Polyurethane foam with flame-retardant properties

Abstract

The invention relates to a crosslinkable foamable polyurethane composition which is suitable for use as a polyurethane foam with flame-retardant properties, containing: - at least one isocyanate group-containing prepolymer, - at least one propellant, and - additives selected from foam stabilizers, catalysts, viscosity regulators, cell openers, flame retardants, non-reactive polymers, dyes or pigments, and / or UV stabilizers, wherein the polyurethane composition contains, in each case based on the total composition, a) between 0.05 and 2.0 wt.% of at least one cell opener, b) between 0.5 and 5 wt.% of at least one foam stabilizer, c) and optionally less than 5 wt.% of halogenated and / or phosphate ester-based flame retardants. The invention is characterized in that the cell opener is selected from unsaturated polyolefin oils, in particular polybutadienes, paraffin oils, silicone oils, or any mixtures thereof. The composition is suitable as an assembly foam with improved flame retardant properties while requiring only very low quantities of conventional flame-retardant additives or while not requiring any conventional flame-retardant additives at all, such as halogenated and / or phosphate ester-based flame retardants.

Description

[0001] POLYURETHANE FOAM WITH FLAME-RETARDANT PROPERTIES

[0002] Technical area

[0003] The invention relates to crosslinkable foamable polyurethane compositions and their use as assembly foams or foam adhesives, as well as aerosol cans containing these compositions.

[0004] State of the art

[0005] Crosslinkable, foamable polyurethane compositions based on prepolymers containing isocyanate groups are widely used, for example, for the production of assembly and insulation foams in the construction industry or in industrial manufacturing. They rely on the ability of prepolymers containing isocyanate groups to solidify into a solid foam and, when extruded from a pressurized container with the aid of blowing agents, bond components together or fill cavities with insulation. Such foam compositions are characterized by good adhesion to a wide variety of substrates, but their adhesive properties are not optimized. Their adhesive properties are based partly on simple adhesion, but also on the ability of the foam composition to reactively bond to substrates containing activated hydrogen atoms.This is often the case with building materials of mineral, biological or synthetic origin.

[0006] Such foam compositions are known as single-component (1K) and two-component (2K) systems. Single-component systems cure with the aid of ambient moisture, such as atmospheric humidity, or, if necessary, with the aid of subsequently added water. 2K systems require a second component, which is usually contained in the pressurized container in the form of a separate crosslinker and requires activation by the user. The crosslinkable, foamable polyurethane compositions according to the invention utilize this principle, primarily being single-component systems in pressurized containers. Single-component polyurethane foams (1K foams) have been known for a long time and are primarily used for sealing and insulating joints in construction and for DIY projects.In such applications, the foam product is applied from an aerosol can (so-called OCF foams) and used, for example, for the installation of door and window frames in buildings.

[0007] Polyurethane-based foams used in construction or industry are subject to specific fire protection regulations in many countries. They must therefore exhibit sufficient flame-retardant properties and, depending on the application, meet the required standard fire behavior requirements. For polyurethane foams, for example, this is defined and classified by the industrial standard DIN 4102 "Fire behavior of building materials and components" or, at the European level, by DIN EN 13501. Depending on the application, the polyurethane foams must meet certain fire classes according to the standard.

[0008] In addition, for many customers, good flame-retardant properties are an additional consideration from the perspective of production and storage safety. Therefore, achieving good and safe fire test results is very important.

[0009] The flame-retardant properties, or in other words, the flame resistance of polyurethane foams, are essentially achieved by the addition of flame retardants to the chemical composition. These are usually halogenated, i.e., brominated or chlorinated, plasticizers or polyols, such as chlorinated paraffins or halogenated polyether polyols. Also frequently used as flame retardants are organic, sometimes halogenated, phosphate esters. Like halogenated flame retardants, these esters are usually used in liquid form and can also act as plasticizers or thinners. However, all of these products generally have the disadvantage of being hazardous to the environment or health, and therefore require correspondingly increased occupational safety, disposal, and labeling requirements. Furthermore, they are very expensive compared to standard polyols or plasticizers.For these reasons, attempts are often made to use such additives only minimally, which, however, comes at the expense of the flame-retardant properties.

[0010] An example of a conventional polyurethane foam composition with application-appropriate flame-retardant properties is disclosed in WO 2011 / 113587 A2. It teaches the use of 5 to 15 wt.% trismonochloropropyl phosphate (TMCP) as a flame-retardant plasticizer, based on the total composition, and 4 to 12 wt.% additional flame retardants, particularly halogenated polyether polyols, to achieve good flame-retardant properties in the polyurethane foam. However, as described above, such amounts are disadvantageous with regard to the resulting unfavorable EHS properties of the formulation.

[0011] WO 2020 / 144004 A1 discloses a composition for producing rigid polyurethane foams containing hydrocarbons and polyether-modified siloxanes as special additives. This document also teaches the use of tris(2-chloroisopropyl) phosphate (TOPP) as a flame retardant.

[0012] The publication EP 2 706 074 A1 describes a low-monomer

[0013] A polyurethane foam composition is taught that contains TDI-based prepolymers, as well as, in the working examples, a silicone-based foam stabilizer and a fluorinated (PTFE-based) cell opener. TOPP is also taught as a flame retardant.

[0014] WO 99 / 51655 teaches a method for producing an open-cell polyurethane or polyisocyanurate foam for insulation applications. The examples disclose a composition comprising a siloxane-based surfactant, a silicone-based cell opener, and a flame retardant.

[0015] EP 0 581 191 A1 discloses an open-cell, rigid polyurethane foam, wherein in the examples a silicone-based foam stabilizer and calcium stearate are used as cell opener and the blowing agents investigated comprise fluorinated and / or chlorinated hydrocarbons.

[0016] US 5,998,067 A discloses a composition for an open-cell, rigid polyurethane foam which, in addition to silicone-based foam stabilizers and calcium stearate as a cell opener and other ingredients, contains perfluorohexane as a nucleating agent.

[0017] Therefore, there is a need for crosslinkable foamable polyurethane compositions that have sufficient flame-retardant properties to achieve the required industry standard classifications without the addition of conventional flame retardants and / or halogenated ingredients or additives in high amounts, while at the same time being able to be formulated in a cost-effective and environmentally friendly manner.

[0018] Description of the invention

[0019] The object of the present invention is to provide a novel, crosslinkable, foamable polyurethane composition which overcomes the disadvantages of the prior art and is suitable for use as a polyurethane foam with flame-retardant properties and can be formulated without or with only very little addition of conventional flame retardants, in particular halogenated plasticizers or polyols and organic phosphate esters, and can still achieve the required flame retardant properties for a required standard classification.

[0020] This object is achieved with a crosslinkable, foamable polyurethane composition as described in claim 1. By using between 0.05 and 2.0 wt. % of at least one cell opener, which is selected from unsaturated polyolefin oils, in particular polybutadienes, paraffin oils, silicone oils, and any mixtures thereof, between 0.5 and 5 wt. % of at least one foam stabilizer, and optionally less than 5 wt. % of halogenated and / or phosphate ester-based flame retardants in a conventional polyurethane foam composition, a foam product is obtained which has sufficiently high flame retardancy for at least a B2 classification according to DIN 4102-1, and which does not require any hazardous substance labeling due to EHS-critical conventional flame retardants.The crosslinkable foamable polyurethane composition according to the invention can also be formulated with a low monomer content and, in these embodiments, does not require any hazardous substance labeling with regard to the diisocyanate monomers it contains.

[0021] Further aspects of the invention are the subject of further independent claims. Particularly preferred embodiments of the invention are the subject of the dependent claims.

[0022] Ways to implement the invention

[0023] The invention relates to a crosslinkable foamable polyurethane composition suitable for use as polyurethane foam with flame-retardant properties, comprising:

[0024] - at least one prepolymer containing isocyanate groups,

[0025] - at least one propellant,

[0026] - and additives selected from foam stabilizers, catalysts, viscosity regulators, cell openers, flame retardants, non-reactive polymers, dyes or pigments, and / or UV stabilizers, wherein the polyurethane composition, in each case based on the total composition, a) between 0.05 and 2.0% by weight, preferably between 0.06 and 1.0% by weight, of at least one cell opener, b) between 0.5 and 5% by weight, preferably between 1.0 and 3.5% by weight, of at least one foam stabilizer, c) and optionally less than 5% by weight, preferably less than 3.5% by weight, of halogenated and / or phosphate ester-based flame retardants, characterized in that the cell opener is selected from unsaturated polyolefin oils, in particular polybutadienes, paraffin oils, silicone oils, and any mixtures thereof.

[0027] The term “molecular weight” refers to the molar mass (in grams per mole) of a molecule or a moiety of a molecule. The term “average molecular weight” refers to the number average molecular weight (M n ) a polydisperse mixture of oligomeric or polymeric molecules or molecular residues. It is determined by gel permeation chromatography (GPC) against polystyrene as a standard, particularly with tetrahydrofuran as the mobile phase, refractive index detector, and evaluation starting at 200 g / mol.

[0028] Substance names beginning with “poly” such as polymercaptan, polyaldehyde, polyisocyanate or polyol refer to substances that formally contain two or more of the functional groups mentioned in their name per molecule.

[0029] A composition is described as “storage-stable” if it can be stored at room temperature in a suitable container for a prolonged period, typically for at least 3 months up to 6 months or more, without its application or use properties being changed by storage to an extent relevant to its use.

[0030] A “monomeric diisocyanate” is an organic compound with two isocyanate groups separated by a divalent hydrocarbon radical with 4 to 15 carbon atoms.

[0031] "Aromatic" refers to an isocyanate group that is directly bonded to an aromatic carbon atom. Isocyanates with exclusively aromatic isocyanate groups are referred to as "aromatic isocyanates." A monomeric diisocyanate with aromatic isocyanate groups is referred to as "monomeric aromatic diisocyanate."

[0032] The "NCO content" refers to the content of isocyanate groups in weight percent. "Room temperature" refers to a temperature of 23 °C.

[0033] The "residual monomer content" of a prepolymer refers to the content of unreacted, excess diisocyanate after reaction of the initially present monomeric diisocyanate with at least one polyol in an excess of NCO groups relative to OH groups. The residual monomer content is preferably determined by HPLC (detection via photodiode array; 0.04 M sodium acetate / acetonitrile as the mobile phase) after prior derivatization with N-propyl-4-nitrobenzylamine.

[0034] All industry standards and norms mentioned in this document refer to the versions valid at the time of filing the initial application. Percentages by weight (wt%) refer to the mass fraction of a component of a composition or molecule relative to the entire composition or molecule, unless otherwise specified. The terms "mass" and "weight" are used synonymously in this document.

[0035] An essential component of the composition according to the invention are prepolymers containing isocyanate groups produced from the reaction of at least one polyol and at least one diisocyanate. These are NCO-reactive prepolymers, which in preferred embodiments are low in monomers. The term "low in monomers" here means that the prepolymers have a residual monomer content of less than 0.5% by weight, based on the prepolymer. The prepolymers contained in the composition according to the invention should also have a suitable viscosity so that they can be processed as a foam, while also preferably developing a sufficiently high initial strength for use as an assembly foam.

[0036] Suitable prepolymers can be prepared by reacting polyols with diisocyanates, with the polyols preferably having only a low degree of branching. The functionality, particularly individually or as a mixture, should be below 2.5, preferably below 2.3. In particular, essentially linear diols should be used. Monohydric alcohols should be avoided to maintain a network after crosslinking. The molar mass of the polyols can be determined individually; however, according to the invention, it is sufficient if the polymer mixture has a corresponding average molar mass.

[0037] In principle, all polyols used for polyurethane foams are suitable as polyols. In particular, essentially linear diols should be used. Polyester polyols and / or polyether polyols, especially polyether polyols, are preferably used for the production of the prepolymers. Examples of suitable prepolymers are those based on polyester polyols. These can be prepared by reacting polyester polyols with an excess of diisocyanates. Suitable polyester polyols are reaction products of polyfunctional, preferably difunctional alcohols, optionally together with small amounts of trifunctional alcohols, and polyfunctional, preferably difunctional and / or trifunctional carboxylic acids. Instead of free polycarboxylic acids, the corresponding polycarboxylic acid anhydrides or corresponding polycarboxylic acid esters with alcohols having preferably 1 to 3 carbon atoms can also be used.Diols suitable for producing such polyester polyols include, for example, ethylene glycol, 1,2- or 1,3-propanediol, 1,2- or 1,4-butanediol, pentanediol, the isomeric hexanediols, octanediol, 1,4-hydroxymethylcyclohexane, 2-methyl-1,3-propanediol, butanetriol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, dibutylene glycol, or polybutylene glycol. Aromatic diols can also be used.

[0038] The polycarboxylic acids used can be aliphatic, cycloaliphatic, aromatic, or heterocyclic, or both. They can optionally be substituted, for example by alkyl groups, alkenyl groups, or ether groups. Suitable polycarboxylic acids include, for example, succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, glutaric anhydride, maleic acid, maleic anhydride, fumaric acid, dicarboxylic fatty acid, or mixtures of two or more thereof. Suitable tricarboxylic acids, which can optionally be present in small amounts, include, for example, citric acid or trimellitic acid. All of the acids mentioned can be used individually or as mixtures of two or more thereof. Such OH-functional polyesters are known to the person skilled in the art, and they are commercially available.Polyester polyols containing three or, in particular, two terminal OH groups are particularly suitable. However, polyester polyols of oleochemical origin can also be used. Such polyester polyols can be produced, for example, by complete ring opening of epoxidized triglycerides of a fat mixture containing at least partially olefinically unsaturated fatty acids with one or more alcohols having 1 to 12 carbon atoms, followed by partial transesterification of the triglyceride derivatives to alkyl ester polyols containing 1 to 12 carbon atoms in the alkyl radical.

[0039] In one embodiment, suitable polyester polyols have an average molecular weight M n from 150 to 5,000 g / mol, especially 200 to 2,000 g / mol.

[0040] Polyester polyols that also contain a proportion of aromatic structures, such as aromatic carboxylic acids, are particularly suitable.

[0041] Further examples of suitable prepolymers are those based on polyether polyols. These are preferred and are produced, for example, by reacting polyether polyols with diisocyanates in stoichiometric excess.

[0042] Suitable polyether polyols are, for example, reaction products of low-molecular-weight polyfunctional alcohols with alkylene oxides. The alkylene oxides preferably have 2 to 4 carbon atoms. Suitable polyols include, for example, the reaction products of ethylene oxide, propylene oxide, butylene oxide, or mixtures thereof with aliphatic diols, such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, the isomeric butanediols, hexanediols, 2,2-dimethyl-1,3-propanediol, 2-methylpropanediol, 1,6-hexanediol, or aromatic diols. Furthermore, the reaction products of polyfunctional alcohols, such as glycerol, trimethylolethane or trimethylolpropane, pentaerythritol, or sugar alcohols, with the alkylene oxides may also be suitable. Other polyols suitable within the scope of the invention are formed by polymerizing tetrahydrofuran (polytetrahydrofuran, polyTHF). The polyether polyols are prepared in a manner known to those skilled in the art and are commercially available.According to the invention, low molecular weight polyethers should preferably be selected, for example polyether polyols with an average molecular weight M. n from 150 to 5,000 g / mol, in particular up to 3,000, preferably 200 to 2,000 g / mol. Diols such as homopolymers of polyethylene glycol, propylene glycol, block or random copolymers of ethylene glycol and propylene glycol are particularly suitable.

[0043] Common aliphatic or aromatic diisocyanates are suitable isocyanates for the production of NCO-containing prepolymers. These preferably have a molecular weight below 500 g / mol.Suitable diisocyanates include, for example, ethylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,4-tetramethoxybutane diisocyanate, 1,5-pentamethylene diisocyanate, 1,6-hexamethylene diisocyanate (HDI), cyclobutane-1,3-diisocyanate, cyclohexane-1,3- and -1,4-diisocyanate, bis(2-isocyanatoethyl)fumarate, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate, IPDI), 2,4- and 2,6-hexahydrotoluene diisocyanate, hexahydro-1,3- or -1,4-phenylene diisocyanate, benzidine diisocyanate, naphthalene-1,5-diisocyanate, 1,6-diisocyanato-2,2,4-trimethylhexane, 1 ,6-Diisocyanato-2,4,4-trimethylhexane, xylylene diisocyanate (XDI), tetramethylxylylene diisocyanate (TMXDI), 1,3- and 1,4-phenylene diisocyanate, 2,4- or 2,6-tolylene diisocyanate (TDI) or isomer mixtures of TDI, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate or 4,4'-diphenylmethane diisocyanate (MDI) and their isomer mixtures.Furthermore, partially or fully hydrogenated cycloalkyl derivatives of MDI are used, for example fully hydrogenated MDI (H12-MDI), alkyl-substituted diphenylmethane diisocyanates, for example mono-, di-, tri- or tetraalkyldiphenylmethane diisocyanate and their partially or fully hydrogenated cycloalkyl derivatives.

[0044] Asymmetric isocyanates containing NCO groups with varying reactivity toward diols can also be used. Examples of suitable cycloaliphatic asymmetric diisocyanates include 1-isocyanatomethyl-3-isocyanato-1,5,5-trimethylcyclohexane (isophorone diisocyanate, IPDI), 1-methyl-2,4-diisocyanatocyclohexane, 1,4-diisocyanato-2,2,6-trimethylcyclohexane (TMCDI), or hydrogenation products of the aforementioned aromatic diisocyanates, for example, hydrogenated MDI in isomerically pure form, preferably hydrogenated 2,4'-MDI. Examples of preferred aromatic asymmetric diisocyanates are 1,3-phenylene diisocyanate, 2,4-tolylene diisocyanate (TDI), either in pure isomeric form or as a mixture of several isomers, naphthalene 1,5-diisocyanate (NDI), diphenylmethane 2,4'-diisocyanate (MDI), and mixtures of 4,4'-diphenylmethane diisocyanate with the 2,4'-MDI isomer. Aromatic diisocyanates are preferably used, especially 4,4'-MDI.

[0045] One embodiment uses asymmetric isocyanates. A preferred embodiment reacts the polyols individually or as a mixture with an excess of symmetric diisocyanates.

[0046] The amounts of polyol and diisocyanate are always chosen so that an NCO-terminated prepolymer is obtained.

[0047] The prepolymer is obtained from the reaction of at least one monomeric diisocyanate and at least one polyol with an excess of isocyanate groups, in particular in an NCO / OH ratio of more than 2 / 1, preferably at least 3 / 1.

[0048] The NCO / OH ratio is preferably in the range of 3 / 1 to 10 / 1, particularly preferably in the range of 3 / 1 to 8 / 1, especially in the range of 4 / 1 to 7 / 1. A higher NCO / OH ratio leads to higher-quality prepolymers because less chain extension and lower polydispersity are achieved.

[0049] The reaction is preferably carried out in the absence of moisture at a temperature in the range from 20 to 160°C, in particular from 40 to 140°C, optionally in the presence of suitable catalysts.

[0050] The selected ratio of polyol to diisocyanate with respect to the NCO / OH ratio ensures that no significant increase in molecular weight (chain extension) of the prepolymers occurs. The resulting prepolymers, if based on diols, should contain between 1.7 and 2.3 NCO groups statistically, in particular two NCO groups per molecular chain. After the reaction, the monomeric diisocyanate remaining in the reaction mixture is preferably removed down to the desired residual content using a suitable separation process.

[0051] The preferred separation process is a distillative process, in particular thin-film distillation or short-path distillation, preferably under vacuum.

[0052] Particularly preferred is a multi-stage process in which the monomeric diisocyanate is removed in a short-path evaporator at a jacket temperature in the range of 120 to 200°C and a pressure of 0.001 to 0.5 mbar.

[0053] In the case of 4,4'-MDI, the preferred monomeric aromatic diisocyanate, distillative removal is particularly challenging. For example, care must be taken to prevent the condensate from solidifying and clogging the system.

[0054] Preferably, the reaction is carried out at a jacket temperature in the range of 160 to 200°C at 0.001 to 0.5 mbar and the removed monomer is condensed at a temperature in the range of 40 to 60°C.

[0055] Preferably, the reaction of the monomeric diisocyanate with the polyol and the subsequent removal of the majority of the monomeric diisocyanate remaining in the reaction mixture takes place without the use of solvents or entraining agents.

[0056] Preferably, the monomeric diisocyanate removed after the reaction is subsequently reused, i.e. used again for the production of prepolymer containing isocyanate groups.

[0057] The prepolymer thus produced preferably has a viscosity at 20°C of at most 50 Pa s, in particular at most 40 Pa s, particularly preferably at most 30 Pa s. The viscosity is determined using a cone-plate viscometer with a cone diameter of 25 mm, cone angle of 1 °, cone tip-plate distance of 0.05 mm at a shear rate of 10 s' 1 .

[0058] However, the reaction of the monomeric diisocyanates with the polyols can also take place in situ, i.e., during formulation, for example, in a pressurized container. For this purpose, the polyol is initially introduced and the diisocyanate is added, forming the prepolymer, particularly in the presence of a catalyst. This can take place at room temperature or with suitable, gentle heating.

[0059] The content of prepolymer in the composition according to the invention is in particular between 60 and 80 wt.%, preferably between 65 and 75 wt.%, based on the total composition.

[0060] Even in cases where the composition uses prepolymers that contain a smaller amount of monomeric isocyanates, it may be advantageous to additionally add non-volatile oligomeric isocyanate derivatives. These can be, for example, aliphatic or aromatic isocyanurates, allophanates, and biurets. Polymeric aromatic isocyanates such as p-MDI can also be used. These oligomeric isocyanate derivatives should preferably be substances that exhibit a low vapor pressure at room temperature, for example, below 0.005 mbar at 25°C. These substances are therefore preferably essentially free of monomeric diisocyanates.

[0061] Furthermore, the composition according to the invention should also contain additives known in the field of polyurethane foams as foam precursors. Such additives are preferably present in the composition according to the invention in an amount of 1 to 20 wt. %, preferably 2 to 10 wt. %, based on the total composition. These can be, for example, plasticizers, stabilizers, adhesion promoters, dyes, fragrances, non-reactive polymers, catalysts, flame retardants, biocides, cell openers and similar additives, whereby cell openers and foam stabilizers must be present according to the invention. It is expedient to keep the proportion of constituents which have not reacted in the polymer, such as plasticizers or flame retardants, as low as possible. Volatile constituents, in particular solvents, should be avoided if possible. Plasticizers can contain up to 30 wt.-%, based on the total composition, preferably less than 5 wt.%, in particular no plasticizers.

[0062] A composition according to the invention can contain, in addition to the reactive prepolymers, up to 25 wt. % of further non-reactive polymers. These are preferably solid polymers that do not contain any functional groups crosslinkable with isocyanate groups. They should be homogeneously miscible with the prepolymers. These additional polymers can be used to influence properties of the crosslinked foam material, such as hardness, elasticity, moisture absorption, etc. Suitable polymers of this type include, for example, poly(meth)acrylates, non-reactive polyurethanes, vinyl acetate copolymers, polyesters, or aromatic block copolymers.

[0063] For the purposes of this invention, the term "stabilizers" refers in particular to antioxidants, UV stabilizers, hydrolysis stabilizers, or foam stabilizers. Examples of these are commercially available sterically hindered phenols and / or thioethers and / or substituted benzotriazoles and / or amines of the "HALS" type (hindered amine light stabilizer). It is preferred for the purposes of the present invention to use a UV stabilizer that bears a silyl group and is incorporated into the final product during crosslinking or curing. Furthermore, benzotriazoles, benzophenones, benzoates, cyanoacrylates, acrylates, or sterically hindered phenols can also be added.

[0064] The composition according to the invention contains at least one cell opener in an amount of between 0.05 and 2.0 wt.%, preferably between 0.06 and 1.0 wt.%, in particular between 0.07 and 0.5 wt.%, based on the total composition. The cell opener is selected from unsaturated polyolefin oils, in particular polybutadienes, paraffin oils, silicone oils, and any mixtures thereof. The cell opener is an essential component that, together with the foam stabilizer also present, contributes to the flame retardancy effect according to the invention.

[0065] Silicone oils, such as Tegiloxan® 100, are particularly preferred as cell openers. Paraffin oils are also preferred. Unsaturated polyolefin oils, especially polybutadienes, such as Lithene® N 5000, are also particularly preferred.

[0066] The composition according to the invention further contains at least one foam stabilizer in an amount of between 0.5 and 5 wt.%, preferably between 1.0 and 3.5 wt.%, in particular between 1.4 and 3.4 wt.%, based on the total composition.

[0067] Examples of suitable foam stabilizers include polyether siloxanes, such as copolymers of ethylene oxide and propylene oxide combined with a polydimethylsiloxane radical, polysiloxane-polyoxyalkylene copolymers branched via allophanate groups, other organopolysiloxanes, such as dimethylpolysiloxanes, oxyethylated alkylphenols, oxyethylated fatty alcohols, and / or paraffin oils. Oligomeric polyacrylates with polyoxyalkylene and / or fluoroalkane radicals as side groups are also suitable for improving the emulsifying effect, the cell structure, and / or for stabilizing the cell structure. Mixtures of foam stabilizers can also be used with preference.

[0068] Preferred foam stabilizers are silicone polymers with polyether side chains, especially polydimethylsiloxane-polyether graft copolymers. These are available, for example, under the trade name Tegostab® from Evonik, especially Tegostab® 8870 and Tegostab® B 8871.

[0069] Preferably, the weight ratio of all cell openers contained to all foam stabilizers contained in the composition is between 0.015:1 and 0.3:1, preferably between 0.02:1 and 0.25:1, in particular between 0.03:1 and 0.2:1. This means that per gram of foam stabilizers in the composition, preferably between 0.015 and 0.3 grams of cell opener are contained in the composition, preferably between 0.02 and 0.25 grams, in particular between 0.03 and 0.2 grams. This ratio of cell opener to foam stabilizer leads to particularly good flame-retardant action.

[0070] A particularly preferred embodiment of the composition according to the invention contains: a) between 0.05 and 0.3% by weight, preferably between 0.1 and 0.2% by weight, of at least one cell opener, b) between 0.5 and 2.5% by weight, preferably between 1.2 and 2.0% by weight, of at least one foam stabilizer, c) and optionally less than 1.0% by weight, preferably less than 0.1% by weight, of halogenated and / or phosphate ester-based flame retardants, wherein the weight ratio of all cell openers contained to all foam stabilizers contained in the composition is in particular between 0.05:1 and 0.15:1.

[0071] This design is particularly EHS-friendly.

[0072] Another particularly preferred embodiment of the composition according to the invention contains: a) between 0.05 and 0.3% by weight, preferably between 0.1 and 0.2% by weight, of at least one cell opener, b) between 0.5 and 2.5% by weight, preferably between 1.2 and 2.0% by weight, of at least one foam stabilizer, c) and between 2.0 and 4.0% by weight, preferably between 2.5% by weight and 3.5% by weight of halogenated and / or phosphate ester-based flame retardants, wherein the weight ratio of all cell openers contained to all foam stabilizers contained in the composition is in particular between 0.05:1 and 0.15:1.

[0073] This embodiment is particularly flame-retardant. If necessary, organofunctional silanes such as hydroxyfunctional, (meth)acryloxyfunctional, mercaptofunctional, aminofunctional, or epoxyfunctional silanes can be used as adhesion promoters. The amounts can range from 0 to 10 wt.%, preferably between 0.5 and 5 wt.%, based on the total composition.

[0074] The composition according to the invention preferably contains at least one catalyst. All known compounds capable of catalyzing isocyanate reactions can be used as catalysts. Examples include titanates such as tetrabutyl titanate and tetrapropyl titanate, tin carboxylates such as dibutyltin dilaulate (DBTL), dibutyltin diacetate and tin octoate, tin oxides such as dibutyltin oxide and dioctyltin oxide, organoaluminum compounds such as aluminum trisacetylacetonate and aluminum trisethylacetoacetate, chelate compounds such as titanium tetraacetylacetonate, amine compounds such as triethylenediamine, guanidines, diphenylguanidine, 2,4,6-tris(dimethylaminomethyl)phenol, morpholine, N-methylmorpholine, 2-ethyl-4-methylimidazole, and 1,8-diazabicyclo-(5,4,0)-undecen-7 (DBU), 1,4-diazabicyclo[2,2,2]octane, N,N-dimethylpiperazine, 1,8-diazabicyclo[5.4.0]undec-7-ene, Dimorpholinodimethyl ether, dimorpholinodiethyl ether (DMDEE) or mixtures thereof.The catalysts are preferably used in an amount of 0.01 to about 5 wt.% based on the total weight of the composition.

[0075] In preferred embodiments, the composition according to the invention contains at least one catalyst in an amount between 0.1 and 5 wt.%, based on the total composition, preferably 2,2'-dimorpholinodiethyl ether.

[0076] The foamable composition according to the invention may also contain at least one, in particular liquid, flame retardant, although less than 5% by weight, preferably less than 3.5% by weight, of halogenated and / or phosphate ester-based flame retardants must be present. In particularly preferred embodiments, no halogenated and / or phosphate ester-based flame retardants are present. This means that the content of halogenated and / or phosphate ester-based flame retardants must be less than 0.1% by weight, in particular less than 0.01% by weight, based on the total composition, and most preferably is below the detection limit of analytical methods.

[0077] The flame retardant can, for example, be selected from the group of halogenated (in particular brominated) ethers or esters, organic phosphates, in particular diethyl ethanephosphonate, triethyl phosphate, dimethylpropylphosphonate, diphenyl cresyl phosphate, and chlorinated phosphates, in particular trismonochloropropyl phosphate, tris(2-chloroethyl)phosphate, tris(2-chloroisopropyl)phosphate, tris(1,3-dichloroisopropyl)phosphate, tris(2,3-dibromopropyl)phosphate and tetrakis(2-chloroethyl)ethylenediphosphate or mixtures thereof.

[0078] A preferred embodiment selects flame retardants that do not contain hydroxyl groups, as these can reduce the content of reactive NCO groups. The mixture preferably contains the flame retardant in an amount of less than 4 wt.%, preferably less than 3.5 wt.%.

[0079] In some embodiments, the composition contains an organic phosphate ester, in particular tris(2-chloroisopropyl)phosphate (TCPP) as a viscosity regulator and flame retardant, preferably in an amount of between 0.5 and 4.5 wt.%, based on the total composition.

[0080] In other preferred embodiments, the composition contains less than 1 wt.%, in particular less than 0.5 wt.%, preferably less than 0.1 wt.%, most preferably no halogenated and / or phosphate ester-based flame retardants.

[0081] A foamable composition according to the invention contains, in addition to the mixture of prepolymers and additives, at least one blowing agent. The blowing agent is preferably present in an amount of 10 to 50 wt.%, based on the total composition. In principle, a variety of highly volatile compounds that are volatile and capable of evaporation at the application temperature, for example, at 20°C, can be used as blowing agents. Blowing agents are preferably selected from hydrocarbons and / or fluorocarbons, each containing 1-5 carbon atoms, and / or ethers with a molecular weight below 120 g / mol, such as dimethyl ether (DME), diethyl ether, dimethoxymethane, dimethoxyethane, and mixtures thereof, for example a mixture of DME / propane / isobutane / n-butane.

[0082] In a particular embodiment, it is advantageous to contain at least a portion of polar propellants. If desired, non-polar propellants can also be used. Non-polar propellants are understood to be the well-known highly volatile hydrocarbons which have 1 to 5 carbon atoms. Polar propellants are understood to be substances which have a considerable vapor pressure at 20°C and a polarity known to a chemically trained person skilled in the art. These are compounds which, in addition to hydrocarbon units, contain further heteroatoms, in particular oxygen, fluorine or chlorine. Examples of such compounds are dimethyl ether (DME), diethyl ether, dimethoxymethane, dimethoxyethane, 1,1-difluoroethane (R152a) or 1,1,1,2-tetrafluoroethane (R134a). Such polar propellants can be contained individually or in a mixture.

[0083] However, preferred embodiments do not contain any halogen-containing blowing agents.

[0084] The blowing agents are preferably used in amounts of 10 to 40 wt.%, preferably 15 to 35 wt.%, preferably between 20 and 30 wt.%, based on the total foamable mixture.

[0085] In particular, a high proportion of polar propellants can be advantageously used; for example, more than 25% of the amount of propellant is preferably present, especially more than 50%. DME and / or dimethoxymethane are very particularly preferred as the polar propellant. In particularly preferred embodiments, the propellant is selected from dimethyl ether, diethyl ether, dimethoxymethane, propane, butane, isobutane, and any mixtures of these propellants, with dimethyl ether preferably being present in an amount of at least 50% by weight, based on all propellants contained in the composition.

[0086] Some particularly preferred embodiments of the foamable composition according to the invention contain 60 to 80 wt.%, preferably 65 to 75 wt.% prepolymers, 0.05 to 0.5 wt.%, preferably 0.08 to 0.3 wt.% cell opener, 1.0 to 5.0 wt.%, preferably 1.5 to 3.5 wt.%

[0087] Foam stabilizers, 0.5 to 2.0 wt.%, preferably 1 to 1.5 wt.% catalysts, and 15 to 35 wt.%, preferably 20 to 30 wt.% blowing agent.

[0088] In the same further preferred embodiments, the composition contains less than 0.1 wt.% monomeric diisocyanates, based on the total composition. Such a composition is particularly advantageous in terms of occupational safety and user-friendliness.

[0089] In the same or other particularly preferred embodiments, the composition contains no halogen-containing substance at all in excess of 0.5 wt.%, based on the total composition. Even more preferred are those embodiments that contain no halogen-containing substances in excess of 0.1 wt.%, based on the total composition.

[0090] Through the simultaneous use of cell openers of the claimed type and in the claimed amounts, and foam stabilizers in the claimed amounts, a foamed composition according to the invention exhibits unexpectedly good flame-retardant properties after crosslinking, despite largely or completely omitting the use of halogenated and / or phosphate ester-based flame retardants, and in particular other halogen-containing ingredients. Thus, highly surprisingly, foamed and cured compositions according to the invention exhibit a previously unknown level of flame retardancy while simultaneously being formulated in an EHS-friendly and cost-effective manner.

[0091] The invention further provides a process for producing the foamable, crosslinkable compositions according to the invention. According to one embodiment of this process, a prepolymer is produced by reacting at least one polyol with a molar excess of monomeric diisocyanates. This excess should preferably comprise an NCO / OH ratio of more than 2 / 1. After the reaction, in preferred embodiments, the unreacted monomeric diisocyanate is removed, in particular distilled off, to a content of less than 0.5 wt.% based on the prepolymer, preferably less than 0.3 wt.%, in particular below 0.2 wt.%. In a particular embodiment, the prepolymer is virtually free of monomeric isocyanates, i.e., contains less than 0.1 wt.%. It is possible to reuse the distilled diisocyanate in the synthesis of the prepolymers.The isocyanates particularly suitable for this process are aromatic isocyanates, such as 2,4'- or 4,4'-MDI, or mixtures thereof. After reducing the monomers, the prepolymer can be filled into the packaging and mixed together with the other additives.

[0092] According to another embodiment of this process, the prepolymer is formed in situ in the composition after adding at least one polyol and an excess of at least one polyisocyanate. This preparation can take place directly in the container, e.g., in the pressurized container.

[0093] Afterwards, all other additives such as cell openers and foam stabilizers are added.

[0094] Furthermore, at least one propellant gas is added to this mixture. A mixture of polar and non-polar propellant gases is preferably used. This can be achieved by mixing the prepolymer / additive mixture with propellant gas, which is then filled into the appropriate disposable pressurized containers. It is also possible to add the prepolymers and additives individually to the appropriate container and then add the propellant gases. The components are mixed together in a known manner. The mixing of the components can also be assisted by heating, so that the processing steps proceed more quickly.

[0095] A further object of the present invention is a one-component aerosol pressure can (disposable pressure container) containing a foamable composition according to the invention.

[0096] To enable good processability of the mixture - especially the filling of the containers - the viscosity of the mixture with the non-volatile components (composition without propellant) is preferably in the range of 3,000 to 150,000 mPas (measured at 50°C). The mixtures, filled in disposable pressurized containers, are storage-stable for a period of at least 6 months, provided they are processed under anhydrous conditions. The composition according to the invention has a viscosity that enables good and easy application in the form of a spray application from a pressurized can. The applied composition foams. The foamable compositions according to the invention cure after dispensing from the aerosol can by reacting with the ambient air humidity to form fine-cell foams, so that the compositions are suitable for sealing, insulating and / or mounting, e.g.of joints, roof surfaces, windows and doors or for filling cavities.

[0097] A further subject of the present invention is therefore also the use of the composition according to the invention as an assembly foam with flame-retardant properties for foaming cavities, in particular for soundproofing and / or thermal insulation in buildings and / or vehicles, or as a foam adhesive composition with flame-retardant properties for bonding materials in the construction sector.

[0098] The foamable compositions according to the invention are particularly suitable for use as one-component canned foams. These are typically used as assembly or construction foams, i.e., they are filled into aerosol cans for production, storage, and transport, and are dispensed and foamed immediately upon use. The composition according to the invention makes it possible to produce isocyanate-reactive polyurethane foams that contain a low proportion of halogenated and / or phosphate ester-based flame retardants or no such additives at all, and in preferred embodiments, have a low monomer content while possessing good flame-retardant properties.

[0099] The compositions according to the invention exhibit sufficient viscosity to be foamable with known blowing agents. The foamable compositions according to the invention cure with the existing atmospheric humidity and produce small-cell, mechanically stable foams. Due to the low content of halogenated and / or phosphate ester-based flame retardants, and in preferred embodiments of monomeric isocyanates, increased requirements regarding environmental protection, occupational safety, and health protection are met. The technical application properties of the foamed materials are at least equivalent to those of known prior art.

[0100] Examples

[0101] The following are exemplary embodiments intended to explain the described invention in more detail.

[0102] Unless otherwise stated, the chemicals used were from Sigma-Aldrich Chemie GmbH.

[0103] Description of the measurement methods:

[0104] The content of monomeric diisocyanate was determined by HPLC (detection via photodiode array; 0.04 M sodium acetate / acetonitrile as mobile phase) after prior derivatization using N-propyl-4-nitrobenzylamine.

[0105] Flame height, as a measure of flame-retardant properties, was determined according to DIN 4102-1. Flame heights of up to 150 mm are considered acceptable. The lower the flame height, the better the flame-retardant properties. Production of prepolymers containing isocyanate groups:

[0106] Prepolymer P-1 :

[0107] A propylene glycol-initiated polyoxypropylene diol with an average molecular weight of 431 g / mol (Voranol® P 400, OH number 260 mg KOH / g, from Dow) was reacted with 4,4'-diphenylmethane diisocyanate (Desmodur® 44 MC L, from Covestro) with an NCO / OH ratio of 4 / 1 at 80 °C using a known method to form an NCO-terminated prepolymer. The volatile components, particularly unreacted 4,4'-diphenylmethane diisocyanate, were then removed by distillation in a short-path evaporator (jacket temperature 180 °C, pressure 0.1 to 0.005 mbar, condensation temperature 47 °C), yielding a prepolymer with a monomeric 4,4'-diphenylmethane diisocyanate content of 0.04 wt. %.

[0108] Production of the example compositions as one-component can foam

[0109] In each experiment, 2,2'-dimorpholinodiethyl ether (DMDEE) (Jeffcat® DMDLS) was added as a catalyst to the initial prepolymer (Prepolymer P-1) and, if necessary, trismonochloropropyl phosphate (TCPP), as well as, depending on the experiment, cell openers (Tegiloxan® 100 (polysiloxane oil); paraffin oil; or Lithene® N 5000 (polybutadiene oil)) and foam stabilizers (Tegostab® 8870 and Tegostab® B 8871).

[0110] A propellant mixture of propane, i-butane (2:1) and dimethyl ether was then added to this mixture. Filling into the pressurized cans takes place at elevated temperature.

[0111] The exact amounts of the components in each example experiment are given in Tables 1 to 3.

[0112]

[0113] Table 1: Example compositions S1 to S6 (all component quantities are in parts by weight) and flame height measurement results according to DIN 4102-1. * Non-inventive example (reference). Table 2: Example compositions S7 to S12 (all component quantities are in parts by weight) and measurement results of the flame height according to DIN 4102-1.

[0114]

[0115] Table 3: Example compositions S13 to S19 (all component amounts are in parts by weight) and flame height measurement results according to DIN 4102-1. * Non-inventive example (reference). The flame height results (Tables 1 to 3) surprisingly show that the inventive compositions have a significantly lower flame height and thus better flame-retardant properties than the non-inventive reference compositions. In particular, Example S1 and Examples S14 to S19, which do not contain halogenated and / or phosphate ester-based flame retardants, exhibit significantly improved flame retardancy compared to Reference Example S6. This is surprising in that S6 contains TCPP, a halogenated phosphate ester. The flame-retardant effect in Examples S1 and S14 to S19 is produced solely by the combination with cell openers and foam stabilizers as defined in claim 1.

[0116] Examples S7 to S12 and S14 to S19 show various further embodiments with partly even further improved flame-retardant properties (S9).

Claims

Patent claims: 1 . A crosslinkable foamable polyurethane composition suitable for use as a polyurethane foam with flame retardant properties, comprising: - at least one prepolymer containing isocyanate groups, - at least one propellant, - and additives selected from foam stabilizers, catalysts, viscosity regulators, cell openers, flame retardants, non-reactive polymers, dyes or pigments, and / or UV stabilizers, wherein the polyurethane composition, in each case based on the total composition, a) between 0.05 and 2.0 wt.%, preferably between 0.06 and 1.0 wt.%, of at least one cell opener, b) between 0.5 and 5 wt.%, preferably between 1.0 and 3.5 wt.%, of at least one foam stabilizer, c) and optionally less than 5 wt.%, preferably less than 3.5 wt.%, of halogenated and / or phosphate ester-based flame retardants; characterized in that the cell opener is selected from unsaturated polyolefin oils, in particular polybutadienes, paraffin oils, silicone oils, and any mixtures thereof.

2. Composition according to claim 1, characterized in that the composition does not contain halogenated and / or phosphate ester-based flame retardants.

3. Composition according to one of claims 1 or 2, characterized in that the foam stabilizer is a silicone polymer with polyether side chains, in particular a polydimethylsiloxane-polyether graft copolymer.

4. Composition according to one of claims 1 to 3, characterized in that at least one catalyst is present in an amount between 0.1 and 5 wt.%, based on the total composition, preferably 2,2'-dimorpholinodiethyl ether.

5. Composition according to one of claims 1 to 4, characterized in that the prepolymer is previously prepared from the reaction of at least one polyether and / or polyester polyol and at least one aromatic diisocyanate in an NCO / OH ratio of > 2 / 1, in particular of between 3 / 1 and 7 / 1, and subsequent removal of excess monomeric diisocyanate, so that the prepolymer after removal has a residual monomer content of less than 0.5% by weight, preferably less than 0.1% by weight, based on the prepolymer, wherein the residual monomer content is measured using the method mentioned in the description.

6. Composition according to one of claims 1 to 5, characterized in that the composition contains less than 0.1 wt.% of monomeric diisocyanates, based on the total composition.

7. Composition according to one of claims 1 to 6, characterized in that the content of prepolymer in the composition is between 60 and 80 wt.%, preferably between 65 and 75 wt.%, based on the total composition.

8. Composition according to one of claims 1 to 4 or 7, characterized in that the prepolymer in the composition is formed in situ after addition of at least one polyol and an excess of at least one polyisocyanate.

9. Composition according to one of claims 1 to 8, characterized in that the prepolymer is based on methylenediphenyl isocyanate (MDI), in particular diphenylmethane-4,4'-diisocyanate (4,4'-MDI).

10. Composition according to one of claims 1 to 9, characterized in that the weight ratio of all cell openers contained to all foam stabilizers contained in the composition is between 0.04:1 and 0.25:1, preferably between 0.05:1 and 0.20:1, in particular between 0.07:1 and 0.15:

1.

11. Composition according to one of claims 1 to 10, characterized in that the propellant is selected from dimethyl ether, diethyl ether, dimethoxymethane, propane, butane, isobutane and from any mixtures of these propellants, wherein dimethyl ether is preferably present in an amount of at least 50% by weight based on all propellants present in the composition.

12. Composition according to one of claims 1 to 11, characterized in that the content of propellant in the composition is between 15 and 35 wt.%, preferably between 20 and 30 wt.%, based on the total composition.

13. Composition according to one of claims 1 to 12, characterized in that the composition does not contain any halogen-containing substance with more than 0.5 wt.%, based on the total composition.

14. A one-component aerosol can containing the composition according to any one of claims 1 to 13.

15. Use of the composition according to any one of claims 1 to 13 as an assembly foam having flame-retardant properties for foaming cavities, in particular for soundproofing and / or thermal insulation in buildings and / or vehicles, or as a foam adhesive composition having flame-retardant properties for bonding materials in the construction sector.

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