Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-12-19
2003-02-11
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...
C525S450000, C525S467000
Reexamination Certificate
active
06518336
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to novel flame-retardant resin compositions.
BACKGROUND ART
Thermoplastic resins are used as materials for producing various devices in many fields such as office automation devices, household electrical appliances, etc. because of their excellent molding processability, mechanical properties, appearance and like features. These resins are often required to have flame retardancy depending on use to eliminate problems on exposure to heat and ignition.
In order to impart flame retardancy to thermoplastic resins, it is general to add a halogen-containing organic compound as a flame retardant, such as tetrabromobisphenol A, decabromodiphenyl oxide or the like. However, the inclusion of halogen-containing organic compounds poses problems of reducing the thermal stability of a thermoplastic resin as the matrix, corroding the mold with a gas given off on decomposition of halogen-containing organic compound during molding, or producing as by-product low molecular toxic halogen compounds in molding or on combustion.
Halogen-free phosphoric ester compounds have been proposed as flame retardant for thermoplastic resins. Compositions are proposed in which triphenylphosphate/polytetrafluoroethylene (PTFE) or condensable phosphoric ester/PTFE are incorporated in a resin mixture of aromatic polycarbonate and rubber-fortified styrene resin (European Patent No. 174,493 and Dutch Patent No. 8,802,346), in which a crystalline powdery aromatic diphosphate compound is added to a thermoplastic resin (Japanese Unexamined Patent Publication No. 1079/1993 and U.S. Pat. No. 5,122,556), etc. Halogen-free phosphoric ester compounds have the drawback of adversely affecting the mechanical properties and molding processability of thermoplastic resins although capable of imparting a certain degree of flame retardancy to thermoplastic resins. Further, phosphoric ester compounds tend to plasticize a resin and thus are likely to cause dripping (falling of live charcoal during burning), so that a dripping inhibitor such as PTFE is essentially used. Especially the prevention of dripping is required for attaining a V-0 level of flame retardancy in a test according to the flame retardancy test UL-94 (Test for Flammability of Plastic Materials for Parts in Devices and Appliances UL-94, Fourth Edition).
On the other hand, in order to impart flame retardancy to a resin composition comprising a thermotropic liquid crystal polymer and other thermoplastic resin, use is made of a bromine-containing organic compound such as brominated polystyrene (Japanese Unexamined Patent Publication No. 179051/1991), a phosphoric ester compound (Japanese Unexamined Patent Publications No. 331051/1995 and No. 59524/1997) or the like. However, the incorporation of a bromine-containing organic compound results in lower thermal stability, corrosion of mold during molding process and generation of toxic bromine compounds, as in the above-mentioned case. When a phosphoric ester is used, it is essential to jointly add a dripping inhibitor such as PTFE, a fibrous inorganic filler or the like.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide a novel flame-retardant resin composition which is free of the foregoing-problems of the prior art.
Another object of the invention is to provide a novel flame-retardant resin composition which is free of the problems arising due to the presence of halogen element, excellent in flame retardancy, mechanical properties, molding processability and the like, and unlikely to cause dripping without use of a dripping inhibitor.
Other objects and features of the invention will become apparent from the following description.
The present inventors carried out extensive research to overcome the foregoing problems and found that when a specific flame retardant is added to a mixture of a thermotropic liquid crystal polymer and other thermoplastic resin, the obtained flame-retardant resin composition is excellent in flame retardancy, mechanical strength, and molding processability, and eliminates the need for a dripping inhibitor. The present invention was completed based on this novel finding.
According to the present invention, there is provided a flame-retardant resin composition comprising:
(A) 100 parts by weight of a thermoplastic resin other than a thermotropic liquid crystal polymer,
(B) 0.01 to 50 parts by weight of a thermotropic liquid crystal polymer, and
(C) 1 to 30 parts by weight of a halogen-free phosphazene compound.
The flame-retardant resin composition of the present invention contains, as essential components, (A) a thermoplastic resin other than a thermotropic liquid crystal polymer, (B) a thermotropic liquid crystal polymer, and (C) a halogen-free phosphazene compound.
Conventional resins may be used as the thermoplastic resin (A) other than a thermotropic liquid crystal polymer in the composition of the invention. Examples of such resins are polyethylene, polypropylene, polyisoprene, polybutadiene, polystyrene, high impact-resistant polystyrene (HIPS), acrylonitrile-styrene resin (AS resin), acrylonitrile-butadiene-styrene resin (ABS resin), methyl methacrylate-butadiene-styrene resin (MBS resin), methyl methacrylate-acrylonitrile-butadiene-styrene resin (MABS resin), acrylonitrile-acrylic rubber-styrene resin (AAS resin), polyalkyl (meth)acrylate, aromatic polycarbonate (PC), polyphenylene ether (PPE), polyphenylene sulfide (PPS), polyether sulfone (PES), polysulfone (PSU), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyamide (PA), polyether ketone (PEK), polyether ether ketone (PEEK), polyamide imide (PAI), polyether imide (PEI), Aft polyimide (PI), etc. Among them, preferred are PC, PBT, PPE, ABS resins, HIPS and the like. These resins may be used either alone or in combination. Preferred combinations of two of the resins are PC/ABS, PC/PBT, PPE/HIPS and the like. Among them, PC/ABS is more preferable. The ratio (by weight) of two resins in this case is usually 10-90/90-10, preferably 20-80/80-20.
The thermotropic liquid crystal polymer (B) in the composition of the invention is not known to have drip inhibitory activity itself, but is considered to act as a dripping inhibitor in coexistence with a halogen-free phosphazene compound as in the composition of the invention. Stated more specifically, the thermotropic liquid crystal polymer densely and firmly reinforces the thermoplastic resin so as not to form an inflammable low molecular compound within the thermoplastic resin during combustion, thereby preventing the resin from becoming less viscous with the result that the resin can be inhibited from inducing the level of dripping specified in the flame retardancy test (UL-94) in the presence of the phosphazene compound.
As the thermotropic liquid crystal polymer (B), known polyester-based polymers can be suitably used. Examples are main-chain type liquid crystal polymers such as those having, as main structural units, aromatic hydroxycarboxylic acid, polyalkylenediol and aromatic dicarboxylic acid; those having, as main structural units, aromatic hydroxycarboxylic acid and hydroxynaphthoic acid; and those having, as main structural units, aromatic hydroxycarboxylic acid, aromatic dicarboxylic acid and dihydroxybiphenyl; and side chain-type liquid crystal polymers such as those having polyphosphazene as a main chain and polyalkylenediol and aromatic carboxylic acid as side chains; and those having polyphosphazene as a main chain and poly(alkyleneoxy)alkoxyazobenzene as a side chain. Among them, preferred are polymers having p-hydroxybenzoic acid and polyethylene terephthalate as main structural units, those having p-hydroxybenzoic acid and 2-hydroxy-6-naphthoic acid as main structural units, and a polycondensate of said polymer with a dihydroxy compound and/or dicarboxy compound. The flame retardancy (especially a degree of drip inhibition) and mechanical properties can be further improved by using suitably selected dihydroxy compounds and dicarboxy compounds. Useful dihydroxy compounds are,
Kameshima Takashi
Nakano Shinji
Nishioka Yoichi
Tada Yuji
Takase Hiroyuki
Knobbe Martens Olson & Bear LLP
Otsuka Chemical Co. Ltd.
Szekely Peter
LandOfFree
Flame-retardent resin compositions compring thermoplastic... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Flame-retardent resin compositions compring thermoplastic..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Flame-retardent resin compositions compring thermoplastic... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3128679