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
2001-07-05
2004-05-18
Mullis, Jeffrey (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S064000, C525S068000, C525S069000, C525S071000, C525S088000, C525S09200D
Reexamination Certificate
active
06737475
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a branched polyacetal resin composition having an excellent sliding property and also excellent in moldability, surface property, mechanical property, etc.
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. For example, there is a demand for a material having a further improved sliding property while maintaining excellent moldability, appearance, etc., which are inherent to the polyacetal resin.
For the purpose of improving the sliding property of the polyacetal resin, incorporation of fluorine resin, silicone, polyolefins and/or lubricants has been conducted. However, in the method of merely incorporating a lubricating component into common polyacetal resins, though sliding properties such as abrasion resistance and slidability can be improved in some degrees, there are various problems such as insufficient molding, poor appearance, etc. caused by the sliding improver incorporated. In particular, a significant deterioration of the appearance, dimensional accuracy, etc. of a molded article occurs, due to the dispersibility and bleeding in case of the polyacetal resin where a liquid lubricant is incorporated, or due to the dispersibility, cohesiveness, phase separation etc. in case of the polyacetal resin where a solid lubricantaing component is incorporated. Such behaviors may often cause a hindrance to mold maintenance, so improvements have been desired. Furthermore, since the incorporation of the above lubricating components generally has a tendency to deteriorate mechanical properties of the polyacetal resins such as rigidity and strength, improvements thereof have been often desired, too.
DISCLOSURE OF THE INVENTION
An object of the present invention is to solve the above-mentioned problems and to provide a polyacetal resin material in which an excellent sliding property is given and the appearance, dimensional accuracy, mechanical property, etc. of the molded article thereof are improved as well.
For achieving the above object, the present inventors have carried out a detail investigation going deeply into the molecular skeleton and physical properties of the polyacetal resin. As a result, they have found a combination of modification of the polymer skeleton, which is effective for achieving the object, and the components effectively incorporated to the polymer, whereupon the present invention has been achieved.
That is, the present invention relates to a branched polyacetal resin composition, in which 100 parts by weight of a branched polyacetal copolymer (A) having an oxymethylene group as the main repeating unit and having a branching unit represented by the following formula (I) are compounded with 0.5 to 40 parts by weight of at least one polymer (B) selected from the group consisting of the following polymers (B-1) and (B-2), i.e.,
polymer (B-1): a graft or block copolymer prepared from an olefin polymer (b-1) and at least one vinyl polymer (b-2); and
polymer (B-2): a modified olefin polymer in which an olefin polymer (b-3) is modified with at least one compound selected from the group consisting of an unsaturated carboxylic acid, an unsaturated carboxylic acid anhydride and derivatives thereof,
and/or 0.1 to 5 parts by weight of a lubricant (C).
wherein m and n each is an integer of 0 to 5; the sum of m+n is 1 to 5; and R is a monovalent organic group having a molecular weight of 40 to 1000.
The composition comprises (A) and at least one of (B) and (C), (B) being at least one selected from (B-1) and (B-2).
It is quite unexpected and surprising that a branched polyacetal copolymer, which is thus modified with a specific branching unit and compounded with a lubricating component, can give an excellent sliding property and improve the appearance, dimensional accuracy, etc. of a molded article thereof as well.
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be explained in detail. First, the branched polyacetal copolymer (A) used as the base resin in the present invention has an oxymethylene group (—CH
2
—O—) as the main repeating unit and has a branching unit represented by the following formula (I). The presence of the branching unit is one of the important elements for achieving the object of the present invention. The object of the present invention cannot be achieved by a common polyacetal resin not having the branching unit, even if the specific polymer (B) or lubricant (C) described below is compounded as the lubricating component.
wherein m and n each is an integer of 0 to 5; the sum of m+n is 1 to 5; and R is a monovalent organic group having a molecular weight of 40 to 1000.
In the branching unit represented by the formula (I), the branching group R is a monovalent organic group having a molecular weight of 40 to 1000. If the molecular weight of R is less than 40, improvements in appearance, dimensional accuracy, rigidity, etc. cannot be expected, while if the molecular weight is more than 1000, there is the problem of a reduction in the degree of crystallization. Preferably, the molecular weight of R is 50 to 500. From the viewpoint of the improvements in appearance, dimensional accuracy, rigidity, etc. and the maintenance of other physical properties, the ratio of the branching unit represented by the formula (I) is preferably 0.001 to 10 parts by weight, more preferably 0.01 to 3 parts by weight, to 100 parts by weight of the oxymethylene unit (—CH
2
—O—).
Although there is no particular limitation for the process for producing the branched polyacetal copolymer (A) of the present invention, the copolymer (A) is preferably prepared by a copolymerization of 100 parts by weight of trioxane (a-1), 0.001 to 10 parts by weight of a monofunctional glycidyl compound (a-2), and 0 to 20 parts by weight of a cyclic ether compound (a-3) copolymerizable with trioxane. The branched polyacetal copolymer (A) comprising such monomers can be produced easily and the resulting copolymers have excellent properties. The trioxane (a-1) used herein is a cyclic trimer of formaldehyde, which is generally obtained by a reaction of an aqueous solution of formaldehyde in the presence of an acid catalyst, and is used after purifying by distillation, etc. It is preferred that the trioxane (a-1) used for the polymerization contains as little as possible of impurities such as water, methanol and formic acid.
The branched polyacetal copolymer (A), composed of oxymethylene units and units (I), may be produced by copolymerizing (a-1) trioxane, (a-2) the monofunctional glycidyl compound and (a-3) the optional cyclic ether compound. Any glycidyl compound may be used to meet the definition of “R” of the formula (I).
The monofunctional glycidyl compound (a-2) refers to organic compounds having one glycidyl group in the molecule. Typical examples thereof include glycidols, glycidyl ethers composed of aliphatic or aromatic alcohols or (poly)alkylene glycol adducts thereof and glycidols, and glycidyl esters composed of fatty or aromatic carboxylic acids or (poly)alkylene glycol adducts thereof and glycidols. The monofunctional glycidyl compound (a-2) is used as a branched structure component of the branched polyacetal copolymer (A) used in the present invention.
As the monofunctional glycidyl compound (a-2), a glycidyl ether compounds represented by the following formulae (II), (III) and (IV) are preferred:
wherein R
1
is a C
1-12
alkyl group, a substituted alkyl group, an alkoxy group, an aryl group, a substituted aryl group or halogen; and n is an integer of 0 to 5 and, when n is 2 or more, the R
1
s may be the same or different:
wherein R
2
is a C
1-30
alkylene group, a substituted alky
Kawaguchi Kuniaki
Okawa Hidetoshi
Tajima Yoshihisa
Mullis Jeffrey
Nixon & Vanderhye PC
Polyplastics Co. Ltd.
LandOfFree
Branched polyacetal resin composition does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Branched polyacetal resin composition, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Branched polyacetal resin composition will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3194290