KR20260012286A - Rigid polyisocyanurate foam obtained using polyethylene terephthalate esters - Google Patents

Abstract

The present invention relates to a process for producing a rigid polyisocyanurate foam, comprising mixing (a) an aromatic polyisocyanate, (b) a compound having at least two hydrogen atoms reactive with isocyanate groups, at least one polyetherester polyol (b1) having an average functionality of ≥ 1.7 and ≤ 2.8 and an OH number of ≥ 170 and ≤ 270 mg KOH/g, and at least one polyester polyol (b2) having a functionality of ≥ 1.7 and ≤ 2.7 and an OH number of ≥ 170 and ≤ 280 mg KOH/g and a free monoethylene glycol content of < 1.3 wt. %, (c) a catalyst, (d) a blowing agent, (e) a flame retardant, and (f) optionally auxiliaries and additives to form a reaction mixture and reacting the mixture to provide a rigid polyisocyanurate foam, wherein the polyetherester Polyol (b1) is obtainable by esterification of a polyether polyol produced by alkoxylation of (b1.1) a dicarboxylic acid composition comprising an aromatic dicarboxylic acid, (b1.2) at least one hydrophobic compound having at least one hydroxyl group and/or carboxyl group or a derivative thereof, (b1.3) at least one diol having 2 to 6 carbon atoms, (b1.4) a starter or a starter mixture having an average functionality of ≥ 2 and ≤ 4, and polyester polyol (b2) is produced using polyethylene terephthalate, the proportion of which is > 25 wt.% based on the total amount of all used components for the production of polyester polyol (b2), and the mass ratio of polyetherester polyol (b1) to polyester polyol (b2) is ≥ 0.3 and ≤ 3.0, and component (b1) and component (b) based on component (b) The sum of the mass-based proportions of (b2) is > 80 wt.%, the mass-based proportion of free monoethylene glycol based on the sum of components (b), (c), (e) and (f) is ≤ 1.4 wt.%, and the mixing to provide the reaction mixture is carried out at an isocyanate index of at least 180. The present invention also relates to a polyol component for producing the rigid polyisocyanurate foam of the present invention, and to a sandwich member comprising the rigid polyisocyanurate foam, in particular the rigid polyisocyanurate foam obtainable by the process of the present invention.

Description

Rigid polyisocyanurate foam obtained using polyethylene terephthalate esters

The present invention relates to a process for producing a rigid polyisocyanurate foam, comprising mixing (a) an aromatic polyisocyanate, (b) at least one polyetherester polyol (b1) and at least one polyester polyol (b2), a compound having at least two hydrogen atoms reactive with isocyanate groups, (c) a catalyst, (d) a blowing agent, (e) a flame retardant, and (f) optionally auxiliaries and additives to form a reaction mixture and reacting the mixture to provide a rigid polyisocyanurate foam, wherein the polyetherester polyol (b1) is obtainable by the following esterification reaction: (b1.1) 10 to 50 mol % of a dicarboxylic acid composition comprising an aromatic dicarboxylic acid, (b1.2) 2 to 20 mol % of at least one hydrophobic compound having at least one hydroxyl group and/or carboxyl group or a derivative thereof, based in each case on the total amount of components (b1.1) to (b1.4). mol%, (b1.3) 10 to 70 mol% of at least one diol having 2 to 6 carbon atoms, (b1.4) 15 to 50 mol% of a polyether polyol prepared by alkoxylation of a starter or starter mixture having an average functionality of ≥ 2 and ≤ 4; The polyetherester polyol (b1) has an average functionality of ≥ 1.7 and ≤ 2.8 and an OH number of ≥ 150 and ≤ 300 mg KOH/g, the polyester polyol (b2) has an average functionality of ≥ 1.7 and ≤ 2.7, an OH number of ≥ 170 and ≤ 280 mg KOH/g and a free monoethylene glycol content of < 1.3 wt.%, wherein the polyester polyol (b2) is produced using polyethylene terephthalate, the proportion of which is > 25 wt.% based on the total amount of all components used to produce the polyester polyol (b2), and the mass ratio of the polyetherester polyol (b1) to the polyester polyol (b2) is ≥ 0.3 and ≤ 3.0, the mass of the component (b1) and the component (b2) based on the component (b) The sum of the reference proportions is > 80 wt.-%, and the mass-based proportion of free monoethylene glycol fed to the reaction mixture is ≤ 1.4 wt.-%, based on the total weight of components (b), (c), (e) and (f), and the mixing to provide the reaction mixture is carried out at an isocyanate index of at least 180. The present invention also relates to a polyol component for producing the rigid polyisocyanurate foam of the present invention, and to a sandwich member comprising the rigid polyisocyanurate foam, in particular the rigid polyisocyanurate foam obtainable by the process of the present invention.

The production of rigid polyisocyanurate foams by reaction of relatively high molecular weight compounds having at least two reactive hydrogen atoms, in particular polyether polyols from alkylene oxide polymerization or polyester polyols from polycondensation of alcohols and dicarboxylic acids, with polyisocyanates in the presence of polyurethane catalysts, chain extenders and/or crosslinking agents, blowing agents, further auxiliaries and additives is known and described in numerous patents and literature publications.

Rigid polyisocyanurate foam is commonly used as an insulating material for insulation. For example, the foam is used in the manufacture of refrigerators, containers, and flat composite components with at least one outer layer. These applications require rigid polyisocyanurate foam with high mechanical strength, particularly compressive strength, low thermal conductivity, low subsequent expansion, high fire resistance, and minimal surface defects.

There have also been attempts to replace crude oil-based starting materials for polyurethane production with recycled raw materials. One approach involves replacing conventional polyesters with esters obtained from recycled polyethylene terephthalate. This is described, for example, in the literature (Damayanti; Wu H.-S., "Strategic Possibility Routes of Recycled PET," Polymers 2021, 13, 1475).

A disadvantage of using decomposition products of polyethylene terephthalate, such as polyesters obtained from the corresponding decomposition of polyethylene terephthalate, is that these esters have negative properties in terms of the mechanical strength of the rigid polyisocyanurate foam, such as compressive strength, subsequent expansion and surface quality, especially when the reaction mixture is foamed between two outer layers in a continuous double belt process.

It is therefore an object of the present invention to provide a rigid polyisocyanurate foam, wherein at least a portion of the isocyanate-reactive component is obtained by a transesterification reaction of polyethylene terephthalate and a glycol, and which has high mechanical strength, in particular high compressive strength, low thermal conductivity, low subsequent expansion, high fire resistance and a minimum level of surface defects. A further object of the present invention is to provide a process for producing such a rigid polyisocyanurate foam, wherein the starting components, in particular the polyol component, have low viscosity and can be easily mixed with additional components for producing the rigid polyisocyanurate foam.

This object is achieved by a rigid polyisocyanurate foam obtained by a process for forming a reaction mixture and reacting a compound having at least two hydrogen atoms reactive with isocyanate groups, comprising (a) an aromatic polyisocyanate, (b) at least one polyetherester polyol (b1) and at least one polyester polyol (b2), (c) a catalyst, (d) a blowing agent, (e) a flame retardant, and (f) optionally auxiliaries and additives, to provide a rigid polyisocyanurate foam, wherein the polyetherester polyol (b1) is obtainable by an esterification reaction comprising: (b1.1) 10 to 50 mol % of a dicarboxylic acid composition comprising an aromatic dicarboxylic acid, in each case based on the total amount of components (b1.1) to (b1.2) at least one hydrophobic compound having at least one hydroxyl group and/or carboxyl group or derivative thereof, 2 to 20 mol%, (b1.3) 10 to 70 mol% of at least one diol having 2 to 6 carbon atoms, (b1.4) 15 to 50 mol% of a polyether polyol prepared by alkoxylation of a starter or starter mixture having an average functionality of ≥ 2 and ≤ 4; The polyetherester polyol (b1) has an average functionality of ≥ 1.7 and ≤ 2.8 and an OH number of ≥ 150 and ≤ 300 mg KOH/g, the polyester polyol (b2) has an average functionality of ≥ 1.7 and ≤ 2.7, an OH number of ≥ 170 and ≤ 280 mg KOH/g and a free monoethylene glycol content of < 1.3 wt.%, wherein the polyester polyol (b2) is produced using polyethylene terephthalate, the proportion of which is > 25 wt.% based on the total amount of all components used to produce the polyester polyol (b2), and the mass ratio of the polyetherester polyol (b1) to the polyester polyol (b2) is ≥ 0.3 and ≤ 3.0, the mass of the component (b1) and the component (b2) based on the component (b) The sum of the reference proportions is > 80 wt.-%, and the mass-based proportion of free monoethylene glycol fed to the reaction mixture is ≤ 1.4 wt.-%, based on the total weight of components (b), (c), (e) and (f), and the mixing to provide the reaction mixture is carried out at an isocyanate index of at least 180. The present invention also relates to a polyol component for producing the rigid polyisocyanurate foam of the present invention, and to a sandwich member comprising the rigid polyisocyanurate foam, in particular the rigid polyisocyanurate foam obtainable by the process of the present invention.

In the context of the present invention, rigid polyisocyanurate foam means a foamed polyisocyanurate, preferably a foam according to DIN 7726 having a compressive strength according to DIN 53 421/DIN EN ISO 604 of at least 80 kPa, preferably at least 150 kPa, more preferably at least 180 kPa. Furthermore, the rigid polyisocyanurate foam has a closed cell content according to DIN ISO 4590 of more than 50%, preferably more than 85%, more preferably more than 90%. The rigid polyisocyanurate foam comprises urethane and isocyanurate bonds.

Useful polyisocyanates (a) are aliphatic, cycloaliphatic, araliphatic, and preferably aromatic polyfunctional isocyanates known per se. These polyfunctional isocyanates are known per se or can be prepared by methods known per se. Polyfunctional isocyanates can also be used, in particular, in the form of mixtures, so that in this case component (a) comprises different polyfunctional isocyanates. Polyfunctional isocyanates useful as polyisocyanates have two isocyanate groups (hereinafter referred to as diisocyanates) or more than two isocyanate groups per molecule.

These are in particular alkylene diisocyanates having 4 to 12 carbon atoms in the alkylene radical, such as dodecane 1,12-diisocyanate, 2-ethyltetramethylene 1,4-diisocyanate, 2-methylpentamethylene 1,5-diisocyanate, tetramethylene 1,4-diisocyanate, preferably hexamethylene 1,6-diisocyanate; Alicyclic diisocyanates, such as cyclohexane 1,3- and 1,4-diisocyanate and any mixtures of these isomers, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (IPDI), hexahydrotolylene 2,4- and 2,6-diisocyanate and the corresponding isomer mixtures, dicyclohexylmethane 4,4'-, 2,2'- and 2,4'-diisocyanate and the corresponding isomer mixtures, preferably aromatic polyisocyanates, such as tolylene 2,4- and 2,6-diisocyanate and the corresponding isomer mixtures (TDI), diphenylmethane 4,4'-, 2,4'- and 2,2'-diisocyanate and diphenylmethane diisocyanate homologues having additional rings and the corresponding mixtures (MDI), Mixtures of diphenylmethane 4,4'-, 2,4'- and 2,2'-diisocyanate and polyphenyl polymethylene polyisocyanate (polymer MDI) and mixtures of MDI and TDI.

Particularly suitable polyisocyanates are diphenylmethane 2,2'-, 2,4'- and/or 4,4'-diisocyanate and diphenylmethane diisocyanate analogues having additional rings (MDI), naphthylene 1,5-diisocyanate (NDI), tolylene 2,4- and/or 2,6-diisocyanate (TDI), 3,3'-dimethyldiphenyl diisocyanate, 1,2-diphenylethane diisocyanate and/or p-phenylene diisocyanate (PPDI), trimethylene, tetramethylene, pentamethylene, hexamethylene, heptamethylene and/or octamethylene diisocyanate, 2-methylpentamethylene 1,5-diisocyanate, 2-ethylbutylene 1,4-diisocyanate, pentamethylene 1,5-diisocyanate, butylene 1,4-diisocyanate, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate, IPDI), 1,4- and/or 1,3-bis(isocyanatomethyl)cyclohexane (HXDI), cyclohexane 1,4-diisocyanate, 1-methylcyclohexane 2,4- and/or 2,6-diisocyanate and dicyclohexylmethane 4,4'-, 2,4'- and/or 2,2'-diisocyanate.

Also frequently used are modified polyisocyanates, i.e. products obtained by chemical reaction of organic polyisocyanates and having at least two reactive isocyanate groups per molecule. Polyisocyanates containing ester, urea, biuret, allophanate, carbodiimide, isocyanurate, uretdione, carbamate and/or urethane groups may be mentioned in particular, as well as frequently unconverted polyisocyanates.

The polyisocyanate of component (a) particularly preferably comprises oligomeric MDI consisting of 2,2'-MDI or 2,4'-MDI or 4,4'-MDI (also called monomeric diphenyl methane or MMDI) or an MDI homologue having at least three aromatic rings and an additional ring having a functionality of at least 3, or a mixture of at least two of these isomers, optionally also a mixture of at least one MDI isomer and at least one MDI homologue having an additional ring or crude MDI obtained in the production of MDI, or preferably a mixture of at least one MDI homologue having an additional ring and at least one of the abovementioned low molecular weight MDI derivatives 2,2'-MDI, 2,4'-MDI or 4,4'-MDI (also called polymeric MDI). The MDI isomers and homologues are generally obtained by distillation of crude MDI.

The use of polymeric MDI as the isocyanate (a) is particularly preferred. The average functionality of the polymeric MDI preferably ranges from 2.2 to 4, more preferably from 2.4 to 3.8, and especially from 2.6 to 3.0. Polymeric MDI is sold, for example, by BASF Polyurethanes GmbH under the name Lupranat® M20 or Lupranat® M50.

Component (a) preferably comprises at least 70 wt.-%, more preferably at least 90 wt.-%, and especially 100 wt.-%, based on the total weight of component (a), of at least one isocyanate selected from the group consisting of 2,2'-MDI, 2,4'-MDI, 4,4'-MDI and MDI oligomers. The content of oligomeric MDI is preferably at least 20 wt.-%, more preferably more than 30 wt.-% and less than 80 wt.-%, based on the total weight of component (a).

The viscosity of the component (a) used can vary within a wide range. Component (a) preferably has a viscosity at 25°C of 100 to 3000 mPa*s, more preferably 100 to 1000 mPa*s, particularly preferably 100 to 600 mPa*s, in particular 200 to 600 mPa*s, and even more particularly 400 to 600 mPa*s.

The compound (b) reactive towards isocyanate groups comprises at least one polyetherester polyol (b1) and at least one polyester polyol (b2). The weight ratio of components (b1) and (b2) is in each case >80 wt.-%, preferably 85 wt.-% to 100 wt.-%, more preferably 90 wt.-% to 100 wt.-%, and in particular 95 wt.-% to 98 wt.-%, based on the total weight of component (b), and the mass ratio of polyetherester polyol (b1) to polyester polyol (b2) is ≥0.3 and ≤3.0, preferably ≥0.4 and ≤2.5, more preferably ≥0.5 and ≤2.0, and in particular ≥0.7 and ≤1.5.

According to the present invention, component (b) comprises at least one aromatic polyetherester polyol (b1), which is producible by esterification of (b1.1) 10 to 50 mol% of a dicarboxylic acid composition comprising an aromatic dicarboxylic acid, (b1.2) 2 to 20 mol% of at least one hydrophobic compound having at least one hydroxyl and/or carboxyl group or a derivative thereof, (b1.3) 10 to 70 mol% of at least one aliphatic or cycloaliphatic diol having 2 to 6 carbon atoms or an alkoxylate thereof, (b1.4) 15 to 50 mol% of a polyether polyol produced by alkoxylation of a starter or a starter mixture having an average functionality of ≥ 2 and ≤ 4, in each case based on the total amount of components (b1.1) to (b1.4). Components b1.1) to b1.4) are preferably combined to be 100 mol%.

The polyetherester polyol (b1) has an average functionality of ≥ 1.7 and ≤ 2.8, preferably ≥ 1.9 and ≤ 2.6, more preferably ≥ 2.0 and ≤ 2.5, in particular 2.5, and an OH number of ≥ 150 and ≤ 300 mg KOH/g, preferably ≥ 170 and ≤ 280, more preferably ≥ 190 and ≤ 260 mg KOH/g.

The dicarboxylic acid composition (b1.1) comprises dicarboxylic acids and/or derivatives thereof, which can typically be used to prepare esters. The dicarboxylic acid composition (b1.1) preferably comprises 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. The component (b1.1) more preferably comprises phthalic anhydride, phthalic acid, terephthalic acid, more particularly phthalic anhydride or terephthalic acid, especially terephthalic acid. In general, the component (b1.1) may also comprise an aliphatic dicarboxylic acid or an aliphatic dicarboxylic acid derivative. When aliphatic dicarboxylic acids are used, they are generally contained in each case in an amount of 0.5-30 mol%, preferably 0.5-10 mol%, based on component (b1.1). The aliphatic dicarboxylic acid used is preferably adipic acid or a dicarboxylic acid mixture of succinic acid, glutaric acid and adipic acid. The dicarboxylic acid composition (b1.1) preferably does not contain any aliphatic dicarboxylic acids or derivatives thereof and thus consists of about 100 mol% of one or more aromatic dicarboxylic acids or derivatives thereof. Most preferably, the dicarboxylic acid composition (b1.1) has a terephthalic acid content of > 80 wt.%, more preferably > 90 wt.%, based on the total weight of component (b1.1), and in particular consists of terephthalic acid.

Component (b1.1) is generally used in an amount of 10 to 50 mol%, preferably 20 to 45 mol%, based on components (b1.1), (b1.2), (b1.3) and (b1.4) used in the production of aromatic polyether ester polyol (b1).

Furthermore, in the production of the aromatic polyether ester polyol (b1), at least one hydrophobic compound (b1.2) having at least one hydroxyl and/or carboxyl group or a derivative thereof is used. In the context of the present invention, the hydrophobic compound (b1.2) having at least one hydroxyl and/or carboxyl group or a derivative thereof is a compound having an aliphatic hydrophobic group. In the context of the present invention, an aliphatic hydrophobic group means an aliphatic hydrocarbyl group having preferably more than 6, more preferably more than 8 and less than 100, in particular at least 10 and at most 50 directly adjacent carbon atoms. The adjacent carbon atoms can be bonded not only via carbon-carbon single bonds but also via carbon-carbon double bonds. The carbon atoms of the hydrophobic group are directly bonded to each other and are not interrupted, for example, by heteroatoms. In contrast, the hydrogen atoms of the hydrocarbon can be substituted, for example, by halogen atoms, OH groups or carboxylic acid groups.

Compound (b1.2) is preferably a freely flowing substance at a temperature of 20° C. and an ambient pressure of 1 bar. Examples of compound (1.2) include carboxylic acid esters, such as lower alkanol esters of carboxylic acids, such as fatty acids or fatty acid derivatives, such as fatty acid ethyl esters or preferably fatty acid methyl esters.

These fatty acids and/or fatty acid derivatives may be of biological or petrochemical origin. Examples of fatty acids are caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, myristoleic acid, palmitic acid, palmitoleic acid, stearic acid, oleic acid, vaccenic acid, petroselinic acid, gadoleic acid, erucic acid, nervonic acid, linoleic acid, linolenic acid, stearidonic acid, arachidonic acid, timnodonic acid, clupanodonic acid, cervonic acid, ricinoleic acid and mixtures thereof. Examples of fatty acid derivatives include glycerol esters of fatty acids, such as castor oil, grape seed oil, black caraway oil, pumpkin seed oil, borage seed oil, soybean oil, wheat seed oil, rapeseed oil, sunflower seed oil, peanut oil, apricot kernel oil, pistachio oil, almond oil, olive oil, macadamia oil, avocado oil, sea buckthorn oil, sesame oil, hemp oil, hazelnut oil, primrose oil, wild rose oil, milk thistle oil, and walnut oil.

Further examples of fatty acid derivatives include hydroxyl-modified fats or fatty acids, hydrogenated fats or fatty acids, epoxidized fats or fatty acids, alkyl-branched fats or fatty acids, fatty acid amides, animal fats such as bovine tallow, alkyl esters or specifically methyl esters of fatty acids such as biodiesel.

Component (b1.2) is generally used in an amount of 2 to 20 mol%, preferably 5 to 15 mol%, and more preferably 7 to 10 mol%, based on all components (b1.1) to (b1.4) used in the production of aromatic polyether ester polyol (b1).

In a particularly preferred embodiment of the present invention, the fatty acid or fatty acid derivative (b1.2) is oleic acid, biodiesel, soybean oil, rapeseed oil or tallow, more particularly oleic acid or biodiesel, especially oleic acid, and is used in an amount greater than 5 mol%, more preferably greater than 8 mol%. One of the effects of the fatty acid or fatty acid derivative is to improve the solubility of the blowing agent in the production of rigid polyisocyanurate foams.

The component (b1.3) used is preferably at least one aliphatic or cycloaliphatic diol having 2 to 6 carbon atoms or an alkoxylate thereof. The component (b1.3) preferably comprises at least one compound from the group consisting of monoethylene glycol, diethylene glycol, propylene glycol, propane-1,3-diol, butane-1,4-diol, pentane-1,5-diol, hexane-1,6-diol, 2-methylpropane-1,3-diol and 3-methylpentane-1,5-diol and alkoxylates thereof. More preferably, the aliphatic diol (b1.3) is monoethylene glycol or diethylene glycol, in particular diethylene glycol. Component (b1.3) is preferably used in an amount of 10 to 70 mol%, more preferably 20 to 65 mol%, and especially 30 to 60 mol%, based on all components used in the production of the aromatic polyether ester polyol (b1) in each case.

The polyether polyol (b1.4) is obtained by alkoxylation of a starter or starter mixture having an average functionality of ≥ 2 and ≤ 4, in particular trifunctional starter molecules, preferably glycerol. The alkylene oxide used may preferably be ethylene oxide and/or propylene oxide. Preferably, at least 80 wt.-%, more preferably entirely, of ethylene oxide is used as alkylene oxide. The hydroxyl number of the polyether polyol (b1.4) is preferably greater than 300 mg KOH/g, more preferably greater than 400 mg KOH/g and less than 800 mg KOH/g, in particular greater than 450 mg KOH/g and less than 600 mg KOH/g.

In a particularly preferred embodiment, the aromatic polyetherester polyol (b1) has an OH value of 190 to 260 mg KOH/g and a functionality of 1.7 to 2.5.

Aromatic polyetherester polyols (b1) can be prepared by condensing a dicarboxylic acid (b1.1), at least one hydrophobic compound having at least one hydroxyl and/or carboxyl group (b1.2), an aliphatic or cycloaliphatic diol having 2 to 18 carbon atoms or an alkoxylate thereof (b1.3) and a high-functionality polyol (b1.4) in a melt, without a catalyst or preferably in the presence of an esterification catalyst, suitably under an atmosphere of an inert gas such as nitrogen, at a temperature of from 150 to 280° C., preferably from 180 to 260° C., optionally under reduced pressure, advantageously up to the desired acid number of less than 10, more preferably less than 2. In a preferred embodiment, the esterification mixture is polycondensed at the above-mentioned temperature to an acid number of from 80 to 20, preferably from 40 to 20, under standard pressure and then at a pressure of less than 500 mbar, preferably from 40 to 400 mbar. Examples of useful esterification catalysts are iron, cadmium, cobalt, lead, zinc, antimony, magnesium, titanium and tin catalysts in the form of metals, metal oxides or metal salts. However, the polycondensation can also be carried out in the liquid phase in the presence of a diluent and/or an entraining agent, such as benzene, toluene, xylene or chlorobenzene, for azeotropic removal of the water of condensation by distillation.

The polyester polyol (b2) has a functionality of ≥ 1.7 and ≤ 2.7, preferably ≥ 1.9 and ≤ 2.6, more preferably ≥ 2.0 and ≤ 2.4, in particular 2.0, and an OH number of ≥ 170 and ≤ 280 mg KOH/g, preferably ≥ 180 and ≤ 260 mg KOH/g, in particular ≥ 190 and ≤ 250 mg KOH/g, wherein the polyester polyol (b2) is produced using polyethylene terephthalate, the proportion of which, based on the total amount of all components used for the production of the polyester polyol (b2), is > 25 wt.-%, preferably ≥ 28 wt.-%, more preferably ≥ 35 wt.-%, in particular ≥ 40 wt.-%. In the present invention, it is essential that the content of free monoethylene glycol is in each case less than 1.3 wt%, preferably less than 1.2 wt%, and more preferably less than 1.1 wt%, based on the total weight of the polyesterol (b2).

Suitable polyester polyols (b2) can be obtained by reacting a polycarboxylic acid, particularly a dicarboxylic acid, with a polyhydric alcohol using an excess of an alcohol component, with the addition of polyethylene terephthalate. The polycarboxylic acid used may be an aliphatic polycarboxylic acid, an aromatic polycarboxylic acid, or mixtures thereof and derivatives thereof. The functionality of the starting materials is selected to obtain a polyester polyol having the required functionality. The carboxylic acid derivative used may be any carboxylic acid derivative commonly used in the production of polyesters suitable for use in the production of polyurethanes. Examples include polycarboxylic acids or polycarboxylic anhydrides of alcohols having 1 to 4 carbon atoms. Polycarboxylic acids also include functionalized carboxylic acids, such as hydroxycarboxylic acids.

The polyester (b2) is preferably produced using at least one aliphatic dicarboxylic acid. Examples include adipic acid, glutaric acid, succinic acid, fumaric acid, malonic acid, maleic acid, oxalic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid or derivatives thereof. It is also possible to use aliphatic polycarboxylic acids. Examples of aliphatic polycarboxylic acid derivatives are dimethyl adipate and diethyl adipate. It is particularly preferred to use dicarboxylic acids having 4 to 6 carbon atoms, such as adipic acid, glutaric acid or succinic acid or derivatives thereof, in particular adipic acid or derivatives of adipic acid. Preferably, the proportion of aliphatic dicarboxylic acids based on all components used for the production of the polyester polyol (b2) is ≥ 10 wt.-%, preferably 12 to 30 wt.-%, in particular 15 to 25 wt.-%.

The aromatic dicarboxylic acid or aromatic dicarboxylic acid derivative used is preferably a mixture or individual phthalic acid, phthalic anhydride, terephthalic acid and/or isophthalic acid, and derivatives thereof, such as dimethyl terephthalate, diethyl terephthalate, dimethyl phthalate, diethyl phthalate, and it is preferred to use phthalic acid, phthalic anhydride and terephthalic acid. It is particularly preferred to use terephthalic acid or dimethyl terephthalate, especially terephthalic acid.

In addition to aliphatic and/or aromatic polycarboxylic acids and/or functionalized aliphatic carboxylic acids, monofunctional carboxylic acids or reaction products of monofunctional carboxylic acids may also be used. The monofunctional carboxylic acids used may be, for example, saturated or unsaturated monocarboxylic acids having from 1 to 24 carbon atoms. Examples are formic acid, acetic acid, propionic acid, acrylic acid, butyric acid, valeric acid, caproic acid, benzoic acid, heptanoic acid, caprylic acid, nonanoic acid, capric acid and fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, ricinoleic acid, linoleic acid and linolenic acid.

Other reaction products of monofunctional carboxylic acids that may be used are fatty acid esters based on biobased starting materials and/or their derivatives, such as castor oil, grape seed oil, black caraway oil, pumpkin seed oil, borage seed oil, soybean oil, wheat seed oil, rapeseed oil, sunflower seed oil, peanut oil, apricot kernel oil, pistachio oil, almond oil, olive oil, macadamia oil, avocado oil, sea buckthorn oil, sesame oil, hemp oil, hazelnut oil, primrose oil, wild rose oil, milk thistle oil, walnut oil, and myristoleic acid, palmitoleic acid, oleic acid, vaccenic acid, petroselinic acid, gadoleic acid, erucic acid, nervonic acid, linoleic acid, o- and y-linolenic acid, stearidonic acid, arachidonic acid, timnodonic acid, clupanodonic acid, cervonic acid.

When a monofunctional carboxylic acid or a derivative thereof is used in the production of the polyester polyol (b2), it is preferably used in an amount such that the polyester polyol (b2) contains ≤ 15 wt.-%, in particular ≤ 5 wt.-%, of fatty acid moieties based on its total weight, especially preferably none at all.

The production of polyesters also involves the use of polyethylene terephthalate, for example, in pellet form. One possible explanation for the incorporation of polyethylene terephthalate into polyester (b2) is that, under the esterification conditions for the production of polyol (b2), a transesterification reaction occurs, resulting in the incorporation of degradation products of polyethylene terephthalate into polyester (b2). Possible degradation reactions of polyethylene terephthalate (PET) leading to incorporation into polyester polyol (b2) are described, for example, in the literature (Damayanti; Wu H.-S., "Strategic Possibility Routes of Recycled PET", Polymers 2021, 13, 1475, especially section 5) or in the literature (Chemistry and Technology of Polyols for Polyurethanes, 2nd Edition, Volume 2, chapter 5.2). In addition to the esters obtainable by conversion of polyethylene terephthalate, the polyester polyol (b2) may also comprise monoethylene glycol, for example from transesterification with polyethylene terephthalate.

Examples of polyhydric alcohols are: ethanediol, diethylene glycol, propane-1,2-diol and -1,3-diol, dipropylene glycol, butane-1,4-diol, pentane-1,5-diol, hexane-1,6-diol, decane-1,10-diol, glycerol, trimethylolpropane, and pentaerythritol and alkoxylates thereof. Preference is given to using ethylene glycol, diethylene glycol, propylene glycol, glycerol, trimethylolpropane or alkoxides thereof or mixtures of at least two of the polyhydric alcohols mentioned, in particular diethylene glycol and/or glycerol.

In a particularly preferred embodiment, the polyester (b2) is prepared using not only polyethylene terephthalate and adipic acid, but also diethylene glycol and optionally a fatty acid or fatty acid derivative. More preferably, the hydroxyl number of the polyester (b2) is less than 200 mg KOH/g and the fatty acid content is > 8 wt.% based on the total weight of the polyester (b2).

In the absence of fatty acids or fatty acid derivatives, the hydroxyl number of the polyester (b2) is preferably > 200 mg KOH/g.

Polyesterol (b2) is prepared in the melt, without a catalyst or preferably in the presence of an esterification catalyst, suitably under an inert gas atmosphere such as nitrogen, at a temperature of from 150 to 280° C., preferably from 180 to 260° C., and polycondensed, optionally under reduced pressure, to the desired acid number, which acid number is advantageously less than 10, more preferably less than 2. In a preferred embodiment, the esterification mixture is polycondensed at the abovementioned temperature to an acid number of from 80 to 20, preferably from 40 to 20, under standard pressure and then at a pressure of less than 500 mbar, preferably from 40 to 400 mbar. Examples of useful esterification catalysts are iron, cadmium, cobalt, lead, zinc, antimony, magnesium, titanium and tin catalysts in the form of metals, metal oxides or metal salts. However, the polycondensation can also be carried out in the liquid phase in the presence of a diluent and/or entrainer, such as benzene, toluene, xylene or chlorobenzene, for azeotropic removal of the water of condensation by distillation.

In addition to the polyether esterol (b1) and the polyester (b2), component (b) may further comprise a polyetherol (b3) having a hydroxyl number of 150 to 300 mg KOH/g and prepared by alkoxylation of a starter or a starter mixture, wherein the alkylene oxide used to prepare the polyether polyol (b3) is preferably at least 80 wt.-% of ethylene oxide, and the polyether polyol (b3) has at least 90%, preferably at least 95%, more preferably at least 99%, in particular exclusively primary hydroxyl end groups.

Polyether polyols (b3) are prepared by known methods, for example, by anionic polymerization of at least one alkylene oxide having 2 to 4 carbon atoms, including ethylene oxide, using conventional catalysts, such as alkali metal hydroxides, such as sodium or potassium hydroxide, alkali metal alkoxides, such as sodium methoxide, sodium or potassium ethoxide or potassium isopropoxide, or aminic alkoxylation catalysts, such as dimethylethanolamine (DMEOA), imidazole and/or imidazole derivatives, using at least one starter molecule or a mixture of starter molecules containing an average of ≤3.0 and ≥2.0, more preferably 2, reactive hydrogen atoms in bound form. In addition to the anionic polymerization of the starter molecules, cationic polymerization can also be performed using Lewis acids, such as antimony pentachloride, boron fluoride etherate or fuller's earth, as catalysts.

Preferred alkoxylation catalysts are KOH and amine alkoxylation catalysts. In some cases, when using KOH as an alkoxylation catalyst, the polyether must first be neutralized and the resulting potassium salt removed. In such cases, the use of an amine alkoxylation catalyst is particularly preferred. Preferred amine alkoxylation catalysts are selected from the group consisting of dimethylethanolamine (DMEOA), imidazole, and imidazole derivatives, and mixtures thereof, particularly preferably imidazole.

Examples of suitable alkylene oxides other than ethylene oxide are tetrahydrofuran, 1,3- and 1,2-propylene oxide, 1,2- and 2,3-butylene oxide, styrene oxide, preferably 1,2-propylene oxide. In one particularly preferred embodiment, only ethylene oxide is used as alkylene oxide. The alkylene oxides can be used individually, sequentially or alternately, or as a mixture. The alkylene oxide used according to the invention for the preparation of the polyether polyol (b3) comprises at least 80 wt.-% ethylene oxide, preferably at least 90 wt.-% ethylene oxide, more preferably at least 95 wt.-% ethylene oxide, in particular at least 98 wt.-%. The alkylene oxide used for the preparation of the polyether polyol (b3) of the invention is particularly preferably exclusively ethylene oxide. That is, in this embodiment, the weight-based amount of ethylene oxide among the total weight of alkylene oxides of component (b3) is 100 wt.%. When ethylene oxide is used in combination with other alkylene oxides, it must be ensured that the polyether polyol produced therefrom according to the present invention has the content of primary hydroxyl terminal groups according to the present invention.

Examples of useful starter molecules include water, organic dicarboxylic acids such as succinic acid, adipic acid, phthalic acid and terephthalic acid, or preferably dihydric or polyhydric alcohols such as ethanediol, propane-1,2- and -1,3-diol, diethylene glycol (DEG), dipropylene glycol, butane-1,4-diol, hexane-1,6-diol, glycerol, trimethylolpropane, bisphenol A, bisphenol F and pentaerythritol. In particular, diethylene glycol, monoethylene glycol, propane-1,2-diol and glycerol, especially diethylene glycol, are preferred as starter molecules.

When polyether polyol (b3) is used, it is preferably used in an amount of from 2 wt.% to 25 wt.%, more preferably from 4 wt.% to 20 wt.%, and in particular from 6 wt.% to 15 wt.%, in each case based on the total weight of component (b).

In the present invention, it is essential that the free monoethylene glycol content based on the sum of components (b), (c), (e) and (f) is less than 1.4 wt% of monoethylene glycol (MEG), preferably less than 1.3 wt%, more preferably less than 1.1 wt%, and especially less than 1.0 wt%.

The compound used as a catalyst (c) for producing the rigid polyisocyanurate foam of the present invention is a compound that significantly accelerates the reaction of the polyisocyanate (a) with a compound containing a reactive hydrogen atom, particularly a hydroxyl group, of components (b) to (f).

Basic polyurethane catalysts, such as tertiary amines, such as triethylamine, tributylamine, dimethylbenzylamine, dicyclohexylmethylamine, dimethylcyclohexylamine, N,N,N',N'-tetramethyldiaminodiethyl ether, bis(dimethylaminopropyl)urea, N-methylmorpholine 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, Suitable compounds include 1,4-diazabicyclo[2.2.2]octane (Dabco) and alkanolamine compounds such as triethanolamine, triisopropanolamine, N-methyldiethanolamine and N-ethyldiethanolamine, dimethylaminoethanol, 2-(N,N-dimethylaminoethoxy)ethanol, N,N',N"-tris(dialkylaminoalkyl)hexahydrotriazines such as N,N',N"-tris(dimethylaminopropyl)-s-hexahydrotriazine and triethylenediamine.

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, and dibutyltin dilaurate, and also mixtures of metal salts such as tertiary amines and organic tin salts. Useful 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 alkoxides such as sodium methoxide and potassium isopropoxide, alkali metal carboxylates, and also alkali metal salts of long-chain fatty acids having from 8 to 20 carbon atoms and optionally having pendant OH groups.

As catalysts, amines that can be mixed, i.e., amines preferably having OH, NH or NH ₂ functional groups, such as ethylenediamine, triethanolamine, diethanolamine, ethanolamine and dimethylethanolamine, are also useful. The amines that can be mixed can be considered as compounds of component (b) or compounds of component (c).

It is also possible to carry out the reaction without a catalyst. In this case, it is common to utilize the catalytic activity of amine-initiated polyols.

Useful catalysts for the trimerization reaction of the excess NCO groups with each other further include catalysts which form isocyanurate groups, such as ammonium ions or salts of alkali metals, especially ammonium carboxylates or alkali metal carboxylates, alone or in combination with tertiary amines. Isocyanurate formation produces flame-retardant PIR foams, which are preferentially used in rigid foams in technical applications, for example as insulating panels or sandwich elements in the construction industry. Preferred trimerization catalysts are potassium salts of aliphatic carboxylic acids having > 5 carbon atoms, especially selected from the group consisting of potassium 2-ethylhexanoate, potassium octoate, potassium neodecanoate, potassium hexanoate and potassium sorbate.

In a preferred embodiment, the catalyst (c) comprises an amine catalyst having a tertiary amino group and an ammonium or alkali metal carboxylate catalyst. In a particularly preferred embodiment, the 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, such as an alkali metal salt of a carboxylic acid, such as potassium formate or potassium acetate, preferably a potassium salt of an aliphatic carboxylic acid having ≥ 5 carbon atoms, particularly selected from the group consisting of potassium 2-ethylhexanoate, potassium octoate, potassium neodecanoate, potassium pivalate, potassium hexanoate and potassium sorbate. Surprisingly, the use of these catalysts in the continuous production of sandwich elements, for example in double belts, results in sandwich elements having particularly low subsequent expansion after the double belts have been formed and particularly small differences between the thickness of the middle of the element and the thickness of the edge of the element.

It is preferable to use 0.001 to 10 parts by weight of the catalyst or catalyst combination based on 100 parts by weight of component (b).

Blowing agents (d) that can be used to produce the rigid polyisocyanurate foam of the present invention include water, formic acid, and formic acid/water mixtures. These react with isocyanate groups to form carbon dioxide and carbon monoxide. Because these blowing agents release gases through a chemical reaction with isocyanate groups, they are called chemical blowing agents. In the context of the present invention, formic acid with a purity exceeding 98% is considered pure formic acid and not a formic acid/water mixture.

Additionally, physical blowing agents, such as low-boiling hydrocarbons, may be used. Suitable physical blowing agents are liquids that are particularly inert toward the polyisocyanate (A), have a boiling point below 100°C, preferably below 50°C, at atmospheric pressure, and thus evaporate under the influence of the exothermic polyaddition reaction.

Examples of physical blowing agents that can be used are alkanes, such as heptane, hexane, n- and isopentane, preferably n- and isopentane, and technical grade mixtures of n-isobutane and propane, cycloalkanes, such as cyclopentane and/or cyclohexane, 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 saturated and unsaturated 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, and unsaturated hydrocarbons, such as Trifluoroproppentane and tetrafluoropropene, such as (HFO-1234), pentafluoropropene, such as (HFO-1225), chlorotrifluoropropene, such as (HFO-1233), chlorodifluoropropene, chlorotetrafluoropropene and hexafluorobutene, and also mixtures comprising one or more of these components. Preferred are tetrafluoropropene, pentafluoropropene, chlorotrifluoropropene and hexafluorobutene, wherein 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). It is also possible to utilize mixtures of these low-boiling-point liquids with each other and/or with other substituted or unsubstituted hydrocarbons.

Additional suitable blowing agents include organic carboxylic acids such as acetic acid, oxalic acid, ricinoleic acid and compounds containing carboxyl groups.

Halogenated hydrocarbons are preferably not used as blowing agents. The chemical blowing agents used are preferably water, a formic acid/water mixture, or formic acid, with a formic acid/water mixture or formic acid being more preferred.

The physical blowing agent used is preferably a pentane isomer or a mixture of pentane isomers. A chemical blowing agent is used in conjunction with the physical blowing agent, preferably a formic acid/water mixture or pure formic acid in conjunction with a pentane isomer or a mixture of pentane isomers.

The amount of the foaming agent or foaming agent mixture used is from 0.1 wt.% to 45 wt.%, preferably from 1 wt.% to 30 wt.%, more preferably from 1 wt.% to 20 wt.%, in particular from 1.5 wt.% to 20 wt.%, in each case based on the sum of components (b) to (f).

Water, formic acid or a formic acid/water mixture is preferably used in an amount of from 0.2 wt.-% to 10 wt.-%, in particular from 0.5 wt.-% to 4 wt.-%, based on component (b). If a formic acid/water mixture is used, the proportion of formic acid, based on the total weight of formic acid and water, is preferably greater than 40 wt.-%, particularly preferably from 50 wt.-% to 98 wt.-%, even more preferably from 70 wt.-% to 95 wt.-%, in particular from 80 wt.-% to 90 wt.-%. Particular preference is given to using formic acid or a formic acid/water mixture in combination with pentane as a chemical blowing agent.

The flame retardant (e) used may generally be a flame retardant known from the prior art. Examples of suitable flame retardants are brominated esters, brominated ethers (Ixol) or brominated alcohols, such as 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, dimethyl methanephosphonate, diethyl diethanolaminomethylphosphonate, and also other commercially available halogenated flame retardant polyols. Other phosphates or phosphonates that may be used as liquid flame retardants include diethyl ethanephosphonate (DEEP), triethyl phosphate (TEP), dimethyl propylphosphonate (DMPP), and diphenyl cresyl phosphate (DPC). In the context of the present invention, compounds containing phosphorus, chlorine, or bromine atoms and also having isocyanate reactive groups are not considered as compounds (b) having at least two isocyanate reactive hydrogen atoms, and are not included in component (b) in the calculation of the amount ratio.

Flame retardants other than the above-mentioned flame retardants which may also be used to provide flame retardancy to rigid polyisocyanurate foams are inorganic or organic flame retardants such as red phosphorus, preparations comprising red phosphorus, aluminum oxide hydrate, antimony trioxide, arsenic oxide, ammonium polyphosphate and calcium sulfate, expandable graphite or cyanuric acid derivatives such as melamine, or mixtures of at least two flame retardants such as ammonium polyphosphate and melamine, as well as optionally corn starch or ammonium polyphosphate, melamine, expandable graphite and optionally an aromatic polyester. Preferred flame retardants do not have groups reactive toward isocyanate groups. The flame retardants are preferably liquid at room temperature. TCPP, DEEP, TEP, DMPP and DPK are preferred, particularly TCPP and TEP, especially TCPP.

Typically, the proportion of the flame retardant (e) is 1 wt% to 20 wt%, preferably 2 wt% to 15 wt%, and more preferably 3 wt% to 10 wt%, based on the total weight-based amounts of components (b) to (f).

Component (e) preferably comprises a phosphorus-containing flame retardant, and the phosphorus content based on the total weight of components (a) to (f) is preferably <0.7 wt.%, more preferably <0.6 wt.%, even more preferably <0.5 wt.%, and in particular <0.4 wt.%.

The reaction mixture for producing the rigid polyisocyanurate foam of the present invention may also optionally be mixed with additional auxiliaries and/or additives (f). These may include, for example, surface-active substances, foam stabilizers, foam control agents, fillers, light stabilizers, dyes, pigments, hydrolysis stabilizers, and fungistatic and bacteriostatic substances.

Useful surface-active substances include, for example, compounds that aid in the homogenization of the starting materials and, optionally, may also be suitable for controlling the cell structure of the plastic. Examples include emulsifiers such as castor oil sulfate or sodium salts of fatty acids, as well as salts of amines and fatty acids, such as diethylamine oleate, diethanolamine stearate, diethanolamine ricinoleate, salts of sulfonic acids, such as the alkali metal or ammonium salts of dodecylbenzene- or dinaphthylmethanedisulfonic acid and ricinoleic acid, and foam stabilizers such as siloxane-oxyalkylene copolymers and other organopolysiloxanes and dimethylpolysiloxanes. Also suitable for improving the emulsifying action, cell structure, and/or foam stabilization are oligomeric acrylates having polyoxyalkylene and fluoroalkane radicals as side groups. The surface-active agent is typically used in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of component (b). The foam stabilizer used may be a conventional foam stabilizer, such as a silicone-based one, such as a siloxane-oxyalkylene copolymer and other organopolysiloxanes.

Fillers, in particular reinforcing fillers, are essentially known conventional organic and inorganic fillers, reinforcing agents, extenders, agents which improve the wear behavior of paints, coating compositions, etc. Individual examples include: inorganic fillers such as silicate minerals, such as 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, barite, and inorganic pigments such as cadmium sulfide and zinc sulfide, as well as glass, etc. Preferably, kaolin (kaolin), coprecipitates of aluminum silicate and barium sulfate and aluminum silicate, as well as natural and synthetic fibrous minerals such as wollastonite, and fibers of various lengths made of metals and especially of glass are used; these can be arbitrarily sized. Examples of useful organic fillers include carbon, melamine, rosin, cyclopentadienyl resins and graft polymers, and also cellulose fibers, polyamide fibers, polyacrylonitrile fibers, polyurethane fibers and polyester fibers based on aromatic and/or aliphatic dicarboxylic acid esters, and in particular carbon fibers. The inorganic and organic fillers can be used individually or in mixtures and are advantageously added to the reaction mixture in amounts of 0.5 wt.-% to 50 wt.-% - 35 wt.-%, preferably 1 wt.-% to 40 wt.-%, based on the weight of components (a) to (f), although their content in mats, nonwovens and wovens made of natural and synthetic fibers can reach up to 80 wt.-%, based on the weight of components (a) to (f).

According to the present invention, a rigid polyisocyanurate foam is prepared by mixing components (a) to (e) and, if present, (f) to obtain a reaction mixture. Complexity can also be reduced by preparing a premix. This comprises at least an isocyanate component (a) comprising a polyisocyanate, and a polyol component comprising a compound (b) having at least two isocyanate-reactive hydrogen atoms. All or part of the additional components (c) to (f) may be added to the isocyanate component and the polyol component, all or partly; due to the high reactivity of isocyanates, components (c) to (f) are often added to the polyol component to avoid side reactions. However, in particular, a physical blowing agent may also be added to the isocyanate component (a). Water, a formic acid/water mixture, or formic acid is typically present in a full or partial solution in the polyol component, while the physical blowing agent (e.g., pentane) and, optionally, the remaining chemical blowing agent are directly metered in "on-line" during preparation. The physical blowing agent is preferably fed online to the reaction mixture in excess stream, and the remaining components (c), (e) and (f) are more preferably added to the polyol component. The catalyst is generally metered online, but may already be present in full or partial solution in the polyol component. The present invention therefore also provides a polyol component comprising component (b) as defined above, optionally a catalyst (c), a blowing agent (d), a flame retardant (e) and optionally auxiliaries and additives (f), wherein the mass ratio of the polyetherester polyol (b1) to the polyester polyol (b2) is ≥ 0.3 and ≤ 3.0, the sum of the mass-based proportions of components (b1) and (b2) based on component (b) is > 80 wt.-%, and the mass-based proportion of free monoethylene glycol fed to the reaction mixture is less than 1.4 wt.-%, based on the total weight of components (b), (c), (e) and (f).

Polyester (b2) is preferably used in an amount such that the polyethylene terephthalate content is in each case at least 2.5 wt.%, more preferably at least 3 wt.%, even more preferably at least 4 wt.%, and in particular at least 5 wt.%, based on the total weight of components (a) to (f).

The polyol component for producing the rigid polyisocyanate foam of the present invention preferably comprises, in each case based on the total weight of components (b) to (f), 70 to 90 wt% of a compound (b) having at least two hydrogen atoms reactive toward isocyanate groups, 0.5 to 10 wt% of a catalyst (c), 2 to 20 wt% of a blowing agent (d), 1 to 20 wt% of a flame retardant (e), and 0 to 20 wt% of additional auxiliaries and additives (f). In a particularly preferred embodiment, the proportions of components (b) to (f) add up to 100%.

The reaction mixture is then reacted to provide a rigid polyisocyanurate foam. In the context of the present invention, the reaction mixture herein refers to a mixture of a polyisocyanate (a), a compound (b) having at least two hydrogen atoms reactive toward isocyanate groups, and all additional components (c), (d), (e), and optionally (f), wherein the reaction conversion based on the isocyanate groups is less than 90%.

The mixing of the components to provide the reaction mixture is carried out at an isocyanate index of at least 180, preferably 220 to 400, more preferably 260 to 360, and especially 280 to 330. The starting components are mixed at a temperature of 15°C to 90°C, preferably 20°C to 60°C, and especially 20°C to 45°C. The reaction mixture can be mixed by mixing in a high-pressure or low-pressure meter.

The reaction mixture can be introduced into a mold, for example, to complete the reaction. This technique is used, for example, to produce discontinuous sandwich components. The rigid foam of the present invention is preferably produced on a continuous double-belt line. Here, the polyol and isocyanate components are preferably metered in by a high-pressure machine and mixed in a mixing head. The catalyst and/or blowing agent can be metered into the polyol mixture in advance using separate pumps. The reaction mixture is applied to a continuously moving lower outer layer, preferably a metal outer layer. The lower outer layer containing the reaction mixture and the upper outer layer, which is also preferably a metal outer layer, are introduced into the double belt, and the reaction mixture foams and hardens. After exiting the double belt, the continuous strand is cut to the desired dimensions. This allows the production of sandwich components having either a metal outer layer or a flexible outer layer. The upper and lower outer layers used may be the same or different, and may be either flexible or rigid outer layers typically used in the double belt process. These include an outer layer of metal, such as aluminum or steel, an outer layer of bitumen, paper, non-woven fabric, a plastic sheet, such as polystyrene, a plastic film, such as polyethylene film, or an outer layer of wood. The outer layer may also be coated, for example, with conventional paint or varnish, or with an adhesion promoter. It is particularly preferred to use an outer layer impermeable to cell gases of rigid polyisocyanate foam.

Such processes are known and are described, for example, in the literature (Kunststoffhandbuch" [Plastics Handbook], volume 7, "Polyurethane" [Polyurethanes], Carl Hanser Verlag, 3rd edition 1993, section 6.2.2) or in EP 2234732. The present invention ultimately provides a polyisocyanate-based rigid foam obtainable by the process of the invention, and a polyurethane sandwich member comprising such a polyisocyanate-based rigid foam of the invention.

The rigid polyisocyanurate foam of the present invention is notable for its excellent mechanical properties, particularly excellent compressive strength, low thermal conductivity, low subsequent expansion, high fire resistance, minimal surface defects, and good adhesion to the outer layer. The method of the present invention for producing such rigid polyisocyanurate foam is particularly notable for its low viscosity, which facilitates processing of the raw materials, thereby enabling the starting components to be readily mixed with additional components for producing the rigid polyisocyanurate foam. Furthermore, the polyisocyanate-based rigid foam of the present invention exhibits excellent fire resistance even when using small amounts of ecologically and toxicologically problematic flame retardants. Furthermore, the reaction mixture used to produce the polyisocyanurate-based rigid foam of the present invention enables the desired reactivity to be achieved along with improved foam curing while using relatively small amounts of ecologically and toxicologically problematic catalysts.

The present invention is explained in more detail by the following examples:

Examples:

The following feedstocks were used:

Polyol:

Polyetheresterol 1: Esterification product of terephthalic acid, oleic acid, diethylene glycol and ethoxylated glycerol having a hydroxyl functionality of 2.5, a hydroxyl number of 240 mg KOH/g and an oleic acid content of 15 wt%.

Polyesterol 2: An esterification product of phthalic anhydride, oleic acid and diethylene glycol having a hydroxyl functionality of 1.75, a hydroxyl number of 215 mg KOH/g and an oleic acid content of 15 wt%.

PET polyester 1: Esterification product of an ester obtainable by reaction of polyethylene terephthalate, adipic acid and diethylene glycol, having a hydroxyl functionality of 2.0 and a hydroxyl number of 245 mg KOH/g, a polyethylene terephthalate content of 40 wt%, an adipic acid content of 22 wt% and a free MEG content of 1.09%.

PET polyester 2: An esterification product of an ester obtainable by reaction of polyethylene terephthalate, adipic acid, soybean oil and diethylene glycol, having a hydroxyl functionality of 1.85 and a hydroxyl number of 190 mg KOH/g, and having a polyethylene terephthalate content of 40 wt%, an adipic acid content of 18 wt%, a fatty acid content of 12 wt% and a free MEG content of 0.79%.

An esterification product of an ester obtainable by reaction of polyethylene terephthalate, adipic acid and diethylene glycol, having a hydroxyl functionality of 3:2 and a hydroxyl number of 240 mg KOH/g, and having a polyethylene terephthalate content of 30 wt% and a free MEG content of 1.4%.

An esterification product of an ester obtainable by reaction of polyethylene terephthalate, adipic acid and diethylene glycol, having a hydroxyl functionality of PET polyester 4:2 and a hydroxyl number of 290 mg KOH/g, and having a polyethylene terephthalate content of 45 wt% and a free MEG content of 1.05%.

A polyether polyol prepared by ethoxylation of ethylene glycol, having a hydroxyl functionality of 1:2 and a hydroxyl value of 190 mg KOH/g.

Flame retardant:

TCPP: Tris(2-chloroisopropyl)phosphate having a chlorine content of 32.5 wt% and a phosphorus content of 9.5 wt%.

Foam stabilizer:

Stabilizer: Silicone-containing foam stabilizer manufactured by Evonik.

catalyst:

Catalyst A: A catalyst comprising 23.1 wt% bis(2-dimethylaminoethyl)ether and 76.9 wt% dipropylene glycol.

Catalyst B: A catalyst composed of 40 wt% potassium formate, 54 wt% monoethylene glycol and 6 wt% water.

Catalyst C: A catalyst composed of 54 wt% potassium 2-ethylhexanoate, 20.5 wt% diethylene glycol, 22.5 wt% triethyl phosphate and 3.0 wt% water.

Chemical blowing agents:

Amasil 85%: A foaming agent mixture consisting of 85% by weight formic acid and 15% by weight water.

Physical blowing agent:

Pentane S80/20: A blowing agent mixture consisting of 80 mol% n-pentane and 20 mol% isopentane.

Isocyanate:

Lupranat® M 50: Polymeric methylene diphenyl diisocyanate (PMDI) manufactured by BASF with a viscosity of approximately 550 mPa*s at 25°C.

The described feedstocks were used to prepare the polyol components described in Table 2, which were reacted in a high-pressure device in a continuous double belt process.

Continuous manufacturing of sandwich members by double belt process:

Composite members with thicknesses of 50 mm and 120 mm were manufactured using a double belt process. Manufacturing was achieved by equilibrating the polyol components specified in Table 2 at 22°C ± 1°C and then reacting Lupranat® M50, also equilibrating at 22°C ± 1°C.

The amount of Lupranat® M50 was chosen so that the isocyanate index of all rigid foams processed into 50 mm sandwich elements was always 305±15 and that of all rigid foams processed into 120 mm sandwich elements was 325±15.

The lower outer layer used in the manufacture of the composite member is either 0.05 mm thick aluminum foil heated to 35°C ± 2°C, or 0.5 mm thick aluminum sheet heated to 40°C ± 2°C and coated on both sides. The two upper layers are industry standard and are also used in the continuous manufacturing process for conventional sandwich members. The temperature of the double belt was always 60°C ± 2°C.

Composite members 50 mm thick were prepared by mixing 100 parts of polyol component with 85% of Amasil as described in Table 2. The amounts of catalyst B and catalyst C were selected so that the proportion of potassium ions was 0.11 ± 0.02 wt.% based on all components for foam preparation. The amounts of catalyst A and physical blowing agent were selected so that the gelation time of the reaction mixture was exactly 25 seconds, the contact time of the reaction mixture with the upper belt was exactly 20 seconds, and the foam had an overall density of 39.5 ± 1.5 g/l.

Composite members 120 mm thick were prepared by mixing 100 parts of polyol component with 85% of Amasil as described in Table 2. The amounts of catalyst B and catalyst C were selected so that the proportion of potassium ions was 0.10 ± 0.02 wt.% based on all components for foam preparation. The amounts of catalyst A and physical blowing agent were selected so that the gelation time of the reaction mixture was exactly 32 seconds, the contact time of the reaction mixture with the upper belt was exactly 26 seconds, and the foam had an overall density of 39.5 ± 1.5 g/l.

To determine the compressive strength and foam surface, after successfully adjusting the foam parameters, sample plaques of 2.0 m in length and 1.25 m in width were taken, and the sample specimens required for the test were always taken from the same location.

Determination of the intermediate thickness of the sandwich form:

The sandwich member thickness of sample plaques manufactured with a gap size of 120 mm between the upper and lower belts was measured at the midpoint of the member width between the groove and tongue sides immediately after leaving the double belts and 24 hours later (after cooling). The values are listed as "Mid-Middle Member Thickness (Immediate)" and "Mid-Middle Member Thickness (24 Hours)". The difference between "Mid-Middle Member Thickness (Immediate)" and the set gap size of 120 mm is listed as "Mid-Middle Member Thickness Difference (Immediate)".

Additionally, the camber of the sandwich member was measured, which is expressed in mm as the difference between the member middle thickness (24 hours) and the member edge thickness (24 hours). The member edge thickness (24 hours) is the average of the two member thicknesses measured 5 cm from the tongue edge and the groove edge.

Determination of compressive strength of sandwich foam:

After 24 hours of storage under standard temperature and humidity conditions, additional test pieces measuring 100 mm x 100 mm x sandwich thickness were cut from the sample specimens using a band saw. The test pieces were taken from equal areas (left, middle, right) distributed across the width of the member, and the compressive strength of the foam was determined according to the sandwich standard DIN EN ISO 14509-A.2 according to EN 826.

Measurement of transverse tensile strength:

Additional test pieces with dimensions of 100 mm x 100 mm x sandwich thickness (50 mm, 100 mm, 170 mm) were cut from the sample specimen using a band saw. The test pieces were taken from identical locations (left, middle, right) distributed across the width of the member, and the transverse tensile strength of the foam or its adhesion to the outer layer was determined according to the sandwich standard DIN EN ISO 14509-A.1 in accordance with EN 1607.

Evaluation of the foam surface after the lower outer layer is torn:

After mechanical removal of the aluminum foil and aluminum sheet (lower outer layer) coated with the liquid reaction mixture in the double belt process, the foam surface was visually estimated and evaluated, where grade 1 represents the best foam surface and grade 5 represents the worst foam surface:

Small flame test according to EN-ISO 11925-2:

Specimens for the small flame test were prepared as follows: 300 g of the reaction mixture, adjusted to the same reaction time and foam density, in a paper cup were vigorously stirred for 10 s at a rotation speed of 1500 rpm using a laboratory stirrer and then transferred into a box mold with internal dimensions of 150 mm x 250 mm (length x width). After 24 h, the rigid foam block was demolded and all edges were reduced to 30 mm. The specimens with dimensions of 190 x 90 x 20 mm were removed from the mold and conditioned for 1 day before being tested by applying a flame to the edges on 90 mm sides according to DIN EN-ISO 11925-2. The values listed in Table 3 are the average of five measurements.

The results in Tables 3 and 4 show the foam and sandwich member properties of the manufactured 50 mm and 120 mm thick sandwich members. The polyol component of Example 1, which contained "polyetheresterol 1" as the sole polyester, produced a shrinkage-free foam surface under the aluminum foil and metal plate, and an acceptable flame height in the small flame test when processed into a 50 mm thick sandwich member. After exiting the double belt, the manufactured 120 mm thick member showed only a very small difference in the middle thickness of the member compared to the set gap size of <2.0 mm. In addition, this member had an acceptable compressive strength value.

As can be seen in Examples 3 and 5, complete replacement of “polyether ester 1” with “PET polyester 1” and “PET polyester 2” results in significant disadvantages in both the production of sandwich members with a thickness of 50 mm and the production of sandwich members with a thickness of 120 mm.

Compared to Example 1, the foams of Examples 3 and 5 exhibited significantly worse foam surfaces after removing the two outer layers. Additionally, the 120 mm member exhibited a significantly increased thickness difference in the middle of the member after exiting the double belt.

Surprisingly, the combination of “polyetherester polyol 1” and “PET polyester 1” or “PET polyester 2” produces foams that meet all requirements in a dual belt process.

Therefore, it can be seen that Examples 2, 4, and 9 of the present invention have a good foam surface beneath the two outer layers, similar to the foam of Example 1. The difference in the thickness between the two outer layers is also within an acceptable range. As can be clearly seen in Example 9, the use of catalyst C again reduces the difference in the thickness between the two outer layers, thereby enabling the use of a higher proportion of PET polyester polyol.

Compared to Example 1, the foams of Examples 2, 4, and 9 of the present invention surprisingly exhibited increased foam compressive strength and improved fire resistance. The use of catalyst C surprisingly further improved foam compressive strength and improved fire resistance to an acceptable level.

The combination of "polyetheresterol 1" and "PET polyester" is essential to the present invention. Therefore, as shown in Example 6, switching from "polyetheresterol 1" to another ester that does not contain polyether units results in a foam that no longer meets all requirements. Therefore, "polyesterol 2" causes defects in the foam surface beneath the two outer layers. The 120 mm member manufactured in Example 6 has a greater difference in member thickness than the 120 mm member manufactured in Example 4.

The present invention also demonstrates that not all PET polyesters are suitable. Thus, PET polyesters with a high free monoethylene glycol content exhibit significantly higher sustained pressure, even when used with "polyetherester polyol 1" (see Examples 7 and 8). PET polyesters with an excessively high OH value are also not optimal, as this results in increased mid-thickness and poor foam surface quality, even when the percentage of free monoethylene glycol is within the scope of the invention (see Example 10).

Claims (16)

A method for manufacturing a rigid polyisocyanurate foam,
a) aromatic polyisocyanates,
b) a compound having at least two hydrogen atoms reactive with an isocyanate group, comprising at least one polyetherester polyol (b1) and at least one polyester polyol (b2);
c) catalyst,
d) foaming agent,
e) flame retardants,
f) Optional supplements and additives
Mixing to form a reaction mixture and reacting to produce a rigid polyisocyanurate foam,
Polyether ester polyol (b1) is, in each case, based on the total amount of components b1.1) to b1.4).
b1.1) 10 to 50 mol% of a dicarboxylic acid composition comprising an aromatic dicarboxylic acid,
b1.2) 2 to 20 mol% of one or more hydrophobic compounds having at least one hydroxyl group and/or carboxyl group or derivative thereof,
b1.3) 10 to 70 mol% of at least one diol having 2 to 6 carbon atoms,
b1.4) 15 to 50 mol% of polyether polyol prepared by alkoxylation of a starter or starter mixture having an average functionality of ≥ 2 and ≤ 4.
It can be obtained by esterification of
The polyether ester polyol (b1) has an average functionality of ≥ 1.7 and ≤ 2.8 and an OH number of ≥ 150 and ≤ 300 mg KOH/g,
The polyester polyol (b2) has a functionality of ≥ 1.7 and ≤ 2.7, an OH number of ≥ 170 and ≤ 280 mg KOH/g, and a free monoethylene glycol content of < 1.3 wt.%, the polyester polyol (b2) is produced using polyethylene terephthalate, the proportion of which is > 25 wt.% based on the total amount of all components used for the production of the polyester polyol (b2),
The mass ratio of the polyether ester polyol (b1) to the polyester polyol (b2) is ≥ 0.3 and ≤ 3.0, and the sum of the mass-based ratios of the component (b1) and the component (b2) based on the component (b) is >80 wt%,
The mass ratio of free monoethylene glycol supplied to the reaction mixture is less than 1.4 wt% based on the total weight of components (b), (c), (e) and (f),
A method for producing a rigid polyisocyanurate foam, wherein mixing to obtain a reaction mixture is carried out at an isocyanate index of at least 180. A manufacturing method in which, in the first paragraph, the proportion of polyethylene terephthalate based on the total amount of all components used for manufacturing polyester polyol (b2) is ≥ 28 wt%. A method for producing polyester polyol (b2) according to claim 1 or 2, wherein the polyester polyol (b2) is produced using at least one aliphatic dicarboxylic acid having 4 to 6 carbon atoms, the proportion of which based on all components used for producing polyester polyol (b2) is ≥ 10 wt%. A method for producing a polyester polyol (b2) according to any one of claims 1 to 3, wherein the polyester polyol (b2) has a hydroxyl value of <200 mg KOH/g and a fatty acid content of >8 wt% based on the total weight of the polyester polyol (b2). A method for producing a polyester polyol (b2) according to any one of claims 1 to 3, wherein the polyester polyol (b2) has a hydroxyl value of >200 mg KOH/g and a fatty acid content of 0 wt% based on the total weight. A method for producing a composition according to any one of claims 1 to 5, wherein the dicarboxylic acid composition (b1.1) has a terephthalic acid content of > 80 wt% based on the total weight of the component (b1.1). A manufacturing method according to any one of claims 1 to 6, wherein oleic acid is used as component (b.1.2), and the proportion of oleic acid based on the total amount of components b1.1) to b1.4) is ≥ 8 mol%. A method for producing a polyether polyol (b1.4) according to any one of claims 1 to 7, wherein the polyether polyol (b1.4) is produced by alkoxylation with ethylene oxide, has a functionality of 3, and has an ethylene oxide content of > 80 wt% based on all alkylene oxides used in producing the polyether polyol (b1.4). A process according to any one of claims 1 to 8, wherein component (b) comprises at least one polyether polyol (b3) having an ethylene oxide content of > 80 wt.%, based on all alkylene oxides used in the preparation of (b3), and having an OH number of 150-300 mg KOH/g, obtained by ethoxylation of a starter or starter mixture having an average functionality of ≥ 2 and ≤ 3. A method for producing a catalyst according to any one of claims 1 to 9, wherein the catalyst (c) comprises a potassium salt of an aliphatic carboxylic acid having > 5 carbon atoms. A manufacturing method according to any one of claims 1 to 10, wherein the blowing agent (d) comprises a chemical and physical blowing agent, and the chemical blowing agent is selected from the group consisting of water, a formic acid/water mixture, and formic acid. A manufacturing method according to any one of claims 1 to 11, wherein the flame retardant (e) comprises a phosphorus-containing flame retardant, and the phosphorus content based on the total weight of components (a) to (f) is <0.7 wt%. A manufacturing method according to any one of claims 1 to 12, wherein the content of polyethylene terephthalate based on the total weight of components (a) to (f) is > 2.5 wt%. A manufacturing method according to any one of claims 1 to 13, wherein the reaction mixture is applied to the outer layer continuously moving on a double belt line for manufacturing a sandwich member. As a polyol component for the production of rigid polyisocyanurate foam,
b) a compound having at least two hydrogen atoms reactive with an isocyanate group, comprising at least one polyether ester polyol (b1) and a polyester polyol (b2), wherein the number average content of the isocyanate-reactive hydrogen atoms of components (b1) and (b2) is at least 1.7;
c) optionally a catalyst,
d) foaming agent,
e) flame retardants, and
f) Optional supplements and additives
Includes,
Polyether ester polyol (b1) is, in each case, based on the total amount of components b1.1) to b1.4).
b1.1) 10 to 50 mol% of a dicarboxylic acid composition comprising an aromatic dicarboxylic acid,
b1.2) 2 to 20 mol% of one or more hydrophobic compounds having at least one hydroxyl group and/or carboxyl group or derivative thereof,
b1.3) 10 to 70 mol% of at least one diol having 2 to 6 carbon atoms,
b1.4) 15 to 50 mol% of polyether polyol prepared by alkoxylation of a starter or starter mixture having an average functionality of ≥ 2 and ≤ 4.
It can be obtained by esterification of
The polyether ester polyol (b1) has an average functionality of ≥ 1.7 and ≤ 2.8 and an OH number of ≥ 170 and ≤ 270 mg KOH/g,
The polyester polyol (b2) has a functionality of ≥ 1.7 and ≤ 2.7, an OH number of ≥ 170 and ≤ 280 mg KOH/g, and a free monoethylene glycol content of < 1.3 wt.%, the polyester polyol (b2) is produced using polyethylene terephthalate, the proportion of which is > 25 wt.% based on the total amount of all components used for the production of the polyester polyol (b2),
The mass ratio of the polyether ester polyol (b1) to the polyester polyol (b2) is ≥ 0.3 and ≤ 3.0, and the sum of the mass-based ratios of the component (b1) and the component (b2) based on the component (b) is >80 wt%,
A polyol component in which the mass ratio of free monoethylene glycol supplied to the reaction mixture is less than 1.4 wt% based on the total weight of components (b), (c), (e) and (f). A rigid polyisocyanurate foam obtainable by a manufacturing method according to any one of claims 1 to 14.