Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-03-08
2004-06-22
Szekely, Peter (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S099000, C524S100000, C524S127000, C524S140000, C524S147000, C524S153000, C524S414000, C523S206000, C523S207000, C523S351000
Reexamination Certificate
active
06753363
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a polyacetal resin composition excellent in flame retardancy and moldability, a process for producing the same, and a shaped article molded therefrom.
BACKGROUND ART
Possessed of excellent mechanical properties, fatigue resistance, resistance to friction and wear, resistance to chemicals, and moldability, the polyacetal resin has found application in a variety of fields such as automotive parts, electrical and electronic parts, other precision machine parts, architectural members and pipeline components, household and cosmetic parts, and medical device parts. However, with the increasing scope and diversification of uses, the resin is required to satisfy more and more sophisticated requirements. For example, the polyacetal resin is small in oxygen index but high in combustibility (flame retardancy), so that it is extremely difficult to render the resin flame-retardant. Accordingly, the application of the polyacetal resin is largely limited.
There have been made many proposals for the way to render the polyacetal resin flame-retardant. For example, Japanese Patent Application Laid-Open No. 43446/1973 (JP-48-43446A) discloses a flame-retardant resin composition formed by adding a nitrate with Mn, Ba, Sr, Ca, or Mg to an oxymethylene polymer. Japanese Patent Publication No. 35421/1980 (JP-55-35421B) discloses a flame-retardant polyoxymethylene composition formed by adding at least one triazine-based flame retardant selected from melamine, guanamine, melam, ammelide, ammeline, and derivatives thereof (e.g., methylol, alkyl, or aryl derivatives), dicyandiamide and its methylol derivatives, to polyoxymethylene. This publication also discloses a polyoxymethylene composition further comprising at least one flame retardant (source of phosphoric acid) selected from phospham, phosphamide, and phosphorus imide. Japanese Patent Application Laid-Open No. 85242/1979 (JP-54-85242A) discloses a flame-retardant resin composition comprising a polyacetal resin and melamine cyanurate. In the specification of U.S. Pat. No. 3,485,793 is disclosed a flame-retardant resin composition constituted of a polyoxymethylene resin, 5 to 30% by weight of a compound selected from amines, ammonium phosphate and amidine phosphate and, if necessary, 1 to 20% by weight of a formaldehyde trapping agent.
Japanese Patent Application Laid-Open No. 324105/1997 (JP-9-324105A) discloses a resin composition comprising a polyoxymethylene resin and a flame retardant constituted of ammonium polyphosphate alone or a combination of ammonium polyphosphate and a melamine compound, in which the volume average particle size of the ammonium polyphosphate is 30 &mgr;m or less. Japanese Patent Publication No. 22671/1968 (JP-43-22671B) discloses a flame-retardant oxymethylene polymer composition containing an oxymethylene polymer, monoammonium phosphate, biammonium phosphate, and a mixture thereof.
However, even with any of the flame retardants recited in these publications, it is still impossible to render a polyacetal resin of low oxygen index flame-retardant to a satisfactory level.
Japanese Patent Application Laid-Open No. 26840/1973 (JP-48-26840A) discloses a self-extinguishable mold material comprising, as a base, polyoxymethylene containing 5 to 15% by weight of fine red phosphorus adjusted to neutral or basic and 1 to 40% by weight of glass fibers. Japanese Patent Application Laid-Open No. 31899/1978 (JP-53-31899A) discloses a flame-retardant polyoxymethylene composition containing, relative to polyoxymethylene, a blend of red phosphorus and a triazine compound, guanidlne, cyanoguanidine, or its derivative (e.g., a phosphate, a condensed phosphate, methylol derivative). Japanese Patent Application Laid-Open No. 84348/1980 (JP-55-84348A) discloses a flame-retardant acetal resin composition formed by incorporating a molybdenum compound and red phosphorus or a phosphorus-containing compound to an acetal resin.
However, even with the use of any of the red phosphorus-based flame retardant recited in these publications, it is still difficult to make the polyacetal resin flame-retardant to a satisfactory level. Particularly, since the polyacetal resin does not become flame-retardant if the amount of the flame retardant is small, the inherent characteristics of the polyacetal resin are largely degraded.
Accordingly, an object of the present invention is to provide a polyacetal resin composition of high flame retardancy and stability, a process for producing the same, and a shaped article made therefrom.
Another object of the present invention is to provide a resin composition the addition of a small amount of which to a polyacetal resin renders high flame retardancy and stability thereto, a process for producing the same, and a shaped article formed therefrom.
Still another object of the present invention is to provide a polyacetal resin composition with improved heat stability (or melt-stability upon molding), a process for producing the same, and a shaped article formed therefrom.
DISCLOSURE OF INVENTION
The inventors of the present invention made intensive studies on the flame retardation and stabilization of a polyacetal resin to achieve the objects mentioned above, and finally found that it is possible to impart high flame retardancy and stability to a polyacetal resin by constituting a flame retardant with a phosphorus-containing compound and a specific aromatic compound and using the resulting flame retardant in combination with a basic nitrogen-containing compound, albeit the amount of the flame retardant to be added is small. The present invention was accomplished based on the above finding.
That is, the resin composition of the present invention comprises a polyacetal resin, a flame retardant, and a basic nitrogen-containing compound, wherein the flame retardant comprises a phosphorus-containing compound and an aromatic compound which in association with the phosphorus-containing compound accelerates the flame-retardation. The phosphorus-containing compound includes red phosphorus, (poly)phosphates, phosphoric acid esters, organic phosphonates, and organic phosphinates. Exemplified as the aromatic compound are compounds having a hydrocarbon ring reactive to formaldehyde or their derivatives (e.g., hydroxyl and/or amino group-containing phenolic compounds, or their derivatives), and the aromatic compound may be an aromatic ring-containing resin. As the basic nitrogen-containing compound, urea and derivative thereof, amidine derivatives, aminotriazine and derivatives thereof, pyrimidine and derivatives thereof, hydrazine and derivatives thereof, amide-series compounds, and urethane-series compounds are available. The resin composition may further contain a dripping inhibitor, an antioxidant, a filler, an inorganic flame retardant, an inhibitor for inhibiting the formation of a phosphoric acid derivative, an impact resistance improver, and others.
The present invention includes a process for producing a flame-retardant polyacetal resin composition by mixing a polyacetal resin, the above-described flame retardant, and a basic nitrogen-containing compound together, and a shaped article formed from the polyacetal resin composition.
BEST MODE FOR CARRYING OUT THE INVENTION
[Polyacetal Resin]
The polyacetal resin is a macromolecular compound containing the oxymethylene group (—CH
2
O—) as a predominant constituent unit and includes polyacetal homopolymers or polyoxymethylene (e.g., “Derlin” manufactured by DuPont, U.S.A; “Tenac 4010” manufactured by Asahi Chemical Industry Co., Ltd.; etc.) and polyacetal copolymers comprising the oxymethylene unit and a comonomer unit (e.g., “Duracon” manufactured by Polyplastics Co., Ltd.). Referring to such copolymers, the comonomer unit includes oxyalkylene units having 2 to 6 carbon atoms (preferably about 2 to 4 carbon atoms) (e.g., oxyethylene (—CH
2
CH
2
O—), oxypropylene, and oxytetramethylene units). The proportion of such comonomer unit may be small and can be selected within the range of about 0.01 to 20 mol %, preferably about 0.
Nixon & Vanderhye PC
Polyplastics Co. Ltd.
Szekely Peter
LandOfFree
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