Polyisocyanurate resin foam with high compressive strength, low thermal conductivity, and high surface quality

Abstract

The present invention relates to a method for producing rigid polyisocyanurate foams, in which (a) an aromatic polyisocyanate, (b) isocyanate-reactive compounds comprising at least one polyetherol (b1) and / or polyesterol (b2), wherein the number-average content of isocyanate-reactive hydrogen atoms of components (b1) and (b2) is at least 1.7, (c) a catalyst, (d) a blowing agent, (e) a flame retardant, (f) optional auxiliary substances and additives, and (g) an optional compound having an aliphatic hydrophobic group and not falling within the definition of compounds (a) to (f), are mixed to obtain a reaction mixture that can be cured to obtain rigid polyisocyanurate foams, wherein the blowing agent (d) has 2 to 5 carbon atoms, at least one The process comprises at least one aliphatic halogenated hydrocarbon compound (d1) consisting of hydrogen atoms and at least one fluorine and / or chlorine atom, wherein compound (d1) comprises a hydrocarbon compound (d2) having at least one carbon-carbon double bond and 4 to 8 carbon atoms, the molar proportion of halogenated hydrocarbon compound (d1) being 20 to 60 mol % and the molar proportion of hydrocarbon compound (d2) being 40 to 80 mol %, based in each case on the total content of blowing agents (d1) and (d2), components (b) to (f) having aliphatic hydrophobic groups, the content of said aliphatic hydrophobic groups being 4.0 mass % or less, based on the total content of components (b) to (g), and the mixing to obtain the reaction mixture is carried out at an isocyanate index of at least 240. The present invention further relates to rigid polyisocyanurate foams obtainable by the process according to the present invention.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a polyisocyanurate foam, comprising mixing (a) an aromatic polyisocyanate, (b) an isocyanate-reactive compound (comprising at least one polyetherol (b1) and / or polyesterol (b2)), wherein the number-average content of isocyanate-reactive hydrogen atoms of components (b1) and (b2) is at least 1.7, (c) a catalyst, (d) a blowing agent, (e) a flame retardant, (f) optionally auxiliary substances and additives, and (g) optionally a compound having an aliphatic hydrophobic group and not falling within the definitions of compounds (a) to (f), to obtain a reaction mixture, which is then cured to obtain a rigid polyisocyanurate foam, wherein the blowing agent (d) has 2 to 5 carbon atoms, at least one hydrogen atom and at least one fluorine atom, and and / or chlorine atoms, compound (d1) comprising a hydrocarbon compound (d2) having at least one carbon-carbon double bond and 4 to 8 carbon atoms, in which the molar proportion of halogenated hydrocarbon compound (d1) is 20 to 60 mol % and the molar proportion of hydrocarbon compound (d2) is between 40 and 80 mol %, based on the total content of blowing agents (d1) and (d2), respectively; components (b) to (f) may comprise a compound having an aliphatic hydrophobic group, the content of which is 4.0 mass % or less, based on the total content of components (b) to (g); and mixing to obtain the reaction mixture is carried out at an isocyanate index of at least 240. The present invention further relates to rigid polyisocyanurate foams obtainable by the process according to the present invention. [Background technology]

[0002] Rigid polyurethane or polyisocyanurate foams are often used as insulating materials for thermal insulation. These foams are particularly used in composite elements with at least one outer layer. The production of composite elements (often called sandwich elements) consisting of a metal outer layer and an isocyanate-based foam core (typically polyurethane (PUR) or polyisocyanurate (PIR) foam) on continuous double-belt lines is currently being carried out on a large scale. In addition to sandwich elements for the insulation of cold storage warehouses, elements for the facades of a wide variety of buildings or as roof elements are becoming increasingly important.

[0003] The essential requirements for polyurethane or polyisocyanurate foams are low thermal conductivity, good mechanical properties, and excellent flame retardancy. The insulating properties of closed-cell rigid foams depend on many factors, particularly the average cell size and the thermal conductivity of the cell gas. In the manufacture of sandwich elements, it is ideal for the foam surface to be free of defects, especially the underside of the foam.

[0004] Chlorofluorocarbons (CFCs) were once used in large quantities as physical blowing agents for the production of polyisocyanate-based rigid foams, particularly due to their very low thermal conductivity. Their stratospheric ozone depletion potential (ODP) has long been known, and therefore their use is no longer permitted under regulatory systems. Hydrochlorofluorocarbons (HCFCs), particularly R141b, were initially seen as promising alternatives to CFCs, but this class of substances also has ozone-depleting properties and their use has been banned. Alternative blowing agents with similarly low thermal conductivity, such as hydrofluorocarbons (HFCs), have virtually no ozone-depleting effects but are generally potent greenhouse gases and therefore have high GWPs (global warming potentials). Consequently, the use of HFCs as physical blowing agents for the production of polyurethane or polyisocyanurate foams is also disadvantageous.

[0005] Due to the above-mentioned disadvantages of CFCs and HFCs, hydrocarbons are now often used as physical blowing agents for the production of polyisocyanate-based rigid foams. Pentane isomers, which are frequently used as physical blowing agents in the continuous and discontinuous production of rigid foam composite components, are of central importance here. In the continuous production of polyurethane or polyisocyanurate sandwich components, the use of n-pentane as a physical blowing agent has become established over time, particularly for economic reasons.

[0006] To improve the processability of polyurethane or polyisocyanurate reaction mixtures in combination with hydrocarbons, polyol components have been developed by incorporating hydrophobic compounds into the polyol structure. For example, EP 2804886 describes the incorporation of fatty acid structures into polyester polyols. Thus, it is possible to use, for example, pure fatty acids or fatty acid derivatives (e.g., vegetable oils) as reactants in the production of polyester or polyether polyols. The fatty acid derivatives are incorporated into the resulting polyester polyols by transesterification during polycondensation. Another option for hydrophobizing polyester polyols is, for example, the use of dimeric fatty acids as units for polyester synthesis (EP 3140333) or the use of hydrophobic alkyl alcohols, such as nonylphenol, or fatty alcohols and their derivatives. EP 2820059 describes the production of such polyetherols by using a proportion of fatty acids or fatty acid derivatives in the starter component used for alkoxylation. In addition to incorporating hydrophobic structures into polyols, improved processability of hydrocarbon-blown polyurethane or polyisocyanurate-containing reaction mixtures can also be achieved by directly incorporating hydrophobic compounds, such as vegetable oils, fatty acids, fatty acid derivatives, or fatty alcohols, into the polyol component. Thus, for example, EP 1023351 describes the use of hydrophobic additives, such as carboxylic acids (especially fatty acids), carboxylic acid esters (especially fatty acid esters), and alkyl alcohols (especially fatty alcohols), in polyol resin mixtures for producing polyurethane- or polyisocyanurate-containing rigid foams. EP 3294786 describes the use of alkoxylated vegetable oils in polyol resin mixtures for producing rigid foams. EP 0742241 describes the use of hydrophobic compatibilizers, such as nonylphenol, to improve the processability of hydrocarbon-blown polyol components.

[0007] Although changing from n-pentane to the physical blowing agent cyclopentane allows for the production of rigid foams with low thermal conductivity from polyurethane or polyisocyanate reaction mixtures, changing to cyclopentane significantly reduces the mechanical properties of the foam, especially compressive strength and dimensional stability.

[0008] Switching from non-flammable CFCs and HFCs to flammable hydrocarbons requires a significant increase in the content of flame retardants in the reaction components to achieve comparable flame retardancy in rigid foams. Increasing the amount of flame retardant added is undesirable for ecotoxicological reasons. Hydrocarbons also have significantly higher thermal conductivities when compared directly with CFCs and HFCs, which similarly makes their use as physical blowing agents alone to produce rigid foams with improved thermal insulation properties unfavorable.

[0009] Non-flammable hydrofluoroolefins (HFOs), such as hydrofluoropropenes or hydrochlorofluoropropenes, are suitable candidates to replace HFCs due to their very low ODP and GWP and low thermal conductivity. Their use in reaction mixtures for producing closed-cell rigid polyurethane or polyisocyanurate foams has been described in many patent publications, including the following: EP 2154223, EP 2739676, EP 2513023, US 20180264303, US 9738768, US 2013 / 0149452, and US 20150322225.

[0010] Among HFO blowing agent compounds, 1-chloro-3,3,3-trifluoropropene [1233zd(E)] and 1,1,1,4,4,4-hexafluoro-2-butene [1336mzz(Z)] have recently gained commercial importance. One drawback of these blowing agents is that they significantly reduce the storage stability of the polyol component when stored together with certain amine catalysts and silicone-containing foam stabilizers. In the production of continuous sandwich elements, the storage stability problem can be overcome, for example, when the amine catalyst, foam stabilizer, or HFO blowing agent is metered into the reaction mixture as separate components; further options for improving storage stability include the use of certain catalysts and certain foam stabilizers.

[0011] In addition to storage stability drawbacks, the use of 1-chloro-3,3,3-trifluoropropene in particular, as well as cyclopentane, has been shown to result in reduced foam compressive strength. The use of excessive amounts of 1,1,1,4,4,4-hexafluoro-2-butene often results in reduced foam quality beneath the outer layer, especially in continuous double-belt processes.

[0012] Patent Document 14 (WO2019096763) describes a polyurethane foam sandwich element for thermal insulation and a method for producing the sandwich element. The blowing agent for producing the polyurethane foam contains cis-1,1,1,4,4,4-hexafluoro-2-butene (HFO-1336mzz-Z) and cyclopentane. The polyurethane foam composite panel according to the present invention has good thermal insulation performance and mechanical strength. Isocyanurate foams, especially foams with an isocyanate index greater than 220, are not disclosed.

[0013] Examples 1 and 2 of Patent Document 15 (WO2018218102) describe rigid polyurethane foams produced using potassium octoate (Dabco® K15), a flame retardant (TMCP), and HFO-1336mzz(Z) (cis-1,1,1,4,4,4-hexafluoro-2-butene) and cyclopentane in a molar ratio of 50:50 or 25:75. The polyol used is Stepanpol PS 2352, a hydrophobic polyesterol containing 7% by weight of fatty acid and 2.5% by weight of nonylphenol.

[0014] Polyisocyanurate foams are also known to be more fire resistant than polyurethane foams.

[0015] Patent Document 16 (WO2016184433) describes the production of polyurethane foam using potassium octoate, a flame retardant, and a mixture of HCFO-1233zd and cyclopentane in a molar ratio of approximately 35:65 in Sample 3 of Example 2. The polyol used was sugar-based polyetherol GR835G from Sinopec, with an OH value of 450 mg KOH / g, resulting in an isocyanate index of 210. [Prior art documents] [Patent documents]

[0016] [Patent Document 1] EP2804886 [Patent Document 2] EP3140333 [Patent Document 3] EP2820059 [Patent Document 4] EP1023351 [Patent Document 5] EP3294786 [Patent Document 6] EP0742241 [Patent Document 7] EP2154223 [Patent Document 8] EP2739676 [Patent Document 9] EP2513023 [Patent Document 10] US20180264303 [Patent Document 11] US9738768 [Patent Document 12] US2013 / 0149452 [Patent Document 13] US20150322225 [Patent Document 14] WO2019096763 [Patent Document 15] WO2018218102 [Patent Document 16] WO2016184433 Summary of the Invention [Problem to be solved by the invention]

[0017] The object of the present invention is therefore to improve the profile of the above-mentioned properties, and in particular to develop a new process which can be used to produce optimized rigid foams which have high flame retardancy, significantly reduced thermal conductivity and which, despite their improved insulating properties, exhibit very good mechanical compressive strength. A further object of the present invention is to develop a process which is particularly suitable for producing polyisocyanurate sandwich elements in a continuous production process, and which provides sandwich elements which have very low thermal conductivity, high compressive strength and high flame retardancy, as well as excellent foam surface quality, especially facing the lower outer layer.

[0018] This object is achieved by a method for producing rigid polyisocyanurate foams, comprising mixing (a) an aromatic polyisocyanate, (b) isocyanate-reactive compounds (comprising at least one polyetherol (b1) and / or polyesterol (b2)), wherein the number-average content of isocyanate-reactive hydrogen atoms of components (b1) and (b2) is at least 1.7, (c) a catalyst, (d) a blowing agent, (e) a flame retardant, (f) optionally auxiliary substances and additives, and (g) optionally a compound having an aliphatic hydrophobic group and not falling within the definition of compounds (a) to (f), to obtain a reaction mixture which is cured to obtain rigid polyisocyanurate foams, wherein the blowing agent (d) is a compound having 2 to 5 carbon atoms, at least one hydrogen atom and at least one fluorine atom. The process further relates to a rigid polyisocyanurate foam obtainable by the process according to the present invention. ... [Means for solving the problem]

[0019] Rigid polyisocyanurate foams are generally understood to mean foams containing both urethane and isocyanurate groups. In the context of the present invention, the term rigid polyurethane foams should also be understood to encompass rigid polyisocyanurate foams, the production of which is based on an isocyanate index of at least 180. The isocyanate index should be understood to mean the ratio of isocyanate groups to isocyanate-reactive groups multiplied by 100. An isocyanate index of 100 corresponds to an equimolar ratio of the isocyanate groups used in component (a) to the isocyanate-reactive groups of components (b) to (g).

[0020] The rigid polyisocyanurate films according to the invention exhibit a compressive stress at 10% compression of at least 80 kPa, preferably at least 120 kPa, particularly preferably at least 140 kPa. Furthermore, the isocyanate-based rigid foams have a closed cell content of more than 80%, preferably more than 90%, according to DIN ISO 4590. Further details regarding the rigid polyisocyanurate foams according to the invention can be found in "Kunststoffhandbuch, Vol. 7, Polyurethane", Carl Hanser Verlag, 3rd Edition 1993, Chapter 6, in particular Chapters 6.2.2 and 6.5.2.2.

[0021] It is essential to the present invention that components (b) to (g) contain from 0 to less than 4% by weight, i.e., 0 to 4% by weight, preferably 0 to 3.5% by weight, and in particular 0.1 to 3.0% by weight, of aliphatic hydrophobic groups, based on the total weight of components (b) to (g). In the context of the present invention, hydrophobic groups are understood to mean aliphatic hydrocarbon groups having preferably more than 6, particularly preferably more than 8, and less than 100, in particular at least 10, and at most 50, directly adjacent carbon atoms. Adjacent carbon atoms may be bonded not only by carbon-carbon single bonds, but also by carbon-carbon double bonds. The carbon atoms of the hydrophobic groups are directly bonded to each other and are not interrupted, for example, by heteroatoms. In contrast, hydrogen atoms of the hydrocarbons may be substituted, for example, by halogen atoms, OH groups, or carboxylic acid groups. Preferably, the hydrocarbons of the hydrophobic groups according to the present invention are unsubstituted.

[0022] When a compound having a hydrophobic group is used, it may be part of any of the compounds (b) to (f) or may be used as a separate compound (g) containing a hydrophobic group. To calculate the proportion of the hydrophobic group, only the mass of the hydrophobic group is used, and any substituents other than hydrogen, such as OH groups or halogen groups, are not taken into account in calculating the proportion.

[0023] The polyisocyanate (a) is an aromatic polyfunctional isocyanate known in the art. Such polyfunctional isocyanates are known and can be prepared by methods known per se. The polyfunctional isocyanates can also be used in the form of a mixture, in which case component (A) contains different polyfunctional isocyanates. The polyisocyanate (a) is a polyfunctional isocyanate having two (hereinafter also referred to as diisocyanate) or more than two isocyanate groups per molecule.

[0024] The isocyanate (a) is in particular selected from the group consisting of aromatic polyisocyanates, such as 2,4- and 2,6-toluene diisocyanate and corresponding isomer mixtures, 4,4'-, 2,4'- and 2,2'-diphenylmethane diisocyanate and corresponding isomer mixtures, mixtures of 4,4'- and 2,4'-diphenylmethane diisocyanate, polyphenylpolymethylene polyisocyanates, mixtures of 4,4'-, 2,4'- and 2,2'-diphenylmethane diisocyanate and polyphenylpolyethylene polyisocyanate (crude MDI), and mixtures of crude MDI and tolylene diisocyanate.

[0025] Particularly suitable are 2,2'-, 2,4'- or 4,4'-diphenylmethane diisocyanate (MDI) and mixtures of two or three of these isomers, 1,5-naphthylene diisocyanate (NDI), 2,4- and / or 2,6-toluene diisocyanate (TDI), 3,3'-dimethyldiphenyl diisocyanate, 1,2-diphenylethane diisocyanate and / or p-phenylene diisocyanate (PPDI).

[0026] Modified polyisocyanates, i.e., products obtained by chemical reaction of organic polyisocyanates and containing at least two reactive isocyanate groups per molecule, are also frequently used, including in particular polyisocyanates containing ester, urea, biuret, allophanate, carbodiimide, isocyanurate, uretdione, carbamate and / or urethane groups, often together with unconverted polyisocyanates.

[0027] The polyisocyanate of component (a) particularly preferably comprises 2,2'-MDI, 2,4'-MDI or 4,4'-MDI, or a mixture of at least two of these isocyanates (also known as monomeric diphenylmethane or MMDI), or oligomeric MDI consisting of higher homologs of MDI having at least three aromatic nuclei and a functionality of at least 3, or a mixture of two or more of the above diphenylmethane diisocyanates, or crude MDI obtained in the production of MDI, or preferably a mixture of at least one oligomer of MDI and at least one of the above low molecular weight MDI derivatives 2,2'-MDI, 2,4'-MDI or 4,4'-MDI (also called polymeric MDI). Isomers and homologs of MDI are generally obtained by distillation of crude MDI.

[0028] In addition to dinuclear MDI (MMDI), polymeric MDI also includes one or more polynuclear condensation products of MDI having a functionality of more than 2, particularly 3, 4, or 5. Polymeric MDI is known and is often referred to as polyphenylpolymethylene polyisocyanates.

[0029] The average functionality of the polyisocyanates containing polymeric MDI can vary from about 2.2 to about 4, particularly from 2.4 to 3.8, and especially from 2.6 to 3.0. Such mixtures of MDI-based polyfunctional isocyanates with different functionalities are in particular crude MDI, which is obtained as an intermediate product in the production of MDI.

[0030] Polyfunctional isocyanates or mixtures of two or more polyfunctional isocyanates based on MDI are known and are commercially available from BASF Polyurethanes GmbH under the trade names Lupranat® M20, Lupranat® M50, or Lupranat® M70.

[0031] Component (a) preferably comprises at least 70% by weight, particularly preferably at least 90% by weight, and in particular 100% by weight, of one or more isocyanates selected from the group consisting of 2,2'-MDI, 2,4'-MDI, 4,4'-MDI, and oligomers of MDI, based on the total weight of component (a). The content of oligomeric MDI is preferably at least 20% by weight, particularly preferably from more than 30% to less than 80% by weight, based on the total weight of component (a).

[0032] The viscosity of the component (a) used may vary over a wide range. Component (a) preferably has a viscosity of 100 to 3000 mPa at 25°C. * s, particularly preferably 100 to 1000 mPa * s, particularly preferably 100 to 800 mPa * s, particularly preferably 200 to 700 mPa * s, and particularly preferably 400 to 650 mPa * The viscosity of component (a) may vary over a wide range.

[0033] The isocyanate-reactive compound (b) used can be any compound having an isocyanate-reactive group known in polyurethane chemistry, preferably a compound having at least one hydroxyl group, -NH group, or NH group, or a carboxylic acid group, preferably at least one NH or OH group, particularly at least one OH group. The functionality relative to the isocyanate group can range from 1 to 8, preferably 2 to 8. Examples of the isocyanate-reactive compound include polyether polyol (b1), polyester polyol (b2), or a mixture thereof, preferably polyesterol (b2), or a mixture of polyetherol (b1) and polyesterol (b2). Polyetherol (b1) and polyesterol (b2) preferably have a number-average molecular weight of 150 to 15,000 g / mol, preferably 150 to 5,000 g / mol, particularly preferably 200 to 2,000 g / mol. In addition to the polyetherol and polyesterol, it is also possible to use low-molecular-weight chain extenders and / or crosslinkers known in polyurethane chemistry. Compound (b) preferably has a number average molecular weight of 62 to 15,000 g / mol. Compound (b) preferably has a number average functionality of at least 1.7, particularly preferably at least 2. According to the invention, polyetherols (b1) and / or polyesterols (b2) have a number average functionality of at least 1.7, more preferably at least 2.0.

[0034] Polyetherols (b1) are prepared, for example, from epoxides such as propylene oxide and / or ethylene oxide, or from tetrahydrofuran using catalysts and active hydrogen starter compounds, such as aliphatic alcohols, phenols, amines, carboxylic acids, water, and compounds based on natural substances such as sucrose, sorbitol, or mannitol. These may include basic catalysts or double metal cyanide catalysts, as described, for example, in PCT / EP2005 / 010124, EP90444, or WO05 / 090440.

[0035] The polyesterols (b2) are preferably prepared in the presence of an esterification catalyst from, for example, aliphatic or aromatic dicarboxylic acids and polyhydric alcohols, polythioether polyols, polyesteramides, hydroxyl-containing polyacetals and / or hydroxyl-containing aliphatic polycarbonates. Further possible polyols are cited, for example, in "Kunststoffhandbuch, Band 7, Polyurethane", Carl Hanser Verlag, 3rd Edition 1993, Chapter 3.1.

[0036] According to the present invention, the isocyanate-reactive compound (b) comprises a polyether polyol (b1) and / or a polyester polyol (b2), preferably a polyester polyol (b2), optionally in combination with the polyether polyol (b1). In each case, based on the total weight of the polyether polyol (b1) and the polyester polyol (b2), the mass fraction of the polyether polyol (b1) is preferably 0 to 30% by weight, particularly preferably 0 to 20% by weight, and in particular 1 to 15% by weight, and the mass fraction of the polyester polyol (b2) is preferably 70 to 100% by weight, particularly preferably 80 to 100% by weight, and in particular 85 to 99% by weight. In the context of the present disclosure, the terms "polyester polyol" and "polyester polyol" are synonymous, as are the terms "polyether polyol" and "polyether polyol".

[0037] Polyetherols (b1) can be obtained by known methods, for example, by anionic polymerization of alkylene oxides in the presence of a catalyst with the addition of at least one starter molecule containing 1 to 8, preferably 2 to 6, reactive hydrogen atoms in combined form, or a mixture of starter molecules, each containing an average of 1.5 to 8, preferably 2 to 6, reactive hydrogen atoms in combined form among all starters present. Fractional functionality can be achieved by using a mixture of starter molecules with different functionalities. The nominal functionality ignores the contribution of side reactions, for example. Usable catalysts include alkali metal hydroxides, such as sodium hydroxide or potassium hydroxide, or alkali metal alkoxides, such as sodium methoxide, sodium or potassium ethoxide, or potassium isopropoxide, or, in the case of cationic polymerization, Lewis acids, such as antimony pentachloride, boron trifluoride etherate, or fuller's earth. Amine alkoxylation catalysts, such as dimethylethanolamine (DMEOA), imidazole, and imidazole derivatives, can also be used. Usable catalysts also include double metal cyanide compounds such as the so-called DMC catalysts.

[0038] The alkylene oxide used is preferably one or more compounds having 2 to 4 carbon atoms in the alkylene radical, such as tetrahydrofuran, 1,2-propylene oxide, ethylene oxide, or 1,2- or 2,3-butylene oxide, in each case alone or in the form of a mixture. Preference is given to using ethylene oxide and / or 1,2-propylene oxide, particularly preferably ethylene oxide.

[0039] Possible starter molecules include hydroxyl or amine-containing compounds, such as ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, bisphenol A, bisphenol F, glycerol, trimethylolpropane, pentaerythritol, sugar derivatives such as sucrose, hexitol derivatives such as sorbitol, methylamine, ethylamine, isopropylamine, butylamine, benzylamine, aniline, toluidine, toluenediamine (TDA), Examples of suitable initiators include naphthylamine, ethylenediamine, methylenedianiline, 2,2'-diaminodiphenylmethane (2,2-MDA), 2,4'-diaminodiphenylmethane (2,4-MDA), 4,4'-diaminodiphenylmethane (4,4-MDA), diethylenetriamine, 4,4'-methylenedianiline, 1,3-propanediamine, 1,6-hexanediamine, ethanolamine, diethanolamine, triethanolamine, and other dihydric or polyhydric alcohols, monofunctional or polyfunctional amines, or water. Because highly functional compounds are often in solid form under conventional alkoxylation reaction conditions, it is common to carry out the alkoxylation of these compounds with a coinitiator. Examples of coinitiators include water, lower polyhydric alcohols such as glycerol, trimethylolpropane, pentaerythritol, diethylene glycol, ethylene glycol, propylene glycol, and their homologues. Further possible coinitiators include, for example: organic fatty acids or monofunctional fatty alcohols, fatty acid monoesters or fatty acid methyl esters, such as oleic acid, stearic acid, methyl oleate, methyl stearate or biodiesel, which serve to improve the solubility of the blowing agent during the production of rigid polyurethane foams.

[0040] Preferred starter molecules for the preparation of polyether polyols (b1) include sorbitol, sucrose, ethylenediamine, TDA, trimethylolpropane, pentaerythritol, glycerol, biodiesel, nonylphenol, ethylene glycol, and diethylene glycol. Further preferred starter molecules include all starters or starter mixtures having an average overall functionality of 3 or less, particularly preferably glycerol, trimethylolpropane, biodiesel, nonylphenol, ethylene glycol, diethylene glycol, propylene glycol, and bisphenol A, in particular ethylene glycol, diethylene glycol, and glycerol.

[0041] The polyether polyols used in the context of component (b1) preferably have an average functionality of 1.5 to 6, in particular 2.0 to 4.0, and a number average molecular weight of preferably 150 to 3000 g / mol, particularly preferably 150 to 1500 g / mol, in particular 250 to 800 g / mol. The OH number of the polyether polyols of component (b1) is preferably 1200 to 50 mg KOH / g, preferably 600 to 100 mg KOH / g, in particular 300 to 150 mg KOH / g.

[0042] Suitable polyester polyols (b2) can be prepared from mixtures of organic dicarboxylic acids having 2 to 12 carbon atoms, preferably aromatic, or aromatic and aliphatic dicarboxylic acids, and polyhydric alcohols, preferably diols, having 2 to 12 carbon atoms, preferably 2 to 6 carbon atoms.

[0043] The dicarboxylic acids used may include, inter alia, succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, maleic acid, fumaric acid, phthalic acid, isophthalic acid, and terephthalic acid. The dicarboxylic acids may be used alone or in mixtures. Instead of the free dicarboxylic acids, it is also possible to use corresponding dicarboxylic acid derivatives, such as dicarboxylic acid esters of alcohols having 1 to 4 carbon atoms or dicarboxylic acid anhydrides. The aromatic dicarboxylic acids or acid derivatives used preferably include phthalic acid, phthalic anhydride, terephthalic acid, and / or isophthalic acid, either alone or in mixtures. The aliphatic dicarboxylic acids used are preferably dicarboxylic acid mixtures of succinic acid, glutaric acid, and adipic acid, in a ratio of, for example, 20-35:35-50:20-32 parts by weight, particularly adipic acid. The polyesterol (b2) used is particularly preferably one obtained exclusively using aromatic dicarboxylic acids or their derivatives. The aromatic dicarboxylic acid preferably used is at least one compound selected from the group consisting of terephthalic acid, dimethyl terephthalate (DMT), polyethylene terephthalate (PET), phthalic acid, phthalic anhydride (PSA) and isophthalic acid, particularly preferably at least one compound from the group consisting of terephthalic acid, dimethyl terephthalate (DMT), polyethylene terephthalate (PET) and phthalic anhydride (PSA), in particular from the group consisting of phthalic acid and / or phthalic anhydride.

[0044] Examples of dihydric and polyhydric alcohols, especially diols, are monoethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, 1,2- or 1,3-propanediol, dipropylene glycol, polypropylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,10-decanediol, glycerol, trimethylolpropane, and pentaerythritol, as well as alkoxylates of the same starters. It is preferred to use monoethylene glycol, diethylene glycol, triethylene glycol, 1,2- or 1,3-propanediol, dipropylene glycol, and ethoxylates of the same starters, such as ethoxylated glycerol, or mixtures of at least one of the aforementioned diols. Particularly preferred are monoethylene glycol, diethylene glycol, glycerol, and ethoxylates of the same starters, or mixtures of at least two of the aforementioned diols, especially diethylene glycol. It is also possible to use polyester polyols derived from lactones, such as ε-caprolactone, or from hydroxycarboxylic acids, such as ω-hydroxycaproic acid.

[0045] The preparation of polyester polyols (b2) can involve polycondensation of aliphatic and aromatic polycarboxylic acids and / or derivatives with polyhydric alcohols in the absence of a catalyst or, preferably, in the presence of an esterification catalyst, advantageously in an atmosphere of an inert gas such as nitrogen in the melt, at temperatures between 150°C and 280°C, preferably between 180°C and 260°C, optionally under reduced pressure, until the desired acid number is reached, advantageously less than 10, but preferably less than 2. Suitable esterification catalysts are, for example, iron, cadmium, cobalt, lead, zinc, antimony, magnesium, titanium, and tin catalysts in the form of metals, metal oxides, or metal salts. However, polycondensation can also be carried out in the liquid phase in the presence of diluents and / or entrainers, such as benzene, toluene, xylene, or chlorobenzene, for azeotropic removal of the condensation water by distillation.

[0046] To prepare the polyester polyols (b2), the organic polycarboxylic acids and / or derivatives and the polyhydric alcohols are polycondensed advantageously in a molar ratio of 1:1 to 2.2, preferably 1:1.05 to 2.1, particularly preferably 1:1.1 to 2.0.

[0047] The resulting polyester polyol (b2) generally has a number average molecular weight of 200 to 3,000, preferably 300 to 1,000, and particularly 400 to 800.

[0048] When component (b) contains a compound having a hydrophobic group, the compound contains not only at least one hydrophobic group but also at least one isocyanate-reactive group (e.g., an acid group, an amino group, or a hydroxyl group). These components may be polyetherols (b1) or polyesterols (b2). Alternatively, or additionally, other compounds containing both one or more isocyanate-reactive groups and one or more hydrophobic groups can be used. When the hydrophobic group is a component of polyetherols (b1) or polyesterols (b2), it can be incorporated into polyols (b1) or (b2) by known reactions such as transesterification or alkoxylation. The starting compound having a hydrophobic group to be incorporated into polyols (b1) or (b2) generally has at least one group that can be esterified, transesterified, or alkoxylated, such as a carboxylic acid group, a carboxylic ester group, a carboxamide group, a carboxylic anhydride group, a hydroxyl group, or a primary or secondary amino group.

[0049] The compounds having hydrophobic groups of component (b) that do not fall within the definition of polyetherols (b1) or polyesterols (b2) are hydroxyl-functional hydrophobic substances such as alkyl alcohols, fatty alcohols, or hydroxyl-functional oleochemical compounds. Examples of such alkyl alcohols and fatty alcohols include octyl, nonyl, decyl, undecyl, dodecyl, oleyl, cetyl, isodecyl, tridecyl, lauryl, and mixed C12-C14 alcohols, 2-ethylhexanol, alkylphenols having more than 6 carbon atoms in the alkyl radical, such as nonylphenol, oxoalcohols having more than 6 carbon atoms obtained by hydroformylation and further reaction of α-olefins, Guerbet alcohols having more than 6 carbon atoms, and mixtures of different alkyl and fatty alcohols.

[0050] When using hydroxy-functional compounds with hydrophobic groups, it is preferable to use the following: castor oil, turmeric oil, oils modified with hydroxyl groups, such as grapeseed oil, black cumin oil, pumpkin seed oil, borage seed oil, soybean oil, wheat germ oil, rapeseed oil, sunflower oil, peanut oil, apricot kernel oil, pistachio kernel oil, almond oil, olive oil, macadamia nut oil, avocado oil, sea buckthorn oil, sesame oil, hazelnut oil, evening primrose oil, wild rose oil, hemp oil, safflower oil, walnut oil, fatty acid esters modified with hydroxyl groups and based on myristoleic acid, palmitoleic acid, oleic acid, vaccenic acid, petroselinic acid, gadoleic acid, erucic acid, nervonic acid, linoleic acid, linolenic acid, stearidonic acid, arachidonic acid, thymnodonic acid, clupanodonic acid or cervonic acid, or mixtures of at least two of these compounds.

[0051] Additional hydroxyl-functional oleochemical groups can be obtained by ring-opening of epoxidized fatty acid esters by simultaneous reaction with alcohols and, optionally, subsequent transesterification. The introduction of hydroxyl groups into fats and oils is primarily achieved by epoxidation of the olefinic double bonds contained in these products, followed by reaction of the resulting epoxy groups with monohydric or polyhydric alcohols. The epoxide ring then becomes a hydroxy group, or, in the case of polyfunctional alcohols, a structure with more OH groups. Since fats and oils are typically glycerol esters, the above reaction is accompanied by a parallel transesterification reaction. The resulting compounds preferably have a molecular weight in the range of 500 to 1500 g / mol.

[0052] The hydrophobic group-containing compound (b) containing an amine group should be understood to mean a compound having preferably between 7 and 40 carbon atoms, examples of which include aliphatic alkanolamines such as decylamine, dodecylamine, tetradecylamine and hexadecylamine.

[0053] Alkanolamides that can be used include, for example, fatty acid alkanolamides such as fatty acid diethanolamide, lauric acid diethanolamide, and oleic acid monoethanolamide.

[0054] As explained above, the hydrophobic group-containing compound (b) can also be understood to mean a compound having at least one carboxylic acid group, such as a monofunctional or difunctional carboxylic acid having 7 to 40 carbon atoms per molecule. Examples include dimeric fatty acids or, preferably, fatty acids. Examples of fatty acids are caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, ricinoleic acid, and mixtures thereof. The acid may be of biological or petrochemical origin. An example of a suitable petrochemical acid is, for example, 2-ethylhexanoic acid.

[0055] The oleochemical compound having hydroxyl functionality, if present, is further preferably a polyesterol (b2a) having hydrophobic groups. The preparation of the polyesterpolyol (b2a) having hydrophobic groups preferably uses, as hydrophobic starting compound, fatty acids, fatty acid derivatives or alkylphenol alkoxylates having 8 or more carbon atoms in the alkyl group.

[0056] The polyester polyol (b2) preferably contains, in each case based on the total amount of the components (b2a1) to (b2a4), (b2a1) 10 to 80 mol% of a dicarboxylic acid composition comprising: (b2a11) 20 to 100 mol % of one or more aromatic dicarboxylic acids or derivatives thereof, based on the dicarboxylic acid composition; (b2a12) 0 to 80 mol % of one or more aliphatic dicarboxylic acids or derivatives thereof, based on the dicarboxylic acid composition; (b2a2) 0 to 30 mol% of one or more fatty acids and / or fatty acid derivatives; (b2a3) 2 to 70 mol % of one or more aliphatic or alicyclic diols having 2 to 18 carbon atoms or alkoxylates thereof; (b2a4) 0 to 80 mol % of an alkoxylation product of at least one starter molecule having an average functionality of at least 2; wherein the total amount of the components (b2a1) to (b2a4) is 100 mol %.

[0057] The polyester polyol of component (b2) preferably has a number average functionality of 1.7 or more, preferably 1.8 or more, particularly preferably 2.0 or more, and in particular 2.2 or more, so that the crosslink density of the polyurethane produced therefrom is higher and, therefore, the mechanical properties of the polyurethane foam are better.

[0058] Component (b) can further contain a chain extender and / or crosslinker, for example, to modify mechanical properties such as hardness. The chain extenders and / or crosslinkers used are diols and / or triols and are amino alcohols having a molecular weight of less than 150 g / mol, preferably 60 to 130 g / mol. Possible compounds include, for example, aliphatic, cycloaliphatic, and / or araliphatic diols having 2 to 8, preferably 2 to 6, carbon atoms, such as ethylene glycol, 1,2-propylene glycol, diethylene glycol, dipropylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, o-, m-, p-dihydroxycyclohexane, and bis(2-hydroxyethyl) cyanoquinone. Similarly, aliphatic and cycloaliphatic triols such as glycerol, trimethylolpropane, and 1,2,4- and 1,3,5-trihydroxycyclohexane are also contemplated.

[0059] If chain extenders, crosslinkers or mixtures thereof are used for the production of rigid polyurethane foams, they are advantageously used in an amount of 0 to 15% by weight, preferably 0 to 5% by weight, based on the total weight of component (b). Component (b) preferably comprises less than 10% by weight, particularly preferably less than 7% by weight, and in particular less than 5% by weight of chain extenders and / or crosslinkers.

[0060] In particular, compounds used as catalysts (c) for producing polyurethane foams include compounds that significantly accelerate the reaction of the reactive hydroxyl group-containing compounds of components (b) to (g) with polyisocyanate (a).

[0061] Basic polyurethane catalysts, for example tertiary amines such as triethylamine, tributylamine, dimethylbenzylamine, dicyclohexylmethylamine, dimethylcyclohexylamine, N,N,N',N'-tetramethyldiaminodiethyl ether, bis(dimethylaminopropyl)urea, N-methyl- or N-ethylmorpholine, N-cyclohexylmorpholine, N,N,N',N'-tetramethylethylenediamine, N,N,N,N-tetramethylbutanediamine, N,N,N,N-tetramethylhexane-1,6-diamine, pentamethyldiethylenetriamine, bis(2-dimethylaminoethyl)ether, dimethylpiperazine , N-dimethylaminoethylpiperidine, 1,2-dimethylimidazole, 1-azabicyclo[2.2.0]octane, 1,4-diazabicyclo[2.2.2]octane (Dabco), and alkanolamine compounds such as triethanolamine, triisopropanolamine, N-methyl- and N-ethyldiethanolamine, dimethylaminoethanol, 2-(N,N-dimethylaminoethoxy)ethanol, N,N',N"-tris(dialkylaminoalkyl)hexahydrazines such as N,N',N"-tris(dimethylaminopropyl)-s-hexahydrotriazine, and triethylenediamine are preferably used. However, suitable catalysts also include metal salts such as iron(II) chloride, zinc chloride, lead octoate and tin salts such as tin dioctoate, tin diethylhexoate, dibutyltin dilaurate, and mixtures of tertiary amines and organic tin salts.

[0062] Possible catalysts further include: amidines, such as 2,3-dimethyl-3,4,5,6-tetrahydropyrimidine, tetraalkylammonium hydroxides, such as tetramethylammonium hydroxide, alkali metal hydroxides, such as sodium hydroxide, and alkali metal alcoholates, such as sodium methanolate and sodium isopropanolate, alkali metal carboxylates, alkali metal salts of long chain fatty acids having 8 to 20 carbon atoms and optionally having pendant OH groups.

[0063] Also contemplated as catalysts are incorporable amines, i.e., preferably amines having OH, NH, or NH2 functional groups, such as ethylenediamine, triethanolamine, diethanolamine, ethanolamine, and dimethylethanolamine. Incorporable catalysts can be considered compounds of component (c) or compounds of component (b).

[0064] Preferably, 0.001 to 10 parts by weight of a catalyst or combination of catalysts is used, based on 100 parts by weight of component (b). The reaction can also be carried out without a catalyst, in which case the catalytic activity of the amine-initiated polyol is typically utilized.

[0065] Possible catalysts for the trimerization reaction of excess NCO groups with one another further include catalysts that form isocyanurate groups, such as salts of ammonium ions or alkali metals, especially ammonium carboxylates or alkali metal carboxylates, alone or in combination with tertiary amines. The formation of isocyanurates results in rigid foams for technical applications, such as flame-retardant PIR foams, which are preferably used, for example, for insulation sheets or sandwich elements in the construction industry.

[0066] In a preferred embodiment, catalyst (c) comprises an amine catalyst having a tertiary amino group and an ammonium or alkali metal carboxylate catalyst. In a particularly preferred embodiment, catalyst (c) comprises at least one amine catalyst selected from the group consisting of pentamethyldiethylenetriamine and bis(2-dimethylaminoethyl)ether and at least one alkali metal carboxylate catalyst selected from the group consisting of potassium formate, potassium acetate, and potassium 2-ethylhexanoate. Surprisingly, it has been found that the use of these catalysts in the continuous production of sandwich elements, for example in a double belt, enables sandwich elements to have a particularly smooth foam surface facing the outer layer, particularly the lower outer layer. This results in sandwich panels with excellent adhesion of the foam to the outer layer and a defect-free surface.

[0067] According to the present invention, the blowing agent (d) used is a blowing agent mixture comprising at least one aliphatic halogenated hydrocarbon compound (d1) consisting of 2 to 5 carbon atoms, at least one hydrogen atom, and at least one fluorine and / or chlorine atom, and a hydrocarbon compound (d2) having 4 to 8 carbon atoms, wherein compound (d1) has at least one carbon-carbon double bond.

[0068] Suitable compounds (d1) include trifluoropropenes and tetrafluoropropenes, such as (HFO-1234), pentafluoropropenes, such as (HFO-1225), chlorotrifluoropropenes, such as (HFO-1233), chlorotetrafluoropropenes and hexafluorobutene, and mixtures of one or more of these components. Tetrafluoropropene, pentafluoropropene, chlorotrifluoropropene and hexafluorobutene are preferred, in which the unsaturated terminal carbon atom has at least one chlorine or fluorine substituent. Examples include 1,3,3,3-tetrafluoropropene (HFO-1234ze); 1,1,3,3-tetrafluoropropene; 1,2,3,3,3-pentafluoropropene (HFO-1225ye); 1,1,1-trifluoropropene; 1,1,1,3,3-pentafluoropropene (HFO-1225zc); 1,1,2,3,3-pentafluoropropene (HFO-1225yc); 1-chloro-2,3,3,3-tetrafluoropropene (HFO-1224yd); 1,1,1,2,3-pentafluoropropene (HFO-1225yez); 1-chloro-3,3,3-trifluoropropene (HCFO-1233zd); 1,1,1,4,4,4-hexafluorobut-2-ene (HFO-1336mzz) or a mixture of two or more of these components.

[0069] Particularly preferred compounds (d1) are trans-1-chloro-3,3,3-trifluoropropene (HCFO-1233zd(E)), cis-1-chloro-2,3,3,3-tetrafluoropropene (HCFO-1224yd), trans-1,1,1,4,4,4-hexafluorobut-2-ene (HFO-1336mzz(E)), cis-1,1,1,4,4,4-hexafluorobut-2-ene (HFO-1336mzz(Z)), or a mixture of two or more of these components. Particularly preferred is trans-1-chloro-3,3,3-trifluoropropene (HCFO-1233zd(E)), which surprisingly produces a foam quality with no defects, particularly in the lower outer layer, in a continuous production process.

[0070] Examples of hydrocarbon compounds (d2) having 4 to 8 carbon atoms are compounds such as heptane, hexane and isopentane, preferably n- and isopentane, technical mixtures such as n- and isobutane and propane, cycloalkanes such as cyclopentane and / or cyclohexane, in particular pentane isomers such as n-pentane, isopentene and cyclopentane. The hydrocarbon compounds (d2) preferably comprise at least 60 mol %, particularly preferably more than 70 mol %, in particular more than 80 mol % of alicyclic hydrocarbon compounds.

[0071] In addition to the blowing agents (d1) and (d2), additional physical blowing agents can be used. Suitable such agents include, in particular, liquids that are inert to the isocyanates used, have a boiling point below 100°C, preferably below 50°C, at atmospheric pressure, and evaporate when subjected to the exothermic polyaddition reaction. Examples include ethers such as furan, dimethyl ether, and diethyl ether, ketones such as acetone and methyl ethyl ketone, alkyl carboxylates such as methyl formate, dimethyl oxalate, and ethyl acetate, and halogenated hydrocarbons such as methylene chloride, dichloromonofluoromethane, difluoromethane, trifluoromethane, difluoroethane, tetrafluoroethane, chlorodifluoroethane, 1,1-dichloro-2,2,2-trifluoroethane, 2,2-dichloro-2-fluoroethane, and heptafluoropropane. Mixtures of these low-boiling liquids with each other and / or with other substituted or unsubstituted hydrocarbons can also be used. The proportion of physical blowing agents not falling within the definition of component (d1) or (d2) is preferably less than 30% by weight, particularly preferably less than 15% by weight, more preferably less than 5% by weight, based in each case on the total weight of blowing agent components (d1) and (d2) and further physical blowing agents, in particular when no further physical blowing agents are used in addition to blowing agent components (d1) and (d2).

[0072] The blowing agents used to produce polyurethane foams according to the present invention also include chemical blowing agents, which react with isocyanate groups to produce carbon dioxide, or, in the case of formic acid, carbon dioxide and carbon monoxide. Suitable chemical blowing agents (d3) also include organic carboxylic acids, such as formic acid, acetic acid, oxalic acid, and other carboxyl-containing compounds having fewer than six carbon atoms, and water.

[0073] It is preferred not to use halogenated hydrocarbons as blowing agents other than compound (d1).The chemical blowing agent (d3) used is preferably water, a formic acid-water mixture, or formic acid, and particularly preferred chemical blowing agents are water or a formic acid-water mixture, especially a water-formic acid mixture having a formic acid content of more than 70% by weight based on the blowing agent (d3), which leads to improved outer layer adhesion and a defect-free foam surface under the lower outer layer.

[0074] When the chemical foaming agent (d3) is used, it is preferably used in an amount of less than 2 mass %, more preferably 0.5 to 1.5 mass %, based on the total mass of the components (b) to (g).

[0075] According to the invention, the molar proportion of the halogenated hydrocarbon compound (d1) is 20 to 60 mol %, preferably 25 to 55 mol %, particularly preferably 30 to 50 mol %, and the molar proportion of the hydrocarbon compound (d2) is 40 to 80 mol %, preferably 45 to 75 mol %, particularly preferably 50 to 70 mol %, in each case based on the total content of the blowing agents (d1) and (d2).

[0076] The blowing agent (d) is preferably used in an amount such that the free foam density of the polyisocyanate-based rigid foam obtained according to the present invention is between 10 and 100 g / l, preferably between 20 and 75 g / l, and particularly between 30 and 50 g / l.

[0077] The flame retardant (e) used can generally be any flame retardant known from the prior art.Examples of suitable flame retardants are brominated esters, brominated alcohols such as brominated ethers (Ixol) and dibromoneopentyl alcohol, tribromoneopentyl alcohol and PHT-4-diol, and also chlorinated phosphates such as tris(2-chloroethyl)phosphate, tris(2-chloropropyl)phosphate (TCPP), tris(1,3-dichloropropyl)phosphate, tricresyl phosphate, tris(2,3-dibromopropyl)phosphate, tetrakis(2-chloroethyl)ethylenediphosphate, dimethylmethanephosphonate, diethyldiethanolaminomethylphosphonate, and commercially available halogenated flame-retardant polyols. Other phosphates or phosphonates that can be used as liquid flame retardants include diethylethanephosphonate (DEEP), triethylphosphate (TEP), dimethylpropylphosphonate (DMPP), and diphenylcresylphosphate (DPC).Flame retardants with isocyanate-reactive groups are considered to belong to both component (e) and component (b) of the flame retardant.

[0078] Flame retardants other than those mentioned above that can be used to impart flame retardancy to rigid polyurethane foams are inorganic or organic flame retardants such as red phosphorus, preparations containing red phosphorus, aluminum oxide hydrate, antimony trioxide, arsenic oxide, ammonium polyphosphate and calcium sulfate, expandable graphite and cyanuric acid derivatives, for example melamine, and mixtures of at least two flame retardants, for example ammonium polyphosphate and melamine, and optionally corn starch or ammonium polyphosphate, melamine and expandable graphite; aromatic polyesters can also be used for this purpose.

[0079] Preferred flame retardants are bromine-free. Particularly preferred flame retardants are comprised of atoms selected from the group consisting of carbon, hydrogen, phosphorus, nitrogen, oxygen and chlorine, more particularly atoms selected from the group consisting of carbon, hydrogen, phosphorus and chlorine.

[0080] Preferred flame retardants do not contain groups reactive with isocyanate groups. The flame retardant is preferably liquid at room temperature. Particularly preferred are TCPP, DEEP, TEP, DMPP, and DPC, as well as oligomeric halogen-free flame retardants such as Fyrol® PNX (ICL) and Levagard® 2000 (Lanxess), and / or incorporable phosphorus-based flame retardants such as Veriquel® R-100 (ICL) and Levagard® 2100 (Lanxess). TCPP and TEP are particularly preferred, and TEP is even more preferred because it provides a defect-free foam surface under the lower outer layer during continuous processing and reduces the release of caustic combustion gases in the event of a fire.

[0081] The proportion of the flame retardant (e) is generally 1% by mass to 40% by mass, preferably 5% by mass to 30% by mass, and particularly preferably 8% by mass to 25% by mass, based on the total mass of the components (b) to (g).

[0082] The reaction mixture for producing the polyurethane foams according to the invention can optionally be mixed with further auxiliaries and / or additives (f), which can include, for example, surface-active substances, foam stabilizers, cell regulators, fillers, light stabilizers, dyes, pigments, hydrolysis stabilizers, and fungicides and bacteriostatic substances.

[0083] Contemplated surfactants include compounds used to aid in the homogenization of the starting materials and, optionally, to adjust the cell structure of the plastic. Examples include emulsifiers such as castor oil sulfate or sodium salts of fatty acids, sodium salts of fatty acids, salts of fatty acids with amines, such as diethylamine oleate, diethanolamine stearate, and diethanolamine ricinoleate; salts of sulfonic acids, such as alkali metal or ammonium salts of dodecylbenzene or dinaphthylmethane disulfonic acid, and ricinoleic acid; siloxane-oxyalkylene copolymers and other organopolysiloxanes and dimethylpolysiloxanes. Similarly, oligomeric acrylates having polyoxyalkylene and fluoroalkane radicals as side groups are suitable for improving the emulsification, cell structure, and / or stability of the foam. Surfactants are typically used in amounts of 0.01 to 10 parts by weight based on 100 parts by weight of component (b).

[0084] The foam stabilizers used may be conventional foam stabilizers, such as those based on silicones, such as siloxane-oxyalkylene copolymers and other organopolysiloxanes.

[0085] Fillers (especially reinforcing fillers) are understood to mean conventional organic and inorganic fillers, reinforcing agents, weighting agents, agents for improving the wear behavior of paints, coating compositions, etc., which are known per se. Specific examples include inorganic fillers such as silica-containing minerals, e.g., phyllosilicates such as antigorite, serpentine, hornblende, amphibole, chrysotile, and talc; metal oxides such as kaolin, aluminum oxide, titanium oxide, and iron oxide; metal salts such as chalk and barite; inorganic pigments such as cadmium sulfide and zinc sulfide; and glass. It is preferable to use fibers of different lengths of natural and synthetic fibrous minerals, such as kaolin (china clay), aluminum silicate, and coprecipitates of barium sulfate and aluminum silicate, as well as wollastonite, and metals, especially glass, which can be sized as desired. Possible organic fillers include, for example, carbon, melamine, rosin, cyclopentadienyl resins and graft polymers, as well as cellulose fibers, polyamide fibers, polyacrylonitrile fibers, polyurethane fibers, polyester fibers derived from aromatic and / or aliphatic dicarboxylic acid esters, in particular carbon fibers.

[0086] The inorganic and organic fillers can be used individually or in the form of a mixture, and the amount thereof added to the reaction mixture is advantageously 0.5 to 50% by weight, preferably 1 to 40% by weight, based on the weight of components (a) to (f), although the content in mats, nonwovens and woven fabrics made of natural and synthetic fibers can reach up to 80% by weight, based on the weight of components (a) to (f).

[0087] Compound (g) is preferably a substance that is free-flowing at a temperature of 20° C. and an ambient pressure of 1 bar. Examples of compound (g) include carboxylic acid esters, such as lower alkanol esters of carboxylic acids, for example fatty acid ethyl esters or, preferably, fatty acid methyl esters, such as methyl caproate, methyl caprylate, methyl caprate, methyl laurate, methyl myristate, methyl palmitate, methyl oleate, methyl stearate, methyl linoleate, methyl linolenate and mixtures thereof, particularly preferably biodiesel.

[0088] As the compound having a hydrophobic group (g), preferably triglycerides, particularly preferably fats and oils, such as rapeseed oil, olive oil, corn oil, palm oil, pumpkin seed oil, sunflower oil, wheat seed oil, soybean oil, coconut oil, tall oil, cottonseed oil, grapeseed oil, apricot kernel oil, safflower oil, avocado oil, macadamia oil, pistachio oil, almond oil, linseed oil, sesame oil, hazelnut oil, peanut oil, walnut oil, evening primrose oil, sea buckthorn oil, safflower oil, borage seed oil, black cumin oil, wild rose oil, tallow, and mixtures thereof can also be used.

[0089] According to the present invention, polyurethane foams are produced by mixing components (a) to (e), and, if present, (f) and (g), to obtain a reaction mixture. To reduce complexity, premixes can also be prepared. These include at least one isocyanate component (A) containing a polyisocyanate (a) and a polyol component (B) containing an isocyanate-reactive compound (b). All or part of components (c) to (g) can be added to the isocyanate component (A) and the polyol component (B). Due to the high reactivity of isocyanates, components (c) to (g) are often added to the polyol component to avoid side reactions. However, blowing agent (d1), in particular, can also be mixed with isocyanate component (A). Physical blowing agents (d1) and (d2) are preferably added to the reaction mixture in separate streams, while the remaining components (d) to (g) are particularly preferably added to the polyol component (B). The reaction mixture is then reacted to obtain a polyurethane foam. In the context of the present invention, reaction mixture is to be understood to mean a mixture of isocyanate (a) and isocyanate-reactive compound (b) at a reaction conversion of less than 90% based on isocyanate groups.

[0090] The mixing of the components to obtain the reaction mixture is carried out at an isocyanate index of 240 to 1000, preferably 240 to 800, preferably 240 to 600, particularly preferably 280 to 500, and in particular 330 to 400. The starting components are mixed at a temperature of 15° C. to 90° C., preferably 20° C. to 60° C., in particular 20° C. to 45° C. The reaction mixture can be mixed by mixing in a high-pressure or low-pressure metering machine.

[0091] The reaction mixture can be reacted, for example, in a mold. By this technique, for example, discrete sandwich elements are produced.

[0092] The rigid foams according to the present invention are preferably produced on a continuously operating double belt line. The polyol and isocyanate components are metered in a high-pressure device and mixed in a mixing head. The catalyst and / or blowing agent can be pre-metered into the polyol mixture using a separate pump. The reaction mixture is continuously applied to the outer layers. The lower and upper outer layers containing the reaction mixture are introduced into a double belt where the reaction mixture foams and hardens. After leaving the double belt, the continuous sheet is cut to the desired dimensions. This allows the production of sandwich elements with either a metal outer layer or a flexible outer layer.

[0093] The upper and lower outer layers used may be the same or different and may be flexible or rigid outer layers commonly employed in double-belt processes. These include metal outer layers such as aluminum or steel, asphalt outer layers, paper, nonwoven fabrics, plastic sheets such as polystyrene, plastic films such as polyethylene films, or wood outer layers. The outer layers may also be coated, for example, with conventional coatings or adhesion promoters. It is particularly preferred to use outer layers that are impermeable to the cell gas of polyurethane foam.

[0094] Such processes are known and are described, for example, in "Kunststoffhandbuch, Volume 7, Polyurethane", Carl Hanser Verlag, 3rd Edition 1993, Chapter 6.2.2 or in EP 2234732.

[0095] The present invention finally provides a polyisocyanate-based rigid foam obtainable by the process according to the invention, and a polyurethane sandwich element comprising such a polyisocyanate-based rigid foam according to the invention.

[0096] The polyisocyanate-based rigid foam according to the invention is characterized by exceptional mechanical properties, in particular exceptional compressive strength and exceptionally low thermal conductivity. The production of the sandwich element, in particular in a continuous double belt process, further provides a sandwich element having an exceptional surface quality of the polyisocyanate-based rigid foam, in particular the surface quality facing the lower outer layer.

[0097] The present invention will now be described with reference to examples.

[0098] The following charges were used to prepare the reaction mixtures shown in Tables 1, 2 and 4: Polyol: Polyesterol 1: in the final product 、2 Terephthalic acid, oleic acid, diethylene glycol with a hydroxyl number of 44 mg KOH / g and a mass fraction of oleic acid of 15% 、 and Has a hydroxyl number of 535 mg KOH / g Esterification product of ethoxylated glycerol, which results in a proportion of hydrophobic groups in the total weight of Polyesterol 1 of about 13.3% by weight, based on the total weight of Polyesterol 1.

[0099] Polyesterol 2: Esterification product of phthalic anhydride, diethylene glycol and monoethylene glycol with a hydroxyl number of 240 mg KOH / g and a mass fraction of oleic acid of 0% in the final product.

[0100] Polyesterol 3: Esterification product of phthalic anhydride, soybean oil and diethylene glycol, having a hydroxyl number of 194 mg KOH / g and a mass fraction of fatty acids of 3.7% in the final product, which results in a proportion of hydrophobic groups in the total mass of Polyesterol 3 of about 3.1% by mass, based on the total mass of Polyesterol 3.

[0101] Polyester polyol 4: esterification product of phthalic anhydride, glycerol, oleic acid and diethylene glycol, with a hydroxyl number of 195 mg KOH / g and a mass fraction of oleic acid of 3.7% in the final product, which results in a proportion of hydrophobic groups in the total mass of Polyesterol 4 of about 3.3% by mass, based on the total mass of Polyesterol 4.

[0102] Polyester polyol 5: esterification product of phthalic anhydride, monoethylene glycol and diethylene glycol, having a hydroxyl number of 215 mg KOH / g and a mass fraction of oleic acid of 15.8% in the final product, which results in a proportion of hydrophobic groups in the total mass of Polyesterol 5 of about 14.0% by mass, based on the total mass of Polyesterol 5.

[0103] Polyetherol 1: Polyethylene glycol with a hydroxyl number of 188 mg KOH / g Flame retardant: TCPP: Tris(2-chloroisopropyl) phosphate, having a chlorine content of 32.5% by weight and a phosphorus content of 9.5% by weight TEP: Triethyl phosphate with a phosphorus content of 17% by weight Foam stabilizer: Tegostab® B8443: A silicone-containing foam stabilizer from Evonik catalyst: Catalyst A: a trimerization catalyst consisting of 36.2% by weight of potassium formate dissolved in 63.7% by weight of monoethylene glycol Catalyst B: a catalyst consisting of 23.1% by mass of bis(2-dimethylaminoethyl) ether and 76.9% by mass of dipropylene glycol Chemical foaming agents: Amasil 85%: formic acid aqueous solution (85% by mass aqueous solution) Physical Blowing Agents: Pentane S80 / 20: A mixture of 80% by weight of n-pentane and 20% by weight of isopentane Cyclopentane 70: A mixture of 70% by weight of cyclopentane and 30% by weight of isopentane Cyclopentane 95: A mixture of 95% by mass of cyclopentane and 5% by mass of isopentane Solstice® LBA: 1-chloro-3,3,3-trifluoropropene from Honeywell Opteon™ 1100: (Z)-1,1,1,4,4,4-hexafluoro-2-butene from Chemours Blowing Agent Blend 1: A mixture of 55.88 wt. % Cyclopentane 70 and 44.12 wt. % Solstice® LBA results in a blowing agent blend containing approximately 70 mol % Cyclopentane 70. Blowing Agent Blend 2: A mixture of 56.12 wt. % Pentane S80 / 20 and 43.88 wt. % Solstice® LBA results in a blowing agent blend containing approximately 70 mol. % Pentane S80 / 20. Isocyanates: Lupranat® M50: Approximately 550 mPa at 25°C * Polymeric methylene diphenyl diisocyanate (PMDI) from BASF, with a viscosity of 1000 s

[0104] The polyol components shown in Tables 1, 2 and 4 were prepared from the starting materials listed above and reacted in a continuous double belt process in the laboratory and in a high pressure apparatus.

[0105] Experimental form to establish identical density and fiber time (gel time): The polyol components shown in Table 1 were used to obtain the same fiber time of 53 seconds ± 2 seconds and cup foam density of 44 kg / m by varying the physical blowing agent and catalyst B. 3 ±2kg / m 3 The amount of catalyst A was chosen so that the finished foams of all settings had the same concentration. The polyol component thus prepared was reacted with Lupranat® M50 in a mixing ratio such that the index of all settings was 330±10. 80 g of the reaction mixture was thus reacted in a paper cup by vigorously mixing at 1400 rpm for 8 seconds using a laboratory stirrer.

[0106] The polyol components shown in Table 2 were varied to obtain the same fiber time of 53 seconds ± 2 seconds and cup foam density of 42 kg / m by varying the physical blowing agent and catalyst B. 3 ±2kg / m 3 The amount of catalyst A was chosen so that the finished foams of all settings had the same concentration. The polyol component thus prepared was reacted with Lupranat® M50 in a mixing ratio such that the index of all settings was 330±10. 80 g of the reaction mixture was thus reacted in a paper cup by vigorously mixing at 1400 rpm for 8 seconds using a laboratory stirrer.

[0107] The polyol components shown in Table 3 were varied to obtain the same fiber time of 53 seconds ± 2 seconds and cup foam density of 42 kg / m by varying the physical blowing agent and catalyst B. 3 ±2kg / m 3 The amount of catalyst A was chosen so that the finished foams of all settings had the same concentration. The polyol component thus prepared was reacted with Lupranat® M50 in a mixing ratio such that the index of all settings was 210±10. 80 g of the reaction mixture was thus reacted in a paper cup by vigorously mixing it at 1400 rpm for 8 seconds using a laboratory stirrer.

[0108] The reaction mixture, adjusted in this way to equivalent density and fiber time, was then used to produce rigid foam blocks, from which test specimens for thermal conductivity and compressive strength measurements were taken. To produce the foam blocks for thermal conductivity measurements, 450 g of the reaction mixture was reacted in a paper cup by vigorously mixing it for 6 seconds at 1400 rpm using a laboratory stirrer. The reaction mixture was then transferred to an open-top box mold measuring 150 mm x 120 mm x 120 mm. Test specimens for thermal conductivity measurements, measuring 200 mm x 200 mm x 30 mm, were always taken from the center of the foam block in the direction of foam rise.

[0109] The thermal conductivity was measured using a λ-Meter EP500e thermal conductivity meter from "Lambda Messtechnik GmbH Dresden" at an average temperature of 23°C. The thermal conductivity values ​​reported in Tables 1 and 2 are the average values ​​of replicate measurements of two specimens from two different but identically produced foam blocks.

[0110] Nine additional specimens measuring 50 mm x 50 mm x 50 mm were taken from the same foam block to determine the compressive strength according to DIN EN 826. Again, the specimens were always taken in the same way. Of the nine specimens, three were rotated so that the test was performed in the direction opposite to the foam rise direction (top). Of the nine specimens, three were rotated specifically so that the test was performed in relation to the foam rise direction (x-direction). Of the nine specimens, three were rotated so that the test was performed perpendicular to the foam rise direction (y-direction).

[0111] The nine measured compressive strengths were then averaged and reported as values ​​in Tables 1 and 2 (Compressive Strength 3D).

[0112] [Table 1]

[0113] [Table 2]

[0114] [Table 3]

[0115] Due to the low thermal conductivity of the blowing agent Solstice® LBA compared to Cyclopentane 70 and Pentane S80 / 20, it is expected that the laboratory foams produced using blowing agent blends 1 and 2 would also have low thermal conductivity. However, it was surprisingly found that using polyol components with a lower content of hydrophobic groups, components (b)-(g), significantly reduced the thermal conductivity and significantly improved the compressive strength of the experimental foams.

[0116] When the inventive polyol component of Example 13 is foamed at a reduced index of 210 (Example 19), the thermal conductivity increases significantly and the compressive strength of the foam decreases significantly. Continuous production of sandwich elements by double belt process: In addition to the experimental foams, 80 mm thick composite elements were produced in a double belt process by reacting the following polyol components, temperature-controlled at 20°C ± 1°C, with Lupranat® M50, also heated to 20°C ± 1°C. The amount of Lupranat® M50 was always chosen so that all rigid foams produced had an isocyanate index of 345 ± 10.

[0117] In the manufacture of the composite elements, the bottom outer layer was either a 0.05 mm thick aluminum foil heated to 35°C ± 2°C or a 0.5 mm thick aluminum plate heated to 40°C ± 2°C. Both top layers are industry standard and are also used in conventional sandwich panel series production methods. The temperature of the double belt was always 60°C ± 1°C.

[0118] To produce a composite element 80 mm thick, the amounts of catalyst B and physical blowing agent were selected so that the gel time of the reaction mixture was exactly 28 seconds, the contact time of the reaction mixture with the upper belt was exactly 23 seconds, and the foam had an overall density of 38.0±1.5 g / l.

[0119] For the determination of thermal conductivity, compressive strength and foam surface, specimens of 2.0 m length and 1.25 m width (specimens required for testing were always taken from the same site) were taken after successful adjustment of foam parameters.

[0120] Determination of compressive strength of sandwich foams: After 24 hours of storage under standard climatic conditions, further specimens with dimensions of 100 mm x 100 mm x sandwich thickness were taken from the sample specimens using a band saw. The specimens were taken from identical locations (left, center, right) distributed across the width of the element (left, center, right), and the compressive strength of the foam was determined according to the sandwich standard DIN EN ISO 14509-A.2 according to EN 826.

[0121] Determination of thermal conductivity of sandwich foams: After 24 hours of storage under standard climatic conditions, further specimens measuring 200 mm x 200 mm x 30 mm were cut from the sample specimens using a band saw. The specimens were cut midway between the thickness and width of the sandwich element.

[0122] The thermal conductivity was measured using a λ-Meter EP500e thermal conductivity meter from "Lambda Messtechnik GmbH Dresden" at an average temperature of 23°C. The thermal conductivity values ​​reported in Table 5 are the average of replicate measurements on two specimens.

[0123] Evaluation of the foam surface after peeling off the bottom outer layer: After mechanically removing the aluminum foil and aluminum sheet (lower outer layer) onto which the reaction mixture liquid was directly applied in the double belt process, the foam surface was first assessed and rated, where grade 1 represents the best foam surface and grade 5 represents the worst foam surface:

[0124] [Table 4]

[0125] [Table 5]

[0126] Even in a double-belt process, when using the same amount of the same blowing agent mixture, it is clear that the use of polyol components of the present invention having a small proportion of hydrophobic groups in components (b)-(g) (Examples 20, 26, and 30) achieves significantly reduced thermal conductivity and increased compressive strength of the resulting foam compared to a polyol component having a high proportion of hydrophobic groups in components (b)-(g) (Example 27). However, polyol components having a smaller proportion of hydrophobic groups in components (b)-(g) do not show a continuous improvement in thermal conductivity even as the proportion of halogenated olefin relative to the molar proportion of cyclopentane 95 continues to increase. The minimum value of thermal conductivity is achieved when the molar ratio of halogenated olefin to the molar ratio of cyclopentane 95 is 20-55 mol%. Surprisingly, an increase in the molar ratio of halogenated olefin in combination with the polyol component of the present invention beyond 70 mol%, preferably 65 mol%, more preferably 60 mol%, and especially 55 mol% results in an increase in the thermal conductivity of the resulting foam. Furthermore, when the proportion of both halogenated olefins exceeds 70 mol%, the foam quality at the bottom surface decreases (Examples 22, 23, and 25). When Pentane S80 / 20 is also used, the polyol components with a low proportion of hydrophobic groups from components (b) to (g) exhibit significantly improved thermal conductivity compared to non-invention polyol components (Example 28 vs. Example 29). However, compared to non-invention reaction mixtures, the use of Pentane S80 / 20 significantly reduces the thermal conductivity and foam quality at the bottom of the different outer layers (Example 28).

Claims

1. A method for producing a polyisocyanurate foam, comprising: a) an aromatic polyisocyanate; b) isocyanate-reactive compounds comprising at least one polyetherol (b1) and / or polyesterol (b2), wherein the number-average content of isocyanate-reactive hydrogen atoms of components (b1) and (b2) is at least 1.7; c) a catalyst; and d) a blowing agent; and e) a flame retardant; and f) optionally auxiliary or additive substances not falling within the definitions of (a) to (e); g) optionally, a compound having an aliphatic hydrophobic group (an aliphatic hydrocarbon group having more than 6 and less than 100 directly adjacent carbon atoms) not falling within the definitions of (a) to (f); are mixed to obtain a reaction mixture which can be cured to obtain a rigid polyisocyanurate foam; the blowing agent (d) comprises at least one aliphatic halogenated hydrocarbon compound (d1) consisting of 2 to 5 carbon atoms, at least one hydrogen atom, and at least one fluorine atom and / or chlorine atom, the compound (d1) comprising at least one carbon-carbon double bond, the blowing agent (d) further comprising a hydrocarbon compound (d2) having 4 to 8 carbon atoms, the molar proportion of the halogenated hydrocarbon compound (d1) being 20 to 60 mol % and the molar proportion of the hydrocarbon compound (d2) being between 40 and 80 mol %, in each case based on the total content of the blowing agents (d1) and (d2); Components (b) to (g) contain 0 to 4.0% by weight of aliphatic hydrophobic groups (aliphatic hydrocarbon groups having more than 6 and less than 100 directly adjacent carbon atoms), based on the total weight of components (b) to (g); 10. A method for producing a polyisocyanurate foam, wherein the mixing to obtain the reaction mixture is carried out at an isocyanate index of at least 240.

2. 2. The method of claim 1, wherein the hydrocarbon compound (d2) comprises at least 60 mol% alicyclic hydrocarbon compounds, based on the total mass of the hydrocarbon compound (d2).

3. 3. The method according to claim 1 or 2, wherein the hydrocarbon compound (d2) is selected from pentane isomers.

4. The method according to any one of claims 1 to 3, wherein the halogenated hydrocarbon compound (d1) is 1-chloro-3,3,3-trifluoropropene.

5. The method of any one of claims 1 to 4, wherein the effervescent agent comprises formic acid.

6. 6. The method of any one of claims 1 to 5, wherein the catalyst (c) comprises at least one amine catalyst having a tertiary amine group and at least one ammonium or alkali metal carboxylate catalyst.

7. 7. The method of claim 6, wherein the at least one amine catalyst having a tertiary amine group is selected from the group consisting of pentamethyldiethylenetriamine and bis(2-dimethylaminoethyl)ether, and the at least one alkali metal carboxylate catalyst is selected from the group consisting of potassium formate, potassium acetate, and potassium 2-ethylhexanoate.

8. 8. The method according to claim 1, wherein the compound (b) having at least one isocyanate-reactive hydrogen atom comprises 0 to 30% by weight of polyetherol (b1) and 70 to 100% by weight of polyesterol (b2), in each case based on the total weight of polyetherpolyol (b1) and polyesterol (b2).

9. 9. The method according to claim 1, wherein the polyether polyol (b1) is a reaction product of a starter molecule having a functionality of 2 to 4 with an alkylene oxide, including ethylene oxide, and has a hydroxyl number of 150 to 300 mg KOH / g.

10. The method according to any one of claims 1 to 9, wherein the polyester polyol (b2) is obtained using an aromatic dicarboxylic acid or a derivative thereof.

11. 11. The method according to any one of claims 1 to 10, wherein the flame retardants (e) used are exclusively halogen-free flame retardants.

12. The method of any one of claims 1 to 11, wherein the reaction mixture is applied to a continuously moving outer layer.

13. 13. The method according to claim 12, wherein the application of the reaction mixture to a continuously moving outer layer is carried out on a double belt line for the production of sandwich elements.

14. 14. The method according to any one of claims 1 to 13, wherein a premix comprising an isocyanate component (A) comprising an aromatic polyisocyanate (a) and a polyol component (B) comprising an isocyanate-reactive compound (b) is used to prepare a reaction mixture, and further components (c) to (g) are added in whole or in part to component (A) or component (B).

15. A rigid polyisocyanurate foam obtainable by the process according to any one of claims 1 to 14.

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