Process for producing granular fire retardant

Compositions – Fire retarding – For solid synthetic polymer and reactants thereof

Patent

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Details

252604, 524281, C09K 2114, C09K 2108, C08K 504, C08K 541

Patent

active

051805251

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to a process for producing a granular fire retardant consisting of a halogenated carbonate compound having excellent processability, workability and heat resistance.


BACKGROUND ART

Polybutylene terephthalate, ABS resin, etc. are in wide use in electric and electronic parts, machine parts, automobile parts and other applications, for their excellent properties. These thermoplastic resins, however, are inherently flammable and accordingly their application fields are restricted. Hence, a halogenated polycarbonate oligomer was proposed as a flame retardant for said resins.
In order to impart fire retardancy to a thermoplastic resin, it has conventionally been necessary to mix a thermoplastic resin ordinarily of pellet or chip form with a fire retardant and, as necessary, other additives and melt-extrude the resulting mixture by the use of an extruder to obtain a fire-retardant thermoplastic resin of pellet form. However, the above fire retardant is a very fine powder, and accordingly this invites poor processability such as generation of layer separation and bridging at the hopper portion of extruder, insufficient biting by the screw portion, and the like; as a result, the fire retardant has a drawback in that its uniform mixing is difficult and the final product obtained has low quality. Further, the fire retardant has a drawback of poor workability; for example, the fire retardant becomes dust by itself, significantly deteriorating the working environment. Furthermore, the fire retardant contains a considerable amount of the solvent (methylene chloride) used in the production thereof, and there is a fear that the solvent may adversely affect the quality of the final product obtained. In order to improve the above-mentioned poor processability and workability, Japanese Laid-Open Patent Publication No. 149738/1987 proposes a granulation method wherein a halogenated hydrocarbon type fire retardant is cold-powderized under pressure. However, to granulate a halogenated polycarbonate oligomer by the above granulation method employing cold powderization under pressure, there are drawbacks in that a large pressure of 100-2,000 kg/cm.sup.2 is required and further the granules obtained are easily disintegrated during transportation or working.


OBJECT OF THE INVENTION

The object of the present invention is to provide a process for producing a granular fire retardant consisting of a halogenated carbonate compound having excellent workability, processability and heat resistance.
The present inventors made extensive study in order to achieve the above object and, as a result, found that a halogenated carbonate compound having a particular specific viscosity can be easily granulated by melt-extruding it by the use of an extruder and then immediately cutting the extrudate and that the solvent content in the granules obtained can be reduced to such a level as to pose no problem. The finding has led to the completion of the present invention.


DISCLOSURE OF THE INVENTION

The present invention resides in a process for producing a granular fire retardant, characterized by melt-extruding a halogenated carbonate compound having at least one unit represented by the following general formula (i) ##STR1## (X is a bromine atom or a chlorine atom, and R.sup.1 is an alkylene group of 1-4 carbon atoms, an alkylidene group or --SO.sub.2 --) and having a specific viscosity of 0.015-0.10, by the use of an extruder and then immediately cutting the extrudate into granules.
The halogenated carbonate compound used in the present invention is a compound having a unit represented by the general formula (i). As the halogenated bisphenol which is a constituent of the unit, there can be mentioned 2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane, 2,2-bis(3,5-dichloro-4-hydroxyphenyl)propane, bis(3,5-dibromo-4-hydroxyphenyl)methane, 1,1-bis(3,5-dibromo-4-hydroxyphenyl)ethane, bis(3,5-dibromo-4-hydroxyphenyl)sulfone, etc. 2,2-Bis(3,5-dibromo-4-hydroxyphenyl)propane which is called tetrabromobisphenol

REFERENCES:
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patent: 4123587 (1978-10-01), Wesch et al.
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patent: 4530880 (1985-07-01), Taniuchi et al.
patent: 4721583 (1988-01-01), Poisson et al.
patent: 4849134 (1989-07-01), Georlette et al.
patent: 4987269 (1991-01-01), Petri
patent: 5047498 (1991-09-01), Petri

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