MXPA97006235A - Rigi polyurethane foams - Google Patents

Abstract

The present invention relates to a process for the preparation of rigid open-cell polyurethane foams comprising the step of reacting an organic polyisocyanate with an isocyanate-reactive material in the presence of a blowing promoter, which is a cyclic carbonate, reactive with isocyanate or cyclic urea, and in the presence of an organic, fluorinated, insoluble liquid and a metal salt catalyst, in which the fluorinated, insoluble organic liquid is an unsaturated, acyclic, perfluoro organic compound

Description

RIGID POLYURETHANE FOAMS DESCRIPTION OF THE INVENTION This invention relates to rigid polyurethane foams and especially rigid open cell polyurethane foams, with methods for their preparation and for use in evacuated insulation panels. The production of foam materials based on polyurethane and other polymer systems derived from organic polyisocyanates is well established. Depending on the formulations used, their manufacture, the products may vary in texture from soft flexible foams used as cushioning materials to rigid foams used as insulation material or structural material. The rigid polyurethane foams can be of the closed cell type or the open cell type. One important application of rigid, open-cell polyurethane foam is as a filler material in evacuated insulation panels as described in European Patent Publications Nos. 188806 and 498628. It is described in European Patent Publication No. 498628 ( incorporated herein by reference) a process for the preparation of rigid open cell polyurethane foam, the process comprises the step of reacting an organic polyisocyanate with an isocyanate-reactive material in the presence of a blowing promoter which is a cyclic compound Isocyanate reagent of the formula: (I) (CR2), r CR wherein Y is 0 or NR1, wherein each of R1 is independently a lower alkyl radical of C - ^ - Cg or a lower alkyl radical substituted with an isocyanate reactive group; each R is independently hydrogen, a lower alkyl radical of C 1 -C 8 or (CH 2) m-X, wherein X is an isocyanate-reactive group which is OH or NH 2 and m is 0, 1 or 2; and n is 1 or 2; with the proviso that at least one of R1 or R is or comprises an isocyanate-reactive group; and in the presence of an insoluble, inert organic liquid, which is present as the dispersed phase of an emulsion or a microemulsion and in the presence of a metal salt catalyst. Preferred compounds for use as an insoluble, inert organic liquid are disclosed in EP-A-498628 as lightly fluorinated or perfluorinated compounds including fluorinated hydrocarbons such as fluorinated cycloalkanes, fluorinated ethers, fluorinated amines, fluorinated hydroxylamines, fluorinated aminoethers and fluorinated sulfones. A disadvantage of the fluorinated compounds listed in EP-A-498628 is their global warming potential due to their relatively long atmospheric duration. It is therefore an object of the present invention to improve the process for preparing the rigid, open cell polyurethane foam with respect to the type of the fluorinated compound used, in particular with respect to its global warming potential. Accordingly, the present invention provides a process for the preparation of rigid, open-cell polyurethane foams comprising the step of reacting an organic polyisocyanate with an isocyanate-reactive material in the presence of a blowing promoter which is a reactive cyclic compound with isocyanate of the formula: (C wherein Y is 0 or NR1, wherein each R1 is independently a lower alkyl radical of C ^ Cg or a lower alkyl radical substituted with an isocyanate-reactive group; each R is independently hydrogen, a lower alkyl radical of C ^ -Cg or (CH2) m-X, wherein X is an isocyanate-reactive group which is OH or NH2 and m is 0, 1 or 2; and n is 1 or 2; with the proviso that at least one of R1 or R is or comprises an isocyanate-reactive group; and in the presence of an insoluble, fluorinated organic liquid, which is present as the dispersed phase of an emulsion or a microemulsion and in the presence of a metal salt catalyst, characterized in that the insoluble, fluorinated organic liquid comprises an unsaturated organic compound acyclic, perfluorinated. The acyclic unsaturated organic compound, perfluorinated to be used in the process of the present invention has a shorter atmospheric duration than The fluorinated compounds described in EP-A-498628, and thus a lower global warming potential. In addition, its use does not lead to lower end products. In this way the present invention provides an environmentally friendlier process for preparing rigid, open cell polyurethane foam. The perfluorinated acyclic unsaturated organic compounds for use in the present process are the perfluoroolefin compounds normally liquid. These compounds may contain some hydrogen bound with residual carbon (generally less than about 0.4 mg / g and preferably less than about 0.1 mg / g) but are preferably completely fluorinated. The perfluoroolefin compound may contain one or more curved heteroatoms, for example, nitrogen or oxygen atoms. Representative examples of suitable perfluorinated, acyclic unsaturated compounds include hexafluoropropene dies, for example, perfluoro (4-methylpent-2-ene) and perfluoro (2-methylpent-2-ene), hexafluoropropene trimers, for example, perfluoro ( 4-methyl-3-isopropyl-2-ene) and perfluoro (2,4-dimethyl-3-ethylpent-2-ene); tetrafluoroethylene oligomers, for example, perfluoro (3-methylpent-2-ene), perfluoro (3,4-dimethylhex-3-ene) and perfluoro (2,4-dimethyl-4-ethylhex-2-ene); perfluoro (1-pentene); perfluoro (2-pentene); perfluorodhexane); perfluoro (1-heptene); perfluoro (2-heptene); perfluoro (3-heptene); perfluoro (oxalkenes), for example, perfluoro (3-oxahex-l-ene), perfluoro (3-oxahept-l-ene) and perfluoro (3-oxa-4-methylpent-l-ene); perfluoro (3-ethyl-3-azapent-1-ene); and mixtures thereof. More preferred is perfluoro (4-methylpent-2-ene). For use in the process of the invention, the perfluorinated acyclic unsaturated compounds preferably have higher boiling points or equal to about 20 ° C. More preferably, the compounds have boiling points in the range of about 45 ° C to about 125 ° C. The perfluoroolefin compounds (as well as the perfluoroolefin compounds containing curved heteroatoms) can be prepared by methods such as decarboxylation of fluorocarboxylic acid salts (see, for example, AM Lovelace, DA Rausch, and Postelnek, " Aliphatic Fluorine Compounds ", Chapter III, Reinhold Publishing Corporation, New York (1958)) and the coupling of two or more perfluoroolefins (as described, for example, in US-P-5, 220, 082), the description of which is incorporated herein by reference). The hexafluoropropene oligomers can be prepared by various liquid phase and gas phase methods such as those described in, for example, US Pat. No. 5,254,774, the disclosures of which are incorporated herein by reference. Hexafluoropropene trimers are also commercially available (for example, from Fluorochem Limited). The tetrafluoroethylene oligomers can be prepared by methods such as those described in, for example, US-P-3, 758, 618 and 4,016,217, the disclosures of which are incorporated herein by reference. In the process of the present invention one or more of the perfluorinated acyclic unsaturated compounds can be used. In addition, perfluorinated acyclic unsaturated compounds can also be used in combination with other fluorinated compounds. Representative examples of such different fluorinated compounds are given in EP-A-498628. The total amount of fluorinated organic compounds, insoluble to be used in the process of the present invention, include the perfluorinated acyclic unsaturated compounds, in the range of 0.05 to 5% by weight based on the total reaction system.

The insolubility of the fluorinated organic liquid in the reaction mixture usually rises from the fact that it is insoluble. in one or more of the main ingredients of the foam formulation, especially the isocyanate-reactive material and / or the polyisocyanate. The solubility in these materials can be determined by conventional techniques. The insoluble, fluorinated organic compounds will usually be incorporated in the reaction mixture that forms the foam in the form of an emulsion or preferably a microemulsion in one of the main components, ie, that is, in the isocyanate-reactive component and / or the polyisocyanate component. Such emulsions or microemulsions can be prepared using conventional techniques and suitable emulsifying agents. Emulsification agents suitable for preparing stable emulsions or microemulsions of fluorinated liquid compounds in organic polyisocyanates and / or isocyanate-reactive compounds include surfactants selected from the group of nonionic, ionic (anionic or cationic) and amphoteric surfactants. Preferred surfactants for emulsifying the fluorinated liquid compound in the isocyanate-reactive composition are silicone surfactants, fluoro surfactants and / or alkoxylated alkanes. Particular examples of fluoro surfactants include fluorinated alkylpolyoxyethylene ethanols, fluorinated alkyl alkoxylates and fluorinated alkyl esters. Preferred surfactants for emulsifying the fluorinated liquid compound in the polyisocyanate composition are not isocyanate-reactive silicone surfactants such as Tegostab B 8407 available from Goldschmidt and SR 234 available from Union Carbide. A preferred compound of the formula (I) to be used in the process of the present invention, wherein Y is 0, is a cyclic carbonate reactive with isocyanate which is glycerol carbonate. Preferred compounds of the formula (I), wherein Y is NR1 are the cyclic isocyanate reactive ureas of the formula: The isocyanate-reactive cyclic blowing promoter is used in amounts in the range of 1 to 99%, preferably 1 to 60% by weight based on the total isocyanate reactive material. The additional blowing agents can be used in the method of the present invention, such as water or inert low boiling compounds having a boiling point above -50 ° C to 1 bar. The amount of water used as the blowing agent may be selected in a known manner to provide foams of the typical amounts, of desired density which is in the range of 0.05 to 5 parts by weight per 100 parts by weight of the reactive ingredients, although it may be a particular embodiment of the present invention to incorporate up to 10% by weight or even up to 20% by weight of water. Suitable inert blowing agents include, for example, hydrocarbons, dialkylethers, alkyl alkanoates, cycloaliphatic and aliphatic hydrofluorocarbons, hydrochlorofluorocarbons, chlorofluorocarbons and fluorine-containing ethers. Suitable hydrocarbon blowing agents include lower cyclic or aliphatic hydrocarbons such as n-pentane, isopentane, cyclopentane, neopentane, hexane and cyclohexane. Preferred metal salt catalysts for use in the present invention are those selected from the group a and metal salts of the group a, most preferably between the metal carboxylates of the group a and the group lia. Particularly suitable catalysts for use in the present invention are potassium acetate and potassium ethylhexoate. The metal salt catalyst is used in the process of the present invention in amounts in the range of 0.01 to 3% by weight based on the total reaction system. The organic polyisocyanates which can be used in the method of the present invention, include aliphatic, cycloaliphatic, araliphatic and aromatic polyisocyanates but especially the polyisocyanates are proposed in the literature for use in the production of foams. Of particular importance are the aromatic diisocyanates such as toluene and diisocyanate diphenylmethane in the unpurified or modified, very pure foams. Special mention may be made of so-called MDI variants (diphenylmethane diisocyanate modified by the introduction of urethane, allophanate, urea, biuret, carbodiimide, uretonimine or isocyanurate residues) and mixtures of diphenylmethane diisocyanates and oligomers thereof, known in the art. as MDI "unpurified" or "polymeric" (polymethylene polyisocyanates, polyphenylene). In carrying out the method of the invention, the polyisocyanate can be reacted with cyclic carbonate reactive with isocyanate or cyclic urea reactive with isocyanate in the absence or presence of other isocyanate-reactive materials. It is preferred, however, to carry out the method of the invention in the presence of other isocyanate-reactive materials. Suitable isocyanate-reactive materials generally include polyols, amines, imines and enamines and mixtures thereof. For the preparation of rigid polyurethane foams, the suitable isocyanate-reactive compounds, especially polyols, generally have a molecular weight of 62 to 1500 and a functionality of 2 to 8, especially 3 to 8. The polymeric polyols have been completely described in the prior art and include reaction products of alkylene oxides, for example ethylene oxide and / or propylene oxide, with initiators containing from 2 to 8 active hydrogen atoms per molecule. Suitable initiators include polyols, for example, glycerol, trimethylolpropane, triethanolamine, pentaerythritol, sorbitol, and sucrose, and polyamines, for example ethylenediane, tolylenediamine, diaminodiphenyl methane, and polymethylene polyamines, polyphenylene, and to indole alcohols, for example, ethanolamine, diethanolamine, and triethanolamine., and mixtures of such initiators. Other polyols suitable for use in the process of the present invention include polyesters obtained by the condensation of appropriate proportions of glycols and polyols of high functionality with dicarboxylic acids. Even the additional suitable polyols include polyether-terminated polyethylenes, polyamides, polyesteramides, polycarbonates, polyacetals, polyolefins and polysiloxanes. In addition to the aforementioned ingredients, the mixture forming the foam may contain one or more other auxiliaries or conventional additives for the isocyanate-based foam formulations. Such optional additives include other conventional catalysts, flame retardants, smoke scavengers, organic or inorganic fillers, thixotropic agents, colorants, pigments, mold release agents, surfactants, foam stabilizers and the like. Isocyanate rates of 70 to 140 will typically be used in the operation of the method of the present invention, but lower rates may be used if desired. Higher rates, for example 150 to 500 or even up to 3000, can be used together with trimerization catalysts to make foams containing isocyanurate bonds. To reduce the number of component streams supplied to the final mixing apparatus, the cyclic isocyanate-reactive blowing promoter, the catalyst, the insoluble fluorinated organic compounds and optionally other additives can be premixed with one of the main components of the foam formulation , in general with the isocyanate reactive component. Therefore, the present invention also provides an isocyanate-reactive composition comprising a blowing promoter which is an isocyanate-reactive cyclic compound of the formula: wherein Y is O or NR1, wherein each of R1 is independently a lower alkyl radical of C - ^ - Cg or a lower alkyl radical substituted with an isocyanate reactive group; each R is independently hydrogen, a lower alkyl radical of C - ^ - Cg or (CH2) m-X, wherein X is an isocyanate-reactive group which is OH or NH2 and m is 0, 1 or 2; and n is 1 or 2; with the proviso that at least one of R1 or R is or comprises an isocyanate-reactive group; an insoluble, fluorinated organic liquid which is present as the dispersed phase of an emulsion or a microemulsion and a metal salt catalyst, characterized in that the fluorinated, insoluble organic liquid comprises an acyclic, perfluorinated, unsaturated organic compound. The method of the present invention can be practiced using conventional techniques. In this way, known mixing methods can be used and the foams can be produced in the form of a supply of roll, molded articles, cavity fillings, sprayed foam, foamed foam or laminates with other materials such as hardboard, cardboard with plaster, paper, plastics or metal.

The rigid polyurethane foams prepared according to the method of the invention are of particular use for applications of the evacuated insulating panel. The evacuated insulating panels generally comprise a low thermal conductivity filler material (such as open cell polyurethane foam) and a container formed of a gas tight film that surrounds the filler material, the tota.l is evacuated to an internal pressure of approximately 5 mbar or less and then sealed hermetically. General descriptions of the construction of evacuated insulating panels and their use in thermal devices can be found in U.S. Patent Nos. 5,066,437, 5,032,439 and 5,076,984 and European Patent Publications Nos. 434266, 434225 and 181778, all incorporated in US Pat. the present for reference as well as the references mentioned therein. The invention is illustrated but not limited by the following example.

Example The following ingredients are used: Polyol A which is a polyether polyol composition with an average hydroxyl value of 365 mg KOH / g and average functionality of 2.9; Tegostab B 8406 which is an eilicone surfactant available from Goldschmidt; LB catalyst which is a catalyst of the metal salt available from Imperial Chemical Industries PLC; Fixapret NF which is a cyclic urea available from BASF; perfluorohexane (PFH); perfluoro (4-methylpent-2-ene) (PFO) available from 3M under the trade name L 12596; SUPRASEC 2185 which is a polymeric MDI available from Imperial Chemical Industries PLC. SUPRASEC is a trademark of Imperial Chemical Industries. The rigid foams are prepared in a commercial laminator at an application rate of 30 kg / minute using the formulations (the amounts are given in parts by weight) as listed in Table 1. Some properties of the foam are also given in the Table 1: isocyanate index, density expressed in kg / m3, closed cell content (CCC) give in% and cell size given in microns. The density (core density) was measured according to DIN 53420. The closed cell content was measured according to the standard of Method 10 BS 4370 and represents the% by volume of closed cells. The size of the cell was measured according to the method described by A. Cunningham in "Proceedings of Conference on Heat and Mass Transfer in Cryoengineering and Refrigeration", September 1986, page 32-49. The foam blocks were heat treated for 10 minutes at 150 ° C, pumped at a pressure of 0.05 mbar and heat sealed in a metallized film. The initial thermal conductivity (lambda value expressed in m / mK) was measured according to ISO 2581. The results are also given in Table 1.

Table 1 Foam Comparative Foam according to the Invention Formulation Polyol A 100.3 100.3 Catalyst LB 0. 1 0. 1 B 8406 Fixapret NF 1 .6 1. 6 SCJPRASEC 2185 154 154 Water 0. 25 0. 25 PFH PFO These results show that by the use of an unsaturated, acyclic, perfluorinated, environmentally friendlier compound, the properties of the foam have no harmful influence.

Claims (7)

1. - A process for the preparation of rigid foams comprising the step of reacting an organic polyisocyanate with an isocyanate-reactive material in the presence of a blowing promoter which is an isocyanate-reactive cyclic compound of the formula: (I) (CR2) f CR wherein Y is 0 or NR1, wherein each R1 is independently a lower alkyl radical of C - ^ - C8 or the lower alkyl radical substituted with an isocyanate reactive group; each R is independently hydrogen, a lower alkyl radical of C - ^ - C or (CH2) m-X, wherein X is an isocyanate-reactive group which is OH or NH2 and m is 0, 1 or 2; and n is 1 or 2; with the proviso that at least one of R1 or R is or comprises an isocyanate-reactive group; and in the presence of 0.05 to 5% by weight based on the total reaction system of an insoluble, fluorinated organic liquid, which is present as the dispersed phase of an emulsion or a microemulsion and in the presence of a metal salt catalyst , characterized in that the fluorinated, insoluble organic liquid comprises an acyclic, perfluorinated, unsaturated organic compound.

2. The process according to claim 1, characterized in that the perfluorinated acyclic unsaturated organic compound comprises perfluoro (4-methylpent-2-ene).

3. The process according to any of the preceding claims, characterized in that the isocyanate-reactive cyclic blowing promoter is a cyclic urea of the formula: OR

4. The process according to any of the preceding claims, characterized in that the isocyanate reactive cyclic blowing promoter is used in amounts in the range of 1 to 99% by weight based on the total isocyanate reactive material.

5. The process according to any of the preceding claims, characterized in that the catalyst of the metal salt is a group or a group Ia of metal carboxylate.

6. The process according to any of the preceding claims, characterized in that the catalyst of the metal salt is used in amounts in the range of 0.01 to 3% by weight based on the total reaction system.

7. An isocyanate-reactive composition comprising a blowing promoter which is an isocyanate-reactive cyclic compound of the formula: (CR wherein Y is 0 or NR1, wherein each R1 is independently a lower alkyl radical of C - ^ - Cg or the lower alkyl radical substituted with an isocyanate reactive group; each R is independently hydrogen, a lower alkyl radical of C - ^ - Cg or (CH2) m-X, wherein X is an isocyanate-reactive group which is OH or NH2 and m is 0, 1 or 2; and n is 1 or 2; with the proviso that at least one of R1 or R is or comprises an isocyanate-reactive group; an insoluble, fluorinated organic liquid, which is present as the dispersed phase of an emulsion or a microemulsion and a metal salt catalyst, characterized in that the fluorinated, insoluble organic liquid comprises an acyclic, perfluorinated, unsaturated organic compound.