Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2000-09-08
2002-10-08
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S335000, C528S488000, C528S492000, C528S932000, C528S934000, C524S575500
Reexamination Certificate
active
06462159
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a cationic deproteinized natural rubber latex and, more particularly, to a cationic deproteinized natural rubber latex suited to bond papers, fibers, cloths and hides, and a method of preparing the same.
Heretofore, natural rubber adhesives wherein the concentration of the rubber contained in a natural rubber latex is concentrated to about 60% have widely been used to bond papers, fibers, cloths and hides.
However, the natural rubber latex contains a protein as a non-rubber component other than the rubber component and the kind and amount of the protein vary depending on the producing district and producing season. Therefore, there arise problems such as scatter in quality and vulcanization characteristics of natural rubber adhesives as well as deterioration of qualities of natural rubber adhesives, for example, mechanical characteristics such as creep characteristics and aging resistance, and electrical characteristics such as insulating properties. There also arise problems that ammonia as a preservative is incorporated in the natural rubber latex to cause a strong odor.
Also there has recently been reported the case where a strong I type allergic symptom is caused by a protein in a natural rubber when using a natural rubber product.
A trial of solving these problems has been made by a method of efficiently removing a protein from a natural rubber latex disclosed in Japanese Published Unexamined patent (Kokai Tokkyo Koho Hei) Nos. 6-56904, 6-56905 and 6-56906. Such a method is capable of removing a protein by adding a proteolytic enzyme (protease) and an anionic or nonionic surfactant are added to a natural rubber latex, thereby to decompose a protein, and then a creamy rubber component is separated by a purification treatment such as centrifugation to remove the protein.
However, the surfactant used in the method of the publications described above is anionic or nonionic and rubber particles in the deproteinized natural rubber latex are negatively charged or in the state free from polarity.
Accordingly, it was not preferable to use, as an adhesive, such deproteinized natural rubber latex in the fibers or papers which are negatively charged when treated in water.
On the other hand, a cationic natural rubber latex incorporated with cetyltrimethylammonium bromide (CTAB) as a cationic surfactant is described in pages 94 to 95 of “Natural Rubber Science and Technology” (edited by A. D. Roberts, published by Oxford University Publication, 1988). As described in such a reference document, when a sufficient amount of the cat ionic surfactant is added to the natural rubber, a latex comprising rubber particles having cations can be obtained. The latex is made cationic in such way, thereby making it possible to improve the close adhesion with the fibers or papers which are negatively charged when treated in water.
However, the natural rubber latex disclosed in the reference documents described above has such a problem that the thickness of an adhesive layer formed by the rubber latex is liable to be decreased to obtain poor bonding strength when coated the adherend with the natural rubber latex, because the concentration of the rubber component is low such as about 30% by weight.
Furthermore, the latex obtained by merely incorporating the cationic surfactant in the natural rubber latex has a problem such as poor workability on coating because of large increase in viscosity with a lapse of time and fear of a solidification action.
Also in such a case, applications of the latex are limited because its use as a natural rubber adhesive is not preferable.
SUMMARY OF THE INVENTION
Thus, an object of the present invention is to provide a cationic deproteinized natural rubber latex which can maintain excellent storage stability and workability on coating even if the concentration of the rubber component is high, and which exhibits excellent adhesion to papers, cloths and hides and also has high safety to the human body.
Another object of the present invention is to provide a treating agent for obtaining a cationic deproteinized natural rubber latex which can maintain excellent storage stability and workability on coating even if the concentration of the rubber component is high, and which exhibits excellent adhesion to papers, cloths and hides and also has high safety to the human body.
The present inventors have intensively studied to solve the problems described above and found such a novel finding that, when rubber particles in the natural rubber latex subjected to the deproteinization treatment are positively charged, the viscosity can be reduced to a sufficiently low value even if the solid content concentration of the rubber particles is increased, thus obtaining a natural rubber latex which has excellent workability on coating for adhesive and has excellent adhesion to papers, fibers, cloths and hides. Thus, the present invention has been completed.
The cationic deproteinized natural rubber latex rubber particles of the present invention is characterized in that rubber particles are positively charged and the concentration of said rubber particles is from 40 to 65% by weight and that the viscosity at 25° C. (hereinafter referred merely to as “viscosity”) of the latex is 200 mPa·s or less.
According to the cationic deproteinized natural rubber latex of the present invention, since the viscosity of the latex is maintained at a low value such as 200 mPa·s or less even if the concentration of the rubber particles (concentration of the rubber component in the latex) is a high value ranging from 40 to 65%, the workability on coating is good and an adhesive layer having a uniform thickness can be formed in case of coating the adherend. Accordingly, neither poor thickness nor unevenness does occur when the adhesive layer is formed, thereby making it possible to obtain a sufficient bonding strength.
The cationic deproteinized natural rubber latex according of the present invention is prepared by subjecting to a deproteinization treatment using a proteolytic enzyme and one or more surfactants selected from cationic and nonionic surfactants, and contains both cationic and nonionic surfactants after the treatment.
That is the cationic deproteinized natural rubber latex is characterized in that a protein in the natural rubber latex is removed by the deproteinization treatment using a deproteinizing agent containing a proteolytic enzyme and cationic and/or nonionic surfactants, and the cationic surfactant and nonionic surfactant finally coexists in the latex.
According to the cationic deproteinized natural rubber latex of the present invention, it is made possible to obtain a latex having excellent dispersion stability and storage stability, to maintain the viscosity of the latex at 200 mPa·s or less even in case of a so-called high-concentration latex having a rubber component in a concentration of more than 40% by weight, and to sufficiently prevent phenomenon such as increase in viscosity with a lapse of time, solidification or cohesion.
The cationic surfactant not only contributes to an improvement in dispersion stability and storage stability of the latex, but also exerts an action of making the latex cationic, i.e. an action of positively charge the rubber particles in the latex to form a suspension of the cation charged particles in water. As a result, the latex of the present invention exhibits excellent adhesion to papers, fibers, cloths and hides.
According to the effects described above, the cationic deproteinized natural rubber latex of the present invention exhibits excellent adhesion and excellent workability on coating for a base latex in a natural rubber adhesive suited to bond to papers, fibers, cloths and hides.
In the present invention, the protein contained in the natural rubber latex as the raw material is removed by the deproteinization treatment. As a result, the latex of the present invention prevents allergy caused by the protein and therefore has high safety to the human body.
The method of preparing a cationic d
Hamada Akihiko
Hayashi Masaharu
Ichikawa Naoya
Bissett Melanie
Seidleck James J.
Sumitomo Rubber Industries, Ltd
LandOfFree
Cationic deproteinized natural rubber latex, method of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Cationic deproteinized natural rubber latex, method of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Cationic deproteinized natural rubber latex, method of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2990320