Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-07-05
2003-06-24
Sanders, Kriellion A. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S100000, C524S102000, C524S205000, C524S291000, C524S343000, C524S359000
Reexamination Certificate
active
06583203
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a branched polyacetal resin composition excellent in weather (light) resistant stability. Particularly, it relates to a polyacetal resin composition excellent in weather (light) resistance, which prevents cracking, discoloration and deterioration in glossiness of a molded article upon light exposure for a long time, and maintains the initial surface conditions thereof.
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 weather (light) resistance.
Interior and exterior parts in automobiles, etc. and parts of electric instruments, etc. sometimes give rise to inconveniences such as discoloration of the surface of the molded article, reduction in surface smoothness to diminish glossiness, and cracking generated on the surface of the parts to deteriorate the appearance, depending on the atmosphere used, such as upon exposure to sunrays and water (rain, moisture condensation, etc.) and a contact to the other atmosphere for a long time. Accordingly, if the polyacetal resin is used in the parts exposed to sunrays etc., it is necessary to use those compositions blended with various weather (light) resistant stabilizers, and addition of various weather (light) resistant stabilizers has been known. For example, JP-A 57-98545, JP-A 59-133245, JP-A 60-195155 and JP-A 61-36339 disclose a combination of a weather (light) resistant stabilizer and a hindered amine substance, JP-A 61-47744 discloses a combination of a weather (light) resistant stabilizer, a hindered amine substance and a fatty ester, and JP-A 7-150006 discloses a combination of a weather (light) resistant stabilizer, a hindered amine substance, an oxyalkylene polymer and acrylic resin.
However, these methods of adding stabilizers etc. do not necessarily give satisfactory results when the stabilizers, etc. are used in small amounts, and they should be added in large amounts in order to maintain long-term weather (light) resistance. In this case, the stabilizers, etc. will easily ooze from the surface of resin to cause the discoloration and deteriorated glossiness of the surface of a molded article, resulting in deterioration of the resin conditions. Therefore, there is a demand in the industrial world for further development of polyacetal resin materials excellent in weather (light) resistance, which prevent cracking, discoloration and deterioration in glossiness of a molded article upon light exposure for a long time, and maintain the initial surface conditions thereof.
DISCLOSURE OF THE INVENTION
An object of the present invention is to solve the above problems and to provide polyacetal resin materials excellent in weather (light) resistance, which prevent cracking, discoloration and deterioration in glossiness of a molded article upon light exposure for a long time, and maintain the initial surface conditions thereof.
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 stabilizing 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 0.01 to 5 parts by weight of a weather (light) resistant stabilizer (B) and 0.01 to 5 parts by weight of a hindered amine substance (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), (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.
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 weather (light) resistance 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 weather (light) resistance and 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), 0.001 to 10 parts by weight of a monofunctional glycidyl compound (b), 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) 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) 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) is used as a branched structure component of the branched polyacetal copolymer (A) used in the present invention.
As the monofunctional glycidyl compound (b), 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 glycol residue; R
3
is a C
1-12
alkyl group, a substituted alkyl group, an alkoxy group, an aryl gro
Kawaguchi Kuniaki
Okawa Hidetoshi
Tajima Yoshihisa
Polyplastics Co. Ltd.
Sanders Kriellion A.
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