WO2024110395A1 - Improving the storage stability of hydrofluoroolefins in amine-containing polyol components for preparing polyurethanes - Google Patents

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

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

Description

(Formel 1) wobei die Reste R¹ bis R⁴ jeweils unabhängig voneinander für einen Wasserstoff-, Fluorid-, Chlorid-, einen Methyl- oder einen Ethylrest stehen und die Wasserstoffatome des Methyl- oder Ethylrests ganz oder teilweise durch Chlorid oder Fluorid substituiert sein können mit der Maßgabe, dass die Verbindung gemäß Formel (1) aufgebaut ist aus 2 bis 5 Kohlenstoffatomen, mindestens einem Wasserstoffatom und mindestens zwei Halogenatomen, ausgewählt aus Fluor- und Chloratomen und dass sowohl mindestens einer der Reste R¹ und R⁴ als auch mindestens einer der Reste R² und R³ mindestens ein Halogenatom aufweisen und dass das Kohlenstoffatom der Kohlenstoff-Kohlenstoff- Doppelbindung, dass eine Methyl- oder Ethylgruppe trägt, noch ein Wasserstoffatom trägt, und (d) gegebenenfalls Zusatzstoffe. Weiter umfasst die vorliegende Erfindung ein Verfahren zur Herstellung von Polyurethanschaumstoffen, man eine solche Polyolkomponente mit einer Isocyanatkomponente, enthaltend mindestens ein Polyisocyanat zu einer Reaktionsmischung vermischt und zum Polyurethan umsetzt und einen Polyurethanschaumstoff, erhältlich nach einem solchen Verfahren. The present invention relates to a polyol component for producing polyurethane foams, comprising (a) compounds having at least two hydrogen atoms reactive towards isocyanates, (b) catalysts comprising at least one polyurethane catalyst (b1) comprising 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 at least 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 ¹ to R ⁴ each independently represent a hydrogen, fluoride, chloride, methyl or ethyl radical and the hydrogen atoms of the methyl or ethyl radical can be completely 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 and at least one of the radicals R ² and R ³ have 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 comprises a process for producing polyurethane foams, such a polyol component is mixed with an isocyanate component containing at least one polyisocyanate to form a reaction mixture and reacted to form the polyurethane, and a polyurethane foam obtainable by such a process.

The production of polyurethane foams, especially polyurethane foams, is well known. In the production of polyurethanes, the reaction of isocyanates and polyols usually takes place in the presence of catalysts, in particular strongly basic Amine catalysts, blowing agents and other auxiliary materials and additives. The raw materials are often put together by the supplier, usually a chemical company, in such a way that they are tailored to the application and lead to the desired properties of the polyurethane. For this purpose, an isocyanate component containing isocyanates and a polyol component containing components that are reactive towards isocyanates are usually formulated, so that the user only has to mix the two components to start the reaction to form the desired polyurethane.

Blowing agents are used to produce polyurethane foams. 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 often used to produce rigid polyurethane foams in particular. 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 when the isocyanates and polyols are reacted, thus causing the reaction mixture to foam. Due to the high reactivity of the isocyanates, physical blowing agents are also added to the polyol component to avoid side reactions.

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 hydrocarbons with a low boiling point, such as pentanes, are primarily used as physical blowing agents. One criterion here is the storage stability of the respective component.

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 separate in many polyurethane systems, so it is advantageous to add the blowing agent just before the foaming process in order to avoid problems with the short storage stability of the polyol component loaded with blowing agent, but this increases the complexity for the user.

Another problem with the use of alkanes as blowing agents is their flammability. This increases the flammability of the polyurethane foams obtained. In addition, the component that contains alkanes as blowing agents, usually the polyol component, is also highly flammable. This requires special precautions when storing and processing systems that contain alkanes as blowing agents. In addition, the alkane can The resulting risk of explosion requires high investments in safety equipment.

Fluorinated hydrocarbons (HFCs) are used whenever the investment in these safety devices to use hydrocarbons as physical blowing agents is too high or cannot be implemented in terms of equipment. HFCs also have the advantage over hydrocarbons that they can lead to foams with a higher insulating effect. However, HFCs are criticized from an environmental point of view due to their contribution to global warming, i.e. their high "global warming potential", and their use is therefore initially being reduced in the EU through regulatory requirements and will be banned in the future.

Preferred physical blowing agents therefore have a low global warming potential. This is the advantage of halogenated olefins, the 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 to foam collapse. The low storage stability is based on the decomposition of the blowing agents in the polyol component. This is described, for example, in WO 2009048807. The degradation reaction of the HFO blowing agents can be slowed down by using specific catalysts such as imidazole derivatives, but this limits the degrees of freedom of the formulation and an optimal catalysis setting is severely impaired, if not impossible.

There are several approaches to improving the storage stability of polyol components that contain 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 which, due to steric hindrance, for example, have only a small influence on the storage stability of the polyol components. One example is WO 2009048807, which discloses polyol components that contain sterically hindered amine catalysts. However, such catalysts are usually expensive.

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, since 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 Polyol components containing water are not storage stable and some of the metal catalysts are already only of limited use due to regulatory requirements.

WO 2009048826 describes the use of blocked amine catalysts, US 20190119461 discloses the use of imidazole-based catalysts. Disadvantages of these catalysts are their often low activity, and blocked catalysts usually only unblock at higher temperatures. This requires an additional step to heat the reaction mixture and limits freedom in adjusting the reaction profile.

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 inexpensive and are capable of a balanced catalysis of gel and blowing reactions.

(Formel 1) wobei die Reste R¹ bis R⁴ jeweils unabhängig voneinander für einen Wasserstoff-, Fluorid-, Chlorid-, einen Methyl- oder einen Ethylrest stehen und die Wasserstoffatome des Methyl- oder Ethylrests ganz oder teilweise durch Chlorid oder Fluorid substituiert sein können mit der Maßgabe, dass die Verbindung gemäß Formel (1) aufgebaut ist aus 2 bis 5 Kohlenstoffatomen, mindestens einem Wasserstoffatom und mindestens zwei Halogenatomen, ausgewählt aus Fluor- und Chloratomen und dass sowohl mindestens einer der Reste R¹ und R⁴ als auch mindestens einer der Reste R² und R³ mindestens ein Halogenatom aufweisen und dass das Kohlenstoffatom der Kohlenstoff-Kohlenstoff- Doppelbindung, dass eine Methyl- oder Ethylgruppe trägt, noch ein Wasserstoffatom trägt, und (d) gegebenenfalls Zusatzstoffe. Weiter umfasst die vorliegende Erfindung ein Verfahren zur Herstellung von Polyurethanschaumstoffen, man eine solche Polyolkomponente mit einer Isocyanatkomponente, enthaltend mindestens ein Polyiso- cyanat zu einer Reaktionsmischung vermischt und zum Polyurethan umsetzt und einen Polyurethanschaumstoff, erhältlich nach einem solchen Verfahren. The object according to the invention is achieved by a polyol component for producing polyurethane foams, containing (a) compounds with 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 at least 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 containing 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 ⁴ each independently represent a hydrogen, fluoride, chloride, methyl or ethyl radical and the hydrogen atoms of the methyl or ethyl radical can be completely 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 and at least one of the radicals R ² and R ³ have 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 The present invention relates to a process for producing polyurethane foams, in which such a polyol component is mixed with an isocyanate component containing at least one polyisocyanate to form a reaction mixture and converted to the polyurethane, and to a polyurethane foam obtainable by such a process.

Polyurethane in the sense of the invention includes all known polyisocyanate polyaddition products. These include addition products of isocyanate and alcohol as well as modified polyurethanes that can 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.

In the context of the invention, polyurethane foams are understood to mean foams in accordance with DIN 7726. Polyurethane flexible 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. Polyurethane semi-rigid 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. Polyurethane semi-rigid foams and polyurethane flexible 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 polyurethane flexible foams and polyurethane semi-rigid foams according to the invention can be found in the "Kunststoffhandbuch, Band 7, Polyurethane", Carl Hanser Verlag, 3rd edition 1993, Chapter 5.

The rigid polyurethane foams according to the invention have 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 the "Kunststoffhandbuch, Band 7, Polyurethane", Carl Hanser Verlag, 3rd edition 1993, Chapter 6.

For the purposes of this invention, elastomeric polyurethane foams are understood to mean polyurethane foams in accordance with DIN 7726 which, after a brief deformation of 50% of the thickness in accordance with DIN 53 577, do not exhibit any permanent deformation of more than 2% of their initial thickness after 10 minutes. This can be, for example, a flexible polyurethane foam. Polyurethane molded foams are polyurethane foams according to DIN 7726 which, due to the molding process, have an outer skin or an edge zone that has a higher density than the core. The total 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 of greater than 100 g/L are usually referred to as integral foams. Polyurethane molded foams within the meaning of the invention can also be polyurethane rigid foams, polyurethane semi-rigid foams or polyurethane flexible foams. Further details on polyurethane integral foams according to the invention can be found in the "Plastics Handbook, Volume 7, Polyurethanes", Carl Hanser Verlag, 3rd edition 1993, Chapter 7. The polyurethanes according to the invention are preferably polyurethane foams, particularly preferably polyurethane rigid foams, polyurethane semi-rigid foams or polyurethane flexible foams, in particular polyurethane rigid foams.

All compounds known in polyurethane chemistry with groups reactive towards isocyanate can be used as compounds (a) reactive towards isocyanate groups, preferably compounds with at least one hydroxyl group, -NH group, or NH2 group or carboxylic acid group, preferably with at least one NH2 or OH group and in particular at least one -OH group. The functionality towards isocyanate groups can be in the range from 1 to 8, preferably 2 to 8. The compounds reactive towards isocyanate groups comprise polyether polyols (a1), polyester polyols (a2) or mixtures thereof, preferably polyester oils (a2) or mixtures of polyether oils (a1) and polyester oils (a2). Polyether oils (a1) and polyester oils (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 polyetherols and polyesterols, low molecular weight chain extenders and/or crosslinking agents known in polyurethane chemistry can also be used, for example. 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 polyetherols (a1) and/or polyesterols (a2) have a number-average functionality of at least 1.7, more preferably of at least 2.0.

Polyetherols (a1) are produced, 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 compounds based on natural substances, such as sucrose, sorbitol or mannitol, using a catalyst. are basic catalysts or double metal cyanide catalysts, as described for example in PCT/EP2005/010124, EP 90444 or WO 05/090440.

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

According to the invention, the compounds (a) reactive toward isocyanate groups contain 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 polyetherol (a1) is preferably 0 to 30% by weight, particularly preferably 0 to 20 and in particular 1 to 15% by weight, and of polyesterol (a2) is preferably 70 to 100, particularly preferably 80 to 100 and in particular 85 to 99% by weight, in each case based on the total weight of polyetherol (a1) and polyesterol (a2). In the context of the present disclosure, the terms “polyester polyol” and “polyesterol” are synonymous, as are the terms “polyether polyol” and “polyetherol”.

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 which contains 1 to 8, preferably 2 to 6 reactive hydrogen atoms bonded, or a starter molecule mixture which, on average over all starters present, contains 1.5 to 8, preferably 2 to 6 reactive hydrogen atoms bonded, in the presence of catalysts. If mixtures of starter molecules with different functionality are used, fractional functionalities can be obtained. Influences on the functionality, for example due to side reactions, are not taken into account in the nominal functionality. Catalysts which can be used are alkali hydroxides, such as sodium or potassium hydroxide, or alkali alkoxides, such as sodium methylate, sodium or potassium ethylate or potassium isopropylate, or in the case of 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. 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- or 2,3-butylene oxide, are used as alkylene oxides, either alone or in the form of mixtures. Preferably, ethylene oxide and/or 1,2-propylene oxide are used, particularly preferably ethylene oxide.

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, glycerin, 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 di or polyhydric alcohols or mono or polyhydric amines or water. Since the highly functional compounds are often in solid form under the usual reaction conditions of alkoxylation, it is generally common to alkoxylate them together with co-initiators. Suitable co-initiators include water, polyfunctional lower alcohols, e.g. glycerine, 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, oleic acid methyl ester, stearic acid methyl ester or biodiesel, which serve to improve the blowing agent solubility in the production of polyisocyanurate rigid foams.

Preferred starter molecules for producing the polyether polyols (a1) are sorbitol, sucrose, ethylenediamine, TDA, trimethylolpropane, pentaerythritol, glycerin, 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 glycerin, trimethylolpropane, biodiesel, nonylphenol, ethylene glycol, diethylene glycol, propylene glycol and bisphenol-A, in particular ethylene glycol, diethylene glycol and glycerin.

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 150 to 1500 and in particular 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.

The following are particularly suitable as dicarboxylic acids: 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 either individually or in a mixture. 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. The aromatic dicarboxylic acids or acid derivatives used are preferably phthalic acid, phthalic anhydride, terephthalic acid and/or isophthalic acid in a mixture or alone. The aliphatic dicarboxylic acids used are preferably 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 aromatic dicarboxylic acids are 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.

Examples of di- and polyhydric alcohols, in particular 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, glycerin, trimethylolpropane and pentaerythritol, and 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 glycerin, or mixtures of at least one of the diols mentioned. In particular, monoethylene glycol, diethylene glycol, glycerin, and ethoxylates of the same starters, or mixtures of at least two of the diols mentioned, in particular diethylene glycol, are used. Polyester polyols made from lactones, e.g. e-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 without catalysts or preferably in the presence of esterification catalysts, expediently 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. Examples of suitable esterification catalysts are 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.

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.

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.

Preferably, the polyester polyols (a2) contain at least one polyesterol (a2a) which is obtainable by esterification of

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

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

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

(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,

(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), where components (a2a1) to (a2a4) add up to 100 mol%.

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 results in a higher crosslinking density of the polyurethane produced with it and thus to better mechanical properties of the polyurethane foam.

Component (a) can also contain chain extenders and/or crosslinking agents, for example to modify the mechanical properties, e.g. the hardness. Diols and/or triols and 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 with 2 to 8, preferably 2 to 6 carbon atoms, such as ethylene glycol, 1,2-propylene glycol, diethylene glycol, dipropylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, o-, m-, p-dihydroxycyclohexane, bis-(2-hydroxyethyl)-hydroquinone. Also considered are aliphatic and cycloaliphatic triols such as glycerol, trimethylolpropane and 1,2,4- and 1,3,5-trihydroxycyclohexane.

If chain extenders, crosslinking agents or mixtures thereof are used to produce the rigid polyurethane foams, these are expediently used in an amount of from 0 to 15% by weight, preferably from 0 to 5% by weight, based on the total weight of component (a). Component (a) preferably contains less than 10% by weight and particularly preferably less than 7% by weight and in particular less than 5% by weight of chain extenders and/or crosslinking agents.

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

It is expedient to use basic polyurethane catalysts, for example tertiary amines, such as triethylamine, tributylamine, dimethylbenzylamine, dicyclohexylmethylamine, dimethylcyclohexylamine, N,N,N',N'-tetramethyldiaminodiethyl ether, bis-(dimethylaminopropyl)-urea, N-methyl- or N-ethylmorpholine, N-cyclohexylmorpholine, N,N,N',N'-tetramethylethylenediamine, N,N,N,N-tetramethylbutanediamine, N,N,N,N-tetramethylhexanediamine-1,6, pentamethyldiethylenetriamine, bis(2-dimethylaminoethyl)ether, dimethylpiperazine, N-dimethylaminoethylpiperidine, 1,2-dimethylimidazole, 1-azabicyclo-(2,2,0)-octane, 1 ,4.Diazabicyclo-(2,2,2)-octane (Dabco) and alkanolamine compounds such as triethanolamine, triisopropanolamine, N-methyl- and N-ethyldiethanolamine, dimethylaminoethanol, 2-(N,N-dimethylaminoethoxy)ethanol, N,N',N”-tris-(dialkylaminoalkyl)hexahydrotriazines, e.g. N,N',N”-tris-(dimethylaminopropyl)-s-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.

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

Furthermore, amines that can be incorporated as catalysts are considered, i.e. preferably amines with an OH, NH or NH2 function, such as ethylenediamine, triethanolamine, diethanolamine, ethanolamine and dimethylethanolamine. Incorporable catalysts can be considered to be compounds of both component (b) and component (a).

In addition, catalysts that can be used for the trimerization reaction of the excess NCO groups with each other are: catalysts that form isocyanurate groups, for example ammonium ion or alkali metal salts, especially ammonium or alkali metal carboxylates, alone or in combination with tertiary amines. The formation of isocyanurates leads to flame-retardant PIR foams, which are preferably used in technical rigid foams, for example in construction as insulation panels or sandwich elements.

According to the invention, the catalysts (b) comprise at least one polyurethane catalyst (b1) which contains at least one tertiary nitrogen atom, where the tertiary nitrogen atom is part of an aliphatic or aromatic ring and/or is bonded to at least one at least secondary carbon atom. The catalyst (b) further 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 have 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 that is directly bonded to only one other carbon atom, a secondary carbon atom is understood to mean one that is directly bonded to exactly two other carbon atoms, and a tertiary carbon atom is understood to mean one that is directly bonded to exactly three other carbon atoms.

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 In one embodiment, the catalyst (b1) contains N,N-dimethylcyclohexylamine; more preferably, the catalyst (b1) consists of N,N-dimethylcyclohexylamine.

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

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.

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

O

HN A ,N-R

X formula (2) where -X- stands for a 1 to 6-membered, preferably 2 to 4-membered and particularly preferably 3-membered radical which can be substituted. This creates a cyclic urea structure according to formula 1 whose ring, 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 radical -CR ⁴ = or -N=, the neighboring member naturally also consists of a -CR ⁴ = or -N= member, so that the double bond can form between the two members. The radicals R ¹ to R ⁴ each independently stand for hydrogen, an alkyl radical, preferably ethyl or methyl, or halogen, for example a fluoride radical or a chloride radical. In a particularly preferred embodiment, X is -(CH2)s-. The radical R according to formula 1 is 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. Examples of possible substituents are halide groups, alkyl groups, hydroxyl groups or amine groups. In a preferred embodiment of the invention, R contains at least one hydrogen atom that is reactive toward isocyanate, for example an -OH or -NH2 group. Preferably, R is 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 R preferably represents methyl, ethyl, oxyethylene, oxypropylene or phenylmethoxyester, very particularly preferably methyl. Bridged cyclic urea structures can also be used as cyclic urea compounds, with two cyclic urea structures being bridged via the R radical.

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

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

Cyclic urea structures according to formula 2 are known and have already 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 reaction of dialkyl carbonates with diamines, as described, for example, in EP 2548869.

Preferably, 0.001 to 10 parts by weight, particularly preferably 0.1 to 8 parts by weight and in particular 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 the catalysts (b), is at least 80% by weight, particularly preferably at least 90% by weight, more preferably at least 95% by weight and in particular no further amine catalysts are present in addition to the catalysts (b1) and (b2).

(Formel 1) wobei die Reste R¹ bis R⁴ jeweils unabhängig voneinander für einen Wasserstoff-, Fluorid-, Chlorid-, einen Methyl- oder einen Ethylrest stehen und die Wasserstoffatome des Methyl- oder Ethylrests ganz oder teilweise durch Chlorid oder Fluorid substituiert sein können mit der Maßgabe, dass die Verbindung gemäß Formel (1) aufgebaut ist aus 2 bis 5 Kohlenstoffatomen, mindestens einem Wasserstoffatom und mindestens zwei Halogenatomen, ausgewählt aus Fluor- und Chloratomen und dass sowohl mindestens einer der Reste R¹ und R⁴ als auch mindestens einer der Reste R² und R³ mindestens ein Halogenatom aufweisen und dass das Kohlenstoffatom der Kohlenstoff-Kohlenstoff- Doppelbindung, dass eine Methyl- oder Ethylgruppe trägt, noch ein Wasserstoffatom trägt. 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 ⁴ each independently represent a hydrogen, fluoride, chloride, methyl or ethyl radical and the hydrogen atoms of the methyl or ethyl radical can be completely 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 at least one of the radicals R ¹ and R ⁴ and at least one of the radicals 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.

Suitable compounds (c1) include trifluoropropenes and terafluoropropenes, such as (HFO-1234), pentafluoropropenes, such as (HFO-1225), chlorotrifluoropropenes, such as (HFO-1233), chlorodifluoropropenes and chlorotetrafluoropropenes, and 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.

The aliphatic, halogenated hydrocarbon compound of general formula (1) particularly preferably 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 of HFO 1233zd(E), 1234ze(E) or mixtures thereof.

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. In addition, physical blowing agents such as low-boiling hydrocarbons can be used. Liquids which are inert towards 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 liquids which are preferably used 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.

In the context 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).

Also suitable as chemical blowing agents (c3) are organic carboxylic acids, such as acetic acid, oxalic acid, ricinoleic acid and compounds containing carboxyl groups. Preferably, no halogenated hydrocarbons are used as blowing agents in addition to 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.

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

The amount of blowing agent or blowing agent mixture used is generally 1 to 30% by weight, preferably 1.5 to 20% by weight, particularly preferably 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 blowing agent, it is preferably added to the polyol component in an amount of 0.2 to 6% by weight, particularly preferably 1 to 4% by weight, based on the total weight of the polyol component.

Examples of auxiliary substances and/or additives (d) are surface-active substances, foam stabilizers, cell regulators, external and internal release agents, fillers, pigments, dyes, flame retardants, antistatic agents, aromatic amine reducing substances, For example, lactams, hydrolysis protection agents and fungistatic and bacteriostatic substances are used. In particular, the use of lactams such as s-caprolactam together with the cyclic ureas according to formula 1 according to the invention leads to a reduction in aromatic amines in the polyurethane.

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

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 compounds (a) that are reactive towards isocyanate with reaction conversions of less than 90%, based on the isocyanate groups. The 2-component process is preferably used, with all of the starting materials being contained either in the isocyanate component or in the polyol component. All of the substances that can react with isocyanate are preferably added to the polyol component, while starting materials that are not reactive towards isocyanates can be added to either the isocyanate component or the polyol component. Preferably, the isocyanate component contains only isocyanate.

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 some 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, particularly preferably 60 to 80 and in particular 65 to 75.

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

The polyol component and the polyisocyanate component are preferably mixed at a temperature in the range between 15 and 120 °C, preferably 20 to 80 °C, and placed in the mold or on the conveyor line. The temperature in the mold is usually in the range between 15 and 120 °C, preferably between 30 and 80 °C.

The polyisocyanates used to produce the polyurethanes according to 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 and any mixtures thereof. Examples are 2,2'-, 2,4'- and 4,4'-diphenylmethane diisocyanate, the 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.

These preferably contain toluene diisocyanate isomers (TDI isomers) and isomers of methylene diphenylene diisocyanate and its higher-nuclear homologues (referred to as MDI). A mixture containing 2,4'-MDI, 4,4'-MDI and higher-nuclear homologues of MDI (referred to below as "polymer MDI" or "PMDI") is particularly preferably used as the aromatic polyisocyanate. Modified isocyanates can also be used, such as isocyanates which are formed by incorporating groups starting from isocyanate groups in which polyisocyanates are formed. 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% by weight and of 4,4'-diphenylmethane diisocyanate is preferably 40 to 80% by weight, 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% by weight, particularly preferably 5 to 25% by weight.

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 that are reactive towards isocyanates. The compounds used as isocyanate-reactive compounds are preferably those mentioned under (a) with at least two hydrogen atoms that are reactive towards isocyanates. If isocyanate prepolymers are used as aromatic isocyanates, they preferably have an NCO content of 16 to 31 wt.%.

Finally, the present invention comprises 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 15 and 100 g/L, more preferably between 20 and 70 g/L and in particular between 25 and 60 g/L.

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. In this case, inexpensive catalysts can be used, with the help of which a reaction profile as is usual in commercial systems can be achieved. 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.

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.

In the following, the invention will be illustrated by means of examples.

The following substances were used in the examples:

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

Polyol 2: Polyetherol starting from glycerin as starter molecule and ethylene oxide and

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

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

Stabilizer 1 : Silicone stabilizer

Propellant 1 : Water

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

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

Catalyst 2: Dimethylcyclohexylamine

Catalyst 3: 1,3,5 T ris(dimethylaminopropyl)-hexahydro-s-triazine

Catalyst 4: s-Caprolactam Catalyst 5: δ-Valerolactam

Catalyst 6: 1-methyltetrahydropyrimidin-2(1H)-one

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

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

NCO content of 31.5%; product of BASF SE).

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, systems 2 to 4 are according to the invention. The aim is to achieve longer storage stability compared to the reference system by adapting the catalysis. The following work was carried out in the laboratory.

Table 1 :

A batch of 1000g of each polyol component consisting of polyol, stabilizer, catalyst and blowing agent according to Table 1 was mixed with a Vollrath laboratory mixer. Then 200g of the mixture was filled into 250mL laboratory glasses and tightly sealed. For each polyol component, two glasses were stored at 23°C and two glasses at 40°C. The remaining polyol component is used directly for the investigation.

This series of tests is intended to determine the influence of storage time and temperature. Systems 2 to 5 were brought to a setting time and density comparable to system 1. This is done by adjusting the amount of catalyst. The laboratory values from day 0 serve as the starting values. The investigation was carried out as follows:

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 disk was used for mixing. The stirring speed was 1400 rpm. The stop watch was started when stirring began. The setting time, needle height, tack-free time and density of the foam were then determined. These values are given in Tables 2 to 6 for systems 1 to 5, both directly after the polyol component was produced and after 28 and 71 days of storage at 23 and 40 °C respectively:

Table 2, directly after production

System 1 System 2 System 3 System 4 System 5

Table 3, 28 days storage at 23 °C

Tabelle 5, 28 Tage Lagerung bei 40 °C

Table 4, 71 days storage at 23 °C

Table 5, 28 days storage at 40 °C

Table 6, 71 days storage at 40 °C

The setting time is defined as the time from the start of mixing to the point in the reaction process when threads can be pulled out of the foam mass using a stick. When the setting time is reached, a needle is simultaneously inserted into the foam directly above the edge of the cup. After the foam has expanded in volume, the distance the needle has traveled is determined using a ruler. The tack-free time is also determined. It is defined as the time between the start of stirring and the point in time when no adhesion can be detected between the foam surface and the pipette when the foam surface is touched with a pipette. After the foam has hardened, the foam head is cut off above the edge of the cup. The contents of the cup are weighed and the density is determined.

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

It can be seen that the reaction parameters for the examples according to the invention 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 large needle height. Strong foam expansion after setting can lead to destruction of the foam structure inside 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. Polyol component for the production of polyurethane foams, containing a) compounds with 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 at least 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 containing 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 ⁴ each independently represent a hydrogen, fluoride, chloride, methyl or ethyl radical and the hydrogen atoms of the methyl or ethyl radical can be completely 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 at least one of the radicals R ¹ and R ⁴ and at least one of the radicals 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 ,N-R 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. 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.