GB1562037A - Production of polyurethane foams - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO THE PRODUCTION OF POLYURETHANE FOAMS (71) We, I.S.C. CHEMICALS LIMITED, a British company of Borax House, Carlisle Place, London SW1P 1HT, 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 the production of polyurethane foams with reduced smoke emits ion on ignition.

Polyurethane foams are normally produced by the reaction between a polyol and a polyisocyanate in the presence of a foaming agent.

The foaming agent may be water which reacts with excess polyisocyanate to evolve carbon dioxide as the blowing gas or it may be an inert halogenated alkane of relatively low boiling point such as dichlorodifluoromethane or tri chloromonofluoromethane, which is evaporated due to the heat of reaction between polyol and poly-isocyanate to yield a gas for blowing purposes. The latter technique is described in detail in British patent specification No. 833,152 dated April 1958.

However, when it is required to reduce the smoke emission of such foamed polyurethanes it is necessary to add a smoke suppressant to one or other of the reactants prior to foaming in order to incorporate this into the foamed product. Previously this has been achieved by mixing the smoke suppressant with one or other of the reactants prior to foaming. However, certain smoke suppressants which are not easily dispersed have proved difficult to incorporate in this way.

This invention consists in a process for the production of a polyurethane foam containing a smoke suppressant, wherein a polyol is reacted with a polyisocyanate in the presence of a previously-prepared solution or suspension of the smoke-suppressant in a liquid halogenated alkane which is volatilised by the heat of reaction of the polyol with polyisocyanate.

Preferably the halogenated alkane is trichloromonofluoromethane or trichloro-trifluoroethane.

Preferably the smoke suppressant is a solid smoke suppressant such as "Ferrocene", i.e.

dicyclo-pentadienyl iron, (C5Hg)2Fe.

Preferably the isocyanate has 2 or 3 functional isocyanate groups.

Preferably the polyol is a dihydroxy-terminated polyester or polyether having a molecular weight of at least 500. Suitable materials are sold under the trademark "DESMOPHEN".

Preferably the solution or suspension of the smoke suppressant in the halogenated alkane is added to the polyol and this is then reacted with the polyisocyanate in a known manner.

The invention will be illustrated by reference to the following examples which relate to the production of rigid polyurethane foams, in which Example 1 is a comparative example, according to the prior art procedure as described in British patent specification 833,152 while Example 2 is according to the procedure of the present invention.

Example 1 To 100 parts by weight of a commerciallyavailable polyol (DESMOPHEN PU 1665), having a hydroxyl number of about 580 (+ 30) was added 18 parts by weight of liquid trichloromonofluoromethane. The polyol reactant was then reacted with 160 parts by weight of diphenylmethane -4-4-diisocyanate, in the presence of the trichloromonofluoromethane which was volatilized by the heat of the reaction to produce a polyurethane foam of a rigid structural grade.This had a density of 61.0 kglcu metre, an oxygen-index of 18.8 and gave an optical smoke density (per gram of foam burn ed), as measured using a Stanton-Redcroft FTB Smoke Chamber, of 0A6.

Example 2 The procedure of Example 1 was repeated exactly, except that 0.5 parts by weight of Ferrocene were dissolved in the 18 parts by weight of trichloromonofluoromethane before this was added to the polyol prior to reaction with the diisocyanate. The foam density was 61.0 kg/cu metre, the oxygen index was 18.8 and the optical smoke density (measured as in Example 1} was 0.21.

WHAT WE CLAIM IS: 1. A process for the production of a polyurethane foam containing a smoke suppressant, Wherein a polyol is reacted with a polyisocyanate in the presence of a previously-prepared solution or suspension of the smoke-suppressant in a liquid halogenated alkane which is volatilized by the heat of reaction of the polyol with the polyisocyanate.

2. A process as claimed in claim 1 in which the halogenated alkane is trichloramonofluoro- methane or trichlorotrifluoroethane.

3. A process as claimed in claims I or 2 in which the smoke-suppressant is "ferrocene" as herein defined.

4. A process as claimed in claims 1 to 3 in which the isocyanate contains 2 or 3 functional isocyanate groups.

5. A process as claimed in any preceding claim in which the polyol is a dihydroxyterminated polyester or polyether, having a molecular weight of at least 500.

6. A process as claimed in claim 1 wherein the previously-prepared solution or suspension of the smoke-suppressant in the halogenated alkane is added to the polyol and this is then reacted with the polyisocyanate.

7. A process for the production of a polyurethane foam substantially as hereinbefore described with reference to Example 2.

8. A polyurethane foam produced by means of a process as claimed in any one of claims I to 7.

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

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. optical smoke density (per gram of foam burn ed), as measured using a Stanton-Redcroft FTB Smoke Chamber, of 0A6. Example 2 The procedure of Example 1 was repeated exactly, except that 0.5 parts by weight of Ferrocene were dissolved in the 18 parts by weight of trichloromonofluoromethane before this was added to the polyol prior to reaction with the diisocyanate. The foam density was 61.0 kg/cu metre, the oxygen index was 18.8 and the optical smoke density (measured as in Example 1} was 0.21. WHAT WE CLAIM IS:

1. A process for the production of a polyurethane foam containing a smoke suppressant, Wherein a polyol is reacted with a polyisocyanate in the presence of a previously-prepared solution or suspension of the smoke-suppressant in a liquid halogenated alkane which is volatilized by the heat of reaction of the polyol with the polyisocyanate.

2. A process as claimed in claim 1 in which the halogenated alkane is trichloramonofluoro- methane or trichlorotrifluoroethane.

3. A process as claimed in claims I or 2 in which the smoke-suppressant is "ferrocene" as herein defined.

4. A process as claimed in claims 1 to 3 in which the isocyanate contains 2 or 3 functional isocyanate groups.

5. A process as claimed in any preceding claim in which the polyol is a dihydroxyterminated polyester or polyether, having a molecular weight of at least 500.

6. A process as claimed in claim 1 wherein the previously-prepared solution or suspension of the smoke-suppressant in the halogenated alkane is added to the polyol and this is then reacted with the polyisocyanate.

7. A process for the production of a polyurethane foam substantially as hereinbefore described with reference to Example 2.

8. A polyurethane foam produced by means of a process as claimed in any one of claims I to 7.