CA2216772A1 - Production of polyisocyanurate foams having a reduced thermal conductivity - Google Patents

Abstract

Polyisocyanurate foams having a reduced thermal conductivity are produced by reacting a) organic and/or modified organic polyisocyanates with b) at least one relatively high molecular weight compound containing at least two reactive hydrogen atoms and, if desired c) low molecular weight chain extenders and/or crosslinkers in the presence of d) catalysts, e) if desired, blowing agents f) and, if desired, further auxiliaries and/or additives, wherein the component b) used comprises at least one recycled polyol which is obtained by glycolysis of polyisocyanurate foams using carrier polyols having an OH number of at most 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

CA 022l6772 lss7-l0-l7 BASF ~ktienge~ell~cha~t 960800 O.Z. 0050/47417 Production of polyisocyanurate foams having a reduced thermal ~ conductivity The present invention relates to a polyisocyanurate foam having a reduced thermal conductivity and obtainable by reacting a) organic and/or modified organic polyisocyanates with b) at least one relatively high molecular weight compound con-taining at least two reactive hydrogen atoms and, if desired c) low molecular weight chain extenders and/or crosslinkers in the presence of d) catalysts, e) if desired, blowing agents f) and, if desired, further auxiliaries and/or additives.

The present invention further relates to the polyisocyanurate foams produced by this process and also their use as thermal insulation materials.

30 Polyisocyanurates (PIRs) are produced as cellular and cell-free foams by the polyaddition process by reacting a mixture of isocyanates, in particular ones based on polymeric diphenylmethane diisocyanate, and polyols with a large excess of isocyanate in the presence of trimerization catalysts. A summary 35 overview of the process is given, for example, in the Kunststoff-Handbuch, Volume VII, "Polyurethane~, 1st edition 1966, edited by Dr R. Vieweg and Dr A. Hochtlen, and 3rd edition 1993, edited by secker/Braun (Carl Hanser Verlag, Munich).

40 In the patent and specialist literature, processes for the chemical recycling of PIR are mentioned relatively rarely compared with polyurethanes (PURs) and PUR/polyureas. In some cases, PIR is mentioned in addition to PUR, but not described specifically in the examples. Thus, DE-A-29 02 509 claims 45 catalysts based on titanium and zirconium for the glycolysis of PUR and PIR, but examples are mentioned only for PUR. US-A-3 708 440 describes a process for the glycolysis of PIR foams.

CA 022l6772 l997-lO-l7 BASF Aktieng~Qll~chaft 960800 O.Z. 0050/47417 Repeating the procedure of this patent gives not the expected homogeneous glycolysate but a solution containing a high propoEtion of solids which makes further processing difficult or impossible.

According to our earlier Patent Application No. 195 25 301.9, the glycolysis of PIR foams leads to liquid products without a significant solids content if a carrier polyol is present in the reaction mixture during the reaction time.

An improvement in the quality o~ the PIR or PUR foams by use of recycled polyols has not been described hitherto.

15 The purpose of PIR production is to obtain particular properties such as high hardness, flame resistance or low thermal conductivity; it is relatively difficult to meet the corresponding wishes of the users.

20 It is an object of the present invention to develop a simple and inexpensive process for producing PIR foams having a reduced thermal conductivity.

We have found that this object is achieved by, in the production 25 of the PIR foams, making use of a recycled polyol which is obtained by glycolysis o~ PIR foams using a carrier polyol.

The present invention accordingly provides ~or a process ~or 30 producing PIR foams having a reduced thermal conductivity by reacting a) organic and/or modified organic polyisocyanates with 35 b) at least one relatively high molecular weight compound con-taining at least two reactive hydrogen atoms and, if desired c) low molecular weight chain extenders and/or crosslinkers in the presence of d) catalysts, 45 e) if desired, blowing agents ~ CA 022l6772 lss7-l0-l7 BASF Alctieng~ellscha~t 960800 O.Z. 0050/47417 f ) and, if desired, further auxiliaries and/or additives, wherein the compo~ent b) used comprises at least one recycled polyol which is obtained by glycolysis of PIR foams using carrier 5 polyols having an OH number of at most 500 mg KOH/g and a molar mass of at least 450 g/mol.

The present invention further provides the PIR foams produced by 10 this process and also provides for their use as thermal insulatlon material.

It is surprising and was in no way foreseeable that the use of recycled polyols prepared from PIR foams by glycolysis would 15 again enable the production of high-quality PIR foams which additionally have a reduced thermal conductivity. Rather, it would have been expected that the mechanical properties of the PIR foam would be worsened by the use of recycled polyols.

20 We have thus found an economical process for producing PIR foams which are very useful as thermal insulation materials.

According to the present invention, the relatively high molecular weight compounds cont~; n; ng at least two reactive hydrogen atoms 25 which are used are completely or partially recycled polyols alone or in admixture with one another. For achieving a thermal conductivity which is as low as possible, use is advantageously made of recycled polyols in a proportion of at least 15% by weight, based on the total amount of the component b). For 30 economic reasons, the amount of recycled polyols used can be substantially above 15% by weight or the component b) can consist entirely of recycled polyol. It is naturally also possible to use less than 15% by weight of recycled polyols.

It is surprising that the use of recycled polyols according to the present invention in the production of the PIR foams without additional use of specific additives enables the therm~l conductivity to be lowered significantly in a reproducible 4 manner.
o The recycled polyols to be used according to the present invention are prepared by glycolysis of PIR foams using carrier polyols having an OH number of at most 500 mg KOH/g and a molar ~ 45 mass of at least 450 g/mol, as described in our earlier Patent Application No. 195 25 301.9.

CA 022l6772 l997-l0-l7 BASF Aktisng~sell~chart Y~U~UU O.Z. 0050/47417 For this purpose, the PIR, usually in comminuted form, is reacted with a mixture of added short-chain, hydroxyl-containing compounds and carrier polyol.

5 According to a particularly advantageous embodiment, the process is carried out by heating the mixture of short-chain, hydroxyl-containing compounds and carrier polyol to from 190 to 240~C, preferably from 210 to 230~C, before addition of the PIR
and lowering the temperature by from 10 to 40~C after addition of 10 the PIR. At this temperature, the reaction is carried out over a period of from 1.5 to 3 hours, preferably from 2 to 2.5 hours, while stirring continuously. After the reaction is complete, the reaction mixture is cooled to from 50 to 150~C, preferably to from 80 to 130~C, and a hydroxide of an alkali metal or alkaline earth 15 metal, preferably sodium hydroxide or potassium hydroxide, is added thereto in an amount of at most 5% by weight, based on the total mixture. The mixture is stirred for from 0.5 to 1.5 hours at this temperature.

According to a further advantageous embodiment, the reaction mixture is cooled to from 100 to 160~C after the reaction is complete and a glycidyl ether is added thereto in an amount of at most 10% by weight, based on the total mixture, and the mixture 25 is stirred for from 0.5 to 1.5 hours at this temperature.

Glycidyl ethers employed here are pre~erably mono~unctional glycidyl ethers, particularly preferably 2-ethylhexyl glycidyl ether.

If desired, this can be followed by work-up of the recycled polyol, for example by filtration.

The ratio of the short-chain, hydroxyl-containing compounds used 35 to the carrier polyol is here generally 5-20:1 and the ratio o~
the mixture of short-chain, hydroxyl-containing compounds and carrier polyol to the PIR is 1-5:1.

40 For the reaction of PIR with short-chain, hydroxyl-cont~;n;ng compounds, use is made according to the present invention of carrier polyols having an OH number of at most 500 mg KOH/g and a molar mass of at least 450 g/mol. Suitable carrier polyols are, for example, polyols which are prepared by addition of propylene ~ 45 oxide onto trifunctional alcohols. Polyols used are preferably ones based on glycerol and/or trimethylolpropane.

CA 022l6772 lss7-l0-l7 BASF ~iktiengesell3chaft 960800 O.Z. 0050/47417 Short-chain, hydroxyl-containing compounds used can in principle be all difunctional or higher-functional alcohols.

Difunctional alcohols are particularly advantageous for the 5 process of the present invention. The alcohols can be used individually or as a mixture.

Preference is given to using ethylene glycol and its higher 10 homologues, in particular diethylene glycol and propylene glycol and its higher homologues, in particular dipropylene glycol, individually or in admixture with one another.

The process can be carried out in the presence of customary 15 polyurethane catalysts. For this purpose, preference is given to using organic tin and titanium compounds.

As PIR, it is possible to use scrap, for example from the production of PIR block foams, PIR moldings or sandwich elements.

To produce the PIR foams by the process of the present invention, use is made of, in addition to the above-described recycled polyols, the formative components known per se about which the following details may be given:

a) Suitable organic and/or modified organic polyisocyanates (a) are the aliphatic, cycloaliphatic, araliphatic and preferably aromatic polyfunctional isocyanates known per se.

Specific examples are: alkylene diisocyanates having from 4 to 12 carbon atoms in the alkylene radical, for example dode-cane 1,12-diisocyanate, 2-ethyltetramethylene 1,4-diisocya-nate, 2-methylpentamethylene 1,5-diisocyanate, tetramethylene 1,4-diisocyanate and preferably hexamethylene 1,6-diisocya-nate; cycloaliphatic diisocyanates such as cyclohexane-1,3-and -1,4-diisocyanate and also any mixtures of these isomers, l-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate), hexahydrotolylene 2,4- and go 2,6-diisocyanate and also the corresponding isomer mixtures, dicyclohexylmethane 4,4~-, 2,2~- and 2,4'-diisocyanate and also the corresponding isomer mixtures, and preferably aro-matic diisocyanates and polyisocyanates such as tolylene 2,4-and 2,6-diisocyanate and the corresponding isomer mixtures, g5 diphenylmethane 4,4'-, 2,4~- and 2,2'-diisocyanate and the corresponding isomer mixtures, mixtures of diphenylmethane 4,4~- and 2,4'-diisocyanates, polyphenylpolymethylene poly-CA 022l6772 l997-l0-l7 BASF Aktlenge~ell~cha~t 960800 O.Z. 0050~47417 isocyanates, mixtures of diphenylmethane 4,4~-, 2,4~- and 2,2'-diisocyanates and polyphenylpolymethylene polyisocya-nates (raw MDI) and mixtures of raw MDI and tolylene diiso-cyanates. The organic diisocyanates and polyisocyanates can be used individually or in the form of their mixtures.

Use is fre~uently also made of modified polyfunctional iso-cyanates, i.e. products which are obtained by chemical reac-tion of organic diisocyanates and/or polyisocyanates.
Examples which may be mentioned are diisocyanates and/or polyisocyanates containing ester, urea, biuret, allophanate, carbodiimide, isocyanurate, uretdione and/or urethane groups.
Specific examples are: organic, preferably aromatic polyiso-cyanates containing urethane groups, having NCO contents of from 33.6 to 15% by weight, pre~erably from 31 to 21% by weight, based on the total weight, and prepared, for example, by reaction with low molecular weight diols, triols, dialky-lene glycols, trialkylene glycols or polyoxyalkylene glycols having molecular weights of up to 6000, in particular up to 1500, modified diphenylmethane 4,4'-diisocyanate, modified diphenylmethane 4,4'- and 2,4'-diisocyanate mixtures, or modified raw MDI or tolylene 2,4- or 2,6-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-polyoxyethylene glycols, triols and/or te-trols. Also suitable are prepolymers containing NCO groups, having NCO contents of from 25 to 3.5% by weight, preferably from 21 to 14% by weight, based on the total weight, and pre-pared from the polyester and/or pre~erably polyether polyols described below and diphenylmethane 4,4'-diisocyanate, mix-tures of diphenylmethane 2,4'- and 4,4'-diisocyanate, toly-lene 2,4- and/or 2,6-diisocyanates or raw MDI . Other modified polyisocyanates which have been found to be useful are liquid polyisocyanates containing carbodiimide groups and/or iso-cyanurate rings and having NCO contents of from 33.6 to 15%
by weight, preferably from 31 to 21% by weight, based on the total weight, for example those based on diphenylmethane 4,4'-, 2,4~- and/or 2,2'-diisocyanate and/or tolylene 2,4-and/or 2,6-diisocyanate.

If desired, the modified polyisocyanates can be mixed with one another or with unmodified organic polyisocyanates such - 45 as diphenylmethane 2,4'-and/or 4,4'-diisocyanate, raw MDI, tolylene 2,4- and/or 2,6-diisocyanate.

CA 022l6772 l997-l0-l7 - BASF Aktienge~Qllschaft 960800 O.Z. 0050/47417 :-Organic polyisocyanates which have been found to be particu-larly useful and are therefore preferably employed are the following aromatic polyisocyanates: raw MDI, mixtures of tolylene diisocyanates and raw MDI or mixtures of modified organic polyisocyanates containing urethane groups and having an NCO content of from 33.6 to 15% by weight, in particular those based on tolylene diisocyanates, diphenylmethane 4,4'-diisocyanate, diphenylmethane diisocyanate isomer mix-tures or raw MDI and in particular raw MDI having a diphe-nylmethane diisocyanate isomer content of from 30 to 80% by weight, preferably from 30 to 55~ by weight.

b) As relatively high molecular weight compounds containing at least two reactive hydrogen atoms, use is made according to the present invention of the above-described recycled poly-ols. In addition to these, concomitant use may be made of further relatively high molecular weight compounds containing at least two reactive hydrogen atoms b). Compounds suitable for this purpose are advantageously those having a function-ality of from 2 to 8, preferably from 2 to 6, and a molecular weight of from 400 to 8000, preferably from 1200 to 6000.
Examples of compounds which have been found to be useful are polyetherpolyamines, and/or preferably polyols selected from the group consisting of polyether polyols, polyester polyols, polythioether polyols, polyester amides, hydroxyl-containing polyacetals and hydroxyl-containing aliphatic polycarbonates or mixtures of at least two of the polyols mentioned. Prefer-ence is given to using polyester polyols and/or polyether polyols. 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, preferably aliphatic dicarboxylic acids having from 4 to 6 carbon atoms, and polyhydric alcohols, preferably diols, hav-ing 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, decanedicarboxylic acid, maleic acid, fumaric acid, phthalic acid, isophthalic acid and terephthalic acid.
The dicarboxylic acids can here be used either individually or in admixture with one another. In place of the free dicar-boxylic acids, it is also possible to use the corresponding - 45 dicarboxylic acid derivatives such as dicarboxylic esters of alcohols having from l to 4 carbon atoms or dicarboxylic anhydrides. Preference is given to using dicarboxylic acid mixtures of succinic, glutaric and adipic acid in weight ..

CA 022l6772 lss7-l0-l7 BAS~ ~iktiengesell~cha~t 960800 O.Z. 0050/47417 ratios of, for examplei 20-35:35-50:20-32, and in particular adipic acid. Examples of dihydric and polyhydric alcohols, in particular diols, are: ethanediol, diethylene glycol, 1,2- or 1,3-propanediol, dipropylene glycol, 1,4-butanediol, 1,5-pen-tanediol, 1,6-hexanediol, l,10-decanediol, glycerol and trimethylolpropane. Preference is given to using ethanediol, diethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol or mixtures of at least two of the diols men-tioned, in particular mixtures of 1,4-butanediol, 1,5-pen-tanediol and 1,6-hexanediol. It is also possible to use poly-ester polyols derived from lactones, e.g.E-caprolactone, or hydroxycarboxylic acids, e.g.~-hydroxycaproic acid.

To prepare the polyester polyols, the organic, e.g. aromatic and preferably aliphatic, polycarboxylic acids and/or deriva-tives and polyhydric alcohols can be polycondensed in the absence of catalysts or preferably in the presence of esteri-fication catalysts, advantageously in an atmosphere of inert gas such as nitrogen, carbon dioxide, helium, argon, etc., in the melt at from 150 to 250~C, preferably from 180 to 220~C, under atmospheric pressure or under reduced pressure to 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 abovemen-tioned temperatures to an acid number of from 80 to 30, pre-ferably from 40 to 30, under atmospheric pressure and subse-quently under a pressure of less than 500 mbar, preferably from 50 to 150 mbar. Suitable esterification catalysts are, for example, iron, cadmium, cobalt, lead, zinc, antimony, magnesium, titanium and tin catalysts 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 entrainers such as benzene, toluene, xylene or chlorobenzene to azeotropically distill off the water of condensation.

To prepare the polyester polyols, the organic polycarboxylic acids and/or derivatives and polyhydric alcohols are advan-tageously polycondensed in a molar ratio of 1:1-1.8, prefera-bly 1:1.05-1.2.

The polyester polyols obtained preferably have a functional-ity of from 2 to 4, in particular from 2 to 3, and a molecu-lar weight of from 480 to 3000, preferably from 1200 to 3000 and in particular from 1800 to 2500.

- BASF Aktienge~ellscha~t 960800 O.Z. 0050/47417 .

g However, polyols used are particularly preferably polyether polyols which are prepared by known methods, for example from - one or more alkylene oxides having from 2 to 4 carbon atoms in the alkylene radical by anionic polymerization using alkali metal hydroxides such as sodium or potassium hydroxide or alkali metal alkoxides such as sodium methoxide, sodium or potassium ethoxide or potassium isopropoxide as catalysts with addition of at least one initiating molecule containing from 2 to 8, preferably from 2 to 6, reactive hydrogen atoms in bonded form or by cationic polymerization using Lewis acids such as antimony pentachloride, boron fluoride ether-ate, etc., or bleaching earth 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, alternately in succession or as mixtures. sxamples of suitable initiator molecules are: water, organic dicarboxylic acids such as suc-cinic acid, adipic acid, phthalic acid and terephthalic acid, aliphatic and aromatic, unalkylated, N-mono-alkylated, N,N-and N,N'-dialkylated diamines having from 1 to 4 carbon atoms in the alkyl radical, for example monoalkylated and dialky-lated ethylenediamine, diethylenetriamine, triethylenetetra-mine, 1,3-propylenediamine 1,3- or 1,4-butylenediamine, 1,2-, 1,3-, 1,4-, 1,5- and 1,6-hexamethylenediamine, phenylenedia-mines, 2,3-, 2,4- and 2,6-tolylenediamine and 4,4~-, 2,4~-and 2,2~-diaminodiphenylmethane.

Burther suitable initiator molecules are: alkanolamines such as ethanolamine, N-methylethanolamine and N-ethylethanol-amine, dialkanolamines such as diethanolamine, N-methyldie-thanolamine and N-ethyldiethanolamine, and trialkanolamines such as triethanolamine, and ammonia. Preference is given to using polyhydric, in particular dihydric and/or trihydric al-cohols such as ethanediol, 1,2- and 1,3-propanediol, diethy-lene glycol, dipropylene glycol, 1,4-butanediol, 1,6-hexane-diol, glycerol, trimethylolpropane, pentaerythritol, sorbitol and sucrose.
The polyether polyols, preferably polyoxypropylene and poly-oxypropylene-polyoxyethylene polyols, have a functionality of preferably from 2 to 6 and in particular from 2 to 4 and have molecular weights of from 400 to 8000, preferably from 1200 to 6000 and in particular from 1800 to 4000, and suitable - CA 022l6772 l997-lO-l7 BASF AUktieng~ell~chaft 960800 O.Z. 0050/47417 polyoxytetramethylene glycols have a molecular weight up to about 3500.
-Further suitable polyether polyols are polymer-modified poly-ether polyols, preferably graft polyether polyols, in par-ticular those based on styrene and/or acrylonitrile which are prepared by in situ polymerization of acrylonitrile, styrene or preferably mixtures of styrene and acrylonitrile, e.g. in a weight ratio of from 90:10 to 10:90, preferably from 70:30 to 30:70, advantageously in the abovementioned polyether polyols using methods similar to those described in the Ger-man 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 11 52 537 (GB 987 618), and also polyether polyol dispersions which contain as dispersed phase, usually in an amount of from l to 50~ by weight, preferably from 2 to 25% by weight: e.g. polyureas, polyhydrazides, polyurethanes containing bonded tert-amino groups and/or melamine and are described, ~or example, in Ep-s-oll 752 (US 4 304 708), US 4 374 209 and DE-A-32 31 497.

Like the polyester polyols, the polyether polyols can be used individually or in the form of mixtures. They can also be mixed with the graft polyether polyols or polyester polyols as well as with the hydroxyl-containing polyester amides, polyacetals, polycarbonates and/or polyether polyamines.

Suitable hydroxyl-cont~;n;ng polyacetals are, for example, the compounds which can be prepared from glycols such as die-thylene glycol, triethylene glycol, 4,4~-dihydroxyethoxydi-phenyldimethylmethane or hexanediol and formaldehyde. Suit-able polyacetals can also be prepared by polymerization o~
cyclic acetals.

Suitable hydroxyl-containing polycarbonates are those of the type known per se which can be prepared, for example, by re-acting diols such as 1,3-propanediol, 1,4-butanediol, and/or 1,6-hexanediol, diethylene glycol, triethylene glycol or tetraethylene glycol with diaryl carbonates, e.g. diphenyl carbonate, or phosgene.

The polyester amides include, for example, the predominantly linear condensates obtained from polybasic, saturated and/or unsaturated carboxylic acids or their anhydrides and poly-functional saturated and/or unsaturated aminoalcohols or mix-CA 022l6772 l997-lO-l7 BASF ~kt~ge~Qll8cha~t 960800 O.Z. 0050/47417 tures of polyfunctional alcohols and aminoalcohols and/or polyamines.

Suitable polyetherpolyamines can be prepared from the abovementioned polyether polyols by known methods. Examples which may be mentioned are the cyanoalkylation of polyoxy-alkylene polyols and subsequent hydrogenation of the nitrile formed (US 3 267 050) or the partial or complete amination of polyoxyalkylene polyols using amines or ammonia in the pres-ence of hydrogen and catalysts (DE 12 15 373).

c) The PIR foams can be produced with or without concomitant useof chain extenders and/or crosslinkers (c). However, the addition of chain extenders, crosslinkers or, if desired, mixtures thereof can prove to be advantageous for modifying the mechanical properties, e.g. the hardness. Chain extenders and/or crosslinkers used are diols and/or triols having mol-ecular weights of less than 400, preferably from 60 to 300.
Examples of suitable chain extenders/crosslinkers are alipha-tic, cycloaliphatic and~or araliphatic diols having from 2 to 14, preferably from 4 to 10, carbon atoms, e.g. ethylene gly-col, 1,3-propanediol, l,10-decanediol, o-, m-, p-dihydroxycy-clohexane, diethylene glycol, dipropylene glycol and prefera-bly 1,4-butanediol, 1,6-hexanediol and bis(2-hydroxyethyl)hy-droquinone, triols such as 1,2,4- or 1,3,5-trihydroxycyclo-hexane, glycerol and trimethylolpropane and low molecular weight hydroxyl-cont~;n-ng polyalkylene oxides based on ethy-lene oxide and/or 1,2-propylene oxide and the abovementioned diols and/or triols as initiator molecules.
If chain extenders, crosslinkers or mixtures thereof are employed for producing the PIR foams, these are advantageous-ly used in an amount of from 0 to 20% by weight, preferably from 2 to 8% by weight, based on the weight of the polyol compound (b).

d) Catalysts (d) used for producing the PIR foams are, in par-ticular, compounds which strongly accelerate the reaction of the compounds containing reactive hydrogen atoms, in particu-lar hydroxyl groups, of the component (b) and, if used, (c) with the organic, modified or unmodified polyisocyanates (a).
Suitable catalysts are organic metal compounds, preferably organic tin compounds such as tin(II) salts of organic car-boxylic acids, e.g. tin(II) acetate, tin(II) octoate, tin(II) ethylhexanoate and tin(II) laurate, and the dialkyltin(IV) salts of organic carboxylic acids, e.g. dibutyltin diacetate, CA 022l6772 l997-lO-l7 ~ BASF ~kt~engesellschaft 960800 O.Z. 0050/47417 dibutyltin dilaurate, dibutyltin maleate and dioctyltin diacetate. The organic metal compounds are used alone or pre-ferably in combination with strongly basic amines. Bxamples -which may be mentioned are amidines such as 2,3-dime-thyl-3,4,5,6-tetrahydropyrimidine, tertiary amines such as triethylamine, tributylamine, dimethylbenzylamine, N-methyl-morpholine, N-ethylmorpholine, N-cyclohexylmorpholine, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetrame-thylbutanediamine, N,N,N',N'-tetramethylhexane 1,6-diamine, pentamethyldiethylenetriamine, bis(dimethylaminoethyl) ether, bis(dimethylaminopropyl)urea, dimethylpiperazine, 1,2-dime-thylimidazole, l-azabicyclo[3.3.0]octane and preferably 1,4-diazabicyclo[2;2.2]octane, and alkanolamine compounds such as triethanolamine, triisopropanolamine, N-methyldietha-nolamine and N-ethyldiethanolamine and dimethylethanolamine.

Further suitable catalysts are: tris(dialkylaminoal-kyl)-s-hexahydrotriazines, in particular tris(M,N-dimethyl-aminopropyl)-s-hexahydrotriazine, tetraalkylammonium hydrox-ide such as tetramethylammonium hydroxide, alkali metal hy-droxides, 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 lateral OH groups. Preference is given to using from 0.001 to 5% by weight, in particular ~rom 0.05 to 2~ by weight, o~ catalyst or catalyst combina-tion, based on the weight of the component (b).

30 e) slowing agents (e) which may, if desired, be used ~or produc-ing the PIR foams include preferably water which reacts with 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 admixture with water, it is also possible to use physi-cally acting blowing agents. Suitable physically acting blow-ing agents are liquids which are inert toward the organic, modified or unmodified polyisocyanates (c) and have boiling points below 100~C, preferably below 50~C, in particular from -50~C to 30~C, at atmospheric pressure so that they vaporize under the action of the exothermic polyaddition reaction.
Examples of such preferred liquids are alkanes such as hep-tane, hexane, n- and iso-pentane, preferably industrial mix-tures of n- and iso-pentanes, n- and iso-butanes and propane, CA 022l6772 l997-l0-l7 BASF Aktiengecell~chaft g60800 O.Z. 0050/47417 .

cycloalkanes such as cyclopentane and/or cyclohexane, ethers such as furan, dimethyl ether and diethyl ether, ketones such as acetone and methyl ethyl ketone, alkyl carboxylates such as methyl formate, dimethyl oxalate and ethyl acetate and ha-logenated hydrocarbons such as methylene chloride, dichloro-monofluoromethane, difluoromethane, trifluoromethane, di-fluoroethane, tetrafluoroethane, chlorodifluoroethanes, 1,1-dichloro-2,2,2-trifluoroethane, 2,2-dichloro-2-fluoro-ethane and heptafluoropropane. Mixtures of these low-boiling li~uids with one another and/or with other substituted or un-substituted hydrocarbons can also be used. Also suitable are organic carboxylic acids such as formic acid, acetic acid, oxalic acid, ricinoleic acid and carboxyl-containing com-pounds.

Preference is given to using water, chlorodifluoromethane, chlorodifluoroethanes, dichlorofluoroethanes, pentane mix-tures, cyclohexane and mixtures of at least two of these, e.g. mixtures of water and cyclohexane, mixtures of chlorodi-fluoromethane and 1-chloro-2,2-difluoroethane and, if de-sired, water.

The amount of physically acting blowing agents required in addition to water can be determined in a simple manner as afunction of the desired foam density and is from about 0 to 25 parts by weight, preferably from 0 to 15 parts by weight, per 100 parts by weight of the polyoxyalkylene polyols. It may be advantageous to mix the modified or unmodified poly-isocyanates (c) with the inert physically acting blowingagent and thereby reduce the viscosity.

~) If desired, auxiliaries and/or additives (~) customary in polyurethane chemistry can also be incorporated into the re-action mixture for producing the PIR foams. Examples whichmay be mentioned are foam stabilizers, fillers, dyes, pig-ments, flame retardants, hydrolysis inhibitors, fungistatic and bacteriostatic substances.

For the purposes of the present invention, fillers, in par-ticular reinforcing fillers, are the customary organic and inorganic fillers, reinforcers, weighting 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 sheet silicates such as antigorite, serpentine, Hornblends, amphiboles, chrysotile, talc; metal oxides such as kaolin, aluminum oxides, titanium - CA 022l6772 l997-l0-l7 B~F Akt~engesell~ahaft 960800 O.Z. 0050/47417 . 14 oxides and iron oxides, metal salts such as chalk, barite and inorganic pigments such as cadmium sulfide, zinc sulfide and also glass, etc. Preference is given to using kaolin (china 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 may, if desired, be coated with a size. Examples of suitable organic fillers are:
carbon, melamine, rosin, cyclopentadienyl resins and graft polymers and also cellulose fibers, polyamide, polyacryloni-trile, polyurethane and polyester fibers based on aromatic and/or aliphatic dicarboxylic esters and, in particular, car-bon fibers.
The inorganic and organic fillers can be used individually or as mixtures and are advantageously incorporated into the re-action mixture in amounts of from 0.5 to 50% by weight, pre-ferably from 1 to 40% by weight, based on the weight of the components (a) to (c), although the content of mats, non-wovens and woven fabrics made of natural and synthetic fibers may reach values up to 80 percent by weight.

Suitable ~lame retardants are, for example, tricresyl phos-2 phate, tris(2-chloroethyl) phosphate, tris(2-chloropropyl) phosphate, tris(l,3-dichloropropyl) phosphate, tris(2,3-di-bromopropyl) phosphate, tetrakis(2-chloroethyl)ethylene di-phosphate, dimethyl methanephosphonate, diethyl diethanolami-nomethylphosphonate and also commercial halogen-containing flame retardant polyols.
Apart from the abovementioned halogen-substituted phosphates, it is also possible to use inorganic or organic flame retard-ants such as red phosphorus, hydrated aluminum oxide, anti-mony trioxide, arsenic oxide, ammonium polyphosphate and cal-cium sulfate, expanded graphite or cyanuric acid derivatives such as melamine, or mixtures of at least two flame retard-ants such as ammonium polyphosphates and melamine and also, if desired, maize starch or ~mmon;um polyphosphate, melamine and expanded graphite and/or aromatic or aliphatic polyesters for making the polyisocyanate polyaddition products flame re-sistant. In general, it has been found to be advantageous to use from 5 to 50 parts by weight, preferably from 5 to 25 parts by weight, of the abovementioned flame retardants per 100 parts by weight of the component (b).

CA 022l6772 lss7-l0-l7 BASF Akt~enge~Qll~chaft 960800 O.Z. 0050/47417 Further details regarding the abovementioned other customary auxiliaries and additives may be found in the specialist lit-erature, for example the monograph by J.~. Saunders and K.C.
Frisch "High Polymers~ Volume XVI, Polyurethanes, parts 1 and 2, Interscience Publishers 1962 and 1964, or the Kunststoff-Handbuch, Polyurethane, Volume VII, Hanser-Verlag, Munich, Vienna, 1st, 2nd and 3rd editions, 1966, 1983 and 1993.

To produce the PIR foams, the organic polyisocyanates (a), 10 relatively high molecular weight compounds containing at least two reactive hydrogen atoms ~b) and, if desired, chain extenders and/or crosslinkers (c) are reacted in amounts such that the equivalence ratio of NCO groups of the polyisocyanates (a) to the sum of the reactive hydrogen atoms of the components (b) and, if 15 used, ~c) is 0.7-1.5:1.

The PIR foams are advantageously produced by the one-shot method or the prepolymer method by means of the high-pressure or 20 low-pressure technique in open or closed molds, for example metal molds, or are free-foamed (in-situ foam). It has been found to be 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 and~or modified organic polyisocyanates (a) or mixtures of said polyisocyanates and, if desired, blowing agents (d) as component (B).

The starting components are mixed at from lS to 90~C, preferably 30 from 20 to 60~C and in particular from 20 to 35~C, and, if molded foams are being produced, introduced into the open or closed mold. The mold temperature is advantageously from 20 to 110~C, preferably from 30 to 60~C and in particular from 45 to 50~C.

35 In the case of free-foaming, blocks are produced for subsequent mach;n;ng, for example by sawing, e.g. into boards. It is likewise possible to set the reactivity of the polyurethane systems of the present invention such that they can be processed by the known processes of foam spraying (sprayed foam process), 40 thus making it possible to coat vertical, horizontal and hanging surfaces (from the top).

The PIR foams produced by the process of the present invention have a density of from 25 to 50 kg/m3, preferably from 30 to 45 40 kg/m3. They have a uniform, fine-celled foam structure.

CA 022l6772 l997-l0-l7 BASF Akt~engesellscha~t 960800 O.Z. 0050/47417 The PIR foams of the present invention have a thermal conductivity of from 17 to 22, preferably from 19 to 21, mW/(m . K).

S The PIR foams produced by the process of the present invention are suitable for all applications customary for PIR foams. In particular, they are used as thermal insulation boards, preferably in building and civil engineering, thermal insulation in piping systems and also for the thermal insulation of 10 structural components, component groups and elements in the construction of apparatus and machinery.

The invention is illustrated by the following examples.

Example 1 (Comparative example):

The A component consisting of a mixture of:

20 63.46 parts by weight of a polyesterol derived from phthalic anhydride, diethylene glycol and polyethylene glycol and having an OHN of 240 mg KO~/g, 1.87 parts by weight of the stabilizer sP SR 321 from Union Car-2Sbide, 0.56 part by weight of a catalyst I (potassium acetate/ethylene glycol), 0.99 part by weight o~ a catalyst II (trisdimethylaminopropyl-hexahydrotriazine/triethylamine) and 30 33.12 parts by weight of R 141 b, was reacted with 174 parts by weight of the B component (diphenylmethane diisocyanate/polyisocyanate).

This gave a PIR foam having the following properties:

Density [kg/m3] 33.2 Dimensional stability at -5~C, 24 h t%] 94.2 40 Compressive strength ~kPa] 346 Thermal conductivity [mW/m-K] 24.4 Flame height tcm] 9 BASF Aktlengesell~chaft 960800 O.Z. 0050/47417 Example 2 (Preparation of the recycled polyol) 700 g of a PIR foam (NCO index:500) were introduced at 215-225~C
into a mixture of 1000 g of diethylene glycol (DEG), 680 g of the 5 polyether polyol Lupranol~3300 from BASF Aktiengesellschaft (1 mol of glycerol and 8.5 mol 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 remained stirrable.
After the addition was complete, the temperature was reduced to 10 190-200~C and maintained for 2 hours while stirring. The mixture was then cooled to 150~C and 90 g of 2-ethylhexyl glycidyl ether were added, and the mixture was stirred further for one hour at this temperature. This gave a homogeneous dark brown liquid having the following properties:

OHN 520 mg KOH/g Acid number 0.6 mg KOH/g Viscosity 3500 mPa.s 20 MDA content c 0.1 Example 3 The A component consisting of a mixture of:

12.70 parts by weight of a recycled polyol prepared as described in Example 2 by glycolysis of waste PIR foam using carrier polyetherols and having an OHN of 520 mg KOH/g, 30 50.77 parts by weight of a polyesterol derived from phthalic anhydride, diethylene glycol and polyethylene glycol and having an OHN of 240 mg KOH/g, 1.87 parts by weight of the stabilizer sP SR 321 from Union Car-bide, 0.56 part by weight of a catalyst I as described in Example 1, 0.99 part 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 B component (diphenylmethane diisocyanate/polyisocyanate).

This gave a PIR foam having the following properties:

CA 022l6772 l997-lO-l7 BASF Aktieng~sell~ah~ft 960800 . O.Z. 0050/47417 Density tkg/m3] 32.4 Dimensional stability at -5~C, 24 h [~] 91.6 Compressive strength [kPa] 338 Thermal conductivity [mW/m K] 19.6 5 Flame height [cm] 9

Claims (8)

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

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

3. A process as claimed in claim 1, wherein carrier polyols based on glycerol and/or trimethylolpropane are used in the preparation of the recycled polyols.

4. A process as claimed in claim 1, wherein the recycled polyol used is low in amines.

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

6. A polyisocyanurate foam as claimed in claim 5, wherein the recycled polyol is used in a proportion of at least 15% by weight, based on the total amount of the component b).

7. A polyisocyanurate foam as claimed in claim 5 which has a thermal conductivity of at most 22 mW/(m . K) at a foam density of from 25 to 50 kg/m3.

8. The use of a polyisocyanurate foam as claimed in claim 5 for thermal insulation.