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
2001-05-23
2004-03-02
Yoon, Tae H. (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...
C524S394000, C524S400000, C524S492000, C524S592000, C524S594000, C523S206000
Reexamination Certificate
active
06699923
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a polyacetal resin composition with excellent flame retardancy, more particularly to a flame-retardant polyacetal resin composition having excellent thermal stability and mechanical properties.
Polyacetal resins are used in a wide sphere of industrial products, most typically automobile and OA equipment parts, as an engineering resin with a good balance of mechanical properties and excellent moldability. However, since polyacetal resins are combustible, their use is limited in applications where flame retardancy is required. So, presently, other types of resins provided with flame retardancy are used for such applications.
Various methods have been proposed for affording flame retardancy to polyacetal resins.
For example, JP-B-43-22671 proposes the addition of ammonium phosphate to polyacetal resins, and JP-B-53-31899 discloses a method in which guanidine phosphate, melamine and ammonium polymetaphosphate are added to polyacetal resins. Further, JP-A-9-324105 teaches the incorporation of ammonium polyphosphate having a particle size of 30 &mgr;m or less either singly or with melamine in polyacetal resins. These methods, however, although capable of providing required flame retardancy to polyacetal resins, have the problem that the innate properties of polyacetal resins might be impaired greatly because of high loadings of the said additive materials.
Further, an idea of adding red phosphorus and a triazine-based compound to polyacetal resins to provide flame retardancy thereto is disclosed in JP-A-48-7044 and JP-B-55-35421. However, in this case, too, it is necessary to add a triazine-based compound such as melamine, guanidine phosphate or cyanoguanidine in a large quantity for obtaining satisfactory flame retardancy, and especially when melamine is used in bulk, there arise such problems as bleeding and mold deposition. JP-A-55-84348 proposes a polyacetal resin composition improved in flame retardancy by the combined use of red phosphorus and a molybdenum compound, but this composition is unsatisfactory in thermal stability and moldability.
On the other hand, incorporation of phenol resins or polycarbonate resins in polyacetal resins has been known in the art. For instance, JP-B-49-42662 teaches the addition of a phenol resin to polyacetal resins as an antioxidant. Also, JP-A-6-248163, JP-A-6-329873, JP-A-7-11101 and JP-A-7-292186 disclose methods featuring the addition of a phenol resin to a composition comprising a polyacetal resin and a polycarbonate, polystyrene, aliphatic polyether or aromatic polyether for improving the affinity and dispersibility of the polyacetal resin and thereby improving the mechanical properties and molding shrinkage of the composition. No disclosure has ever been made, however, regarding the improvement of flame retardancy by the incorporation of a phenol resin and/or a polycarbonate resin in polyacetal resins.
As viewed above, it is very difficult on account of their inherent characteristics to provide flame retardancy to polyacetal resins, and there is yet available no polyacetal resin composition which is possessed of both excellent innate properties of polyacetal resins and high flame retardancy.
SUMMARY OF THE INVENTION
The present invention is designed to provide a polyacetal resin composition which can be used even in the fields where the use of polyacetal resins has been limited because of their poor flame retardancy, by affording flame retardancy to polyacetal resins while maintaining their excellent innate properties.
In the course of research conceiving flame-retardant polyacetal resins, the present inventors found that it is possible to make the polyacetal resins flame-retardant without vitiating their innate properties by incorporating red phosphorus, a phenol resin and/or a polycarbonate resin and a thermal stabilizer in polyacetal resins, and completed the present invention on the basis of this finding.
Thus, the present invention concretely comprehends the following embodiments [1] to [11]:
[1] A flame-retardant polyacetal resin composition comprising (A) 60 to 90% by weight of a polyacetal resin, (B) 1 to 30% by weight of red phosphorus, (C) 1 to 40% by weight of at least one resin selected from the group consisting of phenol resins and polycarbonate resins, and (D) 0.1 to 5% by weight of a metal salt of a fatty acid as a thermal stabilizer.
[2] A resin composition set out in [1] above, wherein the red phosphorus is coated with an inorganic material and/or a resin.
[3] A resin composition set out in [1] or [2] above, wherein the red phosphorus has an average particle size of 0.1 to 100 &mgr;m.
[4] A resin composition set out in any one of [1] to [3] above, wherein the amount of red phosphorus in the whole composition is 5 to 15% by weight.
[5] A resin composition set out in any one of [1] to [4] above, wherein the component (C) is a novolak phenol resin having a weight-average molecular weight of 500 to 10,000.
[6] A resin composition set out in any one of [1] to [5] above, wherein the component (C) is a phenol resin modified with paraxylylene or alkylbenzene.
[7] A resin composition set out in any one of [1] to [6] above, wherein the component (C) is a phenol resin containing 5% by weight or less of unreacted phenol.
[8] A resin composition set out in any one of [1] to [7] above, wherein the metal salt (D) is at least one substance selected from the group consisting of alkaline metal salt of a fatty acid and an alkaline earth metal salt of a fatty acid.
[9] A resin composition set out in [8] above, wherein the metal salt (D) is a lithium salt of a fatty acid.
[10] A resin composition set out in [9] above, wherein the lithium salt is lithium stearate.
[11] A resin composition set out in any one of [1] to [10] above further comprising 5% by weight or less of (E) a silicon-based lubricant.
DETAILED DESCRIPTION OF THE INVENTION
A detailed description of the present invention follows.
The polyacetal resins usable as the component (A) in the present invention are not specified; it is possible to use, for instance, homopolymers obtained by homopolymerizing the monomers of formaldehyde, its trimer trioxane or its tetramer tetraoxane, with their molecular end closed with an ester or an ether; copolymers containing C2-C8 oxyalkylene units obtained by copolymerizing said trioxane or tetraoxane and cyclic ethers such as ethylene oxide, 1,3-dioxolane, 1,4-butanediol, etc.; block polymers obtained by introducing a different component segment such as polyoxyalkylene into the polyacetal backbone; branched polymers obtained by reacting a glycidyl ether, etc. with formaldehyde or trioxane to introduce a branch structure into the polyacetal backbone; and crosslinked polymers obtained by reacting a glycidyl ether, etc., with formaldehyde or trioxane for crosslinking of the polyacetal.
The amount of the polyacetal resin in the whole composition is 60 to 90% by weight, preferably 70 to 85% by weight.
The polymerization degree of the polyacetal resin used in the present invention is not subject to any restriction as long as it has the desired moldability. (For instance, its melt flow rate (MFR) at 190° C. under a load of 2,160 g can be 1 to 100).
Red phosphorus used as component (B) in the present invention is commercially available. The commonly used non-treated red phosphorus is self-ignited and also hydrolyzed to generate phosphine at about 260° C. Ordinary non-treated red phosphorus or stabilized red phosphorus which has been elevated to its self-ignition temperature by a surface treatment is used in the present invention.
Such surface-treated red phosphorus, to be specific, includes the following: red phosphorus coated with an inorganic material; red phosphorus coated with a resin; red phosp
Tanigawa Yukio
Yamatou Hidehiko
Asahi Kasei Kabushiki Kaisha
Yoon Tae H.
LandOfFree
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