Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-03-09
2002-01-01
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S259000, C524S552000, C524S433000, C526S294000, C526S295000, C526S336000
Reexamination Certificate
active
06335391
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
This invention relates to a copolymer latex used as a base material for an adhesive for rubber/metal adhesion, and a process for producing the copolymer latex.
(2) Description of the Related Art
An adhesive for a rubber/metal adhesion is widely used for the production of, for example, automobile rubber articles, industrial rubber articles and building rubber articles. A typical example of the adhesive for rubber/metal adhesion includes a polymer or copolymer of 2,3-dichloro-1,3-butadiene (hereinafter abbreviated to “2,3-DCB”) as an essential ingredient. 2,3-DCB polymers and copolymers are used in the form of a solution in an organic solvent, and thus, these polymers and copolymers must be soluble in organic solvents. Usually a homopolymer of 2,3-DCB is difficult to dissolve in organic solvents, and therefore, 2,3-DCB homopolymer is brominated, or 2,3-DCB is copolymerized with, for example, &agr;-haloacrylonitrile or &agr;-chlorostyrene, to give a polymer soluble in organic solvents. For example, a process for brominating a 2,3-DCB polymer to impart solubility to the 2,3-DCB polymer is described in U.S. Pat. No. 2,725,373. A process for copolymerizing 2,3-DCB with acrylonitrile or chlorostyrene to give a 2,3-DCB copolymer having solubility in organic solvents is described in U.S. Pat. No. 3,562,192. However, acrylonitrile, &agr;-haloacrylonitrile and chlorostyrene are expensive and toxic, and thus, restricted in handling.
In recent years, the use of organic solvents for adhesives has been restricted in view of cleaning up of the environment and preservation of good working hygiene. There is an increasing demand for developing an organic solvent-free adhesive or an aqueous adhesive. For example, aqueous adhesives for rubber/metal adhesion have been proposed in U.S. Pat. No. 5,036,122, ibid. U.S. Pat. No. 5,200,459 and Japanese Unexamined Patent Publication No. H2-1793.
SUMMARY OF THE INVENTION
In view of the foregoing technical background, an object of the present invention is to provide a latex used as a base material for an adhesive for rubber/metal adhesion, which exhibits an enhanced adhesion of rubber to metal, and which latex is obtained without the use of a toxic and expensive monomer.
In one aspect of the present invention, there is provided a copolymer latex used for an adhesive for rubber/metal adhesion, which comprises a copolymer consisting of, based on the weight of the copolymer, (A) 90.0 to 97.0% by weight of 2,3-dichloro-1,3-butadiene units, (B) 1.5 to 5.0% by weight of 1,2-dichloro-1,3-butadiene units, and (C) 1.5 to 5.0% by weight of 1,3-dichloro-1,3-butadiene units.
In another aspect of the present invention, there is provided a process for producing a copolymer latex used for an adhesive for rubber/metal adhesion, which comprises polymerizing a monomer mixture consisting of, based on the weight of the monomer mixture, (A) 90.0 to 97.0% by weight of 2,3-dichloro-1,3-butadiene, (B) 1.5 to 5.0% by weight of 1,2-dichloro-1,3-butadiene , and (C) 1.5 to 5.0% by weight of 1,3-dichloro-1,3-butadiene, in the presence of a free-radical initiator by an emulsion polymerization procedure.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The copolymer constituting the latex of the invention comprises, based on the weight of the copolymer, (A) 90.0 to 97.0% by weight of 2,3-dichloro-1,3-butadiene units, (B) 1.5 to 5.0% by weight of 1,2-dichloro-1,3-butadiene units, and (C) 1.5 to 5.0% by weight of 1,3-dichloro-1,3-butadiene units. If the amount of the monomer units (A) is smaller than 90% by weight, the copolymer has poor strength and the adhesive has a reduced adhesion strength. In contrast, if the amount of the monomer units (A) is in excess of 97% by weight, the adhesive also has a reduced adhesion strength although the reason therefor is not clear. If the amount of each of the monomer units (B) and (C) is smaller than 1.5% by weight, or, in excess of 5.0% by weight, the adhesive has a reduced adhesion strength although the reason therefor is not clear.
The copolymer latex of the invention is prepared by polymerizing a monomer mixture comprising the three monomer ingredients (A), (B) and (C) by an emulsion polymerization procedure. The emulsion polymerization may be conducted by an ordinary procedure wherein water, monomers, an emulsifying agent, a free-radical initiator and a chain transfer agent are mixed together to prepare an aqueous emulsion, and the emulsion is subjected to polymerization at a predetermined temperature. The monomers may be incorporated collectively, sequentially or in lots. It is to be noted, however, that 2,3-DCB has an extremely high polymerizability, and thus, the rate of polymerization should be controlled so that the polymerization is safely conducted. Therefore, the monomers are preferably incorporated sequentially or in lots. The incorporation of monomers in lots is more preferable because undesirable scaling can be minimized.
The emulsifying agent used is not particularly limited, and includes carboxylic acid type, sulfonic acid type and sulfuric acid ester type anionic emulsifying agents and nonionic emulsifying agents. As specific examples of the emulsifying agent, there can be mentioned alkali metal salts, ammonium salts and amine salts of disproportionated rosin acid; alkali metal salts, ammonium salts and amine salts of alkylsulfonic acid; alkali metal salts, ammonium salts and amine salts of alkylsulfuric acid ester; alkali metal salts, ammonium salts and amine salts of alkylarylsulfonic acid; alkali metal salts, ammonium salts and amine salts of alkylarylsulfuric acid ester; alkali metal salts, ammonium salts and amine salts of polyoxyethylene alkylphenyl ether sulfuric acid ester; alkali metal salts, ammonium salts and amine salts of polyoxyethylene alkyl ether sulfuric acid ester; a condensate of sodium napthalenesulfonate with formaldehyde, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenol, sorbitan fatty acid ester, polyoxyethylene acyl ester, polyvinyl alcohol, and alkali metals salts and amines salts of alkyldiphenyl ether disulfonic acid. The amount of the emulsifier is preferably in the range of 0.5 to 10 parts by weight based on 100 parts by weight of the total monomers in view of polymerization stability and adhesion of the adhesive.
The free-radical initiator used can be chosen from known free-radical initiators, which include, for example, persulfates such as potassium persulfate and ammonium persulfate, and organic and inorganic peroxides such as hydrogen peroxide and t-butyl hydroperoxide. These free-radical initiators may be used either alone or as a redox initiator which is a combination of the free-radical initiator with a reducing substance. A redox initiator is preferable because the reaction can be carried out at a low temperature. As the reducing substance, the use of ascorbic acid alone is preferable in view of control of the polymerization. That is, 2,3-DCB has an extremely high polymerizability and the runaway of polymerization can be desirably controlled by using ascorbic acid.
The amount of the free-radical initiator is usually in the range of 0.001 to 2 parts by weight, preferably 0.01 to 0.5 parts by weight, based on 100 parts by weight of the total monomers. The amount of the reducing substance used in combination with the free-radical initiator is in the range of 0.001 to 2parts by weight, preferably 0.01 to 0.5 parts by weight, based on 100 parts by weight of the total monomers.
The polymerization is effected usually at a temperature of 0 to 80° C., preferably 10 to 50° C.
A chain transfer agent is used as a molecular weight modifier. As specific examples of the chain transfer agent, there can be mentioned alkylmercaptans, halogenated hydrocarbons, dialkylxanthogen disulfides, tetraalkylthiuram disulfides, an &agr;-methylstyrene dimer, 1,1-diphenylethylene and sulfur. The amount of the chain transfer agent is preferably in the range of 0.01 to 3% by weight based on the weight of the total monomers.
The termination time of polymerization is not part
Hironaka Tsuneo
Matsumoto Seiji
Ozoe Shinji
Sato Tamotsu
Harlan R.
Nixon & Vanderhye
Tosoh Corporation
Wu David W.
LandOfFree
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