SILICONE-FREE FOAM STABILIZERS FOR THE PRODUCTION OF POLYURETHANE FOAMS

Description

[0001] The present invention relates to a process for the production of polyurethane foams, in which (a) polyisocyanate, (b) polymeric compounds having groups reactive towards isocyanates, (c) non-silicone-containing stabilizer, (d) optionally chain extender and / or crosslinking agent, (e) catalysts, (f) blowing agent and (g) optionally auxiliaries and additives are mixed to form a reaction mixture and the reaction mixture is allowed to react to give the polyurethane, wherein the non-silicone-containing stabilizer (c) is obtainable by alkoxylation of a 1 to 8-functional starter molecule with alkylene oxides, wherein 0 to 9% by weight of the alkylene oxides used is ethylene oxide, 0 to 50% by weight of the alkylene oxides used is 1,2 propylene oxide and at least 50% by weight of the alkylene oxides used have at least 4 carbon atoms and the number average molecular weight of the non-silicone-containing stabilizer (c) is 500 to 20.000 g / mol, the proportion of the non-silicone-containing foam stabilizer (c), based on the total weight of the compounds (b), (c), (d), (e) and (f), is 0.01 to 10 wt. %, and wherein the content of silicone-based foam stabilizer is less than 0.3 wt. %, based on the total weight of the compounds (b), (c), (d), (e) and (f). The present invention further relates to a polyol component comprising the silicone-free stabilizer (c), a polyurethane foam obtainable by a process according to the invention and the use of the polyurethane foam according to the invention in enclosed spaces or in the interior of vehicles.

[0002] In the production of polyurethane foams, liquid polyisocyanates are typically mixed with similarly liquid compounds containing higher molecular weight groups that are reactive toward isocyanates and blowing agents, and the resulting polyurethane foam is formed. The blowing agents used can be chemical blowing agents that react with isocyanate groups to form carbon dioxide, and / or physical blowing agents that evaporate due to the heat released during polyurethane production. The polyurethane formation reaction and the blowing reaction essentially proceed in parallel. Foam stabilizers are typically used to ensure the formation of a stable foam.These compounds ensure that the gas produced during the polyurethane reaction does not escape from the reaction mixture and that the resulting foam remains stable until the polyurethane reaction is completed to such an extent that the resulting foam can no longer collapse.

[0003] Commonly used foam stabilizers are polysiloxane-polyoxyalkylene copolymers or polyethersiloxanes. Such siloxane-based foam stabilizers are described, for example, in the "Kunststoffhandbuch, Volume 7, Polyurethane," Carl Hanser Verlag, 3rd edition 1993, Chapter 3.4.4.2. These silicone stabilizers are typically quite expensive; in many cases, they represent the most expensive component in the production of polyurethane foam. Therefore, attempts are being made to replace silicone-based foam stabilizers with other, similarly effective substances.

[0004] WO 2016095128 describes perfluoro-based, surface-active substances containing isocyanate groups for the production of polyurethane foams.

[0005] Furthermore, WO 95 / 16721 describes non-silicone-based polyether compounds as foam stabilizers in the production of polyurethane foams. These are used particularly in the production of rigid polyurethane foams and consist of a polyether which, based on the weight fraction of oxyalkylene units in the polyether, contains 10 to 90 wt. % oxyethylene units and 90 to 10 wt. % oxyalkylene units having at least 4 carbon atoms, and which is essentially free of oxypropylene units. A particular disadvantage of these foam stabilizers is their poor applicability in the production of flexible polyurethane foams.

[0006] US 2013 / 178548 relates to viscoelastic polyurethane foams with high air permeability. A special isocyanate-reactive component containing (i) 35 to 74 wt.% propylene oxide-rich polyols, (ii) 24 to 50 wt.% ethylene oxide-rich polyols, and (iii) 2 to 10 wt.% butylene oxide-rich polyols is used as the reaction system for producing the viscoelastic polyurethane foam.

[0007] The object of the present invention was therefore to develop a process for the production of polyurethane foams which leads to a fine-cell polyurethane foam, in particular flexible polyurethane foam, without the use of conventional, silicone-based foam stabilizers.

[0008] This object is achieved by a process for the production of polyurethane foams, in which (a) polyisocyanate, (b) polymeric compounds having groups reactive towards isocyanates, (c) non-silicone-containing stabilizer, (d) optionally chain extender and / or crosslinking agent, (e) catalysts, (f) blowing agent and (g) optionally auxiliaries and additives are mixed to form a reaction mixture and the reaction mixture is allowed to react to give the polyurethane, wherein the non-silicone-containing stabilizer (c) is obtainable by alkoxylation of a 1 to 8-functional starter molecule with alkylene oxides, wherein 0 to 9% by weight of the alkylene oxides used is ethylene oxide, 0 to 50% by weight of the alkylene oxides used is 1,2 propylene oxide and at least 50% by weight of the alkylene oxides used have at least 4 carbon atoms and the number average molecular weight of the non-silicone-containing stabilizer (c) is 500 to 20.000 g / mol, the proportion of the non-silicone-containing foam stabilizer (c), based on the total weight of the compounds (b), (c), (d), (e) and (f), is 0.01 to 10 wt.% and wherein the content of silicone-based foam stabilizer is less than 0.3 wt.%, based on the total weight of the compounds (b), (c), (d), (e) and (f).

[0009] Polyurethane foams within the meaning of the invention encompass all known foamed polyisocyanate polyaddition products. These include addition products of isocyanate and alcohol as well as modified polyurethanes, which may contain isocyanurate, allophanate, urea, carbodiimide, uretonimine, biuret structures, and other isocyanate addition products. These polyurethane foams according to the invention include, in particular, flexible foams, semi-rigid foams, rigid foams, or integral skin foams based on polyurethanes. Furthermore, polyurethane foams within the meaning of the invention also include foamed polymer blends containing polyurethanes and other polymers. The polyurethane foams according to the invention are preferably those which, apart from the polyurethane building blocks (a) to (g) explained below and their reaction products, contain no further polymers.

[0010] In the context of the invention, polyurethane foams are understood to mean foams according to 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 and a density of preferably 10 to 100 g / L. 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.

[0011] 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 the "Kunststoffhandbuch, Volume 7, Polyurethane," Carl Hanser Verlag, 3rd edition 1993, Chapter 6.

[0012] For the purposes of this invention, elastomeric polyurethane foams are polyurethane foams according to DIN 7726 that, after a brief deformation of 50% of their thickness according to DIN 53 577, exhibit no permanent deformation exceeding 2% of their initial thickness after 10 minutes. This can be a rigid polyurethane foam, a semi-rigid polyurethane foam, or a flexible polyurethane foam.

[0013] Polyurethane integral skin foams are polyurethane foams according to DIN 7726 with an edge zone that, due to the molding process, has a higher density than the core. The total bulk density averaged over the core and edge zone is preferably above 100 g / L. Polyurethane integral skin 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, Volume 7, Polyurethane," Carl Hanser Verlag, 3rd edition 1993, Chapter 7.

[0014] Polyurethanes according to the invention are obtained by mixing polyisocyanates (a) with polymeric compounds having groups reactive towards isocyanates (b), non-silicone-containing stabilizer (c), optionally chain extenders and / or crosslinking agents (d), catalysts (e), blowing agents (f) and optionally auxiliaries and additives (g) to form a reaction mixture and allowing the reaction mixture to react to form the polyurethane.

[0015] In a preferred embodiment, the polyurethane foam according to the invention is a polyurethane foam with an average density of 10 to 850 g / L, preferably a semi-rigid polyurethane foam or a flexible polyurethane foam or a rigid polyurethane foam, particularly preferably an elastomeric flexible polyurethane foam, a semi-rigid polyurethane foam or an elastomeric integral polyurethane foam. The elastomeric integral polyurethane foam preferably has a density averaged over the core and the edge zone of 150 to 500 g / L. The flexible polyurethane foam preferably has an average density of 10 to 100 g / L, the semi-rigid polyurethane foam preferably has an average density of 70 to 150 g / L, and the rigid polyurethane foam preferably has an average density of 30 to 120 g / L.

[0016] The polyurethane according to the invention is preferably used in interior spaces, for example interiors of buildings or means of transport, particularly preferably in the interior of means of transport such as ships, aircraft, trucks, cars or buses, more preferably cars or buses and in particular cars. The interior of cars and buses is referred to below as the automotive interior part. A flexible polyurethane foam can be used in furniture construction, for example as seat cushions, as mattresses or as backing for carpets; a semi-rigid polyurethane foam can be used as backing for door side elements or instrument panels; an integral polyurethane foam can be used as a steering wheel, gear knob or headrest; and a rigid polyurethane foam can be used as a headliner.

[0017] The polyisocyanate components (a) 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 desired 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.

[0018] Preferred isocyanates are 2,4- and / or 2,6-tolylene diisocyanate (TDI) or mixtures thereof, monomeric diphenylmethane diisocyanates and / or higher-nuclear homologues of diphenylmethane diisocyanate (polymer MDI) and mixtures thereof. Other possible isocyanates are listed, for example, in the "Kunststoffhandbuch, Volume 7, Polyurethane," Carl Hanser Verlag, 3rd edition 1993, Chapters 3.2 and 3.3.2.

[0019] The polyisocyanate component (a) can be used in the form of polyisocyanate prepolymers. These polyisocyanate prepolymers are obtainable by reacting the above-described polyisocyanates (component (a-1)) in excess, for example at temperatures of 20 to 100 °C, preferably at about 80 °C, with polymeric compounds containing isocyanate-reactive groups (b) (component (a-2)) and / or chain extenders (d) (component (a-3)) to form the isocyanate prepolymer.

[0020] Polymeric compounds with isocyanate-reactive groups (a-2) and chain extenders (a3) ​​are known to the person skilled in the art and are described, for example, in "Kunststoffhandbuch, 7, Polyurethane," Carl Hanser-Verlag, 3rd edition 1993, Chapter 3.1. Thus, for example, the polymeric compounds with isocyanate-reactive groups described below under (b) can also be used as polymeric compounds with isocyanate-reactive groups (a-2).

[0021] As polymeric compounds with isocyanate-reactive groups (b), all known compounds having at least two isocyanate-reactive hydrogen atoms can be used, for example those with a functionality of 2 to 8 and a number-average molecular weight of 400 to 20,000 g / mol. For example, compounds selected from the group of polyether polyols, polyester polyols, or mixtures thereof can be used.

[0022] Polyetherols 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 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. The number-average molecular weight M of the polyetherols is determined from the formula M = F ⋅ 56100 OHZ where F stands for the functionality of the starter molecule, in the case of mixtures of starter molecules for the number-average functionality of the starter molecules and OHZ for the hydroxyl number determined by titration.

[0023] Polyesterols 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.

[0024] In addition to the polyetherols and polyesterols described, filler-containing polyetherols or polyesterols, also referred to as polymer polyetherols or polymer polyesterols, can also be used. Such compounds preferably contain dispersed particles of thermoplastics, for example composed of olefinic monomers such as acrylonitrile, styrene, (meth)acrylates, (meth)acrylic acid, and / or acrylamide. Such filler-containing polyols are known and commercially available. Their preparation is described, for example, in DE 111 394, US 3,304,273, US 3,383,351, US 3,523,093, DE 1 152 536, DE 1 152 537, WO 2008 / 055952, and WO2009 / 128279.

[0025] In a particularly preferred embodiment, the polymeric compounds having isocyanate-reactive groups (b) used are polyetherols (b1), obtainable by addition of ethylene oxide, 1,2-propylene oxide, or mixtures thereof to a starter molecule. These polyetherols particularly preferably have an average functionality of 1.8 to 3 and an OH number of 20 to 120, particularly preferably 25 to 100, and in particular 30 to 80 mg KOH / g. The proportion of propylene oxide and ethylene oxide, based on the total weight of the alkylene oxides used to prepare the polyether alcohol (b1), is preferably at least 80% by weight, particularly preferably at least 90% by weight, more preferably in particular 95% by weight, and in particular 100% by weight.

[0026] The non-silicone-containing stabilizer (c) is obtainable by alkoxylation of a 1 to 8-functional starter molecule with alkylene oxides, wherein 0 to 9 wt.% of the alkylene oxides used are ethylene oxide, 0 to 50 wt.% of the alkylene oxides used are 1,2-propylene oxide and at least 50 wt.% of the alkylene oxides used have at least 4 carbon atoms and the number-average molecular weight of the non-silicone-containing stabilizer (c) is 500 to 20,000 g / mol, preferably 1,000 to 15,000 g / mol, particularly preferably 1,500 to 8,000 g / mol, further preferably 1,800 to 7,000 g / mol and in particular 2,000 to 5,000 g / mol and even more preferably 2,500 to 4,500 g / mol.

[0027] All known starter molecules with a functionality of 1 to 8 can be used as starter molecules for the preparation of the non-silicone-containing foam stabilizer (c). These include the above-mentioned starter molecules for the preparation of the polyetherols. Such starter molecules are, for example, methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, nonanol, decanol, water, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, glycerol, trimethylolpropane, pentaerythritol, sugar derivatives such as sucrose, hexitol derivatives such as sorbitol, methylamine, ethylamine, isopropylamine, butylamine, benzylamine, aniline, toluidine, toluenediamine, naphthylamine, ethylenediamine, diethylenetriamine, 4,4'-methylenedianiline, 1,3,-propanediamine, 1,6-hexanediamine, ethanolamine, diethanolamine, triethanolamine and other mono-, di- or polyhydric alcohols or mono- or polyhydric amines or mixtures thereof.Polyether polyols, for example polyalkylene oxides such as polyethylene oxide or polypropylene oxide, can also be used as starter molecules. If polyalkylene oxides are used as starter molecules, they preferably have a functionality of 2 to 6 and a number-average molecular weight of 200 to 5000, particularly preferably 300 to 3000, further preferably 500 to 2000, and in particular 500 to 1000 g / mol. Furthermore, compounds containing groups that accelerate the polyurethane reaction can also be used as starter molecules. Examples of such starter molecules are 3-(dimethylamino)-1-propylamine and 3-(pyrrolidin-1-yl)propan-1-amine. The average functionality, preferably the average hydroxy functionality, of the starter molecules for preparing the non-silicone-containing stabilizer (c) is preferably 1 to 6, more preferably 1 to 4, further preferably 1 to 3, particularly preferably 1.5 to 2.5, and in particular 2.Preferred starter molecules are methanol, ethanol, propanol, butanol, water, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, and particularly preferably water or dipropylene glycol.

[0028] At least 50% by weight of alkylene oxides having at least 4 carbon atoms are used as alkylene oxides for producing the non-silicone-containing foam stabilizer, for example having 4 to 20, preferably 4 to 12, and in particular 4 to 10 carbon atoms, such as epoxybutane, epoxypentane, epoxyhexane, epoxyheptane, epoxyoctane, epoxynonane, or epoxydecane. Further preference is given to using the 1,2-epoxides of these compounds. The alkylene oxides having at least 4 carbon atoms particularly preferably contain 1,2-epoxybutane and / or 1,2-epoxypentane, in particular 1,2-epoxybutane. In a particularly preferred embodiment, the alkylene oxide having at least 4 carbon atoms consists of 1,2-epoxybutane, 1,2-epoxypentane, or mixtures thereof, in particular 1,2-epoxybutane. Preferably, the proportion of alkylene oxides having at least 4 carbons in the preparation of component (c) is at least 70% by weight, particularly preferably at least 90% by weight, more preferably at least 95% by weight.-% and in particular 100 wt.%, in each case based on the total weight of the alkylene oxides used to prepare the non-silicone-containing foam stabilizer (c).

[0029] Furthermore, the alkylene oxides for preparing the non-silicone-containing foam stabilizer (c) contain less than 9 wt. %, preferably less than 5 wt. %, more preferably less than 2 wt. %, and in particular no ethylene oxide. If propylene oxide, preferably 1,2-propylene oxide, is present, the proportion of propylene oxide is less than 50 wt. %, preferably 5 to 40 wt. %, and particularly preferably 10 to 30 wt. %, based in each case on the total weight of the alkylene oxide used for preparing the non-silicone-containing foam stabilizer (c). In a further, likewise preferred embodiment, no propylene oxide is used for preparing the compound (c).The alkylene oxides can be arranged randomly or in blocks along the chain. For example, it is possible to add a block of butylene oxide followed by propylene oxide, or first propylene oxide followed by butylene oxide, or a mixture of propylene oxide and butylene oxide to the starter molecule. Conventional catalysts for polyalkoxylation can be used as catalysts. Examples include basic catalysts or double metal cyanide catalysts, as described, for example, in PCT / EP2005 / 010124, EP 90444, or WO 05 / 090440.

[0030] After alkoxylation, all or some of the resulting OH groups of the non-silicone-containing stabilizer (c) can be "capped." This refers to reactions of the polyol hydroxy groups, for example, a) to form urethanes, e.g., with isocyanates; b) to form esters, e.g., with anhydrides, acid chlorides, or similar; c) to form ethers, e.g., with alkylating agents or sulfonic acid derivatives; and d) to form silyl ethers, e.g., with silanes or silyl halides. This reduces the functionality toward isocyanates and, in the case of complete conversion of all OH groups, can also lead to stabilizers (c) that are non-isocyanate-reactive. The non-silicone-containing foam stabilizers (c) preferably contain 1 to 8, particularly preferably 1.5 to 4, and especially 1.8 to 2.5, isocyanate-reactive groups, in particular hydroxyl groups. If component (c) has isocyanate-reactive groups, it is part of the compounds with isocyanate-reactive groups (b).If the compound (c) has groups reactive towards isocyanates, in addition to the non-silicone-containing foam stabilizers (c) having groups reactive towards isocyanate, further compounds having groups reactive towards isocyanate are preferably used, particularly preferably polyetherols and in particular polyetherols (b1).

[0031] The proportion of the non-silicone-containing foam stabilizer (c), based on the total weight of the compounds (b), (c), (d), (e) and (f) is 0.01 to 10 wt.%, preferably 0.05 to 5 wt.%, more preferably 0.05 to 3 wt.%, particularly preferably 0.1 to 2 wt.%, even more preferably 0.1 to 1.5 wt.%, even more preferably 0.1 to 1 wt.% and in particular 0.1 to 0.5 wt.%, it is also possible to use mixtures of different non-silicone-containing foam stabilizers.

[0032] Compounds having at least two isocyanate-reactive groups and a molecular weight of less than 400 g / mol can be used as chain extenders and crosslinking agents (d). Molecules having two isocyanate-reactive hydrogen atoms are referred to as chain extenders, and molecules having more than two isocyanate-reactive hydrogen atoms are referred to as crosslinkers. However, the chain extender or crosslinking agent can also be omitted. However, to modify the mechanical properties, e.g., hardness, the addition of chain extenders, crosslinking agents, or, where appropriate, mixtures thereof can prove advantageous.

[0033] If chain extenders and / or crosslinking agents (d) are used, the chain extenders and / or crosslinkers known in the production of polyurethanes can be used. These are preferably low-molecular-weight compounds with functional groups reactive toward isocyanates, for example, glycerol, trimethylolpropane, glycol, and diamines. Other possible low-molecular-weight chain extenders and / or crosslinking agents are listed, for example, in "Kunststoffhandbuch, Volume 7, Polyurethane," Carl Hanser Verlag, 3rd edition 1993, Chapters 3.2 and 3.3.2.

[0034] Catalysts (e) greatly accelerate the reaction of the polyols (b) and optionally chain extenders and crosslinkers (d) and chemical blowing agent (f) with the organic, optionally modified polyisocyanates (a). The catalysts (e) preferably contain incorporable amine catalysts, for example when emissions of organic compounds are to be kept as low as possible. These have at least one, preferably 1 to 8 and particularly preferably 1 to 2 groups that are reactive towards isocyanates, such as primary amine groups, secondary amine groups, hydroxyl groups, amides or urea groups, preferably primary amine groups, secondary amine groups, hydroxyl groups. Incorporable amine catalysts are usually used to produce low-emission polyurethanes, which are used in particular in automotive interiors. Such catalysts are known and described, for example, in EP1888664. These comprise compounds which, in addition to the orThe isocyanate-reactive groups preferably contain one or more tertiary amino groups. Preferably, at least one of the tertiary amino groups of the incorporable catalysts carries at least two aliphatic hydrocarbon radicals, preferably having 1 to 10 carbon atoms per radical, particularly preferably having 1 to 6 carbon atoms per radical. The tertiary amino groups particularly preferably carry two radicals, independently selected from methyl and ethyl radicals, and one further organic radical, such as the pyrrolidinyl radical.Examples of usable, incorporable catalysts include bisdimethylaminopropylurea, bis(N,N-dimethylaminoethoxyethyl)carbamate, dimethylaminopropylurea, N,N,N-trimethyl-N-hydroxyethylbis(aminopropyl ether), N,N,N-trimethyl-N-hydroxyethylbis(aminoethyl ether), diethylethanolamine, bis(N,N-dimethyl-3-aminopropyl)amine, dimethylaminopropylamine, 3-(pyrrolidin-1-yl)propan-1-amine, 3-dimethylaminopropyl-N,N-dimethylpropan-1,3-diamine, dimethyl-2-(2-aminoethoxyethanol) and (1,3-bis(dimethylamino)-propan-2-ol), N,N-bis-(3-dimethylaminopropyl)-N-isopropanolamine, bis-(dimethylaminopropyl)-2-hydroxyethyl-amine, N,N,N-trimethyl-N-(3-aminopropyl)-bis(aminoethyl ether), 3-dimethylaminoisopropyl-diisopropanolamine or mixtures thereof.

[0035] In addition to the amine catalysts that can be incorporated, other conventional catalysts can be used to produce the polyurethanes. Examples include amidines such as 2,3-dimethyl-3,4,5,6-tetrahydropyrimidine, tertiary amines such as triethylamine, tributylamine, dimethylbenzylamine, N-methyl-, N-ethyl-, N-cyclohexylmorpholine, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetramethylbutanediamine, N,N,N',N'-tetramethylhexanediamine, pentamethyldiethylenetriamine, tetramethyldiaminoethyl ether, bis(dimethylaminopropyl)urea, dimethylpiperazine, 1,2-dimethylimidazole, 1-azabicyclo-(3,3,0)octane and preferably 1,4-diazabicyclo-(2,2,2)octane and alkanolamine compounds such as triethanolamine, triisopropanolamine, N-methyl- and N-ethyl-diethanolamine and dimethylethanolamine. Also suitable are organic metal compounds, preferably organic tin compounds, such as tin(II) salts of organic carboxylic acids, e.g.Tin(II) acetate, tin(II) octoate, tin(II) ethylhexoate and tin(II) laurate and the dialkyltin(IV) salts of organic carboxylic acids, e.g. dibutyltin diacetate, dibutyltin dilaurate, dibutyltin maleate and dioctyltin diacetate, as well as bismuth carboxylates, such as bismuth(III) neodecanoate, bismuth 2-ethylhexanoate and bismuth octanoate or mixtures thereof. The organic metal compounds can be used alone or, preferably, in combination with strongly basic amines. If component (b) is an ester, it is preferable to use exclusively amine catalysts. In a particularly preferred embodiment, exclusively incorporable catalysts are used as catalysts (e).

[0036] If catalysts (e) are used, they can be used, for example, in a concentration of 0.001 to 5 wt.%, in particular 0.05 to 2 wt.% as catalyst or catalyst combination, based on the weight of component (b).

[0037] All blowing agents known for the production of polyurethanes can be used as blowing agents (f). These can include chemical and / or physical blowing agents. Such blowing agents are described, for example, in "Kunststoffhandbuch, Volume 7, Polyurethane," Carl Hanser Verlag, 3rd edition 1993, Chapter 3.4.5. Chemical blowing agents are compounds that form gaseous products by reacting with isocyanate. Examples of such blowing agents are water or carboxylic acids. Physical blowing agents are compounds that are dissolved or emulsified in the starting materials used in polyurethane production and evaporate under the conditions of polyurethane formation.These include, for example, hydrocarbons, halogenated hydrocarbons, and other compounds, such as perfluorinated alkanes such as perfluorohexane, chlorofluorocarbons, and ethers, esters, ketones, acetals, and / or liquid carbon dioxide. The blowing agent can be used in any desired amount. The blowing agent is preferably used in an amount such that the resulting polyurethane foam has a density of 10 to 850 g / L, more preferably 20 to 800 g / L, and especially 25 to 500 g / L. Blowing agents containing water, and in particular water as the sole blowing agent, are particularly preferred.

[0038] Furthermore, auxiliaries and / or additives (g) can be used. All auxiliaries and additives known for the production of polyurethanes can be used. Examples include surfactants, cell regulators, release agents, fillers, dyes, pigments, flame retardants, hydrolysis inhibitors, fungistatic and bacteriostatic substances. Such substances are known and are described, for example, in "Kunststoffhandbuch, Volume 7, Polyurethane", Carl Hanser Verlag, 3rd edition 1993, Chapters 3.4.4 and 3.4.6 to 3.4.11. Known silicone-based foam stabilizers can also be used. Silicone-based foam stabilizers are silicone-based compounds that reduce the surface tension of the polyols (b) and in which at least two silicon atoms are each bonded by oxygen atoms. These compounds are preferably compoundswhich have an amphiphilic structure, i.e., two molecular moieties with different polarity. The silicone-based cell stabilizer preferably has one molecular moiety with organosilicon building blocks, such as dimethylsiloxane or methylphenylsiloxane, and one molecular moiety with a chemical structure similar to the polyols (b). These are preferably polyoxyalkylene units. Particularly preferred silicone-based foam stabilizers are polysiloxane-polyoxyalkylene block copolymers with an oxyethylene content of less than 75 wt. %, based on the total proportion of polyoxyalkylene units. These preferably have polyethylene oxide and / or polypropylene oxide units. The molecular weight of the polyoxyalkylene side chains is preferably at least 1000 g / mol side chains. These compounds are known and described, for example, in "Kunststoffhandbuch, Volume 7, Polyurethane", Carl Hanser Verlag, 3rd edition 1993.Chapter 3.4.4.2 and can be prepared, for example, by reacting siloxane, for example polydimethylsiloxane, with polyoxyalkylenes, in particular polyethylene oxide, polypropylene oxide, or copolymers of polyethylene oxide and polypropylene oxide. This makes it possible to obtain polysiloxane-polyoxyalkylene block copolymers which have the oxyalkylene chain as an end group or as one or more side chains. The silicone-based foam stabilizers can have OH groups, but these are preferably free of OH groups. This can be achieved by using monohydric alcohols, such as butanol, as initiators for preparing the polyoxyalkylenes. For example, known foam stabilizers based on silicones can be used as silicone-based cell stabilizers, such as Niax Silicone L1501, L 1505, L1540, L 1593, L 1602, or L 1609 from Monentive; Dabco ®< DC 193, Dabco ®< DC 3041, Dabco ®< DC 3042, Dabco ®< DC 3043, Dabco ®< DC 5000, Dabco ®< DC 5169,Dabco ®< DC 2525, Dabco ®< DC 2584, Dabco ®< SI 1101, Dabco ®< SI 1103 or Dabco ®< DC 5160 from Air Products; Tegostab ®< BF 2270, Tegostab ®< BF 2370, Tegostab ®< BF 2470, Tegostab ®< B 8110, Tegostab ®< B 8225, Tegostab ®< B 8255, Tegostab ®< B 8317, Tegostab ®< B 8325, Tegostab ®< B 8905, Tegostab ®< B 8946 PF, Tegostab ®< B 8948, Tegostab ®< B 8950, Tegostab ®< B 8952, Tegostab ®< B 8960 Tegostab ®< B 8715 LF2, Tegostab ®< B 8734 LF2, Tegostab ®< B 8736 LF2, Tegostab ®< B 8761 LF2, Tegostab ®< B 8724 LF2, Tegostab ®< B 8738 LF2, Tegostab ®< B 8742 LF2, Tegostab ®< B 8747 LF2, Tegostab ®< B 8745 LF2, Tegostab ®< B 8749 LF2 or Tegostab ®< B 8486 from Goldschmidt. In the context of the present invention, less than 0.3 wt.% of silicone-based stabilizer, based on the total weight of compounds (b), (c), (d), (e) and (f), is used. In a preferred embodiment of the invention, less than 0.2 wt.%, particularly preferably less than 0.1 wt.%, more preferably less than 0.01 wt.%, based on the total weight of compounds (b), (c), (d), (e) and (f), and in particular no silicone-based foam stabilizer is used.

[0039] In general, in the preparation of the polyurethane according to the invention, the compounds (a) to (g) are reacted in amounts such that the equivalence ratio of NCO groups of the polyisocyanates (a) to the sum of the reactive hydrogen atoms of components (b), (c), (e) and (f) and optionally (d) and (g) is 0.60 to 1.5:1, preferably 0.70 to 1.25:1 and particularly preferably 0.80 to 1.10:1. If the cellular plastics contain at least partially isocyanurate groups, a ratio of NCO groups of the polyisocyanates (a) to the sum of the reactive hydrogen atoms of components (b), (c), (e), (f) and optionally (d) and (g) of 1.5 to 20:1, preferably 1.5 to 8:1 and particularly preferably 1.50 to 5:1 is used. A ratio of 1:1 corresponds to an isocyanate index of 100.

[0040] The specific starting materials (a) to (g) for the production of polyurethanes according to the invention differ only slightly in terms of quantity and quality when the polyurethane according to the invention is to be produced as a flexible foam, a semi-rigid foam, a rigid foam, or an integral skin foam. For example, the elasticity and hardness of the polyurethane according to the invention can be varied by varying the functionality and chain length of the higher molecular weight compound containing at least two reactive hydrogen atoms. Such modifications are known to those skilled in the art.

[0041] The reactants for producing a flexible foam are described, for example, in PCT / EP2005 / 010124 and EP 1529792; the reactants for producing a semi-rigid foam are described in "Kunststoffhandbuch, Volume 7, Polyurethane," Carl Hanser Verlag, 3rd edition 1993, Chapter 5.4; the reactants for producing a rigid foam are described in PCT / EP2005 / 010955; and the reactants for producing an integral skin foam are described in EP 364854, US 5506275, or EP 897402. The non-silicone-containing foam stabilizer (c) is then added to the reactants described in these documents. The polyurethane foams of the invention are particularly preferably flexible polyurethane foams.

[0042] The so-called "two-component process" is frequently used to produce the polyurethane foams of the invention. For this purpose, the isocyanate-reactive components, as well as frequently non-reactive components, for example from the group of auxiliaries and additives (g), are combined to form a polyol component, which is then mixed with the isocyanates of the isocyanate component during the production of the polyurethane foam. In this process, the isocyanate component may also contain other compounds in addition to the isocyanates (a).The invention therefore also relates to a polyol component comprising (b) polymeric compounds having groups reactive towards isocyanates, (c) non-silicone-containing stabilizer, (d) optionally chain extenders and / or crosslinking agents, (e) catalysts, (f) blowing agents and (g) optionally auxiliaries and additives, wherein the non-silicone-containing stabilizer (c) is obtainable by alkoxylation of a 1 to 8-functional starter molecule with alkylene oxides, wherein 0 to 9 wt.% of the alkylene oxides used are ethylene oxide, 0 to 50 wt.% of the alkylene oxides used are 1,2-propylene oxide and at least 50 wt.% of the alkylene oxides used have at least 4 carbon atoms and the number-average molecular weight of the non-silicone-containing stabilizer (c) is 500 to 20,000 g / mol and wherein the content of silicone-based foam stabilizer is less than 0.3 wt.%, based on the total weight of the compounds (b), (c), (d), (e) and (f).The non-silicone-containing stabilizer (c) can also be added to the isocyanate component, in particular if the non-silicone-containing stabilizer (c) does not contain any groups reactive towards isocyanate.

[0043] In addition to the process according to the invention, the invention also relates to a polyurethane foam obtainable by a process according to the invention. The polyurethanes according to the invention surprisingly exhibit only low emissions of organic substances and are therefore preferably used in enclosed spaces, for example as thermal insulation materials in residential buildings, such as insulation for pipes and refrigerators, in furniture construction, for example as seat cushions or mattresses, and in automotive interiors, for example as steering wheels, dashboards, door panels, carpet backing, acoustic foams, such as headliners, as well as headrests or gear knobs.Finally, a non-silicone-containing stabilizer (c) according to the invention is also subject of the invention, in particular a non-silicone-containing stabilizer (c) which is obtainable by alkoxylation of a 1 to 8-functional starter molecule with 1,2-epoxybutane and / or 1,2-epoxypentane, wherein at least 50% by weight of the alkylene oxides used to prepare the stabilizer (c) are 1,2-epoxybutane and / or 1,2-epoxypentane and the number-average molecular weight of the non-silicone-containing stabilizer (c) is 500 to 20,000 g / mol.

[0044] In the following, the present invention will be illustrated by examples.

[0045] The following materials were used: Polyol A: Glycerin-initiated polyether polyol based on ethylene oxide and propylene oxide with an average OH number of 28 mg KOH / g and a propylene oxide content, based on the total weight of the polyether, of 84 wt.%. Polyol B: Glycerin-initiated polyether polyol based on ethylene oxide and propylene oxide with an average OH number of 42 mg KOH / g and an ethylene oxide content, based on the total weight of the polyether, of 74 wt.%. Isocyanate 1: Mixture of 41.5 wt.% 4,4'-MDI, 25.3 wt.% 2,4'-MDI, and 33.2 wt.% of a mixture of diphenylmethane diisocyanate and higher-nuclear homologues of diphenylmethane diisocyanate (Lupranat®< M20S from BASF SE). Catalyst 1: Lupragen®< N201, amine catalyst from BASF SE. Catalyst 2: Niax A-1, an amine catalyst from Momentive. Catalyst 3: Jeffcat®< ZF10, an amine catalyst from Huntsman. Catalyst 4: Jeffcat®< Z-130, an amine catalyst from Huntsman.Stabilizer 1: Tegostab®< B 8715 LF2, organosiloxane-polyether copolymer, conventional silicone-based foam stabilizer from Evonik. Stabilizer 2: 1,2-propylene glycol-initiated polyether polyol with an average OH number of 74 mg KOH / g and 53.7 wt.% butylene oxide and 42.2 wt.% ethylene oxide, each based on the total weight of the polyether polyol, with the ethylene oxide used as the end block. Stabilizer 3: 1,2-propylene glycol-initiated polyether polyol with an average OH number of 34 mg KOH / g and 79 wt.% butylene oxide and 19.3 wt.% ethylene oxide, each based on the total weight of the polyether polyol, with the ethylene oxide used as the end block. Stabilizer 4: 1,2-propylene glycol initiated polyether polyol with an average OH number of 26 mg KOH / g and 60.6 wt% butylene oxide and 38.3 wt% ethylene oxide, each based on the total weight of the polyether polyol, with the ethylene oxide being used as an end block.Stabilizer 5: Dipropylene glycol-initiated polyether polyol with exclusively 1,2-epoxybutane as the alkylene oxide and with an average OH number of 44 mg KOH / g. Stabilizer 6: Dipropylene glycol-initiated polyether polyol with exclusively 1,2-epoxybutane as the alkylene oxide and with an average OH number of 33 mg KOH / g. Stabilizer 7: Dipropylene glycol-initiated polyether polyol with exclusively 1,2-epoxybutane as the alkylene oxide and with an average OH number of 26 mg KOH / g. Stabilizer 8: Dipropylene glycol-initiated polyether polyol with exclusively 1,2-epoxybutane as the alkylene oxide and with an average OH number of 21 mg KOH / g. Stabilizer 9: Dipropylene glycol initiated polyether polyol with exclusively 1,2-epoxypentane as alkylene oxide and with an average OH number of 47 mg KOH / g. Synthesis of non-silicone foam stabilizers

[0046] The foam stabilizers Stabilizers 1 to 8 were prepared in a steel reactor using a two-stage process. In a first step, a precursor was prepared by butoxylating propylene glycol or dipropylene glycol under KOH catalysis. This precursor was then butoxylated and optionally ethoxylated in a second step, also under KOH catalysis. The hydroxyl number of the resulting polyol was determined by titration after purification and drying. The procedure for preparing Stabilizer 9 was analogous, using CsOH instead of KOH.

[0047] To prepare the examples and comparative examples, 94 parts by weight of polyol A, 6 parts by weight of polyol B, 0.6 part by weight of catalyst 1, 0.1 part by weight of catalyst 2, 3.3 parts by weight of water, and the amount of the respective stabilizer specified in Table 1 were mixed for 2 minutes with a laboratory mixer at room temperature and allowed to stand for 30 minutes. Isocyanate 1 was then added and, at an isocyanate index of 90, mixed for 5 seconds at 1800 rpm with a laboratory mixer and converted in a beaker to form polyurethane foam. The free foam densities were approximately 45 g / L. The quality, cell structure, and appearance of the foam were assessed. Molded foams were obtained analogously by pouring the reaction mixture, after mixing, into an 8-liter mold (40 cm x 40 cm x 5 cm) heated to 50 °C. The application quantity was chosen so that the molded foam had an average density of 53 g / L.After 4 minutes, the foam was demolded, drummed, and allowed to rest at room temperature for 24 hours. Samples were taken from the molded foams for mechanical and emission measurements. The quality of the free-form foams and the molded foams was rated "good" if they were dimensionally stable and did not shrink, had an open, fine-cell structure, and a uniform surface without defects. Foams with a coarse-cell structure and holes in the foam core and surface were rated "poor." Table 1 Comparison examples Stabilizers Quantity [parts by weight] Quality free-form foam Quality molded foam 1 without stabilizer 0 bad bad 2 Stabilizer 1 0,5 good good 3 Stabilizer 2 0,5 bad bad 4 Stabilizer 2 1 bad bad 5 Stabilizer 3 0,25 bad bad 6 Stabilizer 3 0,5 bad bad 7 Stabilizer 3 1 bad bad 8 Stabilizer 4 0,25 bad bad 9 Stabilizer 4 0,5 bad bad 10 Stabilizer 4 1 bad bad Example 1 Stabilizer 5 0,5 good good 2 Stabilizer 5 1 good good 3 Stabilizer 6 0,5 good good 4 Stabilizer 6 1 good good 5 Stabilizer 7 0,25 good good 6 Stabilizer 8 0,25 good good 7 Stabilizer 9 0,5 good good Mechanical measurements

[0048] The mechanical measurements in Table 2 were determined as follows: Density: DIN EN ISO 845 Compressive strength and hysteresis: DIN EN ISO 3386 Tensile strength and elongation at break: DIN EN ISO 1798, Compression set: DIN EN ISO 1856 Air permeability: DIN EN ISO 7231 Rebound resilience: DIN EN ISO 8307 Table 2 Mechanical properties of selected example foams Characteristics Unit Comparison example 1 Example 3 Example 5 density kg / m 3< 53 53 53 Compressive strength 40% kPa 4,9 4,7 4,4 Hysteresis % 23,9 23 22,7 Tensile strength kPa 85 94 85 Elongation at break % 84 102 97 Compression set % 7,4 6,9 7,8 Air permeability dm 3< / s 1 0,8 0,7 Rebound resilience % 57 58 59

[0049] The results in Tables 1 and 2 demonstrate that the use of the non-silicone foam stabilizers according to the present invention results in foams that are typically only obtained using silicone-based foam stabilizers. Furthermore, the foam stabilizers according to the invention exhibit significantly lower emissions of organic substances. This is shown in Table 4. Emissions

[0050] To determine the emission values, foam samples were prepared analogously to the examples and comparative examples above. The starting materials shown in Table 3 were used. Isocyanate 1 was used as the isocyanate component. The isocyanate index was 90. The density of the resulting foams was approximately 50 kg / m 3 . The emissions were determined as shown below. Table 3: Comparison example I Example I Example II Polyol A 90,6 90,6 90,6 Polyol B 3 3 3 Catalyst 3 0,1 0,1 0,1 Catalyst 4 1 1 1 Water 3,9 3,9 3,9 Glycerin 0,5 0,5 0,5 Diethanolamine 0,4 0,4 0,4 Stabilizer 1 0,5 Stabilizer 5 0,5 Stabilizer 6 0,5

[0051] Formaldehyde emissions were determined in a chamber test: The procedure for determining formaldehyde and acetaldehyde was analogous to ASTM D-5116-06. The chamber size was 4.7 liters. Pieces measuring 100 mm x 100 mm x 25 mm from the interior of the foam were used as polyurethane samples. The temperature in the measuring chamber during the measurement was 65 °C, and the relative humidity was 50%. The air exchange rate was 3.0 liters per hour. The exhaust air stream containing volatile aldehydes from the polyurethane was passed through a cartridge containing 2,4-dinitrophenylhydrazine-coated silica for 120 minutes. The DNPH cartridge was then eluted with a mixture of acetonitrile and water. The concentration of formaldehyde and acetaldehyde in the eluate was determined using HPLC. Using this setup, the detection limit for formaldehyde emissions is ≤ 11 µg / m 3< . and for acetaldehyde emissions at ≤ 6 µg / m 3<

[0052] VOC and FOG were determined according to VDA 278. Table 4: Comparison example I Example I Example II Unit Chamber test formaldehyde µ g / m 3< 924 679 843 acetaldehyde µg / m 3< 74 45 72 VDA278 VOC ppm 163 44 59 VOC - Anteil Siloxan 79 ppm Siloxan's 0 ppm Siloxan 0 ppm Siloxan FOG ppm 77 54 58

Claims

1. A process for producing polyurethane foams comprising mixing (a) polyisocyanate, (b) polymeric compounds having isocyanate-reactive groups, (c) silicone-free stabilizer, (d) optionally chain extending and / or crosslinking agents, (e) catalysts, (f) blowing agents, (g) optionally auxiliaries and additives, to form a reaction mixture and reacting the reaction mixture to afford the polyurethane, wherein the silicone-free stabilizer (c) is obtainable by alkoxylation of a 1- to 8-functional starter molecule with alkylene oxides, wherein 0% to 9% by weight of the employed alkylene oxides is ethylene oxide, 0% to 50% by weight of the employed alkylene oxides is 1,2-propylene oxide and at least 50% by weight of the employed alkylene oxides comprise at least 4 carbon atoms and the number-average molecular weight of the silicone-free stabilizer (c) is 500 to 20 000 g / mol, the proportion of the silicone-free foam stabilizer (c), based on the total weight of the compounds (b), (c), (d), (e) and (f), is 0.01% to 10% by weight and the content of silicone-based foam stabilizer is less than 0.3% by weight, based on the total weight of the compounds (b), (c), (d), (e) and (f).

2. The process according to claim 1, wherein at least 90% by weight of the employed alkylene oxides in the production of the silicone-free stabilizer (c) comprise at least 4 carbon atoms.

3. The process according to claim 1 or 2, wherein the alkylene oxides comprising at least 4 carbon atoms employed in the production of the silicone-free stabilizer (c) are selected from the group consisting of 1,2-epoxybutane, 1,2-epoxypentane and mixtures thereof.

4. The process according to any of claims 1 to 3, wherein the average functionality of the starter molecules for production of the silicone-free stabilizer (c) has a functionality of 1 to 3.

5. The process according to any of claims 1 to 4, wherein some or all of the retained OH groups of the silicone-free stabilizer (c) are capped after the alkoxylation.

6. The process according to any of claims 1 to 5, wherein the polymeric compounds having isocyanate-reactive groups comprise polyether alcohols (b1) obtainable by addition of ethylene oxide, propylene oxide or mixtures thereof onto a starter molecule, wherein at least 90 mol% of the alkylene oxides used for production of polyether alcohol (b1) are selected from the group consisting of ethylene oxide, 1,2-propylene oxide and mixtures thereof.

7. The process according to any of claims 1 to 6, wherein no silicone-based foam stabilizer is employed.

8. The process according to any of claims 1 to 7, wherein the polyurethane foam is a flexible polyurethane foam having a compressive stress at 10% compression according to DIN 53 421 / DIN EN ISO 604 of 15 kPa or less and a density of 10 to 100 g / liter.

9. The process according to any of claims 1 to 8, wherein the catalysts (e) comprise incorporable amine catalysts.

10. A polyol mixture comprising (b) polymeric compounds having isocyanate-reactive groups, (c) silicone-free stabilizer, (d) optionally chain extending and / or crosslinking agents, (e) catalysts, (f) blowing agents and (g) optionally auxiliaries and additives, wherein the silicone-free stabilizer (c) is obtainable by alkoxylation of a 1- to 8-functional starter molecule with alkylene oxides, wherein 0% to 9% by weight of the employed alkylene oxides is ethylene oxide, 0% to 50% by weight of the employed alkylene oxides is 1,2-propylene oxide and at least 50% by weight of the employed alkylene oxides comprise at least 4 carbon atoms and the numberaverage molecular weight of the silicone-free stabilizer (c) is 500 to 20 000 g / mol, the proportion of the silicone-free foam stabilizer (c), based on the total weight of the compounds (b), (c), (d), (e) and (f), is 0.01% to 10% by weight and the content of silicone-based foam stabilizer is less than 0.3% by weight, based on the total weight of the compounds (b), (c), (d), (e) and (f).

11. A polyurethane obtainable by a process according to any of claims 1 to 9.

12. The use of a polyurethane according to claim 11 in enclosed spaces or in the interior of vehicles.

13. The use according to claim 12 for production of mattresses or seat cushions or headrests in vehicles.