight of aliphatic conjugated diene-based monomer, ethylenically unsaturated acid monomer 0.5-
Copolymer latex having an average particle size (DA) of 60 to 200 nm, obtained by emulsion copolymerization of 100 parts by weight of a monomer mixture containing 5 parts by weight, copolymer latex (B): aliphatic conjugated diene-based monomer 15-55 parts by weight, ethylenically unsaturated acid monomer 4-20
By weight, 100 parts by weight of a monomer mixture containing 4 to 20 parts by weight of an ethylenically unsaturated amide monomer is obtained by emulsion copolymerization and has an average particle diameter (DB) of 30 to 100 nm and DB.
The copolymer latex which is <DA-10. 2. A composition for coated paper, which comprises the copolymer latex according to claim 1.