JPH11279336A - Copolymer latex - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a copolymer latex useful as a binder for paper coating compositions, which improves the surface strength of the coated paper, has a high water resistance, ink drying property and print gloss, has a good coating workability with an improved sticking inhibiting property and yields a coated paper which exerts the above-mentioned high printability at a wide range of printing speed. SOLUTION: The latex is obtained by emulsion-polymerizing a monomer comprising (a) from 20 to 80 wt.% aliphatic conjugated diene monomer, (b) from 0.1 to 10 wt.% ethylene unsaturated carboxylic acid monomer and (c) from 10 to 79.9 wt.% other monomers copolymerizable with monomer (a) and monomer (b). This emulsion polymerization is carried out in the presence of diphenyl ethylene and/or nuclear substitution product thereof. The copolymer has at least one glass transition temperature within the range of from -100 to 60 deg.C, and the difference ΔT between the lowest temperature T1 and the highest temperature T2 within the transition area in the thermogram obtained using the differential scanning calorimeter is 30 deg.C or more preferably 35 deg.C or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copolymer latex, and more particularly, to a coating latex having excellent coating operability and excellent printability such as print gloss, surface smoothness and surface strength.
The present invention also relates to a copolymer latex useful as a binder for a paper coating composition capable of obtaining a coated paper having the above excellent printability over a wide printing speed range.

[0002]

BACKGROUND ART Conventionally, a paper coating composition mainly composed of a pigment and an aqueous binder has been applied to paper to produce a coated paper having excellent printability. Copolymer latex is used as a main binder in paper coating compositions due to its excellent adhesive strength.

In recent years, as printing has become more sophisticated and faster,
The performance required for coated paper has also become severe, and improvements in surface strength, water resistance, ink transfer properties, print gloss, and the like have come to be required. At the same time, in recent years, there has been an increasing demand for reducing the amount of binder for the purpose of cost reduction. For this reason, there has been a demand for a binder exhibiting sufficient surface strength even with a smaller amount of addition.

[0004] Further, with the development of the technology for increasing the printing speed, the range of the required printing speed has been widened. Since the applicable printing speed range of conventional copolymer latex is narrow, it is necessary to individually select a copolymer latex suitable for the printing speed according to the printing speed. It is a heavy burden on the surface. For this reason, there is a demand for a copolymer latex applicable to a wide range of printing speeds.

[0005] Furthermore, the production speed of coated paper itself has been increased, and the coating operability has been improved, and in particular, the backing roll stainability, which is a major obstacle, has been reduced, ie, the tackiness of the copolymer latex has been reduced (prevention of stickiness). Sex) is also required.

[0006] Copolymer latexes are required to have the above properties, especially improved surface strength. For this purpose, for example, methods such as adjusting the gel content of the copolymer and adjusting the copolymer composition are required. A method has been proposed. However, the surface strength and other properties often conflict with each other, and it is very difficult to balance all the properties to a high level.

For example, a method of increasing the amount of a conjugated diene monomer to lower the glass transition temperature of a copolymer has been attempted for the purpose of improving the adhesive strength. However, this method has a problem of water resistance and non-stickiness. Is remarkably deteriorated. Conversely, when the glass transition temperature is increased, the water resistance is good, but the adhesive strength and print gloss are significantly reduced. In the method using a large amount of a monomer having a functional group, the adhesive strength is improved, but the viscosity of the latex is abnormally high, so that the workability is significantly reduced, and the production cost of the copolymer latex is high. Become.

As described above, none of these methods can satisfy the requirements for all the characteristics even if the improvement of any of the characteristics is achieved, and satisfy the increasingly severe requirements in printing. Is not possible at present.

[0009]

SUMMARY OF THE INVENTION The present invention has been made under the above-mentioned technical background, and it is an object of the present invention to greatly improve the surface strength of coated paper, water resistance, and ink drying. Paper coating composition that is excellent in coating properties, printing gloss, and has improved tackiness and excellent coating operability, and can obtain coated paper having the above-mentioned excellent printability over a wide range of printing speeds. To provide a copolymer latex useful as a binder for a product.

[0010]

The copolymer latex of the present invention comprises (a) 20 to 80% by weight of an aliphatic conjugated diene monomer and (b) 0.1% of an ethylenically unsaturated carboxylic acid monomer.
And (c) another monomer copolymerizable with the monomer (a) and the monomer (b).
Is obtained by emulsion polymerization of a monomer consisting of: the copolymer has at least one glass transition temperature in the range of -100 to 60 ° C, and the copolymer has a differential scanning calorimeter obtained by a differential scanning calorimeter. In the calorific value curve, the minimum temperature T1 of the transition region
ΔT between the temperature and the maximum temperature T2 is 30 ° C. or more. Less than,
This copolymer latex is referred to as copolymer latex (A).

When there are a plurality of transition regions, T1 indicates the lowest temperature in the lowest transition region and T2 indicates the highest temperature in the highest transition region.

In the present invention, the copolymer latex (A) of the present invention is used, for example, in a paper coating composition because the difference ΔT is 30 ° C. or more in the differential calorimetric curve of the copolymer. In some cases, the printability described above can be maintained at a high level over a wide range of printing speeds, and as a result,
A coated paper applicable to a wide printing speed range can be obtained. This coated paper has high resistance to shocking deformation at an extremely high deformation speed in high-speed printing.

Further, the copolymer of the copolymer latex (A) of the present invention may have either a single glass transition temperature or a plurality of glass transition temperatures in the transition region of the differential calorimetric curve. Good. Preferably, only one point is present, and the effect of the object of the present invention is further enhanced.

When the copolymer latex (A) of the present invention is used as a binder for a paper coating composition, it exhibits the above-described excellent printability over a wide range of printing speeds, In particular, it can be suitably used for offset printing, more preferably for sheet offset printing, and for web offset printing.

Further, the copolymer latex of the present invention comprises
(A) 20 to 80% by weight of an aliphatic conjugated diene monomer,
(B) 0.1 to 10 ethylenically unsaturated carboxylic acid monomers
% By weight, and (c) monomer (a) and monomer (b)
A monomer consisting of 10 to 79.9% by weight of another monomer copolymerizable with 2 to 100% by weight of a compound represented by the following general formula (1) per 100 parts by weight of the monomer. 98% by weight of another polymerization chain transfer agent.
The copolymer is obtained by emulsion polymerization in the presence of 1 to 20 parts by weight, and the glass transition temperature of the obtained copolymer is -100 to 6
At least one point exists in the range of 0 ° C., and the copolymer has a difference Δ between the minimum temperature T1 and the maximum temperature T2 in the transition region in the differential calorimetry curve obtained by the differential scanning calorimeter.
T is 30 ° C. or higher.

[0016]

Embedded image (In the formula, Ph represents a phenyl group, and X ¹ , X ² , X ³ and X ⁴ each independently represent a hydrogen atom, a halogen atom,
Represents an alkyl group having 1 to 4 carbon atoms, a methoxy group, a hydroxyl group, a glycidyl group, an acetyl group or an alkylmercapto group) The copolymer latex thus obtained (hereinafter referred to as “copolymer latex (B)”) ) Is a conventional polymerization chain transfer agent when the copolymer latex (B) is applied to a binder for paper coating by including the compound represented by the general formula (1) in the polymerization chain transfer agent. Are more excellent in adhesive strength and non-stickiness as compared with a copolymer latex obtained by using the same.

When there are a plurality of transition regions, T1 indicates the lowest temperature in the lowest transition region, and T2 indicates the highest temperature in the highest transition region.

In the present invention, the copolymer latex (B) of the present invention is used, for example, in a paper coating composition because the difference ΔT is 30 ° C. or more in the differential calorimetric curve of the copolymer. In some cases, the printability described above can be maintained at a high level over a wide range of printing speeds, and as a result,
A coated paper applicable to a wide printing speed range can be obtained. This coated paper has high resistance to shocking deformation at an extremely high deformation speed in high-speed printing.

Further, the copolymer of the copolymer latex (B) of the present invention may have only one glass transition temperature or a plurality of glass transition temperatures in the transition region of the differential calorimetric curve. Good. Preferably, only one point is present, and the effect of the object of the present invention is further enhanced.

The compound of the general formula (1) is preferably 1,1-diphenylethylene. By using 1,1-diphenylethylene, excellent adhesive strength and non-stickiness can be more reliably developed.

When the copolymer latex (B) of the present invention is used as a binder in a paper coating composition, it exhibits the above-described excellent printability over a wide range of printing speeds, In particular, it can be suitably used for offset printing, more preferably for sheet offset printing, and for web offset printing.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. (Copolymer Latex (A)) As the (a) aliphatic conjugated diene monomer used in the production of the copolymer latex (A) of the present invention, 1,3-butadiene, isoprene,
Examples thereof include 2-chloro-1,3-butadiene and chloroprene, and preferably 1,3-butadiene.
These (a) aliphatic conjugated diene monomers can be used alone or in combination of two or more.

The (a) aliphatic conjugated diene monomer is an essential component for imparting appropriate flexibility and elongation to the resulting polymer and imparting impact resistance. 20 to 80% by weight, preferably 30%, based on the monomer
７０70% by weight. If the amount of the component (a) is less than 20% by weight, the copolymer becomes too hard, and the adhesive strength is not improved. On the other hand, if the amount of the component (a) exceeds 80% by weight, the anti-stick property is deteriorated.

Examples of the (b) ethylenically unsaturated carboxylic acid monomer include itaconic acid, acrylic acid, methacrylic acid, fumaric acid, and maleic acid. These (b) ethylenically unsaturated carboxylic acid monomers can be used alone or in combination of two or more.

The amount of the ethylenically unsaturated carboxylic acid monomer (b) used is 0.1 to 10% by weight, preferably 0.3 to 8% by weight, more preferably 0.3 to 8% by weight, based on all monomers. Is 0.5 to 5% by weight. (B) Component is 0.1% by weight
If it is less than 1, the stability of the latex at the time of polymerization is poor, and a large amount of coagulated product is generated. On the other hand, when the component (b) exceeds 10% by weight, the viscosity of the latex increases significantly, and the workability deteriorates.

The other vinyl monomers copolymerizable with the monomer (a) and the monomer (b) (c) include aromatic vinyl compounds, alkyl (meth) acrylates and vinyl cyanide. Compounds, vinyl acetate, acrylamide compounds, N-methylolacrylamide, and the like.

Of these, examples of the aromatic vinyl compound include styrene, α-methylstyrene, p-methylstyrene, vinyltoluene, and chlorostyrene, and styrene is particularly preferred.

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, with methyl methacrylate being particularly preferred.

Examples of the vinyl cyanide compound include acrylonitrile and methacrylonitrile, and acrylonitrile is particularly preferable.

Further, as the acrylamide compound,
Acrylamide, methacrylamide, N, N-dimethylacrylamide, N, N-dimethylaminopropyl (meth) acrylamide and the like can be mentioned.

These components (c) may be used alone or in combination of two or more.

The component (c) is used mainly to give the copolymer an appropriate glass transition temperature according to the purpose, and its use ratio is 10 to 79.9% by weight, preferably 25 to 99.9% by weight. 69.5% by weight.

The copolymer latex (A) of the present invention is obtained by emulsion polymerization of the above-mentioned monomer components (a), (b) and (c), and has a glass transition temperature of -100. ~
At least one point in the range of 60 ° C, preferably -80 to 50 ° C, more preferably -70 to 50 ° C, and
The copolymer has T1 and T1 in the transition region of the differential calorimetric curve.
The difference ΔT from 2 is 30 ° C. or more, preferably 35 ° C. or more,
More preferably at least 40 ° C, particularly preferably at least 45 ° C.
120 ° C.

When the glass transition temperature exceeds 60 ° C., the adhesive strength is poor, and when the glass transition temperature is less than -100 ° C., the anti-stick property decreases.

If the difference ΔT is less than 30 ° C., it is not possible to maintain a high level of printability in a wide range of printing speeds, so that a sufficient printing speed range cannot be secured. At the same time, the surface strength and impact resistance of the coated paper are reduced, and the coated paper cannot withstand a shocking deformation at an extremely high deformation speed in high-speed printing.

In the emulsion polymerization of the monomer used in the present invention, the monomer can be produced in an aqueous medium using an emulsifier, a polymerization initiator and the like.

As the emulsifier, anionic surfactants, nonionic surfactants, amphoteric surfactants, etc. can be used alone or in combination of two or more.

Here, as the anionic surfactant,
For example, sulfates of higher alcohols, alkylbenzene sulfonates, aliphatic sulfonates, sulfates of polyethylene glycol alkyl ethers and the like can be mentioned.

As the nonionic surfactant, there can be used, for example, an alkyl ester type, an alkyl ether type, an alkyl phenyl ether type or the like of ordinary polyethylene glycol.

Examples of the amphoteric surfactant include carboxylate, sulfate, sulfonate, and phosphate as anionic portions, and amine salts and quaternary as cation portions.
Examples thereof include those having a quaternary ammonium salt, and specifically, betaines such as lauryl betaine and 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, a redox-based polymerization initiator in combination with a reducing agent, and the like can be used alone or in combination.

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

Examples of the molecular weight regulator include halogenated hydrocarbons such as chloroform and carbon tetrabromide, and mercaptans such as n-hexylmercaptan, n-octylmercaptan, n-dodecylmercaptan, t-dodecylmercaptan and thioglycolic acid. , Xanthogens such as dimethylxanthogen disulfide and diisopropylxanthogen disulfide, terpinolene, α-methylstyrene dimer, compounds of the following general formula (1) (for example, 1,1-diphenylethylene), compounds of the following general formula (1) Any of those usable in ordinary emulsion polymerization, such as a nucleus-substituted product thereof, can be used.

[0044]

Embedded image (In the formula, Ph represents a phenyl group, and X ¹ , X ² , X ³ and X ⁴ each independently represent a hydrogen atom, a halogen atom,
(C1-C4 alkyl group, methoxy group, hydroxyl group, glycidyl group, acetyl group or alkyl mercapto group is shown.) As a polymerization method, after partially polymerizing a monomer, the rest is continuously or A method of adding the monomer intermittently or a method of continuously adding the monomer from the beginning of the polymerization (polymerization type) can be used. In addition, as another method, a method of preparing a plurality of copolymer latexes having different glass transition temperatures of the copolymer in advance and mixing them to obtain the copolymer latex of the present invention (mixing type) can be mentioned. . Preferably, the former polymerization type is used.

The polymerization temperature is usually preferably from 20 to 85.
° C, more preferably 25-80 ° C. The polymerization time is
Usually 10 to 30 hours. (Copolymer latex (B)) (a) an aliphatic conjugated diene monomer, (b) an ethylenically unsaturated carboxylic acid monomer and (b) used in the production of the copolymer latex (B) of the present invention. (C) The details of the monomer (a) and the other monomer copolymerizable with the monomer (b) are the same as those of the copolymer latex (A).

The copolymer latex (B) of the present invention comprises the above-mentioned monomer (a), monomer (b) and monomer (c)
Is emulsified in the presence of 0.1 to 20 parts by weight of a polymerization chain transfer agent comprising 2 to 100% by weight of a compound represented by the following general formula (1) and 98 to 0% by weight of another polymerization chain transfer agent. Obtained by polymerization.

[0047]

Embedded image (In the formula, Ph represents a phenyl group, and X ¹ , X ² , X ³ and X ⁴ each independently represent a hydrogen atom, a halogen atom,
The compound represented by the above general formula (1) is an alkyl group having 1 to 4 carbon atoms, a methoxy group, a hydroxyl group, a glycidyl group, an acetyl group or an alkyl mercapto group. is there.
Of the compounds represented by the general formula (1), 1,1-diphenylethylene is preferable, and one or two or more of them can be used in combination.

As the other polymerization chain transfer agent used in combination with the compound represented by the general formula (1), a known polymerization chain transfer agent used in general emulsion polymerization can be used. As such a polymerization chain transfer agent, specifically, for example, octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-hexadecyl mercaptan, n-tetradecyl mercaptan, t-
Mercaptans such as tetradecyl mercaptan; xanthogen disulfides such as dimethyl xanthogen disulfide, diethyl xanthogen disulfide, diisopropyl xanthogen disulfide; thiuram disulfides such as tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide; Halogenated hydrocarbons such as ethylene; hydrocarbons such as pentaphenylethane and α-methylstyrene dimer; and acrolein, methacrolein, allyl alcohol, 2-ethylhexylthioglycolate, terpinolene, α-terpinene, γ-terpinene, And dipentene. These can be used alone or in combination of two or more. Among them, mercaptans, xanthogen disulfides, thiuram disulfides, carbon tetrachloride, α-methylstyrene dimer and the like are preferably used.

The proportion of the compound represented by the above general formula (1) in the polymerization chain transfer agent is 2 to 100% by weight, preferably 3 to 100% by weight.
-100% by weight, more preferably 5-95% by weight.

When the proportion of the compound represented by the general formula (1) is less than 2% by weight, a copolymer latex excellent in adhesive strength, blister resistance and non-stickiness cannot be obtained. Further, by using the compound represented by the general formula (1) in combination with another polymerization chain transfer agent, the reactivity during polymerization can be increased.

The amount of the polymerization chain transfer agent used is 100
0.1 to 20 parts by weight, preferably 0.2 to 20 parts by weight per part by weight
The amount is 15 parts by weight, more preferably 0.2 to 10 parts by weight, particularly preferably 0.3 to 8 parts by weight. If the amount of the polymerization chain transfer agent is less than 0.1 part by weight, the blister resistance is inferior, while if it exceeds 20 parts by weight, the adhesive strength is undesirably reduced.

The glass transition temperature of the copolymer of the copolymer latex (B) of the present invention is at least 1 in the range of -100 to 60 ° C, preferably -80 to 50 ° C, more preferably -70 to 50 ° C. There is a point, and the copolymer has a difference ΔT between T1 and T2 in the transition region of the differential calorific value curve,
The temperature is 30 ° C. or higher, preferably 35 ° C. or higher, more preferably 40 ° C. or higher, and particularly preferably 45 ° C. to 120 ° C.

When the glass transition temperature exceeds 60 ° C., the adhesive strength is poor, and when the glass transition temperature is less than -100 ° C., the non-stickiness decreases.

If the difference ΔT is less than 30 ° C., the printability cannot be maintained at a high level over a wide range of printing speeds, so that a sufficient printing speed range cannot be secured. At the same time, the surface strength and impact resistance of the coated paper are reduced, and the coated paper cannot withstand a shocking deformation at an extremely high deformation speed in high-speed printing.

In the emulsion polymerization of the monomer used in the present invention, the monomer can be produced in an aqueous medium using an emulsifier, a polymerization initiator and the like. The details of the emulsifier and the polymerization initiator are the same as those of the copolymer latex (A).

In the polymerization of the present invention, known chelating agents and inorganic electrolytes can be used.

The details of the polymerization method, polymerization temperature and polymerization time are the same as those of the copolymer latex (A). (Paper Coating Composition) Copolymer Latex of the Present Invention (A)
And a paper coating composition in which a copolymer latex (B) (hereinafter referred to as “copolymer latex”) is used, in which an inorganic or organic pigment is added to the copolymer latex, and if necessary, another binder; Various auxiliaries are compounded and used. The compounding amount of the copolymer latex is usually
Copolymer latex 1 to 30 with respect to 100 parts by weight of pigment
Parts by weight (as solids), 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 reduced. On the other hand, when the amount is more than 30 parts by weight, the ink drying property is remarkably reduced.

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

The paper coating composition comprising the copolymer latex of the present invention, particularly the paper coating composition for offset printing, is suitably used as a pigment adhesive. Also,
This paper coating composition can be used in combination with a water-soluble substance such as casein, modified casein, starch, modified starch, polyvinyl alcohol, and carboxymethyl cellulose in addition to the copolymer latex as necessary.

In the paper coating composition, various commonly used additives such as a water resistance improver, a pigment dispersant, a viscosity modifier, a coloring pigment, a fluorescent dye and a pH regulator are used. They can be arbitrarily compounded.

Further, the paper coating composition is suitably used for sheet offset printing paper and web offset printing paper, and is also used for various printing papers such as letterpress printing, gravure printing and paper coating agents. be able to.

[0062]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the present invention. In Examples, "parts" and "%" indicating percentages mean parts by weight and% by weight, respectively. (Production of copolymer latex) (Examples 1 to 6) 200 parts of water, 0.5 parts of sodium dodecylbenzenesulfonate and 1 part of sodium persulfate were charged into an autoclave equipped with a stirrer and capable of controlling the temperature. Then, the components shown in Table 1 were charged all at once,
Allowed to react for hours. Thereafter, the first and second stages shown in Table 2
The stage components were continuously added at a rate of 10 parts / hour to continue the polymerization, and 70 hours after the completion of the continuous addition for 70 hours.
The reaction was carried out at ℃. The final polymerization conversion was 98%.

With respect to the obtained copolymer latex, the glass transition temperature, the average particle diameter of the latex, the toluene insoluble content, and the difference ΔT were determined by the following methods. Table 3 shows the results.

A. Glass transition temperature The obtained copolymer latex was vacuum-dried at 100 ° C. for 20 hours to produce a film. The dried film was subjected to AS using a differential scanning calorimeter (DSC: manufactured by DuPont).
It was measured according to the TM method.

B. Average particle size of latex The average particle size of the obtained copolymer latex was measured using a Coulter submicron analyzer (model N4).
It was determined by an ordinary method.

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

D. Differential calorimetry curve Using a differential scanning calorimeter (DSC: manufactured by DuPont),
The measurement was performed according to the STM method, and the differential calorific value curve was obtained. Thus, the difference ΔT (° C.) between the minimum temperature T1 and the maximum temperature T2 in the transition region of the copolymer of each copolymer latex was determined. The differential calorific value curve of Example 1 is shown in FIG. (Examples 7 to 12) 200 parts of water, 0.5 parts of sodium dodecylbenzenesulfonate and 1 part of sodium persulfate were charged into an autoclave equipped with a stirrer and capable of controlling the temperature, and then the components shown in Table 6 were added. It was charged all at once and reacted at 60 ° C. for 1 hour. Thereafter, the first-stage and second-stage components shown in Table 7 were continuously added at a rate of 10 parts / hour to continue the polymerization.
The reaction was performed at 0 ° C. The final polymerization conversion was 98%.

With respect to the obtained copolymer latex, the glass transition temperature, the average particle diameter of the latex, the toluene insoluble content and the difference ΔT were determined in the same manner as in Example 1. Table 8 shows the results. (Examples 13 and 14) 200 parts of water, 0.5 parts of sodium dodecylbenzenesulfonate and 1 part of sodium persulfate were charged into an autoclave equipped with a stirrer and capable of controlling the temperature. Further, the second-stage component was continuously added at a rate of 10 parts / hour to continue polymerization, and further reacted at 70 ° C. for 6 hours after completion of the continuous addition.
The final polymerization conversion was 98%.

With respect to the obtained copolymer latex, the glass transition temperature, the average particle size of the latex, the toluene insoluble content and the difference ΔT were determined in the same manner as in Example 1. Table 8 shows the results. (Comparative Examples 1 to 3) 200 parts of water, 0.5 parts of sodium dodecylbenzenesulfonate and 1 part of sodium persulfate were charged into an autoclave equipped with a stirrer and capable of controlling the temperature. Eye ingredients are batched, 60
The reaction was carried out at a temperature of 1 hour. Thereafter, the second-stage components shown in Table 4 were continuously added at a rate of 10 parts / hour to continue polymerization, and further reacted at 70 ° C. for 6 hours after completion of the continuous addition. The final polymerization conversion was 98%.

With respect to the obtained copolymer latex, the glass transition temperature, the average particle diameter of the latex, the toluene insoluble content and the difference ΔT were determined in the same manner as in Example 1. Table 5 shows the results. (Comparative Examples 4 to 6) 200 parts of water, 0.5 parts of sodium dodecylbenzenesulfonate and 1 part of sodium persulfate were charged into an autoclave equipped with a stirrer and capable of controlling the temperature. Eye ingredients are batched, 60
The reaction was carried out at a temperature of 1 hour. Thereafter, the second-stage components shown in Table 9 were continuously added at a rate of 10 parts / hour to continue polymerization, and further reacted at 70 ° C. for 6 hours after completion of the continuous addition. The final polymerization conversion was 98%.

With respect to the obtained copolymer latex, the glass transition temperature, the average particle diameter of the latex, the toluene insoluble content and the difference ΔT were determined in the same manner as in Example 1. Table 10 shows the results. (Preparation of Composition for Paper Coating) Using the copolymer latexes produced in Examples 1 to 14 and Comparative Examples 1 to 6, a paper coating composition for offset printing was prepared according to the following formulation. Compounding: 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 is 60% An appropriate amount is added so that the composition for paper coating is applied onto a base paper to be coated in an amount of 1
The coating was performed with an electric blade coater (manufactured by Kumagaya Riki Kogyo Co., Ltd.) at 8.0 ± 0.5 g / m ² and dried for 15 seconds with a 150 ° C. electric hot air dryer. The resulting coated paper was left in a constant temperature / humidity bath at a temperature of 23 ° C. and a humidity of 50% for 24 hours.
Thereafter, a super calender treatment was performed four times under the conditions of a linear pressure of 100 kg / cm and a roll temperature of 50 ° C. The performance evaluation of the obtained coated paper was performed by the following method. 1) Dry pick strength The degree of picking when printed with an RI printing machine was visually judged, and evaluated on a five-point scale. The lower the picking phenomenon, the higher the score. The numerical values are shown as an average value of six measurements.

In this measurement, a method for measuring a printing speed of 1000 m / min is referred to as a method (A), and a method for measuring a printing speed of 100 m / min is referred to as a method (B). 2) Wet pick strength Using a RI printer, the surface of the coated paper was moistened with a water-absorbing roll, and then the degree of picking when printing with the RI printer was visually judged and evaluated on a five-point scale. The lower the picking phenomenon, the higher the score. The numerical values are shown as an average value of six measurements.

In this measurement, the method for measuring the printing speed at 1000 m / min is referred to as method (A), and the method for measuring the printing speed at 100 m / min is referred to as method (B). 3) Printing gloss Using an RI printing machine, the offset ink is solid-coated,
The measurement was performed at an angle of 60 degrees using a Murakami gloss meter. 4) Anti-stickiness Latex was coated on polyethylene terephthalate film with 18 rods, 30 seconds at 120 ° C,
Dry to form a film. Combine this film and Kurosa paper, and apply a linear pressure of 200 kg using a bench super calendar.
/ M, at a temperature of 70 ° C. Both are peeled off, and the degree of transfer of the black kraft paper to the latex is visually evaluated on a five-point scale. The lower the transfer, the higher the score. The numerical values are shown as an average value of six measurements.

The results evaluated by the above evaluation methods are shown in Tables 3, 5, 8 and 10.

As is clear from Table 3, the copolymer latexes of Examples 1 to 6 achieve the object of the present invention.
On the other hand, the copolymer latexes of Comparative Examples 1 to 3 have a large printing speed dependency, and the copolymer latex of Comparative Example 3 is further inferior in stickiness prevention.

As can be seen from Tables 8 and 10, the copolymer latexes of Examples 7 to 14 are superior to the copolymer latexes of Comparative Examples 4 to 6 in terms of tackiness and adhesive strength.

[0077]

[Table 1]

[0078]

[Table 2]

[0079]

[Table 3]

[0080]

[Table 4]

[0081]

[Table 5]

[0082]

[Table 6]

[0083]

[Table 7]

[0084]

[Table 8]

[0085]

[Table 9]

[0086]

[Table 10]

[Brief description of the drawings]

FIG. 1 is a diagram showing a differential calorific value curve of Example 1.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08F 220: 04 212: 32) (72) Inventor Katsuhiko Tsuruoka 2-1-2-11 Tsukiji, Chuo-ku, Tokyo Inside JSR Corporation

Claims (5)

[Claims] 1. An aliphatic conjugated diene monomer (a)
80% by weight, (b) 0.1 to 10% by weight of an ethylenically unsaturated carboxylic acid monomer, and (c) another monomer copolymerizable with the monomer (a) and the monomer (b) Body 10-79.9
It is a copolymer latex obtained by emulsion polymerization of a monomer consisting of weight%, at least one glass transition temperature of the copolymer is in the range of -100 to 60 ° C, and the copolymer is A copolymer latex, wherein a difference ΔT between a minimum temperature T1 and a maximum temperature T2 in a transition region is 30 ° C. or more in a differential calorimetry curve obtained by a differential scanning calorimeter. 2. The copolymer latex according to claim 1, wherein the copolymer latex is used as a binder of a paper coating composition. 3. An aliphatic conjugated diene monomer (a)
80% by weight, (b) 0.1 to 10% by weight of an ethylenically unsaturated carboxylic acid monomer, and (c) another monomer copolymerizable with the monomer (a) and the monomer (b) Body 10-79.9
% By weight of the monomer per 100 parts by weight of the monomer,
Emulsion polymerization was carried out in the presence of 0.1 to 20 parts by weight of a polymerization chain transfer agent comprising 2 to 100% by weight of a compound represented by the following general formula (1) and 98 to 0% by weight of another polymerization chain transfer agent. The glass transition temperature of the obtained copolymer is −100 to 60 ° C.
At least one point in the range, and the copolymer has a differential calorimetry curve obtained by a differential scanning calorimeter,
The difference ΔT between the minimum temperature T1 and the maximum temperature T2 of the transition region is 3
A copolymer latex having a temperature of 0 ° C or higher. Embedded image (In the formula, Ph represents a phenyl group, and X ¹ , X ² , X ³ and X ⁴ each independently represent a hydrogen atom, a halogen atom,
Which represents an alkyl group having 1 to 4 carbon atoms, a methoxy group, a hydroxyl group, a glycidyl group, an acetyl group or an alkyl mercapto group) 4. The copolymer latex according to claim 3, wherein the compound of the general formula (1) is 1,1-diphenylethylene. 5. The copolymer latex according to claim 3, wherein the copolymer latex is used as a binder for a paper coating composition.