Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1999-03-02
2001-10-23
Mulcahy, Peter D. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S704000, C524S925000
Reexamination Certificate
active
06306955
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a process for the production of deproteinized natural rubber latex.
BACKGROUND OF THE INVENTION
Because of the characteristic properties of natural rubber, such as large elongation, high elasticity, high tensile strength, good cohesive strength and the like, it has been used in various fields ranging from industrial articles including automobile tires, belts and adhesives to household articles such as gloves, as well as nursing tools, contraceptives and the like.
Since natural rubber is produced by collecting the rubber from natural rubber latex by coagulation and further carrying out various operations such as mastication, blending of various compounding ingredients, molding, vulcanizing and the like, it contains non-rubber components such as protein and the like as impurities originally contained in natural rubber latex.
Since kinds and quantity of such protein vary depending on the locality and production season of natural rubber latex, it causes variations in the quality, vulcanizing characteristic and the like of natural rubber and reduces mechanical characteristics such as creep characteristic, aging resistance and the like mechanical characteristics and electric characteristics of natural rubber such as insulation and the like electric characteristics of natural rubber.
In addition, it has been reported in recent years that dyspnea and anaphylactic symptoms (vascular edema, urticaria, collapse, cyanosis and the like) seemingly caused by the protein in natural rubber were induced by the use of medical tools made of natural rubber, such as surgical gloves for operation use, various types of catheter, masks for anesthesia use and the like.
In order to resolve these problems, attempts have been made to remove protein by concentrating natural rubber latex after washing with water, adding a surfactant if necessary, or by decomposing protein with a proteolytic enzyme.
These prior art methods, however, are not effective in sufficiently removing protein contained as contaminant in natural rubber latex.
SUMMARY OF THE INVENTION
In view of the above, it therefore becomes an object of the present invention to provide a process for the production of deproteinized natural rubber latex, which can remove protein easily and efficiently from natural rubber latex and produce deproteinized natural rubber latex with high productivity and low cost.
With the aim of overcoming the aforementioned problems involved in the prior art, the inventors of the present invention have conducted intensive studies and found as the result that protein contained in natural rubber latex can be removed simply and efficiently, by treating natural rubber latex with a proteolytic enzyme and a surfactant to decompose protein in natural rubber latex, and washing the treated natural rubber latex in the presence of a salt. The present invention has been accomplished on the basis of this finding. Other objects and advantages of the present invention will be made apparent as the description progresses.
DETAILED DESCRIPTION OF THE INVENTION
According to the process of the present invention, deproteinized natural rubber latex is produced by adding a proteolytic enzyme and a surfactant to a sufficiently diluted natural rubber latex to carry out decomposition treatment of protein on standing or with mixing, and adding one or more salts to the resulting latex which is subsequently washed and concentrated to get deproteinized natural rubber latex.
Natural rubber latex to be used as the material of the deproteinized natural rubber latex of the present invention may be either commercially available ammonia-preserved latex or fresh field latex.
Various inorganic salts and organic salts may be used as the salt to be used in the present invention. Examples of the inorganic salt include carbonates, bicarbonates, thiosulfates, borates and the like, and examples of the organic salt include organic acid (e.g., acetic acid) salts, amine salts and the like. Examples of metal atoms to form these salts include alkali metals (sodium, potassium and the like), alkaline earth metals (calcium, magnesium and the like), zinc and the like.
Specific examples of the aforementioned salts include sodium carbonate, sodium bicarbonate, sodium thiosulfate, sodium tetraborate, sodium acetate and the like, and these salts may be used alone or as a mixture of two or more.
It is preferable to use a salt having a monovalent cation, because latex becomes unstable and coagulates in some cases when a salt having divalent or more cation is used.
Any one of known proteases such as alkaline protease and the like can be used as the proteolytic enzyme with no particular limitation. The protease may be of any origin such as of a bacterium, a fungus, a yeast or the like, of which a bacterial protease is preferred. The protease may be used jointly with other enzymes such as lipase, esterase, amylase, laccase, cellulase and the like.
The surfactant used in the present invention can be the same as the salt used in the washing step. Therefore, the surfactant can be selected from any of the salts discussed above in connection with the washing step. Alternatively, the surfactant and salt can be different.
As the surfactant, any one of anionic, nonionic and amphoteric surfactants may be used.
Examples of the anionic surfactant include a carboxylic acid surfactant, a sulfonic acid surfactant, a sulfuric ester surfactant, a phosphoric ester surfactant and the like.
Specific examples of the carboxylic acid surfactant include a fatty acid salt, a polyvalent carboxylic acid salt, a rosin acid salt, a dimer acid salt, a polymer acid salt, a tall oil fatty acid salt and the like, each having 6 to 30 carbon atoms, of which a carboxylic acid salt having 10 to 20 carbon atoms is preferred. If the number of carbon atoms is smaller than 6, it would entail insufficient dispersion and emulsification of protein and impurities and if it is larger than 30, it would be difficult to disperse in water.
Specific examples of the sulfonic acid anionic surfactant include an alkyl benzene sulfonic acid salt, an alkyl sulfonic acid salt, an alkyl naphthalene sulfonic acid salt, a naphthalene sulfonic acid salt, a diphenyl ethersulfonic acid salt and the like.
Specific examples of the sulfuric ester anionic surfactant include an alkyl sulfuric ester salt, a distyrenated phenol sulfuric ester salt, a tristyrenated phenol sulfuric ester salt, a polyoxyalkylene alkyl sulfuric ester salt, a polyoxyalkylene alkyl phenyl ether sulfuric acid salt, a polyoxyalkylene distyrenated phenol sulfuric ester salt, a polyoxyalkylene tristyrenated phenol sulfuric ester salt, an &agr;-olefin sulfuric ester salt, an alkyl succinic acid sulfuric ester salt and the like.
Specific examples of the phosphoric ester anionic surfactant include an alkyl phosphoric ester salt, a polyoxyalkylene phosphoric ester salt and the like.
Specific examples of the salt of these compounds include metal salts (Na, K, Ca, Mg, Zn and the like), ammonium salt, amine salts (triethanolamine salt, for example) and the like.
On the other hand, examples of the nonionic surfactant include a polyoxyalkylene ether surfactant, a polyoxyalkylene ester surfactant, a polyhydric alcohol fatty acid ester surfactant, a sugar fatty acid ester surfactant, an alkyl polyglycoside surfactant and the like.
Specific examples of the polyoxyalkylene ether nonionic surfactant include a polyoxyalkylene alkyl ether, a polyoxyalkylene alkyl phenyl ether, a polyoxyalkylene polyol alkyl ether, a polyoxyalkylene styrenated phenol ether, a polyoxyalkylene distyrenated phenol ether, a polyoxyalkylene tristyrenated phenol ether and the like. Specific examples of the just mentioned polyol include polyhydric alcohols having 2 to 12 carbon atoms, such as propylene glycol, glycerol, sorbitol, glucose, sucrose, pentaerythritol, sorbitan and the like.
Specific examples of the polyoxyalkylene ester nonionic surfactant include a polyoxyalkylene fatty acid ester and the like.
Specific examples of the polyhydric alcohol fatty acid ester
Kawasaki Atsuko
Nakade Shinichi
Sakaki Toshiaki
Mulcahy Peter D.
Sughrue Mion Zinn Macpeak & Seas, PLLC
Sumitomo Rubber Industries, Ltd
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