PRODUCTION OF POLYURETHANE FOAMS

Description

[0001] The invention lies in the field of polyurethanes and relates in particular to a process for producing polyurethane foams by reacting at least one polyol component with at least one isocyanate component in the presence of one or more catalysts which catalyze the isocyanate-polyol and / or isocyanate-water and / or isocyanate trimerization reactions, wherein the reaction is carried out in the presence of component A comprising a polyhydrazide, a polysulfonyl hydrazide and / or carbodihydrazide, in particular a polyhydrazide, and correspondingly produced polyurethane foams. Polyurethane systems within the meaning of this invention are... Polyurethane foams / foams.

[0002] Polyurethanes are used in a wide variety of applications due to their outstanding mechanical and physical properties. A particularly important market for various types of polyurethanes is the foam sector, such as conventional flexible foams based on ether and ester polyols, cold foams (often referred to as HR foams), rigid foams, integral skin foams, and microcellular foams, as well as foams with properties that lie between these classifications, such as semi-rigid systems. Rigid foams are used, for example, for headliners, ester foams for the interior trim of doors with flame-laminated upholstery fabrics and for punched sun visors, cold and flexible foams for seating systems and instrument panels, as well as mattresses. Adhesives and coatings are also areas where polyurethanes demonstrate outstanding properties.

[0003] The release of aldehydes during the production and storage of polyurethane foams is problematic. Many consumers are reluctant to use aldehyde-emitting products due to health concerns, regardless of whether these health concerns are actually justified.

[0004] In addition, the Chinese authorities in particular have recently tightened their requirements, requiring, for example, very strict limits for interior emissions for cars sold in China. In addition to aromatic hydrocarbons, particular emphasis is again placed on aldehydes. Thus, there is a general desire for polyurethane foams that release as few aldehydes as possible.

[0005] Various approaches have already been proposed to meet this requirement. WO 2009 / 117479, for example, assumes that the formaldehyde originates from the raw material and is contained, in particular, in the amine catalysts (tertiary amines) used. This document therefore proposes adding a primary amine to the tertiary amine catalyst to achieve low formaldehyde emissions. Dimethylaminopropylamine is preferred.

[0006] DE 10003156 A1 does not directly address low-emission foams, but rather the development of polymers with excellent adsorption capabilities for various compounds, particularly heavy metal ions. To solve this problem, polyurethane foams containing ethyleneimine, polyethyleneimine, polyvinylamine, carboxymethylated polyethyleneimines, phosphonomethylated polyethyleneimines, quaternized polyethyleneimines, and / or dithiocarbamitized polyethyleneimines are proposed. These foams can also be used for the adsorption of organic substances such as formaldehyde.

[0007] DE 10258046 A1 addresses the problem of producing polyurethane foams with reduced formaldehyde emissions. In contrast to DE 10003156 A1, the problem of DE 10258046 A1 is thus the reduction of formaldehyde emissions from the polyurethane foam itself, rather than the adsorption of formaldehyde from the ambient air. To solve this problem, a process is proposed that involves adding polymers containing amino groups to the polyurethane foam. This addition can occur before and / or during the production of the polyurethane foam.

[0008] However, in EP 3459983 A1 it was found that, depending on the polyurethane formulation used, the use of aldehyde-trapping substances can lead to foam disturbances and may also have an impact on the efficiency of aldehyde absorption.

[0009] Therefore, there is still a need for further solutions in the provision of polyurethane foams that enable a reduction in aldehyde emissions without compromising processability and without negatively affecting the foam structure, particularly the cell structure, or demoldability. Against this background, the specific object of the present invention was to enable the provision of polyurethane foams that exhibit reduced aldehyde emissions without compromising processability and without negatively affecting the foam structure, particularly the cell structure, or demoldability. In particular, the interest of customers in being able to use additives that have particularly good storage stability of at least 3 months, whereby these additives do not undergo any visual or effect-related changes during this time, should also be taken into account.

[0010] Surprisingly, it has now been found that if the reaction is carried out in the presence of a component A comprising a polyhydrazide, a polysulfonyl hydrazide and / or carbodihydrazide, in particular a polyhydrazide, wherein component A is used in the form of a mixture C, which further comprises a component B containing a dispersant, this object is achieved.

[0011] The invention thus relates to a process for the production of polyurethane foams by reacting at least one polyol component with at least one isocyanate component in the presence of one or more catalysts which catalyze the isocyanate-polyol and / or isocyanate-water and / or isocyanate trimerization reactions, wherein the reaction is carried out in the presence of a component A comprising a polyhydrazide, a polysulfonyl hydrazide and / or carbodihydrazide, in particular a polyhydrazide, wherein the aforementioned component A is used in the form of a mixture C, wherein this mixture C further comprises a component B, component B comprising a dispersant from the group of phthalic acid alkyl esters, dicarboxylic acid alkyl esters, adipic acid alkyl esters, sebacic acid alkyl esters, dodecanoic acid alkyl esters, polyesters, phosphate esters, fatty acid esters, straight-chain and modified natural oils or mineral oils, sulfonated oils,ethoxylated oils, epoxidized oils, fatty acids, sulfonamides, glycols, polyglycols, 1,2,4-benzenetricarboxylic acid alkyl esters and / or lecithin, in particular butyldiglycol, 1,2,4-benzenetricarboxylic acid tris(decyl)ester or 1,2-cyclohexanedicarboxylic acid diisononyl ester.

[0012] The inventive product enables the provision of polyurethane foams that exhibit reduced aldehyde emissions and exhibit no loss of processability and no negative impact on the foam structure, particularly the cell structure, or demoldability. Mixture C used according to the invention, comprising components A and B, exhibits particularly good storage stability of over 3 months and does not undergo any visual or performance-related changes upon prolonged storage.

[0013] According to a particularly preferred embodiment of the invention, component A comprises a polyhydrazide, preferably oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, dodecanoic acid dihydrazide, isophthalic acid dihydrazide, piperazine-N,N'-dihydrazide, m-benzene dihydrazide and / or p-benzene dihydrazide, in particular adipic acid dihydrazide and / or carbodihydrazide. Adipic acid dihydrazide is most preferred and achieves particularly good results within the meaning of the invention.

[0014] According to a further preferred embodiment of the invention, the mixture C comprises, in addition to component A and component B, polyethylene glycol tridecyl ether phosphate, phosphoric acid esters, organophosphates and / or polyether (mono)ols such as 2-ethyl hexanol EO-PO polyether.

[0015] A further preferred embodiment of the invention is achieved when the mixing ratio of component A to component B is 3:1 to 1:3, preferably 2:1 to 1:2, more preferably 1.5:1 to 1:1.5, in particular 1.1:1 to 1:1.1. This refers to parts by weight.

[0016] As already explained, the subject matter of the invention enables the reliable minimization of aldehyde emissions. A further particular advantage of the present invention is that the mixture C used in the process according to the invention provides the user with an important advantage, since this mixture is very stable in storage, i.e., it does not deteriorate in appearance or quality, and thus reliably minimizes aldehyde emissions even after extended storage.

[0017] In this context, it has proven particularly advantageous if component A is present as a ground material dispersed in component B, which corresponds to a preferred embodiment. Grinding is the comminution of solids, in particular by means of or in a mill or grinder. A possible instrument is a ball mill, e.g. a planetary ball mill. These are used wherever the highest demands are placed on fineness. The extremely high centrifugal forces of a planetary ball mill cause the release of very high comminution energies, which results in very short process times. The underlying comminution principle is based on impact or friction.

[0018] In process engineering, a dispersion is a heterogeneous mixture of at least two substances that are insoluble or chemically bonded. One or more substances (disperse phase) are finely dispersed in another continuous substance (dispersant). The individual phases can be clearly separated from one another and can usually be separated again using physical methods (e.g., filtration, centrifugation).

[0019] Overall, it has proven advantageous if the particle size of the ground material or dispersion is from 0.5 to 200 µm, preferably from 0.5 to 60 µm, and most preferably from 0.5 to 30 µm, which corresponds to a preferred embodiment. Furthermore, it has proven advantageous if the process according to the invention is characterized in that the mixture C is used in a mass fraction of 0.01 to 20 parts, preferably from 0.05 to 5, in particular from 0.1 to 3, based on 100 parts of polyol component.

[0020] In particular, it is preferred that a polyurethane foam be produced as the polyurethane system. A rigid polyurethane foam, a flexible polyurethane foam, a viscoelastic PU foam, a high-density polyurethane foam, a semi-rigid polyurethane foam, a thermoformable polyurethane foam, or a PU integral skin foam are particularly preferred.

[0021] The compounds used according to the invention, their preparation, and the use of the compounds for producing the polyurethane foams themselves are described below by way of example.

[0022] If the following data are given in percent, they are in weight percent unless otherwise stated. If the following mean values ​​are given, they are the number average unless otherwise stated. If the following material properties, such as viscosities or the like, are given, they are the material properties at 25°C unless otherwise stated. If chemical (molecular) formulas are used in the present invention, the specified indices can represent both absolute numbers and mean values. In the case of polymeric compounds, the indices preferably represent mean values.

[0023] The polyurethane systems can in principle be prepared in the customary manner and as described in the prior art. This is well known to those skilled in the art; a basic overview can be found, for example, in G. Oertel, Polyurethane Handbook, 2nd Edition, Hanser / Gardner Publications Inc., Cincinnati, Ohio, 1994, pp. 177-247. In the preparation of the polyurethane systems according to the invention, the mixtures C are preferably used in a mass fraction of 0.01 to 20 parts, preferably 0.05 to 5 parts, and particularly preferably 0.1 to 3 parts, based on 100 parts of polyol component.

[0024] When carrying out the process according to the invention for producing the polyurethane foams, it may be advantageous if water, physical blowing agents, flame retardants and / or other additives are also added.

[0025] All isocyanates, in particular the known aliphatic, cycloaliphatic, araliphatic, and preferably aromatic polyfunctional isocyanates, can be used as the isocyanate component in the process according to the invention. Suitable isocyanates for the purposes of this invention are preferably all polyfunctional organic isocyanates, such as 4,4'-diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), hexamethylene diisocyanate (HMDI), and isophorone diisocyanate (IPDI). Particularly suitable is the mixture known as "polymeric MDI" ("crude MDI") of MDI and more highly condensed analogues with an average functionality of 2 to 4, as well as the various isomers of TDI in pure form or as an isomer mixture. Particularly preferred isocyanates are mixtures of TDI and MDI. Also particularly suitable is the binuclear product referred to as "pure MDI," consisting predominantly of 2,4'- and 4,4'-isomer mixtures or their prepolymers.MDI prepolymers are particularly suitable. Examples of particularly suitable isocyanates are listed in EP 1712578, EP 1161474, WO 00 / 58383, US 2007 / 0072951, EP 1678232, and WO 2005 / 085310.

[0026] Polyols suitable as polyol components within the meaning of this invention are preferably all organic substances having several isocyanate-reactive groups, as well as preparations thereof. Preferred polyols are all polyether polyols and polyester polyols commonly used for the production of polyurethane systems, in particular polyurethane foams. The polyols are preferably not compounds that have at least one 5- or 6-membered ring composed of one or two oxygen atoms and carbon atoms.

[0027] Polyether polyols can be obtained, for example, by reacting polyhydric alcohols or amines with alkylene oxides. Polyester polyols are preferably based on esters of polybasic carboxylic acids (which can be either aliphatic, such as adipic acid, or aromatic, such as phthalic acid or terephthalic acid) with polyhydric alcohols (usually glycols). Natural oil-based polyethers (NOPs) can also be used. These polyols are obtained from natural oils such as soybean or palm oil and can be used unmodified or modified.

[0028] Another class of polyols are those which are obtained as prepolymers by reacting polyol with isocyanate in a molar ratio of 100 to 1 to 5 to 1, preferably 50 to 1 to 10 to 1.

[0029] Another class of preferably used polyols are the so-called filler polyols (polymer polyols). These are characterized by the fact that they contain solid organic fillers with a solids content of up to 40 wt.% or more in a dispersed distribution. Examples of suitable polyols include: SAN polyols: These are highly reactive polyols containing a dispersed styrene / acrylonitrile (SAN) copolymer. PHD polyols: These are highly reactive polyols containing polyurea in dispersed form. PIPA polyols: These are highly reactive polyols containing a dispersed polyurethane, formed, for example, by the in situ reaction of an isocyanate with an alkanolamine in a conventional polyol.

[0030] The solids content, which, depending on the application, can preferably be between 5 and >40 wt.% based on the polyol, is responsible for improved cell opening, allowing the polyol to be foamed in a controlled manner, especially with TDI, and preventing foam shrinkage. The solids content thus acts as an essential process aid. Another function is to control the hardness via the solids content, as higher solids content results in greater foam hardness.

[0031] Formulations with solid-containing polyols are significantly less inherently stable and therefore require additional physical stabilization in addition to chemical stabilization through the crosslinking reaction.

[0032] Depending on the solids content of the polyols, they can be used alone or in a mixture with the unfilled polyols mentioned above.

[0033] Preferred polyols are so-called cell opener polyols. These are polyether polyols with a high ethylene oxide content, preferably at least 40 wt.%, in particular from 50 to 100 wt.%, based on the alkylene oxide content.

[0034] A preferred ratio of isocyanate component to polyol component within the scope of this invention, expressed as an index, is in the range from 10 to 1000, preferably 40 to 350. This index describes the ratio of the isocyanate actually used to the isocyanate calculated (for a stoichiometric reaction with polyol). An index of 100 represents a molar ratio of the reactive groups of 1 to 1.

[0035] Suitable catalysts that can be used in the process according to the invention are preferably substances that catalyze the gel reaction (isocyanate-polyol), the blowing reaction (isocyanate-water) or the di- or trimerization of the isocyanate. Typical examples are amines such as triethylamine, dimethylcyclohexylamine, tetramethylethylenediamine, tetramethylhexanediamine, pentamethyldiethylenetriamine, pentamethyldipropylenetriamine, triethylenediamine, dimethylpiperazine, 1,2-dimethylimidazole, N-ethylmorpholine, tris(dimethylaminopropyl)hexahydro-1,3,5-triazine, dimethylaminoethanol, dimethylaminoethoxyethanol and bis(dimethylaminoethyl) ether, tin salts of organic carboxylic acids, tin compounds such as dibutyltin dilaurate and potassium salts such as potassium acetate. Preference is given to using further catalysts that do not contain organic tin compounds, in particular no dibutyltin dilaurate.

[0036] Suitable amounts of these catalysts used in the process according to the invention depend on the type of catalyst and are usually in the range of 0.01 to 5 pphp (= parts by weight based on 100 parts by weight of polyol) or 0.1 to 10 pphp for potassium salts.

[0037] Suitable water contents in the process according to the invention depend on whether physical blowing agents are used in addition to the water or not. For purely water-blown foams, the values ​​are typically preferably 1 to 20 pphp. If other blowing agents are also used, the amount used is usually reduced to, for example, 0 or, for example, 0.1 to 5 pphp. To achieve high foam densities, neither water nor other blowing agents are preferably used.

[0038] Suitable physical blowing agents within the meaning of this invention are gases, for example liquefied CO 2 , and highly volatile liquids, for example hydrocarbons with 4 or 5 carbon atoms, preferably cyclo-, iso- and n-pentane, fluorocarbons, preferably HFC 245fa, HFC 134a and HFC 365mfc, but also olefinic fluorocarbons such as HHO 1233zd or HHO1336mzzZ, chlorofluorocarbons, preferably HCFC 141b, oxygen-containing compounds such as methyl formate and dimethoxymethane, or chlorinated hydrocarbons, preferably dichloromethane and 1,2-dichloroethane. Ketones (e.g. acetone) or aldehydes (e.g. methylal) are also suitable as blowing agents.

[0039] The substances mentioned in the prior art can be used as stabilizers. The compositions according to the invention can advantageously contain one or more stabilizers. These are, in particular, silicon compounds containing carbon atoms, preferably selected from polysiloxanes, polydimethylsiloxanes, organomodified polysiloxanes, polyether-modified polysiloxanes, and polyether-polysiloxane copolymers.

[0040] The substances mentioned in the prior art can be used as silicon compounds containing one or more carbon atoms. Preference is given to using Si compounds that are particularly suitable for the respective foam type. Suitable siloxanes are described, for example, in the following documents: EP 0839852, EP 1544235, DE 102004001408, WO 2005 / 118668, US 2007 / 0072951, DE 2533074, EP 1537159 EP 533202, US 3933695, EP 0780414, DE 4239054, DE 4229402, EP 867465. The Si compounds can be prepared as described in the prior art. Suitable examples are, for example, E.g. described in US 4147847, EP 0493836 and US 4855379.

[0041] In particular, organically modified Si compounds can be used. Particularly preferred organically modified Si compounds that can be used are, for example, those according to the following formula (IV) M k D m D' n T o Q p (IV) with M= [R 2< R 1< 2 SiO 1 / 2 ] D= [R 1< R 1< SiO 2 / 2 ] D'= [R 3< R 1< SiO 2 / 2 ] T= [R 1< SiO 3 / 2 ] Q= [SiO 4 / 2 ] k = 0 to 22, preferably 2 to 10, particularly preferably 2 m = 0 to 400, preferably 0 to 200, particularly preferably 2 to 100 n = 0 to 50, preferably 0.5 to 20, particularly preferably 0.7 to 9 o = 0 to 10, preferably 0 to 5, particularly preferably 0 p = 0 to 10, preferably 0 to 5, particularly preferably 0 R 2< = R 1< or R 3< R 1< = independently of one another alkyl or aryl radicals or H, preferably methyl, ethyl, propyl or phenyl, preferably methyl or phenyl R 3< = organic modifications, e.g. polyether or a monovalent radical having 1 to 30 C atoms with at least one heteroatom selected from the group N, S, O, P, F, Cl, Br

[0042] Preferably, R 3< in formula (IV) are radicals from the group, -CH 2 CH 2 CH 2 O[CH 2 CH 2 O] a [CH 2 CH(CH 3 )O] b [CHR 4< CHR 4< O] c R 5< -CH 2 CH 2 CH 2 CN -CH 2 CH 2 CF 3 -CH 2 CH 2 CH 2 Cl with R 5< = alkyl, aryl, urethane, carboxyl, silyl or H, preferably H, -Me, or -C(O)Me R 4< = alkyl, aryl, which may optionally be interrupted by oxygen, particularly preferably H, Me, Et or Ph, a = 0 to 100, preferably 0.5 to 70, particularly preferably 1 - 40 b = 0 to 100, preferably 0.5 to 70, particularly preferably 0 - 40 c = 0 to 50, preferably 0 to 15, particularly preferably 0 a + b + c > 3.

[0043] In particular, unmodified Si compounds can be used.

[0044] Particularly preferred, usable unmodified Si compounds are, for example, those of the following formula (V) M q D r (V) with M, D as defined in the previous formula (IV), and q = 2 r = 0 to 50, preferably 1 to 40, particularly preferably 2 to 30.

[0045] Particularly preferably, the above-mentioned Si compounds, in particular of formula (IV) and / or (V), can be used individually or in combination with one another. In the case of mixtures, a compatibilizer can additionally be used. This can be selected from the group of aliphatic or aromatic hydrocarbons, particularly preferably aliphatic polyethers or polyesters.

[0046] It may be advantageous if in the siloxane compounds of formula (IV) at least 10 equivalent% (and at most 50 equivalent%) of the radicals R 2< are alkyl groups having 8 to 22 carbon atoms (based on the total number of radicals R2 in the siloxane compound).

[0047] Preferably, from 0.00001 to 20 parts by mass of silicon compounds per 100 parts by mass of polyol components can be used.

[0048] In particular, the use of the aforementioned silicon compounds in combination with the mixtures C to be used according to the invention enables very good results with regard to the polyurethanes aimed at according to the invention.

[0049] In addition to or instead of water and, if appropriate, physical blowing agents, other chemical blowing agents which react with isocyanates to evolve gas, such as formic acid, carbamates or carbonates, may also be present in the additive composition according to the invention.

[0050] Suitable optional flame retardants within the meaning of the present invention are preferably liquid organic phosphorus compounds, such as halogen-free organic phosphates, e.g., triethyl phosphate (TEP), halogenated phosphates, e.g., tris(1-chloro-2-propyl)phosphate (TCPP) and tris(2-chloroethyl)phosphate (TCEP), and organic phosphonates, e.g., dimethylmethanephosphonate (DMMP), dimethylpropanephosphonate (DMPP), or solids such as ammonium polyphosphate (APP) and red phosphorus. Furthermore, halogenated compounds, for example, halogenated polyols, and solids such as expandable graphite and melamine are suitable as flame retardants.

[0051] The process according to the invention can be used to produce polyurethane foams which are particularly low in aldehyde emissions and have good processability.

[0052] For the purposes of the invention, the term polyurethane is to be understood as a generic term for a polymer produced from di- or polyisocyanates and polyols or other isocyanate-reactive species, such as amines, whereby the urethane bond need not be the exclusive or predominant bond type. Polyisocyanurates and polyureas are also expressly included.

[0053] The inventive production of polyurethane foams can be carried out by any process familiar to the skilled person, for example, by hand mixing or, preferably, using high-pressure or low-pressure foaming machines. The inventive process can be carried out continuously or batchwise. Discontinuous processing is preferred for the production of molded foams, refrigerators, shoe soles, or panels. Continuous processing is preferred for the production of insulation boards, metal composite elements, blocks, or in spraying processes.

[0054] In the process according to the invention, the mixtures C used according to the invention can preferably be added directly before or during the reaction (to form the urethane bonds). The combination is preferably combined / dosed in a mixing head, as well as in a batch process for finished polyol systems.

[0055] Another object of the present invention is a polyurethane foam produced according to a process according to the invention as described above.

[0056] The polyurethane foams according to the invention can preferably comprise 0.001 to 20 wt.%, advantageously 0.005 to 5 wt.%, in particular 0.01 to 3 wt.%, based on the total composition of the polyurethane system, of a total amount of mixture C.

[0057] The polyurethane systems according to the invention can preferably be a polyurethane foam, in particular, for example, a rigid polyurethane foam, a flexible polyurethane foam, a viscoelastic foam, an HR foam, a semi-rigid polyurethane foam, a thermoformable polyurethane foam or an integral foam, preferably a polyurethane HR foam.

[0058] The polyurethane systems according to the invention, preferably polyurethane foams, can be used, for example, as refrigerator insulation, insulation panels, sandwich elements, pipe insulation, spray foam, 1- and 1.5-component can foam (a 1.5-component can foam is a foam produced by destroying a container in the can), wood imitation, model foam, packaging foam, mattress, furniture upholstery, automotive seat upholstery, headrest, instrument panel, automotive interior trim, automotive headliner, sound absorption material, steering wheel, shoe sole, carpet backing foam, filter foam, sealing foam, sealant and adhesive, binder or coating for the production of corresponding products.

[0059] The invention further provides a composition for producing polyurethane foam, comprising at least one urethane and / or isocyanurate catalyst, at least one blowing agent, at least one isocyanate component, and at least one polyol component, wherein a mixture C is present as an additive, mixture C as described above. In particular with regard to mixture C, reference is made in full to what has already been said to avoid repetition.

[0060] The term "composition" in this sense also includes multicomponent compositions in which two or more components are mixed to produce a chemical reaction leading to the production of polyurethane foam. The term "composition" in this sense particularly encompasses the mixture (mixture) of at least one urethane and / or isocyanurate catalyst, at least one blowing agent, at least one isocyanate component, and a mixture C, as described above.

[0061] A preferred composition according to the invention for producing polyurethane foam can contain polyol, for example in amounts of 25 to 75% by weight, water, for example in amounts of 1 to 7% by weight, catalyst, for example in amounts of 0.05 to 3% by weight, physical blowing agent, for example in amounts of 0 to 25% by weight (for example 0.1 to 25% by weight), stabilizers (such as Si-containing and non-Si-containing, in particular Si-containing and non-Si-containing organic stabilizers and surfactants), for example in amounts of 0.3 to 5% by weight, isocyanate, for example in amounts of 20 to 50% by weight, and the mixture C to be used according to the invention, for example in amounts of 0.001 to 20% by weight (preferably 0.005 to 5% by weight).

[0062] With regard to preferred embodiments of these aforementioned compositions, reference is made to the preceding description, particularly with regard to mixture C.

[0063] The invention further provides a process for reducing the total aldehyde emission, in particular aldehyde emissions comprising formaldehyde and acetaldehyde, from polyurethane foams by adding mixture C (mixture C as described above) to the polyurethane foam, preferably in an amount of 0.001 to 20% by weight, advantageously 0.005 to 5% by weight, in particular 0.01 to 3% by weight, based on the total weight of the polyurethane foam, wherein the addition can be carried out before and / or during the production of the polyurethane foam.

[0064] The invention further provides a polyurethane foam comprising mixture C, as described above, in an amount of preferably 0.001 to 20 wt.%, advantageously 0.005 to 5 wt.%, in particular 0.01 to 3 wt.%, based on the total weight of the polyurethane foam, in particular obtainable by adding mixture C before and / or during the production of the polyurethane foam.

[0065] The invention further provides the use of mixture C, as described above, for producing polyurethane foams that are low in aldehyde emissions, preferably comprising formaldehyde and acetaldehyde. The invention further provides the use of mixture C, as described above, for reducing the emissions of aldehydes, preferably comprising formaldehyde and acetaldehyde, from polyurethane foams, compared to polyurethane foams that are otherwise identical but produced without the use of mixture C.

[0066] A further object of the invention is the use of a mixture C, in particular as described above, for reducing aldehyde emissions, in particular comprising formaldehyde and acetaldehyde, from polyurethane foams.

[0067] The present invention is described by way of example in the examples given below. Examples:

[0068] Table 1: Solutions and dispersions Additive Description Solution 1* 10% adipic acid dihydrazide (TNJ, China) in water Dispersion 1** 50% adipic acid dihydrazide dispersed in 1,2,4-benzenetricarboxylic acid tris(decyl)ester * A freshly prepared solution was used. To produce an aqueous solution containing 10% adipic acid dihydrazide, the solution had to be heated to 40-45°C for approximately 30 minutes. Even at 60°C, however, 100% solubility of the active ingredient was not achieved. When this solution was stored at room temperature, a precipitate was observed. Therefore, a freshly prepared solution was used. ** Adipic acid dihydrazide was mixed 1:1 with 1,2,4-benzenetricarboxylic acid tris(decyl)ester in the presence of 0.5% polyethylene glycol tridecyl ether phosphate and sheared in a Dispermat ball mill at 5000 rpm for approximately 1.5 hours. Table 2: Raw materials used for the production of foams Polyol 1 Polyetherol trifunctional, MW 6000, Covestro AG Polyol 2 Polyetherol trifunctional, MW 4500, Dow Chemicals Networker Tegoamine DEOA pure (diethanolamine 100%), Overlack GmbH Catalyst 1 DABCO NE 300 (N-[2-[2-(dimethylamino)ethoxy]ethyl]-N-methyl-1,3-propanediamine), Evonik Industries AG Catalyst 2 DABCO NE 1082 (1,3-Bis[3-(dimethylamino)propyl]urea, N'-[3-(dimethylamino)propyl]-N,N-dimethylpropane-1,3-diamine, Evonik Industries AG Silicone stabilizer TEGOSTAB B 8715 LF 2, Evonik Industries AG Isocyanate Methylene diisocyanate, Suprasec 2447, NCO=32.7%, Huntsman Example 1: Preparation of the dispersions

[0069] Adipic acid dihydrazide was mixed in a ratio of 1:1 with 1,2,4-benzenetricarboxylic acid tris(decyl)ester in the presence of 0.5% polyethylene glycol tridecyl ether phosphate and sheared in a Dispermat ball mill (planetary ball mill) (manufacturer: Retsch, designation: PM 100) at 5000 rpm for approximately 1.5 hours. Production of polyurethane foams

[0070] The foaming was carried out using a hand-mixing method. Polyol, crosslinker, catalyst, additive, water, and silicone stabilizer were weighed into a beaker (see Table 3) and premixed with a paddle stirrer at 1000 rpm for 60 seconds. The isocyanate was then added and stirred for 7 seconds at a stirrer speed of 2500 rpm. The reaction mixture was poured into a box mold (dimensions 40 x 40 x 10 cm) maintained at 57°C and sealed. The finished foam was demolded after 3.5 minutes. The quantities and starting materials used can be found in Table 3.

[0071] The molded foams produced according to the process described above were then analyzed for their formaldehyde and acetaldehyde content in accordance with VDA 275 (VDA 275 "Molded parts for vehicle interiors - Determination of formaldehyde release." Measurement method according to the modified bottle method; Source: VDA 275, 07 / 1994, www.vda.de). Spiking the foams

[0072] Since the ingredients used in the polyurethane formulation only produce comparatively low acetaldehyde emissions after foaming, they are mixed with 30 ppm of acetaldehyde to measure an increased starting value and obtain meaningful data on the reduction in aldehyde emissions, thus demonstrating the effectiveness of the active ingredient. The results from foam V1 in Table 3 serve as reference values ​​for formaldehyde and acetaldehyde. Measuring principle

[0073] In this method, test specimens of a specific mass and dimension were placed in a sealed 1L glass bottle above distilled water and stored at a constant temperature for a defined period of time. The bottles were then cooled, and the absorbed formaldehyde and acetaldehyde in the distilled water were determined. The determined amount of formaldehyde and acetaldehyde was related to the dry weight of the molded part (mg / kg). Analytics Test specimen: sample preparation, sampling and specimen dimensions

[0074] After demolding, the foams were stored for 24 hours at 21°C and approximately 50% relative humidity. Samples were then taken from suitable and representative locations, evenly distributed across the width of the (cooled) molded part. The foams were then wrapped in aluminum foil and sealed in a polyethylene bag.

[0075] The sample size was 100x40x40mm (approx. 9g). Three samples were taken from each molded part for aldehyde determination. Testing: Formaldehyde / acetaldehyde release

[0076] Immediately after receipt of the sealed test specimens, they were subjected to direct determination. Before starting the analysis, the samples were weighed to an accuracy of 0.001 g on the analytical balance. 50 ml of distilled water was pipetted into each of the glass bottles used. After placing the test specimens in the glass bottle, the container was closed and stored in an oven at a constant temperature of 60°C for 3 hours. After the test time had elapsed, the containers were removed from the oven. After standing for 60 minutes at room temperature, the test specimens were removed from the test bottle. Subsequently, derivatization was carried out using the DNPH method (dinitrophenylhydrazine). For this purpose, 900 µl of the aqueous phase were mixed with 100 µl of a DNPH solution. The DNPH solution is prepared as follows: 50 mg DNPH in 40 mL MeCN (acetonitrile) is acidified with 250 µL HCl (1:10 diluted) and made up to 50 mL with MeCN.After derivatization, a sample is analyzed by HPLC, separating it into its individual aldehyde homologues. HPLC device parameters

[0077] The following device was used for the analysis: Agilent Technologies 1260 Chromatography Column: Phenomenex Luna 250*4.6mm C18, 5µ particle size Mobile phase: Water Acetonitrile Gradient Detection: UV 365 nm Table 3: Formulation for the production of the molded parts and results of the mold and acetaldehyde measurements, as well as foam properties such as hardness and processability V1 V2 E1 E2 Polyol A 100 100 100 100 Polyol B 1,3 1,3 1,3 1,3 Networker 0,59 0,59 0,59 0,59 Water, addition 3,51 0 3,51 3,51 Water, total 3,51 3,51 3,51 3,51 Catalyst 1 0,2 0,2 0,2 0,2 Catalyst 2 0,8 0,8 0,8 0,8 Silicone stabilizer 1 1 1 1 Isocyanate, index 95 56,9 55,8 55,8 55,8 Solution 1 ----- 3,90 ------ ----- Dispersion 1 ----- ----- 0,78 1,00 Content of active substance [pphp] 0 0,39 0,39 0,50 Formaldehyde emissions, ppm (VDA 275, mod.) 0,77 0,15 0,16 0,08 Acetaldehyde emissions, ppm (VDA 275, mod.) 0,68 0,56 0,57 0,31 Process capability OK OK OK OK Number of cells [cells / cm] 14 14 14 14

[0078] The quantities of raw materials are given in grams. Description of the results:

[0079] When Dispersion 1 was used in the above-mentioned foam formulation from Table 3, it was shown that, with the same active ingredient content, a comparably good effect in the foam with regard to reducing formaldehyde and acetaldehyde emissions could be achieved, both with the aqueous solution 1 (V2) and with Dispersion 1 (E1). For both dosage forms, the processability of the foam is very good. There is no negative impact on the foam structure—especially the cell structure—or on demoldability. When the active ingredient concentration in the foam of Dispersion 1 (E2) was increased, even lower values ​​for formaldehyde and acetaldehyde were measured, while the process properties remained consistently good.

[0080] However, the use of aqueous solution 1 (V2) proved to be extremely disadvantageous in terms of handling, reproducibility and storage stability.

[0081] To prepare an aqueous solution containing 10% adipic acid dihydrazide, the solution had to be heated to 40-45°C for approximately 30 minutes. However, even at 60°C, 100% solubility of the active ingredient was not achieved. When this solution was stored at room temperature, a precipitate was observed, at the latest after about 10 days. When attempts were made to minimize the precipitation of the precipitate, e.g., by using a lower active ingredient content (higher water content), using the same procedure, the observation remained that a white, fine-crystalline precipitate formed after about 10 days at the latest. Adipic acid dihydrazide therefore proved to be completely unstable in aqueous solution, and reproducible results could therefore not be achieved unless the aqueous solution was freshly prepared and used immediately.

[0082] Apart from that, the water quantities contained in this further test, at 0.99 parts, were too high when using the aqueous solution in the product, so that the water quantities used in the formulation described above in Table 3 (see water, total 3.51 parts) could not be adhered to. This would result in such large quantities of water being introduced into the system via the aldehyde scavenger that the desired foam density would be undercut, which in turn would lead to instability.

[0083] Furthermore, there is no freedom to pass on such a product to customers who use very small amounts of water. For example, steering wheel systems made of microcellular polyurethane applications typically contain water contents of less than or equal to 1%. To circumvent this issue, the concentration of the active ingredient was increased, which resulted in the formation of the fine crystalline precipitate being even more severe and occurring even faster. Storage stability and reproducibility were thus even more deficient.

[0084] In contrast, the dispersion 1 according to the invention proved to be extremely storage-stable, showed no visual or effect-related changes even after storage, but consistently led to particularly reproducible results.

Claims

1. Process for producing polyurethane foam by reacting at least one polyol component with at least one isocyanate component in the presence of one or more catalysts which catalyse isocyanate-polyol and / or isocyanate-water and / or isocyanate trimerization reactions, characterized in that the reaction is performed in the presence of a component A comprising a polyhydrazide, a polysulfonyl hydrazide and / or carbodihydrazide, in particular a polyhydrazide, wherein the component A is employed in the form of a mixture C which further comprises a component B comprising a dispersion medium from the group of alkyl phthalates, alkyl dicarboxylates, alkyl adipates, alkyl sebacates, alkyl dodecanoates, polyesters, phosphate esters, fatty acid esters, straight-chain and modified natural oils or mineral oils, sulfonated oils, ethoxylated oils, epoxidized oils, fatty acids, sulfonamides, glycols, polyglycols, alkyl 1,2,4-benzenetricarboxylates and / or lecithin, in particular butyl diglycol, tris(decyl) 1,2,4-benzenetricarboxylate or diisononyl 1,2-cyclohexanedicarboxylate.

2. Process according to Claim 1, characterized in that component A comprises a polyhydrazide, preferably oxalic dihydrazide, malonic dihydrazide, succinic dihydrazide, adipic dihydrazide, sebacic dihydrazide, dodecanoic dihydrazide, isophthalic dihydrazide, piperazine-N,N'-dihydrazide, m-benzenedihydrazide and / or p-benzenedihydrazide, in particular adipic dihydrazide and / or carbodihydrazide.

3. Process according to Claim 1 or 2, characterized in that the mixture C further comprises polyethylene glycol tridecyl ether phosphate, phosphate esters, organophosphates and / or polyether (mono)ols such as preferably 2-ethylhexanol EO-PO polyether.

4. Process according to any of the preceding claims, characterized in that the mixing ratio of component A to component B is 3:1 to 1:3, preferably 2:1 to 1:2, more preferably 1.5:1 to 1:1.5, in particular 1.1:1 to 1:1.1.

5. Process according to any of the preceding claims, characterized in that the component A is in the form of a ground material dispersed in the component B.

6. Process according to Claim 5, characterized in that the particle size of the ground material or of the dispersion is from 0.01 to 200 µm, preferably from 0.5 to 60 µm and most preferably from 0.1 to 30 µm.

7. Process according to at least one of the preceding claims, characterized in that the mixture C is employed in a mass fraction of altogether 0.01 to 20 parts, preferably of 0.05 to 5 parts, in particular of 0.1 to 3 parts, based on 100 parts of polyol component.

8. Process according to at least one of the preceding claims, characterized in that the polyurethane foam produced is a rigid polyurethane foam, a flexible polyurethane foam, a viscoelastic PU foam, an HR polyurethane foam, a semi-rigid polyurethane foam, a thermoformable polyurethane foam or a PU integral foam, preferably an HR polyurethane foam.

9. Polyurethane foam produced by a process according to any of Claims 1 to 8.

10. Polyurethane foam according to Claim 9, characterized in that it comprises from 0.001% to 20% by weight, preferably 0.005% to 5% by weight, in particular 0.01% to 3% by weight, of mixture C, where mixture C is as defined in the preceding claims.

11. Polyurethane foam according to either of Claims 9 or 10, characterized in that it is a rigid polyurethane foam, a flexible polyurethane foam, a viscoelastic PU foam, an HR polyurethane foam, a semi-rigid polyurethane foam, a thermoformable polyurethane foam or a PU integral foam, preferably an HR polyurethane foam.

12. Use of polyurethane foam according to at least one of Claims 9 to 11 as refrigerator insulation, insulation panel, sandwich element, pipe insulation, spray foam, 1- and 1.5-component can foam, imitation wood, modelling foam, packaging foam, mattress, furniture cushioning, automotive seat cushioning, headrest, instrument panel, automotive interior trim, automotive headlining, sound absorption material, steering wheel, shoe sole, carpet backing foam, filter foam, sealing foam, sealant and adhesive or coating or for producing corresponding products.

13. Process for reducing the total aldehyde emission, in particular aldehyde emissions comprising formaldehyde and acetaldehyde, from polyurethane foams, by addition of mixture C, as stated in any of the preceding claims, to the polyurethane foam, preferably in an amount of 0.001% to 20% by weight, advantageously 0.005% to 5% by weight, in particular 0.01% to 3% by weight, based on the total weight of the polyurethane foam, wherein the addition may be effected before and / or during production of the polyurethane foam.

14. Use of a mixture C, as stated in any of the preceding claims, for producing polyurethane foams that have low emissions with regard to aldehydes, in particular comprising formaldehyde and acetaldehyde.

15. Use of a mixture C, as stated in any of the preceding claims, for reducing the aldehyde emissions, in particular comprising formaldehyde and acetaldehyde, from polyurethane foams.