JP3053034B2 - Diene copolymer latex - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aliphatic conjugated diene copolymer latex suitable for binders for paper and fiber processing and adhesives. More specifically, the present invention relates to a diene-based copolymer latex having excellent performance as a pigment binder for coated paper, particularly in the paper processing field.

[0002]

2. Description of the Related Art Conventionally, synthetic copolymer latexes have been widely used as binders for paper coating, binders for carpet back sizing, binders for bonding fibers such as nonwoven fabrics and artificial leather, and adhesives for various materials. Used.

[0003] For example, coated paper is coated on the surface of a base paper made with the aim of improving the printability of the paper and the optical characteristics such as gloss and the like, such as kaolin clay, calcium carbonate, satin white, talc, titanium oxide and the like. Pigment, a copolymer latex as a binder thereof and starch as a water retention agent or an auxiliary binder, polyvinyl alcohol, a paint having a water-soluble polymer such as carboxymethylcellulose as a main component, was applied, Conventionally, styrene-butadiene-based copolymer latex, which is obtained by emulsion polymerization of styrene and butadiene as main monomer components, so-called SB-based latex has been widely used.

In recent years, with the rapid increase in demand for magazines, brochures, advertisements, and packaging materials printed in multicolor,
Production of coated paper or coated paperboard has increased significantly.
In particular, with the speeding up of offset printing, the required level of the quality of the pigment binder in coated paper and coated paperboard has been further advanced.

For example, in general offset printing,
Surface strength of coated paper, ie, dry pick strength or wet topic strength involving fountain solution, water absorption of coated paper after fountain solution transfer and uniform and good inking property of ink (ink transferability), It is strongly desired to improve basic properties such as the drying speed of the transferred ink (ink setting property) and the gloss of the printed ink surface (print gloss).

[0006] In offset rotary printing, in addition to the above basic characteristics, the blister resistance (blister resistance) of the coated paper during heating and drying of the printing ink is also important. In addition, in the gravure printing of the intaglio printing method, it is required that the smoothness of the coated paper, particularly the dot reproducibility involving dynamic smoothness at the time of printing be excellent together with the surface strength of the coated paper. .

On the other hand, in the production of coated paper, the tendency of high-speed coating has become more remarkable, and accordingly, a backing roll, a super calender roll stain or a streak, which is a major obstacle to the coating operability. Troubles, such as scratches, occur frequently. In order to suppress such operational troubles, for example, in the case of a blade coating method, high mechanical stability and a low viscosity are provided directly under the blade at the time of high-speed coating, and non-adhesion (stickiness resistance) ) Is required.

[0008] The SB-based latex used as a pigment binder is closely related to the above-mentioned various printing aptitudes and coating operability, and many of them have a negative correlation with each other. Various studies have been made from the viewpoints of the type, composition, polymerization method, additives, and the like of monomers used to balance these properties to a high level.

For example, as a pigment binder for offset printing paper, a monomer of a specific type and composition including an ethylenically unsaturated carboxylic acid and an ethylenically unsaturated amine is emulsion-polymerized under special conditions, and a specific range of the monomer is obtained. By a paper coating composition using a copolymer latex having a gel point as a pigment binder, to prevent a decrease in the water absorption of the coated paper,
It has been proposed that a coated paper having good ink transfer properties for the second and subsequent colors during offset printing can be obtained (Japanese Patent Publication No. 59-49360).

[0010] However, the paper coating composition has improved ink transferability and wet pick strength, but has the drawback of significantly increasing the viscosity of the coating liquid and has a sufficient ink transferability. An attempt to obtain an improvement effect resulted in a decrease in dry pick strength. Further, with respect to a copolymer latex that provides a coated paper having good printing gloss, ink transferability and pick strength, a monomer mixture of a specific composition is prepared under the condition of pH 6 or more in the presence of at least one amphoteric surfactant. A method of emulsion polymerization has been proposed (JP-A-61-268709).

However, even with the copolymer latex, the drawbacks of an increase in the viscosity of the coating solution, that is, a decrease in fluidity, and a decrease in the coating operability due to a decrease in the mechanical stability of the coating solution have been solved. In addition, it has a tendency to decrease the wet topic strength and blank gloss of the coated paper, and it is hardly satisfactory.

In addition, from the viewpoint of an additive for the copolymer latex, a C 3 -C 3 having at least two amino groups is preferred.
Means for improving the ink transferability of coated paper by adding up to 30 amino compounds to a specific copolymer latex has also been proposed (JP-A-59-59996). In this case as well, a decrease in dry pick strength and a decrease in coating operability due to an increase in the viscosity of the coating liquid are caused.

Further, it has been proposed to improve the flowability of a coating solution by adding a viscosity reducing agent comprising a block polymer of propylene oxide and ethylene oxide in addition to the amino compound (Japanese Patent Application Laid-Open (JP-A) no. 60-19
No. 9998). However, although a decrease in fluidity can be suppressed to some extent, it is difficult to say that it is satisfactory because of a further decrease in pick strength.

In the case of carboxy-modified copolymer latex, emulsion polymerization is usually carried out in an acidic region having a pH of about 2 to 6. The polymerized latex is generally neutralized with an inorganic basic substance such as sodium hydroxide, potassium hydroxide, and ammonia, and is adjusted to a pH of about 4 to 11 so as to have a required dispersion stability. For example, when sodium hydroxide is used, the water resistance of the latex film is reduced, which tends to cause a decrease in the wet topic strength of the coated paper.

Further, when potassium hydroxide or ammonia is used, compared with the case where sodium hydroxide is used,
Although the wet topic strength is good, it has advantages and disadvantages such as a tendency to cause a decrease in the fluidity of the coating liquid, and is currently used with some compromise.

On the other hand, in gravure printing paper, a copolymer latex having a specific gel content and containing an unsaturated linear amine monomer and / or a quaternary salt thereof as a copolymer monomer is used as a binder. Accordingly, means for improving dot reproducibility and surface strength have been proposed (Japanese Patent Application Laid-Open No. 61-225394). However, the effect is insufficient, and the fluidity of the coating liquid is inevitably reduced. As described above, in order to simultaneously improve all required performances such as good coating operability in the manufacturing process of coated paper, optical properties of coated paper and printability to a high level, the above-described technology is used. Were not completely satisfactory.

[0017]

DISCLOSURE OF THE INVENTION The present invention overcomes the above-mentioned drawbacks of the conventional copolymer latex and has good stickiness resistance, good coating fluidity and good mechanical stability. That is, a coating liquid having excellent coating operability is provided,
And, without sacrificing the other required properties regarding the optical properties and printability of the coated paper, it has excellent wet topic strength and ink transfer property especially on offset printing paper, and excellent dot reproducibility on gravure printing paper. The purpose of the present invention is to provide a diene copolymer latex suitable as a pigment binder for coated paper having the following.

[0018]

The present inventors have conducted various studies with the aim of providing a copolymer latex having the above-mentioned properties, and as a result, have found that an amine compound having a specific structure is used as a neutralizing agent. The present inventor has found that the diene-based copolymer latex used can surprisingly achieve the above object, and based on such findings, has completed the present invention.

That is, the features of the present invention are as follows:
A diene-based copolymer latex obtained by emulsion polymerization of an aliphatic conjugated diene monomer, an ethylenically unsaturated carboxylic acid monomer and other monomers copolymerizable therewith, and at least one The pH is adjusted to 4 to 11 using an amine compound represented by the following formula (1).

Embedded image

[Where R ₁ is a hydrogen atom or a carbon atom 1
And R ₂ and R ₃ have 1 to 10 carbon atoms.
X, Y, and Z each represent hydrogen, a hydrocarbon group having 1 to 5 carbon atoms, an amino group, a hydroxyl group, a carboxyl group, a cyano group, a halogen group, or an ester group. ]

Hereinafter, the present invention will be described in detail. The diene-based copolymer of the present invention is obtained by emulsion-polymerizing an aliphatic conjugated diene monomer, an ethylenically unsaturated carboxylic acid monomer, and other monomers copolymerizable therewith.

The aliphatic conjugated diene monomer (a) is an essential component for imparting the necessary flexibility to the copolymer and increasing the adhesive strength. This amount is 20 parts by weight based on the weight of all monomers.
To 80% by weight, preferably 25 to 70% by weight. If the amount is less than 20% by weight, it is difficult to impart the necessary flexibility to the copolymer, and if it exceeds 80% by weight, the copolymer becomes too soft and the adhesive strength is undesirably reduced.

Examples of the aliphatic conjugated diene monomer include 1,3-butadiene, pentadiene, 2-methyl-1,
Preferred examples include 3-butadiene, 2-chloro-1,3-butadiene, chloroprene and the like, and these may be used alone or in combination of two or more.

Ethylenically unsaturated carboxylic acid monomer (b)
Is an essential component for improving the dispersion stability of the copolymer latex, mainly the mechanical stability and the adhesive strength. The amount used is in the range of 0.5 to 10% by weight, preferably 1 to 5% by weight based on the weight of all monomers. If the amount is less than 0.5% by weight, it becomes difficult to impart necessary dispersion stability to the copolymer latex, and sufficient adhesive strength cannot be obtained. On the other hand, if the content exceeds 10% by weight, the viscosity of the copolymer latex and the coating liquid becomes extremely high, making it difficult to handle, and the wet topic strength of the coated paper is lowered due to a decrease in the water resistance of the latex film. Absent.

Preferred examples of the ethylenically unsaturated carboxylic acid monomer include monobasic carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid and cinnamic acid; and fumaric acid, itaconic acid and maleic acid. Examples include dibasic carboxylic acids or their acid anhydrides and monoalkyl esters. These ethylenically unsaturated carboxylic acid monomers may be used alone or in combination of two or more. In particular, among these, the dibasic carboxylic acid is
High stability can be imparted to the copolymer latex,
Further, the effects of the present invention can be favorably exhibited, which is preferable.

The diene copolymer latex of the present invention comprises
In addition to the components (a) and (b), other monomers copolymerizable therewith (component (c)) must be present in an amount of 10 to 79.5% by weight. By appropriately selecting the component (c), it is possible to impart various properties to the copolymer latex.

Among the examples of (c), the most representative and effective one is an aromatic (di) vinyl monomer, followed by (meth) acrylic acid ester, vinyl cyanide, ethylenic amide and the like. It is a monomer.

Examples of the aromatic (di) vinyl monomer include styrene, α-methylstyrene, chlorostyrene, alkylstyrene, divinylbenzene and the like. Examples of the (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, and 2- (meth) acrylate.
Examples include ethylhexyl (meth) acrylate, hydroxyethyl (meth) acrylate, glycidyl (meth) acrylate, and ethylene glycol di (meth) acrylate.

Examples of the vinyl cyanide monomer include acrylonitrile and methacrylonitrile. Examples of the ethylenic amide monomer include (meth) acrylamide, N-methylol (meth) acrylamide, N-methoxymethylacrylamide, N-butoxymethylacrylamide and the like.

In addition, vinyl esters such as vinyl acetate; vinyl halides such as vinyl chloride and vinylidene chloride; aminoethyl (meth) acrylate, dimethylethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, 2-vinyl Pyridine,
Examples include ethylenic amines such as 4-vinylpyridine; and monomers such as sodium styrenesulfonate. These can be used alone or in combination of two or more depending on the purpose.

In the present invention, the following (1)
The use of the specific amine compound (d) represented by the formula is essential.

Embedded image

[Where R ₁ is a hydrogen atom or a carbon atom 1
And R ₂ and R ₃ have 1 to 10 carbon atoms.
X, Y, and Z each represent hydrogen, a hydrocarbon group having 1 to 5 carbon atoms, an amino group, a hydroxyl group, a carboxyl group, a cyano group, a halogen group, or an ester group. ]

The amount of the amine compound to be used is 0.05 to 5.0 per 100% by weight of the solid content of the copolymer latex.
%, Preferably 0.1 to 3.0% by weight. When the amount is less than 0.05% by weight, the effect of the present invention is poorly expressed, and when the amount exceeds 5% by weight, the coating solution is particularly unfavorably thickened.

Preferred examples of the effects of the present invention include 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane and 1-amino-3-aminoethyl-3,5,5-trimethylcyclohexane. , 1-amino-3-aminopropyl-3,5,5-trimethylcyclohexane, 1-amino-3-aminomethyl-3-ethyl-5,5-dimethylcyclohexane, 1-amino-3-
Aminomethyl-3-methyl-5,5-dimethylcyclohexane, 1-amino-3-aminomethyl-3-methyl-
5-methyl-5-ethylcyclohexane, 1-amino-
3-diaminomethyl-3,5,5-trimethylcyclohexane, 1-amino-3-aminomethyl-3,5-dimethyl-5-chloro-cyclohexane, 1-amino-3-
Aminomethyl-3,5-dimethyl-5-aminomethyl-
Cyclohexane, 1-amino-3-aminomethyl-3-
Methyl-5,5-diaminomethyl-cyclohexane and the like. These can be used alone or in combination of two or more depending on the purpose.

Further, other known amine compounds or
It may be used in combination with an alkali metal hydroxide such as sodium hydroxide or potassium hydroxide or a basic substance such as ammonia. The timing of adding the amine compound and the inorganic basic substance of the present invention is not particularly limited, and they may be added before, during or after the polymerization.

The diene copolymer latex of the present invention comprises
The pH is adjusted to 4 to 11, preferably 6 to 10 using these basic substances, and the dispersion is provided with required dispersion stability and used for various applications. The qualitative and quantitative determination of these amine compounds added to the diene-based copolymer latex can be easily performed by gas chromatography, liquid chromatography, or the like.

In the present invention, known chain transfer agents can be used. For example, as a chain transfer agent containing a sulfur element, alkanethiols such as t-dodecylmercaptan and n-dodecylmercaptan; thioalkyl alcohols such as mercaptoethanol and mercaptopropanol; thioalkyl alcohols such as thioglycolic acid and thiopropionic acid Carboxylic acids; alkyl thiocarboxylates such as octyl thioglycolate and octyl thiopropionate; and sulfides such as dimethyl sulfide and diethyl sulfide.
Preferred examples of the chain transfer agent containing the sulfur element include thioalkylcarboxylic acid alkyl esters.

Other examples of the chain transfer agent include α-
Examples include alkylstyrene dimers, terpineolene, dipentene, t-terpinene, and halogenated hydrocarbons such as carbon tetrachloride. The chain transfer agent is 1
Species or two or more can be used. Also, if necessary,
When used in combination with the chain transfer agent, diphenylethylene, 2,6
It is preferable to use an oil-soluble polymerization rate inhibitor such as -di-t-butyl-hydroxytoluene.

As for the method of using these chain transfer agents, any of the well-known methods can be used. That is, a batch addition method, a continuous addition method, an intermittent addition method, a concentration gradient addition method in which the addition rate is sequentially changed, and the like. Among these addition methods, a method in which a part of the chain transfer agent is continuously added even after the completion of the addition of the monomer is preferable, since the effect of the present invention is favorably exhibited.

Next, the manufacturing method will be described. The diene-based copolymer latex of the present invention is obtained by subjecting these raw materials to radical emulsion polymerization in a dispersion system comprising water, a surfactant, a monomer, a radical polymerization initiator, and if necessary, other raw materials. Is obtained as an aqueous dispersion of copolymer particles. Generally, a copolymer concentration of 4
It is in the range of 0 to 60% by weight.

The particle size of the copolymer latex can be adjusted by the use ratio of the surfactant and / or the seed latex. Generally, the higher the use ratio, the smaller the particle size of the produced copolymer latex. here,
The preferred range of the particle size is 0.05 to 1 μm, and more preferably 0.07 to 0.5 μm.

Examples of the surfactant include anionic surfactants such as fatty acid soap, rosin acid soap, alkyl sulfonate, dialkylaryl sulfonate, alkyl sulfosuccinate, polyoxyethylene alkyl sulfate, and polyoxyethylene alkylaryl sulfate. Surfactants; nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl aryl ether, polyoxyethylene sorbitan fatty acid ester, and oxyethylene-oxypropylene block copolymer;
There are cationic surfactants. Other examples of these surfactants include the Surfactant Handbook (Takahashi, Namba,
Koike, Kobayashi, edited by Kogaku Tosho Co., Ltd., 1972).

The surfactant is usually used in the form of an anionic surfactant alone or in a mixed system of anionic and nonionic surfactants, and is preferably used in a proportion of 0.05 to 2% by weight based on the monomer. .

The polymerization initiator is one that initiates addition polymerization of a monomer by radical decomposition in the presence of heat or a reducing substance, and is an aqueous or oil-soluble peroxodisulfate, peroxide, An azobis compound or the like is generally used. Examples include potassium peroxodisulfate,
There are sodium peroxodisulfate, ammonium peroxodisulfate, hydrogen peroxide, t-butyl hydroperoxide, benzoyl peroxide, 2,2-azobisisobutyronitrile, cumene hydroperoxide and the like, and “POLYMER HANDBOOK 3rd”.
Ed. (J. Brandrup, EH Immerg
out: John Willy & Sons, 198
9) ". Among these, peroxodisulfate is particularly preferable because it exerts the effects of the present invention well.

The proportion of the polymerization initiator used is usually 0.2 to 2.0% by weight based on the monomer. The polymerization temperature is generally in the range of 60 to 90 ° C. However, when it is desired to accelerate the polymerization rate or to carry out the polymerization at a lower temperature, sodium bisulfite, ascorbic acid or its salt, erythorbic acid or its salt, Rongalit A so-called redox polymerization method in which a reducing agent such as the above is used in combination with a polymerization initiator can be used.

Further, various polymerization regulators are often added as desired. For example, pH adjusters such as sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium hydrogen carbonate, sodium carbonate, disodium hydrogen phosphate, and various chelating agents such as sodium ethylenediaminetetraacetate.

Further, various additives can be added to the copolymer latex, if desired. Examples of these additives include a dispersant, a bactericide, a viscosity modifier, a water-resistant agent and other salts, and these may be added before polymerization, during polymerization, or after completion of polymerization, if necessary. You may.

When the diene copolymer latex of the present invention is used as a binder for a paper coating composition, it can be carried out in a usual manner. That is, this copolymer latex is mixed with an inorganic pigment and / or an organic pigment, a water-soluble polymer, and various additives in water in which a dispersant is dissolved to form a uniform dispersion. The coating liquid can be applied to the base paper by an ordinary method such as a blade coater or a roll coater.

[0049]

Next, the present invention will be described in more detail with reference to examples and application examples, but the present invention is not limited to these examples. (Examples and Comparative Examples) 3 parts by weight of an aqueous dispersion of seed particles having a diameter of 0.035 µm (concentration of a solid content of seeds of 30% by weight) was placed in a pressure-resistant reaction vessel equipped with a stirrer and a jacket for temperature control. 70 parts by weight, 0.2 parts by weight of sodium lauryl sulfate and 2.5 parts by weight of itaconic acid were charged, the internal temperature was raised to 80 ° C., and an oily liquid mixture comprising a monomer mixture and t-dodecyl mercaptan was added. Water 1
An aqueous solution consisting of 5 parts by weight, 1 part by weight of sodium peroxodisulfate, 0.2 part by weight of sodium hydroxide, and 0.1 part by weight of sodium lauryl sulfate was added at a constant flow rate over 4 hours and 5 hours, respectively. Then, after maintaining the temperature of 80 ° C. as it is for 1 hour to complete the polymerization reaction,
Cool. The pH of the copolymer latex was 3.5.

Next, potassium hydroxide was added as a primary neutralizing agent to adjust the copolymer latex to the pH shown in Table 1, and then unreacted monomers were removed by a usual steam stripping method. Then, the mixture was filtered with a filter cloth having a mesh of 75 μm. Further, a secondary neutralizer 1-amino-3-aminomethyl-3,5,5-trimethylcyclohexane (Huls
(Aktiengesellschaft, hereinafter simply referred to as isophorodiamine) was added in a predetermined amount shown in Table 1, and the pH was adjusted to 9 to obtain the diene copolymer latex of the present invention of A to C. On the other hand, only isophorodiamine as the secondary neutralizer was changed to dimethylamine, sodium hydroxide, potassium hydroxide and ammonia, respectively, to obtain comparative copolymer latexes of D to H.

Incidentally, all the copolymer latexes were prepared so that the solid content concentration finally became 50% by weight. Table 1 shows the details of the raw materials and the amounts used (parts by weight).

[0052]

[Table 1] (Composition of copolymer latex)

(Application Example 1) The performance of the copolymer latex prepared in each of Examples and Comparative Examples as a binder for paper coating was evaluated. Table 4 shows the results. The coating composition was formulated as shown in Table 2 and had a nonvolatile content of 64.
It was prepared with a high-speed stirrer with the amount of water to be wt%. Paint pH
Was adjusted to 9.5 with aqueous ammonia. Table 3 shows the preparation conditions of coated paper using this paint. The performance evaluation of the latex, the coating liquid and the coated paper was performed by the following method.

[0054]

[Table 2] (Composition of coating liquid)

(Note) 1) "Ultra White 90" manufactured by Engelhard Co., Ltd. 2) "Ultracoat" manufactured by Engelhard Co., Ltd. 3) "Escalon 1500" manufactured by Sankyo Flour Milling Co., Ltd. 4) "Alon T-40" manufactured by Toa Gosei Chemical Co., Ltd. 5) "MS4600" manufactured by Japan Food Processing Co., Ltd.

[0056]

[Table 3] (Coated paper preparation conditions)

(A) Stickiness resistance It is applied with 15 rods and heated at 50 ° C. for 1 hour to form a film. The film and the black rasha paper are combined and pressed under a condition of 200 kg / m and 70 ° C. using a bench super calender. This was peeled off, and the degree of transfer to the latex film of the black brush paper was visually judged by a 5-point relative evaluation method (the higher the score, the less the transfer, the better).

(B) Low shear viscosity of the coating solution The viscosity at 60 rpm was measured with a No. 4 rotor using a B-type viscometer. (C) High shear viscosity of the coating solution, using a Hercules viscometer, F Bob at 8800 rpm
Was measured. (D) Mechanical stability of coating liquid The mechanical stability of the coating liquid was measured by a Maron type tester. The test method was as follows: 100 g of paint was loaded at 30 kgw for 2 hours
The resulting aggregate was collected on a # 325 mesh under a 0-minute condition using a Malon tester, and the dry weight of the aggregate was calculated as a percentage by weight based on the solid content of the sample. The smaller the rate of occurrence of agglomerates, the better the mechanical stability.

(E) Gloss on white paper The gloss was measured at 75 ° to 75 ° using a Murakami GM-26D gloss meter. (F) Dry pick strength Using a RI printing tester, printing ink (SD Super Deluxe 50 red B; tack value 18, manufactured by Toka Pigment Co., Ltd.)
Overprinting is performed 4 times 5 times, and the picking state that has appeared on the rubber roll is backed on another backing paper, and the degree is observed.
The evaluation was performed by a 5-point relative evaluation method, and the smaller the picking phenomenon, the higher the score.

(G) Wet topic strength Using a RI printing tester, wet the coated paper surface with a water-absorbing roll, and then print ink (SD Super Deluxe 50 red B; tack value 18, manufactured by Toka Pigment Co., Ltd.) 0 .4 cc is printed once, and the picking state appearing on the rubber roll is backed up on another backing paper, and the degree is observed. The evaluation was performed by a 5-point relative evaluation method, and the smaller the picking phenomenon, the higher the score.

(H) Ink transferability After water was applied with a Molton roll using an RI printing suitability tester, solid printing was performed under conditions that did not cause paper peeling, and the ink transferability (density of the printed ink) was measured. Was visually determined. The evaluation was performed by a 5-point relative evaluation method, and the higher the ink transfer, the higher the score.

(I) Blister resistance Printing ink (WebbZett yellow, manufactured by Dainippon Ink Co., Ltd.) on both sides of the coated paper using an RI printing tester (manufactured by Meiji Seisakusho)
Print 0.3cc solid. The printed coated paper is cut into an appropriate size, the test piece is immersed in a silicone oil thermostat adjusted to a predetermined temperature, and it is observed whether or not blisters are generated. The test is performed by changing the temperature of the thermostat, and the lowest temperature at which blistering is observed is determined. The higher the temperature, the better the blister resistance.

(D) Dot Reproducibility A test piece was printed under appropriate conditions using a halftone printing plate by a gravure printing tester (manufactured by Kumagaya Riki Co., Ltd.) under the Ministry of Finance, and printing was performed. The percentage of the number of missing dots to the total number of halftone dots (dot missing ratio) was determined. The smaller the number, the better the dot reproducibility.

[0064]

[Table 4] (Physical properties of latex, coating liquid and coated paper)

As is clear from the results in Table 4, the comparative copolymer latex F using a conventionally known inorganic neutralizing agent,
Compared with G and H, it is clear that the diene copolymer latexes A, B and C of the present invention respectively are superior in stickiness resistance, mechanical stability, wet topic strength and ink transferability by several steps. It is.

In addition, the comparative copolymer latexes D and E using a conventionally known amine neutralizing agent, which has particularly excellent wet topic strength and ink transferability, as compared with the inorganic neutralizing agent, have improved stickiness resistance and mechanical stability. While no significant improvement in the mechanical stability is recognized, it is clear that the diene copolymer latexes A and C of the present invention have significantly improved these physical properties that govern the coating operability. It is. From the above, it can be seen that the copolymer latex of the present invention has a highly balanced physical property relating to coated paper properties and coating operability.

[0067]

EFFECT OF THE INVENTION The mechanical stability, stickiness and fluidity of the coating liquid relating to the coating operability are excellent, and the pick strength, ink transfer and blister resistance of the coated paper when used as a pigment binder. And the balance of dot reproducibility is improved.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-52-134660 (JP, A) JP-A-3-185055 (JP, A) JP-A-2-286737 (JP, A) JP-A-58-134 176958 (JP, A) JP-A-57-59936 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 9/00 C08K 5/17 C08L 13/00 D21H 19/56

Claims (2)

(57) [Claims] 1. A copolymer latex obtained by emulsion polymerization of an aliphatic conjugated diene monomer, an ethylenically unsaturated carboxylic acid monomer and another monomer copolymerizable therewith, and A diene-based copolymer latex, wherein the pH is adjusted to 4 to 11 using at least one amino compound represented by the following formula (1). Embedded image [However, R ₁ is a hydrogen atom or a hydrocarbon group having 1 to 5 carbon atoms, R ₂ and R ₃ are a hydrocarbon group having 1 to 10 carbon atoms, and X, Y and Z are hydrogen or carbon, respectively. It represents a hydrocarbon group of formulas 1 to 5, or an amino group, a hydroxyl group, a carboxyl group, a cyano group, a halogen group, or an ester group. ] 2. A water-dispersible paper coating composition comprising an inorganic pigment and a binder as main components, wherein the copolymer latex according to claim 1 is used as a binder component in a solid content with respect to 100 parts by weight of the inorganic pigment. A water-dispersible paper coating composition, which is used in an amount of 3 to 30 parts by weight.