JPS591427B2 - Polychloroprene latex adhesive composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to polychloroprene latex adhesive compositions.

More specifically, polychloroprene latex which essentially does not contain emulsifiers, is stabilized with carboxyl groups, and has excellent mixing stability, or powdered polychloroprene obtained by separating it from wood and metal. This invention relates to a polychloroprene latex adhesive composition with excellent adhesive properties. Conventionally, polychloroprene has been widely used as the mainstay of organic solvent-based rubber adhesives because it has great adhesive properties and high green strength based on the strong polarity of the chlorine atoms present in its molecules.

However, in recent years, these organic solvent-based adhesives have been used due to problems such as fire danger due to the flammability of the organic solvent, toxicity to the human body due to inhalation or contact with gas, and pollution caused by diffusion into the atmosphere. There is a growing demand for replacement with adhesives that do not use solvents, and the development of such adhesives is desired. One solution to these demands is a water-based adhesive that uses water as a solvent or dispersant. Polychloroprene latex, which is an aqueous dispersion of polychloroprene, has been attempted for a long time to be used as a base material for water-based adhesives, and is also commercially available. However, the base material, polychloroprene latex, is manufactured using the conventional emulsion polymerization method;
It is stabilized using surfactants conventionally used in the production of synthetic rubber latex, such as anionic surfactants such as fatty acid soaps or cationic surfactants such as quaternary salts of higher amines, as emulsifiers. be. These surfactants are physically adsorbed on the surface of rubber particles in latex, and the stabilization by these surfactants is due to the presence of polyvalent metals added when manufacturing latex adhesive compositions. It is often observed that surfactants are inhibited and destabilized by various compounding agents such as ions, cement, glass, and aggregates, which reduce or destroy the ionicity of surfactants. This fact means that coagulum occurs during the production of adhesive compositions, which often causes problems such as work stoppages. In addition, conventional polychloroprene latex adhesives have poor adhesion to adherends such as wood and metal, and in order to improve these defects, compounding agents such as rosin derivatives have been added, but the results have not been satisfactory. has not been obtained. For this reason, only a small number of adhesives are currently used with extremely limited adherends and bonding conditions. As a result of intensive research aimed at improving these drawbacks, the present invention has developed polychloroprene latex, which has excellent mixing stability for compounding agents and excellent adhesion to adherends such as wood and metal, or a polychloroprene latex obtained separately from this. We have now completed an adhesive composition based on powdered polychloroprene. The latex is essentially free of conventional emulsifiers, is stabilized with carboxyl groups, and has excellent freeze stability. That is, it has the property of being easily coagulated by freezing, but returning to the original latex without any formation of aggregates when the coagulated product is left at room temperature or heated. It also has excellent mechanical stability and does not generate any coagulated material even after long periods of high-speed stirring. In addition to these inherent advantages of latex, the powdered polychloroprene obtained by separating it from the latex has the characteristic that it can be re-emulsified with water. It has a practical advantage in that a uniformly dispersed latex adhesive composition can be obtained by producing chloroprene and adding and mixing various compounding agents and water as necessary.

The production of the polychloroprene latex used in the present invention is carried out in three stages. Each stage of polymerization can be carried out separately or sequentially. The purpose of the polymerization in the first stage is to obtain an essentially emulsifier-free vinyl polymer latex.

That is, 0.1 to 80% by weight of at least one unsaturated acid in water in the presence of 0.2 to 20% by weight, preferably 3 to 10% by weight of at least one unsaturated acid. In this method, radical polymerization is carried out by adding a vinyl monomer. If the amount of unsaturated acid relative to water is less than 0.2% by weight, a latex will not be formed and will separate into two layers, a vinyl monomer layer and an aqueous layer, so use at least 0.2% by weight or more. This is desirable. Furthermore, if the amount of unsaturated acid exceeds 20% by weight, the viscosity of the polymerization system will increase, making it difficult to carry out stable polymerization. Suitable examples of unsaturated acids include acrylic acid, methacrylic acid, maleic acid, fumaric acid,
Examples include itaconic acid, crotonic acid, citraconic acid, and the like. Is the amount of vinyl monomer relative to water 0.1 weight? If the amount is less than 0.1% by weight, a polymer mainly composed of unsaturated acids will be produced and its hydrophilicity will be too high.

Examples of vinyl monomers used here include styrene, α-methylstyrene, styrene derivatives such as P-chlorostyrene, methacrylic acid esters such as methyl methacrylate and ethyl methacrylate, methyl acrylate, and ethyl acrylate. Examples include acrylic ester, acrylonitrile, vinyl acetate, vinyl chloride, vinylpyridine, and the like. The first stage polymerization should be carried out in a wide range of pH ranges, from an acidic region with a pH of 2 to an alkaline region with a pH of 12, which includes addition of an alkaline substance such as sodium hydroxide, potassium hydroxide, sodium bicarbonate, or aqueous ammonia. is possible,
It can be arbitrarily determined and used depending on the solubility of the unsaturated acid used in the aqueous medium.

Although not necessarily required in the first stage of polymerization, surfactants conventionally used for the purpose of further improving polymerization stability, such as sulfated esters of fatty acids, alkylaryl sulfonates, and organic phosphorus, may be used. Acid esters, fluorine-based surfactants, polyoxyethylene alkyl ethers, etc. may be used in small amounts, such as not exceeding 170%. In order to carry out the second and/or third stage polymerization continuously, it is preferable to omit operations such as distilling off unreacted monomers as much as possible. It is preferable to carry out the polymerization up to a conversion rate of 10,070. In the second stage polymerization, radical polymerization of chloroprene monomer is carried out using the vinyl polymer latex obtained in the first stage polymerization as a base.

In addition to chloroprene, other conjugated diene monomers may be used in combination as long as the essence of the present invention is not impaired. Examples of these include butadiene, isoprene, 2-cyanobutadiene, 2,3-dichlorobutadiene, and the like. The amount of chloroprene monomer or a mixture of chloroprene monomer and conjugated diene monomer is 10 to 120% by weight, preferably 50 to 1% by weight, based on the vinyl polymer latex obtained in the first stage polymerization.
It can be added all at once, in parts, or continuously in a range of 0.00 to 70.0 by weight. Taking into account the solid content concentration used industrially, these monomers have a concentration of at least 10
It is necessary to use a weight of 70 or more. Furthermore, since the second stage of polymerization is carried out using a vinyl polymer latex which essentially does not contain an emulsifier, if the weight exceeds 120 and 70, the monomers will be liberated and cause the formation of coagulum. Polymerization cannot be carried out stably. In the second stage polymerization, a small amount of the unsaturated acid or vinyl monomer used in the first stage polymerization may be added as long as the essence of the present invention is not impaired.

Furthermore, for the purpose of producing crosslinked polymers, anolequinolemenolecaptan,
Molecular weight modifiers such as anolequinolexanthogen disulfide, halogenated hydrocarbons, etc. may be added. Radical polymerization in the third stage is carried out using the polychloroprene latex obtained in the second stage polymerization as a matrix.

The base polychloroprene latex obtained in the second stage polymerization may be one that has been polymerized to a conversion rate of 100%, or, if unreacted monomers are present, the unreacted monomers may have been removed. Well, there are no particular restrictions. The third stage polymerization is carried out by adding at least 70% by weight of a vinyl monomer or a mixture of a vinyl monomer and an unsaturated acid to the polychloroprene fiber obtained in the second stage polymerization. These vinyl monomers and unsaturated acids may be any of those used in the first stage polymerization and can be freely selected. At least 1 weight of these to get? It is necessary to polymerize in addition to the above, and if the weight is less than 70%, sufficient effects cannot be obtained. The upper limit of the amount of these monomers is not particularly limited as long as it is present at 70% by weight or more, but generally, if the amount of the total polymer in the latex is 1.5 times the weight or more of the amount of the aqueous medium, Since the polymerization system becomes unstable, it is naturally limited by the amount of polymer present in the polychloroprene latex obtained in the second stage. The initiator used in the present invention may be any initiator used in emulsion polymerization, including persulfates such as potassium persulfate and ammonium persulfate, alkyl hydroperoxides, and the like.

These initiators can be used alone or in combination with thiosulfates, thiosulfites, organic amines, etc.
It can be added all at once initially, dividedly to each polymerization stage, or continuously. The polymerization at each stage can be carried out at a temperature at which polymerization in a normal aqueous medium is carried out, and the polymerization temperature is not particularly limited.

That is, from around 0°C to 1°C using a redox initiator.
Temperatures can be freely selected up to around 00°C. Whether each step of polymerization is carried out continuously or separately, the polymerization proceeds stably, and the resulting polymer latex is stable, with no polymer particles remaining even after being left for more than three months. No sedimentation occurs. Moreover, the polychloroprene latex finally obtained solidifies easily by freezing, but returns to the original latex without any polymer aggregates when heated, and is further heated for a long time under high-speed stirring. It is a highly stable latex that does not show any coagulum formation even when exposed to water. Furthermore, when this polychloroprene latex is poured into a lower alcohol such as methanol, polychloroprene particles are obtained as a powdery precipitate, but the powdery polychloroprene obtained by separating and drying this is re-emulsified when stirred at high speed in an aqueous medium. It has the property of becoming polychloroprene latex. The polychloroprene latex of the present invention obtained in this manner can be used with inorganic vulcanizing agents such as zinc white, magnesium silicate, and colloidal sulfur, organic vulcanizing agents such as diepoxide and dimethylol urea, clay, calcium carbonate, etc. fillers, other vulcanization accelerators,
Adhesive compositions are prepared by mixing with various compounding agents such as anti-aging agents, and are extremely stable when mixed with these compounding agents.

In addition, the powdered polychloroprene obtained as described above can be uniformly mixed with each compounding agent in advance, and then water is added and stirred with a high-speed stirrer such as a dispersing mixer, so that the compounding agents are uniformly mixed. It can be a latex adhesive composition dispersed in The method of using powdered polychloroprene is to prepare a dispersion of a vulcanizing agent, a vulcanization accelerator, a filler, etc. in advance and then add it to latex to form a latex-based adhesive composition. This method is advantageous in that the working process can be simplified, and the solid content can be controlled freely. Furthermore, it also has the practical advantage of being advantageous in terms of storage and transportation since it is a powder. In addition, in the polychloroprene latex adhesive composition obtained in the present invention, the polychloroprene latex as a base material is stabilized with carboxyl groups, and the carboxyl groups are present on the surface of the polychloroprene particles. Compared to conventional products, it has superior adhesion to adherends such as wood, glass, and metal.

Therefore, in addition to the conventional application fields of polychloroprene latex, such as adhesion between adherends such as cardboard, paper, cotton cloth, and fibers, it can also be used for adhesion between these adherends and metals, wood, glass, etc. It can also be applied to adhesion between adherends such as metal and wood, expanding its range of applications. Next, in order to make the present invention even easier to understand, examples will be shown and explained.

Unless otherwise specified in the examples, parts represent parts by weight.
1. Manufacture of polychloroprene latex Manufacturing examples A-B Polymerization was carried out in a reaction vessel equipped with a stirrer, a cooler, and a temperature detection end.

That is, in a nitrogen stream, a predetermined amount of unsaturated acid, lauryl alcohol sulfated ester (LAS) sodium bicarbonate as shown in Table 1 was added to 100 parts of water, and then in a nitrogen stream, while stirring. , 9.0 parts of styrene were added. When the temperature reached 70°C, 1.0 part of potassium persulfate was added to initiate polymerization, heated for 150 minutes, and substantially
Polymerization was carried out to a conversion rate of 0.070. After the polymerization is completed, the polymerization system is
The mixture was cooled to .degree. C., and 80 parts of chloroprene in which 0.4 parts of n-dodecylmercaptan had been dissolved was added dropwise over 60 minutes, and the polymerization was continued for an additional 4 hours to substantially achieve a conversion of 10,070. Next, the temperature of the polymerization system was raised to 70°C, a mixture of 16 parts of styrene and 2.0 parts of acrylic acid was added, and heating was continued for 2 hours to obtain a polychloroprene latex.

This polychloroprene latex was a white, stable latex with low viscosity.

Production Example C Production Example A except that in the second stage of polymerization, 100 parts of chloroprene in which 0.6 parts of diisopropylxandogen disulfide was dissolved was used to polymerize to a conversion rate of 7070, and unreacted chloroprene was removed. A polychloroprene latex was obtained in the same manner as in Production Example A.

Production Example D-G Using the latex obtained in the first stage of polymerization in Production Example A as a matrix, polymerization was performed according to the polymerization recipe shown in Table 2,
Polychloroprene latexes were obtained - Examples 1 to 7 and Comparative Example 1 Each of the latexes obtained in Production Examples A to G and commercially available latexes were mixed with compounding agents in the following formulation to form an adhesive composition. Obtained.

Latex (5070 solids) 200 parts Epicote 8281) 5 parts Anti-aging agent 2)
2-part dispersant 3) 1.
5 parts 1) Diepoxide (manufactured by Ciel Chemical Co., Ltd.) 2) Sumilizer MDP (manufactured by Sumitomo Chemical Co., Ltd.) 3) Formaldehyde-sodium naphthalene sulfonate condensate Cotton canvas/iron, iron/iron, aluminum/of each adhesive composition Adhesion to various adherends such as aluminum, copper/copper, and wood/wood was examined.

The test piece for the adhesion test is 10 x 10 in the case of cotton canvas/iron.
Brush each adhesive composition onto a No. 9 cotton canvas and heat at 80°C.
Dry for 10 minutes at
10×0. 1C7rL), apply each adhesive composition with a brush, stick them together, press them together with a hand roller, and heat at 120°C.
and heated for 20 minutes. After cooling down to room temperature in a test room at 23°C and 50% humidity, it was placed on an iron plate with a width of 2.5 (V7).
It was cut into strips of 1.5 cm and the peel strength was measured.

For metal/metal, width 2.5 x length 10 x thickness 0.1
Using cTn iron plate, aluminum plate, copper plate, in the case of wood/wood, use beech wood of width 2.5 × length 10 × thickness 0.5 °, and apply the adhesive composition once to each test piece. Brush paint,
Glue 2.5 x 2.5 square pieces together and tighten to 120℃.
and heated for 20 minutes.

Shear strength was measured after cooling to room temperature in a test room at 23° C. and 50% humidity.

As is clear from the adhesive test results in Table 3, the adhesive composition based on polychloroprene latex produced in the present invention has superior adhesion to metal and wood compared to conventional adhesive compositions. I know that there is.

Examples 8 to 14 When the polychloroprene latex obtained in Production Examples A to G was poured into methanol, white powdery polychloroprene precipitated.

This powdered polychloroprene can be easily passed through the mouth. After passing through the mouth, it is centrifugally dehydrated and dried to a size of about 0.5 mm.
It was possible to obtain uniform dry powder polychloroprene with a size of . Each compounding agent was added to this powdered polychloroprene in the following formulation and mixed uniformly. Water was added to these mixtures so that the solid content was 52%, and a high-speed stirrer (Mitamura Riken Kogyo Co., Ltd., Disperva Mixer, Ul.
When the mixture was stirred for 5 minutes at 5 ooorpm using a tra-Turrax, it became latex-like.

Adhesion tests were conducted on these adhesive compositions in the same manner as in Example 1 using the same test pieces as in Example 1.
As is clear from the results in Table 4, the latex adhesive composition based on re-emulsifiable powdered polychloroprene was found to have excellent adhesion to metal or wood.

Claims (1)

[Claims] 1 (a) in the presence of 0.2 to 20% by weight of at least one unsaturated acid in water, from 0.1 to 80% by weight thereof;
(b) add 10 to 120% by weight of chloroprene monomer to the obtained vinyl polymer latex and perform radical polymerization; (c)
Then, the resulting polychloroprene latex is stabilized with carboxyl groups obtained by adding 1% by weight or more of a vinyl monomer or a mixture of a vinyl monomer and an unsaturated acid and performing radical polymerization. was done,
A polychloroprene latex adhesive composition based on polychloroprene lux or powdered polychloroprene obtained by separating it.