Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-12-06
2004-05-18
Yoon, Tae H. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S138000, C524S233000, C524S235000, C524S395000
Reexamination Certificate
active
06737453
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a flame retardant thermoplastic resin composition. More particularly, it relates to a non-halogen-based flame retardant thermoplastic resin composition which are excellent in impact resistance, heat resistance and flame retardancy, especially practical impact resistance.
Conventionally, ABS resins having flame retardant properties have been extensively used in various applications such as electric and electronic devices and office automation (OA) devices because these resins are excellent in moldability, mechanical properties or the like. In recent years, there is a tendency that the use of halogen-based flame retardants in these products should be avoided from the viewpoint of environmental protection. For this reason, there have been presently marketed such flame retardant materials composed of a polycarbonate (PC)/ABS alloy resin as a base resin and a phosphate-based flame retardant.
However, in the case where the polycarbonate (PC)/ABS alloy resin is used in combination with the phosphate-based flame retardant, the obtained materials tend to show a poor moldability and be deteriorated in chemical resistance.
In consequence, conventionally, many studies have been made to produce flame retardant materials from ABS base resins and a non-halogen-based flame retardant without using the PC resins. However, there have not been developed any practical materials capable of exhibiting a flammability evaluation rating of V-0 or higher as prescribed in UL94 as well as satisfactory properties.
As a result of the present inventors' earnest study to solve the above problem, it has been found that the problem can be solved by such a flame retardant thermoplastic resin composition comprising a specific rubber-reinforced thermoplastic resin and a specific phosphorus-based flame retardant. The present invention has been attained on the basis of the above finding.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a flame retardant thermoplastic resin composition containing an ABS resin as a base resin and a phosphoric acid-based flame retardant which is capable of exhibiting a flammability rating of V-2 as prescribed in UL94 and can be used in extensive applications due to excellent properties thereof.
To attain the above aim, in an aspect of the present invention, there is provided a flame retardant thermoplastic resin composition comprising:
(A) 100 parts by weight of a rubber-reinforced thermoplastic resin comprising:
a graft copolymer (A1) produced by graft-polymerizing a monomer component (b) containing an aromatic vinyl compound, a cyanided vinyl compound and, if required, the other copolymerizable monomer in the presence of a rubber polymer (a) containing polymer particles having a particle size of not more than 150 nm in an amount of 0 to 15% by weight, polymer particles having a particle size of from more than 150 to less than 350 nm in an amount of 60 to 100% by weight and polymer particles having a particle size of not less than 350 nm in an amount of 0 to 40% by weight, or a mixture of the graft copolymer (A1) and a copolymer (A2) of monomer component (b′),
said rubber-reinforced thermoplastic resin (A) having a graft ratio of 20 to 150% and a rubber polymer content of 8 to 20% by weight; and
(B) 5 to 20 parts by weight of a phosphorus-based flame retardant comprising a condensed phosphoric acid ester, a phosphazene compound or mixture thereof, which condensed phosphoric acid ester is represented by the general formula (I):
wherein R
1
, R
2
, R
3
and R
4
are independently phenyl or xylenyl; X is a divalent group derived from resorcinol or bisphenol A; and n is 0.5 to 1.2.
DETAILED DESCRIPTION OF THE INVENTION
The rubber-reinforced thermoplastic resin (A) used in the present invention (hereinafter referred to as “rubber-reinforced resin”) comprises a graft copolymer (A1) produced by graft-polymerizing a monomer component (b) containing an aromatic vinyl compound, a cyanided vinyl compound and, if required, the other copolymerizable monomer in the presence of a rubber polymer (a) having a specific particle size distribution, or a mixture of the graft copolymer (A1) and a copolymer (A2) of a monomer component (b′).
As the rubber polymers (a), there may be exemplified polybutadiene, hydrogenated products of polybutadiene, styrene/butadiene copolymers, butadiene/acrylonitrile copolymers, ethylene/propylene or ethylene/propylene
on-conjugated diene copolymers, ethylene/butene-1 or ethylene/butene-1
on-conjugated diene copolymers, isobutylene/isoprene copolymers, acrylic rubbers, styrene/butadiene/styrene block copolymers, styrene/isoprene/styrene block copolymers, polyurethane rubbers, silicone rubbers or the like. Examples of the styrene/butadiene copolymers may include styrene/butadiene random copolymers, styrene/butadiene block copolymers or hydrogenated products thereof.
The rubber polymers may be used alone or in the form of a mixture of any two or more thereof. Among these rubber polymers, polybutadiene, styrene/butadiene copolymers, ethylene/propylene or ethylene/propylene
on-conjugated diene copolymers and silicone rubbers are preferred. The rubber polymers used in the present invention are preferably latex-like polymers though not limited thereto.
In the present invention, the particle size distribution of the rubber polymer (a) is very important. The rubber polymer is required to have the following particle size distribution. Namely, the rubber polymer contains polymer particles having a particle size of not more than 150 nm in an amount of 0 to 15% by weight, preferably 0 to 12% by weight; polymer particles having a particle size of from more than 150 to less than 350 nm in an amount of 60 to 100% by weight, preferably 65 to 100% by weight; and polymer particles having a particle size of not less than 350 nm in an amount of 0 to 40% by weight, preferably 0 to 35% by weight.
When the particle size distribution of the rubber polymer which has a large influence on rubber orientation of molded products, lies within the above-specified range, the obtained molded products can exhibit a good practical impact strength. Here, the “rubber orientation” means such a phenomenon that rubber particles are deformed in the flowing direction by shear force applied upon molding. When the rubber orientation becomes remarkable, the practical impact strength of the obtained molded product is lowered. When the content of the rubber polymer having a particle size of not more than 150 nm is more than 15% by weight, the stress distribution effect by rubber particles within the molded product may be deteriorated, resulting in poor practical impact strength of the molded product. When the content of the rubber polymer having a particle size of not less than 350 nm is more than 40% by weight, the rubber orientation of the molded product becomes considerably increased, resulting in poor practical impact strength of the molded product. Meanwhile, the “practical impact strength” used in the present invention means a falling weight impact strength.
The particle size distribution of the rubber polymer (a) may be controlled by appropriately selecting kind and amount of emulsifier, kind and amount of initiator, polymerization time, polymerization temperature, stirring conditions, etc., which are ordinarily used upon the production of the rubber polymer. Alternatively, the particle size distribution of the rubber polymer (a) may also be controlled by blending at least two kinds of rubber polymers (a) having different particle sizes with each other.
The rubber polymer (a) has a gel fraction of preferably 40 to 98% by weight, more preferably 50 to 95% by weight, especially preferably 60 to 90% by weight. When the gel fraction of the rubber polymer (a) lies within the above specified range, the obtained molded product is more excellent in gloss and impact resistance on the surface thereof.
Meanwhile, the gel fraction of the rubber polymer (content of toluene-insoluble components) is determined by the follow
Matsusaka Kunio
Noro Masahiko
Sumimoto Norifumi
Techno Polymer Co., Ltd.
Yoon Tae H.
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