Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From aldehyde or derivative thereof as reactant
Reexamination Certificate
2001-07-05
2002-04-02
Acquah, Samuel A. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From aldehyde or derivative thereof as reactant
C528S241000, C528S250000, C528S253000, C528S232000, C528S233000, C525S472000, C525S532000
Reexamination Certificate
active
06365704
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a polyacetal copolymer having a high rigidity, an excellent creep property, a high surface hardness and an excellent slidability.
PRIOR ART
A polyacetal resin has excellent properties in mechanical property, thermal property, electric property, slidability, moldability, etc. and has been widely used mostly as structural materials, functional parts, etc. in electric instruments, car parts, precision machine parts, etc. However, as the field where a polyacetal resin is utilized is expanded, there is a tendency that the properties requested are becoming more and more high, complex and special. Among such requests, there is a demand for further improvement in rigidity while the excellent slidability, appearance, etc. which are inherent to polyacetal resin are still retained. For such a demand, a method where a fibrous filler or the like is filled in a polyacetal resin is common when the object is to just improve the rigidity. But, in this method, there is a problem of poor appearance, lowered slidability, etc. of the molded article as a result of filling the fibrous filler, etc. and, in addition, there is another problem of a lowered tenacity. It has been also known that, in a polyacetal copolymer, rigidity can be improved without a substantial deterioration of slidability and appearance by reducing the amount of a comonomer to be copolymerized. However, in a means where the amount of a comonomer is reduced, there are problems that not only tenacity lowers but also thermal stability of the polymer lowers, and the means does not always meet with the demand.
In view of such problems in the prior art, the present inventors presumed that, in order to improve the rigidity while various excellent properties inherent to polyacetal resin are retained, denaturation of the polymer skeleton per se of polyacetal resin and design of the resin composition based upon such a polymer hold the important key to the solution of the problems.
With regard to such a denaturation of the polymer skeleton per se of a polyacetal resin, JP-A 3-170526 discloses a modified polyacetal copolymer prepared by copolymerization of trioxane, at least one cyclic ether compound selected from ethylene oxide, 1,3-dioxolane, 1,3-dioxepane, 1,3,5-trioxepane and 1,3,6-trioxocane and at least one compound selected from glycidyl phenyl ether, styrene oxide and glycidyl naphthyl ether. However, an object of the modified polyacetal copolymers is to improve the moldability by an increase in crystallizing rate, particularly a high recycling ability and, further, according to the investigation by the present inventors, those copolymers have a poor thermal stability.
DISCLOSURE OF THE INVENTION
An object of the present invention is to solve the above-mentioned problems and to provide a resin material in which rigidity is improved while various properties of polyacetal resin such as excellent appearance, slidability and thermal stability are still retained.
The present inventors have carried out an intensive investigation for achieving the above object and have found that the above problems can be solved by a polyacetal copolymer wherein a branched and crosslinked structure is introduced by copolymerization of a specific polyfunctional compound whereupon the present invention has been achieved. They also have found that the above problems can be solved by a polyacetal copolymer wherein the amount of the terminal group is controlled whereupon the present invention has been achieved.
Thus, the present invention relates to a polyacetal copolymer which is prepared by a copolymerization of 100 parts by weight of trioxane (A), 0.0005 to 2 parts by weight of the component (B), which is a compound (B-1) having at least three glycidyl groups in the molecule or a compound (B-2) having at least two epoxy groups in the molecule, and 0 to 20 parts by weight of a cyclic ether compound (C) copolymerizable with trioxane, and which has a total terminal group amount of 15 to 150 mmol/kg, when (B) is (B-2).
It is preferable that the copolymerizing ratio of the cyclic ether compound (C) is 0.01 to 15 parts by weight and that a weight-average molecular weight of the polyacetal copolymer is 10,000 to 500,000.
The present invention further provides A process for producing a polyacetal copolymer by a copolymerization of 100 parts by weight of trioxane (A), 0.0005 to 2 parts by weight of a compound (B-2) having at least two epoxy groups in the molecule and 0 to 20 parts by weight of a cyclic ether compound (C) copolymerizable with trioxane using a cationic polymerization catalyst, wherein an alkoxy-containing compound is added so as to adjust the amount of the terminal group of the resulting polyacetal copolymer to 15 to 150 mmol/kg in total.
The present invention has a form in which the component (B) is (B-1) and a form in which the component (B) is (B-2). Thus, a polyacetal copolymer of the present invention is produced by a copolymerization of trioxane (A) and a compound (B-1) having at least three glycidyl groups in a molecule as essential components, preferably, to which a cyclic ether compound (C) copolymerizable with trioxane is further added. Another polyacetal copolymer of the present invention is prepared by a copolymerization of trioxane (A) and a compound (B-2) having at least two epoxy groups in the molecule as essential components, preferably, to which a cyclic ether compound (C) copolymerizable with trioxane is further added.
DETAILED DESCRIPTION OF THE INVENTION
As hereunder, the polyacetal copolymer of the present invention will be explained in detail.
Trioxane (A) which is used in the present invention is a cyclic trimer of formaldehyde. Usually it is prepared by the reaction of an aqueous solution of formaldehyde in the presence of an acidic catalyst and is used after purifying by means of distillation or the like. It is preferred that trioxane used for the polymerization is liquid and its temperature is 65 to 135° C.
Next, the compound (B-1) having at least three glycidyl groups in a molecule used in the present invention is preferably selected from a group consisting of triglycidyl ether compound and tetraglycidyl ether compound. Examples thereof include glycerol triglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, sorbitol polyglycidyl ether, sorbitan polyglycidyl ether, polyglycerol polyglycidyl ether and diglycerol polyglycidyl ether. Those compounds may be used for a copolymerization with trioxane (A) either solely or jointly by using two or more of them. In the present invention, the compound (B-1) having at least three glycidyl groups in a molecule is used within a range of 0.0005 to 2 parts by weight to 100 parts by weight of trioxane (A). It is used preferably within a range of 0.001 to 1 part by weight and, particularly preferably, within a range of 0.003 to 0.5 part by weight. When the amount of the component (B-1) used is less than 0.0005 part by weight, it is difficult to give a polyacetal copolymer having desired properties while, when it is more than 2 parts by weight, proccessability for molding, resistance to impact and surface properties of the resulting polyacetal copolymer lower and they are not preferred.
The component (B-2) used in the present invention is a compound having at least two epoxy groups in a molecule. Among that, a compound selected from a group consisting of diglycidyl ether compound, triglycidyl ether compound and tetraglycidyl ether compound is particularly preferred. Examples thereof include ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, hexamethylene glycol diglycidyl ether, resorcinol diglycidyl ether, bisphenol A diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, polybutylene glycol diglycidyl ether, glycerol triglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, sorbitol polyglycidyl ether, sorbitan polyglycidyl ether, polyglycerol polyglycidyl ether and
Okawa Hidetoshi
Yamamoto Kaoru
Acquah Samuel A.
Nixon & Vanderhye P.C.
Polyplastics Co. Ltd.
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