GB2094315A

GB2094315A - Highly-resilient polyether urethane foams

Info

Publication number: GB2094315A
Application number: GB8205167A
Authority: GB
Original assignee: Dunlop Ltd
Current assignee: Dunlop Ltd
Priority date: 1981-03-10
Filing date: 1982-02-22
Publication date: 1982-09-15
Also published as: GB2094315B

Abstract

An intumescent, high-resilient polyethaurethane foam is made from a reaction mixture comprising one or more polyether polyols, one or more polyisocyanates, one or more catalysts, one or more surface-active agents and one or more blowing agents, together with (a) an intumescent catalyst and (b) a carbonific element. A spumific element may also be included in the reaction mixture. When foams according to the present invention are exposed to a flame, they melt, froth and char. The char prevents further combustion of the foam.

Description

SPECIFICATION High-resilient polyether urethane foams This invention relates to high-resilient polyether urethane foams.

The melts produced from these foams under the action of a flame are characterised by relatively high surface tension and relatively low surface elasticity.

The magnitude of the surface elasticity of the molten foam has an important effect on the behaviour of the foam when exposed to a flame. The action of the flame upon the foam leads to chemical breakdown (cracking) of the foam matrix into iow molecular weight volatile products, which are generally flammable. If the rate of flow of the molten foam away from the flame is sufficient to prevent further cracking (and therefore sufficient to prevent the continued evolution of flammable products) then the foam will be inherently difficult to ignite.

It is, for many foam applications, desirable to increase the hardness of a high-resilient foam and it is known to achieve such an increase in hardness either by the addition of fillers to the foam-forming reaction mixture or by the post-treatment of an already-produced foam. However, conventional methods of increasing the hardness of a high-resilient foam have been found to bring about a corresponding increase in the surface elasticity of the molten foam, and consequently to reduce its inherent flame-retardance.

We have now found that the addition of an intumescent catalyst and a carbonific element to a polyether foam-forming reaction mixture, together with the optional addition of a spumific element, leads to the production of a high-resilient polyether foam which intumesces and chars when exposed to a flame.

Accordingly, the present invention provides an itumescent, high-resilient polyether urethane foam, the foam having been produced by reacting in a foam-forming reaction mixture one or more polyether polyols, one or more organic polyisocyanates, one or more catalysts for the foam-forming reaction, one or more surface active agents and one or more blowing agents, in which the foamforming reaction mixture also includes (a) an intumescent catalyst and (b) a carbonific element.

The present invention also provides an intumescent, high-resilient polyether urethane foam as described in the immediately-preceding paragraph, in which the foam-forming reaction mixture also includes a spumific element.

The main function of the intumescent catalyst is to dehydrate the carbonific element to a carbonaceous char. It is believed that this is achieved by the liberation of an acid from the catalyst, the acid serving to catalyse dehydration of the carbonific element.

The carbonific element according to the present invention comprises an organic polyhydric compound which forms a carbonaceous char by reaction with the acid liberated from the intumescent catalyst. The carbonaceous char acts to prevent the spread of flame and to insulate the underlying areas of foam.

Where a spumific element is used, non-flammable gases are evolved which may contribute to the intumescence and to a reduction of the effects of a flame on the surface of the foam.

The intumescent catalyst may be mono- or di-ammonium phosphate, preferably an ammonium polyphosphate. Other intumescent catalysts which may be used include urea phosphate, guanylurea phosphate, mono-, di- or tri-melamine phosphates, polyphosphorylamide and phosphoryl trianilide.

The carbonific element may be a starch (e.g. maize, wheat, potato, or rice starch) or a starch derivative (such as those disclosed in our published UK Patent Application No 2070041 A). Other carbonific elements which may be used include polyhydric materials such as sorbitol, pentaerythritol, gelatin, wool flock and cellulose (e.g. as wood flour).

The spumific element may be, for example, melamine or urea.

The polyether polyol is conveniently one with a high proportion (e.g. 40 to 70%) of primary hydroxyl groups and a molecular weight in the range 2000 to 10000 (preferably 3000 to 7000).

The organic polyisocyanate can be, for example, a mixture of the 2,4- and 2,6-isomers or tolylene dilsocyanate (TDl:80/20 or 65/35), a modified TDI, trimerised TDI, methylene-bis-2,4-phenyldiisocyanate (MDl-in crude, pure or modified form) or blends of any of the aforementioned polyisocyanates.

The catalysts for the foam-forming reaction can be, for example, tertiary amines, alkanolamines, or organo-metallic compounds, e.g. dibutyltin dilaurate and stannous octoate.

The surface active agents are those customarily employed in high-resilient foam formations, e.g.

polydimethyl siloxanes or polyphenyl dimethyl siloxanes.

The blowing agents can be water (or a water-generator), or halogenated hydrocarbons such as dichloromethane or a fluoro carbon.

Cross-linking agents (e.g. glycerol) may be added to the reaction mixture.

If desired, a filler, such as zinc borate or one of the hydrated aluminas, may be included in the foam-forming reaction mixture.

The intumescent catalyst is present in the foam-forming reaction mixture in an amount in the range 5 to 30 parts by weight per hundred parts polyol (php), preferably in the range 10 to 20 php.

The carbonific element is present in the foam-forming reaction mixture in an amount in the range 5 to 30 php, preferably 10 to 20 php.

If a filler is employed, an amount of up to 50 php, preferably up to 20 php, may be used.

Conventional flame-retardant additives, such as are well known to those skilled in the art, may be incorporated in the foam-forming reaction mixture if desired.

Although it is not intended that the present invention be construed with reference to any particular theory, it is believed that the polyetherurethane matrix in the foam performs two functions.

Before exposure to a flame, the foam matrix holds the intumescent and carbonaceous elements in readiness as an integral part of the foam. On exposure to a flame, the molten foam intumesces and acts as a source of carbon, leading to the formation of a protective char on that surface of the foam which is exposed to the flame.

The present invention will be illustrated by way of the following Examples.

Examples 1-3 The formulations shown in Table A (below) were used to make flexible, free-rise polyurethane foams as follows: The polyol(s), intumescent catalyst and carbonific element were mixed at high speed. The surface active agent, the organometallic catalyst and amine catalysts were added to the resulting highlyviscous mixture and the whole stirred for 1 5 seconds. The water and the inert blowing agent were then added and the mixture stirred for a further 10 seconds. Stirring was maintained during the addition of the polyisocyanate and the mixture allowed to "cream" before being transferred to a suitable receiver.

Table A Amounts (parts by weight) Ingredient Ex 1 Ex2 Ex3 Main Polyol (a) 83 83 100 Subsidiary Poiyol (b) 17 17 Polyisocyanate 50(c) 53(d) 70(e) Amine catalyst (f) 2 2 2 1 st ethanolamine catalyst (g) 1.6 1.6 1.6 2nd ethanolamine catalyst (gel) 5 - - Organometallic catalyst (h) 0.7 0.7 0.7 Surface active agent (i) 0.5 0.5 0.5 Water 1.7 1.7 3 Inert blowing agent (j) 6.3 3.3 3.3 Intumescent catalyst (k) 20 30 30 Carbonific element 10(1) 10(1) 10(m) Spumific element (n) - 10 Notes to table A (a) An ethylene oxide-tipped polyol, of molecular weight 6000 available from Shell Chemicals as E43.

(b) A branched polyether modified with an organic filler polyol, available from Bayer AG as PU 3119.

(c) 80/20 TDI (d) A blend comprising 80/20 TDI (80 parts) and a modified TDI (20 parts). The modified TDI is available from Bayer AG as MT 10.

(e) Crude MDI.

(f) Triethylene diamine, available from Air Products as DABCO 33 LV.

(g) Dimethylethanolamine, available from Diamond Shamrock Limited as PROPAMINE A.

(gi) A blend of diethanolamine (2 parts) and dipropylene glycol (1 part).

(h) Stannous octoate, available from Durham Raw Materials as NUOCURE N28.

(i) A polyoxyalkylene silicone copolymer, available from Union Carbide Inc. as L 5307.

(j) A fluorocarbon blowing agent, available from ICI Limited as ARCTON 11.

(k) Ammonium polyphosphate, available from Albright and Wilson as AMGARD IU.

(I) Maize starch (containing 13% water) available from Corn Products as AMISOL 05374.

(m) Sorbitol.

(n) Melamine.

The words DABCO, PROPAMINE, NUOCURE, ARCTON, AMGARD and AMISOL are Registered Trade Marks.

The foams of Examples 1 to 3 were subjected to some or all of the following burn tests: A. Federal FMVSS 302.

B. B.S. Specification 4735.

C. Bunsen test.

D. D.o.E. Draft for Development 58 (Crib tests). (Foam sample covered with a non-flammable fabric).

The results were as follows: Example 1 Test A Flame failed to pass the first timing mark. The sample selfextinguished.

Test B Burn length 28 mm after 27 seconds. The sample self-extinguished.

Test C The foam was exposed to a Bunsen flame for 30 seconds. Melting and intumescence occurred.

On removal of the flame, the foam self-extinguished.

Example 2 Test A As for Example 1.

Test B Burn length 23 mm after 34 seconds. The sample self-extinguished.

Test C As for Example 1.

Test D The sample passed Crib Tests 4 and 5.

Example 3 Test A As for Example 1.

Test B Burn iength 26 mm after 42 seconds. The sample self-extinguished.

Test C The foam was exposed to a roaring Bunsen flame for 3 minutes. A hard protective intumescent char formed on the surface and the foam self-extinguished on removal of the flame.

Test D The sample passed Crib Tests 4, 5, and 6.

Example 4 A flexible, cold cure moulded polyurethane foam was obtained using the following formulation: Parts by weight Ethylene oxide-tipped polyol (M. wt. 4000) 100 Modified 4,4'-diphenylmethane diisocyanate 64.3 Triethylene diamine 1.0 Dimethyl ethanolamine 0.5 Bis-(2-dimethylaminoethyl)ether (70%) Dipropylene glycol (30%) 0.2 Polyoxyalkylene silicone copolymer 1.0 Amine cross-linker 2.0 Water 2.9 ARCTON II (blowing agent) 10.0 Ammonium polyphosphate 10.0 Starch (containing 13% water) 10.0 Chlorinated phosphate ester-flame retardant 10.0 The foam-forming mixture, obtained using the procedure of Example 1, was dispensed into a metal mould which had been pre-heated to 500C. A close-fitting lid was clamped into place on the mould and the mould left for 10 minutes without any application of heat.The moulded product was then removed from the mould.

The test results on the foam of Example 4 were as follows: Test A As for Example 1.

Test B Burn length 125 mm after 3 minutes 22 seconds.

Test C The foam was exposed to a roaring Bunsen flame for 5 minutes. A hard intumescent coating formed. The foam self-extinguished on removal of the flame.

Test D The sample passed Crib Tests 4, 5 and 6.

Examples 5-19 The formulation shown in Table B (below) were prepared as follows: The polyol(s), surface active agents, foam-forming catalysts and water were blended. The intumescent catalyst and carbonific element were added to the blend and stirred thoroughly. Finally, the inert blowing agent, organometallic catalyst and polyisocyanate were added and the foaming mixture transferred to a suitable receiver where foaming was completed.

Table B Ingredient 5* 6 7 8 9 10 11 12 13 14 15 16 17 18 19 Main Polyol (a) 100 83 83 83 83 83 83 83 83 83 100 100 100 100 100 Subsidiary polyol (b) - 17 17 17 17 17 17 17 17 17 - - - - Polyisocyanate 34 50 50 53 53 53 53 53 53 53 70 70 70 70 30(e) (c) (c) (c) (d) (d) (d) (d) (d) (d) (d) (e) (e) (e) (eI) 30(el) Amine catalyst (f) 0.5 2 2 2 2 2 2 2 2 2 2 1 1 1 2 Ethanolamine catalyst (g) - 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.05 1.05 1.05 1 Organometallic catalyst (h) 0.15 0.7 0.7 0.7 0.7 0.7 1 1 1 1 0.7 - - - Surface active agent (i) 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 - - - Water 1.2 1.7 1.7 1.7 1.7 1.7 2.1 2.1 1.7 1.7 1.7 2.5 1.7 1.7 Inert blowing agent (j) - 6.3 6.3 3.7 3.7 3.7 3.7 3.7 3.7 3.7 6.6 6.6 6.6 6.6 6.6 Intumescent catalyst (k) - 20 30 30 30 30 30 30 30 30 30 20 20 20 10 Carbonific element (I) (I) (I) (I) (I) (I) (m) (n) (I) (o) (I) (I) (I) (I) (I) Spumific element - - - 10 - - - - 20 - - - - - (p) (q) Filler - - - - 10 10 - - - - - - - - (r) (s) *"Control" Example Notes to table B (a) A poly(oxyethylene) poly(oxypropylene) polyol having an average molecular weight of 4800 and a primary hydroxyl content of about 60% available from Diamond Shamrock Limited as PROPYLAN M12.

(b) A modified polyol available from Bayer AG as PU 3119.

(c) 80/20 TDI.

(d) A modified 80/20 TDI, available from Bayer AG as MT 58.

(e) Crude MDI.

(el) Modified MDI.

(f) Triethylene diamine, available from Air Products Ltd as DABCO 33LV.

(g) N-dimethylethanolamine, available from Diamond Shamrock Limited as PROPAMINE A.

(h) Stannous octoate, available from Durham Raw Materials as NUOCURE N28.

(i) A polysiloxane available from Hythe Chemicals as L5307.

(j) A fluorocarbon blowing agent, available from ICI Ltd, as ARCTON 11.

(k) Ammonium polyphosphate, available from Albright 8 Wilson as AMGARD IU.

(I) Maize starch available from Corn Products as AMISOL 05374.

(m) Pentaerythritol.

(n) Sorbitol.

(o) Gelatin.

(p) Melamine.

(q) Urea.

(r) Alumina Hydrate, available from British Aluminium Co. as BACO FRF 40.

(s) Zinc borate.

The words PROPYLAN, DABCO, PROPAMINE, NUOCURE, ARCTON, AMGARD, AMISOL and BACO are Registered Trade Marks.

In Table B, above, Example 5 was a "control" example and the foam did not show intumescence on exposure to a flame.

The remaining Examples 6 to 1 9 all exhibited intumescence under the conditions of one or more of the burn tests (described hereinabove with reference to Examples 1 to 4).

Claims

1. An intumescent, high-resilient polyether urethane foam, the foam having been produced by reacting in a foam-forming reaction mixture one or more polyether polyols, one or more organic polyisocyanates, one or more catalysts for the foam-forming reaction, one or more surface active agents and one or more blowing agents, in which the said reaction mixture also includes (a) an intumescent catalyst and (b) a carbonific element.

2. A foam according to Claim 1, in which the intumescent catalyst (a) is monoammonium phosphate, diammonium phosphate or an ammonium polyphosphate.

3. A foam according to Claim 1, in which the intumescent catalyst (a) is urea phosphate, guanylurea phosphate, mono-, di- or tri-melamine phosphate, polyphosphorylamide or phosphoryl trianilide.

4. A foam according to Claim 1,2 or 3, in which the intumescent catalyst (a) comprises 5 to 30 parts by weight per hundred parts polyol (php) in the reaction mixture.

5. A foam according to Claim 4, in which the intumescent catalyst (a) comprises 10 to 20 php in the reaction mixture.

6. A foam according to any one of Claims 1 to 5, in which the carbonific element (b) comprises an organic polyhydric compound which forms a carbonaceous char when the foam is exposed to a flame.

7. A foam according to Claim 6, in which the carbonific element (b) is a starch or a starch derivative.

8. A foam according to Claim 7, in which the carbonific element (b) is maize, wheat, potato or rice starch.

9. A foam according to Claim 6, in which the carbonific element (b) is sorbitol, pentaerythritoi, gelatin, wool flock or cellulose.

10. A foam according to any one of Claims 1 to 9, in which the carbonific element (b) comprises 5 to 30 php in the reaction mixture.

11. A foam according to Claim 10, in which the carbonific element (b) comprises 10 to 20 php in the reaction mixture.

12. A foam according to any one of Claims 1 to 11, in which the foam-forming reaction mixture includes a spumific element.

13. A foam according to Claim 12, in which the spumific element is a substance which evolves a non-flammable gas on exposure of the foam to a flame.

14. A foam according to Claim 12 or 13, in which the spumific element is melamine or urea.

1 5. A foam according to any one of Claims 1 to 14, in which the polyether polyol has from 40% to 70% primary hydroxyl groups and a molecular weight in the range 2000 to 10000.

1 6. A foam according to Claim 1 5, in which the polyether polyol has a molecular weight in the range 3000 to 7000.

1 7. A foam according to any one of Claims 1 to 16, in which the organic polyisocyanate is 80/20 TDI, 65/35 TDI (both as hereinbefore defined), a modified TDI, trimersed TDI, MDI or a blend of any two or more of said polyisocyanates.

1 8. A foam according to any one of Claims 1 to 17, in which the catalyst for the foam-forming reaction is a tertiary amine, an alkanolamine or an organometallic compound.

1 9. A foam according to Claim 18, in which the catalyst for the foam-forming reaction is dibutyltin dilaurate or stannous octoate.

20. A foam according to any one of Claims 1 to 19, in which the surface active agent is polydimethyl siloxane or a polyphenyl dimethyl siloxane.

21. A foam according to any one of Claims 1 to 20, in which the blowing agent is water or a water generator.

22. A foam according to any one of Claims 1 to 20, in which the blowing agent is a halogenated hydrocarbon.

23. A foam according to Ciaim 22, in which the blowing agent is dichloromethane or a fluorocarbon.

24. A foam according to any one of Claims 1 to 23, in which a filler is included in the foamforming reaction mixture.

25. A foam according to Claim 24, in which the filler comprises up to 50 php in the reaction mixture.

26. A foam according to Claim 25, in which the filler comprises up to 20 php in the reaction mixture.

27. A foam according to Claims 24, 25 or 26, in which the filler is zinc borate or a hydrated alumina.

28. A foam according to any one of Claims 1 to 27, in which a cross-linking agent is included in the foam-forming reaction mixture.

29. A foam according to Claim 28, in which the cross-linking agent is glycerol.

30. An intumescent, high-resilient polyether urethane foam, substantially as hereinbefore described with reference to any one of Examples 1 to 4 and 6 to 19.