JP3465429B2 - Method for producing copolymer latex - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a copolymer latex suitable for paper coating, and more specifically, it has excellent coating operability, water resistance, surface strength, printing gloss, rigidity and the like. To a method for producing a copolymer latex which gives a coated paper excellent in printability.

[0002]

BACKGROUND OF THE INVENTION Conventionally, a paper coating composition mainly composed of a pigment and an aqueous binder is applied to paper to produce a coated paper having excellent printability. Due to its excellent adhesive strength, it is used as the main binder of paper coating compositions.

In recent years, as printing has become more sophisticated and faster,
The performance required for coated paper is becoming more severe, and improvements in surface strength, water resistance, rigidity, ink transferability, printing gloss and blister resistance have come to be required. Further, in recent years, there has been an increasing demand for reducing the amount of binder for the purpose of cost reduction, and therefore, a binder showing sufficient surface strength even with a smaller addition amount is required.

Further, the production of coated paper itself has been accelerated, and the coating operability is improved, that is, the main obstacle is the improvement of roll fouling property, that is, the reduction of the tackiness of the copolymer latex (prevention of stickiness). Sex) is also strongly required.

The above-mentioned properties, especially the adhesive strength, are required to be improved for the copolymer latex. Therefore, for example, the method for adjusting the gel content of the copolymer and the adjustment of the copolymer composition are required. A method has been proposed. However, the adhesive strength and other properties are almost contrary to each other, and it is very difficult to achieve a high level with good balance of all properties.

For example, a method of lowering the glass transition point of the copolymer obtained by increasing the amount of the conjugated diene monomer for the purpose of improving the adhesive strength has been tried, but in this method, the water resistance and the rigidity are increased. In addition, the property of anti-stick property is remarkably deteriorated. On the other hand, when the glass transition point is increased, the water resistance and rigidity are good, but the adhesive strength and print gloss characteristics are significantly deteriorated. Further, in a method using a large amount of a monomer having a functional group, the adhesive strength is improved, but the viscosity of the latex becomes abnormally high, so the workability is significantly reduced, and the production cost of the copolymer latex is high. Become.

As described above, none of these methods, even if the improvement of any of the characteristics is achieved, cannot satisfy the requirements for all the characteristics, and satisfy the requirements for increasingly severe printing. The present situation is that it cannot be done.

[0008]

SUMMARY OF THE INVENTION The present invention has been made based on the above technical background, and its object is to significantly improve the surface strength of coated paper, and to improve water resistance and printing gloss. Another object of the present invention is to provide a method for producing a copolymer latex which has excellent rigidity, reduced stickiness and excellent coating operability and is suitable for paper coating, particularly for high speed offset printing paper.

[0009]

Means for Solving the Problems and Embodiments of the Invention
That is, the method for producing the copolymer latex of the present invention,
(a) 50-95% by weight of aliphatic conjugated diene-based monomer, (b) 5-50% by weight of aromatic vinyl-based monomer, (c) 0-2% by weight of ethylenically unsaturated carboxylic acid monomer (However, (a) + (b)
+ (C) = 100% by weight) in the presence of 30-80 parts by weight of copolymer [I] obtained by polymerizing (a) 10-50% by weight of the aliphatic conjugated diene monomer, (c) ) 0.5 to 30% by weight of ethylenically unsaturated carboxylic acid monomer, and (d) 20 to 89.5% by weight of another monomer copolymerizable therewith (provided that (a) + (c) + (D) = 100% by weight of a monomer [II] 20 to 70 parts by weight (provided that [I] + [II] = 10)
0 part by weight) is polymerized.

In the method for producing the copolymer latex of the present invention, the copolymer [I] has a glass transition point in the range of -100 to 0 ° C., and the copolymer of the monomer [II] is used. The glass transition point of the polymer is preferably 5 ° C. or more higher than the glass transition point of the copolymer [I].

The copolymerized latex obtained by the production method according to the present invention has the purpose of having a copolymer having a low glass transition point and a copolymer having a high glass transition point in the same latex particle. The performance to do is obtained.
That is, since this copolymer latex has a copolymer having a low glass transition point in the latex particles, it has a high resistance to shock deformation at an extremely high deformation rate in high-speed printing. Shows high adhesive strength. In addition, as a copolymer having a low glass transition point,
High water resistance is exhibited by using a highly hydrophobic copolymer. Further, since this copolymer latex also has a copolymer having a high glass transition point in the same latex, other physical properties such as rigidity can be maintained at a high level, and the tackiness is improved, which is excellent. It has good coating operability.

Up to now, studies have been made to achieve compatibility of contradictory performances by mixing latices having different glass transition points, but the desired performances could not be obtained.

The copolymer [I] of the present invention comprises (a) 50 to 95% by weight of an aliphatic conjugated diene monomer, (b) 5 to 50% by weight of an aromatic vinyl monomer, and (c). Ethylenically unsaturated carboxylic acid monomer 0-2% by weight (however, (a) + (b) + (c) =
It is obtained by polymerizing a monomer consisting of 100% by weight).

Examples of the (a) aliphatic conjugated diene-based monomer used in the copolymer [I] include 1,3-butadiene, isoprene, 2-chloro-1,3-butadiene and chloroprene. But particularly preferably 1,3
-Butadiene. These (a) aliphatic conjugated diene-based monomers can be used alone or in combination of two or more.

The (a) aliphatic conjugated diene-based monomer is
Providing the obtained polymer with appropriate flexibility and elongation, it is an essential component for imparting impact resistance, and its use ratio is
50-9 based on all monomers used in copolymer [I]
It is 5% by weight, preferably 60 to 90% by weight. If the amount of component (a) is less than 50% by weight, the copolymer becomes too hard,
The adhesive strength is not improved. If the amount of the component (a) exceeds 95% by weight, the water resistance will be extremely reduced.

Examples of the aromatic vinyl-based monomer (b) include styrene, α-methylstyrene, p-methylstyrene, vinyltoluene and chlorostyrene, and styrene is particularly preferable. These (b) aromatic vinyl monomers can be used alone or in combination of two or more.

The ratio of the (b) aromatic vinyl-based monomer used is 5 with respect to all the monomers used in the copolymer [I].
-50% by weight, preferably 10-40% by weight, more preferably 10-30% by weight. If the amount of the component (b) is less than 5% by weight, the water resistance strength is extremely reduced. When the amount of the component (b) exceeds 50% by weight, the copolymer becomes too hard and the adhesive strength and printing gloss are extremely reduced.

Examples of the (c) ethylenically unsaturated carboxylic acid monomer include itaconic acid, acrylic acid, methacrylic acid, fumaric acid, maleic acid and the like. these
The ethylenically unsaturated carboxylic acid monomer (c) may be used alone or in combination of two or more.

The proportion of the (c) ethylenically unsaturated carboxylic acid monomer used is 0 to 2% by weight, preferably 0 to 1% by weight, based on all the monomers used in the copolymer [I]. %. When the amount of the component (c) exceeds 2% by weight, the stability of the latex during polymerization is poor and coagulation tends to occur.

The glass transition temperature of the copolymer [I] is preferably in the range of -100 to 0 ° C, more preferably in the range of -70 to -5 ° C. If the glass transition temperature is higher than 0 ° C, the copolymer becomes hard and sufficient adhesive strength cannot be obtained. Also, the glass transition temperature is -100 ° C.
If it is lower, the water resistance is extremely reduced.

The monomer [II] of the present invention comprises (a) 10 to 50% by weight of an aliphatic conjugated diene monomer and (c) 0.5 to 30% by weight of an ethylenically unsaturated carboxylic acid monomer. , And (d)
Other monomers copolymerizable with these 20 to 89.5% by weight
(However, (a) + (c) + (d) = 100% by weight).

The (a) aliphatic conjugated diene-based monomer and (c) ethylenically unsaturated carboxylic acid monomer used in the monomer [II] were used in the above-mentioned copolymer [I]. Similar ones can be used.

In the monomer [II], the aliphatic conjugated diene-based monomer (a) is an essential component for imparting appropriate flexibility and elongation to the resulting copolymer, and its use ratio is simple. 10 to 50% by weight, preferably 15 to 50% by weight of the monomer [II]
It is 45% by weight. If the amount of the component (a) is less than 10% by weight, the copolymer will be too hard and the adhesive strength will be poor. If the amount of the component (a) exceeds 50% by weight, the water resistance and the stickiness preventive property are extremely deteriorated.

The proportion of the (c) ethylenically unsaturated carboxylic acid monomer used is 0.5 to 30% by weight, preferably 2 to 10% by weight, based on the monomer [II]. The component (c) is 0.
If it is less than 5% by weight, the stability of the latex during polymerization is poor,
Coagulation is likely to occur and the latex obtained has poor mechanical and chemical stability. On the other hand, the component (c) is 30% by weight
If it exceeds, the viscosity of the latex obtained will be too high,
It becomes difficult to handle, the workability deteriorates, and it becomes impractical.

Further, other monomers copolymerizable with the components (d), (a) and (c) include, for example, aromatic vinyl monomers, alkyl (meth) acrylates and vinyl cyanide monomers. , Vinyl acetate, (alkylmeth) acrylamide-based monomers and the like.

Among these, as the aromatic vinyl monomer,
Examples thereof include styrene, α-methylstyrene, p-methylstyrene, vinyltoluene, chlorostyrene, etc., and styrene is particularly preferable.

As the alkyl (meth) acrylate,
For example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, benzyl (meth) acrylate, lauryl (meth) acrylate. , Stearyl (meth) acrylate, glycidyl (meth) acrylate, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, isobornyl (meth) acrylate, 2-cyanoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylamino Examples thereof include ethyl (meth) acrylate, of which methylmethacrylate is particularly preferable.

The vinyl cyanide monomer may, for example, be acrylonitrile or methacrylonitrile, of which acrylonitrile is particularly preferred.

Further, examples of the (alkylmeth) acrylamide type monomer include acrylamide, methacrylamide, N-methylolacrylamide, N, N-dimethylacrylamide, N, N-dimethylaminopropyl (meth) acrylamide and the like. .

These monomers of component (d) may be used alone or in combination of two or more.

Further, the component (d) is mainly for imparting appropriate hardness and adhesiveness to the copolymer, and the proportion of the component (d) used is 20 to 89% relative to the monomer [II]. It is 5% by weight, preferably 30 to 88.5% by weight. If the amount of component (d) is less than 20% by weight, the copolymer becomes too soft,
Anti-stickiness and rigidity are inferior, while component (d) is 89.
On the other hand, if it exceeds 5% by weight, it will be too hard and the adhesive strength will be poor.

Further, the glass transition temperature of the copolymer obtained by polymerizing the monomer [II] is preferably higher than the glass transition temperature of the copolymer [I] by 5 ° C. or more. The difference is more preferably 10 to 150 ° C, further preferably 20 to 100 ° C. Difference in glass transition point is 5
When the temperature is lower than ° C, a large difference from that having a uniform structure does not appear.

The amount of the copolymer [I and / or the monomer [II] used is 30 to 80/70 to 20 parts by weight, preferably 30 to 70/30 to 70 parts by weight, in terms of the ratio of the two. is there. When the amount of the copolymer [I] used is less than 30 parts by weight (when the amount of the monomer [II] exceeds 70 parts by weight), the impact resistance is insufficient, the adhesive strength is poor, and the water resistance is low. Inferior strength. On the other hand, when the amount of the copolymer [I] used exceeds 80 parts by weight (the amount of the monomer [II] used is less than 20 parts by weight), the outer layer portion having a relatively high glass transition point becomes too small. , The rigidity and anti-stickiness are extremely reduced.

The particle size of the copolymer latex obtained by the production method of the present invention is preferably 60 to 350 nm,
More preferably, it is 70 to 250 nm.

The emulsion polymerization of the monomer used in the present invention can be carried out by a known method using an emulsifier, a polymerization initiator, a molecular weight modifier and the like in an aqueous medium.

Here, as the emulsifier, an anionic surfactant, a nonionic surfactant, an amphoteric surfactant and the like can be used alone or in combination of two or more kinds.

Here, as the anionic surfactant,
Examples thereof include sulfuric acid esters of higher alcohols, alkylbenzene sulfonates, aliphatic sulfonates, and sulfuric acid esters of polyethylene glycol alkyl ethers.

As the nonionic surfactant, an ordinary polyethylene glycol alkyl ester type, alkyl ether type, alkyl phenyl ether type or the like is used. Examples of the amphoteric surfactant include those having a carboxylate salt, a sulfuric acid ester salt, a sulfonate salt, and a phosphoric acid ester salt as the anion portion, and those having an amine salt or a quaternary ammonium salt as the cation portion. Betaines such as lauryl betaine and stearyl betaine, amino acid types such as lauryl-β-alanine, stearyl-β-alanine, lauryl di (aminoethyl) glycine, and octyl di (aminoethyl) glycine are used.

As the polymerization initiator, sodium persulfate,
Water-soluble polymerization initiators such as potassium persulfate and ammonium persulfate, benzoyl peroxide, lauryl peroxide,
An oil-soluble polymerization initiator such as 2,2′-azobisisobutylnitrile and a redox polymerization initiator in combination with a reducing agent can be used alone or in combination.

Known molecular weight regulators, chelating agents, inorganic electrolytes and the like can be used.

As the molecular weight regulator, 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. , Xanthogens such as dimethylxanthogen disulfide and diisopropylxanthogendisulfide, terpinolene, α-methylstyrene dimer, and the like usable in ordinary emulsion polymerization can all be used.

As the polymerization method, similar to the seed polymerization,
A method in which the copolymer [I] is previously polymerized in another polymerization system and a predetermined amount is added, and then the monomer [II] is polymerized, or both are polymerized in at least two stages in the same polymerization vessel. The method of doing is adopted.

As a method for polymerizing the copolymer [I],
A method in which the entire amount of the monomer mixture is charged and polymerized, a method in which a part of the monomer mixture is polymerized and then the rest is continuously or intermittently added, or the monomer mixture is continuously added from the beginning of the polymerization. It is possible to adopt a method such as a method of selectively adding. In addition, as a method for polymerizing the monomer [II], in the presence of a predetermined amount of the copolymer [I], the whole amount of the monomer mixture is charged and polymerized, or the monomer mixture is continuously added. It is possible to adopt a method such as adding to.

The polymerization temperature is preferably 5 to 80 ° C., more preferably 5 to 80 ° C. when polymerizing the copolymer [I].
When polymerizing the monomer [II] at 50 ° C., preferably 2
The temperature is 0 to 80 ° C, more preferably 20 to 70 ° C. The polymerization time is usually 10 to 30 hours.

The composition for paper coating in which the copolymer latex obtained by the present invention is used, comprises an inorganic or organic pigment, the above-mentioned copolymer latex, and optionally other binders and various auxiliaries. Used by blending. The blending amount of the above copolymer latex is 1 to 30 parts by weight (as solid content) of the copolymer latex with respect to 100 parts by weight of the pigment,
It is preferably 3 to 25 parts by weight. When the amount of the copolymer latex is less than 1 part by weight, the adhesive strength is remarkably lowered, while when it exceeds 30 parts by weight, the ink drying property is remarkably lowered.

Examples of the inorganic pigment include clay, barium sulfate, titanium oxide, calcium carbonate, satin white, talc, aluminum hydroxide and zinc oxide, and examples of the organic pigment include polystyrene latex and urea formalin resin. . These may be used alone or in combination of two or more depending on the purpose.

In the paper coating composition, a water-soluble substance such as casein, casein modified product, starch, starch modified product, polyvinyl alcohol and carboxymethyl cellulose is required as a pigment adhesive in addition to the above copolymer latex. It can be used in combination according to.

Further, in the paper coating composition, various commonly used compounding agents such as a water resistance improver, a pigment dispersant, a viscosity modifier, a coloring pigment, a fluorescent dye and a pH modifier may be optionally used. Can be blended with.

The copolymer latex produced by the present invention is preferably used for an offset sheet-fed printing machine. In addition, various printing papers such as an offset rotary printing machine, letterpress printing and gravure printing, and paper It can be used as a coating agent, a carpet backing agent, other adhesives, and also as a paint.

[0050]

EXAMPLES Next, the present invention will be described in detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist. In the examples, "parts" and "%" indicating proportions are parts by weight and% by weight, respectively.
Is meant.

(Production of Copolymer Latex) (Examples 1 to 3) 200 parts of water, 0.5 part of sodium dodecylbenzenesulfonate and 1.0 part of potassium persulfate were placed in an autoclave equipped with a stirrer and capable of controlling temperature. Parts, 0.5 parts of sodium bisulfite and the components of the first step shown in Table 1 were charged all at once and reacted at 45 ° C. for 6 hours, and it was confirmed that the polymerization conversion rate was 90% or more. Subsequently, the second-stage component was continuously added at 60 ° C. for 7 hours to continue the polymerization, and the reaction was continued at 70 ° C. for 6 hours after the completion of the continuous addition. Final polymerization conversion rate is 98-9
It was 9%.

The glass transition point and latex particle diameter of the obtained copolymer latex were determined by the following methods.
The results are shown in Table 2.

A. The copolymer latex obtained at the glass transition point was vacuum dried at 100 ° C. for 20 hours to form a film. The dry film was subjected to AS using a differential scanning calorimeter (DSC: manufactured by DuPont).
According to the TM method, measurement was performed at a temperature rising rate of 20 ° C./min.

In the copolymer latexes obtained in Examples 1 to 3, two glass transition points were observed by DSC measurement.

B. Latex particle size The average particle size of the obtained copolymer latex was measured with a Coulter submicron analyzer (model N4).
Obtained by a conventional method.

[0056]

[Table 1]

[0057]

[Table 2]

(Preparation of Paper Coating Composition) Using the copolymer latexes produced in Examples 1 to 3, a paper coating composition for offset sheet-fed printing was prepared according to the following formulation. Blended kaolin clay 70.0 parts Calcium carbonate 30.0 parts Dispersant 0.2 parts Sodium hydroxide 0.1 parts Starch 4.0 parts Latex (as solid content) 10.0 parts Water So that the total solid content is 60% Add an appropriate amount to this coated paper composition on the base paper to be coated on one side 1
It was coated with an electric blade coater (manufactured by Kumagai Riki Kogyo Co., Ltd.) so as to be 8.0 ± 0.5 g / m ² and dried for 15 seconds by an electric hot air dryer at 150 ° C. The coated paper thus obtained is allowed to stand in a thermo-hygrostat at a temperature of 23 ° C. and a humidity of 50% for one day and night,
Then, super calender treatment was performed 4 times under the conditions of linear pressure of 100 kg / cm and roll temperature of 50 ° C. The performance of the obtained coated paper was evaluated by the following method.

1) Dry pick strength The degree of picking when printed by an RI printing machine was judged with the naked eye and evaluated in 5 levels. The less the picking phenomenon, the higher the score. The numerical value was shown as the average value of 6 times of measurement.

2) Wet pick strength Using a RI printing machine, after moistening the coated paper surface with a water-absorbing roll, the picking degree when printing with the RI printing machine was judged visually and evaluated in five levels. . The less the picking phenomenon, the higher the score. The numerical value was shown as the average value of 6 times of measurement.

3) Printing gloss Using the RI printing machine, the offset ink is solidly coated,
It was measured at an angle of 60 degrees using a Murakami gloss meter.

4) Stiffness It was measured using an automatic Clark stiffness tester (Kumagaya Riki Kogyo Co., Ltd.) according to JIS P8143.

5) The non-sticky latex was coated on a polyethylene terephthalate film with No. It is coated with 18 rods and dried at 120 ° C. for 30 seconds to form a film. This film and Kuroshisa paper are combined, and a line pressure of 200 kg /
Pressure is applied under the conditions of m and temperature of 70 ° C. Peel off both, and visually check the degree of transfer of Kurorasha paper to latex.
Graded. The less the transfer, the higher the score. The numerical value was shown as the average value of 6 times of measurement.

Table 2 shows the results of evaluation by the above evaluation method. Examples 1 to 3 are compositions for paper coating for offset sheet-fed printing using the copolymer latex within the scope of the present invention, which are the objects of the present invention, that is, excellent in adhesive strength,
In addition, a product having excellent water resistance, rigidity and anti-stickiness was obtained.

(Examples 4 and 5) (1) Preparation of copolymer [I] 150 parts of water and sodium dodecylbenzene sulfonate 2 in an autoclave equipped with a stirrer and capable of controlling temperature.
Parts, 0.2 parts of potassium persulfate and the components shown in Table 3 were charged all at once and reacted at 45 ° C. for 8 hours. When the polymerization conversion rate reached 80%, N, N′-dimethylhydroxylamine 0 The polymerization was stopped by adding 1 part. Then, unreacted monomers were removed by steam stripping, and after cooling, the solid content was adjusted to 25%.

(2) Polymerization of copolymer latex 160 parts (40 parts as solid content) of latex of the copolymer [I] obtained in (1) after preparation of solid content, water 60
Parts, 0.5 parts of sodium dodecylbenzene sulfonate,
1.0 part of potassium persulfate and the components shown in Table 4 were charged all at once and reacted at 65 ° C. for 8 hours. The final polymerization conversion rate was 98 to 99%. The obtained copolymer latex had two glass transition points by using a differential scanning calorimeter in the same manner as in Examples 1 to 3. It was confirmed. In addition, the particle size was determined. The results are shown in Table 5.

[0067]

[Table 3]

[0068]

[Table 4]

[0069]

[Table 5]

Using the copolymer latexes produced in Examples 4 and 5, a paper coating composition for offset sheet-fed printing was prepared in the same manner as in Examples 1 to 3, and the physical properties of the coated paper were evaluated. did. The results are shown in Table 5. The paper coating compositions for offset sheet-fed printing obtained in Examples 4 and 5 were excellent in adhesive strength, water resistance, rigidity, and anti-stickiness.

Comparative Examples 1 and 2 In the same manner as in Examples 1 to 3, 200 parts of water, 0.5 part of sodium dodecylbenzenesulfonate and 1 part of potassium persulfate were placed in an autoclave equipped with a stirrer and capable of controlling temperature. 0.0 part, 0.5 part of sodium bisulfite and the components of the first step shown in Table 6 were charged all at once and reacted at 55 ° C. for 6 hours. After confirming that the polymerization conversion rate was 90% or more, the second stage component was continuously added at 70 ° C for 7 hours to continue the polymerization, and further, 75 ° C for 6 hours after the continuous addition was completed.
It was made to react with. The final polymerization conversion rate was 98 to 99%.

The particle size and glass transition point of the obtained copolymer latex were measured in the same manner as in Examples 1-3. In each of the copolymers, the monomer composition, particularly the proportion of styrene or butadiene and the styrene monomer in the first stage is outside the scope of the present invention. The results are shown in Table 7.

Using the copolymer latexes prepared in Comparative Examples 1 and 2, a paper coating composition for offset sheet-fed printing was prepared in the same manner as in Examples 1 to 3, and the physical properties of the coated paper were measured. evaluated. The results are shown in Table 7.

From the results of Table 7, Comparative Example 1 is a case where the amount of styrene in the first stage is less than 5% by weight and Examples 1 to 3 are used.
It can be seen that the wet strength is inferior compared to. In Comparative Example 2, the amount of butadiene in the first stage was less than 50% by weight and the amount of styrene was more than 50% by weight. It turns out that is inferior.

[0075]

[Table 6]

[0076]

[Table 7]

(Comparative Example 3) In the same manner as in Examples 1 to 3,
An autoclave equipped with a stirrer and capable of controlling the temperature, 200 parts of water, sodium dodecylbenzenesulfonate.
5 parts, 1.0 part of potassium persulfate, 0.5 part of sodium bisulfite and the components of the first step shown in Table 6 were charged all at once and reacted at 50 ° C. for 6 hours to obtain a polymerization conversion rate of 90%.
It was confirmed that the above. Then, the second-stage component was continuously added at 70 ° C. for 7 hours to continue the polymerization, and further 75 hours for 6 hours after the completion of the continuous addition.
The reaction was carried out at ° C. The final polymerization conversion rate was 98 to 99%.

The copolymer latex thus obtained was prepared according to Example 1
The glass transition point and the particle size were measured in the same manner as in (1) to (3). Only one glass transition point of this copolymer latex was observed. The results are shown in Table 7.

Using the copolymer latex produced in Comparative Example 3, a paper coating composition for offset sheet-fed printing was prepared in the same manner as in Examples 1 to 3, and the physical properties of the coated paper were evaluated. . The results are shown in Table 7. It can be seen that in Comparative Example 3, the dry strength is almost the same as that of Example 1, but the wet strength, the rigidity and the stickiness preventing property are poor.

Comparative Example 4 (1) Production of Copolymer Latex [A] In the same manner as in Examples 1 to 3, 100 parts of water and dodecylbenzene sulfonic acid were placed in an autoclave equipped with a stirrer and capable of controlling temperature. Sodium 0.3 parts, potassium persulfate 0.
8 parts, 0.5 part of sodium bisulfite and the components shown in Table 8 were charged all at once and reacted at 45 ° C. for 7 hours.
The temperature was raised to 70 ° C., and the reaction was continued for 7 hours. The final polymerization conversion rate was 98 to 99%.

(2) Production of copolymer latex [B] In the same manner as in Examples 1 to 3, 100 parts of water and 0.3 part of sodium dodecylbenzenesulfonate were placed in an autoclave equipped with a stirrer and capable of controlling temperature. , Potassium persulfate 0.
8 parts, 0.5 part of sodium bisulfite and the components shown in Table 9 were charged all at once and reacted at 45 ° C. for 7 hours.
The temperature was raised to 70 ° C., and the reaction was continued for 7 hours. The final polymerization conversion rate was 98 to 99%.

The copolymer latex [A] obtained in (1) and the copolymer latex [B] obtained in (2) were blended at 50/50 in terms of solid content.
A paper coating composition for offset sheet-fed printing was prepared in the same manner as in Examples 1 to 3, and the physical properties of the coated paper were evaluated. The results are shown in Table 10.

[0083]

[Table 8]

[0084]

[Table 9]

[0085]

[Table 10]

From the results shown in Table 10, it can be seen that the dry strength, wet strength, rigidity and anti-stickiness are inferior only by blending two kinds of copolymer latex, and the desired performance cannot be obtained.

[0087]

EFFECTS OF THE INVENTION According to the present invention, a specific monomer is seed-polymerized or multi-stage-polymerized, so that it has excellent water resistance strength, adhesive strength, printing gloss, rigidity and anti-stickiness, and is suitable for printing. Further, it is possible to provide a method for producing a copolymer latex that gives a composition for paper coating having excellent coating operability.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigeru Niigae 2-11-24 Tsukiji, Chuo-ku, Tokyo Japan Synthetic Rubber Co., Ltd. (56) Reference JP-A-7-48423 (JP, A) Kai 63-99395 (JP, A) JP 64-6462 (JP, A) JP 7-97414 (JP, A) JP 7-324113 (JP, A) JP 7-324112 ( JP, A) JP 8-269143 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C08F 265/06 C08F 279/02

Claims (2)

(57) [Claims] 1. (a) Aliphatic conjugated diene monomer 50 to 9
5% by weight, (b) 5 to 50% by weight of an aromatic vinyl monomer,
(c) Ethylenically unsaturated carboxylic acid monomer 0 to 2% by weight
(However, in the presence of 30 to 80 parts by weight of a copolymer [I] obtained by polymerizing (a) + (b) + (c) = 100% by weight,
(a) 10 to 50 wt% of aliphatic conjugated diene monomer, (c) 0.5 to 30 wt% of ethylenically unsaturated carboxylic acid monomer,
And (d) Other monomers 20 to 8 copolymerizable with these
20 to 70 parts by weight of a monomer [II] composed of 9.5% by weight (however, (a) + (c) + (d) = 100% by weight (however, [I] + [II] = 100 parts by weight) ) Is polymerized, a method for producing a copolymer latex. 2. The copolymer [I] has a glass transition point of −
2. The glass transition point of the copolymer obtained from the monomer [II] is higher than that of the copolymer [I] by 5 ° C. or more in the range of 100 to 0 ° C. 3. The method for producing the copolymer latex of.