Rigid polyisocyanurate foams obtainable using polyethylene terephthalate-based esters

Abstract

The present invention relates to a process for producing rigid polyisocyanurate foam by mixing (a) aromatic polyisocyanate, (b) compounds having at least two hydrogen atoms reactive with isocyanate groups, including at least one polyetherester polyol (b1) having a mean functionality of ≥ 1.7 and ≤ 2.8 and an OH number of ≥ 170 and ≤ 270 mg KOH / g and at least one polyester polyol (b2) having a functionality of ≥ 1.7 and ≤ 2.7, an OH number of ≥ 170 and ≤ 280 mg KOH / g and a free monoethylene glycol content of < 1.3% by weight, (c) catalyst, (d) blowing agent, (e) flame retardant and (f) optionally auxiliaries and adjuvants to form a reaction mixture and causing this mixture to react fully to form the rigid polyisocyanurate foam, where polyetherester polyol (b1) is obtainable by esterification of: (b1.1) a dicarboxylic acid composition, including aromatic dicarboxylic acids, (b1.2) one or more hydrophobic compounds having at least one hydroxyl and / or carboxyl group, or derivatives thereof, (b1.3) one or more diols having 2 to 6 carbon atoms, (b1.4) a polyether polyol prepared by alkoxylating a starter or a starter mixture having a mean functionality ≥ 2 and ≤ 4, where polyester polyol (b2) is prepared using polyethylene terephthalate in a fraction, based on the total amount of all input components for the preparation of polyester polyol (b2), > 25% by weight, with the mass ratio of polyetherester polyol (b1) to polyester polyol (b2) being ≥ 0.3 and ≤ 3.0 and the sum total of the mass fractions of component (b1) and component (b2), based on component (b), being > 80% by weight, the mass fraction of free monoethylene glycol, based on the sum total of components B, C, E and F, being ≤ 1.4% by weight, and the mixing to form the reaction mixture taking place at an isocyanate index of at least 180. The present invention further relates to a polyol component for producing a rigid polyisocyanurate foam of the invention and to a rigid polyisocyanurate foam, more particularly a sandwich element comprising rigid polyisocyanurate foam, obtainable by a process of the invention.

Description

[0001] Polyisocyanurate rigid foams available by using polyethylene terephthalate based esters

[0002] The present invention relates to a process for the production of rigid polyisocyanurate foam, in which (a) aromatic polyisocyanate, (b) compounds having at least two hydrogen atoms reactive with isocyanate groups, containing at least one polyetherester polyol (b1) and at least one polyester polyol (b2), (c) catalyst, (d) blowing agent, (e) flame retardant and (f) optionally auxiliaries and additives, are mixed to form a reaction mixture and allowed to react to give rigid polyisocyanurate foam, wherein polyetherester polyol (b1) is obtainable by esterification of: (b1.1) 10 to 50 mol% of a dicarboxylic acid composition containing aromatic dicarboxylic acids, (b1.2) 2 to 20 mol% of one or more hydrophobic compounds having at least one hydroxyl and / or carboxyl group or derivatives thereof, (b1.3) 10 to 70 mol% one or more diols with 2 to 6 C atoms, (b1.4) 15 to 50 mol% of a polyether polyol, prepared by alkoxylation of a starter or a starter mixture having an average functionality of > 2 and < 4, in each case based on the total amount of components (b1.1) to (b1.4), and the polyether ester polyol (b1) has an average functionality of > 1.7 and < 2.8 and an OH number of > 150 and < 300 mg KOH / g, and polyester polyol (b2) has an average functionality of > 1.7 and < 2.7, an OH number of > 170 and < 280 mg KOH / g and a free mono-ethylene glycol content of < 1.3 wt.%, wherein polyethylene terephthalate is used to produce polyester polyol (b2), the proportion of which, based on the total amount of all components used to produce polyester polyol (b2), is > 25 wt.%, wherein the mass ratio of polyether ester polyol (b1) to polyester polyol (b2) > 0.3 and < 3.0 and the sum of the mass fractions of component (b1) and component (b2), based on component (b) > 80 wt.-%, the mass fraction of free monoethylene glycol which is added to the reaction mixture, based on the total weight of components (b) (c) (e) and (f), is < 1.4 wt.%, and the mixing to form the reaction mixture takes place at an isocyanate index of at least 180. Furthermore, the present invention relates to a polyol component for producing a rigid polyisocyanurate foam according to the invention and to a rigid polyisocyanurate foam, in particular a sandwich element containing rigid polyisocyanurate foam, obtainable by a process according to the invention.

[0003] The production of polyisocyanurate rigid foams by reacting polyisocyanates with higher molecular weight compounds having at least two reactive hydrogen atoms, in particular with polyether polyols from alkylene oxide polymerization or polyester polyols from the polycondensation of alcohols with dicarboxylic acids in the presence of polyurethane catalysts, chain extenders and / or crosslinking agents, blowing agents and other auxiliaries and additives is known and is described in numerous patent and literature publications.

[0004] Rigid polyisocyanurate foams are frequently used as thermal insulation materials. These foams are used, for example, in the manufacture of refrigeration units, containers, or flat composite elements with at least one cover layer. These require rigid polyisocyanurate foams with high mechanical strength, particularly compressive strength, low thermal conductivity, low post-expansion behavior, high fire resistance, and a surface that is as free from defects as possible.

[0005] In addition, attempts are being made to replace crude oil-based starting materials for the production of polyurethanes with recycled raw materials. One approach is to replace conventional polyesters with esters obtained from the recycling of polyethylene terephthalate. This is described, for example, in Damayanti; Wu H.-S., "Strategy Possibility Routes of Recycled PET," Polymers 2021, 13, 1475.

[0006] A disadvantage of using polyesters obtained from degradation products of polyethylene terephthalate, for example from the glycolysis of polyethylene terephthalate, is that these esters have negative properties on the mechanical strength of the polyisocyanurate rigid foams, for example on the compressive strength, the post-expansion behavior and the surface quality, especially when the foaming of the reaction mixture between two cover layers takes place in a continuous double-belt process.

[0007] The object of the present invention was therefore to provide a rigid polyisocyanurate foam, wherein at least a portion of the isocyanate-reactive component used is obtained by transesterification of polyethylene terephthalate with glycols, wherein the rigid polyisocyanurate foams exhibit high mechanical strength, in particular high compressive strength, low thermal conductivity, low post-expansion behavior, high fire resistance, and a surface that is as defect-free as possible. Furthermore, the object of the present invention was to provide a process for producing such rigid polyisocyanurate foams, in which the starting components, in particular the polyol component, have a low viscosity and can be easily mixed with the other components for producing rigid polyisocyanurate foams.

[0008] This object is achieved by a polyisocyanurate rigid foam obtained by a process in which (a) aromatic polyisocyanate, (b) compounds having at least two hydrogen atoms reactive with isocyanate groups, containing at least one polyetherester polyol (b1) and at least one polyester polyol (b2), (c) catalyst, (d) blowing agent, (e) flame retardant and (f) optionally auxiliaries and additives, are mixed to form a reaction mixture and allowed to react to give the polyisocyanurate rigid foam, wherein polyetherester polyol (b1) is obtainable by esterification of: (b1.1) 10 to 50 mol% of a dicarboxylic acid composition containing aromatic dicarboxylic acids, (b1.2) 2 to 20 mol% of one or more hydrophobic compounds having at least one hydroxyl and / or carboxyl group or derivatives thereof, (b1.3) 10 to 70 mol% of a or more diols with 2 to 6 C atoms, (b1.4) 15 to 50 mol% of a polyether polyol, prepared by alkoxylation of a starter or a starter mixture having an average functionality of > 2 and < 4, in each case based on the total amount of components (b1.1) to (b1.4), and the polyether ester polyol (b1) has an average functionality of > 1.7 and < 2.8 and an OH number of > 150 and < 300 mg KOH / g, and polyester polyol (b2) has an average functionality of > 1.7 and < 2.7, an OH number of > 170 and < 280 mg KOH / g and a free mono-ethylene glycol content of < 1.3 wt.%, wherein polyethylene terephthalate is used to produce polyester polyol (b2), the proportion of which, based on the total amount of all components used to produce polyester polyol (b2), is > 25 wt.%, wherein the mass ratio of polyether ester polyol (b1) to polyester polyol (b2) > 0.3 and < 3.0 and the sum of the mass fractions of component (b1) and component (b2), based on component (b) > 80 wt.-%, the mass fraction of free mono-ethylene glycol which is added to the reaction mixture, based on the total weight of components (b), (c), (e) and (f), is < 1.4 wt.%, and the mixing to form the reaction mixture takes place at an isocyanate index of at least 180. Furthermore, the present invention relates to a polyol component for producing a rigid polyisocyanurate foam according to the invention and to a rigid polyisocyanurate foam, in particular a sandwich element containing rigid polyisocyanurate foam, obtainable by a process according to the invention.

[0009] For the purposes of the invention, rigid polyisocyanurate foam is understood to mean a foamed polyisocyanurate, preferably a foam according to DIN 7726, which has a compressive strength according to DIN 53 421 / DIN EN ISO 604 of greater than or equal to 80 kPa, preferably greater than or equal to 150 kPa, particularly preferably greater than or equal to 180 kPa. Furthermore, the rigid polyisocyanurate foam according to DIN ISO 4590 has a closed-cell content of greater than 50%, preferably greater than 85%, and particularly preferably greater than 90%. A rigid polyisocyanurate foam contains both urethane and isocyanurate bonds.

[0010] Suitable polyisocyanates (a) include the known aliphatic, cycloaliphatic, araliphatic, and preferably aromatic polyfunctional isocyanates. Such polyfunctional isocyanates are known per se or can be prepared by known methods. The polyfunctional isocyanates can, in particular, also be used as mixtures, so that component (a) in this case contains various polyfunctional isocyanates. Polyfunctional isocyanates suitable as polyisocyanates have two (hereinafter referred to as diisocyanates) or more than two isocyanate groups per molecule.

[0011] Specifically, the following may be mentioned: alkylene diisocyanates having 4 to 12 carbon atoms in the alkylene radical, such as 1,12-dodecanediisocyanate, 2-ethyltetramethylene-1,4-diisocyanate, 2-methylpentamethylene-1,5-diisocyanate, tetramethylene-1,4-diisocyanate, and preferably hexamethylene-1,6-diisocyanate;cycloaliphatic diisocyanates such as cyclohexane-1,3- and 1,4-diisocyanate and any mixtures of these isomers, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (IPDI), 2,4- and 2,6-hexahydrotoluene diisocyanate and the corresponding isomer mixtures, 4,4'-, 2,2'- and 2,4'-dicyclohexylmethane diisocyanate and the corresponding isomer mixtures, and preferably aromatic polyisocyanates such as 2,4- and 2,6-toluene diisocyanate and the corresponding isomer mixtures (TDI), 4,4'-, 2,4'- 2,2'- diphenylmethane diisocyanate and higher-nuclear homologues of diphenylmethane diisocyanate and the corresponding mixtures (MDI), mixtures of 4,4'-, 2,4'- and 2,2'- Diphenylmethane diisocyanates and polyphenylpolymethylene polyisocyanates (polymer MDI) and mixtures of MDI and TDI.;

[0012] Particularly suitable are 2,2'-, 2,4'- and / or 4,4'-diphenylmethane diisocyanate, as well as higher-nuclear homologues of diphenylmethane diisocyanate (MDI), 1,5-naphthylene diisocyanate (NDI), 2,4- and / or 2,6-tolylene diisocyanate (TDI), 3,3'-dimethyldiphenyl diisocyanate, 1,2-diphenylethane diisocyanate and / or p-phenylene diisocyanate (PPDI), tri-, tetra-, penta-, hexa-, hepta- and / or octamethylene diisocyanate, 2-methylpentamethylene-1,5-diisocyanate, 2-ethylbutylene-1,4-diisocyanate, pentamethylene-1,5-diisocyanate, butylene-1,4-diisocyanate, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane (Isophorone diisocyanate, IPDI), 1,4- and / or 1,3-bis(isocyanatomethyl)cyclohexane (HXDI), 1,4-cyclohexane diisocyanate, 1-methyl-2,4- and / or -2,6-cyclohexane diisocyanate and 4,4'-, 2,4'- and / or 2,2'-dicyclohexylmethane diisocyanate.

[0013] Modified polyisocyanates, ie products obtained by chemical conversion of organic polyisocyanates and containing at least two reactive isocyanate groups per molecule, are also frequently used.Particularly suitable polyisocyanates are those containing ester, urea, biuret, allophanate, carbodiimide, isocyanurate, uretdione, carbamate and / or urethane groups, frequently also together with unreacted polyisocyanates. The polyisocyanates of component (a) particularly preferably contain 2,2'-MDI or 2,4'-MDI or 4,4'-MDI (also referred to as monomeric diphenylmethane or MMDI) or oligomeric MDI, which consists of higher-nuclear homologues of MDI, which have at least 3 aromatic nuclei and a functionality of at least 3, or mixtures of at least two of these isomers, optionally also mixtures of at least one isomer of MDI with at least one higher-nuclear homologue of MDI, or crude MDI, which is obtained during the production of MDI, or preferably mixtures of at least one higher-nuclear homologue of MDI and at least one of the aforementioned low-molecular MDI derivatives. 2,2'-MDI, 2,4'-MDI or 4,4'-MDI (also called polymeric MDI).Typically, the isomers and homologues of MDI are obtained by distillation of crude MDI.

[0014] Polymeric MDI is particularly preferably used as the isocyanate (a). The average functionality of a polymeric MDI preferably ranges from 2.2 to 4, particularly preferably from 2.4 to 3.8, and especially from 2.6 to 3.0. Polymeric MDI is marketed, for example, by BASF Polyurethanes GmbH under the names Lupranat® M20 or Lupranat® M50.

[0015] Component (a) preferably contains at least 70, more preferably at least 90, and especially 100 wt. %, based on the total weight of component (a), of one or more isocyanates selected from the group consisting of 2,2'-MDI, 2,4'-MDI, 4,4'-MDI, and oligomers of MDI. The content of oligomeric MDI is preferably at least 20 wt. %, more preferably greater than 30 to less than 80 wt. %, based on the total weight of component (a).

[0016] The viscosity of the component (a) used can vary within a wide range. Component (a) preferably has a viscosity of 100 to 3000 mPa*s, more preferably 100 to 1000 mPa*s, especially preferably 100 to 600 mPa*s, more specifically 200 to 600 mPa*s, and especially 400 to 600 mPa*s at 25°C.

[0017] The isocyanate-reactive compounds (b) contain at least one polyetherester polyol (b1) and at least one polyester polyol (b2). The weight fraction of component (b1) and component (b2) is > 80 wt. %, preferably 85 to 100 wt. %, more preferably 90 to 100 wt. %, and in particular 95 to 98 wt. %, based in each case on the total weight of component (b), wherein the mass ratio of polyetherester polyol (b1) to polyester polyol (b2) is > 0.3 and < 3.0, preferably > 0.4 and < 2.5, particularly preferably > 0.5 and < 2.0, and in particular > 0.7 and < 1.5. According to the invention, component (b) contains at least one aromatic polyetherester polyol (b1) preparable by esterification of (b1.1) 10 to 50 mol% of a dicarboxylic acid composition containing aromatic dicarboxylic acids, (b1.2) 2 to 20 mol% of one or more hydrophobic compounds having at least one hydroxyl and / or carboxyl group or derivatives thereof (b1.3) 10 to 70 mol% of one or more aliphatic or cycloaliphatic diols having 2 to 6 carbon atoms or alkoxylates thereof; (b1.4) 15 to 50 mol% of a polyether polyol prepared by alkoxylation of a starter or a starter mixture with an average functionality of > 2 and < 4, each based on the total amount of components (b1.1) to (b1.4). Preferably, components b1.1) to b1.4) add up to 100 mol%.

[0018] The polyetherester polyol (b1) has an average functionality of > 1.7 and < 2.8, preferably > 1.9 and < 2.6 and particularly preferably > 2.0 and < 2.5 and in particular 2.5 and an OH number of > 150 and < 300 mg KOH / g, preferably > 170 and < 280 and particularly preferably > 190 and < 260 mg KOH / g.

[0019] The dicarboxylic acid composition (b1.1) contains dicarboxylic acids and / or their derivatives, which can typically be used to produce esters. Preferably, the dicarboxylic acid composition (b1.1) contains at least one compound selected from the group consisting of terephthalic acid, dimethyl terephthalate (DMT), polyethylene terephthalate (PET), phthalic acid, phthalic anhydride (PSA), and isophthalic acid. Component (b1.1) particularly preferably contains phthalic anhydride, phthalic acid, terephthalic acid, and in particular phthalic anhydride or terephthalic acid, specifically terephthalic acid. In general, component (b1.1) can also contain aliphatic dicarboxylic acids or aliphatic dicarboxylic acid derivatives. If aliphatic dicarboxylic acids are used, they are generally present in an amount of 0.5 - 30 mol%, preferably 0.5 to 10 mol%, based in each case on component (b1 .1).Adipic acid or dicarboxylic acid mixtures of succinic, glutaric, and adipic acid are preferably used as aliphatic dicarboxylic acids. The dicarboxylic acid composition (b1.1) preferably contains no aliphatic dicarboxylic acids or derivatives thereof and thus consists of 100 mol% of one or more aromatic dicarboxylic acids or derivatives thereof. Most preferably, the dicarboxylic acid composition (b1.1) has a terephthalic acid content, based on the total weight of component (b1.1), of >80 wt. %, more preferably >90 wt. %, and consists in particular of terephthalic acid. In general, component (b1.1) is used in amounts of 10 to 50 mol%, preferably in amounts of 20 to 45 mol%, based on the components (b1.1), (b1.2), (b1.3) and (b1.4) used to prepare the aromatic polyetherester polyol (b1).

[0020] To prepare the aromatic polyetherester polyol (b1), one or more hydrophobic compounds having at least one hydroxyl and / or carboxyl group or derivatives thereof (b1.2) are also used. For the purposes of the present invention, hydrophobic compounds having at least one hydroxyl and / or carboxyl group or derivatives thereof (b1.2) are compounds having aliphatic hydrophobic groups. For the purposes of the present invention, an aliphatic hydrophobic group is understood to mean an aliphatic hydrocarbon group having preferably more than 6, particularly preferably more than 8 and fewer than 100, and in particular at least 10 and at most 50 directly adjacent carbon atoms. The adjacent carbon atoms can be linked by carbon-carbon single bonds or carbon-carbon double bonds.The C atoms of the hydrophobic group are directly bonded to each other and not interrupted by heteroatoms, for example. Hydrogen atoms of hydrocarbons, however, can be substituted, for example, by halogen atoms, OH groups, or carboxylic acid groups.

[0021] The compounds (b1.2) are preferably flowable substances at a temperature of 20 °C and an ambient pressure of 1 bar. Examples of compounds (1.2) are carboxylic acid esters, such as lower alkanol esters of carboxylic acids, for example fatty acids or fatty acid derivatives, such as fatty acid ethyl esters or, preferably, fatty acid methyl esters.

[0022] The fatty acids and / or fatty acid derivatives can be of either biological or petrochemical origin. Examples of fatty acids are caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, myristoleic acid, palmitic acid, palmitoleic acid, stearic acid, oleic acid, vaccenic acid, petroselinic acid, gadoleic acid, erucic acid, nervonic acid, linoleic acid, linolenic acid, stearidonic acid, arachidonic acid, timnodonic acid, clupanodonic acid, cervonic acid, ricinoleic acid, and mixtures thereof. Examples of fatty acid derivatives are glycerol esters of fatty acids such as castor oil, grape seed 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 oil, avocado oil, sea buckthorn oil, sesame oil, hemp oil, hazelnut oil, primrose oil, wild rose oil, thistle oil, walnut oil.Further examples of fatty acid derivatives are hydroxyl-modified fats or fatty acids, hydrogenated fats or fatty acids, epoxidized fats or fatty acids, alkyl branched fats or fatty acids, fatty acid amides, animal tallow such as beef tallow, alkyl or especially methyl esters of fatty acids such as biodiesel.

[0023] In general, component (b1.2) is used in amounts of 2 to 20 mol%, preferably in amounts of 5 to 15 mol%, particularly preferably in amounts of 7 to 12 mol%, based on all components (b1.1) to (b1.4) used to prepare the aromatic polyetherester polyol (b1).

[0024] In a particularly preferred embodiment of the present invention, the fatty acid or fatty acid derivative (b1.2) is oleic acid, biodiesel, soybean oil, rapeseed oil, or tallow, in particular oleic acid or biodiesel, especially oleic acid, and is used in an amount of greater than 5 mol%, particularly preferably greater than 8 mol%. The fatty acid or fatty acid derivative improves, among other things, the blowing agent solubility in the production of rigid polyisocyanurate foams.

[0025] As component (b1.3), one or more aliphatic or cycloaliphatic diols, preferably having 2 to 6 carbon atoms, or their alkoxylates are used. Component (b1.3) preferably contains at least one compound from the group consisting of monoethylene glycol, diethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2-methyl-1,3-propanediol, and 3-methyl-1,5-pentanediol, and alkoxylates thereof. The aliphatic diol (b1.3) is particularly preferably monoethylene glycol or diethylene glycol, especially diethylene glycol. Component (b1.3) is preferably used in amounts of 10 to 70 mol%, particularly preferably in amounts of 20 to 65 mol%, and in particular in amounts of 30 to 60 mol%, in each case based on all components used for preparing the aromatic polyetherester polyol (b1).

[0026] The polyether polyol (b1.4) is obtained by alkoxylation of a starter or a starter mixture having an average functionality of > 2 and < 4 and in particular trifunctional starter molecules, preferably glycerol. Ethylene oxide and / or propylene oxide can preferably be used as the alkylene oxide. Preferably, at least 80% by weight, particularly preferably exclusively ethylene oxide, is used as the alkylene oxide. The hydroxyl number of the polyether polyol (b1.4) is preferably greater than 300 mg KOH / g, particularly preferably greater than 400 to less than 800 mg KOH / g, and in particular greater than 450 to less than 600 mg KOH / g. In a particularly preferred embodiment, the aromatic polyether ester polyol (b1) has an OH number of 190 to 260 mg KOH / g and a functionality of 1.7 to 2.5.

[0027] To prepare the aromatic polyetherester polyol (b1), the dicarboxylic acids (b1.1), the at least one hydrophobic compound having at least one hydroxyl and / or carboxyl group or derivatives thereof (b1.2), the aliphatic or cycloaliphatic diols having 2 to 18 C atoms or alkoxylates thereof (b1.3) and the higher-functionality polyols (b1.4) can be polycondensed catalyst-free or preferably in the presence of esterification catalysts, advantageously in an atmosphere of inert gas such as nitrogen in the melt at temperatures of 150 to 280 °C, preferably 180 to 260 °C, optionally under reduced pressure to the desired acid number, which is advantageously less than 10 and particularly preferably less than 2.According to a preferred embodiment, the esterification mixture is polycondensed at the above-mentioned temperatures up to an acid number of 80 to 20, preferably 40 to 20, under atmospheric pressure and then under a pressure of less than 500 mbar, preferably 40 to 400 mbar. Suitable esterification catalysts include, 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, for azeotropic distillation of the condensation water.

[0028] The polyester polyol (b2) has a functionality of > 1.7 and < 2.7, preferably > 1.9 and < 2.6, particularly preferably > 2.0 and < 2.4 and in particular 2.0 and an OH number of > 170 and < 280 mg KOH / g, preferably > 180 and < 260 mg KOH / g and in particular > 190 and < 250 mg KOH / g, wherein polyethylene terephthalate is used to produce polyester polyol (b2), the proportion of which, based on the total amount of all components used to produce polyester polyol (b2), is > 25% by weight, preferably > 28% by weight, particularly preferably > 35% by weight and in particular > 40% by weight. It is essential to the invention that the content of free monoethylene glycol is less than 1.3 wt.%, preferably less than 1.2 and particularly preferably less than 1.1 wt.%, in each case based on the total weight of the polyesterol (b2).

[0029] Suitable polyester polyols (b2) can be obtained by reacting polycarboxylic acids, in particular dicarboxylic acids, and polyhydric alcohols with the addition of polyethylene terephthalate, the alcohol component being used in excess. Suitable polycarboxylic acids include aliphatic polycarboxylic acids, aromatic polycarboxylic acids, or mixtures thereof, as well as their derivatives. The functionalities of the starting substances are selected such that a polyester polyol with the required functionality is obtained. Suitable carboxylic acid derivatives include all carboxylic acid derivatives commonly used for the production of polyester polyols suitable for use in the production of polyurethanes. These include, for example, polycarboxylic acid esters of alcohols having 1 to 4 carbon atoms or polycarboxylic acid anhydrides.Furthermore, polycarboxylic acids also include functionalized carboxylic acids, such as hydroxycarboxylic acids.

[0030] Preferably, at least one aliphatic dicarboxylic acid is used to produce the polyester (b2). Examples include adipic acid, glutaric acid, succinic acid, fumaric acid, malonic acid, maleic acid, oxalic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, or derivatives thereof. Furthermore, an aliphatic polycarboxylic acid can also be used. Examples of derivatives of aliphatic polycarboxylic acids are dimethyl adipate and diethyl adipate. Particular preference is given to dicarboxylic acids having 4 to 6 carbon atoms, such as adipic acid, glutaric acid, or succinic acid or derivatives thereof, especially adipic acid or derivatives of adipic acid. The proportion of aliphatic dicarboxylic acids, based on all components used to produce the polyester polyol (b2), is preferably > 10% by weight, preferably 12 to 30% by weight, and in particular 15 to 25% by weight.

[0031] As aromatic dicarboxylic acids or aromatic dicarboxylic acid derivatives, phthalic acid, phthalic anhydride, terephthalic acid, and / or isophthalic acid, as well as their derivatives, such as dimethyl terephthalate, diethyl terephthalate, dimethyl phthalate, and diethyl phthalate, are preferably used in mixtures or alone. Phthalic acid, phthalic anhydride, and terephthalic acid are preferred. Terephthalic acid or dimethyl terephthalate, especially terephthalic acid, is particularly preferred.

[0032] In addition to aliphatic and / or aromatic polycarboxylic acids and / or functionalized aliphatic carboxylic acids, monofunctional carboxylic acids or reaction products of monofunctional carboxylic acids can also be used. Saturated or unsaturated monocarboxylic acids with 1 to 24 carbon atoms can be used as monofunctional carboxylic acids. Examples include formic acid, acetic acid, propionic acid, acrylic acid, butyric acid, valeric acid, caproic acid, benzoic acid, heptanoic acid, caprylic acid, nonanoic acid, capric acid, and fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, ricinoleic acid, linoleic acid, and linolenic acid.

[0033] Bio-based starting materials and / or their derivatives can also be used as reaction products of monofunctional carboxylic acids, such as: B. Castor oil, polyhydroxy fatty acids, hydroxyl-modified oils, grape seed 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, and fatty acid esters based on myristoleic acid, palmitoleic acid, oleic acid, vaccenic acid, petroselinic acid, gadoleic acid, erucic acid, nervonic acid, linoleic acid, o- and y-linolenic acid, stearidonic acid, arachidonic acid, timnodonic acid, clupanodonic acid and cervonic acid.

[0034] Insofar as monofunctional carboxylic acids or their derivatives are used in the preparation of the polyester polyols (b2), this is preferably done in such amounts that the polyester polyol (b2), based on its total weight, contains < 15 wt.%, in particular < 5 wt.%, and in particular no fatty acid residues.

[0035] Furthermore, polyethylene terephthalate is used to produce the polyester, for example in the form of granules. One possible explanation for the incorporation of polyethylene terephthalate into the polyester (b2) is that transesterification reactions occur under the esterification conditions for producing polyol (b2), leading to the incorporation of the degradation products of polyethylene terephthalate into the polyester (b2). Possible degradation reactions of polyethylene terephthalate (PET) leading to incorporation into polyester polyol (b2) are described, for example, in "Damayanti; Wu H.-S., "Strategie Possibility Routes of Recycled PET, Polymers 2021, 13, 1475, especially in Chapter 5" or "Chemistry and Technology of Polyols for Polyurethanes, 2nd Edition, Volume 2, Chapter 5.2". In addition to esters obtainable by reaction of polyethylene terephthalate, the polyester polyol (b2) can also contain monoethylene glycol, for example from transesterification with polyethylene terephthalate.

[0036] Examples of polyhydric alcohols are: ethanediol, diethylene glycol, 1,2- or 1,3-propanediol, dipropylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,10-decanediol, glycerol, trimethylolpropane, and pentaerythritol, or their alkoxylates. Preference is given to using ethylene glycol, diethylene glycol, propylene glycol, glycerol, trimethylolpropane, or their alkoxylates, or mixtures of at least two of the polyhydric alcohols mentioned, in particular diethylene glycol and / or glycerol.

[0037] In a particularly preferred embodiment, in addition to polyethylene terephthalate and adipic acid, diethylene glycol and optionally fatty acid or fatty acid derivatives are used to produce the polyester (b2). Particularly preferably, the hydroxyl number of the polyester (b2) is less than 200 mg KOH / g and the fatty acid content is > 8 wt.%, based on the total weight of the polyester (b2). If no fatty acid or fatty acid derivative is present, the hydroxyl number of the polyester (b2) is preferably > 200 mg KOH / g.

[0038] The polyesterol (b2) is prepared catalyst-free or preferably in the presence of esterification catalysts, advantageously in an atmosphere of inert gas such as nitrogen, in the melt at temperatures of 150 to 280 °C, preferably 180 to 260 °C, optionally under reduced pressure, to the desired acid number, which is advantageously less than 10 and particularly preferably less than 2. According to a preferred embodiment, the esterification mixture is polycondensed at the abovementioned temperatures to an acid number of 80 to 20, preferably 40 to 20, under atmospheric pressure and subsequently under a pressure of less than 500 mbar, preferably 40 to 400 mbar. Suitable esterification catalysts include, 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 entraining agents, such as benzene, toluene, xylene, or chlorobenzene, for azeotropic distillation of the condensation water.

[0039] In addition to the polyetheresterol (b1) and the polyester (b2), component (b) may further comprise a polyetherol (b3) which has a hydroxyl number of 150 to 300 mg KOH / g and is prepared by alkoxylation of a starter or starter mixture, wherein at least 80% by weight of ethylene oxide is preferably used as the alkylene oxide for preparing polyetherpolyol (b3) and polyetherpolyol (b3) has at least 90%, preferably at least 95%, particularly preferably at least 99% and in particular exclusively primary hydroxyl end groups.

[0040] The polyether polyols (b3) are prepared by known processes, for example by anionic polymerization of one or more alkylene oxides having 2 to 4 carbon atoms, containing ethylene oxide, with conventional catalysts, such as alkali metal hydroxides, such as sodium or potassium hydroxide, alkali metal alkoxides, such as sodium methylate, sodium or potassium ethylate, or potassium isopropylate, or aminic alkoxylation catalysts, such as dimethylethanolamine (DMEOA), imidazole, and / or imidazole derivatives, using at least one starter molecule or starter molecule mixture containing on average < 3.0 and > 2.0, and particularly preferably two, bonded reactive hydrogen atoms. In addition to the anionic polymerization of the starter molecules, production can also be carried out by cationic polymerization, using Lewis acids, such as antimony pentachloride, boron fluoride etherate, or bleaching earth, as catalysts.Preferred alkoxylation catalysts are KOH and amine alkoxylation catalysts. In some cases, when using KOH as the alkoxylation catalyst, the polyether must first be neutralized and the resulting potassium salt separated. In such cases, the use of amine alkoxylation catalysts is particularly preferred. Preferred amine alkoxylation catalysts are selected from the group consisting of dimethylethanolamine (DMEOA), imidazole and imidazole derivatives, and mixtures thereof, particularly preferably imidazole.

[0041] Suitable alkylene oxides, in addition to ethylene oxide, are, for example, tetrahydrofuran, 1,3- or 1,2-propylene oxide, 1,2- or 2,3-butylene oxide, styrene oxide and preferably 1,2-propylene oxide. In a particularly preferred embodiment, ethylene oxide is used exclusively as the alkylene oxide. The alkylene oxides can be used individually, alternately one after the other or as mixtures. According to the invention, at least 80% by weight of ethylene oxide, preferably at least 90% by weight of ethylene oxide, more preferably at least 95% by weight and especially at least 98% by weight of ethylene oxide is used as the alkylene oxide for preparing polyether polyol (b3). Very particular preference is given to using ethylene oxide exclusively as the alkylene oxide for preparing the polyether polyol (b3) according to the invention, ie the amount by weight of ethylene oxide based on the total weight of alkylene oxide in component (b3) is 100% by weight in this embodiment.If ethylene oxide is used in a mixture with other alkylene oxides, it must be ensured according to the invention that the polyether polyol produced therefrom has the content of primary hydroxyl end groups according to the invention.

[0042] Examples of suitable starter molecules include: water, organic dicarboxylic acids such as succinic acid, adipic acid, phthalic acid, and terephthalic acid, or preferably dihydric or polyhydric alcohols such as ethanediol, 1,2- and 1,3-propanediol, diethylene glycol (DEG), dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, glycerol, trimethylolpropane, bisphenol A, bisphenol F, and pentaerythritol. Particular preference is given to diethylene glycol, monoethylene glycol, 1,2-propanediol, and glycerol, especially diethylene glycol, as starter molecules.

[0043] If polyether polyol (b3) is used, this is preferably done in an amount of 2 to 25 wt.%, preferably 4 to 20 wt.% and in particular 6 to 15 wt.%, in each case based on the total weight of component (b).

[0044] It is essential to the invention that the content of free monoethylene glycol, based on the sum of components (b), (c), (e) and (f), is less than 1.4% by weight, preferably less than 1.3% by weight, particularly preferably less than 1.1% by weight, and in particular less than 1.0% by weight of monoethylene glycol (MEG). Catalysts (c) used for producing the rigid polyisocyanurate foams according to the invention are, in particular, compounds which greatly accelerate the reaction of the compounds of components (b) to (f) containing reactive hydrogen atoms, in particular hydroxyl groups, with the polyisocyanates (a).

[0045] It is advantageous to use basic polyurethane catalysts, 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-tetramethylhexanediamine-1,6,-pentamethyldiethylenetriamine, bis(2-dimethylaminoethyl)ether, dimethylpiperazine, N-dimethylaminoethylpiperidine, 1,2-dimethylimidazole, 1-azabicyclo-(2,2,0)-octane, 1 ,4.Diazabicyclo-(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)hexahydrotriazines, e.g. N,N',N"-tris-(dimethylaminopropyl)-s-hexahydrotriazines, and triethylenediamine.

[0046] However, metal salts such as iron(II) chloride, zinc chloride, lead octoate, and tin salts such as tin dioctoate, tin diethylhexoate, and dibutyltin dilaurate, as well as mixtures of tertiary amines and metal salts, especially organic tin salts, are also suitable. Other suitable catalysts 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 alkali metal alcoholates such as sodium methylate and potassium isopropylate; alkali metal carboxylates; and alkali metal salts of long-chain fatty acids with 8 to 20 carbon atoms and optionally pendant OH groups.

[0047] Also suitable as catalysts are incorporable amines, ie, preferably amines with an -OH, -NH, or -NH2 function, such as ethylenediamine, triethanolamine, diethanolamine, ethanolamine, and dimethylethanolamine. Incorporable catalysts can be considered as compounds of both component (b) and component (c).

[0048] It is also possible to run the reactions without catalysis. In this case, the catalytic activity of amine-initiated polyols is typically utilized.

[0049] Other possible catalysts for the trimerization reaction of the excess -NCO groups are isocyanurate group-forming catalysts, for example, ammonium ion or alkali metal salts, especially ammonium or alkali metal carboxylates, alone or in combination with tertiary amines. Isocyanurate formation leads to flame-retardant PIR foams, which are preferably used in rigid foams, for example in construction as insulation panels or sandwich elements. Preferred trimerization catalysts are potassium salts of an aliphatic carboxylic acid with > 5 carbon atoms, in particular selected from the group consisting of potassium 2-ethylhexanoate, potassium octoate, potassium neodecanoate, potassium hexanoate, and potassium sorbate.

[0050] In a preferred embodiment, the catalyst (c) contains an amine catalyst having a tertiary amino group and an ammonium or alkali metal carboxylate catalyst. In a particularly preferred embodiment, the catalyst (c) contains at least one amine catalyst selected from the group consisting of pentamethyldiethylenetriamine and bis(2-dimethylaminoethyl) ether and at least one alkali metal carboxylate catalyst, for example an alkali metal salt of a carboxylic acid, such as potassium formate or potassium acetate, preferably the potassium salt of an aliphatic carboxylic acid having > 5 carbon atoms, in particular selected from the group consisting of potassium 2-ethylhexanoate, potassium octoate, potassium neodecanoate, potassium pivalate, potassium hexanoate, and potassium sorbate.Surprisingly, the use of these catalysts in the continuous production of sandwich elements, for example in a double belt, leads to sandwich elements that have a particularly low post-expansion behavior after leaving the double belt and also have a particularly small difference between the element center thickness and the element edge thicknesses.

[0051] Preferably, 0.001 to 10 parts by weight of catalyst or catalyst combination are used, based on 100 parts by weight of component (b).

[0052] Blowing agents (d) that can be used to produce the inventive rigid polyisocyanurate foams include water, formic acid, and formic acid-water mixtures. These react with isocyanate groups to form carbon dioxide and carbon monoxide. Since these blowing agents release the gas through a chemical reaction with the isocyanate groups, they are referred to as chemical blowing agents. For the purposes of the present invention, formic acid with a purity of greater than 98% is considered pure formic acid and not a formic acid-water mixture.

[0053] In addition, physical blowing agents, such as low-boiling hydrocarbons, can be used. Particularly suitable as physical blowing agents are liquids that are inert toward the polyisocyanates (A) and have boiling points below 100 °C, preferably below 50 °C, at atmospheric pressure, so that they evaporate under the influence of the exothermic polyaddition reaction.

[0054] Examples of physical blowing agents that can be 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 halogenated saturated and unsaturated hydrocarbons such as methylene chloride, dichloromonofluoromethane, difluoromethane, trifluoromethane, difluoroethane, tetrafluoroethane, chlorodifluoroethane, 1,1-dichloro-2,2,2-trifluoroethane, 2,2-dichloro-2-fluoroethane and heptafluoropropane, and unsaturated hydrocarbons such as trifluoropropenes and tetrafluoropropenes, such as (HFO-1234), pentafluoropropenes, such as (HFO-1225), chlorotrifluoropropenes, such as (HFO-1233), chlorodifluoropropenes, chlorotetrafluoropropenes and hexafluorobutenes, as well as mixtures of one or more of these components.Tetrafluoropropenes, pentafluoropropenes, chlorotrifluoropropenes, and hexafluorobutenes are preferred, where the unsaturated terminal carbon atom carries at least one chlorine or fluorine substituent. Examples are 1,3,3,3-tetrafluoropropene (HFO-1234ze); 1,1,3,3-tetrafluoropropene; 1,2,3,3,3-pentafluoropropene (HFO-1225ye); 1,1,1-trifluoropropene; 1,1,1,3,3-pentafluoropropene (HFO-1225zc); 1,1,2,3,3-pentafluoropropene (HFO-1225yc); 1-chloro-2,3,3,3-tetrafluoropropene (HFO-1224yd); 1,1,1,2,3-pentafluoropropene (HFO-1225yez); 1-chloro-3,3,3-trifluoropropene (HCFO-1233zd); 1,1,1,4,4,4-hexafluorobut-2-ene (HFO-1336mzz). Mixtures of these low-boiling liquids with each other and / or with other substituted or unsubstituted hydrocarbons can also be used.

[0055] Organic carboxylic acids such as acetic acid, oxalic acid, ricinoleic acid and compounds containing carboxyl groups are also suitable as propellants.

[0056] Preferably, no halogenated hydrocarbons are used as blowing agents. Chemical blowing agents used are preferably water, formic acid-water mixtures, or formic acid, particularly preferably formic acid-water mixtures or formic acid.

[0057] Pentane isomers or mixtures of pentane isomers are preferably used as physical blowing agents. The chemical blowing agents are used together with physical blowing agents, with preference being given to the use of formic acid-water mixtures or pure formic acid together with pentane isomers or mixtures of pentane isomers. The amount of blowing agent or blowing agent mixture used is from 0.1 to 45% by weight, preferably from 1 to 30% by weight, particularly preferably from 1 to 20% by weight, and in particular from 1.5 to 20% by weight, based in each case on the sum of components (b) to (f).

[0058] Water, formic acid, or a formic acid-water mixture is preferably used in an amount of 0.2 to 10 wt.%, in particular in an amount of 0.5 to 4 wt.%, based on component (b). If formic acid-water mixtures are used, the proportion of formic acid, based on the total weight of formic acid and water, is preferably greater than 40 wt.%, particularly preferably 50 to 98 wt.%, more preferably 70 to 95 wt.%, and in particular 80 to 90 wt.%. Particular preference is given to using formic acid or a formic acid-water mixture as a chemical blowing agent in combination with pentane.

[0059] Flame retardants known from the prior art can generally be used as flame retardants. Suitable flame retardants include, for example, brominated esters, brominated ethers (Ixol), or brominated alcohols such as dibromoneopentyl alcohol, tribromoneopentyl alcohol, and PHT-4-diol, as well as chlorinated phosphates such as tris-(2-chloroethyl) phosphate, tris-(2-chloropropyl) phosphate (TCPP), tris(1,3-dichloropropyl) phosphate, tricresyl phosphate, tris-(2,3-dibromopropyl) phosphate, tetrakis-(2-chloroethyl)ethylene diphosphate, dimethyl methanephosphonate, diethyl diethanolaminomethylphosphonate, and commercially available halogen-containing flame retardant polyols. Other phosphates or phosphonates that can be used as liquid flame retardants include diethyl ethane phosphonate (DEEP), triethyl phosphate (TEP), dimethyl propyl phosphonate (DMPP), and diphenyl cresyl phosphate (DPK).Compounds containing phosphorus, chlorine or bromine atoms which also have groups reactive towards isocyanate are not regarded in the context of the present invention as compounds having at least two hydrogen atoms (b) reactive towards isocyanate groups and are not considered to belong to component (b) when calculating proportions.

[0060] In addition to the flame retardants already mentioned, inorganic or organic flame retardants, such as red phosphorus, red phosphorus-containing dressings, aluminum oxide hydrate, antimony trioxide, arsenic oxide, ammonium polyphosphate and calcium sulfate, expandable graphite or cyanuric acid derivatives, such as melamine, or mixtures of at least two flame retardants, such as ammonium polyphosphates and melamine and optionally corn starch or ammonium polyphosphate, melamine, expandable graphite and optionally aromatic polyesters, can also be used to flame-retard the rigid polyisocyanurate foams. Preferred flame retardants do not contain any groups reactive toward isocyanate groups. The flame retardants are preferably liquid at room temperature. TOPP, DEEP, TEP, DMPP and DPK are preferred, particularly TOPP and TEP, especially TOPP.

[0061] In general, the proportion of flame retardants (e) is 1 to 20 wt.%, preferably 2 to 15 wt.%, particularly preferably 3 to 10 wt.%, based on the sum of the weight amounts of components (b) to (f).

[0062] Preferably, component (e) comprises a phosphorus-containing flame retardant and the phosphorus content, based on the total weight of components (a) to (f), is preferably <0.7 wt.%, more preferably <0.6 wt.%, particularly preferably <0.5 and in particular <0.4 wt.%.

[0063] If desired, further auxiliaries and / or additives (f) may be added to the reaction mixture for producing the rigid polyisocyanurate foams of the invention. Examples include surfactants, foam stabilizers, cell regulators, fillers, light stabilizers, dyes, pigments, hydrolysis inhibitors, and fungistatic and bacteriostatic substances.

[0064] Suitable surface-active substances include compounds that support the homogenization of the starting materials and, where appropriate, are also 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., oleic acid diethylamine, stearic acid diethanolamine, ricinoleic acid diethanolamine; salts of sulfonic acids, e.g., alkali or ammonium salts of dodecylbenzenesulfonic acid or dinaphthylmethanedisulfonic acid and ricinoleic acid; foam stabilizers such as siloxaneoxyalkylene copolymers and other organopolysiloxanes and dimethylpolysiloxanes. Oligomeric acrylates with polyoxyalkylene and fluoroalkane residues as side groups are also suitable for improving the emulsifying effect, the cell structure, and / or stabilizing the foam. The surface-active substances are usually used in amounts of 0.01 to 10 wt.Parts, based on 100 parts by weight of component (b), are used. Conventional foam stabilizers, for example silicone-based ones such as siloxaneoxyalkylene copolymers and other organopolysiloxanes, can be used as foam stabilizers.

[0065] Fillers, in particular reinforcing fillers, are understood to mean the usual organic and inorganic fillers, reinforcing agents, weighting agents, agents for improving abrasion behavior in paints, coatings, etc. The following are specifically mentioned as examples: inorganic fillers such as silicate minerals, for example layered silicates such as antigorite, serpentine, hornblende, amphiboles, chrysotile and talc, metal oxides such as kaolin, aluminum oxides, titanium oxides and iron oxides, metal salts such as chalk, barite and inorganic pigments such as cadmium sulfide and zinc sulfide, as well as glass, among others. Preference is given to using kaolin (China Clay), aluminum silicate and coprecipitates of barium sulfate and aluminum silicate as well as natural and synthetic fibrous minerals such as wollastonite, metal fibers and in particular glass fibers of various lengths, which may be sized if desired.Examples of suitable 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 in particular carbon fibers. The inorganic and organic fillers can be used individually or as mixtures and are advantageously added to the reaction mixture in amounts of 0.5 to 50% by weight, preferably 1 to 40% by weight, based on the weight of components (a) to (f). However, the content of mats, nonwovens, and woven fabrics made of natural and synthetic fibers can reach values ​​of up to 80% by weight, based on the weight of components (a) to (f).

[0066] According to the invention, the rigid polyisocyanurate foams are produced by mixing components (a) to (e) and, if present, (f), to form a reaction mixture. To reduce complexity, premixes can also be prepared. These comprise at least one isocyanate component containing polyisocyanates (a) and a polyol component containing compounds having at least two isocyanate-reactive hydrogen atoms (b). All or some of the further components (c) to (f) can be added in whole or in part to the isocyanate component and polyol component. Due to the high reactivity of the isocyanates, components (c) to (f) are often added to the polyol component to avoid side reactions. However, physical blowing agents, in particular, can also be added to the isocyanate component (a).Typically, water, formic acid-water mixtures, or formic acid are present fully or partially dissolved in the polyol component, and the physical blowing agent (e.g., pentane) and, if appropriate, the remainder of the chemical blowing agent are metered online directly during production. Preferably, the physical blowing agents are added online in a separate stream to the reaction mixture, and particularly preferably, the remaining components (c), (e), and (f) are added to the polyol component. Typically, the catalyst is added online, but it may also already be partially or completely dissolved in the polyol component. The present invention thus also relates to a polyol component comprising components (b), optionally catalyst (c), blowing agent (d), flame retardant (e), and optionally auxiliaries and additives (f) as defined above, wherein the mass ratio of polyetherester polyol (b1) to polyester polyol (b2) is > 0.3 and < 3.0 and the sum of the mass fractions of component (b1) and component (b2), based on component (b), is > 80 wt.%, and the mass fraction of free mono-ethylene glycol which is fed to the reaction mixture is less than 1.4 wt.%, based on the total weight of components (b), (c), (e) and (f).

[0067] The polyester (b2) is preferably used in amounts such that the polyethylene terephthalate content is at least 2.5% by weight, particularly preferably at least 3% by weight, further preferably at least 4% by weight and in particular at least 5% by weight, in each case based on the total weight of components (a) to (f).

[0068] The polyol component for producing the rigid polyisocyanate foams according to the invention preferably contains 70 to 90% by weight of the compounds having at least 2 hydrogen atoms reactive toward isocyanate groups (b), 0.5 to 10% by weight of catalysts (c), 2 to 20% by weight of blowing agent (d), 1 to 20% by weight of flame retardant (e), and 0 to 20% by weight of further auxiliaries and additives (f), each based on the total weight of components (b) to (f). In a particularly preferred embodiment, the proportions of components (b) to (f) add up to 100% by weight.

[0069] The reaction mixture is then allowed to react to form the rigid polyisocyanate foam. For the purposes of the present invention, a reaction mixture refers to the mixture of polyisocyanates (a) with the compounds containing at least two hydrogen atoms reactive toward isocyanate groups (b) and all other components (c), (d), (e), and optionally (f), with reaction conversions of less than 90%, based on the isocyanate groups.

[0070] The components are mixed to form the reaction mixture at an isocyanate index of at least 180, preferably 220 to 400, particularly preferably 260 to 360, and especially 280 to 330. The starting components are mixed at a temperature of 15 to 90 °C, preferably 20 to 60 °C, especially 20 to 45 °C. The reaction mixture can be mixed by mixing in high- or low-pressure metering machines.

[0071] The reaction mixture can, for example, be placed in a mold for complete reaction. Discontinuous sandwich elements, for example, are produced using this technology. The rigid foams according to the invention are preferably produced on continuously operating double-belt systems. The polyol and isocyanate components are preferably metered using a high-pressure machine and mixed in a mixing head. Catalysts and / or blowing agents can be metered into the polyol mixture beforehand using separate pumps. The reaction mixture is applied to a continuously moving, lower cover layer, preferably a metal cover layer. The lower cover layer containing the reaction mixture and the upper cover layer, preferably also a metal cover layer, enter the double belt, where the reaction mixture foams and cures. After leaving the double belt, the continuous strand is cut to the desired dimensions.In this way, sandwich elements with metallic or flexible facings can be manufactured. Flexible or rigid facings, typically used in the double-belt process, can be used as the lower and upper facings, which can be identical or different. These include metal facings such as aluminum or steel, bitumen facings, paper, nonwovens, plastic sheets such as polystyrene, plastic films such as polyethylene films, or wooden facings. The facings can also be coated, for example, with a conventional varnish or an adhesion promoter. Particular preference is given to facings that are diffusion-tight to the cell gas of the polyisocyanate rigid foam.

[0072] Such processes are known and described, for example, in "Kunststoffhandbuch, Band 7, Polyurethane", Carl Hanser Verlag, 3rd edition 1993, Chapter 6.2.2 or EP 2234732. Finally, the present invention relates to a polyisocyanate-based rigid foam obtainable by a process according to the invention and to a polyurethane sandwich element comprising such a polyisocyanate-based rigid foam according to the invention.

[0073] A rigid polyisocyanurate foam according to the invention is characterized by excellent mechanical properties, in particular excellent compressive strength, low thermal conductivity, low post-expansion behavior, high fire resistance, a surface that is as defect-free as possible, and good adhesion to the cover layer. The process according to the invention for producing such rigid polyisocyanurate foams is characterized by the easy processing of the raw materials, particularly due to their low viscosities, so that the starting components can be easily mixed with the other components for producing rigid polyisocyanurate foams. In addition, the polyisocyanate-based rigid foams according to the invention exhibit excellent fire resistance even when using small amounts of ecologically and toxicologically harmful flame retardants.In addition, the reaction mixtures used to produce the polyisocyanate-based rigid foam according to the invention make it possible to achieve the required reactivities with improved foam curing when using smaller amounts of ecologically and toxicologically harmful catalysts.

[0074] The invention is further illustrated by the following examples:

[0075] Examples:

[0076] The following materials were used:

[0077] Polyols:

[0078] Polyetheresterol 1 Esterification product of terephthalic acid, oleic acid, diethylene glycol and ethoxylated glycerol, with a hydroxyl functionality of 2.5, a hydroxyl number of 240 mg KOH / g and an oleic acid content of 15 wt%.

[0079] Polyesterol 2: Esterification product of phthalic anhydride, oleic acid and diethylene glycol with a hydroxyl functionality of 1.75, a hydroxyl number of 215 mg KOH / g and an oleic acid content of 15 wt%.

[0080] PET Polyesterol 1 : Esterification product of ester, obtainable by reacting polyethylene terephthalate, adipic acid and diethylene glycol with a hydroxy functionality of 2.0 and a hydroxyl number of 245 mg KOH / g with a polyethylene terephthalate content of 40 wt.%, an adipic acid content of 22 wt.% and a free MEG content of 1.09%

[0081] PET Polyesterol 2: Esterification product obtained by reacting polyethylene terephthalate, adipic acid, soybean oil and diethylene glycol with a hydroxyl functionality of 1.85 and a hydroxyl number of 190 mg KOH / g, with a polyethylene terephthalate content of 40 wt.%, an adipic acid content of 18 wt.%, a fatty acid content of 12 wt.%, and a free MEG content of 0.79%

[0082] PET Polyesterol 3: Esterification product of ester, obtainable by reacting polyethylene terephthalate, adipic acid and diethylene glycol with a hydroxyl functionality of 2 and a hydroxyl number of 240 mg KOH / g, with a polyethylene terephthalate content of 30 wt.% and a free MEG content of 1.4%.

[0083] PET Polyesterol 4: Esterification product of ester, obtainable by reacting polyethylene terephthalate, adipic acid and diethylene glycol with a hydroxyl functionality of 2 and a hydroxyl number of 290 mg KOH / g, with a polyethylene terephthalate content of 45 wt.% and a free MEG content of 1.05%.

[0084] Polyetherol 1 : Polyether polyol produced by ethoxylation of ethylene glycol with a hydroxyl functionality of 2 and a hydroxyl number of 190 mg KOH / g.

[0085] Flame retardants:

[0086] TOPP: Tris(2-chloroisopropyl)phosphate with a chlorine content of 32.5 wt% and a phosphorus content of 9.5 wt%.

[0087] Foam stabilizers:

[0088] Stabilizer: Silicone-based foam stabilizer from Evonik. Catalysts:

[0089] Catalyst A: Catalyst consisting of 23.1 wt% bis(2-dimethylaminoethyl) ether and 76.9 wt% dipropylene glycol.

[0090] Catalyst B: Catalyst consisting of 40 wt% potassium formate, 54 wt% monoethylene glycol and 6 wt% water.

[0091] Catalyst C: Catalyst consisting of 54 wt% potassium 2-ethylhexanoate, 20.5 wt% diethylene glycol, 22.5 wt% triethyl phosphate and 3.0 wt% water.

[0092] Chemical blowing agents:

[0093] Amasil 85%: Propellant mixture consisting of 85% by weight formic acid and 15% by weight water.

[0094] Physical blowing agents:

[0095] Pentane S80 / 20: Propellant mixture consisting of 80 mol% n-pentane and 20 mol% iso-pentane.

[0096] Isocyanates:

[0097] Lupranat® M 50: Polymeric methylene diphenyl diisocyanate (PMDI) from BASF, with a viscosity of approx. 550 mPa*s at 25 °C.

[0098] Using the described starting materials, the polyol components described in Table 2 were prepared and converted on a high-pressure machine in a continuous double-belt process.

[0099] Continuous production of sandwich elements using the double-belt process: 50 mm and 120 mm thick composite elements were produced using the double-belt process. For production, the polyol components listed in Table 2, tempered to 22 ± 1 °C, were reacted with Lupranat® M50, which was also tempered to 22 ± 1 °C.

[0100] The amount of Lupranat® M50 was always selected so that all rigid foams processed into 50 mm sandwich elements had an isocyanate index of 305 ± 15 and all rigid foams processed into 120 mm sandwich elements had an isocyanate index of 325 ± 15.

[0101] To manufacture the composite elements, both a 0.05 mm thick aluminum foil heated to 35 ± 2 °C and a 0.5 mm thick, double-sided coated aluminum sheet heated to 40 ± 2 °C served as the lower face layer. Both face layers are industry standards and are also used in the conventional continuous production process for sandwich elements. The temperature of the double belt was always 60 ± 2 °C.

[0102] To produce the 50 mm thick composite elements, 100 parts of polyol component were mixed with the parts of Amasil 85% described in Table 2. The amount of catalyst B and catalyst C was selected such that the proportion of potassium ions, based on all components used to produce the foam, was 0.11 ± 0.02 wt.%. Catalyst A and the amount of physical blowing agent were selected such that the gel time of the reaction mixture was exactly 25 seconds, the contact time of the reaction mixture with the upper belt was exactly 20 seconds, and the foam had a total density of 39.5 ± 1.5 g / l.

[0103] To produce the 120 mm thick composite elements, 100 parts of the polyol component were mixed with the parts of Amasil 85% described in Table 2. The amount of catalyst B and catalyst C was selected such that the proportion of potassium ions, based on all components used to produce the foam, was 0.10 ± 0.02 wt.%. Catalyst A and the amount of physical blowing agent were selected such that the gel time of the reaction mixture was exactly 32 seconds, the contact time of the reaction mixture with the upper belt was exactly 26 seconds, and the foam had a total density of 39.5 ± 1.5 g / l.

[0104] To determine the compressive strengths and foam surfaces, after successful adjustment of the foaming parameters, test plates with a length of 2.0 m and a width of 1.25 m were taken, from which the test specimens required for the tests were always taken at identical locations.

[0105] Determination of the element center thickness of the sandwich foams:

[0106] The sandwich element thickness of the sample panels, manufactured with a gap of 120 mm between the upper and lower belts, was measured immediately after leaving the double belt and 24 hours later (after cooling) at the center of the element width between the tongue and groove sides. The values ​​are listed as "Element center thickness (immediate)" and "Element center thickness (24h)". The difference between "Element thickness (immediate)" and the set gap of 120 mm is listed as "Element center thickness difference (immediate)".

[0107] In addition, the crowning of the sandwich elements was determined, which describes the difference between the element center thickness (24 h) and the element edge thickness (24 h) in mm. The element edge thickness (24 h) is the average of the two element thicknesses, measured 5 cm from the tongue and groove edges.

[0108] Determination of the compressive strength of sandwich foams:

[0109] After storage for 24 hours at standard conditions, additional test specimens measuring 100 mm x 100 mm x sandwich thickness were cut from the test specimens using a band saw. The test specimens were taken from identical locations across the width of the element (left, center, right), and the compressive strengths of the foam were determined according to the sandwich standard DIN EN ISO 14509-A.2 according to EN 826.

[0110] Determination of transverse tensile strength:

[0111] Additional test specimens measuring 100 mm x 100 mm x sandwich thickness (50 mm, 100 mm, 170 mm) were cut from the test specimens using a band saw. The test specimens were taken at identical locations across the width of the element (left, center, right), and the transverse tensile strength of the foam and the adhesion to the facing layer were determined according to the sandwich standard DIN EN ISO 14509-A.1 according to EN 1607.

[0112] Assessment of the foam surfaces after removal of the lower cover layers:

[0113] After mechanical removal of the aluminum foil and the aluminum sheets to which the liquid reaction mixture is applied using the double-belt method (lower cover layer), the foam surfaces were visually assessed and evaluated, with grade 1 representing the best foam surface and grade 5 the worst foam surface:

[0114] Table 1: Visual assessment of foam quality

[0115] Small burner test according to EN-ISO 11925-2:

[0116] The test specimens for the small burner test were prepared as follows: 300 g of the reaction mixture, adjusted to identical reaction times and foam densities, were vigorously stirred in a paper cup using a laboratory stirrer at a rotation speed of 1500 revolutions / minute for 10 seconds and then transferred to a box mold with internal dimensions of 150 mm x 250 mm (length x width). 24 hours later, the rigid foam block was demolded and trimmed by 30 mm at all edges. The test specimens, measuring 190 x 90 x 20 mm, were then conditioned for one day and tested according to DIN EN-ISO 11925-2 using edge flame application on the 90 mm side. The values ​​listed in Table 3 are the averages of a five-fold determination.

[0117] Table 2: Polyol components for the production of 50 and 120 mm thick sandwich elements

[0118] X = used

[0119] Table 3: Properties of the manufactured 50 mm thick sandwich elements Table 4: Properties of the manufactured 120 mm thick sandwich elements The results in Tables 3 and 4 show the foam and sandwich element properties of the manufactured 50 and 120 mm thick sandwich elements. The polyol component from Example 1 contains "Polyetheresterol 1" as the only polyester. When processed into 50 mm thick sandwich elements, this results in void-free foam surfaces beneath the aluminum foil and sheet metal, as well as an acceptable flame height in the small burner test. The manufactured 120 mm thick elements exhibit only a very small center-to-center thickness difference from the set gap of < 2.0 mm after leaving the double belt. Furthermore, the elements exhibit acceptable compressive strength values.

[0120] As can be seen from examples 3 and 5, a complete replacement of “Polyetheresterol 1” with “PET Polyesterol 1” and “PET Polyesterol 2” leads to significant disadvantages in the production of both 50 mm thick and 120 mm thick sandwich elements.

[0121] Compared to Example 1, the foams from Examples 3 and 5 exhibit significantly poorer foam surfaces after removal of both cover layers. Furthermore, the 120 mm elements exhibit a significantly increased element center-to-center thickness difference after leaving the double belt. Surprisingly, the use of a combination of "Polyetherester Polyol 1" and "PET Polyesterol 1" or "PET Polyesterol 2" results in foams that meet all requirements in the double belt process.

[0122] It can be seen that Examples 2, 4, and 9 according to the invention exhibit foam surfaces beneath both cover layers that are identical to the foams from Example 1. The element center thickness differences are also within an acceptable range. Example 9 clearly shows that the use of Catalyst C leads to even smaller element center thickness differences, which allows the use of even higher proportions of PET polyester polyols.

[0123] Compared to Example 1, the foams from inventive Examples 2, 4, and 9 surprisingly exhibit increased foam compressive strengths and improved fire resistance. The use of Catalyst C surprisingly leads to a further improvement in foam compressive strengths and acceptable fire resistance.

[0124] The combination of "Polyetheresterol 1" and "PET Polyester" is essential to the invention. Example 6 demonstrates that replacing "Polyetheresterol 1" with another ester that does not contain a polyether component results in foams that no longer meet all requirements. "Polyesterol 2," for example, leads to deficiencies in the foam surface beneath both cover layers. The 120 mm elements produced in Example 6 also exhibit a greater element thickness difference compared to the 120 mm elements in Example 4.

[0125] The invention also shows that not all PET polyester films are suitable. For example, PET polyesters with a higher free monoethylene glycol content result in significantly higher post-pressing, even when used in combination with "Polyetherester Polyol 1" (cf.

[0126] Examples 7 and 8). PET polyesters with an excessively high OH number are also not optimal, as they also lead to increased element center thicknesses and poorer foam surfaces, even if their content of free monoethylene glycol is within the range of the invention (cf. Example 10).

Claims

Patent claims 1 . A process for the production of rigid polyisocyanurate foam, in which a) aromatic polyisocyanate, b) compounds having at least two hydrogen atoms reactive with isocyanate groups, containing at least one polyetherester polyol (b1) and at least one polyester polyol (b2), c) catalyst, d) blowing agent, e) flame retardant f) optionally auxiliaries and additives are mixed to form a reaction mixture and allowed to react to give rigid polyisocyanurate foam, wherein the polyetherester polyol (b1) is obtainable by esterification of: b1 .1) 10 to 50 mol% of a dicarboxylic acid composition containing aromatic dicarboxylic acids, b1.2) 2 to 20 mol% of one or more hydrophobic compounds having at least one hydroxyl and / or carboxyl group or derivatives thereof, b1 .3) 10 to 70 mol% of one or more diols having 2 to 6 C atoms, b1.4) 15 to 50 mol% of a polyether polyol, prepared by alkoxylation of a starter or a starter mixture having an average functionality of > 2 and < 4, in each case based on the total amount of components b1.1) to b1.4), and the polyether ester polyol (b1) has an average functionality of > 1.7 and < 2.8 and an OH number of > 150 and < 300 mg KOH / g, and the polyester polyol (b2) has a functionality of > 1.7 and < 2.7, an OH number of > 170 and < 280 mg KOH / g and a free monoethylene glycol content of < 1.3 wt.%, wherein polyethylene terephthalate is used to produce polyester polyol (b2), the proportion of which, based on the total amount of all components used to produce polyester polyol (b2), is > 25 wt.%, wherein the mass ratio of polyether ester polyol (b1) to polyester polyol (b2) > 0.3 and < 3.0 and the sum of the mass fractions of component (b1) and component (b2), based on component (b), is > 80 wt.%. the mass fraction of free mono-ethylene glycol added to the reaction mixture is less than 1.4 wt.%, based on the total weight of components (b), (c), (e) and (f), and the mixing to form the reaction mixture takes place at an isocyanate index of at least 180.

2. Process according to claim 1, characterized in that the proportion of polyethylene terephthalate, based on the total amount of all components used for the preparation of polyester polyol (b2), is > 28 wt.%.

3. Process according to one or more of claims 1 to 2, characterized in that at least one aliphatic dicarboxylic acid having 4 - 6 carbon atoms is used to produce polyester polyol (b2), the proportion of which, based on all components used to produce the polyester polyol (b2), is > 10% by weight.

4. Process according to one or more of claims 1 to 3, characterized in that the polyester polyol (b2) has a hydroxyl number of < 200 mg KOH / g and, based on the total weight of the polyester polyol (b2), has a fatty acid content of > 8 wt.%.

5. Process according to one or more of claims 1 to 3, characterized in that the polyester polyol (b2) has a hydroxyl number of > 200 mg KOH / g and, based on the total weight, has a fatty acid content of 0 wt.%.

6. Process according to one or more of claims 1 to 5, characterized in that the dicarboxylic acid composition (b1.1) has a terephthalic acid content, based on the total weight of component (b1.1), of > 80 wt.%.

7. Process according to one or more of claims 1 to 6, characterized in that oleic acid is used as component (b.1.2) and the proportion of oleic acid based on the total amount of components b1.1) to b1.4) is > 8 mol%.

8. Process according to one or more of claims 1 to 7, characterized in that the polyether polyol (b1.4) is prepared by alkoxylation with ethylene oxide and has a functionality of 3 and the ethylene oxide content, based on all alkylene oxides used for the preparation of polyether polyol (b1.4), is > 80 wt.%.

9. The process according to one or more of claims 1 to 8, characterized in that component (b) contains at least one polyether polyol (b3) which is obtained by ethoxylation of a starter or a starter mixture having an average functionality of > 2 and < 3, has an ethylene oxide content of > 80% by weight based on all alkylene oxides used to prepare (b3), and has an OH number of 150 - 300 mg KOH / g.

10. Process according to one or more of claims 1 to 9, characterized in that catalyst (c) contains the potassium salt of an aliphatic carboxylic acid having > 5 carbon atoms.

11. Process according to one or more of claims 1 to 10, characterized in that the blowing agent (d) contains chemical and physical blowing agents, wherein the chemical blowing agent is selected from the group consisting of water, formic acid-water mixtures and formic acid.

12. Process according to one or more of claims 1 to 11, characterized in that the flame retardant (e) comprises a phosphorus-containing flame retardant and the phosphorus content, based on the total weight of components (a) to (f), is < 0.7 wt.%.

13. Process according to one or more of claims 1 to 12, characterized in that the content of polyethylene terephthalate, based on the total weight of components (a) to (f), is > 2.5 wt.%.

14. Process according to one or more of claims 1 to 13, characterized in that the reaction mixture is applied to a continuously moving cover layer in a double-belt system for producing sandwich elements.

15. Polyol component for the production of rigid polyisocyanurate foams, comprising b) compounds having at least two hydrogen atoms reactive with isocyanate groups, comprising at least one polyetherester polyol (b1) and one polyester polyol (b2), wherein the number-average content of isocyanate-reactive hydrogen atoms of components (b1) and (b2) is at least 1.7, c) optionally catalyst, d) blowing agent, e) flame retardants and f) optionally auxiliaries and additives, wherein the polyetheresterpolyol (b1) is obtainable by esterification of: b1.1) 10 to 50 mol% of a dicarboxylic acid composition containing aromatic dicarboxylic acids, b1.2) 2 to 20 mol% of one or more hydrophobic compounds having at least one hydroxyl and / or carboxyl group or derivatives thereof, b1.3) 10 to 70 mol% of one or more diols having 2 to 6 C atoms, b1.4) 15 to 50 mol% of a polyetherpolyol prepared by alkoxylation of a starter or a starter mixture having an average functionality of > 2 and < 4, in each case based on the total amount of components b1.1) to b1.4) and the polyetheresterpolyol (b1) has an average functionality of > 1.7 and < 2.8 and an OH number of > 170 and < 270 mg KOH / g, and the polyester polyol (b2) has a functionality of > 1.7 and < 2.7, an OH number of > 170 and < 280 mg KOH / g and a free mono-ethylene glycol content of < 1.3 wt.-%, wherein for the production of polyester polyol (b2) polyethylene terephthalate is used, the proportion of which, based on the total amount of all components used for the production of polyester polyol (b2), is > 25 wt.%, wherein the mass ratio of polyetherester polyol (b1) to polyester polyol (b2) is > 0.3 and < 3.0 and the sum of the mass proportions of component (b1) and component (b2), based on component (b), is > 80 wt.%, the mass proportion of free mono-ethylene glycol which is fed to the reaction mixture is less than 1.4 wt.%, based on the total weight of components B, C, E and F.

16. Polyisocyanurate rigid foam obtainable by the process according to one or more of claims 1 to 14

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