GB2414735A

GB2414735A - Combustion modified foam

Info

Publication number: GB2414735A
Application number: GB0511450A
Authority: GB
Inventors: Paul Cookson; Alexander Mcintyre
Original assignee: Kay Metzeler Ltd
Current assignee: Kay Metzeler Ltd
Priority date: 2004-06-03
Filing date: 2005-06-03
Publication date: 2005-12-07
Anticipated expiration: 2025-06-03
Also published as: GB0511450D0; GB0412382D0; GB2414735B

Abstract

A formulation for producing combustion-modified, flexible polyurethane foam comprising:- <SL> <LI>1. from 80 to 99 parts by weight (pbw) of one or more polyether polyols having a molecular weight in the range 2000 to 15,000; <LI>2. from 1 to 20 pbw of one or more polyols (to a total of 100 pbw of total polyol) having a molecular weight in the range from 2500 to 5500, an average nominal functionality of at least two, and an ethylene oxide content in the range from 40% to 90%; <LI>3. isocyanate comprising one or more of the following:- toluene diisocyanate, diphenylmethane diisocyanate (MDI) and polymeric MDI; <LI>4. up to 40 pbw of a flame retardant package consisting of one or more flame retardant additives; <LI>5. optionally, one or more surfactants; <LI>6. optionally, one or more catalysts for the reaction of polyol and isocyanate; and <LI>7. water. </SL>

Description

24 1 4735

COMBUSTION-MODIFIED FOAM

The present invention relates to a new formulation for producing polyurethane (PU) foam, and more particularly, combustion-modified, flexible polyurethane foam.

The U.K. Department of Trade and Industry introduced the Furniture and Furnishings Regulations in 1988. These regulations specify that the fillings and coverings of all furniture should pass flammability tests which are stricter than the requirements for other European countries. Since 1988 it has not been possible to buy, in the U.K., new upholstered furniture which does not comply with the Furniture and Furnishings (Fire Safety) Regulations 1988 (now as amended in 1989 and 1993) which sets levels of fire resistance for domestic upholstered furniture, furnishings and other products containing upholstery.

The ignitability requirements for foam fillings are set out below.

Polyurethane foams must meet the requirements of the test given in Schedule 1, Part 1 of the Regulations using an ignition source 5 (as defined in BS 5852: Part 2) and a standard flame retardant (FR) polyester fabric.

Natural rubber latex (NRL) foam must meet the requirements of the test given in Schedule 1, Part 1 of the Regulations using an ignition source 2 (as defined in BS 5852: Part 2) and a standard FR polyester fabric.

The ignition source for latex foam is a small gas flame which is applied for seconds to the foam and standard fabric composite. For polyurethanes the ignition source is a wooden crib weighing 16- 18 g which is placed in the centre of the test rig and ignited in the presence of propan-2-ol.

The flammability requirements for polyurethane foam are more stringent than for latex foam. For latex foam to be resistant to a Crib 5 ignition source, high levels of flame retardant need to be added which then destroys physical properties such as resiliency, low hysteresis loss, tear and tensile strengths.

If natural rubber latex (NRL) foam had to comply with Crib 5 the flame retardant package required would adversely affect the physical properties of the foam.

Previously NRL products formed a large percentage of the total foamed mattress market but more recently polyurethane has come to dominate the bedding sector so that latex mattresses are only used at the top/quality end of the bedding market.

Longevity and performance of cushioning materials has never been more critical than in today's market. Latex is marketed as a luxury product having superior support, resilience and recovery to alternative cushioning materials such as flexible PU foam. The inclusion of traditional flame retardant fillers very often impairs the mechanical properties and has a high mass penalty, due to the high levels required. Liquid flame retardants, such as organo-halogen compounds or phosphate- or boron-based systems, even at relatively low levels, greatly affect the resilience of the foams produced. Therefore, in order to produce a polyurethane foam product capable of replicating, or even surpassing, the physical properties and performance of latex foam, a flame retardant package must be employed which, whilst helping to meet current fire regulations, does not adversely affect the properties and performance.

The present invention seeks to provide a latex-like polyurethane foam which complies with the U.K. furniture fire regulations whilst exhibiting the high resiliency and low hysteresis properties of latex rubber foams.

According to a first aspect of the present invention there is provided a formulation for producing combustion-modified, flexible polyurethane foam comprising: 1. from 80 to 99 parts by weight (plow) of one or more polyether polyols having a molecular weight in the range 2000 to 15,000; 2. from 1 to 20 pbw of one or more polyols (to a total of 100 pbw of total polyol) having a molecular weight in the range from 2500 to 5500, an average nominal functionality (fin) of at least two, and an ethylene oxide content in the range from 40% to 90%; 3. isocyanate comprising one or more of the following:- toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI) and polymeric MDI; 4. up to 40 pbw of a flame retardant package consisting of one or more flame retardant additives; 5. optionally, one or more surfactants; 6. optionally, one or more catalysts for the reaction of polyol and isocyanate; and 7. water.

According to a second aspect of the invention there is provided a foam made using the formulation as hereinbefore defined.

The combustion-modified foams formed using the formulation of the invention exhibit the feel, comfort and performance of latex whilst meeting current UK Furniture and Furnishings (Fire Safety) Regulations BS 5852: Part 2 (Crib 5).

The polyol of the invention comprises a polyether polyol or combination of polyols having a molecular weight in the range from 2000 to 15,000 and preferably from 4000 to 8000. The preferred polyol has a molecular weight of 5000 to 7000 and is ideally substantially 6000. The preferred polyol of the invention ideally has a primary to secondary hydroxyl ratio of at least 50 %. The preferred functionality is in the range from 2 to 4.5 Suitable polyether type polyols include any of the following either alone or in combination: polyoxypropylene dials, trials tetrols and higher analogues; ethylene oxide capped diols, trials, tetrols and higher analogues; and random block polymers of the aforesaid polyethers in which the polyol is made with both ethylene and propylene oxides.

"Modified polyether polyols" which contain organic fillers formed by the in-situ polymerization of suitable monomers are also suitable for use in the present invention. Three classes of polyol are identified, namely (i) polymer polyols; (ii) PHD polyols and (iii) PIPA polyols. In such polyols, in addition to the polyether polyol itself, the polyol contains at least one other polymer dispersed therein.

Thus, a polymer polyol additionally includes a vinyl polymer dispersion, formed in-situ in the polyol, as well as the reaction product of the polyol and a vinyl monomer. A PHD polyol contains a dispersion of a polyurea in a polyether s polyol, formed in-situ by polymerization of allamine and an isocyanate, while a PIPA (polyisocyanate polyaddition) polyol contains a polymer dispersion formed by the reaction of an alkanolamine with an isocyanate.

That said, a comprehensive review of polyols which are suitable for use in the present invention can be found in: Chapter 9 (Polyols for Polyurethane Production) in "Telechelic Polymers: Synthesis and Applications", Ed. E. J. Goethals, CRC Press Inc., Florida 1989.

The formulation of the invention further comprises from 1 to 20 pbw of a high ethylene oxide (EO) containing polyol (to a total of 100 pbw of total polyol) having a molecular weight in the range from 2500 to 5500 and ideally substantially 4500, an average nominal functionality (fn) of at least two, an ethylene oxide content of 40 to 90% and ideally substantially 70%. Preferably the primary to secondary hydroxyl ratio is at least 50%.

The formulation of the invention further comprises an isocyanate selected from toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI) and polymeric diphenylmethane diisocyanate and mixtures thereof.

When the isocyanate is TDI, it may be a mixture of 2,4- and 2,6-TDI in a molar ratio of 80:20 or 65:35, each of which mixtures is commercially available.

Alternatively, these respective mixtures may be blended to provide any ratio of 2,4-:2,6- isomers within the range 80:20 to 65:35 thereby influencing the stability and cell opening effect of the final foam as derived.

However, more preferably, the isocyanate is an MDI, modified MDI or polymeric MDI. Such MDI type isocyanates are commercially available e.g. the Voranate series available from Dow and the Lupranate M series from Elastogran (UK) Ltd. Processing can be achieved over a wide range of isocyanate indices (50-120).

The polyurethane is prepared using water as a blowing agent in the range of from I to 7 pbw, and preferably 1 to 5 pbw.

The process is preferably carried out in the presence of one or more catalysts and/or surfactants. A combination of one or more catalysts is preferably used in the range of 0.01 to 2 pbw. Widely used catalysts to produce polyurethane foam are generally tertiary amines, tin catalysts or other organometallic compounds. Examples of suitable catalysts include tertiary amines, such as N,N'-dimethylethanolamine, bis(dimethylaminoethyl) ether, triethylene diamine, 1,4-diazobiscyclo(2,2,2) octane, tin catalysts such as stannous octoate and dibutyl tin dilaurate and organometallic compounds such as bismuth carboxylates, zinc carboxylates and potassium-2-ethyl hexanoate. Preferably one or more surfactants are used in the range 0.01 to 2 pbw. Preferred surfactants include any of the following either alone or in combination:- one or more polydimethyl siloxanes, one or more polydimethyl siloxane block copolymers and one or more alky- pendant dimethyl siloxanes.

Typically, a reaction mixture can include any one or more of the following components, namely an auxiliary blowing agent, fillers, chain extender, crosslinker, stabiliser, antistatic additive, colourant antioxidant and antibacterial additive, and indeed more than one of any such component may be present.

In addition a flame retardant package comprising up to 40 pbw of flame retardant additives, such as melamine, aluminium trihydroxide, ammonium polyphosphate, expandable graphite or zinc borate, alone or in conjunction with up to 20 pbw of a liquid flame retardant, such as one or more halogenated phosphates, is incorporated into the foam formulation. The melamine powder ideally has a particle size of 40 Am or less. The reduced particle size allows a minimum level of melamine to be added to achieve Crib 5 FR performance and subsequently the reduced filler content minimises the effect on physical properties.

The selected polyol combination of the invention enables use of a small flame retardant package which allows the latex-like foam to meet current UK fire regulations without markedly deteriorating physical properties.

The formulation of the invention can be used to manufacture slabstock foam in a well known manner, using a continuous or discontinuous process.

Moulded foams can also be produced.

The resulting latex-like polyurethane foams have the same stress/strain behaviour, and therefore feel and resilience, in the region O to 65% strain as natural latex of comparable density. The flame retardant package has been optimised such that the performance, properties and ageing of the foams are not adversely affected.

By changing the polyols, polyol ratios, isocyanate index, water and ancillary chemical levels, polyurethane foam can be produced at a range of densities and hardness whilst still retaining latex-like properties.

Mattresses are made in a range of densities nominally from 55 to 90 kg/m3 whilst pillows are lighter and nominally have a density range of 40 to 50 kg/m3.

In order that the invention may be more readily understood a specific embodiment thereof will now be described by way of example only.

TABLE 1: EXAMPLE FORMULATION Ingredient Pbw Polyol (1) 95 Polyol (2) 5 Water 1.65 Surfactant (3) 0.30 Catalyst (4) 0 47 Catalyst (5) 0.14 FR additive (6) 10 Liquid FR (7) 3.0 Isocyanate (8) 31.2 Index 93 Notes to above: 1. Lupranol 2090 is a polyol based on glycerol with a molecular weight of 6000, a hydroxyl number of 28 and primary OH groups. It is commercially available from Elastogran.

2. Desmophen 41WB-01 is a polyol based on glycerol with a molecular weight of 4500, a hydroxyl number of 38 and a random distribution of oxyethylene and oxypropylene units in the ratio 75:25. It is commercially available from Bayer.

3. Tegostab B8680 is a low activity silicone surfactant for highresilience type foam available from Th. Goldschmidt.

4. Dabco 33LV, 33% triethylene diamine in dipropylene glycol available from Air Products.

5. Nlax Al, 70% bis(N,N-dimethlamino ethyl) ether in dipropylene glycol available from Osi Crompton.

6. Melamine powder.

7. Trischlorophenyl phosphate (TCCP).

8. Lupranat VP9237, an MDI prepolymer of equivalent weight 136 g molt' available from BASE TABLE 2: PHYSICAL PROPERTIES The physical properties of the formulation of Table 1 were compared with the

properties of a prior art natural rubber latex.

Property Example Natural

Table 1 Rubber

( ) Latex Density / kg my 74 88 Hardness / kPa 1.8 1.8 2Hysteresis loss / % 27 28 3Sag factor 3.9 3.5 4Hardness Loss / % -2.1 - 4Height Loss / % -1.2 - 5Time to Extinguish / s 286 N/A sWeight Loss /g 22 FAIL Compression load deflection, CLD at 40%.

2CLD H t i 1 area under loading curve - area under unloading curve 100 % area under loading curve 3The sag or support factor Is defined as the ratio of 65% ILD to 25% ILD.

4Hardrless (ILD 40%) and height losses were measured after pounding tests (80,000 cycles) as per BS EN ISO 3385 1995 5Results for BS5852: Part 2 (Crib 5) burn test.

It is to be understood that the above described embodiments are by way of example only. Many modifications and variations are possible.

Claims

1. A formulation for producing combustion-modified, flexible polyurethane foam comprising: 1. from 80 to 99 parts by weight (plow) of one or more polyether polyols having a molecular weight in the range 2000 to 15,000; 2. from 1 to 20 pbw of one or more polyols (to a total of 100 pbw of total polyol) having a molecular weight in the range from 2500 to 5500, an average nominal functionality of at least two, and an ethylene oxide content in the range from 40% to 90%; 3. isocyanate comprising one or more of the following:- toluene diisocyanate, diphenylmethane diisocyanate (MDI) and polymeric MDI; 4. up to 40 pbw of a flame retardant package consisting of one or more flame retardant additives; 5. optionally, one or more surfactants; 6. optionally, one or more catalysts for the reaction of polyol and isocyanate; and 7. water.

2. A formulation as claimed in claim 1, wherein said one or more polyether polyols have a molecular weight in the range from 4000 to 8000.

3. A formulation as claimed in claim 1, wherein said one or more polyether polyols have a molecular weight in the range from 5000 to 7000.

4. A formulation as claimed in claim 1, wherein said one or more polyether

- A

polyols have a molecular weight of substantially 6000.

5. A formulation as claimed in claim 1, wherein the polyther polyol has a primary to secondary hydroxyl ratio of at least 50%.

6. A formulation as claimed in any preceding claim, wherein said one or more polyether polyols comprises any of the following: polyoxypropylene dials, triols tetrols and higher analogues; ethylene oxide capped dials, trials, tetrols and higher analogues; and random block polymers of the aforesaid polyethers in which the polyol is made with both ethylene and propylene oxides.

7. A formulation as claimed in any preceding claim, wherein the one or more polyols having an ethylene oxide content in the range from 40% to 90% has a molecular weight of substantially 4500.

8. A formulation as claimed in any preceding claim, wherein the one or more polyols having an ethylene oxide content in the range from 40% to 90% has an ethylene oxide content of substantially 70%.

9. A formulation as claimed in any preceding claim, wherein the flame retardant package comprises one or more of melamine, aluminium trihydroxide, ammonium polyphosphate, graphite or zinc borate, alone or in conjunction with up to 20 pbw of a liquid flame retardant, such as one or more halogenated phosphates.

10. A formulation as claimed in any preceding claim, wherein the flame retardant package comprises melamine.

11. A formulation as claimed in claim 9 or claim 10, wherein the melamine has a particle size of 40,um or less.

12. A flexible polyurethane foam made from the formulation as claimed in any preceding claim.

13. A method of making a flexible polyurethane foam comprising the mixing together of the components of the formulation defined in any of claims I to 11.