KR970002520B1 - Rigid foam - Google Patents

Abstract

A method is claimed for prepn. of rigid foams comprising reacting under foam forming conditions: a) a polymethylene polyphenyl polyisocyanate compsn. (I) contg. not more than 20 (pref. less than 15)wt. % diisocyanates and not more than 20 (pref. less than 10)wt. % polyisocyanates contg. more than 5 NCO gps. per mol.; with b) a polyfunctional active H cpd. Pref. the reaction is carried out wtih greater than a stoichiometric amount of (I) in the presence of a trimerisation catalyst. Also claimed is a polyisocyanate compsn. contg. 0-20 wt. % diisocyanate, 40-80 wt. % triisocyanate, 5-25 wt. % tetra/pentaisocyanate and not more than 20 wt. % polyisocyanate, and wherein the NCO value is 32-33.3 wt. %.

Description

Rigid foam

The present invention relates to rigid foams and in particular to polymeric foams derived from polymethylene polyphenyl polyisocyanate compositions of melanoma.

Polymethylene polyphenyl polyisoanate compositions are industrially produced by phosgenating a mixture of polyamines obtained by acid condensation of aniline and formaldehyde. Polyisocyanate mixtures of maximum commercial importance contain from about 30% by weight to about 70% by weight diphenylmethane diisocyanate with varying amounts in the relevant methylene-linked polyphenylene tri- to penta- and larger polyisocyanates; The actual composition depends very much on the initial aniline / formaldehyde ratio.

Such compositions are formulated based on various forms of isocyanates, and in particular polyurethane and polyisocyanate rigid foams as described, for example, in British Patents Nos. 848671, 874430, 114661, 11184893 and 1223415. Was used in the production of

It has been found that better rigid foams can be prepared from polymethylene polyphenyl polyisocyanate mixtures with increased tri-penta-isocyanate content corresponding to the reduced content of diisocyanates and high molecular weight polyisocyanates. In particular, it has been found that polyisocyanate foams with improved combustion properties and polyurethane foams with enhanced surface properties, in particular lower surface friability, as measured by oxygen index, can be prepared from the mixture.

Accordingly, the present invention provides a process for preparing a rigid foam comprising reacting a polymethylene polyphenyl polyisocyanate composition with an active hydrogen compound of a multifunctional group under conditions of foaming, wherein the polyisocyanate composition does not exceed 20% by weight. And no more than 20% by weight polyisocyanate containing diisocyanate and more than 5 isocyanate groups per molecule.

Characteristic polyisocyanate compositions for use in the process of the invention contain:

0-2% by weight diphenylmethane diisocyanate

40-80% by weight Dimethylene Triphenylene Triisocyanate

5-25% by weight polymethylene polyphenylene tetra- and pentaisocyanate and

0-20% by weight higher polymethylene polyphenylene polyisocyanate.

Preferred polyisocyanate compositions for use in the process of the invention have NCO-values in the range of 32-333% by weight, which constitutes a novel composition which is a particular target material of the invention.

It is preferred that the diisocyanate content of the polyisocyanate composition is less than 15% by weight. It is also preferred that the content of polyisocyanates having at least 6 NCO-groups is less than 10% by weight. Suitable compositions preferably have a viscosity of less than 1000 centipoise (cP) at 25 ° C.

Polyisocyanate mixtures and processes for their preparation which can be used according to the invention are described in the prior art, for example in DE-OS 3245678 and EP 133538. In general, this mixture is prepared by a solvent extraction process carried out on the original polymethylene polyphenyl polyamine mixture before phosgenation or on the polymethylene polyphenyl polyisocyanate. Any excess diisocyanate can then be removed by distillation.

In particular, a method for obtaining a polyisocyanate composition by phosgenating a polyamine fraction containing at least 94% by weight of triamine is described in DE 3245678.

A mixture containing di- and polyphenylene polymethylene polyamine resulting from acid condensation of aniline and formaldehyde is fractionally distilled to obtain a polyamine fraction.

Active hydrogen compounds of the multifunctional group which can be used in the process of the present invention include polyols, polyamines and water, each of which reacts with polyisocyanates forming polyurethane and polyurea products. Such polyisocyanates may react with active hydrogen compounds in about stoichiometric amounts (NCO index 100) or, for example, 500 or 1000 or larger NCO indexes may be combined with trimerization catalysts to form polyisocyanate modified products. Can be used.

Useful polyols and polyamids include conventional materials used or suggested to be used to make polyurethane, polyurea, and polyisocyanate hard foams.

Suitable polyols generally have a molecular weight of at least two hydroxyl groups and 62-1500, and suitable molecular weights and functionality for polyurethane or polyisocyanate foams are selected by known methods. Examples of such polyols include ethylene glycol, glycerol, trimethylolpropane, triethanolamine and low molecular weight oxyalkylation products thereof. Alkanol amines such as monoethanol amines may also be used. Other useful polyols include bis-phenol and polyether and polyester polyols as well as low molecular weight oxyalkylated products of sorbitol, sucrose and aromatic polyamines such as tolylene diamine and polymethylene polyphenyl polyamine.

Suitable polyamines generally have at least two primary or secondary amino groups and a molecular weight of 60-1500.

Mixtures of polyols and / or polyamines and / or water can be used.

The polyisocyanate composition and the active hydrogen compound of the multifunctional group can react under the usual conditions of forming a foam. In general, this involves preparing a reaction mixture containing a blowing agent in addition to the polyisocyanate and active hydrogen compound.

Such reaction mixtures may also contain other conventional components such as catalysts, surfactants, flame retardants and trimerization catalysts.

Suitable blowing agents include inert volatile liquids, in particular halogenated alkanes such as trichlorofluoromethane and dichlorodifluoromethane. In some cases, water may be used as blowing agent in addition to or instead of an inert liquid.

Surfactants useful for preparing foams include siloxane oxyalkylene copolymers and conventional nonionic surfactants. Catalysts useful in the preparation of polyurethanes and polyurea foams are common tertiary amine and tin compounds and the trimerization catalysts required for polyisocyanate foams include alkali and alkaline earth metal hydroxides, alkoxides and alkanoates. Particularly useful catalysts for the production of polyisocyanate foams are salts of the formula

Mixtures with the following structural salts.

Wherein M is an alkali metal or tetraalkylammonium, Q is a group IIA metal or zinc, and R ¹ , R ² and R ³ are the same or different and are hydrogen, lower alkyl, cycloalkyl, phenyl or alkylphenyl.

Such catalysts are particularly preferred when the isocyanate index is greater than 500. Such foams may be prepared using any conventional mixing and preparation techniques. Therefore, spraying techniques or molding or lamination methods can be used as desired. The reduced surface and fracture properties of polyurethane foams are particularly beneficial for lamination methods to the same extent as the adhesion between the foam and the materials facing it is significantly improved.

The invention is illustrated in the following examples, but not by way of limitation, in the examples all parts are by weight.

Example 1

Two polyurethane foams were prepared from the following formulations.

Polyisocyanate 1 was a polymethylene polyphenyl polyisocyanate composition having an NCO value of 33.0 and containing 16% by weight diisocyanate and 6% by weight polyisoanate having a molecular weight greater than 650.

Polyisocyanate 2 was a conventional polymethylene polyphenyl polyisocyanate composition having an NCO value of 30.6 and containing 50% by weight diisocyanate.

Close examination showed that the surface crushability of foam 1 was more effective than that of foam 2.

Example 2

Polyisocyanate foams were prepared from the following formulations.

Three such foams were prepared from the same formulation except that polyisocyanate 1 was replaced with polyisocyanate 2 (as in Example 1). The six hard polyisocyanate foams thus obtained were subjected to an oxygen index tesheet (ASTM 2863) to obtain the following results.

Claims (14)

A polymethylene polyphenyl polyisocyanate composition containing not more than 20% by weight of diisocyanate and not less than 20% by weight of polyisocyanate containing at least 5% of isocyanate groups per molecule and with the active hydrogen compound of the multifunctional group A method for producing a rigid foam, which is composed of reacting. The polyisocyanate composition of claim 1, wherein the polyisocyanate composition comprises 0-20% by weight of diphenylmethane diisocyanate, 40-80% by weight of dimethylene triphenylene triisocyanate, 5-25% by weight of polymethylene polyphenylene tetra- and Penta-isocyanate, 0-20% by weight of high polymethylene polyphenylene polyisocyanate. The method of claim 2 wherein the polyisocyanate composition has an NCO content of 32-33.3 weight percent. The method of claim 1 or 2, wherein the polyisocyanate composition contains less than 15% by weight diisocyanate. The method of claim 1 or 2 or 3, wherein the polyisocyanate composition contains less than 10% by weight polyisocyanate containing at least 5 isocyanate groups per molecule. The method of claim 1 or 2 or 3, wherein the polyisocyanate composition has a viscosity of less than 1000 centipoise (cP) at 25 ° C. The process according to claim 1 or 2 or 3, wherein the multifunctional group active hydrogen compound is polyol, polyamine, water or one or more of these mixtures. The process according to claim 1 or 2 or 3, wherein the polyisocyanate composition is used in an amount greater than stoichiometric amount with the trimerization catalyst. The process of claim 8 wherein the catalyst is a salt of the formula

Method consisting of a mixture of salts of the following structural formula

Wherein M is an alkali metal or tetraalkylammonium, Q is a group IIA metal or zinc, and R ¹ , R ² and R ³ (which may be the same or different) are hydrogen, lower alkyl, cycloalkyl, phenyl or alkylphenyl. 10. The method of claim 9, wherein the NCO index is greater than 500. Having a diisocyanate content of 0-20% by weight, a triisocyanate content of 40-80% by weight, a tetra / pentaisocyanate content of 5-25% by weight, and a polyisocyanate content of no greater than 20% by weight, with an NCO value of 33- Polyisocyanate composition, characterized in that 33.3% by weight. 12. The polyisocyanate composition of claim 11 containing less than 15% by weight diisocyanate. 13. The polyisocyanate composition according to claim 11 or 12, containing less than 10% by weight polyisocyanate containing at least 5 isocyanate groups per molecule. The polyisocyanate composition according to claim 11 or 12 having a viscosity of less than 1000 centipoise (cP) at 25 ° C.