Process for obtaining polyacetalpolyols from water solution of formaldehyde and alcohols

Abstract

The present invention relates to a process for the preparation of a polyacetal polyol (PAP) comprising reacting a compound (D1) having at least one OH group with an aldehyde (C1) in the presence of a fluorine-free catalyst in an aqueous solution, wherein the aldehyde is formaldehyde and the polyacetal polyol obtained or obtainable according to said process. The present invention further relates to the use of said polyacetal polyol for the preparation of polyurethanes, a process for preparing a polyurethane as well as a process for recycling the polyurethane.

Description

Process for obtaining polyacetalpolyols from water solution of formaldehyde and alcoholsThe present invention relates to a process for the preparation of a polyacetal polyol (PAP) comprising reacting a compound (D1) having at least one OH group with an aldehyde (01) in the presence of a fluorine-free catalyst in an aqueous solution, wherein the aldehyde is formaldehyde and the polyacetal polyol obtained or obtainable according to said process. The present invention further relates to the use of said polyacetal polyol for the preparation of polyurethanes, a process for preparing a polyurethane as well as a process for recycling the polyurethane.Polyurethane materials are an important class of plastic materials used in numerous applications spanning a variety of industries due to their robustness, longevity, and ability to be tailored for specific end-use applications. Moreover, polyurethane materials are more environmentally friendly and sustainable materials when compared to some plastic materials used in industry, for example due to their use in energy conserving end-use applications such as thermal insulation (e.g., building and pipe insulation) and light weighting of components. As a result of increasing demand and quantity of produced PU materials a large amount of PU waste is generated every year which is either used for incineration or ending up in landfills, posing severe environmental problems. However, polyurethane materials are difficult to recycle via either mechanical or chemical recycling methods.Conventional PUs can also be chemically recycled via for example aminolysis, alcoholysis, including glycolysis, hydrolysis, acidolysis, or hydrogenation. However, the products obtained in these recycling methods are mixtures that contain high molecular weight oligomers (polyols) which cannot be separated, thus making closed-loop recycling challenging. Furthermore, both mechanical and chemical recycling methods are energy-consuming processes that require a combination of high temperature, high pressure, and a large excess of reactants or solvents. As a consequence of the challenges and downsides of both mechanical and chemical recycling, the large majority of PU waste is currently incinerated for energy recovery or ends up in landfills. There is still a need in the polyurethane industry to develop other processes that ease the recyclability of polyurethane materials thereby reducing the total amount of energy, time, machinery, and reagents needed to recycle such materials.The incorporation of special functional groups or smart monomers into the polymers allows to depolymerize the resulting polymer in a simple process which reduces the effort for a recycling process of the material. Several suitable monomers for the synthesis of polyurethanes which can be easily depolymerized are described in the literature. For example, WO 2021 / 236385 A1 discloses the synthesis of polyols suitable for the preparation of polyurethanes via polyaddition of triethylene glycol divinylether (TEGDVE) and diols in bulk at 40 °C using p-toluenesulfonic acid as a homogeneous catalyst. However, this process leads to the formation of huge amounts of by-products when 1,4-bu- tanediol or smaller diols are used as monomers. Furthermore, colored polyols are obtained. The synthesis of these polyols is exothermic and a control of the reaction needs to be guaranteed by cooling. This results in processes, which can be hardly up-scaled and safely controlled.It was an object of the present invention to provide polyols for the preparation of polyurethanes which result in polyurethanes which can be easily decomposed under controlled conditions and which can be prepared in high purity in a simple process.The problem is solved in accordance with the invention by a process for the preparation of polyacetal polyol (PAP) comprising(i) reacting a compound (D1) having at least one OH group with an aldehyde (C1) in the presence of a fluorine-free catalyst in an aqueous solution, wherein the aldehyde is formaldehyde.It has been surprisingly found that polyols containing acetal groups can be prepared using formaldehyde in the presence of a fluorine-free catalysts in a simple process and preferably also minimizing side reactions. The polyacetal polyols obtained are stable under neutral and basic conditions and can be easily cleaved using controlled acidic conditions.According to the present invention, a polyacetal polyol (PAP) is prepared. The process comprises step (i). Compound (D1 ) having at least one OH group is reacted with an aldehyde (01) in the presence of a fluorine-free catalyst in an aqueous solution. According to the present invention, formaldehyde is used.Suitable formaldehyde solutions or precursors are in principle known to the person skilled in the art. Preferably, formaldehyde is used as an aqueous solution, more preferable as an unstabilized aqueous solution.Preferably, formaldehyde is used as an aqueous solution comprising 30 to 60% formaldehyde by weight, more preferable 40 to 50% by weight of formaldehyde.Preferably, the solution of formaldehyde used according to the present invention comprises less than 15% by weight of methanol, preferable less than 5%, more preferable less than 1 .5% by weigh.According to a further embodiment, the present invention is directed to the process for preparing a polyacetal polyol as disclosed above, wherein the formaldehyde is used in form of an unstabilized aqueous solution, preferably wherein the aqueous solution comprises less than 15% by weight of methanol, preferably less than 5%, in particular less than 1 .5 %by weight of methanol.Compound (D1) has at least one OH group. Compound (D1) may also have further functional groups, in particular further OH groups. Preferably, compound (D1) has 1 to 8, preferably 2 to 6, more preferable 2, 3, 4, 5 or 6, 7, 8 OH groups, particularly preferable 2 to 3 OH groups or 5 to 6 OH groups.According to a further embodiment, the present invention is directed to the process for preparing a polyacetal polyol as disclosed above, wherein compound (D1) has a functionality of from 1 to 8, preferably from 2 to 6.Suitable compounds (D1) may for example have a molecular weight of less than 5000 g / mol, preferable less than 2000 g / mol, more preferable less than 1000 g / mol, even more referable less than 500 g / mol and the most preferable less than 200 g / mol.Suitable compounds (D1) may in particular be selected from the group consisting of monools, diols, and triols with 1 to 20 C-atoms, preferably from the group consisting of monools, diols and triols with 1 to 18 C-atoms, preferably 2 to 12 C-atoms and even more preferable with 2-6 C-atoms. According to a further embodiment, the present invention therefore is also directed to the process for the preparation of polyacetal polyol as disclosed above, wherein the compound (D1) is selected from the group consisting of monools, diols, and triols with 1 to 18 C-atoms, preferably from the group consisting of monools, diols and triols with 2 to 6 C-atoms. Suitable components (D1) may be selected from monoethylene glycol, 1 ,2-propanediol, 1 ,3-propanediol, 1 ,4-butanediol, 1 ,5-pentanediol, 1 ,6-hexanediol, 1,7- heptanediol, 1 ,8-octanediol, 1 ,9-nonanediol or 1 ,10-decanediol, in particular 1 ,4-butanediol, 1 ,5-pentanediol and 1 ,6- hexanediol. Furthermore, preferable diols are diethylene glycol and dipropylene glycol, tripropylene glycol, triethylene glycol or mixtures of two or more of these.Also suitable are polyether diols and higher functional polyetherols.According to the present invention, also compounds having three or more OH groups may be used as compound (D1). Suitable are for example 1,2,4 butanetriol, trimethylolethane, 1,2,6 hexanetriol, trimethylolethane, butane- 1 ,2,3,4-tetrol, benzene-1 ,2,3-triol, xylose, deoxyribose, mannose, sorbose, tagatose, galactose, ribose, fructose, mannitol, sorbitol, fucitol, galactitol, iditol, xylitol, volemitol, glycerol, glucose, sucrose, dextrose, sucrose pentaerythritol, dipentaerythritol, diglycerolor trimethylolpropane and also alkoxylated derivatives of the compounds having three or more OH groups or mixtures thereof.Furthermore, alkoxylated aromatic amines with 2 to 8, preferably 2 to 6, in particular 2 to 4 functional groups may be used as component (D1), for example alkoxylated TDA.According to the present invention, a further component (D2) may be added in step (i). Component (D2) preferably has at least 2 OH groups, for example 2 to 3 OH groups, in particular 2 OH groups. Suitable components (D2) may be selected from monoethylene glycol, 1 ,2-propanediol, 1 ,3-propanediol, 1 ,4-butanediol, 1 ,5-pentanediol, 1,6-hex- anediol, 1 ,7-heptanediol, 1 ,8-octanediol, 1 ,9-nonanediol or 1 ,10-decanediol, in particular 1 ,4-butanediol, 1,5-pentane- diol and 1 ,6-hexanediol or glycerol. Furthermore, preferable diols are diethylene glycol and dipropylene glycol., triethylene glyclole, tripropylene glycol or mixtures thereof.Also suitable are polyether diols and higher functional polyetherols, in particular polyethylene glycols HO(CH2CH2O)n-H, higher polypropylene glycols HO(CH[CH3]CH2O)n-H, where n is an integer and n > 4, e.g. , 4 to 20, and polyethylene-polypropylene glycols, more particularly those having 4 to 20 repeating units, it being possible for the sequence of the ethylene oxide and pro-pylene oxide units to be blockwise or random, and polytetramethylene glycols, more particularly those having 4 to 20 repeating units, and poly-1, 3-propanediols, more particularly those having 4 to 20 repeating units.According to step (I), compounds (D1) and (C1) and preferably (D2) are reacted under suitable conditions. Typically, the reaction is carried out at temperature higher than 0°C, typically at 0°C to 250°C, more preferable at 10 °C to 150 °C, more preferable on 20 °C to 110 °C, even more preferable 25 °C to 100 °C and the most preferable 40 °C to 100 °C. The reaction may be carried out at a suitable pressure, preferably in the range of from 0.1 mbar to 20 bar, more preferable in a range of from 1 mbar to 10 bar, in particular in a range of from 50 mbar to 5 bar, particularly preferable in a range of from 100 mbar to 1 bar.According to the present invention, it is also possible that small amounts of organic solvents may be added, for example in an amount of up to 30 % by weight, in particular up to 15 %by weight, preferably in an amount of up 10% by weight. Preferably organic solvents are used, which form with water a minimum azeotrope. Suitable organic solvents may be selected from toluene, benzene, xylene, dioxane, ethylacetate, tetrahydrofurane, formic acid, preferentially toluene.According to the present invention, homogeneous or heterogeneous catalysts may be used. Suitable homogeneous catalysts may for example be selected from nitric acid, sulfuric acid, phosphoric acid, boric acid, hydrobromic acid, Examples of organic acids are oxalic acid, formic acid, acetic acid, citric acid, benzoic acid, dicarboxylic acids such as adipic acid, glutaric acid or succinic acid, methanesulfonic acid and p-toluolsulfonic acid. Preferably, homogeneous catalysts are used selected from the group consisting of nitric acid, sulfuric acid, methanesulfonic acid and p-toluolsulfonic acid. Homogeneous catalyst needs neutralization and filtration after completion of the reaction.Heterogeneous catalysts are also used. When used, the polyacetal polyols can be easily separated from the catalyst without further neutralizationAccording to the present invention, the use of a heterogeneous catalyst such as for example aluminosilicate K10 and Siral 70 allows for simple filtration of the reaction mixture, yielding pure polyol and enabling reuse of the recovered catalyst.Preferably, the solid catalysts according to the present invention are solid acid catalysts. Typically, the solid catalysts, in particular the solid acid catalysts are heterogeneous catalysts in the process according to the present invention. Solid acids in the context of the present invention are solids which possess acidic sites at their (inner and outer) surface on which a base may be chemically adsorbed. Preferably, according to the definition of Bronsted and Lewis, asolid acid in the context of the present invention has the tendency to donate a proton or to accept an electron pair. The solid acid catalysts suitable in the context of the present invention may differ in their chemical composition, in the amount, type and strength of acidic sites and also in physical properties like for examples specific surface area and porosity and therefore accessibility of the catalytic active sites.Suitable solid acid catalysts in the context of the present invention preferably have a specific surface area of at least 10 m2 / g, especially of at least 100 m2 / g, more preferable of at least 200 m2 / g.Solid acid catalysts suitable in the context of the present invention include silico-aluminates or alumo-silicates, such as for example zeolites, silicoaluminophosphates, amourphous alumosili-cates, clays. Suitable zeolites are for example ordered microporous alumosilicates (BEA, MOR...). Alumosilicates which are available in an amorphous, less ordered and less acidic form as ASA (=amorphous silica alumina) catalyst may also be used in the context of the present in-vention. Also clay catalysts belonging to the class of silicates with a certain acidity, or mesopo-rous alumosilicates materials like MCM-22 may be used. Furthermore, silica-alumina hydrates and the corresponding oxides may be used in the context of the present invention, for example “Siral” and “Siralox” materials from Sasol.Suitable are also metal oxides and metal oxide mixtures which are acidic, such as for example titania, zirconia, nio- bia, solid phosphoric acid, sulfated zirconia or heteropolyoxometallates.Another group of suitable solid acid catalysts which may be used are polymers and resins containing acidic structural units such as polystyrene with sulfonic acid groups. One example of such cationic ion exchange resins is Amberlyst 15.Suitable further catalysts can be Metalorganic Frameworks (MOFs) as they are described, for example, in. US 5,648,508, EP-A-0 709 253, M. O’Keeffe et al., J. Sol.State Chem., 152 (2000) p. 3-20, H. Li et al., Nature 402 (1999) p. 276 seq., M. Eddaoudi et al., Topics in Catalysis 9 (1999) p. 105-111 , B. Chen et al., Science 291 (2001) p. 1021- 23.Preferred catalysts are selected from the group of mixed oxides containing alumina and silica (alumosilicates). They can be obtained by co-precipitation or controlled hydrolysis of salts (e.g. using A^NOa^^F O and / or NaAIO2 and / or AICI3 as Al precursor and tetraethoxysilane = TECS as Si precursor), also both the Al and Si precursors can be alcoholate. Suitable materials may also be obtained as natural occurring material, for example clays, which after activation with a mineral acid like HOI, H2SO4 or HNO3 for example acts as a solid acid catalyst.Suitable catalysts may for example be selected from catalyst obtained by a process which comprises calcining a precursor of an oxide of one or more elements selected from the group consisting of Ge, Sn, B, Al, Ga, Zn, Cu, Fe, Mn, Ni, Cr, Mo, P, S, W, Nb, Ti, Zr, Hf, Y, La, Ce, Yb, and Si at a temperature in the range of from 150 °C to 1150 °C to obtain an oxide; silica-alumina hydrates; a clay compound containing Si and Al; zeolites having a structure selectedfrom the group consisting of BEA, EMT, ERI, EUO, FAU, HEU, LTA, LTL, MAZ, MOR, MTW, NES, OFF and TON; or cation exchange resin.According to a further embodiment, the present invention therefore is also directed to the process for the preparation of polyacetal polyol as disclosed above, wherein the solid acid catalyst is selected from the group consisting of catalyst obtained by a process which comprises calcining a precursor of an oxide of one or more elements selected from the group consisting of Ge, Sn, B, Al, Ga, Zn, Cu, Fe, Mn, Ni, Cr, Mo, P, S, W, Nb, Ti, Zr, Hf, Y, La, Ce, Yb, and Si at a temperature in the range of from 150 °C to 1150 °C to obtain an oxide; silica-alumina hydrates a clay compound containing Si and Al; zeolites having a structure selected from the group consisting of BEA, EMT, ERI, EUO, FAU, HEU, LTA, LTL, MAZ, MOR, MTW, NES, OFF and TON; cation exchange resin;MOF catalysts.Particularly suitable are selected from clay compounds, mixed oxides and MOF catalysts.According to a further embodiment, the present invention is directed to the process for preparing a polyacetal polyol as disclosed above, wherein the catalyst is selected from the group consisting of clay compounds, mixed oxides and MOF catalysts.The process according to the present invention comprises step (I) and may also comprise further steps, in particular purification steps or separation steps. Preferably, the catalyst is separated from the reaction mixture after the reaction according to step (I). The catalyst may for example be separated by filtration or in case a homogeneous catalyst is used, neutralization steps. The catalyst separated from the reaction mixture might also be subjected to a purification step such as for example a washing step and may also be reused in the process. The process may also comprise further washing steps. Preferably, the process further comprises a distillation step to remove water.According to the process of the present invention, polyacetal polyols are obtained. The polyacetal polyols obtained may have one or more acetal groups and OH end groups, for example 1 to 8 OH end groups, preferably 1 to 6, more preferable 1 to 6, in particular 2 to 6 OH end groups, particularly preferable 2, 3, 4, 5 or 6 OH end groups. Preferably, the molecular weight of the polyacetal polyols is in the range of up to 12.000 g / mol, in particular up to 10.000 g / mol, for example in the range of from 100 to 8.000 g / mol, preferably in the range of from 150 to 6000 g / mol, more preferred in the range of from 200 to 4000 g / mol, in particular in the range of from 1000 to 5000 g / mol, calculated from the OH number. The OH value of the polyacetal polyols may be in the range of from 5 to 1200 mgKOH / g, preferably in the range of from 8 to 800 mgKOH / g, more preferable in the range of from 10 to 700 mgKOH / g, in particular in the range of from 12 to 600 mgKOH / g and the most preferable from 15 to 600 mgKOH / g..According to a further aspect, the present invention is also directed to the polyacetal polyol obtained or obtainable according to a process for the preparation of polyacetal polyol as disclosed above.The dynamic viscosity of the polyacetal polols according to the present invention preferably is in the range of below 100000 mPas (at 25°C). The dynamic viscosity is measured with the Haake Viscotester IQ (Thermo Fisher Scientific) and a cone-plate setup. The cone and plate pairs used are 20 mm, 35 mm or 60 mm in diameter. For dynamic viscosities > 100,000 mPas the 20 mm pair with 0.1 ml, for dynamic viscosities > 5,000 mPas and < 100,000 mPas the 35 mm pair with 0.4 ml and for dynamic viscosities < 5,000 mPas the 60 mm pair with 2.0 ml of polyol sample is used. The dynamic viscosities are measured at 25 °C with a shear rate of 100 s“1.It has been found that the polyacetal polyols according to the present invention are particularly suitable for the preparation of polyurethanes. The resulting polyurethanes can be depolymerized using controlled and mild conditions and the products can easily be separated. According to a further aspect, the present invention is also directed to the use of a polyacetal polyol obtained or obtainable according to a process for the preparation of polyacetal polyol as disclosed above or a polyacetal polyol according to the present invention for the preparation of polyurethanes.Processes for the preparation of polyurethanes are in principle known. Usually, a polyol component is reacted with an isocyanate component. Typically, polyurethanes are prepared using processes comprising mixing (a) polyisocyanate, (b) a polyol composition comprising polymeric compounds having isocyanate-reactive groups, (c) catalysts and optionally (d) blowing agents, (e) chain-extending and / or crosslinking agents and (f) auxiliaries and / or additives to afford a reaction mixture and reacting the reaction mixture to afford polyurethane."Polyurethane” in the context of the invention comprises all known polyisocyanate polyaddition products. These comprise addition products of isocyanate and alcohol and modified polyure-thanes which may comprise isocyanurate, allophanate, urea, carbodiimide, uretonimine and biu-ret structures and further isocyanate addition products. These polyurethanes according to the invention comprise in particular solid polyisocyanate polyaddition products, such as elastomers, thermoplastic PU elastomers, duromers, and foams based on polyisocyanate-polyaddition products, such as flexible foams, semi-rigid foams, rigid foams or integral foams and also polyurethane coatings, adhesives and binders. "Polyurethanes” are further to be understood as meaning polymer blends comprising polyurethanes and further polymers, and also foams made of these polymer blends.According to a further aspect, the present invention is also directed to a process for preparing a polyurethane at least comprising step (I)(I) reacting a polyol composition (PC) comprising at least one polyacetal polyol (PAP) obtained or obtainable according to a process as disclosed above or a polyacetal polyol as disclosed above with at least one polyisocyanate composition (IC).The polyisocyanate composition (IC) used for the preparation of polyurethane may comprise one or more polyisocyanates. In some embodiments, the polyisocyanate component includes one or more diisocyanates. Suitable polyisocyanates include aromatic diisocyanates, aliphatic diisocyanates, cyclo aliphatic diisocyanates or combinations thereof. In some embodiments, the polyisocyanate component includes one or more aromatic diisocyanates. In some embodiments, the polyisocyanate component is essentially free of, or even completely free of, aliphatic diisocyanates. In other embodiments, the polyisocyanate component includes one or more aliphatic diisocyanates and / or cyclo aliphatic diisocyanates. In some embodiments, the polyisocyanate component is essentially free of, or even completely free of, aromatic diisocyanates. In some embodiments, mixtures of aliphatic and aromatic diisocyanates may be useful. Examples of useful polyisocyanates include aromatic diisocyanates such as 4,4'-methylenebis(phenyl isocyanate (4,4'-MDI), 2,4-diphenylmethane diisocyanate (2,4-MDI), 2,2'-diphenylmethane diisocyanate (2,2'-MDI), m-xylene diisocyanate (XDI), phenylene-1,4-diisocyanate (1 ,4-PDI), naphthalene-l,5-diisocyanate (NDI), 4,4'-diisocyanato-1,2- diphenylethane, 3,3'-dimethyl-4,4'-biphenylene diisocyanate (TODI) and toluene diisocyanate (TDI); as well as aliphatic diisocyanates such as ethylene diisocyanate (EDI), 1,4-butane diisocyanate (BDI), 1,6-hexamethylene diisocyanate (HDI), decane-1, 10-diisocyanate, 1,12-dodecane diisocyanate (DDI), lysine diisocyanate (LDI); and cyclo aliphatic diisocyanates like isophorone diisocyanate (IPDI), 1 ,4-cyclohexyl diisocyanate (CHDI), and dicyclohexylme- thane-4,4'-diisocyanate (H12MDI). Isomers of these diisocyanates may also be useful. Mixtures of two or more polyisocyanates may be used. If an isocyanate prepolymer is employed as isocyanate (a) this preferably has an isocyanate content (NCO content) of more than 5%, more preferably 10% to 45%, yet more preferably 12% to 40%, particularly preferably 15% to 35% and especially 15% to 30% and the most preferably 15% to 25% by weight.The polyol composition (PC) comprises at least one polyacetal polyol (PAP). The polyol composition may also comprise further polyols, in particular further polyacetal polyols. The polyol composition (b) may for example comprise the polyacetal polyols according to the pre-sent invention in an amount of 1 to 100% by weight based on the composition. Depending on the composition of the polyol composition the features of the polyurethanes obtained may be influenced. Preferably, the polyol composition (PC) comprises one or more polyacetal polyols (PAP) in an amount of from 20 to 100 % by weight based on the weight of the polyol composition (PC), more preferable in an amount of from 40 to 100% by weight, in particular in an amount of from 50 to 100% by weight based on the weight of the polyol composition (PC).According to a further embodiment, the present invention is directed to the process for preparing a polyurethane as disclosed above, wherein the polyol composition (PC) comprises one or more polyacetal polyols (PAP) in an amount of from 20 to 100 % by weight based on the weight of the polyol composition (PC).Suitable further polyols having isocyanate-reactive groups (b) and chain extenders and / or crosslinkers (e) are known to those skilled in the art and described for example in "Kunststoffhandbuch [Plastics Handbook], volume 7, Polyurethane [Polyurethanes]”, Carl Hanser Verlag, 3rd edition 1993, chapter 3.1.In particular, the active hydrogen compounds may be selected from aliphatic diol compounds having 2 to 20 carbon atoms, for example ethylene glycol, 1 ,2-propanediol, 1 ,3-propanediol, 1 , 1 -dimethylethane-1 ,2-diol, 2-butyl-2- ethyl- 1 ,3-propanediol, 2-ethyl-1 ,3-propanediol, 2-methyl-1 ,3-propanediol, neopentyl glycol, hydroxypivalic acid neopentyl glycol ester, 1,2-, 1,3- and 1 ,4-butanediol, 1 ,6-hexanediol, 1 ,10-decanediol, 2-ethyl-1 ,3-hexanediol, 2,4-diethy- loctane-1 ,3-diol, cyclic aliphatic diol compounds having 3 to 14 carbon atoms, for example tetramethylcyclobu-tane- diol, 1,2-, 1,3- and 1 ,4-cyclohexanediol, 1,1-, 1,2-, 1,3- and 1,4-cyclohexanedimethanol, 1,2-, 1,3- or 1,4-cyclooctane- diol, norbornanediol, pinanediol, decalindiol, 2,2-bis(4-hydroxycyclohexyl)propane, bis(4-hydroxycyclohexane)iso- propylidene; and aliphatic aminoalco-hols having 2 to 20 carbon atoms, such as monoethanolamine, diethanolamine, monopropanola-mine, dipropanolamine, N-methyl diethanolamine and N-methyl dipropanolamine.Particular preference is given to compounds which are selected from aliphatic diols having 2 to 12 carbon atoms such as ethylene glycol, 1 ,4-butanediol, 1 ,5-pentanediol and 1 ,6-hexanediol.Chain extenders with acetal groups may also be used according to the present invention.In the context of the present invention, also compounds having a molecular weight of at most 500 g / mol and having 3 or more OH groups per molecule as sole functional groups may be used as cross-linkers (e). Also cross-linkers having acetal groups may be used according to the present invention. Suitable compounds are for example glycerol, and trimethylolpropane.The liquid mixture may contain further components, such as for example a catalyst (c) which catalyzes the polyurethane formation of the reactive components contained in the liquid mixture with the isocyanate compound. The amount of catalyst will be typically not exceed 5% by weight, based on the total weight of the liquid mixture and is typically in the range of 0.1 to 3% by weight. Suitable catalysts include, but not limited to, tin compounds such as tin octoate, dibutyltin dilaurate, bismuth neodecanoate or bismuth dioctoate, and tertiary amines such as di-methylben- zylamine, trimethylamine, 1,4-diazabicyclo[2.2.2]octane or any other catalyst known to the person skilled in the art which furthers the formation of urethane groups by the reaction of the hydroxyl groups in compounds (b) and (e) with the isocyanate groups of the isocyanate com-pound (a). Further catalysts are described in, for example, Houben- Weyl, Methoden der Organischen Chemie, Vol. XIV / 2, Thieme-Verlag, Stuttgart 1963, p. 60f. and also Ullmanns En- zyklopadie der Technischen Chemie, 4th ed., Vol. 19 (1981), p. 306.The polyurethane obtained according to the process may be a compact material which may for example be used as a compact material, such as an adhesive a cast elastomer, a sealant or a coating. The polyurethane may also be a polyurethane foam, in particular a rigid polyurethane foam.When the polyurethane according to the invention is to be in the form of a polyurethane foam, reaction mixtures according to the invention further comprise blowing agent (d). Any blowing agents known for the production of polyurethanes may be employed. These may comprise chemical and / or physical blowing agents. Such blowing agents aredescribed in, for example, "Kunststoffhandbuch [Plastics Handbook], volume 7, Polyurethane [Polyurethanes]”, Carl Hanser Verlag, 3rd edition 1993, chapter 3.4.5. "Chemical blowing agents” is understood to mean com-pounds that form gaseous products by reaction with isocyanate. Examples of such blowing agents are water or carboxylic acids. "Physical blowing agents” is understood to mean com-pounds that are dissolved or emulsified in the input materials of polyurethane production and vaporize under the conditions of polyurethane formation. Examples thereof include hydrocarbons, halogenated hydrocarbons and other compounds, for example perfluorinated alkanes such as perfluorohexane, chlorofluorohydrocarbons, and ethers, esters, ketones, acetals and / or liquid carbon dioxide. The blowing agent may be employed in any desired amount. The blowing agent is preferably employed in an amount such that the resulting polyurethane foam has a density of 10 to 850 g / L, particularly preferably 20 to 800 g / L and in particular 25 to 500 g / L. It is particularly preferable to employ blowing agents comprising water.Further auxiliaries and / or additives (f) may also be employed. Any auxiliary and additive sub-stances known for the production of polyurethanes may be used. Examples include surface-active substances, foam stabilizers, cell regulators, release agents, fillers, dyes, pigments, flame retardants, hydrolysis stabilizers, fungistatic and bacteriostatic substances and also antioxidants. Such substances are known and described for example in "Kunststoffhandbuch, volume 7, Polyurethane”, Carl Hanser Verlag, 3rd edition 1993, chapters 3.4.4 and 3.4.6 to 3.4.11.Step (I) generally comprises mixing the compounds and heating the thus obtained mixture until the compounds are mutually dissolved in each other. Mixing and heating can be done simultaneously or consecutively. Suitable conditions depending on the components used and the material prepared are in principle known to the person skilled in the art.Mixing may for example be carried out at room temperature but may also be carried out at elevated temperatures, e.g. at a temperature of at least 50°C, in particular at a temperature in the range of 50 to 150°C.The reaction conditions for polyurethane formation will depend on the reactivity of the components present in the polyol composition, the reactivity of the isocyanate and the presence or absence of a catalyst.According to a further aspect, the present invention is also directed to the polyurethane obtained or obtainable according to a process for preparing a polyurethane as disclosed above.The polyurethane according to the present invention comprises acetal groups which can be cleaved under acidic conditions. This allows for a recycling of an end-of-life polyurethane or waste material under mild conditions. The specific structure of the polyacetal polyols according to the present invention allows to decompose the polyacetal polyol and consequently the polyurethane into small building blocks which may be separated due to the differences in their solubility or also in the boiling point. The decomposition may also be achieved stepwise.Accordingly, in one embodiment, the present invention is directed to a process for recycling a polyurethane material. Specifically, the process comprises: contacting the polyurethane material with an acid solution and allowing at least a portion of the polyurethane material to decompose into a recovered raw material composition.Preferably, the polyurethanes obtained according to the present invention are biodegradable. In the context of the present invention, biodegradable means that the polyurethane can be disintegrated (decomposed) by the action of micro-organisms such as bacteria or fungi biological (with or without oxygen) while getting assimilated into the natural environment.According to a further aspect, the present invention is also directed to a process for recycling a polyurethane obtained according to a process as disclosed above or a polyurethane according to the present invention, at least comprising the step(x) treating the polyurethane with an aqueous solution at a pH in the range of 0 to 6.Typically, the acetal bond can be easily hydrolyzed in mild acid conditions.Typically, the treatment according to step (x) comprise a treatment at a pH below 5, preferably below 4, in particular below 2 or below 1. Step (x) can be conducted by treating the article at elevated temperature. Typically, the treatment according to step (x) could be carried out at a temperature in the range from 50 °C to 160 °C, preferably in a range of from 50 °C to 120 °C, more preferable in a range of from 60 °C to 100 °C. Preferably, the treatment according to step (x) is carried out at a pH value below 5 at a temperature of 20°C, preferably of more than 40°C, more preferable at a temperature in the range of from 60°C to 100°C, in particular at a pH value in the range of below 2 at a temperature in the range of from 60°C to 100°C. Preferably, treatment according to step (x) is applied for a suitable time, preferably for less than 24 hours, more preferable for less than 15 hours, in particular for less than 10 hours. Step (x) can be conducted by treating the polyurethane at elevated temperature for a time period of 1 second to 24 hours, preferentially 1 hour to 10 hours.The acid aqueous solution that is used in the process can comprise any acid compound provided that it has a pH of less than or equal to about 5, preferably of less than 4, in particular less than 2. In certain embodiments, the acid solution may comprise other components in addition to the acid compound. These components can include solvents such as alcohols, THF, toluene, or further solvents. The solution also may comprise surfactants.The treatment according to step (x) may also be carried out stepwise, for example comprising treatment steps at different pH values to allow for a stepwise decomposition of the polyurethane and stepwise isolating the monomers obtained.Suitable acids for step (x) are generally inorganic and organic acids. Examples of inorganic acids are hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, boric acid, hydrobromic acid, Examples of organic acids are oxalicacid, formic acid, acetic acid, citric acid, benzoic acid, dicarboxylic acids such as adipic acid, glutaric acid or succinic acid, methanesulfonic acid and p-toluolsulfonic acidThere are also a variety of ways to promote the acidolysis depolymerization process and, ultimately, the decomposition of the polyurethane material into the various components comprising the recovered raw material composition. Usually, the polyurethane is comminuted using suit-able methods such as cutting or grinding prior to depolymerization. Usually, once submerged in the acid solution, the polyurethane material may be agitated using techniques known in the art. Additionally, heat may be applied to one or both the acid solution and the polyurethane material to facilitate the acidolysis depolymerization process. For example, the acid solution in which the polyurethane material is submerged may be heated to a temperature ranging from 60°C to 100°C. Only if necessary, material may be heated to a temperature above 100 °C, e.g. from 100-200 °C. The total amount of time needed to decompose the polyurethane material into the recovered raw material composition may vary depending on a number of factors, such as the thickness of the polyurethane material.While it is desirable to submerge the entire polyurethane material to be decomposed into the acid solution, there are embodiments where only a portion of the polyurethane material is contacted with the acid solution. In these embodiments, the remaining portion of the polyurethane material (i.e. the portion that does not contact the acid solution) will not be decomposed. In other words, partial recycling of a polyurethane material is also contemplated by the present disclosure.The process may also comprise further steps, in particular further steps after step (x) such as purification and separation steps. The process may comprise further steps such as separation steps separating obtained liquid and solid phase or neutralization and purification steps, for example by distillation, precipitation or extraction. Residues for example remaining parts of the hardphase of the polyurethane may be treated in a separate recycling step.The recovered materials, such as a recovered compound (D1) and (D2) or formaldehyde can then be used as a raw material to prepare the virgin original polyol or other materials.The process of the present disclosure enables the conversion of certain polyurethane materials into a raw material compound that can be used as a reactive ingredient in the preparation of original virgin polyols or preparation of another material, such as another type of polyurethane material or another polymer type.According to a further aspect, the present invention is also directed to a process preferably a process as disclosed above, comprising the step: converting the composite and / or the composite obtainable by or obtained by the process as disclosed above or a chemical material obtainable by or obtained by the process as disclosed above to obtain a product.According to a further embodiment, the present invention is also directed to a process as dis-closed above,wherein the product is selected from: i) building block or monomer; orII) polymer, preferably polymer A, polymer composition, preferably polymer composition A, or polymer product, preferably polymer product A; or iii) cleaning polymer, cleaning surfactant, descaling compound, cleaning biocide or composition or formulation thereof; or iv) agrochemical composition, agrochemical formulation auxiliary or agrochemically active ingredient; or v) active pharmaceutical ingredient or intermediate thereof, pharmaceutical excipient, animal feed additive, human food additive, dietary supplements, aroma chemical or aroma composition; or vi) aqueous polymer dispersion, preferably polyurethane or polyurethane - poly(meth)acrylate hybrid polymer dispersion, emulsion, binder for paper and fiber coatings, UV-curable acrylic polymer for hot melts and coatings polyisocyanates, hyperbranched polyester polyol, polymeric dispersant for inorganic binder compositions, unsaturated polyester polyol or 100% curable composition; or vii) cosmetic surfactant, emollient, wax, cosmetic polymer, UV filter, further cosmetic ingredient or composition or formulation thereof; or viii) polymer B, polymer composition B, coating composition, other functional composition, foil, molded body, coating or coated substrate.According to a further embodiment, the present invention is also directed to a process as dis-closed above, wherein the content of the polymeric material (PM) in the polymer product is 1 weight-% or more, preferably 2 weight- % or more, more preferably 5 weight-% or more, more preferably 15 weight-% or more, more preferably 30 weight-% or more, more preferably 40 weight-% or more, more preferably 60 weight-% or more, more preferably 80 weight-% or more, more preferably 90 weight-% or more, more preferably 95 weight-% or more; and / or wherein the content of the polymeric material (PM) in the polymer product is 100 weight-% or less, preferably 95 weight-% or less, more preferably 90 weight-% or less, more preferably 50 weight-% or less, more preferably 25 weight-% or less, more preferably 10 weight-% or less; and preferably wherein the content is determined based on identity preservation and / or segregation and / or mass balance and / or book and claim chain of custody models, preferably based on mass balance, preferably the International Sustainability and Carbon Certification (ISCC) standard.The publication Prior Art Disclosure; Issue 684; paragraphs

[1000] to

[8005] ; ISSN: 2198-4786; published: February 12, 2024 will be regarded as Reference RF1, which is incorporated herein by reference in its entirety. Preferably, the product is a product as described in Reference RF1; paragraphs

[1000] to

[8005] , Preferably, the process described herein is further a process for the production of a product.The converting step to obtain the product preferably comprises one or more step(s) as described below and can be performed by conventional methods well known to a person skilled in the art. The converting step preferably comprises one or more step(s) selected from: recycling, preferably depolymerizing, gasifying, pyrolyzing, and / or steam cracking; and / or purifying, preferably crystallizing, (solvent) extracting, distilling, evaporating, hydrotreating, absorbing, adsorbing and / or subjecting to ion exchanger; and / or assembling, preferably foaming, synthesizing, chemical conversion, chemically transforming, polymerizing and / or compounding; and / or forming, preferably foaming, extruding and / or molding; and / or finishing, preferably coating and / or smoothing.In addition, the one or more step(s) are described in detail in Reference RF1; paragraphs

[1000] to

[8005] ,The term "building block”, as used herein, comprises compounds, which are in a gaseous or liquid state under standard conditions of 0 °C and 0.1 MPa. Building blocks are typically used in chemical industry to form secondary products, which provide a higher structural complexity and / or higher molecular weight than the building block on which the secondary product is based. The building block is preferably selected from the group consisting of hydrogen, carbon monoxide, carbon dioxide, ethylene oxide, ethylene glycols, syngas comprising a mixture of hydrogen and carbon monoxide, alkanes, alkenes, alkynes and aromatic compounds. The alkanes, alkenes, alkynes and aromatic compounds comprise in particular 1 to 12 carbon atoms, respectively.The term "monomer”, as used herein, comprises molecules, which can react with each other to form polymer chains by polymerization. The monomer is preferably selected from the group consisting of (meth)acrylic acid, salts of (meth)acrylic acid; in particular sodium, potassium and zinc salts; (meth)acrolein and (meth)acrylates. (Meth)acry- lates comprising 1 to 22 carbon atoms are preferred, in particular comprising 1 to 8 carbon atoms. The terms (meth)acrylic acid, (meth)acrolein or (meth)acrylate relate to acrylic acid, acrolein or acrylate and also to methacrylic acid, methacrolein or methacrylate, where applicable. Further, the monomer can be selected from hexamethylenediamine (HMD) and adipic acid.The building block can further be an intermediate compound. The term "intermediate compound”, as used herein, comprises organic reagents, which are applied for formation of compounds with higher molecular complexity. The intermediate compound can be selected for example from the group consisting of phosgene, polyisocyanates and propylene oxide. The polyisocyanates are in particular aromatic di- and polyisocyanates, preferably toluene diisocyanate (TDI) and / or diphenylmethane diisocyanate (MDI).The building block and the monomer and typical converting step(s) to obtain the building block or monomer are described in more detail in paragraphs

[1000] to

[1012] of Reference RF1.The term "polymer A”, as used herein, comprises thermoplastic, e.g., polyamide or thermoplastic polyurethane, thermoset, e.g., polyurethane, elastomer, e.g., polybutadiene, or a copolymer or a mixture thereof and is defined in more detail in paragraphs

[2001] to

[2007] of Reference RF1.The term "polymer composition A”, as used herein, comprises all compositions comprising a polymer as described above and one or more additive(s), e.g. reinforcement, colorant, modifier and / or flame retardant, and is defined in more detail in paragraph

[2008] of Reference RF1.The term "polymer product A”, as used herein, comprises any product comprising the polymer A and / or polymer composition A as described above and is defined in more detail in paragraphs

[2009] and

[2010] of Reference RF1 . The step(s) to obtain the polymer, preferably polymer A, polymer composition, preferably polymer composition A or polymer product, preferably polymer product A is / are described in more detail in paragraph

[2011] of Reference RF1 .The term "industrial use polymer”, as used herein, comprises rheology, polycarboxylate, alkox-ylated polyalkylenamine, alkoxylated polyalkylenimine, polyether-based, dye inhibition and soil release cleaning polymers defined in more detail in paragraphs

[3035] to

[3044] of Reference RF1. The term "industrial use surfactant”, as used herein, comprises non-ionic, anionic and amphoteric industrial use surfactants defined in more detail in paragraphs

[3008] to

[3034] of Reference RF1. The term "industrial use descaling compound”, as used herein, comprises non-phosphate based builders (NPB) and phosphonates (CoP) described in more detail in paragraphs

[3001] to

[3005] of Reference RF1. The term "industrial use biocide”, as used herein, refers to a chemical compound that kills microorganisms or inhibits their growth or reproduction defined in more detail in paragraphs

[3006] to

[3007] of Reference RF1. The term "industrial use solvent”, as used herein, comprises alkyl amides, alkyl lactamides, alkyl esters, lactate esters, alkyl diester, cyclic alkyl diester, cyclic carbonates, aromatic aldehydes and aromatic esters defined in more detail in paragraphs

[3045] to

[3055] of Reference RF1. The term "industrial use dispersant”, as used herein, comprises anionic and non-ionic industrial use dispersants defined in more detail in paragraphs

[3056] to

[3058] of Reference RF1. The term "composition and / or formulation thereof' with reference to the industrial use polymers, industrial use surfactants, descaling compounds and / or industrial use biocides refers to industrial use compositions and / or institutional use products and / or fabric and home care products and / or personal care products defined in more detail in paragraph

[3059] of Reference RF1. The converting step(s) to obtain the industrial use polymer, industrial use surfactant, descaling compound and / or industrial use biocide are defined in more detail in paragraph

[3060] of Reference RF1 . The converting steps to obtain the industrial use composition or formulation of the industrial use polymer, industrial use surfactant, descaling compound and / or industrial use biocide are defined in more detail in paragraph

[3061] of Reference RF1.The term "agrochemical composition”, as used herein, typically relates to a composition comprising an agrochemi- cally active ingredient and at least one agrochemical formulation auxiliary. Examples of agrochemical compositions, active ingredients and auxiliaries are described in more detail in Reference RF1, paragraph

[4001] ,The agrochemical composition may take the form of any customary formulation. The agrochemical compositions are prepared in a known manner, e.g. described by Mollet and Grubemann, Formulation technology, Wiley VCH, Weinheim, 2001; or Knowles, New developments in crop protection product formulation, Agrow Reports DS243, T&F Informa, London, 2005. The converting step(s) to obtain the agrochemically active ingredients and auxiliaries may be conducted in analogy to the production step(s) of their analogues that are based on petrochemicals or other precursors that are not gained by recycling processes. In addition, conversion to compounds mentioned in sections "Polymer” and "Cosmetic surfactant, emollient, wax, cosmetic polymer, UV filter, further cosmetic ingredient or compositions or formulations thereof' may be performed as described in these sections as well as the respective paragraphs in Reference RF1.The term active pharmaceutical ingredients and / or intermediates thereof, as used herein, comprises substances that provide pharmacological activity or other direct effect in the diagnosis, cure, mitigation, treatment, or prevention of disease, or to affect the structure or any function of the body. Intermediates thereof are isolated products that are generated during a multi-step route of synthesis of an active pharmaceutical ingredient. The term pharmaceutical excipients, as used herein, comprises compounds or compound mixtures used in compositions for various pharmaceutical applications, which are not substantially pharmaceutically active on itself. Active pharmaceutical ingredients and / or intermediates thereof and pharmaceutical excipients are defined in more detail in paragraph

[5001] of Reference RF1.The converting step(s) to obtain the active pharmaceutical ingredients and / or intermediates thereof and pharmaceutical excipients may comprise one or more synthesis steps and can be performed by conventional synthesis and techniques well known to a person skilled in the art.The terms animal feed additives, human food additives, dietary supplements, as used herein, comprises Vitamins, Pro-Vitamins and active metabolites thereof including intermediates and precursors, especially Vitamin A, B, E, D, K and esters thereof, like acetate, propionate, palmitate esters or alcohols thereof like retinol or salts thereof and any combinations thereof; Tetraterpenes, especially isoprenoids like carotenoids and xanthophylls including their intermediates and precursors as well as mixtures and derivates thereof, especially beta carotene, Canthaxanthin, Citranax- anthin, Astaxanthin, Zeaxanthin, Lutein, Lycopene, Apocarotenoids, and any combinations thereof; organic acids, especially formic acid, propionic acid and salts thereof, such as sodium, calcium or ammonium salts, and any combinations thereof, such as but not limited to mixtures of formic acid and sodium formiate, propionic acid and ammonium propionate, formic acid and propionic acid, formic acid and sodium formiate and propionic acid, propionic acid and sodium propionate and formic acid and sodium formiate; glycerides of carboxylic acids and short and medium chain fatty acids, conjugated linoleic acids, such as omega-6 fatty acid (C18:2) methyl ester and 1 ,2-propandiol and beverage stabilizers, such as polyvinylpyrrolidone-polymer or polyvinylimidazole / polyvinylpyrrolidone-copolymer. Animal feed additives, human food additives and dietary supplements are defined in more detail in paragraph

[5002] of Reference RF1.The converting step(s) to obtain the animal feed additives, human food additives, dietary supplements may comprise one or more synthesis steps and can be performed by conventional synthesis and techniques well known to a person skilled in the art.The terms aroma chemical and aroma composition as used herein, comprise a volatile organic substance with a molecular weight between 70-250 g / mol comprising a functional group with a carbon skeleton of C5-C16 carbon atoms comprising linear, branched, cyclic, for example with a ring size of C5-C18, bicyclic or tricyclic aliphatic chains and but not necessarily one or more un-saturated structural elements like double bonds, triple bonds, aromatics or heteroaromatics and preferably the one or more additional functional groups are selected from alcohol, ether, ester, ketone, aldehyde, acetal, carboxylic acid, nitrile, thiol, amine. In one aspect, the aroma chemical is a terpene-based aroma chemical, for example selected from monoterpenes and monoterpe-noids, sesquiterpenes and sesquiterpe- noids, diterpenes, triterpenes or tetraterpenes. Aroma chemicals can be combined with further aroma chemicals to give an aroma composition. Aroma chemicals and aroma compositions are defined in more detail in paragraph

[5003] of Reference RF1 .The converting step(s) to obtain the aroma chemical and aroma composition may comprise one or more synthesis steps and can be performed by conventional synthesis and techniques well known to a person skilled in the art.The term "aqueous polymer dispersion”, as used herein, comprises aqueous composition(s) comprising dispersed polymer(s) and is defined in more detail in the section

[6001] entitled "aqueous polymer dispersion” of Reference RF1. The dispersed polymer(s) may be selected from acrylic emulsion polymer(s), styrene acrylic emulsion poly- mer(s), styrene butadiene dispersion(s), aqueous dispersion(s) comprising composite particles, acrylate alkyd hybrid dispersion(s), polyurethane(s) (including UV-curable polyurethanes) and polyurethane - poly(meth)acrylate hybrid polymer(s). The term "emulsion polymer”, as used herein, comprises polymer(s) made by free-radical emulsion polymerization. Aqueous polyurethane dispersion(s) are defined in more detail in the section

[6002] entitled "Polyurethane dispersions” of Reference RF1. UV-curable polyurethane(s) is / are defined in more detail in the section

[6017] of Reference RF1. Polyurethane - poly(meth)acrylate hybrid polymer(s) is / are defined in more detail in the section

[6016] of Reference RF1 .The term "polymeric dispersant”, as used herein, comprises preferably polymer(s) comprising polyether side chain, in particular polycarboxylate ether polymer(s) and polycondensation prod-ct(s) defined in more detail in paragraph

[6020] entitled "Polymeric dispersant” of Reference RF1.The converting (polymerization) step(s) to obtain the aqueous polymer dispersion(s) comprising emulsion polymer(s) is / are defined in more detail in the section

[6003] entitled "Emulsion polymerization” of Reference RF1.The converting (polymerization) step(s) to obtain the aqueous polyurethane dispersion(s) is / are defined in more detail in the section

[6014] entitled "Process for the preparation of aqueous polyuuethane dispersions” and section [6017)] entitled "Aqueous UV-curable polyurethane dispersions, their preparation and use and compositions containing them” of Reference RF1 .Composition(s) and uses of aqueous polymer dispersion(s) and of polymeric dispersant(s) are defined in more detail in the following sections of Reference RF1 : section

[6004] entitled "Uses of aqueous polymer dispersions”, section

[6005] entitled "Binders for architectural and construction coatings” section

[6006] entitled "Binders for paper coating” section

[6007] entitled "Binders for fiber bonding” section

[6008] entitled "Adhesive polymers and adhesive compositions” section

[6015] entitled "Aqueous polyurethane dispersions suitable for use in coating compositions” section

[6016] entitled "Aqueous polyurethane - poly(meth)acrylate hybride polymer dispersions suitable for use in coating compositions” section

[6017] entitled "Aqueous UV-curable polyurethane dispersions, their preparation and use and compositions containing them” section

[6018] entitled "Inorganic binder compositions comprising polymeric dispersants and their use”

[6019] 100% curable coating compositionsUV-crosslinkable poly(meth)acrylate(s) and its / their uses are defined in more detail in section

[6009] entitled "UV- crosslinkable poly(meth)acrylates for use in UV-curable solvent-free hotmelt adhesives and their use for making pressure-sensitive self-adhesive articles” of Reference RF1.Polyisocyanate(s), composition(s) comprising them and their uses are defined in more detail in section

[6010] entitled "Polyisocyanates” of Reference RF1.Hyperbranched polyester polyol(s) and its / their uses are defined in more detail in section

[6011] entitled "Organic solvent based hyperbranched polyester polyols suitable for use in coating com-positions” of Reference RF1. The converting step(s) to obtain the hyperbranched polyester polyols is / are defined in more detail in the section

[6012] entitled "Preparation of organic solvent based hyperbranched polyester polyols” of Reference RF1 . Coating compositions) comprising hyperbranched polyester polyol(s), polyisocyanate(s) and additive(s) and substrate(s) coated therewith are defined in more detail in section

[6013] entitled "Organic solvent based two component coating compositions comprising hyperbranched polyester polyols and polyisocyanates” of Reference RF1.Unsaturated polyester polyol(s), solvent-based coating composition(s) comprising said unsaturated polyester pol- yol(s) and substrate(s) for coating with said coating composition(s) are defined in more detail in section

[6018] entitled "Organic solvent based coating composition comprising unsaturated polyester polyols” of Reference RF1. 100% curable coating composition(s) is / are defined in more detail in section

[6019] of Reference RF1.Polymeric dispersant(s) for inorganic binder compositions is / are defined in more detail in section

[6020] of Reference RF1. The inorganic binder composition(s) comprising the polymeric dispersants and their use are defined in more detail in section

[6021] of Reference RF1. The converting step(s) to obtain the polymeric dispersant(s) are defined in more detail in section

[6020] of Reference RF1. The term "inorganic binder composition” comprising the polymericdispersant(s), as used herein, comprises preferably in particular hydraulically setting compositions and compositions comprising calcium sulfate and is defined in more detail in section

[6021] of Reference RF1 entitled "Inorganic binder compositions comprising the polymeric dispersant and their use”. Specific building material formulation(s) comprising polymeric dispersant(s) or building product(s) produced by a building material formulation comprising a polymeric dispersant are disclosed in more detail in section

[6021] of Reference RF1.The term "cosmetic surfactant”, as used herein, comprises non-ionic, anionic, cationic and amphoteric surfactants and is defined in more detail in paragraph

[7002] of Reference RF1. The term "emollient”, as used herein, refers to a chemical compound used for protecting, moisturizing, and / or lubricating the skin and is defined in more detail in paragraph

[7003] of Reference RF1. The term "wax”, as used herein, comprises pearlizers and opacifiers and is defined in more detail in paragraph

[7004] of Reference RF1. The term "cosmetic polymer”, as used herein, comprises any polymer that can be used as an ingredient in a cosmetic formulation and is defined in more detail in paragraph

[7005] of Reference RF1. The term "UV filter”, as used herein, refers to a chemical compound that blocks or absorbs ultraviolet light and is defined in more detail in para-graph

[7006] of Reference RF1. The term "further cosmetic ingredient”, as used herein, comprises any ingredient suitable for making a cosmetic formulation. Several sources disclose cosmetically acceptable ingredients. E. g. the database Cosing on the internet pages of the European Commission discloses cosmetic ingredients and the International Cosmetic Ingredient Dictionary and Handbook, edited by the Personal Care Products Council (PCPC), discloses cosmetic ingredients. The term "composition and / or formulation thereof' with reference to the cosmetic surfactant, emollient, wax, cosmetic polymer, UV filter and / or further cosmetic ingredient refers to personal care and / or cosmetic compositions or formulations defined in more detail in paragraph

[7007] of Reference RF1. The converting step(s) to obtain the cosmetic surfactant, emollient, wax, cosmetic polymer, UV filter or further cosmetic ingredient is / are defined in more detail in paragraph

[7008] of Reference RF1 .The terms "polymer B”, "polymer composition B”, "coating composition”, "other functional composition”, "foil”, "molded body”, "coating” and "coated substrate” are well known to the person skilled in the art and are defined in more detail from paragraph

[8000] to

[8005] of Reference RF1.Bried description of the figures:Fig. 1 : shows pictures of cup foam samples obtained according to the examples (left: V1 , center V2, right 3);Fig. 2: shows microscopic (REM) pictures of the foams (left: V1, center V2, right 3; upper image row: 63x magnification, lower image row: 125 x magnification).Further embodiments of the present invention can be found in the claims and the examples. It will be appreciated that the features of the subject matter / processes / uses according to the invention that are mentioned above and elucidated below are usable not only in the combination specified in each case but also in other combinations without departing from the scope of the invention. For example, the combination of a preferred feature with a particularly preferred feature or of a feature not characterized further with a particularly preferred feature etc. is thus also encompassed implicitly even if this combination is not mentioned explicitly.Illustrative embodiments of the present invention are listed below, but these do not restrict the present invention. In particular, the present invention also encompasses those embodiments which result from the dependency references and hence combinations specified hereinafter.1 . Process for the preparation of polyacetal polyol (PAP) comprising(I) reacting a compound (D1) having at least one OH group with an aldehyde (C1) in the presence of a fluorine-free catalyst in an aqueous solution, wherein the aldehyde is formaldehyde.2. The process according to embodiment 1, wherein the aqueous solution comprises less than 15% , by weight of methanol.3. The process according to embodiment 1 or 2, wherein the formaldehyde is used in form of an unstabilized aqueous solution.4. The process according to any one of embodiments 1 to 3, wherein compound (D 1 ) has a functionality of from 1 to 8, preferably from 2 to 6.5. The process according to any one of embodiments 1 to 4, wherein the catalyst is selected from the group consisting of clay compounds, mixed oxides and MOF catalysts.6. The process according to any one of embodiments 1 to 4, wherein the catalyst is homogeneous and preferentially selected from the group consisting of nitric acid, sulfuric acid, methanesulfonic acid and p-toluolsulfonic acid.7. Polyacetal polyol obtained or obtainable according to a process according to any one of embodiments 1 to 6.8. Polyacetal polyol obtained or obtainable according to a process for the preparation of polyacetal polyol (PAP) comprising(i) reacting a compound (D1) having at least one OH group with an aldehyde (C1) in the presence of a fluorine-free catalyst in an aqueous solution, wherein the aldehyde is formaldehyde.9. The polyacetal polyol according to embodiment 1 , wherein the aqueous solution comprises less than 15%, by weight of methanol.10. The process according to embodiment 1 or 2, wherein the formaldehyde is used in form of an unstabilized aqueous solution.11 . The process according to any one of embodiments 1 to 3, wherein compound (D1) has a functionality of from 1 to 8, preferably from 2 to 6.12. The process according to any one of embodiments 1 to 4, wherein the catalyst is selected from the group consisting of clay compounds, mixed oxides and MOF catalysts.13. The process according to any one of embodiments 1 to 4, wherein the catalyst is homogeneous and preferentially selected from the group consisting of nitric acid, methanesulfonic acid and p-toluolsulfonic acid..14. The polyacetal polyol according to any one of embodiments 7 to 13, wherein the polyol has an OH value in the range of from 5 to 1200 mgKOH / g, preferably in the range of from 8 to 800 mgKOH / g, more preferable in the range of from 10 to 700 mgKOH / g, in particular in the range of from 12 to 600 mgKOH / g and the most preferable from 15 to 600 mgKOH / g measured according to EN ISO 4629-1 :201615. Use of a polyacetal polyol obtained or obtainable according to a process according to any one of embodiments 1 to 6 or a polyacetal polyol according to any one of embodiments 7 to 13 for the preparation of polyurethanes.16. Process for preparing a polyurethane at least comprising(I) reacting a polyolcomposition (PC) comprising at least one polyacetal polyol (PAP) obtained or obtainable according to a process according to any one of embodiments 1 to 6 or at least one polyacetal polyol according to any one of embodiments 7 to 13 with at least one polyisocyanate composition (IC).17. The process according to embodiment 16, wherein the polyol composition (PC) comprises one or more polya- cetal polyols (PAP) in an amount of from 20 to 100 % by weight based on the weight of the polyol composition (PC).Polyurethane obtained or obtainable according to a process according to embodiment 17. Process for recycling a polyurethane obtained according to a process according to embodiment 16 or 17 or a polyurethane according to embodiment 18, at least comprising the step(x) treating the polyurethane with an aqueous solution at a pH in the range of 0 to 6. Process, preferably according to any one of the embodiments 16 or 17, comprising the step: converting the polyurethane obtainable by or obtained by the process according to any one of embodiments 16 or 17 or a chemical material obtainable by or obtained by the process according to any one of embodiments 16 or 17 to obtain a product. Process according to embodiment 20, wherein the product is selected from: i) building block or monomer; or ii) polymer, preferably polymer A, polymer composition, preferably polymer composition A, or polymer product, preferably polymer product A; or iii) cleaning polymer, cleaning surfactant, descaling compound, cleaning biocide or com-position or formulation thereof; or iv) agrochemical composition, agrochemical formulation auxiliary or agrochemically active ingredient; or v) active pharmaceutical ingredient or intermediate thereof, pharmaceutical excipient, animal feed additive, human food additive, dietary supplements, aroma chemical or aroma composition; or vi) aqueous polymer dispersion, preferably polyurethane or polyurethane - poly(meth)acrylate hybrid polymer dispersion, emulsion, binder for paper and fiber coatings, UV-curable acrylic polymer for hot melts and coatings polyisocyanates, hyperbranched polyester polyol, polymeric dispersant for inorganic binder compositions, unsaturated polyester polyol or 100% curable composition; or vii) cosmetic surfactant, emollient, wax, cosmetic polymer, UV filter, further cosmetic ingredient or composition or formulation thereof; or viii) polymer B, polymer composition B, coating composition, other functional composition, foil, molded body, coating or coated substrate Process according to any one of embodiments 20 or 21 , wherein the content of the polymeric material (PM) in the product is 1 weight-% or more, preferably 2 weight- % or more, more preferably 5 weight-% or more, more preferably 15 weight-% or more, more preferably 30 weight-% or more, more preferably 40 weight-% or more, more preferably 60 weight-% or more, more preferably 80 weight-% or more, more preferably 90 weight-% or more, more preferably 95 weight-% or more; and / orwherein the content of the polymeric material (PM) in the polymer product is 100 weight-% or less, preferably 95 weight-% or less, more preferably 90 weight-% or less, more preferably 50 weight-% or less, more preferably 25 weight-% or less, more preferably 10 weight-% or less; and preferably wherein the content is determined based on identity preservation and / or segre-gation and / or mass balance and / or book and embodiment chain of custody models, preferably based on mass balance, preferably the International Sustainability and Carbon Certification (ISCC) standard.23. Process for the preparation of polyacetal polyol (PAP) comprising(I) reacting a compound (D1) having at least one OH group with an aldehyde (C1) in the presence of a fluorine-free catalyst in an aqueous solution, wherein the aldehyde is formaldehyde, wherein the aqueous solution comprises less than 15% by weight of methanol..24. The process according to embodiment 23, wherein the formaldehyde is used in form of an unstabilized aqueous solution.25. The process according to any one of embodiments 23 or 24, wherein compound (D1) has a functionality of from 1 to 8,.26. The process according to any one of embodiments 23 to 3, wherein compound (D1) has a functionality of from 2 to 6.27. The process according to any one of embodiments 23 to 26, wherein the catalyst is selected from the group consisting of clay compounds, mixed oxides and MOF catalysts.28. The process according to any one of embodiments 23 to 26, wherein the catalyst is homogeneous and preferentially selected from the group consisting of nitric acid, sulfuric acid, methanesulfonic acid and p-tolu- olsulfonic acid.29. Polyacetal polyol obtained or obtainable according to a process according to any one of embodiments 23 to 28.30. The polyacetal polyol according to embodiment 29, wherein the polyol has an OH value in the range of from 5 to 1200 mgKOH / g, preferably in the range of from 8 to 800 mgKOH / g, more preferable in the range of from 10 to 700 mgKOH / g, in particular in the range of from 12 to 600 mgKOH / g and the most preferable from 15 to 600 mgKOH / g measured according to EN ISO 4629-1 :201631 . Use of a polyacetal polyol obtained or obtainable according to a process according to any one of embodiments 23 to 28 or a polyacetal polyol according to any one of embodiments 29 to 30 for the preparation of polyurethanes.32. Process for preparing a polyurethane at least comprising(I) reacting a polyolcomposition (PC) comprising at least one polyacetal polyol (PAP) obtained or obtainable according to a process according to any one of embodiments 23 to 28 or at least one polyacetal polyol according to embodiment 7or 8 with at least one polyisocyanate composition (IC).33. The process according to embodiment 32, wherein the polyol composition (PC) comprises one or more polyacetal polyols (PAP) in an amount of from 20 to 100 % by weight based on the weight of the polyol composition (PC).34. Polyurethane obtained or obtainable according to a process according to embodiment 32 or 33.35. Process for recycling a polyurethane obtained according to a process according to embodiment 32 or 33 or a polyurethane according to embodiment 34, at least comprising the step(x) treating the polyurethane with an aqueous solution at a pH in the range of 0 to 6.The invention is further described by examples. The examples relate to practical and in some cases preferred embodiments of the invention that do not limit the scope of the invention.EXAMPLES1. Materials used2. Methods2.1 The OH numbers were determined according to EN ISO 4629-1 :20162.2 Determination of the weight-average molecular weight via Gel-Permeation Chromatography: Gel-Permeation Chromatography Determination under the following conditions:• Solvent and eluent: 1,5 % (w / w) Formic acid (99 - 100% VWR), Water for HPLC (Honeywell)• Flow: 0.8 ml / min• Injection volume: 100 l• Samples are filtrated with a Macherey-Nagel Chromafil RC-20 / 25 (0,2 pm) filter• Column material: hydroxylated polymethacrylate 2*(TSKgel G3000PWXL 7pm), (TSKgel G4000PWXL 10pm)• Column size: inside diameter 7.8 mm, length 30 cm• Column temperature: 50 °C• Detector: Agilent System RID 1260; temperature 35°C• Calibration with Dextran standards in the molar mass range from 180 to 400000 Da (from PSS, Mainz, Germany)• Software: PSS Win GPC2.3 Determination of the number-average molecular weight via NMR , measured with Bruker Avance 400MHz NMR Spectrometer in deuterated Chloroform. The Mn is determined via quantification of the polymer end groups and the amount of acetal groups per polymer.2.4 The dynamic viscosity is measured with the Haake Viscotester ID (Thermo Fisher Scientific) and a cone-plate setup. The cone and plate pairs used are 20 mm, 35 mm or 60 mm in diameter. For dynamic viscosities > 100,000 mPas the 20 mm pair with 0.1 ml, for dynamic viscosities > 5,000 mPas and < 100,000 mPas the 35 mm pair with 0.4 ml and for dynamic viscosities < 5,000 mPas the 60 mm pair with 2.0 ml of polyol sample is used. The dynamic viscosities are measured at 25 °C with a shear rate of 100 s“1.3. Preparation of polyols3.1 FA + 1,6 Hexanediol + high-purity acidic silica alumina hydrate, without stripping15.4 g of Siral 70 (high-purity acidic silica alumina hydrate) and 2 M (122 g, 110 mL) of 49% aqueous unstabilized formaldehyde were mixed under ambient conditions and heated to 40°C. 2 M (236 g) 1 ,6-hexanediol was added and a vacuum of 100 mbar was applied. When the vacuum was achieved, the mix was heated to 100°C. After 3 h normal pressure was reset, and the mix was cooled down to 90°C and pressure filtered hot using a Seitz K300 (Pall) filter.The product was obtained without further purification as a viscous liquid that crystallized slowly to a white turbid wax-like solid. Mn (NMR) = 1050 g / mol, OH# = 98 mg KOH / g,.3.2 FA + 1,6 Hexanediol + Siral 70, with stripping15.4 g of Siral 70 (high-purity acidic silica alumina hydrate) and 2 M (122 g, 110 mL) of 49% aqueous unstabilized formaldehyde were mixed under ambient conditions and heated to 40°C. 2 M (236 g) 1 ,6-hexanediol was added and a vacuum of 100 mbar was applied. When the vacuum was achieved, the mix was heated to 100°C. After the temperature was reached, 20 mL H2O were added and distilled off. This process was repeated 2 more times. After 3 h normal pressure was reset, and the mix was cooled down to 90°C and pressure filtered hot using a Seitz K300 (Pall) filter.The product was obtained without further purification as a viscous liquid that crystallized slowly to a white turbid wax-like solid. Mn (NMR) = 1080 g / mol,3.3 FA + 1,6 Hexanediol + Montmorillonite, with stripping15.4 g of K10 (Montmorillonite) (acidic layered clay mineral (2:1 phyllosilicate)) and 2 M (122 g, 110 mL) of 49% aqueous unstabilized formaldehyde were mixed under ambient conditions and heated to 60°C. 2 M (236 g) 1 ,6-hexanediol was added and a vacuum of 100 mbar was applied. When the vacuum was achieved, the mix was heated to 100°C. After the temperature was reached, 20 mL H2O were added and distilled off. This process was repeated 2 more times. After 3 h normal pressure was reset and the mix was cooled down to 90°C and pressure filtered hot using a Seitz K300 (Pall) filter.The product was obtained without further purification as a viscous liquid that crystallized slowly to a brownish turbid wax-like solid. Mn (NMR) = 1340 g / mol.3.4 FA + 1,6 Hexanediol + HNO3, w / o stripping5 mL 30% water solution ofnitric acid (1.5 g, 0.024 mol, 1.2 mol%) and 2 M (122 g, 110 mL) of 49% aqueous unstabilized formaldehyde were mixed under ambient conditions and heated to 40°C. 2 M (236 g) 1,6-hexan- diol was added and a vacuum of 100 mbar was applied. When the vacuum was achieved, the mix was heated to 100°C. After 3 h normal pressure was reset, and the mix cooled down to 40°C. 4 mL 25% water solution of NaOHwas added to reach a pH of 7-8. The mix was pressure filtered at 90°C using a Seitz K300 (Pall) filter.The product was obtained without further purification as a viscous liquid that crystallized slowly to a yellowish turbid wax-like solid. Mn (NMR) = 700 g / mol, FA + 1,6 Hexanediol + HNO3, w / o stripping10 mL 30% water solution of nitric acid (3 g, 0.048 mol, 2.4 mol%) and 2 M (122 g, 110 mL) of 49% aqueous unstabilized formaldehyde were mixed under ambient conditions and heated to 40°C. 2 M (236 g) 1,6-hexan- diol was added and a vacuum of 100 mbar was applied. When the vacuum was achieved, the mix was heated to 100°C. After 3 h normal pressure was reset, and the mix cooled down to 40°C. 4 mL 25% water solution ofNaOH was added to reach a pH of 7-8. The mix was pressure filtered at 90°C using a Seitz K300 (Pall) filter.The product was obtained without further purification as a viscous liquid that crystallized slowly to a yellowish turbid wax-like solid. Mn (NMR) = 850 g / mol,. FA + 1,6 Hexanediol + p-toluenesulfonic acid, w / o stripping0.77 g of para-toluenesulfonic acid monohydrate (4 mmol, 0.2 mol%) and 2 M (122 g, 110 mL) of 49% aqueous unstabilized formaldehyde were mixed under ambient conditions and heated to 60°C. 2 M (236 g) 1,6- hexanediol was added and a vacuum of 100 mbar was applied. When the vacuum was achieved, the mix was heated to 100°C. After 3 h normal pressure was reset, and the mix cooled down. 0.46g of diazabicyclounde- cen (DABCO) (4 mmol) was added to reach a pH of 7-8. The mix was pressure filtered at 90°C using a Seitz K300 (Pall) filter.The product was obtained without further purification as a viscous liquid that crystallized slowly to a yellowish turbid wax-like solid. Mn (NMR) = 1060 g / mol, OH# = 102 mg KOH / g,. FA + 1,6 Hexanediol + methanesulfonic acid, w / o stripping0.10 / 0.19 / 0.38 g of methanesulfonic acid (4 / 2 / 1 mmol, 0.2 / 0.1 / 0.05 mol%) and 2 M (122 g, 110 mL) of 49% aqueous unstabilized formaldehyde were mixed under ambient conditions and heated to 60°C. 2 M (236 g) 1 ,6-hexandiol was added and a vacuum of 100 mbar was applied. When the vacuum was achieved, the mixwas heated to 100°C. After 3 h normal pressure was reset, and the mix cooled down. 0.11 / 0.23 / 0.46 g of di- azabicycloundecen (DABCO) (1 / 2 / 4 mmol) was added to reach a pH of 7-8. No solid precipitated, the mix was used without filtration.The product was obtained without further purification as a viscous liquid that crystallized slowly to a yellowish turbid wax-like solid. 0.1 mol%: Mn (NMR) = 1100 g / mol, OH# = 103 mg KOH / g.3.8 FA + 1,6 Hexanediol + sulfuric acid, w / o stripping0.78 g of 50% sulfuric acid (4 mmol, 0.2 mol%) and 2 M (122 g, 110 mL) of 49% aqueous unstabilized formaldehyde were mixed under inert / ambient conditions and heated to 60°C. 2 M (236 g) 1 ,6-hexandiol was added and a vacuum of 100 mbar was applied. When the vacuum was achieved, the mix was heated to 100°C. After 3 h normal pressure was reset, and the mix cooled down. 0.46 g of diazabicycloundecen (DABCO) (4 mmol) was added to reach a pH of 7-8. The mix was pressure filtered at 90°C using a Seitz K300 (Pall) filter.The product was obtained without further purification as a viscous liquid that crystallized slowly to a yellowish turbid wax-like solid. Mn (NMR) = 1000 g / mol, OH# = 114 mg KOH / g,.3.9 FA + Sucrose + Diethyleneglycol (DEG) + methanesulfonic acid, w / o stripping34.2 g (0.10 mol) sucrose and 108,1 g DEG (1,01 mol) were dissolved / dispersed in 34.2 mL deionized water and added to a mix of 71.6 g 49% aqueous unstabilized formaldehyde (1.17 mol) and 0.022 g methanesulfonic acid (2 mmol, 0,2 mol%) at 60°C. When the sugar dispersion was added completely the pressure was reduced to 100 mbar and the mix subsequently heated to 90°C. The temperature was reached after 2 h. After 3 h at 90°C, normal pressure was reset, and the mix cooled down. 0.23 g of diazabicycloundecen (DABCO) (2 mmol) was added to reach a pH of 7-8. The mix was pressure filtered at 90°C using a Seitz K300 (Pall) filter.The product was obtained without further purification as a viscous brown liquid. Mn (GPC) = 450 g / mol, OH# = 334 mg KOH / g4. Preparation of rigid polyurethane foams4.1 Chemicals usedPolyol 1 : Sugar polyol, obtained by propoxylation of sucrose and glycerol. OH number = 430 mg KOH / g, viscosity = 37500 mPas@23°C.Polyol 2: Sugar polyol obtained by propoxylation of sorbitol. OH number = 490, viscosity = 22750 mPas@23°C.Polyol 3: Sugar polyacetal polyol based on sucrose, diethylene glycol and formaldehyde. OH number = 334 mg KOH / g.Si stabilizer: Tegostab B 84214 from Evonik.Catalysts: DMCHA = dimethylcyclohexylamine.Lupragen N600: Amine catalyst from BASF.Bis(2-dimethylaminoethyl ether): Amine catalyst.Isocyanate: Lupranate M20 from BASF SE.4.2 Production of cup foamsThe polyol and isocyanate components were tempered to 20°C and mixed with a Vollrath mixer for 5 s at a speed of 1500 rpm and then transferred to a paper cup. The catalyst quantities were adjusted so that equal proportions of amine catalysts were used in relation to the fully reacted foam in order to take into account the different mixing ratios of the systems.Table 1 : Composition of the foamsTable 2: Properties of the foamsA comparison of the morphology of the foams shows that a more homogeneous foam structure was achieved with the foam according to the invention (Sample 3).Literature cited:WO 2021 / 236385 A1US 5,648,508EP-A-0 709 253M. O’Keeffe et al., J. Sol.State Chem., 152 (2000) p. 3-20H. Li et al., Nature 402 (1999) p. 276 seq.M. Eddaoudi et al., Topics in Catalysis 9 (1999) p. 105-111B. Chen et al., Science 291 (2001) p. 1021-23Houben-Weyl, Methoden der Organischen Chemie, Vol. XIV / 2, Thieme-Verlag, Stuttgart 1963, p. 60f.Ullmanns Enzyklopadie der Technischen Chemie, 4th ed., Vol. 19 (1981), p. 306"Kunststoffhandbuch, volume 7, Polyurethane”, Carl Hanser Verlag, 3rd edition 1993, chapters 3.1, 3.4.4, 3.4.5 and3.4.6 to 3.4.11

Claims

Claims1 . Process for the preparation of polyacetal polyol (PAP) comprising(i) reacting a compound (D1) having at least one OH group with an aldehyde (01) in the presence of a fluorine-free catalyst in an aqueous solution, wherein the aldehyde is formaldehyde, wherein the aqueous solution comprises less than 15% by weight of methanol.

2. The process according to claim 1, wherein the formaldehyde is used in form of an unstabilized aqueous solution.

3. The process according to any one of claims 1 or 2, wherein compound (D1) has a functionality of from 1 to 8, preferably of from 2 to 6.

4. The process according to any one of claims 1 to 3, wherein the catalyst is selected from the group consisting of clay compounds, mixed oxides and MOF catalysts.

5. The process according to any one of claims 1 to 3, wherein the catalyst is homogeneous and preferentially selected from the group consisting of nitric acid, sulfuric acid, methanesulfonic acid and p-toluolsulfonic acid.

6. Polyacetal polyol obtained or obtainable according to a process according to any one of claims 1 to 5.

7. The polyacetal polyol according to claim 6, wherein the polyol has an OH value in the range of from 5 to 1200 mgKOH / g, preferably in the range of from 8 to 800 mgKOH / g, more preferable in the range of from 10 to 700 mgKOH / g, in particular in the range of from 12 to 600 mgKOH / g and the most preferable from 15 to 600 mgKOH / g measured according to EN ISO 4629-1 :20168. Use of a polyacetal polyol obtained or obtainable according to a process according to any one of claims 1 to 5 or a polyacetal polyol according to any one of claims 6 to 7 for the preparation of polyurethanes.

9. Process for preparing a polyurethane at least comprising(I) reacting a polyolcomposition (PC) comprising at least one polyacetal polyol (PAP) obtained or obtainable according to a process according to any one of claims 1 to 5 or at least one polyacetal polyol according to claim 6 or 7 with at least one polyisocyanate composition (IC).

10. The process according to claim 9, wherein the polyol composition (PC) comprises one or more polyacetal polyols (PAP) in an amount of from 20 to 100 % by weight based on the weight of the polyol composition (PC).11 . Polyurethane obtained or obtainable according to a process according to claim 9 or 10.

12. Process for recycling a polyurethane obtained according to a process according to claim 9 or 10 or a polyurethane according to claim 11, at least comprising the step(x) treating the polyurethane with an aqueous solution at a pH in the range of 0 to 6.

13. Process, preferably according to any one of the claims 9 or 10, comprising the step: converting the polyurethane obtainable by or obtained by the process according to any one of claims 10 or 11 or a chemical material obtainable by or obtained by the process according to any one of claims 10 or 11 to obtain a product.

14. Process according to claim 13, wherein the product is selected from:I) building block or monomer; orII) polymer, preferably polymer A, polymer composition, preferably polymer composition A, or polymer product, preferably polymer product A; or ill) cleaning polymer, cleaning surfactant, descaling compound, cleaning biocide or composition or formulation thereof; or iv) agrochemical composition, agrochemical formulation auxiliary or agrochemically ac-tive ingredient; or v) active pharmaceutical ingredient or intermediate thereof, pharmaceutical excipient, animal feed additive, human food additive, dietary supplements, aroma chemical or aroma composition; or vi) aqueous polymer dispersion, preferably polyurethane or polyurethane - poly(meth)acrylate hybrid polymer dispersion, emulsion, binder for paper and fiber coatings, UV-curable acrylic polymer for hot melts and coatings polyisocyanates, hyperbranched polyester polyol, polymeric dispersant for inorganic binder compositions, unsaturated polyester polyol or 100% curable composition; or vii) cosmetic surfactant, emollient, wax, cosmetic polymer, UV filter, further cosmetic ingredient or composition or formulation thereof; or viii) polymer B, polymer composition B, coating composition, other functional composition, foil, molded body, coating or coated substrate15. Process according to any one of claims 13 or 14, wherein the content of the polymeric material (PM) in the product is 1 weight-% or more, preferably 2 weight- % or more, more preferably 5 weight-% or more, more preferably 15 weight-% or more, more preferably 30weight-% or more, more preferably 40 weight-% or more, more preferably 60 weight-% or more, more preferably 80 weight-% or more, more preferably 90 weight-% or more, more preferably 95 weight-% or more; and / or wherein the content of the polymeric material (PM) in the polymer product is 100 weight-% or less, preferably 95 weight-% or less, more preferably 90 weight-% or less, more preferably 50 weight-% or less, more prefera- bly 25 weight-% or less, more preferably 10 weight-% or less; and preferably wherein the content is determined based on identity preservation and / or segre-gation and / or mass balance and / or book and claim chain of custody models, preferably based on mass balance, preferably the International Sustainability and Carbon Certification (ISCC) standard.

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