FLAMEPROOF THERMOPLASTIC RESIN COMPOSITION Field of the Invention The present invention relates to a flame retardant thermoplastic resin composition. More particularly, the present invention relates to a thermoplastic resin composition with good flame retardancy and heat resistance by employing a ring-shaped phosphonic acid compound to the blend of rubber modified polystyrene resin and polyphenylene ether resin.

Background of the Invention Polyphenylene ether resin has good thermal resistance, high impact strength, and good dimensional stability. Accordingly, the resin has been widely applied for common uses. However, the disadvantage could be observed that the polyphenylene ether resin has poor processability due to its excessively high thermal resistance. For this reason, the polyphenylene ether resin is blended with a rubber-modified styrenic resin or a styrenic resin to improve processability for use of electronic appliances such as personal computers, facsimiles, and the like.

Further, in case that a blend of a polyphenylene ether and a rubber modified styrene-containing resin is applied to the fields of electric or electronic goods, flame-retardant property should be given to the resin.

A widely known method for giving the flame retardant property is that a halogen-containing compound or an antimony-containing compound is added to a rubber modified styrene-containing resin. However, the disadvantages could be observed that the halogen-containing compound results in the corrosion of the mold itself by the hydrogen halide gases released during the molding process and is fatally harmful due to the toxic gases liberated in case of fire. Especially, polybromodiphenyl ether, mainly used for a halogen containing flame retardant, can

produce toxic gases such as dioxin or furan during combustion. So, flame-retardants that are prepared without a halogen-containing compound have become a major concern in this field.

U. S. patent No. 3, 639, 506 discloses a resin composition using triphenyl phosphate (TPP) as a flame retardant for giving flame retardancy to a polyphenylene ether resin and a stryrenic resin. However, in this case, halogen-containing compound should be added in order to overcome the degradation of heat resistance, because the heat resistance of the resin composition is lowered due to the addition of TPP.

U. S. patent No. 3,883, 613 discloses a resin composition using trimesityl phosphate as a flame retardant to a polyphenylene ether resin and a stryrenic resin.

U. S. patent No. 4,526, 917 discloses a resin composition using TPP and trimesityl phosphate as flame retardants. However, a large amount of flame retardant is needed to obtain sufficient flame retardancy.

Accordingly, the present inventors have developed a flame retardant thermoplastic resin composition which has excellent flame retardancy but not show deterioration of heat resistance by employing a ring-shaped phosphonic acidcompound to the blend of rubber modified polystyrene resin and polyphenylene ether resin.

Objects of the Invention An object of the present invention is to provide a flame retardant thermoplastic resin composition with good flame retardancy by using ring-shaped phosphonic acidcompound as a flame retardant.

Another object of the present invention is to provide a flame retardant thermoplastic resin composition with good heat resistance.

Other objects and advantages of this invention will be apparent from the ensuing disclosure and appended claims.

Summary of the Invention The flameproof thermoplastic resin composition according to the present invention comprises (A) 20 to 90 parts by weight of a rubber modified polystyrene resin; (B) 10 to 80 parts by weight of a polyphenylene ether resin; (C) 0.1 to 30 parts by weight of a ring-shaped phosphonic acid compound, per 100 parts by weight of the sum of (A) and (B); and (D) 0 to 25 parts by weight of an aromatic phosphoric acid ester compound, per 100 parts by weight of the sum of (A) and (B).

Detailed Description of the Invention (A) Rubber modified polystyrene resin The rubber-modified polystyrene resin used in the present invention as a base resin can be prepared by blending a rubber, an aromatic mono-alkenyl monomer and/or alkyl ester monomer and polymerizing with heat or a polymerization initiator.

The Rubber which can be used in this invention includes butadiene rubbers, isoprene rubbers, styrene-butadiene copolymers and alkylacrylic rubbers. The amount of the rubber is 0 to 30 parts by weight, preferably 0 to 15 parts by weight.

Further, the monomer used in rubber-modified polystyrene is one or more monomer selected from the group consisting of aromatic mono-alkenyl monomer, alkyl ester monomers of acrylic acid or methacrylic acid. The amount of the monomers is 70-100 parts by weight, preferably 85-97 parts by weight.

The resin composition of the present invention can be polymerized with heat or a polymerization initiator. The polymerization initiator used in the present invention may be one or more selected from the group consisting of organic peroxides such as benzoyl peroxide, t-butyl hydroperoxide, acetyl peroxide and cumene hydroperoxide or azo compounds such as azobisisobutyronitrile (AIBN).

The rubber-modified polystyrene resin of the present invention can be

produced by a known polymerization method such as bulk polymerization, suspension polymerization, emulsion polymerization or combination thereof.

Among them, the bulk polymerization is preferred.

To acquire optimum physical properties in consideration of the blend of rubber-modified polystyrene resin and polyphenylene ether, the average size of rubber particles is preferably in the range of from 0.1 to 6. 0, um (z-average), more preferably 0.25 to 3.5 tan (z-average). The rubber-modified polystyrene resin or polystyrene resin without rubber may be used in single or in combination as a mixture.

(B) Polyphenylene Ether (PPE) Polyethylene ether is added to the rubber-modified polystyrene resin to improve flame retardancy and heat resistance.

Examples of the polyphenylene ether resin include poly (2,6-dimethyl- 1, 4-phenylene) ether, poly (2, 6-diethyl-1, 4-phenylene) ether, poly (2,6-dipropyl - 1, 4-phenylene) ether, poly (2-methyl-6-ethyl-1, 4-phenylene) ether, poly (2-methyl-6-propyl-1,4-phenylene) ether, poly (2-ethyl-6-propyl-1,4-phenylene) ether, poly (2,6-diphenyl-1, 4-phenylene) ether, copolymer of poly (2, 6-dimethyl-1, 4-phenylene) ether and poly (2,3, 6-trimethyl-1, 4-phenylene) ether, and copolymer of poly (2, 6-dimethyl-1, 4-pheylene) ether and poly (2,3, 5-triethyl-1, 4-phenylene) ether. Preferably, copolymer of poly (2, 6-dimethyl-1, 4-phenylene) ether and poly (2,3, 6-trimethyl-1, 4-phenylene) ether, and poly (2, 6-dimethyl-1, 4-phenylene) ether are preferably used, more preferably poly (2, 6-dimethyl-1, 4-phenylene) ether is preferably used.

The degree of polymerization of polyphenylene ether is not limited specifically, but considering heat-stability or processability of the resin composition, it is preferable that the viscosity of polypheylene ether is in the

range of about 0.2 to 0.8 measured in chloroform solvent at 25 C.

The base resin is composed of 20-90 parts by weight of the rubber-modified polystyrene resin (A) and 10-80 parts by weight of the polyphenylene ether resin (B).

(C) Ring-Shaped Phosphonic Acid Ester Compound The ring-shaped phosphonic acid ester compound of the present invention is represented by the following chemical Formula (I): wherein R1 and R2 are independently of each other substituted or non-substituted Cl-C20 alkylene group, substituted or non-substituted Cl-C20 alkenylene group, substituted or non-substituted Cl-C20 alkynylene group, substituted or non-substituted C6-C30 arylene group, substituted or non-substituted C6-C30 arylakylene group, substituted or non-substituted C-C30 heteroalkylene group, substituted or non-substituted C6-C30 heteroarylene group, substituted or non-substituted C6-C30 hetero arylakylene group; and x is 0 or 1.

Examples of the ring-shaped phosphonic acid ester compound having the structural formula (I) include methyl-bis (5-ethyl-2-methyl-1, 3,2-dioxaphorinan- Syl) methyl methyl phosphonic acid ester P-oxide, methyl-bis (5-ethyl-2-methyl- 1, 3, 2-dioxaphorinan-Syl) phosphonic acid ester P, P'-dioxide.

The ring-shaped phosphonic acid ester compound (C) of present invention is used in the amount of from 0.1 to 30 parts by weight 100 parts by weight of the base resin containing (A) + (B).

(D) Aromatic phosphoric acid ester compound The aromatic phosphoric acid ester compound used in the present invention is a compound having the following structural formular (H) : wherein R3, R4 and R5 independently of one another are hydrogen or CI-4 alkyl ; X is a C6 20 aryl group or alkyl-substituted Cg. 2o aryl group that are derivatives from a dialcohol derivative such as resorcinol, hydroquinol and bisphenol-A; and n is 0-4.

Where n is 0, the compound represented in the structural formular (II) is triphenyl phosphate, tricresyl phosphate, trixyrenyl phosphate, tri (2,6-dimethyl phenyl) phosphate, tri (2,4, 6-trimethyl phenyl) phosphate, tri (2,4-ditertiary butyl phenyl) phosphate, tri (2,6-ditertiary butyl phenyl) phosphate, and the like, and where n is 1, the compounds include resorcinolbis (diphenyl) phosphate, resorcinolbis (2,6-dimethyl phenyl) phosphate, resorcinolbis (2, 4-ditertiary butyl phenyl) phosphate, hydroquinolbis (2, 6-dimethyl phenyl) phosphate,

hydroquinolbis (2, 4-ditertiary butyl phenyl) phosphate, and the like. The compounds can be used alone or in combination therewith.

In the present invention, the aromatic phosphoric acid ester can be used in the amount of 0 to 25 parts by weight per 100 parts by weight of base resin.

Other additives may be contained in the resin composition of the present invention. The additives include an anti-dripping agent, an impact modifier, a plasticizer, inorganic filler, a heat stabilizer, an anti-oxidant, a compatibilizer, a light stabilizer, a pigment, and/or dye. The inorganic filler is such as metal oxide, asbestos, glass fiber, talc, ceramics, a carbonate, and a sulphate. The additives are employed in the amount of 0 to 30 parts by weight on the basis of 100 parts by weight of the base resin.

The present invention may be better understood by reference to the following examples that are intended for the purpose of illustration and are not to be construed as in any way limiting the scope of the present invention, which is defined in the claims appended hereto.

Examples The components to prepare flameproof thermoplastic resin compositions in Examples and Comparative Examples are as follows: (A) Rubber Modified Polystyrene Resin (al) Rubber modified polystyrene resin: High impact polystyrene of Cheil Industries Inc. of Korea (Product name: HR-1380F) was used. The particle size of butadiene rubber was 1.5 tan. And the content of rubber was 6.5 % by weight.

(a2) Styrenic resin : General purpose polystyrene (GPPS) of Cheil Industries Inc. (product name: HF-2680) with a weight average molecular weight of 210, 000 was used.

(B) Polyphenylene Ether Resin (PPE) (bl) Poly (2,6-dimethyl-phenyl ether) by Asahi Kasei Co. of Japan (product name: P-402) in the form of powder was used. The particles had the average size of several microns (µm).

(b2) Poly (2,6-dimethyl-phenyl ether) by GE (product name: HPP-820) in the form of powder was used. The particles had the average size of several microns (, tan).

(C) Ring-shaped phosphonic acid ester Compound Antiblaze 1045 of Rhodia Co. which contains 20.8 % of phosphorus [a mixture of 8 % by weight of methyl-bis (5-ethyl-2-methyl-1, 3, 2-dioxaphorinan-Syl) methyl methyl phosphonic acid ester P-oxide and 85 % by weight of methyl-bis (5-ethyl-2-methyl-1, 3, 2-dioxaphorinan-Syl) phosphonic acid ester P, P'-dioxide] was used.

(D) Aromatic Phosphoric Acid Ester Compound (dl) Triphenylphosphate produced by Daihachi Chemical of Japan with a melting point of 48 °C was used.

(d2) Resorcinol bis (2,6-dimethylphenyl) phosphate produced by Daihachi Chemical of Japan (product name: PX200) was used.

(d3) Bisphenol-A diphosphate produced by Daihachi Chemical of Japan (product name: CR-741) was used.

(d4) Resorcinol diphosphate produced by Daihachi Chemical of Japan (product name: CR-733S) was used.

(E) Additives Teflon (registered trademark) 7AJ by Dupont company was used.

Examples 1-11 The components as shown in Table 1 were mixed and the mixture was extruded at 200-280 °C with a conventional twin screw extruder in pellets. The resin pellets were dried at 80 °C for 3 hours, and molded into test specimens using a 6 oz injection molding machine at 180-280 °C and barrel temperature of 40-80 °C. The flame retardancy of the test specimens was measured in accordance with UL94VB with a thickness of 1/8". The heat resistance was measured according to ASTM D-1525 under 5 kg. The test results are presented in Table 1.

Table 1 Comparative Examples Eszmples 1 2 3 4 5 6 7 8 9 10 11 1 2 3 4 (a1) 67 67 67 67 67 67 67 37 67 70 75 67 67 67 67 (A) (a2) - - - - - - - 30 - - - - - - - (b1) 33 33 33 33 33 33 33 33 - - - 33 33 33 33 (B) (b2) - - - - - - - - - 33 30 25 - - - - (C) 3 3 3 3 5 10 15 3 3 4 5 - - - - (d1) 9 - - - - - - - - - - 12 - - - (d2) - 16 - - 14 9 4 10 10 10 10 - 19 - - (D) (d3) - - 17 - - - - - - - - - - - 20 - (d4) - - - 12 - - - - - - - - - - 15 (E) 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 UL941/8" V-0 V-0 V-0 V-0 V-0 V-0 V-0 V-0 V-0 V-0 V-0 V-1 V-1 V-1 V-1 VST 87 86.5 86 86.5 88 92 96 94 94 90 86 83 84 83 83

As shown above, the resin compositions employing a ring-shaped phosphonic acid ester compound and aromatic phosphoric acid ester compound as a flame retardant show higher flame retardancy and heat resistance compared to those employing an aromatic phosphoric acid ester compound alone.

The present invention can be easily carried out by an ordinary skilled person in the art. Many modifications and changes may be deemed to be with the scope of the present invention as defined in the following claims.