Organic compounds -- part of the class 532-570 series – Organic compounds – Phosphorus esters
Reexamination Certificate
1999-08-12
2003-07-22
Mulcahy, Peter D. (Department: 1713)
Organic compounds -- part of the class 532-570 series
Organic compounds
Phosphorus esters
C564S013000, C524S086000
Reexamination Certificate
active
06596893
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to crosslinked phenoxyphosphazene compounds, flame retardants, flame-retardant resin compositions and moldings of flame-retardant resins.
BACKGROUND ART
Plastics are used for applications such as electric and electronic products, office automation equipment, office equipment and communications equipment because of their excellent processability, mechanical properties, appearance and the like. The resins used in these applications are required to have flame retardancy for protection against the heat and ignition of internal parts in devices and appliances.
In order to impart flame retardancy to thermoplastic resins or thermosetting resins, a flame retardant is generally added to the resin prior to molding of the resin. Known as flame retardants are inorganic hydroxides, organic phosphorus compounds, organic halogen compounds, halogen-containing organic phosphorus compounds and the like.
Among said flame retardants, those having high flame-retardancy are halogen-containing compounds such as organic halogen compounds, halogen-containing organic phosphorus compounds and the like.
However, these halogen-containing compounds undergo thermal decomposition during molding of the resin to generate hydrogen halide, thereby causing corrosion of the metallic mold and degradation and discoloration of the resin. Another problem is that, when the resin is burned in a fire or the like, hydrogen halide and the like are evolved as gases and smokes detrimental to organisms.
On the other hand, halogen-free flame retardants are magnesium hydroxide, aluminum hydroxide and like inorganic hydroxides and organic phosphorus compounds.
However, the inorganic hydroxides exhibit flame retardancy due to water generated by thermal decomposition, and therefore produce only low flame-retardancy. Consequently, the inorganic hydroxide must be added in a large amount, but such a large amount addition entails a disadvantage that the inherent properties of resins are impaired.
The organic phosphorus compounds are widely. used because they give relatively high flame-retardancy. Known as typical organic phosphorus compounds are triphenyl phosphate (TPP), tricresyl phosphate (TCP) and the like. However, these organic phosphorus compounds are liquid or low melting solid and thus have a high volatility, posing problems such as lowering of the molding temperature of resins, blocking and their migration to the surface (juicing) during kneading.
Furthermore, resin compositions containing said organic phosphorus compound have the drawback of dripping (falling of molten resin droplets) during burning and spreading of a fire due to the dripping. Consequently, in order to obtain a rating of V-0 (flaming does not continue for more than a specified period, and there are no molten resin drips which ignite cotton) in a flame retardancy test UL-94 (Testing for Flammability of Plastic Materials for Parts in Devices & Appliances) which is a standard test for evaluating flame retardancy, by adding an organic phosphorus compound to a resin, it is necessary to add a fluorine-containing resin such as polytetrafluoroethylene (PTFE) as an agent for preventing dripping of molten resin during burning. However, the fluorine-containing resin contains halogen and evolves gases harmful to human body during combustion, as stated above.
In view of the foregoing prior art drawbacks, it is desired to develop a novel flame retardant which is free of halogen, which has a high melting point and a low volatility, which would not impair the inherent properties of resins such as mechanical properties and processability, which is free from the problems of inducing blocking and juicing during kneading and which does not permit dripping during flaming.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide a compound useful as a flame retardant.
Another object of the invention is to provide a halogen-free flame retardant.
A further object of the invention is to provide a flame retardant which has a high melting point and a low volatility and which does not impair the inherent properties of resins, such as mechanical properties and processability.
A still further object of the invention is to provide a flame retardant which does not present the problems of blocking and juicing in kneading.
Another object of the invention is to provide a flame retardant which does not induce dripping during burning.
An additional object of the invention is to provide a flame retardant which is free from the prior art problems.
A still further object of the invention is to provide a flame-retardant resin composition containing the foregoing flame retardant.
Another object of the invention is to provide a molded articles of flame-retardant resin produced by molding said flame-retardant resin composition.
Another object of the invention is to provide a method for imparting flame retardancy to molded articles of resins.
An additional object of the invention is to provide use of a phosphazene compound for imparting flame retardancy to resin molded articles.
Other features of the present invention will become apparent from the following description.
The inventors of the present invention conducted extensive research to overcome the foregoing prior art problems and found that certain partly crosslinked phenoxyphosphazene compounds can be the desired flame retardants. The present invention was completed based on this novel finding.
According to the present invention, there is provided a crosslinked phenoxyphosphazene compound characterized in that at least one phosphazene compound selected from the group consisting of a cyclic phosphazene compound represented by the formula (1)
wherein m is an integer of 3 to 25 and Ph is phenyl group and a straight-chain phosphazene compound represented by the formula (2)
wherein X represents a group —N═P(OPh)
3
or a group —N═P(O)OPh, Y represents a group —P(OPh)
4
or a group —P(O)(OPh)
2
, and n is an integer of 3 to 1000, and Ph is as defined above is crosslinked with at least one crosslinking group selected from the group consisting of o-phenylene group, m-phenylene group, p-phenylene group, biphenylene group, and a group
wherein A is —C(CH
3
)
2
—, —SO
2
—, —S— or —O—; wherein each of said crosslinking groups is interposed between the two oxygen atoms left after the elimination of phenyl groups from the phosphazene compound; and wherein the amount of the phenyl groups in the crosslinked compound is 50 to 99.9% based on the total amount of the phenyl groups in said phosphazene compound represented by the formula (1) and/or said phosphazene compound represented by the formula (2).
According to the present invention, there is also provided a flame retardant comprising said crosslinked phenoxyphosphazene compound (this flame retardant will hereinafter be referred to as “flame retardant A”).
Flame retardant A comprising the crosslinked phenoxyphosphazene compound of the present invention does not contain halogen, and therefore does not cause the corrosion of the mold and degradation and discoloration of the resin due to the generation of hydrogen halide by thermal decomposition during the resin molding operation, and does not produce gases and smokes detrimental to organisms, such as hydrogen halide, when the resin is burned in a fire or the like. Further, the crosslinked phenoxyphosphazene compound of the present invention has a low volatility and does not lower the molding temperature, and is free from the shortcomings such as blocking or their migration to the surface (juicing) during kneading, and dripping during burning. The incorporation of flame retardant A does not impair inherent properties of resins, such as impact resistance and like mechanical properties, heat resistance, processability and the like.
According to the present invention, there are also provided: (a) a flame-retardant resin composition comprising 100 parts by weight of a thermoplastic resin or a thermosetting resin and 0.1 to 100 parts by weight of flame retardant A; (b) a flame-retarda
Nakacho Yoshifumi
Nishioka Yoichi
Tada Yuji
Yabuhara Tadao
Mulcahy Peter D.
Otsuka Chemical Co. Ltd.
Sughrue & Mion, PLLC
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