Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2001-03-23
2003-11-04
Short, Patricia A. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S472000
Reexamination Certificate
active
06642321
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field to Which the Invention Belongs
The present invention relates to a polyacetal resin composition having high rigidity, and in addition, high surface hardness and excellent sliding property.
2. Prior Art
Polyacetal resins have excellent properties in terms of mechanical property, thermal property, electric property, sliding property, molding property, etc. and have been widely used in electric appliances, automobile parts, precision instrument parts, etc. mostly as constituting materials, mechanical parts, etc. thereof. However, as a result of expansion of the fields to which polyacetal resins are used, there are some cases where further improvements in rigidity, surface hardness and sliding property are demanded. As a means for improving the rigidity to meet such a demand, a method where fibrous fillers are filled in polyacetal resin has been known. In this method, however, problems such as a poor appearance of the molded product and a-lowering of the sliding property are resulted. In case of polyacetal copolymers, it is known that reducing the copolymerizing amount of comonomers brings an improvement in the rigidity, etc. In this method, however, the rigidity is only slightly improved and the sliding property, even though not damaged, is not in the least improved whereas problems such as a lowering of thermal stability of the polymer are resulted, and therefore, the method does not always meet with the demands.
In view of such problems in the prior art, the present inventors thoroughly changed their position and paid attention to modification of the polymer structure of polyacetal copolymers itself and an improvement in rigidity, surface hardness and sliding property by using the resin composition comprising such a modified polymer. Conventionally, although there are some references teaching modification of the polymer structure of polyacetal resins, e.g., JP-A 3-170526, it is not too much say that there has been little disclosure on the improvement in the rigidity and sliding property of a polyacetal resin on the basis of the above conception.
DISCLOSURE OF THE INVENTION
An object of the present invention is to solve the above problems and to offer a copolymerized polyacetal resin composition having high rigidity, high surface hardness, excellent sliding property, etc.
The present inventors have carried out an intensive investigation for achieving the above-mentioned object and have unexpectedly found that it is now possible to increase a rigidity and surface hardness and to improve a sliding property to such an extent that have been unforeseeable by blending the polyacetal copolymers where branched structures are introduced by copolymerization of a polyacetal resin, as the substrate, and a certain type of specific glycidyl ether compound whereupon the present invention has been achieved.
That is, the present invention relates to a polyacetal resin composition, produced by blending 100 parts by weight of a polyacetal resin (A) with 0.01-100 part(s) by weight of a branched polyacetal copolymer (B), which is obtained by copolymerization of 100 parts by weight of trioxane (a), 0.01-10 part(s) by weight of a monofunctional glycidyl compound (b) and 0-20 part(s) by weight of a cyclic ether compound (c) which is copolymerizable with trioxane.
The present invention is a polyacetal resin composition comprising 100 parts by weight of the polyacetal resin (A) and 0.01-100 part(s) by weight of the branched polyacetal copolymer (B).
The monofunctional glycidyl compound (b) is preferably any glycidyl ether compound represented by the following formulas (I), (II), (III) and (IV):
wherein R
1
is a C
1-20
polyalkylene oxide glycol residue, an alkylene group or a substituted alkylene group; R
2
is a substituent for hydrogen in a phenyl group and is a C
1-12
alkyl group, a substituted alkyl group, an alkoxy group, an aryl group, a substituted aryl group or halogen; n is an integer of 0-5; and, when n is 2 or more, R
2
may be the same or different;
wherein R
3
is a substituent for hydrogen in a phenyl group and is a C
1-12
alkyl group, a substituted alkyl group, an alkoxy group, an aryl group, a substituted aryl group or halogen; n is an integer of 1-5; and, when n is 2 or more, R
3
S may be the same or different;
wherein R
4
is an alkyl group having 1-30 carbon(s) or an alkenyl or alkynyl group having 2-20 carbons; R
5
is an alkylene group having 1-30 carbons; and m is an integer of 1-20; and
wherein R
6
is an alkyl group having 1-30 carbon(s).
DETAILED DESCRIPTION OF THE INVENTION
The structure of the polyacetal resin composition of the present invention will be explained in detail.
Firstly, a polyacetal resin (A), which is a substrate of the resin composition of the present invention, is a polymer compound wherein an oxymethylene unit (—CH
2
O—) is a major structural unit. Examples thereof include polyacetal homopolymers such as “Derlin” (trademark), manufactured by Du Pont USA and polyacetal copolymers containing an oxymethylene group and other comonomer units such as “Duracon” (trademark) manufactured by Polyplastics Co., Ltd. The comonomer unit of the polyacetal copolymer includes an oxyalkylene unit having about 2 to 6 carbon atoms, preferably about 2 to 4 carbon atoms, such as an oxyethylene group (—CH
2
CH
2
O—), oxypropylene group and oxytetramethylene group. The comonomer unit is contained in such an amount that the crystallinity of the resin is not largely impaired. Specifically, the proportion of the comonomer unit to the structural unit of the polyacetal polymer may usually be selected from the range between 0.01 and 20 mol %, preferably 0.03 and 10 mol % and more preferably 0.1 to 7 mol %. The polyacetal copolymer may be a copolymer composed of two components or a terpolymer composed of three components. Further, the polyacetal copolymer may be a random copolymer, a block copolymer or a graft copolymer. No particular limitation is imposed on the polymerization degree and the branched or cross-linking degree of the polyacetal resin (A) and any polyacetal resin may be used as far as it can be melt-molded. As the polyacetal resin (A) compounded in the present invention, a polyacetal copolymer is particularly preferable in view of the thermal stability. Also, when the polyacetal copolymer is a substrate resin, the effect of improving the rigidity by compounding a branched polyacetal copolymer (B) is more significant.
Next, the branched polyacetal copolymer (B) added to the polyacetal resin (A) in the resin composition of the present invention, is obtained by polymerizing a trioxane (a) and a monofunctional glycidyl compound (b) and further, if required, a cyclic ether compound (c) which can be copolymerized with a trioxane, thereby forming a branched structure.
Trioxane (a) herein used 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 it by means of distillation or the like. It is preferred that trioxane used for the polymerization contains as little as possible of impurities such as water, methanol and formic acid.
The monofunctional glycidyl compound (b) is a compound having one glycidyl group and is used as a branched structure component of the branched polyacetal copolymer (B) to be compounded in the present invention.
As the monofunctional glycidyl component (b), glycidyl ether compounds shown by the above-shown formulae (I), (II), (III) and (IV) are preferred. Examples of the preferable compounds include p-tertiarybutylphenyl glycidyl ether, sec-butylphenyl glycidyl ether, n-butylphenyl glycidyl ether, phenylphenol glycidyl ether, cresyl glycidyl ether, dibromocresyl glycidyl ether, glycidyl 4-methylphenyl ether, glycidyl ether compounds having the following structures:
methyl glycidyl ether, ethyl glycidyl ether, butyl glycidyl ether, 2-ethylhexyl glycidyl ether and 2-methyloctyl glycidyl ether.
Among them, compounds represented by the formulae (I) and (II) and having R
2
or R
3
at the
Kawaguchi Kuniaki
Okawa Hidetoshi
Tajima Yoshihisa
Nixon & Vanderhye P.C.
Polyplastics Co. Ltd.
Short Patricia A.
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