Stock material or miscellaneous articles – Hollow or container type article – Polymer or resin containing
Reexamination Certificate
2002-05-13
2004-01-06
Acquah, Samuel A. (Department: 1711)
Stock material or miscellaneous articles
Hollow or container type article
Polymer or resin containing
C525S398000, C525S400000, C524S086000, C524S081000, C524S096000, C524S100000, C524S110000, C524S115000, C524S107000, C524S129000, C524S284000, C524S356000, C524S359000, C524S401000, C524S091000, C428S031000, C428S423100, C428S524000, C428S931000
Reexamination Certificate
active
06673405
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a polyacetal resin composition having excellent weather (light)-resistance and effectively inhibited from emitting (or generating) formaldehyde, to a process of producing the same, and to shaped or molded articles formed with the resin composition.
BACKGROUND ART
A polyacetal resin is inherently unstable in an oxidative atmosphere at an elevated temperature or in an acidic or alkaline environment because of its chemical structure. Therefore, the essential need that must be fulfilled for a polyacetal resin is that of insuring high thermal stability and minimal emission (or generation) of formaldehyde in the course of processing and from shaped articles. In the case of having low thermal stability, a polyacetal resin is heated during a processing step such as extruding or molding to decompose or resolve a polymer thereof, as a result formation or generation of a deposit on a mold (mold deposit) occurs, and the moldability, the mechanical property and others are deteriorated. Formaldehyde generated from decomposition or resolution of a polyacetal resin is chemically active and ready to be oxidized to formic acid to thereby adversely affect the heat resistance of resin and, when the resin is used as electrical or electronic parts, cause corrosion of metallic contacts or their discoloration due to organic deposits, resulting in contact errors. Furthermore, formaldehyde as such contaminates the working environment for parts assembling and the ecology in the field of use of end products.
Therefore, in order to stabilize a polyacetal resin, an antioxidant or other stabilizer has been used. As the antioxidant added to the polyacetal resin, a phenol-series (phenolic) compound having steric hindrance (hindered phenol), an amine compound having steric hindrance (hindered amine), and others have been known. As other stabilizers, melamine, a polyamide, an alkaline metal hydroxide, an alkaline earth metal hydroxide, and others have been used. Moreover, antioxidants are generally used in combination with other stabilizers. However, even when such an additive(s) is/are used, it is difficult to give the polyacetal resin high stability.
Moreover, with the increasing scope and diversification of application of a polyacetal resin, the resin is required to satisfy more and more sophisticated requirements in quality. Furthermore, depending on the use, the polyacetal resin is influenced by a circumferential environment such as ultraviolet rays, wind and rain, temperature, oxygen in the atmosphere, ozone, artificial light and loading on the use. As a result, the polyacetal resin has some problems such as a change of color (or discoloration), a change in quality and degradation (or aging).
Japanese Patent Publication No. 14709/1992 (JP-4-14709B) discloses a polyacetal resin composition in which a polyacetal resin is blended with a hindered amine-series antioxidant, an antistatic agent, and a guamanine derivative such as 3,9-bis[2-(3,5-diamino-2,4,6-triazaphenyl)ethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane (CTU guanamine), to raise high thermal stability and improve the propensity for discoloring caused by a magnetic tape. In this literature, in order to decrease discoloration of the polyacetal resin, a hindered amine-series antioxidant is used instead of a conventional hindered phenol-series (phenolic) antioxidant. Moreover, Japanese Patent Application Laid-Open No. 190248/1987 (JP-62-190248A) discloses a stabilized polyacetal resin composition in which a polyacetal resin is blended with a guanamine derivative (such as benzoguanamine) as a stabilizer to decrease a formaldehyde smell thereof and improve a moldability thereof. However, these resin composition are not capable of having practically enough weather(ing) (light)-resistance, and it is difficult to apply to a use which needs weather (light)-resistance.
Therefore, an object of the present invention is to provide a polyacetal resin composition given excellent weather (light)-resistance, particularly a polyacetal resin composition prevented from degrading or aging due to light after molding, and a process of producing the same, as well as shaped articles made or formed with the polyacetal resin composition.
It is another object of the invention to provide a polyacetal resin composition conducive to a marked inhibition of formaldehyde emission at a low level of addition and contributory to improvements in the circumferential environment, and a process of producing the same, as well as shaped articles as molded therefrom.
It is a still another object of the invention to provide a polyacetal resin composition adapted to inhibit emission of formaldehyde even under severe conditions to suppress deposition of decomposition products on the mold and blooming or bleeding of such products from a shaped article and thermal deterioration of the article, thus contributing to upgrading of the moldability of the shaped articles, and a process of producing the same.
DISCLOSURE OF INVENTION
The inventors of the present invention made intensive studies on a series of nitrogen-containing compounds about a stabilizer of a polyacetal resin to achieve the objects mentioned above, and finally found that certain spiro-compounds give remarkable effects as a stabilizer of the polyacetal resin and are capable of greatly improving weather (light)-resistance of the polyacetal resin by using a hindered phenol-series (phenolic) compound and a weather (light)-resistant stabilizer (a stabilizer for weather (light)-resistance) in combination. The present invention was accomplished based on the above finding.
That is, the polyacetal resin composition of the present invention comprises a polyacetal resin, a hindered phenol-series (phenolic) compound, a weather (light)-resistant stabilizer and a spiro-compound having a triazine ring. The weather (light)-resistant stabilizer (weather(ing) (light) stabilizer) may comprise at least one member selected from the group consisting of a benzotriazole-series compound, a benzophenone-series compound, an aromatic benzoate-series compound, a cyanoacrylate-series compound, an oxalic anilide-series compound, and a hindered amine-series compound. The weather (light)-resistant stabilizer may comprise at least a benzotriazole-series compound, particularly a benzotriazole-series compound and a hindered amine-series compound. The spiro-compound may have two guanamine rings as its end groups. For example, the spiro-compound may be a compound represented by the following formula (1):
wherein R
1
and R
2
are the same or different, each representing an alkylene group, an arylene group, or an aralkylene group.
The polyacetal resin composition may comprise, relative to 100 parts by weight of the polyacetal resin, about 0.001 to 5 parts by weight of the hindered phenol-series compound, about 0.01 to 5 parts by weight of the weather (light)-resistant stabilizer, and about 0.001 to 10 parts by weight of the spiro-compound. The polyacetal resin composition may further comprise a coloring agent, aprocessing stabilizer, a heat stabilizer, and others.
In the process of the present invention, a polyacetal resin composition is produced by mixing a polyacetal resin, a hindered phenol-series compound, a weather (light)-resistant stabilizer, and a spiro-compound having a triazine ring. Furthermore, the present invention includes a shaped or molded article comprising the polyacetal resin composition.
BEST MODE FOR CARRYING OUT THE INVENTION
The resin composition of the present invention comprises a polyacetal resin, a hindered phenol-series compound, a weather (light)-resistant stabilizer and a spiro-compound having a triazine ring.
Polyacetal Resin
The polyacetal resin is a macromolecular compound containing oxymethylene group (—CH
2
O—) as a predominant constituent unit and includes polyacetal homopolymers (e.g. trade name “Delrin”, manufactured by DuPont, U.S.A.; trade name “Tenac 4010”, manufactured by Asahi Chemical Industry Co., Ltd.; etc.) and polyacetal copolymers comprising at least one other
Acquah Samuel A.
Nixon & Vanderhye PC
Polyplastics Co. Ltd.
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