Method for obtaining a high performance polyisocyanurate foam from polyisocyanurate foam waste

Abstract

The present invention relates to a method for obtaining a recycled polyol (RP) from a polyisocyanurate material (a) wherein the polyisocyanurate material (a) comprises isocyanurate structures wherein the method comprises mixing (a) the polyisocyanurate material, (b) at least one polyalcohol, wherein the polyalcohol (b) has at least two primary alcohol groups and a hydroxyl value of 200 to 800 mg KOH / g, (c) at least one aliphatic monocarboxylic acid, (d) at least one catalyst comprising at least one basic catalyst (d1) catalyzing esterification of alcohol groups and carboxylic acids and (e) optionally at least one deamination agent and reacting the mixture to obtain a recycled polyol having an OH-number of 150 to 300 mg KOH / g, a viscosity of less than 25.000 mPas at 25 °C a and a content of polyisocyanurate material (a), based on the total amount of compounds (a) to (e), of at least 20 % by weight. The invention is further directed to a recycled polyol obtainable according to such a method and a process for the production of a polyisocyanurate rigid foam.

Description

[0001] Method for obtaining a high performance polyisocyanurate foam from polyisocyanurate foam waste

[0002] The present invention relates to a method for obtaining a recycled polyol (RP) from a polyisocyanurate material (a) wherein the polyisocyanurate material (a) comprises isocyanurate structures, wherein the method comprises mixing (a) the polyisocyanurate material, (b) at least one polyalcohol, wherein the polyalcohol (b) has at least two primary alcohol groups and a hydroxyl value of 180 to 800 mg KOH / g, (c) at least one aliphatic monocarboxylic acid, (d) at least one catalyst comprising at least one basic catalyst (d1) catalyzing esterification of alcohol groups and carboxylic acids and (e) optionally at least one deamination agent and reacting the mixture to obtain a recycled polyol having an OH-number of 150 to 300 mg KOH / g, a viscosity of less than 25000 mPas at 25 °C a and a content of polyisocyanurate material (a), based on the total amount of compounds (a) to (e), of at least 20 % by weight. The invention is further directed to a recycled polyol obtainable according to such a method and a process for the production of a polyisocyanurate rigid foam.

[0003] Rigid polyurethane foams (PUR foams) are a common type of foams used in many applications, such as in the construction and appliance industries. They are very popular due to their durability and insulating properties. However, their use also results in a significant amount of waste that needs to be disposed of or recycled. One promising method for recycling rigid polyurethane foams is alcoholysis. In this process, the foams are chemically decomposed and converted into recycled polyols by the addition of alcohols of a functionality of at least 2. These recycled polyols can then be used again in new systems as part of the polyol component.

[0004] Diethylene glycol is one of the most commonly used alcohols for the alcoholysis of rigid polyurethane foams. It is an inexpensive glycol that enables efficient conversion of the foams into recycled polyols. These recycling polyols have comparatively low viscosities, which facilitates their use in new polyurethane systems. By using diethylene glycol for the alcoholysis of rigid polyurethane foams, low viscosity recycled polyols can be produced cost-effectively which can be used as polyol components in new systems. This recycling method is a promising solution for reducing the amount of waste and recovering valuable raw materials at the same time.

[0005] During the alcoholysis of rigid polyurethane foams, there is a risk of the undesirable formation of free aromatic amines, in particular Methylenedianiline, also known as MDA. These aromatic amines are potentially harmful to health and the environment. It is therefore of great importance to develop processes to reduce the content of aromatic amines. Various methods have been identified to minimize the MDA content. One possibility is to use epoxides, which can inhibit the formation of free aromatic amines. Esters based on natural oils have also been found to be effective additives to reduce MDA. In addition, carboxylic acids have been shown to have a reducing effect on MDA levels. The amount of these compounds added depends on the expected residual concentration of free aromatic amines. It is important to carefully determine the optimal amount to ensure an effective reduction of the MDA content without negatively affecting the properties of the recycled polyols. By implementing these processes and the targeted addition of epoxides, esters or carboxylic acids, the content of free aromatic amines in the recycled polyols can be significantly reduced. This helps to improve the quality of the recycled rigid polyurethane foams while minimizing the potential impact on health and the environment.

[0006] Polyisocyanurate foams (PI R foams) were developed about 30 years ago as an alternative to PUR foams in order to achieve rigid foams with improved flame retardancy due to the intrinsic flame retardancy of the isocyanurate structures. One of the main motivations of the work at that time was to be able to develop rigid foams that do not require any flame retardants at all. The PIR systems at that time were still foamed at very high index values of 400 and higher, as the primary goal was still to be able to develop PIR systems without the addition of flame retardants. This direction of development was later discarded, and the index was lowered in order to circumvent problems regarding excessive brittleness of the foams. However, this made it necessary to use additional flame retardants but in significantly smaller quantities than in classic PUR systems. As flame retardants mainly halogenated phosphorous esters were used such as Tris(2-chlorisopropyl)phosphate (TCPP).

[0007] When PIR-foams are reacted with glycols under alcoholysis conditions, recycled polyols are obtained, comprising isocyanurate structures. The use of recycled polyols containing isocyanurate groups to produce polyisocyanurate (PIR) systems offers an attractive opportunity to improve both the sustainability and flame -retardant properties of PIR systems.

[0008] ES2277554 discloses the glycolysis of polyurethane- and / or polyisocyanurate foams in the presence of titan catalysts or alkali metal based catalysts. In the examples section of ES2277554 only polyurethane foams are glycolyzed and only polyols having a OH number of more than 500 mg KOH / g are obtained.

[0009] DE 2304444 describes a process for the degradation of PIR foams in which mixtures of glycols such as DEG and dialkanolamines e.g. diethanolamine are used. The PIR foam described in Example 1 is obtained by reaction of PMDI and a mixture of an epoxy and a chlorinated aliphatic ester. The obtained recycled polyol has a very high viscosity.

[0010] DE 2902509 describes the use of metal catalysts for alcoholysis of PUR and PIR rigid foams. These are Ti or Zr catalysts such as titanium(IV) butoxyde. These catalysts have advantages over previously described catalysts such as amines or alkali hydroxides since they have almost no effect on the intrinsic reactivity of the polyols obtained. The rigid foams used in the examples for alcoholysis are declared as PUR foams and are not further specified, the obtained recycled polyols have a hydroxyl number of about 500 my KOH / g.

[0011] The quality of these recycled polyols is often unsatisfactory. The products obtained according to the state of the art have a high viscosity and often a deep dark brown color mainly due to the presence of high molecular weight oligomers containing isocyanurate groups and have high hydroxyl values. To limit viscosity, only low amounts of PIR- foam can be added in the recycling process. The polyol then obtained usually has a even higher hydroxyl value due to the high amount of glycol added. To produce modern polyisocyanurate foams it is important that the reaction mixture cures fast, and the obtained foams have high mechanical properties as high pressure resistance, the foams have a fine cell structure and a low heat conductivity and, when produced on a modern double belt plant, have smooth surfaces.

[0012] Recycled polyols according to the state-of-the-art result in PIR-foams showing a massive deterioration in foam curing, compressive strength, and flame resistance. To produce high performance polyisocyanurate foams these recycled polyols are not sufficient.

[0013] It was the object of the present invention to provide a recycled polyol which is obtained from alcoholysis of a PI R - foam and wherein the content of the PIR-foam, based on the total weight of the educts to produce the recycled polyol, is at least 20 % by weight. It was further the object of the present invention to provide a method for the production of a PIR-foam having good mechanical properties, low heat conductivity, a high flame resistance, a fast foam curing, a fine cell structure and, when produced in a double belt plant, a smooth surface, wherein a recycled polyol is applied in an amount of at least 20 % by weight, based on the total weight of the polyols applied, and wherein the recycled polyol is obtained from alcoholysis of a PI R foam wherein the content of PIR foam, based the total weight of the educts to produce the recycled polyol, is at least 20 % by weight.

[0014] The object is solved by a method for obtaining a recycled polyol (RP) from a polyisocyanurate material (a) wherein the polyisocyanurate material (a) comprises isocyanurate structures, wherein the method comprises mixing (a) the polyisocyanurate material, (b) at least one polyalcohol, wherein the polyalcohol (b) has at least two primary alcohol groups and a hydroxyl value of 180 to 800 mg KOH / g, (c) at least one aliphatic monocarboxylic acid preferably having a boiling point of at least 140 °C and an acid number of 190 to 760, (d) at least one catalyst comprising at least one basic catalyst (d1 ) catalyzing esterification of alcohol groups and carboxylic acids and (e) optionally at least one deamination agent and reacting the mixture to obtain a recycled polyol having an OH -number of 150 to 300 mg KOH / g, a viscosity of less than 25000 mPas at 25 °C a and a content of polyisocyanurate material (a), based on the total amount of compounds (a) to (e), of at least 20 % by weight, based on the total weight of components (a) to (e).

[0015] The present invention is further directed to a recycled polyol obtainable according to the method according to the present invention.

[0016] In addition, the present invention is directed to a process for the production of a polyisocyanurate rigid foam, comprising mixing (f) at least one aromatic polyisocyanate, (g) at least one isocyanate reactive compound comprising the recycled polyol (RP) according to the present invention and at least one polyetherpolyol (g2), (h) at least one catalyst, (I) at least one blowing agent, (j) optionally at least one flame retardant and (k) optionally additives to form a reaction mixture and reacting the mixture to form a polyisocyanurate rigid foam, wherein the amount of the recycled polyol (RP), based on the total weight of components (g), is at least 20 % by weight, the polyether polyol (g2) has a hydroxyl number of 160 - 300 mg KOH / g and is produced by alkoxylation of a starter molecule or starter molecule mixture with an average functionality of > 1 .5 and < 3, wherein at least 80% ethylene oxide is used as alkylene oxide for the production of polyether polyol (g2) and polyether polyol (g2) has at least 90 % primary hydroxyl end groups, the mass ratio of recycled polyol (RP) to polyether polyol (g2) is 0.75 to 2.2 and the sum of the mass fractions of recycled polyol (RP) and polyether polyol (g2), based on the total weight of component (g) is at least 65% by weight, and the mixing to form the reaction mixture takes place at an isocyanate index of > 180.

[0017] Polyisocyanurate material (a) according to the present invention comprises isocyanurate structures. In a preferred embodiment, the polyisocyanurate material (a) according to the present invention further comprises carboxylic ester structures. In addition, the polyisocyanurate material (a) according to the present invention may contain an organic phosphorous ester. Such polyisocyanurates are commonly used when a flame -retardant insulation foam is required, for example as insulation materials for the insulation of buildings.

[0018] The polyisocyanurate material (a) is usually obtained by reacting polyisocyanates and isocyanate reactive materials at an isocyanate index of at least 160, preferably 180 to 400, more preferred 190 to 350 and especially preferred 200 to 320 in presence of a trimerization catalyst. The isocyanate index is the ratio of isocyanate groups to isocyanatereactive groups multiplied by 100. An isocyanate index of 100 corresponds to an equimolar ratio of the isocyanate groups used and isocyanate reactive groups used. Under these conditions the isocyanurate structures, i.e. a ring obtained by reacting 3 isocyanate groups, within the polyisocyanurate material (a) are formed. The production of polyisocyanurate foams (a) is well known and for example disclosed in “Polyurethane Handbook”, Hanser / Gardener publications, 2nd edition 1993, especially in chapter 6.

[0019] The isocyanurate structures can be detected via I R spectroscopy. The IR spectrum of a polyisocyanurate material (a) according to the present invention shows a ratio of the height of the isocyanurate oscillation band at approximately 1410 cm1to the aromatic oscillation band at approx. 1600 cnr1of at least 0.5, preferably at least 1 , more preferably at least 2 and especially preferred at least 4. In a preferred embodiment the ratio of the isocyanurate oscillation band to the aromatic oscillation band is at most 7, more preferably at most 6. Preferably foam samples for the IR spectroscopy measurement are taken from the core of the foam to be tested.

[0020] Suitable isocyanates to produce the polyisocyanurate material (a) are well known in the field. They include the aliphatic, cycloaliphatic, araliphatic and preferably the aromatic polyvalent isocyanates known in technology. Such polyfunctional isocyanates are known and can be produced using known methods. In particular, the polyfunctional isocyanates can also be used as mixtures, so that isocyanate component in this case contains various polyfunctional isocyanates. Polyisocyanate is a polyfunctional isocyanate with two (hereinafter also referred to as diisocyanates) or more than two isocyanate groups per molecule. In particular, the isocyanates are selected from the group consisting of aromatic polyisocyanates, such as 2,4- and 2,6-toluene diisocyanate and the corresponding isomer mixtures, 4,4’-, 2,4’- and 2,2’-diphenylmethane diisocyanate (monomeric MDI) and the corresponding mixtures of isomers, mixtures of 4,4’- and 2,4’-diphenylmethane diisocyanates, mixtures of monomeric MDI and higher homologues of MDI (polymer MDI or pMDI), and mixtures of crude MDI and toluene diisocyanates. Particularly suitable are 2,2’-, 2,4’- or 4,4’-diphenylmethane diisocyanate (MDI) and mixtures of two or three of these isomers or mixtures of diphenylmethandiisocyanate and higher homologues. Such polyisocyanates are for example disclosed in the “Polyurethane Handbook”, Hanser / Gardener publications, 2ndedition 1993, chapter 3.2.

[0021] Isocyanate reactive materials are well known in the art. Examples are polyols like polyetherols and polyesterols. Such polyols are for example disclosed in the “Polyurethane Handbook”, Hanser / Gardener publications, 2ndedition 1993, chapter 3.1 . The carboxylic ester structures in the polyisocyanurate material (a), if present, can be obtained by reacting polyesterpolyols with polyisocyanate during the production of the polyisocyanurate material (a). The isocyanate reactive component for the production of the polyisocyanurate material (a) thus comprises polyester polyols, often in combination with polyether polyols. Suitable polyester polyols can be prepared from organic dicarboxylic acids having 2 to 12 carbon atoms, preferably aromatic, or mixtures of aromatic and aliphatic dicarboxylic acids and polyhydric alcohols, preferably diols, having 2 to 12 carbon atoms, preferably 2 to 6 carbon atoms.

[0022] Organic phosphorous esters are usually added as flame retardants. Examples for organic phosphorous esters are chlorinated phosphates such as tris-(2-chloroethyl)-phosphate, tris-(2-chloroisopropyl)phosphate (TCPP), tris(1 ,3- dichloropropyl)phosphate, tricresylphosphate, tris-(2,3-dibromopropyl)phosphate, tetrakis-(2-chloroethyl)-ethylene diphosphate, dimethylmethanphosphonate and diethanolaminomethyl-phosphonicacid-diethylester. Diethylethanephosphonate (DEEP), triethylphosphate (TEP), dimethylpropyl phosphonate (DMPP), diphenylcresylphosphate (DPK) can be used as organic phosphorous esters as well. In a preferred embodiment of the present invention the polyisocyanurate material comprises Phosphourous esters selected from the group of triethylphosphate (TEP) and tris(2-chloroisopropyl)phosphate (TCPP).

[0023] In addition, the polyisocyanurate material (a) may comprise suitable catalysts, blowing agents and additives known in the field. Examples of catalysts, blowing agents and suitable additives are mentioned in the “Polyurethane Handbook”, Hanser / Gardener publications, 2nd edition 1993. In a preferred embodiment, the polyisocyanurate material (a) comprising a tertiary amine catalyst (d). Further a PI R forming catalyst as the potassium salt of carboxylic acids might be present.

[0024] The amount of the polyisocyanurate material (a), based on the total weight of the components (a) to (e) is at least 20 % by weight, preferably 25 to 70 % by weight, more preferred 30 to 60 % by weight and especially preferred 35 to 50 % by weight.

[0025] As polyalcohol (b) any at least dihydric alcohol can be applied which has at least two primary alcohol groups and a hydroxyl value of 200 to 800 mg KOH / g. As polyalcohol (b) also mixtures of two or more dihydric and / or polyhydric alcohols can be used. If mixtures are used the hydroxyl value is calculated from the mixture. Preferably suitable polyalcohols (b) are liquid at 40 °C. Examples of polyhydric, preferably dihydric alcohols are triethylene glycol, polyethylene glycol, 1 ,4-butanediol, 1 ,5-pentanediol, 1,6- hexanediol, 1 ,10-decanediol, pentaerythritol as well as alkoxylates of common starter molecules as for example of the same starters and / or of other common polyalcoholes, such as monoethylene glycol, diethylene glycol, 1 ,2- or 1 ,3-propanediol, dipropylene glycol, polypropylene glycol, glycerol, trimethylolpropane, pentaerythritol. Preferably used is triethylene glycol.

[0026] The amount of polyol (b) used is preferably 10 to 50 % by weight, more preferred 15 to 40 % by weight and especially preferred 20 to 35 % by weight, each based on the total weight of the components (a) to (e). It is known by a person, skilled in the art, that molar amount and hydroxyl value of the polyol (b) applied influences the hydroxyl value of the recycled polyol obtained. The higher the molar amount of polyol (b) the higher the final hydroxyl value of the recycled polyol (RP) and the higher the OH number of the polyol (b) the higher the OH value of the recycled polyol (RP) obtained.

[0027] As at least one aliphatic monocarboxylic acid any monocarboxylic acid (c) having an acid number of 190 to 760, preferably 250 to 600, more preferred 280 to 500 and especially preferred 300 to 450 mg KOH / g. Preferably the monocarboxylic acid (c) has a boiling point of at least 140 °C, more preferred at least 200 °C and especially preferred at least 220 °C. Further, in a preferred embodiment the monocarboxylic acid (c) has a melting point of less than 70 °C, more preferred less than 60 °C and especially preferred less than 25 °C. In a preferred embodiment the monocarboxylic acid is free of groups reactive towards isocyanate groups such as amin groups -NH2 or hydroxyl groups -OH and is especially free of hydroxyl groups. Examples of suitable monocarboxylic acids are C3 to C18, preferably C3 to C12 monocarboxylic acids. These compounds can be saturated or unsaturated and can be linear or branched. Examples of C3 to C18 monocarboxylic acids include propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, margaric acid and stearic acid. More preferred are C8 to C12 monocarboxylic acids even more preferred C8 to C11 and especially preferred is caprylic acid. The preferred acids combine a high boiling temperature and a low molecular weight which results in a higher concentration of carboxylic groups.

[0028] The amount of monocarboxylic acid (c) used is preferably 5 to 25 % by weight, more preferred 8 to 18 % by weight and especially preferred 10 to 16 % by weight, each based on the total weight of the components (a) to (e). Monocarboxylic acid can be used to influence the viscosity of the recycled polyol (RP) obtained. The higher the molar amount of monocarboxylic acid the lower the viscosity of the recycled polyol (RP).

[0029] As catalyst (d) catalysts can be used comprising at least one basic catalyst (d) catalyzing esterification of alcohol groups and carboxylic acids. Such catalysts are used for the production of polyesters and their transesterification and are well known in the art. Examples of catalysts (d) are alkali- or alkali earth metal carboxylates (d1) as for example potassium carboxylate and transition metal-based catalysts (d2) as iron based catalysts, cadmium based catalysts, cobalt based catalysts, lead based catalysts, zinc based catalysts, antimony based catalysts, titanium based catalysts, and tin based catalysts such as metal oxides or metal salts as well as alkali metal or alkali earth metal carboxylates. Transition metal based catalysts (d2) include metal catalysts such as titanium catalysts, as described in "Modern Polyesters: Chemistry and Technology of Polyesters and Copolyesters", Chapter 2, Wiley, 2003, ISBN 0- 471-49856-4. Examples of transition metal based catalysts (d2) are tin(ll) salts of organic carboxylic acids, e.g. tin(ll) acetate, tin(ll) octoate, tin(ll) ethyl hexanoate and tin(ll) laurate, and the dialkyltin(IV) salts of organic carboxylic acids, e.g. dibutyltin diacetate, dibutyltin dilaurate, zinc(ll) acetate, dibutyltin maleate and dioctyltin diacetate, and the titanium alkoxides, e.g. tetrabutyl orthotitanate, and also bismuth carboxylates, such as bismuth(lll) neodecanoate, bismuth 2-ethy I hexanoate and bismuth octanoate, or mixtures thereof.

[0030] In a preferred embodiment, the catalyst (d), comprises at least one alkali- or alkali earth metal carboxylate catalyst (d1) and at least one transition metal based catalyst (d2). Examples of carbonate based catalysts (d1) are alkali and alkaline-earth carbonates and hydrogencarbonates. In an especially preferred embodiment, the carbonate -based catalyst (d2) is selected from the group, consisting of as sodium carbonate, potassium carbonate, sodium hydrogencarbonate, calcium carbonate, calcium hydrogencarbonate, magnesium carbonate, magnesium hydrogencarbonate and mixtures of two or more thereof. Especially preferred as catalyst (d2) is sodium carbonate or potassium carbonate.

[0031] Catalysts (d) can be used by way of example at a concentration of from 0.01 to 10% by weight, in particular from 0.5 to 8% by weight, as catalyst or, respectively, catalyst combination, based on the weight of components (a), (b), (c), (d) and (e).

[0032] Deamination agents (e) are compounds which, when added to mixtures of alcohols and aromatic amines, react preferentially with the aromatic amines, even if there is an excess of alcohol. These include such as fatty acids, preferably fatty acids having 16 and more carbon atoms, isocyanates, glycidyl ethers or epoxidized native oils.

[0033] For example, stearic acid, palmitic acid, , erucaic acid, linoleic acid, linolenic acid, oleic acid or mixtures of fatty acids can be used as fatty acids. Fatty acids and their use for deamination are described, for example, in DE 102009026898.

[0034] Isocyanates for deamination are preferably those that have exclusively secondary or tertiary or secondary and tertiary aliphatic bound Isocyanate groups, for example bis-1,3(2-isocyanatopropyl)benzene. Isocyanates and their use for deamination are described, for example, in EP899292.

[0035] As glycidyl ethers (e) any compound comprising epoxide groups preferably compounds containing one or two epoxy groups in the molecule can be used. The monofunctional glycidyl ethers of the general formula (i) proved to be particularly suitable: Wherein R = Phenyl, Cyclohexyl, Methylcyclohexyl, Benzyl, i-Propyl, i-Butyl or methyl- and / or ethyl-branched hydrocarbon chains having 5 to 10 carbon atoms in the straight chain and / or a group of the general formula (II):

[0036] Wherein A stands for an alkyl residue having 1 bis 8 carbon atoms, n is 3 to 12 and m is 1 to 6.

[0037] As difunctional glycidyl ethers compounds according to formula (ill) are especially preferred: wherein R' = diphenylmethylene, 2,2-diphenylpropylene (bisphenol A), unbranched hydrocarbon chains with 4 to 10 carbon atoms or methyl and / or ethyl branched hydrocarbon chains with 4 to 8 carbon atoms in the straight chain. Glycidylethers and their use for deamination are for example disclosed in EP592952.

[0038] Epoxidized native fatty oils are those products that are obtained from at least single, preferably at least triple unsaturated natural oils, e.g. from soy, flax, castor and nuts of all kinds. The term "unsaturated" refers to a carbon - carbon double bond. Glycidylethers and their use for deamination are for example disclosed in EP718349.

[0039] As deamination agents (e) preferably glycidylethers are used. Preferred glycidylethers are monofunctional epoxy resins, such as 2 -ethylhexyl glycidyl ether, isopropyl glycidyl ether, butyl glycidyl ether, cresyl glycidyl ether or monofunctional glycidyl ethers based on 2-ethylhexanol (Epilox P13-16, LEUNA-Harze GmbH), C12-C14 alcohols (Epilox P 13-18, LEUNA-Harze GmbH) or C13-C15 alcohols (Epilox P 13-19, LEUNA-Harze GmbH).

[0040] The amount of the deamination agent (e) added to the reaction mixture preferably is 0 to 40 % by weight, more preferred 5 to 30 wt.-% and especially preferred 10 to 20 % by weight, each based on the total weight of the polyisocyanurate material (a)

[0041] Polyisocyanurate material (a), a polyalcohol (b), a monocarboxylic acid (c), catalyst (d) and, if present, deamination agent (e) are mixed to form a reaction mixture wherein the content of the polyisocyanurate material (a) in the reaction mixture is at least 20 % by weight, based on the total weight of components (a) to (e), and reacting the reaction mixture at temperatures of 130 to 280 °C, preferably 160 to 250 °C and especially preferred 180 to 220 °C. The order in which they are added to the mixture is not limited. For example, all components can be added at the same time. Alternatively, the polyisocyanurate material (a) can be mixed with the poly alcohol (b) in a first step and the monocarboxylic acid (c) and the catalyst (d) can be added afterwards. In a preferred embodiment, at least part of the polyalcohol (b) and the monocarboxylic acid (c) are first premixed and can also be converted into an ester (be) in whole or in part. Under reaction conditions in the reaction mixture, such an ester (be) behaves similarly to the individual components (b) and (c).

[0042] The reaction is conducted in a way that the resulting recycled polyol (RP) has an OH -number of 150 to 300 mg KOH / g, preferably 180 to 290 mg KOH / g and especially preferred 200 to 280 mg KOH / g. The OH value of the recycled polyol (RP) is controlled by the amount and OH-value of the polyol (b) added. The lower the molar amount of the polyol (b), the lower the OH-number. Nevertheless, a certain minimal amount by weight of the polyol (b), as specified above, is required to sufficiently wet and dissolve the polyisocyanurate containing material (a). It is therefore necessary for the present invention to use polyols (b) or mixtures of polyols (b) having an average OH- number of 200 to 800 mg KOH / g as disclosed above. If the viscosity and molecular weight of the polyol (b) is too high, also the viscosity of the recycled polyol (RP) will be very high. In addition, the viscosity of the recycling polyol (RP) is less than 25000mPas, preferably less than 15000 mPas, more preferred less than 10000 mPas and especially preferred less than 6000 mPas at 25 °C measured according to DIN EN ISO 3219. Viscosity can be lowered for example by increasing the amount of polyol (b) and by increasing the molar amount of monocarboxylic acid (c). Preferably polyalcohol (b) and monocarboxylic acid (c) are used in an amount that the theoretical average OH-functionality after esterification of all carboxylic groups of the mono carboxylic acid (c) and OH-groups of the polyalcohol (b) is from 1 to 2.5, more preferred 1 .2 to 2.3 and especially preferred 1 .5 to 2.0.

[0043] The obtained recycled polyol (RP) may be further purified by filtration. So, by filtration unsoluble components, as for example unreacted carbonates can be separated. In addition, by distillation volatile substances might be separated. According to the invention, the content of polyisocyanurate material (a) in the recycled polyol (RP) is at least 20 % by weight, preferably at least 30 % by weight, more preferred at least 35 % by weight and especially preferred more than 40 % by weight.

[0044] The recycled polyol (RP) according to the present invention is suitable for the production of high performance rigid polyisocyanurate foams having good mechanical properties, low heat conductivities, for example of < 21 ,5 mW / mK at an average temperature of 10 °C, a high flame resistance with a flame height in the B2 -small burner fire test of preferably < 12 cm , a fast foam curing, a fine cell structure and, when produced in a double belt plant, a smooth surface wherein the recycled polyol (RP) is applied in a significant amount of at least 20 % by weight, preferably at least 30 % by weight more preferred at least 35 % by weight and especially preferred at least 40 % by weight, each based on the total weight of isocyanate reactive components applied.

[0045] The process for the production of the polyisocyanurate rigid foam, comprises mixing at least one aromatic polyisocyanate (f), at least one isocyanate reactive compound (g) comprising the recycled polyol (RP) according to the present invention and at least one polyetherpolyol (g2), at least one catalyst (h), at least one blowing agent (I), optionally at least one flame retardant (j) and optionally additives (k) to form a reaction mixture and reacting the mixture to form a polyisocyanurate rigid foam, wherein the amount of the recycled polyol (RP), based on the total weight of components (g), is at least 20 % by weight, the polyether polyol (g2) has a hydroxyl number of 160 - 300 mg KOH / g and is produced by al koxy lation of a starter molecule or starter molecule mixture with an average functionality of > 1 .5 and < 3, wherein at least 80% ethylene oxide is used as alkylene oxide for the production of polyether polyol (g2) and polyether polyol (g2) has at least 90 % primary hydroxyl end groups, the mass ratio of recycled polyol (RP) to polyether polyol (g2) is 0.75 to 2.2 and the sum of the mass fractions of recycled polyol (RP) and polyether polyol (g2), based on the total weight of component (g) is at least 65% by weight, and the mixing to form the reaction mixture takes place at an isocyanate index of > 180.

[0046] Rigid polyisocyanurate foams according to the present invention have a compressive strength at 10% compression of not less than 80 kPa, preferably not less than 120 kPa, particularly preferably not less than 140 kPa. The isocyanate-based rigid foam according to the invention moreover has a closed cell content according to DIN ISO 4590 of more than 80%, preferably more than 90%. Further details of the rigid polyisocyanurate foams according to the invention may be found in "“Polyurethane Handbook”, Hanser / Gardener publications, 2nd edition 1993, chapter 6, in particular chapter 6.2.2 and 6.5.2.2.

[0047] The polyisocyanates (f) are the aliphatic, cycloaliphatic, araliphatic and preferably the aromatic polyfunctional isocyanates known in the prior art. Such polyfunctional isocyanates are known and may be produced by methods known per se. The polyfunctional isocyanates may in particular also be used as mixtures, so that the component (f) in this case comprises different polyfunctional isocyanates. Polyisocyanate (f) is a polyfunctional isocyanate having two (hereinbelow also referred to as diisocyanates) or more than two isocyanate groups per molecule. The isocyanates (f) are in particular selected from the group consisting of aromatic polyisocyanates, such as 2,4- and 2,6- toluene diisocyanate and the corresponding isomer mixtures, 4,4'-, 2,4'- and 2,2'-diphenylmethane diisocyanate and the corresponding isomer mixtures (also known as monomeric diphenylmethane or MMDI), for example mixtures of 4,4'- and 2,4'-diphenylmethane diisocyanates, mixtures of at least one isomer of diphenylmethane diisocyanate and higher-nuclear homologues of diphenylmethane diisocyanate which have at least 3 aromatic nuclei and a functionality of at least 3 and are also known as polyphenyl-polymethylene polyisocyanates, polymeric MDI or pMDI. The isomers and homologues of MDI are generally obtained by distillation of crude MDI. In addition to dinuclear MDI (MMDI) polymeric MDI also comprises one or more polynuclear condensation products of MDI having a functionality of more than 2, in particular 3 or 4 or 5. Polymeric MDI is known and is often described as polyphenyl-polymethylene polyisocyanate. Also employable as isocyanate (f) are mixtures of 4,4'-, 2,4'- and 2,2'-diphenylmethane diisocyanates and polyphenylpolyethylene polyisocyanates (crude MDI) and mixtures of crude MDI and toluene diisocyanates. 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). Frequent use is also made of modified polyisocyanates, i.e. products obtained by chemical reaction of organic polyisocyanates and comprising at least two reactive isocyanate groups per molecule. Particular mention may be made of polyisocyanates comprising ester, urea, biuret, allophanate, carbodiimide, isocyanurate, uretdione, carbamate and / or urethane groups, often also together with unconverted polyisocyanates.

[0048] The polyisocyanates of the component (f) particularly preferably comprise 2,2'-MDI or 2,4'-MDI or 4,4'-MDI or mixtures of monomeric diphenylmethane diisocyanate or mixtures of monomeric diphenylmethane diisocyanate and higher-nuclear homologues of MDI. The average functionality of a polyisocyanate comprising polymeric MDI may vary in the range from about 2.2 to about 4, preferably from 2.4 to 3.8 and in particular from 2.6 to 3.0. Polyfunctional isocyanates or mixtures of two or more MDI-based polyfunctional isocyanates are known and are commercially available from BASF Polyurethanes GmbH under the trade names Lupranat® M20, Lupranat® M50, oder Lupranat® M70.

[0049] The component (f) preferably comprises at least 70% by weight, particularly preferably at least 90% by weight and in particular 100% by weight, based on the total weight of the component (f), of one or more isocyanates selected from the group consisting of 2,2'-MDI, 2,4'-MDI, 4,4'-MDI and higher-nuclear homologues of MDI. The content of higher- nuclear homologues of MDI is preferably at least 20% by weight, particularly preferably more than 30% to less than 80% by weight, based on the total weight of the component (f).

[0050] The viscosity of the employed component (f) may be varied over a wide range. The component (f) preferably has a viscosity of 100 to 3000 mPa*s, particularly preferably from 100 to 1000 mPa*s, particularly preferably from 100 to 800 mPa*s, particularly preferably from 200 to 700 mPa*s and particularly preferably from 400 to 650 mPa*s at 25°C and results from the choice of the isocyanates (f) and the mixtures thereof.

[0051] The employed isocyanate-reactive compounds (g) may be selected from any compounds having isocyanate -reactive groups known in polyurethane chemistry, preferably compound having on average at least 1.5 isocyanate-reactive groups, such as hydroxyl groups, -NH groups, NH2 groups or carboxylic acid groups, preferably NH2 or OH groups and in particular at least 1 .5 OH groups. The average functionality of the compounds of the component (g) towards isocyanate groups in a preferred embodiment is in the range from at least 1 .5, preferably 1 .6 to 8.0, particularly preferably 1.7 to 3.0 and in particular 1.8 to 2.5. Suitable isocyanate-reactive compounds are for example polyetherpolyols, polyesterpolyols and chain extenders and crosslinking agents, wherein chain extenders and crosslinking agents preferably have a molecular weight of less than 300 g / mol, preferably less than 200 g / mol and especially preferred less than 150 g / mol while polyetherols and polyesterols preferably have a molecular weight of at least 300 g / mol, more preferred between 350 and 12 000 g / mol, even more preferred 400 to 6000 g / mol and especially preferred 450 to less than 3000 g / mol. For the purposes of the present disclosure, the expressions “polyester polyol” and “polyesterol” are equivalent, as also are the expressions “polyether polyol” and “polyetherol”.

[0052] The isocyanate reactive compounds (g) comprise as component (g1) the recycled polyol (RP) according to the present invention in an amount of at least 20 % by weight, preferably at least 25 to 60 % by weight and especially preferred 35 to 50 % by weight, each based on the total weight of component (g). In addition, the isocyanate reactive compounds (g) comprise at least one polyether polyol (g2). The mass ratio of the component (g1) to component (g2) is 0.75 to 2.2, preferably 1 .0 to 2.0 and especially preferred 1 .2 to 1 .8. and the sum of the mass fractions of component (g1) and component (g2) based on component (g) is more than 65% by weight, preferably more than 70 % by weight, more preferred more than 75 % by weight and especially preferred more than 80 % by weight, each based on the total weight of isocyanate reactive compound (g). In a preferred embodiment the remaining part of the isocyanate reactive component (g) includes polyetherols different from polyetherpolyol (g2), polyesterols or chain extenders or crosslinking agents. In an especially preferred embodiment the isocyanate reactive component comprises, in addition to components (g1) and (g2) a polyesterpolyol (g3).

[0053] According to the invention the polyetherpolyol (g2) has a hydroxyl number of 160-300 KOH / g, preferably 170 to 270 mg KOH / g and especially preferred 180 to 220 mg KOH / g and is produced by alkoxylation of a starter or start the mixture, wherein the alkylene oxide employed for producing polyether polyol (g2) is preferably at least 80% by weight, preferably at least 90 % by weight and especially preferred 100 % by weight, based on the total weight of the alkylene oxide used, of ethylene oxide and polyether polyol (g2) comprises at least 90%, preferably at least 95%, particularly preferably at least 99% and in particular exclusively primary hydroxyl end groups.

[0054] The polyether polyols (g2) are produced by known processes, for example by anionic polymerization of one or more alkylene oxides having 2 to 4 carbon atoms, comprising ethylene oxide, with customary 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 dimethylethanol - amine (DMEOA), imidazole and / or imidazole derivatives, using at least one starter molecule or starter molecule mixture comprising on average < 3.0 and > 1 .5, preferably < 2.5 and > 2.0 and particularly preferably 2 reactive hydrogen atoms in bonded form. In addition to the anionic polymerization of the starter molecules production may also be carried out by using cationic polymerization, wherein catalysts employed include Lewis acids, such as antimony pentachloride, boron fluoride etherate or fuller’s earth.

[0055] In addition to ethylene oxide suitable alkylene oxides also include for example tetrahydrofuran, 1 ,3- and 1 ,2-propy- lene oxide, 1,2- and 2,3-butylene oxide, styrene oxide and preferably 1 ,2-propylene oxide. In a particularly preferred embodiment, the alkylene oxide employed is exclusively ethylene oxide. The alkylene oxides may be used individually, alternately in succession or as mixtures. According to the invention the alkylene oxide used for producing polyether polyol (g2) is at least 80% by weight of ethylene oxide, preferably at least 90% by weight of ethylene oxide, particularly preferably at least 95% by weight and especially at least 99% by weight of ethylene oxide. The alkylene oxide used for producing the polyether polyol (g2) according to the invention is very particularly preferably exclusively ethylene oxide, i.e. , the weight fraction of ethylene oxide in the total weight of alkylene oxide in component (g2) is 100% by weight in this embodiment. When ethylene oxide is employed in a mixture with other alkylene oxides it is to be ensured according to the invention that the polyether polyol produced therefrom comprises the inventive content of primary hydroxyl end groups. Examples of useful starter molecules include: water, organic dicarboxylic acids, such as succinic acid, adipic acid, phthalic acid and terephthalic acid, aliphatic and aromatic, optionally N-mono-, N,N- and N, N'-dialkyl-substituted diamines having 1 to 4 carbon atoms in the alkyl radical, such as optionally mono- and dialkyl-substituted ethylenediamine, diethylenetriamine, triethylenetetramine, 1,3-propylenediamine, 1,3- and 1 ,4-butylenediamine, 1,2-, 1 ,3-, 1 ,4-, 1 ,5- and 1,6-hexamethylenediamine, phenylenediamines, 2,3-, 2,4- and 2,6-tolylenediamine and 4,4'-, 2,4'- and 2,2'-diaminodiphenylmethane. The recited by primary amines are particularly preferred, preferably ethylenediamine. Useful starter molecules further include: alkanolamines, for example ethanolamine, N-methyl- and N-ethylethanolamine, dialkanolamines, for example diethanolamine, N-methyl und N-ethyldiethanolamine and trialkanolamines, for example triethanolamine, and ammonia.

[0056] It is preferable to employ di- or polyhydric alcohols, such as ethanediol, 1 ,2- and 1 ,3-propanediol, diethylene glycol (DEG), dipropylene glycol, 1 ,4-butanediol, 1 ,6-hexanediol, glycerol, trimethylolpropane, bisphenol A, bisphenol F, pentaerythritol, sorbitol and sucrose, particularly preferably diethylene glycol, monoethylene glycol, 1 ,2-propanediol and glycerol, especially diethylene glycol or ethylene glycol.

[0057] In the context of the present invention, the functionality of a polyether polyol is to be understood as the functionality of the starter molecule or the average functionality of the mixture of starter molecules, even if in reality the functionality is lowered by side reactions compared to the functionality of the starter molecules.

[0058] In a preferred embodiment the starter molecules comprise no fatty acids.

[0059] The proportion of the component (g2) is generally from 20% to 50 % by weight, preferably from 25% to 45 % by weight, particularly preferably from 30% to 40 % by weight, based on the sum of the weight of the isocyanate reactive compound (g).

[0060] In a preferred embodiment the isocyanate reactive component (g) comprises, in addition to component (g1) and component (g2), at least one aromatic polyester polyol (g3) with an average functionality of > 1 .7 and < 2.5, an average hydroxyl number of > 180 and < 250 mg KOH / g and in a preferred embodiment a fatty acid content of > 12 and < 16 weight-%, based on the total weight of the aromatic polyesterpolyol (g3).

[0061] Polyester (g3) can, for example, be obtained by condensation of di- or polycarboxylic acids and di- or polyalcohols. In a preferred embodiment the polyesterpolyol (g3) is producible by esterification of (g3.1 ) 10 to 50 mol% of a dicarboxylic acid composition comprising aromatic dicarboxylic acids, (g3.2) 0 to 20 mol% of one or more fatty acids and / or fatty acid derivatives, (g3.3) 10 to 70 mol% of one or more aliphatic or cycloaliphatic diols having 2 to 18 carbon atoms or alkoxylates thereof, (g3.4) 0 to 50 mol% of a higher-functional polyol selected from the group consisting of glycerol, alkoxylated glycerol, trimethylolpropane, alkoxylated trimethylolpropane, pentaerythritol, alkoxylated pentaerythritol. The dicarboxylic acid composition (g3.1 ) comprises dicarboxylic acids and / or derivatives thereof which may typically be used for producing esters. The dicarboxylic acid composition (g3.1 ) 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. It is particularly preferable when the component (g3.1 ) comprises phthalic anhydride, phthalic acid, terephthalic acid or polyethylene terephthalate (PET) and in particular phthalic anhydride or terephthalic acid, in particular phthalic anhydride. Component (g3.1 ) may generally also comprise aliphatic dicarboxylic acids or aliphatic dicarboxylic acid derivatives. If aliphatic dicarboxylic acids are used these are generally present in amounts of 0.5-30 mol%, preferably 0.5 to 10 mol%, in each case based on the component (g3.1 ). The aliphatic dicarboxylic acids employed preferably include adipic or dicarboxylic acid mixtures of succinic, glutaric and adipic acid. It is preferable when the dicarboxylic acid composition (g3.1 ) comprises no aliphatic dicarboxylic acids and thus consists to an extent of 100 mol% of one or more aromatic dicarboxylic acids or derivatives thereof.

[0062] Component (g3.1 ) is generally employed in amounts of 10 to 50 mol%, preferably in amounts of 20 to 45 mol%, based on the components (g3.1 ), (g3.2), (g3.3) and (g3.4) used for producing the aromatic polyester polyol (g3).

[0063] It is also possible to use one or more fatty acids and / or fatty acid derivatives (g3.2) for producing the aromatic polyester polyol (g3). The acids and / or fatty acid derivatives may be of either 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 are glycerol esters of fatty acids, for example castor oil, grapeseed oil, black cumin oil, pumpkin kernel oil, borage seed oil, soybean oil, wheat germ oil, rapeseed oil, sunflower seed oil, peanut oil, apricot kernel oil, pistachio oil, almond oil, olive oil, macadamia nut oil, avocado oil, sea buckthorn oil, sesame oil, hemp oil, hazelnut oil, primula oil, wild rose oil, safflower oil, walnut oil.

[0064] Further examples of fatty acid derivatives are hydroxyl-modified fats or fatty acids, hydrogenated fats or fatty acids, epoxidized facts acids, alky l-branched or fatty acid, fatty acid amides, animal tallow such as for example beef tallow, alkyl or especially methyl esters of fatty acids such as biodiesel.

[0065] Component (g3.2) is generally employed in amounts of 0 to 20 mol%, preferably in amounts of 5 to 18 mol%, particularly preferably in amounts of 8 to 15 mol%, based on all components (g3.1) to (g3.4) used for producing the aromatic polyester polyol (g3).

[0066] In a particularly preferred embodiment of the present invention the fatty acid or the fatty acid derivative (g3.2) is oleic acid, biodiesel, soybean oil, rapeseed oil or tallow, in particular oleic acid or biodiesel, especially oleic acid, and is used in an amount of 8 to 15 mol%. The fatty acid or the fatty acid derivative improves inter alia blowing agent solubility in the production of rigid polyurethane or polyisocyanurate foams. It is very particularly preferable when component (g3.2) comprises no triglyceride, in particular no oil or fat. The glycerol liberated through esterification or transesterification from the triglyceride impairs the dimensional stability of the rigid foam.

[0067] The component (g3.3) employed is one or more aliphatic or cycloaliphatic diols having 2 to 18 carbon atoms or alkoxylates thereof. Component (g3.3) preferably comprises at least one compound from the group consisting of ethylene glycol, diethylene glycol, propylene glycol, 1 ,3-propanediol, 1 ,4-butanediol, 1 ,5-pentanediol, 1 ,6-hexanediol, 2-methyl-1 ,3-propanediol and 3-methyl-1 ,5-pentanediol and alkoxylates thereof. The aliphatic diol (g3.3) is particularly preferably monoethylene glycol or diethylene glycol, in particular diethylene glycol. Component (g3.3) is generally employed in amounts of 10 to 80 mol%, preferably in amounts of 20 to 75 mol%, particularly preferably in amounts of 30 to 60 mol%, based on all components used for producing the aromatic polyester polyol (g3).

[0068] Suitable higher-functional polyols (g3.4) that may be employed for producing the aromatic polyester polyol (g3) include any desired polyols having a functionality of more than 2. The higher-functional polyol (g3.4) is preferably selected from the group consisting of glycerol, alkoxylated glycerol, trimethylolpropane, alkoxylated trimethylolpropane, pentaerythritol, alkoxylated pentaerythritol and mixtures of 2 or more of these higher-functional polyols. The higher-functional polyol (g3.4) is preferably glycerol, ethoxylated glycerol or mixtures thereof.

[0069] The higher-functional polyol (g3.4) is employed in amounts of 0 to 50 mol%, preferably in amounts of 5 to 40 mol%, particularly preferably in amounts of 10 to 25 mol%, based on all components used for producing the aromatic polyester polyol (b1 ). In a particularly preferred embodiment of the present invention no higher-functional polyol (g3.4) is used for producing the aromatic polyester.

[0070] According to the invention the aromatic polyester polyol (g3) has a number-average functionality of > 1.7 to < 3.0, preferably of > 1 .7 to < 2.5, particularly preferably of > 1 .75 to < 2.2.

[0071] The aromatic polyester polyol (g3) preferably has a hydroxyl number of 180 to 250 mg KOH / g, preferably of 200 to 240 mg KOH / g. In a particularly preferred embodiment, the aromatic polyester polyol (g3) as an OH number of 190 to 250 mg KOH / g and a functionality of 1 .7 to 2.5.

[0072] To produce the aromatic polyester polyol (g3) the dicarboxylic acids (g3.1), fatty acids and / or fatty acid derivatives (g3.2), the aliphatic or cycloaliphatic diols 2 to 18 carbon atoms or alkoxylates thereof (g3.3) and the higher- functional polyols (g3.4) may be subjected to polycondensation in the melt at temperatures of 150°C to 280°C, preferably 180°C to 260°C, optionally under reduced pressure up to the desired acid number which is advantageously less than 10 and particularly preferably less than 2 in the absence of catalyst or preferably in the presence of esterification catalysts, advantageously in an atmosphere of inert gas such as nitrogen. In a preferred embodiment the esterification mixture is subjected to polycondensation at the abovementioned temperatures up to an acid number of 80 to 20, preferably 40 to 20, under standard pressure and subsequently at a pressure of less than 500 mbar, preferably 40 to 400 mbar. Suitable as esterification catalysts are basic catalysts, for example, iron, cadmium, cobalt, lead, zinc, antimony, magnesium, potassium, titanium and tin catalysts in the form of metals, metal oxides or metal salts. However, the polycondensation may also be carried out in the liquid phase in the presence of diluents and / or entraining agents, for example benzene toluene, xylene or chlorobenzene for azeotropic distillative removal of the water of condensation.

[0073] Preferably, polyesterpolyol (g3) has a fatty acid content of > 8 % by weight, more preferred 10 to 20 % by weight and especially preferred 12 to 16 % by weight, each based on the total weight of the aromatic polyesterpolyol (g3).

[0074] The proportion of the polyester polyols (g3) according to the invention, if present, is generally 5 to 35 % by weight, preferably 8 to 30 and especially preferred 10 to 20 % by weight, each based on the total weight of the isocyanate reactive compound (g).

[0075] According to the invention the sum of the mass fractions of component (g1 ), (g2) and component (g3) based on component (g) > 80% by weight, preferably > 90% by weight, particularly preferably > 95% by weight. It is very particularly preferable when the sum of the mass fractions of component (g1 ), (g2) and component (g3) based on the isocyanate reactive component (g) is 100% by weight, i.e. in this embodiment no further compounds having isocyanate-reactive hydrogen atoms are employed as component (g1 ), component (g2) and component (g3).

[0076] In a preferred embodiment of the present invention the viscosity of isocyanate reactive component (g) according to the invention is at most 5000 mPas at 25 °C, more preferred at most 4000 mPas at 25 °C and especially preferred at most 3500 mPas at 25 °C. If the viscosity is too high, it will cause mixing problems when mixing with the isocyanate component. This leads to inconsistent foams of inferior quality, especially poorer mechanical properties, inconsistent and coarse cell structure, high heatl conductivity, and an irregular surface with surface defects.

[0077] Preferably, the recycled content, i.e. the content of polyisocyanurate material (a), in the at least one isocyanate reactive compound (g) based on the total weight of the isocyanate reactive component (g) is at least 10 % by weight, more preferred at least 12.5 % by weight, more preferred at least 15 % by weight, even more preferred at least 17.5 % by weight and especially preferred at least 20 % by weight.

[0078] Catalysts (h) used for producing the rigid polyisocyanurate foams according to the invention are in particular compounds which markedly accelerate the reaction of the compounds comprising reactive hydrogen atoms, in particular hydroxyl groups, of the components (g) with the polyisocyanates (f).

[0079] Advantageously employed compounds include for example 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-ethyl- morpholine, 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-di- azabicyclo(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)hexahydrotriazine, for example N, N', N" -tris(dimethylaminopropyl)-s-hexahydrotriazine and triethylenediamine.

[0080] However, further suitable catalysts include metal salts, such as iron(ll) chloride, zinc chloride, lead octoate and tin salts, such as tin dioctoate, tin diethylhexoate and dibutyltin dilaurate and mixtures of tertiary amines and metal salts, in particular organic tin salts. Contemplated 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 alkali metal salts of long-chain fatty acids having 8 to 20 carbon atoms and optionally pendant OH-groups.

[0081] Contemplated catalysts further include incorporable amines, preferably amines having an -OH, -NH or -NH2 function, for example ethylenediamine, triethanolamine, diethanolamine, ethanolamine and dimethylethanolamine.

[0082] Incorporable catalysts may be regarded as compounds of the component (g) as well as compounds of the component (h).

[0083] It is also possible to carry out the reactions without catalysis. In this case, it is usual to utilize the catalytic activity of amine-started polyols.

[0084] Contemplated catalysts for the trimerization reaction of the excess NCO groups with one another further include: Isocyanurate-forming catalysts, for example ammonium ion salts or alkali metal salts, especially ammonium carboxylates or alkali metal carboxylates, alone or in combination with tertiary amines. Formation of isocyanurate leads to flame-retardant PI R foams which are preferably used in rigid foam for technical applications, for example in the construction industry as insulation sheet or sandwich elements.

[0085] In a preferred embodiment the catalyst (h) comprises an amine catalyst having a tertiary amino group and an ammonium or alkali metal carboxylate catalyst. In a particularly preferred embodiment, the catalyst (h) 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, potassium 2-ethylhexanoate, potassium neodecanoate and potassium 3,5,5- trimethylhexanoate. It has surprisingly been found that the use of these catalysts in the continuous production of sandwich elements, for example in a double-belt process, affords sandwich elements having a particularly smooth surface area facing the outer layer, in particular the lower outer layer. This results in sandwich elements having exceptional adhesion of the foam to the outer layer and in defect-free surfaces. It is preferable to employ 0.001 to 10 parts by weight of catalysts / catalyst combination based on 100 parts by weight of the component (g).

[0086] Blowing agents (i) used for producing the rigid polyisocyanurate foams according to the invention include formic acid and formic acid-water mixtures. These react with isocyanate groups to form carbon dioxide and carbon monoxide. Since these blowing agents liberate the gas via a chemical reaction with the isocyanate groups they are referred to as chemical blowing agents. Physical blowing agents, such as low-boiling hydrocarbons, are employed in addition. Suitable physical blowing agents include in particular liquids which are inert toward the polyisocyanates (f) and have boiling points below 100°C, preferably below 50°C, at atmospheric pressure and therefore evaporate under the influence of the exothermic polyaddition reaction.

[0087] Employable physical blowing agents include for example alkanes, such as heptane, hexane, n- and isopentane, preferably industrial mixtures of n-pentane and isopentane, n-butane and 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 trifluoropropenes and tetrafluoropropenes, such as (HFO-1234), pentafluoropropenes, such as (HFO-1225), chlorotrifluoropropenes, such as (HFO-1233), chlorodifluoropropenes, chlorotetrafluoropropenes and hexafluorobutenes, and also mixtures of one or more of these components. Preference is given to tetrafluoropropenes, pentafluoropropenes, chlorotrifluorpropenes and hexafluorobutenes, wherein the unsaturated, terminal carbon atom bears at least one chloro or fluoro 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;

[0088] 1 ,1 ,1 ,3,3-pentafluoropropene (HFO-1225zc); 1 ,1 ,2,3,3-pentafluoropropene (HFO-1225yc); 1 -chloro-2, 3,3,3- tetrafluorpropene (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 use mixtures of these low- boiling-point liquids with one another and / or with other substituted or unsubstituted hydrocarbons.

[0089] Chemical blowing agent employed include acid-water mixtures or acids as formic acid. Physical blowing agents used are preferably pentane isomers / mixtures of pentane isomers. The chemical blowing agents may be used together with physical blowing agents, wherein the use of formic acid-water mixtures together with pentane isomers or mixtures of pentane isomers are preferred.

[0090] The employed amount of the blowing agent / the blowing agent mixture is 0.1 % to 45% by weight, preferably 1 % to 30% by weight, particularly preferably 1 % to 20% by weight and in particular 1 .5% to 20% by weight, in each case based on the sum of the components (f) to (j). Formic acid or a formic acid-water mixture is preferably employed in an amount of 0.2% to 10% by weight, in particular in an amount of 0.5% to 4% by weight, based on the component (g). When formic acid-water mixtures are employed the proportion of formic acid, based on the total weight of formic acid and water, is preferably greater than 40% by weight, particularly preferably 50% to 99% by weight, more preferably 70% to 95% by weight and in particular 80% to 90% by weight. It is particularly preferable to employ formic acid or a formic acid-water mixture as the chemical blowing agent without the use of physical blowing agent. If formic acid or a formic acid -water mixture as the chemical blowing agent are used in combination with physical blowing agents in a preferred embodiment they are used in combination with pentane as physical blowing agent.

[0091] Employable flame retardants (j) generally include the flame retardants known from the prior art. Suitable flame retardants are for example 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-chlorisopropyl)phosphate (TCPP), tris(1 ,3-dichloropropyl) phosphate, tricresyl phosphate, tris(2,3-dibromopropyl) phosphate, tetrakis(2-chloroethyl) ethylenediphosphate, dimethylmethane phosphonate, diethyl diethanolaminomethylphosphonate and also commercially available halogen -containing flameretardant polyols. Other phosphates or phosphonates used can comprise diethyl ethanephosphonate (DEEP), triethyl phosphate (TEP), dimethyl propylphosphonate (DMPP), diphenyl cresyl phosphate (DPC) and Diethylhydroxymethylphosphonate as liquid flame retardants. In the context of the present invention compounds which comprise phosphorus, chlorine or bromine atoms and also comprise isocyanate-reactive groups are not considered compounds having isocyanate-reactive hydrogen atoms (g) and not included in the calculation of the molar ratios of the component (g).

[0092] Also employable for endowing the rigid polyisocyanate foams with flame retardancy in addition to the abovementioned flame retardants are inorganic or organic flame retardants, such as red phosphorus, red phosphorus-containing preparations, aluminum oxide hydrate, antimony trioxide, arsenic oxide, ammonium polyphosphate and calcium sulfate, expandable graphite or cyanuric acid derivatives, for example melamine, or mixtures of at least two flame retardants, for example ammonium polyphosphates and melamine and also optionally corn starch or ammonium polyphosphate, melamine, expandable graphite and optionally aromatic polyesters. Preferred flame retardants comprise no isocyanate-reactive groups. It is preferable that the flame retardants are liquid at room temperature. Preferred flame retardants are TCPP, DEEP, TEP, DMPP and DPK, particularly preferably TCPP and TEP, in particular TEP.

[0093] The proportion of the flame retardant (j) is generally 1 % to 25% by weight, preferably 2% to 20% by weight, particularly preferably 3% to 15% by weight, based on the total weight of components (g). Component (j) preferably comprises a phosphorus-containing flame retardant and the content of phosphorus, based on the total weight of the components (f) to (k), is < 0.8% by weight, preferably < 0.6% by weight and particularly preferably < 0.4% by weight.

[0094] The reaction mixture for producing the polyisocyanate foam according to the invention may optionally also be admixed with further auxiliaries and / or additives (k). These include for example surface-active substances, foam stabilizers, cell regulators, fillers, light stabilizers, dyes, pigments, anti-hydrolysis agents, fungistatic and bacteriostatic substances.

[0095] Examples of surface-active substances that can be used are compounds which serve to support homogenization of the starting materials, and which optionally are also suitable for regulating the cell structure of the plastics. Examples include emulsifiers, such as the sodium salts of castor oil sulfates or of fatty acids and salts of fatty acids with amines, for example diethylamine oleate, diethanolamine stearate, diethanolamine ricinoleate, salts of sulfonic acids, for example alkali metal or ammonium salts of dodecylbenzenedisulfonic acid or dinaphthylmethanedisulfonic acid and ricinoleic acid, foam stabilizers, such as siloxane oxyalkylene mixed polymers and other organopolysiloxanes and dimethylpolysiloxanes. Also suitable for improving emulsifying action, cell structure and / or stabilization of the foam are oligomeric acrylates having polyoxyalkylene and fluoroalkane radicals as side groups. The surface -active substances are typically employed in amounts of 0.01 to 10 parts by weight, preferably in amounts of 0.1 to 3 parts by weight based on 100 parts by weight of the component (g). Foam stabilizers used may be customary foam stabilizers, for example those based on silicone, such as siloxane oxyalkylene mixed polymers and other organopolysiloxanes.

[0096] Fillers, in particular reinforcing fillers, are to be understood as meaning the customary organic and inorganic fillers, reinforcers, weighting agents, agents for improving abrasion characteristics in paints, coating agents etc. which are known per se. These especially include for example: inorganic fillers such as silicious minerals, for example phyllosilicates such as antigorite, serpentine, hornblendes, amphiboles, chrysotile and talc, metal oxides such as kaolin, aluminum oxides, titanium oxides and iron oxides, metal salts, such as chalk, barite and inorganic pigments such as cadmium sulfide and zinc sulfide and also glass inter alia. It is preferable to use kaolin (china clay), aluminum silicate and coprecipitates of barium sulfate and aluminum silicate, and also natural and synthetic fibrous minerals, for example wollastonite, and fibers of various lengths made of metal and in particular of glass; these can optionally have been sized. Contemplated organic fillers include for example: carbon, melamine, colophony, 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 esters and in particular carbon fibers. The inorganic and organic fillers may be used individually or as mixtures and are advantageously added to the reaction mixture in amounts of 0.5% to 50% by weight, preferably 1 % to 40% by weight, based on the weight of the components (f) to (k) but wherein the content of mats, nonwoven and woven fabrics made of natural and synthetic fibers may achieve values of up to 80% by weight based on the weight of the components (f) to (k). According to the invention the production of the rigid polyisocyanurate foams according to the invention is carried out by mixing the components (f) to (i) and, if present, (j) and / or (k) to afford a reaction mixture. Premixtures may also be produced to reduce complexity. These comprise at least one isocyanate component comprising polyisocyanates (f) and a polyol component comprising isocyanate-reactive compounds (g). All or some of the further components (h) to (k) may be added to the isocyanate component and polyol component in whole or in part, wherein due to the high reactivity of the isocyanate in many cases the components (h) to (k) are added to the polyol component to avoid side reactions. However physical blowing agents in particular may also be admixed with the isocyanate component (f). Formic acid-water mixtures or formic acid are generally generally present in the polyol component in entirely or partially dissolved form and the physical blowing agent (for example pentane) and optionally the remainder of the chemical blowing agent may be added by direct “online” metering during production. The physical blowing agents are preferably supplied to the reaction mixture online in an extra stream and the remaining components (I), (j) and (k) are particularly preferably added to the polyol component. The catalyst is generally metered online but may also be present in the polyol component in partially or completely dissolved form.

[0097] The polyol component for producing the rigid polyisocyanurate foams according to the invention preferably comprises 70% to 90% by weight of the compounds having at least 1 .5 isocyanate -reactive hydrogen atoms (g), 0.5% to 10% by weight of catalysts (h), 1 % to 20% by weight of blowing agent (I), 0.0% to 20% by weight of flame retardant (j) and 0.0% to 20% by weight of further auxiliary and additive substances (k), in each case based on the total weight of the components (g) to (k). In a particularly preferred embodiment, the proportions of the components (g) to (k) sum to 100% by weight.

[0098] The reaction mixture is subsequently reacted to afford the rigid polyisocyanurate foam. In the context of the present invention a reaction mixture is to be understood as meaning the mixture of the polyisocyanates (f) with the isocyanate-reactive compounds (g) and all further components (h), (I) and optionally (j) and (k) as long as the gel time has not been reached. Gel point is determined in accordance with Annex E of European Standard EN 14315-1 .

[0099] The mixing of the components to afford the reaction mixture is carried out at an isocyanate index of at least 180, preferably at 220 to 600, more preferred at 260 to 400 and particularly preferably at 280 to 350. 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 may be mixed by mixing in high- or low-pressure metering machines.

[0100] The reaction mixture may be introduced into a mold for example for the reaction to progress to completion. Discontinuous sandwich elements for example are produced by this technology. The rigid foams according to the invention are preferably produced on continuous double-belt plants. The polyol and isocyanate components are metered with a high-pressure machine and mixed in a mixing head. Catalysts and / or blowing agents may be metered into the polyol mixture with separate pumps. The reaction mixture is applied to a continuously moving lower layer. The lower layer with the reaction mixture and the upper layer enter the double belt in which the reaction mixture undergoes foaming and curing. After exiting the double belt the continuous strand is cut to the desired dimensions. This makes it possible to produce sandwich elements having metallic lower- and upper layers or having flexible lower- and upper layers. The upper and lower layers which may be the same or different may be flexible or rigid layers typically employed in double-belt processes. These include metal layers such as aluminum or steel, bitumen layers, paper, nonwoven fabrics, plastic sheets such as polystyrene, plastic films such as polyethylene films or wood layers. The layers may also be coated, for example with a conventional lacquer or an adhesion promoter. It is particularly preferable to employ layers which are diffusion-resistant toward the cell gas of the rigid polyisocyan urate foam.

[0101] Such processes are known and described for example in "Polyurethane Handbook”, Hanser / Gardener publications, 2nd edition 1993, chapter 6.2.2 or EP 2234732. The present invention finally provides a polyisocyanate-based rigid foam obtainable by a process according to the invention and a polyisocyanurate sandwich element comprising such a polyisocyanurate-based rigid foam according to the invention.

[0102] A polyisocyanate-based rigid foam according to the invention features exceptional mechanical properties, in particular an exceptional compressive strength, coupled with reduced surface brittleness and smooth surfaces, which is apparent in particular through improved layer adhesion in the production of sandwich elements in the continuous double-belt process, and coupled with low heat conductivities. In addition, the polyisocyanate-based rigid foams according to the invention also exhibit exceptional flame retardancies using only small amounts of ecologically and toxicologically questionable flame retardants. The reaction mixtures used for producing the polyisocyanate-based rigid foams also make it possible to achieve the required reactivities coupled with improved foam curing using only small amounts of ecologically and toxicologically questionable catalysts.

[0103] In a preferred embodiment the compression strength of the foam according to the present invention, at a density of 43 kg / m3, measured according to DIN EN 826, is preferably at least 0,08 MPa, more preferred at least 0,10 MPa and especially preferred at least 0,15 MPa and a flame height according to DIN EN 11925-2 of preferably less than 14 cm, more preferred less than 12 cm and especially preferred less than 10 cm.

[0104] The invention is elucidated hereinbelow with reference to examples.

[0105] The PI R foam to be transferred into a recycled polyol was produced in the following manner:

[0106] The following components were used: polyesterol 1 : Esterification product of terephthalic acid, oleic acid, diethylene glycol and ethoxylated glycerol, with a hydroxyl functionality of 2.5, a hydroxyl number of 240 mg KOH / g, a viscosity of 2500 mPa*s at 25°C and an oleic acid content of 15% by weight., polyetherol 1 : Polyether polyol produced by ethoxylation of diethylene glycol with a hydroxyl functionality of 2 and a hydroxyl count of 180 mg KOH / g. stabilizer: polyether siloxane from Evonik flame retardant tris-(2-chloroisopropyl) phosphate blowing agent 1 : formic acid and water (mass ratio 85:15), blowing agent 2: n-pentane and iso-pentane with a mass ratio of 80:20 catalyst: tertiary amine catalyst and a potassium carboxylate (PIR catalyst), isocyanate: polymeric MDI (Lupranat® M 50 from BASF)

[0107] The PIR foam slabs were produced by high-pressure mixing of the components on a double-belt system using aluminum foil as cover layers. The mixing ratio between A+C and B components was 115.3:230. The mixing ratio corrected to 100 parts A+C is 100:199. This corresponds to an index of 335. The cover layers of the PIR foam slabs obtained were then removed and the PIR foams were ground into a powder using a microfine grinder (hole diameter of the sieve: 4 mm).

[0108] This PIR foam powder was used in the following glycolysis examples.

[0109] In the examples section, the following methods to determine polyisocyanurate content, OH number and viscosity of the polyols were used: Determination of the isocyanurate content in PIR foams

[0110] The PIR content can be determined by I R spectroscopy. The PIR content results from the ratio of the absorption maxima at 1410 and 1600 cm-1: PIR content = absorbance PIR at 1410 cm-1 / (absorbance aromatic at 1600 cm-1).

[0111] Determination of OH number of the polyols

[0112] The OH number was determined in accordance with DIN 53240. The method uses phthalic anhydride to esterify the hydroxyl groups in pyridine solution at a temperature of 108 ± 5°C for one hour. The acid is then titrated with potassium hydroxide.

[0113] Determination of viscosity of the polyols

[0114] The dynamic viscosity is measured with the Haake Viscotester IQ (Thermo Fisher Scientific) and a cone-plate setup. The measuring geometries (cone and plate pairs) used are C20 2° / Ti, C35 2° / Ti, and C60 2° / Ti, with the two-digit number representing the diameter of the cone or plate. For dynamic viscosities > 100000 mPas the C20 2 ° / Ti geometry with 0.08 ml, for dynamic viscosities > 5000 mPas and < 100000 mPas the C35 2° / Ti geometry with 0.4 ml and for dynamic viscosities < 5000 mPas the C60 2° / Ti geometry with 2.0 ml of polyol sample is used. The dynamic viscosities are measured at 25 °C with a typical shear rate of 100 s-1. Deviating measurement parameters are indicated for the corresponding viscosities.

[0115] Determination of MDA content of the polyols

[0116] To determine the MDA content, the polyol samples are mixed with acetonitrile and the resulting suspension is filtered through a syringe top filter. The chromatographic determination of the MDA content is carried out using HPLC-UV with a methanol / ammonium bicarbonate buffer mixture as a flow agent and at a wavelength of 254 nm.

[0117] Glycolysis examples

[0118] Comparative glycolysis 1 :

[0119] Diethylene glycol (700 g) and potassium hydroxide (10 g) were added to a reaction flask at room temperature. The reaction mixture was stirred with a mechanical stirrer and the temperature was raised to 150 °C. PIR foam powder (700 g) was added to the reaction mixture in a stepwise manner. After complete addition of the foam powder the temperature was raised to 200 °C and held for 4 hours. Then 2-ethylhexanoic acid (120 g) and titanium (IV) isopropoxide (0.3 g) were added and the reaction mixture was heated under vacuum to 200 °C for 4 hours. No complete degradation took place. The majority (>50 pbw) of the added PIR rigid foam powder was not converted. The product is unsuitable as a raw material to produce novel polyurethanes. Complete degradation could not be observed.

[0120] Comparative glycolysis 2:

[0121] 1095 g of dipropylene glycol and 12 g of potassium carbonate were heated to 210°C. To this mixture, 800 g of PIR foam was added as a ground powder in several portions, waiting after each addition until the particles had completely decomposed. The reaction mixture was then cooled to 100°C and 90 g of 2 -ethy I hexylglycidy I ether was added. After a post-reaction time of 30 minutes at 100°C, a recycled polyol with the following characteristics was obtained: OH number: 475 mg KOH / g,

[0122] Weight proportion of PI R in the polyol: 40%,

[0123] Free MDA content: < 500 ppm,

[0124] Viscosity: 81605 mPas (± 1020 mPas, 25 °C, C35 2° / TI, 100 s“1shear rate).

[0125] The total reaction time was 5 hours and 40 minutes.

[0126] Comparative glycolysis 3:

[0127] 1098 g of tripropylene glycol and 12 g of potassium carbonate were heated to 210°C. To this mixture, 720 g of PIR foam was added as a ground powder in several portions, waiting after each addition until the particles had completely decomposed. The reaction mixture was then cooled to 100°C and 90 g of 2 -ethy I hexylglycidy I ether was added. After a post-reaction time of 30 minutes at 100°C, a recycled polyol with the following characteristics was obtained: OH number: 350 mg KOH / g,

[0128] Weight proportion of PIR in the polyol: 37.5%,

[0129] Free MDA content: < 500 ppm,

[0130] Viscosity: 82890 mPas (± 320 mPas, 25 °C, C35 2° / TI, 100 s“1shear rate).

[0131] The total reaction time was 5 hours and 30 minutes.

[0132] Comparative glycolysis 4:

[0133] 500 g of dipropylene glycol, 500 g tripropylene glycol and 12 g of potassium carbonate were heated to 210°C. To this mixture, 734 g of PIR foam was added as a ground powder in several portions, waiting after each addition until the particles had completely decomposed. The reaction mixture was then cooled to 100°C and 90 g of 2- ethy I hexy I g ly cidy I ether was added. After a post-reaction time of 30 minutes at 100°C, a recycled polyol with the following characteristics was obtained:

[0134] OH number: 400 mg KOH / g,

[0135] Weight proportion of PIR in the polyol: 40%,

[0136] Free MDA content: < 500 ppm,

[0137] Viscosity: 104300 mPas (± 360 mPas, 25 °C, C35 2° / TI, 75 s“1shear rate).

[0138] The total reaction time was 5 hours and 25 minutes.

[0139] Comparative glycolysis 5:

[0140] 1320 g of a glycerine-initiated propylene glycol having an OH-number of 400 mg KOH / g and 12 g of potassium carbonate were heated to 210°C. To this mixture, 540 g of PIR foam was added as a ground powder in several portions, waiting after each addition until the particles had completely decomposed. The reaction mixture was then cooled to 100°C and 90 g of 2-ethylhexylglycidyl ether was added. After a post-reaction time of 30 minutes at 100°C, a recycled polyol with the following characteristics was obtained: OH number: 285 mg KOH / g, Weight proportion of PI R in the polyol: 27.5%,

[0141] Free MDA content: < 500 ppm,

[0142] Viscosity: 185750 mPas (± 1060 mPas, 25 °C, C20 2° / TI, 50 s“1shear rate).

[0143] The total reaction time was 6 hours and 40 minutes.

[0144] Comparative glycolysis 6:

[0145] 998 g of triethylene glycol and 15.5 g of potassium carbonate were heated to 210°C. To this mixture, 1100 g of PIR foam was added as a ground powder in several portions, waiting after each addition until the particles had completely decomposed. The reaction mixture was then cooled to 100°C and 90 g of 2 -ethy I hexylglycidy I ether was added. After a post-reaction time of 30 minutes at 100°C, a recycled polyol with the following characteristics was obtained: OH number: 350 mg KOH / g,

[0146] Weight proportion of PIR in the polyol: 50%,

[0147] Free MDA content: < 500 ppm,

[0148] Viscosity: 432200 mPas (± 4365 mPas, 25 °C, C20 2° / TI, 25 s“1shear rate).

[0149] The total reaction time was 9 hours and 15 minutes.

[0150] Comparative glycolysis 7:

[0151] 1451 g of trimethylolpropane initiated ethylene glycol having an OH-number of 250 mg KOH / g and 9 g of potassium carbonate were heated to 210°C. To this mixture, 450 g of PIR foam was added as a ground powder in several portions, waiting after each addition until the particles had completely decomposed. The reaction mixture was then cooled to 100°C and 90 g of 2-ethylhexylglycidyl ether was added. After a post-reaction time of 30 minutes at 100°C, a recycled polyol with the following characteristics was obtained:

[0152] OH number: 195 mg KOH / g,

[0153] Weight proportion of PIR in the polyol: 22.5%,

[0154] Free MDA content: < 500 ppm,

[0155] Viscosity: 38440 mPas (± 138 mPas, 25 °C, C35 2° / TI, 100 s“1shear rate).

[0156] The total reaction time was 9 hours and 30 minutes.

[0157] Comparative glycolysis 8:

[0158] 549 g of triethylene glycol, 549 g of of trimethylolpropane initiated ethylene glycol having an OH -number of 250 mg KOH / g and 22.5 g of potassium carbonate were heated to 210°C. To this mixture, 900 g of PIR foam was added as a ground powder in several portions, waiting after each addition until the particles had completely decomposed. The reaction mixture was then cooled to 100°C and 90 g of 2-ethylhexylglycidyl ether was added. After a post-reaction time of 30 minutes at 100°C, a recycled polyol with the following characteristics was obtained:

[0159] OH number: 273 mg KOH / g,

[0160] Weight proportion of PIR in the polyol: 42.5%,

[0161] Free MDA content: < 500 ppm,

[0162] Viscosity: 318450 mPas (± 3545 mPas, 25 °C, C20 2° / TI, 50 s“1shear rate). The total reaction time was 12 hours and 40 minutes.

[0163] Inventive glycolysis 1 :

[0164] 1016 g of triethylene glycol and 29.1 g of potassium carbonate were heated to 210°C. To this mixture, 1125 g of PIR foam was added as a ground powder in several portions, waiting after each addition until the particles had completely decomposed. After the reaction was complete, 345 g of enanthic acid was added and stirred at 210 °C for a further 30 minutes. The reaction mixture was then cooled to 150°C and stirred for a further 30 minutes. Subsequently the reaction mixture was cooled to 100°C and 132.5 g of Epilox P13-16 was added. After a post-reaction time of 30 minutes at 100°C, a recycled polyol with the following characteristics was obtained:

[0165] OH number: 250 mg KOH / g,

[0166] Weight proportion of PIR in the polyol: 42.5%,

[0167] Free MDA content: < 500 ppm

[0168] Viscosity: 25000 mPas (± 60 mPas, 25 °C, C35 2° / Ti, 100 s“1shear rate).

[0169] The total reaction time was 7 hours and 15 minutes.

[0170] Inventive glycolysis 2:

[0171] 800 g of triethylene glycol, 300 g of polyethylene glycol having an OH-number of 180 mg KOH / g and 25 g of potassium carbonate were heated to 210°C. To this mixture, 1000 g of PIR foam was added as a ground powder in several portions, waiting after each addition until the particles had completely decomposed. After the reaction was complete, 250 g of caprylic acid was added and stirred at 210 °C for a further 30 minutes. The reaction mixture was then cooled to 150°C and stirred for a further 30 minutes. Subsequently the reaction mixture was cooled to 100°C and 125 g of Epilox P13-16 was added. After a post-reaction time of 30 minutes at 100°C, a recycled polyol with the following characteristics was obtained: OH number: 240 mg KOH / g,

[0172] Weight proportion of PIR in the polyol: 40%,

[0173] Free MDA content: 1286 ppm (344 ppm 2,4’-MDA and 942 ppm 4,4’-MDA), Viscosity: 10000 mPas (± 20 mPas, 25 °C, C35 2° / Ti, 100 s“1shear rate). The total reaction time was 4 hours and 20 minutes.

[0174] Inventive glycolysis 3:

[0175] 950 g of triethylene glycol, and 25 g of potassium carbonate were heated to 210°C. To this mixture, 1000 g of PIR foam was added as a ground powder in several portions, waiting after each addition until the particles had completely decomposed. After the reaction was complete, 400 g of caprylic acid was added and stirred at 160 °C for a further 30 minutes. The reaction mixture was then heated to 210°C and stirred for a further 60 minutes. Subsequently the reaction mixture was cooled to 100°C and 125 g of Epilox P13-16 was added. After a post-reaction time of 30 minutes at 100°C, a recycled polyol with the following characteristics was obtained: OH number: 240 mg KOH / g, Weight proportion of PIR in the polyol: 40%, Free MDA content: 766 ppm (195 ppm 2,4’-MDA and 571 ppm 4,4’-MDA), Viscosity: 6930 mPas (± 15 mPas, 25 °C, C35 2° / TI, 100 s“1shear rate). The total reaction time was 5 hours and 5 minutes.

[0176] Inventive glycolysis 4

[0177] 900 g of triethylene glycol and 25 g of potassium carbonate were heated to 210°C. To this mixture, 1000 g of PI R foam was added as a ground powder in several portions, waiting after each addition until the particles had completely decomposed. After the reaction was complete, 450 g of lauric acid was added and stirred at 150 °C for a further 30 minutes. The reaction mixture was then heated to 210°C and stirred for a further 45 minutes. Subsequently the reaction mixture was cooled to 100°C and 125 g of Epilox P13-16 was added. After a post-reaction time of 30 minutes at 100°C, a recycled polyol with the following characteristics was obtained:

[0178] OH number: 240 mg KOH / g,

[0179] Weight proportion of PIR in the polyol: 40%,

[0180] Free MDA content: < 500 ppm,

[0181] Viscosity: 16255 mPas (± 25 mPas, 25 °C, C35 2° / TI, 100 s“1shear rate).

[0182] The total reaction time was 5 hours and 25 minutes.

[0183] The following raw materials were used to produce the PIR foams:

[0184] Polyesterol 1 : see above

[0185] Polyesterol 2: Esterification product of phthalic anhydride, oleic acid and diethylene glycol with a hydroxyl functionality of 1 .75, a hydroxyl number of 215 mg KOH / g, a viscosity of 2750 mPa*s at 25 °C and an oleic acid content of 15 % by weight.

[0186] Polyetherol 1 : see above

[0187] Flame retardant: T ris(2-ch Io roisop ropy I) p hosp h ate with a chlorine content of 32.5% by weight and a phosphorus content of 9.5% by weight.

[0188] Foam stabilizer 1 : Niax® L-6895 (silicone-based foam stabilizer from Momentive).

[0189] Catalyst 1 : Catalyst consisting of 23.1 % bis(2-d I methyl am inoethy l)ethe r by weight and 76.9% dipropylene glycol by weight.

[0190] Catalyst 2: Catalyst consisting of 40% potassium formate by weight, 54% monoethylene glycol by weight and 6% water by weight.

[0191] Blowing agent 1 : blowing agent mixture consisting of 85% formic acid by weight and 15% water by weight.

[0192] Blowing agent 2: blowing agent mixture consisting of 80 mol% n-pentane and 20 mol% iso-pentane.

[0193] Isocyanate: polymeric methylene diphenyl diisocyanate (PMDI) from BASF, with a viscosity of approx. 550 mPa*s at 25 °C.

[0194] The foams according to table 1 were produced and tested as disclosed in the following:

[0195] Laboratory foaming: With the help of the above raw materials, the polyol components described in Table 1 were produced and then made to react with identical PMDI proportions. The amount of flammable blowing agent 2 and trimerization catalyst (catalyst 2) was kept constant. By varying the amount of blowing agent 1 and catalyst 1 , all foams were then adjusted to comparable gel times of 49 s ± 3 s and cup foam densities of 43 kg / m3± 2 kg / m3.

[0196] Surface hardening:

[0197] The surface hardening of the curing foam was determined by the bolt test. For this purpose, 2.5; 3; 4; 5; 6 and 7 minutes after intensive mixing of 80 g reaction components according to table 1 (6 seconds at 1500 rpm) in a 1 .15 liter polystyrene cup, a steel bolt with a ball dome of 10 mm radius pressed 10 mm deep into the foam mushroom with a tensile / compression testing machine. The maximum force in N required for this is a measure of the hardening of the foam at the respective time. Each hardening measurement was carried out at a fresh foam site at the same distance from the foam edge.

[0198] Production of rigid foam blocks for determination of heat conductivity, B2 fire resistance and compressive strength: 600 g of the reaction mixture set to identical reaction times and foam densities as disclosed above, were applied in a paper cup and intensively mixed with the help of a laboratory stirrer at 1500 rpm for 6 seconds and transferred into a box with the internal dimensions 22 cm x 22 cm x 22 cm (length x width x height). 24 hours after the reaction mixture had hardened, the hard foam block produced in this way was demolded. Subsequently, test specimens were cut from the rigid foam block, which were used for further investigations. The test specimens used for the individual examination were always taken at identical locations with a minimum distance of 3 cm from the edges.

[0199] Determination of heat conductivity:

[0200] After storage for 24 hours at 23 °C ± 2°C and 50 % ± 5 % relative humidity, additional test specimens with dimensions of 200 mm x 200 mm x 30 mm were taken from the foam blocks at identical locations in the upright direction. The heat conductivity was measured using the TCA 300 heat conductivity meter from Taurus at an average temperature of 10 °C in accordance to DIN EN 12661. The measuring setup was enclosed and the measuring device was located in an air-conditioned laboratory (23°C ± 2°C, 50% ± 5% relative humidity).

[0201] Determination of B2-fire resistance (Small burner test):

[0202] 5 test specimens measuring 190 x 90 x 20 mm were taken from each rigid foam block and tested in accordance with DIN EN 11925-2 by means of edge flame on the 90 mm side tested. The test specimens were conditioned for 24 hours at 20 ± 2°C and 50 ± 20 % humidity before the test. The mean value of the flame heights is given as "0 flame height" in Table 1.

[0203] Determination of Gel time

[0204] Gel time, also known as string time, was determined as the interval between mixing and the juncture at which threads could be drawn from the reaction mixture. Gel time was determined in accordance with Annex E of European Standard EN 14315-1. Determination of compressive strengths:

[0205] 9 test specimens measuring 50 x 50 x 50 mm were taken from each rigid foam block to determine the compressive strength according to DIN EN 826. 3 of the 9 test specimens were rotated in such a way that the test took place against the rising direction of the foam (in the Z direction). 3 of the 9 test specimens were rotated in such a way that the test took place perpendicular to the rising direction of the foam (in the X direction). 3 of the 9 test specimens were rotated in such a way that the test took place perpendicular to the rise direction of the foam (in the Y direction). An average value was then formed from all the measurement results, which is given in Table 1 "0 Compressive strength 3D". Determination of viscosities:

[0206] The viscosities of the polyol components were determined with the laboratory viscometer CAP 2000 +from Brookfield at 20 °C in accordance with the industry standard DIN EN ISO 3219.

[0207] Recycled content in the polyol component: The recycled content in the polyol component in table 1 is defined as the amount of glycolyzed PIR Foam powder in the polyol component, which consists of polyols, crosslinking agents, chain extenders, flame retardants, and further auxiliaries and / or additives like surfactants.

[0208] Table 1

[0209] Comparative Example 1 represents a state-of-the-art PIR-foam without the use of recycled polyols (RP) and shows good mechanical properties as well as surface properties, hardening and flame resistance. Based on comparative example 2, it can be seen that even a partial exchange of polyesterol 1 to comparative glycolysis example 6, which does not contain monocarboxylic acids and which has an OH number of 350 mg KOH / g that is not according to the invention, leads to a significant deterioration of all properties. Due to its very high viscosity, the mixing quality is significantly reduced, and the reaction mixture can no longer be processed suitably on an industrial scale. Furthermore, a massive deterioration in foam curing, compressive strength, heat conductivity and flame resistance can be seen.

[0210] A partial exchange of polyester polyol 1 to comparative glycolysis example 7 (comparative example 3), which is based on a low recycling content, does not contain monocarboxylic acids and has an OH number of which is in the range of the invention, leads to a significant improvement in curing, compressive strength and flame resistance, but even with this PIR foams it is not yet possible to achieve PIR foams that have a comparable property level to reaction mixtures that do not contain recycled polyols. In addition, the viscosity of this polyol component is still far too high to be processed on an industrial scale.

[0211] Based on comparative example 4 it can be seen that a combined use of Polyetherol 1 with comparative glycolysis example 7 leads surprisingly to a further improvement of the foam properties (polyol component viscosity, foam curing and compression strength). Anyhow, the heat conductivity of comparative example 4 is higher and based on the low recycling content of comparative glycolsis example 7, the total recycling content in the polyol component of comparative example 4 is only very low (< 10 weight-%).

[0212] A partial exchange of polyester polyol 1 to comparative glycolysis example 8 (comparative example 5), which is based on a high recycling content, does not contain monocarboxylic acids and has an OH number of which is in the range of the invention, leads again to very strong deterioration of most properties. Due to its very high viscosity, the mixing quality is significant reduced and the reaction mixture can no longer be processed suitably on an industrial scale. Furthermore, a massive deterioration in foam curing compressive strength and thermal insulation can be seen.

[0213] Based on comparative example 6 it can be seen that even a combined use of Polyetherol 1 with comparative glycolysis example 8, which is based on a high recycling content, does not lead to a strong enough improvement of all foam properties. The polyol component viscosity is still > 3500 mPa*s, the foam curing is still lower, the foam compression strength is still significant lower and the heat conductivity is still significant higher.

[0214] Inventive Example 7, 8 and 10 represents that only the use of recycled polyols from a polyisocyanurate material which are in the range of the invention can lead to properties which meet all requirements. For example, all polyol components from inventive Example 7, 8 and 10 show a low viscosity and lead to fast-curing foams in the reaction mixture that have good compressive strengths, which safely pass the B2 fire test with flame heights < 12 cm and which have low heat conductivities which are comparable to reaction mixtures that do not contain recycled polyols. Additionally the total recycled content in the polyol component of inventive example 7 and 8 is high (> 15 weight-%) and the total recycled content in the polyol component of inventive example 10 is even higher (> 20 weight-%).

[0215] Based on comparative example 9 it can be seen that a slight deterioration of some foam properties (foam curing, compression strength) takes place, if the mass ratio of the recycled polyol (RP) to the polyether polyol (g2) is too high.

Claims

Claims1 . Method for obtaining a recycled polyol (RP) from a polyisocyanurate material (a) wherein the polyisocyanurate material (a) comprises isocyanurate structures wherein the method comprises mixing(a) the polyisocyanurate material,(b) at least one polyalcohol, wherein the polyalcohol (b) has at least two primary alcohol groups and a hydroxyl value of 200 to 800 mg KOH / g,(c) at least one aliphatic monocarboxylic acid(d) at least one catalyst comprising at least one basic catalyst, catalyzing esterification of alcohol groups and carboxylic acids and(e) optionally at least one deamination agent and reacting the mixture to obtain a recycled polyol (RP) having an OH-number of 150 to 300 mg KOH / g, a viscosity of less than 25000 mPas at 25 °C and a content of polyisocyanurate material (a), based on the total amount of compounds (a) to (e), of at least 20 % by weight.

2. Method according to claim 1 wherein polyalcohol (b) and monocarboxylic acid (c) are used in an amount that the theoretical average OH-functionality after esterification of all carboxylic groups of the mono carboxylic acid (c) and OH-groups of the polyalcohol (b) is from 1 to 2.5.

3. Method according to claim 1 or 2 wherein optionally at least a part of the at least one polyalcohol (b) and the at least one monocarboxylic acid (c) are reacted to form an ester (be) and the ester (be) is added to the reaction mixture.

4. Method according to any of claims 1 to 3, wherein the basic catalyst (d) comprises at least one carbonate- based catalyst (d1).

5. Method according to any of claims 1 to 4, wherein the basic catalyst (d) catalyzing esterification of alcohol groups comprises at least one transition metal based catalyst (d2) selected from the group, consisting of tin based catalysts, titan based catalysts, zinc based catalysts and bismuth based catalysts.

6. Method according to any of claims 1 to 5, wherein the polyisocyanurate material (a) comprises at least one phosphorous ester and the phosphorus esters is preferably selected from the group of triethylphosphate (TEP) and Tris(2-chlorisopropyl)phosphate (TCPP).

7. Method according to any of claims 1 to 6 wherein the polyisocyanurate material (a) comprising a tertiary amine catalyst (d).

8. Method according to any of claims 1 to 7 wherein the I R spectrum of a polyisocyan urate material (a) shows a ratio of the height of the isocyanurate oscillation band at approximately 1410 cm1to the aromatic oscillation band at approx. 1600 cnr1of at least 10.

9. Method according to any of claims 1 to 8, wherein the deamination agent (d) is a glycidyl ether.

10. Recycled polyol (RP), obtained by any of claims 1 to 9.11 . Process for the production of a polyisocyanurate rigid foam, comprising mixing(f) at least one aromatic polyisocyanate,(g) at least one isocyanate reactive compound comprising the recycled polyol (RP) according to claim 10, and at least one polyetherpolyol (g2)(h) at least one catalyst,(I) at least one blowing agent,(j) optionally at least one flame retardant,(k) optionally additives, to form a reaction mixture and reacting the mixture to form a polyisocyanurate rigid foam, wherein the amount of the recycled polyol (RP), based on the total weight of components (g) is at least 20 % by weight, polyether polyol (g2) has a hydroxyl number of 160 - 300 mg KOH / g and is produced by alkoxylation of a starter or starter mixture with an average functionality of > 1 .5 and < 3, wherein at least 80% ethylene oxide is used as alkylene oxide for the production of polyether polyol (g2) and polyether polyol (g2) has at least 90 % primary hydroxyl end groups, the mass ratio of recycled polyol (RP) to polyether polyol (g2) is 0.75 to 2.2 and the sum of the mass fractions of recycled polyol (RP) and polyether polyol (g2), based on the total weight of component (g) is > 65% by weight, and the mixing to form the reaction mixture takes place at an isocyanate index of > 180.

12. Process according to any of claim 1 1 , wherein component (g) contains at least one aromatic polyester polyol (g3) with an average functionality of > 1 .7 and < 2.5, an average hydroxyl number of > 180 and < 250 mg KOH / g.

13. Process according to claim 1 1 or 12, wherein the viscosity of the isocyanate reactive component (g) is at most 5000 mPas at 25 °C.

14. Process according to any of claims 1 1 to 13, wherein the blowing agent comprises mixtures of formic acid and water.

15. Process according to any of claims 1 1 to 14, wherein the catalyst (h) comprises at least one amine catalyst comprising at least one tertiary amine group (hi) and at least one alkali metal carboxylate catalyst (h2).

16. Process according to according to any of claims 1 1 to 15, wherein the recycled content in the component g is at least > 10 weight-%.

17. Process according to any of claims 1 1 to 16, wherein the reaction mixture is applied to a continuously moving lower layer in a double-belt for the production of sandwich elements.

18. Polyisocyanurate foam obtained by a process according to any of claims 1 1 to 17.