GB1594474A - Flameretardant polyurethane foam crumb - Google Patents

Description

(54) FLAME-RETARDANT POLYURETHANE FOAM CRUMB (71) We, DUNLOP LIMITED, a British Company of Dunlop House, Ryder Street, St. James's, London S.W.1, 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: This invention relates to a method for imparting flame-retardant properties to polyurethane foam crumb, and to flameretardant polyurethane foam crumb obtained thereby.

It is known to produce flame-retardant foams by incorporating flame-retardant additives into a foam-forming reaction mixture, and it is also known to impregnate an already-produced foam with a flameretardant additive in solution or suspension.

Whilst these methods can achieve satisfactory levels of flame-retardance in sheets or blocks or foam, they are unsuitable for the treatment of foams in the form of foam crumb.

We have found that flame-retardant properties can be imparted to foam crumb by treating already-produced foam crumb with a particulate flame-retardant additive, the additive having previously been coated with a foam precursor.

Accordingly, the present invention provides, in one aspect, a method for imparting flame-retardant properties a polyurethane foam crumb, in which the foam crumb is treated with a particulate flame-retardant additive, the particles of said additive having previously been coated with a polyurethane prepolymer.

In another aspect, the present invention provides a flame-retardant polyurethane foam crumb, obtained by the method described in the immediately-preceding paragraph.

The foam crumb may be a "loose" polyurethane foam crumb (particle size generally in the range 1/8 to 1/2 inch) or a "bonded" polyurethane foam crumb such as the polyurethane crumb, bonded by means of an isocyanate/polyol prepolymer, available from Dunlopillo Limited as Repol.

(Repol is a Registered Trade Mark).

The particulate flame-retardant additive may advantageously be a hydrated alumina, preferred additives being selected from the range available from the British Aluminium Company as BACO FRF. (BACO is a Registered Trade Mark).

The particle size of the additive is suitably in the range 45 to 75 microns, preferably 50 to 75 microns.

The polyurethane prepolymer may be, for example, a prepolymer made by reacting 100 parts by weight of a polyether triol of molecular weight 3500 with 33 parts by weight of an 80:20 mixture of 2,4- and 2,6tolylyene diisocyanaSe (80:20 TDI).

The foam crumb may conveniently be treated with the coated particulate additive by tumbling the crumb and additive together and then passing steam through the mixture to cure the prepolymer and bind the additive to the crumb. Where "bonded" foam crumb is to be treated, the tumbling is followed by compaction under pressure and subsequent passage of steam through the compacted mixture.

After treatment, excess particulate additive which has not bonded to the crumb may be removed by shaking.

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

In the Examples, foam crumb was treated with an alumina hydrate which had been pre-coated with a polyurethane prepolymer by mixing the crumb and the hydrate together and passing steam through the mixture for 2 minutes. The mixture was kept overnight at 70"C and excess hydrate removed by shaking. The flammability of each sample was tested by placing approximately 400 cm3 of treated crumb on a shallow metal tray and applying a lighted match to the lower edge of the crumb.

EXAMPLE 1 (Control) A standard 3/8" polyurethane foam crumb was tested for flammability. The foam burned fiercely to a melt in less than 1 minute after application of a lighted match.

The melt continued to burn for a further 22 minutes.

EXAMPLE 2 The crumb used in Example 1 (above) was treated with 300 parts by weight per hundred of foam of prepolymer coatedalumina hydrate followed by passage of steam to cure the prepolymer and bond the hydrate to the crumb.

A single lighted match was insufficient to cause ignition of the foam. A further two lighted matches were applied at the same place and the foam then burned very slowly and gently in a localised area for about 1 minute.

EXAMPLE 3 The treated foam used in Example 2 (above) was shaken for It hours, after which time around 90% by weight of the hydrate remained in the foam.

On ignition, the foam burned slowly and gently for 2 to 3 minutes after application of a lighted match. A black particulate ash formed on the surface of the foam and prevented burning of the remainder. A very slight degree of melting of the foam was observed.

WHAT WE CLAIM IS: 1. A method for imparting flameretardant properties to a polyurethane foam crumb, in which the foam crumb is treated with a particulate flame-retardant additive, the - particles of said additive having previously been coated with a polyurethane prepolymer.

2. A method according to claim 1, in which the foam crumb comprises loose polyurethane foam crumb.

3. A method according to Claim 2, in which the crumb has a particle size in the range 1/8 inch to 1/2 inch.

4. A method according to Claim 1, in which the crumb comprises polyurethane foam crumb bonded with an isocyanatepolyol prepolymer.

5. A method according to any one of Claims 1 to 4, in which the particulate flame-retardant additive is a hydrated alumina.

6. A method according to Claim 5, in which the hydrated alumina has a particle size in the range 45 to 75 microns.

7. A method according to Claim 6, in which the hydrated alumina has a particle size in the range 50 to 75 microns.

8. A method according to any one of the preceding claims, in which the polyurethane prepolymer comprises the reaction product of 100 parts by weight of a polyether triol of molecular weight 3500 and 33 parts by weight of an 80:20 mixture of 2,4- and 2,6tolylene diisocyanate.

9. A method according to any one of the preceding claims, in which the crumb and the additive are tumbled together and steam is passed through the mixture to cure the polyurethane prepolymer and bond the additive to the crumb.

10. A method for imparting flameretard ant properties to a polyurethane foam crumb, substantially as hereinbefore described with reference to either of Examples 2 or 3.

11. A flame-retardant polyurethane foam crumb obtained by the method of any one of the preceding claims.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (11)

**WARNING** start of CLMS field may overlap end of DESC **. approximately 400 cm3 of treated crumb on a shallow metal tray and applying a lighted match to the lower edge of the crumb. EXAMPLE 1 (Control) A standard 3/8" polyurethane foam crumb was tested for flammability. The foam burned fiercely to a melt in less than 1 minute after application of a lighted match. The melt continued to burn for a further 22 minutes. EXAMPLE 2 The crumb used in Example 1 (above) was treated with 300 parts by weight per hundred of foam of prepolymer coatedalumina hydrate followed by passage of steam to cure the prepolymer and bond the hydrate to the crumb. A single lighted match was insufficient to cause ignition of the foam. A further two lighted matches were applied at the same place and the foam then burned very slowly and gently in a localised area for about 1 minute. EXAMPLE 3 The treated foam used in Example 2 (above) was shaken for It hours, after which time around 90% by weight of the hydrate remained in the foam. On ignition, the foam burned slowly and gently for 2 to 3 minutes after application of a lighted match. A black particulate ash formed on the surface of the foam and prevented burning of the remainder. A very slight degree of melting of the foam was observed. WHAT WE CLAIM IS:

1. A method for imparting flameretardant properties to a polyurethane foam crumb, in which the foam crumb is treated with a particulate flame-retardant additive, the - particles of said additive having previously been coated with a polyurethane prepolymer.

2. A method according to claim 1, in which the foam crumb comprises loose polyurethane foam crumb.

3. A method according to Claim 2, in which the crumb has a particle size in the range 1/8 inch to 1/2 inch.

4. A method according to Claim 1, in which the crumb comprises polyurethane foam crumb bonded with an isocyanatepolyol prepolymer.

5. A method according to any one of Claims 1 to 4, in which the particulate flame-retardant additive is a hydrated alumina.

6. A method according to Claim 5, in which the hydrated alumina has a particle size in the range 45 to 75 microns.

7. A method according to Claim 6, in which the hydrated alumina has a particle size in the range 50 to 75 microns.

8. A method according to any one of the preceding claims, in which the polyurethane prepolymer comprises the reaction product of 100 parts by weight of a polyether triol of molecular weight 3500 and 33 parts by weight of an 80:20 mixture of 2,4- and 2,6tolylene diisocyanate.

9. A method according to any one of the preceding claims, in which the crumb and the additive are tumbled together and steam is passed through the mixture to cure the polyurethane prepolymer and bond the additive to the crumb.

10. A method for imparting flameretard ant properties to a polyurethane foam crumb, substantially as hereinbefore described with reference to either of Examples 2 or 3.

11. A flame-retardant polyurethane foam crumb obtained by the method of any one of the preceding claims.