Thermoplastic open-cell flexible polyurethane foam

Abstract

The present invention is a foam density of 15 to 100 g / dm 3 1. A process for producing a thermoplastic molded polyurethane flexible foam having a density of 110 to 800 g / dm3, comprising mixing (a) a diisocyanate, (b) a polyol having an OH number of less than 280 mg KOH / g and an average isocyanate number of 1.9 to 2.2, (c) one or more chain extenders in an amount of 3 to 20% by weight, based on the total weight of components a) to c), (d) optionally a catalyst, and (e) optionally a filler and / or polyurethane additive, with an isocyanate index of 80 to 110 to form a reaction mixture, wherein the amount of water added to the reaction mixture is less than 0.1% by weight, based on the total weight of components a) to e), and mixing the reaction mixture with a gas at an isocyanate content of the reaction mixture of greater than 0.05% by weight, based on the total weight of the mixture, to form a polyurethane flexible foam having a density of 110 to 800 g / dm3. 3 The present invention further relates to a thermoplastic flexible polyurethane foam obtained from such a method, a composite material comprising such a thermoplastic flexible polyurethane foam, and a method for recycling such a composite material.

Description

[Technical field]

[0001] The present invention is a foam density of 15 to 100 g / dm 3 1. A process for producing a thermoplastic molded polyurethane flexible foam having a density of 110 to 800 g / dm3, comprising mixing (a) a diisocyanate, (b) a polyol having an OH number of less than 280 mg KOH / g and an average isocyanate number of 1.9 to 2.2, (c) one or more chain extenders in an amount of 3 to 20% by weight, based on the total weight of components a) to c), (d) optionally a catalyst, and (e) optionally a filler and / or polyurethane additive, with an isocyanate index of 80 to 110 to form a reaction mixture, wherein the amount of water added to the reaction mixture is less than 0.1% by weight, based on the total weight of components a) to e), and mixing the reaction mixture with a gas at an isocyanate content of the reaction mixture of greater than 0.05% by weight, based on the total weight of the mixture, to form a polyurethane flexible foam having a density of 110 to 800 g / dm3. 3 The present invention further relates to a thermoplastic flexible polyurethane foam obtained from such a method, a composite material comprising such a thermoplastic flexible polyurethane foam, and a method for recycling such a composite material. [Background technology]

[0002] Recycling of polyurethane foams remains an unmet need by the industry. Recycling of flexible polyurethane foams into compressed or foamed components by extrusion or injection molding, which does not require chemical post-processing and reduces the overall consumption of virgin-grade raw materials, is highly desirable due to its potential to replace virgin-grade thermoplastic polyurethanes.

[0003] Conventional polyurethane flexible foams are produced by the reaction of a polyisocyanate with a polyol having an average functionality of 2.4 to about 4 and water as the blowing agent. This results in a crosslinked polyurethane, where the higher functionality polyol forms the chemical crosslinks and the urea groups form the physical crosslinks.

[0004] It is well known in the polyurethane field that flexible polyurethane foams are usually not recyclable by thermoplastic processing due to the crosslinking of the polyol phase and the high melting temperature of the urea hard phase, which usually exceeds the decomposition temperature of polyurethane. Both properties lead to problems in that the materials are not meltable under conventional extrusion or injection molding conditions or they have very low melt flows, making them unsuitable for extrusion or injection molding applications.

[0005] WO2019 / 122122 discloses a method for producing preferably water-blown flexible open-cell polyurethane foams processable by extrusion. This is achieved by limiting the crosslink density in the polyol phase to 1.9-2.2 and by a relatively low water content leading to a relatively low urea content in the final material. A drawback of this invention is that due to the high melt viscosity of urea-containing polyurethane foams, this foaming material must be combined with virgin grade thermoplastic polyurethane to be processable.

[0006] WO2021 / 094239 discloses a method for producing physically expanded flexible open-cell polyurethane foams processable by extrusion, which are based on linear polyols and linear isocyanates and which can be expanded to a density of <200 g / dm3 by a physical blowing agent as a necessary component. 3While reference is made to the use of gases such as nitrogen and CO2 as physical blowing agents, the skilled artisan will appreciate that in methods such as those disclosed in WO2021 / 122122 (WO2021122122), a polyurethane formulation with a viscosity of 100 psig (250 g / dm 3 It has been recognized that it is difficult to achieve low densities below 1000 . In the described examples, water and hydrohaloolefins that are liquid at room temperature are used as blowing agents. In this method, flexible foams with a large amount of closed cells are obtained, which, in addition to high density, show a high undesirable tendency to shrink after cooling. Furthermore, this approach has the disadvantages of low economic efficiency due to the high cost of the physical blowing agent, and the release of organic physical blowing agents into the environment. Furthermore, residues of the physical blowing agent can be trapped within the material and released at a later stage as an undesirable release. It is also known that foaming methods based on the evaporation of physical blowing agents are very sensitive to temperature variations, which can lead to large variations in density, for example between the hot core of the foam, which leads to a lower density, and the cooler outer layer, which leads to a higher density. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2019 / 122122 [Patent Document 2] International Publication No. 2021 / 094239 [Patent Document 3] International Publication No. 2021 / 122122 Summary of the Invention [Problem to be solved by the invention]

[0008] The object of the present invention is to provide a foam with a density of 15 to 100 g / dm 3The objective of the present invention was to provide a flexible thermoplastic polyurethane foam having a high open cell content, good mechanical properties such as low compression set, low hardness, and uniform density, which can be recycled by thermoplastic processing. Furthermore, it was an object to provide a foam which can be recycled by thermoplastic processing without the addition of virgin thermoplastic polyurethane, the thermoplastic polyurethane having a high melt flow index, also known as melt flow rate. [Means for solving the problem]

[0009] Surprisingly, foam density ranges from 15 to 100 g / dm 3 1. A process for producing a thermoplastic molded polyurethane flexible foam having a density of 110 to 800 g / dm3, comprising mixing (a) a diisocyanate, (b) a polyol having an OH number of less than 280 mg KOH / g and an average isocyanate number of 1.9 to 2.2, (c) one or more chain extenders in an amount of 3 to 20% by weight, based on the total weight of components a) to c), (d) optionally a catalyst, and (e) optionally a filler and / or polyurethane additive, with an isocyanate index of 80 to 110 to form a reaction mixture, wherein the amount of water added to the reaction mixture is less than 0.1% by weight, based on the total weight of components a) to e), and mixing the reaction mixture with a gas at an isocyanate content of the reaction mixture of greater than 0.05% by weight, based on the total weight of the mixture, to form a polyurethane flexible foam having a density of 110 to 800 g / dm3. 3 In one embodiment, the method includes forming a preform having a diameter of about 100 mm, injecting the preform into a mold, applying a vacuum to the mold to further expand the preform, and curing the expanded preform.

[0010] The preparation of thermoplastic polyurethanes (TPUs) requires a mixture of isocyanates and polyols. The further addition of chain extenders, catalysts, fillers, polyurethane additives is optional and can be carried out individually or in all possible variants.

[0011] Preferred embodiments utilize aliphatic, cycloaliphatic, araliphatic and / or aromatic diisocyanates as diisocyanate (a), and mixtures thereof. Examples of preferred diisocyanates are trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, heptamethylene diisocyanate, octamethylene diisocyanate, 2-methyl-1,5-pentamethylene diisocyanate, 2-ethyl-1,4-butylene diisocyanate, 1,5-pentamethylene diisocyanate, 1,4-butylene diisocyanate, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane, 1,4-bis(isocyanatomethyl)cyclohexane, 1,3-bis(isocyanatomethyl)cyclohexane, 1,4-cyclohexane diisocyanate, 1-methyl-2,4-cyclohexane diisocyanate, 1-methyl-2,6-cyclohexane diisocyanate, 2,2'-dicyclo Hexylmethane diisocyanate, 2,4'-dicyclohexylmethane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, isomers of diphenylmethane diisocyanate (MDI), such as 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate (2,4'-MDI) and 4,4'-diphenylmethane diisocyanate (4,4'-MDI), 1 ,5-naphthylene diisocyanate (1,5-NDI), isomers of tolylene diisocyanate (TDI), such as 2,4-tolylene diisocyanate (2,4-TDI) and 2,6-tolylene diisocyanate (2,6-TDI), 3,3'-dimethylbiphenyl diisocyanate, p-phenyl diisocyanate, 1,2-diphenylethane diisocyanate, and phenylene diisocyanate. In a preferred embodiment, the isocyanate (a) is selected from the group consisting of 1,5-pentamethylene diisocyanate, 2,4'-MDI, 4,4'-MDI, mixtures of MDI, such as mixtures of 2,4'-MDI and 4,4'-MDI, mixtures of 2,4-TDI, 2,6-TDI and NDI.Particularly preferably, the isocyanate (a) contains at least 97% by mass of 4,4'-MDI, more preferably 97 to 99% by mass of 4,4'-MDI, based on the total mass of the isocyanate (a).

[0012] As polyol (b) having an OH number of less than 280 mg KOH / g and an average functionality of 1.9 to 2.2, all polyols commonly used in the field of thermoplastic polyurethanes can be used. The isocyanate-reactive hydrogen-containing groups are preferably hydroxyl groups. It is particularly preferred that the polyols are selected from polyetherols, polyesterols and polycarbonate diols or mixtures thereof. In a further preferred embodiment, the polyols used to prepare the thermoplastic polyurethanes have a hydroxyl number of 225 to 14 mg KOH / g, more preferably 190 to 20 mg KOH / g and in particular 190 to 28 mg KOH / g. In a further preferred embodiment, the polyols have an average functionality of 1.97 to 2.05, more preferably 1.99 to 2.01 and in particular 2.00.

[0013] The thermoplastic polyurethanes are preferably prepared from polyetherols. It is particularly preferred to use polyetherdiols, such as polypropylene glycol, ethylene oxide-capped polypropylene glycol, polytetramethylene glycol or polytrimethylene oxide. Polytetramethylene glycol is a particularly preferred polyetherdiol. It is preferred to use polyether alcohols and polytetramethylene glycols having a hydroxyl number of 190-45 mg KOH / g. The polyether alcohols are used individually or as a mixture of various polyether alcohols.

[0014] In an alternative embodiment, polyester alcohols are used to prepare the thermoplastic polyurethanes. In this regard, in a preferred embodiment, polyester diols are used. Preferred polyester diols are prepared from adipic acid and / or succinic acid and diols having 2 to 8 carbon atoms, with 1,4-butanediol being particularly preferred. Preferred embodiments of polyester alcohols have a hydroxyl number of 190 to 45 mg KOH / g.

[0015] In a particularly preferred embodiment, the polyol comprises at least 80% by weight of the polyol component (b) polytetramethylene glycol, with polytetramethylene glycol being particularly preferred, where polytetramethylene glycol has a hydroxyl number of 190 to 55 mg KOH / g.

[0016] As the chain extender (c), a chain extender generally known in the field of thermoplastic polyurethanes can be used in an amount of 3 to 20 mass%, preferably 3 to 10 mass%, more preferably 3 to 9 mass%, and particularly preferably 3 to 8 mass%, based on the total mass of each of the components a) to c). For example, aromatic compounds such as hydroquinone bis(2-hydroxyethyl) ether (HQEE) or 3,5-diethyltoluene-2,4-diamine, C2-C 10 Mention may be made of aliphatic compounds such as .-diols, or cycloaliphatic compounds. The chain extender has two hydrogen groups reactive towards isocyanates, preferably two hydroxyl groups, and a molecular weight of 62 to less than 400 g / mol, preferably 62 to less than 300 g / mol, and particularly preferably 76 to less than 200 g / mol. In a preferred embodiment of the present invention, the chain extender (c) is selected from the group consisting of ethanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol and mixtures thereof, in a particularly preferred embodiment the chain extender (c) is 1,4-butanediol.

[0017] When a catalyst is present, it is possible to use a catalyst generally known in the field of thermoplastic polyurethanes. Such catalysts in particular catalyze the reaction between the isocyanate group of diisocyanate (a) and the isocyanate-reactive compounds, preferably hydroxyl groups, of polyol (b), chain extender (c) and other compounds having isocyanate-reactive hydrogen groups, such as chain extenders. In a preferred embodiment, the catalyst is selected from the group of tertiary amines, such as triethylamine, dimethylcyclohexylamine, N-methylmorpholine, N,N'-dimethylpiperazine, 2-(dimethylaminoethoxy)ethanol, diazabicyclo(2,2,2)octane and similar substances. In a further preferred embodiment, the at least one catalyst is selected from the group of organometallic compounds, for example titanium esters, iron compounds such as iron(III) acetylacetonate, tin compounds such as tin diacetate, tin dioctoate, tin dilaurate or tin dialkyl salts of aliphatic carboxylic acids such as dibutyltin diacetate, dibutyltin dilaurate, etc. may be mentioned.

[0018] Some embodiments utilize individual catalysts while other embodiments utilize a mixture of catalysts. In one preferred embodiment, the catalyst used is a mixture of catalysts in an amount of 0.0001% to 0.1% by weight relative to a compound having at least two isocyanate-reactive hydrogen-containing groups, preferably a polyhydroxy compound.

[0019] Useful additives (e) include, for example, surface-active substances, flame retardants, oxidation stabilizers, slip and release aids, dyes and pigments, optionally additional further stabilizers, for example against hydrolysis, light, heat or discolouration, reinforcing agents and plasticisers. Optional fillers may be organic and / or inorganic.

[0020] Suitable catalysts and additives can be identified from standard references, such as Gerhard W. Becker and Dietrich Braun, Kunststoffhandbuch, Vol. 7 "Polyurethanes", Carl Hanser Verlag, Munich, Vienna, 1993, cited above, and include hydrolysis control agents, flame retardants, chain transfer agents.

[0021] Hydrolysis control agents, such as polymers and low molecular weight carbodiimides, may also be added to the reaction mixture, optionally either directly or via the addition of polyol (b) or isocyanate (a).

[0022] If fillers are included, they are for example organic and inorganic powdered or fibrous materials, and mixtures thereof. Useful organic fillers include for example wood flour, starch, flax fibres, hemp fibres, ramie fibres, jute fibres, sisal fibres, cotton fibres, cellulose fibres or aramid fibres. Useful inorganic fillers include for example silicates, barytes, glass spheres, zeolites, metals or metal oxides. It is particularly preferred to use powdered minerals, such as chalk, kaolin, aluminium hydroxide, magnesium hydroxide, aluminium nitrite, aluminium silicate, barium sulphate, calcium carbonate, calcium sulphate, silica, powdered quartz, aerosil, china clay, mica or wollastonite, or spherical or fibrous minerals, such as iron powder, glass balls, glass fibres or carbon fibres. The average particle size, or, in the case of fibrous fillers, the length of the fibres, should be in the range of less than or equal to the size of the cells. Average particle sizes or average fibre lengths in the range of 0.1 to 100 μm, and preferably in the range of 1 to 50 μm, are preferred. The filler may be used in an amount of 0 to 40% by weight, based on the total weight of components (a) to (c). In a preferred embodiment, 0 to 10% by weight, more preferably 0 to 5, and particularly preferably 0% by weight of the filler is used.

[0023] Surface-active substances useful for inclusion in the thermoplastic molding composition include compounds that are used, for example, to increase the homogenization of the starting material and can also control cell structure.Suitable surface-active substances include, for example, emulsifiers, such as sodium salts of sulfated castor oil or fatty acids, and salts of fatty acids with amines, such as diethylamine oleate, diethanolamine stearate, diethanolamine ricinoleate, salts of sulfonic acids, such as alkali metal or ammonium salts of dodecylbenzene- or dinaphthylmethane disulfonic acid and ricinoleic acid; foam stabilizers, such as siloxane-oxyalkylene copolymers and other organosiloxanes, ethoxylated alkylphenols, ethoxylated fatty alcohols, paraffin oil, castor oil esters or ricinoleic acid esters, loquat oil and peanut oil, and cell regulators, such as paraffins, fatty alcohols and dimethylpolysiloxanes. Oligomeric polyacrylates having polyoxyalkylene and fluoroalkane moieties as side groups are furthermore useful for improving the emulsifying action, the cell structure and / or their stabilization. The surface-active substances are typically used in an amount of 0.01 to 5% by weight based on 100% by weight of the compound having at least two isocyanate-reactive hydrogen-containing groups.

[0024] In a preferred embodiment of the invention, the thermoplastic molded polyurethane flexible foam according to the invention comprises at least 0.5% by weight, preferably 0.8-4% by weight, more preferably 1-2.5% by weight, and particularly preferably 1.2-2% by weight of a surface-active substance, preferably at least one organosiloxane, and particularly preferably at least one siloxane-oxyalkylene copolymer, as stabilizer, based on the total weight of compounds (a), (b) and (c). Such siloxane-oxyalkylene copolymers are well known and are commercially available, for example, under the trade names Tegostab® B 8476, Tegostab® BF 2370, Tegostab® B 8110, Tegostab® B 8418, Tegostab® B 8467 (Evonik), Niax® L 634 (Momentive), or combinations thereof.

[0025] Suitable flame retardants include, for example, tricresyl phosphate, tris(2-chloroethyl)phosphate, tris(2-chloropropyl)phosphate, tris(1,3-dichloropropyl)phosphate, tris(2,3-dibromopropyl)phosphate and tetrakis(2-chloroethyl)ethylene diphosphate. In addition to the halogen-substituted phosphates already mentioned, inorganic flame retardants including red phosphorus, aluminum oxide hydrate, antimony trioxide, arsenic trioxide, ammonium polyphosphate and calcium sulfate, or cyanuric acid derivatives, such as melamine, or mixtures of at least two flame retardants, such as ammonium phosphate and melamine and optionally starch and / or expandable graphite, can also be used to impart flame retardancy to the produced polyurethane foam. It has generally proven advantageous to use from 0% to 50% by weight, and preferably from 5% to 25% by weight, of a flame retardant or a flame retardant mixture per 100 parts by weight each of diisocyanate (a), polyol (b) and chain extender (c).

[0026] In a further embodiment, the thermoplastic polyurethane may contain a phosphorus compound as an antioxidant.A preferred embodiment uses an organic phosphorus compound of trivalent phosphorus, such as phosphites and phosphonites.Examples of suitable phosphorus compounds are triphenyl phosphite, diphenyl alkyl phosphite, phenyl dialkyl phosphite, tris(nonylphenyl) phosphite, trilauryl phosphite, trioctadecyl phosphite, distearyl pentaerythritol diphosphite, tris(2,4-di-tert-butylphenyl) phosphite, diisodecyl pentaerythritol diphosphite, di(2,4-di-tert-butylphenyl) pentaerythritol diphosphite, tristearyl sorbitol triphosphite, tetrakis(2,4-di-tert-butylphenyl)-4,4'-biphenylylene diphosphonite, triisodecyl phosphite, diisodecyl phenyl phosphite, and diphenyl isodecyl phosphite or mixtures thereof.

[0027] Particularly preferred embodiments include phosphorus compounds that are difficult to hydrolyze, because the hydrolysis of phosphorus compounds to the corresponding acids can cause damage to polyurethanes, especially polyester polyurethanes.Therefore, phosphorus compounds that are particularly difficult to hydrolyze are particularly suitable for polyester polyurethanes.Preferred embodiments of phosphorus compounds that are difficult to hydrolyze are dipolypropylene glycol phenyl phosphite, diisodecyl phosphite, triphenyl monodecyl phosphite, triisononyl phosphite, tris(2,4-di-tert-butylphenyl) phosphite, tetrakis(2,4-di-tert-butylphenyl)-4,4'-biphenylylene diphosphonite, and di(2,4-di-tert-butylphenyl) pentaerythritol diphosphite, or mixtures thereof.

[0028] In addition, chain transfer agents can be used. When chain transfer agents are used, they typically have a molecular weight of 30 g / mol to 500 g / mol. Chain transfer agents are compounds that have only one functional group with respect to reaction with isocyanates. Examples of chain transfer agents are monofunctional alcohols, monofunctional amines, preferably methylamine and / or monofunctional polyols. Chain transfer agents can be used to specifically control the flow properties of the mixture of the individual components. The chain transfer agents in a preferred embodiment are used in an amount ranging from 0 parts by weight to 5 parts by weight, and more preferably from 0.1 parts by weight to 1 part by weight, based on 100 parts by weight of the compound having at least two isocyanate-reactive hydrogen-containing groups.

[0029] The reaction to form thermoplastic polyurethane is initiated by mixing diisocyanate (a) and isocyanate-reactive components (b) and (c), and optionally catalyst (d) and fillers and additives (e). The formation of the reaction mixture is carried out by a conventional index. The index is defined as the ratio of the total number of isocyanate groups of the aromatic, aliphatic and / or cycloaliphatic diisocyanate (a) used in the reaction to the total number of isocyanate-reactive groups, i.e. the number of active hydrogens, of any compounds having isocyanate-reactive hydrogen atoms in the polyol (b) and chain extender (c), and catalyst (d) and additives (e). An index of 100 means that there is one active hydrogen atom, i.e. one isocyanate-reactive functional group, per isocyanate group of diisocyanate (a). An index of more than 100 means that there are more isocyanate groups than there are isocyanate-reactive groups, e.g. hydroxyl groups.

[0030] In a particularly preferred embodiment, the reaction to form the thermoplastic polyurethane is carried out at an index of 80-110, and more preferably 90-105, even more preferably 95-102, and especially 99-101.

[0031] It is essential for the present invention that the amount of water added to the reaction mixture is less than 0.1% by weight, preferably less than 0.05% by weight, and in particular less than 0.01% by weight, based on the total weight of each of the components a) to e). Water may be added separately, but also as part of one of the components, for example the polyol (b) or the chain extender (c).

[0032] At an isocyanate group content (also known as NCO content) of the reaction mixture of more than 0.05% by weight, preferably more than 0.1% by weight and less than 15% by weight, more preferably more than 1% by weight and less than 10% by weight, and particularly preferably more than 1.5% by weight and less than 5% by weight, based on the total weight of diisocyanate (a), polyol (b) and chain extender (c), respectively, the reaction mixture is mixed with a gas to produce a gas having a density of 110 to 800 g / dm 3 , preferably 200 to 350 g / dm 3 A preform having a temperature of 100° C. is formed. Preferably, this gas does not react with the components of the reaction mixture. Suitable as gases in the sense of the present invention are compounds having a boiling point below 20° C., preferably below 0° C., at atmospheric pressure (standard pressure, 1013 hPa). Suitable gases are carbon dioxide, nitrogen, nitric oxide or air. Mixing can be carried out by conventional means, for example by mechanical mixers.

[0033] The preform obtained is then poured into a mould. The amount of preform in the mould is calculated so that the desired density of the thermoplastic flexible foam according to the invention can be achieved. A vacuum is applied to the mould to expand the preform. It is essential for the present invention that the NCO content of the preform at the time of applying the vacuum is in the range of 0.1% to less than 15% by weight, more preferably more than 1% and less than 10% by weight, and particularly preferably more than 1.5% and less than 5% by weight, based on the total weight of the diisocyanate (a), the polyol (b) and the chain extender (c), respectively. The mould can be heat-treated at normal temperatures, for example 20°C to 120°C, preferably 30°C to 80°C, and particularly preferably 40°C to 70°C. The vacuum applied is generally at least as low as required to fill the mould, depending on the density of the preform, the volume of the mould and the amount of preform poured into the mould. Generally, the absolute pressure of the applied vacuum is less than 60,000 Pa, preferably greater than 1000 Pa and less than 60,000 Pa, more preferably greater than 5,000 Pa and less than 30,000 Pa, and more preferably greater than 10,000 Pa and less than 25,000 Pa.

[0034] Once the foam has hardened, it is removed from the mold. The foam can be removed, for example, when the volume does not change by more than 20% relative to the total volume of the mold upon removal of the vacuum, preferably 10% or less, 5% or less.

[0035] The thermoplastic polyurethane flexible foam according to the present invention has 15~100g / dm 3 , preferably 20 to 80 g / dm 3 , more preferably 25 to 60 g / dm 3 and particularly preferably 30 to 50 g / dm 3 Foam density, 0.1dm 3 / sec, preferably above 0.15dm 3 Air flow according to DIN EN ISO 7231 (December 2010) as a parameter for the open cell content > 100 / s Compression set according to DIN EN ISO 1856 (November 2020) at 22h / 70°C / 50%, preferably less than 20%, more preferably less than 15% and more preferably less than 10%; It preferably has a hardness CLD at 40% according to DIN EN ISO 3386 (October 2015) of less than 10 kPa, more preferably less than 7 kPa, and most preferably less than 5 kPa.

[0036] The thermoplastic polyurethanes of the foams according to the invention preferably have a melt flow index according to ASTM D 1238 B of greater than 0 g / 10 min at 220° C. and 21.6 kg weight, more preferably greater than 10 g / 10 min, greater than 50 g / 10 min at 220° C. and 21.6 kg weight, more preferably greater than 5 g / 10 min at 190° C. and 21.6 kg weight, and most preferably greater than 20 g / 10 min at 190° C. and 21.6 kg weight. In a particularly preferred embodiment of the invention, the melt flow index at 190° C. and 21.6 kg weight is between 5 g / 10 min and 150 g / 10 min.

[0037] In a preferred embodiment of the present invention, the foam is part of a mattress, a seat upholstery, a part of a car seat or an office chair, a part of a shoe sole, a cushion or a sofa. The thermoplastic foam according to the present invention may be part of a composite comprising a thermoplastic polyurethane flexible foam according to the present invention and a thermoplastic polyurethane different from said thermoplastic polyurethane flexible foam. This may be, for example, a fibrous material as a woven or nonwoven material covering the foam when applied as a cushion foam or a seat foam, a solid or foamed thermoplastic elastomer (TPE), for example expanded thermoplastic elastomer beads (also called bead foam or particle foam), for example TPU beads (E-TPU), for example in shoe applications as a sole or upper material. Preferably such multi-material TPU laminates contain less than 10% by weight of different TPUs in their starting materials, and preferably the same TPU building blocks are used.

[0038] When TPE beads, or more preferably TPU beads, are used in combination with the TPU foams described above, they can be added to a preform to obtain a mixture thereon to obtain a combination of particle and block foams, or they can be used as a bead foam portion obtained, for example, by steam chest molding, and either placed adjacent to, attached to, or melted directly onto the thermoplastic molded polyurethane flexible foams described herein.

[0039] The TPU foam according to the invention can be easily modified by applying heat and / or pressure to its surface, for example by this heat treatment to obtain a solid surface layer, or the foam can be attached to any other surface material by melting its surface and contacting the other material.

[0040] The TPU foam according to the invention can be easily recycled, for example, by simply melting the TPU in an extruder. For such a process, no additional virgin TPU is required, since the molten foam according to the invention has a very high melt flow index. The molten TPU can then be used to produce new TPU materials.

[0041] The advantages of the thermoplastic polyurethane flexible foam according to the invention, in addition to good mechanical properties and the possibility of recycling and reuse, are that the thermoplastic polyurethane material exhibits low emissions of volatile organic materials, in particular emissions of residual physical blowing agents, a uniform density and a low MDA content on the surface compared to conventional flexible polyurethane foams. [Brief description of the drawings]

[0042] [Figure 1] FIG. 1 shows DMA measurements of foams. EXAMPLES

[0043] The invention is illustrated by the following examples.

[0044] The following substances were applied: Polyol 1 PolyTHF 1000, BASF, a linear polytetramethylene glycol with an OH number of 112.

[0045] Polyol 2 PolyTHF 2000, BASF, a linear polytetramethylene glycol having an OH number of 56.

[0046] Polyol 3 Lupranol 1000 / 1, BASF, linear polypropylene glycol catalyzed by KOH catalyst and with an OH number of 55.

[0047] Isocyanate 1 Lupranat ME, BASF, 4,4'-MDI of at least 97% purity.

[0048] Isocyanate 2 is a prepolymer based on 4,4'-MDI of at least 97% purity and linear polytetramethylene glycol having an OH number of 56, and has a composition of 46.5% polytetramethylene glycol and 53.5% isocyanate.

[0049] Chemical foaming agent: Water.

[0050] Physical blowing agent: Opteon® 1100, Chemours.

[0051] Conventional experimental procedures (Examples 1, 3-5) Polyols, chain extenders, catalysts, and optionally chemical and physical blowing agents are mixed according to Table 1 at 25° C., or at 50° C. if raw materials that are solid at room temperature are used. Then, 100 grams of this mixture are mixed with the appropriate amount of isocyanate (index 100) and poured into an open mold at a temperature of 40° C.

[0052] Example of processing according to the present invention (Example 2) Polyol, chain extender, catalyst, and optionally chemical and physical blowing agents are mixed according to Table 1 at 25 ° C, or at 50 ° C if raw materials that are solid at room temperature are used. Then 100 grams of this mixture are mixed with the corresponding amount of isocyanate (index 100) and gas is added under intensive mixing to reduce the bulk density of the mixture to less than 300 g / l, resulting in a pourable preform with closed cells that is not fully cured. With a residual NCO content of 3.8% by weight of the preform, an open mold is filled with this preform to 1 / 10 of its volume and immediately placed in a vacuum chamber and a vacuum with an absolute pressure of about 10,000 to 20,000 Pa is applied. The sample is cured under constant vacuum. The vacuum is then removed. Measurements of the physical properties were performed at ambient conditions after at least 24 hours.

[0053] [Table 1-1]

[0054] [Table 1-2]

[0055] The compressive load deflection (CLD) hardness and density of the foams were determined according to DIN EN ISO 3386 (October 2015).

[0056] The airflow was determined according to DIN EN ISO 7231 (December 2010).

[0057] The tensile strength and elongation were determined in accordance with DIN EN ISO 1798 (April 2008).

[0058] The compression set was determined according to DIN EN ISO 1856 (2020) for 22 hours at 70°C and 50% compression.

[0059] The rebound elasticity was determined in accordance with DIN EN ISO 8307 (2018).

[0060] The wet compression set was determined according to DIN EN ISO 1856 (2020) for 22 hours at 50° C., 95% relative humidity and 70% compression.

[0061] The release from the blowing agent was measured according to VDA 277 (1995). After storing the samples at ambient conditions for 24 hours, 0.5 g of the sample was filled into a test vial and heat-treated for 1 hour at 120° C. The gas phase was injected into a gas chromatograph.

[0062] To determine the density variation within the foam, a 50x50x50 cm sample is produced according to the instructions, with a mould temperature of 40°C. After 24 hours at ambient conditions, the foam sample is cut horizontally and the upper 20 cm and the lower 10 cm are discarded. The remaining sample is cut into measuring samples of size 10x10x5 cm. The density variation is given as a percentage value by dividing the density of the measuring sample with the highest density by the density of the measuring sample with the lowest density.

[0063] The NCO content is determined by titration in accordance with DIN EN ISO 14896 (2009). The hydroxyl number or OH number is determined via titration in accordance with DIN EN ISO 4692-2 (2016).

[0064] Dynamic mechanical analysis (DMA) was performed on an instrument from Rheometric Scientific (ARES) according to DIN EN ISO 6721 (2019).

[0065] Figure 1 shows the DMA measurements of foams according to Comparative Example 1 and Inventive Example 2. It can be observed that the foams according to the invention exhibit several advantages over foams according to the prior art.

[0066] Compared to prior art foams, the foams of the present invention exhibit a superior viscoelastic plateau in the range of 0° C. to 50° C., which is desirable for comfort applications such as mattresses, upholstery and cushioning.

[0067] It is believed that the physical blowing agent acts as a solvent and can lead to dissolution of the crystalline MDI / chain extender hard phase in the soft phase, which prevents phase separation and leads to much higher hardness for the same polyurethane matrix composition in the application range of 0°C to +50°C, which is not desirable for comfortable application of the foam. The method of the present invention leads to very good phase separation, which is indicated by a good viscoelastic plateau in the DMA measurements in the application range. In the final application, this leads to a dramatically reduced CLD hardness, which is desirable for comfortable application.

Claims

1. Foam density 15-100g / dm 3 1. A method for producing a thermoplastic molded polyurethane flexible foam comprising: a) diisocyanates, b) polyols having an OH number of less than 280 mg KOH / g and an average OH number of 1.9 to 2.2; c) 3 to 20% by weight, based on the total weight of components a) to c), of one or more chain extenders; d) optionally a catalyst, and e) Optionally, fillers and / or polyurethane additives at an isocyanate index of 80 to 110 to form a reaction mixture, wherein the amount of water added to the reaction mixture is less than 0.1% by weight, based on the total weight of components a) to e); mixing the reaction mixture with a gas at an isocyanate content of the reaction mixture greater than 0.05% by weight, based on the total weight of the mixture, to form a preform having a density of 110 to 800 g / liter; pouring the preform into a mold; applying a vacuum to the mold to further expand the preform; and Curing the expanded preform The method comprising:

2. 2. The method of claim 1, wherein the gas is a compound or mixture of compounds having a boiling point below 20° C. at standard pressure.

3. 3. The method according to claim 1 or 2, characterized in that the pressure of the applied vacuum is less than 800 mbar.

4. 3. The method according to claim 1 or 2, characterized in that the filler and / or additive (e) comprises at least 0.5% by weight, relative to the total weight of compounds (a), (b) and (c), of a surface-active substance comprising at least one siloxane-oxyalkylene copolymer.

5. 3. The method of claim 1 or 2, wherein the polyol component (b) comprises polytetramethylene glycol.

6. 3. The method according to claim 1, wherein the diisocyanate (a) comprises at least 97% by weight of 4,4'-diphenylmethane diisocyanate, based on the total weight of the diisocyanate (a).

7. 3. The method according to claim 1, wherein the chain extender is selected from the group consisting of ethanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol and 1,6-hexanediol.

8. The foam density obtained by the method according to claim 1 or 2 is 15 to 100 g / dm 3 A thermoplastic polyurethane flexible foam having

9. Airflow is 0.1 dm 3 / seconds, a compression set of less than 20% after 22 hours of heat storage at 70°C and 50% compression; and Compressive load deflection (CLD) hardness is less than 10 kPa 9. The thermoplastic polyurethane flexible foam according to claim 8, wherein

10. 9. The thermoplastic polyurethane flexible foam according to claim 8, wherein the thermoplastic polyurethane of the foam has a melt flow index according to ASTM D 1238 B at 190°C and 3.4 kg of greater than 0, preferably greater than 10.

11. 9. The thermoplastic polyurethane flexible foam of claim 8, wherein the foam is part of a mattress or upholstery for a seat.

12. 9. A composite comprising the thermoplastic polyurethane flexible foam of claim 8 and a thermoplastic polyurethane different from said thermoplastic polyurethane flexible foam and having at least 90% by weight of the same composition as said foam.

13. 13. The composite of claim 12, wherein all components of the thermoplastic polyurethane of the composite are identical.

14. 14. A method for recycling a composite material according to claim 13, comprising melting the composite material to form a new thermoplastic polyurethane product.

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