Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2001-07-05
2004-06-22
Sanders, Kriellion A. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S366000
Reexamination Certificate
active
06753368
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a branched polyacetal resin composition having high rigidity and excellent in antistatic performance.
PRIOR ART
A polyacetal resin has excellent properties in mechanical property, fatigue properties, 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, since the polyacetal resin itself has high'surface specific resistance, and obstacles attributable to charging, such as static electricity noises, adhesion of foreign matter onto the surface thereof, etc. are estimated depending on use, the field of utilization thereof has been limited by itself. To cope with such obstacles caused by static electricity, it has been proposed to compound the polyacetal resin with various antistatic agents.
For example, it is known that polyalkylene glycols such as polyethylene glycol and fatty esters of polyvalent alcohols having hydroxyl group are suitably hygroscopic and improve electrical conductivity and antistatic properties by incorporating into the polyacetal resin. However, when the polyacetal resin is compounded with polyalkylene glycols, etc., the strength of the resin is significantly reduced to cause a problem in practical use. Further, a long-term stability of the antistatic properties is insufficient. Accordingly, the means of merely compounding the polyacetal resin with the additives cannot meet with the properties demanded, which are becoming more and more high, complex, and special in recent years.
In view of the prior art described above, the present inventors presumed that, in order to endow the polyacetal resin with antistatic properties while maintaining various properties inherent thereto, modification of the polymer skeleton of a polyacetal resin and design of the resin composition based on such a polymer hold the important key to the solution of the problems. With regard to such a modification of the polymer skeleton of a polyacetal resin, JP-A 3-170526 discloses a modified polyacetal copolymer prepared by a copolymerization of 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 these modified polyacetal copolymers is to the improvement of moldability, particularly high cycling ability, by an increase in crystallizing rate, and there is no or less disclosure therein of improvement of other characteristics.
DISCLOSURE OF THE INVENTION
An object of the present invention is to solve the above problems and to provide a resin material endowed with antistatic property while maintaining various properties of polyacetar resin such as excellent appearance and rigidity.
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) is compounded with 0.1 to 30 parts by weight of a compound (B) having a polyalkylene ether unit as the main constituting component, and/or 0.01 to 10 parts by weight of an ester (C) of fatty acid with polyhydric alcohol having a hydroxyl group:
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).
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 compounds (B) or (C) described below is compounded.
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, the maintenance or improvement of rigidity cannot be expected, whereas if the molecular weight exceeds 1000, there is the problem of a lowering of crystallinity. Preferably, the molecular weight of R is 50 to 500. The monovalent organic group forming R is preferably one having an aromatic ring, which is remarkably effective on maintenance or improvement of rigidity.
From the viewpoint of maintaining or improving rigidity and toughness and of maintaining other physical properties, it is preferable that the branching unit represented by the formula (I) is present at random in the polymer skeleton, and the ratio of the branching unit 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), 0.001 to 10 parts by weight of a monofunctional glycidyl compound (b-1) and 0 to 20 parts by weight of a cyclic ether compound (c) 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) 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) 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) trioxane, (b-1) the monofunctional glycidyl compound and (c) 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 (b-1) 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 (b-1) is used as a branched structure component of the branched polyacetal copolymer (A) used in the present invention.
As the monofunctional glycidyl compound (b-1), 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 alkylene group or a polyalkylene oxide glyc
Kawaguchi Kuniaki
Okawa Hidetoshi
Tajima Yoshihisa
Nixon & Vanderhye P.C.
Polyplastics Co. Ltd.
Sanders Kriellion A.
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