Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2000-09-13
2003-10-14
Short, Patricia A. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S437000, C525S450000, C525S462000, C525S467000, C528S168000, C528S287000, C528S354000, C528S363000
Reexamination Certificate
active
06632891
ABSTRACT:
This application is the National Stage Application of PCT/JP99/01169 filed Mar. 11,1999.
TECHNICAL FIELD
The present invention relates to a flame-retardant resin composition and a process for preparing the same, and more particularly to a halogen-free flame-retardant resin prepared by reacting a reactive phosphazene compound as a flame retardant with a polyester resin to impart remarkably increased flame retardance to the resin without vaporization or loss, a composition thereof and a process for preparing the same.
BACKGROUND ART
Because of their superiority in moldability, mechanical properties, electrical characteristics and appearance, plastics are useful as materials for office automation equipment such as computers, word processors, printers and copying machines, electrical appliances such as television sets, videos and game machines, and communications equipment such as telephones and facsimile machines. However, plastics have a drawback of being more flammable than metal materials and inorganic materials. From the viewpoint of safety, there is an increased world-wide demand for making plastics flame-retardant, and regulations were tightened. A variety of methods have been proposed for rendering flammable plastics flame-retardant. Generally the proposed methods comprise mixing plastics with a chlorine compound, a bromine compound or like halogen compounds capable of producing a high flame retardant effect. It is also known to achieve a synergistic flame retardant effect by further adding antimony oxide in the method. Useful bromine compounds include, for example, decabromodiphenyl ether, tetrabromobisphenol-A, brominated phthalimide and like nuclear bromine-substituted aromatic compounds. The addition of these excellent flame retardants imparts a high flame retardance to plastics but poses the following problems: the impact resistance is decreased and heat deformation temperature is lowered; the flame retardant bleeds out on the surface of plastics moldings, resulting in impaired appearance of the moldings; and the mold and screw are eroded in the presence of a decomposition gas of halogen compound in the molding process. Also undesirable from safety and hygiene viewpoints is poison generated from a low-molecular-weight bromine compound or chlorine compound when plastics are processed or burned. In this background, it has been desired to provide a flame-retardant resin composition substantially free of a bromine or chlorine compound or like halogen compounds.
Known methods of rendering plastics flame-retardant without use of a halogen compound include methods wherein plastics are mixed with an inorganic metal hydroxide such as aluminum hydroxide or magnesium hydroxide (JP-A-51-132254, JP-A-56-136832 and JP-A-60-13832). However, the methods require a large amount of the inorganic metal hydroxide to give satisfactory degree of flame retardance, and have a shortcoming that the inherent properties of plastics are lost.
On the other hand, prior art literature disclose techniques for imparting flame retardance without using such inorganic metal hydroxide wherein plastics are mixed with a phosphorus compound such as phosphoric acid ester to impart flame retardance. For example, the proposed flame-retardant resin compositions include a resin composition comprising a blend of mixed resins, i.e. an aromatic polycarbonate and rubber reinforced styrene resin, with triphenyl phosphate and polytetrafluoroethylene (PTFE) (JP-B-9-19003) and a resin composition comprising a blend of mixed resins, i.e. an aromatic polycarbonate and rubber reinforced styrene resin, with an oligomer of phosphoric acid ester and PTFE (NL 8802346). These methods, however, entail various problems in terms of properties of plastics and processability thereof. Stated more specifically, the phosphoric acid ester has a low melting point and poor compatibility with resins so that the resin composition is given low heat resistance, and that the phosphoric acid ester oozes out from the resin in the molding process, thereby soiling the mold and becoming vaporized. JP-A-5-1079 and U.S. Pat. No. 5,122,556 disclose techniques for preparing a flame-retardant resin by mixing a thermoplastic resin with a crystalline powder of aromatic diphosphate flame retardant. The disclosed methods, however, failed to produce a resin composition which is satisfactory both in properties and in processability. Since the phosphoric acid esters used in these techniques have an activity to plasticize the resin, the techniques essentially use PTFE as a drip inhibitor (for inhibiting dripping of live charcoal in burning) and therefore failed to produce a substantially halogen-free flame-retardant resin composition.
Techniques for rendering plastics flame-retardant by mixing plastics with a phosphazene compound as a flame retardant are disclosed in literature. For example, it is proposed to provide a flame-retardant resin composition comprising a polycarbonate resin and a phosphazene compound admixed therewith (JP-A-51-37149), a flame-retardant resin composition comprising a phosphazene compound and a polycarbonate compound or a mixture of the same and other thermoplastic resin (JP-A-7-292233), and a flame-retardant resin composition comprising a phosphazene compound and a mixture of an aromatic polycarbonate resin and a rubber reinforced styrene resin (JP-A-9-53009). When a phosphazene compound is added to the resin, the flame retardance is enhanced as clear from the increase of limiting oxygen index (LOI). Yet, problems remain unresolved since the phosphazene compound used has a low melting point, and the resin composition is lowered in heat deformation temperature, heat resistance and mechanical properties. Further, since PTFE is essentially used as the drip inhibitor, a substantially halogen-free flame-retardant resin composition has not been obtained.
An object of the present invention is to provide a flame-retardant resin which is molded without bleed of flame retardant and which neither reduces the heat deformation temperature of flame-retardant resin composition nor impairs the heat resistance and mechanical properties thereof, its composition and a process for preparing the same.
Another object of the invention is to provide a flame-retardant resin prepared without essential use of PTFE as the drip inhibitor and which is substantially free of halogen, its composition and a process for preparing the same.
DISCLOSURE OF THE INVENTION
The present invention provides a flame-retardant resin composition comprising a phosphazene flame retardant and a polyester resin, wherein the flame retardant is bonded to the molecules of the polyester resin via the ester group thereof.
Preferred embodiments of the invention are as follows.
(1) A flame-retardant resin comprising a phosphazene flame retardant and a polyester resin, wherein the flame retardant is bonded to the molecules of the polyester resin via the ester group thereof.
(2) A flame-retardant resin comprising a phosphazene flame retardant and a polyester resin, wherein ester exchange reaction is carried out using the flame retardant in an amount of 0.1 to 100 parts by weight per 100 parts by weight of the polyester resin.
(3) A process for preparing a flame-retardant resin comprising a phosphazene flame retardant and a polyester resin, the process comprising conducting ester exchange reaction between the flame retardant and the polyester resin in a molten state.
(4) A process for preparing a flame-retardant resin comprising a phosphazene flame retardant and a polyester resin, wherein the phosphazene flame retardant is at least one species selected from cyclic phosphazene compounds and straight-chain phosphazene compounds as defined in claim
2
.
The present inventors found the following. A reactive phosphazene compound as the flame retardant is subjected to ester exchange reaction with a polyester resin to bond to the molecules of polyester resin via the ester group thereof without vaporization or loss of retardant. Using the obtained resin, a flame-retardant resin composition excellent in h
Kameshima Takashi
Nakano Shinji
Nishioka Yoichi
Tada Yuji
Yabuhara Tadao
Otsuka Kagaku Kabushiki Kaisha
Rothwell Figg Ernst & Manbeck
Short Patricia A.
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