GB2142638A

GB2142638A - Flame retardant for polymers, and polymers containing same

Info

Publication number: GB2142638A
Application number: GB08416200A
Authority: GB
Inventors: Alan Docherty; Alan Gordon Walker
Original assignee: ANZON Ltd
Current assignee: ANZON Ltd
Priority date: 1983-07-04
Filing date: 1984-06-26
Publication date: 1985-01-23
Also published as: GB8416200D0

Abstract

Plastics materials are provided with flame retardant properties at reasonable cost and without the disadvantage of evolution of a toxic or corrosive substance by flame retardant compositions which consist of an inorganic phosphate and a polyhydroxy compound, which components are preferably present in a ratio of from 15:1 to 0.5:1. The polyhydroxy compound is preferably penta-, dipenta- or tripenta- erythritol and the inorganic phosphate is preferably annmonium polyphosphate.

Description

SPECIFICATION Flame retardant for polymers, and polymers containing same The use of antimony oxide and other antimony compounds asflame retardants is well established. It has been found, however, that to achieve the required properties, antimonay compounds have to be used with a halogenated organic additive. The presence of such a compound gives riseto the evolution during a fire of a hydrogen halide (e.g. HC1 and HBr) which can cause corrosion of metal components. This is seen as a particular problem when very sensitive electronic equipment (e.g. computers) is exposed to the halide.

Consequently, there has been a significant increase in the need for non-halogenated flame retardant polymeric systems.

There are already available a number of organic phosphorus based products which can be incorporated into some polymers in orderto reduce their flammability. These products do not provide a com plete solution to the problem, however, because they are expensive and in a fire some of them can produce unacceptable levels of smoke and toxic fumes.

Anotherwayto flame retard plastics materials is to incorporate in the material agents which when heated produce an insulating surface layer offoam, thus preventing decomposition ofthe plastics material beneath the surface layer of foam and so substantially preventing evolution oftoxic or flammable gases.

This foaming phenomenon has been referred to as "intumescence". It is well established in the literature that to achieve a satisfactory effectthree components are necessary, that isto say:- (a) a carbon producing product-e.g. polyhydric alcohol (b) a catalyst-e.g. ammonium polyphosphate (c) a gas producing product-e.g. an organonitrogen compound The catalyst (b} catalyses the decomposition of components (a) and (c) to form afoamed carbonaceous mass.

The literature relating to this method of flame retardancy points out the necessity of using all three components and also ensuring that decomposition occurs at the right temperature and in the right sequence.

U.S. Patent 4,312,805, while indicating that, for polymers which can easilyform carbon, it is not necessaryto provide a carbon-producing product as a separate additive, supports the other literature to the extent that the presence of an organo-nitrogen compound is necessary. U.S. Patent 4,312,805 is very specific in its choice of such nitrogen compounds.

Itis an object ofthe present invention to provide a solution to the problem of endowing plastics materials with flame retardant properties at reasonable cost and without the disadvantage of evolution of a toxic or corrosive substance.

According to a first aspect of the present invention there is provided an additive composition for endowing a flammable, non-halogen containing, plastics material with a flame retardant property, the additive composition comprising a polyhydroxycompound and a catalyst of the dehydrating reaction of the polyhydroxy compound in the presence of heat, the additive being substantially free of content of any organo-nitrogen compound.

According to a second aspect of the present invention there is provided a combination of a flammable, non-haiogen containing, plastics material and an additive composition comprising a polyhydroxy compound and a catalyst of the dehydrating reaction of the polyhydroxy compound in the presence of heat, the combination being substantially free of content of any organo-nitrogen compound and having a flame-retardant property and being free of evolution of a toxic or corrosive substance when resisting spread of flame.

Tests have shown that, for many polymers, the use of an organo-nitrogen compound is unnecessary. To achieve flame retardancy, all that is required is a mixture of a catalyst (preferabiy an inorganic phosphate, most preferably ammonium polyphosphate) and a polyhydroxy compound.

Preferably addition of the additive to a polymer is made in an amount of from lotto 45 parts per hundred (pph). Preferably, the additive comprises a mixture of the inorganic phosphate and the polyhydroxy compound in the ratio offrom 15:1 to 0.5:1.

A more preferred level of addition is a range of from 25to35 pph.

A particularly preferred ratio is a range of from 3:1 to 1:1.

Specific examples of polymers susceptible of treatmentwith the present invention are: polyethylene, polypropylene, polyester, epoxy, ABS and polystyrene.

Examples of polyhydroxy compounds useful in the invention are sugars, erythritol, pentaerythritol, de pentaerythritol and tripentaerythritol, arabitol, sorbitol, inositol, resorcinol and starches.

The usefulness of the invention is demonstrated in the following Table of Test Results. Those skilled in the are will befamiliarwith the designations "UL-94", which is a reference to Underwriters Laboratories- USA, and "Limiting Oxygen Index"which is a reference to the proportion of oxygen in an atmosphere, justsufficientto allow the composition under test to burn.

TABLE

Identification Polymer Polypropylene I ABS Polystyrene High density Epoxy of Additive Polyethylene Resin Component and Flame Test pphpolymer 100 100 100 100 100 100 pph ammonium polyphosphate 15 10 22.5 22.5 30 12 pph penta erythritol 15 20 7.5 7.5 15 4 UL94Rating V-O V-O nottested not tested V-O V-O Limiting Oxygen Index 26.1 26.3 22.5 23.9 27.0 29.0

Claims

1. Aflame retardant composition comprising a poylhydroxy compound and a catalyst ofthe dehyd- rating reaction ofthe polyhydroxy compound in the presence of heat, the composition being substantially free of content of any organo-nitrogen compound.

2. Aflame retardant composition consisting of a polyhydroxy compound and a catalystofthe dehydrating reaction ofthe polyhydroxy compound in the presence of heat.

3. Acomposition as claimed in claim 1 or2 wherein the catalyst is an inorganic phosphate.

4. Aflame retardant composition comprising a polyhydroxycompound and an inorganic phosphate, the composition being substantiallyfree of content of any organo-nitrogen compound.

5. Aflame retardant composition consisting of a polyhydroxy compound and an inorganic phosphate.

6. Acomposition as claimed in any one of claims 3, 4and 5 wherein the inorganic phosphate and the polyhydroxy compound are present in a ratio which is in a range offrom 15:1 to 0.5:1.

7. Acomposition as claimed in claim 6 wherein the said ratio is in a rangeoffrom3:1 to 1:1.

8. A composition as claimed in any one of claims 3 to 7 wherein the inorganic phosphate is ammonium polyphosphate.

9. A composition as claimed in any one of the preceding claimswherein the polyhydroxy compound is pentaerythritol, dipentaerylthritol or tripentaerylthritol.

10. Aflame retardant polymeric composition comprising a non-halogen containing, plastics material and a flame retardant composition as claimed in any one ofthe preceding claims.

11. Acomposition as claimed in claim 10 wherein theflame retardant composition is present in an amountoffrom 10to45 parts per 100 parts ofthe plastics material.

12. A composition as claimed in claim 10 or 11 wherein the plastics material is polypropylene.

13. A composition as claimed in claim 10 or 11 wherein the plastics material is polyethylene.

14. A composition as claimed in claim 10 or 11 wherein the plastics material is an epoxy resin.