Dimensionally stable open-cell fine-cell polyurethane rigid foams

Abstract

The present invention relates to dimensionally stable open-cell, fine-cell polyurethane rigid foams, methods for their production and their use.

Description

DIMENSIONALLY STABLE OPEN-CELL FINE-CELL POLYURETHANE FOAMS The present invention relates to dimensionally stable open-cell, fine-cell polyurethane rigid foams, processes for their production and their use. Rigid polyurethane foams can contain not only urethane groups (PUR) but also isocyanurate groups (PIR). In this application, the term "rigid polyurethane foam" or "PUR / PIR rigid foam" refers to both rigid foams containing primarily urethane groups and rigid foams containing both urethane and isocyanurate groups, unless otherwise stated. Rigid polyurethane foams have been around for a long time. A key application is thermal insulation. The use of vacuum insulation panels (VIPs) containing rigid polyurethane foams for insulation is becoming increasingly important. The foam quality has a decisive influence on the insulating properties of foams used for vacuum insulation: on the one hand, the smallest possible cell size and the most homogeneous cell sizes are advantageous; on the other hand, a high proportion of open cells is beneficial for easy foam evacuation. The production of open-cell rigid polyurethane foams is also known in principle. Generally, certain cell-opening substances are added to the reaction mixture to cause the cells to open during the foaming process. WO 2018 / 162372 A1 discloses a process for producing a fine-cell, open-cell rigid polyurethane foam. A reaction mixture containing supercritical CO2 is introduced into a mold under counterpressure and suddenly decompressed. The special composition of the reaction mixture results in foams with particularly low density, high open-cell density, and small cell size. One problem with open-cell rigid foams used in VIPs is their lack of stability at elevated temperatures. Typically, an internal pressure in the range of 0.1 to 3 mbar is generated during production of open-cell rigid foams used in VIPs. The open-cell rigid foams known from the prior art lack dimensional stability, particularly in the evacuated state—i.e., at pressures of 0.03 to 20 mbar, in particular 0.1 to 3 mbar—when stored at elevated temperatures, i.e., at least 30°C, for example, 50 to 100°C, or at least 60°C, for example, 60 to 100°C, and ambient pressure, i.e., 980 to 1050 mbar. The object of the present invention was therefore to provide open-cell PUR / PIR rigid foams that remain dimensionally stable in the evacuated state at elevated temperatures and exhibit an improved, particularly flatter, surface finish. PUR / PIR rigid foams with increased compressive strength are particularly advantageous in this regard. Surprisingly, the object was achieved by a process for producing a PUR / PIR rigid foam comprising the steps of i. preparing a reaction mixture R) comprising an isocyanate-reactive composition A) comprising a polyol component A1) with a functionality f of > 2.5 comprising at least one polyether polyol, polyester polyol, polycarbonate polyol, polyether-polycarbonate polyol, polyether ester polyol, or mixtures thereof, optionally a catalyst component A2), optionally an auxiliary and additional component A3); a polyisocyanate component B); and a blowing agent component C) comprising CO2 in the supercritical state, ii. introducing the reaction mixture R) from step i. into a closed mold, wherein a counterpressure in the closed mold during the introduction is 2.0 - 90 bar, iii. allowing the reaction mixture R) to foam in the closed mold to obtain the PUR / PIR rigid foam and iv.Demolding of the PUR / PIR rigid foam, wherein the polyisocyanate component B) is used in an amount such that the isocyanate number is at least 110 and / or the polyisocyanate component B) has a viscosity at 25 °C of > 400 mPa s and an NCO content of < 31.3%; in particular wherein the polyisocyanate component B) is used in an amount such that the isocyanate number is at least 110 and the polyisocyanate component B) has a viscosity at 25 °C of > 400 mPa s and an NCO content of < 31.3%. In step i., a reaction mixture is prepared by mixing at least CO2 in the supercritical state as blowing agent, an isocyanate-reactive composition A) and a polyisocyanate component B). The isocyanate-reactive Composition A) comprises at least one polyol component A1) with a functionality of 2.5, comprising at least one polyether polyol, polyester polyol, polycarbonate polyol, polyether-polycarbonate polyol, polyetherester polyol, or mixtures thereof. Furthermore, a catalyst component A2), an auxiliary and additional component A3), or both a catalyst component A2) and an auxiliary and additional component A3) may be present in composition A). Finally, low-molecular-weight isocyanate-reactive compounds A4) and / or further isocyanate-reactive compounds A5), such as graft polyols, polyamines, polyamino alcohols, and polythiols, may also be present in composition A).All combinations of Al) with A2), A3), A4) and / or A5 are conceivable here, i.e. Al) with A2); Al) with A3); Al) with A4); Al) with A5); Al) with A2) and A3); Al) with A2) and A4); Al) with A2) and A5); Al) with A3) and A4); Al) with A3) and A5); Al) with A4) and A5); Al) with A2), A3) and A4); Al) with A2), A3) and A5); Al) with A2), A4) and A5). In step ii., the reaction mixture obtained in step i. is introduced into a closed mold, in which a counterpressure of 2.0 to 90 bar prevails. In step iii, the reaction mixture is allowed to foam in the closed mold, thus obtaining the PUR / PIR rigid foam. In step iv, the PUR / PIR rigid foam is demolded. For the purposes of this application, the indication of an NCO content in % means the proportion of NCO groups in wt.% of the substance or mixture of substances to which the indication of the NCO content refers. In one embodiment, the proportion of all primary OH functions present in the polyol component Al) to the total number of terminal OH functions in the polyol component Al) is at least 30%. In one embodiment, the number of NCO groups in the polyisocyanate component B) and the number of isocyanate-reactive hydrogen atoms in the isocyanate-reactive composition A) are in a numerical ratio of > 110: 100 to < 300: 100. In a further embodiment, the reaction mixture R) is essentially free of cell-opening compounds or does not contain any cell-opening compounds. The term "essentially free of" here means that the reaction mixture R) contains cell-opening compounds at most in an amount corresponding to an unintentional impurity, e.g., less than 0.1 wt. %, based on the total amount of the isocyanate-reactive composition A. In a further embodiment, step i) takes place under conditions that are supercritical for the CO2. In a preferred embodiment, both steps i and ii take place under conditions that are supercritical for the CO2. In a further embodiment, in step iii. the back pressure is maintained for a period 1 of 1 - 40 s after the end of step ii. and then the back pressure is relieved during a period 2 at a pressure relief rate of 1 - 90 bar / s. In a further embodiment, the polyol component Al) has a hydroxyl number of 280 - 600 mg KOH / g, measured according to DIN 53240-2:2007. In one embodiment, the isocyanate-reactive composition A) consists of at least 65% by weight of the polyol component A1), which has a hydroxyl number between 280 and 600 mg KOH / g, measured according to DIN 53240-2:2007, and a functionality of > 2.8 to < 6.0. In a further embodiment, the proportion of primary OH functions present in the isocyanate-reactive composition A) relative to the total number of all terminal OH functions in the isocyanate-reactive composition A is at least 35%. In a preferred embodiment, the isocyanate-reactive composition A) consists of at least 65% by weight.-%, based on the total amount of A) excluding A2) and A3), from the polyol component A1), which has a hydroxyl number between 280 and 600 mg KOH / g, measured according to DIN 53240-2:2007, and a functionality of > 2.8 to < 6.0 and the proportion of the primary OH functions present in the isocyanate-reactive composition A) in relation to the total number of all terminal OH functions in the isocyanate-reactive composition A is at least 35%. In a further embodiment, the isocyanate-reactive composition A) consists of at least 60 wt.% polyether polyol. The isocyanate-reactive composition A) contains at least one polyol component A1) selected from the group consisting of polyether polyols, polyester polyols, polyetherester polyols, polycarbonate polyols and polyether-polycarbonate polyols. The proportion of primary OH functions in the total number of terminal OH functions in the polyol component A1) is preferably at least 30%, more preferably at least 35%, particularly preferably at least 38%. The polyol component A1) is further characterized in that it has a functionality f of > 2.5, preferably > 2.6 to < 6.5 and particularly preferably > 2.8 to < 6.1. Isocyanate-reactive compositions in which the polyol component A1) has a functionality in these areas, an optimal viscosity increase is found during injection until the back pressure is released and the foams can be demolded more quickly. The polyol component A1) preferably has a hydroxyl number of 280-600 mg KOH / g, particularly preferably 300-580 mg KOH / g, and especially preferably 350-540 mg KOH / g. This has a particularly favorable effect on the mechanical properties of the foams. For the purposes of this application, “a polyether polyol” may also be a mixture of different polyether polyols; this applies analogously to the other polyols listed here. The polyether polyols which can be used according to the invention are the polyether polyols which are known to the person skilled in the art and which can be used in polyurethane synthesis. Examples of suitable polyether polyols are polytetramethylene glycol polyethers, which are obtained by polymerization of tetrahydrofuran by cationic ring opening. Also suitable polyether polyols are addition products of styrene oxide, ethylene oxide, propylene oxide, butylene oxide, and / or epichlorohydrin to di- or polyfunctional starter molecules. The addition of ethylene oxide and propylene oxide is particularly preferred. Suitable starter molecules include, for example, water, ethylene glycol, diethylene glycol, butyldiglycol, glycerol, diethylene glycol, trimethylolpropane, propylene glycol, pentaerythritol, sorbitol, sucrose, ethylenediamine, toluenediamine, triethanolamine, bisphenols, in particular 4,4'-methylenebisphenol, 4,4'-(l-methylethylidene)bisphenol, 1,4-butanediol, 1,6-hexanediol, as well as low-molecular-weight, hydroxyl-containing esters of such polyols with dicarboxylic acids, and oligoethers of such polyols. The isocyanate-reactive composition A) preferably contains at least 50 wt.%, preferably at least 60 wt.%, particularly preferably at least 70 wt.% polyether polyol, based on its total weight. In a preferred embodiment, component A1) consists of 100 wt.% polyether polyol. These preferred embodiments are characterized by particularly good hydrolytic stability. 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, as well as, in particular, glutaric acid, fumaric acid, succinic acid, adipic acid, phthalic acid, terephthalic acid, and isoterephthalic acid. In addition to organic dicarboxylic acids, derivatives of these acids, such as their anhydrides and their esters and semiesters with low-molecular-weight, monofunctional alcohols with > 1 to < 4 carbon atoms, can also be used. The partial use of the above-mentioned bio-based starting materials, particularly fatty acids or fatty acid derivatives (oleic acid, soybean oil, etc.), is also possible and can offer advantages, e.g., with regard to the storage stability of the polyol formulation, dimensional stability, fire behavior, and compressive strength of the foams. Polyether polyols, which are obtained by alkoxylating starter molecules such as polyhydric alcohols, are used as a further component in the production of polyetherester polyols. These starter molecules are at least difunctional, but may optionally also contain portions of higher-functionality, particularly trifunctional, starter molecules. Starter molecules are, for example, diols with number-average molecular weights Mn of preferably > 18 g / mol to < 400 g / mol, preferably from > 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. In addition to the diols, compounds with > 2 Zerewitinoff-active hydrogens, in particular with number-average functionalities of > 2 to < 8, in particular from > 3 to < 6, can also be used as starter molecules for the production of the polyethers, for example 1,1,1-trimethylolpropane, triethanolamine, glycerol, sorbitan and pentaerythritol as well as trioien or tetraoien-started polyethylene oxide polyols with average molecular weights Mn of preferably > 62 g / mol to < 400 g / mol, in particular from > 92 g / mol to < 200 g / mol. Polyetherester polyols can also be prepared by alkoxylation, particularly by ethoxylation and / or propoxylation, of reaction products obtained by reacting organic dicarboxylic acids and their derivatives, as well as components containing Zerewitinoff-active hydrogens, particularly diols and polyols. Derivatives of these acids can include, for example, their anhydrides, such as phthalic anhydride. Suitable polyester polyols include polycondensates of di- and tri-, and tetracarboxylic acids and di- and tri- and tetracarboxylic acids or 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. Examples of suitable diols include ethylene glycol, butylene glycol, diethylene glycol, triethylene glycol, polyalkylene glycols such as polyethylene glycols, 1,2-propanediol, 1,3-propanediol, 1,3- and 1,4-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. Monohydric alkanols can also be used. Examples of polycarboxylic acids that can be used include phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, cyclohexanedicarboxylic acid, adipic acid, azelaic acid, sebacic acid, glutaric acid, tetrachlorophthalic 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, endomethylenetetrahydrophthalic acid, dimer fatty acid, trimer fatty acid, citric acid, or trimellitic acid. The corresponding anhydrides can also be used as acid sources. Monocarboxylic acids such as benzoic acid and alkanecarboxylic acids can also be used. 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. Bio-based starting materials and / or their derivatives are particularly suitable for the production of polyester polyols, such as: B. Castor oil, polyhydroxy fatty acids, ricinoleic acid, 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, wild rose oil, safflower oil, walnut oil, fatty acids, hydroxyl-modified and epoxidized fatty acids and fatty acid esters, for example based on myristoleic acid, palmitoleic acid, oleic acid, vaccenic acid, petroselic 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. Particularly preferred are esters of Ricinoleic acid with polyfunctional alcohols, e.g., glycerin. The use of mixtures of such bio-based acids with other carboxylic acids, e.g., phthalic acids, is also preferred. Suitable polycarbonate polyols are polycarbonates containing hydroxyl groups, for example, polycarbonatediols. These are obtainable by reacting carbonic acid derivatives, such as diphenyl carbonate, dimethyl carbonate, or phosgene, with polyols, preferably diols, or by copolymerizing alkylene oxides, such as propylene oxide, with CO2. 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-trimethylpentane-1,3-diol, 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, which are obtainable, for example, by copolymerization of alkylene oxides, such as propylene oxide, with CO2. Polyol production processes have been described, for example, by Ionescu in "Chemistry and Technology of Polyols for Polyurethanes", Rapra Technology Limited, Shawbury 2005, p. 55 ff. (Chapter 4: Oligo-Polyols for Elastic Polyurethanes), p. 263 ff. (Chapter 8: Polyester Polyols for Elastic Polyurethanes) and in particular on p. 321 ff. (Chapter 13: Polyether Polyols for Rigid Polyurethane Foams) and p. 419 ff. (Chapter 16: Polyester Polyols for Rigid Polyurethane Foams). It is also possible to obtain polyester and polyether polyols via glycolysis of suitable polymer recyclates. Suitable polyether polycarbonate polyols and their production are described, for example, in EP 2910585 A,

[0024] -

[0041] Examples of polycarbonate polyols and their preparation can be found, inter alia, in EP 1359177 A. The preparation of suitable polyetherester polyols is described, inter alia, in WO 2010 / 043624 A and EP 1 923 417 A. Polyether polyols, polyether carbonate polyols, and polyether ester polyols with a high proportion of primary OH functions are obtained when the alkylene oxides used for the alkoxylation have a high proportion of ethylene oxide. In particular, the molar proportion of ethylene oxide structures, based on the total alkylene oxide structures present in the polyols of component A1, is at least 50 mol%. The use of 100 mol% ethylene oxide is also a preferred embodiment. Furthermore, the isocyanate-reactive composition A) may contain low molecular weight isocyanate-reactive compounds A4), in particular di- or trifunctional amines and alcohols, particularly preferably diols and / or triols with molecular weights Mn less than 400 g / mol, preferably from 60 to 300 g / mol, are used, e.g., triethanolamine, diethylene glycol, ethylene glycol, glycerol. If such low-molecular-weight compounds that are reactive toward isocyanates are used to produce rigid polyurethane foams, e.g., as chain extenders and / or crosslinking agents, and these do not also fall under the definition of the polyol component A1), they are advantageously used in an amount of up to 5 wt.%, based on the total weight of composition A). In addition to the polyols and isocyanate-reactive compounds described above, composition A) may contain other isocyanate-reactive compounds A5), for example, graft polyols, polyamines, polyamino alcohols, and polythiols. Of course, the isocyanate-reactive components described also include compounds with mixed functionalities. A preferred isocyanate-reactive composition A) comprises the polyol component A1), which has a hydroxyl number of 280 to 600 mg KOH / g and a functionality of > 2.8 to < 6.0, in an amount of at least 65 wt.%, in particular at least 80 wt.% and very particularly preferably more than 90 wt.%, based on the total amount of A) excluding components A2) and A3), and the proportion of primary OH functions in composition A) is at least 35% (based on all terminal OH functions in composition A). In the production of PUR / PIR rigid foam, supercritical CO2 is used as blowing agent component C). Blowing agent component C) is used in the amount necessary to achieve a dimensionally stable foam matrix and the desired bulk density. Typically, this is 0.5–30 parts by weight of blowing agent per 100 parts by weight of composition A), excluding A2) and A3). The CO2 used as a physical blowing agent is in the supercritical or near-critical state. For the purposes of the present invention, near-critical conditions exist when the following condition is met: (Tc - T) / T < 0.4 and / or (pc - p) / p < 0.4. Here, T is the temperature prevailing in the process, Tc is the critical temperature of the blowing agent or blowing agent mixture, p is the pressure prevailing in the process, and pc is the critical pressure for the blowing agent or blowing agent mixture. Near-critical conditions are preferably present when: (Tc - T) / T < 0.3 and / or (pc - p) / p < 0.3 and particularly preferably (Tc - T) / T < 0.2 and / or (pc - p) / p < 0.2. Particularly suitable conditions for carrying out the process according to the invention are Using CO2, pressures and temperatures above the critical point of CO2, i.e. > 73.7 bar and > 30.9 °C, preferably between 74 bar and 350 bar and between 31 °C and 100 °C, particularly preferably between 75 bar and 200 bar and between 32 °C and 60 °C. Physical blowing agents can be used as additional blowing agents in addition to supercritical CO2. For the purposes of the present invention, "physical blowing agents" are understood to be compounds that, due to their physical properties, are highly volatile and do not react with the polyisocyanate component B). The additional physical blowing agents can be selected from the group of hydrocarbons (e.g. n-pentane, isopentane, cyclopentane, butane, isobutane, propane), ethers (e.g. methylal), halogenated ethers, perfluorinated and partially fluorinated hydrocarbons having 1 to 8 carbon atoms, e.g. B. Perfluorohexane, HFC 245fa (1,1,1,3,3-pentafluoropropane), HFC 365mfc (1,1,1,3,3-pentafluorobutane), HFC 134a or mixtures thereof, as well as (hydro)fluorinated olefins, such as HFO 1233zd(E) (trans-l-chloro-3,3,3-trifluoro-l-propene) or HFO 1336mzz(Z) (cis-l,l,l,4,4,4-hexafluoro-2-butene) or additives such as FA 188 from 3M (l,l,l,2,3,4,5,5,5-nonafluoro-4-(trifluoromethyl)pent-2-ene), as well as mixtures thereof. If further blowing agents are added, the blowing agent component C) in one embodiment preferably contains more than 60 wt.% supercritical CO2, particularly preferably more than 75 wt.%. In addition to or instead of the physical blowing agents, chemical blowing agents (also called "co-blowing agents") can also be used. These are particularly preferably water and / or formic acid. The co-blowing agents are preferably used in an amount of 0 to 6 wt. %, particularly preferably 0.5 to 4 wt. %, based on the total amount of compounds containing hydrogen atoms reactive toward isocyanate groups in the foam-forming reaction mixture R). The proportion of the blowing agent C), based in each case on the total amount of components A) and C), is preferably > 1 wt.% to < 30 wt.%, more preferably > 4 wt.% to < 20 wt.%, particularly preferably > 6 wt.% to < 16 wt.%; the proportion of the blowing agent in the reaction mixture R) is 0.5 wt.% to 15 wt.%, preferably 2 wt.% to 10 wt.%, particularly preferably > 3 wt.% to < 8 wt.%, based in each case on the total amount of R). In a further embodiment, the isocyanate-reactive composition A) comprises a catalyst component A2), preferably a catalyst component A2) in an amount of > 0.01 to < 2.0 wt.%, based on the total weight of the isocyanate-reactive composition A). As catalyst component A2), compounds are usually used which accelerate the reaction of the compounds of composition A) containing hydroxyl groups or isocyanate-reactive groups with the isocyanate groups of component B. The catalyst component A2) can A2a) be at least one catalytically active amine compound with functional groups which have Zerewitinoff-active hydrogens and can therefore react with isocyanate (so-called “incorporable catalysts”). Examples of usable, incorporable catalysts are bis-dimethylaminopropylurea, bis(N,N-dimethylaminoethoxyethyl)carbamate, di-methylaminopropylurea, N,N,N-trimethyl-N-hydroxyethylbis(aminopropyl ether), N,N,N-trimethyl-N-hydroxyethylbis(aminoethyl ether), diethylethanolamine, bis(N,N-dimethyl-3-aminopropyl)amine, dimethylaminopropylamine, 3-dimethylaminopropyl-N,N-dimethylpropane-1,3-diamine, dimethyl -2-(2-amino->ethoxyethanol) and (1,3-bis(dimethylamino)-propan-2-ol), N,N-bis-(3-dimethylaminopropyl)-N-isopropanolamine, bis-(dimethylaminopropyl)-2-hydroxyethylamine, N,N,N-trimethyl-N-(3-aminopropyl)-bis(aminoethyl ether), 3-Dimethylaminoisopropyl-diisopropanolamine or mixtures thereof. In addition, one or more further compounds A2b), in particular the catalytically active compounds known for PUR / PIR chemistry, can be used, in addition to other amine compounds also salts such as tin(II) acetate, tin(II) octoate, tin(II) ethylhexoate, tin(II) laurate, dibutyltin diacetate, dibutyltin dilaurate, dibutyltin maleate, dioctyltin diacetate, tris(N,N-dimethylaminopropyl)-s-hexahydrotriazine, tetramethylammonium hydroxide, Sodium acetate, sodium octoate, potassium acetate, potassium octoate, sodium hydroxide. Catalyst component A2) is generally used in an amount of 0.001 to 5 wt.%, in particular 0.05 to 2.5 wt.%, based on the weight of composition A). Particularly preferably, catalyst component A2) contains both incorporable catalysts A2a) and non-incorporable catalysts A2b). In particular, it is preferred that incorporable amine compounds and catalytically active salts be used in combination. The catalysts A2a) and A2b) are preferably used in a molar ratio A2a) / A2b) of 0.1 to 16.3, particularly preferably from 0.3 to 10, and very particularly preferably from 0.8 to 6.0. The catalyst component A2) preferably contains, as catalytically active compound A2a), an amine compound that can be incorporated into the polyurethane and furthermore the catalytically active compound A2b), which is a catalytically active salt that cannot be incorporated into the polyurethane, and the molar ratio of A2a) / A2b) is 0.1 to 16.3, particularly preferably from 0.3 to 10, and very particularly preferably from 0.8 to 6.0. In a particularly preferred embodiment, 3-(dimethylamino)propylurea and potassium acetate are used in a molar ratio A2a) / A2b) of 0.1 to 6.0, particularly preferably of 0.3 to 10 and most particularly preferably from 0.8 to 6.0. The preferred catalyst ratios or catalysts have a particularly favorable effect on a defined viscosity buildup. In one embodiment, the isocyanate-reactive composition A) comprises an auxiliary and additional component A3) which comprises a stabilizer, preferably a stabilizer in an amount of > 0.05 to < 5 wt.%, based on the total weight of the isocyanate-reactive composition A). The reaction mixture R) may contain auxiliaries and additives A3). The auxiliaries and additives may contain cell-opening compounds, but preferably comprise essentially none or are free of cell-opening compounds. Cell-opening compounds are described, for example, in Kunststoff-Handbuch, Volume 7, Polyurethane, Carl Hanser Verlag, Munich / Vienna, 3rd edition, 1993, pages 104-127. These are, for example, silicones, such as polyether-polydimethylsiloxane copolymers, or organic polymers, e.g. those based on polybutadiene (e.g. Ortegol 500 and 501 from Evonik Industries), surfactants, such as the sodium salt of ethoxylated and sulfated isotridecyl alcohol, which is available under the trade name Sermul EA266 (Elementis Specialties, Netherlands), and mixtures of different components, e.g. mixtures of amine-stabilized, macromolecular, unsaturated hydrocarbons and phthalic acid esters. Further auxiliaries and additives A3) that can be used in the process according to the invention are the auxiliaries and additives known and customary from the prior art and to the person skilled in the art. Examples include surfactants, stabilizers, in particular foam stabilizers, cell regulators, fillers, dyes, pigments, flame retardants, antistatic agents, hydrolysis stabilizers, and / or fungistatic and bacteriostatic substances. Polyether-polydimethylsiloxane copolymers are frequently used as foam stabilizers, preferably a polyethylene oxide polyether with oligodimethylsiloxane end groups, wherein the number of dimethylsiloxane units is preferably < 5. Saturated and unsaturated hydrocarbons such as paraffins, polybutadienes, fatty alcohols, and esters, e.g., carboxylic acid esters, can also be used as stabilizers. Stabilizers that do not have a cell-opening effect are preferred, especially foam stabilizers. Composition A) preferably contains a maximum of 3 wt.% of silicones and polybutadienes, based on the total weight of composition A). Surfactants can also be used as stabilizers, for example alkoxylated alkanoics such as ethers of linear or branched alkanols having > 6 to < 30 carbon atoms with polyalkylene glycols having > 5 to < 100 alkylene oxide units, alkoxylated alkylphenols, alkoxylated fatty acids, carboxylic acid esters of an alkoxylated sorbitan (especially polysorbate 80), fatty acid esters, polyalkyleneamines, alkyl sulfates, phosphatidylinositols, fluorinated surfactants, surfactants containing polysiloxane groups, and / or bis(2-ethyl-l-hexyl)sulfosuccinate. Fluorinated surfactants can be perfluorinated or partially fluorinated. Examples include partially fluorinated ethoxylated alkanols or carboxylic acids. The composition A) preferably contains a total of not more than 5% by weight of surfactants, particularly preferably not more than 3% by weight, more preferably less than 2% by weight and particularly preferably not more than 1.6% by weight of surfactants, based on the total weight of the composition A). The reaction mixture R) comprises a polyisocyanate component B), i.e. an isocyanate with an NCO functionality of > 2, wherein the polyisocyanate component B) is used in an amount such that the isocyanate number is at least 110 and / or the polyisocyanate component B) has a viscosity at 25 °C of > 400 mPa-s and an NCO content < 31.3%; in particular wherein the polyisocyanate component B) is used in an amount such that the isocyanate number is at least 110 and the polyisocyanate component B) has a viscosity at 25 °C of > 400 mPa-s and an NCO content < 31.3%. If the polyisocyanate component B) is used in an amount such that the isocyanate number is at least 110, suitable polyisocyanates can be, for example, 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 mixtures thereof with 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 (MDI) and / or higher homologues, 1,3- and / or l,4-bis-(2-isocyanato-prop-2-yl)-benzene (TMXDI), l,3-bis-(isocyanatomethyl)benzene (XDI), as well as alkyl 2,6-diisocyanatohexanoates (lysine diisocyanates) with CI to C6 alkyl groups. In this case, mixtures of the isomers of diphenylmethane diisocyanate (“monomeric MDI”, abbreviated to “mMDI”) and its oligomers (“oligomeric MDI”) are preferably used as isocyanate component B). Mixtures of monomeric MDI and oligomeric MDI are generally referred to as “polymeric MDI” (pMDI). The oligomers of MDI are polyphenyl polymethylene polyisocyanates with higher cores, i.e., mixtures of the higher core homologues of diphenyl methylene diisocyanate, which have an NCO functionality f > 2 and have the following structural formula: C15H10N2O2 [C8H5NO]n, where n = integer > 0, preferably n = 1. 2, 3, and 4. Higher-nuclear homologues (C15H10N2O2 [C8H5NO]m, m = integer > 4) may also be present in the mixture of organic polyisocyanates a). Further preferred isocyanate components B) are mixtures of mMDI and / or pMDI with a maximum of up to 20% by weight, more preferably a maximum of 10% by weight, of other aliphatic, cycloaliphatic, and especially aromatic polyisocyanates known for the production of polyurethanes, especially TDI. 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. Instead of or in addition to the above-mentioned polyisocyanates, suitable NCO prepolymers can also be used as organic isocyanate component B). The prepolymers can be prepared by reacting one or more polyisocyanates with one or more polyols, corresponding to the polyols described under components A1) and A2). It is possible that the isocyanate is a prepolymer obtainable by reacting an isocyanate with an NCO functionality of > 2 and polyols with a molecular weight of > 62 g / mol to < 8000 g / mol and OH functionalities of > 1.5 to < 6. The NCO content is preferably from > 29.0 wt.% to < 32.0 wt.%, and preferably has a viscosity at 25°C of > 80 mPa s to < 2000 mPa s, particularly preferably from > 100 mPa s to < 800 mPa s (dynamic viscosity determined according to DIN 53019, at 25°C). If a polyisocyanate component B) is used which has a viscosity at 25°C of > 400 mPa s and an NCO content of < 31.3%, all of the aforementioned isocyanates can be used which simultaneously meet the requirements of a viscosity at 25°C of > 400 mPa s and an NCO content of < 31.3%. In this case, the number of NCO groups in the polyisocyanate component B) and the number of isocyanate-reactive groups in component A) can, for example, be in a numerical ratio of > 50: 100 to < 300: 100. To produce the rigid polyurethane foams, components A) and B) are generally reacted in amounts such that the isocyanate number of the formulation is 80-150, preferably 105-135, particularly preferably 110-125. Urethane groups are preferably formed in this range. In another preferred embodiment, the isocyanate number is 150-400. In this range, the foams have a high proportion of isocyanurate functions, which, for example, impart inherent flame retardancy to the foams. Particularly preferably, the polyisocyanate component B) has a viscosity at 25 °C of > 400 mPa-s and an NCO content of < 31.3% and is used in an amount such that the isocyanate index is 110 - 125 or 150 - 400. At least the method according to the invention consists of steps i. to iv. In step i. of the process according to the invention, the reaction mixture R) is prepared from the components A), B) and C). For this purpose, composition A) can be placed in a vessel, for example, then mixed with the blowing agent component C), and then added with the polyisocyanate B). The components can also be mixed in a mixing head. Mixing, particularly with components C) and B), can be carried out under pressure. In a preferred embodiment, components A) and C) are mixed with component B) in a high-pressure mixing head. The blowing agent component C) is CO2 in the supercritical state, and the reaction of the components preferably takes place under conditions that are supercritical for CO2. In this case, suitable pressures in the mixing head and / or in the discharge line(s) for producing the polyurethane foam are, for example, in the range from > 73.7 bar to < 350 bar, and preferably in the range from > 75 bar to < 200 bar. Suitable temperatures are, for example, > 30.9 °C to < 100 °C, and preferably > 32 °C to < 60 °C. At such pressures, supercritical conditions for the blowing agent used can be maintained. In a further embodiment, the residence time of the mixture in the mixing head under supercritical conditions of the blowing agent is > 0 seconds to < 20 seconds, preferably from > 0.1 seconds to < 10 seconds, and particularly preferably from > 0.5 seconds to < 5 seconds. This allows the mixture to polymerize under supercritical conditions. The residence time can be determined by the volume of the reaction chamber (=mixing chamber and / or piping) in which supercritical conditions prevail, divided by the volume of the mixture conveyed in a specific unit of time. In step ii. of the process according to the invention, the reaction mixture R) according to the invention comprising components A), B) and C) is introduced into a closed mold, wherein a counterpressure in the mold during the introduction is 2.0 - 90 bar, preferably 2.0 - 80 bar, particularly preferably 5.0 - 40 bar. Possible embodiments for this are the following: the counter pressure is applied by applying gas (compressed air or nitrogen) to the mold either directly (preferred) and / or through a floating seal that divides the pressurized space into gas and reaction space (less preferred), and is adjusted, maintained and ultimately relieved via a proportional valve. In step iii of the process, the reaction mixture is allowed to foam. A preferred embodiment of step iii) is as follows: after the end of step ii, the backpressure in the mold is kept constant for a period 1, which is preferably 1-40 seconds, more preferably 2-30 seconds, and most preferably 3-20 seconds, during which the viscosity of the reaction mixture initially increases without foaming of the reaction mixture. It has been shown that maintaining the pressure for the preferred period results in particularly favorable viscosity ranges of the mixture for this reaction section. After the end of period 1, the mold is released. The pressure is released from the mold within a period 2, at a pressure release rate of 1-90 bar / s, preferably 1-80 bar / s, more preferably 2-70 bar / s. The release can take place in particular via a proportional valve. During period 2, the reaction mixture foams.Too rapid a release of pressure has a negative effect on cell stability, while too slow a release has a negative effect on the foaming reaction. In step iv of the process, the PUR / PIR rigid foam is demolded. The present invention also provides an open-cell PUR / PIR rigid foam obtainable or obtained by the process according to the invention. The foam according to the invention exhibits good mechanical properties, in particular good dimensional stability at elevated temperatures and preferably also good compressive strength. This open-cell PUR / PIR rigid foam preferably has a density of 30 - 90 kg / m 3 , preferably 30 - 70 kg / m 3 , according to ISO 845:2006, an open cell content of > 90%, preferably > 94%, according to ISO 4590:2002 and an average (arithmetically averaged) cell diameter of 70 - 130 pm according to light microscopic evaluation. Foamed moldings and composite systems containing these moldings can preferably be produced from the PUR / PIR foams of the invention. The composite systems are often bordered by decorative layers on both the top and bottom sides. Suitable decorative layers include metals, plastics, wood, and paper. Areas of application for such discontinuously produced PUR / PIR composite systems include, in particular, the technical insulation of appliances such as refrigerators, freezers, fridge-freezers, boilers, refrigerated containers, and coolers, as well as pipes. The use of PUR / PIR foams in these fields is generally known to those skilled in the art and has been described many times. The PUR / PIR foams according to the invention are exceptionally well-suited for these purposes, as they are characterized by high dimensional stability and, advantageously, also by high compressive strength and low thermal conductivity, which can be further increased by applying a vacuum. Furthermore, the invention relates to a vacuum insulation panel containing a PUR / PIR rigid foam obtainable according to the process according to the invention. Finally, the invention also relates to a refrigerator, freezer or a refrigerator-freezer combination containing a PUR / PIR rigid foam obtainable according to the method according to the invention or a vacuum insulation panel according to the invention. Designations used in this application have the following meaning: The index (also called isocyanate index, isocyanate index, or index) is the quotient of the actual amount of substance [mol] of isocyanate groups used and the actual amount of substance [mol] of hydrogen atoms reactive towards isocyanates, multiplied by 100: Index = (Isocyanate groups [mol] / hydrogen atoms reactive towards isocyanates [mol]) • 100 For the purposes of this application, "functionality" or "f" of a compound refers to the theoretical functionality: for example, the functionality of an exclusively glycerol-initiated polyol is f = 3, and that of an exclusively ethylenediamine-initiated polyol is f = 4. For the purposes of this application, "functionality" or "f" of a component mixture refers to the number-average functionality of the mixture to which the information refers. Thus, the functionality of the polyol component A1) refers, for example, to the number-average functionality of the mixture of the polyols contained in component A1 with respect to all isocyanate-reactive hydrogen atoms contained therein. For the purposes of this application, “molar weight” or “molar mass” or “Mn” means the number-weighted average molecular mass. The OH number (also: hydroxyl number) indicates the OH number of a single added polyol. OH number values ​​for mixtures refer to the number-average OH number of the mixture, calculated from the OH numbers of the individual components in their respective molar proportions. The OH number indicates the amount of potassium hydroxide in milligrams that is equivalent to the amount of acetic acid bound during the acetylation of one gram of substance. It is in the context of the present invention determined according to the standard DIN 53240-2, as of November 2007. The invention will be explained in more detail with reference to the following examples and comparative examples, without the scope being restricted by the examples. Examples: Standards and measuring instruments used: Determination of density: Foams made of rubber and plastics - Determination of density (ISO 845:2006); German version EN ISO 845:2009 Determination of open-cell density: Determination of the volume fraction of open and closed cells (ISO 4590:2002); German version EN ISO 4590:2003 Determination of the OH number: Determination of the hydroxyl number - Part 2: Method with catalyst according to DIN 53240-2, as of November 2007 Determination of dimensional stability: Plates made of rigid foam of a defined size, e.g. width x depth x height is 20x20x2 cm 3(Height is approximately 10-40% of the width) are evacuated and sealed in a foil bag. The internal pressure of the foil bag with foam board is less than 30 mbar. The evacuated and sealed bag is stored in a drying cabinet at a temperature of 60°C. Dimensional deviations from the dimensions measured immediately after sealing (in mm) and changes in the optical quality of the surface (indentations measured in mm) are determined at regular intervals. If deviations of > 10% in width, depth, or height and indentations of > 10% occur after 24 hours of storage at 60°C, the foam board is considered to be dimensionally unstable. The entry "Yes" in Table 1 means that the respective lack of dimensional stability (dimensional deviations or indentations on the surface) is present. Cell size determination: Optical microscopic evaluation using a VHX 5000 light microscope. The sample to be measured is examined at three different locations, each over a circular area with a diameter of 5 mm. The resolution is selected so that the selected area captures more than 100 cells. All cells are then analyzed using the freely available ImageJ software, and the arithmetically averaged cell diameter is calculated from the obtained ECD (equivalent circle diameter) values. The average functionality f in Table 1 refers to the number-average functionality of the mixture of polyols contained in the formulation. The percentage of primary OH functions in [%] in Table 1 refers to the percentage of primary OH functions in the total number of OH functions in the mixture of polyols contained in the formulation. Examples 1 and comparative examples 1 to 3: Supercritical CO2-blown polyurethane foams were manufactured according to the formulations listed in Table 1 below. Unless otherwise stated, quantities are given as parts by weight. The following materials were used: Polyol 1 : Trimethylol-initiated polyether polyol with propylene oxide as alkylene oxide with a Hydroxyl number of 800 mg KOH / g, a functionality of 3 and a viscosity at 25 °C of 6100 mPa-s Polyol 2: Trimethylol-initiated polyether polyol with ethylene oxide as alkylene oxide with a Hydroxyl number of 550 mg KOH / g, a functionality of 3 and a viscosity at 25 °C of 505 mPa- s Polyol 3: Ethylene glycol and sucrose initiated polyether polyol with propylene oxide as Alkylene oxide with a hydroxyl number of 440 mg KOH / g, a functionality of 2.8 and a viscosity at 25 °C of 450 mPa-s Polyol 4: 1,2-propanediol-initiated polyether polyol with propylene oxide as alkylene oxide with a hydroxyl number of 56 mg KOH / g, a functionality of 2 and a viscosity at 25 °C of 310 mPa-s Polyol 5: 1,2 propanediol-initiated polyether polyol with propylene oxide as alkylene oxide with a hydroxyl number of 112 mg KOH / g, a functionality of 2 and a viscosity at 25 °C of 140 mPa-s Polyol 6: Glycerol-initiated polyether polyol with propylene oxide as alkylene oxide with a Hydroxyl number of 231 mg KOH / g, a functionality of 3 and a viscosity at 25 °C of 350 mPa- s Tegostab B 8443: Polyetherpolydimethylsiloxane copolymer foam stabilizer (Evonik). Desmorapid PU 1792: Catalyst, potassium acetate in diethylene glycol (Covestro) Amine ZZ: Catalyst, N'-(3-(Dimethylamino)propyl)-N,N-dimethylpropane-1,3-diamine, Air Products Isocyanate 1: Mixture of MDI and PMDI with a functionality of approximately 2.8, an NCO content of approximately 31.5%, and a viscosity at 25 °C of approximately 200 mPa-s (Desmodur 44V20E, Covestro) Isocyanate 2: Mixture of MDI and PMDI with a functionality of approximately 3.0, an NCO content of approximately 31.2%, and a viscosity at 25 °C of approximately 685 mPa-s (Desmodur 44V70L, Covestro) Production of polyurethane molded foams on a high-pressure system: To produce polyurethane molded foams on a high-pressure system, a polyol formulation was prepared from the isocyanate-reactive compounds, stabilizers, and catalysts listed in Table 1 below. This was used as the polyol component in a standard high-pressure mixing system and mixed with CO2 at a pressure of 160 bar and a temperature of 35 °C. Supercritical conditions prevailed for the blowing agent (supercritical CO2, also known as "scCCh"). In a high-pressure mixhead, this mixture was mixed with a polyisocyanate delivered at a pressure of 160 bar and a temperature of 35 °C. The shot quantity was 1000 g / s, corresponding to a volume flow of 833 ml / s (density of the mixture: 1.2 g / ml). The resulting reaction mixture was metered into a closed mold preloaded with a counterpressure of 11 bar and a mold temperature of 55 °C.After the end of the injection, the pre-stressed counterpressure was maintained for a further 8 s and only then was it suddenly released to ambient pressure within < 2 seconds and the thus produced molded article was demolded from the mold after 10 minutes. The comparison of comparative examples 1 - 3 with example 1 shows that the selection of the appropriate index and the isocyanate with suitable viscosity and NCO content determines the dimensional stability of the resulting rigid foams when stored at elevated temperature in an evacuated bag: Comparative Examples 1 and 2 produce rigid foams that exhibit significant deformation after 24 hours of storage at 60 °C: their dimensions deviate by more than 10% and 5-10%, respectively, from the dimensions immediately after sealing, i.e., before storage at 60 °C. The foam of Example 1 is not only dimensionally stable after 24 hours of storage at 60 °C – like the foam of Comparative Example 3 – but also exhibits particularly good surface qualities after storage, even improved compared to Comparative Examples 1-3. Table 1

Claims

Claims 1. A process for producing a PUR / PIR rigid foam comprising the steps: i. Preparing a reaction mixture R) comprising an isocyanate-reactive composition A) comprising a polyol component Al) with a functionality f of > 2.5 comprising at least one polyether polyol, polyester polyol, polycarbonate polyol, polyether-polycarbonate polyol, polyether ester polyol, or mixtures thereof, optionally a catalyst component A2), optionally an auxiliary and additive component A3); a polyisocyanate component B); and a blowing agent component C) comprising CO2 in the supercritical state, ii. Introducing the reaction mixture R) from step i. into a closed mold, wherein a back pressure in the closed mold during introduction is 2.0 - 90 bar, iii. Allowing the reaction mixture R) to foam up in the closed mold to obtain the PUR / PIR rigid foam, and iv.Demolding of the PUR / PIR rigid foam, wherein the polyisocyanate component B) is used in an amount such that the isocyanate number is at least 110 and the polyisocyanate component B) has a viscosity at 25 °C of > 400 mPa- s and an NCO content < 31.3%.

2. Method according to claim 1, wherein the number of NCO groups in the polyisocyanate component B) and the number of hydrogen atoms reactive towards isocyanates in the isocyanate-reactive composition A) are in a numerical ratio of > 110:100 to < 300:100 to each other.

3. Method according to claim 1 or 2, wherein the proportion of all primary OH functions present in the polyol component Al) to the total number of terminal OH functions in the polyol component Al) is at least 30%.

4. Method according to any one of claims 1 to 3, wherein the reaction mixture R) is substantially free of cell-opening compounds or contains no cell-opening compounds.

5. Method according to any one of claims 1 to 4, wherein step i) and optionally ii) takes place under conditions supercritical for the CO2.

6. Method according to any one of claims 1 to 5, wherein in step iii. the back pressure is maintained for a period 1 of 1 - 40 s after the end of step ii. and subsequently the back pressure is relieved during a period 2 with a pressure relief rate of 1 - 90 bar / s.

7. Method according to any one of claims 1 to 6, wherein the polyol component Al) has a hydroxyl number of 280 - 600 mg KOH / g, measured according to DIN 53240-2:2007.

8. A method according to any one of claims 1 to 7, wherein the isocyanate-reactive composition A) consists of at least 65 wt.% of the polyol component Al) having a hydroxyl number between 280 and 600 mg KOH / g, measured according to DIN 53240-2:2007, and a functionality of > 2.8 to < 6.0, and the proportion of primary OH functions present in the isocyanate-reactive composition A) to the total number of all terminal OH functions in the isocyanate-reactive composition A is at least 35%.

9. Method according to any one of claims 1 to 8, wherein the composition A) that is reactive towards isocyanates consists of at least 60 wt.% polyether polyol.

10. Method according to any one of claims 1 to 9, wherein the content of propellant component C) is 0.5 wt.% to 15 wt.%, based on the total weight of R).

11. Method according to any one of claims 1 to 10, wherein the isocyanate-reactive composition A) comprises a catalyst component A2), preferably a catalyst component A2) in an amount of > 0.01 to < 2.0 wt.%, based on the total weight of the isocyanate-reactive composition A).

12. Method according to any one of claims 1 to 11, wherein the isocyanate-reactive composition A) comprises an auxiliary and additive component A3, which includes a stabilizer, preferably a stabilizer in an amount of > 0.05 to < 5 wt.%, based on the total weight of the isocyanate-reactive composition A).

13. Open-cell PUR / PIR rigid foam obtainable by the method according to any one of claims 1 to 12. Vacuum insulation panel comprising a PUR / PIR rigid foam according to claim 13. Refrigerator, freezer or fridge-freezer combination comprising a PUR / PIR rigid foam according to claim 13 or a vacuum insulation panel according to claim 14.

Images