MXPA01008131A - Fine-cell, water-driven rigid expanded polyurethanes - Google Patents

Abstract

The invention relates to a method for producing water-driven, fine-cell rigid foams containing urethane and/or isocyanurate groups by reacting polyisocyanates with a polyol component in the form of an emulsion. The invention also relates to foam-mouldable open-cell polyurethane foams.

Description

Hard thin-walled polyurethane foams expanded with water The invention relates to a process for the manufacture of water-thinned, fine-cell thin foams having urethane and / or isocyanurate groups by reacting polyisocyanates with a polyol component present as an emulsion. In addition, the invention relates to foamed open cell polyurethane foams.

The hard polyurethane foams are manufactured according to the state of the art from polyols with at least three hydroxyl groups per molecule of media, at least difunctional isocyanates, catalysts, blowing agents and copolymerized polysiloxane-polyoxyalkylene block, as well as usual additives case. A synthetic presentation of the state of the art, of the raw materials used and of usable processes is found in G. Oertel (Ed.): "Kunststoff-handbuch", vol. Vil, C. Hanser Verlag, Munich, 1983, in Houben-Weyl: "Methoden der organischen Chemie", vol. E20, Thieme Verlag, Stuttgart 1987, p. 1561 to 1757, and in Ullmann's Encyclopedia of Industrial Chemistry, vol. A21, VCH, Weinheim, 4th edition, 1992, pp. 665 to 715. In general polyether or polyester polyols or mixtures thereof are used, being present in the mixture REF: 131894 polyol used on average at least three hydroxyl groups per molecule and the hydroxyl number of the polyol mixture used between 100 and 900 being found. The hard polyurethane foams that are formed are most of the time predominantly of closed cell. Its cubic weight is between 5 and 950 kg.m3, mostly between 10 and 350 kg.m3, being used with special frequency cubic weights between 20 and 70 kg.m3. New developments in the field of hard polyurethane foams refer to the chosen manufacture of polyurethane hard foams, largely open-cell, modified with polyurethane or polyisocyanurate groups, which are used as insulation materials, eg in aluminum panels. empty. For the use of open cell hard foams indicated in vacuum panels, a cell diameter as small as possible is especially important, since this determines the efficiency of the insulation. The smaller the cell diameter the less must be evacuated to achieve a definite insulating effect. The average cell diameter of the hard polyurethane foams expanded with water obtained according to processes of the state of the art is usually above 150 μm; foams with a similar cell diameter are not usually suitable for vacuum applications. The manufacture of hard open-cell polyurethane foams is basically known. Thus, US-A 5 350 777 describes the use of alkaline earth salts of long chain fatty acids as cell opener. From EP-A 498 628 the manufacture of open cell hard foams is carried out by the action of a thermally activated blowing agent. This process has the disadvantage that the foam cells can only be opened where a minimum temperature is exceeded during the foaming process, so that the foams obtained do not have a high proportion of homogeneous open cells through the filled volume with the foam. DE-A 43 03 809 discloses a process for the manufacture of hard foams with a greater proportion of open cells in which the action of cellular opening of a liquid polyolefin additive is used. This process has the drawback of a narrow field of application and the additional drawback that with larger doses of the polyolefin additive a thickening of the cells rapidly occurs. US-A 5 250 579 and US-A-5 312 846 disclose the effect of cellular opening of substances with a surface tension lower than 23 mJ.rrf2. These have the disadvantage that they contain organically bound halogen.

It has been the object of the present invention to find a process for the production of hard, thin-walled polyurethane foams and, where appropriate, expanded cells with water, in which the hard polyurethane foams according to the invention maintain the desired final properties - open cells and fine cells - also in a foaming mold. It has now been found that in the foaming of a polyisocyanate with a polyol formulation present as an emulsion and containing water, hard foams of thin cell polyurethane and, where appropriate, open cell are obtained. Accordingly, the invention relates to a process for the production of hard polyurethane foams and / or thin-film polyisocyanurates by reacting A) a polyisocyanate having an NCO content of 20 to 48% by weight with B) a polyol component present as an emulsion having on average at least two groups reactive towards isocyanate, containing 1) at least one at least difunctional polyol, 2) water, 3) catalyst, 4) optionally adjuvants and additives. Another object of the invention is a polyurethane or polyisocyanurate molding foam with a proportion of open cells measured according to DIN ISO 4590-92 > 85%, preferably > 90%, with a degree of compaction > 3%, referred to the minimum amount of filling. This foam can be manufactured by the process according to the invention. The polyol formulations according to the invention contain at least one water-immiscible polymer with at least one functional group having hydrogen atoms reactive with isocyanate and having an average number-average molecular weight of 150 to 12,500 g / mol, preferably 200 at 1,500 g / mol. Examples of these are triglycerides, for example castor oil or castor oil modified by transesterification / amidation reactions with mono- or polyfunctional alcohols or amines, or fatty acids such as stearic acid, oleic acid, linoleic acid or ricinoleic acid. The polyol formulation contains from 5 to 99 parts by weight, preferably 20-80 parts by weight of this component. Preferably, the water immiscible polymer turns out to be at least a difunctional polyol. To achieve the functionality required for foaming, the polyol formulations according to the invention contain at least one polyol having at least two hydrogen atoms reactive with isocyanates and an average number-average molecular weight of 150 to 12,500 g / mol, preferably 200. at 1,500 g / mol. Such polyols can be obtained by polyaddition of alkylene oxides such as ethylene oxide, propylene oxide, butylene oxide, dodecyl oxide or styrene oxide, preferably propylene oxide or ethylene oxide, to initiating compounds such as water or polyhydric alcohols. , such as sucrose, sorbitol, pentaerythritol, trimethylolpropane, glycerin, propylene glycol, ethylene glycol, diethylene glycol as well as mixtures of the indicated initiator compounds. Ammonia or compounds having at least one primary, secondary or tertiary amino group, for example aliphatic amines such as ethylenediamine, oligomers of ethylenediamine (eg diethylenetriamine, triethylenenetetramine or pentaethylenehexamine), ethanolamine, diethanolamine, triethanolamine can also be used as initiator compounds. , N-methyl- or N-ethyl-diethanolamine, 1,3-propylene diamine, 1,3- or 1,4-butylene diamine, 1,2-hexamethylenediamine, 1,3-hexamethylenediamine, 1/4-hexamethylenediamine, 1, 5 -hexamethylenediamine or 1,6-hexamethylenediamine, aromatic amines such as phenylenediamines, toluylenediamines (2,3-toluylenediamine, 3,4-toluylenediamine, 2,4-toluylenediamine, 2,5-toluylenediamine, 2,6-toluylenediamine or mixtures of the isomers) indicated), 2,2'-diaminodiphenylmethane, 2,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane or mixtures of these isomers. The polyol formulation contains from 0 to 95 parts by weight, preferably 10-40 parts by weight, of this component. The polyol formulations according to the invention can also contain polyester polyols with a number average molecular weight of 100 to 30,000 g / mol, preferably from 150 to 10,000 g / mol, particularly preferably from 200 to 600 g / mol, which have been prepared from aromatic and / or aliphatic dicarboxylic acids and polyols having at least two hydroxyl groups. Examples of dicarboxylic acids are phthalic acid, fumaric acid, maleic acid, azelaic acid, glutaric acid, adipic acid, suberic acid, terphtalic acid, isophthalic acid, decanedicarboxylic acid, malonic acid, glutaric acid and succinic acid. Individual dicarboxylic acids can be used as well as discrete mixtures of different dicarboxylic acids. Instead of the free dicarboxylic acids, the corresponding dicarboxylic acid derivatives can also be used, such as, for example, mono or diesters of dicarboxylic acids and alcohols with one to four carbon atoms or dicarboxylic acid anhydrides. The following are preferably used as the alcohol component for the esterification: ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1, 10-decanodiol, glycerin, trimethylolpropane or mixtures thereof. The polyol formulations according to the invention can also contain polyether esters such as those obtainable, for example, from EP-A 250 967 by reaction of phthalic anhydride with diethylene glycol and then with ethylene oxide. The polyol formulation can contain from 0 to 90, preferably from 5 to 30 parts by weight of polyester. The polyol formulations according to the invention also contain at least one catalyst. In amounts of 0 to 10 parts by weight, preferably 0.5 to 5 parts by weight. According to the invention, the catalysts customary in the chemistry of polyurethanes can be used. Examples of such catalysts are: triethylenediamine, N, N-dimethylcyclohexylamine, tetramethylenediamine, l-methyl-4-dimethyl-aminoethylpiperazine, triethylamine, tributylamine, dimethylbenzylamine, N, N ', N "-tris- (dimethylaminopropyl) -hexahydrotriazine, dimethylaminopropylformamide, N, N, N ', N'-tetramethylethylenediamine, N, N, N', N '-tetramethylbutanediamine, tetramethylhexanediamine, pentamethylethylenetriamine, tetramethyldiamine ethylether, dimethylpiperazine, 1/2-dimethylimidazole, 1-azabicyclo [3, 3, o] octane, bis- (di-ethylaminopropyl) -urea, N-methylmorpholine, N-ethylmorpholine, N-cyclohexylmorpholine, 2,3-dimethyl-3,4,5,6-tetrahydropyrimidine, triethanolamine, diethanolamine, triisopropylamine, N-methyldiethanolamine, N-ethyldiethanolamine, dimethylethanolamine, tin acetate (II), tin octoate (II), tin (II) ethylhexoate, tin (II) laurate, dibutyltin diacetate, dibutyltin dilaurate, dibutyltin maleate, dioctyltin diacetate, tris- (N, N-dimethylaminopropyl) -s-hexahydrotriazine, tetramethylammonium hydroxide, potassium acetate , sodium acetate, sodium hydroxide or mixtures of these or similar catalysts. According to the invention, ionic and nonionic emulsifiers can also be combined in amounts of from 0 to 10 parts by weight, preferably from 0.5 to 2 parts by weight. Such emulsifiers are described, for example, in "Rummp Chemie Lexikon", vol. 2, Thieme Verlag Stuttgart, 9th edition, 1991, p. 1156 and next. The polyol component according to the invention contains from 0.1 to 10 parts by weight, preferably from 0.5 to 5 parts by weight, of water. It is essential for the process according to the invention that the polyol component be used as an emulsion. This means that at least one of the ingredients of the polyol component must not be miscible with the other ingredients, that is to say that it generally contains at least one compound that is not soluble in water or immiscible with water and has reactive hydrogen atoms in front of it. to isocyanate. It has been found that the use of a polyol component present as an emulsion leads to essentially thin-cell foams. As the isocyanate component, aromatic polyisocyanates such as those described in Justus Liebigs Annalen der Chemie, 562 (1949) 75, for example those of formula Q (NCO) n, wherein n can adopt values of 2 to 4, preferably 2, and Q means an aliphatic hydrocarbon residue of 2 to 18, preferably of 6 to 10, C atoms, a cycloaliphatic hydrocarbon residue of 4 to 15, preferably 5 to 10, C atoms or an aromatic hydrocarbon residue from 8 to 15, preferably from 8 to 13 C atoms. Preferably they are polyisocyanates such as those described in DE-OS 28 32 253. Particularly preferred are readily available technical polyisocyanates, eg 2,4- and 2,6 -toluylenediisocyanate as well as discrete mixtures of these isomers ("TDI"), polyphenylenepolymethylenepolyisocyanates, such as those prepared by condensation of aniline-formaldehyde and subsequent phosgenation ("crude MDI") and polyisocyanates having carbodiimide groups, urethane groups, allophanate groups, isocyanurate groups, urea groups or biuret groups ("modified polyisocyanates"), in particular modified polyisocyanates derived from 2,4- and 2,6-toluylene diisocyanate or 4,4'- and / or 2, '-diphenylmethane diisocyanate. Prepolymers of the indicated isocyanates and organic compounds with at least one hydroxyl group can also be used. By way of example, mention may be made of polyols or polyester polyols with molecular weights (number average) of from 60 to 1400. Paraffins or fatty alcohols or dimethyl polysiloxanes can also be used as well as pigments or dyes, as well as stabilizers against aging and the influence of weathering, plasticizers and substances with fungistatic and bacteriostatic activity as well as fillers, such as barium sulfate, diatomaceous earth, soot or creta washed. These are mostly added to the polyol component in amounts of 0 to 10 parts by weight, preferably 0 to 5 parts by weight. Other examples of surfactant additives and foam stabilizers to be used, such as cell regulators, reaction retarders, stabilizers, flame retardants, dyes and fillers as well as substances with fungistatic and bacteriostatic activity as well as details on the mode of use and action of these additives are described in Vieweg / Hochtlen (Ed.): Kunststoff-Handbuch ", Vol VII, Cari Hanser Verlag, Munich, 1996, pages 121 to 205, and G. Oertel (Ed.): "Kunststoff-Handbuch", vol. VII, Cari Hanser Verlag, 2nd edition, Munich, 1983 .. The polyurethane or polyisocyanurate molding foams according to the invention have an open cell proportion measured according to DIN ISO 4590-92 > 85%, preferably > 90%, with a degree of compaction > 3%, referred to the minimum amount of filling. The minimum amount of filler of a molding body is the amount of hard polyurethane foam that has already reacted finished needed to exactly fill the mold. It is also an object of the invention to use the hard polyurethane foams according to the invention as an intermediate layer for composite elements, as a filling substrate for vacuum insulation panels and for the foaming of hollow spaces in refrigerated rooms as well as in construction From containers. Preferably, the method according to the invention is used for the foaming of hollow spaces of refrigerators and freezers. It can also be used in thermal insulation, eg hot water tanks and hot fluid lines. Naturally, foams can also be produced by block foaming or by the double conveyor method (see "Kunststoff-Handbuch", Vol 7, Polyurethane, Cari Hanser Verlag, Munich, Vienna, 3rd edition 1993, page 148).

Examples Polyol A: Polyoxyethylenepolyether (Mn = 300) based on trimethylolpropane Polyol B: Polyether ester (Mn = 375) based on phthalic anhydride, diethylene glycol and ethylene oxide Polyol C: Castor oil [Fa. Alberding + Boley, Krefeld] Isocyanate: Polyphenylpolymethylenepolyisocyanate, NCO content 31.5% by weight (Desmodur® 44V20, Bayer AG) Stabilizer: Silicone stabilizer (Tegostab B 8404, Th. Goldschmidt AG, Essen) Emulsifier: Sulphate salt sodium of an ethoxylated fatty acid alcohol, 30% by weight in water (Servo Fa, NL-Delden) Catalyst 1: Dimethylcyclohexylamine Catalyst 2: Potassium acetate (25% by weight in diethylene glycol) The foams were made in a machine high pressure HK 165 of the Fa. Hennecke. Two test pieces were produced: Test piece 1: Free foamed block of dimensions 50 x 50 x 40 cm3 Test piece 2: Foamed test piece in mold of dimensions 9 x 40 x 70 cm3; compaction degree 8% Example 1 (according to the invention) 100 parts by weight of a mixture of 92 parts by weight of polyol C, 2.5 parts by weight of catalyst 1.1 part by weight of catalyst 2 were reacted, 2.5 parts by weight of water and 2 parts by weight of stabilizer with 145 parts by weight of isocyanate. The polyol mixture was a white emulsion. Test tube 1: Apparent density 52 kg / m3; Open cell proportion (DIN ISO 4590-92): 95% Cell size according to optical microscope photography: 100 μm Test tube 2: Apparent density 75 kg / m3; Open cell proportion (DIN ISO 4590-92): 93% Cell size according to optical microscope photography: 90 μm Example 2 (according to the invention) 100 parts by weight of a mixture of 19.2 parts by weight were reacted of polyol A, 19.7 parts by weight of polyol B, 5.77 parts by weight of polyol C, 0.8 parts by weight of catalyst 1, 0.9 parts by weight of catalyst 2, 3.6 parts by weight of emulsifier, 0.9 parts by weight of water and 1.4 parts by weight of stabilizer with 127 parts by weight of isocyanate. The polyol mixture was a white emulsion. Test tube 1: Apparent density 46 kg / m3; Open cell proportion (DIN ISO 4590-92): 98% Cell size according to optical microscope photography: 90 μm Test tube 2: Apparent density 69 kg / m3; Open cell proportion (DIN ISO 4590-92): 96% Cell size according to optical microscope photography: 80 μm Example 3 (comparative example) 100 parts by weight of a mixture of 46.3 parts by weight of polyol A, 46.3 parts by weight of polyol B, 2.5 parts by weight of catalyst 1.1 part by weight of catalyst 2, 2 parts by weight of water and 2 parts by weight of stabilizer with 127 parts by weight of isocyanate. The polyol mixture was a clear solution. Test tube 1: Apparent density 46 kg / m3; Open cell proportion (DIN ISO 4590-92): 9% Cell size according to optical microscope photography: 160 μm Test tube 2: Apparent density 69 kg / m3; Open cell proportion (DIN ISO 4590-92): 9% Cell size according to optical microscope photography: 1500 μm The examples show that polyol emulsions are used to obtain particularly fine hard cell foams.

It is noted that in relation to this date the best method known by the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (4)

R E I V I N D I C A C I O N S Having described the invention as above, property is claimed as contained in the following claims.

1. Process for the manufacture of hard polyurethane foams and / or thin cell polyisocyanurates by reaction of A) a polyisocyanate having an NCO content of 20 to 48% by weight with B) a polyol component present as an emulsion having on average less two groups reactive towards isocyanate, containing 1) at least one at least one difunctional polyol, 2) water, 3) catalyst, 4) optionally adjuvants and additives.

2. Use of the foam manufactured according to claim 1 as an intermediate layer for composite elements, as a filling substrate for vacuum insulation panels and as insulation material for refrigerating appliances.

3. Use of foam for the foaming of hollow spaces of refrigerators and freezers, for the manufacture of foam block or by the double conveyor belt process.

4. Polyurethane or polyisocyanurate molding foam with a proportion of open cells measured according to DIN ISO 4590-92 > 85% and a degree of compaction > 3%, referred to the minimum amount of filling.