Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Including a second component containing structurally defined...
Reexamination Certificate
1998-10-06
2001-01-30
Le, Hao T. (Department: 1773)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Including a second component containing structurally defined...
C428S404000
Reexamination Certificate
active
06180225
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to silicon oxide on which tannic acid being a polyhydric phenol compound is adsorbed, which is used as a so-called degradation preventive for preventing a thermoplastic resin from being decomposed to decrease in a molecular weight by adding to the thermoplastic resin.
2. Description of the Related Art
In general, thermoplastic resins such as polycarbonate, polyester and polyolefin, particularly polycarbonate base resins are decomposed by hydrolysis caused by moisture for a long period of time or heating in molding to decrease in a molecular weight, and this results in lowering in various dynamic properties. Because of performances thereof, a polycarbonate resin is used in many cases in such uses that heat resistance and mechanical dynamic properties are required. Accordingly, a reduction in the molecular weight caused by a change with the passage of time, heating, kneading and the like not only has caused the use purposes thereof to be lost in many cases but also has made it difficult to recycle the molded articles.
SUMMARY OF THE INVENTION
An object of the present invention is to provide tannic acid-adsorbed silicon oxide prepared by allowing tannic acid to be adsorbed on silicon oxide by making use of a hydroxyl group contained in tannic acid, which inhibits a degradation of a thermoplastic resin caused by a reduction in the molecular weight brought about by thermal decomposition of the thermoplastic resin by adding to the thermoplastic resin to maintain the dynamic properties thereof and makes it possible to provide a resin showing excellent recycling.
DETAILED DESCRIPTION OF THE INVENTION
As described above, it has been found that the preceding object of the present invention can be achieved by silicon oxide having tannic acid adsorbed thereon and by adding said silicon oxide to a thermoplastic resin. Next, the present invention shall be explained in further detail.
Intensive researches of surface treatment of various materials with tannic acid continued by the present inventors over a long period of time have resulted in completing an invention for preventing a reduction in the molecular weight of a thermoplastic resin by adding silicon oxide having tannic acid adsorbed thereon to the thermoplastic resin. That is, according to the present invention, a reduction in the molecular weight of the resin can be inhibited by allowing tannic acid to be adsorbed on silicon oxide and adding this tannic acid-adsorbed silicon oxide to the thermoplastic resin.
Silicon oxide used in the present invention may be natural or synthetic. It is said that the natural product contains a lot of impurities and has a dispersed quality, but it is inexpensive and is excellent in profitability. The synthetic product has an excellent quality but is expensive. In the present invention, silicon oxide may be synthetic or natural or a mixture thereof and can freely be selected considering an economical part. At present, natural silicon oxide is obtained in various places in the world and produced in the forms of opal, feldspar, quartz and quartz crystal. Natural silicon oxide is used for a glass material, an abrasive and synthetic ceramics. In the present invention, these naturally produced silicon oxides may be pulverized or molten by heating and pulverized again. Silicon oxide preferably used in the present invention includes silicate glass, silicic acid anhydride and silica gel, and they are used in the form of powder.
The particle diameter of silicon oxide shall not specifically be restricted and is suitably selected according to use purposes.
In the present invention, tannic acid is preferably bonded to silicon oxide by treating 100 parts by weight of silicon oxide with a tannic acid aqueous solution containing 0.5 to 8.0 parts by weight of tannic acid. Next, tannic acid used in the present invention is expressed synonymously with tannin such as pentaploid tannin in many cases, and tannin is not distinguished strictly from tannic acid in the present invention. Tannic acid used in the present invention means a polyhydric phenol compound forming gallic acid shown by the following formula (1) by hydrolysis. In recent years, it has been made clear that in ordinary tannic acid, for example, pharmacopoeial tannic acid (Chinesegal lotannin), eight gallic acid groups are disposed in the circumference of a glucose residue and on the same plane thereof as shown in a formula (2) and further two gallic acid groups are bonded in a vertical direction [site marked by * in the formula (2)] [J. Shore: J. Soc. Dyers Colorists, 87, 3 (1971)].
However, the central part of the compound shall not necessarily be restricted to glucose and may be a cellulose base compound. Further, didepside of gallic acid represented by a formula (3) obtained by hydrolysis of tannic acid can be used as well.
Thus, tannic acid is a compound contained widely in plants in the nature, and therefore it can easily be anticipated that tannic acid includes compounds having partially different chemical structures.
At present, uses of tannic acid include an ink additive, an anastaltic for pharmaceutical uses and a fixative for dyes and a tanning agent for leathers for industrial uses. A polyhydric phenol compound having a dye-fixing effect and a tanning effect of leathers is called “synthetic tannin”. In the present invention, among synthetic tannins, compounds which are effectively used as a matter of course for the object of the present invention can be used as well. Tannic acid is dissolved very well in various solvents, and therefore various solutions of high concentrations can be prepared. Solvents used in the present invention include water, lower alcohols, tetrahydrofuran, toluene, benzene, acetophenone, various ketones and ethers. Water and alcohols are preferably used. The concentration of a tannic acid solution used in the present invention shall not specifically be restricted as long as it is lower than a saturated concentration of tannic acid at a temperature in allowing it to be adsorbed on silicon oxide, and any concentrations can be used. A temperature in allowing tannic acid to be adsorbed on silicon oxide shall not specifically be restricted and is usually a room temperature.
Tannic acid is used in the form of a solution containing 0.5 to 8 parts by weight, preferably 1.0 to 5.0 parts by weight of tannic acid per 100 parts by weight of silicon oxide to be treated. The tannic acid-adsorbed silicon oxide of the present invention is produced by adding silicon oxide to such solution of tannic acid and stirring to allow almost all of tannic acid to be adsorbed and bonded and then filtering, washing and drying silicon oxide having tannic acid adsorbed thereon.
If the amount of tannic acid is less than 0.5 part by weight per 100 parts by weight of silicon oxide, an effect of inhibiting a thermoplastic resin from being decomposed is small, and if it exceeds 8 parts by weight, a capacity of silicon oxide adsorbing tannic acid is saturated, and silicon oxide can not adsorb more tannic acid. Further, tannic acid which has physically been adsorbed produces a lot of decomposed matters in the resin and can not inhibit the resin from being decomposed. Accordingly, it can be understood that such is meaningless.
If the amount of silicon oxide having tannic acid adsorbed thereon which is added to the resin is less than 0.2% by weight, the effect is small. In contrast with this, if the tannic acid-adsorbed silicon oxide exceeding 3.4% by weight is added to the resin, the proportion of silicon oxide occupied in the resin increases, and a lot of discontinuous layers between the resin and silicon oxide are formed, which results in reducing the dynamic characteristics. Accordingly, such is not preferred. The reason why tannic acid-adsorbed silicon oxide inhibits a reduction in the molecular weight of a thermoplastic resin is not certain and is supposed due to that the hydroxyl groups of tannic acid absorb an energy of radical molecules formed when a th
Le Hao T.
Tohoku Munekata Co Ltd
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