GB1560759A - Flame-retardant additive for polymeric compositions - Google Patents

Description

(54) AN IMPROVED FLAME-RETARDANT ADDITIVE FOR POLYMERIC COMPOSITIONS (71) We, ASSOCIATED LEAD MANUFACTURERS LIMITED, of Clements House, 14--18 Gresham Street, London, EC2V 7AT, a British Company, ANZON LIMITED, of Cookson House, Willington Quay, Walisend, Tyne & Wear, NE28 6UQ, a British Company, ALAN GORDON WALKER, of 5 Langton Co:lrt, Darras Hall, Ponteland, Northumberland, a British subject, and ARTHUR ROY PEPPER, of 59 Wyresdale Crescent, Perivale, Greenford, Middlesex, a British subject, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:: It has long been known to incorporate antimony trioxide in polymeric compositions containing a source of halogen for the purpose of rendering the composition flame-retardant Such flame-retardant properties are required, in particular, in the case of compositions used in colliery belting, in the manufacture of artificial leather, as cable coverings, as building panels and as components of vehicles.

Halogen-containing polymers, such as polyvinyl chloride and polyvinylidene chloride, contain a halogen as part of the polymer. In the case of other polymers, such for example as polyolefins, polyesters, polystyrene, epoxy resins and acrylonitrilebutadiene-styrene copolymers, it is necessary, for flame retardency, to incorporate in the composition, in addition to the antimony trioxide, a chlorinated or brominated organic compound such, for example, as a chlorinated paraffin or decabromodiphenyl oxide.

The present invention is based on the discovery that it is possible to reduce the amount of expensive antimony trioxide required to attain a given degree of flame retardency, and indeed to enhance the flame retardency achieved by incorporation in the composition of a given amount of additive, by using in place of antimony trioxide a mixture in suitable proportions of antimony oxide and zinc phosphate. It has been found that the presence of zinc phosphate has the added advantage of reducing afterglow and smoke evolution, while total replacement of antimony trioxide by zinc phosphate does not produce the desired flame-retardant properties.

The invention accordingly provides a flame-retardant additive, for incorporation in polymeric compositions containing a source of halogen, which consists of a mixture of 90 20% by weight of antimony trioxide and 1()80% by weight of zinc phosphate. Preferably the mixture contains 20 60of by weight of zinc phosphate. If the mixture contains less than 10 ó of zinc phosphate the reduction in cost is not sufficient to make the substitution effective. If the mixture contains more than 80 ó of zinc phosphate the flame-retardant properties of the polymer containing the mixture are not satisfactory.

In practice, as the antimony trioxide present as a flame retardant in a polymeric composition is gradually replaced by zinc phosphate the flame retardancy of the composition, as measured by the limiting oxygen index test noted below, rises and eventually reaches a maximum. Thereafter, as the amount of zinc phosphate used to replace antimony trioxide is further increased, the flame retardancy begins to decrease to that of the initial composition and below this value until, with total replacement, the flame retardency is little different from that of the base polymer, plus halogenated compound (if one was required), as zinc phosphate alone contributes nothing to the flame retardancy. The amount of antimony trioxide which can be replaced before the limiting oxygen index again reaches that of the initial composition varies considerably from composition to composition.

There is thus an economic advantage to be gained in using combinations of antimony trioxide and zinc phosphate up to the point where the limiting oxygen index falls back to that of the initial composition containing antimony trioxide alone.

The additive according to the invention has been shown to be useful in polymers in which the halogen is an integral part of the polymer molecule and in those in which an organic halogen compound is added to the polymer.

In the following Examples parts are by weight, unless otherwise stated: EXAMPLE 1 Unsaturated polyester compositions were prepared using Filabond 8000 resin supplied by Synthetic Resins Limited, to which was added 12 pphr of a solid chlorinated paraffin containing 70% chlorine by weight and the mixtures of antimony trioxide and zinc phosphate shown below. After addition of the appropriate accelerator and catalyst the compositions were cast into sheets 3 mm thick.The flame-retardant properties were determined using the oxygen index method described in ASTM specification D 2863, with the following results: Polyester 100 100 100 100 100 Solid chlorinated paraffin 12 12 12 12 12 Antimony trioxide 8 6 4 18 12.6 Zinc phosphate - 2 4 5A Limiting oxygen index 25.2 29.2 28.2 28.6 31.5 EXAMPLE 2 Unsaturated polyester compositions were prepared as in Example 1 but containing 15 pphr of solid chlorinated paraffin containing 70% chlorine by weight and the mixtures of antimony trioxide and zinc phosphate shown below.After curing as in Example 1, the flame-retardant properties were assessed using the ASTM D 2865 procedure, with the following results: Polyester 100 100 100 100 Solid chlorinated paraffin 15 15 15 15 Antimony trioxide 15 9 10 6 Zinc phosphate - 6 - 4 Limiting oxygen index 31.2 34.7 28,6 31.4 EXAMPLE 3 Polyester compositions prepared as in Example 2 were used to produce glass reinforced laminates containing approximately 25 % glass fibre.The flame-retardant properties were assessed using the small scale spread of flame apparatus described in BS 476 Part 7, with the following results: Polyester 100 100 Solid chlorinated paraffin 15 15 Antimony trioxide 15 9 Zinc phosphate - 6 Max. spread of flame after 10 mins. 35 mm 30 mm.

EXAMPLE 4 Polyvinyl chloride compositions based on Breon S110/10 supplied by BP Chemicals plasticised with 50 pphr of dioctyl phthalate were prepared using a two roll mill. They contained 8 pphr of antimony trioxide. Further compositions were prepared in which 12%; and 25% of the antimony trioxide were replaced by zinc phosphate.The compositions contained appropriate stabilisers and lubricants and after compounding were formed into 3 mm thick sheets which were then used to determine the limiting oxygen index, with the following results: PVC 100 100 100 Dioctyl phthalate 50 50 50 Antimony trioxide 8 7 6 Zinc phosphate - 1 2 Tribasic lead stearate 5 5 5 Bisphenol A 0.1 0.1 0.1 Stearic acid 0.5 0.5 0.5 Limiting oxygen index 31.5 32.2 32.3 EXAMPLE 5 Polyvinyl chloride plastisol compounds, based on Corvic P65/55 supplied by ICI Limited, were prepared incorporating 75 pphr of dioctyl phthalate plasticiser and the appropriate stabilisers. They contained 10 pphr of antimony trioxide. Further com positions were prepared in which 25 % and 50 % of the antimony trioxide were replaced by zinc phosphate.The compositions were formed into sheets 3 mm thick by curing at 180 C. These were then used to determine the limiting oxygen index, with the following results: PVC 100 100 100 Dioctyl phthalate 75 75 75 Antimony trioxide 10 7.5 5 Zinc phosphate - 2.5 5 Epoxy soya oil 2 2 2 Barium/cadmium stabiliser 2 2 2 Limiting oxygen index 28.7 29.0 28.6 EXAMPLE 6 A polyethylene composition was prepared containing 12 pphr of antimony trioxide and 18 pphr of solid chlorinated paraffin. Another composition was prepared in which 50% of the antimony trioxide was replaced by zinc phosphate.The compositions were formed into sheets 3 mm thick which were then used to determine the limiting oxygen index, with the following results: Low density polyethylene 100 100 Solid chlorinated paraffin 18 18 Antimony trioxide 12 6 Zinc phosphate 6 Tin stabiliser 0.5 0.5 Bentone 27 4 4 Limiting oxygen index 26.3 26.3 The tin stabiliser was added to stabilise the chlorinated paraffin during processing.

Bentone 27 supplied by Steetley Limited is a bentonite derivative, added to reduce dripping during flammability testing.

EXAMPLE 7 Polypropylene compositions were prepared containing 18 pphr of chlorinated paraffin and 12 pphr antimony trioxide. Further compositions were prepared in which 50% and 75% of the antimony trioxide were replaced by zinc phosphate. After forming into sheets 3 mm thick, the limiting oxygen index was determined, with the following results: Polypropylene 100 100 100 Solid chlorinated paraffin 18 18 18 Antimony trioxide 12 6 3 Zinc phosphate - 6 9 Tin stabiliser 0.5 0.5 0.5 Bentone 27 4 4 4 Limiting oxygen index 21.5 22.4 21.9 EXAMPLE 8 Polypropylene compositions were prepared as in Example 7 but using decabromodiphenyl oxide supplied by I.S.C. Chemicals Limited in place of chlorinated paraffin.

The results were as follows: Polypropylene 100 100 Decabromodiphenyl oxide 18 18 Antimony trioxide 12 6 Zinc phosphate - 6 Tin stabiliser 0.5 0.5 Bentone 27 4 4 Limiting oxygen index 22.1 22.0 EXAMPLE 9 High impact polystyrene samples were prepared containing 18 pphr of decabromodiphenyl oxide and 12 pphr of antimony trioxide. Further compositions were prepared in which 25% and 50% of the antimony trioxide were replaced by zinc phosphate.

The compositions were formed into sheets, 3 mm thick and the limiting oxygen index determined, with the following results : - High impact polystyrene 100 100 100 Decabromodiphenyl oxide 18 18 18 Antimony trioxide 12 9 6 Zinc phosphate 3 6 Tin stabilizer 0.5 0.5 0.5 Limiting oxygen index 25.3 25.3 25.3 The zinc phosphate used in all the Examples was normal zinc phosphate.

It should be noted that values of limiting oxygen index, which differ by 0.1 units, are identical within the limits of experimental error of the test. Thus Examples 5 and 8 both show that 50% of the antimony trioxide can be replaced by zinc phosphate, with corresponding saving in cost, without reducing the flame retardancy of the polymer.

"Filabond", "Breon", "Corvic" and "Bentone" are Registered Trade Marks.

U.S. Specification No. 3,945,974 discloses the incorporation in halogen-containing polymer compositions of zinc or a compound of zinc as a smoke suppressant and preferably also of a flame retardant. Example 16 in Table II of this specification discloses specifically a polyvinyl chloride formulation containing zinc as a smoke suppressant and of the following composition: PVC resin Geon 102 EPFS (B.F.Goodrich Co.) 100 parts Clarite NS-2 (Modified dibutyltin maleate stabilizer) 1.5 parts Dioctyl phthalate 50 parts Antimony trioxide (flame retardant) 3.0 parts Tribasic zinc phosphate 1.12 parts Test results showing the DM value of this composition when tested under nonflaming conditions in the NES Smoke Chamber are given but there is no suggestion or disclosure that the presence of the tribasic zinc phosphate affected in any way the flame retardancy of the composition. We make no claim to said polyvinyl chloride composition disclosed in Example 16 of U.S. Specification No. 3,945,974.

Subject to the foregoing disclaimer, WHAT WE CLAIM IS: 1. A flameretardant additive, for incorporation in polymeric compositions containing a source of halogen, which consists of a mixture of 90-20 , by weight of antimony trioxide and 10-80% by weight of zinc phosphate.

2. An additive according to claim 1, in which the mixture contains 2060 íJ by weight of zinc phosphate.

3. A halogenated polymer containing a flame-retardant additive according to claim

Claims (1)

1 or claim 2.

4. A polymeric composition in which the polymer is not halogenated and which contains a chlorinated or brominated organic compound and a flame-retardant additive according to claim 1 or claim 2.

5. A polymeric composition according to claim 4, which contains chlorinated paraffin as the chlorinated organic compound.

6. A polymeric composition according to claim 4, which contains decabromodiphenyl oxide as the brominated organic compound.

7. A polymer according to claim 3, substantially as described herein with reference to the foregoing Example 4 or Example 5.

8. A polymeric composition according to claim 4, substantially as described herein with reference to any of the foregoing Examples 1, 2, 3 and 6 to 9.