JP2933985B2 - Method for producing diene copolymer latex - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement in a method for producing a copolymer latex. More specifically, the present invention relates to a method for efficiently producing a high-performance copolymer latex suitable as a binder for paper coating, carpet bike sizing, fiber bonding and the like.

Conventional technology Conventionally, synthetic copolymer latex is, for example, a binder for paper coating, a binder for carpet backsizing,
It is widely used as a binder for bonding fibers such as nonwoven fabric and artificial leather, or as an adhesive for various materials.
When the copolymer latex is used for such a purpose, the copolymer latex is required to have high adhesive strength and excellent water resistance, blister resistance by drying and heating, and the like.

For example, coated paper, for the purpose of improving the printability of paper and the improvement of optical properties such as gloss, on the surface of the base paper made, kaolin clay, calcium carbonate, satin white, talc, pigments such as titanium oxide, Coated with a water-soluble polymer as a main component such as starch, casein, polyvinyl alcohol, carboxymethyl cellulose as a copolymer latex as a binder and a water retention agent or an auxiliary binder, Conventionally, styrene and butadiene are used as main monomer components as a copolymer latex, and a styrene-butadiene copolymer latex obtained by emulsion polymerization of these is used,
So-called SB latex is widely used.

By the way, in recent years, the production of coated paper has increased remarkably with the increase in demand for magazines, pamphlets and advertisements printed in color. In particular, with the trend toward high-speed printing in offset printing, the required level for the quality of coated paper and pigment binders is becoming increasingly sophisticated, and therefore, among the quality of coated paper, especially ink pick resistance, so-called pick strength There is a strong demand for improvement. Moreover, this pick strength performance is different from other print properties, such as wet pick strength,
Blister resistance, halftone dot reproducibility, and the like are in a negative correlation, and therefore, further improvement is required to balance these various properties to a high level.

Since these properties of coated paper strongly depend on the performance of SB latex used as a pigment binder,
Various studies have been made on the performance of the SB latex.

For example, it has been confirmed that the proportion of the insoluble portion of the copolymer latex film in solvents such as benzene, toluene, and tetrahydrofuran is a controlling factor of pick strength and blister resistance. Specifically, by adjusting the composition of the latex copolymer and the gel fraction to specific ranges,
It has been proposed to exhibit excellent performance
59-3598, JP-B-60-17879, JP-A-58-4
No. 894). Although the gel fraction of this latex varies depending on various polymerization factors such as the monomer composition and the polymerization temperature, a method of adjusting the gel fraction to a desired level generally and simply involves adding a chain transfer agent.

However, when the gel fraction is adjusted by the amount of the chain transfer agent, generally, the pick strength of the coated paper is the highest in SB latex when the gel fraction is in the range of 75 to 95% by weight. On the other hand, it has been recognized that the lower the gel fraction, the better the blister resistance is, and the above techniques are all sufficient to simultaneously improve both the pick strength and the blister resistance to a high level. Is not satisfactory.

On the other hand, an adhesive for carpet backsizing is generally a composition obtained by blending a filler such as calcium carbonate or aluminum hydroxide and other additives such as a thickener with a copolymer latex, and comprises a tufted carpet and a needle. In the production of punched carpets and the like, it is mainly used for preventing piles from dropping off and bonding to a secondary base fabric such as jute. Therefore, in this case, the improvement of the adhesive strength, which is the most important physical property of the carpet, is one of the biggest technical problems in the industry, and therefore, an improvement from the viewpoint of the blending of the copolymer latex and the composition has been studied. However, in reality, satisfactory levels have not yet been obtained.

As described above, the conventional technology cannot cope with a further increase in the speed of printing of coated paper, and the emergence of a copolymer latex as a binder capable of producing high quality coated paper is strongly demanded. In carpets and adhesives, there is a demand for a copolymer latex having high adhesive strength.

Problem to be Solved by the Invention Under such circumstances, the present invention further improves the balance between pick strength and other performance in coated paper for printing, and further improves the adhesive strength in carpet backsizing and adhesive. The purpose of the present invention is to provide a high-performance copolymer latex.

Means for Solving the Problems The present inventors have conducted intensive studies to develop a copolymer latex having the above-mentioned preferable properties, and as a result, when producing a diene copolymer latex by emulsion polymerization, a specific It has been found that the purpose can be achieved by sequentially adding two kinds of chain transfer agents into the polymerization system, and the present invention has been completed based on this finding.

That is, the present invention provides a method for producing a diene copolymer latex by emulsion-polymerizing a conjugated diene compound, an ethylenically unsaturated carboxylic acid, and other copolymerizable monomers in an aqueous medium. A) adding a mixture of 50-80% by weight of the total weight mixture added as a first step and an alkylthiol-based chain transfer agent, and (b) adding the remaining monomer mixture added as a second step; It is intended to provide a method for producing a diene-based copolymer latex, which comprises adding a mixture with a chain transfer agent other than an alkylthiol-based.

 Hereinafter, the present invention will be described in detail.

Examples of the alkylthiol chain transfer agent used in the present invention include t-dodecyl mercaptan, n-
Examples thereof include alkyl mercaptans such as dodecyl mercaptan and mercaptoethanol, and thioglycolic acid esters such as pentaerythritol tetrathioglycolate.

Further, examples of the chain transfer agent other than the alkylthiol type used in the present invention include a halogen compound such as carbon tetrachloride and 2,4-diphenyl-4-methyl-1.
-Nuclear substituted α-methylslen dimers such as pentene; aromatic compounds such as ethylbenzene; naphthol and its nuclear-substituted derivatives.

The alkyl thiol chain transfer agent may be used singly or in combination of two or more kinds, and the amount of the alkyl thiol chain transfer agent is usually 0.1 to 0.2 per 100 parts by weight of the total amount of monomers.
Parts by weight, preferably in the range of 0.1 to 1.0 parts by weight.
On the other hand, the chain transfer agent other than the alkylthiol-based chain transfer agent may be used alone, or two or more kinds may be used in combination. The amount of the chain transfer agent is usually 0.2 to 10 parts by weight, preferably 0.2 to 5 parts by weight. Selected in the range of parts.

In the present invention, first, (a) a mixture of 50 to 80% by weight of the total monomer mixture to be additionally added as the first step and the alkylthiol-based chain transfer agent is added,
(B) As the second step, it is necessary to add a mixture of the remaining chain transfer agent to be added additionally and the above-mentioned chain transfer agent other than the alkylthiol type. Thus, the object of the present invention can be achieved by sequentially adding two kinds of chain transfer agents to the polymerization system.

As the conjugated diene compound used in the present invention, for example, butadiene, isoprene, 2-chloro-1,3
-Butadiene and the like. One of these conjugated diene compounds may be used, or two or more thereof may be used in combination. The amount of the conjugated diene compound may be in the range of 5 to 90% by weight based on the weight of all monomers. desirable. Further, in the case of a copolymer latex for coated paper, the more preferred use amount of this conjugated diene compound is selected in the range of 20 to 70% by weight.

As the ethylenically unsaturated carboxylic acid used in the present invention, for example, monobasic carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, dibasic carboxylic acids such as fumaric acid and monoesters thereof Can be mentioned. One of these ethylenically unsaturated carboxylic acids may be used alone, or two or more thereof may be used in combination. The amount of the ethylenically unsaturated carboxylic acid used is usually 0.2% by weight or more, preferably Is selected in the range of 0.2 to 15% by weight.

Other copolymerizable monomers used in the present invention include aromatic monovinyl compounds and divinyl compounds, acrylates and methacrylates, vinyl cyanide compounds, and ethylenic amides.

Examples of the aromatic monovinyl compound and divinyl compound include styrene, α-methylstyrene, chlorostyrene, alkylstyrene, and divinylbenzene. As the acrylate or methacrylate, for example, methyl of acrylic acid or methacrylic acid,
Examples include ethyl, propyl, butyl, 2-ethylhexyl, hydroxyethyl, glycidyl esters, and ethylene glycol diacrylate and dimethacrylate. Examples of the vinyl cyanide compound include acrylonitrile and methacrylonitrile, and examples of the ethylenic amide include acrylamide, methacrylamide, N-methylolacrylamide, and N-methylolmethacrylamide.

Further, in addition to these monomers, vinyl esters such as vinyl acetate, vinyl chloride, vinyl halides such as vinylidene chloride, aminoethyl acrylate or methacrylate, dimethylaminoethyl acrylate or methacrylate, diethylaminoethyl acrylate or methacrylate and the like Ethylenic amines, sodium styrenesulfonate and the like can also be used.

One of these copolymerizable monomers may be used,
Two or more kinds may be used in combination.

In the present invention, the copolymer latex is obtained by emulsion-polymerizing the conjugated diene compound, the ethylenically unsaturated carboxylic acid, and another copolymerizable monomer in an aqueous medium. This emulsion polymerization is not particularly limited as long as the addition of the chain transfer agent satisfies the above conditions, and a conventionally known method can be used.

The concentration of the copolymer in the copolymer latex is usually selected in the range of 40 to 60% by weight.

The average particle size of the copolymer latex in the present invention can be adjusted by the use ratio of the surfactant or the seed latex, and generally, the higher the use ratio, the smaller the average particle size of the produced copolymer latex tends to be. There is. This average particle size is 0.05 to 1 μm, preferably 0.1.
It is preferably in the range of 07 to 0.3 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. Examples of the surfactant include nonionic surfactants such as an activator, polyoxyethylene alkyl ether, polyoxyethylene alkyl aryl ether, polyoxyethylene sorbitan fatty acid ester, and oxyethylene oxypropylene block copolymer. This surfactant is usually used in an anionic surfactant alone or in an anionic / nonionic mixed system, and the amount of the surfactant is usually 0.05 to 0.05% based on the weight of all monomers.
It is selected in the range of 2% by weight.

The radical polymerization initiator necessary for the initiation of polymerization is one having a function of causing radical decomposition by heat or a reducing substance to cause addition polymerization of a monomer, such as water-soluble or Oil-soluble peroxodisulfates, peroxides, azobis compounds, etc., specifically, potassium peroxodisulfate, sodium peroxodisulfate, ammonium peroxodisulfate, hydrogen peroxide, tert-butyl hydroperoxide, benzoyl peroxide, 2, Examples thereof include 2-azobisisobutyronitrile and cumene hydroperoxide. Of these, peroxodisulfate is particularly preferable. The amount of the polymerization initiator used is usually selected in the range of 0.2 to 1.5% by weight based on the weight of all monomers.

The polymerization temperature in this emulsion polymerization is usually selected in the range of 60 to 100 ° C., but if it is desired to accelerate the polymerization rate or to carry out the polymerization at a lower temperature, sodium acid sulfite, ascorbic acid or a salt thereof, erythorbic acid or the like Salt, using a reducing agent such as Rongalit in combination with the polymerization initiator,
A so-called redox polymerization method can be employed.

In the present invention, if desired, various polymerization regulators such as sodium hydroxide, potassium hydroxide, sodium hydrogen carbonate, sodium carbonate, disodium hydrogen phosphate, etc.
Various chelating agents such as pH adjusters and sodium ethylenediaminetetraacetate can be added.

When the copolymer latex produced according to the present invention is used as a binder for a paper coating composition, a method generally used, for example, an inorganic pigment or an inorganic / organic pigment, water-soluble in water in which a dispersant is dissolved, may be used. A method can be adopted in which the copolymer latex is added and mixed together with a water-soluble polymer compound and various additives and used as a homogeneous dispersion. The coating material for paper coating can be applied to base paper by an ordinary method using various blade coaters, roll coaters and the like.

Effects of the Invention According to the present invention, a high-performance copolymer latex that can further improve the balance between pick strength and other properties in coated paper for printing and the adhesive strength in carpet backsizing and adhesives can be easily prepared. Can be obtained.

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

 In addition, each characteristic was calculated | required as follows.

Evaluation of paper coating performance (a) Blister resistance Using a RI printing tester (manufactured by Meiji Seisakusho), 0.3 ml of printing ink (Webb Zett yellow, manufactured by Dainippon Ink and Co., Ltd.) is solid printed on both sides of the coated paper. The printed coated paper is cut into an appropriate size, and the test piece is immersed in a silicone oil thermostat adjusted to a predetermined temperature to observe whether blisters are generated. This test is performed by changing the temperature of the thermostat, and the temperature at which blisters are generated is compared. The evaluation was performed by a 10-point evaluation method, and the higher the blister resistance, the higher the score.

(B) Dry pick strength Using a RI printing tester, print ink (SD
Super Deluxe 50 crimson B; tack value 18) 0.4 ml was overprinted 5 times, and the picking condition that appeared on the rubber roll was lined up on another backing paper, and the situation was observed. The evaluation was performed by a 10-point evaluation method, and the smaller the picking phenomenon, the higher the score.

Examples and Comparative Examples 1 and 2 4 parts by weight of an aqueous dispersion of seed particles having a diameter of 0.04 μm (seed solid concentration 25% by weight) were 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 fumaric acid were charged, the internal temperature was raised to 80 ° C., and then the monomer mixture (A) shown in Table 1 was added in 2 hours. Thereafter, the monomer mixture (B) was added over 2 hours. Separately, simultaneously with the start of the addition of the monomer mixture (A), an aqueous solution consisting of 15 parts by weight of water, 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 is added in 5 hours. Was added. After 6 hours from the start of the polymerization, the mixture was cooled, and then the pH of the produced copolymer latex was adjusted with sodium hydroxide.

Application Examples The performance of the copolymer latexes prepared in Examples and Comparative Examples 1 and 2 as a binder for paper coating was evaluated. Table 4 shows the results.

The coating composition was prepared by a high-speed stirrer with the composition shown in Table 2 and an amount of water at which the nonvolatile content was 63% by weight. The pH of the paint was adjusted to 9.0 with ammonium water. Table 3 shows the preparation conditions of the coated paper using this paint.

From Table 4, it is understood that the coated paper using the copolymer latex of the present invention as a binder has a highly balanced pick strength and other physical properties.

Continuation of the front page (72) Inventor Yasuyuki Nakahara 1-3-1 Yoko, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Inside Asahi Kasei Kogyo Co., Ltd. (56) References JP-A-3-109451 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) C08F 2/00-2/38

Claims (1)

(57) [Claims] 1. A conjugated diene compound in an aqueous medium,
In producing the diene-based copolymer latex by emulsion-polymerizing the ethylenically unsaturated carboxylic acid and other copolymerizable monomers, (a) 50% of the total monomer mixture added as the first step is added. A mixture of .about.80% by weight and an alkylthiol-based chain transfer agent is added, and then (b) a mixture of the remaining monomer mixture to be added as a second step and a non-alkylthiol-based chain transfer agent is added. A method for producing a diene-based copolymer latex, comprising: