CA1161980A

CA1161980A - Flame-retardant resin compositions

Info

Publication number: CA1161980A
Application number: CA000355382A
Authority: CA
Inventors: Kenji Seki; Takashi Nakagawa
Original assignee: Idemitsu Kosan Co Ltd
Current assignee: Idemitsu Kosan Co Ltd
Priority date: 1979-07-07
Filing date: 1980-07-03
Publication date: 1984-02-07
Also published as: DE3025139A1; FR2460977B1; GB2054610B; DE3025139C2; IT8049164A0; IT1145666B; GB2054610A; FR2460977A1

Abstract

ABSTRACT OF THE DISCLOSURE
A flame-retardant resin composition comprising a thermoplastic resin, an oryanohalogen compound, and a condensate resin of an aromatic hydrocarbon and formaldehyde or said resin which has been modified by a phenol, organic acid, alcohol or amine. The preferred embodiment of said flame-retardant resin composition also contains sulfur or a sulfur-containing antioxidant. The flame-retardant resin composition disclosed has improved physical properties and coloration as compared to known flame-retardant resins. The flame-retardant resin disclosed can be effectively used as raw material in the production of electrical appliances, mechanical parts, materials for automobiles and ornamental products.

Description

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1 BACKGROUND OF T~-IE INVENTION
Thermoplastic resins exemplified by styrene basea resins have been used only in limited applications from the point of safety since they are generally easily ~lamrnable.
For the purpose of irnproving the ~lame retardant properties of the thermoplastic resins, therefore, flame retardants, e.g., organohalogen compounds, phosphoric acid esters, etc. t and additionally auxiliary flame retardants, e.g., antimony trioxide, etc., have been added.
Recently, the standards for flame resistance, e.g., the UL standard, have been raised year by year. Therefore, in order to ob~ain resins exhibiting excellent ~lame retardant properties, it has been necessary to add a large amount o~ flame retardant to the resin.
However, an increase in -the amount of the flame retardant which is added causes deterioration of the physical properties of the resin composition and also gives rise to various problems, e.g., discoloration of the resin, liberation of poisonous corrosive gas or deterioration in weather resistance of molded resin products due to the pyrolysis of the flame retardant during melt molding, toxicity of the flame retardant itself, etc.

THE INVENTION
It has now been discovered that by adding to a thermo-plastic resin, a condensate resin of an aromatic hydrocarbon and ~ormaldehyde and optionally other additives, toge-ther with an organohalogen compound which is conven-tionally used as a flame re-tardant, the flame retardant properties of the thermo-plastic resin are improved. A flame retardan-t thermoplastic resin composition can be obtained which is ~ree from the aforedescribed disadvantages.

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1 The invention provides a flame retardant resin composition comprising:
A a thermoplastic resin;
B an organohalogen cornpound; and C a condensate resin of an aromatic hydrocarbon and formaldehyde or said condensate resin modified by at least one substance selected from the group consisting of phenol, organic acid, alcohol and arnine.

It also provides a flame retardant resin composition comprising:

The above components A, B, C and D sulfur and/or a sulfur containing antioxidant.
Component A of this invention, the thermoplastic resin, is the basic component of the present composition. Examples of such thermoplastic resins are styrene base resins such as polystyrene, rubber-modified polystyrene, i~e., polystyrene modified with rubber, HI polystyrerle, styrene-butadiene copolymer, - styrene-acrylonitrile copolymer (AS resin), and styrene-butadiene-acrylonitrile copolymer (ABS resin); polyolefin resins such as polyethylene, polypropylene and ethylene-propylene copolymer, etc.; polyamide resins; polycarbonate resins;
polyester resins; vinyl chloride based resins; methyl methacrylate resins, etc. Of these thermoplastic resins, the styrene based resins, especially rubber-containing styrene based resins, are preferred.
Component B of this invention, an organohalogen compound, functions as a flame retardant, All organohalogen compounds having a flame retarding effect, such as aromatic, alicyclic and aliphatic compounds containing a halogen atom or atoms, e.g., bromine, chlorine and fluorine, in the molecule can be used. Representative examples include aromatic halogen

2--compounds such as hexabromobenzene, pentabromotoluene, biphenyl bromide, triphenyl chloride, diphenyl ether bromide, tetrachlorophthalic acid, tetrabromophkhalic anhydride, txibromophenol, tribromophenyl-dibromoalkyl éther, tetra-bromobisphenol S, tetrachlorobisphenol A, 2,2-bis(~-hydroxy-

3,5-dibromophenol)-propane (hereinafter referred to as "tetrabromobisphenol A"), etc.; alicyclic halogen compounds such as monochloropentabromocyclohexane, hexabromocyclododecane, perchloropentacyclodecane, hexachloroendomethylenetetrahydro-phthalic anhydride, etc.; and aliphatic halogen compounds such as chlorinated paraffin (chlorinated wax), chlorinated polyethylene, tetrabromoethane, tetrabromobutane, tris-(~-chloroethyl)phosphate, tris(dichloropropyl)phosphate, tris-(dibromopropyl)phosphate, tris(chlorobromopropyl)phosphate, etc. A mixture of an organobromine compound and an organo-chlorine compound which provides a synergistic effect is preferred. In said mixture, it is preferred to have an atomic ratio of Cl/(Br ~ Cl) from O.Ol to O.l as the Component B in the composition of the present invention.
~0 While the amount of Component B, i.e., the organo-halogen compound, to be added varies depending upon the type and amount of the other components and other conditions/ it is usually from 2 parts by weight to 30 parts by weight per lO0 parts by weight of Component A, i.e., the thermoplastic resin, with the range of from 5 parts to 20 parts by weight bein~
preferred. When it is less than 2 parts by weight, the resin composition product has unsatisfactory (low) flame retardant properties. When it exceeds 30 parts by weight, varic~us disadvantages, e.g~, deterioration in physical properties of the compostion, liberation of poisonous gases during melt molding or the burniny of the molded product, an increase in - corrosion, etc., take place.

1 Component C of this invention, i.e~, the condensa~e resin o~ an aromatic hydrocarbon and formaldehyde, ~unctions in combina~ion with Component B to provide the final resin composition with flame retardant properties. It is e~eckive in preventing fusion dropping during burning of the molded product. Various condensate resins can be used as Component C, including ~ylene-formaldehyde resins and mesitylene-formaldehyde resins, which are obtained by condensatiny xylene or mesitylene and formaldehyde in the presence of a strong acid catalyst, and modified resins prepared by modifying the xylene- or mesitylene-formaldehyde resin by at least one substance selected from the group consisting of a phenol or alkylphenol, an organic acid, an alcohol and an amine. Examples o~
alkylphenol are o-cresol, m-cresol, p-cresol, 3,5-xylenol, p,p'-dihydroxylphenyl methane, etc. Examples of an oxganic acid are acetic acid, propionic acid, benzoic acid, etc.
Examples of an alcohol are methanol, ethanol, etc. ~xamples of an amine are aniline, etc. The modified and unmodified xylene-formaldehyde resins and the modified and unmodified mesitylene-formaldehyde resins are hereinafter referred to as "a xylene resin" and "a mesitylene resin", respectivelyO
Resins of this type is described in U.S. Pat. No. 4,082,728.
These condensate resins may be in any state of li~uid, syrup, powder and solid, and they are subject to no special limitations in molecular weight. However, taking into account the physical properties, e.g., heat resistance of the product composition, powdered or solid condensate resin having a relatively high melting point if preEerred.

I'he use of a novolak resin, a melamine resin, a phenoxy resin or like in place of the xylene resin or mesitylene resin of this invention brings a~out almost no inarease in the flame retardant properties of the resin composition.

8 ~) 1 The amount of Component C, i.e., -the condensate resin, which is added can appropriately be determined according to various conditions. Usually it is from 0.2 part to 30 parts by weight per 100 parts by weight o~ Component ~, with the range of from 0.5 part by weight to 20 parts by weight being preferred and the range of from 2 parts by weight to 15 parts by weight being more preferred. When it is less than 0.2 part by weight, an insufficient effect is obtained. When it exceeds 30 parts by weight, the physical properties o~ the composition 1~ may be reduced, and it is not desirable from an economic standpoint.
By adding sulfur and/or a sulfur-containing antioxidan-t as Component D in addition to Components A, B, and C, the flame retardant properties of the resin composition can be further improved. While the details o~ the mechanism by which Component D contributes to the improvement in the flame retardant properties of the resin composition is not clear, it is considered that it causes a certain chemical reaction during burning of the molded product.
- 20 These sulfur and sulfur-containing antioxidants can be used singly or in admixtures comprising two or more thereof.
Those compounds generally known as vulcanization accelerators for rubber can be used. Examples are dithiocarbamic acid salts such as zinc N-ethyl-N~phenyldithiocarbamate, zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate and zinc dibutyldithiocarbamate; xanthogenic acid salts such as sodium isopropylxanthogenate, zinc isopropylxanthogenate and nickel isopropylxanthogenate; thiurarns such as te-tramethylthiuram monosulfide, tetraethylthiuram disulfide and dimethyldiphenyl-thiuram disulfide; thiazoles such as 2-mercaptobenzothiazole, zinc salt of 2~mercaptobenzothiazole and dibenzothiazole 1 disulfide; and benzoirrlidazoles such as 2-mercaptobenzoimidazole, zinc salt of 2-mercap-tobenzoimidazole and 2-mercaptomethylbenæo-imidazole. Of these antioxidants, those having low volatilities are preferred.
If trinonylphenyl phosphite (T.N.P.), tricresyl phosphate (T.C.P.), 2~6~di-t-butyl-p-cresol, etc., which are often used as an antioxidant for thermoplastic resins, are used in place of the sulfur-containing antioxidant of this invention, almost no improvement in the flame retardant properties is observed.
The amount of Component D, i.e., the sulfur or sulfur-containing antioxidant, to be added can appropriately be determined accordiny to various conditions. Usually it is from 0.1 part by weight to 15 parts by weight per 100 parts by weight of Component A, with the range of from 0.2 part to 8 parts by weight being preferred. When it is less than 0.1 part by weight, an insufficient effect is obtained. When it exceeds 15 parts by weight, the physical properties of the composition deteriorate and it is not desirable fro~ an economic standpoint.
BRIEF DESCRIPTION OF THE DRAWING
_ .. . .. . _ Fig. l is a graph depicting the flame retardant Pffect when a mixture of an organobromine compound and an organochlorine compound is used as the organohalogen compound in the presence of Component C of this invention.
~ n addition to Cornponents A, B, C, and D, such adjuvants (additives) as an auxiliary ~lame retardant, a reinforcing agent, a filler, a thermal ~tabilizer, an ultraviolet absoring agent, a plasticizer, a lubricant, a coloring agent, 3~
etc., can be incorporated in the resin composition.

As the auxiliary f lame re-tardant, antimony trioxide is mainly used and additionally zirconium dioxide, moly~denurn oxide, aluminum hydroxide, zinc borate, barium methaborate, etc., can be used. The amount of the auxiliary flame retardant to be added is not critical. Usually it is from 1 part by weight to 10 parts by weight per 100 parts by weight of Component A, with the range of from 2 par-ts to 6 parts by weight being preferred.
~ arious reinforcing agents and fillers can be used depending upon the end use o~ the composition, etc. E~amples are rubbers, organic fibers, inorganic fibers such as glass fiber and carbon fiber, calcium carbonate, talc, clay and aluminum hydroxide.
When producing the composition of this invention, Components A, B, C, and D and, as desired, various additives are mixed in a predetermined ratio and fully kneaded by use of a roll mill, a Banbury mixer, a kneader, a Henschel mixèr, a monoaxial extruder, a diaxial extruder, or the like.
In the composition of this invention, due to the aromatic hydrocarbon-formaldehyde condensate resin incorporated therein, sufficient flame retardant e~fect can be obtained even when the amount of the organohalogen compound is smaller than that in conventional thermoplastic resins. By further adding Component D, superior flame retardant effects are ob~ained. According to this invention, the halogen content in the resin composition can be reduced. This effectively prevents the various problems which result from the presence of excess halogen, e.g./ deterioration in the physical properties such as weather resistance, mechanical streng-th, etc., and liberation of poisonous gases. Furthermore, since the drip resistance of the resin composition is improved, almost no fusion dropping is observed.

~ 3 The resin composition of this invention can effec-tively be utilized as raw materials in the produc-tion of electrical appliances, mechanical parts, materials for automo~iles, building materials, ornamental productsl etc.
The following examples and comparative examples are given to illustrate this invention in greater detail.
Examples 1 and 2 To lO0 parts by weight of a rubber-modified polystyrene (Idemitsu Polystyrene HT-58 produced by Idemitsu Petrochemical 1 Co., Ltd.) were added tetrabromobisphenol A, antimony trioxide and a xylene resin in the amount as described in Table l. The resulting mixtures were each melt-kneaded with a Banbury*mixer and pelletized with a sheet pelletizer. These pellets were injection-molded to prepare test piece of 3 millimeters x 6.5 millimeters x 127 millimeters, and the oxygen index (O~Io ? of these pieces we~e measured according to ASTM D 286370.
The results are shown in Table 1.

~3~ ' The procedure of Examples 1 and 2 was repeated except that the xylene resin was not added.
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C~ ~ lt g 1 xample 3 In the same manner as in Exarnples 1 and 2 except that an ABS resin (ABS Resin JSR-35 produced by Japan Synthetic Rubber Co., Ltd.) was used in place of the rubber-modi~ied polystyrene, test pieces were produced by addiny to 100 parts by weight of the ABS resin, tetrabromobisphenol A, antimony trioxide and a xylene resin in the amount as shown in Table 2.
The oxygen index (O.I.) of these pieces were measured.

The results are shown in Table 2.
Comparative E m ~ 3 The same procedure as in Example 3 was repeated except that xylene resin was not added.
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8 ~) 1 Exa~les 4 to 9 In the same manner as in Exarnples land 2, test pieces were produced by adding the components as described in Table 3, and the oxygen index (O.I.) of these pieces was measured.
Additionally, test pieces (thickness 1/8 inch) for the burniny test were molded and subjected to UL 94 Standard Vertical Burning Test. The results are shown in Table 3.
In these examples, 100 parts by weight of polystyrene modified with rubber (Idemitsu Polystyrene HT-58 produced by Idemitsu Petrochemical Co., Ltd.) was used as the thermoplastic resin.
Comparative Example 4 The same procedure as in Example 4 was repeated éxcept that xylene resin and chlorinated wax were not added.

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# () 1 Comparative Exam~le 5 In the method of Example 1, a novolak resin, a melamirle resin or a phenoxy resin was added in an amount of 6 parts by weight in place of the xylene resin to produce khe corresponding test pieces. These pieces were measured for their oxygen index (O.I.) and found 22.0, 22.5 and 23.0, respectively. Almost no improvement in the flame retardant properties was observed.
Examples 10 to 12 To 100 parts by weight of polystyrene modified with rubber (Idemitsu Polystyrene HT-58 produced by Idemitsu Petrochemical Co., Ltd.) were added tetrabromobisphenol A, antimony trioxide and a mesitylene resin in the amount as shown in Table 4. The resulting mixtures were each melt-kneaded with a Banbury mixer and pelletized with a sheet pelletizer~ These pellets were injection-molded to prepare test pieces of 3 x 6.5 x 127 (millimeters),~and these pieces were measured for their oxygen index (O.I.) according to ASTM D 286370. The results are shown in Table 4.
Comparative Examples 6 and 7 The procedure of Examples 10 to 12 was repeated wherein no mesitylene resin was added. The results are shown in Table

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Exam le 13 In the same manner as in Example 10 except that an Ass resin (ABS Resin JSR-35 produced by ~apan Synthetic Rubber Co., Ltd.) was used in place of polystyrene modified wi-th rubber, a test piece was produced by addiny to 100 parts by weight of the ABS resin tetrabromobisphenol A, antimony tri-oxide and a mesitylene resin in the amoun-ts as described in Table 5. The oxygen index of this piece was measured.

The results are shown in Table 5.
Comparative Example 8 The procedure of Example 13 was repeated except tha~
the mesitylene resin was not added~
The results are shown in Table 5.
Table 5 Antimony Mesitylene*
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weight) ~ _ - weight) ........ _ _ Example 13 15 4 4 35 20Example 8 15 4 - Z3 *Trade Name: Mesitylene resin modified with alkylphenol, Nikanol HP 150 produced by Mitsubishi Gas Chemical Co., Ltd.

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1 Examples 14 to 19 In the same manner as in Example 10, pellets were produced. The pellets were injection-moldea for preparing test pieces (thickness 1/8 inch) for the burning test were produced, and they were subjec-ted to UL 94 Standard Vertical Burning Test.
The results are shown in Table 6.
In these examples, 100 parts by weight of rubber-modified polystyrene (Idemitsu Polystyrene HT-58 produced by Idemitsu Petrochemical Co., Ltd.) was used as a thermoplastic resin.
Comparative~ le 9 The procedure of Examples 14 to 19 was repeated except that mesitylene resin was not added.
The results are shown in Table 6.

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1 Examples 20 to 25 To 100 parts by weight of polystyrene modified with rubber (Idemitsu Polystyrene HT-58 produced by Idemitsu Petrochemical Co., Ltd.) were added tetrabromobisphenol A, antimony trioxide, chlorinated wax and a mesitylene resin in the amounts as shown in Table 7, and the resulting mixtures were processed in the same manner as in Example 10 to produce the corresponding test pieces.
The results are shown in Table 7 and Fig. 1 Comparative Exam~les 10 to _ The procedure of Examples 20 to 25 was repeated except that mesitylene resin was not added.
The results are shown in Table 7 and Fig, 1.

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1 Comparative_Exam~le 16 In the ~ethod of Example 10, a novolak resin, a melamine resin or a phenoxy resin was added in an amount of 6 parts by weight in place of the mesitylene resin to produce the corresponding test pieces. The oxygen index of these pieces was measured and found 22.0, 22.5 and 23.0, respectively.
Accordingly, almost no improvement in the flarne retardant properties was observed.
Examples 26 to 30 1~ To 100 parts by weight of polystyrene modified with rubber styrene (Idemi~su Polystyrene HT-58 produced by Idemitsu Petrochemical Co., Ltd.) were added tetrabromobisphenol A
(T~B~Ao ) ~ antimony trioxide, a xylene resin and an Additive in the amounts as described in Table 8. The reswlting mixtures were each melt-kneaded with a Banbury mixer and pelletized with a sheet pelletizer. These pellets were in~ection-molded to prepare test pieces of 3 x 6.5 x 127 (millimeters), and the oxygen index of these pieces was measured according to ASTM D 2863-70.
The results are shown in Table 8.
Comparative Examples 17 to 20 The procedure of Examples 26 to 30 was repeated except that either the xylene resin or the Additive was not added~
The results are shown in Table 8.

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1 Examples 31_and 3?
In the sc~me manner as in Exa~ple 26 except that 100 parts by weight of an ABS resin ~ABS Resin JSR-35 produced by Japan Synthetic Rubber Co., Ltd.) was used as the thermoplastic resin and a mesitylene resin was used in place of the xylene resin, the test pieces were produced, and the oxygen index (O.I.) of the pieces was measured.
The results are shown in Table 9.

Comparative E ~ o ~
The procedure of Examples 31 to 32 was repeated except that either the mesitylene resin or the Additive was not added.
The results are shown in Table 9.
Comparative Example 24 The procedure of ExampleS 31 and 32 was repeated except that the mesitylene resin and the Additive were not added. The result is shown in Table 9.

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The procedure of Example 32 was repeated wherein a non-sulfur-containing antioxidant was used in place of the sulfur-containing antioxidant. The results are shown in Table 9.

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1 Examples 33 to 39 To 100 parts by weight of polystyrene modi~ied with rubher styrene (Idemitsu Polystyrene HT 58 produced by Idemitsu Petrochemical Co., Ltd.) were added tetrabromobisphenol A
(T.B.A.), antimony trioxide, a xylene resin (or a mesitylene resin) and an Additive in the amounts as shown in Tahle 10.
The resulting mixtures were each melt-kneaded with a Banbury mixer and pelletized with a sheet pelletizer. These pellets were injection-molded to produce the corresponding tes-t pieces (thickness 1/8 inch) for the burning test, and these pieces were subjected to UL-94 Standard Vertical Burning Test.
The results are shown in Table 10.
Comparative Exam~_es 27 and 28 The procedure of Examples 33 to 39 was repeated except that the Additive was not added.
The results are shown in Table 10.
Comparative Examples 29 and 30 - The procedure of Examples 36 to 39 was repeated excep-t thàt a non-sulfur-containing antioxidan-t was used ln place of the sulfur-containing antioxidant. The results are shown in Table 10.

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Claims

The embodiments of the invention in which an exclusive property of privilege is claimed are defined as follows:

1. A flame-retardant resin composition comprising A a thermoplastic resin;
B an organohalogen compound; and C a condensate resin of an aromatic hydrocarbon and formaldehyde or said condensate resin modified by at least one substance selected from the group consisting of phenols, organic acids, alcohols and amines.

2. The composition of Claim 1, wherein the weight ratio of said components A : B : C is 100 : (2 to 30) : (0.2 to 30).

3. The composition of Claim 1, wherein the weight ratio of said components A : B : C is 100 : (5 to 20) : (2 to 15).

4. The composition of Claim 2, wherein said thermoplastic resin A is a styrene base resin.

5. The composition of Claim 4, wherein said styrene base resin is selected from the group consisting of polystyrene, rubber-modified polystyrene, styrene-butadiene copolymer, styrene-acrylonitrile copolymer, and styrene butadiene acrylonitrile copolymer.

6. The composition of Claim 1, wherein the aromatic hydrocarbon of Component C is xylene.

7. The composition of Claim 1, wherein the aromatic hydrocarbon of Component C is mesitylene.

8. The composition of Claim 1, wherein the organohalogen compound is a mixture of an organobromine compound and an organochlorine compound.

9. The composition of Claim 6, wherein the organohalogen compound is a mixture of an organobromine compound and an organochlorine compound having an atomic ratio of C1/ (Br + Cl) of from 0.01 to 0.1.

10. The composition of Claim 7, wherein the organohalogen compound is a mixture of an organobromine compound and an organochlorine compound having an atomic ratio of C1/ (Br + Cl) of from 0.01 to 0.1.

11. A flame-retardant resin composition comprising A a thermoplastic resin;
B an organohalogen compound;
C a condensate resin of an aromatic hydrocarbon and formaldehyde or said condensate resin modified by at least one substance selected from the group consisting of phenols, organic acids, alcohols and amines; and D at least one sulfur antioxidant selected from the group consisting of sulfur and sulfur-containing antioxidants.

12. The composition of Claim 11, wherein said sulfur antioxidant is at least one sulfur-containing antioxidant selected from the group consisting of dithiocarbamic acid salts, xanthogenic acid salts, thiurams, thiazoles, and mercaptobenzoimidazoles.

13. The composition of Claim 12, wherein the weight ratio of said Components A : B : C : D is 100 : (2 to 30) :
(0.2 to 30) : (0.1 to 15).

14. The composition of Claim 12, wherein the weight ratio of said Components A : B : C : D is 100 : (5 to 20) :
(2 to 15) : (0.2 to 8).

15. The composition of Claim 12 t wherein said thermoplastic resin A is a styrene base resin.

16. The composition of Claim 12, wherein said aromatic hydrocarbon of Component C is xylene.

17. The composition of Claim 12, wherein said aromatic hydrocarbon of Component C is mesitylene.

18. The composition as claimed in Claim 11, wherein the organohalogen compound is a mixture of an organobromine compound and an organochlorine compound.

19. The composition as claimed in Claim 16, wherein the organohalogen compound is a mixture of an organobromine compound and an organochlorine compound having an atomic ratio of Cl/ (Br + Cl) of from 0.01 to 0.1.

20. The composition as claimed in Claim 17, wherein the organohalogen compound is a mixture of an organobromine compound and an organochlorine compound having an atomic ratio of Cl/ (Br + Cl) of from 0.01 to 0.1.