PROCESS FOR THE FORMATION OF ISOCYANURATES

Abstract: Silicate esters which catalyse the formation of isocyanu­ rates or isocyanaurate linkages in isocyanate condensation polymers have the formula wherein R₁ is a C₂-C₄ alkylene radical and R₂ is either a methyl or alkyl radical. The catalysts may be used to prepare polyurethanes, poly(isocyanurates) and poly(2-oxazolidones).

Description: SILICATE CATALYSTS FOR THE FORMATION OF ISOCYANURATES The present invention relates to a process for preparing isocyanurates by the trimerisation of isocyanates and to a method for introducing isocyanurate linkages into condensation polymers in which one of the reactive monomers is an isocyanate. In particular, the invention relates to the use of a novel class of silicate catalysts which catalyse the formation of isocyanurates or the formation of isocyanurate linkages in isocyanate based condensation polymers. US 4,072,626, UK 1,497,956 and US 4,133,781 disclose the addition of organic silicates to modified isocyanurate foams for the purpose of smoke suppression. However, no catalytic activity for these materials has been reported. It has now been found that the silicates of the present invention not only act as a smoke suppressing agent but also catalyse the formation of isocyanurates from isocyanates. Accordingly, the present invention provides a process for the preparation of an isocyanurate from an isocyanate or mixture thereof by addition to the isocyanate or mixture of isocyanates a silicate catalyst having the formula 1) Si(R1-N(R9)9)A EMI1.1 wherein R1 is a C2- C4 alkylene radical and R2 is an alkyl radical. An embodiment of the present invention provides a process for the preparation of isocyanate condensation polymers containing isocyanurate linkages by addition, to the mixture which produces the polymer, of a silicate catalyst of the type described herein. The silicate catalysts may be of the general formula Si( -Rl-N(R2)2)4 or Si((o-Rl)2-NR2)2 wherein R1 is a C2-C4 alkylene radical and R2 is an alkyl radical. Preferred examples of such silicates are Sl(O-C2H4-N(CH3)2)4, the two Si(O-C3H7-N(CH3)2)4 isomers, Si((O-C2H4)2-NCH3)2 and Si((O-C2H4)2NC2R5)2. The catalysts themselves may be conveniently prepared from a lower alkyl orthosilicate, e.g. Si(OCH3)4 or Si(OCH2CH2CH2CH3)4 and the appropriate alkanolamine by a transesterification reaction. Thus, Si(O-C2H4-N(CH3)2)4 can be prepared from tetramethyl orthosilicate and N,N-dimethylethanolamine Si(OCH3)4 + 4(CH3)2NC2H40H3 SitO-C2H4N(CH3)2)4 + 4CH30H The reaction which forms isocyanurate or isocyanurate linkages can occur at room temperature but in certain cases it may be desirable to work at elevated temperature to increase reaction rates. Conveniently the reaction is carried out in the temperature range from room temperature to 1500C preferably in the range from room temperature to 1000C. By the term isocyanate condensation polymers is meant polymers which are derived either exclusively from a polyfunctional isocyanate monomer or from a polyfunctional isocyanate monomer in combination with a second polyfunctional monomer. The second monomer may be, for example a polyol, a polymer polyol, or a polyepoxide. When the second monomer is a polyol or polymer polyol, it is possible to produce a polyurethane containing isocyanurate linkages, whilst if the second monomer is a polyepoxide poly(2-oxazolidones) containing isocyanurate linkages can be produced. The presence of such isocyanurate linkages in the polymer product can confer favourable physical properties, such as mechanical strength and resistance to smoulder, on the product. Methods for producing such polymers are well known and the skilled man will be familiar with the addition of blowing agents, surfactants and the like to improve the reaction or modify the physical characteristics of the final polymer. In particular techniques which can be used to prepare the polymtr in a variety of physical forms, e.g. as an elastomer, resin, foam or fib, a contemplated as being used in con jucnt ion with the present invention. The present invention is now illustrated by the following examples. Example 1 This example illustrates the use of the silicate cataysts to catalyse the trimerisation of isocyanates. 0.1 moles of phenyl isocyanate, 0.01 moles of Si(OC2H4N(CH3)2)4 and 40 mls of benzene were heated to reflux for 5 hours. At the end of 5 hours, the reaction mixture was cooled and the product allowed to crystallise from solution overnight. Analysis of the product by melting point revealed that it was triphenyl isocyanurate (mp-282-284 C). The yield of product was 63X. Example 2 The method of example 1 was followed using Si((OC2H4)2NCH3)2 as the catalyst. Again triphenyl isocyanurate was formed at a yield of 78.2%. Exaple 3-7 These examples illustrate the preparation of flexible polyurethane foams containing isocyanurate linkages from TDI (toluene diisocyanate) and Niax 11-34 and 34-28 (polyfunctional alcohols). EMI4.1 <tb> <SEP> EXAMPLE <tb> <SEP> COMPONENT <SEP> (g) <SEP> 3 <SEP> 4EXAMPLE <SEP> 4 <SEP> 5 <SEP> 6 <SEP> 7 <tb> Niax <SEP> 11-34 <SEP> 30 <SEP> 30 <SEP> 30 <SEP> 30 <SEP> 30 <tb> Niax <SEP> 34-28 <SEP> 20 <SEP> 20 <SEP> 30 <SEP> 20 <SEP> 20 <tb> Surfactant <SEP> SC <SEP> 152 <SEP> 0.5 <SEP> 1.0 <SEP> 1.0 <SEP> 1.0 <SEP> 1.0 <tb> Water <SEP> 1.5 <SEP> 1.5 <SEP> 1.5 <SEP> 1.5 <SEP> 1.5 <tb> Si(OC2H4N(CH3)2)4 <SEP> 0.5 <SEP> 0.5 <SEP> 0.5 <SEP> 0.5 <SEP> 0.5 <tb> T-12 <SEP> 0 <SEP> 0.1 <SEP> 0 <SEP> 0 <SEP> 0 <tb> DABCO <SEP> 33LV <SEP> 0 <SEP> 0 <SEP> 0 <SEP> 0.1 <SEP> 0 <tb> NIAX <SEP> <RTI ID=4.4> A-1 <SEP> O <SEP> 0 <SEP> 0 <SEP> 0 <SEP> 0.1 <tb> TDI <SEP> (80/20) <SEP> 22.2 <SEP> 22.2 <SEP> 22.2 <SEP> 22.2 <SEP> 22.2 <tb> TDI <SEP> INDEX <SEP> 1 <SEP> 130 <SEP> 130 <SEP> 130 <SEP> 130 <SEP> 130 <tb> <SEP> PRODUCT <tb> Cream <SEP> time <SEP> (secs) <SEP> 15 <SEP> 30 <SEP> 14 <SEP> 20 <SEP> 18 <tb> Rise <SEP> time <SEP> (secs) <SEP> 130 <SEP> 129 <SEP> 198 <SEP> 185 <SEP> 95 <tb> Tack <SEP> free <SEP> time <SEP> (secs) <SEP> 450 <SEP> 438 <SEP> 500 <SEP> 425 <SEP> 370 <tb> Density <SEP> 63.8 <SEP> 34.1 <SEP> 52.6 <SEP> 38.8 <SEP> 35.2 <tb> Flammability <SEP> (TG <SEP> 90 <SEP> 59 <SEP> 105 <SEP> 80 <SEP> 77 <tb> ASTM <SEP> D <SEP> 1592-68 <tb> Example 8 A poly(2-oxaxolidone) foam with isocyanurate linkages was prepared as follows 26 g of the diglycidyl ether of bisphenol A, 30 g of CCl3F, 2 g of silicone surfactant DC-193, 6 g of Si(OC2H4N(CH3)2)4 and 100 g of PAPI 135 (a polymeric isocyanate were stirred vigorously. This mixture had an NCO:epoxy ratio of 5:1. The foam produced had the following properties. foam density = 39.6 Kgm3 Butter chimney test result = 91.2% wt retention Tumbling friability = 88Z The mixture which had a cream time of 18 secs and a rise time of 14 mins produced a polymer which, by infrared spectroscopy, was shown to exhibit both isocyanurate and 2-oxazolidone linkages.

Claims: Claims: 1. A process for the preparation of an isocyanurate from an isocyanate or mixture of isocyanates by reacting the isocyanate or mixture thereof in the presence of a silicate catalyst having the formula 1) Si(O-R1-N(R2)2)4 EMI5.1 wherein R1 is a C2-C4 alkylene radical and R2 is an alkyl radical. 2. A process for the preparation of isocyanate condensation polymers containing isocyanurate linkages by reacting a polyfunctional isocyanate with a polyfunctional monomer, under conditions which cause polymerisation, in the presence of a silicate catalyst having the formula 1) Si(O-R2-N(R9)9) EMI5.2 wherein R1 is a C2- C4 alkylene radical and R2 is an alkyl radical. 3. A process as claimed in Claim 2 wherein the isocyanate condensation polymer is a polyurethane and the polyfunctional monomer is either a polyol or polymer polyol. 4. A process as claiimed in Claim 2 wherein the isocyanate condensation polymer is a poly(2-oxazolidone) and the polyfunctional monomer is a polyfunctional epoxide. 5. A process as claimed in Claim 1 wherein the isocyanate is a polyfunctional isocyanate and the isocyanate condensation polymer formed is a polyisocyanurate. 6. A process as claimed in Claim 1 or 2 wherein the silicate catalyst is selected from the group comprising Si(0CH2CH2N(CH3)2)4, Si(OCH2CH2N(C2Hs)2)4, Si((OCH2CH2)2NCH3 )2 and Si((oCH2CH2)2NC2Hs )2* 7. Isocyanate condensation polymers containing isocyanurate linkages produced by a process as claimed in Claim 2.

Inventors: ASHIDA, KANEYOSHI
Applicants: BP CHEMICALS LIMITED
Application year: 1985
Main classification: C08G18
IPC codes: C08G18, C07D251