GB2054610A

GB2054610A - Flame-retardant resin compositions

Info

Publication number: GB2054610A
Application number: GB8021409A
Authority: GB
Original assignee: Idemitsu Kosan Co Ltd
Current assignee: Idemitsu Kosan Co Ltd
Priority date: 1979-07-07
Filing date: 1980-06-30
Publication date: 1981-02-18
Also published as: IT8049164A0; DE3025139A1; GB2054610B; FR2460977A1; CA1161980A; IT1145666B; DE3025139C2; FR2460977B1

Abstract

A flame-retardant resin composition comprises a thermoplastics resin, an organohalogen compound, and a condensate resin of an aromatic hydrocarbon and formaldehyde or such a condensate resin modified by a phenol, an alkyl phenol, an organic acid, an alcohol or an amine. The flame-retardant resin composition preferably further comprises an "antioxidant" being or containing sulphur.

Description

SPECIFICATION Flame-retardant resin compositions The invention relates to flame-retardant resin compositions.

The use of thermoplastics resins in some applications has been limited for safety reasons, since they are generally easily flammable. To improve the flame retardant properties of thermoplastics resins, flame retardants such as organohalogen compounds and phosphoric acid esters and additionally auxiliary flame retardants such as antimony trioxide have been added.

Recently, standards for flame resistance, for example the UL standard, have been raised year by year. To meet the required standards it has been necessary to add increasingly large amounts of flame retardants to the resin.

However, increasing the amount of flame retardant added causes deterioration of the physical properties of the resin composition and also gives rise to various problems, including discolouration of the resin, liberation of poisonous or corrosive gases during melt moulding due to pyrolysis of the flame retardant, deterioration of the weather resistance of the resin and toxicity of the flame retardant itself.

The invention provides a flame-retardant resin composition comprising a thermoplastics resin, an organohalogen compound, and a condensate resin of an aromatic hydrocarbon and formaldehyde or such a condensate resin modified by a phenol, an organic acid, an alcohol or an amine.

A flame-retardant resin composition according to the invention may further comprise an antioxidant being or containing sulphur.

The thermoplastics resin is the base component of a composition according to the invention.

Examples of suitable thermoplastics resins are styrene based resins such as polystyrenes, rubbermodified polystyrenes, HI polystyrenes, styrene-butadiene copolymers, styrene-acrylonitrile copolymers and styrene-butadiene-acrylonitrile copolymers; polyolefin resins such as polyethylenes, polypropylenes and ethylene-propylene copolymers; polyamide resins; polycarbonate resins; polyester resins; vinyl chloride based resins; and methyl methacrylate resins. Of these thermoplastic resins, the styrene based resins, especially rubber-containing styrene based resins, are preferred.

The 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, for example bromine, chlorine or fluorine, in the molecule can be used.

Representative examples include aromatic halogen compounds such as hexabromobenzene, pentabromotoluene, biphenyl bromide, triphenyl chloride, diphenyl ether bromide, tetrachlorophthalic acid, tetrabromophthalic anhydride, tribromophenol, tribromophenyl dibromoalkyl ether, tetrabromobisphenol S, tetrachlorobisphenol A, and 2, 2-bis(4-hydroxy-3, 5-dibromophenol)pro- pane (hereinafter referred to as "tetrabromobisphenol A"); alicyclic halogen compounds such as monochloropentabromocyclohexane, hexabromocyclododecane, perchloropentacyclodecane, and hexachloroendomethylenetetrahydrophthalic anhydride; and aliphatic halogen compounds such as chlorinated paraffin (chlorinated wax), chlorinated polyethylene, tetrabromoethane, tetrabromobutane, tris(P-chloroethyl)phosphate, tris(dichloropropyl)phosphate, tris(dibromopropyl)phosphate, and tris(chlorobromopropyl)phosphate. A mixture of an organobromine compound and an organochlorine compound which provides a synergistic effect is preferred. In such a mixture, it is preferred to have an atomic ratio of Cl/(Br + Cl) of from 0.01 to 0.1.

Although the amount of the organohalogen compound included in the composition according to the invention varies depending upon the type and amount of the other components and other conditions, it is preferably from 2 to 30 parts by weight, more preferably from 5 to 30 parts by weight per 100 parts by weight of the thermoplastics resin. 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, various disadvantages, such as deterioration in physical properties of the composition, liberation of poisonous gases during melt moulding or the burning of the moulded product, and an increase in corrosion, are imparted.

The condensate resin of an aromatic hydrocarbon and formaldehyde functions in combination with the organohalogen compound to provide the final resin composition with flame retardant properties. It is effective in preventing fusion dropping during burning of the moulded product.

Various condensate resins can be used, including xylene-formaidehyde resins and mesityleneformaldehyde resins, which are obtained by condensing xylene or mesitylene and formaldehyde in the presence of a strong acid catalyst, and modified resins prepared by modifying the xyleneor mesitylene-formaldehyde resin with a phenol or alkylphenol, an organic acid, an alcohol and an amine. Examples of suitable alkylphenols are ocresol, nxcresol, Rcresol, 3,5-xylenol and p,p-dihydroxylphenyl methane. Examples of suitable organic acids are acetic acid, propionic acid and benzoic acid. Examples of suitable alcohols are methanol and ethanol. A suitable amine is aniline.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", respectively. Resins of this type are described in United States Patent Specification No. 4082728.

These condensate resins may be in any state, liquid, syrup, powder or solid, and they are subject to no special limitations in molecular weight. However, taking into account the physical properties, for example heat resistance of the product composition, powdered or solid condensate resins having a relatively higher melting point are preferred.

The use of a novolak resin, a melamine resin, a phenoxy resin or the like in place of the xylene resin or mesitylene resin brings about almost no increase in the flame retardant properties of the resin composition.

The amount of the condensate resin, which is added can appropriately be determined according to various conditions. Usually it is from 0.2 to 30 parts by weight per 100 parts by weight of the thermoplastics resin, the range of 0.5 to 20 parts by weight being preferred and the range of from 2 to 1 5 parts by weight being more preferred. When it is less than 0.2 parts by weight, an insufficient effect is obtained. When it exceeds 30 parts by weight, the physical properties of the composition may be reduced, and it is not desirable from an economic standpoint.

By further including in the composition according to the invention a sulphur and/or a sulphurcontaining antioxidant, the flame retardant properties of the resin composition can be further improved. While the details of the mechanism the antioxidant contributes to the improvement in the flame retardant properties of the resin composition is not clear, it is considered that it may cause a certain chemical reaction during burning of the moulded product.

These sulphur and sulphur-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-Nphenyldithiocarbamate, zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate and zinc dibutyldithiocarbamate; xanthogenic acid salts such as sodium isopropylxanthogenate, zinc isopropylxanthogenate and nickel isopropylxanthogenate; thiurams such as tetramethylthiuram monosulphide, tetraethylthiuram disulphide and dimethyldiphenylthiuram disulphide; thiazoles such as 2-mercaptobenzothiazole, zinc salt of 2-mercaptobenzothiazole and dibenzothiazole disulphide; and benzoimidazoles such as 2-mercaptobenzoimidazole, zinc salt of 2-mercaptobenzoimidazole and 2-mercaptomethylbenzoimidazole.Of these antioxidants, those having low volatilities are preferred.

If trinonylphenyl phosphite, tricresyl phosphate, 2,6-di-t-butyl- cresol or other commonly used antioxidants for thermoplastics resins, are used in place of the sulphur-containing antioxidant, almost no improvement in the flame retardant properties is observed.

The amount of the sulphur or sulphur-containing antioxidant included in a composition according to the invention can appropriately be determined according to various conditions.

Usually it is from 0.1 to 1 5 parts by weight per 100 parts by weight of the thermoplastics resin with the range of from 0.2 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 1 5 parts by weight, the physical properties of the composition deteriorate and it is not desirable from an economic standpoint.

In addition to the aforementioned components of a composition according to the invention, such adjuvants (additives) as an auxiliary flame retardant, a reinforcing agent, a filler, a thermal stabilizer, an ultraviolet absorbing agent, a plasticizer, a lubricant and a colouring agent, can be incorporated in the resin composition.

As the auxiliary flame retardant, antimony trioxide is mainly used and additionally zirconium dioxide, molybdenum oxide, aluminium hydroxide, zinc borate or barium methaborate can be used. The amount of the auxiliary flame retardant to be added is not critical. Usually it is from 1 to 10 parts by weight per 100 parts by weight of the thermoplastics resin, the range of from 2 to 6 parts by weight being preferred.

Various reinforcing agents and fillers can be used depending upon the end use of the composition. Examples are rubbers, organic fibres, inorganic fibres such as glass fibre and carbon fibre, calcium carbonate, talc, clay and aluminium hydroxide.

When producing the composition according to the invention, the components 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 mixer, a monoaxial extruder, a diaxial extruder, or the like.

In the composition according to the invention, due to the aromatic hydrocarbon-formaldehyde condensate resin incorporated therein, sufficient flame retardant effect can be obtained even when the amount of the organohalogen compound is smaller than that in conventional thermoplastics resins. By further adding the sulphur or sulphur-containing antioxidant, superior flame retardant effects are obtained. 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, for example deterioration in physical properties such as weather resistance and mechanical strength, and liberation of poisonous gases. Furthermore, since the drip resistance of the resin composition is improved, almost no fusion dropping is observed.

The resin compositions according to the invention are useful as raw materials in the production of electrical applicances, mechanical parts, materials for automobiles, building materials, ornamental products, and the like.

The following Examples, in which all parts and percentages are parts and percentages by weight, illustrate the invention.

Examples 1 and 2 To 100 parts of a rubber-modified polystyrene (Idemitsu Polystyrene HT-58 produced by Idemitsu Petrochemical Co. Ltd) were added *11 parts of tetrabromobisphenol A, 3 parts of antimony trioxide and 6 parts of a xylene resin. The xylene resin in Example 1 was xylene S100 produced by Mitsubishi Gas Chemical Co. Ltd. and the xylene resin in Example 2 was a xylene residue modified with alkylphenol HP-100 also produced by Mitsubishi Gas Chemical Co.

Ltd. The resulting mixtures were each melt-kneaded with a Banbury mixer and pelletized with a sheet pelletizer. These pellets were injection moulded to prepare test pieces of 3 X 6.5 x 127 mm. The bromine content of both compositions was 5.4%. The oxygen index of the test piece of Example 1, measured according to ASTM D 286370 was 27.5 and that of the test piece of Example 2 was 30.5.

Example 3 From 100 parts of an acrylonitrile-butadiene-styrene resin (ABS Resin JSR-35, produced by Japan Synthetic Rubber Co. Ltd.), 1 5 parts of tetrabromobisphenol A, 4 parts of antimony trioxide and 8 parts of a xylene resin modified with alkylphenol J-20, produced by Matsushita Denko K.K., a test piece was prepared by the method described in Examples 1 and 2.

The oxygen index of this test piece was 31.0.

Examples 4 to 9 In the manner described in Examples 1 and 2, test pieces were produced from 100 parts of the rubber-modified polystyrene of Examples 1 and 2, 4 parts of antimony trioxide, 1 5 parts of tetrabromobisphenol A (except Example 6 in which 1 2 parts thereof were used together with 3 parts of chlorinated wax A-70, produced by Toyo Soda Kogyo K.K.) and the number of parts specified in Table 1 of the xylene resin of Example 3. The oxygen indices of these pieces were measured, and the results are shown in Table 1 which also shows the results of the UL 94 Standard Vertical burning test carried out on Tinch thick moulded test pieces produced from pelletized compositions obtained in Examples 5 and 8.

Table 1 First Second Xylene burning burning resin Oxygen time time Cotton Burning Example (parts) index (secs) (secs) ignition property 4 2 25.0 - - - - 5 4 26.0 3.1 9.3 No 94V-1 6 4 31.5 - - - - 7 6 26.5 - - - - 8 8 28.0 1.2 3.7 No 94V-0 9 12 29.0 - - - - Examples 10 to 12 To 100 parts of the rubber-modified polystyrene of Examples 1 and 2 were added 1 5 parts of tetrabromobisphenol A, 4 parts of antimony trioxide and an amount specified in Table 2 of a mesitylene resin. The mesitylene residue used in Example 10 was Nikanol M, produced by Mitsubishi Gas Chemical Co.Ltd; that used in Examples 11 and 1 2 was an alkyl phenol modified mesitylene residue produced by the same company as Nikanol HP 1 50. The resulting mixtures were each melt-kneaded with a Ban bury mixer and pelletized with a sheet pelletizer.

These pellets were injection moulded to prepare test pieces of 3 X 6.5 X 127 mm, and these pieces were measured for their oxygen index according to ASTM D 286370. The results are shown in Table 2.

Example 13 In the manner described in Examples 10 to 12, a test piece was produced from 100 parts of the acrylonitrilebutadiene-styrene residue of Example 3, 1 5 parts of tetrabromobisphenol A, 4 parts of antimony trioxide and 4 parts of the mesitylene resin of Examples 11 and 1 2. The oxygen index of this test piece was 35.

Table 2 Mesitylene Bromine content resin in resin Oxygen Example (parts) composition (%) index 10 2 7.3 25.5 11 2 7.3 29.0 12 4 7.2 34.0 Examples 14 to 19 Pellets were produced in the manner described in Example 10 from 100 parts of the rubbermodified polystyrene of Examples 1 and 2, 4 parts of antimony trioxide, 1 5 parts of tetrabromobisphenol A (except Examples 1 4 and 1 9 in which 14 parts thereof were used together with 1 part of the chlorinated wax used in Example 6, and Example 1 5 in which 14 parts of tetrabromobisphenol A were used together with 1 part of decrolan [Decrolanplus 515 produced by Fukka Chemical Shat) and the number of parts specified in Table 3 of mesitylene resin.The mesitylene resin used in Examples 1 4 and 1 5 was the same as that used in Example 10 and the mesitylene resin used in Examples 1 6 to 1 9 was the same as that used in Examples 11 and 1 2. The pellets were injection moulded to prepare test pieces (thickness T inch) which were subjected to UL 94 Standard Vertical Burning Test. The results are shown in Table 3.

Examples 20 to 25 To 100 parts of the rubber-modified polystyrene of Examples 1 and 2 were added 4 parts of antimony trioxide, 2 parts of the mesitylene resin of Examples 11 and 12, the number of parts specified in Table 4 of tetrabromobisphenol A and the number of parts specified in Table 4 of the chlorinated wax of Example 6. The parts of tetrabromobisphenol A and of chlorinated wax were chosen such that the molar ratio of halogens in the composition is constant. The resulting mixtures were processesd in the manner described in Example 10 to produce test pieces.

The results are shown in Table 4 and in the drawing, which is a plot of the oxygen index against the atomic ratio of chlorine to (bromine + chlorine).

Table 3 First Second Mesitylene burning burning resin time time Cotton Burning Example (parts) (secs) (secs) ignition property 14 1 3.2 1.6 No V-O 15 1 2.9 2.5 No V-O 16 2 4.3 9.1 Yes V-2 17 3 2.5 5.6 No V-l 18 4 1.3 1.2 No V-O 19 2 1.6 2.1 No V-O Table 4 Tetrabromo- Chlorinated bisphenol A wax Oxygen Atomic ratio Example (parts) (parts) index Cl/(Br + Cl) 20 15 0 29.0 0 21 14 0.34 31.5 0.03 22 13 0.68 30.5 0.06 23 11 1.37 28.5 0.13 24 9 2.05 27.5 0.25 25 0 5.13 24.0 1.00 Examples 26 to 30 To 100 parts of the rubber-modified polystyrene of Examples 1 and 2 were added 1 5 parts of tetrabromobisphenol A, 4 parts of antimony trioxide, 4 parts of a xylene resin and 1 part of an additive. The xylene resin used in Example 26 was the same as that used in Example 1; in Examples 27 to 30 it was the same as that used in Example 2.The nature of the additive is given in Table 5. The resulting mixtures were each melt-kneaded with a Banbury mixer and pelletized with a sheet pelletizer. These pellets were injection moulded to prepare test pieces of 3 X 6.5 X 127 mm, and the oxygen index of these pieces was measured according to ASTM D 2863-70.

The results are shown in Table 5.

Examples 31 and 32 Examples 26 and 27 were repeated except that the rubber modified polystyrene was replaced by the acrylonitrile-butadiene-styrene resin of Example 3 and the xylene resin was replaced in Example 26 by the mesitylene resin of Example 10 and in Example 27 by the mesitylene resin of Examples 11 and 12.

The oxygen index of the composition of Example 31 was 34.5 and that of the composition of Example 32 was 38.0.

Table 5 Oxygen Example Additive Index 26 2-mercaptobenzothiazole 32.0 27 2-mercaptobenzothiazole 35.0 28 Zinc N-ethyl-N-phenyldithiocarbamate 33.0 29 Zinc salt of 2-mercaptobenzoimidazole 39.5 30 Sulphur 36.5 Examples 33 to 39 To 100 parts of the rubber-modified polystyrene of Examples 1 and 2 were added 1 5 parts of tetrabromobisphenol A, 4 parts of antimony trioxide, either the xylene resin of Example 2 or the mesitylene resin of Examples 11 and 12, and an additive. The numbers of parts of xylene resin, mesitylene resin and additive added are given in Table 6 together with the nature of the additive. The resulting mixtures were each melt-kneaded with a Banbury mixer and pelletized with a sheet pelletizer.These pellets were injection-moulded to produce test pieces (thickness r inch) which were subjected to UL-94 Standard Vertical Burning Test.

The results are shown in Table 6.

Table 6 Xylene Mesitylene resin resin Additive Example (parts) (parts) (parts) 33 4 0 2-mercaptobenzothiazole (0.5) 34 4 0 Zinc N-ethyl-N-phenyldithio- carbamate (0.5) 35 4 0 Zinc salt of 2-mercaptobenzo imidazole (0.5) 36 0 2 2-mercaptobenzothiazole (0.5) 37 0 2 Zinc N-ethyl-N-phenyldithio- carbamate (0.5) 38 0 2 Zinc salt of 2-mercaptobenzo imidazoje (0.25) 2-mercaptobenzothiazole 39 0 1 (0.25) Zinc salt of 2-mercaptobenzo imidazole (0.25) Table 6 continued First Second burning burning time time Cotton Burning Example (secs) (secs) ignition property 33 0.7 2.1 No V-O 34 0.6 1.1 No V-O 35 0.6 1.3 No V-0 36 0.7 2.2 No V-0 37 0.7 1.2 No V-0 38 0.7 1.5 No VO 39 2.2 1.8 No V-0

Claims

1. A flame-retardant resin composition comprising a thermoplastics resin, an organohalogen compound, and a condensate resin of an aromatic hydrocarbon and formaldehyde or such a condensate resin modified by a phenol, an organic acid, an alcohol or an amine.

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. A composition according to any preceding claim wherein the thermoplastics resin is a styrene based resin.

5. A composition according to any preceding claim wherein the thermoplastics resin is a polystyrene, a rubber-modified polystyrene, a styrene-butadiene copolymer, a styrene-acrylonitrile copolymer, or a styrene-butadiene-acrylonitrile copolymer.

6. A composition according to any preceding claim wherein the aromatic hydrocarbon of Component C is xylene.

7. A composition according to any of claims 1 to 5, wherein the aromatic hydrocarbon of Component C is mesitylene.

8. A composition according to any preceding claim wherein the organohalogen compound is a mixture of an organobromine compound and an organochlorine compound.

9. A composition according to claim 8 wherein the atomic ratio of chlorine to (bromine plus chlorine) is from 0.01 to 0.1.

10. A composition according to any preceding claim further comprising an antioxidant being or containing sulphur.

11. A composition according to claim 10 wherein the sulphur-containing antioxidant is a dithiocarbamic acid salt, a xanthogenic acid salt, a thiuram, a thiazole, or a benzoimidazole.

1 2. A composition according to claim 10 or claim 11 wherein the antioxidant is present in an amount of from 0.1 to 1 5 parts by weight per 100 parts by weight of the thermoplastics resin.

1 3. A composition according to any of claims 10 to 1 2 wherein the antioxidant is present in an amount of from 0.2 to 8 parts by weight per 100 parts by weight of the thermoplastics resin.

14. a flame-retardant resin composition substantially as described herein with reference to any of the Examples.