MXPA97007991A - Production of polyisocianurate foams that have a thermal conductivity reduc - Google Patents

Abstract

The present invention relates to polyisocyanurate foams having reduced thermal conductivity and are obtained by the reaction. a) organic and / or organic polyisocyanates modified with b) at least one compound of relatively high molecular weight containing at least 2 atoms of reactive hydrogen and, if desired, c) chain extenders and / or low molecular weight crosslinkers . in the presence of d) catalysts, e) if desired, blowing agents f) and, if desired, other auxiliaries and / or additives, Wherein component b) which is used consists of at least one recycled piliol which is the amount obtained by glycolysis of the polyisocyanurate foams using carrier polyols with an OH number of the further 500 mg KOH / g and a molar mass of at least 450 g / mol. The PIR foams produced by this process can be used for thermal insulation

Description

PRODUCTION OF ISOCIANURATE POLY FOAMS THAT HAVE REDUCED THERMAL CONDUCTIVITY The present invention relates to a polyisocyanurate foam having a reduced thermal conductivity and is obtained by the reaction. a) organic and / or organic polyisocyanates modified with b) at least one relatively high molecular weight compound containing at least 2 reactive hydrogen atoms and, if desired, c) molecular weight chain extenders and / or crosslinkers low. in the presence of d) catalysts, e) if desired, blowing agents f) and, if desired, other auxiliaries and / or additives. The present invention also relates to the polyisocyanurate foams produced by this process and also to their use as materials for thermal insulation. The polyisocyanurates (PIR) are produced as cell foams and cells by the polyaddition process by reacting a mixture of isocyanates, in particular those based on polymeric diphenylmethane diisocyanate, and polyols with a large excess of isocyanate in the presence of trimerization catalysts. A brief overview of the process is given, for example, in Kunststoff-Handbuch, vol. VII, "Polyurethane" the. 1966 edition, edited by Dr. R. Vieweg and Dr. A. Höchtlen, and 3rd edition 1993, edited by Becker / Braun (Carl Hanser Verlag, Munich). In the patent and the specialized literature, the processes for the chemical reuse of the PIR are mentioned on relatively rare occasions in comparison with the polyurethanes (PUR) and PUR / polyureas. In some cases, PIRs are mentioned in addition to PUR, but are not specifically described in the examples. Thus, DE-A-29 02 509 claims catalysts based on titanium and zirconium for the glycolysis of PUR and PIR, but the examples are mentioned only for PUR. US Patent A-3 708 440 describes a process for glycolysis of PIR foams. The repetition of the procedure of this patent does not give the expected homogeneous glucolysis but a solution containing a high proportion of solids that makes processing more difficult or impossible. According to our Patent Application No. 195 25 301.9 above, the glycolysis of the PIR foams gives rise to liquid products without a significant solids content if during the reaction time a carrier polyol is present in the reaction mixture. An improvement in the quality of PIR or PUR foams through the use of recycled polyols has not been described to date. The purpose of the production of the PIR is to obtain the particular properties such as high hardness, flame resistance or low thermal conductivity; It is relatively difficult to comply with the corresponding wishes of the users. An object of the present invention is to develop a simple and inexpensive process for producing PIR foams with reduced thermal conductivity. We have found that this objective is achieved through, in the production of PIR foams, the use of a recycled polyol obtained by glycolysis of the PIR foams using a carrier polyol. The present invention, therefore, provides a process for producing PIR foams with reduced thermal conductivity by reacting a) organic and / or organic polyisocyanates modified with b) at least one relatively high molecular weight compound containing at least two atoms of reactive hydrogen and, if desired c) chain extenders and / or low molecular weight crosslinkers. In the presence of d) catalysts, e) if desired, blowing agents f) and, if desired, other auxiliaries and / or additives, wherein component b) which is used consists of at least one recycled polyol which is obtained by glycolysis of the PIR foams using carrier polyols with an OH number of the more 500 mg KOH / g and a molar mass of at least 450 g / mol. The present invention further provides the PIR foams produced by this process and also provides its use as a material for thermal insulation. It is surprising and in no sense foreseeable that the use of the recycled polyols prepared from the PIR foams by glycolysis again would allow the production of higher quality PIR foams which additionally have a reduced thermal conductivity. Instead, it would be expected that the mechanical properties of the PIR foam would be worsened by the use of recycled polyols. We have found an economic process to produce PIR foams that are very useful as materials for thermal insulation. In accordance with the present invention, relatively high molecular weight compounds containing at least 2 reactive hydrogen atoms which are used are fully or partially recycled polyols, alone or in mixtures. To achieve a thermal conductivity that is as low as possible, advantageous use is made of recycled polyols in a proportion of at least 15% by weight based on the total amount of component b). For economic reasons, the amount used of the recycled polyols may be substantially greater than 15% by weight or component b) may consist entirely of recycled polyols. Of course it is also possible to use less than 15% by weight of the recycled polyols. It is surprising that the use of the recycled polyols, according to the present invention, for the production of the PIR foams without the additional use of specific additives allows to significantly reduce the thermal conductivity in a reproducible form. The recycled polyols which are used according to the present invention are prepared by glycolysis of the PIR foams using carrier polyols with an OH number of the further 500 mg KOH / g in a molar mass of at least 450 g / mol , as described in our previous Patent Application No. 195 25 301.9. for this purpose, the PIR, usually in crushed form, is reacted with a mixture of short chain compounds, containing hydroxyl and carrier polyol. According to a particularly advantageous embodiment, the process is carried out by heating the mixture of the hydroxyl-containing short chain compounds and the carrier polyol from 190 to 240 ° C, preferably from 210 to 230 ° C, before the addition of the PIR, and the temperature is reduced from 10 to 40 ° C after the addition of the PIR. At this temperature, the reaction is carried out for a period of from 1.5 to 3 hours, preferably from 2 to 2.5 hours with continuous stirring. After the reaction is complete, the reaction mixture is cooled to 50 to 150 ° C, preferably 80 to 180 ° C, and a hydroxide of an alkali metal or alkaline earth metal, preferably sodium hydroxide or potassium hydroxide. , it is added to it in an amount of plus 5% by weight, based on the total mixture. The mixture is stirred for 0.5 to 1.5 hours at this temperature. According to another advantageous embodiment, the reaction mixture is cooled from 100 to 160 ° C after the reaction is finished and a glucidyl ether is added thereto in an amount of the most 10% by weight, based on the total mixture and the mixture is stirred for 0.5 to 1.5 hours at this temperature. The glucidyl ethers which are preferably used are monofunctional glucidyl ethers, particularly preferably 2-ethylhexyl-glucidyl ether. If desired, this can be followed by the treatment of the recycled polyol, for example, by filtration. The ratio of the short chain compounds containing hydroxyls used to the carrier polyol is generally 5-20: 1 and the ratio of the mixture of the hydroxyl-containing short chain compounds and the polyol carrier to the PIR is 1-5: 1. The reaction of the PIR with the hydroxyl-containing short chain compounds makes use, in accordance with the present invention, of the carrier polyols with an OH number of the further 500 mg KOH / g and a molar mass of at least minus 450 g / mol. Suitable carrier polyols are, for example, polyols which are prepared by the addition of propylene oxide in trifunctional alcohols. The polyols used are preferably based on glycerol and / or trimethylolpropane. The short chain compounds containing hydroxyl used can, in principle, be all superior functional or difunctional alcohols. The difunctional alcohols are particularly advantageous for the process of the present invention. The alcohols can be used individually or as a mixture.

Preference is given to the use of ethylene glycol and its higher homologs, in particular diethylene glycol and propylene glycol and their higher homologs, in particular dipropylene glycol, individually or in mixtures with each other. The process can be carried out in the presence of the customary polyurethane catalysts. For this purpose, the use of organic tin and titanium compounds is preferred. As a PIR, it is possible to use waste, for example from the production of PIR block foams, PIR moldings or interleaved elements. In order to produce the PIR foams by the process of the present invention, use is made, in addition to the recycled polyols described in the foregoing, of the forming components known per se on which the following details are given: a) the organic polyisocyanates and / or suitable modified organics (a) are the polyfunctional aliphatic, cycloaliphatic, araliphatic and preferably aromatic isocyanates known per se. Specific examples are alkylene diisocyanates having from 4 to 12 carbon atoms in the alkylene radical, for example, 1, 12-dodecane diisocyanate, 1,4-di-2-ethylhetramethylene diisocyanate, 1,5-diisocyanate 2 -methylpenethylene, 1,4-ethylene tetraisocyanate and preferably 1,6-hexane-ethylene diisocyanate; cycloaliphatic diisocyanates such as 1,3- and 1,4-cyclohexane diisocyanate and also any of the mixtures of these isomers, l-isocyanato-3,5-trimethyl-5-isocyanate methylcyclohexane (isophorone diisocyanate), 2,4- and 2, 6-hexahydrotolylene diisocyanate and also the corresponding isomeric mixtures, 4,4'-, 2,2'- and 2,4'-dicyclohexyl ethanocyanate and also the corresponding isomeric mixtures and preferably the aromatic diisocyanates and polyisocyanates such as 2,4- and 2,6-toluene diisocyanate and the corresponding isomeric mixtures, 4,4'-, 2, 4'- and 2,2'-diphenylmethane diisocyanate and corresponding isomer mixtures, mixtures of 4,4 'and 2,4'-diphenylmethane diisocyanates, polyphenylenepolymethylene polyisocyanates, mixtures of 4,4'-, 2,4 '- and 2,2'-diphenylmethane diisocyanates and polyphenylenepolyethylene polyisocyanates (MDI raw material) and mixtures of raw material MDI and toluene diisocyanates. The organic diisocyanates and polyisocyanates can be used individually or in the form of mixtures. Also, modified polyfunctional isocyanates, ie, products obtained by chemical reaction of diisocyanates and / or organic polyisocyanates, are often used. Examples which may be mentioned are diisocyanates and / or polyisocyanates containing ester groups, urea, biuret, halofanate, carbodiimide, isocyanurate, uretdione and / or urethane. Specific examples are: organic urethane groups preferably containing aromatic polyisocyanates, with NCO content from 33.6 to 15% by weight, preferably from 31 to 21% by weight based on total weight and are prepared, for example, by reaction with low molecular weight diols, triols, dialkylene glycols, trialkylene glycols or polyoxyalkylene glycols having molecular weights of up to 6000, in particular up to 1500, 4, 4 '- modified diphenylmethane diisocyanate, mixtures of 4,4' and 2, 4'-modified diphenylmethane diisocyanate or MDI modified raw material or 2,4- or 2,6-toluene diisocyanate with examples of dialkylene or polyoxyalkylene glycols which can be used individually or as mixtures being: diethylene glycol, dipropylene glycol, polyoxyethylene, polyoxypropylene and polyoxypropylene-polyexyethylene glycols, triols and / or tetraols. Also suitable are prepolymers containing NCO groups, with NCO content from 25 to 3.5% by weight, preferably from 21 to 14% by weight based on total weight, and are prepared from polyester and / or preferably polyether polyols, as described below, and 4,4'-diphenylmethane diisocyanate, mixtures of, 4'- and 4, 4 '- diphenylmethane diisocyanate, 2,4- and / or 2,6-toluene diisocyanates or raw material MDI. Other modified polyisocyanates which have been found useful are liquid polyisocyanates containing carbodiimide groups and / or isocyanurate rings and having NCO content from 33.6 to 15% by weight, preferably from 31 to 21% by weight based on total weight , for example, those based on 4,4'-, 2,4'- and / or 2, 2'-diphenylmethane diisocyanate and / or 2,4- and / or 2,6-toluene diisocyanate. If desired, the modified polyisocyanates can be mixed with one another or with unmodified organic polyisocyanates such as 2,4'- and / or 4,4'-diphenylmethane diisocyanate, MDI raw material, 2,4- and / or 2,6 - toluene diisocyanate. Organic polyisocyanates which have been found to be particularly useful and, therefore, are preferably used, are the following aromatic polyisocyanates: MDI raw material, mixtures of toluene diisocyanate and MDI raw material or mixtures of modified organic polyisocyanates containing urethane groups and an NCO content from 33.6 to 15% by weight, in particular those based on toluene diisocyanates, 4,4 '- diphenylmethane diisocyanate, isomeric mixtures of diphenylmethane diisocyanate or MDI raw material and in particular MDI raw material with a content of isomer diphenylmethane diisocyanate from 30 to 80% by weight, preferably from 30 to 55% by weight. As relatively high molecular weight compounds containing at least two reactive hydrogen atoms, use is made, according to the present invention, of the recycled polyols described above. In addition to these, concomitant use can be made of another relatively high molecular weight compound containing at least two reactive hydrogen atoms b). Suitable compounds for this purpose are advantageously those having functionality from 2 to 8, preferably from 2 to 6 and a molecular weight from 400 to 8000, preferably from 1200 to 6000. Examples of the compounds that have been found useful are polyether polyamines and / or preferably polyols selected from the group consisting of polyether polyols, polyester polyols, polythioethers, polyols, polyester amides, hydroxyl-containing polyacetals and aliphatic polycarbonates containing hydroxyls or mixtures of at least two of the polyols mentioned. Preferably, polyester polyols and / or polyether polyols are used. The hydroxyl number of the polyhydroxyl compounds is generally from 150 to 850 and preferably from 200 to 600. Suitable polyester polyols can be prepared, for example, from organic dicarboxylic acids having from 2 to 12 carbon atoms. carbon, preferably the aliphatic dicarboxylic acids having from 4 to 6 carbon atoms and the polyhydric alcohols, preferably the diols having from 2 to 12 carbon atoms, preferably from 2 to 6 carbon atoms. Examples of suitable dicarboxylic acids are: succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, decandicarboxylic acid, maleic acid, fumaric acid, phthalic acid, isophthalic acid and terephthalic acid. The dicarboxylic acids can be used individually or in mixtures with each other. Instead of the free dicarboxylic acids, it is also possible to use the corresponding dicarboxylic acid derivatives as dicarboxylic esters of the alcohols having from 1 to 4 carbon atoms or dicarboxylic anhydrides. Preference is given to the use of mixtures of dicarboxylic acids of succinic, glutaric and adipic acid in weight ratios of, for example, 20-35: 35-50: 20-32, and in particular of adipic acid. Examples of the dihydric and polyhydric alcohols, in particular the diols, are: ethanediol, diethylene glycol 1,2- or 1,3-propanediol, dipropylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,10-decanodiol, glycerol and trimethylolpropane. Preference is given to the use of ethanediol, diethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol or mixtures of at least 2 of the diols mentioned, in particular mixtures of 1,4-butanediol, 1 , 5-pentanediol and 1,6-hexanediol. It is also possible to use polyether polyols derived from lactones, for example, e-caprolactone, hydrocarboxylic acids, for example,? -hydroxycaproic acid. To prepare the polyester polyols, the polycarboxylic acids and / or polycarboxylic acids and the polyhydric alcohols can be polycondensed in the absence of catalysts or preferably in the presence of esterification catalysts, advantageously in an atmosphere of inert gas such as nitrogen, carbon dioxide, helium, argon, etc., melting from 150 to 250 ° C, preferably from 180 to 220 ° C, under atmospheric pressure or under reduced pressure for the desired acid number which is advantageously less than 10, preferably less than 2. According to a preferred embodiment, the esterification mixture is polycondensed at the aforementioned temperatures for an acid number from 80 to 30, preferably from 40 to 30, under atmospheric pressure and subsequently at a pressure lower than 500 mbar, preferably from 50 to 150 mbar. Suitable catalysts for esterification are, for example, catalysts of iron, cadmium, cobalt, lead, zinc, antimony, magnesium, titanium and tin in the form of metals, metal oxides or metal salts. However, the polycondensation can also be carried out in the liquid phase in the presence of diluents and / or separating agents such as benzene, toluene, xylene or chlorobenzene to azeotropically distill the condensation water. To prepare the polyol polyesters, the organic polycarboxylic acids and / or polyhydric alcohols and polyhydric alcohols are advantageously polycondensed in a molar ratio of 1: 1-1.8, preferably 1: 1.05-1.2.

The polyester polyols which are preferably obtained have a functionality from 2 to 4, in particular from 2 to 3, and a molecular weight from 480 to 3000, preferably from 1200 to 3000 and in particular from 1800 to 2500. However, the polyols which are used are particularly preferably polyether polyols which are prepared by known methods, for example, from one or more alkylene oxides, having 2 to 4 carbon atoms in the alkylene radical, by anionic polymerization using the alkali metal hydroxides as sodium or potassium hydroxide or the alkali metal alkoxides, such as sodium methoxide, sodium or potassium ethoxide or potassium isopropoxide as catalysts with the addition of at least one cleaning molecule containing 2 to 8, preferably 2 to 6 atoms of reactive hydrogen in bound form or by cationic polymerization using Lewis acids such as antimony pentachloride, fluoroe boron terato, etc., or bleaching earths as catalysts. Suitable alkylene oxides are, for example, tetrahydrofuran, 1,3-propylene oxide, 1,2- or 2,3-butylene oxide styrene oxide and preferably ethylene oxide and 1,2-propylene oxide. . The alkylene oxides can be used individually or alternatively in succession or as mixtures. Examples of suitable initiator molecules are: water, organic dicarboxylic acids such as succinic acid, adipic acid, phthalic acid and terephthalic acid, aliphatic and aromatic diamines, non-alkylated, N-monoalkylated, N, N- and N, N '- dialkylated having 1 to 4 carbon atoms in the alkyl radical, for example, monoalkylated and dialkylated ethylenediamine, diethylenetriamine, triethylenetetramine, 1,3-propylenediamine, 1,3- or 1,4-butylenediamine, 1,2-, 1,3-, 1,4-, 1,5- and 1,6-hexamethylenediamine, phenylenediamines, 1,3-, 2,4- and 2,6-tolylenediamine and 4,4'-, 2,4'- and 2, 2'-diaminodiphenylmethane. Other suitable starter molecules are: alkanolamines such as ethanolamine, N-methylethanolamine and N-ethylethanolamine, dialkanolamines, such as diethanolamine, N-methyldiethanolamine and N-ethyldiethanolamine and trialkanolamines such as triethanolamine and ammonia. Preference is given to the use of polyhydric alcohols, in particular dihydric and / or trihydric alcohols such as ethanediol, 1,2- and 1,3-propanediol, diethylene glycol, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, glycerol, trimethylolpropane , pentaerythritol, sorbitol and sucrose. The polyether polyols, preferably polyoxypropylene and polyoxypropylene polyoxyethylene polyols, have a functionality preferably from 2 to 6 and in particular from 2 to 4 and have molecular weights from 400 to 8000, preferably from 1200 to 6000 and in particular from 1800 to 4000, and suitable polyoxytetramethylene glycols have molecular weights up to about 3500. Other suitable polyether polyols are the polyether polyols modified in the polymer, preferably the graft polyether polyols, in particular those based on styrene and / or acrylonitrile which are prepared by polymerization in situ of acrylonitrile, styrene or preferred mixtures of styrene and acrylonitrile, for example, in a weight ratio from 90:10 to 10:90, preferably from 70:30 to 30:70, advantageously in the aforementioned polyether polyols using methods similar to those described in German Patents 11 11 394, 12 22 669 (US 3 304 273, 3 383 351, 3 523 093), 11 52 536 (GB 10 40 452) and (GB 987 618), and also the dispersions of polyether polyols containing as dispersed phase, in general, in an amount from 1 to 50% by weight, preferably from 2 to 25% by weight: for example polyureas, polyhydrazides, polyurethanes containing linked ter-amines and / or melamine groups and are described, for example, in EP-B-011 752 (US 4 304 708), US 4 374 209 and DE-A-32 31 497. Like polyester polyols, polyether polyols can be used individually or in mixtures. These can also be mixed with polyether polyols grafting or polyester polyols, as well as with the polyester amides containing hydroxyls, polyacetals, polycarbonates and / or polyether polyamines. Suitable polyacetals containing hydroxyl are, for example, compounds that can be prepared from glycols such as diethylene glycol, triethylene glycol, 4,4'-dihydroxyethoxydiphenyldimethyl methane or hexanediol and formaldehyde. Suitable polyacetals can be prepared by polymerization of the cyclic acetals. Polycarbonates containing suitable hydroxyls are those of the type known per se which can be prepared, for example, by the reaction of diols such as 1,3-propanediol, 1,4-butanediol and / or 1,6-hexanediol, diethylene glycol, triethylene glycol or tetraethylene glycol with diaryl carbonates, for example, diphenyl carbonate or phosgene.

Polyester amines include, for example, predominantly linear condensates obtained from polybasic, saturated and / or unsaturated carboxylic acids or their anhydrides and saturated and / or unsaturated polyfunctional aminoalcohols or mixtures of alcohols polyfunctional and aminoalcohols and / or polyamines. Suitable polyether polyamines can be prepared from the aforementioned polyether polyols by known methods. Examples which may be mentioned are the cyanoalkylation of polyoxyalkylene glycols and the subsequent hydrogenation of the formed nitrile (US Pat. No. 3 267 050) or the partial or complete amination of the polyoxyalkylene polyols using amines or ammonia in the presence of hydrogen and catalysts (DE 12 15 373 ). PIR foams can be produced with or without the concomitant use of chain extenders and / or crosslinkers (c). However, the addition of chain extenders, crosslinkers or, if desired, mixtures of these can prove to be advantageous for modifying the chemical properties, for example hardness. The chain extenders and / or crosslinkers used are diols and / or triols having molecular weights of less than 400, preferably from 60 to 300. Examples of suitable chain extenders / crosslinkers are aliphatic, cycloaliphatic and / or diols. araliphatics having from 2 to 14, preferably from 4 to 10 carbon atoms, for example, ethylene glycol, 1,3-propanediol, 1, 10-decanediol, o-, m-, p-dihydroxycyclohexane, diethylene glycol, dipropylene glycol and preferably 1,4-butanediol, 1,6-hexanediol and bis (2-hydroxyethyl) hydroxyquinone, triols such as 1,2,4- or 1,3,5-trihydroxycyclohexane, glycerol and trimethylol propane and polyalkylene oxides containing hydroxyls , of low molecular weight, based on ethylene oxide and / or 1,2-propylene oxide and the aforementioned diols and / or triols as starter molecules. If the chain extenders, crosslinkers or mixtures thereof are used to produce the PIR foams, these are advantageously used in an amount of 2 to 20% by weight, preferably 2 to 8% by weight based on the weight of the compound polyol (b). The catalysts (d) used to produce the PIR foams are, in particular, compounds that strongly accelerate the reaction of the compounds containing reactive hydrogen atoms, in particular hydroxyl groups, of component (b) and, if used (c) , with the organic polyisocyanates, modified or unmodified (a). Suitable catalysts are organic metal compounds, preferably organic tin compounds such as tin (II) salts of organic carboxylic acids, for example tin (II) acetate, tin (II) octoate, tin (II) ethylhexanoate and laurate of tin (II) and the dialkyltin (IV) salts of the organic carboxylic acids, for example, dibutyltin diacetate, dibutyltin dilaurate, dibutyltin maleate and dioctyltin diacetate. The organic metal compounds are used alone or preferably in combination with strongly basic amines. Examples which may be mentioned are amines such as 1,3-dimethyl-3,4,5,6-tetrahydropyrimidine, tertiary amines such as triethylamine, tributylamine, dimethylbenzylamine, N-methylmorpholine, N-ethylmorpholine, N-cyclohexylmorpholine, N , N, N'N'-tetramethylethylenediamine, N, N, N ', N' -tetramethylbutanediamine, N, N, N ', N' -tetramethylhexane, 1,6-diamine, pentamethyldiethylenetriamine, bis (di-ethylaminoethyl) ether, bis (di-ethylaminopropyl) urea, dimethylpiperazine, 1,2-di-ethylimidazole, l-azabicyclo [3.3.0] octane and preferably 1,4-diazabicyclo [2.2.2] octane and alkanolamine compounds such as triethanolamine, triisopropanolamine N-methyldiethanolamine and N -ethyldiethanolamine and dimethylethanola ina. Other suitable catalysts are: tris (dialkylalkalkyl) -s-hexahydrotriazine, in particular, tris (N, N-dimethylaminopropyl) -s-hexahydrotriazine, tetraalkylammonium hydroxide as tetramethylammonium hydroxide, alkali metal hydroxides such as sodium hydroxide and alkali metal alkoxides such as sodium methoxide and potassium isopropoxide and also alkali metal salts of long chain fatty acids having from 10 to 20 carbon atoms and possibly side OH groups. Preference is given to the use of 0.001 to 5% by weight, in particular, from 0.05 to 2% by weight of the catalyst or combination of catalysts based on the weight of component (b). The blowing agents (e) which can be used, if desired, to produce the PIR foams, preferably include water which reacts with the isocyanate groups to form carbon dioxide. The amounts of water which are advantageously used are from 0.1 to 8 parts by weight, preferably from 1.5 to 5.0 parts by weight and in particular from 2.5 to 3.5 parts by weight based on 100 parts by weight of the polyoxyalkylene polyols.

In mixing with the water it is also possible to use the blowing agents that act physically. Suitable physically active blowing agents are liquids which are inert towards the organic polyisocyanates, modified or unmodified (c) and having boiling points below 100 ° C, preferably below 50 ° C, in particular from minus 50 ° C to 30 ° C, at atmospheric pressure, so that they vaporize under the action of the exothermic polyaddition reaction. Examples of these preferred liquids are alkanes such as heptane, hexane, n- and iso-pentane, preferably the industrial mixtures of n- and iso-pentanes, n- and iso-butanes and propane, cycloalkanes such as cyclopentane and / or cyclohexane, ethers such as furan, di ethyl ether and diethylether, ketones such as ketones, and ethylethyl ketone, alkyl carboxylates such as methyl formate, dimethyl oxalate and ethyl acetate and halogenated hydrocarbons such as methylene chloride, dichloromonofluoromethane, difluoromethane, trifluoromethane and di-fluoroethane, tetrafluoroethane , chlorodifluoroethanes, 1,1-dichloro-2,2,2-trifluoroethane, 2,2-dichloro-2-fluoroethane and heptafluoropropane. Mixtures of these liquids with low boiling point and / or other substituted or unsubstituted hydrocarbons can also be used. Also suitable are organic carboxylic acids such as formic acid, acetic acid, oxalic acid, ricinoleic acid and carboxyl-containing compounds. Preference is given to the use of water, mixtures of chlorodifluoromethane, chlorodifluoroethanes, dichlorofluoroethanes, pentane, cyclohexane and mixtures of at least two of these, for example, mixtures of water and cyclohexane, mixtures of chlorodifluoromethane and 1, -chloro-2, 2 -difluoroethane and, if desired, water. The amount of the physically active blowing agents required in addition to the water can be determined in a simple manner as a function of the desired density of the foam and is from 0 to 25 parts by weight, preferably from 0 to 15 parts by weight, per one hundred parts by weight of the polyoxyalkylene polyols. It may be advantageous to mix the modified or unmodified polyisocyanates (c) with the physically active, inert blowing agent and thereby reduce the viscosity. If desired, auxiliaries and / or additives (f) customary in polyurethane chemistry can also be incorporated into the reaction mixture to produce the PIR foams. Examples that may be mentioned are the stabilizers of foams, fillers, dyes, pigments, flame retardants, hydrolysis inhibitors, fungistatic and bacteriostatic substances. For the purpose of the present invention, the loading materials, in particular, the reinforcing fillers, are the customary organic and inorganic fillers, the reinforcing agents, compensating agents, agents for improving the abrasion in paints, coating compositions, etc. ., known per se. Specific examples are: inorganic fillers such as siliceous minerals, for example, lamellar silicates such as antigorite, serpentine, furnace, amphibole, fibrous serpentine, talc; metal oxide such as kaolin, aluminum oxides, titanium oxides and iron oxides, metal salts such as calcium carbonate, barite and inorganic pigments such as cadmium sulfide, zinc sulphide and also glass, etc. Preference is given to the use of kaolin (Chinese clay), aluminum silicate and coprecipitates of barium sulfate and aluminum silicate and also natural and synthetic fibrous minerals such as wollastonite, metal fibers and in particular glass fibers of various lengths which, if desired, may be coated with a sizing Examples of suitable organic fillers are: carbon, melamine, rosin, cyclopentadienyl resins, and graft polymers and also include cellulose fibers, polyamide, polyacrylonitrile, polyurethane and polyester fibers based on aromatic and / or aliphatic dicarboxylic esters and , in particular, carbon fibers.

The inorganic and organic fillers can be used individually or as mixtures and can advantageously be incorporated into the reaction mixture in amounts of 0.5 to 50% by weight, preferably from 1 to 40% by weight, based on the weight of the components (a) to (c), although the content of the woven or rugs, woven and non-woven fabrics made of natural and synthetic fibers can reach values up to 80% by weight. Suitable flame retardants are, for example, tricrecyl phosphate, tris (2-chloroethyl) phosphate, tris (2-chloropropyl) phosphate, tris (1,3-dichloropropyl) phosphate, tris (2,3-dibromopropyl) phosphate. ), tetrakis (2-chloroethyl) ethylene diphosphate, dimethyl methanphosphonate, diethyl diethanolaminomethyl phosphonate and also commercial halogen-containing flame retardant polyols. Apart from the above-mentioned halogen-substituted phosphonates, it is also possible to use inorganic or organic flame retardants such as red phosphorus, hydrous aluminum oxide, antimony trioxide, arsenic oxide, ammonium polyphosphate and calcium sulfate, expanded graphite or cyanuric acid derivatives as melamine, or mixtures of at least two flame retardants such as ammonium and melamine polyphosphates, and also, if desired, corn starch or ammonium polyphosphate, melamine and expanded graphite and / or aromatic or aliphatic polyesters to make the flame retardant products of the polyisocyanate polyaddition. In general, it has been found advantageous to use from 5 to 50 parts by weight, preferably from 5 to 25 parts by weight of the aforementioned flame retardants per 100 parts by weight of component (b). More details in connection with other customary auxiliaries and additives mentioned above can be found in the specialized literature, for example, the monograph by J.H. Saunders and K.C. Frish "High Polymers" Volume XVI, Polyurethanes, part 1 and 2, Interscience Publishers 1962 and 1964, or The Kunststoff-Handbuch, Polyurethane, vol. VII, Hanse-Verlag, Munich, Vienna, Ist, 2a. and 3a. editions, 1969, 1983 and 1993. To produce PIR foams, organic polyisocyanates (a), relatively high molecular weight compounds containing at least 2 reactive hydrogen atoms (b) and, if desired, extenders chain and / or crosslinkers (c) are reacted in amounts such that the equivalence ratio of the NCO groups of the polyisocyanates (a) to the sum of the reactive hydrogen atoms of the components (b) and, if used , (c) is 0.7-1.5: 1. PIR foams are advantageously produced by a one-step method or the prepolymer method by means of the high pressure or low pressure technique in open or closed molds, for example metal molds the foam is formed in free form (formation of foam in situ). It has been found particularly advantageous to employ the two-component method and to combine the formative components (b), (d), and if desired (c), (e) and (f) as the component (A) and to use the organic polyisocyanates and / or modified organics (a) or mixtures of the polyisocyanates and, if desired, blowing agents (d) such as component (B). The initial components are mixed at 15 to 90 ° C, preferably at 20 to 60 ° C and in particular at 20 to 35 ° C, and, if molded foams are to be produced, it is introduced into the open or closed mold, the The temperature of the mold is advantageously from 20 to 110 ° C, preferably from 30 to 60 ° C and in particular from 45 to 50 ° C. In the case of free formation of the foam, the blocks are produced by subsequent machining, for example by cutting, for example, into boards. In the same way, it is possible to establish the reactivity of the polyurethane systems of the present invention so that they can be processed by the known processes of foam spraying (spray foam process), thus making vertical surfaces possible, horizontal and hanging covered (from the top). The PIR foams produced by the process of the present invention have a density from 25 to 50 kg / m3, preferably from 30 to 40 kg / m3. These have a uniform foam structure, of fine cells. The PIR foams of the present invention have a thermal conductivity of 17 to 22, preferably 19 to 21 raW / (m-K). The PIR foams produced by the process of the present invention are suitable for all applications customary for PIR foams. In particular, thermal insulation in pipe systems is used as boards for thermal insulation, preferably in the construction industry and civil engineering, as well as the thermal insulation of components, groups of components and structural elements in construction. of appliances and machinery.

The invention is illustrated by the following examples.

Example 1 (comparative example): Component A consists of a mixture of: 63.46 parts by weight of polyesterol derived from phthalic anhydride, diethylene glycol and polyethylene glycol and with an OHN of 240 mg KOH / g, 1.87 parts by weight of the stabilizer BP SR 321 of Union Carbide, 0.56 parts by weight of a catalyst I (potassium acetate / ethylene glycol), 0.99 parts by weight of a catalyst II (trisdi ethylaminopropyl-hexahydrotriazine / triethylamine) and 33.19 parts by weight of R 141b, were reacted with 174 parts by weight of component B (diisocyanate / diphenylmethane polyisocyanate). This gave a PIR foam with the following properties: Density [kg / m3] 33.2 Dimensional stability at -5 ° C, 24 h [%] 94.2 Compressive strength [kPa] 346 Thermal conductivity [mW / m »K] 24.4 Flame height [cm] 9 Example 2 (preparation of the recycled polyol) 700 g of PIR foam (NCO index: 500) introduced at 215-225 ° C in a mixture of 1000 g of diethylene glycol (DEG), 680 g of polyetherpolyol Lupranol® 3300 from BASF Aktiengesellschaft (1 mole of glycerol and 8.5 mole of propylene oxide) and 0.3% by weight of titanium tetrabutoxide (based on DEG and PIR foam) in such a way that the contents of the flask could shake. After finishing addition, the temperature was reduced to 190-200 ° C and maintained for 2 hours with stirring. The mixture was then cooled to 150 ° C and 90 g of 2-ethylhexylglycidyl ether were added and the mixture was stirred another hour at this temperature. This gave a dark brown, homogeneous liquid with the following properties: OHN 520 mg KOH / g Acid number 0.6 mg KOH / g Viscosity 3500 mPa.s MDA content < 0.1% Example 3 Component A consisting of a mixture of: 12.70 parts by weight of recycled polyol prepared as described in Example 2 by glycolysis of waste PIR foam using carrier polyetherols and with a OHN of 520 mg KOH / g, 50.77 parts by weight of a polyesterol derived from phthalic anhydride, diethylene glycol and polyethylene glycol and with an OHN of 240 mg KOH / g, 1.87 parts by weight of the stabilizer BP SR 321 of Union Carbide, 0.56 parts by weight of a catalyst I as described in Example 1, 0.99 parts by weight of a catalyst II, as described in Example 1 and 33.12 parts by weight of R 141b, were reacted with 174 parts by weight of the component B (diisocyanate / diphenyl methane polyisocyanate). This gave a PIR foam with the following properties: Density [kg / m3] 32.4 Dimensional stability at -5 ° C, 24 h [%] 91.6 Compressive strength [kPa] 338 Thermal conductivity [mW / m »K] 19.6 Height of the flame [cm] 9

Claims (5)

1. A process for producing polyisocyanurate foams with reduced thermal conductivity, by reacting: a) organic and / or organic polyisocyanates modified with b) at least one relatively high molecular weight compound containing at least 2 reactive hydrogen atoms and, if desired, c) chain extenders and / or low molecular weight crosslinkers. in the presence of d) catalysts, e) if desired, blowing agents f) and, if desired, other auxiliaries and / or additives, wherein component b) which is used consists of at least one recycled polyol which is The amount obtained by glycolysis of the polyisocyanurate foams using the carrier polyols with an OH number of the further 500 mg KOH / g and a molar mass of at least 450 g / mol.

2. The process according to claim 1, wherein the recycled polyol is used in a proportion of at least 15% by weight based on the total amount of component b).

3. The process according to claim 1, wherein the carrier polyols based on glycerol and / or trimethylolpropane are used in the preparation of the recycled polyols.

4. The process, according to claim 1, wherein the recycled polyol that is used is low in amines.

5. A polyisocyanurate foam with a reduced thermal conductivity and obtainable by the reaction. a) organic and / or organic polyisocyanates modified with b) at least one relatively high molecular weight compound containing at least 2 reactive hydrogen atoms and, if desired, c) molecular weight chain extenders and / or crosslinkers low. in the presence of d) catalysts, e) if desired, blowing agents f) and, if desired, other auxiliaries and / or additives, wherein the component b) used consists of at least one recycled polyol which is obtained by glycolysis of the polyisocyanurate foams using carrier polyols with an OH number of the most 500 mg KOH / g and a molar mass of at least 450 g / mol. The polyisocyanurate foam according to claim 5, wherein the recycled polyol is used in a proportion of at least 15% by weight, based on the total amount of component b). The polyisocyanurate foam, according to claim 5, having a thermal conductivity of at least 22 mW / (m-K) with a foam density of 25 to 50 kg / m3. The use of a polyisocyanurate foam, according to claim 5, for thermal insulation.