JP2675816C - - Google Patents

Description

The present invention relates to rigid foams, and more particularly to rigid polymeric foams obtained from certain polymethylene polyphenyl polyisocyanate compositions. BACKGROUND ART Polymethylene polyphenyl polyisocyanate compositions are industrially produced by phosgenating a polyamine mixture obtained by the acid condensation of aniline and formaldehyde. The most commercially important polyisocyanate mixtures are from about 30 to about 70% by weight of diphenylmethane diisocyanate, together with various amounts of related methylene-bridged polyphenylene or penters and higher (higher) polyisocyanates. And the actual composition is
It largely depends on the initial aniline / formaldehyde ratio. Such compositions are described, for example, in British Patent Nos. 848,671, 874430,
It has been used in the manufacture of many types of isocyanate-containing formulations, and particularly polyurethane and polyisocyanurate rigid foams, as described in US Pat. Nos. 1,146,661, 1,148,893 and 1,234,415. The problem to be solved here is: from the polymethylene polyphenyl polyisocyanate mixture, which has a reduced diisocyanate content and a higher molecular weight polyisocyanate content, and accordingly a correspondingly increased content of tree or pentaisocyanate, is obtained from the excellent rigidity. It has been discovered that foams can be produced. More specifically, polyisocyanurate foams having improved flame resistance as measured by the oxygen index, and polyurethane foams having enhanced surface properties, especially low surface brittleness, can be produced from the above mixtures. Means for Solving the Problems: Accordingly, the present invention comprises reacting a polymethylene polyphenyl polyisocyanate composition with a polyfunctional active hydrogen-containing compound under foam-forming conditions, wherein the polyisocyanate composition comprises a diisocyanate. 2 polyisocyanates containing no more than 20% by weight and having more than 5 isocyanate groups per molecule
Provided is a method for producing a rigid foam, wherein the method does not contain more than 0% by weight. A typical polyisocyanate composition for use in the process of the present invention comprises, on a weight basis, 0-20% diphenylmethane diisocyanate, 40-80% dimethylene triphenylene triisocyanate, 5-25% polymethylene polyphenylene Contains toller and pentaisocyanate, and 0 to 20% higher polymethylene polyphenylene polyisocyanate. Preferred polyisocyanate compositions for use in the method of the present invention are 32-33
It has an NCO content of 0.3% by weight, which constitutes a novel composition which is another subject of the present invention. In the present invention, the NCO content of the polyisocyanate is the ratio of reactive NCO groups in the molecule (expressed in% by weight). That is, the following formula (42 × functionality ÷ molecular weight) × 100 [wherein, 42 is the molecular weight of NCO, the molecular weight is that of polyisocyanate, and the functionality is the total number of NCO groups present in polyisocyanate. ]. Preferably, the diisocyanate content of the polyisocyanate composition is not more than 15% by weight. It is also preferred that the content of polyisocyanate having 6 or more NCO groups is not more than 10% by weight. Suitable compositions preferably have a viscosity at 25 ° C. of 1,000 centipoise or less. The polyisocyanate compositions (mixtures) which can be used according to the invention and their preparation are known and are described, for example, in DE-OS 3,245,678 and EP 133,538. Generally, this mixture is prepared by a solvent extraction method performed on the initial polymethylene polyphenyl polyamine mixture before phosgenation, or the corresponding polymethylene polyphenyl polyisocyanate. Excess diisocyanate can then be removed by distillation. Specifically, a method for obtaining a polyisocyanate composition by phosgenating a polyamine component containing at least 94% by weight of a triamine is disclosed in German Patent DE 3,24.
The polyamine fraction described in US Pat. No. 5,678 is obtained by fractional distillation of a mixture containing di- and polyphenylenepolymethylene polyamines resulting from the acid condensation of aniline and formaldehyde. Polyfunctional active hydrogens that can be used in the process of the present invention include polyols, polyamines and water, each of which reacts with polyisocyanates to form polyurethane and polyurea products. The polyisocyanate can be reacted with the active hydrogen compound in an approximately stoichiometric amount (NCO index = 100), or a higher NCO index, such as 500 or 1,000 or even higher, is employed with the trimerization catalyst Thus, a polyisocyanurate-modified product can be obtained. Useful polyols and polyamines include those conventionally used (or proposed) to make rigid foams of polyurethane, polyurea and polyisocyanurate. Suitable polyols are usually two or more hydroxyl groups and 62
The appropriate functionality and molecular weight for a foam of either polyurethane or polyisocyanurate, having a molecular weight of ~ 1,500, is selected by known methods. Examples of such polyols include ethylene glycol, glycerol, trimethylolpropane, triethanolamine and their low molecular weight oxyalkylated products. Alkanolamines such as monoethanolamine could also be used. Other useful polyols include low molecular weight oxyalkylated products of sorbitol, sucrose and aromatic polyamines such as tolylenediamine and polymethylene polyphenylpolyamine, and bisphenols,
Examples include polyether polyols and polyester polyols. Suitable polyamines usually have two or more primary or secondary amino groups, and a molecular weight of 60-1,500. Mixtures of polyols and / or polyamines and / or water may be used. The polyisocyanate composition and the polyfunctional active hydrogen compound are reacted under conventional foam forming conditions. Generally, the reaction operation involves preparing a reaction mixture that includes a blowing agent in addition to the polyisocyanate composition and the active hydrogen compound. Such a reaction mixture may also contain other conventional components such as catalysts, surfactants, flame retardants and trimerization catalysts. Suitable blowing agents include inert volatile liquids, especially halogenated alkanes such as trichlorofluoromethane and dichlorodifluoromethane. In some cases, water can be used as a blowing agent instead of or in addition to the inert volatile liquid. Surfactants useful in foam production include siloxane oxyalkylene copolymers and conventional nonionic surfactants. Catalysts useful for the production of polyurethane and polyurethane foams include the usual tertiary amines and tin compounds, and the trimerization catalysts required for polyisocyanurate foams include alkali metals and alkaline earths. There are metal hydroxides, alkoxides and alkanates. Particularly useful catalysts for the production of polyisocyanurate foams include A salt of the formula There is a mixture with a salt of the formula In the above formula, M represents an alkali metal or tetraalkylammonium, Q represents a Group IIA metal or zinc, and R ¹ , R ² and R ³ may be the same or different and include hydrogen, lower alkyl, , Cycloalkyl, phenyl or alkylphenyl. Such catalysts are particularly preferred when the isocyanate index is at least 500. Foams can be manufactured using any of the conventional mixing and processing techniques. Therefore,
A spray method, a molding or laminating method, or the like can be used as desired. The low surface brittleness of the polyurethane foams according to the invention is particularly advantageous in laminating processes. This is because the adhesion between the foam and the facing material is significantly improved. The present invention will be described with reference to the following examples, but the present invention is not limited thereto. In Examples, "parts" and "%" are based on weight. Example 1 A polyurethane foam was made from the following two compositions. "Polyisocyanate 1" was a polymethylene polyphenyl polyisocyanate composition having an NCO content of 33.0 and containing 16% by weight of diisocyanate and 6% by weight of polyisocyanate having a molecular weight of 650 or more. "Polyisocyanate 2" is a polymethylene polyphenyl polyisocyanate composition (25%) having an NCO content of 30.6 and containing 50% by weight of diisocyanate.
(C viscosity of 920 centipoise at ° C). Tactile inspection revealed that the surface brittleness of foam 1 was lower than that of foam 2. Example 2 Polyisocyanurate foams A, B and C were prepared from the following three formulations. Three corresponding foams were also made from the same three formulation compositions except that "polyisocyanate 2" (same as in Example 1) was used instead of "polyisocyanate 1" above. The six foams thus obtained were subjected to an oxygen index test (ASTM 2863), and the following results were obtained. Oxygen index (ASTM2863)

Claims (1)

[Claims] 1. Reacting a polymethylene polyphenyl polyisocyanate composition with a polyfunctional active hydrogen compound under foam-forming conditions, wherein the polyisocyanate composition has a viscosity of less than 1000 centipoise at 25 ° C., and Contains no more than 20% by weight of diisocyanate and no more than 20% by weight of a polyisocyanate having more than 5 isocyanate groups per molecule. 2. The polyisocyanate composition comprises, on a weight basis, 0-20% diphenylmethane diisocyanate, 40-80% dimethylene triphenylene triisocyanate, 5-25% polymethylene polyphenylene tetra- and pentaisocyanate and 0-20% higher 2. The method according to claim 1, which comprises a novel polymethylene polyphenylene polyisocyanate. 3. 2. The process according to claim 1, wherein the NCO content of the polyisocyanate composition is between 32 and 33.3% by weight. 4. 3. The method according to claim 1, wherein the polyisocyanate composition does not contain more than 15% by weight of diisocyanates. 5. 5. The method according to claim 1, wherein the polyisocyanate composition does not contain more than 10% by weight of a polyisocyanate having more than 5 isocyanate groups per molecule. 6. The polyfunctional active hydrogen compound is a polyol, a polyamine, water or one of these.
A method according to any one of claims 1 to 5, which is a mixture of species or more. 7. A process according to any of claims 1 to 6, wherein the polyisocyanate composition is used in a greater than stoichiometric amount with a trimerization catalyst. 8. The catalyst has the following formula And the following formula (Wherein M represents an alkali metal or tetraalkylammonium;
Represents a Group IIA metal or zinc, and R ¹ , R ² and R ³ may be the same or different and represent hydrogen, lower alkyl, cycloalkyl, phenyl or alkylphenyl. 9. The method of claim 7, wherein the method comprises: 9. 9. The method of claim 8, wherein the NCO index is greater than 500.