Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From aldehyde or derivative thereof as reactant
Reexamination Certificate
2000-09-21
2001-07-03
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
C528S230000, C528S248000, C528S249000, C528S403000, C528S419000, C528S421000
Reexamination Certificate
active
06255440
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to polyacetal resins having high rigidity, excellent creep property, 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 and creep property are demanded. As a means for improving such physical properties, a method where fibrous fillers are filled inpolyacetal resin, a method where a comonomer amount is reduced in the case of polyacetal copolymers, etc. have been known. However, in filling the fibrous filler, problems such as a poor appearance of the molded product and a lowering of the sliding property are resulted while, in the means of reducing the amount of comonomers, problems such as a lowering of thermal stability of the polymer are resulted and, therefore, they do not always meet with the demands.
In view of such problems in the prior art, the present inventors paid their attention to an essential improvement in rigidity and creep property of the polymer by modification of the polymer structure itself.
In the meanwhile, with regard to modification of the polymer structure itself, there are disclosures in JP-A3-170526 and others on modified polyacetal copolymers 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 molding property, particularly the high cycling property, by an increase in crystallizing rate and, in addition, the effect of improving the rigidity by those copolymers has been found to be not so satisfactory according to the test by the present inventors.
DISCLOSURE OF THE INVENTION
An object of the present invention is to solve the above problems and to offer copolymerized polyacetal resins having high rigidity, excellent creep property and, in addition, excellent surface property, 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 to improve a creep property to such an extent that have been unforeseeable by the polyacetal copolymers where branched structures are introduced by copolymerization of a certain type of specific glycidyl ether compound whereupon the present invention has been achieved.
Thus, the present invention relates to polyacetal copolymers obtained by copolymerizing (A) 100 parts by weight of trioxane, (B) 0.01 to 10 part(s) by weight of at least one compound selected from glycidyl ether compounds represented by the following formula (I), (II) or (III) and (C) 0 to 20 part(s) by weight of a cyclic ether compound [excluding the glycidyl ether compound (B) mentioned hereinabove] which is copolymerizable with trioxane:
wherein R
1
is a substituent for hydrogen(s) on a phenyl group and is a C
1-12
alkyl group, a substituted alkyl group, an aryl group, a substituted aryl group or halogen; n is an integer of 1 to 5; and when n is 2 or more, the R
1
groups may be the same or different;
wherein R
2
represents a C
2-20
polyalkylene oxide glycol residue, a C
1-20
alkylene group or a substituted alkylene group; R
3
represents a replacement for hydrogen atoms of the phenyl group and is a C
1-12
alkyl group, a substituted alkyl group, an aryl group, a substituted aryl group or a halogen; and n represents an integer of 0 to 5, provided when n is 2 or more, R
3
's may be the same or different. The C
2-20
polyalkylene oxide glycol residue may be a poly(oxyalkylene) group having 2 to 20 carbon atoms and the alkylene may be preferably ethylene or propylene;
wherein R
4
represents an alkyl group having 1 to 30 carbon atoms, or an alkenyl or alkynyl group having 2 to 20 carbon atoms; R
5
represents an alkylene group having 1 to 30 carbon atoms; and n represents an integer of 0 to 20.
The component (B) is any one of the formulae (I), (II), (III).
The phenyl group of the component (B) preferably has at least an ortho-substituent R
1
, particularly in the formula (I). Preferably, the ortho-substituent R
1
exerts a steric hindrance.
DETAILED DESCRIPTION OF THE INVENTION
As hereunder, the polyacetal copolymers of the present invention will be illustrated in detail.
Firstly, trioxane (A) 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 it by means of distillation or the like. It is preferred that trioxane (A) used for the polymerization contains as little as possible of impurities such as water, methanol and formic acid.
Secondly, specific examples of the compound of the component (B) represented by the formula (I) are tert-butylphenyl glycidyl ether, sec-butylphenyl glycidyl ether, n-butylphenyl glycidyl ether, phenylphenol glycidyl ether, cresyl glycidyl ether and dibromocresyl glycidyl ether. From the standpoint of thermal stability of the resultant polyacetal copolymers, the glycidyl ether compounds used in the present invention preferably has at least an ortho-subsituent R
1
and further exerts steric hindrance, for example, a phenyl group and a tert-butyl group, in particular.
Preferred examples of the compound of the component (B) represented by the formula (II) include benzyl glycidyl ether and a compound of the following structural formula (II′):
wherein n is an integer of 1 to 10.
Examples of the preferred compound of the component (B) include the following formula (III′):
wherein R
4
represents an alkyl group having 1 to 30 carbon atoms. In addition, methyl glycidyl ether, ethyl glycidyl ether, butyl glycidyl ether, 2-ethylhexyl glycidyl ether and 2-methyloctyl glycidyl ether are cited.
The copolymerizing amount of the component (B) to 100 parts by weight of trioxane [the component (A)] is 0.01-10 part(s) by weight or, preferably, 0.1-10 part(s) by weight.
When the copolymerizing amount of the component (B) is less than that, production of the branched structure due to the component (B) is too little to give the improving effect in rigidity and creep properties which is an object of the present invention while, when it is more than that, disadvantages such as a lowering of crystallinity causing a decrease in rigidity are resulted.
Examples of the cyclic ether compound (C) which is copolymerizable with trioxane (A) in the polyacetal copolymers of the present invention are ethylene oxide, propylene oxide, butylene oxide, epichlorohydrin, epibromohydrin, styrene oxide, oxetane, 3,3-bis(chloromethyl)oxetane, tetrahydrofuran, trioxepane, 1,3-dioxolane, ethylene glycol formal, propylene glycol formal, diethylene glycol formal, triethylene glycol formal, 1,4-butanediol formal, 1,5-pentanediol formal and 1,6-hexanediol formal. The copolymerizing amount of the cyclic ether compound (C) in the present invention is 0-20 part(s) by weight, preferably 0.05-15 part(s) by weight or, particularly preferably 0.1-10 part(s) by weight, to 100 parts by weight of trioxane, component (A). Although such a cyclic ether compound (C) is not particularly necessary for improvement of rigidity and creep property which is an object of the present invention, it is preferred to use the cyclic ether compound (c) as a copolymerizing component for stabilizing the polymerization reaction and also for increasing the thermostability of the resulting polyacetal copolymer. On the
Okawa Hidetoshi
Tajima Yoshihisa
Acquah Samuel A.
Nixon & Vanderhye P.C.
Polyplastics Co. Ltd.
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