Water-foamed environmentally friendly high yield spray polyurethane foams

Abstract

The invention relates to a method for producing a polyurethane foam having a density of 5 g / dm3 to 20 g / dm3 by mixing the following substances to obtain a reaction mixture: (a) a polyisocyanate comprising PMDI; (b) a compound having at least two hydrogen atoms reactive with isocyanate groups, comprising (b1) at least one polyether polyol obtained by the alkoxylation of a difunctional or trifunctional starting molecule having a hydroxyl number of 210 mg KOH / g to 400 mg KOH / g and (b2) at least one polyether polyol obtained by the alkoxylation of an aliphatic diamine; (c) a catalyst comprising (c1) at least one entrainable amine catalyst and (c2) at least one catalyst comprising a urea structure; (d) a blowing agent comprising water; (e) optionally, a flame retardant; and (f) optionally auxiliary agents and additional substances, the reaction mixture is sprayed onto a substrate and the reaction mixture is hardened to obtain the polyurethane foam, and wherein the reaction mixture comprises less than 1 part by weight of a phosphorus-containing flame retardant. The invention further relates to polyurethane foams obtainable according to the method according to the invention.

Description

[0001] The present invention relates to a process for producing polyurethane foam having a density of 5 g / dm 3 to 20 g / dm 3 by mixing the following to obtain a reaction mixture: (a) a polyisocyanate comprising PMDI; (b) a compound having at least two hydrogen atoms reactive towards isocyanate groups, the compound comprising (b1) at least one polyether polyol obtained by alkoxylation of a difunctional or trifunctional starting molecule having a hydroxyl value of 210 mg KOH / g to 400 mg KOH / g and (b2) at least one polyether polyol obtained by alkoxylation of an aliphatic diamine; (c) a catalyst comprising (c1) at least one incorporable amine catalyst; (d) a blowing agent comprising water; (e) an optional flame retardant; and (f) optional auxiliaries and additional substances, spraying the reaction mixture onto a substrate and hardening the reaction mixture to obtain the polyurethane foam, and wherein the reaction mixture comprises less than 1 part by weight of a phosphorus-containing flame retardant. The present invention further relates to a polyurethane foam obtainable by the process according to the present invention.

[0002] Many publications in the patent literature and other literature describe the known production of polyurethane foams, in particular rigid polyurethane foams, by reaction of polyisocyanates with compounds having at least two hydrogen atoms reactive towards isocyanate groups, in particular with polyether polyols from the polymerization of alkylene oxides or with polyester polyols from the polycondensation of alcohols and dicarboxylic acids, in the presence of polyurethane catalysts, blowing agents and other auxiliaries and additional substances.

[0003] Polyurethane spray foam is a polyurethane foam applied directly in situ by spraying. This also allows application, by way of example, to vertical areas and also overhead application. The main applications of polyurethane spray foam are found in the construction industry, sound absorption or insulation, for example in roof insulation.

[0004] Important requirements for polyurethane spray foam are low thermal conductivity and / or good sound absorption properties, low viscosity for good flowability and sprayability and on the other hand rapid reactivity to prevent dripping, sufficient foam adhesion to a very wide range of substrates, low density and good mechanical properties. Polyurethane foams are generally produced by the so-called two-component process, in which an isocyanate component comprising isocyanate and a polyol component comprising a component reactive towards isocyanate are mixed. Usually other starting materials here, such as blowing agents and catalysts, are added to one of these components.

[0005] Additional requirements for spray foams, especially if they are used in enclosed spaces, such as inside buildings, call for reduced emissions of volatile organic compounds. To ensure a rapid reaction and prevent dripping, especially in the case of using chemical blowing agents such as water, additional catalysts are needed. Known amine-based catalysts contribute to the emission of volatile organic compounds. Therefore, these catalysts are replaced by reactive amine-based catalysts which contain groups reactive towards isocyanates and can thus be incorporated into the polyurethane network. The disadvantage of the catalysts that can be incorporated is that they are less active and therefore a higher amount of catalyst is needed. However, a higher amount of amine-based catalyst results in a higher corrosivity of the polyol component.

[0006] It is known that the polyurethane foam industry uses chemical and / or physical blowing agents to foam the polymer during its formation. Chemical blowing agents are blowing agents that react with isocyanate functional groups to form a gas, while physical blowing agents have a low boiling point and are thus converted into the gaseous state by the heat of reaction. Here, chemical blowing agents as well as physical blowing agents are usually added to the polyol component.

[0007] Hitherto, the mainly used physical blowing agents have included chlorofluorocarbons. Since physical blowing agents reduce the viscosity of the polyol component as well as the viscosity of the reaction mixture of the polyol component and the isocyanate component, physical blowing agents are usually used to improve the sprayability of the reaction mixture. However, these physical blowing agents have now been banned in many parts of the world due to their role in ozone layer depletion. Nowadays, the mainly used physical blowing agents include fluorinated hydrocarbons, HFCs and low-boiling hydrocarbons such as pentane. The shelf life of the corresponding components is a criterion here, and also the flammability of the hydrocarbons. Additionally, HFCs are expensive. Therefore, a partial replacement of physical blowing agents is needed.

[0008] Another method of reducing viscosity is to add a liquid flame retardant as a phosphor-based flame retardant, such as TCPP. The addition of TCPP has the disadvantage of forming a large amount of 1,2-dichloropropane. 1,2-Dichloropropane has been classified as a carcinogenic VOC. The replacement of TCPP is not easy because many inert substances that reduce the viscosity of the reaction mixture slowly migrate out of the foam and cause VOC emissions.

[0009] The object of the present invention is to provide a polyurethane spray foam with a very low density, which has good mechanical properties, especially dimensional stability, and low emissions of volatile organic compounds and especially no 1,2-dichloropropane emissions. Another object is to provide a method for producing a spray foam, in which the reaction is fast enough to prevent dripping, and in which the polyol component is non-corrosive, and the polyol component as well as the reaction mixture have a low viscosity.

[0010] The object of the present invention has been achieved by a polyurethane spray foam with a density of 5 g / dm3 to 20 g / dm 3 The polyurethane foam is solved by a polyurethane foam having a density of from 100 g / dm³ to 200 g / dm³ and a thermal conductivity of from 0.020 W / (m·K) to 0.025 W / (m·K), which polyurethane foam is obtained by a process comprising mixing the following to obtain a reaction mixture: (a) a polyisocyanate comprising PMDI; (b) a compound having at least two hydrogen atoms reactive towards isocyanate groups, the compound comprising (b1) at least one polyether polyol obtained by alkoxylation of a difunctional or trifunctional starting molecule having a hydroxyl value of from 210 mg KOH / g to 400 mg KOH / g and (b2) at least one polyether polyol obtained by alkoxylation of an aliphatic diamine; (c) a catalyst comprising (c1) at least one incorporable amine catalyst; (d) a blowing agent comprising water; (e) an optional flame retardant; and (f) optional auxiliaries and additional substances, spraying the reaction mixture onto a substrate and hardening the reaction mixture to obtain the polyurethane foam, and wherein the reaction mixture comprises less than 1 part by weight of a phosphorus-containing flame retardant. The invention further relates to a process for producing a polyurethane foam according to the invention.

[0011] The invention relates to spray polyurethane foams which are applied directly in situ by spraying onto a substrate which is, by way of example, part of a building, such as a wall or a ceiling.

[0012] The polyisocyanate (a) used comprises polymeric diphenylmethane diisocyanate. Diphenylmethane diisocyanate is also referred to below as "MDI". Polymeric MDI is a mixture of MDI having two aromatic rings with MDI homologues having a greater number of aromatic rings (such as homologues having 3, 4 or 5 aromatic rings), i.e. with 3-functional isocyanates, 4-functional isocyanates or 5-functional isocyanates. Polymeric MDI can be used together with other diisocyanates conventionally used in polyurethane chemistry, such as toluene diisocyanate (TDI) or naphthalene diisocyanate (NDI). The diisocyanate preferably comprises, in each case based on the total weight of the diisocyanate, at least 80% by weight of diphenylmethane diisocyanate, particularly preferably at least 90% by weight of diphenylmethane diisocyanate, and in particular only diphenylmethane diisocyanate. Here, the polyisocyanate (a) preferably has a viscosity at 25 °C of from 250 mPas to 1000 mPas, more preferably from 300 mPas to 800 mPas, particularly preferably from 400 mPas to 700 mPas, and in particular from 450 mPas to 550 mPas.

[0013] The compound (b) having a group reactive to isocyanate used may include all known compounds having at least two hydrogen atoms reactive to isocyanate, such as those having a functionality of 2 to 8 and a number-average molar mass of 62 g / mol to 15,000 g / mol: By way of example, polyether polyols may be used, and the molar mass of the polyether alcohol is preferably 200 g / mol to 15,000 g / mol. In addition to polyether alcohols, low molecular weight chain extenders and / or crosslinking agents may also be used. For the purposes of the present disclosure, the expressions "polyether polyol" and "polyether alcohol" are equivalent.

[0014] Polyether alcohols are produced, by way of example, from epoxides (such as propylene oxide and / or ethylene oxide), or from tetrahydrofuran, by using starting compounds having active hydrogen (such as aliphatic alcohols, phenols, amines, carboxylic acids, water or compounds based on natural materials, such as sucrose, sorbitol or mannitol), using a catalyst. Here, basic catalysts or double metal cyanide catalysts may be mentioned, as described, by way of example, in PCT / EP2005 / 010124, EP 0090444 or WO 05 / 090440.

[0015] Component (b) may further comprise a chain extender and / or a crosslinking agent, for example in order to change mechanical properties, such as hardness. The chain extender and / or crosslinking agent used includes diols and / or triols, and also amino alcohols having a molar mass of less than 200 g / mol, preferably 60 g / mol to 150 g / mol. Examples are difunctional alcohols such as monoethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, tetraethylene glycol, dipropylene glycol, cyclohexanediol, and chain extenders based on aliphatic or aromatic amines such as aliphatic or aromatic diamines, such as ethylenediamine, triethylenediamine and / or diethyltoluenediamine (DETDA). Aliphatic and alicyclic triols such as glycerol, trimethylolpropane and 1,2,4-trihydroxycyclohexane and 1,3,5-trihydroxycyclohexane may also be used.

[0016] In the case where a chain extender, a crosslinking agent or a mixture thereof is used for the production of rigid polyurethane foams, the useful amount of these substances is 0% by weight to 15% by weight, preferably 0% by weight to 5% by weight, based on the total weight of component (b).

[0017] In the present invention, the compound (b) having at least two hydrogen atoms reactive to isocyanate groups comprises (b1) at least one polyether polyol obtained by alkoxylation of a difunctional starting molecule or a trifunctional starting molecule having a hydroxyl value of 210 mg KOH / g to 400 mg KOH / g and (b2) at least one polyether polyol obtained by alkoxylation of an aliphatic diamine.

[0018] In a preferred embodiment, the compound (b) may further comprise at least one chain extender (b3) based on an aliphatic or aromatic diamine. Preferably, the chain extender (b3) based on an aliphatic or aromatic diamine is diethyltoluenediamine.

[0019] In a preferred embodiment of the present invention, the compound (b) comprises at least one polyether polyol (b4) obtained by alkoxylation of a difunctional or trifunctional starting molecule having a hydroxyl value of 20 mg KOH / g to 50 mg KOH / g and / or at least one polyether polyol (b5) obtained by alkoxylation of a difunctional or trifunctional starting molecule having a hydroxyl value of 100 mg KOH / g to less than 210 mg KOH / g.

[0020] In a preferred embodiment, the polyether polyol (b1) is propylene glycol having a hydroxyl value preferably of 215 mg KOH / g to 350 mg KOH / g, and more preferably of 220 mg KOH / g to 300 mg KOH / g.

[0021] In a further preferred embodiment, the polyol (b2) can be obtained by propoxylation of ethylenediamine having an OH value preferably of 350 mg KOH / g to 550 mg KOH / g, and more preferably of 420 mg KOH / g to 520 mg KOH / g.

[0022] In a further preferred embodiment, the polyol (b4) can be obtained by propoxylation and ethoxylation of a difunctional starting molecule having an OH value preferably of 20 mg KOH / g to 50 mg KOH / g, and more preferably of 25 mg KOH / g to 30 mg KOH / g.

[0023] In a further preferred embodiment, the polyol (b5) can be obtained by alkoxylation of a difunctional starting molecule with ethylene oxide having an OH value preferably of 120 mg KOH / g to 200 mg KOH / g, and more preferably of 150 mg KOH / g to 200 mg KOH / g.

[0024] Particularly preferred is when the compound (b) having at least two hydrogen atoms reactive toward isocyanate groups comprises polyols (b1), (b2), (b3), (b4) and (b5). In a particularly preferred embodiment, the content of polyol (b1) is 5 wt% to 30 wt%, preferably 10 wt% to 20 wt%, the content of polyol (b2) is 5 wt% to 30 wt%, preferably 12 wt% to 25 wt%, the content of polyol (b3) is 0.5 wt% to 5 wt%, preferably 1.5 wt% to 2.5 wt%, the content of polyol (b4) is 30 wt% to 60 wt%, preferably 40 wt% to 55 wt%, and the content of polyol (b5) is 5 wt% to 30 wt%, preferably 12 wt% to 25 wt%, these polyols each being based on the total weight of the compound (b) having at least two hydrogen atoms reactive toward isocyanate groups. In an even more preferred embodiment, the content of polyols (b1) to (b5) is at least 80 wt%, more preferably at least 90 wt%, particularly preferably at least 95 wt%, and in particular 100 wt%, based on the total weight of compound (b).

[0025] The catalyst (c) greatly accelerates the reaction of the compound (b) having at least two hydrogen atoms reactive toward isocyanate groups and the chemical blowing agent (d) with the polyisocyanate (a). Typical catalysts are strongly basic amines. The catalyst (c) preferably comprises an incorporable amine catalyst (c1).

[0026] Typical catalysts that can be used in the production of polyurethanes include, for example: amidines such as 2,3-dimethyl-3,4,5,6-tetrahydropyrimidine, tertiary amines such as triethylamine, tributylamine, dimethylbenzylamine, N-methyl-, N-ethyl- and N-cyclohexylmorpholine, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetramethylbutanediamine, N,N,N',N'-tetramethylhexanediamine, pentamethyldiethylenetriamine, tetramethyldiaminoethyl ether, bis(dimethylaminopropyl)urea, dimethylpiperazine, 1,2-dimethylimidazole, 1-azabicyclo[3.3.0]octane and preferably 1,4-diazabicyclo[2.2.2]octane, and alkanolamine compounds such as triethanolamine, triisopropanolamine, N-methyl- and N-ethyldiethanolamine, and dimethylethanolamine. Also known polyurethane catalysts are organometallic compounds, preferably organotin compounds, such as tin(II) salts of organic carboxylic acids, for example tin(II) acetate, tin(II) octoate, tin(II) ethylhexanoate and tin(II) laurate, and dialkyltin(IV) salts of organic carboxylic acids, for example dibutyltin diacetate, dibutyltin dilaurate, dibutyltin maleate and dioctyltin diacetate; and also bismuth carboxylates, such as bismuth(III) neodecanoate, bismuth 2-ethylhexanoate and bismuth octoate, or mixtures thereof. The organometallic compounds can be used in combination with strongly basic amines. However, since organometallic catalysts are generally unstable in the presence of water, these catalysts are less preferred. The use of amine catalysts that do not contain groups reactive towards isocyanates is less preferred because these catalysts tend to increase the emission of volatile organic compounds.

[0027] The incorporable amine catalyst (c1) has at least one, preferably 1 to 8, particularly preferably 1 to 2, isocyanate-reactive groups, such as primary amine groups, secondary amine groups, hydroxyl groups, amide groups or urea groups, preferably primary amine groups, secondary amine groups, hydroxyl groups. The incorporable amine catalysts are mainly used for the production of low-emission polyurethanes, especially for use in automotive interiors. Such catalysts are known and are described, for example, in EP1888664. These catalysts include compounds that preferably contain one or more tertiary amino groups in addition to the isocyanate-reactive groups. At least one tertiary amino group in the incorporable catalyst preferably bears at least two aliphatic hydrocarbon radicals, preferably each radical having 1 to 10 carbon atoms, particularly preferably each radical having 1 to 6 carbon atoms. Particularly preferably, the tertiary amino group bears two radicals independently selected from methyl radicals and ethyl radicals, plus another organic radical. Examples of incorporable catalysts that can be used are bis(dimethylaminopropyl)urea, bis(N,N-dimethylaminoethoxyethyl)carbamate, dimethylaminopropylurea, N,N,N-trimethyl-N-hydroxyethylbis(aminopropyl ether), N,N,N-trimethyl-N-hydroxyethylbis(aminoethyl ether), diethylethanolamine, bis(N,N-dimethyl-3-aminopropyl)amine, dimethylaminopropylamine, 3-dimethylaminopropyl-N,N-dimethylpropane-1,3-diamine, dimethyl-2-(2-aminoethoxyethanol), (1,3-bis(dimethylamino)propan-2-ol), N,N-bis(3-dimethylaminopropyl)-N-isopropanolamine, bis(dimethylaminopropyl)-2-hydroxyethylamine, N,N,N-trimethyl-N-(3-aminopropyl)-bis(aminoethyl ether), 1,4-diazabicyclo[2.2.2]octane-2-methanol and 3-dimethylaminoisopropyldiisopropanolamine, or mixtures thereof.

[0028] Preferably, the catalyst (c) further comprises an amine catalyst comprising a urea structure (c2). Typical examples of catalysts comprising a urea structure are 3-(dimethylamino)propylurea and 1,3-bis(3-(dimethylamino)propyl)urea. In a preferred embodiment, the catalyst (c2) comprises a mixture comprising 3-(dimethylamino)propylurea and 1,3-bis(3-(dimethylamino)propyl)urea. In a preferred embodiment, the catalyst (c) contains 1% to 8% by weight, more preferably 2% to 6% by weight, and particularly preferably 3% to 5% by weight of the catalyst (c2) based on the total weight of compounds (b) to (f).

[0029] In a preferred embodiment of the present invention, in addition to the incorporable amine catalyst (c1) and the catalyst (c2) containing a urea structure, the catalyst (c) further contains an unincorporable amine catalyst of less than 1% by weight, preferably less than 0.1% by weight, based on the total weight of the compound (b) having at least two hydrogen atoms reactive with isocyanate groups. Most preferably, the catalyst (c) does not contain any catalyst other than the catalysts (c1) and (C2).

[0030] In a particularly preferred embodiment, in addition to the catalyst (c2) containing a urea structure, the content of the catalyst (c) is less than 8% by weight, more preferably 3% to 6% by weight, and particularly preferably 3.5% to less than 5% by weight, based on the total weight of the compounds (b) to (f).

[0031] At least one blowing agent (d) containing water is used in the present invention. The blowing agent may further include additional chemical blowing agents and / or physical blowing agents. These blowing agents are described by way of example in "Polyurethane Handbook" (Carl Hanser Verlag), 2nd edition 1994, Chapter 3.4.5. The term chemical blowing agent herein means a compound that forms a gaseous product by reacting with isocyanate. Examples of these blowing agents are water and carboxylic acids. The term physical blowing agent means a compound that is dissolved or emulsified in the starting materials for the polyurethane production reaction and evaporates under the polyurethane-forming conditions. These are, by way of example, hydrocarbons, halogenated hydrocarbons, hydrogen halide olefins and other compounds, examples being perfluorinated alkanes such as perfluorohexane, chlorofluorocarbons and ethers, esters, ketones, acetals and / or liquid carbon dioxide.

[0032] In a preferred embodiment, as the blowing agent according to the present invention, a physical blowing agent of less than 10% by weight, based on the total weight of the blowing agent (d), is used, and particularly preferably only water is used as the blowing agent (d). The amount of the blowing agent is selected to obtain a spray foam density of 5 g / dm 3 to 20 g / dm 3 , preferably 7 g / dm 3 to 15 g / dm 3 , particularly preferably 8 g / dm 3 to 12 g / dm 3 . To obtain these densities, a blowing agent (d) of preferably 10% to 30% by weight, more preferably 15% to 26% by weight, and particularly preferably 20% to 25% by weight, based on the total weight of the compounds (b) to (f), is used.

[0033] According to the present invention, flame retardants can be added. Examples of suitable flame retardants are brominated esters, brominated ethers (Ixol), and brominated alcohols such as dibromoneopentyl glycol, tribromoneopentyl glycol, and PHT-4-diol, and also chlorinated phosphates such as tris(2-chloroethyl) phosphate, tris(1,3-dichloropropyl) phosphate, tricresyl phosphate, tris(2,3-dibromopropyl) phosphate, tetra(2-chloroethyl) ethylenediphosphate, dimethyl methylphosphonate, diethyldiethanolaminomethyl phosphate, and also commercially available halogenated flame-retardant polyols. Other phosphates or phosphonates used may include diethyl ethylphosphonate (DEEP), triethyl phosphate (TEP), dimethyl propylphosphonate (DMPP), and diphenyltolyl phosphate (DPC) as liquid flame retardants.

[0034] In addition to the above-mentioned flame retardants, materials that can be used to provide flame retardancy to rigid polyurethane foams are inorganic or organic flame retardants such as red phosphorus, preparations containing red phosphorus, alumina hydrate, antimony trioxide, arsenic oxide, ammonium polyphosphate, and calcium sulfate, expandable graphite, and cyanuric acid derivatives such as melamine, and mixtures of at least two flame retardants such as ammonium polyphosphate and melamine, and also optionally corn starch or ammonium polyphosphate, melamine, and expandable graphite; aromatic polyesters can also be optionally used for this purpose.

[0035] Preferred flame retardants do not contain any bromine. Particularly preferred flame retardants are composed of atoms selected from the group consisting of carbon, hydrogen, phosphorus, nitrogen, oxygen, and chlorine, and more particularly selected from the group consisting of carbon, hydrogen, phosphorus, and chlorine.

[0036] Preferred flame retardants do not contain groups that are reactive towards isocyanate groups. Preferably, the flame retardant is a liquid at room temperature. Particularly preferred are DEEP, TEP, DMPP, and DPC.

[0037] Since flame retardants, especially liquid flame retardants, tend to cause emissions of volatile organic compounds, it is necessary to use less than 1% by weight, preferably 0% to 0.5% by weight, based on the total weight of compounds (b) to (f) respectively. More preferably, flame retardant (e) does not contain tris(2-chloropropyl) phosphate (TCPP), and particularly preferably, phosphorus-containing flame retardants are not used.

[0038] Optionally, additional auxiliaries and / or additives (f) can also be added to the reaction mixture for producing the polyurethane foams according to the invention. By way of example, surface-active substances, foam stabilizers, cell regulators, fillers, light stabilizers, dyes, pigments, hydrolysis stabilizers, and substances having a fungistatic and bacteriostatic action, as well as antioxidants, can be mentioned. Such substances are known and are described, for example, in "The Polyurethane Handbook", Hanser Publishers Munich, 2nd Edition 1993, Chapters 3.4.4 and 3.4.6 to 3.4.11.

[0039] Examples of surface-active substances which can be used are compounds which support the homogenization of the starting materials and which are optionally also suitable for regulating the cell structure of the plastics. By way of example, emulsifiers such as sodium salts of castor oil sulfate and sodium salts of fatty acids, and salts of fatty acids with amines such as diethylamine oleate, diethanolamine stearate, diethanolamine ricinoleate, sulfonates such as alkali metal salts or ammonium salts of dodecylbenzene- or dinaphthylmethanedisulfonic acid and ricinoleic acid; foam stabilizers such as siloxane-alkylene oxide copolymers and other organopolysiloxanes, ethoxylated alkylphenols, ethoxylated fatty alcohols, paraffin oil, castor oil esters or ricinoleic acid esters, Turkey red oil and peanut oil, and cell regulators such as paraffin, fatty alcohols and dimethylpolysiloxane. Other materials which are suitable for improving the emulsification and the cell structure and / or the foam stabilization are the abovementioned low molecular weight polyacrylates having polyalkylene oxide moieties and fluoroalkane moieties as side groups. The amount of surface-active substances is generally from 0.01 to 10 parts by weight, based on 100 parts by weight of component (b).

[0040] The foam stabilizers used can include conventional foam stabilizers, such as those based on siloxanes, examples being siloxane-alkylene oxide copolymers and other organopolysiloxanes and / or ethoxylated alkylphenols and / or ethoxylated fatty alcohols.

[0041] The light stabilizers used may include light stabilizers known in polyurethane chemistry. These light stabilizers include phenolic stabilizers such as 3,5-di-tert-butyl-4-hydroxytoluene and / or Irganox products from BASF; phosphites such as triphenyl phosphite and / or tris(nonylphenyl) phosphite; ultraviolet (UV) absorbers such as 2-(2-hydroxy-5-methylphenyl) benzotriazole, 2-(5-chloro-2H-benzotriazol-2-yl)-6-(1,1-dimethylethyl)-4-methylphenol, branched and straight-chain 2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methylphenol, and 2,2'-(2,5-thiophenediyl) bis[5-tert-butylbenzoxazole]; and also those known as HALS stabilizers (hindered amine light stabilizers) such as bis(1-octyloxy-2,2,6,6-tetramethyl-4-piperidyl) sebacate, n-butyl-(3,5-di-tert-butyl-4-hydroxybenzyl) bis(1,2,2,6-pentamethyl-4-piperidyl) malonate, and the polymer of diethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol.

[0042] Examples of antioxidants are phenolic substances such as 2,6-di-tert-butyl-4-methylphenol, benzenepropanolic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy-C7-C9 branched alkyl esters; aminic antioxidants such as N,N'-diisopropyl-p-phenylenediamine; thio synergists such as dilauryl 5-thiodipropionate; phosphites and phosphonites such as triphenyl phosphite, diphenylalkyl phosphite, benzofuranone and indolinone; other antioxidants such as O-benzyl compounds, N-benzyl compounds and S-benzyl compounds, triazine compounds, amides of β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid, esters of substituted and unsubstituted benzoic acids, nickel compounds and esters of β-1,10-thiodipropionic acid or mixtures of two or more of these antioxidants. Such antioxidants are described, for example, in WO2017125291 and are commercially available, for example, under the trade names Irganox1076, Irganox 245, Irganox2000, Irganox E201 (vitamin E), Irganox5057 or Irgafos 38.

[0043] The term filler, in particular reinforcing filler, means conventional organic and inorganic fillers, reinforcing agents, weighting agents, and agents for improving the abrasion properties in paints, coating compositions, etc., which are known per se. Individual examples which may be mentioned are: inorganic fillers such as silicate minerals, for example phyllosilicates such as antigorite, serpentine, amphibole, tremolite, chrysotile asbestos and talc; metal oxides such as kaolin, alumina, titanium oxide and iron oxide; metal salts such as chalk, barite; and inorganic pigments such as cadmium sulfide and zinc sulfide; and also glass, etc. Preference is given to using kaolin (china clay), aluminum silicate and coprecipitates of barium sulfate and aluminum silicate, and also natural and synthetic fibrous minerals such as wollastonite, and fibers of various lengths made of metal and in particular glass; these may optionally be sized. Examples of organic fillers which may be used are: carbon, melamine, rosin, cyclopentadienyl resins and graft polymers, and also cellulose fibers, polyamide fibers, polyacrylonitrile fibers, polyurethane fibers and polyester fibers derived from aromatic and / or aliphatic dicarboxylic esters, and in particular carbon fibers.

[0044] The inorganic and organic fillers can be used alone or in the form of a mixture, and the amount of these fillers added to the reaction mixture is advantageously from 0.5% by weight to 50% by weight, preferably from 1% by weight to 40% by weight, based on the weight of components (a) to (f), although the content of mats, nonwovens and woven fabrics made of natural and synthetic fibers can be up to 80% by weight based on the weight of components (a) to (f).

[0045] The production of the polyurethanes according to the invention generally comprises mixing (a) a polyisocyanate, (b) a polymeric compound having isocyanate-reactive groups, (c) a catalyst and optionally (d) a blowing agent, (e) a chain extender and / or crosslinker and (f) auxiliaries and / or additives to provide a reaction mixture, and reacting the reaction mixture to provide a polyurethane. For the purposes of the present invention, the expression reaction mixture here means a mixture of the isocyanate (a) and the compound (b) which is reactive towards the isocyanate when the conversion of the reaction is less than 90% based on the isocyanate groups.

[0046] Preferably, a two-component method is used, in which all starting materials (a) to (f) are present in the isocyanate component (A) or in the polyol component (B). Preferably, all substances reactive with isocyanate are added to the polyol component (B), while starting materials that are not reactive towards isocyanate can be added to the isocyanate component (A) or to the polyol component (B). Particularly preferably, the additives added to the isocyanate component (A) are only those that do not carry functional groups reactive with the NCO functional groups of the isocyanate, i.e., the only additives used are those that are inert with respect to the isocyanate. The isocyanate component (A) and the polyol component (B) are mixed to form a reaction mixture. In a preferred embodiment, an isocyanate component (A) containing polyisocyanate (a) and a polyol component (B) containing a compound (b) having at least two hydrogen atoms reactive towards isocyanate groups, a catalyst (c), and a blowing agent (d) are produced, and then the isocyanate component (A) and the polyol component (B) are mixed to obtain the reaction mixture. The polyol component and the isocyanate component preferably react in a weight ratio of 90 to 150 parts by weight of the isocyanate component (A) to 100 parts by weight of the polyol component (B), more preferably 100 to 120 parts by weight of the isocyanate component (A) to 100 parts by weight of the polyol component (B), and particularly preferably 110 to 125 parts by weight of the isocyanate component (A) to 100 parts by weight of the polyol component (B).

[0047] Component (a) to component (c) and optionally component (d) to (f) react in an amount such that the equivalent ratio of the NCO groups of polyisocyanate (a) to the sum of the reactive hydrogen atoms of component (b), component (c), component (d) and optionally component (e) and component (f) is preferably 0.2 to 1.5:1, more preferably 0.25 to 0.8:1, and particularly preferably 0.28 to 0.5:1. A ratio of 1:1 corresponds to an isocyanate index of 100 herein.

[0048] The isocyanate component (A) and the polyol component (B) are storage-stable and can generally be stored at room temperature for several months. After storage, it may be necessary to homogenize component (A) and / or component (B). In a preferred embodiment, the polyol component (B) has a viscosity of 50 mPas to 800 mPas at 25 °C, more preferably 150 mPas to 600 mPas, and particularly preferably 210 mPas to 550 mPas.

[0049] In a preferred embodiment, the reaction proceeds in such a way that the drawing time is from 7 seconds to 15 seconds, more preferably from 8 seconds to 12 seconds, and the tack-free time is preferably from 10 seconds to 30 seconds, more preferably from 11 seconds to 22 seconds, and particularly preferably from 12 seconds to 16 seconds. This allows spraying on the walls and above the head without the reaction mixture dripping. Additionally, the polyol component is non-corrosive.

[0050] The polyurethane foam obtained by the method according to the invention has a low density, good mechanical properties and low emissions of volatile organic compounds, and in particular no 1,2-dichloropropane emissions. In a preferred embodiment, the emissions of volatile organic compounds VOC according to international standards ISO 16000-3-6-9-11 and EN 16516 are less than 10 mg / m³ of air 3 days after foam production and less than 1 mg / m³ of air 28 days after foam production. The method according to the invention allows spraying on various substrates such as stone, wood, concrete or fibers.

[0051] The following examples are used to explain the invention.

[0052] The following parameters are measured:

[0053] Opalescent time :

[0054] The cream time is measured as the time between the start of mixing and the start of volume expansion of the mixture. The cream time is measured according to Appendix E of European standard EN 14315-1.

[0055] Drawing time

[0056] The drawing time (also known as the gel time) is measured as the interval between mixing and the moment when a thread can be withdrawn from the reaction mixture. The gel time is measured according to Appendix E of European standard EN 14315-1.

[0057] Debonding time

[0058] The tack-free time is measured as the interval between mixing and the moment when the upper surface of the foam is no longer sticky. The tack-free time is measured according to Appendix E of European standard EN 14315-1.

[0059] Total free foam density

[0060] The total free foam density is measured by using the procedure for determining the core-shell density and taking foam samples from the middle of the sample (all skins from the base to the surface). These samples are weighed and their volume is measured, and then these values are used to calculate the density. The total free foam shell density is measured according to Appendix C of European standard EN 14315-2.

[0061] The following substances were used to produce the examples:

[0062] Polyol 1: A polyether polyol starting from a mixture of sucrose and glycerol as starting molecules and propylene oxide with a hydroxyl value of 490 mg KOH / g

[0063] Polyol 2: A polyether polyol starting from propylene glycol as the starting molecule and ethylene oxide and propylene oxide with a hydroxyl value of 30 mg KOH / g

[0064] Polyol 3: A polyether polyol starting from ethylenediamine as the starting molecule and propylene oxide with a hydroxyl value of 470 mg KOH / g

[0065] Polyol 4: A polyether polyol starting from diethylene glycol as the starting molecule and ethylene oxide with a hydroxyl value of 180 mg KOH / g

[0066] Polyol 5: A polyether polyol starting from propylene glycol as the starting molecule and propylene oxide with a hydroxyl value of 250 mg KOH / g

[0067] Catalyst 1: Tri-(dimethylaminopropyl)amine

[0068] Catalyst 2: Pentamethyldiethylenetriamine (PMDETA)

[0069] Catalyst 3: Diethyltoluenediamine (DETDA)

[0070] Catalyst 4: 2-[(2-[2-(dimethylamino)ethoxy]ethyl)methylamino]ethanol, from Huntsman ZF-10

[0071] Catalyst 5: N,N,N'-trimethylaminoethyl ethanolamine from BASF

[0072] Catalyst 6: A mixture of 3-(dimethylamino)propylurea and 1,3-bis[3-(dimethylamino)propyl]urea (Dabco NE 1070 from Evonik)

[0073] Surfactant 1: A silicone surfactant, Tegostab B from Evonik

[0074] Surfactant 2: Tall oil

[0075] Flame retardant 1 (FR1): Tris(2-chloropropyl) phosphate (TCPP)

[0076] Flame retardant 2 (FR2): Triethyl phosphate

[0077] Isocyanate: having a viscosity of about 210 mPa*s at 25°C M20 S (polymeric methylene diphenyl diisocyanate (PMDI)

[0078] Production method

[0079] The polyol component (B) and the isocyanate component (A) are produced as disclosed in Table 1. All amounts are given in parts by weight, based on the polyol component or the isocyanate component, respectively. The components are thoroughly mixed and then foamed by the following method. The components are foamed by thoroughly mixing the polyol component.

[0080] Table 1

[0081]

[0082] Table 2

[0083]

[0084] Examples 1 to 4 are comparative examples. According to the international standards ISO 16000-3-6-9-11, the emissions of 1,2-dichloropropane (1,2-DCP) and the catalyst are measured after 28 days by the following method: placing the foam sample of each example in a stainless steel test chamber for volatile organic compounds (VOC), extracting air samples from the outlet of the test chamber after the specified storage duration, and analyzing these air samples using gas chromatography and mass spectrometry.

[0085] The LCI value is a health-based reference concentration for volatile organic compounds for inhalation exposure, which is used to assess the emissions from a single product during the laboratory test chamber process after 28 days. The LCI value should be applied to product safety assessment, where the ultimate goal is to avoid health risks from long-term exposure of the general population. They are usually expressed as μg / m 3 .

[0086] Examples 5 and 6 produce foams without 1,2-DCP, which have a very low density and low emissions of volatile organic compounds below the lowest concentration of interest (LCI). In addition, compared with Example 5, the emissions of the foam according to Example 6 have even lower emissions of amine-based compounds. The polyol components according to Examples 5 and 6 of the present invention have low viscosity, are easy to process and are not classified as dangerous goods.

Claims

1. A method for producing polyurethane foam with a density of 5 g / dm 3 to 20 g / dm 3 is carried out by mixing the following substances to obtain a reaction mixture: (a) Polyisocyanate containing PMDI (b) A compound having at least two hydrogen atoms reactive with isocyanate groups, the compound comprising (b1) at least one polyether polyol obtained by alkoxylation of a difunctional or trifunctional starting molecule having a hydroxyl value of 210 mg KOH / g to 400 mg KOH / g and (b2) at least one polyether polyol obtained by alkoxylation of an aliphatic diamine (c) A catalyst, the catalyst comprising (c1) at least one incorporable amine catalyst (d) A blowing agent, the blowing agent comprising water (e) Optional flame retardant (f) Optional auxiliaries and additional substances Spray the reaction mixture onto a substrate and harden the reaction mixture to obtain the polyurethane foam wherein the reaction mixture contains less than 1 part by weight of a phosphorus-containing flame retardant 2. The method according to claim 1, wherein an isocyanate component (A) containing polyisocyanate (a) and a polyol component (B) containing a compound (b) having at least two hydrogen atoms reactive with isocyanate groups, a catalyst (c) and a blowing agent (d) are produced, and then the isocyanate component (A) and the polyol component (B) are mixed to obtain the reaction mixture 3. The method according to claim 1 or 2, wherein in addition to the at least one incorporable amine catalyst (c1), the catalyst (c) further comprises at least one catalyst (c2) containing a urea structure 4. The method according to any one of claims 1 to 3, wherein in addition to the catalyst (c2) containing a urea structure, the content of the catalyst (c) is less than 8% by weight based on the total weight of compounds (b) to (f) 5. The method according to any one of claims 1 to 4, wherein the isocyanate and the isocyanate-reactive compound are mixed at an isocyanate index of 25 to 80 6. The method according to any one of claims 1 to 5, wherein water is used in an amount of 10% to 30% by weight based on the total weight of compounds (b) to (f) 7. The method according to any one of claims 1 to 6, wherein the compound (b) having at least two hydrogen atoms reactive with isocyanate groups comprises at least one chain extender (b3) based on an aliphatic or aromatic diamine 8. The method according to any one of claims 1 to 7, wherein the compound (b) having at least two hydrogen atoms reactive with isocyanate groups comprises at least one polyether polyol (b4) obtained by alkoxylation of a difunctional or trifunctional starting molecule having a hydroxyl value of 20 mg KOH / g to 50 mg KOH / g 9. The method according to any one of claims 1 to 8, wherein the compound (b) having at least two hydrogen atoms reactive with isocyanate groups comprises at least one polyether polyol (b5) obtained by alkoxylation of a difunctional or trifunctional starting molecule having a hydroxyl value of 100 mg KOH / g to less than 210 mg KOH / g 10. The method according to any one of claims 1 to 9, wherein the compound (b) having at least two hydrogen atoms reactive toward isocyanate groups comprises 5% to 30% by weight of a polyol (b1), 5% to 30% by weight of a polyol (b2), 0.5% to 5% by weight of a chain extender (b3) based on an aliphatic or aromatic diamine, 30% to 60% by weight of a polyol (b4), and 5% to 30% by weight of a polyol (b5), each based on the total weight of the compound (b) having at least two hydrogen atoms reactive toward isocyanate groups.

11. The method according to any one of claims 1 to 10, wherein the viscosity of the polyol component (B) is from 50 mPa·s to 800 mPa·s.

12. The method according to any one of claims 1 to 11, wherein the drawing time is from 7 seconds to 15 seconds and the tack-free time is from 10 seconds to 30 seconds.

13. A polyurethane foam obtainable by the method according to any one of claims 1 to 12.

14. The polyurethane foam according to claim 13, wherein the total VOC emissions of volatile organic compounds are less than 1 mg / m according to the international standard ISO 16000-3-6-9-11 after 28 days 3 .

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