Compressed fine continuous cell PUR / PIR rigid foam

Abstract

The present invention relates to a method for producing a compressed fine-cell rigid polyurethane foam, the obtained rigid polyurethane foam, and its use.

Description

Technical Field

[0001] The present invention relates to a method for producing a compressed fine-cell rigid polyurethane foam, the resulting rigid polyurethane foam, and its use.

Background Art

[0002] Rigid polyurethane foams can contain not only urethane groups (PUR) but also isocyanurate groups (PIR). In the present application, unless otherwise specified, the description of a rigid polyurethane foam or a rigid PUR / PIR foam is to be interpreted as meaning not only a rigid foam substantially containing urethane groups but also a rigid foam containing both urethane groups and isocyanurate groups.

[0003] Rigid polyurethane foams have been known for a long time. Their substantial field of application is insulation. The use of vacuum insulation panels (VIPs) containing rigid polyurethane foams for insulation is becoming increasingly important. The quality of the foam has a decisive influence on the insulation properties of the foam used for vacuum insulation. On the one hand, it is advantageous for the cell size to be very small and for the cell size to be very uniform, and on the other hand, it is advantageous for the proportion of open cells to be high in order to make it easier to evacuate the foam.

[0004] The production of open-cell rigid polyurethane foams is also known in principle. Generally, a specific cell-opening substance is added to the reaction mixture to bring about cell-opening during the foaming process.

[0005] Patent Document 1 discloses a method for producing a fine-cell rigid polyurethane foam. This method includes introducing a supercritical CO2-containing reaction mixture into a mold under back pressure and then rapidly reducing the pressure. Due to the specific composition of the reaction mixture, a foam with a particularly low density, a high open-cell content, and a small cell size is obtained.

[0006] Generally, there is a constant need to achieve a further improved combination of properties in rigid polyurethane foams, for example, to further improve (i.e., lower) the thermal conductivity of the foam without having to accept a large penalty with respect to mechanical properties.

[0007] Compressing open-cell rigid polyurethane foams has been proposed many times. Thus, Patent Document 2 discloses a method of compressing a rigid polyurethane foam for VIP after curing and before evacuation. However, neither the chemical composition, open-cell content, cell size, nor density of the rigid polyurethane foam is disclosed. Since Patent Document 1 first disclosed a rigid polyurethane foam showing both a low density and a small cell size and having a large proportion of open cells, the foam of Patent Document 2 may not be such a foam. This document particularly teaches that compressing a rigid polyurethane foam necessarily involves a decrease in mechanical properties.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0009] An object of the present invention is to further lower the thermal conductivity of a low-density fine open-cell rigid polyurethane foam known from the prior art, particularly without having to accept a large penalty with respect to mechanical properties, such as the compressive strength in the parallel and / or transverse directions with respect to the foaming direction.

Means for Solving the Problems

[0010] This object is surprisingly achieved by a method for producing a compressed closed-cell rigid PUR / PIR foam, i. the following components: a polyol component A1) having a functionality f greater than 2.5, comprising at least one polyether polyol, polyester polyol, polycarbonate polyol, polyether carbonate polyol, polyether ester polyol, or a mixture thereof, optionally a catalyst component A2), optionally an auxiliary component and an additive component A3), comprising an isocyanate-reactive composition A), a polyisocyanate component B), a blowing agent component C) comprising supercritical CO2, and producing a reaction mixture R) comprising: ii. introducing the reaction mixture R) from step i into a closed mold, wherein the back pressure in the closed mold during introduction is from 2.0 bar to 90 bar, iii. foaming the reaction mixture R) in the closed mold in the foaming direction to obtain a rigid PUR / PIR foam having a thickness D e in a dimension substantially perpendicular to the foaming direction, iv. demolding the rigid PUR / PIR foam, v. compressing the rigid PUR / PIR foam from a thickness D e to a thickness D k to obtain a compressed rigid PUR / PIR foam, wherein D k is from 0.05·D e to 0.95·D e and step v can be carried out before or after step iv, which is achieved by a method comprising:

[0011] Thus, step i involves producing a reaction mixture by at least mixing supercritical CO2, an isocyanate-reactive composition A), and a polyisocyanate component B) with each other. The isocyanate-reactive composition A) in this case contains at least one polyol component A1) having a functionality of 2.5, which includes at least one polyether polyol, polyester polyol, polycarbonate polyol, polyether polycarbonate polyol, polyether ester polyol, or a mixture thereof. The composition A) may further contain a catalyst component A2), an auxiliary component and an additive component A3), or both the catalyst component A2) and the auxiliary component and the additive component A3). The composition A) may ultimately also contain a low molecular weight isocyanate-reactive compound A4) and / or a further isocyanate-reactive compound A5), such as a graft polyol, polyamine, polyamino alcohol, and polythiol. All combinations of A1) with A2), A3), A4), and / or A5) are conceivable in this case, i.e., the combination of A1) and A2), the combination of A1) and A3), the combination of A1) and A4), the combination of A1) and A5), the combination of A1) and A2) and A3), the combination of A1) and A2) and A4), the combination of A1) and A2) and A5), the combination of A1) and A3) and A4), the combination of A1) and A3) and A5), the combination of A1) and A4) and A5), the combination of A1) and A2), A3), and A4), the combination of A1) and A2), A3), and A5), the combination of A1) and A2), A4), and A5), the combination of A1) and A3), A4), and A5).

[0012] Step ii involves introducing the reaction mixture obtained in step i into a closed mold, where a back pressure of 2.0 bar to 90 bar is applied in the closed mold.

[0013] Step iii involves foaming the reaction mixture in a closed mold to obtain a rigid PUR / PIR foam. The foaming is carried out in a specific direction called the so-called foaming direction. For example, the reaction mixture is placed on the bottom of a cuboid before foaming. When the foam formed during foaming rises vertically, the upward vertical direction is the foaming direction. The obtained foam has a thickness D that is substantially perpendicular to the foaming direction. e In the context of this application, a direction Y that is "substantially perpendicular" to a direction X is a direction Y that is at an angle of (90 ± 10)° with respect to the direction X.

[0014] Step iv involves demolding the rigid PUR / PIR foam.

[0015] Step v involves compressing the rigid PUR / PIR foam. This compression may be carried out after demolding or in the closed mold before demolding. In this case, the thickness D e is compressed to 0.05·D e ~0.95·D e of the thickness D k until.

[0016] This solution is surprising because the underlying foam already has very fine bubbles, i.e., the polyurethane foam sometimes has a very small bubble size of less than 100 μm. First, it is unexpected that such a fine bubble foam can withstand the compression according to the present invention without destroying the bubble structure. Also, in a given foam, the thermal conductivity generally increases with an increase in density. Therefore, in the case of such a fine bubble foam, it is unexpected that the compression causes a decrease in thermal conductivity. In particular, it should be expected that the compression of the fine bubble foam would make the conductivity of the polymer material dominant and increase the conductivity of the foam. Finally, it is also surprising that the mechanical properties of the obtained foam, especially the compressive strength, are retained.

[0017] In one embodiment, the proportion of all primary OH functional groups present in the polyol component A1) based on the total number of terminal OH functional groups in the polyol component A1) is at least 30%.

[0018] In a further embodiment, the thickness D e is from 0.20·D e to 0.95·D e , preferably from 0.35·D e to 0.95·D e , or from 0.35·D e to 0.95·D e , more preferably from 0.50·D e to 0.95·D e or from 0.50·D e to 0.90·D e of the thickness D k is compressed up to.

[0019] In one embodiment, the number of NCO groups in the polyisocyanate component B) and the number of isocyanate-reactive hydrogen atoms of the isocyanate-reactive composition A) are in a numerical ratio to each other of 110 or more:100 to 300 or less:100.

[0020] In a further embodiment, the reaction mixture R) substantially does not contain a continuous foaming compound or contains no continuous foaming compound at all. In this case, the expression "substantially does not contain" is to be interpreted as meaning that the reaction mixture R) contains the continuous foaming compound in an amount of at most an amount corresponding to an unintentional contamination, for example less than 0.1% by weight based on the total amount of the isocyanate-reactive composition A).

[0021] In another embodiment, step i) is carried out under supercritical conditions with respect to CO2. In a preferred embodiment, both step i and step ii are carried out under supercritical conditions with respect to CO2.

[0022] In a further embodiment, step iii) comprises maintaining a reverse pressure for a period 1 of from 1 second to 40 seconds after the end of step ii) and subsequently releasing the reverse pressure at a decompression rate of from 1 bar / second to 90 bar / second for a period 2.

[0023] In another embodiment, the polyol component A1) has a hydroxyl value of 280 mg KOH / g to 600 mg KOH / g measured according to DIN 53240-2:2007.

[0024] In one embodiment, the isocyanate-reactive composition A) consists of at least 65% by weight of a polyol component A1) having a hydroxyl value between 280 mg KOH / g and 600 mg KOH / g and a functionality of 2.8 or more and 6.0 or less, measured according to DIN 53240-2:2007. In a further embodiment, the proportion of primary OH functional groups present in the isocyanate-reactive composition A) based on the total number of all terminal OH functional groups in the isocyanate-reactive composition A is at least 35%. In a preferred embodiment, at least 65% by weight of the isocyanate-reactive composition A), based on the total amount of A) excluding A2) and A3), consists of a polyol component A1) having a hydroxyl value between 280 mg KOH / g and 600 mg KOH / g and a functionality of 2.8 or more and 6.0 or less, measured according to DIN 53240-2:2007, and the proportion of primary OH functional groups present in the isocyanate-reactive composition A) based on the total number of all terminal OH functional groups in the isocyanate-reactive composition A is at least 35%.

[0025] In a further embodiment, the isocyanate-reactive composition A) consists of at least 60% by weight of a polyether polyol.

[0026] The isocyanate-reactive composition A) contains at least one polyol component A1) selected from the group consisting of polyether polyols, polyester polyols, polyether ester polyols, polycarbonate polyols, and polyether polycarbonate polyols.

[0027] The proportion of primary OH functional groups based on the total number of terminal OH functional groups in the polyol component A1) is preferably at least 30%, more preferably at least 35%, and particularly preferably at least 38%.

[0028] The polyol component A1) has a further characteristic of having a functionality f of more than 2.5, preferably 2.6 or more and 6.5 or less, particularly preferably 2.8 or more and 6.1 or less. The isocyanate-reactive composition in which the polyol component A1) has a functionality within these ranges provides an optimal increase in viscosity until the back pressure during injection is reduced, enabling more rapid demolding of the foam.

[0029] The polyol component A1) preferably has a hydroxyl value of 280 mgKOH / g to 600 mgKOH / g, particularly preferably 300 mgKOH / g to 580 mgKOH / g, and particularly preferably 350 mgKOH / g to 540 mgKOH / g. This has a particularly advantageous effect on the mechanical properties of the foam.

[0030] In the context of the present application, "polyether polyol" can also be a mixture of various polyether polyols. This also applies equally to the other polyols listed in this specification.

[0031] The polyether polyols that can be employed according to the present invention are known to those skilled in the art and are polyether polyols that can be employed in polyurethane synthesis.

[0032] The polyether polyols that can be employed include, for example, polytetramethylene glycol polyethers obtained via the polymerization of tetrahydrofuran by cationic ring-opening.

[0033] Similarly suitable polyether polyols include adducts of styrene oxide, ethylene oxide, propylene oxide, butylene oxide, and / or epichlorohydrin to bifunctional or polyfunctional starting molecules. The addition of ethylene oxide and propylene oxide is particularly preferred. Suitable starting molecules are, for example, water, ethylene glycol, diethylene glycol, butyl diglycol, glycerol, diethylene glycol, trimethylolpropane, propylene glycol, pentaerythritol, sorbitol, sucrose, ethylenediamine, toluenediamine, triethanolamine, bisphenol, in particular, 4,4'-methylenebisphenol, 4,4'-(1-methylethylidene)bisphenol, 1,4-butanediol, 1,6-hexanediol, and low molecular weight hydroxyl-containing esters of such polyols with dicarboxylic acids, and oligoethers of such polyols.

[0034] The isocyanate-reactive composition A) preferably contains, based on its total weight, at least 50% by weight, preferably at least 60% by weight, particularly preferably at least 70% by weight of polyether polyol. In a preferred embodiment, component A1) consists of polyether polyol in the range up to 100% by weight. These preferred embodiments are characterized by particularly good hydrolysis stability.

[0035] The polyether ester polyols that can be used are compounds containing ether groups, ester groups, and OH groups. To produce polyether ester polyols, organic dicarboxylic acids having up to 12 carbon atoms, preferably aliphatic dicarboxylic acids or aromatic dicarboxylic acids having 4 to 6 carbon atoms, are suitable, and these are used alone or as mixtures. Examples include suberic acid, azelaic acid, decanedicarboxylic acid, maleic acid, malonic acid, phthalic acid, pimelic acid, and sebacic acid, particularly glutaric acid, fumaric acid, succinic acid, adipic acid, phthalic acid, terephthalic acid, and isophthalic acid. In addition to the organic dicarboxylic acids, derivatives of these acids, such as anhydrides of these acids, as well as esters and monoesters of these acids with low molecular weight monofunctional alcohols having 1 to 4 carbon atoms, can also be employed. The use of the above-mentioned bio-based starting materials, particularly fatty acids or fatty acid derivatives (oleic acid, soybean oil, etc.) is likewise possible and can have advantages, for example, with respect to the storage stability, dimensional stability, combustion behavior, and compression strength of the foam of the polyol formulation.

[0036] Polyether polyols obtained by alkoxylation of starting molecules such as polyhydric alcohols are further components used to produce polyether ester polyols. The starting molecules are at least bifunctional, but optionally may contain a proportion of higher functionality, particularly trifunctional starting molecules.

[0037] The starting molecule is, for example, preferably a diol having a number average molecular weight Mn of 18 g / mol or more and 400 g / mol or less, preferably 62 g / mol or more and 200 g / mol or less, 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, etc., ether diols such as diethylene glycol, triethylene glycol, tetraethylene glycol, dibutylene glycol, tributylene glycol, tetrabutylene glycol, dihexylene glycol, trihexylene glycol, tetrahexylene glycol, etc., and oligomer mixtures of alkylene glycols such as diethylene glycol. Starting molecules having functionality other than OH can also be used alone or in a mixture.

[0038] In addition to the diol, compounds having more than 2 Zerewitinoff active hydrogens, particularly compounds having a number average functionality of more than 2 and 8 or less, particularly 3 or more and 6 or less, such as 1,1,1-trimethylolpropane, triethanolamine, glycerol, sorbitan, and pentaerythritol, and further, preferably having an average molar mass Mn of 62 g / mol or more and 400 g / mol or less, particularly 92 g / mol or more and 200 g / mol or less, triol or tetraol starting polyethylene oxide polyols can also be used in combination as starting molecules for producing polyethers.

[0039] Polyether ester polyols can also be produced by alkoxylation, particularly ethoxylation and / or propoxylation, of reaction products obtained by reacting organic dicarboxylic acids and their derivatives with components having Zerewitinoff active hydrogen, particularly diols and polyols. Derivatives of these acids that can be used include, for example, their anhydrides, such as phthalic anhydride.

[0040] Suitable polyester polyols are, inter alia, polycondensates of diols, furthermore triols and tetraols, with dicarboxylic acids, furthermore tricarboxylic acids and tetracarboxylic acids, or hydroxycarboxylic acids or lactones. In the production of polyesters, it is also possible to employ the corresponding polycarboxylic acid anhydrides or polycarboxylic acid esters of the corresponding lower alcohols instead of the free polycarboxylic acids.

[0041] Examples of suitable diols are ethylene glycol, butylene glycol, diethylene glycol, triethylene glycol, polyalkylene glycols, such as polyethylene glycol, etc., and furthermore 1,2-propanediol, 1,3-propanediol, 1,3-butanediol and 1,4-butanediol, 1,6-hexanediol, and isomers, neopentyl glycol or neopentyl glycol hydroxypivalate. In addition, polyols such as trimethylolpropane, glycerol, erythritol, pentaerythritol, trimethylolbenzene, or tris(hydroxyethyl)isocyanurate can also be employed.

[0042] Also, additional monohydric alkanols can be used in combination.

[0043] 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. It is also possible to use the corresponding anhydrides as the acid source.

[0044] It is also possible to additionally use monocarboxylic acids such as benzoic acid and alkane carboxylic acids in combination.

[0045] Hydroxycarboxylic acids that can be used in combination as reaction participants in the preparation of polyester polyols having terminal hydroxyl groups include, for example, hydroxycaproic acid, hydroxybutyric acid, hydroxydecanoic acid, hydroxystearic acid, etc. Preferred lactones are, in particular, caprolactone, butyrolactone, and homologues.

[0046] In addition, compounds suitable for the production of polyester polyols include, in particular, bio-based starting materials and / or their derivatives, such as castor oil, polyhydroxy fatty acids, ricinoleic acid, hydroxyl-modified oils, grape seed oil, black cumin oil, pumpkin seed oil, lycium barbarum seed oil, soybean oil, wheat germ oil, rapeseed oil, sunflower seed oil, peanut oil, almond oil, pistachio oil, macadamia nut oil, avocado oil, sea buckthorn oil, sesame oil, linseed oil, hazelnut oil, primrose oil, wild rose oil, safflower oil, walnut oil, fatty acids, hydroxyl-modified and epoxidized fatty acids and fatty acid esters, such as myristoleic acid, palmitoleic acid, oleic acid, vaccenic acid, petroselinic acid, gadolenic acid, erucic acid, nervonic acid, linoleic acid, α-linolenic acid and γ-linolenic acid, stearidonic acid, arachidonic acid, timnodonic acid, clupanodonic acid and cervonic acid-based fatty acids and fatty acid esters. Esters of ricinoleic acid with polyfunctional alcohols, such as glycerol, are particularly preferred. The use of mixtures of such bio-based acids with other carboxylic acids, such as phthalic acid, is also preferred.

[0047] The polycarbonate polyol that can be used is a polycarbonate having a hydroxyl group, such as polycarbonate diol. This can be obtained through the reaction of a carbonic acid derivative such as diphenyl carbonate, dimethyl carbonate, or phosgene with a polyol, preferably a diol, or through the copolymerization of an alkylene oxide, such as propylene oxide, and CO2.

[0048] Examples of such diols are ethylene glycol, 1,2-propanediol and 1,3-propanediol, 1,3-butanediol and 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, neopentyl glycol, 1,4-bishydroxymethylcyclohexane, 2-methylpropane-1,3-diol, 2,2,4-trimethylpentane-1,3-diol, dipropylene glycol, polypropylene glycol, dibutylene glycol, polybutylene glycol, bisphenol A, and lactone-modified diols of the above types.

[0049] Instead of or in addition to pure polycarbonate diols, polyether polycarbonate diols, which can be obtained, for example, by copolymerization of alkylene oxides, such as propylene oxide, with CO2, can also be employed.

[0050] Methods for preparing polyols are described, for example, by Ionescu in "Chemistry and Technology of Polyols for Polyurethanes", Rapra Technology Limited, Shawbury 2005, from page 55 onwards (Chapter 4: Oligo-Polyols for Elastic Polyurethanes), from page 263 onwards (Chapter 8: Polyester Polyols for Elastic Polyurethanes), and especially from page 321 onwards (Chapter 13: Polyether Polyols for Rigid Polyurethane Foams) and from page 419 onwards (Chapter 16: Polyester Polyols for Rigid Polyurethane Foams). It is also possible to obtain polyester polyols and polyether polyols by the glycolysis of suitable polymer recycling materials. Suitable polyether polycarbonate polyols and their production are described, for example, in

[0024] to

[0041] of European Patent Application Publication No. 2910585. Examples of polycarbonate polyols and their production can be found, inter alia, in European Patent Application Publication No. 1359177. The production of suitable polyether ester polyols is described, inter alia, in International Publication No. 2010 / 043624 and European Patent Application Publication No. 1923417.

[0051] When the alkylene oxide used for alkoxylation contains ethylene oxide in a high proportion, polyether polyols, polyether carbonate polyols, and polyether ester polyols with a high proportion of primary OH functional groups can be obtained. The molar ratio of the ethylene oxide structure to the entire alkylene oxide structure present in the polyol of Component A1 is at least 50 mol%. Similarly, the use of 100 mol% of ethylene oxide is a preferred embodiment.

[0052] The isocyanate-reactive composition A) may further contain a low molecular weight isocyanate-reactive compound A4), in particular bifunctional or trifunctional amines and alcohols, particularly preferably diols and / or triols having a molar mass Mn of less than 400 g / mol, preferably 60 g / mol to 300 g / mol, for example, triethanolamine, diethylene glycol, ethylene glycol, glycerol can be used. When such low molecular weight isocyanate-reactive compounds are used as, for example, chain extenders and / or crosslinking agents in the production of rigid polyurethane foams and are not included in the definition of the polyol component A1), these compounds are advantageously used in an amount of up to 5% by weight, based on the total weight of the composition A).

[0053] In addition to the above polyols and isocyanate-reactive compounds, the composition A) may contain further isocyanate-reactive compounds A5), such as graft polyols, polyamines, polyamino alcohols, and polythiols. It will be understood that the isocyanate-reactive components described also include compounds having a mixed functionality.

[0054] A preferred isocyanate-reactive composition A) contains a polyol component A1) having a hydroxyl value of 280 mgKOH / g to 600 mgKOH / g and a functionality of 2.8 or more and 6.0 or less in an amount of at least 65% by weight, particularly at least 80% by weight, very particularly preferably more than 90% by weight, based on the total amount of A) excluding components A2) and A3), and the proportion of primary OH functional groups in the composition A) is at least 35% (based on all terminal OH functional groups in the composition A).

[0055] In the production of rigid PUR / PIR foams, supercritical CO2 is employed as the blowing agent component C). The blowing agent component C) is employed in an amount sufficient to achieve a dimensionally stable foam matrix and the desired apparent density. This is generally 0.5 part by weight to 30 parts by weight of blowing agent, based on 100 parts by weight of the composition A) excluding A2) and A3).

[0056] CO2 as a physical blowing agent is employed in a supercritical state or a near-critical state. In the context of the present invention, the condition is near-critical when the following conditions are satisfied: (Tc - T) / T ≤ 0.4 and / or (pc - p) / p ≤ 0.4. In this case, T is the temperature applied during the process, Tc is the critical temperature of the blowing agent or the blowing agent mixture, p is the pressure applied during the process, and pc is the critical pressure of the blowing agent or the blowing agent mixture. Preferably, when (Tc - T) / T ≤ 0.3 and / or (pc - p) / p ≤ 0.3, particularly preferably when (Tc - T) / T ≤ 0.2 and / or (pc - p) / p ≤ 0.2, the condition is near-critical.

[0057] Particularly suitable conditions for carrying out the method according to the invention when using CO2 are pressures and temperatures above the critical point of CO2, i.e., 73.7 bar or higher and 30.9 °C or higher, 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.

[0058] In addition to supercritical CO2, a physical blowing agent may be employed as an additional blowing agent. In the context of the present invention, the "physical blowing agent" is to be interpreted as meaning a compound that is volatile due to its physical properties and does not react with the polyisocyanate component B).

[0059] Additional physical blowing agents can be selected from the group consisting of hydrocarbons (e.g., n-pentane, isopentane, cyclopentane, butane, isobutane, propane), ethers (e.g., methylal), halogenated ethers, perfluorinated hydrocarbons and partially fluorinated hydrocarbons having 1 to 8 carbon atoms, for example, perfluorohexane, HFC 245fa (1,1,1,3,3-pentafluoropropane), HFC 365mfc (1,1,1,3,3-pentafluorobutane), HFC 134a, or mixtures thereof, and also (hydro)fluorinated olefins, for example, HFO 1233zd(E) (trans-1-chloro-3,3,3-trifluoro-1-propene) or HFO 1336mzz(Z) (cis-1,1,1,4,4,4-hexafluoro-2-butene) or additives such as FA 188 (1,1,1,2,3,4,5,5,5-nonafluoro-4-(trifluoromethyl)penta-2-ene) manufactured by 3M, and also mixtures of these with each other can be used.

[0060] When adding a further blowing agent, in one embodiment, the blowing agent component C) preferably contains more than 60% by weight of supercritical CO2, particularly preferably more than 75% by weight of supercritical CO2.

[0061] In addition to or instead of the physical blowing agent, it is also possible to use chemical blowing agents (also called "co-blowing agents"). These are particularly preferably water and / or formic acid. The co-blowing agent is preferably employed in an amount of 0% to 6% by weight, particularly preferably 0.5% to 4% by weight, based on the total amount of compounds having isocyanate-reactive hydrogen atoms in the foam-forming reaction mixture R).

[0062] In each case, the proportion of the blowing agent C) based on the total amount of components A) and C) is preferably 1% to 30% by weight, more preferably 4% to 20% by weight, particularly preferably 6% to 16% by weight, and the proportion of the blowing agent in the reaction mixture R) is 0.5% to 15% by weight, preferably 2% to 10% by weight, particularly preferably 3% to 8% by weight, in each case based on the total amount of R).

[0063] In a further embodiment, the isocyanate-reactive composition A) comprises a catalyst component A2), and preferably comprises the catalyst component A2) in an amount of 0.01 wt% or more and less than 2.0 wt%, based on the total weight of the isocyanate-reactive composition A).

[0064] Typically employed as the catalyst component A2) is a compound that promotes the reaction between the hydroxyl group-containing compound or isocyanate-reactive group-containing compound of the composition A) and the isocyanate groups of the component B).

[0065] The catalyst component A2) may contain at least one catalytically active amine compound (so-called "incorporable catalysts") having a functional group capable of reacting with an isocyanate by containing Tschugaeff active hydrogen. Examples of incorporable catalysts that can be employed are bis(dimethylaminopropyl)urea, bis(N,N-dimethylaminoethoxyethyl)carbamate, dimethylaminopropylurea, 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-aminoethoxyethanol), 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-dimethylaminoisopropyldiisopropanolamine, or a mixture thereof.

[0066] One or more further compounds A2b), in particular, catalyst-active compounds known in PUR / PIR chemistry can also be employed. Such compounds include not only further amine compounds but also salts such as tin(II) acetate, tin(II) octoate, tin(II) ethylhexanoate, 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, etc.

[0067] The catalyst component A2) is generally employed in an amount of 0.001% to 5% by weight, in particular 0.05% to 2.5% by weight, based on the weight of the composition A). It is particularly preferred when the catalyst component A2) contains both the incorporable catalyst A2a) and the non-incorporable catalyst A2b). It is especially preferred to employ a combination of an incorporable amine compound and a catalyst-active salt.

[0068] The catalysts A2a) and A2b) are preferably employed at a molar ratio A2a) / A2b) of 0.1 to 16.3, particularly preferably 0.3 to 10, and very particularly preferably 0.8 to 6.0. It is preferred when the catalyst component A2) contains an amine compound incorporable into the polyurethane as the catalyst-active compound A2a) and a catalyst-active salt as the catalyst-active compound A2b) that is non-incorporable into the polyurethane, and the molar ratio of A2a) / A2b) is 0.1 to 16.3, particularly preferably 0.3 to 10, and very particularly preferably 0.8 to 6.0. In a particularly preferred embodiment, 3-(dimethylamino)propylurea and potassium acetate are employed at a molar ratio A2a) / A2b) of 0.1 to 6.0, particularly preferably 0.3 to 10, and very particularly preferably 0.8 to 6.0. The preferred catalyst ratio / catalyst particularly advantageously results in a defined increase in viscosity.

[0069] In one embodiment, the isocyanate-reactive composition A) comprises a stabilizer, preferably an auxiliary component and an additive component A3) comprising a stabilizer in an amount of 0.05 wt% or more and less than 5 wt% based on the total weight of the isocyanate-reactive composition A).

[0070] In a further embodiment, the reaction mixture R) substantially does not contain a continuous foaming compound or does not contain a continuous foaming compound at all. In this case, the expression "substantially does not contain" is to be interpreted as meaning that the reaction mixture R) contains a continuous foaming compound in an amount corresponding at most to an unintentional contamination, for example less than 0.1 wt% based on the total amount of the isocyanate-reactive composition A).

[0071] The reaction mixture R) may contain auxiliary substances and additive substances A3). The auxiliary substances and additive substances may contain a continuous foaming compound, but preferably do not contain a continuous foaming compound at all or substantially do not contain a continuous foaming compound. Continuous foaming compounds are described, for example, in the Plastics Handbook (Kunststoff-Handbuch), Volume 7, Polyurethanes, Carl Hanser Verlag, Munich / Vienna, 3rd Edition, 1993, pages 104 to 127. These are, for example, silicones, such as polyether-polydimethylsiloxane copolymers, or organic polymers, such as those based on polybutadiene (e.g., Ortegol 500 and 501 from Evonik Industries), surfactants, such as the sodium salt of ethoxylated sulfated isotridecyl alcohol obtained under the trade name Sermul EA266 (Elementis Specialties, Netherlands), and furthermore mixtures of various components, such as mixtures of amine-stabilized polymeric unsaturated hydrocarbons and phthalic acid esters.

[0072] Moreover, the auxiliary substances and additive substances A3) that can be employed in the method according to the present invention are common auxiliary substances and additive substances known in the prior art and to those skilled in the art. Examples of auxiliary substances and additive substances include, for example, surfactants, stabilizers, particularly foam stabilizers, bubble regulators, fillers, dyes, pigments, flame retardants, antistatic agents, anti-hydrolysis agents, and / or antifungal and antibacterial substances.

[0073] As the foam stabilizer, polyether-polydimethylsiloxane copolymers, preferably polyethylene oxide-polyethers having oligo-dimethylsiloxane end groups, are often used, where the number of dimethylsiloxane units is preferably 5 or less.

[0074] Examples of stabilizers that can be employed include paraffin, polybutadiene, fatty alcohols, and esters, such as saturated and unsaturated hydrocarbons like esters of carboxylic acids. It is preferable to employ stabilizers that do not have a continuous foaming effect, particularly foam stabilizers.

[0075] Composition A) preferably contains a combined total of 3 wt% or less of silicone and polybutadiene.

[0076] As stabilizers, surfactants can also be employed, such as ethers of alkoxylated alkanols, for example linear or branched alkanols having 6 to 30 carbon atoms and polyalkylene glycols having 5 to 100 alkylene oxide units, alkoxylated alkylphenols, alkoxylated fatty acids, carboxylic acid esters of alkoxylated sorbitan (especially polysorbate 80), fatty acid esters, polyalkylene amines, alkyl sulfates, phosphatidylinositol, fluorinated surfactants, surfactants containing polysiloxane groups, and / or bis(2-ethyl-1-hexyl)sulfosuccinate. The fluorinated surfactants may be perfluorinated or partially fluorinated. Examples thereof are partially fluorinated ethoxylated alkanols or carboxylic acids.

[0077] Composition A) contains, based on the total weight of composition A), preferably in total 5% by weight or less, particularly preferably 3% by weight or less, more preferably less than 2% by weight, and particularly preferably 1.6% by weight or less of a surfactant.

[0078] Reaction mixture R) contains a polyisocyanate component B), i.e., an isocyanate having an NCO functionality of 2 or more. Examples of such suitable polyisocyanates include 1,4-butylene diisocyanate, 1,5-pentane diisocyanate, 1,6-hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), 2,2,4-trimethylhexamethylene diisocyanate and / or 2,4,4-trimethylhexamethylene diisocyanate, isomer bis(4,4'-isocyanatocyclohexyl)methane or a mixture of any desired isomer content thereof, 1,4-cyclohexylene diisocyanate, 1,4-phenylene diisocyanate, 2,4-tolylene diisocyanate and / or 2,6-tolylene diisocyanate (TDI), 1,5-naphthylene diisocyanate, 2,2'-diphenylmethane diisocyanate and / or 2,4'-diphenylmethane diisocyanate and / or 4,4'-diphenylmethane diisocyanate (MDI) and / or higher homologues, 1,3-bis(2-isocyanatopropan-2-yl)benzene and / or 1,4-bis(2-isocyanatopropan-2-yl)benzene (TMXDI), 1,3-bis(isocyanatomethyl)benzene (XDI), and furthermore 2,6-diisocyanatohexanoic acid alkyl (lysine diisocyanate) having a C1-C6-alkyl group is included.

[0079] The material used as the isocyanate component B) is preferably a mixture of isomers of diphenylmethane diisocyanate ("monomeric MDI") (abbreviated as "mMDI") and its oligomers ("oligomeric MDI"). A mixture of monomeric MDI and oligomeric MDI is generally referred to by the term "polymeric MDI" (pMDI). The oligomers of MDI are polyphenylpolymethylene polyisocyanates having a relatively large number of rings, that is, having a relatively large number of rings, having an NCO functionality f of more than 2, and having the following structural formula: C 15 H 10 N2O2[C8H5NO] n (wherein n is an integer greater than 0, preferably n is 1, 2, 3, and 4) and is a mixture of homologues of diphenylmethane diisocyanate. Homologues C having a relatively large number of rings 15 H 10 N2O2[C8H5NO] m (m is an integer of 4 or more) may also be present in the mixture of the organic polyisocyanate a). As the isocyanate component B), a mixture of mMDI and / or pMDI containing up to 20% by weight, more preferably up to 10% by weight, of further aliphatic polyisocyanates, cycloaliphatic polyisocyanates, and especially aromatic polyisocyanates, especially TDI, known in the production of polyurethanes is also preferably used.

[0080] In addition to the above polyisocyanates, modified diisocyanates having a uretdione structure, isocyanurate structure, urethane structure, carbodiimide structure, uretonimine structure, allophanate structure, biuret structure, amide structure, iminooxadiazinedione structure and / or oxadiazinetrione structure, and furthermore, unmodified polyisocyanates having 3 or more NCO groups per molecule, for example, 4-isocyanatomethyl-1,8-octane diisocyanate (nonane triisocyanate) or triphenylmethane 4,4',4''-triisocyanate can also be used in combination in part.

[0081] Instead of or in addition to the above polyisocyanates, suitable NCO prepolymers can also be used as the organic isocyanate component B). The prepolymer can be produced by reacting one or more polyisocyanates with one or more polyols corresponding to the polyols described in components A1) and A2).

[0082] The isocyanate can be a prepolymer obtainable by reacting an isocyanate having an NCO functionality of 2 or more with a polyol having a molecular weight of 62 g / mol or more and 8000 g / mol or less and an OH functionality of 1.5 or more and 6 or less.

[0083] The NCO content is preferably 29.0% by weight or more and 32.0% by weight or less, and preferably has a viscosity at 25 °C (dynamic viscosity determined in accordance with DIN 53019 at 25 °C) of 80 mPas or more and 2000 mPas or less, particularly preferably 100 mPas or more and 800 mPas or less.

[0084] The number of NCO groups in the polyisocyanate component B) and the number of isocyanate-reactive groups in the composition A) can be, for example, a numerical ratio to each other of 50 or more:100 to 300 or less:100. Rigid polyurethane foams are generally produced by reacting component A) and component B) in an amount such that the isocyanate index in the formulation is 80 to 150, preferably 90 to 130, particularly preferably 95 to 125. In this range, urethane groups are preferably formed. In another preferred embodiment, the isocyanate index is 150 to 300. In this range, the foam contains a high proportion of isocyanurate functional groups, which results in, for example, the inherent flame retardancy of the foam.

[0085] The method according to the invention consists of at least steps i to v.

[0086] In step i of the method according to the invention, a reaction mixture R) is produced from component A), component B), and component C).

[0087] For this purpose, the composition A) can be initially filled into a container, for example, and subsequently mixed with the blowing agent component C), and the polyisocyanate B) can be added. The mixing of the components can also be carried out in a mixing head.

[0088] In particular, the mixing with the components C) and B) can be carried out under pressure. In a preferred embodiment, the components A) and C) are mixed with the component B) in a high-pressure mixing head.

[0089] The blowing agent component C) is supercritical CO2, and the reaction of the components is preferably carried out under supercritical conditions for CO2. In this case, the appropriate pressure in the mixing head and / or the discharge conduit(s) (in case of multiple) for producing the polyurethane foam is, for example, in the range of 73.7 bar or more and 350 bar or less, preferably in the range of 75 bar or more and 200 bar or less. The appropriate temperature is, for example, 30.9 °C or more and 100 °C or less, preferably 32 °C or more and 60 °C or less. At such pressures, the supercritical conditions for the blowing agent used can be maintained.

[0090] In a further embodiment, the residence time of the mixture in the mixing head under supercritical conditions for the blowing agent is more than 0 seconds and 20 seconds or less, preferably 0.1 seconds or more and 10 seconds or less, particularly preferably 0.5 seconds or more and 5 seconds or less. As a result, the mixture can polymerize under supercritical conditions. The residence time can be determined by dividing the volume of the reaction chamber (= mixing chamber and / or conduit) under supercritical conditions by the volume of the mixture conveyed in a specific unit of time.

[0091] In step ii of the method according to the invention, the reaction mixture R) according to the invention composed of the components A), B), and C) is introduced into a closed mold, where the back pressure in the mold during the introduction is 2.0 bar to 90 bar, preferably 2.0 bar to 80 bar, particularly preferably 5.0 bar to 40 bar.

[0092] Possible embodiments in this regard are as follows. The back pressure is achieved either by directly pressurizing the mold with a gas (compressed air or nitrogen) and / or by pressurizing through a floating seal that divides the pressurizing space into a gas space and a reaction space, established, maintained, and finally released via a proportional valve.

[0093] In step iii) of the method, the reaction mixture foams.

[0094] A preferred embodiment of step iii) is as follows. After the end of step ii, the back pressure in the mold is kept constant over a period 1, preferably for 1 second to 40 seconds, particularly preferably for 5 seconds to 20 seconds, and very particularly preferably for 8 seconds to 17 seconds. During this time, the viscosity of the reaction mixture initially increases without the reaction mixture foaming. It has been found that maintaining the pressure over a preferred period results in a viscosity range of the mixture that is particularly advantageous for this reaction stage. After the end of period 1, the mold is depressurized. The release of pressure from the mold is carried out over a period 2 at a decompression rate of 1 bar / second to 90 bar / second, preferably 1 bar / second to 80 bar / second, and particularly preferably 2 bar / second to 70 bar / second. The release can be carried out particularly via a proportional valve. The reaction mixture foams over period 2. A release that is too fast has an adverse effect on the bubble stability, and a release that is too slow has an adverse effect on the foaming reaction.

[0095] In step iv) of the method, the rigid PUR / PIR foam is demolded.

[0096] In step v) of the method, the rigid PUR / PIR foam is compressed. The compression can be carried out before or after step iv). This includes reducing the thickness of the rigid PUR / PIR foam.

[0097] This can be achieved, for example, by reducing the volume of the reaction mold by inserting a plate and closing the mold containing the rigid foam again. The volume of the reaction mold can be reduced by 5% to 95%, preferably 40% to 70%. D e from D k A 40% reduction to D ecorresponds to a decrease to (100 - 40)% = 60%. That is, for a rigid foam with a thickness D e = 100 mm, compressing it by 40% is equivalent to compressing it to a compressed rigid foam with a thickness D k = (100 - 0.4×100) mm = 60 mm.

[0098] Compression in a mold with reduced volume can be carried out after foaming the reaction mixture and after a certain period. This period can be from 10 seconds to 30 minutes, preferably from 1 minute to 10 minutes. It can also be compressed before or after the hardening of the foam. The duration of compression, that is, the duration of maintaining the volume reduction in the closed mold, is from 1 minute to 30 minutes, preferably from 2 minutes to 15 minutes. The time point and duration of compression affect the resulting thickness D of the compressed foam measured 24 hours after the end of compression k thereof.

[0099] Alternatively, the rigid foam can also be compressed in a hydraulic press after step iv.

[0100] The present invention also provides a closed-cell rigid PUR / PIR foam that can be obtained or is obtained by the method of the present invention. The foam according to the present invention has good mechanical properties, particularly good dimensional stability at high temperatures, and also preferably good compressive strength.

[0101] This closed-cell rigid PUR / PIR foam preferably has an apparent density of 30 kg / m 3 ~ 90 kg / m 3 , preferably 30 kg / m 3 ~ 120 kg / m 3 , a closed-cell content of more than 90%, preferably 94% or more according to ISO 4590:2002, and an average (arithmetic mean) cell diameter of 70 μm to 130 μm according to optical microscope evaluation. The value of the average cell diameter relates to the foam that has not yet been compressed in step v.

[0102] The PUR / PIR foam according to the present invention enables the production of foamed molded articles and composite material systems containing these molded articles in a preferred manner. In many cases, both the upper surface and the bottom surface of the composite material system are bounded by a decorative layer. Suitable decorative layers include, inter alia, metals, plastics, wood, and paper. Suitable fields of use for such discontinuously produced PUR / PIR composite material systems include, in particular, equipment such as refrigerators, chest freezers, refrigerator-freezers and boilers, cold storage containers and cold storage boxes, and industrial heat insulators for pipes.

[0103] The use of PUR / PIR foams in these fields is known per se to those skilled in the art and has already been described on many occasions. The PUR / PIR foams according to the present invention are extremely suitable for these purposes. This is because they are characterized by high dimensional stability and, advantageously, high compressive strength and low thermal conductivity, which can be further enhanced by the application of a vacuum.

[0104] Finally, the present invention also provides a refrigerator, a freezer, or a refrigerator-freezer containing a rigid PUR / PIR foam obtainable by the method of the present invention.

[0105] The terms used in this application have the following meanings.

[0106] The index (also known as the isocyanate index) is to be interpreted as meaning 100 multiplied by the quotient of the amount of substance (mol) of the isocyanate groups actually employed and the amount of substance (mol) of the isocyanate-reactive hydrogen atoms actually employed: Index = (isocyanate groups (mol) / isocyanate-reactive hydrogen atoms (mol)) · 100

[0107] In the context of the present application, the "functionality" of a compound, i.e., "f", is to be interpreted as meaning the theoretical functionality. Thus, in the case of a polyol starting only from glycerol, the functionality f is 3, and in the case of a polyol starting only from ethylenediamine, f is 4. In the context of the present application, the "functionality" of a mixture of components, i.e., "f", is to be interpreted as meaning the number average functionality of each of the mixtures mentioned. Thus, for example, the functionality of polyol component A1) is to be interpreted as meaning the number average functionality of the mixture of polyols present in component A1 based on all the isocyanate-reactive hydrogen atoms present.

[0108] In the context of the present application, "molar weight" or "molar mass", i.e., "Mn", is to be interpreted as meaning the number-weighted average molar mass in each case.

[0109] When adding a single polyol, the OH value (also known as the hydroxyl value) specifies the OH value of the above polyol. The OH value reported for a mixture is related to the number average OH value of the mixture calculated from the OH values of the individual components in their respective molar ratios. The OH value indicates the amount of potassium hydroxide in milligrams, which corresponds to the amount of acetic acid that 1 gram of the substance binds during acetylation. In the context of the present invention, the OH value is determined in accordance with DIN 53240-2 standard (as of November 2007).

[0110] Here, the present invention will be described in more detail with reference to the following examples and comparative examples, but the scope of the present invention is not limited by the examples.

Examples

[0111] Specifications / Analytical Instruments Employed: Determination of apparent density: Foams composed of rubber and plastics - determination of apparent density (ISO 845:2006); German version DIN EN ISO 845:2009 Determination of open-cell content: Determination of volume fraction of open and closed cells (ISO 4590:2002); German version DIN EN ISO 4590:2003 Determination of compressive strength: Rigid foams - determination of pressure properties (ISO 844:2014); German version DIN EN ISO 844:2014 Determination of OH number: Determination of hydroxyl number according to DIN 53240-2 (November 2007 version) - Part 2: Method with catalyst Determination of cell size: Optical microscope evaluation using a VHX 5000 optical microscope; The test specimens to be analyzed are tested at three different locations over a circular area with a diameter of 5 mm in each case. The observation is in the transverse direction with respect to the foaming direction. The resolution is selected so that the selected area captures more than 100 cells. Subsequently, all cells are evaluated using the freely available software ImageJ, and the arithmetic mean cell diameter is calculated using the obtained ECD (equivalent circular diameter) values.

[0112] The percentage (%) of primary OH functional groups specified in Table 1 is related to the percentage of primary OH functional groups based on the total number of OH functional groups in the polyol mixture present in the formulation.

[0113] Examples 1 to 3 and Comparative Examples 1 and 2 A polyurethane foam foamed using supercritical CO2 was produced according to the formulation described in Table 1 below. Unless otherwise specified, the specified amounts shall be interpreted as weight fractions. The following substances were used: Polyol 1: A trimethylol-initiated polyether polyol having a hydroxyl value of 880 mg KOH / g, a functionality of 3, and a viscosity of 6100 mPa·s at 25°C, with propylene oxide as the alkylene oxide Polyol 2: A trimethylol-initiated polyether polyol having a hydroxyl value of 550 mg KOH / g, a functionality of 3, and a viscosity of 505 mPa·s at 25°C, with ethylene oxide as the alkylene oxide Polyol 3: A 1,2-propanediol-initiated polyether polyol having a hydroxyl value of 56 mg KOH / g, a functionality of 2, and a viscosity of 310 mPa·s at 25°C, with propylene oxide as the alkylene oxide Polyol 4: A 1,2-propanediol-initiated polyether polyol having a hydroxyl value of 112 mg KOH / g, a functionality of 2, and a viscosity of 140 mPa·s at 25°C, with propylene oxide as the alkylene oxide Polyol 5: A trimethylolpropane-initiated polyether polyol having a hydroxyl value of 235 mg KOH / g, a functionality of 3, and a viscosity of 350 mPa·s at 25°C, with propylene oxide as the alkylene oxide Polyol 6: A hydroxy-functional fatty acid ester having a hydroxyl value of 160 mg KOH / g and a functionality of 3 Tegostab B 8443: A polyether-polydimethylsiloxane copolymer foam stabilizer (Evonik) Desmorapid PU 1792: A catalyst, potassium acetate in diethylene glycol (Covestro) Amine ZZ: A catalyst, N’-(3-(dimethylamino)propyl)-N,N-dimethylpropane-1,3-diamine (Air Products) Isocyanate: A mixture of MDI and PMDI having a functionality of approximately 2.8, an NCO content of approximately 31.5 wt%, and a viscosity at 25 °C of approximately 200 mPa·s (Desmodur 44V20L, Covestro)

[0114] Manufacture of polyurethane molded foams in a high-pressure apparatus: To manufacture a polyurethane molded foam in a high-pressure apparatus, a polyol formulation was prepared from the isocyanate-reactive compounds, stabilizers, and catalysts shown in Table 1 below. The above formulation was employed as the polyol component in a standard high-pressure mixing apparatus and mixed with CO2 at a pressure of 160 bar and a temperature of 50 °C. The blowing agent was under supercritical conditions (also known as supercritical CO2, "scCO2"). This mixture was mixed with a polyisocyanate conveyed at a pressure of 160 bar and a temperature of 35 °C in a high-pressure mixing head. The shot quantity was 180 g / second, which corresponds to a volume flow rate of 95 ml / second (mixture density 1.2 g / ml). The resulting reaction mixture was metered into a closed mold pre-pressurized at a back pressure of 11 bar at a mold temperature of 55 °C. After the injection was completed, the pre-pressurized back pressure was maintained for an additional 8 seconds and then rapidly depressurized to ambient pressure within 2 seconds.

[0115] In the method according to the invention, after a predetermined time (see Table 1), the mold was opened and, to perform compression, a plate of the desired thickness (Example 1, Example 2: 38% of the foam thickness) was inserted into the mold and the mold was closed again. Subsequently, the foam was compressed for a predetermined time (Example 1 and Example 2: 5 minutes, Example 3: 10 minutes) in a mold with reduced volume and then demolded. In a method not according to the invention (Comparative Example 1), the mold was simply opened after a predetermined time and the resulting foam was only demolded. The foams of Examples 1 to 3 before compression were identical to the foam of Comparative Example 1. In Comparative Example 2, a smaller amount of scCO2 was employed, and thus the foam obtained without compression had a higher apparent density than Example 1 and an apparent density equivalent to Example 2.

[0116] Example 3 shows that even for a fully cured foam, its thermal conductivity can be improved by compression, that is, the thermal conductivity does not decrease by compression.

[0117] Examples 1 to 3 show that compression brings about a higher apparent density and at the same time reduces the arithmetically determined cell size. Thereby, a foam having very fine cells with an elliptical cell shape is formed, which surprisingly has a low thermal conductivity under vacuum. The compressed foams are characterized in that their mechanical properties do not deteriorate compared to the non-compressed foam (Comparative Example 1).

[0118] The non-compressed foam, for example, the starting foam in Comparative Example 1, has a higher thermal conductivity despite a lower apparent density. A comparison of foams having an apparent density similar to that of the compressed foam (Comparative Example 2 vs. Examples 1 to 3) clearly shows that a foam having very fine cells cannot be produced without compression and the thermal conductivity increases significantly.

[0119] [Table 1]

Claims

1. A method for producing a compressed continuous-cell rigid PUR / PIR foam, comprising: i. The following components: A polyol component A1) having a functionality f greater than 2.5, comprising at least one of polyether polyol, polyester polyol, polycarbonate polyol, polyether carbonate polyol, polyether ester polyol, or a mixture thereof, Optionally a catalyst component A2), Optionally an auxiliary component and an additive component A3), To form an isocyanate-reactive composition A), And a polyisocyanate component B), Supercritical CO ２ and a blowing agent component C) containing To produce a reaction mixture R); ii. Introducing the reaction mixture R) from step i) into a closed mold, wherein the back pressure in the closed mold during introduction is from 2.0 bar to 90 bar; iii. Foaming the reaction mixture R) in the closed mold in the foaming direction to obtain a rigid PUR / PIR foam having a thickness D in a direction substantially perpendicular to the foaming direction ｅ and a step of obtaining a rigid PUR / PIR foam having a dimension of iv. Demolding the rigid PUR / PIR foam; v. the thickness D of the rigid PUR / PIR foam ｅ to a thickness D ｋ by compressing to obtain the compressed rigid PUR / PIR foam, where D ｋ is 0.05·D ｅ to 0.95·D ｅ and step v can be carried out before or after step iv, a step A method comprising the above steps.

2. The method according to claim 1, wherein the proportion of all primary OH functional groups present in the polyol component A1) based on the total number of terminal OH functional groups in the polyol component A1) is at least 30%.

3. The method according to claim 1 or 2, wherein the reaction mixture R) substantially does not contain or completely does not contain a continuous cell-forming compound.

4. Process i and optionally process ii are carried out under supercritical conditions for CO ２ The method according to any one of claims 1 to 3, wherein the process is carried out under supercritical conditions for CO

5. Step iii) comprises maintaining the back pressure for a period 1 of from 1 second to 40 seconds after the end of step ii), and subsequently releasing the back pressure at a decompression rate of from 1 bar / second to 90 bar / second over a period 2. The method according to any one of claims 1 to 4.

6. The method according to any one of claims 1 to 5, wherein the polyol component A1) has a hydroxyl value of from 280 mg KOH / g to 600 mg KOH / g measured according to DIN 53240-2:2007.

7. The method according to any one of claims 1 to 6, wherein at least 65% by weight of the isocyanate-reactive composition A) consists of a polyol component A1) having a hydroxyl value between 280 mg KOH / g and 600 mg KOH / g and a functionality of from 2.8 to 6.0 measured according to DIN 53240-2:2007, and the proportion of primary OH functional groups present in the isocyanate-reactive composition A) based on the total number of all terminal OH functional groups in the isocyanate-reactive composition A is at least 35%.

8. The rigid PUR / PIR foam has a compressive strength determined according to DIN EN ISO 844:2014 in the parallel and transverse directions with respect to the foaming direction of a rigid PUR / PIR foam of the same apparent density produced by the same method but not compressed, which is 40% or less, preferably 30% or less, more preferably 20% or less lower than that in both directions, and has a compressive strength determined according to DIN EN ISO 844:2014 in the parallel and transverse directions with respect to the foaming direction. The method according to any one of claims 1 to 7.

9. The content of the blowing agent component C) is 0.5% by weight to 15% by weight based on the total weight of R). The method according to any one of claims 1 to 8.

10. The isocyanate-reactive composition A) contains a catalyst component A2), and preferably contains the catalyst component A2) in an amount of 0.01% by weight or more and less than 2.0% by weight based on the total weight of the isocyanate-reactive composition A). The method according to any one of claims 1 to 9.

11. The isocyanate-reactive composition A) contains a stabilizer, and preferably contains an auxiliary component containing the stabilizer and an additive component A3 in an amount of 0.05% by weight or more and less than 5% by weight based on the total weight of the isocyanate-reactive composition A). The method according to any one of claims 1 to 10.

12. A compressed closed-cell rigid PUR / PIR foam obtainable by the method according to any one of claims 1 to 11.

13. 30 kg / m in accordance with ISO 845:2006 ３ to 120 kg / m ３ preferably 30 kg / m ３ to 70 kg / m ３ The compressed open-cell rigid PUR / PIR foam according to claim 12, having an apparent density of 30 kg / m to 120 kg / m, preferably 30 kg / m to 70 kg / m in accordance with ISO 845:2006, a closed-cell content of more than 90%, preferably 94% or more in accordance with ISO 4590:2002, and an average cell diameter of 40 μm to 130 μm according to optical microscope evaluation.

14. A vacuum insulation panel comprising the rigid PUR / PIR foam according to claim 13.

15. A refrigerator, freezer, or refrigerator-freezer comprising the compressed closed-cell rigid PUR / PIR foam according to claim 12 or 13, or the vacuum insulation panel according to claim 14.

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