Improving the storage stability of hydrofluoroolefins in amine-containing polyol components for preparing polyurethanes

Abstract

The present invention relates to a polyol component for preparing polyurethane foams, said polyol component containing: (a) compounds having at least two isocyanate-reactive hydrogen atoms; (b) catalysts comprising at least one polyurethane catalyst (b1) containing at least one tertiary nitrogen atom, the tertiary nitrogen atom being part of an aliphatic or aromatic ring and / or being bonded to at least one at least secondary carbon atom, and at least one polyurethane catalyst (b2) selected from the group consisting of cyclic amides, the polyurethane catalysts (b1) and (b2) having no dimethylamino groups that are bonded to a primary carbon atom; (c) blowing agents comprising hydrofluoroolefin; and (d) optionally additives. The present invention also relates to a method for preparing polyurethane foams by mixing such a polyol component with an isocyanate component containing at least one polyisocyanate to form a reaction mixture and reacting said reaction mixture to form the polyurethane; and a polyurethane foam that can be obtained using such a method.

Description

[0001] Improving the storage stability of hydrofluoroolefins in amine-containing polyol components for the production of polyurethanes

[0002] Description

[0003] The present invention relates to a polyol component for the production of polyurethane foams, comprising (a) compounds having at least two hydrogen atoms reactive towards isocyanates, (b) catalysts comprising at least one polyurethane catalyst (b1) containing at least one tertiary nitrogen atom, wherein the tertiary nitrogen atom is part of an aliphatic or aromatic ring and / or is bonded to at least one secondary carbon atom, and at least one polyurethane catalyst (b2) selected from the group consisting of cyclic amides, wherein the polyurethane catalysts (b1) and (b2) do not have dimethylamino groups bonded to a primary carbon atom, (c) blowing agents comprising at least one physical blowing agent (c1) comprising at least one aliphatic, halogenated hydrocarbon compound (c11) of the general formula (1) (Formula 1) where the radicals R 1 to R4 each independently of one another represents a hydrogen, fluoride, chloride, methyl or ethyl radical and the hydrogen atoms of the methyl or ethyl radical may be wholly or partially substituted by chloride or fluoride, with the proviso that the compound according to formula (1) is composed of 2 to 5 carbon atoms, at least one hydrogen atom and at least two halogen atoms selected from fluorine and chlorine atoms and that both at least one of the radicals R 1 and R 4 as well as at least one of the residues R 2 and R 3have at least one halogen atom and that the carbon atom of the carbon-carbon double bond that carries a methyl or ethyl group also carries a hydrogen atom, and (d) optionally additives. The present invention further encompasses a process for producing polyurethane foams, comprising mixing such a polyol component with an isocyanate component containing at least one polyisocyanate to form a reaction mixture and reacting the mixture to form the polyurethane, and a polyurethane foam obtainable by such a process.

[0004] The production of polyurethane foams, especially polyurethane foams, is well known. During polyurethane production, the reaction of isocyanates and polyols typically occurs in the presence of catalysts, particularly strongly basic amine catalysts, blowing agents, and other auxiliaries and additives. The raw materials are often combined by the supplier, usually a chemical company, to tailor them to the application and result in the desired polyurethane properties. For this purpose, an isocyanate component containing isocyanates and a polyol component containing isocyanate-reactive components are usually formulated, so that the user only needs to mix the two components to initiate the reaction to produce the desired polyurethane.

[0005] Blowing agents are used in the production of polyurethane foams. Both chemical blowing agents, such as water or carboxylic acids, and physical blowing agents can be used as blowing agents. Physical blowing agents, often in combination with chemical blowing agents, are frequently used, particularly in the production of rigid polyurethane foams. Chemical blowing agents are compounds that react with isocyanate to form gas, usually carbon dioxide. Physical blowing agents are usually low-boiling liquids that evaporate due to the heat of reaction during the reaction of the isocyanates and polyols, thus causing the reaction mixture to foam. Due to the high reactivity of isocyanates, physical blowing agents are also added to the polyol component to prevent side reactions.

[0006] In the past, chlorofluorocarbons were primarily used as physical blowing agents. However, these are now banned in many parts of the world due to their ozone-depleting effects. Today, fluorinated hydrocarbons (HFCs) and low-boiling-point hydrocarbons, such as pentanes, are primarily used as physical blowing agents. One criterion is the storage stability of the respective component.

[0007] Due to the apolarity of the hydrocarbons, primarily pentanes, the solubility of these blowing agents in polyurethane systems is limited. The polyol component therefore tends to segregate in many polyurethane systems, so it is advantageous to add the blowing agent shortly before the foaming process to avoid problems with the short storage stability of the blowing agent-laden polyol component. However, this increases the complexity for the user.

[0008] Another problem with the use of alkanes as blowing agents is their flammability. This increases the flammability of the resulting polyurethane foams. Furthermore, the component containing alkanes as blowing agents, usually the polyol component, is also highly flammable. This requires special precautions when storing and processing systems containing alkanes as blowing agents. Furthermore, the alkane can be partially released during the foaming process. The resulting risk of explosion requires significant investments in safety equipment.

[0009] Fluorinated hydrocarbons (HFCs) are used when the investment in these safety devices, which would otherwise be necessary to use hydrocarbons as physical blowing agents, is too high or not feasible due to the equipment. HFCs also offer the advantage over hydrocarbons in that they can lead to foams with higher insulating properties. However, HFCs are under environmental criticism due to their contribution to global warming, i.e., their high "global warming potential." Therefore, their use is currently being reduced in the EU through regulatory requirements and will be banned in the future.

[0010] Preferred physical blowing agents therefore have a low global warming potential. This is the advantage of halogenated olefins, so-called HFOs (hydrofluoroolefins). A disadvantage of HFO-containing polyol components, especially those containing special HFOs such as HFO-1234ze and / or HCFO-1233zd, is the storage stability of the polyol component. Even a short storage period of the HFO-containing polyol component can lead to a significant change in the reaction profile and to foams of significantly lower quality, even leading to foam collapse. The low storage stability is due to the decomposition of the blowing agents in the polyol component. This is described, for example, in WO 2009048807.The degradation reaction of HFO blowing agents can be slowed down by the use of specific catalysts, such as imidazole derivatives, but this limits the formulation's degrees of freedom and makes optimal catalysis adjustment severely impaired, if not impossible.

[0011] There are several approaches to improving the storage stability of polyol components containing halogenated olefins as blowing agents. Most approaches are based on either blocking the amine catalysts or using alternative catalysts, such as metal catalysts. Furthermore, optimized amine catalysts are also described that, due to steric hindrance, for example, have only a minor impact on the storage stability of the polyol components. One example is WO 2009048807, which discloses polyol components containing sterically hindered amine catalysts. However, such catalysts are usually expensive.

[0012] WO 2018170107 discloses the use of metal catalysts as a replacement for strongly basic amine catalysts. However, replacing amine catalysts with metal catalysts is not effective, as metal catalysts are strong gel catalysts and cannot be used as a replacement for blowing catalysts to optimize the reaction profile. In addition, many metal catalysts are not sufficiently stable against hydrolysis and therefore cannot be stored in water-containing polyol components. Some metal catalysts are already limited in their use due to regulatory requirements.

[0013] WO 2009048826 describes the use of blocked amine catalysts, while US 20190119461 discloses the use of imidazole-based catalysts. Disadvantages of these catalysts include their often low activity; moreover, blocked catalysts typically only deblock at higher temperatures. This requires an additional heating step for the reaction mixture and limits the flexibility in adjusting the reaction profile.

[0014] The object of the present invention was to provide a storage-stable polyol component containing HFO blowing agent which does not have the disadvantages described above and in particular has catalysts which are cost-effective and capable of balanced catalysis of gel and blowing reactions.

[0015] The object of the invention is achieved by a polyol component for the production of polyurethane foams, comprising (a) compounds having at least two hydrogen atoms reactive towards isocyanates, (b) catalysts comprising at least one polyurethane catalyst (b1) containing at least one tertiary nitrogen atom, wherein the tertiary nitrogen atom is part of an aliphatic or aromatic ring and / or is bonded to at least one secondary carbon atom, and at least one polyurethane catalyst (b2) selected from the group consisting of cyclic amides, wherein the polyurethane catalysts (b1) and (b2) do not have any dimethylamino groups bonded to a primary carbon atom, (c) blowing agents comprising at least one physical blowing agent (c1) comprising at least one aliphatic, halogenated hydrocarbon compound (c11) of the general formula (1) (Formula 1) where the radicals R 1to R 4 each independently of one another represents a hydrogen, fluoride, chloride, methyl or ethyl radical and the hydrogen atoms of the methyl or ethyl radical may be wholly or partially substituted by chloride or fluoride, with the proviso that the compound according to formula (1) is composed of 2 to 5 carbon atoms, at least one hydrogen atom and at least two halogen atoms selected from fluorine and chlorine atoms and that both at least one of the radicals R 1 and R 4 as well as at least one of the residues R 2 and R 3have at least one halogen atom and that the carbon atom of the carbon-carbon double bond that carries a methyl or ethyl group also carries a hydrogen atom, and (d) optionally additives. The present invention further encompasses a process for producing polyurethane foams, comprising mixing such a polyol component with an isocyanate component containing at least one polyisocyanate to form a reaction mixture and converting the mixture to form the polyurethane, and a polyurethane foam obtainable by such a process.

[0016] Polyurethane within the meaning of the invention encompasses all known polyisocyanate polyaddition products. These include addition products of isocyanate and alcohol, as well as modified polyurethanes that may contain isocyanurate, allophanate, urea, carbodiimide, uretonimine, biuret structures, and other isocyanate addition products. The polyurethane is a polyurethane foam. These polyurethane foams according to the invention include, in particular, flexible foams, semi-rigid foams, rigid foams, or molded foams.

[0017] For the purposes of the invention, polyurethane foams are understood to mean foams in accordance with DIN 7726. Flexible polyurethane foams according to the invention have a compressive stress at 10% compression or compressive strength according to DIN 53 421 / DIN EN ISO 604 of 15 kPa and less, preferably 1 to 14 kPa and in particular 4 to 14 kPa. Semi-rigid polyurethane foams according to the invention have a compressive stress at 10% compression according to DIN 53 421 / DIN EN ISO 604 of greater than 15 to less than 80 kPa. Semi-rigid polyurethane foams and flexible polyurethane foams according to the invention have an open-cell content of preferably greater than 85%, particularly preferably greater than 90%, according to DIN ISO 4590. Further details on flexible polyurethane foams and semi-rigid polyurethane foams according to the invention can be found in "Kunststoffhandbuch, Volume 7, Polyurethane", Carl Hanser Verlag, 3rd edition 1993, Chapter 5.

[0018] The rigid polyurethane foams according to the invention exhibit a compressive stress at 10% compression of greater than or equal to 80 kPa, preferably greater than or equal to 120 kPa, particularly preferably greater than or equal to 150 kPa. Furthermore, the rigid polyurethane foam according to DIN ISO 4590 has a closed-cell content of greater than 80%, preferably greater than 90%. Further details on rigid polyurethane foams according to the invention can be found in "Kunststoffhandbuch, Volume 7, Polyurethane," Carl Hanser Verlag, 3rd edition 1993, Chapter 6.

[0019] For the purposes of this invention, elastomeric polyurethane foams are understood to mean polyurethane foams according to DIN 7726 which, after brief deformation by 50% of their thickness according to DIN 53 577, exhibit no permanent deformation exceeding 2% of their initial thickness after 10 minutes. This can, for example, be a flexible polyurethane foam. Molded polyurethane foams are polyurethane foams according to DIN 7726 which, due to the molding process, have an outer skin or edge zone that has a higher density than the core. The total bulk density averaged over the core and the edge zone can be in the range from 15 to 800 g / L. Molded foams with a density greater than 100 g / L are usually referred to as integral skin foams. Molded polyurethane foams within the meaning of the invention can also be rigid polyurethane foams, semi-rigid polyurethane foams, or flexible polyurethane foams.Further details on polyurethane integral skin foams according to the invention can be found in the "Kunststoffhandbuch, Band 7, Polyurethane", Carl Hanser Verlag, 3rd edition 1993, Chapter 7. The polyurethanes according to the invention are preferably polyurethane foams, particularly preferably rigid polyurethane foams, semi-rigid polyurethane foams or flexible polyurethane foams, in particular rigid polyurethane foams.

[0020] All compounds known in polyurethane chemistry having isocyanate-reactive groups can be used as isocyanate-reactive compounds (a), preferably compounds having at least one hydroxyl group, -NH group, or NH2 group, or carboxylic acid group, preferably having at least one NH2 or OH group, and in particular at least one -OH group. The functionality toward isocyanate groups can range from 1 to 8, preferably 2 to 8. The isocyanate-reactive compounds include polyether polyols (a1), polyester polyols (a2), or mixtures thereof, preferably polyester polyols (a2) or mixtures of polyether polyols (a1) and polyester polyols (a2). Polyetherols (a1) and polyesterols (a2) preferably have a number-average molecular weight of 150 to 15,000 g / mol, preferably 150 to 5,000 g / mol and particularly preferably 200 to 2,000 g / mol.In addition to polyethers and polyesters, low-molecular-weight chain extenders and / or crosslinking agents known in polyurethane chemistry, for example, can also be used. The compounds (a) preferably have a number-average molecular weight of 62 to 15,000 g / mol. The compounds (a) preferably have a number-average functionality of at least 1.7, particularly preferably at least 2. According to the invention, the polyethers (a1) and / or polyesters (a2) have a number-average functionality of at least 1.7, more preferably at least 2.0.

[0021] Polyetherols (a1) are prepared, for example, from epoxides, such as propylene oxide and / or ethylene oxide, or from tetrahydrofuran with hydrogen-active starter compounds, such as aliphatic alcohols, phenols, amines, carboxylic acids, water, or natural product-based compounds, such as sucrose, sorbitol, or mannitol, using a catalyst. Examples include basic catalysts or double metal cyanide catalysts, as described, for example, in PCT / EP2005 / 010124, EP 90444, or WO 05 / 090440.

[0022] Polyesterols (a2) are produced, for example, from aliphatic or aromatic dicarboxylic acids and polyhydric alcohols, polythioether polyols, polyesteramides, hydroxyl-containing polyacetals, and / or hydroxyl-containing aliphatic polycarbonates, preferably in the presence of an esterification catalyst. Other possible polyols are listed, for example, in "Kunststoffhandbuch, Volume 7, Polyurethane," Carl Hanser Verlag, 3rd edition 1993, Chapter 3.1.

[0023] According to the invention, the compounds (a) reactive toward isocyanate groups comprise at least one polyether polyol (a1) and / or at least one polyester polyol (a2), preferably at least one polyester polyol (a2), optionally in combination with at least one polyether polyol (a1). The weight fraction of polyether polyol (a1) is preferably 0 to 30 wt. %, particularly preferably 0 to 20 and in particular 1 to 15 wt. %, and of polyester polyol (a2) is preferably 70 to 100 wt. %, particularly preferably 80 to 100 and in particular 85 to 99 wt. %, based in each case on the total weight of polyether polyol (a1) and polyester polyol (a2). In the context of the present disclosure, the terms "polyester polyol" and "polyesterol" are synonymous, as are the terms "polyether polyol" and "polyetherol."

[0024] The polyethers (a1) are obtained by known processes, for example by anionic polymerization of alkylene oxides with the addition of at least one starter molecule containing 1 to 8, preferably 2 to 6, reactive hydrogen atoms, or a starter molecule mixture containing, on average over all starters present, 1.5 to 8, preferably 2 to 6, reactive hydrogen atoms, in the presence of catalysts. If mixtures of starter molecules with different functionalities are used, fractional functionalities can be obtained. Influences on functionality, for example, due to side reactions, are not taken into account in the nominal functionality.Catalysts that can be used are alkali metal hydroxides, such as sodium or potassium hydroxide, or alkali metal alkoxides, such as sodium methylate, sodium or potassium ethylate, or potassium isopropylate, or in cationic polymerization, Lewis acids such as antimony pentachloride, boron trifluoride etherate, or bleaching earth. Aminic alkoxylation catalysts such as dimethylethanolamine (DMEOA), imidazole, and imidazole derivatives can also be used. Furthermore, double metal cyanide compounds, so-called DMC catalysts, can also be used as catalysts. The alkylene oxides used are preferably one or more compounds having 2 to 4 carbon atoms in the alkylene radical, such as tetrahydrofuran, 1,2-propylene oxide, ethylene oxide, 1,2-butylene oxide, or 2,3-butylene oxide, either alone or in the form of mixtures. Ethylene oxide and / or 1,2-propylene oxide are preferably used, particularly preferably ethylene oxide.

[0025] Starter molecules include compounds containing hydroxyl groups or amine groups, for example ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, bisphenol-A, bisphenol-F, glycerol, trimethylolpropane, pentaerythritol, sugar derivatives such as sucrose, hexitol derivatives such as sorbitol, methylamine, ethylamine, isopropylamine, butylamine, benzylamine, aniline, toluidine, toluenediamine (TDA), naphthylamine, ethylenediamine, methylenedianiline, 2,2-diaminodiphenylmethane (2,2-MDA), 2,4'-diaminodiphenylmethane (2,4-MDA), 4,4'-diaminodiphenylmethane (4,4-MDA), diethylenetriamine, 4,4'-methylenedianiline, 1,3, -Propanediamine, 1,6-hexanediamine, ethanolamine, diethanolamine, triethanolamine and other dihydric or polyhydric alcohols or monohydric or polyhydric amines or water.Since the highly functional compounds are often present in solid form under the usual reaction conditions for alkoxylation, it is generally customary to alkoxylate them together with co-initiators. Suitable co-initiators include, for example, water, polyfunctional lower alcohols, e.g., glycerol, trimethylolpropane, pentaerythritol, diethylene glycol, ethylene glycol, propylene glycol, and their homologues. Other co-initiators include, for example, organic fatty acids or monofunctional fatty alcohols, fatty acid monoesters or fatty acid methyl esters such as oleic acid, stearic acid, methyl oleate, methyl stearate, or biodiesel, which serve to improve blowing agent solubility in the production of rigid polyisocyanurate foams.

[0026] Preferred starter molecules for preparing the polyether polyols (a1) are sorbitol, sucrose, ethylenediamine, TDA, trimethylolpropane, pentaerythritol, glycerol, biodiesel, nonylphenol, ethylene glycol, and diethylene glycol. Further preferred starter molecules are all starters or starter mixtures with an average total functionality of <3, particularly preferred are glycerol, trimethylolpropane, biodiesel, nonylphenol, ethylene glycol, diethylene glycol, propylene glycol, and bisphenol A, especially ethylene glycol, diethylene glycol, and glycerol.

[0027] The polyether polyols used in component (a1) preferably have an average functionality of 1.5 to 6 and in particular of 2.0 to 4.0 and number-average molecular weights of preferably 150 to 3000, particularly preferably of 150 to 1500 and in particular of 250 to 800 g / mol. The OH number of the polyether polyols of component (a1) is preferably from 1200 to 50, preferably from 600 to 100 and in particular from 300 to 150 mg KOH / g. Suitable polyester polyols (a2) can be prepared from organic dicarboxylic acids having 2 to 12 carbon atoms, preferably aromatic, or mixtures of aromatic and aliphatic dicarboxylic acids and polyhydric alcohols, preferably diols, having 2 to 12 carbon atoms, preferably 2 to 6 carbon atoms.

[0028] Particularly suitable dicarboxylic acids are: succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, maleic acid, fumaric acid, phthalic acid, isophthalic acid, and terephthalic acid. The dicarboxylic acids can be used individually or in mixtures. Instead of the free dicarboxylic acids, the corresponding dicarboxylic acid derivatives, such as dicarboxylic acid esters of alcohols with 1 to 4 carbon atoms or dicarboxylic acid anhydrides, can also be used. Phthalic acid, phthalic anhydride, terephthalic acid, and / or isophthalic acid are preferably used as aromatic dicarboxylic acids or acid derivatives, either alone or in mixtures. Preferably used aliphatic dicarboxylic acids are dicarboxylic acid mixtures of succinic, glutaric, and adipic acid in ratios of, for example, 20 to 35:35 to 50:20 to 32 parts by weight, and in particular adipic acid.Particularly preferred polyester films (a2) are those obtained using exclusively aromatic dicarboxylic acids or their derivatives. Preferably used as the aromatic dicarboxylic acid is at least one compound selected from the group consisting of terephthalic acid, dimethyl terephthalate (DMT), polyethylene terephthalate (PET), phthalic acid, phthalic anhydride (PSA), and isophthalic acid, particularly preferably at least one compound from the group consisting of terephthalic acid, dimethyl terephthalate (DMT), polyethylene terephthalate (PET), and phthalic anhydride (PSA), and in particular phthalic acid and / or phthalic anhydride.

[0029] Examples of di- and polyhydric alcohols, especially diols, are: monoethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, 1,2- or 1,3-propanediol, dipropylene glycol, polypropylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,10-decanediol, glycerol, trimethylolpropane, and pentaerythritol, as well as alkoxylates of the same starters. Preference is given to using monoethylene glycol, diethylene glycol, triethylene glycol, 1,2- or 1,3-propanediol, dipropylene glycol, and ethoxylates of the same starters, for example, ethoxylated glycerol, or mixtures of at least one of the diols mentioned. Monoethylene glycol, diethylene glycol, glycerin, and ethoxylates of the same starters, or mixtures of at least two of the diols mentioned, especially diethylene glycol, are particularly used. Polyester polyols derived from lactones, e.g., ε-caprolactone, or hydroxycarboxylic acids, e.g., o-hydroxycaproic acid, can also be used.To prepare the polyester polyols (a2), the aliphatic and aromatic polycarboxylic acids and / or derivatives and polyhydric alcohols can be polycondensed catalyst-free or preferably in the presence of esterification catalysts, advantageously in an atmosphere of inert gas such as nitrogen in the melt at temperatures of 150 to 280 °C, preferably 180 to 260 °C, optionally under reduced pressure, to the desired acid number, which is advantageously less than 10, preferably less than 2. Suitable esterification catalysts include, for example, iron, cadmium, cobalt, lead, zinc, antimony, magnesium, titanium, and tin catalysts in the form of metals, metal oxides, or metal salts. However, the polycondensation can also be carried out in the liquid phase in the presence of diluents and / or entraining agents, such as benzene, toluene, xylene or chlorobenzene, for the azeotropic distillation of the condensation water.

[0030] To prepare the polyester polyols (a2), the organic polycarboxylic acids and / or derivatives and polyhydric alcohols are advantageously polycondensed in a molar ratio of 1:1 to 2.2, preferably 1:1.05 to 2.1 and particularly preferably 1:1.1 to 2.0.

[0031] The polyester polyols (a2) obtained generally have a number-average molecular weight of 200 to 3000, preferably 300 to 1000 and in particular 400 to 800.

[0032] The polyester polyols (a2) preferably contain at least one polyesterol (a2a) which is obtainable by esterification of

[0033] (a2a1) 10 to 80 mol% of a dicarboxylic acid composition containing

[0034] (a2a11) 20 to 100 mol%, based on the dicarboxylic acid composition, of one or more aromatic dicarboxylic acids or derivatives thereof,

[0035] (a2a12) 0 to 80 mol%, based on the dicarboxylic acid composition, of one or more aliphatic dicarboxylic acids or derivatives thereof,

[0036] (a2a2) 0 to 30 mol% of one or more fatty acids and / or fatty acid derivatives, (a2a3) 2 to 70 mol% of one or more aliphatic or cycloaliphatic diols having 2 to 18 C atoms or alkoxylates thereof,

[0037] (a2a4) 0 to 80 mol% of an alkoxylation product of at least one starter molecule having an average functionality of at least two, in each case based on the total amount of components (a2a1) to (a2a4), wherein components (a2a1) to (a2a4) add up to 100 mol%.

[0038] Preferably, a polyester polyol of component (a2) has a number-weighted average functionality of greater than or equal to 1.7, preferably greater than or equal to 1.8, particularly preferably greater than or equal to 2.0 and in particular greater than 2.2, which leads to a higher crosslinking density of the polyurethane produced therewith and thus to better mechanical properties of the polyurethane foam.

[0039] Component (a) may also contain chain extenders and / or crosslinking agents, for example to modify the mechanical properties, e.g., hardness. Diols and / or triols, and also amino alcohols with molecular weights of less than 150 g / mol, preferably from 60 to 130 g / mol, are used as chain extenders and / or crosslinking agents. Examples of suitable diols are aliphatic, cycloaliphatic, and / or araliphatic diols having 2 to 8, preferably 2 to 6, carbon atoms, such as, for example, ethylene glycol, 1,2-propylene glycol, diethylene glycol, dipropylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, o-, m-, p-dihydroxycyclohexane, and bis(2-hydroxyethyl)hydroquinone. Also suitable are aliphatic and cycloaliphatic triols such as glycerol, trimethylolpropane and 1,2,4- and 1,3,5- trihydroxycyclohexylene.

[0040] If chain extenders, crosslinking agents, or mixtures thereof are used to produce the rigid polyurethane foams, they are advantageously used in an amount of 0 to 15 wt.%, preferably 0 to 5 wt.%, based on the total weight of component (a). Component (a) preferably contains less than 10 wt.%, more preferably less than 7 wt.%, and especially less than 5 wt.% of chain extenders and / or crosslinking agents.

[0041] As catalysts (b) for the production of polyurethane foams, compounds are used in particular which strongly accelerate the reaction of the compounds of components (a) containing reactive hydrogen atoms, in particular hydroxyl groups, with polyisocyanates.

[0042] It is advantageous to use basic polyurethane catalysts, for example tertiary amines, such as triethylamine, tributylamine, dimethylbenzylamine, dicyclohexylmethylamine, dimethylcyclohexylamine, N,N,N',N'-tetramethyldiaminodiethyl ether, bis-(dimethylaminopropyl)-urea, N-methyl- or N-ethylmorpholine, N-cyclohexylmorpholine, N,N,N',N'-tetramethylethylenediamine, N,N,N,N-tetramethylbutanediamine, N,N,N,N-tetramethylhexane-1,6-diamine, pentamethyldiethylenetriamine, bis(2-dimethylaminoethyl) ether, dimethylpiperazine, N-dimethylaminoethylpiperidine, 1,2-dimethylimidazole, 1-azabicyclo-(2,2,0)-octane, 1 ,4.Diazabicyclo-(2,2,2)-octane (Dabco) and alkanolamine compounds such as triethanolamine, triisopropanolamine, N-methyl- and N-ethyldiethanolamine, dimethylaminoethanol, 2-(N,N-dimethylaminoethoxy)ethanol, N,N',N"-tris-(dialkylaminoalkyl)hexahydrotriazines, e.g. N,N',N"-tris-(dimethylaminopropyl)-s-hexahydrotriazine, and triethylenediamine.However, metal salts such as iron(II) chloride, zinc chloride, lead octoate and tin salts such as tin dioctoate, tin diethylhexoate and dibutyltin dilaurate as well as mixtures of tertiary amines and organic tin salts are also suitable.

[0043] Other suitable catalysts are: amidines such as 2,3-dimethyl-3,4,5,6-tetrahydropyrimidine, tetraalkylammonium hydroxides such as tetramethylammonium hydroxide, alkali metal hydroxides such as sodium hydroxide and alkali metal alcoholates such as sodium methylate and potassium isopropylate, alkali metal carboxylates and alkali metal salts of long-chain fatty acids having 8 to 20 C atoms and optionally pendant OH groups.

[0044] Furthermore, incorporable amines are considered as catalysts, ie, preferably amines with an OH, NH, or NH2 function, such as ethylenediamine, triethanolamine, diethanolamine, ethanolamine, and dimethylethanolamine. Incorporable catalysts can be considered as compounds of both component (b) and component (a).

[0045] Other catalysts considered for the trimerization reaction of the excess NCO groups are isocyanurate-forming catalysts, such as ammonium ion or alkali metal salts, especially ammonium or alkali metal carboxylates, alone or in combination with tertiary amines. Isocyanurate formation leads to flame-retardant PIR foams, which are preferably used in rigid foams, for example, in construction as insulation panels or sandwich elements.

[0046] According to the invention, the catalysts (b) comprise at least one polyurethane catalyst (b1) containing at least one tertiary nitrogen atom, wherein the tertiary nitrogen atom is part of an aliphatic or aromatic ring and / or is bonded to at least one secondary carbon atom. Furthermore, the catalyst (b) comprises at least one polyurethane catalyst (b2) selected from the group consisting of cyclic amides. It is essential to the invention that the polyurethane catalysts (b1) and (b2) do not contain any dimethylamino groups bonded to a primary carbon atom.In the context of the present invention, a primary carbon atom is understood to mean one which is directly bonded to only one other carbon atom, a secondary carbon atom is understood to mean one which is directly bonded to exactly two other carbon atoms and a tertiary carbon atom is understood to mean one which is directly bonded to exactly three other carbon atoms.

[0047] The polyurethane catalyst (b1) preferably has at least one tertiary nitrogen atom which is directly bonded to at least one cyclic aliphatic or aromatic hydrocarbon, a preferred example being N,N-dimethylcyclohexylamine. In a preferred embodiment, the catalyst (b1) contains N,N-dimethylcyclohexylamine, particularly preferably the catalyst (b1) consists of N,N-dimethylcyclohexylamine.

[0048] The cyclic amide (b2) can be a lactam. Lactams, in the context of the invention, are understood to mean cyclic amides that may be substituted. The amide bond is located in the ring; preferably, there is only one amide group in the ring. Examples of lactams according to the invention are β-propiolactam, 2-pyrrolidone, N-methylpyrrolidone, γ-butyrolactam, δ-valerolactam (2-piperidone), and ε-lactam (ε-caprolactam).

[0049] Preferably, the cyclic amide is selected from the group consisting of at least one lactam, for example caprolactam and / or valerolactam, at least one cyclic urea or mixtures thereof, particularly preferably the catalyst (b2) consists of caprolactam and / or valerolactam.

[0050] In a particularly preferred embodiment, the cyclic amide (b2) contains at least one cyclic urea of ​​the general formula 2:

[0051] O

[0052] HN A ,NR

[0053] X Formula (2) where -X- represents a 1 to 6-membered, preferably 2 to 4-membered and particularly preferably 3-membered radical, which may be substituted. This gives a cyclic urea structure according to formula 1, the ring of which, including the urea structure -NH-C(O)-NR-, has 4 to 9 members, in particular 6 members. Preferably, the members of the radical X are selected from the group consisting of -NR 1 -, -O-, -CR 2 R 3 -, -N= and -CR 4 =. In the case of the remainder -CR 4 = or -N= the neighboring term also consists of a -CR 4 = or -N= member, so that the double bond can form between the two members. The residues R 1 to R 4each independently of one another represents hydrogen, an alkyl radical, preferably ethyl or methyl, or halogen, for example a fluoride radical or a chloride radical. In a very particularly preferred embodiment, X is -(CH2)s-. The radical R according to formula 1 represents a substituted or unsubstituted alkyl or heteroalkyl group, a substituted or unsubstituted aryl group or a substituted or unsubstituted alkyl-aryl or heteroalkyl-aryl group. Suitable substituents include, for example, halide groups, alkyl groups, hydroxyl groups or amine groups. In a preferred embodiment of the invention, R contains at least one isocyanate-reactive hydrogen atom, for example an -OH or -NH2 group. R preferably represents methyl, ethyl, propyl, pentyl, hexyl, one or more alkylene oxide units, for example oxyethylene, oxypropylene or mixtures of oxyethylene and oxypropylene, and phenyl, or phenyl ether.Particularly preferably, R is methyl, ethyl, oxyethylene, oxypropylene, or phenyl methoxyester, most preferably methyl. Bridged cyclic urea structures, in which two cyclic urea structures are bridged via the R radical, can also be used as cyclic urea compounds.

[0054] In one embodiment, R has an isocyanate-reactive group, preferably a reactive group selected from a terminal -OH or NH2 group. In another, particularly preferred embodiment, R is unsubstituted.

[0055] Most preferably, R represents a linear, unsubstituted hydrocarbon radical selected from methyl, ethyl, propyl, pentyl and hexyl, in particular R represents a methyl radical.

[0056] Cyclic urea structures according to formula 2 are known and have been described several times, for example in US 2013281451. The synthesis can be carried out, for example, starting from / V-haloalkyl-3-alkylurea, such as 1-(2-chloroethyl)-3-methylurea. These urea compounds are cyclized in the presence of sodium hydride. This synthesis is also described in US 2013281451. Alternatively, the synthesis can be carried out starting from urea and diamines, as described, for example, in EP 976796, or by reacting dialkyl carbonates with diamines, as described, for example, in EP 2548869.

[0057] Preferably, 0.001 to 10 parts by weight, particularly preferably 0.1 to 8 parts by weight, and especially 0.5 to 5 parts by weight of catalyst combination are used, based on 100 parts by weight of component (a). The catalysts preferably contain no metal catalysts and no alkali metal carboxylates. Particularly preferably, the proportion of catalysts (b1) and (b2), based on the total weight of catalysts (b), is at least 80% by weight, particularly preferably at least 90% by weight, and more preferably at least 95% by weight. In particular, no further amine catalysts are present besides catalysts (b1) and (b2).

[0058] Blowing agents (c) according to the invention contain at least one physical blowing agent (c1) comprising at least one aliphatic, halogenated hydrocarbon compound (c11) of the general formula (1) (Formula 1) where the radicals R 1 to R 4each independently of one another represents a hydrogen, fluoride, chloride, methyl or ethyl radical and the hydrogen atoms of the methyl or ethyl radical may be wholly or partially substituted by chloride or fluoride, with the proviso that the compound according to formula (1) is composed of 2 to 5 carbon atoms, at least one hydrogen atom and at least two halogen atoms selected from fluorine and chlorine atoms and that both at least one of the radicals R 1 and R 4 as well as at least one of the residues R 2 and R 3 have at least one halogen atom and that the carbon atom of the carbon-carbon double bond which carries a methyl or ethyl group also carries a hydrogen atom.

[0059] Suitable compounds (c1) include trifluoropropenes and tetrafluoropropenes, such as (HFO-1234), pentafluoropropenes, such as (HFO-1225), chlorotrifluoropropenes, such as (HFO-1233), chlorodifluoropropenes and chlorotetrafluoropropenes, as well as mixtures of one or more of these components. Particular preference is given to tetrafluoropropenes, pentafluoropropenes and chlorotrifluoropropenes, where the unsaturated, terminal carbon atom carries more than one chlorine or fluorine substituent. Examples are 1,3,3,3-tetrafluoropropene (HFO-1234ze); 1,1,3,3-tetrafluoropropene; 1,2,3,3,3-pentafluoropropene (HFO-1225ye); 1,1,1-trifluoropropene; 1,1,1,3,3-pentafluoropropene (HFO-1225zc); 1,1,1,3,3,3-hexafluorobut-2-ene, 1,1,2,3,3-pentafluoropropene (HFO-1225yc); 1,1,1,2,3-pentafluoropropene (HFO-1225yez); 1-chloro-3,3,3-trifluoropropene (HCFO-1233zd); 1,1,1,4,4,4-hexafluorobut-2-ene or mixtures of two or more of these components.

[0060] Particularly preferably, the aliphatic, halogenated hydrocarbon compound of general formula (1) has 3 carbon atoms and at least 4 halogen atoms. Examples of such particularly preferred compounds (c1) are hydroolefins selected from the group consisting of trans-1-chloro-3,3,3-trifluoropropene (HCFO-1233zd(E)), cis-1-chloro-3,3,3-trifluoropropene (HCFO-1233zd(Z)), trans-1,3,3,3-tetrafluoroprop-1-ene (HFO-1234ze(E)), cis-1,3,3,3-tetrafluoroprop-1-ene (HFO-1234ze(Z)) or mixtures of one or more components thereof, in particular HFO 1233zd(E), 1234ze(E) or mixtures thereof.

[0061] Blowing agents used to produce the polyurethane foams according to the invention also preferably include water, formic acid, and mixtures thereof. These react with isocyanate groups to form carbon dioxide, and in the case of formic acid, carbon dioxide and carbon monoxide. Since these blowing agents release the gas through a chemical reaction with the isocyanate groups, they are referred to as chemical blowing agents. Physical blowing agents, such as low-boiling hydrocarbons, can also be used. Particularly suitable are liquids that are inert toward the isocyanates used and have boiling points below 100°C, preferably below 50°C at atmospheric pressure, so that they evaporate under the influence of the exothermic polyaddition reaction.Examples of such preferably used liquids are aliphatic or cycloaliphatic hydrocarbons having 4 to 8 carbon atoms, such as heptane, hexane, and isopentane, preferably technical mixtures of n- and isopentanes, n- and isobutane and propane, cycloalkanes, such as cyclopentane and / or cyclohexane, ethers, such as furan, dimethyl ether and diethyl ether, ketones, such as acetone and methyl ethyl ketone, carboxylic acid alkyl esters, such as methyl formate, dimethyl oxalate and ethyl acetate and halogenated hydrocarbons, such as methylene chloride, dichloromonofluoromethane, difluoromethane, trifluoromethane, difluoroethane, tetrafluoroethane, chlorodifluoroethanes, 1,1-dichloro-2,2,2-trifluoroethane, 2,2-dichloro-2-fluoroethane and heptafluoropropane. Mixtures of these low-boiling liquids with each other and / or with other substituted or unsubstituted hydrocarbons can also be used.

[0062] For the purposes of the present invention, physical blowing agents that do not fall under the definition of (c1) are referred to as physical blowing agents (c2). Chemical blowing agents are referred to as chemical blowing agents (c3).

[0063] Also suitable as chemical blowing agents (c3) are organic carboxylic acids, such as acetic acid, oxalic acid, ricinoleic acid, and carboxyl-containing compounds. Preferably, no halogenated hydrocarbons are used as blowing agents other than the compounds (c1). Preferably, water, formic acid-water mixtures, or formic acid are used as chemical blowing agents (c3). Particularly preferred chemical blowing agents are water or formic acid-water mixtures.

[0064] Preferably, in addition to component (c1), at least one chemical blowing agent (c3) is used.

[0065] The amount of blowing agent or blowing agent mixture used is generally from 1 to 30% by weight, preferably from 1.5 to 20% by weight, particularly preferably from 2.0 to 15% by weight, based in each case on the sum of components (a) to (d). If water or a formic acid-water mixture is used as the blowing agent, it is preferably added to the polyol component in an amount of from 0.2 to 6% by weight, particularly preferably from 1 to 4% by weight, based on the total weight of the polyol component.

[0066] Examples of auxiliaries and / or additives (d) used include surfactants, foam stabilizers, cell regulators, external and internal release agents, fillers, pigments, dyes, flame retardants, antistatic agents, aromatic amine-reducing substances, such as lactams, hydrolysis inhibitors, and fungistatic and bacteriostatic substances. In particular, the use of lactams, such as s-caprolactam, together with the inventive cyclic ureas according to formula 1, leads to a reduction in aromatic amines in the polyurethane.

[0067] Further information on the raw materials used can be found, for example, in the Plastics Handbook, Volume 7, Polyurethanes, edited by Günter Oertel, Carl-Hanser-Verlag, Munich, 3rd edition 1993, Chapter 5, Flexible Polyurethane Foams

[0068] The present invention further relates to a process for producing a polyurethane foam, in which a polyol component according to the invention is mixed with an isocyanate component containing at least one polyisocyanate to form a reaction mixture and reacted to form the polyurethane foam. According to the invention, the polyurethane foams are produced by mixing the polyol component and an isocyanate component containing polyisocyanates to form a reaction mixture and allowing the reaction mixture to react to form the polyurethane foam. In the context of the present invention, a reaction mixture refers to the mixture of the isocyanates and the isocyanate-reactive compounds (a) at reaction conversions of less than 90%, based on the isocyanate groups. The 2-component process is preferably used, with all starting materials being present either in the isocyanate component or in the polyol component.Preferably, all substances that can react with isocyanate are added to the polyol component, while starting materials that are not reactive with isocyanates can be added either to the isocyanate component or the polyol component. The isocyanate component preferably contains only isocyanate.

[0069] In general, the equivalence ratio of NCO groups of the polyisocyanates to the sum of the reactive hydrogen atoms is 0.75 to 1.5:1, preferably 0.80 to 1.25:1. If the polyurethanes are to contain at least partially isocyanurate groups, a ratio of NCO groups of the polyisocyanates (a) to the sum of the reactive hydrogen atoms of 1.5 to 20:1, preferably 1.5 to 8:1 is usually used. A ratio of 1:1 corresponds to an isocyanate index of 100. If flexible polyurethane foams are produced, the mixing ratios are preferably selected so that the isocyanate index is preferably 50 to 95, more preferably 60 to 80 and in particular 65 to 75.

[0070] The polyurethanes of the invention are preferably produced using a one-shot process, for example, using high-pressure or low-pressure technology. The polyurethanes of the invention are produced, for example, on a belt or, preferably, in a mold. The molded polyurethane foams can be produced in open or closed molds, for example, metal molds.

[0071] The polyol component and polyisocyanate component are preferably mixed at a temperature in the range between 15 and 120 °C, preferably 20 and 80 °C, and then introduced into the mold or onto the conveyor line. The temperature in the mold is usually in the range between 15 and 120 °C, preferably between 30 and 80 °C.

[0072] The polyisocyanates used to produce the polyurethanes of the invention include all polyisocyanates known for producing polyurethanes. These include the aliphatic, cycloaliphatic, and aromatic di- or polyfunctional isocyanates known from the prior art, as well as any mixtures thereof. Examples are 2,2'-, 2,4'-, and 4,4'-diphenylmethane diisocyanate, mixtures of monomeric diphenylmethane diisocyanates and higher-nuclear homologues of diphenylmethane diisocyanate (polymer MDI), isophorone diisocyanate (IPDI) or its oligomers, 2,4- or 2,6-tolylene diisocyanate (TDI) or mixtures thereof, tetramethylene diisocyanate or its oligomers, hexamethylene diisocyanate (HDI) or its oligomers, naphthylene diisocyanate (NDI), or mixtures thereof.

[0073] These preferably contain toluene diisocyanate isomers (TDI isomers) and isomers of methylenediphenylene diisocyanate, as well as its higher-nuclear homologues (referred to as MDI). A particularly preferred aromatic polyisocyanate is a mixture containing 2,4'-MDI, 4,4'-MDI, and higher-nuclear homologues of MDI (hereinafter referred to as "polymer MDI" or "PMDI"). Modified isocyanates, such as isocyanates formed by incorporating groups starting from isocyanate groups, in which polyisocyanates are formed, can also be used. Examples of such groups are allophanate, carbodiimide, illiretonimine, isocyanurate, urea, and biuret groups. In a preferred embodiment, the proportion of 2,4'-diphenylmethane diisocyanate is preferably 5 to 30 wt.% and of 4,4'-diphenylmethane diisocyanate is preferably 40 to 80 wt.%, in each case based on the total weight of the aromatic polyisocyanates (a).In a preferred embodiment, the proportion of higher-nuclear homologues of diphenylmethane diisocyanate is 3 to 30 wt.%, particularly preferably 5 to 25 wt.%.

[0074] The aromatic polyisocyanates can also be used in the form of prepolymers. For this purpose, the aromatic polyisocyanates described above are reacted in excess with compounds containing isocyanate-reactive compounds. The isocyanate-reactive compounds used are preferably those listed under (a) containing at least two isocyanate-reactive hydrogen atoms. If isocyanate prepolymers are used as aromatic isocyanates, they preferably have an NCO content of 16 to 31 wt.%.

[0075] Finally, the present invention encompasses a polyurethane foam obtainable by a process according to the invention. The density of such foams according to the invention is preferably between 10 and 150 g / L, particularly preferably between 15 and 100 g / L, more preferably between 20 and 70 g / L, and in particular between 25 and 60 g / L.

[0076] The polyol component according to the invention is characterized by improved storage stability both at room temperature and at elevated temperatures, for example, 70°C. Cost-effective catalysts can be used, which help achieve a reaction profile similar to that of commercial systems. Thus, the start times of the reaction mixtures according to the invention are preferably in the range of 10 to 20 seconds, the setting times are 50 to 80 seconds, and the tack-free times are 120 to 200 seconds.

[0077] In particular, with an isocyanate index of less than 100 and a water content of greater than 1%, the process according to the invention can achieve a strong reduction in the concentration of aromatic amines, for example on the surface of the polyurethane foams.

[0078] In the following, the invention will be illustrated by examples.

[0079] The following substances were used in the examples:

[0080] Polyol 1 : Polyetherol starting from a mixture of sucrose, pentaerythritol and diethylene glycol as starter molecules and propylene oxide with a hydroxyl number of 403 mg KOH / g

[0081] Polyol 2: Polyetherol starting from glycerol as starter molecule and ethylene oxide and

[0082] Propylene oxide with a hydroxyl number of 158 mg KOH / g

[0083] Polyol 3: Polyetherol starting from toluenediamine as starter molecule and ethylene oxide and propylene oxide with a hydroxyl number of 390 mg KOH / g

[0084] Stabilizer 1: Silicone stabilizer

[0085] Propellant 1 : Water

[0086] Propellant 2: 1-chloro-3,3,3-trifluoropropene (1233zd)

[0087] Catalyst 1 : Bis(2-dimethylaminoethyl) ether in 30% dipropylene glycol

[0088] Catalyst 2: Dimethylcyclohexylamine

[0089] Catalyst 3: 1,3.5 Tris(dimethylaminopropyl)-hexahydro-s-triazine

[0090] Catalyst 4: s-caprolactam Catalyst 5: δ-valerolactam

[0091] Catalyst 6: 1-Methyltetrahydropyrimidin-2(1H)-one

[0092] Catalyst 7: 1,2 dimethylimidazole in 30% diethylene glycol

[0093] Isocyanate 1 : Lupranat M20 (Polymeric MDI with a functionality of 2.7 and a

[0094] NCO content of 31.5%; product of BASF SE).

[0095] The polyol components used in the systems are listed in Table 1; the quantities are given in parts by weight. System 1 is the reference system, while systems 2 to 4 are according to the invention. The goal is to achieve longer storage stability compared to the reference system by adapting the catalysis. The following work was carried out in the laboratory.

[0096] Table 1 :

[0097] A 1000g batch of each polyol component consisting of polyol, stabilizer, catalyst, and blowing agent according to Table 1 was mixed using a Vollrath laboratory mixer. Subsequently, 200g of the mixture was poured into 250mL laboratory vials and tightly sealed. For each polyol component, two vials were stored at 23°C and two at 40°C. The remaining polyol component was used directly for testing.

[0098] This series of tests aims to determine the influence of storage time and temperature. Systems 2 to 5 were adjusted to a setting time and density comparable to System 1. This was achieved by adjusting the catalyst quantity. The laboratory values ​​from day 0 served as the baseline. The investigation was conducted as follows:

[0099] The polyol component according to Table 1 and an isocyanate component consisting of isocyanate 1 were heated to 20 ± 1 °C. The polyol component was placed in a paper cup, and the isocyanate component was added. The mixing ratio of polyol component to isocyanate component was 100 to 116. A Vollrath mixer with a Lenart disc was used for mixing. The stirring speed was 1400 rpm. The stopwatch was started at the start of stirring. The setting time, needle height, tack-free time, and foam density were then determined. These values ​​are shown in Tables 2 to 6 for systems 1 to 5, both directly after preparation of the polyol component and after 28 and 71 days of storage at 23 and 40 °C, respectively:

[0100] Table 2, directly after production

[0101] System 1 System 2 System 3 System 4 System 5

[0102] Table 3, 28 days storage at 23 °C

[0103] Table 4, 71 days storage at 23 °C Table 5, 28 days storage at 40 °C

[0104] Table 6, 71 days storage at 40 °C

[0105] The setting time is defined as the time from the start of mixing until the point in the reaction process at which threads can be pulled out of the foam mass using a rod. When the setting time is reached, a needle is simultaneously inserted into the foam directly above the rim of the beaker. After the foam has ceased to expand in volume, the distance traveled by the needle is determined using a ruler. The tack-free time is also determined. It is defined as the period of time between the start of stirring and the point at which no adhesion can be detected between the foam surface and the pipette when a pipette is touched to the foam surface. After the foam has hardened, the foam head is cut off above the rim of the beaker. The contents of the beaker are weighed, and the density is determined.

[0106] The start and rise times are determined using a foam qualification system – the Foamat measuring device from Format Messtechnik. The start time is defined as the time between the start of stirring and the beginning of volume expansion of the reaction mixture due to foam formation. The rise time is defined as the time between the start of stirring and the end of volume expansion.

[0107] It can be seen that the reaction parameters for the inventive examples change only slightly even after storage. In contrast, the reaction times, such as start, setting, rise, and tack-free times, for the comparative example according to system 1 increase significantly; after 71 days of storage at 40 °C, no foam can be obtained at all. Comparative example 2 according to system 5, on the other hand, shows very slow start times and an undesirably high needle height. Thus, strong foam expansion after setting can lead to destruction of the foam structure within the foam. Figure 1 graphically illustrates the changes in setting time, based on the storage time at 23 and 40 °C.

Claims

Patent claims 1. A polyol component for producing polyurethane foams, comprising a) compounds having at least two hydrogen atoms reactive towards isocyanates, b) catalysts comprising b1) at least one polyurethane catalyst (b1) containing at least one tertiary nitrogen atom, wherein the tertiary nitrogen atom is part of an aliphatic or aromatic ring and / or is bonded to at least one secondary carbon atom, and b2) at least one polyurethane catalyst (b2) selected from the group consisting of cyclic amides, wherein the polyurethane catalysts (b1) and (b2) do not have any dimethylamino groups bonded to a primary carbon atom, c) blowing agents comprising at least one physical blowing agent (c1) comprising at least one aliphatic, halogenated hydrocarbon compound (c11) of the general formula (1) (Formula 1) where the radicals R 1to R 4 each independently of one another represents a hydrogen, fluoride, chloride, methyl or ethyl radical and the hydrogen atoms of the methyl or ethyl radical may be wholly or partially substituted by chloride or fluoride, with the proviso that the compound according to formula (1) is composed of 2 to 5 carbon atoms, at least one hydrogen atom and at least two halogen atoms selected from fluorine and chlorine atoms and that both at least one of the radicals R 1 and R 4 as well as at least one of the residues R 2 and R 3 have at least one halogen atom and that the carbon atom of the carbon-carbon double bond which carries a methyl or ethyl group also carries a hydrogen atom, and d) optionally additives.

2. Polyol component according to claim 1, characterized in that the aliphatic, halogenated hydrocarbon compound of general formula (1) has 3 carbon atoms and at least 4 halogen atoms 3. Polyol component according to claim 1 or 2, characterized in that the aliphatic, halogenated hydrocarbon compound of general formula (1) is HFO 1233zd(E) or 1234ze(E).

4. Polyol component according to one of claims 1 to 3, characterized in that the polyurethane catalyst (b1) has at least one tertiary nitrogen atom which is directly bonded to at least one cyclic aliphatic or aromatic hydrocarbon.

5. Polyol component according to claim 4, characterized in that the polyurethane catalyst (b1) contains N,N-dimethylcyclohexylamine.

6. Polyol component according to one of claims 1 to 5, characterized in that the cyclic amide (b2) is selected from the group consisting of caprolactam, valerolactam or at least one cyclic urea.

7. Polyol component according to one of claims 1 to 6, characterized in that the cyclic amide (b2) is s-caprolactam and / or valerolactam.

8. Polyol component according to one of claims 1 to 6, characterized in that the cyclic amide (b2) is a cyclic urea of ​​the general formula 2: O HN A ,NR X Formula (2) wherein -X- represents a substituted or unsubstituted, 1 to 6-membered radical, and R represents a radical selected from a substituted or unsubstituted alkyl or heteroalkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted alkyl-aryl or heteroalkyl-aryl group.

9. Polyol component according to claim 8, characterized in that X is -(CH2)s-.

10. Polyol component according to claim 8 or claim 9, characterized in that R has an -OH group or an -NH2 group.

11. Polyol component according to one of claims 1 to 10, characterized in that besides the catalysts (b1) and (b2) no further amine catalysts are present. Polyol component according to one of claims 1 to 11, characterized in that it contains water. A process for producing a polyurethane foam, characterized in that a polyol component according to one of claims 1 to 12 is mixed with an isocyanate component containing at least one polyisocyanate to form a reaction mixture and reacted to form the polyurethane foam. Polyurethane foam obtainable according to claim 13.

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