JPH1192509A - Conjugated diene copolymer latex, its manufacture and paper coating composition therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a copolymer latex which does not leave much unreacted monomers at the end of polymerization and suitable for a paper coating compsn. having an excellent balance between adhesion strength and anti-blister property, its manufacturing method, and the above-mentioned paper coating compsn. SOLUTION: In this manufacturing method of a copolymer latex, while a monomer comprising 15-80 wt.% conjugated diene monomer, 0.5-10 wt.% ethylenic unsaturated carboxylic acid monomer, and 20-89.5 wt.% other monomer capable of copolymerizing with these monomers is emulsion polymerized, by a continuous monomer addn. method or a step-wise monomer addn. method, a polymn. inhibitor is added during monomer addn. period so that the ratio of the addn. dose of polymn. of the addn. dose of monomer is not constant but increase, all the time during the addn. of the monomer, and the polymn. conversion of the monomer is kept not higher than 75 wt.% during the monomer addn. period, and 60-75 wt.% at the end of the monomer addn. This conjugated diene copolymer latex is obtd. by this manufacturing method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a conjugated diene copolymer latex, a method for producing the same, and a paper coating composition using the same.

[0002]

2. Description of the Related Art Copolymer latex is used in various fields such as paper processing, fiber processing, paints, adhesives, and the like.
In particular, when used as a binder for paper processing or a binder for carpet backing, it is required that the adhesive strength be high and the blister resistance during heating and drying be excellent.

[0003] As a method for obtaining such a copolymer latex, conventionally, the composition and gel fraction of the copolymer in the latex have been adjusted to specific ranges. However, the range of the gel fraction for maximizing the adhesive strength of the coated paper and the range of the gel fraction for maximizing the blister resistance are different from each other. It is difficult to keep strength and blister resistance at a good level at the same time.

[0004] Recently, even in copolymers having the same amount of gel, the theory that the molecular weight of a portion soluble in a solvent affects the above balance is influential. That is, it is required to maintain the gel amount within a certain range and increase the molecular weight of the soluble component. By the way, the gel amount is usually
It is adjusted by controlling the polymerization temperature and the amount of the chain transfer agent used. However, with these means, the gel amount and the molecular weight of the soluble component are almost determined by the polymerization temperature or the amount of the chain transfer agent used, and it is difficult to control both independently.

As a method for maintaining a good balance between adhesive strength and blister resistance, Japanese Patent Application Laid-Open No. 4-41501 discloses a method in which polymerization is stopped when the polymerization conversion of a monomer is 85 to 95% by weight. A method has been proposed. In Japanese Patent Application Laid-Open No. Hei 9-12647, there is a technique disclosed in Japanese Patent Application Laid-Open No. 3-109451 using an α-methylstyrene dimer as a polymerization chain transfer agent. A method has been proposed in which the final polymerization conversion of the monomer is made to be 80 to 95% by weight in the presence of a. However, these methods are not practical because a large amount of unreacted monomer remains at the time of termination of polymerization and needs to be removed.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a paper coating composition having a good balance between adhesive strength and blister resistance without leaving a large amount of unreacted monomer when polymerization is stopped. It is an object of the present invention to provide a copolymer latex, a method for producing the same, and the above-mentioned paper coating composition.

[0007]

DISCLOSURE OF THE INVENTION The present inventors have studied diligently to produce a copolymer latex which, when used as a paper coating composition, has an excellent balance between adhesive strength and blister resistance. However, while adding the monomer continuously, the polymerization inhibitor is added by a specific method during the monomer addition period, and the polymerization conversion rate of the monomer during the monomer addition is within a certain range. It has been found that this object can be achieved by the control described above, and the present invention has been completed based on this finding.

That is, a first aspect of the present invention is that 10 to 80% by weight of a conjugated diene monomer, 0.5 to 10% by weight of an ethylenically unsaturated carboxylic acid monomer, and other monomer copolymerizable therewith. When a monomer comprising 20 to 89.5% by weight of the monomer is emulsion-polymerized by a monomer continuous addition method or a monomer division addition method, a polymerization inhibitor is added during the monomer addition period. During the monomer addition period, the ratio of the amount of the polymerization inhibitor added to the amount of the monomer added at each time point is not constant but is in an increasing direction, and the polymerization conversion rate of the monomer is determined in the monomer addition period. 75% by weight or less, 60% at the end of monomer addition
To 75% by weight.

The second aspect of the present invention relates to a copolymer latex obtained by the above-mentioned production method.

A third aspect of the present invention relates to a paper coating composition containing the copolymer latex.

The conjugated diene monomer in the present invention includes 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene and 2-chloro-1,3. -Butadiene, 1,3-pentadiene, and the like. These can be used alone or in combination of two or more.
As the conjugated diene monomer, 1,3-butadiene is particularly preferred.

The conjugated diene monomer is used for imparting appropriate elasticity and film hardness to the obtained copolymer. The amount of the conjugated diene monomer is from 10 to 80% by weight of all monomers. %, Preferably 15 to 60% by weight. 80 consumed
If the amount is more than 10% by weight, water resistance and adhesive strength tend to decrease. If the amount is less than 10% by weight, desired adhesive strength cannot be obtained.

The ethylenically unsaturated carboxylic acid monomer in the present invention includes ethylenically unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid and crotonic acid; and ethylene such as itaconic acid, maleic acid, fumaric acid and citraconic acid. Ethylenically unsaturated polycarboxylic acids; partially esterified ethylenically unsaturated polycarboxylic acids such as monobutyl fumarate, monobutyl maleate, and mono-2-hydroxypropyl maleate; anhydrides of ethylenically unsaturated polycarboxylic acids;
These can be used alone, or two or more of them can be used in combination.
These acids can also be used as alkali metal salts or ammonium salts. Of these, ethylenically unsaturated monocarboxylic acids and ethylenically unsaturated polycarboxylic acids are preferred, and itaconic acid is particularly preferred.

The amount of the ethylenically unsaturated carboxylic acid monomer used is 0.5 to 10% by weight of the total monomer, preferably 0.1 to 10% by weight.
5 to 8% by weight. If the amount is less than 0.5% by weight, the stability of the copolymer latex at the time of the polymerization reaction and after the completion of the polymerization is reduced, so that aggregates and the like are easily generated and the adhesive strength is reduced. If the content exceeds 10% by weight, the viscosity of the copolymer dispersion becomes high, and the operability is undesirably reduced.

Other monomers copolymerizable with the conjugated diene monomer and the ethylenically unsaturated carboxylic acid include an aromatic vinyl monomer; an ethylenically unsaturated carboxylic acid ester monomer; Unsaturated nitrile monomers; ethylenically unsaturated carboxylic acid amide monomers; vinyl halide monomers; carboxylic acid vinyl esters; and basic group-containing monomers. These monomers are used for imparting appropriate hardness, elasticity and water resistance to the obtained copolymer.

Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, vinyltoluene, and chlorostyrene, and styrene is particularly preferred.

The ethylenically unsaturated carboxylic acid ester monomers include methyl (meth) acrylate, (meth)
Ethyl acrylate, propyl (meth) acrylate, butyl (meth) acrylate, n-amyl (meth) acrylate, isoamyl (meth) acrylate, hexyl (meth) acrylate, ethylhexyl (meth) acrylate, (meth) ) Ethylenically unsaturated monocarboxylic acid ester monomers such as octyl acrylate, lauryl (meth) acrylate, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, glycidyl (meth) acrylate, and maleic acid Examples include ethylenically unsaturated polycarboxylic acid ester monomers such as dimethyl, dimethyl fumarate, diethyl maleate, diethyl fumarate, dimethyl itaconate, and bis (2-hydroxyethyl) maleate.

Examples of the ethylenically unsaturated nitrile monomer include ethylenically unsaturated nitrile monomers such as acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethylacrylonitrile, and the like. Particularly, acrylonitrile Is preferred.

Examples of the ethylenically unsaturated carboxylic acid amide monomer include (meth) acrylamide, N-methylol (meth) acrylamide, N-butoxymethyl (meth) acrylamide, and N, N-dimethyl (meth) acrylamide. be able to.

Examples of the vinyl halide monomer include vinyl chloride and vinylidene chloride, and examples of the vinyl carboxylate include vinyl acetate and vinyl propionate.

In addition, 2-vinylpyridine, 4-vinylpyridine, dimethylaminoethyl (meth) acrylate,
Monomers containing basic groups such as N, N-diethylaminoethyl (meth) acrylate; vinyl ether monomers such as methyl vinyl ether and allyl vinyl ether; sulfonic acid group-containing monomers such as styrene sulfonic acid and sodium sulfopropyl methacrylate In addition to monomers, crosslinkable monomers such as divinylbenzene, trimethylolpropane tri (meth) acrylate, diallyl phthalate, and ethylene glycol di (meth) acrylate can be used.

The amount of these copolymerizable monomers to be used is 20 to 89.5% by weight, preferably 32 to 84.5% by weight, based on all monomers. If the amount is less than the above range, the water resistance is inferior. If the amount is too large, the copolymer becomes too hard and the adhesive strength is undesirably reduced.

In the method for producing a copolymer latex of the present invention, a polymerization initiator or a part of a polymerization initiator and a monomer, if necessary, together with other polymerization auxiliary materials are charged into a polymerization vessel to carry out a reaction. After the initiation, polymerization is carried out by adding the monomer continuously or intermittently. Here, in the method for continuously adding monomers, it is not necessary to continuously add all the monomers, and some of the monomers (for example, some or all of the ethylenically unsaturated carboxylic acid monomers) may be used. After the addition to the reactor first, the reaction can be started and the remaining monomer can be added. However,
When a part of the monomer is added to the reactor first, the amount is desirably 1/10 or less of the total monomer. Also,
“Intermittently added” means that the monomer is added in such a manner that the amount of one division is less than one-third, preferably less than one-tenth of the total monomer. That means. The object of the present invention cannot be achieved by a polymerization method in which monomers are added all at once.

As a method of adding the monomer, it is preferable to add the monomer to the reaction system as an emulsion in which the monomer is emulsified in advance with a surfactant, but it is also possible to add the monomer separately from the surfactant. good.

The composition of the monomer to be added may be the same over the entire addition period or may be changed at any time.

For the purpose of controlling the particle size of the obtained latex, a seed latex can be used. The amount used depends on the particle size of the seed latex, but is usually 0.5 to 10 parts by weight of the seed latex (in terms of solid content) based on 100 parts by weight of the monomer used for the polymerization.

In the method for producing a copolymer latex of the present invention, the polymerization conversion must be 75% by weight or less during the monomer addition period. If it exceeds 75% by weight, the balance between the adhesive strength and the blister resistance is reduced. After at least one hour has elapsed from the start of the monomer addition, it is desirable to maintain the polymerization conversion at 30% by weight or more, preferably 40% by weight or more. If the polymerization conversion is too low, the polymerization stability will be poor. In order to keep the polymerization conversion within this range, a method of increasing the rate of addition of the monomer can be considered, but it cannot be adopted because a problem occurs in polymerization stability. The polymerization conversion at the end of the monomer addition must be 60 to 75% by weight. If it exceeds 75% by weight, the balance between the adhesive strength and the blister resistance is reduced. If the amount is less than 60% by weight, the polymerization stability is deteriorated, and fine coagulated products are easily generated.

The polymerization conversion (final polymerization conversion) at the end of the polymerization is preferably at least 90% by weight, more preferably at least 95% by weight, further preferably at least 98% by weight. If the final polymerization conversion is too low, an operation such as removal of unreacted monomers is required, and there is a problem in production.

In the present invention, in order to control the polymerization conversion during the monomer addition period, it is desirable to add a polymerization inhibitor during the monomer addition period. By using a polymerization inhibitor,
It is possible to independently control the gel amount and the soluble molecular weight of the copolymer constituting the latex. The polymerization inhibitor is
Although it may be added separately from the monomer, it is convenient for operation to add it in a mixture with the monomer. The addition of the polymerization inhibitor is preferably performed only during the monomer addition period. Even if it is added after the monomer addition period, the intended effect of the present invention cannot be obtained. In the present invention, as a polymerization inhibitor, in batch polymerization (a polymerization method in which all the monomers to be used are added all at once to a reactor), when this is added, there is almost no induction period, compared with the case where it is not added It is preferred that the polymerization conversion is reduced to 10 to 60%, preferably 20 to 50%.

Examples of the polymerization inhibitor which can be used in the present invention include quinones such as o-, m- and p-benzoquinone; nitrobenzene, o-, m- and p-
Nitro compounds such as dinitrobenzene and 2,4-dinitro-6-chlorobenzene; amines such as diphenylamine; catechol derivatives such as tert-butylcatechol; 1,1-diphenylethylene, α-methylstyrene dimer and the like. Particularly preferred is 1,1-diphenylethylene. These can be used alone or in combination of two or more.

In the method for producing a latex of the present invention, the ratio of the amount of the polymerization inhibitor added to the amount of the monomer added at each time point (the ratio of the instantaneous addition amount at each time point) over the monomer addition period. ) Must be in the increasing direction. Examples of the method of increasing the ratio in the increasing direction include a method of gradually increasing the ratio, a method of gradually increasing the ratio, a method of combining these, and the like. Of course, it is also possible to keep this ratio constant for a certain period of time in the middle, and for a certain period of time after the start of monomer addition (preferably, while the polymerization conversion rate is 30% or less),
One of the embodiments is that no polymerization inhibitor is added. By adopting such a method of adding a polymerization inhibitor, it is possible to improve the polymerization stability at the start of polymerization, to control the particle size of the obtained latex easily, and to apply the obtained latex to paper coating. In the case of a composition for use, the balance between the adhesive strength and the blister resistance is improved.

The polymerization inhibitor is used in an amount of 0.01 to 10 parts by weight, preferably 0.0 to 10 parts by weight, per 100 parts by weight of the monomer.
It is 2 to 5 parts by weight.

In the method for producing a copolymer latex of the present invention, the polymerization temperature during the addition of the monomer is preferably from 70 ° C. to 90 ° C. If the temperature is lower than 70 ° C., the polymerization rate becomes slow, the productivity is poor, and the polymerization stability is not good.

In the method for producing a copolymer latex of the present invention, it is preferable to use a chain transfer agent. The use of the chain transfer agent makes it possible to improve the polymerization stability and the balance between adhesive strength and blister resistance.
Further, the addition of the chain transfer agent must be completed at the same time as or before the completion of the addition of the monomer. If the addition is continued after the end of the addition of the monomer, there arises a problem that the blocking resistance of the latex film is deteriorated and the adhesive strength is reduced. There is no particular limitation on the method of adding the chain transfer agent, and the chain transfer agent may be added by mixing with the monomer, or may be added separately from the monomer. Further, the ratio of the amount of the chain transfer agent to the amount of the monomer added at each time is not particularly limited, and may be constant or change with time.

As the chain transfer agent used in the present invention, n-
Hexyl mercaptan, n-octyl mercaptan, t
-Octyl mercaptan, n-dodecyl mercaptan,
alkyl mercaptans such as t-dodecyl mercaptan, n-stearyl mercaptan; xanthogen compounds such as dimethyl xanthogen sulfide, diethyl xanthogen disulfide, diisopropyl xanthogen disulfide; terpinolene, α-terpinene, γ-terpinene, dipentene; tetramethylthiuram disulfide; Tetraethylthiuram disulfide,
Thiuram compounds such as tetramethylthiuram monosulfide; phenol compounds such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; allyl compounds such as acrolein, methacrolein and allyl alcohol; dichloromethane and dibromo Halogenated hydrocarbon compounds such as methane, carbon tetrachloride, carbon tetrabromide, and ethylene bromide; vinyl ethers such as α-benzyloxystyrene, α-benzyloxyacrylonitrile, α-benzyloxyacrylamide; triphenylethane, pentaphenylethane Hydrocarbons such as thioglycolic acid,
Examples thereof include thiomalic acid and 2-ethylhexyl thioglycolate, with mercaptan being particularly preferred. One or more of these can be used.

The amount of the chain transfer agent used is usually 100
0.1 to 5 parts by weight, preferably 0.2 to 5 parts by weight
３3 parts by weight.

The polymerization initiator used in the emulsion polymerization of the present invention is not particularly limited, and examples thereof include hydroperoxides such as cumene hydroperoxide, diisopropylbenzene hydroperoxide, and paramenthane hydroperoxide; benzoyl peroxide, lauroyl. Peroxides such as peroxides and azo compounds such as azobisisobutyronitrile; persulfates such as potassium persulfate, sodium persulfate and ammonium persulfate; and the like can be used.
Persulfates are particularly preferred.

If necessary, a so-called redox polymerization initiator may be used in combination with a reducing agent such as sodium bisulfite, ascorbic acid and salts thereof, erythorbic acid and salts thereof, Rongalit, Fe, Fe / chelating agent, and the like. It can be used as

The amount of the polymerization initiator used in the present invention is usually from 0.1 to 5 parts by weight, preferably from 0.5 to 2 parts by weight, based on 100 parts by weight of the total monomers. To improve the content, 1 to 2 parts by weight is preferable.

As the emulsifier used in the present invention, anionic surfactants, nonionic surfactants and amphoteric surfactants can be used alone or in combination. Examples of the anionic surfactants include sulfates of higher alcohols such as sodium lauryl sulfate, alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate, and sulfonates of aliphatic carboxylic esters such as sodium dioctyl sulfosuccinate. And the like. Examples of the nonionic surfactant include an alkyl ester type, an alkyl phenyl ether type, and an alkyl ether type of polyethylene glycol. Examples of the amphoteric surfactant include those having a carboxylate, a sulfate, a sulfonate, a phosphate or a phosphate as an anion portion, and an amine salt or a quaternary ammonium salt as a cation portion. Can be mentioned. Examples thereof include lauryl betaine, stearyl betaine, cocoamidopropyl betaine and 2-undecylhydroxyethyl imidazolium betaine as alkyl betaine salts, and lauryl-β-alanine and stearyl-β as amino acid types. -Salts of alanine, lauryl di (aminoethyl) glycine, octyldi (aminoethyl) glycine, dioctyldi (aminoethyl) glycine.

Among these emulsifiers, anionic surfactants, especially alkyl benzene sulfonates, are preferably used. More specifically, sodium dodecylbenzenesulfonate and the like are particularly preferably used.

The amount of the emulsifier to be used is generally 0.05 to 2 parts by weight, preferably 0.05 to 1 part by weight, per 100 parts by weight of the total monomers. If the amount of the emulsifier exceeds 2 parts by weight, the water resistance is poor, and the foaming of the paper coating composition becomes remarkable, which causes a problem during coating. When the alkylbenzene sulfonate is used in combination with another anionic or nonionic surfactant, the proportion of the alkylbenzene sulfonate is preferably 50% by weight or more of the total emulsifier.

In the emulsion polymerization of the present invention, various polymerization regulators, pH regulators, particle size regulators, various chelating agents and the like can be used as desired.

The paper coating composition of the present invention is prepared as an aqueous dispersion of the copolymer latex of the present invention together with a pigment and, if necessary, other binders.

At this time, the copolymer latex of the present invention is preferably used in an amount of 2 to 1 based on 100 parts by weight of the pigment in terms of solid content.
00 parts by weight, more preferably 5 to 30 parts by weight, and other binders of 0 to 30 parts by weight can be used.

As the pigment, known inorganic and organic pigments can be used. As inorganic pigments, alumina, magnesium hydroxide, calcium hydroxide, magnesium carbonate,
Examples include zinc oxide, barium sulfate, silica, calcium carbonate, kaolin, calcined kaolin, diatomaceous earth, talc, titanium oxide, and aluminum hydroxide. Examples of the organic pigment include a urea-formalin resin, a styrene-methacrylic acid copolymer, a polystyrene resin, and an amino resin filler. These are used alone or in combination.

Examples of the binder include partially or completely saponified polyvinyl alcohol, carboxy-modified polyvinyl alcohol, amide-modified polyvinyl alcohol, sulfonic acid-modified polyvinyl alcohol, butyral-modified polyvinyl alcohol, other modified polyvinyl alcohol, starch and derivatives thereof. , Cellulose derivatives such as methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose and ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide / acrylate copolymer, acrylamide / acrylate / methacrylate terpolymer, styrene / Maleic anhydride copolymer alkali salt, isobutylene / maleic anhydride copolymer alkali salt, Water-soluble polymers such as acrylamide, sodium alginate, gelatin, casein, as well as vinyl chloride resins, vinyl acetate resins, vinyl acetate / acrylic acid copolymers, styrene / acrylic ester copolymers, acrylic ester resins, and polyvinyl butyral , Polyamide resin, polyurethane resin and the like.

To prepare the paper coating composition, other auxiliaries such as dispersants (sodium pyrophosphate, sodium polyacrylate, sodium hexametaphosphate), defoamers (polyglycol, fatty acid ester, Phosphate ester, silicone oil, etc.), leveling agents (funnel oil, dicyandiamide, urea, etc.), preservatives,
Waterproofing agents (formalin, hexamine, melamine resin, urea resin, glyoxal, etc.), release agents (calcium stearate, paraffin emulsion, etc.), fluorescent dyes, color water retention improvers (carboxymethylcellulose, sodium alginate, etc.), lubricants (wax And the like, and an ultraviolet absorber (benzophenone-based, triazole-based).

The preparation of the paper coating composition is carried out by a conventional method, for example, in water in which a dispersant is dissolved, together with a water-soluble polymer such as an inorganic pigment or an inorganic / organic pigment, and various additives. A method in which a combined latex is added and mixed, and used as a homogeneous dispersion can be employed.

The paper coating composition of the present invention usually contains 20 to
It is prepared as an aqueous liquid having a concentration of 80% by weight, preferably 30 to 75% by weight, and is applied to paperboard, high quality paper, medium quality paper and the like. The coating method is not particularly limited, and can be in accordance with well-known conventional techniques, for example, an air knife coater, a rod blade coater, a bill plate coater,
An off-machine coating machine or an on-machine coating machine equipped with a coater such as a roll coater is used. After application, the surface can be dried and finished with a calender ring or the like. The coating amount varies depending on the type of coated paper and is not particularly limited, but is generally in the range of 0.1 to 50 g / m ^{2 in} terms of solid content.

[0051]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples unless it exceeds the gist. In the examples, parts and% indicating percentages are based on weight unless otherwise specified. The amount of the latex used is in terms of solid content. In addition, all polymerization was performed under nitrogen atmosphere which is an inert gas. Measurement of various physical properties in the examples was based on the following methods.

Polymerization conversion rate About 1.0 g of a latex sample was accurately weighed,
After drying in an oven at 60 ° C. for 60 minutes, the residual amount was measured, and the polymerization conversion was calculated by the following calculation. Solid content = weight after drying (g) / weight before drying (g)

(Equation 1)

Average particle diameter Light scattering particle size analyzer (Model 600, manufactured by CN Wood Co., Ltd.)
The average particle diameter of the polymer latex was measured according to 0).

THF-insoluble content An appropriate amount of latex is cast on a glass plate and air-dried to form a film having a thickness of about 0.3 mm. About 0.25 g of the film was cut out, cut into about 1 mm square pieces, precisely weighed, placed in a basket made of 80 mesh stainless steel wire mesh, and this basket was immersed in a 200 cc beaker containing 100 cc of tetrahydrofuran. And allowed to stand at room temperature for 48 hours. Thereafter, the basket was taken out, left at room temperature for 12 hours, and dried in a vacuum dryer at 100 ° C. for 1 hour. After the temperature was returned to room temperature, the weight of the tetrahydrofuran-insoluble portion remaining in the basket was determined by precision weighing, and the result was shown as a percentage of the weight of the sample film.

THF soluble matter molecular weight About 0.3 g of a film made in the same manner as for measuring the THF insoluble matter was cut out, cut into small pieces of about 1 mm square, and placed in a basket made of 80 mesh stainless steel wire mesh. Put this basket in 100cc of tetrahydrofuran.
It was immersed in a 00 cc beaker and allowed to stand at room temperature for 48 hours. Thereafter, the cage was taken out, and the liquid remaining on the beaker side was used as a sample, and the weight average molecular weight in terms of polystyrene was determined using a GPC measuring device manufactured by Tosoh Corporation.

Toluene swelling degree About 0.3 g of a film prepared in the same manner as for measuring the THF-insoluble content was cut out, cut into approximately 1 mm square pieces, and placed in a basket made of 80 mesh stainless steel wire mesh. This basket was immersed in a 200 cc beaker containing 100 cc of toluene and allowed to stand at room temperature for 48 hours. afterwards,
The basket was taken out and left on filter paper for 5 minutes to remove the toluene adhering to the basket and the like, and the basket containing the sample swollen with toluene was weighed. Next, after removing toluene by drying under reduced pressure at 100 ° C. in a vacuum dryer, toluene-insoluble matter was weighed together with the basket. The degree of toluene swelling is determined by the following equation. Degree of toluene swelling (times) = (BA) / (CA) A: Weight of basket made of stainless steel wire mesh of 80 mesh B: Weight when weighed together with basket containing sample swollen with toluene C : Weight when toluene was removed by drying under reduced pressure at 100 ° C. in a vacuum dryer and toluene insolubles were weighed together with the basket.

Blister resistance generation temperature Printing ink (Webb Zett yellow, manufactured by Dainippon Ink) on both sides of the coated paper using an RI printing tester (manufactured by Meiji Seisakusho).
0.3cc was solid printed. The printed coated paper was left in an atmosphere at a temperature of 25 ° C. and a relative humidity of 65% for 24 hours to adjust the moisture content to 6%, and then cut into an appropriate size. It was charged into a silicon oil thermostat heated to a predetermined temperature of ° C., and the lowest temperature at which blisters were generated was determined. The higher the temperature, the better the blister resistance. The coated paper used in each test was coated on one or both sides so that the coating amount on one side was 11 to 12 g / m ^2, and then dried for 12 seconds with a hot air dryer at 100 ° C. I got it.

Air permeability Using a Gurley High Pressure Densometer (manufactured by Kumagaya Riki Kogyo Co., Ltd.) as a sample,
The time when the air of c permeated was measured.

Gloss of white paper The coated paper was measured by a gloss meter (GM-26D, manufactured by Murakami Color Research Laboratory) with an incident angle of 75 degrees and a reflection angle of 75 degrees.
It was measured under the condition of degree.

Printing gloss Printing ink (Newmark V indigo, manufactured by Toyo Ink Co., Ltd.)
Using a RI tester (manufactured by Akira Seisakusho) having 0.3 cm ³ adhered to a rubber roll, the coated paper was solid printed, and
After leaving in a thermo-hygrostat at 65 ° C. and a relative humidity of 65% for 24 hours, a gross meter (GM-2 manufactured by Murakami Color Research Laboratory, GM-2)
6D) was measured under the conditions of an incident angle of 75 degrees and a reflection angle of 75 degrees.

Dry strength 0.4 cm ³ of printing ink (tack value: 20) was adhered to a rubber roll of an RI tester (manufactured by Meiji Seisakusho), and
Coated paper was overprinted four times using an I tester. Peeling of the paper surface (picking state) was observed and evaluated by a five-point method. The higher the score, the higher the dry strength.

Wet strength Water was applied to the coated paper with a Molton roll, and then solid printing was performed using an RI tester (manufactured by Mei Seisakusho) having 0.4 cm ³ of a printing ink (tack value: 14) adhered to a rubber roll. . Peeling of the paper surface was evaluated by a 5-point method in the same manner as in the evaluation method of dry strength.

Example 1 In a 10-liter autoclave, 40 parts of water, 0.2 parts of sodium dodecylbenzenesulfonate, 1.5 parts of t-dodecylmercaptan, 0.4 parts of sodium hydrogen carbonate and the composition shown in Table 1 below were prepared. The resulting monomer mixture was stirred and mixed to form a monomer emulsion. In another 10 liter autoclave, 40 parts of water, seed latex (styrene / butadiene system, solid concentration 25%, particle size 30)
0 °) 1.5 parts and 0.2 parts of sodium dodecylbenzenesulfonate were added, and the mixture was heated to 70 ° C. while stirring and mixing. To this was added 0.5 parts of potassium persulfate, and immediately
The addition of the monomer emulsion was started, and the addition was continued over 5 hours. In addition, the addition of 1,1-diphenylethylene (polymerization inhibitor) was started at the same time as the addition of the monomer emulsion, and the addition was completed at the same time as the addition of the monomer emulsion. The amount of 1,1-diphenylethylene added at each time was a constant ratio such that it was 0.3 parts by weight at the start of the addition and 0.9 parts by weight at the end of the addition, based on 100 parts by weight of the monomer added simultaneously. Continuously increased. The total amount of 1,1-diphenylethylene added is 0.6 parts by weight based on 100 parts by weight of the monomer. further,
At the same time as the addition of the monomer emulsion, the addition of a 3% aqueous solution of 0.5 parts by weight of potassium persulfate was started, and the addition was completed over 3 hours. The polymerization conversion during the addition period of the monomer emulsion is up to 70%, and the polymerization conversion at the end of the addition is 7%.
1%. Subsequently, the temperature of the polymerization reaction system was maintained at 70 ° C., and when the polymerization conversion reached 90%, the temperature was raised to 85 ° C., and the reaction was continued for another 3 hours. When the polymerization conversion was 98%, the reaction was started. finished. Thereafter, unreacted monomers were removed under reduced pressure, and after cooling to room temperature, the pH of the latex was adjusted to 8.5 with sodium hydroxide to obtain Latex A.
Table 3 shows the properties of the obtained latex.

Example 2 Table 1 shows the proportions of the monomers and additives. At each time point, 1,1 based on 100 parts by weight of monomer added simultaneously
-The amount of diphenylethylene was 0.1 parts by weight from the start of addition of the monomer emulsion to 1 hour, and then 0.725 parts by weight for 4 hours until the end of addition of the monomer emulsion (1,1-diphenylethylene). The total amount of monomer 1
0.6 parts by weight * with respect to 00 parts by weight). Except that in the same manner as in Example 1, latex B was obtained. Table 3 shows the properties of the obtained latex. * 0.1 × 20% of all monomers + 0.725 × 80% of all monomers = 0.6

Example 3 The proportions of the monomers and additives are shown in Table 1. Latex C was prepared in the same manner as in Example 1 except that α-methylstyrene dimer was used in place of 1,1-diphenylethylene.
I got Table 1 shows the properties of the obtained latex.

Comparative Example 1 Table 2 shows the proportions of the monomers and additives. At each time point, 1,1 based on 100 parts by weight of monomer added simultaneously
-The amount of diphenylethylene was always 0.6 parts by weight from the start of monomer emulsion addition to the end of monomer emulsion addition (total amount of 1,1-diphenylethylene added to 100 parts by weight of monomer) Latex D was obtained in the same manner as in Example 1 except for the above. Table 4 shows the properties of the obtained latex.

Comparative Example 2 Table 2 shows the proportions of the monomers and additives. Latex E was obtained in the same manner as in Example 1, except that the polymerization inhibitor was not used and the amount of t-dodecyl mercaptan was 2.3 parts by weight. Table 4 shows the properties of the obtained latex.

Comparative Example 3 Table 2 shows the proportions of the monomers and additives. At each time point, 1,1 based on 100 parts by weight of monomer added simultaneously
-The amount of diphenylethylene was continuously increased at a constant ratio so as to be 0 parts by weight at the start of addition of the monomer emulsion and 0.6 parts by weight at the end of addition of the monomer emulsion (total amount of 1,1-diphenylethylene). The amount of the monomer 1
0.3 parts by weight with respect to 00 parts by weight. ), Latex F was obtained in the same manner as in Example 1, except that the amount of t-dodecyl mercaptan was changed to 1.9 parts by weight. Table 4 shows the properties of the obtained latex.

[0069]

[Table 1]

[0070]

[Table 2]

[0071]

[Table 3]

[0072]

[Table 4]

[0073]

[Table 5]

Examples 4 to 6 and Comparative Examples 4 to 6 Paper coating compositions were prepared according to the formulations shown in the following table.

[Table 6] * 1: Ultra white 90 manufactured by Engelhard Co., Ltd. * 2: Ultracoat manufactured by Engelhard Co., Ltd. * 3: Carbital 90 manufactured by ECC * 4: Alon T-40 manufactured by Toagosei * 5: Nippon Shokuhin Processing Co., Ltd. , Phosphated starch (MS-4600)

[0075]

[Table 7] * 1: Ultra white 90 manufactured by Engelhard Co., Ltd. * 2: Ultracoat manufactured by Engelhard Co., Ltd. * 3: Carbital 90 manufactured by ECC * 4: Alon T-40 manufactured by Toagosei * 5: Nippon Shokuhin Processing Co., Ltd. , Phosphated starch (MS-4600)

The specific preparation methods of Examples 4 to 6 and Comparative Examples 4 to 6 are as follows. That is, after mixing the above components, the solid content was adjusted to be 58%. This composition was applied on a base paper for coating using a wire bar so that the coating amount was 11 g / m ^{2 on} one side, and immediately after coating, the composition was dried with a hot air drier at 120 ° C. for 10 seconds. . After the obtained coated paper was conditioned overnight in a constant temperature and humidity room at 20 ° C. and a relative humidity of 65%, the coated paper was heated at 40 ° C. and a linear pressure of 100 kg.
The supercalender treatment was performed twice under the condition of / cm, and then the following tests were performed. In addition, each test was performed five times, and the results were averaged. The results are shown in Tables 8 and 9.

[0077]

[Table 8]

[0078]

[Table 9]

Hereinafter, preferred embodiments of the present invention will be listed. (1) 10 to 80% by weight of a conjugated diene monomer, 0.5 to 10% by weight of an ethylenically unsaturated carboxylic acid monomer and 20 to 89.5% by weight of another monomer copolymerizable therewith
In the emulsion polymerization of a monomer consisting of a monomer continuous addition method or a monomer division addition method, a polymerization inhibitor is added during the monomer addition period, and the polymerization inhibitor is added during the monomer addition period. The ratio of the amount of the polymerization inhibitor added to the amount of the monomer added at each time point is not constant, and the polymerization conversion of the monomer is 75% by weight or less during the monomer addition period, and at the end of the monomer addition. A method for producing a copolymer latex, comprising 60 to 75% by weight. (2) The method of (1), wherein the method of adding the polymerization inhibitor gradually increases the ratio of the amount of the polymerization inhibitor added to the amount of the monomer added at each time during the addition of the monomer. A method for producing a combined latex. (3) The method of the above (1), wherein the method of adding the polymerization inhibitor is to gradually increase the ratio of the amount of the polymerization inhibitor to the amount of the monomer added at each time during the addition of the monomer. A method for producing a polymer latex. (4) The method for producing a copolymer latex according to any one of (1) to (3), wherein the polymerization inhibitor is not added for a certain period of time after the start of the monomer addition. (5) After the start of the monomer addition, the polymerization inhibitor is not added until the polymerization conversion rate becomes 30%.
(4) The method for producing a copolymer latex. (6) The method for producing a copolymer latex of (1) to (5), wherein the polymerization retarder is 1,1-diphenylethylene. (7) The above (1) in which a polymerization retarder and a chain transfer agent are used in combination.
(6) The method for producing a copolymer latex according to (6). (8) The method for producing a copolymer latex according to (1) to (7), wherein the addition of the chain transfer agent is completed at the same time as or before the completion of the monomer addition. (9) The method for producing a copolymer latex according to the above (1) to (8), wherein the polymerization temperature during the addition of the monomer is 70 ° C to 90 ° C. (10) The method for producing a copolymer latex according to the above (1) to (9), wherein a ratio of the conjugated diene-based monomer to be used is 15 to 65% by weight of all monomers. (11) The method for producing a copolymer latex according to the above (1) to (10), wherein the ratio of the ethylenically unsaturated carboxylic acid used is 0.5 to 8% by weight of all monomers. (12) The method for producing a copolymer latex according to (1) to (11), wherein the ethylenically unsaturated carboxylic acid is itaconic acid.

[0080]

According to the present invention, when used in a paper coating composition,
A copolymer latex exhibiting extremely excellent performance in a balance between the adhesive strength and the blister resistance and a method for producing the same can be provided. Further, according to the present invention, it was possible to provide a paper coating composition having an extremely excellent balance between adhesive strength and blister resistance.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI // (C08F 212/08 236: 04 220: 14 220: 44 220: 06 222: 02 220: 56)

Claims (3)

[Claims] 1. A conjugated diene monomer in an amount of 10 to 80% by weight,
0.5 to 10% by weight of ethylenically unsaturated carboxylic acid monomer
And other monomers copolymerizable therewith.
When emulsion-polymerizing a monomer consisting of 5% by weight by a monomer continuous addition method or a monomer division addition method, a polymerization inhibitor is added during the monomer addition period. The ratio of the amount of the polymerization inhibitor added to the amount of the monomer added at each point in time is not constant and is in an increasing direction, and the polymerization conversion of the monomer is 75% by weight or less during the monomer addition period. And a method for producing a copolymer latex, wherein the content of the monomer latex is 60 to 75% by weight. 2. A copolymer latex produced by the production method according to claim 1. 3. A paper coating composition comprising the copolymer latex according to claim 2.