MXPA96003803A - Production of flexible polyurethane foam ignifu - Google Patents

Abstract

Flexible flame retardant polyurethane foams are produced by reacting a) modified organic and / or organic polyisocyanates, b) relatively high molecular weight compounds containing at least two reactive hydrogen atoms, and c) low chain elongation agents if desired. molecular weight, in the presence of d) catalysts, e) swelling agents, f) flame retardant agents, and, if desired, g) additives and / or additives, wherein the flame retardant agents f) used are melamine in combination with at least an anionic dispersant. Isocyanate, MDI prepolymer NCO content from 24 percent to 28 percent based on M

Description

"PRODUCTION OF FLEXIBLE POLYURETHANE FOAMS IGNIFIES" The production of elastic flexible polyurethane (PU) foams is known and described in many patent and literature publications. Examples that can be mentioned are Kunststoff-Handbuch, Volume VII, Polyurethane, Cari Hanser Verlag, Munich, first edition, 1966, edited by Dr. R. Vieweg and Dr. A. Höchtlen, and second edition, 1983, edited by Dr. G. Oertel, and also the monograph "Integralschaumstoffe" by Dr. H. Piechota and Dr. H. Róhr, 1975, published by the same editor. Flexible PU foams are usually produced using commercial toluene diisocyanates such as polyisocyanates, polyoxyalkylene polyols based on 1,2-propylene oxide and / or ethylene oxide and also mixtures of these polyoxyalkylene polyols and graft polyoxyalkylene polyols, such as such as polyfunctional compounds of relatively high molecular weight, and an alkanediol or hydroxyl and / or amino containing compounds, having a functionality higher than 2, for example glycerol, trimethylolpropane or alkanola inas, as chain-lengthening agents. These flexible PU foams are not fireproof; A specific disadvantage is its rapid flammability. To reduce this disadvantage, fire retardant agents, preferably halogen and / or phosphorus-containing compounds, are incorporated into the foamable PU mixtures. However, the addition of these products often have a detrimental effect on the mechanical properties of the PU foams obtained. Therefore, there have been many attempts to develop new flame retardant agents and use these to completely and at least partially replace the halogen and / or phosphorus containing compounds in the PU foams. A compound mentioned as suitable for this purpose is, for example, melamine which melts at a temperature of 354 ° C and is polyfunctional. According to DE-A-23 48 838, the melamine is suspended in the polyol and / or polyisocyanate component and the suspension obtained is immediately processed in non-combustible PU plastics containing isocyanurate groups. The rigid non-flammable PU foams are obtained in accordance with US Pat. No. A-4 221 875 (DE-A-28 09 084) by reacting organic polyisocyanates and polyoxyalkylene polyols in the presence of swelling agents and silicones as a surfactant additive. from 20 to 100 parts by weight of melamine as a flame retardant agent per 100 parts by weight of the polyoxyalkylene polyol.

EP-A-0 004 618 (US Patent Number 4 258 141) discloses a process for producing flexible PU foams fire retardant using a mixture of diphenylmethane diisocyanates and polyphenylenepolymethylene polyisocyanates (crude MDl) having an isomer content of diisocyanate diphenylmethane from 40 percent to 90 percent by weight, based on total weight, such as polyisocyanates and using cyanuric acid derivatives, in particular melamine, as flame retardant agents. Even though the fireproofing of the PU foams was able to be significantly improved by means of these processes, the intense sedimentation of the melamine in the polyol, which occurs after only a short period of storage time, has to be considered as a disadvantage in these processes also. To overcome this disadvantage, EP-B-0 23 987 (US Patent A-4 293 657) describes stable dispersions of melamine-polyol wherein the melamine is ground in situ in the polyol in the presence of at least one stabilizer at a Local energy density of 10 to 3000 kW / cubic meter up to a particle size of less than 10 micrometers. This measure of the additional process requires a high investment in terms of the apparatus and is expensive. In addition, attempts have been made to improve the processability of PU formulations containing melamine by means of appropriate additives., without reducing the fireproofing of the related foams. In accordance with DE-A-35 30 519 (Great Britain Patent -A-21 63 762A), a mixture of melamine and an addition product of alkanolamine and isocyanate which is dispersed in a polyol, is used as the additive. flame inhibitor. Patents of Great Britain Number A-21 77 405A and 2177 405A describe blends of the melamine and styrene-acrylonitrile-polyoxypropylene graft-polyoxyethylene polyols, dispersed in customary polyoxypropylene-polyoxyethylene polyols and also, if desired, compounds which they contain phosphorus and / or halogen as the flame retardant additive. Even when the foams produced by these processes have good fireproofing, their mechanical properties often do not meet the requirements. Another disadvantage is that the formulations have to be processed in multi-component mixers since the melamine-containing component is not storage-stable enough. EP-B-439 719 discloses stable melamine preparations comprising melamine, cyanuric acid, chlorides or bromides of cyanuric acid or isocyanuric acid, ameline (2,4-diamino-6-hydroxy-1,3,5-triazine) or amelide (2-amino-4,6-dihydroxy-1,3,5-triazine).

EP-A-391 116 describes dispersions comprising melaine and substituted or unsubstituted urea, thiourea or biuret in polyetherols. EP-A-492 139 discloses microcapsules comprising melamine encapsulated in plastic to produce flame retardant plastics. EP-A-377 868 proposes specific polyol combinations to stabilize polyol components containing melamine. EP-A-377 891 discloses dispersions of elamine-polyetherpolyol comprising melamine, 1,6-hexanediol and / or trimethylolpropane and at least one polyether polyol, while EP-A-482 507 discloses graphite-polyol dispersions. of polyether expanded with melamine. The processes described in the prior art have in common the fact that some of the dispersants described herein have a detrimental effect on the properties of the foam and that satisfactory dispersion stability is not achieved in each case. An object of the present invention is to develop a process for producing non-combustible flexible polyurethane foams, wherein melamine is used as a flame retardant agent and melamine is present as a stable dispersion in the polyol component, without the manner of the dispersion of resulting in disadvantages in the processing and properties of the foam. We have found that this object is achieved by the melamine being present in the polyol component together with at least one anionic dispersant. In a preferred embodiment of the invention, an organic acid is added in addition to the anionic dispersant and / or an ester of an organic acid. The invention accordingly provides a process for producing flexible, flame retardant polyurethane foams, by reacting a) modified organic and / or organic polyisocyanates, b) relatively high molecular weight compounds containing at least two reactive hydrogen atoms, and c) if desired , low molecular weight chain elongation agents in the presence of d) catalysts, e) swelling agents f) flame retardant agents, and, if desired g) auxiliaries and / or additives, wherein the flame retardant agents f) used are melamine in combination with at least one anionic dispersant. The melamine used according to the present invention as a flame retardant agent can be used in commercial form. These products usually have the following particle size distribution: 10 weight percent of the particles are greater than 30 microns. 30 weight percent of the particles are greater than 24 microns. 50 weight percent of the particles are greater than 20 microns. 70 percent by weight of the particles are greater than 16 microns. 90 percent by weight of the particles are greater than 11 microns. Melamine having an average particle size of 20 to 50 microns and a volumetric density of 300 to 800 grams per liter, in particular 500 to 650 grams per liter, has been found to be particularly useful and therefore is used for preference. Melamine is advantageously used in an amount of 5 percent to 50 percent by weight, in particular 10 percent to 40 percent by weight and particularly preferably 10 percent to 20 percent by weight, based on the component b). Conveniently, only melamine is used as a flame retardant agent. However, it can also be advantageous, and achieve specific effects such as homogenization and stabilization of the starting component mixtures, reduction of smoke formation in the case of fire, improvement of mechanical properties of the PU foams produced, etc. combining the melamine with other customary organic or inorganic flame retardants, for example with starch, which is advantageously selected from the group of corn starch, rice, potato or wheat or mixtures thereof and also, if desired, chemically modified starch derivatives and / or flame retardant agents of the tricresyl phosphate group, tris (2-chloroethyl) phosphate, tris (2-chloropropyl) phosphate, tris (1,3-dichloropropyl) phosphate, tris (2,3-dibromopropyl) phosphate, tetrakis (2-chloroethyl) ethylene diphosphate, hydrates of oxide of aluminum, ammonium sulfate, ammonium phosphate and ammonium polyphosphates. The anionic dispersants used are, in particular, those which have at least one sulfonate or sulfate group in the molecule. Particularly suitable dispersants are (diphenyl oxide) -disulfonates containing linear or branched C6 to C16 alkyl radicals which are supplied under the trade name Dowfa ™ (R) by Dow Chemical Co. Particularly suitable additional compounds are sulphated alkylphenyl ethoxylates or their alkali metal salts. Very suitable compounds are octylphenolyl sulfate and its sodium salt, which is supplied under the name Emulphor (R) OPS 25 by BASF AG. In a particularly advantageous embodiment of the invention, at least one additional organic acid and / or a particular ester thereof, alkyl ester, is additionally added. Particularly suitable compounds of this type are the dibasic and tribasic carboxylic acids or their esters, particularly those which are selected from the group consisting of malonic acid, oxalic acid, lactic acid and their alkyl esters of 1 to 4 carbon atoms. The anionic dispersants are used in an amount of 0.1 percent to 2 percent by weight, preferably 0.5 percent to 2 percent by weight, particularly 0.5 percent to 1 percent by weight, in each case based on b) ag).

The organic acid and / or the esters are used in an amount of 0.001 percent to 0.1 percent by weight, in particular 0.03 percent to 0.07 percent by weight, based on b) to g). If the concentration of the anionic dispersant is too low, the melamine settles prematurely; if the content is too high, it can lead to alterations of the structure of the foam in particular to an undesired closed cell content. If the content of the organic acid is too high, it can interfere with the catalysis. Particularly stable melamine-containing polyol components are obtained when there are present in b) from 10 percent to 20 percent by weight of melamine, from 0.3 percent to 0.6 percent by weight each of a (diphenyl oxide) -disulfonate containing an alkyl radical of 6 to 16 carbon atoms and of a sulfated alkylphenyl ethoxylate and from 0.03 percent to 0.06 percent by weight of an organic acid and / or an ester of an organic acid, in each case based on b). Particularly in the case of the polyol components containing water, an addition of the acid and / or ester should be used. In the combinations of melamine, anionic dispersants and possible organic acids and / or esters used in accordance with the present invention, only very small settlement of the melamine occurs in the polyol component. The polyol component was able to be stored without settling the melamine for up to one month. The otherwise necessary stirring of the polyol component before processing is not required, and no melamine settling occurred in the drums and containers of the machine. Surprisingly, no disadvantages occurred in the properties of the foam, of the flexible foams produced by the process of the present invention. In contrast, the molded parts produced in this manner had an improved foam surface, a dense homogeneous distribution, in the cushion and improved demolding capability. The requirements of the flame test in accordance with DIN 5510, Part 2, were of course filled. The flexible polyurethane foams produced in accordance with the present invention are preferably used for interior seat cushions of vehicles. The following can be said about the starting components that can be used for the process of the present invention. a) the polyisocyanates suitable for producing the flexible fire-resistant elastic PU foams, preferably the molded flexible PU foams, are the known organic compounds, e.g., di- and / or aliphatic, cycloaliphatic, araliphatic, cycloaliphatic-aromatic polyisocyanates and preferably aromatics. Specific examples of the aromatic polyisocyanates are: mixtures of MDl isomers and the polyphenol polymethylene polyisocyanates, which are known as crude MDl, having an MDI isomer content of at least 50 weight percent, preferably 60 percent to 90 percent by weight and more, based on the total weight of the mixture, 2,4- and 2,6-toluene diisocyanate and also the corresponding commercial isomer mixtures, mixtures of toluene diisocyanates and MDl and / or raw MDl, for example, those having an MDl content of 30 percent to 90 percent by weight, preferably 40 percent to 80 percent by weight based on the total weight of the raw MDl. Modified polyfunctional isocyanates, that is, products obtained by chemical reaction of the organic di- and / or polyisocyanates, are also suitable. Examples which may be mentioned are di- and / or polyisocyanates containing ester, urea, biuret, allophanate, isocyanurate and preferably carbodiimide, uretonimine and / or urethane groups. Specific examples are: prepolymers containing urethane groups and having an NCO content of 14 or hundred to 2.8 weight percent, preferably from 12 weight percent to 3.5 weight percent, or pseudoprepolymers having an NCO content of 35 percent to 14 percent by weight, preferably 34 percent to 22 percent by weight, wherein the polyisocyanates modified with urethane groups and formed from toluene diisocyanates have , in particular, an NCO content of 34 percent to 28 percent by weight and those of the isomer mixtures of 4,4 '-MDl, 4,4'- and 2, 4' -MDl or the raw MDl, they have in particular an NCO content of 28 percent to 22 percent by weight, based on total weight, and are prepared by reacting diols, oxyalkylene glycols and / or polyoxyalkylene glycols having molecular weights of 62 to 6000, preferably 134.18 to 4200, with tolylene diisocyanates, mixtures of 4, '-MD1, MD1 isomer and / or crude MD1, for example at a temperature of 20 ° to 110 ° C, preferably 50 ° to 90 ° C, with examples of the oxyalkylene and polyoxyalkylene glycols, which can be used individually or as a mixture being: diethylene, dipro pilen-, polyoxyethylene-, polyoxypropylene- and polyoxypropylene-polyoxyethylene glycols, polyisocyanates, e.g., those based on isomers of MDl and / or tolylene diisocyanates, containing carbodiimide groups and / or isocyanurate groups.

However, isocyanates which have been found to be particularly useful and are therefore preferably used are: 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, mixtures of 2,4- and 2,6 tolylene diisocyanate and polyisocyanates containing urethane groups and having an NCO content of 34 percent to 28 percent by weight, particularly preferably 34 percent to 30 percent by weight, which are prepared from the mixtures of 2,4- and 2,6-tolylene diisocyanate, advantageously in a weight ratio of 80:20, and polyoxypropylene-polyoxyethylene glycols having a molecular weight of 2800 to 4200. Appropriate relatively high molecular weight compounds containing reactive hydrogen atoms (b) are those having an average functionality of 2 to 4 and an average molecular weight of 2200 to 8000. Polyoxyalkylene polyols having an average functionality of 2 to 4, in particular 2.0 to 2.4, and a molecular weight r average of 250 to 8000, in particular of 3600 to 6500, suitable for this purpose, can be prepared by known methods, for example, by anionic polymerization using alkali metal hydroxides such as sodium or potassium hydroxide, or alkali metal alkoxides such as sodium methoxide, sodium or potassium ethoxide or potassium isopropoxide as catalysts or by cationic polymerization using Lewis acids such as antimony pentachloride, boron trifluoride etherate, etc., or bleaching earth as catalysts, of one or more alkylene oxides having from 2 to 4 carbon atoms in the alkylene radical and an initiator molecule containing 2 to 4, preferably 2 or 3, reactive hydrogen atoms in bound form. Suitable alkylene oxides are, for example, tetrahydrofuran, 1,3-propylene oxide, 1,2- or 2,3-butylene oxide and preferably ethylene oxide and 1,2-propylene oxide. The alkylene oxides can be used individually alternatively in succession or as mixtures. Examples of suitable initiator molecules are: water, organic dicarboxylic acids such as succinic acid, adipic acid, phthalic acid and terephthalic acid, aliphatic and aromatic, non-alkylated or N-monoalkylated diamines or N, N- or N, N '- dialkylated having 1 to 4 carbon atoms in the alkyl radical, for example, ethylenediamine, diethylenetriamine, triethylenetetramine, 1,3-propylenediamine, 1,3- or 1,4-butylenediamine, 1,2-, 1/3 -, 1,4-, 1,5- and 1,6-hexamethylenediamine, phenylenediamine, 2,4- and 2,6-tolylenediamine and 4,4'-, 2,4'- and 2, 2'-diaminodiphenylmethane not alkylated, monoalkylated or dialkylated Other suitable starter molecules: alkanolamines such as ethanolamine, diethanolamine, N-methylethanolamine and N-ethylethanolamine, N-methyldiethanolamine and N-ethyldiethanolamine and triethanolamine, and ammonia Preference is given to using polybasic alcohols, in particular, dibasic and / or tribasic, for example ethanediol, 1,2- and 1,3-propanediol, diethyl glycol, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, glycerol, trimethylolpropane and pentaerythritol. The polyoxyalkylene polyols can be used individually or in the form of mixtures, preference being given to those products which contain both ethylene oxide and 1,2-propylene oxide units in bound form in the oxyalkylene chain, these being capable of placed either randomly or in block form. In particular, use is made of polyoxypropylene-polyoxyethylene polyols having more than 50 percent of terminal primary hydroxyl groups, a functionality of 2 to 3 and a molecular weight of 3600 to 6500, polyoxytetramethylene glycols, advantageously those having molecular weights of 250 to 3000, preferably 800 to 2200, or mixtures of the specified polyols.

The polymer-modified polyoxyalkylene polyols known as polymer polyols having average functionality preferably from 2 to 4 and in particular from 2 to 3, and an average molecular weight preferably from 1200 to 8000, in particular from 2200 to 6500, which are preferably used as graft polyoxyalkylene polyols. These can be prepared by in situ polymerization of olefinically unsaturated monomers or mixtures such as co-styrene, acrylonitrile or preferably styrene / acrylonitrile mixtures in the polyoxyalkylene glycols, vg., The polyoxyalkylene polyols described above, using a similar method. that which is provided in German Patents Nos. 11 11 394, 12 22 669 (North American Patents Nos. 3,304,273,3, 383,351,323,093), 11,552,536 (Great Britain Patent Number 1 040 452) and 11 52 537 (Great Britain Patent Number 987 658) or by dispersing the graft polymers that have been prepared above by free-radical polymerization in solvents, in polyoxyalkylene polyols using a method similar to that provided in US Patent Numbers 3 391 092, 4 014 846, 4 093 573. The graft polyoxyalkylene polyols can be prepared from either the saturated polyoxyalkylene polyols. mentioned above that, in accordance with the - IÍ Reissue of US Patent Number 28 715, are essentially free of ethylenically unsaturated units or olefinically unsaturated polyoxyalkylene polyols as described, for example, in U.S. Patent Number 3 652 659 and U.S. Reissue Number 29 014. Polyoxyalkylene Polyols Further suitable modified polymers are the polyurethane-polyoxyalkylene polyol dispersions containing linked groups of polyurea, polyhydrazide or tertiary amino as described, for example, in Patent Number EO-B-0 011 752 (US Patent Number 4 304 708), Patent No. A-4 374 209 and Patent Number DE-A-32 31 497. Polymer-modified polyoxyalkylene polyols advantageously contain from 2 percent to 35 percent by weight, preferably from 3 percent by weight to 25 percent by weight, based on the total weight, of polymer particles, and can, like polyoxy-alkylene polyols and polyoxyalkylene polyamines, be used individually or in the form of mixtures. Suitable polyoxyalkylenepolyamines, preferably having an average functionality of 2 to 4, in particular of 2 to 3, and an average molecular weight preferably of 1800 to 8000, in particular, of 2500 to 6500, are advantageously those whose amino groups are linked to aliphatic radicals and comprising at least 70 percent, preferably more than 90 percent, of primary amino groups. Polyoxyalkylene polyamines containing amino groups linked to aliphatic radicals are preferably used according to the present invention, they can be prepared by known methods for example by cyanoalkylation of the described polyoxyalkylene polyols and subsequent hydrogenation of formed nitrile (US Patent Number 3 257 050) or by amination of the polyoxyalkylene polyols with ammonia in the presence of hydrogen and catalysts (Patent Number DE-A-12 15 373). c) In order to modify the mechanical properties of flexible flexible fire-proof PU foams, in particular molded flexible foams, it may be advantageous to use a low molecular weight chain elongation agent (c) in addition to component (b) in production. Suitable agents of this type are the polyfunctional, in particular difunctional and trifunctional compounds having molecular weights of 17 to about 400, preferably 62 to about 300. For example, dialkanolamines and / or trialkanolamines such as diethanolamine and triethanolamine are used, diols and / or aliphatic triols having from 2 to 6 carbon atoms in the alkylene radical, for example ethanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, glycerol and / or trimethylolpropane, and low molecular weight ethoxylation and / or propoxylation products prepared from dialkanolamines, trialkanolamines, diols and / or triols or aliphatic and / or aromatic diamines such as 1,2-ethanediamine, 1,4-butanediamine, 1,6 hexane diamine, 2,4- and / or 2,6-tolylenediamine, 4,4'-diaminodiphenylmethane as initiator molecules and alkylene oxide or mixtures of alkylene oxide. The chain-lengthening agents (c) which are preferably used are dialkanolamines, diols and / or triols and, in particular, 1,6-hexanediol, diethanolamine, trimethylolpropane and glycerol or mixtures thereof. The chain elongation agents that are preferably used to produce the flexible PU foams are advantageously used in amounts such as from 0.01 to 8 moles, in particular from 0.1 to 3 moles, of the chain elongation agent (c) per mole of the relatively high molecular weight compound (b) was present in the reaction mixture. d) to accelerate the reaction between component (b), the water is incorporated as the swelling agent (e) and, if used, chain elongation agent (c) and the organic polyisocyanates and / or the modified polyisocyanates (a), and customary polyurethane catalysts. Preference is given to using basic polyurethane catalysts, for example tertiary amines such as dimethylbenzylamine, dicyclohexylmethylamine, dimethylcyclohexylamine, bis (N, N-dimethylaminoethyl) ether, bis (dimethylaminopropyl) urea, N-methylmorpholine or N-ethylmorpholine, di-ethylpiperazine, N -dimethylaminoethylpiperidine, 1,2-dimethylimidazole, 1-azobicyclo [2.2.0] octane, dimethylaminoethanol, 2- (N, N-dimethylaminoethoxy) ethanol, N, N ', N "-tris- (dialkylaminoalkyl) hexahydrotriazines, v. g, N, N ", Nutris (dimethylaminopropyl) -s-hexahydrotriazine and, in particular, triethylenediamine, However, metal salts for example of iron (II) chloride, zinc chloride, lead octoate and preferably salts of tin, such as dioctoate, tin di (ethylhexanoate) and dibutyltin dilaurate, and in particular mixtures of tertiary amines and organic tin salts are also suitable, advantageously from 0.1 percent to 10 percent by weight, preferably of 0.3 p or percent to 3 weight percent, of a tertiary amine based catalyst and / or from 0.01 to 0.5 weight percent, preferably from 0.03 percent to 0.25 weight percent, of metal salts, based on weight of component (b). e) Inflating agents (e) that can be used to produce the flexible PU foams preferably include water that reacts with the isocyanate groups to form carbon dioxide. The amounts of water that are advantageously used are from 0.1 to 5 parts by weight, preferably from 1.0 to 3.5 parts by weight and in particular from 2.5 to 3.0 parts by weight, based on 100 parts by weight of component (b). It is also possible to use swelling agents that physically act in admixture with water. The physically appropriate swelling agents are liquids which are inert to the modified or unmodified organic polyisocyanates (a) and which have boiling temperatures of less than 100 ° C, preferably less than 50 ° C, and in particular of -50 ° C. C at 30 ° C, at atmospheric pressure so that the exothermic polyaddition reaction causes them to evaporate. Examples of these liquids that are preferably used are hydrocarbons such as pentane, n- and iso-butane and propane, ethers such as dhyl ether and diethyl ether, ketones such as acetone and methylethyl ketone, ethyl acetate and, preferably, halogenated hydrocarbons. such as methylene chloride, trichlorofluoromethane, dichlorodifluoromethane, dichloromonofluoromethane, dichlorotetrafluoroethane and 1,1,2-trichloro-1,2,2-trifluoroethane. It is also possible to use mixtures of these low boiling point liquids with another and / or with other substituted or unsubstituted hydrocarbons. The amount of physically acting swelling agents that are required in addition to water can be determined in a simple manner, depending on the desired foam density, and is from about 0 to 25 parts by weight preferably from 0 to 15 parts by weight , per 100 parts by weight of component (b). It may be advantageous to mix the modified or unmodified polyisocyanates with the physically active swelling agent and thereby reduce the viscosity. f) The flame retardant agents used are the above-described compounds, if desired mixed with other known flame retardant agents. g) It is also possible to incorporate auxiliaries and / or additives (g) in the reaction mixture. Examples which may be mentioned are surfactants, stabilizers, hydrolysis inhibitors, pore regulators, fungistatic and bacteriostatic substances, dyes, pigments and fillers or fillers. For example, surface-active substances can be used which aid in the homogenization of the starting materials and can also be suitable for regulating the cell structure of the foams. Examples which may be mentioned are siloxane-oxyalkylene copolymers and other organopolysiloxanes, ethoxylated alkylphenols, ethoxylated fatty alcohols, paraffin oils, castor oil or turmeric ricin red oil esters of Turkey, which are used in amounts of 0.05 to 5 parts by weight. weight, preferably from 0.1 to 2 parts by weight, per 100 parts by weight of the starting component (b). Additional details related to the customary additive auxiliaries mentioned above can be found in the specialized literature for example the monograph by J.H. Saunders and K.C. Frisch "High Polymers", Volume XVI, Polyurethanes, Parts 1 and 2, Interscience Publishers, 1962 or 1964 or Kunststoff-Handbuch, Polyurethane, Volume VII, Hanser-Verlag, Munich, Vienna, first and second editions, 1966 and 1983. For producing flexible PU foams, organic (modified) or unmodified (a) polyisocyanates, relatively high molecular weight compounds containing at least two hydrogen atoms reacted (b) and, if desired, chain elongation agents (e) are reactive in the presence of the catalysts (d), the swelling agents (e) the flame retardant agents (f) and, if desired, auxiliaries and / or additives (g) at a temperature of 0 ° to 100 ° C, preference from 15 ° to 80 ° C, in these mixing ratios that are from 0.5 to 2, preferably from 0.8 to 1.3 and in particular from approximately one, than the reactive hydrogen atom (s) and bound to the starting components (b) and, if used , (c) are present by NCO group. Flexible PU foams are advantageously produced by a single operation process by mixing two components A and B, with components (b), (d), (e), (f) and, if used, (c) and (g) starting in combination to form the component A and component B that are used comprising the starting component (a), if desired, mixed with (f), (g) and the inert physically acting swelling agents. Since component A has shelf life of at least 6 months, components A and B only have to be intensively mixed before the production of flexible PU foams. The reaction mixture can be formed into a foam in open or closed molds, it is also suitable for the production of block foams. As already indicated, the process of the present invention is preferably used to produce flexible PU foams. For this purpose, the reaction mixture is introduced at a temperature of 15 ° to 80 ° C, preferably 30 ° C to 65 ° C, in a metal mold capable of being advantageously heated. The temperature of the mold is usually from 20 ° to 90 ° C, preferably from 35 ° to 70 ° C. The reaction mixture is allowed to cure with consolidation, v.gr, at consolidation degrees from 1.1 to 8, preferably from 2 to 6 and in particular from 2.2 to 4, in a closed mold. The flexible PU foams produced by the process of the present invention have densities of 35 to 120 grams per liter, preferably 40 to 80 grams per liter. They have good fire resistance passing the Korrosin burner test (FAR 25.853 (c)), and have good mechanical properties. The molded foams are preferably used as lining or padding elements, e.g., as seat cushions, arm rests, head rests, sun visors and vehicle interior safety coatings. The invention is illustrated by the following examples.

Examples The additives, indicated in the table, are supplied in a regulated manner to a polyol component comprising 61.7 parts by weight of a polyether polyol having a hydroxyl number of 35 milligrams of KOH per gram and a molecular weight Mw of about 4500, 5.0 parts by weight of a polymer polyol having a hydroxyl number of 28 milligrams of KOH per gram and a molecular weight Mw of about 4300, 0.2 part by weight of diethanolamine, 0.2 part by weight of silicone stabilizer B 8680 from Goldsch idt, 0.2 part by weight of the tertiary amine catalyst Dabco 33 LV from Airproducts, 0.5 part by weight of the amine catalyst blocked with Toyocat SF2 acid from Tosho, 2.2 parts by weight of water, 5.0 parts by weight of trichloropropyl phosphate and parts by weight of melamine, and the mixture was homogenized using an agitator at approximately 1300 minutes-1. A part of the polyol component was removed immediately afterwards, placed in a closed bottle and the sedimentation behavior was determined. The results are shown in the table. 100 parts by weight of the homogenized polyol component were reacted with 34 parts by weight of a prepolymer formed of a polyether polyol having a functionality of 2 and an OH number of 250 milligrams of KOH per gram, dipropylene glycol and diphenylmethane diisocyanate. which have an NCO content of 28 weight percent. The reaction mixture had an initiation time of 9 to 10 seconds and an expansion time of 86 to 90 seconds. The foams had a bulk density of approximately 80 grams per liter. The materials from the results are shown in Table 1.

TABLE 1 EXAMPLE ADDITIVE CONC [% IN WEIGHT] * (of comparison) none Emulphor OPS 25 0.5-2.0 Dowfax 3B2 0.5 Emulphor OPS 25 0.5 Dowfax 3B2 0.5 Emulphor OPS 25 0.5 Malonic acid 0.05 Dowfax 3B2 ,, 0.5 Emulphor OPS 25 0.5 Oxalic acid 0.05 Dowfax 3B2 0.5 Emulphor OPS 25 0.5 Diethyl malonate 0.05 TABLE 1 (CONTINUED) EXAMPLE SEDIMENTATION BEHAVIOR IN [] ** AFTER (DAYS) 15 20 30 1 50 2 0 2 8 3 0 0 5 8 15 25 4 0 0 0 3 5 5 0 1 13 20 6 0 1 10 15 * based on the polyol component ** based on the amount of melamine The physical properties of the flexible PU foams are shown in Table 2.

TABLE 2 FORMULATION INDEX DENSITY RESISTANCE TO (GRAM / LITER) TENSION [kPa] Without dispersant (Ejem100 65 111 plo 1) With dispersant (Ex em100 67 115 plo 4) TABLE 2 (CONTINUED) FORMULATION EXTENSION TEST HARDNESS TO [%] FLAME INDENTATION *** [N] Without dispersant (Ejem90 490 step plo 1) With dispersant (Ejem92 480 step plo 4) *** Flame test in accordance with DIN 5510, Part 2

Claims (17)

R E I V I N D I C A C I O N E S:

1. A process for producing flame retardant flexible polyurethane foams by reacting a) organic and / or modified organic polyisocyanates, b) relatively high molecular weight compounds containing at least two reactive hydrogen atoms, and c) if present, elongation agents of chain of low molecular weight in the presence of d) catalysts, e) swelling agents, f) flame retardant agents, and, if desired g) auxiliaries and / or additives, wherein the flame retardant agents f) used with melamine in combination with minus an anionic dispersant.

2. A process according to claim 1, wherein the anionic dispersants used are those having at least one sulfonate and / or sulfate group in the molecule.

3. A process according to claim 1, wherein the anionic dispersants used are (diphenyl oxide) -disulfonates that contain alkyl groups.

4. A process according to claim 1, wherein the anionic dispersants used are (diphenyl oxide) -disulfonates containing linear or branched alkyl groups of 6 to 16 carbon atoms.

5. A process according to claim 1, wherein the anionic dispersants used are sulphated alkylphenyl ethoxylates and / or their alkali metal salts.

6. A process according to claim 1, wherein the anionic dispersants used are mixtures of at least one (diphenyl oxide) -disulfonate containing alkyl groups and at least one sulfated alkylphenyl ethoxylate.

7. A process according to claim 1, wherein the anionic dispersants are used in an amount of 0.1 percent to 2 percent by weight, based on the sum of components b) to g).

8. A process according to claim 1, wherein the anionic dispersants are used in an amount of 0.5 percent to 2 percent by weight, based on the sum of components b) to g).

9. A process according to claim 1, wherein the anionic dispersants are used in an amount of 0.5 percent to 1 percent by weight based on the sum of the components b) to g).

10. A process according to claim 1, wherein the melamine is used in combination with at least one anionic dispersant and at least one organic acid and / or an alkyl ester thereof.

11. A process according to claim 10, wherein the organic acids used are dibasic or tribasic acids.

12. A process according to claim 10, wherein the organic acid is selected from the group consisting of malonic acid, oxalic acid and lactic acid. A process according to claim 10, wherein the organic acids and / or esters thereof are added in an amount of 0.001 percent to 0.1 percent by weight, based on the sum of the components b) ag) . A process according to claim 10, wherein the organic acids and / or esters thereof are used in an amount of 0.03 percent to 0.07 percent by weight, based on the sum of the components b) ag) . 15. A stable dispersion of melamine in polyether alcohols having a melamine content of 5 percent to 50 percent by weight and containing, if desired, additional customary additives whose dispersion contains at least one anionic dispersant. 16. A stable dispersion of melamine in polyether alcohols according to claim 15, which contains at least one anionic dispersant and at least one organic acid and / or an alkyl ester thereof. 17. A stable dispersion of melamine in polyether alcohols according to claim 15, which contains a combination of at least one (phenyl oxide) -disulfonate containing alkyl groups, at least one sulphated alkylphenyl ethoxylate and, at least one organic acid or an alkyl ester thereof.