JPH07324113A - Production of paper coating copolymer latex - Google Patents

Abstract

PURPOSE:To provide a process for producing a paper coating copolymer latex excellent not only in coating workability but also in printability including surface strength, blistering resistance, printing gloss and rigidity. CONSTITUTION:According to a process for producing a paper coating copolymer latex, (A) 10-95 pts.wt. monomer mi,xture comprising 10-60wt.% (a) aliph. conjugated diene monomer, 0.5-30wt.%. (c) ethylenically unsatd. carboxylic acid monomer, and 10-89.5wt.% (e) other monomer copolymerizable with the monomer (a) and (c) [provided that (a)+(c)+(e)=100wt.%] is polymerized in the presence of (B) 5-90 pts.wt. copolymer obtd. by polymerizing 35-95wt.% (a) aliph. conjugated diene monomer, 5-50wt.% (b) vinyl cyanide monomer, 0-2wt.% (c) ethylenically unsatd. carboxylic acid monomer, and 0-60wt.% (d) other vinyl monomer copolymerizable with the monomers (a), (b) and (c) [provided that (a)+(b)+(c)+(d)=100-wt.%].

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a copolymer latex suitable for paper coating, more specifically, it has excellent coating operability and printing gloss, surface smoothness, surface strength, The present invention relates to a method for producing a copolymer latex which gives a coated paper excellent in printability such as rigidity and blister resistance.

[0002]

2. Description of the Related Art Conventionally, a coated paper composition having a pigment and an aqueous binder as a main component is applied to a paper to produce a coated paper having excellent printability. The copolymer latex is used as a main binder of a paper coating composition because of its excellent adhesive strength.

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

Also, the production of coated paper itself has been accelerated, and the coating operability is improved, especially the roll soiling property which is the main obstacle is improved, that is, the tackiness of the copolymer latex is reduced (anti-stickiness). ) Is also strongly demanded.

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 often conflict with each other, and it is very difficult to achieve a well-balanced and high level of all properties.

For example, a method of increasing the amount of the conjugated diene-based monomer to lower the glass transition point of the copolymer has been tried for the purpose of improving the adhesive strength, but in this method, the water resistance, the rigidity and the tackiness are reduced. The deterioration of the preventive property is remarkable.
On the contrary, when the glass transition point is increased, the water resistance and the rigidity are good, but the adhesive strength and the printing gloss are significantly lowered.
Further, in the method of using a large amount of a monomer having a functional group,
Although the adhesive strength is improved, the viscosity of the latex becomes abnormally high, so that the workability is significantly reduced and the production cost of the copolymer latex is increased.

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 in view of the above technical problems, and it significantly improves the surface strength of coated paper, and also has blister resistance, water resistance, rigidity,
Suitable for paper coating, which has excellent ink drying properties and printing gloss, and has improved stickiness prevention properties and coating operability.
It is an object of the present invention to provide a method for producing a copolymer latex which is particularly suitable for coating high-speed offset printing paper.

[0009]

That is, the present invention is
(A) 35-95% by weight of aliphatic conjugated diene-based monomer,
(B) 5 to 50% by weight of vinyl cyanide monomer, (c) 0 to 2% by weight of ethylenically unsaturated carboxylic acid monomer, and (d) monomers (a), (b) and (c). ) Other vinyl-based monomer copolymerizable with 0 to 60% by weight (provided that (a)
(A) Aliphatic conjugation in the presence of 5 to 90 parts by weight of a copolymer (A) obtained by polymerizing a monomer consisting of + (b) + (c) + (d) = 100% by weight). Diene monomer 10-6
0% by weight, (c) 0.5 to 30% by weight of an ethylenically unsaturated carboxylic acid monomer, and (e) another monomer 10 which is copolymerizable with the monomers (a) and (c). 89.5% by weight
(However, 10 to 95 parts by weight of the monomer (B) consisting of (a) + (c) + (e) = 100% by weight (however, (A)
+ (B) = 100 parts by weight) is polymerized.

In the method for producing a copolymer latex of the present invention, the copolymer latex obtained has a copolymer having at least two glass transition points, and the highest glass transition point and the lowest glass transition point. It is preferable that the difference between and is 5 ° C or more.

Further, in these copolymer latex production methods, the copolymer (A) has a glass transition point in the range of 0 ° C. or lower, and the copolymer of the monomer (B) is The glass transition point is preferably higher than that of the copolymer (A) by 5 ° C. or more.

This copolymer latex has a different phase structure in which a copolymer having a low glass transition point and a copolymer having a high glass transition point are present in the same latex particle, so that the desired performance is obtained. can get. 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 a shocking deformation with an extremely large deformation speed in high-speed printing. Therefore, it has high adhesive strength. Further, since this copolymer latex also has a polymer having a high glass transition point in the same latex particle, other physical properties such as water resistance and rigidity can be maintained at a high level, and the stickiness prevention property is obtained. It has an improved coating runnability.

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

The copolymer (A) comprises (a) 35 to 95% by weight of an aliphatic conjugated diene monomer, (b) 5 to 50% by weight of a vinyl cyanide monomer, and (c) an ethylenically unsaturated monomer. 0 to 2% by weight of a carboxylic acid monomer, and (d) 0 to 60% by weight of another vinyl-based monomer copolymerizable therewith (however,
It is obtained by polymerizing a monomer consisting of (a) + (b) + (c) + (d) = 100% by weight.

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

The aliphatic conjugated diene-based monomer (a) is an essential component for imparting appropriate flexibility and elongation to the resulting polymer and impact resistance, and the ratio of its use is 35. ˜95 wt%, preferably 40-90 wt%. When the amount of the component (a) is less than 35% by weight, the copolymer becomes too hard and the adhesive strength is not improved. (A) component is 9
If it exceeds 5% by weight, the polymerization rate is extremely reduced and the productivity is reduced.

Examples of the vinyl cyanide monomer (b) include acrylonitrile and methacrylonitrile.
These may be used alone or in combination of two or more.

The vinyl cyanide monomer (b) imparts a suitable oil resistance to the resulting copolymer, and its proportion is 5 to 50% by weight, preferably 10 to 45% by weight. . If the amount of the component (b) is less than 5% by weight, the printing gloss is significantly reduced, and if it exceeds 50% by weight, the copolymer becomes too hard and the adhesive strength is reduced.

(C) Ethylenically unsaturated carboxylic acid monomers include, for example, itaconic acid, acrylic acid, methacrylic acid, fumaric acid, maleic acid, and the like. Alternatively, two or more kinds can be used in combination.

The amount of the (c) ethylenically unsaturated carboxylic acid monomer used is 0 to 2% by weight, preferably 0 to 1% by weight. If 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 other vinyl-based monomers copolymerizable with (d) monomers (a), (b) and (c) include aromatic vinyl monomers, alkyl (meth) acrylates, Examples thereof include vinyl acetate and acrylamide monomers.
Among these, examples of the aromatic vinyl monomer include styrene, α-methylstyrene, p-methylstyrene, vinyltoluene and chlorostyrene, and styrene is particularly preferable.

As the alkyl (meth) acrylate,
Methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth)
Acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, benzyl (meth)
Examples thereof include acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, isobornyl (meth) acrylate, and 2-cyanoethyl (meth) acrylate. Of these, methylmethacrylate is particularly preferable.

Further, as the acrylamide monomer,
Acrylamide, methacrylamide, N-methylol acrylamide, N, N-dimethyl acrylamide, N,
N-dimethylaminopropyl (meth) acrylamide etc. are mentioned.

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

(D) The other copolymerizable vinyl monomer is
The copolymer is mainly used to give an appropriate glass transition point according to the purpose, and its use ratio is 0.
-60% by weight, preferably 0-50% by weight.
When the amount of the component (d) exceeds 60% by weight, the copolymer becomes too hard and the adhesive strength becomes poor.

The glass transition point of the copolymer (A) is
The temperature is preferably 0 ° C or lower, more preferably -5 ° C or lower, and further preferably -10 to -60 ° C. If the glass transition point is higher than 0 ° C, the copolymer becomes hard and sufficient adhesive strength cannot be obtained.

Further, the copolymer latex of the present invention is
It is desirable that the molecular weight of the copolymer (A) is high, and preferably, the weight average molecular weight in terms of polyethylene dissolved in tetrahydrofuran is 100,000 or more, more preferably 200,000 or more. When this molecular weight is less than 100,000, the adhesive strength and the stickiness preventive property are poor.

The proportion of the copolymer (A) used is 5 to 90 parts by weight, preferably 10 to 8 parts by weight, based on the total copolymer.
0 parts by weight. When the proportion of the copolymer (A) used is less than 5 parts by weight, the impact resistance is insufficient and the adhesive strength is poor. On the other hand, when the usage ratio exceeds 90 parts by weight, the outer layer portion having a relatively high glass transition point becomes too small, and the rigidity and the stickiness preventing property are extremely lowered.

The monomer (B) of the present invention comprises (a) 10 to 60% by weight of an aliphatic conjugated diene monomer and (c) 0.5 to 30% by weight of an ethylenically unsaturated carboxylic acid monomer. , And (e) Other monomers 10 to 89.5 copolymerizable with them.
% (However, (a) + (c) + (e) = 100% by weight).

The (a) aliphatic conjugated diene monomer and (c) ethylenically unsaturated carboxylic acid used for the monomer (B) are the same as those used for the copolymer (A). Can be used.

In the monomer (B), the aliphatic conjugated diene monomer (a) is an essential component for imparting appropriate flexibility and elongation to the resulting copolymer, and its proportion is 1
It is 0 to 60% by weight, preferably 15 to 50% 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. When the amount of the component (a) exceeds 60% by weight, the water resistance strength and the stickiness prevention property are extremely deteriorated.

The amount of the (c) ethylenically unsaturated carboxylic acid monomer used is 0.5 to 30% by weight, preferably 2 to 10% by weight. When the amount of the component (c) is less than 0.5% by weight, the stability of the latex at the time of polymerization is poor, coagulation is likely to occur, and the latex obtained is inferior in mechanical and chemical stability.
On the other hand, if the content of the component (c) exceeds 30% by weight, the viscosity of the latex obtained becomes too high, and its handling becomes difficult, the workability deteriorates, and it becomes impractical.

Further, (e) monomers (a) and (c)
Other monomers copolymerizable with are aromatic vinyl monomers, alkyl (meth) acrylates, vinyl cyanide monomers, vinyl acetate, and (alkylmeth) acrylamide-based monomers.

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,
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, dimethylamino Examples thereof include ethyl (meth) acrylate and diethylaminoethyl (meth) acrylate. Of these, methyl methacrylate is particularly preferable.

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

Further, as the (alkylmeth) acrylamide type monomer, acrylamide, methacrylamide,
N-methylolacrylamide, N, N-dimethylacrylamide, N, N-dimethylaminopropyl (meth)
Examples include acrylamide.

These monomers of component (e) can be used alone or in combination of two or more.

The component (e) is mainly used for imparting appropriate hardness and adhesiveness to the copolymer, and the amount thereof is 10-89.5% by weight, preferably 30-8.
It is 3% by weight. When the amount of the component (e) used is less than 10% by weight, the copolymer becomes too soft and the stickiness preventing property is
On the other hand, when the component (e) exceeds 89.5% by weight, it becomes too hard and the adhesive strength is poor.

Further, the glass transition point of the copolymer obtained by polymerizing the monomer (B) is preferably higher than that of the copolymer (A) by 5 ° C. or more, and the difference between the glass transition points is more preferable. Is 10 to 150 ° C., more preferably 30 to 100
℃. When the difference in glass transition point is less than 5 ° C, a large difference from that of a uniform structure is not exhibited.

The amount of the monomer (B) used is 10 to 95 parts by weight, preferably 20 to 90 parts by weight, more preferably 30 to 80 parts by weight, based on the whole copolymer. If the amount used is less than 10 parts by weight, the outer layer will be relatively small and the rigidity and anti-stickiness will be poor. When the amount used exceeds 95 parts by weight, the amount of the copolymer (A) having a relatively low glass transition point decreases, resulting in poor adhesive strength.

The particle size of the copolymer latex of the present invention is
Usually 50 to 350 nm, preferably 70 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.

As the emulsifier, an anionic surfactant, a nonionic surfactant, an amphoteric surfactant or 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.

As the amphoteric surfactant, a carboxylate, a sulfate, a sulfonate, and a phosphate are used as the anion moiety, and an amine salt is used as the cation moiety.
Those having a class ammonium salt, specifically, lauryl betaine, betaines such as stearyl betaine, lauryl-β-alanine, stearyl-β-alanine, lauryl di (aminoethyl) glycine, octyldi (aminoethyl) glycine, Amino acid type and the like 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.

Examples of the molecular weight modifier 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. , 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 (A) is previously polymerized in another polymerization system and a predetermined amount thereof is added, and then the monomer (B) is added to perform polymerization, or both are prepared in at least two stages in the same polymerization container. A method of polymerizing in multiple stages is adopted.

As a method for polymerizing the copolymer (A),
A method in which the entire amount of the monomer mixture is charged and polymerized, a part of the monomer mixture is polymerized, and then the rest is continuously or intermittently added for polymerization, or the monomer mixture is polymerized. A method of continuously adding and polymerizing from the beginning can be adopted. In addition, as a method for polymerizing the monomer (B), a method of charging the entire monomer mixture in a batch in the presence of a predetermined amount of the copolymer (A) or continuously polymerizing the monomer mixture. It is possible to adopt a method such as adding to the above and polymerizing.

The polymerization temperature is preferably 5 to 80 ° C., more preferably 5 to 70 when polymerizing the copolymer (A).
℃, when polymerizing the monomer (B) is preferably 20-8
It is 0 ° C, more preferably 30 to 70 ° C. The polymerization time is usually 10 to 30 hours.

The paper coating composition in which the copolymer latex of the present invention is used comprises an inorganic or organic pigment, the above-mentioned copolymer latex and, if necessary, another binder.
Used in combination with various auxiliaries. The blending amount of the above-mentioned copolymer latex is usually 1 to 30 parts by weight (as a solid content) of the copolymer latex, preferably 3 to 25 parts by weight, based on 100 parts by weight of the pigment. When the amount of the copolymer latex is less than 1 part by weight, the adhesive strength is remarkably reduced, while 30
If the amount is more than parts by weight, the ink drying property is significantly deteriorated.

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

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

Further, in the paper coating composition, various commonly used compounding agents such as water resistance improvers, pigment dispersants, viscosity modifiers, color pigments, viscosity modifiers,
A fluorescent dye and a pH adjusting agent can be optionally mixed.

The copolymer latex of the present invention is preferably used for a paper coating composition for an offset sheet-fed printing press and an offset rotary printing press, but in addition, various printing such as letterpress printing and gravure printing. It can also be used as a paper and a coating agent for paper.

[0059]

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 5) 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 70% or more. Then the second
The components in the second step were 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, latex particle size and toluene insoluble content of the obtained copolymer latex were determined by the following methods. The results are shown in Table 2.

A. Glass transition point The obtained copolymer latex was vacuum dried at 100 ° C. for 20 hours to form a film. Using a differential scanning calorimeter (DSC: manufactured by DuPont), this dried film was subjected to A
According to the STM method, it was measured at a temperature rising rate of 20 ° C./min.

In the copolymer latexes obtained in Examples 1 to 5, 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.

C. Toluene-insoluble matter The toluene-insoluble matter of the copolymer latex was measured as follows. After the copolymer latex was adjusted to pH 8.0, it was coagulated with isopropanol and the coagulated product was washed,
After drying, a predetermined amount (about 0.03 g) of the sample is immersed in a predetermined amount (100 ml) of toluene for 20 hours. Then, the mixture is filtered through a 120-mesh wire net, and the weight% of the total solid content of the resulting residual solid content is determined.

[0066]

[Table 1]

[0067]

[Table 2]

(Preparation of Composition for Paper Coating) Using the copolymer latexes produced in Examples 1 to 5, a paper coating composition for offset sheet-fed printing was prepared according to the following formulation.

Compounded 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 Total solid content 60 Add an appropriate amount so that the coating amount is 1% on one side of the base paper to be coated.
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 on a scale of 5. 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 After the surface of the coated paper was moistened with a water absorbing roll using an RI printing machine, the degree of picking when printed with the RI printing machine was judged with the naked eye 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 an 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 (manufactured by Kumagai Riki Kogyo Co., Ltd.) according to JIS P8143.

5) Anti-Stickiness Latex was placed on a polyethylene terephthalate film in No. Apply with 18 rods, 120 ℃ for 30 seconds,
Allow to dry and form a film. This film and Kuroshisa paper are combined, and the line pressure is 200 kg using a bench super calendar.
/ Cm, the temperature of 70 ℃ under pressure. Both of them are peeled off, and the degree of transfer of Kurora sandpaper to latex is visually evaluated on a scale of 5 levels. 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 5 are paper coating compositions 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 printing gloss, rigidity and anti-stickiness was obtained.

Examples 6 to 8 (1) Production of Copolymer (A) (Core Layer) 150 parts of water and 2 parts of sodium dodecylbenzenesulfonate 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 70%, N, N′-diethylhydroxylamine 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 120 parts of the latex of the copolymer (A) obtained in (1) and having the solid content prepared (30 parts as solid content), 60 parts of water
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 copolymer latexes obtained are from Example 1
It was confirmed that two glass transition points were present by using a differential scanning calorimeter in the same manner as in 5. Further, the particle size and the toluene insoluble content were determined. The results are shown in Table 5.

[0079]

[Table 3]

[0080]

[Table 4]

[0081]

[Table 5]

Using the copolymer latexes produced in Examples 6-8, coating compositions for offset sheet-fed printing were prepared in the same manner as in Examples 1-5, and the physical properties of the coated papers were evaluated. . The results are shown in Table 5. The paper coating compositions for offset sheet-fed printing obtained in Examples 6 to 8 were excellent in adhesive strength, printing gloss, rigidity and anti-stickiness.

Comparative Examples 1 and 2 In the same manner as in Examples 1 to 5, 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 60 ° C. for 2 hours. Then the second
The components in the second step were continuously added at 70 ° C. for 7 hours to continue the polymerization, and the reaction was continued at 75 ° C. for 6 hours after the completion of the continuous addition. Final polymerization conversion rate is 98-9
It was 9%.

The particle diameter, toluene insoluble content and glass transition point of the obtained copolymer latex were measured in Examples 1-5.
I went in the same way. Only one glass transition point was observed in each of the copolymers. The results are shown in Table 7.

Using the copolymer latexes produced in Comparative Examples 1 and 2, the physical properties of coated paper were evaluated in the same manner as in Examples 1-5. The results are shown in Table 7. In Comparative Example 1, the dry strength is almost the same as that of Example 1, but the wet strength,
Poor rigidity, anti-stickiness and blister resistance. In Comparative Example 2, the stickiness prevention property and the rigidity are excellent, but the dry strength is poor.

[0086]

[Table 6]

[0087]

[Table 7]

(Comparative Example 3) In the same manner as in Examples 1 to 5,
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 ingredients 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 80%.
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 the reaction was continued at 75 ° C. for 6 hours after the completion of the continuous addition. The final polymerization conversion rate was 98 to 99%.

The copolymer latexes obtained were obtained from Examples 1 to 1.
It was confirmed that two glass transition points were present by using a differential scanning calorimeter in the same manner as in 5. Other properties of the copolymer latex are shown in Table 7.

Using the copolymer latex produced in Comparative Example 3, the physical properties of the coated paper were evaluated in the same manner as in Examples 1-5. The results are shown in Table 7. The copolymer of Comparative Example 3 has two glass transition points, but the amount of butadiene in the copolymer (A) is less than the range of the present invention, the glass transition point is considerably high, and the dry strength and stickiness are prevented. Both sex and rigidity are poor.

(Examples 9 to 13) 200 parts of water, 0.5 part of sodium dodecylbenzenesulfonate, 1.0 part of potassium persulfate, 0.5 part of sodium bisulfite were placed in an autoclave having a stirrer and capable of controlling temperature. Parts and the components of the first step shown in Table 8 were charged all at once and reacted at 45 ° C. for 6 hours, and it was confirmed that the polymerization conversion rate was 70% or more. Then, the second stage component was continuously added at 60 ° C. for 7 hours to continue the polymerization, and the reaction was continued at 65 ° C. for 6 hours after the completion of the continuous addition. The final polymerization conversion rate was 98 to 99%.

The copolymer latexes obtained are from Example 1
It was confirmed that two glass transition points were present by using a differential scanning calorimeter in the same manner as in 5. The results of each property are shown in Table 9.

[0093]

[Table 8]

[0094]

[Table 9]

Examples 1 to 5 except that the copolymer latexes produced in Examples 9 to 13 were used for double-sided coating.
A paper coating composition for offset rotary printing was prepared in the same manner as above, the physical properties of the coated paper were evaluated, and the blister resistance was evaluated as follows.

The blister resistance was shown as the lowest temperature at which blister occurs when the double-sided coated paper is conditioned (about 6%) and then placed in a heated oil bath.

Examples 9 to 13 are paper coating compositions for rotary offset printing using the copolymer latex within the scope of the present invention, which are the objects of the present invention, that is, excellent coating operability, In addition, the adhesive strength, the blister resistance, and the printing gloss were excellent.

(Comparative Examples 4 to 6) In the same manner as in Examples, water 2 was placed in an autoclave equipped with a stirrer and capable of controlling temperature.
00 parts, sodium dodecylbenzene sulfonate 0.5
Parts, potassium persulfate 1.0 part, sodium bisulfite 0.
5 parts and the components of the first step shown in Table 10 were charged all at once and reacted at 60 ° C. for 4 hours. Subsequently, the second stage component was continuously added at 70 ° C. for 7 hours to continue the polymerization, and 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 glass transition point and other properties of the obtained copolymer latex were measured in the same manner as in Examples 1-5. In each of the copolymers, the monomer composition, particularly the proportion of the butadiene and carboxylic acid monomers in the first stage was out of the range of the present invention, and only one glass transition point was observed. The results are shown in Table 11.

[0100]

[Table 10]

[0101]

[Table 11]

Using the copolymer latexes produced in Comparative Examples 4 to 6, the physical properties of coated paper were evaluated in the same manner as in Examples 1 to 5. The results are shown in Table 11. In Comparative Examples 4 and 5, the blister resistance is almost the same as that of the example, but the dry strength, wet strength, rigidity and anti-stickiness are inferior. In Comparative Example 6, the stickiness prevention property and the rigidity are excellent, but the dry strength and the blister resistance are inferior. Each of the comparative examples is inferior in terms of physical property balance to the examples.

[0103]

EFFECTS OF THE INVENTION According to the present invention, particles having a different phase structure are contained by seed polymerization or multi-stage polymerization of a specific monomer, and excellent adhesion strength, blister resistance, printing gloss, rigidity, and stickiness prevention are achieved. It is possible to provide a method for producing a copolymer latex for paper coating having properties such as excellent printability and coating operability.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigeru Niigae 2-11-24 Tsukiji, Chuo-ku, Tokyo Within Nippon Synthetic Rubber Co., Ltd. No. 24 within Japan Synthetic Rubber Co., Ltd.

Claims (3)

[Claims] 1. (a) 35-35 aliphatic conjugated diene-based monomer
95% by weight, (b) 5 to 50% by weight of vinyl cyanide monomer, (c) 0 to 2% by weight of ethylenically unsaturated carboxylic acid monomer, and (d) monomers (a) and (b) ) And (c)
Obtained by polymerizing a monomer composed of 0 to 60% by weight of another vinylic monomer copolymerizable with (however, (a) + (b) + (c) + (d) = 100% by weight) Copolymer (A)
In the presence of 5 to 90 parts by weight, (a) 10 to 60% by weight of the aliphatic conjugated diene monomer, (c) 0.5 to 30% by weight of the ethylenically unsaturated carboxylic acid monomer, and (e) ) Other monomers 10 to 8 copolymerizable with the monomers (a) and (c)
9.5% by weight (however, (a) + (c) + (e) = 10
Production of a copolymer latex for paper coating, which comprises polymerizing 10 to 95 parts by weight of a monomer (B) consisting of 0% by weight (however, (A) + (B) = 100 parts by weight). Method. 2. The copolymer latex according to claim 1, wherein the copolymer has at least two glass transition points, and a difference between the highest glass transition point and the lowest glass transition point is 5 ° C. or more. A method for producing a copolymer latex for paper coating, characterized in that 3. The copolymer (A) according to claim 1 or 2, wherein the glass transition point is in the range of 0 ° C. or lower, and the copolymer of the monomer (B) has a glass transition point. A method for producing a copolymer latex for paper coating, which is higher than the copolymer (A) by 5 ° C. or more.