POLYOL FORMULATIONS AND A PROCESS FOR THE PRODUCTION OF PUR / PIR FOAMS BASED ON THESE POLYOL FORMULATIONS

Description

[0001] The present invention relates to polyol formulations comprising a polyester polyol component and a specific polyether polyol component. The present invention also relates to a process for producing rigid polyurethane foams or polyurethane / polyisocyanurate rigid foams (hereinafter referred to individually or collectively as "rigid PUR / PIR foams") using this polyol formulation and to the rigid PUR / PIR foams produced thereby.

[0002] Like other polymers, PUR / PIR rigid foams become brittle in cold temperatures and tend to crack and break even under low loads. When subjected to mechanical stress with a knife in cold temperatures, for example, metal composite elements containing a PUR / PIR rigid foam core exhibit damage in the form of longitudinal cracks. This occurs particularly in polyol formulations containing predominantly aromatic polyols and is particularly pronounced in the first few weeks after production.

[0003] The object of the invention described here is to reduce the susceptibility to cracking in the cold of such metal composite elements after production, in particular during the first four weeks after production.

[0004] This problem could surprisingly be solved by using an isocyanate-reactive component A, which, based on the total weight of A, contains the following components: A1) a polyol formulation comprising 50-80 wt.% (particularly preferably 60-79 wt.%) of a polyol component a1) consisting of one or more polyols selected from polyester polyols, polycarbonate polyols or polyetherester polyols having a hydroxyl number of 100 to 300 mg KOH / g and an average functionality of 1.5 to 2.5, wherein the polyol component a1) comprises at least one aromatic or aromatic / aliphatic polyester polyol or polyetherester polyol, 0-5 wt.% (particularly 0-3 wt.%) of a polyol component a2) consisting of one or more polyols selected from polyester polyols and polyetherester polyols having a hydroxyl number of 320 to 450 mg KOH / g and an average functionality of 3 to 4.5, wherein the polyol component a2) comprises at least one aromatic or aromatic / aliphatic polyester polyol or polyetherester polyol comprises 8.0 - 12.0 wt.% of a polyol component a3)consisting of one or more polyols selected from polyether polyols having an OH number of 10 to 80 KOH / g and an average functionality of ≥ 2.0 to ≤ 3.0, prepared by alkoxylation of a suitable starter component, with a mixture of ethylene oxide (EO) and propylene oxide (PO) having an EO content of 15-70 wt.% based on the total amount of EO and PO, 0.0 - 7.5 wt.% (particularly preferably 0 - 5 wt.%) of a polyol component a4) consisting of one or more polyols selected from polyether polyols having an OH number in the range of 350 - 500 mg KOH / g, in particular 390 - 440 mg KOH / g, prepared by alkoxylation of an aromatic amine with at least one alkylene oxide, 0.0 - 3.0 wt.% (particularly preferably 0.3 - 1.0 wt.%) of a polyol component a5) consisting of one or more polyols selected from polyester polyols having an OH number in the range of 600 - 900 mg KOH / g, in particular 750 - 850 mg KOH / g; A2)0 - 5 wt.% (particularly preferably 0 - 3 wt.%) low molecular weight isocyanate-reactive compounds, and A3) if necessary catalysts, A4) if necessary, auxiliary substances and additives A5) 0 - 1.5 wt% water and A6) 0 - 7.5 wt.% (particularly preferably 0 - 5 wt.%) castor oil, contain.

[0005] All percentages by weight refer to the total weight of A.

[0006] Polyol formulations generally containing long-chain polyether polyols, which also include compounds a3), are known. For example, WO 2018 / 206624 A describes the use of a maximum of 20 wt. %, based on the total reaction mixture, of long-chain polyethers in combination with short-chain polyether polyols to improve adhesion properties. Based on the polyol formulation, the examples use approximately 6 wt. % of a polyether polyol (polycondensate of an unspecified PO / EO mixture, glycerol as starter) with an OH number of 56 and a number-average molecular weight of 3000 g / mol.

[0007] WO 2013 / 080988 A1 discloses a system for producing spray foams with higher bulk densities than those usual for metal composite elements, containing as blowing agent amounts of water > 1.5 wt.% based on the isocyanate-reactive component.

[0008] WO 2018 / 206624 A1 discloses a process for producing polyurethane / polyisocyanurate (PUR / PIR) rigid foams and their use in composite elements which exhibit improved fire behavior.

[0009] WO 2013 / 010988 A1 discloses the production of water-blown polyurethane / polyisocyanurate (PUR / PIR) rigid foams with improved sprayability.

[0010] Surprisingly, it was found that the susceptibility to cracking in cold temperatures, e.g., at -10° and -20°C, of ​​metal composite elements with a core made of PUR / PIR foams is significantly reduced with the polyol formulation according to the invention. In contrast, metal composite elements manufactured with a PIR system that does not contain component a3) or contains an insufficient amount of component a3) exhibit damage patterns in the form of longitudinal cracks when subjected to mechanical stress with a knife when subjected to cold temperatures. This is particularly pronounced in the first few weeks after production. At the same time, the PUR / PIR foams exhibit good mechanical properties, such as tensile strength, elongation at break, toughness, and open-cell structure of the PUR / PIR foams.

[0011] The polyester polyols used for component a1) include polycondensates of di-, tri-, and tetraols, and di-, tri-, and tetracarboxylic acids, or hydroxycarboxylic acids, or lactones. "Aromatic polyesters" are polyesters produced using only polycarboxylic acids containing an aromatic component. "Aromatic / aliphatic polyesters" are polyesters produced using aromatic and aliphatic polycarboxylic acids. This also applies analogously to the polyetherester polyols described below. Instead of the free polycarboxylic acids, the corresponding polycarboxylic anhydrides or corresponding polycarboxylic esters of lower alcohols can also be used to produce the polyesters.

[0012] Examples of suitable diols include ethylene glycol, butylene glycol, diethylene glycol, triethylene glycol, polyalkylene glycols such as polyethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,3-butanediol, 1,6-hexanediol and isomers, neopentyl glycol, or neopentyl glycol hydroxypivalate. Polyols such as trimethylolpropane, glycerol, erythritol, pentaerythritol, trimethylolbenzene, or trishydroxyethyl isocyanurate can also be used.

[0013] Examples of aromatic polycarboxylic acids that can be used are phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, trimesic acid (1,3,5-benzenetricarboxylic acid), pyromellitic acid and endomethylenetetrahydrophthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid and / or tetrachlorophthalic acid, in particular phthalic acid and its isomers and derivatives.

[0014] Examples of suitable aliphatic polycarboxylic acids include cyclohexanedicarboxylic acid, adipic acid, azelaic acid, sebacic acid, glutaric acid, maleic acid, fumaric acid, itaconic acid, malonic acid, suberic acid, succinic acid, 2-methylsuccinic acid, 3,3-diethylglutaric acid, 2,2-dimethylsuccinic acid, dodecanedioic acid, dimer fatty acid, trimer fatty acid and / or citric acid.

[0015] Monocarboxylic acids and their derivatives can also be added to the polycarboxylic acids used. Bio-based starting materials and / or their derivatives are particularly suitable, such as: B. Castor oil, polyhydroxy fatty acids, ricinoleic acid, stearic acid, soybean oil fatty acid, hydroxy-modified oils, grapeseed oil, black cumin oil, pumpkin seed oil, borage seed oil, soybean oil, wheat seed oil, rapeseed oil, sunflower seed oil, peanut oil, apricot kernel oil, pistachio oil, almond oil, olive oil, macadamia nut oil, avocado oil, sea buckthorn oil, sesame oil, hemp oil, hazelnut oil, primrose oil, rosehip oil, safflower oil, walnut oil, fatty acids, hydroxy-modified and epoxidized fatty acids and fatty acid esters, for example based on myristoleic acid, palmitoleic acid, oleic acid, vaccenic acid, petroselinic acid, gadoleic acid, erucic acid, nervonic acid, linoleic acid, alpha- and gamma-linolenic acid, stearidonic acid, arachidonic acid, timnodonic acid, clupanodonic acid and cervonic acid.

[0016] Examples of hydroxycarboxylic acids that can be used as reactants in the preparation of a hydroxyl-terminated polyester polyol include hydroxycaproic acid, hydroxybutyric acid, hydroxydecanoic acid, hydroxystearic acid, and the like. Suitable lactones include caprolactone, butyrolactone, and homologues.

[0017] Polycarbonate polyols can also be used as polyols in component a1). Polycarbonate polyols are polycarbonates containing hydroxyl groups, for example, polycarbonate diols. These are obtained by reacting carbonic acid derivatives, such as diphenyl carbonate, dimethyl carbonate, or phosgene, with polyols, preferably diols, or from carbon dioxide.

[0018] Examples of such diols are ethylene glycol, 1,2- and 1,3-propanediol, 1,3- and 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, neopentyl glycol, 1,4-bishydroxymethylcyclohexane, 2-methyl-1,3-propanediol, 2,2,4-trimethylpentanediol-1,3, dipropylene glycol, polypropylene glycols, dibutylene glycol, polybutylene glycols, bisphenol A and lactone-modified diols of the type mentioned above. Instead of or in addition to pure polycarbonate diols, polyether polycarbonate diols can also be used.

[0019] Suitable polyetherester polyols are compounds containing ether groups, ester groups, and OH groups. Organic dicarboxylic acids with up to 12 carbon atoms are suitable for producing the polyetherester polyols, preferably aliphatic dicarboxylic acids with > 4 to < 6 carbon atoms or aromatic dicarboxylic acids, which are used individually or in mixtures. Examples include suberic acid, azelaic acid, decanedicarboxylic acid, maleic acid, malonic acid, phthalic acid, pimelic acid, and sebacic acid, and in particular glutaric acid, fumaric acid, succinic acid, adipic acid, phthalic acid, terephthalic acid, and isoterephthalic acid. Derivatives of these acids include, for example, their anhydrides, as well as their esters and semiesters with low-molecular-weight, monofunctional alcohols with > 1 to < 4 carbon atoms.

[0020] The polyols of component a1) have average functionalities of ≥1.2 to ≤2.9, in particular ≥1.5 to ≤2.5, and a hydroxyl number between 100 and 300 mg KOH / g, particularly preferably 150 to 270 mg KOH / g, and especially preferably 160-260 mg KOH / g. The polyols preferably contain more than 70 mol%, preferably more than 80 mol%, in particular more than 90 mol%, of primary OH groups.

[0021] Component a1) comprises at least one aromatic or aromatic / aliphatic polyester polyol or polyetherester polyol. This means that component a1) has an aromatic moiety. In a preferred embodiment, more than 50 wt. % of component a1) is aromatic or aromatic / aliphatic polyester polyols and / or polyetherester polyols, in particular more than 80 wt. %, and very particularly preferably, component a1) consists of aromatic and / or aromatic / aliphatic polyester polyols and / or polyetherester polyols.

[0022] The polyols of component a2) are prepared by the same known processes as the polyester polyols or polyetherester polyols of polyol component a1). The polyols of component a2) have average functionalities of ≥3.0 to ≤6.0, in particular ≥3.0 to ≤4.5, and a hydroxyl number of 310 to 500 mg KOH / g, particularly preferably 320 to 450 mg KOH / g. The polyester polyols a2) preferably contain more than 70 mol%, preferably more than 80 mol%, in particular more than 90 mol%, of primary OH groups.

[0023] Component a2) comprises at least one aromatic or aromatic / aliphatic polyester polyol or polyetherester polyol. This means that component a2) has an aromatic moiety. In a preferred embodiment, more than 50 wt. % of component a2) is aromatic or aromatic / aliphatic polyester polyols and / or polyetherester polyols, in particular more than 80 wt. %, and very particularly preferably, component a2) consists of aromatic and / or aromatic / aliphatic polyester polyols and / or polyetherester polyols.

[0024] Polyether polyols a3) are used as a further component for the production of the polyol formulation. These polyols are obtained by alkoxylating starter molecules such as polyhydric alcohols. The starter molecules are at least difunctional, but may optionally also contain portions of higher-functionality, particularly trifunctional, starter molecules.

[0025] Starter molecules are, for example, diols with number-average molecular weights Mn of preferably ≥ 18 g / mol to 400 ≤ g / mol, preferably ≥ 62 g / mol to 200 ≤ g / mol, such as 1,2-ethanediol, 1,3-propanediol, 1,2-propanediol, 1,4-butanediol, 1,5-pentenediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,10-decanediol, 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, 2-butene-1,4-diol and 2-butyne-1,4-diol, ether diols such as diethylene glycol, triethylene glycol, tetraethylene glycol, dibutylene glycol, tributylene glycol, tetrabutylene glycol, dihexylene glycol, trihexylene glycol, tetrahexylene glycol, and oligomer mixtures of alkylene glycols, such as diethylene glycol. Starter molecules with functionalities other than OH can also be used alone or in mixtures.

[0026] In addition to the diols, compounds with 3 Zerewitinoff-active hydrogens, for example 1,1,1-trimethylolpropane, triethanolamine, glycerol, as well as triol-started polyethylene oxide polyols with average molecular weights Mn of preferably ≥ 62 g / mol to ≤ 400 g / mol, in particular ≥ 92 g / mol to 200 ≤ g / mol, can also be used as starter molecules for the production of the polyethers.

[0027] As the alkylene oxide component, a mixture of ethylene oxide and propylene oxide is used with an ethylene oxide content of 15 to 70 wt.%, preferably 15-50 wt.%, particularly preferably 20 to 40 wt.%, based on the total amount of alkylene oxide.

[0028] The polyether polyols a3) are prepared by known processes, such as, for example, by anionic polymerization with alkali hydroxides, such as sodium or potassium hydroxide or alkali alkoxides, such as sodium methylate, sodium or potassium ethylate or potassium isopropylate, as catalysts and with the addition of at least one starter molecule or mixtures of starter molecules.

[0029] The polyether polyol a4) preferably has a hydroxyl number of ≥ 350 mg KOH / g to ≤ 500 mg KOH / g, and particularly preferably of ≥ 390 mg KOH / g to ≤ 440 mg KOH / g. In the context of the present invention, hydroxyl numbers can generally be determined using DIN 53240. The polyether polyol a4 is prepared by reacting at least one aromatic amine with at least one alkylene oxide. Preferred aromatic amines are selected from the group consisting of tolylenediamine, diaminodiphenylmethane, and polymethylene polyphenylene polyamine.

[0030] The alkylene oxide used can preferably be ethylene oxide, propylene oxide, or a mixture thereof. Ethylene oxide is particularly preferred. The average functionality of this polyether polyol a4) is preferably 4.

[0031] The weight-average molecular weight of the polyether polyols a4) is preferably in the range between 400 g / mol and 700 g / mol, particularly preferably in the range between 500 g / mol and 600 g / mol.

[0032] The polyether polyols a4) are prepared by known processes, such as, for example, by anionic polymerization with alkali hydroxides, such as sodium or potassium hydroxide or alkali alkoxides, such as sodium methylate, sodium or potassium ethylate or potassium isopropylate, as catalysts and with the addition of at least one aromatic amine as starter molecule with one or more alkylene oxides having 2 to 4 carbon atoms in the alkylene radical.

[0033] The polyester polyol a5) can, for example, be a polycondensate of polyols and aromatic dicarboxylic acids, and optionally tri- and tetracarboxylic acids, hydroxycarboxylic acids, or lactones. Instead of the free polycarboxylic acids, the corresponding polycarboxylic acid anhydrides or corresponding polycarboxylic acid esters of lower alcohols can also be used to produce the polyesters.

[0034] Examples of suitable polyols include ethylene glycol, propylene glycol-(1,2) and -(1,3), butylene glycol-(1,4) and -(2,3), hexanediol-(1,6), octanediol-(1,8), neopentyl glycol, 1,4-bishydroxymethylcyclohexane, 2-methyl-1,3-propanediol, glycerin, trimethylolethane, hexanetriol-(1,2,6), butanetriol-(1,2,4), quinol, methyl glucoside, triethylene glycol, tetraethylene glycol and higher polyethylene glycols, dipropylene glycol and higher polypropylene glycols, diethylene glycol, glycerin, pentaerythritol, trimethylolpropane, sorbitol, mannitol, dibutylene glycol and higher polybutylene glycols. Particularly suitable polyols are alkylene glycols and oxyalkylene glycols, for example ethylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, tetraethylene glycol, tetrapropylene glycol, trimethylene glycol, tetramethylene glycol and 1,4-cyclohexanedimethanol (1,4-bis-hydroxymethylcyclohexane).

[0035] Examples of aromatic dicarboxylic acids that can be used include phthalic acid, isophthalic acid, terephthalic acid, and / or tetrachlorophthalic acid. The corresponding anhydrides can also be used as acid sources.

[0036] If the average functionality of the polyol to be esterified is ≥ 2, monocarboxylic acids such as benzoic acid and hexanecarboxylic acid can also be used.

[0037] Hydroxycarboxylic acids that can be used as reactants in the preparation of an aromatic polyester polyol with terminal hydroxyl groups include, for example, hydroxycaproic acid, hydroxybutyric acid, hydroxydecanoic acid, hydroxystearic acid, and the like. Suitable lactones are caprolactone, butyrolactone, and homologues. Caprolactone is preferred.

[0038] The polyester polyol a5) is preferably obtained from phthalic anhydride and diethylene glycol.

[0039] The polyester polyol a5) has a hydroxyl number of ≥ 600 mg KOH / g to ≤ 900 mg KOH / g and particularly preferably ≥ 750 mg KOH / g to ≤ 850 mg KOH / g. In the context of the present invention, hydroxyl numbers can generally be determined using DIN 53240. The average functionality of this polyester polyol a5) is advantageously ≥ 1.8 to ≤ 2.2. The weight-average molecular weight of the polyester polyols a5) is preferably in the range between 130 g / mol and 400 g / mol, particularly preferably in the range between 130 g / mol and 300 g / mol.

[0040] Furthermore, the isocyanate-reactive component A may contain low molecular weight isocyanate-reactive compounds A2), preferably di- or trifunctional amines and alcohols, preferably diols and / or triols with molar masses M n of less than 400 g / mol, in particular from 60 to 300 g / mol. Examples of compounds used include triethanolamine, diethylene glycol, ethylene glycol, and glycerol. If such low molecular weight isocyanate-reactive compounds are used to produce rigid polyurethane foams, e.g., as chain extenders and / or crosslinking agents, they are advantageously used in an amount of up to 5% by weight, based on the total weight of component A.

[0041] Compounds that accelerate the reaction of reactive hydrogen atoms, especially hydroxyl-containing compounds, with isocyanate component B, such as tertiary amines or metal salts, are used as catalyst A3) for the production of PUR / PIR foams. The catalyst components can be added to the reaction mixture or, in whole or in part, initially introduced into the isocyanate-reactive component A.

[0042] For example, tertiary amines such as triethylamine, tributylamine, dimethylbenzylamine, dicyclohexylmethylamine, dimethylcyclohexylamine, N, N,N',N'-tetramethyldiaminodiethyl ether, bis-(dimethylaminopropyl)-urea, N-methyl- or N-ethylmorpholine, N-cyclohexylmorpholine, N,N,N',N'-tetramethylethylenediamine, N,N,N,N-tetramethylbutanediamine, N, N, N, N-tetramethylhexane-1,6-diamine, pentamethyldiethylenetriamine, bis[2-(dimethylamino)ethyl] ether, dimethylpiperazine, N-dimethylaminoethylpiperidine, 1,2-dimethylimidazole, 1-azabicyclo-(3,3,0)-octane, 1,4-Diaza-bi-cyclo-(2,2,2)-octane (Dabco) and alkanolamine compounds such as triethanolamine, triisopropanolamine, N-methyl- and N-ethyldiethanolamine, dimethylaminoethanol, 2-(N,N-dimethylaminoethoxy)ethanol, N,N',N"-tris-(dialkylaminoalkyl)hexahydrotriazine, e.g. N,N',N"-tris-(dimethylaminopropyl)hexahydrotriazine and triethylenediamine.

[0043] Metal salts such as alkali metal or transition metal salts can also be used. Examples of transition metal salts used include zinc, bismuth, iron, lead, or preferably tin salts. Examples of transition metal salts used are iron(II) chloride, zinc chloride, lead octoate, tin dioctoate, tin diethylhexoate, and dibutyltin dilaurate. The transition metal salt is particularly preferably selected from at least one compound from the group consisting of tin dioctoate, tin diethylhexoate, and dibutyltin dilaurate. Examples of alkali metal salts are alkali metal alkoxides, such as sodium methylate and potassium isopropylate, alkali metal carboxylates, such as potassium acetate, and alkali metal salts of long-chain fatty acids having 10 to 20 carbon atoms and optionally pendant OH groups. One or more alkali metal carboxylates are preferably used as the alkali metal salt.

[0044] Other suitable catalysts A3) include: amidines, such as 2,3-dimethyl-3,4,5,6-tetrahydropyrimidine, tetraalkylammonium hydroxides, such as tetramethylammonium hydroxide, alkali metal hydroxides, such as sodium hydroxide, and tetraalkylammonium or phosphonium carboxylates. Mannich bases and phenol salts are also suitable catalysts. It is also possible to run the reactions without catalysis. In this case, the catalytic activity of amine-initiated polyols is utilized.

[0045] If a larger excess of polyisocyanate is used during foaming, other catalysts that can be considered for the trimerization reaction of the excess NCO groups are isocyanurate group-forming catalysts, such as ammonium ion or alkali metal salts, especially ammonium or alkali metal carboxylates, alone or in combination with tertiary amines. Isocyanurate formation leads to particularly flame-retardant PIR foams.

[0046] The above-mentioned catalysts can be used alone or in combination with each other.

[0047] If necessary, one or more additives can be used as component A4). Examples of component A4) are surfactants, foam stabilizers, cell regulators, flame retardants, fillers, dyes, pigments, hydrolysis inhibitors, and fungistatic and bacteriostatic substances.

[0048] Suitable surface-active substances include compounds that support the homogenization of the starting materials and may also be suitable for regulating the cell structure of the plastics. Examples include emulsifiers such as the sodium salts of castor oil sulfates or fatty acids, as well as salts of fatty acids with amines, e.g., diethylamine oleate, diethanolamine stearate, diethanolamine ricinoleate; salts of sulfonic acids, e.g., alkali or ammonium salts of dodecylbenzenesulfonic acid or dinaphthylmethanedisulfonic acid and ricinoleic acid; foam stabilizers such as siloxane-oxyalkylene copolymers and other organopolysiloxanes, ethoxylated alkylphenols, ethoxylated fatty alcohols, paraffin oils, castor oil or ricinoleic acid esters, Turkey red oil, and peanut oil; and cell regulators such as paraffins, fatty alcohols, and dimethylpolysiloxanes.The oligomeric acrylates described above with polyoxyalkylene and fluoroalkane residues as side groups are also suitable for improving the emulsifying effect, the cell structure and / or stabilization of the foam. Suitable fillers, in particular reinforcing fillers, include the conventional organic and inorganic fillers, reinforcing agents, weighting agents, agents for improving abrasion behavior in paints, coating materials, etc. Specific examples include: inorganic fillers such as silicate minerals, for example phyllosilicates such as antigorite, serpentine, sepiolite, hornblende, amphiboles, chrisotile, montmorillonite and talc, metal oxides such as kaolin, aluminum oxides, titanium oxides and iron oxides, metal salts such as chalk, huntite, barite and inorganic pigments such as magnetite, goethite, cadmium sulfide and zinc sulfide, as well as glass, among others.as well as natural and synthetic fibrous minerals such as wollastonite, metal and, in particular, glass fibers of various lengths, which may be sized if desired. Examples of organic fillers include carbon, melamine, rosin, cyclopentadienyl resins and graft polymers, as well as cellulose fibers, polyamide, polyacrylonitrile, polyurethane, and polyester fibers based on aromatic and / or aliphatic dicarboxylic acid esters, and carbon fibers.

[0049] The auxiliaries and additives preferably also include flame retardants such as phosphates, e.g. B. Triethyl phosphate (TEP), triphenyl phosphate (TPP), tricresyl phosphate, diphenyl cresyl phosphate (DPK), tert-butylphenyl diphenyl phosphate, resorcinyl diphenyl phosphate (also as oligomer) and bisphenol A bis(diphenyl phosphate) (also as oligomer), and phosphonates, e.g. diethyl ethyl phosphonate (DEEP), dimethyl propyl phosphonate (DMPP), diethanolaminomethylphosphonic acid diethyl ester, Veriquel ®< R100 or "E06-16" from ICL, and also mixed phosphonates such as ethyl butyl hydroxymethyl phosphonate and phosphinates such as 9,10-dihydro-9-oxa-10-phosphorylphenanthrene 10-oxide (DOPO), salts of diphenylphosphinous acid and salts of diethylphosphinous acid Et2PO2H (Exolit ®< OP 1235, Exolit ®< OP 935, Exolit ®< OP 935, Exolit ®< OP L 1030).Other suitable flame retardants include, for example, brominated esters, brominated ethers (Ixol), or brominated alcohols such as dibromoneopentyl alcohol, tribromoneopentyl alcohol, and tetrabromophthalate diol, as well as chlorinated phosphates such as tris(2-chloroethyl) phosphate, tris(2-chloropropyl) phosphate (TCPP), tris(1,3-dichloropropyl) phosphate, tris(2,3-dibromopropyl) phosphate, and tetrakis(2-chloroethyl)ethylene diphosphate, as well as commercially available halogen-containing flame retardant polyols. Diphenyl cresyl phosphate, triethyl phosphate, and bisphenol A bis(diphenyl phosphate) are preferred. It is particularly preferred that no halogen-containing flame retardant is used.

[0050] Component A contains > 0 to ≤ 1.5 wt.% water (A5). Higher water contents lead to embrittlement and / or poor adhesion of the foam.

[0051] The isocyanate-reactive component A is preferably limited essentially to the components A1) - A6) described above. "Essentially" in this context means that further components, e.g., technical impurities, other reactive or non-reactive compounds, solvents, or the like, are present in a maximum amount of up to 10 wt. %, preferably up to 5 wt. %, in particular up to 2 wt. %.

[0052] The invention also relates to a reaction mixture prepared from the isocyanate-reactive component A and an isocyanate component B. The index of the reaction mixture is preferably > 270; in a particularly preferred embodiment, the index is 290-440.

[0053] For the production of PUR / PIR rigid foams, the reaction mixture is stirred in the presence of CBlowing agents, in particular containing one or more compounds selected from the group consisting of halogen-free chemical blowing agents, halogen-free physical blowing agents and (hydro)fluorinated olefins.

[0054] The invention also relates to a process for reacting the isocyanate-reactive component according to the invention A with B an isocyanate component in the presence of C Blowing agent containing one or more compounds selected from the group consisting of halogen-free chemical blowing agents, halogen-free physical blowing agents and (hydro)fluorinated olefins, for PUR / PIR rigid foams.

[0055] As a suitable isocyanate component BFor example, polyisocyanates, i.e. isocyanates with an NCO functionality of at least 2, can be used. Examples of such suitable polyisocyanates are 1,4-butylene diisocyanate, 1,5-pentane diisocyanate, 1,6-hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), 2,2,4- and / or 2,4,4-trimethylhexamethylene diisocyanate, the isomeric bis(4,4'-isocyanatocyclohexyl)methanes or their mixtures of any isomer content, 1,4-cyclohexylene diisocyanate, 1,4-phenylene diisocyanate, 2,4- and / or 2,6-tolylene diisocyanate (TDI), 1,5-naphthylene diisocyanate, 2,2'- and / or 2,4'- and / or 4,4'-diphenylmethane diisocyanate (monomeric MDI) and / or higher homologues (oligomeric MDI), 1,3- and / or 1,4-bis-(2-isocyanatoprop-2-yl)benzene (TMXDI), 1,3-bis-(isocyanatomethyl)benzene (XDI), and alkyl 2,6-diisocyanatohexanoates (lysine diisocyanates) with C1 to C6 alkyl groups. Mixtures of oligomeric and optionally monomeric MDI are also called "polymeric MDI." The isocyanate component is preferred.B selected from at least one compound from the group consisting of polymeric MDI and TDI.

[0056] In addition to the polyisocyanates mentioned above, modified diisocyanates with uretdione, isocyanurate, urethane, carbodiimide, uretonimine, allophanate, biuret, amide, iminooxadiazinedione and / or oxadiazinetrione structure as well as unmodified polyisocyanate with more than 2 NCO groups per molecule, such as 4-isocyanatomethyl-1,8-octane diisocyanate (nonane triisocyanate) or triphenylmethane-4,4',4"-triisocyanate, can also be used proportionally.

[0057] Instead of or in addition to the above-mentioned polyisocyanates, suitable NCO prepolymers can also be used as isocyanate components B The prepolymers can be prepared by reacting one or more polyisocyanates with one or more polyols, corresponding to the polyols described under isocyanate-reactive components A.

[0058] The PUR / PIR foams according to the invention are produced by a single-stage process known to those skilled in the art, in which the reaction components are reacted with one another continuously or discontinuously and then, after discharge onto a conveyor belt or into suitable molds, are cured either manually or with the aid of mechanical equipment in a high-pressure or low-pressure process.

[0059] The blowing agent C can be added to one of the components A or B, especially A, or added during mixing. At least one compound selected from the group consisting of physical and chemical blowing agents is used as the blowing agent.

[0060] Physical blowing agents are, for example, low-boiling organic compounds such as hydrocarbons, ethers, ketones, carboxylic acid esters or carbonic acid esters. Organic compounds which are particularly suitable for the isocyanate component Bare inert and have boiling points below 100 °C, preferably below 50 °C at atmospheric pressure. These boiling points have the advantage that the organic compounds evaporate under the influence of the exothermic polyaddition reaction. Examples of such organic compounds that are preferably used are alkanes, such as heptane, hexane, n- and isopentane, preferably technical mixtures of n- and isopentanes, n- and isobutane and propane, cycloalkanes, such as cyclopentane and / or cyclohexane, ethers, such as furan, dimethyl ether and diethyl ether, ketones, such as acetone and methyl ethyl ketone, carboxylic acid alkyl esters, such as methyl formate, dimethyl oxalate and ethyl acetate and. The use of (hydro)fluorinated olefins, such as e.g. B. HFO 1233zd(E) (trans-1-chloro-3,3,3-trifluoro-1-propene) or HFO 1336mzz(Z) (cis-1,1,1,4,4,4-hexafluoro-2-butene) or additives such as FA 188 from 3M (1,1,1,2,3,4,5,5,5-nonafluoro-4-(trifluoromethyl)pent-2-ene).Mixtures of two or more of the above-mentioned organic compounds can also be used. The organic compounds can also be used in the form of an emulsion of small droplets.

[0061] Chemical blowing agents such as water, carboxylic acids, and mixtures thereof can also be used as blowing agent C. These react with isocyanate groups to form the blowing gas. For example, in the case of water, carbon dioxide is formed, and in the case of formic acid, carbon dioxide and carbon monoxide are formed. The preferred carboxylic acid is at least one compound selected from the group consisting of formic acid, acetic acid, oxalic acid, and ricinoleic acid. Water is particularly preferred as the chemical blowing agent.

[0062] In a preferred embodiment, a mixture of a physical and a chemical blowing agent is used. The proportion of water in the blowing agent mixture is in particular <10 wt.%, particularly preferably <5 wt.%, based on all blowing agents in the reaction mixture. The blowing agent preferably contains only enough water so that the mixture of components A-C contains a maximum of 1.5 wt.% water (based on the isocyanate-reactive component A).

[0063] The isocyanate index (also called index or isocyanate number) is the quotient of the actual amount of isocyanate groups used [mol] and the actual amount of isocyanate-reactive groups used [mol], multiplied by 100: Kennzahl = Mole Isocyanat − Gruppen / Mole Isocyanat − reaktive Gruppen * 100

[0064] In the process according to the invention, a characteristic number in a range of ≥ 180 is preferably used, in particular in a range of ≥ 270. The PIR structures lead to a higher flame retardancy of the foam itself. In a more preferred embodiment, the characteristic number of the reaction mixture is 240-440, in a very particularly preferred embodiment the characteristic number is 290-440.

[0065] The invention also relates to a PUR / PIR rigid foam produced by the process according to the invention. The PUR / PIR foams according to the invention are preferably used for the production of composite elements. Foaming typically takes place continuously or discontinuously against at least one cover layer.

[0066] The PUR / PIR rigid foam according to the invention has in particular a bulk density of ≤ 45 kg / m 3 < (determined according to DIN EN ISO 3386-1 (October 2015)).

[0067] A further subject of the invention is therefore the use of a PUR / PIR foam according to the invention as an insulating foam and / or as an adhesion promoter in composite elements, wherein the composite elements comprise a layer comprising a PUR / PIR foam according to the invention and at least one cover layer. The cover layer is at least partially contacted by a layer comprising the PUR / PIR foam according to the invention. Composite elements of the type of interest here are also referred to as sandwich elements or insulation panels and are generally used as building elements for soundproofing, insulation, for hall construction or for facade construction. The cover layers can be, for example, metal sheets, plastic sheets or up to 7 mm thick chipboard, depending on the intended use of the composite elements. The one or two cover layers can each be a flexible cover layer, e.g.It can be an aluminum foil, paper, multi-layer covering layers made of paper and aluminum, or mineral fleece, and / or a rigid covering layer, e.g., made of sheet steel or chipboard. In particular, at least one covering layer is made of metal (metal composite element).

[0068] The number-average molar mass Mn (also: the weight-average molecular weight) is determined in the context of this invention by gel permeation chromatography according to DIN 55672-1 of August 2007.

[0069] The "hydroxyl number" indicates the amount of potassium hydroxide in milligrams equivalent to the amount of acetic acid bound during the acetylation of one gram of substance. It is determined in the context of this invention according to the standard DIN 53240-1 (June 2013).

[0070] In the context of the present invention, "functionality" refers to the theoretical number-average functionality (number of functions in the molecule that are reactive towards isocyanates or polyols) calculated from the known starting materials and their quantitative ratios.

[0071] The NCO value (also: NCO content, isocyanate content) is determined using EN ISO 11909 (May 2007). Examples

[0072] The OH number (hydroxyl number) was determined according to DIN 53240-1 (June 2013). The acid number was determined according to DIN EN ISO 2114 (November 2006). The NCO value (also: NCO content, isocyanate content) was determined using EN ISO 11909 (May 2007). Production of metal composite elements:

[0073] The production of PUR / PIR composite elements based on the formulations described in the tables is carried out using a one-step process known to those skilled in the art. In this process, the reaction components are continuously reacted with one another and then, with the aid of mechanical equipment, cured at 60°C after being discharged onto a conveyor belt. Steel coils with a thickness of 0.45 mm from ArcelorMittal Construction were used as the top and bottom cover layers. The 2 m elements were then stored in a cooling gel for 24 hours. The formulations and results of the physical measurements on the resulting samples are shown in the tables. Knife test:

[0074] To assess the susceptibility of metal composite elements to cracking during processing in cold temperatures, a so-called knife test was conducted. The metal composite elements were stored in a cooling chamber for 24 hours at either 0, -10, or -20°C and immediately afterwards pierced with a knife in the center of the foam layer at several positions (close to the center and near the joint or nose). Panels tested at room temperature were stacked directly after being unstacked from the cooling rack. Panels in which cracks formed parallel to the production direction when the knife blade was slightly rotated or even when the blade itself was inserted were deemed to have failed. Loud cracking during piercing is considered an indication of existing stress and is also considered a failure criterion. If no cracking noises were noted and no longitudinal cracks formed, the test was declared passed. Raw materials used:

[0075] Polyol P1-a Aromatic polyester polyol (a1) produced by reacting phthalic anhydride, adipic acid, ethylene glycol and diethylene glycol with an OH number of 240 mg KOH / g from Covestro Deutschland AG Polyol P 1-b Aromatic polyester polyol (a1) based on recycled polyethylene terephthalate with an OH number of 230-240 mg KOH / g from Synthesia Technology Polyol P 2-a Aromatic polyester polyol (a2) produced by reacting trimethylolpropane, phthalic anhydride, soybean oil fatty acid and adipic acid with an OH number of 370 mg KOH / g from Covestro Deutschland AG Polyol P4-a Polyether polyol (a4) based on ortho-toluenediamine, ethylene oxide and propylene oxide with an OH number of 415 mg KOH / g and functionality of 4 from Covestro Deutschland AG Polyol P4-b Polyether polyol based on sucrose, propylene glycol and propylene oxide with an OH number of 450 mg KOH / g and a functionality of 4.6 from Covestro Deutschland AG Polyol P5-a Polyester polyol (a5) made from phthalic anhydride and diethylene glycol with an OH number of 795 mg KOH / g from Covestro Deutschland AG Polyol P3-a Polyether polyol (a3) ​​based on propylene glycol, ethylene oxide and propylene oxide in the ratio (29.8% / 70.2%) with an OH number of 28 mg KOH / g and a functionality of 2 from Covestro Deutschland AG Polyol P3-b Polyether polyol based on glycerol, propylene oxide and ethylene oxide in the ratio (72.7% / 27.3%) with an OH number of 37 mg KOH / g and functionality of 3 from Covestro Deutschland AG Polyol P3-c Polyether polyol based on propylene glycol, ethylene oxide and propylene oxide in the ratio (13.3% / 86.7%) with an OH number of 28 mg KOH / g and functionality of 2 from Covestro Deutschland AG Polyol P3-d Polyether polyol based on glycerol, monopropylene glycol, ethylene oxide and propylene oxide in the ratio (1% / 99%) with an OH number of 44.5 mg KOH / g and functionality of 2.98 from Covestro Deutschland AG castor oil castor oil TCPP Tris(1-chloro-2-propyl) phosphate from Lanxess GmbH TEP Triethyl phosphate from Lanxess GmbH TP Triphenyl phosphate from Lanxess GmbH Veriquel R100 Halogen-free, phosphorus-containing flame retardant with an OH number of 270 mg KOH / g from ICL Industrial Products Stabilizer B8443 Polyetherpolysiloxane copolymer from Evonik Desmodur ®< 44V70L polymeric polyisocyanate based on 4,4-diphenylmethane diisocyanate with an NCO content of approximately 31.5 wt.% Covestro Deutschland AG Additive CA Carbon dioxide-releasing additive based on monoisopropanolamine from Covestro Deutschland AG Desmorapid ®< DB Benzyldimethylamine from Covestro Deutschland AG, Leverkusen, Germany Desmorapid ®< 1792 Potassium acetate (potassium ethanoate according to IUPAC), 25 wt-% in diethylene glycol Desmorapid ®< 30HB 14 Potassium formate (potassium methanoate according to IUPAC) 36 wt-% in monoethylene glycol Composition of the polyol formulations and results of the knife tests:

[0076] Table 1: Knife test on panels aged for different lengths with an element thickness of 100 mm. Components Example 1* Example 2* Example 3* Example 4* Polyol P1-a [Tle] 66,5 66,5 66,5 66,5 Polyol P4-a [Tle] 5,2 5,2 5,2 5,2 TCPP [Tle] 20,8 20,8 20,8 20,8 TEP [Tle] 5,2 5,2 5,2 5,2 Polyol P5-a [Tle] 2,3 2,3 2,3 2,3 B8443 [Tle] 2,5 2,5 2,5 2,5 Additive CA [Tle] 1,5 Desmorapid DB [Tle] 1,5 1,0 2,5 Desmorapid 1792 [Tle] 4,1 4,6 Desmorapid 30HB14 [Tle] 2,9 2,2 44V70L [Tle] 228,0 197,0 195,0 190,0 n-pentane [Tle] 17,0 16,0 15,4 15,0 Index (100 NCO / OH) 344,0 344,0 345,0 348,0 Cracks @ -20°C, 48h Yes Yes Yes Yes Cracks @ -20°C, 4w Yes Yes Yes Yes Cracks @ -20°C, 8w no no no no

[0077] Table 1 summarizes the results of the knife test experiments at -20°C of metal panels with an element thickness of 100 mm, which were produced with a non-inventive formulation (without component a3) with different catalyst packages or catalyst ratios.

[0078] Panels based on a polyol formulation not according to the invention exhibited cracking in the foam when subjected to the knife test at a temperature of -20°C (@ -20°C) 48 hours after the production date. Panels stored at room temperature for four weeks (4w) and subsequently pierced with a knife at -20°C also exhibited the same damage pattern. However, no cracking was observed when the panels were stored for a further four weeks (a total of eight weeks (8w)) before the knife test. Table 2 Knife test experiments with 100mm panels. component Unit Example 5* Example 6 Example 7* Example 8* Example 9* Polyol P1-a [Tle] 66,5 56,5 56,5 56,5 56,5 Polyol P1-b [Tle] Polyol P4-a [Tle] 5,2 5,2 5,2 5,2 5,2 Polyol P3-a [Tle] 10,0 Polyol P3-b [Tle] 10,0 Polyol P3-c 10 Polyol P3-d 10,0 TCPP [Tle] 20,8 20,8 20,8 20,8 20,8 TEP [Tle] 5,2 5,2 5,2 5,2 5,2 Polyol P5-a [Tle] 2,3 2,3 2,3 2,3 2,3 B8443 [Tle] 3,0 3,0 3,0 3 3,0 Desmorapid DB [Tle] 1,5 0,8 0,5 1,2 1,5 Desmorapid 1792 [Tle] 4,1 3,2 3,0 3,3 3,6 44V70L [Tle] 185,0 165,0 165,0 167,4 170,4 n-pentane [Tle] 15,5 15,5 15,2 15,2 15,4 Index (100 NCO / OH) 322,4 326,6 327,7 330 330 Cracks / cracks @ -20°C* yes / yes no no no / yes yes / yes yes / yes Cracks / cracks @ -10°C* no / yes no no no no no no yes / yes Surface image top + + + + - Surface image underside + + + + - * Knife tests were conducted 3 weeks after element manufacture. Table 3 Investigation of surface defects in 100 mm panels. component Example 10 Example 11* Polyol P1-a [Tle] 56,5 56,5 Polyol P4-a [Tle] 5,2 5,2 Polyol P3-a [Tle] 10,0 Polyol P3-b [Tle] 10,0 TCPP [Tle] 20,8 20,8 TEP [Tle] 5,2 5,2 Polyol P5-a [Tle] 2,3 2,3 B8443 [Tle] 2,0 2,0 Desmorapid DB [Tle] 0,8 0,5 Desmorapid 1792 [Tle] 3,2 3,0 44V70L [Tle] 165,0 165,0 n-pentane [Tle] 15,5 15,2 Index (100 NCO / OH) 326,6 327,7 Surface image top + + Surface image underside + -

[0079] The results in Table 2 show that in panels with an element thickness of 100 mm, which were produced with a polyol formulation according to the invention and subjected to the knife test at -20°C within the first three weeks after production, no cracks developed at this temperature and no cracking noises were produced when the knife was inserted, which would indicate existing stresses in the panel. Furthermore, the elements containing polyols a3 with an EO / PO ratio according to the invention have better surface qualities than those with component a3 of a different composition (see Table 2 and Table 3). Furthermore, Table 4 shows that in panels based on non-inventive formulations with ≤5 parts by weight of a polyol a3 in the polyol formulation, cracking was observed in the knife test at -20°C. Table 4 Knife test experiments with 100mm panels at different proportions of polyol a3. Components Example 12* Example 13* Example 14* Example 15 Example 16 Example 17 Polyol P1-b [Tle] 89,2 89,5 68,8 74,00 77,00 67,00 Polyol P1-a [Tle] 10,00 Polyol P2-a [Tle] 2,00 2,00 Polyol P4-b [Tle] 10,0 Polyol P4-a [Tle] 5,2 Polyol P3-a [Tle] 0,0 0,0 5,0 10,00 10,00 10,00 castor oil [Tle] 5,00 TEP [Tle] 10,0 10,0 10,0 10,00 10,00 10,00 Polyol P5-a [Tle] 0,5 0,5 0,5 0,5 Water [Tle] 0,8 0,5 0,5 0,5 0,5 0,5 B8443 [Tle] 3,0 3,0 3,0 2,5 2,5 2,5 Desmorapid DB [Tle] 1,0 1,0 1,2 1,4 1,4 1,4 Desmorapid 1792 [Tle] 3,8 3,5 3,4 2,9 2,7 2,7 44V70L [Tle] 226,0 210,0 240,0 201 205 205 n-pentane [Tle] 14,2 14,5 16,7 14,4 15 14,6 Index (100 NCO / OH) 319,0 320,0 331,0 334 335 335 Cracks / cracks @ -20°C* yes / yes yes / yes yes / yes no no no no no no *Knife tests were conducted 3 weeks after the elements were manufactured.

Claims

1. Isocyanate-reactive component A) containing the following components: A1) a polyol formulation comprising 50-80% by weight of a polyol component a1) consisting of one or more polyols selected from polyester polyols, polycarbonate polyols or polyether ester polyols having a hydroxyl number of 100 to 300 mg KOH / g and an average functionality of 1.5 to 2.5, wherein the polyol component a1) comprises at least one aromatic or aromatic / aliphatic polyester polyol or polyether ester polyol, 0-5% by weight of a polyol component a2) consisting of one or more polyols selected from polyester polyols and polyether ester polyols having a hydroxyl number of 320 to 450 mg KOH / g and an average functionality of 3 to 4.5, wherein the polyol component a2) comprises at least one aromatic or an aromatic / aliphatic polyester polyol or polyether ester polyol, 8.0-12.0% by weight of a polyol component a3) consisting of one or more polyols selected from polyether polyols having an OH number of 10 to 80 mg KOH / g and an average functionality of ≥ 2.0 to ≤ 3.0 produced by alkoxylation of a suitable starter component with a mixture of ethylene oxide (EO) and propylene oxide (PO) having an EO content of 15-70% by weight based on the total amount of EO and PO, 0.0-7.5% by weight of a polyol component a4) consisting of one or more polyols selected from polyether polyols having an OH number in the range of 350-500 mg KOH / g produced by alkoxylation of an aromatic amine with at least one alkylene oxide, 0.0-3.0% by weight of a polyol component a5) consisting of one or more polyols selected from polyester polyols having an OH number in the range of 600-900 mg KOH / g, in particular of 750-850 mg KOH / g; A2) 0-5% by weight of low molecular weight isocyanate-reactive compounds and A3) optionally catalysts, A4) optionally auxiliary and additive substances, A5) 0-1.5% by weight of water and A6) 0-7.5% by weight (especially preferably 0-5% by weight) of castor oil, wherein all percentages by weight are in each case based on the total weight of A.

2. Isocyanate-reactive component A) according to Claim 1, wherein more than 50% by weight of component a1), especially more than 80% by weight, are aromatic and / or aromatic / aliphatic polyester polyols and / or polyether ester polyols.

3. Isocyanate-reactive component A) according to Claim 1 or 2, wherein a mixture of ethylene oxide and propylene oxide having an ethylene oxide content of 15-50% by weight is used for alkoxylation of the polyether polyols in component a3).

4. Isocyanate-reactive component A) according to any of the preceding claims, wherein the polyether polyols of component a4) are started on the basis of tolylenediamine, diaminodiphenylmethane and / or polymethylene-polyphenylene-polyamine.

5. Isocyanate-reactive component according to any of the preceding claims, wherein the polyol component a5) employed is a polyester polyol obtainable from phthalic anhydride and diethylene glycol.

6. Isocyanate-reactive component according to any of the preceding claims containing > 0% to ≤ 1.5% by weight of water (A5).

7. Reaction mixture consisting of an isocyanate-reactive component A according to any of Claims 1 to 6 and an isocyanate component B, wherein the reaction mixture preferably has an index > 270, in a very particularly preferred embodiment 290 - 440.

8. Process for reacting a reaction mixture of an isocyanate-reactive component A according to any of Claims 1-6 with B an isocyanate component in the presence of C blowing agent containing one or more compounds selected from the group consisting of halogen-free chemical blowing agents, halogen-free physical blowing agents and (hydro)fluorinated olefins.

9. Process according to Claim 8, wherein the reaction mixture has an isocyanate index of ≥ 180, preferably ≥ 270, in particular 290-440.

10. Production of rigid PUR / PIR foams comprising a process according to any of Claims 8 or 9.

11. Rigid PUR / PIR foam obtainable by a process according to Claim 8, 9 or 10, in particular having a bulk density of ≤ 45 kg / m3.

12. Use of a rigid PUR / PIR foam according to Claim 11 as an insulation foam and / or as an adhesion promoter in composite elements, wherein the composite elements comprise a layer comprising the rigid PUR / PIR foam, and at least one outer layer.

13. Composite elements which have a core of a rigid PUR / PIR foam produced using a process for reacting a reaction mixture of an isocyanate-reactive component A with B an isocyanate component in the presence of C blowing agent containing one or more compounds selected from the group consisting of halogen-free chemical blowing agents, halogen-free physical blowing agents and (hydro)fluorinated olefins, characterized in that the isocyanate-reactive component A) contains the following components: A1) a polyol formulation comprising 50-80% by weight of a polyol component a1) consisting of one or more polyols selected from polyester polyols, polycarbonate polyols or polyether ester polyols having a hydroxyl number of 100 to 300 mg KOH / g and an average functionality of 1.5 to 2.5, wherein the polyol component a1) comprises at least one aromatic or aromatic / aliphatic polyester polyol or polyether ester polyol, 0-5% by weight of a polyol component a2) consisting of one or more polyols selected from polyester polyols and polyether ester polyols having a hydroxyl number of 320 to 450 mg KOH / g and an average functionality of 3 to 4.5, wherein the polyol component a2) comprises at least one aromatic or an aromatic / aliphatic polyester polyol or polyether ester polyol, 7.0-15.0% by weight of a polyol component a3) consisting of one or more polyols selected from polyether polyols having an OH number of 10 to 80 mg KOH / g and an average functionality of ≥ 2.0 to ≤ 3.0 produced by alkoxylation of a suitable starter component with a mixture of ethylene oxide (EO) and propylene oxide (PO) having an EO content of 15-70% by weight based on the total amount of EO and PO, 0.0-7.5% by weight of a polyol component a4) consisting of one or more polyols selected from polyether polyols having an OH number in the range of 350-500 mg KOH / g produced by alkoxylation of an aromatic amine with at least one alkylene oxide, 0.0-3.0% by weight of a polyol component a5) consisting of one or more polyols selected from polyester polyols having an OH number in the range of 600-900 mg KOH / g, in particular of 750-850 mg KOH / g; A2) 0-5% by weight of low molecular weight isocyanate-reactive compounds and A3) optionally catalysts, A4) optionally auxiliary and additive substances, A5) 0-1.5% by weight of water and A6) 0-7.5% by weight (especially preferably 0-5% by weight) of castor oil, wherein all percentages by weight are in each case based on the total weight of A.

14. Composite elements according to Claim 13 containing a core of a rigid PUR / PIR foam and one or two outer layers.

15. Composite elements according to Claim 14, wherein at least one of the two outer layers is made of metal.