JPH07258308A - Conjugated diene copolymer layer, manufacture of the same and coating composition, for paper, using the same - Google Patents

Abstract

PURPOSE:To prepare a conjugated diene copolymer latex having excellent bonding strength, water resistance, blistering resistance, wet strength and other properties by polymerizing a conjugated diene monomer and other specific monomer(s) under particular conditions. CONSTITUTION:In the first step, a monomer mixture, which contains (A) 40 to 64.5wt.% (hereinafter referred to as '%') conjugated diene monomer, (B) 35 to 59.5% hydrophobic monomer, and 0.5 to 25% hydrophilic monomer, and can provide a polymer having a glass transition temp. of below -20 deg.C, is added in an amt. of 10 to 70% based on the whole monomer to the reaction system to conduct polymerization. In the second step, a monomer mixture contg. 5 to 35% (A), 25 to 40% (B), and 25 to 70% hydrophilic monomer comprising at least one member selected from (a) an unsatd. carboxylic acid monomer, (b) a hydroxyl ester monomer, and an amide monomer (c) and other hydrophilic monomer(s) (y) (provided that, when the total amount of the monomers in the second step is presumed to be 100%, 0.5%<=a+b+c<15%) is added in an amt. of 30 to 90% based on the whole monomers to conduct polymerization.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a conjugated diene copolymer latex used for paper coating, carpet backing and various other adhesives, and a high-performance conjugated latex obtained by this method. The present invention relates to a diene copolymer latex and a coating composition for paper using the latex, more specifically, a conjugated diene excellent in coating operability and printability such as adhesive strength, water resistance, and blister resistance. -Based copolymer latex, a method for producing the same, and
The present invention relates to a coating composition for paper using the latex.

[0002]

2. Description of the Related Art Conventionally, conjugated diene-based copolymer latex has been used for paper coating, non-woven fabric, artificial leather binder,
Widely used for fiber treatment, the conjugated diene copolymer latex used for such pigment binder applications is required to have high adhesive strength, high water resistance, and high blister properties capable of withstanding dry heating. ing. Particularly in the case of paper use, the conjugated diene copolymer latex is used alone as an auxiliary binder such as starch, casein and polyvinyl alcohol, together with various clays, calcium carbonate,
It is used as a binder when applying pigments such as titanium oxide to the surface of base paper. As the conjugated diene copolymer latex, a latex obtained by emulsion copolymerizing a monomer containing styrene and butadiene as main components,
That is, SB latex is widely and commonly used.

[0003] In recent years, especially with high-speed printing in offset printing and high-speed coating in the production of coated paper, demands for latex binders to be used have also become higher day by day. Among such high requirements, the most important characteristic is the surface strength, that is, the adhesive strength of the binder that prevents the coating layer from falling off and peeling.

In the case of offset printing, because of the characteristics of the printing method, "blister" or so-called blisters are likely to occur because high-speed printing is followed by high-temperature and high-speed drying. The occurrence of this blister significantly reduces the commercial value of printed matter,
Further, since the generation thereof largely depends on the properties of the latex binder, it is necessary that the properties of the latex binder used for producing coated paper have a blister resistance as high as possible.

Further, in the case of offset printing, "damping water" is used as its characteristic, so that it is required that the surface strength of the coating layer when it is wet, that is, the so-called water resistance strength is also high. On the other hand, in the production of coated paper, high-speed coating is required in order to further improve productivity, and high solidification of coating liquid is being promoted in order to further reduce drying energy.
With such high-speed coating and high solidification of the coating liquid, various roll stains are likely to occur during the coating process. In order to reduce such operational problems during the production of coated paper, latex binders are required to have high stickiness resistance and high mechanical and chemical stability.

[0006] In the prior art, as a method for improving the surface strength, it is known to set the toluene insoluble content, which is a measure of the degree of crosslinking, to a high level. Must be reduced, and it is difficult to maintain a high balance between the two with this method. The improvement of the surface strength can also be achieved by increasing the content of butadiene, but this method causes a significant decrease in water resistance and stickiness resistance, which causes troubles during high-speed printing and in coated paper manufacturing operations. It has been found to be more likely to cause it.

Latex produced by a two-step polymerization method and a power feed method has been developed for the purpose of satisfying these contradictory balance requirements of physical properties (JP-A-56-12071).
7, JP-A-57-51703, JP-A-57.
-51704, JP-A-59-43193,
JP-A-62-117897, JP-A-3-1994
93, JP-A-3-199495). However, in the present technical field in recent years, there is a demand for achieving a higher physical property balance, and further development is required.

[0008]

SUMMARY OF THE INVENTION Therefore, the present invention provides a conjugated diene-based copolymer latex having a better balance of physical properties such as adhesive strength, blister resistance, water resistance, and stickiness resistance than ever before, and a method for producing the same. The object of the present invention is to provide a coating composition for paper which uses the same and has an excellent balance of physical properties.

[0009]

The present inventors have conducted extensive studies to develop the above-mentioned high-performance conjugated diene copolymer latex. Under the specific polymerization conditions, a method for producing a conjugated diene-based copolymer latex having a remarkably excellent physical property balance, which was difficult to obtain by the conventional technique, was developed, and the above object was achieved.

That is, the present invention is a method for producing a conjugated diene-based copolymer latex obtained by emulsion polymerization of a conjugated diene monomer and other copolymerizable monomers, the first step of which is: A) 40 to 64.5% by weight of the conjugated diene monomer, 35 to 59.5% by weight of the hydrophobic monomer and 0.
A monomer mixture (A) containing 5 to 25% by weight and having a glass transition temperature of less than -20 ° C of a polymer obtained from the composition is added to the reaction system in an amount of 10 to 70% by weight of all monomers. Polymerization is carried out, and in the second step (b) Conjugated diene monomer 5 to 35% by weight Hydrophobic monomer 25 to 40% by weight Hydrophilic hydrophilic unsaturated carboxylic acid monomer (a), hydroxyl ester monomer A monomer containing 25 to 70% by weight of a hydrophilic monomer (z) consisting of a monomer (b), at least one selected from an amide monomer (c), and another hydrophilic monomer (y). 30 to 90% by weight of the monomer mixture (B) based on the total amount of monomers, provided that the weight ratio of (a), (b), (c), and (y) (when the second step monomer is 100% by weight). ) Is 0.5% by weight = <
(A) + (b) + (c) <15% by weight, and (a) + (b) + (c) + (y) = (z) 25 to 70% by weight is added and polymerization is carried out. Is a method for producing a conjugated diene-based copolymer latex.

[0012] Further, there is provided a coating composition for paper characterized by using the conjugated diene copolymer latex produced by the above production method and the latex. Hereinafter, the present invention will be described in detail. Examples of the conjugated diene monomer in the present invention include compounds containing a conjugated diene in the molecule, such as butadiene, isoprene, 2-chloro-1,3-butadiene, 2-methyl-1,3-butadiene, and the like. Used alone or in combination of two or more. The other monomer is a polymerizable monomer other than the conjugated diene monomer.

Examples of the conjugated diene monomer that can be used in the first step include butadiene, isoprene and 2-chloro-
1,3-Butadiene, 2-methyl-1,3-butadiene and the like are mentioned, and these are used alone or in combination of two or more. Butadiene is generally used as a conjugated diene monomer, and its amount is required to be 40 to 64.5% by weight in order to maintain the required surface strength. More preferable range of use of butadiene is 45 to
55% by weight. If it is less than 40% by weight, the balance of surface strength and blister resistance cannot be obtained. Further, if the amount of butadiene exceeds 64.5% by weight, the elongation / tensile strength balance of the film-forming film is disturbed, and when it is used as a binder for paper coating, the rigidity of paper is lowered, which is not preferable.

The hydrophobic monomer has a solubility in water at 25 ° C. of less than 0.2 g / 100 g. Examples of the hydrophobic monomer that can be used in the first step include styrene, chlorostyrene, α-methylstyrene, vinyltoluene, methoxystyrene, ethylhexyl acrylate, ethylhexyl methacrylate, and these are one kind or two or more kinds. Used in combination. The amount used is 35-5
It is 9.5% by weight. If it is less than 35% by weight, the balance between stickiness resistance, water resistance and surface strength required in the present invention cannot be maintained. Further, if it is 59.5% by weight or more, the strength required for the present invention cannot be obtained.

The hydrophilic monomer has a solubility in water at 25 ° C. of 0.2 g / 100 g or more. Examples of the hydrophilic monomer component that can be used in the first step include an alkyl fatty acid ester monomer which is a compound having an unsaturated double bond in the molecule such as methyl (meth) acrylate and ethyl (meth) acrylate. Carboxylic acid groups such as acrylonitrile, methacrylonitrile, vinyl cyanide monomer, which is an unsaturated compound having a cyano group in the molecule, acrylic acid, methacrylic acid, fumaric acid, itaconic acid, and maleic acid. Unsaturated carboxylic acid monomer which is an unsaturated compound having a hydroxyl group, hydroxy ester monomer which is an unsaturated ester compound having a hydroxyl group in a molecule such as 2-hydroxy (meth) acrylate, acrylamide, methacrylamide etc. Include an unsaturated amide monomer that is an unsaturated compound having an amide group. Al is used Te Preferably the one or more unions, the amount used is 0.5 to 25 wt%. When the content of the hydrophilic monomer is 25% by weight or more, the stickiness resistance and water resistance are significantly reduced,
Not desirable in terms of physical property balance.

If it is less than 0.5% by weight, the polymerization stability cannot be maintained, which is not preferable. It is preferably 0.5 to less than 15% by weight. In addition, 2- which is a monomer having particularly high hydrophilicity
More preferably, the use of hydroxy ester monomers such as hydroxy (meth) acrylate is less than 5.0% by weight. The monomer mixture (A) of the present invention is a mixed composition comprising the monomer usable in the first step, a chain transfer agent and the like.

The glass transition temperature of the polymer of the above-mentioned first step monomer mixture (A) must be lower than -20 ° C. If it exceeds -20 ° C, the surface strength will decrease. The conjugated diene monomer that can be used in the second step is the same as the conjugated diene monomer example that can be used in the first step, for example, butadiene,
Isoprene, 2-chloro-1,3-butadiene, 2-methyl-1,3-butadiene and the like can be mentioned, and it is possible to use one kind or a combination of two or more kinds thereof, and butadiene is mainly used. It The usage is 5
~ 35 wt%, more preferably 15-35
% By weight. If it is 35% by weight or more, it is difficult to achieve the required stickiness resistance and water resistance, and if it is less than 5% by weight, the balance between the surface strength and the blister resistance, which is the objective of the present invention, cannot be maintained.

The hydrophobic birthmer used in the second step is 25 ° C.
The water solubility in is less than 0.2 g / 100 g. The hydrophobic monomer component that can be used in the second step is the same as the monomer example that can be used in the first step, for example, styrene,
Chlorostyrene, α-methylstyrene, vinyltoluene, methoxystyrene, ethylhexyl acrylate,
Ethylhexyl methacrylate is mentioned, and it is possible to use one kind or a combination of two or more kinds thereof. The amount used is 25-40% by weight. 40
If the content exceeds 10% by weight, stickiness resistance deteriorates, which is not preferable.
If it is less than 25%, the required water resistance cannot be obtained.

The hydrophilic monomer used in the second step is 25 ° C.
The solubility in water is 0.2 g / 100 g or more. The unsaturated carboxylic acid monomer (a) is an unsaturated compound having a carboxylic acid group in the molecule, and examples thereof include acrylic acid, methacrylic acid, fumaric acid, itaconic acid, maleic acid, etc. Used in combination of two or more. The hydroxyester monomer (b) is an unsaturated ester compound having a hydroxyl group in the molecule, and examples thereof include 2-hydroxy (meth) acrylate, and these are used alone or in combination of two or more. The amide monomer (c) is an unsaturated compound having an amide group in the molecule, and examples thereof include acrylamide and methacrylamide, and these are used alone or in combination of two or more. The amount of unsaturated carboxylic acid monomer (a), hydroxyester monomer (b), and amide monomer (c) used is 0.5% by weight = <(a) + (b) + (c) < 1
It is in the range of 5% by weight. If it is less than 0.5% by weight, the polymerization stability and storage stability of the latex and the mechanical stability of the coating composition for paper cannot be maintained. If it is 15% by weight or more, the latex viscosity and the viscosity of the paper coating composition remarkably increase, which is not preferable. Examples of the other hydrophilic monomer (y) include an alkyl fatty acid ester monomer which is a compound having an unsaturated double bond in the molecule such as methyl (meth) acrylate and ethyl (meth) acrylate, and acrylonitrile and methacrylic acid. Examples thereof include vinyl cyanide monomers, which are unsaturated compounds having a cyano group in the molecule such as ronitrile, and these are used alone or in combination of two or more. Hydrophilic monomer (z) is at least one selected from unsaturated carboxylic acid monomer (a), hydroxyl ester monomer (b), amide monomer (c), and other hydrophilic monomers. It consists of the body (y). Hydrophilic monomer (z)
The range of use is 25 to 70% by weight. If it is less than 25% by weight, stickiness resistance is deteriorated, which is not preferable. Again 7
If it exceeds 0% by weight, water resistance deteriorates, which is not preferable.

The monomer mixture (B) of the present invention comprises the conjugated diene monomer, the hydrophobic monomer, the hydrophilic monomer (z) and the chain transfer agent which can be used in the second step. It is a mixed composition. Weight ratio (A) of the monomer mixture (A) polymerized in the first step and the monomer mixture (B) polymerized in the second step
/ (B) is the composition content of (A) and (B), the monomer conversion rate,
Although it cannot be unconditionally determined due to the mutual compatibility between the polymers derived from each mixture, usually 1/9 to 7/3 is selected. If the weight ratio (A) / (B) is less than 1/9, the strength of the final latex produced cannot be maintained, and 7/3
If it is larger than the above values, the effect of improving stickiness resistance and water resistance is not observed. The more preferable weight ratio (A) / (B) is in the range of 1/9 to 4.5 / 5.5, and the best balance of physical properties is shown in this range.

In the method for producing the conjugated diene copolymer latex of the present invention, both the first step and the second step are usually 30 to 10
Although the polymerization is carried out at 0 ° C., it is possible to change the polymerization temperature in the first step and the second step, if necessary. The polymerization rate of the first step monomer mixture (A) at the start of the second step needs to be 50% or more. When the polymerization rate of the mixture (A) is less than 50%, it is difficult to maintain a high balance of surface strength, blister resistance, wet strength and stickiness resistance, which is the object of the present invention. A more preferable polymerization rate is 65% or more.

The first step and the second step can be switched immediately with respect to the addition of the monomer, or can be opened at regular intervals. Normally, the latter is selected because it requires less monomer tank for latex production, but depending on the composition and weight ratio of each of the monomer mixtures (A) and (B) and the polymerization reaction rate of the monomers, Since the former is sometimes selected, the superiority or inferiority of the method cannot be generally stated.

The emulsion polymerization method carried out for obtaining the product of the present invention includes conventionally known methods such as seed polymerization, internal seed polymerization, and flying seed polymerization. It can be carried out using a chain transfer agent, a polymerization retarder, a surfactant, an initiator, various polymerization regulator components added, and the like. The particle size can be controlled by the number of seed particles used or the amount of surfactant used, and the average particle size is 0.05 to 1.00 μm.
And is preferably in the range of 0.07 to 0.3 μm.

As the chain transfer agent, various chain transfer agents generally used in radical polymerization can be used, and examples thereof include mercaptans such as n-butyl mercaptan and t-dodecyl mercaptan, tetraethyl thiuram sulfide, dipentamethylene thiuram hexasulfide and the like. And α-methylstyrene dimer, carbon tetrachloride and the like, and these can be used alone or in combination of two or more. In addition, if necessary, JP-A-4-415
Continuous sequential addition of a chain transfer agent as shown in JP-A-11, JP-A-4-41512 and the like can be used in combination with the present invention.

As the polymerization retarder, various polymerization retarders generally used in radical polymerization can be used. For example, o
Quinones such as-, m- or p-benzoquinone, nitro compounds such as nitrobenzene, o-, m- or p-dinitrobenzene, amines such as diphenylamine, catechol derivatives such as tert-butylcatechol,
Examples include 1.1-disubstituted vinyl compounds such as 1.1-diphenylethylene and α-methylstyrene, and these can be used alone or in combination of two or more.

As the surfactant, a surfactant generally used in emulsion polymerization can be used, and examples thereof include fatty acid soap, soap of rosin acid, sodium alkylbenzenesulfonate, sodium alkylsulfonate, sodium dialkylarylsulfonate and alkyl. Examples thereof include anionic surfactants such as sodium sulfosuccinate and sodium polyoxyethylene alkyl sulfate, and nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkylphenol ether, and polyoxyethylene sorbitan fatty acid ester. It is also possible to use a reactive emulsifier having a functional group reactive with a monomer such as sodium styrenesulfonate, and if necessary, an amphoteric surfactant such as betaine type.
Usually, the anionic surfactant is used alone or a mixture of two or more kinds of anionic, nonionic and amphoteric surfactants is used.

The polymerization initiator is one which is radically decomposed in the presence of a heat or reducing substance generally used for radical polymerization to initiate addition polymerization of a monomer, and is both oil-soluble and water-soluble. Can be used. Peroxodisulfates such as potassium peroxodisulfate, sodium peroxodisulfate, ammonium peroxodisulfate, and peroxides such as benzoyl peroxide, cumene hydroxide peroxide, t-butyl peroxide, hydrogen peroxide, Azobis compounds such as 2.2-azobisisobutyronitrile and 4.4′-azobis (4-cyanovaleric acid) are generally used. Among these, peroxodisulfate brings out the effect of the present invention particularly well. The initiator in the present invention may be sodium bisulfite, ascorbic acid and its salts, erythorbic acid and its salts, Rongalit, F, if necessary.
It is possible to use it together with a reducing agent such as e, Fe / chelating agent, etc. to use it as a so-called redox type polymerization initiator.

As the various polymerization regulators, polymerization regulators generally used in emulsion polymerization can be used. For example, sodium hydroxide, potassium hydroxide, sodium hydrogen carbonate,
There are pH adjusting agents such as sodium carbonate and disodium hydrogen phosphate, chelating agents such as ethylenediaminetetrasodium, and the like, and these are added to the reaction system as needed.

When the conjugated diene-based copolymer latex produced by the present invention is used as a binder for a coating composition for paper, a general method is used, that is, inorganic / organic pigments are dissolved in water in which a dispersant is dissolved. A water-soluble polymer, various additives, and components properly selected from other latices can be added to a stirrer and mixed to be used as a uniform dispersion liquid. Examples of the pigment that can be used in the present invention include inorganic pigments such as clay, calcium carbonate, aluminum hydroxide, titanium oxide, satin white, and talc, polystyrene, and organic pigments such as phenolic resin. Examples thereof include starch, casein, polyvinyl alcohol and the like. As the additive, for example, a water resistance improver, a water resistance reaction accelerator, a pigment dispersant,
Viscosity modifiers, color pigments, fluorescent dyes, and pH modifiers can be mentioned. The use ratio of the pigment and the conjugated diene-based copolymer latex of the product of the present invention can be appropriately determined depending on the purpose of use of the composition, but is preferably 3 to 30 parts of latex relative to 100 parts of the pigment. The coating composition for paper can be applied to the base paper by using a known technique such as various blade coaters and roll coaters.

[0029]

The present invention will now be described in detail with reference to examples, but the present invention is not limited to these examples. The number of parts in the examples means parts by weight unless otherwise specified.

[0030]

Example 1 80 parts of ion-exchanged water, 0.2 part of sodium lauryl sulfate, and seed particles (solids concentration 20%) 0.4 were placed in a pressure resistant reactor equipped with a stirrer and a temperature controller.
A part was charged, and after nitrogen substitution, the internal temperature was raised to 80 ° C. Then, in the first step, the composition is butadiene 52.
0 parts, styrene 35.40 parts, methyl methacrylate 4.73 parts, itaconic acid 4.72 parts, fumaric acid 3.15
1.23 parts of α-methylstyrene dimer and 0.28 part of t-dodecyl mercaptan as a chain transfer agent component were added to 1 part of the monomer component (total of 100 parts of monomer), and a monomer mixture (A) was added.
(Total 101.64 parts) was weighed.

Thereafter, 32.23 of the monomer mixture (A) was added.
A part was taken out, and itaconic acid and fumaric acid were added all at once into the reactor at the initial stage of the polymerization. The remaining monomer mixture contains 15 parts of ion-exchanged water, 0.8 part of sodium peroxodisulfate, 0.15 part of sodium hydroxide, and 0.1% of sodium lauryl sulfate.
Polymerization was carried out by continuously adding to the reactor together with 1 part of the initiator system mixture.

Next, as a second step, butadiene 25.6
Parts, styrene 35.39 parts, methyl methacrylate 26.
7 parts, acrylonitrile 10.26 parts, hydroxyethyl acrylate 2.05 parts monomer components (monomer total 1
00 parts) to 1.77 parts of α-methylstyrene dimer, t-
The chain transfer agent component of 1.44 parts of dodecyl mercaptan was added, and the monomer mixture (B) (total 103.21 parts) was weighed.

Thereafter, 70.44 of the monomer mixture (B) was added.
A part was taken out and continuously added to the reaction system together with the initiator system mixture having the same composition as in the first step to polymerize. The polymerization was carried out for 8 hours including the first step and the second step, and the second step was started 1 hour after the addition of the monomer mixture (A) in the first step was completed. Then, the latex obtained was p-treated with sodium hydroxide.
After adjusting to H7.0, unreacted monomers were removed by the steam stripping method, and the mixture was filtered through a wire mesh of 200 mesh. The final solid content concentration of the latex was adjusted to 50%.

[0034]

[Examples 2, 3, 5, 9, 10 and Comparative Examples 1 and 6] Table 1
Polymerization was carried out by the method shown in Example 1 using the compositions and amounts shown in Examples 3, 5, and 6. However, the second step was started immediately after the completion of the addition of the monomer in the first step.

[0035]

[Examples 4, 6, 7, 8, 11 and Comparative Examples 2, 3, 4,
5 Polymerization was carried out by the method shown in Example 1 using the compositions and amounts shown in Tables 1-3, 5 and 6.

[0036]

Examples 12, 13, 14 Polymerization was carried out using the compositions and amounts shown in Tables 3 and 4. However, the second step was started immediately after the completion of the addition of the monomer in the first step. The second step monomer mixture (B) was added to the reaction system together with the initiator system mixture as in Example 1 except for methacrylamide. Methacrylamide was separately added as an aqueous solution in the same manner as other monomer mixtures. The initiator mixture used had the same composition as in Example 1.

[0037]

Comparative Example 7 Polymerization was attempted in the same manner as in Example 1 using the compositions and amounts shown in Table 6. However, as shown in Table 6, the polymerization rate in the first step was low, and the particle size control of the polymer was not achieved.

[0038]

Comparative Examples 8 and 9 80 parts of ion-exchanged water, 0.2 part of sodium lauryl sulfate and seed particles (solid content 20%) were placed in a pressure resistant reaction vessel equipped with a stirrer and a temperature controller.
0.4 part was charged, and after nitrogen substitution, the internal temperature was raised to 80 ° C. Then, in the composition shown in Table 7, itaconic acid,
Fumaric acid was added all at once at the beginning of the reaction, and then the remaining monomer was continuously added to the reactor together with the initiator mixture having the composition shown in Example 1 for polymerization.

The glass transition temperature and the minimum film formation temperature of each latex were measured. The measuring method is as follows. (1) Properties of copolymer latex (a) Glass transition temperature The latex sample was thoroughly dried and measured with a differential scanning calorimeter. (B) Minimum film forming temperature Measured with a thermal gradient tester, the measuring temperature range is 0 to 30 ° C.,
The magnitude of the thermal gradient was about 10 ° C./10 cm. (2) Evaluation of paper coating performance Using the conjugated diene latex produced in the above Examples 1 to 8 and Comparative Examples 9 to 12, a coating composition for paper was prepared according to the formulation shown in Table 8. The coating composition for paper was hand-painted on high-quality paper (74 g / m ² ) using an appropriate applicator bar so as to be 14 g / m ^2, and immediately 1 with a hot air dryer.
It was dried at 80 ° C. for 20 seconds. The coated paper obtained is 25
After curing for one day in a thermostatic chamber at a temperature of 65% and a humidity of 65%, super calender treatment was performed twice under the conditions of 50 ° C. and a linear pressure of 150 kg / cm to obtain a coated paper for surface strength and wet strength tests. Also, double-sided coating was carried out in the same manner to obtain a coated paper for blister resistance test.

(C) Surface Strength Using an RI printer, printing ink (red tack value 18) was used to perform overprinting 0.4 cc three times, and the picking state that appeared on the rubber roll was lined on another mount. , The degree was observed. The evaluation was carried out by the 5-point evaluation method, and the smaller the picking phenomenon, the higher the score. (D) Blister resistance A web offset ink (WebbZett yellow, manufactured by Dainippon Ink and Chemicals, Inc.) is applied to both sides of coated paper using an RI printer.
After printing 0.3 cc solid and sufficiently drying it at room temperature, the coated paper is cut into an appropriate size, and the test piece is kept at 25 ° C. for 8 hours.
Humidity was sufficiently adjusted in an environment of 5%. The test piece was dipped in a silicon oil thermostatic bath adjusted to a predetermined temperature to observe the occurrence of blisters. This test was conducted by changing the temperature of the constant temperature bath, and the minimum temperature at which blister formation was observed was determined. The higher this temperature, the better the blister resistance.

(E) Wet strength Using an RI printer, the surface of the coated paper was dipped in a water-absorbing roll, and 0.4 cc of printing ink (Red Tack 15) was used to print once to appear on a rubber roll. The state of picking was lined on another mount and the extent of that was observed. The evaluation was performed by using a 5-point method, and the less scored the picking phenomenon, the higher the score. (F) Anti-stick property Latex was placed on a polyethylene terephthalate film. It was applied with 18 rods and heated at 100 ° C. for 1 minute to form a film. The film and the black Racha paper were combined and pressure-bonded under a condition of 200 kg / m · 80 ° C by a bench super calender, and the transfer of the black Racha paper onto the latex film when the film was peeled off was observed. The degree of transfer of this black rusher paper was evaluated by the 5-point method, and the less transfer the higher the score. The results of the above coated paper test are shown in Table 9.

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

[Table 3]

[0045]

[Table 4]

[0046]

[Table 5]

[0047]

[Table 6]

[0048]

[Table 7]

[0049]

[Table 8]

[0050]

[Table 9]

[0051]

The conjugated diene-based copolymer latex obtained by the present invention and the paper coating composition using the same are
It has a very good balance of surface strength, blister resistance, wet strength, and stickiness resistance.

Claims (3)

[Claims] 1. A method for producing a conjugated diene-based copolymer latex, which is obtained by emulsion-polymerizing a conjugated diene monomer and other copolymerizable monomers, wherein in the first step, (a) 40 to 64.5% by weight of conjugated diene monomer, 35 to 59.5% by weight of hydrophobic monomer and 0.5 of hydrophilic monomer.
Monomer mixture (A) containing from 25 to 25% by weight, and the glass transition temperature of the polymer obtained from the composition is less than -20 ° C.
Is added to the reaction system in an amount of 10 to 70% by weight of all monomers, and polymerization is carried out. In the second step, (b) conjugated diene monomer 5 to 35% by weight hydrophobic monomer 25 to 40% by weight hydrophilicity Which is at least one selected from unsaturated carboxylic acid monomer (a), hydroxyl ester monomer (b), amide monomer (c), and other hydrophilic monomer (y) The monomer mixture (B) containing the hydrophilic monomer (z) in an amount of 25 to 70% by weight is contained in an amount of 30 to 90% by weight based on the total amount of the monomers (a), (b), (c), (y). ) Weight ratio (assuming 100% by weight of the second step monomer) is 0.5% by weight = <
(A) + (b) + (c) <15% by weight, and (a) + (b) + (c) + (y) = (z) 25 to 70% by weight is added and polymerization is carried out. A method for producing a conjugated diene-based copolymer latex characterized by: 2. A conjugated diene-based copolymer latex produced by the production method of claim 1. 3. A paper coating composition comprising the conjugated diene-based copolymer latex according to claim 2.