MXPA99011149A - Method for producing closed-cell rigid polyurethane foams having low thermal conductivity - Google Patents

Abstract

The invention relates to a method for producing rigid polyurethane foams from polyols, polyisocyanates, expansion agents and possibly foaming agents. Said method is characterized in that the rigid polyurethane foam is obtained by reacting A. a polyol component containing (1) 40 to 80 weight percent of a polyethylene oxide/propylene oxide polyether having a molar mass of 300 to 800 and based on sucrose or sorbitol, (2) 3 to 40 weight percent of a polyethylene oxide/propylene oxide polyether having of molar mass of 300 to 800 and based on anaromatic mono-, di- or polyamine, (3) 3 to 40 weight percent of a polyethylene oxide/propylene oxide polyether having a molar mass of 200 to 800 and based on an aliphatic mono-, di- or polyamine, (4) 3 to 40 weight percent of a linear polyethylene oxide/propylene oxide polyether having a molar mass of 500 to 1500, (5) possibly other compounds having a molar mass of 150 to 12500 g/Mol and at least two hydrogen atoms reactive to isocyanates, (6) catalysts, (7) water, (8) expansion agents from the group of alkanes, cycloalkanes, hydrofluorochlorohydrocarbons, hydrofluorohydrocarbons, and (9) possibly auxiliary agents and/or additives, with B. an organic and/or modified organic polyisocyanate having an NCO content of between 20 and 48 weight percent.

Description

Procedure for the manufacture of closed cell polyurethane hard foams with low thermal conductivity Hard polyurethane foams are used because of their low thermal conductivity, in the insulation of refrigerators and freezers, industrial installations, storage tanks, tubular pipes, in shipbuilding and in the construction industry. A summarized overview of the manufacture of hard polyurethane foams and their use is in "Kunststoff-Handbuch", volume 7 (Polyuret ane), 2nd edition, 1983, edited by Dr. Günter Oertel (Carl Hanser Verlag, Munich). The thermal conductivity of a hard polyurethane foam of predominantly closed cells depends to a large extent on the type of blowing agent or cellular gas used. Especially suitable in this respect are fully halogenated fluorochlorohydrocarbons (FCHC), especially trichlorofluoromethane (Rll), which has a particularly low thermal conductivity. These substances are chemically inert and non-toxic. Fully halogenated fluorochlorohydrocarbons reach, as a consequence of their high stability, the stratosphere, where due to their chlorine content they contribute to the decomposition of the ozone present there (Molina, Rowland, REF .: 32007 Nature 249 (1974) 810). As a substitute for fluorochlorohydrocarbons, it has been proposed to use hydrofluoroalkanes, such as, for example, R 141b (dichlorofluoroethane), as blowing agents (US Pat. No. 5,272,183). It has also been proposed (EP 344 537, US Pat. No. 4,931,482) to use partially fluorinated hydrocarbon (hydrofluoroalkane) expansion agents, which have at least one carbon-hydrogen bond. Substances of this class of compounds do not contain any chlorine atom and consequently have an ODP (Ozone Depletion Potential) value of zero (in comparison: Rll: ODP = 1). Typical representatives of this class of substances are, for example, 1, 1, 1, 4, 4, 4-hexafluorobutane (R356) or 1,1,1,3,3-pentafluoropropane (245fa). Furthermore, it is known from EP 0 421 269 to use cyclopentane or cyclopentane as blowing agent mixed with other alkanes, such as, for example, i-butane, n-butane, n-pentane or iso-pentane. Depending on the blowing agent used, the polyol formulation must be modified to obtain hard polyurethane foams of comparatively small thermal conductivity. Polyol formulations which, using different systems of blowing agents, would provide a similar thermal conductivity without the need for costly modifications of the formulation or changes in the parameters of the machines for the foaming formulation would therefore be desirable. . It has therefore been the task of the present invention to find a process for the manufacture of hard polyurethane foams of closed cells of low thermal conductivity in which also using different systems of blowing agents can be obtained hard foams of polyurethane with a similarly low thermal conductivity . Surprisingly, it has now been found polyol formulations which can be foamed with all the substitute substances of the fluorochlorohydrocarbons indicated, especially with cyclopentane, mixtures of cyclopentane / i-butane, mixtures of cyclopentane / i-pentane, R 141 b, R 245 fa, and which always provide hard polyurethane foams with a similarly low thermal conductivity and a profile of outstanding properties especially suitable for the insulation of refrigerators and freezers. This is especially advantageous for the manufacturer of such formulations, since in the case of a possible change of expansion agent, eg for legal reasons, no special adaptation of the parameters of the machines and no modification of the storage and modification are required. therefore a rapid and economical expansion agent change can be made.

The object of the invention is a process for the production of closed cell polyurethane hard foams of low thermal conductivity from polyols and polyisocyanates as well as blowing agents and, where appropriate, foam coagulants, characterized in that the hard polyurethane foam is obtained by the reaction of A. a polyol component containing (1) 40-80% by weight of a poly (ethylene oxide / propylene oxide) polyether of molar mass 300-800 based on sucrose or sorbitol, (2) 3-40% by weight of a poly (ethylene oxide / propylene oxide) polyether of molar mass 300-800 based on mono, di or aromatic polyamine, (3) 3-40% by weight of a poly (ethylene oxide / propylene oxide) polyether of molar mass 200-800 based on mono, di or aliphatic polyamine, (4) 3-40% by weight of a linear poly (ethylene oxide / propylene oxide) polyether of molar mass 500-1,500, (5) optionally other compounds having at least two hydrogen atoms reactive with respect to isocyanates, of molecular weight 150 to 12,500 g / mol, (6) catalysts, (7) water, (8) expansion agents of the group of alkanes, cycloalkanes, hydrofluorochlorohydrocarbons, hydrofluorohydrocarbons and (9) optionally adjuvants and / or additives , with B. a polyisocyanate optionally modified with an NCO content of 20 to 48% by weight. The polyol formulations used according to the invention contain a compound with a molecular weight of 300 to 800 g / mol having at least two hydrogen atoms reactive towards isocyanates. They are obtained by polyaddition of alkylene oxides, such as for example ethylene oxide, propylene oxide, butylene oxide, dodecyl oxide or styrene oxide, preferably propylene oxide or ethylene oxide, to starting compounds. Starting compounds are polyvalent alcohols such as sucrose and sorbitol and mixtures of these alcohols in water, glycerin, propylene glycol, ethylene glycol or diethylene glycol. By means of these polyols to be used according to the invention, the mechanical properties of the hard polyurethane foams common in practice can be achieved. The polyol formulations used according to the invention also contain at least one compound with a molecular weight of 300 to 800 g / mol which has at least two hydrogen atoms reactive towards isocyanates which are obtained by polyaddition of alkylene oxides, for example ethylene oxide, propylene oxide, butylene oxide, dodecyl oxide or styrene oxide, preferably propylene oxide or ethylene oxide, to mono, di or aromatic polyamines such as aniline, phenylenediamines, toluenediamine (2,3-toluylenediamine, , 4-toluylenediamine, 2,4-toluylenediamine, 2,5-toluylenediamine, 2,6-toluylenediamine or mixtures of the indicated isomers), 2,2'-diaminodiphenylmethane, 2,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane or mixtures of these isomers. The polyol formulations used according to the invention also contain at least one compound of molecular weight 200 to 800 g / mol which has at least two hydrogen atoms reactive towards isocyanates which are obtained by polyaddition of alkylene oxides, such as, for example, oxide of ethylene, propylene oxide, butylene oxide, dodecyl oxide or styrene oxide, preferably propylene oxide or ethylene oxide, to mono, di or aromatic polyamines such as ethylenediamine, oligomers of ethylenediamine (for example diethylenetriamine, triethylenetriamine or pentaethylenehexamine), ethanolamine, diethanolamine, triethanolamine, N-methyl- or N-ethyl-diethanolamine, 1,3-propylenediamine, 1,3- or 1,4-butylenediamine, 1,2-, 1 , 3-, 1,4-1,5- or 1,6-hexamethylenediamine. The polyol formulations used according to the invention also contain at least one compound of molecular weight 500 to 1500 g / mol which has at least two hydrogen atoms reactive towards isocyanates. These are obtained by polyaddition of alkylene oxides, such as for example ethylene oxide, propylene oxide, butylene oxide, dodecyl oxide or styrene oxide, preferably propylene oxide or ethylene oxide, to starting compounds such as water, propylene glycol, ethylene glycol or diethylene glycol. In the process according to the invention, the usual polyurethane chemistry catalysts can be used. Examples of these catalysts are: triethyleneamine, 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' -tetramethylbutanediamine, tetramethylhexane-diamine, pentanomethyldiethylenetriane, tetramethyldiamine-ethyl ether, dimethylpiperazine, 1,2-dimethylimidazole, 1-aza-bicyclo- (3 , 3, 0) -octane, bis- (dimethylaminopropyl) -urea, N-methylmorpholine, N-ethylmorpholine, N-cyclohexylmorpholine, 2,3-dimethyl-3,4,5,6-tetrahydropyrimidine, triethanolamine, diethanolamine, triisopropanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, dimethylethanolamine, tin (II) acetate, tin (II) octoate, tin (II) ethylhexoate, tin (II) laurate, dibutyltin diacetate, dibutyltin maleate, dioctyltin diacetate, tris- (N, N-dimethyl-aminopropyl) -s-hexahydro t iaz ina, tetramethylammonium hydroxide, sodium acetate, potassium acetate, sodium hydroxide or mixtures of such catalysts. The polyol formulations used in the process according to the invention contain from 0.5 to 7.0 parts by weight, preferably from 1.0 to 3.0 parts by weight, of water per 100 parts by weight of component polyol A. According to the invention, expansion agents from the group of alkanes, in particular from 4 to 5 carbon atoms, are used, such as, for example, i-pentane, n-pentane, n-butane, isobutane, 2, 2- dimethylbutane, or cycloalkanes, especially cyclopentane or cyclohexane, or hydrofluorochlorohydrocarbons, preferably R 141b (dichlorofluoroethane) or hydrofluorohydrocarbons, preferably R 245fa as well as mixtures of the blowing agents indicated. As the isocyanate component are, for example, aromatic polyisocyanates such as those described, eg, by W. Sief in Justus Liebigs Annalen der Chemie, 562, pages 75 to 136, for example those of the formula Q (NCO) n where n 2 to 4, preferably 2, and Q are an aliphatic hydrocarbon radical of 2 to 18, preferably 6 to 10, C atoms, a cycloaliphatic hydrocarbon radical of 4 to 15, preferably 5 to 10, C atoms, an aromatic hydrocarbon residue from 8 to 15, preferably from 8 to 13, C atoms, for example polyisocyanates such as those described in DE-OS 28 32 253, pages 10 to 11. As a rule, the readily accessible technical polyisocyanates, for example 2,4- and 2,6-toluylene diisocyanate, as well as discrete mixtures of these isomers ("TDI"), polyphenyl polyethylene polyisocyanates, are generally preferred. such as those obtained by condensation of aniline-formaldehyde and subsequent phosgenation ("crude MDI") and "modified polyisocyanates", polyisocyanates having carbodiimide groups, urethane groups, allophanate groups, isocyanurate groups, urea groups or biuret groups, especially modified polyisocyanates derived from 2,4- and 2,6-toluylene diisocyanate or 4,4'- and or 2, 4 '-diphenyl ethane diisocyanate. It is also possible to use prepolymers of the indicated isocyanates and organic compounds with at least one hydroxyl group, such as, for example, polyol or polyester components having from 1 to 4 hydroxyl groups of molecular weight 60 to 1. 400. Paraffins or fatty alcohols or dimethyl polysiloxanes can be used as well as pigments or dyes, as well as stabilizers against the influences of aging and weathering, plasticizers and substances with fungistatic and bacteriostatic activity as well as fillers such as barium sulfate, diatomaceous earth, soot or creta washed. Further examples of surfactant additives and foam stabilizers which can optionally be used according to the invention, as well as cellular regulators, reaction reagents, stabilizers, flame retardant substances, dyes and fillers as well as substances with fungistatic and bacteriostatic activity as well as details on the The manner of use and action of these additives are described in "Kunsstoff-Handbuch", Volume VII, edited by Vieweg and Höchtlen, Carl Hanser Verlag, Munich 1966, eg on pages 121 to 205, and in the 2nd edition of 1983, edited by G. Oertel (Cari Hanser Verlag, Munich). In the manufacture of foams, foaming is carried out according to the invention in closed molds. For this, the reaction mixture is loaded in a mold. Metal is the material of the mold, eg aluminum, or plastic, eg epoxy resin. In the foam molds the foaming reaction mixture and forms the molding body. The mold foaming can be carried out here in such a way that the molded part has a cellular structure on its surface. However, it can also be carried out in such a way that the molded part has a compact surface and a cell core. According to the invention, in the first case it is proceeded by loading into the mold such amount of foaming reaction mixture that just fills the mold. The way of operating in the aforementioned case consists in loading more foaming reaction mixture in the mold than is necessary to fill the mold with the foam. In the latter case, therefore, "overcharging" is used, a similar procedure being known, for example, from US Pat. Nos. 3 178 490 and 3 182 104. Preferably the process according to the invention is used to fill foam hollow spaces of refrigerators and freezers with foam. Of course, foams can also be manufactured by block foaming or in accordance with the process known per se as a double conveyor belt. The hard foams which can be obtained according to the invention find application, eg, in the construction sector as well as for the insulation of remote heat transport pipes and containers. It is also an object of the invention to use hard foams manufactured according to the invention as an intermediate layer for composite elements and for the foam filling of hollow spaces in the manufacture of refrigerators. The following examples will illustrate the invention without however limiting its scope.

EXAMPLES Raw materials used: Polyol A: Poly (ethylene oxide / propylene oxide) polyether of molar mass 550 based on sucrose / glycerin Polyol B: Poly (ethylene oxide / propylene oxide) polyether of molar mass 560 based on a mixture of 2,3- and 3,4-toluylenediamine Polyol C: Molar mass polypropylene polyether 540 based on ethylenediamine Polyol D: Polypropylene oxide polyether of 900 molar mass based on propylene glycol A mixture according to the invention in the ratio 50: 25: 15: 10 (p: p: p: p) was prepared from the AB polyethers. This mixture was processed according to the specifications indicated in the following table in a HK 270 high pressure machine from Hennecke firm at 20 ° C, obtaining hard polyurethane foams. Catalyst: Dimethylcyclohexylamine (Bayer AG, Leverkusen) Silicone stabilizer: Commercial silicone stabilizer from Goldschmidt AG, Essen Cyclopentane: Signature Erdolchemie, Dormagen Iso-butane: Signature Linde AG Iso-pentane: Signature Exxon R 141b: Signature Solvay R 245 fa: Signature Allied Signal Isocyanate: "polymer MDI" _ Desmodur ^ 44V20 (Bayer AG Leverkusen) Example Example Example Example Example 1 2 3 4 5 Blend of polyol 100 100 100 100 100 Silicone stabilizer 2 2 2 2 2 Catalyst c-Pentane 14 c-Pentane / i-Butane (80:20) 14 c-Pentane / i-Pentane (80:20) 14 R 141 b 31 R 245 fa 28 Isocyanate 142 142 142 142 142 Free apparent density (kg / m3) 22.0 21.6 21.0 21.8 24 Nuclear apparent density (kg / m3) 32.6 31.5 31.0 31.4 32 Thermal conductivity according to DIN 20.6 21.4 21.6 18.5 19.9 52616-77 (mW / m.K) Compression strength according to DIN 0.15 0.15 0.15 0.13 0.16 52421-84 (MPa) Shape stability according to DIN 0 0 0 0 0 53431-77, 3h, -30 ° C Dimensional variation in% Examples 1 to 5 indicate that in the foaming of the polyol formulation according to the invention with commercial blowing agents, hard foams are always obtained with outstanding properties adapted to the practice; this with a substantially apparent nuclear density for the person skilled in the art.

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

Claims (12)

1. Having described the invention as above, the content of the following claims is claimed as property: 1. Procedure for the manufacture of hard polyurethane foams from polyols and polyisocyanates as well as blowing agents and optionally foam coadjuvants, characterized in that the hard polyurethane foam is obtained by reaction of A. a polyol component containing (1) 40-80% by weight of a poly (ethylene oxide / propylene oxide) polyether of molar mass 300-800 based on sucrose or sorbitol, (2) 3-40% by weight of a poly (ethylene oxide / propylene oxide) polyether of molar mass 300-800 based on mono, di or aromatic polyamine, (3) 3-40% by weight of a poly (ethylene oxide / propylene oxide) polyether of molar mass 200-800 based on mono, di or aliphatic polyamine, (4) 3-40% by weight of a linear poly (ethylene oxide / propylene oxide) polyether of molar mass 500-1,500, (5) optionally other compounds having at least two hydrogen atoms reactive with respect to isocyanates, of molecular weight 150 to 12,500 g / mol, (6) catalysts, (7) water, (8) expansion agents of the group of alkanes, cycloalkanes, hydrofluorochlorohydrocarbons, hydrofluorohydrocarbons and (9) optionally adjuvants and / or additives , with B. a polyisocyanate optionally modified with an NCO content of 20 to 48% by weight.
2. 2. Process for the manufacture of polyurethane hard foams according to claim 1, characterized in that the component (1) is a polyether initiated with sucrose based on 70 to 100% by weight of 1,2-propylene oxide and 0 to 30% of ethylene oxide.
3. 3. Process for the manufacture of hard polyurethane foams according to claim 1, characterized in that the component (2) is a polyether initiated with o-toluylenediamine based on 70 to 100% by weight of 1,2-propylene oxide and 0 to 30 % ethylene oxide.
4. 4. Process for the manufacture of hard polyurethane foams according to claim 1, characterized in that the component (3) is a polyether initiated with ethylenediamine based on 50 to 100% by weight of 1,2-propylene oxide and 0 to 50% of ethylene oxide.
5. 5. Process for the manufacture of hard polyurethane foams according to claim 1, characterized in that the component (1) is a polyether initiated with sorbitol based on 70 to 100% by weight of 1,2-propylene oxide and 0 to 30% ethylene oxide.
6. 6. Process for the manufacture of hard polyurethane foams according to claim 1, characterized in that the component (4) is a polyether initiated with propylene glycol based on 70 to 100% by weight of 1,2-propylene oxide and 0 to 30% of ethylene oxide.
7. 7. Process for the production of hard polyurethane foams according to one of claims 1 to 6, characterized in that the water content reaches 0.5 to 7.0 parts by weight per 100 parts by weight of polyol component A.
8. 8. Process for the manufacture of hard polyurethane foams according to one of claims 1 to 7, characterized in that cyclopentane and / or cyclohexane are used as blowing agent (8).
9. 9. Process for the manufacture of hard polyurethane foams according to one of claims 1 to 7, characterized in that mixtures of n- and / or i-pentane and / or cyclopentane and / or cyclohexane are used as blowing agent (8).
10. 10. Process for the production of hard polyurethane foams according to one of claims 1 to 7, characterized in that mixtures of cyclopentane with n-butane and / or isobutane and / or 2,2-di-ethylbutane are used as blowing agents (8). . *
11. 11. Process for the manufacture of hard polyurethane foams according to one of claims 1 to 7, characterized in that n- and / or i-pentane is used as blowing agent (8).
12. 12. Process for the manufacture of hard polyurethane foams according to one of claims 1 to 7, characterized in that as blowing agent (8) is used1, 1, 1-dichlorofluoroethane (R 141 b) or 1,1,1,3,3-pentanofluoropropane (R 245fa).