PU based on polyols containing cleavable bonds

Abstract

The present invention relates to a composite comprising a first part (P1) which is at least partially connected with an adhesive layer (LA) and a second part (P2) which is at least partially connected with the adhesive layer (LA), wherein the adhesive layer comprises a polyurethane (PU-1) which comprises functional groups (FG-1) which are labile at a pH value below 5 at a temperature of 20°C, preferably of more than 40°C, and are stable at a pH of 7 at a temperature of 80°C for at least 24 h, preferably for at least 72 h. The present invention further relates to a process for preparing said composite, and a process for separating the composite into its parts by applying debonding conditions (CD), preferably wherein the debonding conditions (CD) comprise treatment with an acidic solution or treatment with an acidic solution and heat.

Description

PU based on polyols containing cleavable bondsThe present invention relates to a composite comprising a first part (P1) which is at least partially connected with an adhesive layer (LA) and a second part (P2) which is at least partially connected with the adhesive layer (LA), wherein the adhesive layer comprises a polyurethane (PU-1 ) which comprises functional groups (FG-1) which are labile at a pH value below 5 at a temperature of 20°C, preferably of more than 40°C, and are stable at a pH of 7 at a temperature of 80°C for at least 24 h, preferably for at least 72 h. The present invention further relates to a process for preparing said composite, and a process for separating the composite into its parts by applying debonding conditions (CD), preferably wherein the debonding conditions (CD) comprise treatment with an acidic solution or treatment with an acidic solution and heat.Many consumer goods are made of multiple components of different materials which are bonded to one another by an adhesive. Such bonded articles are difficult to recycle, and it is difficult to re-use the single materials because they have to be debonded before re-use. Consumer good manufactures increasingly demand concepts to increase sustainability by increasing recycle rates of used bonded articles. However, traditional adhesive bonding methods typically yield irreversible bonds, making disassembly and recycling difficult or impossible without damaging the bonded materials. Several techniques and mechanisms are employed to achieve debonding on demand in adhesive systems, for example thermal activation, chemical debonding, photoresponsive adhesives, pH-sensitive adhesives, hydrolysis or enzymatic breakdown. To allow for debonding of an adhesive, complete reformulation of the whole adhesive is required.Polyurethanes are widely used as adhesives. However, polyurethane adhesives cannot be debonded easily. There have been attempts to introduce sensitive functional groups in the polyurethanes to allow for debonding. For example S. Kirchhecker et al. (Green Chem., 2021 , 23, 957-965) disclose diols prepared via solvent-free acetalisation of hydroxymethylfurfural with glycerol which were incorporated as additives into polyurethanes based on a bioderived polyether polyol to prepare polyurethane adhesives suitable for debonding. However, these diols are solids and difficult to be processed under real industrial conditions and debonding may be achieved only using harsh conditions. WO 2018 / 156689 describes de-bondable adhesives and uses thereof for making and debonding articles of footwear. Debonding is achieved by use of carboxylic acids and salts thereof and by use of microwave irradiation. US 9,683,152 discloses_a two-component polyurethane adhesive for the preparation of bonded articles. Debonding is performed at high temperature, i.e. temperatures above 140°C.There remains a need for improved methods particularly that facilitate the recycling of composites, in particular composites which comprise different materials which have to be separated prior to a recycling process. The composites should, under normal storage, use and cleaning conditions, exhibit high resistance to premature debonding. It is a challenge to provide materials with high bond strength during regular use of the articles but which when subjected to stimulation by suitable conditions are easily debonded on demand in short time for recycling purposes.It was an object of the present invention to provide materials which are suitable as adhesives or for bonding two or more components and allow for the debonding of the respective articles obtained. This also allows to reuse the components without complete decomposition of the respective components.The problem is solved in accordance with the invention by a composite comprising a first part (P1 ) which is at least partially connected with an adhesive layer (LA) and a second part (P2) which is at least partially connected with the adhesive layer (LA), wherein the adhesive layer comprises a polyurethane (PU-1) which comprises functional groups (FG-1) which are labile at a pH value below 5 at a temperature of 20°C, preferably of more than 40°C, and are stable at a pH of 7 at a temperature of 80°C for at least 24 h, preferably for at least 72 h.It has been found that composites can be prepared according to the present invention which can be debonded using mild conditions. This allows to separate the parts and reuse or recycle the separate parts.According to the present invention, the composite comprises a first part (P1) which is at least partially connected with an adhesive layer (LA) and a second part (P2) which is at least partially connected with the adhesive layer (LA). The adhesive layer comprises a polyurethane (PU-1) which comprises functional groups (FG-1). According to the present invention, the polyurethane preferably comprises the functional groups (FG-1) in a suitable amount in the polymer backbone to allow for debonding under mild conditions.The functional groups (FG-1) are labile 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. Preferably, the functional groups (FG-1) are labile at a pH of below 4, more preferable below 3, in particular below 2, particularly preferred below 1 . Preferably, the conditions for debonding are 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.According to the present invention, the functional groups (FG-1) are stable at a pH of 7 at a temperature of 80°C, preferably of 100°C, in particular at a temperature of 100°C and for a time of at least 3 hours, more preferable at a temperature of 100°C and for at least 12 hours and even more preferable at a temperature of 100°C and for at least 24 hours.According to a further embodiment, the functional groups (FG-1) are stable in aqueous solution at a pH in the range of 5 to 9, preferably 6 to 8, at a temperature of 80°C, preferably of 100°C, in particular for a time of at least 3 hours, more preferable at least 12 hours and even more preferable at least 24 hours.According to a further embodiment, the present invention is also directed to the composite as disclosed above, wherein the functional groups (FG-1) are labile at a pH value in the range of below 2 at a temperature in the range of from 60°C to 100°C.Preferably, the polyurethane (PU-1 ) comprises functional groups (FG-1) in the polymer backbone, in particular in the polyol derived parts of the polymer backbone.Suitable functional groups (FG-1) may for example be acetal groups or imine or aldimine groups. According to a further embodiment, the present invention is also directed to the composite as disclosed above, wherein groups (FG-1) are selected from acetal groups and (ald)imine groups. The functional groups (FG-1) may be introduced in the polyurethane structure by using suitable polyols or also chain extenders and / or crosslinkers which comprise functional groups (FG-1).To allow for debonding, the polyurethane of the adhesive layer has to contain a suitable amount of functional groups (FG-1). The content of functional groups (FG-1) in the polyurethane may for example be calculated as the amount of functional groups per gram of the polyurethane. The amount may for example be in a range of from 0.1 mmol / g to 9 mmol / g. In case the functional groups (FG-1) are for example acetal groups, the amount may for example be in a range of from 0.3 to 5 mmol / g, preferably in a range of from 1 .2 to 2.8 mmol / g, more preferable in a range of from 1 .3 to 2.7 mmol / g. In case the functional groups (FG-1) are for example imine groups, the amount may for example be in a range of from 0.1 to 9 mmol / g, preferably in a range of from 0.11 to 5 mmol / g, more preferable in a range of from 0.12 to 3 mmol / g and the most preferable in the range of from 0.12 to 0.3 mmol / g .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.Preferably, the polyurethane (PU-1) comprising functional groups (FG-1) is prepared using a polyol composition which comprises a suitable polyol comprising functional groups (FG-1), for example a polyacetal polyol or a polyimine polyol.Suitable polyacetal polyols or polyimine polyols are in principle known.Suitable polyacetal polyols are for example disclosed in EP 22216457.6. Suitable polyacetal polyols preferably 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 5, 2 to 5, 2 to 4, in particular 2 to 3 OH end groups or 2 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 offrom 500 to 8.000 g / mol, preferably in the range of from 500 to 8000 g / mol, more preferred in the range of from 800 to 6000 g / mol, in particular in the range of from 1000 to 5000 g / mol, calculated from the OH number according to EN ISO 4629-1 :2016. The OH value of the polyacetal polyols may be in the range of from 10 to 1200 mgKOH / g, preferably in the range of from 10 to 600 mgKOH / g, more preferable in the range of from 15 to 500 mgKOH / g, in particular in the range of from 15 to 400 mgKOH / g and the most preferable from 20 to 250 mgKOH / g.Polyacetal polyols may for example be prepared by reacting a compound (D1) having at least one OH group with a compound (C1) in the presence of a solid acid catalyst, wherein the compound (C1) is selected from the group consisting of vinylethers, aldehydes and acetals.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 to 4, particularly preferable 2 to 3 OH groups and the most preferable 2 OH groups. Also water or acids and / or esters such as dicarboxylic or tricarboxylic acids and esters may be used as compound (D1).Suitable compounds (D1) may for example have a functionality of from 1 to 8, preferably from 2 to 3. According to a further embodiment, the present invention is also directed to the process for the preparation of polyacetal polyol as disclosed above, wherein compound (D1) has a functionality from 1 to 8, preferably from 2 to 3.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.In case compound (C1) is selected from vinylethers, suitable compounds are for example divinyl ethers such as 1 ,4- butanediol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether or 1 ,4-cyclohexanedimethanol divinyl ether, hydroxy functional mono vinyl ethers such as for example ethylene glycol vinyl ether, 1 ,4-butanediol vinyl ether, diethylene glycol vinyl ether, 1 ,6-hexanediol vinyl ether or 1,4-cyclohexanedimethanol vinyl ether. Also mono- or divinylethers of polytetrahydrofuranes having a molecular weight in the range of from 200 to 1400 g / mol may be used such as for example PTHF 250 or PTHF 1000, mono vinyl ethers such as for example ethyl vinyl ether, 2-ethylhexyl vinyl ether, tetra ethylene glycol methyl vinyl ether, dodecyl vinyl ether and in general vinyl ethers containing between 3 and 20 carbon atoms. Also mixtures of two or more vinylethers can be used.In case compound (C1) is selected from aldehydes, such aldehydes are aliphatic aldehydes such as mono-aliphatic aldehydes with 1 to 12 carbon atoms or aromatic aldehydes such as for example benzaldehyde. Suitable compounds are also for example dialdehydes such as glutaraldehyde, glyoxal, terephthalaldehyde and trialdehydes or aldehydes with further functional groups, for example hydroxy-functionalized aldehydes such as for example vanillin, 7-hydroxy- 3,7-dimethyl-octanal, 2-hydroxybenzaldehyde, 4-hydroxybenzaldehyde, 2,3-dihydroxybenzaldehyde, hydroxymethylfurfural, lactaldehyde, 3-hydroxybutanal, hydroxypivaldehyde, 5-Hydroxymethyl-2-furaldehyde. Particularly suitable are monoaldehydes such as linear aliphatic monoaldehydes, for example formaldehyde, paraformaldehyde, trioxane, acetaldehyde, paraldehyde, propionaldehyde , valeraldehyde, hexanaldehyde, heptaldehyde and aldehydes with up to 12 C-atoms, 2-trans-hexen-1-al, 4-heptenal, 3-ethoxy-2-methylpropenal branched aliphatic monoaldehydes such as for example 2-ethylhexanal, 2-methylpentanal, isobutyraldehyde, 2-methylbutyraldehyde, 2,2-dimethylpropio- naldehyde , 3-methylvaleraldehyde, 4-methylvaleraldehyde, 2-ethylbutyraldehyde, benzenepropanal, cyclohex- anecarboxaldehyde, 2,2-dimethylbutyraldehyde, 3,3-dimethylbutyraldehyde 3-methylbutanal, aromatic monoaldehydes such as for example benzaldehyde, 4-methoxybenzaldehyde, or phenyl acetic aldehyde, 4-isopropylbenzalde- hyde, furfural, methoxybenzaldehyde, 1 -naphthaldehyde, and also aliphatic ketones such as for example cyclo-pen- tanone, 2,3-butanedione 2,6-dimethy l-4-heptanone, 5-methyl-2-hexanone, acetone, methylhept-5-en-2-one, diethylketone, cyclododecanone, methyl ethyl ketone aromatic ketones such as acetophenone, 1-phenylpentan-1-one, diphenylmethanone and ketones containing other functional groups such as 3-hydroxyacetophenone and 3-hydroxy- butanone. More preferable aldehydes (C1) are monoaldehydes such as benzaldehyde, heptaldehyde, valeraldehyde and aldehyde precursors such as paraldehyde and paraformaldehyde. Also mixtures of two or more aldehydes can be used.In case compound (C1) is selected from acetals, suitable compounds are for example acetals such as aliphatic acetals with one or more acetal groups, for example dimethoxymethane, 1,1 -dimethoxyethane, 1,1 -diethoxyethane, 1,1- diethoxypropane, 1,1,3,3-tetramethoxypropane, succinaldehyde bis(dimethyl acetal), 2-chloro-1 ,1 -diethoxyethane, isobutyraldehyde diethyl acetal, methylglyoxal 1,1 -dimethyl acetal, nonanal diethyl acetal, 1 , 1,2-trimethoxyethane aromatic ace-tals, for example benzaldehyde dimethyl acetal, 4-methoxybenzaldehyde dimethyl acetal, phe-nyla- cetaldehyde dimethyl acetal, 2-furaldehyde diethyl acetal, or diacetales such as for example 1,1,3,3-tetramethoxypropane and tetrahydro-2, 5-dimethoxyfuranand also ketals such as 1,1 -dimethoxycyclohexane, 2,2-diethoxypropane, 1,1 -dimethoxycyclopentane and acetone dibutyl acetal. More preferable acetals (C1) are monoacetals such as dimethoxymethane, 1,1 -diethoxyethane, 1 ,1-diethoxypropane and benzaldehyde dimethyl acetal.Suitable acetal containing polyols may contain various types of acetal groups. Preferably, the polyacetal polyol used according to the present invention comprises at least one functional group of the general structure (I):wherein R1 and R2 could comprise various groups including but not limited to hydrogen, aliphatic or cycloaliphatic carbon chains with a length between 1-20 carbons, aromatic groups, and groups ending in functional groups such as hydroxyl groups. Preferably, the polyacetal polyol used according to the present invention comprises at least one functional group of the general structure (la) or (lb):Suitable polyimine polyols may for example be obtained by the reaction of Vanillin or a derivative thereof and at least one amine A having at least one amino group or the reaction of hydroxymethylfurfural or a derivative thereof and at least one amine A having at least one amino group. Suitable polyimine polyols are for example disclosed in EP 23186236.8.Suitable polyimine polyols may for example be obtained by the reaction of Vanillin or a derivative thereof and at least one amine A having at least one amino group. Suitable Vanillin derivatives have preferable general structure:wherein R1 is selected from aliphatic or cycloaliphatic residues with 1 to 18 C-atoms, more preferably is an aliphatic, cycloaliphatic or aromatic residue with 1 to 12 C-atoms or polyoxyethylene, polyoxypropylene or polyoxypropyleneoxyethylene residue with molecular weight from 50 to 2000 g / mol, more preferable from 50 to 500 g / mol.Furthermore, suitable polyimine polyols may for example be obtained by the reaction of 4-hydroxybenzaldehyde or a derivative thereof and at least one amine A having at least one amino group. Suitable derivatives of 4-hydroxybenzal- dehyde has preferable general structure:wherein R1 is selected from aliphatic or cycloaliphatic residues with 1 to 18 C-atoms, more preferably is an aliphatic, cycloaliphatic or aromatic residue with 1 to 12 C-atoms or polyoxyethylene, polyoxypropylene or polyoxypropyleneoxyethylene residue with molecular weight from 50 to 2000 g / mol, more preferable from 50 to 500 g / mol.Suitable polyimine polyols based on Vanillin preferably have a general structure (Ila and b):wherein R1 is selected from aliphatic or cycloaliphatic residues with 1 to 18 C-atoms, more preferably is an aliphatic, cycloaliphatic or aromatic residue with 1 to 12 C-atoms or polyoxyethylene, polyoxypropylene or polyoxypropyleneoxyethylene residue with molecular weight from 50 to 2000 g / mol, more preferable from 50 to 500 g / mol, and R2 and R3 preferably is an aliphatic, cycloaliphatic or aromatic residue with 2 to 18 C-atoms or polyoxyethylene, polyoxypropylene or polyoxypropylene-oxyethylene residue with molecular weight from 50 to 5000 g / mol, more preferable from 50 to 2000 g / mol.In case amines A having 3 or more amine groups are used, also polyimine polyols comprising 3 or more Vanillin units can be prepared.Suitable amines A are in principle known to the person skilled in the art. Preferred amines A for the preparation of aldimines are for example aliphatic or cycloaliphatic primary mono-, di- or triamines, especially hexamethylene-1 ,6- diamine, isophoronediamine, a,co-polyoxypropylenediamines having an average molecular weight in the range from 200 to 4000 g / mol, a,co-polyoxypropylene-oxyethylenediamines having an average molecular weight in the range from 200 to 4000 g / mol, or glycerol or trimethylolpropane-started amines such as tris(co-polyoxypropyleneamine) having an average molecular weight in the range from 300 to 5000 g / mol. Amine A has 1 to 4 or preferably 1 to 3 amino groups. Suitable amines for the preparation of aldimines may have a molecular weight of up to 6000 g / mol, preferably in the range of from 30 to 5000 g / mol, more preferable in the range of from 100 to 2000 g / mol, in particular in the range of from 200 to 1000 g / mol. Preferably, aliphatic amines such as aliphatic amines with 1 to 4 amino groups, in particular mono-, di-or triamines are used. Therefore, according to a further embodiment, the present invention is also directed to the aldimine as disclosed above, wherein the amine is an aliphatic amine. Suitable amines are for example aliphatic polyamines such as ethylenediamine, 1,2- and 1 ,3-propanediamine, 2-methyl-1 ,2-propanediamine, 2,2-dimethyl-1 ,3-propanediamine, 1 ,3- and 1 ,4-butanediamine, 1 ,3- and 1 ,5-pentanediamine, 1 ,6-hexanediamine, 2,2,4- and 2,4,4-trimethylhexamethylenediamine and mixtures thereof, 1,7-heptanediamine, 1 ,8-octanediamine, 4-aminomethyl-1,8-octanediamine, 1,9-nonanediamine, 1,10-decanediamine, 1,11 -undecanediamine, 1,12-dodecane- diamine, methylbis(3-aminopropyl)amine, 1,5-diamino-2-methylpentane (MPMD), 1,3-diaminopentane (DAMP), p- xylenediamine, m-xylenediamine, o-xylenediamine, 2,5-dimethyl-1,6-hexamethylenediamine, cycloaliphatic polyamines such as 1,2-, 1,3- and 1,4-diaminocyclohexane, bis(4-aminocyclohexyl)methane, bis(4-amino-3-methylcyclo- hexyl)methane, bis(4-amino-3-ethylcyclohexyl)methane, bis(4-amino-3,5-dimethylcyclohexyl)methane, 1 -amino-3- aminomethyl-3,5,5-trimethylcyclohexane (=isophoronediamine or IPDA), 2- and 4-methyl-1,3-diaminocyclohexane and mixtures thereof, 1,3- and 1,4-bis(aminomethyl)cyclohexane, 1-cyclohexylamino-3-aminopropane, 2, 5(2,6)- bis(aminomethyl)bicyclo[2.2.1]heptane (NBDA), 3(4),8(9)bis(aminomethyl)tricyclo[5.2.1.]decane, 1 ,4-diamino-2,2,6- trimethylcyclohexane (TMCDA), 3,9-bis(3-aminopropyl)-2,4,8,10-tetraoxaspiro[5.5]undecane, 1,3- and 1 ,4-xylylenedi- amine, aliphatic polyamines containing ether groups such as bis(2-aminoethyl)ether, 4,7-dioxadecane-1,10-diamine, 4,9-dioxadodecane-1,12-diamine and higher oligomers thereof, 1,8-diamino-p-menthane, 4,4’-diaminodicyclohexyl- methane, tris(2-aminoethyl)amine, 4,7,10-trioxa-1 ,13- tridecanediamine; polyoxyalkylene-polyamines having in theory two or three amino groups, obtainable for example under the name Jeffamine® (manufactured by Huntsman Chemicals) such as JEFFAMINE® diamines (D-230, D-400, D-2000, D-4000), JEFFAMINE® ED Series (ED-600, ED-900, ED-2003), JEFFAMINE® THF Series (THF-100, THF-170), JEFFAMINE® T Series (T-403, T-3000, T- 5000), Jeffamine EDR series such as JEFFAMINE® EDR-148 or JEFFAMINE® EDR-176 and also mixtures of the aforementioned polyamines. More preferable are Jeffamine® D230 (Polypropylene glycol) bis(2-aminopropyl ether), Mn~230), Jeffamine® ED900 (O,O'-Bis(2-aminopropyl) polypropylene glycol-block-polyethylene glycol-block-polypro- pylene glycol, Mn~900, CAS No: 65605-36-9), Jeffamine® D2000 (Polypropylene glycol) bis(2-aminopropyl ether), Mn~2000). Suitable are also monoamines with a molecular weight of up to 6000 g / mol, preferably in the range of from 30 to 5000 g / mol, more preferable in the range of from 100 to 2000 g / mol, in particular in the range of from 200 to 1000 g / mol. Preferable monoamines are ethylamine, propylamine, n-butylamine, t-butylamine, hexylamine, octylamine, tridecylamine, dodecylamine, 2-phenylethylamine, benzylamine, furfurylamine, 2-ethylhexylamine and Jeffamine M series such as JEFFAMINE® M-600, M-2005, M-1000, M-2070, M-2095 and M-3085.Suitable are also amino alcohols with a molecular weight of up to 6000 g / mol, preferably in the range of from 30 to 5000 g / mol, more preferable in the range of from 100 to 2000 g / mol, in particular in the range of from 200 to 1000 g / mol. Preferable amino alcohols are ethanolamine, 3-amino-1 -propanol, 4-amino-1 -butanol, 5-amino-1 -pentanol, isopropanolamine, 2-(2-aminoethoxy)ethanol, aminomethylpropanol, 2-amino-3-methylbutan-1-ol, 2-amino-2-methyl- 1 -propanol, 3-amino-1,2-propanediol, serinol, 2-amino-2-methyl-1,3-propanediol. Also cycloaliphatic or aromatic amines may be used according to the present invention. Suitable amines are for example 1-amino-3-aminomethyl- 3,5,5-trimethylcyclohexane (isophoronediamine or IPDA), 1,8-diamino-p-menthane and 4,4'-diaminodicyclohexylme- thane. Also aromatic amines such as naphthylene diamine, methylene diphenyl diamines, toluenediamines, p-phe- nylenediamine, o-phenylenediamine, m-phenylenediamine.The isocyanate component used for the preparation of polyurethane (PU-1) may comprise one or more polyisocyanates. In some useful embodiments, the polyisocyanate component includes one or more diisocyanates. Suitablepolyisocyanates 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'-diisocy- anato-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-butylene diisocyanate (BDI), 1,6-hexameth- ylene 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 dicy- clohexylmethane-4,4'-diisocyanate (H12MDI). Isomers of these diisocyanates may also be useful. Polymeric MDI with isocyanate functionality higher than 2 can be used as well. Mixtures of two or more polyisocyanates may be used.The polyol component may also comprise further polyols. Depending on the composition of the polyol composition the features of the polyurethanes obtained may be influenced. Polyols useful in the present invention include polyester polyols, polyether polyols, polycarbonate polyols and combinations thereof. The polyester polyols preferably are linear polyesters. Furthermore polyols useful in the present invention include hydroxyl terminated polymeric intermediates having a number average molecular weight (Mn) of preferably from about 300 to about 10,000, for example, about 400 to about 8,000 Daltons, further for example about 500 to about 6,000 Daltons. The molecular weight is determined by assay of the terminal functional groups and is related to the number average molecular weight. Unless otherwise noted, the molecular weight can be determined via end group quantification or can be calculated from the OH number according to EN ISO 4629-1 :2016 in the context of the present invention. Suitable polyols are in principle known to the person skilled in the art. According to the present invention, suitable polyols may have a functionality in the range of from 2 to 8, preferably in the range from 2 to 6, more preferable in the range from 2 to 3.Suitable chain extenders include low molecular weight diols (molecular weight less than 500 g / mol), diamines, and combination thereof. Suitable chain extenders include relatively small polyhydroxy compounds, for example lower aliphatic or short chain glycols having from 2 to 20, or 2 to 12, or 2 to 10 carbon atoms. Suitable examples include ethylene glycol (MEG), diethylene glycol (DEG), propylene glycol (PG), dipropylene glycol (DPG), 1 ,4-butanediol (BDO), 2-methyl-1 ,3-propanediol (MPO), 1 ,6-hexanediol (HDO), 1 ,3-butanediol (1,3-BDO), 1 ,5-pentanediol (1,5- PDO), neopentyl glycol (NPG), 1,4-cyclohexanedimethanol (CHDM), 2,2-bis[4-(2-hydroxyethoxy)phenylpropane (HEPP), heptanediol, nonanediol (NDO), dodecanediol (DDO), 3-methyl-1 ,5-pentanediol (MPD), hydroquinone bis(2- hydroxyethyl) ether (HQEE), ethylenediamine (EDA), butanediamine (BDA), hexamethylenediamine (HDA), and hydroxyethyl resorcinol (HER), and the like, as well as mixtures thereof.According to the present invention, also crosslinkers may be used. Suitable crosslinkers are for example higher-functionality molecules having a plurality of isocyanate-reactive functional groups or higher-functionality polyisocyanates. Examples of suitable crosslinkers are 1,2,4 butanetriol, trimethylolethane, 1,2,6 hexanetriol, trimethylolethane, bu- tane-1,2,3,4-tetrol, benzene-1 ,2,3-triol, glycerol, pentaerythritol, dipentaerythritol, diglycerol or trimethylolpropane, more ptreferable glycerol and trimethylolpropane. Examples of higher-functionality isocyanates are triisocyanates, for example triphenylmethane 4, 4',4"-triisocy anate and isocyanurates, and also the cyanurates of the aforementioned diisocyanates, and the oligomers obtainable by partial reaction of diisocyanates with water, for example the biurets of the aforementioned diisocyanates, and also oligomers obtainable by controlled reaction of semiblocked diisocyanates with polyols having an average of more than two and prefer-ably three or more hydroxyl groups.Within the context of the present invention, the amount of crosslinker, for example of higher-functionality isocyanates and higher-functionality polyols or higher-functionality chain extenders, preferably is no greater than 50 % by weight, preferably less than 30% by weight, most preferable less than 10% by weight, further preferably less than 5 % by weight of the active component, based on the total mixture of the components. Preferably, the amount of chain extender and / or crosslinker used are adjusted to allow for debonding.Optionally, one or more polymerization catalysts may be present during the polymerization reaction. Generally, any conventional catalyst can be utilized to react the diisocyanate with the polyol intermediates or the chain extender. Examples of suitable catalysts which in particular accelerate the reaction between the NCO groups of the isocyanates and the hydroxy groups of the polyols and chain extenders are the conventional tertiary amines known from the prior art, e.g. triethylamine, dimethylcyclohexyl-amine, N-methylmorpholine, N,N'-dimethylpiperazine, 2-(dimethyl- aminoethoxyjethanol, diazabi-cyclo[2.2.2]octane and the like, and also in particular organometallic compounds, such as titanic esters, iron compounds, e.g. ferric acetylacetonate, tin compounds, e.g. stannous diacetate, stannous octoate, stannous dilaurate, bismuth compounds, e.g. bismuth tri neodecanoate, or the dialkyltin salts of aliphatic carboxylic acids, e.g. dibutyltin diacetate, dibutyltin dilaurate, or the like. The amounts usually used of the catalysts are from 0.001 to 2 part by weight per 100 parts by weight of polyol component. In some embodiments, the reaction to form the PU used according to the present invention is substantially free of or completely free of catalyst.In addition, the composition according to the invention may comprise further additives, depending on the application of the composition, such as for example surface-active substances, for example mold-release agents and / or defoamers, inhibitors, plasticizers, inorganic and / or organic fillers such as sand, kaolin, chalk, barium sulfate, silica, and carbon black, oxidation stabilizers, melt auxiliaries such as thermoplastic polymers, dyes and pigments, stabilizers, for example against hydrolysis, light, heat or discoloration, emulsifiers, flame retardants, aging stabilizers, and adhesion promoters typically used in polyurethane chemistry.Suitable fillers are especially ground or precipitated calcium carbonates, optionally coated with fatty acids, especially stearates, or barytes, quartz flours, quartz sands, dolomites, wollastonites, kaolins, calcined kaolins, sheet silicatessuch as mica or talc, zeolites, aluminum hydroxides, magnesium hydroxides, silicas including finely divided silicas from pyrolysis processes, cements, gypsums, fly ashes, industrially produced carbon blacks, graphite, metal powders, for example of aluminum, copper, iron, silver or steel, PVC powders or hollow beads.Suitable plasticizers are especially carboxylic esters such as phthalates, especially diisononyl phthalate (DINP), diisodecyl phthalate (DIDP) or di(2-propylheptyl) phthalate (DPHP), hydrogenated phthalates, especially hydrogenated diisononyl phthalate (DINCH), terephthalates, especially dioctyl terephthalate, trimellitates, adipates, especially dioctyl adipate, azelates, sebacates, benzoates, glycol ethers, glycol esters, organic phosphoric or sulfonic esters, polybutenes, polyisobutenes, or plasticizers derived from natural fats or oils, especially epoxidized soybean oil or linseed oil.In addition, the composition according to the invention may comprise further solvents. Suitable solvents are especially acetone, methyl ethyl ketone, methyl n-propyl ketone, diisobutyl ketone, methyl isobutyl ketone, methyl n-amyl ketone, methyl isoamyl ketone, acetylacetone, mesityl oxide, cyclohexanone, methylcyclohexanone, ethyl acetate, propyl acetate, butyl acetate, n-butyl propionate, diethyl malonate, 1-methoxy-2-propyl acetate, ethyl 3-ethoxypropio- nate, diisopropyl ether, diethyl ether, dibutyl ether, diethylene glycol diethyl ether, ethylene glycol diethyl ether, ethylene glycol monopropyl ether, ethylene glycol mono-2-ethylhexyl ether, THF, DMF, toluene, xylene, heptane, octane, naphtha, white spirit, petroleum ether or benzine, especially Solvesso™ products (from Exxon), and also methylene chloride, propylene carbonate, butyrolactone, N-methylpyrrolidone or N-ethylpyrrolidone.The composition may comprise further additives commonly used for polyurethane compositions such as for example inorganic or organic pigments, fibers, dyes, desiccants, adhesion promoters, further latent hardeners or crosslinkers, rheology modifiers, flame-retardant substances, additives, especially wetting agents, leveling agents, defoamers, deaerators, stabilizers against oxidation, heat, light or UV radiation, or biocides, or further substances customarily used in adhesive compositions.Various additives may be present in the composition such as for example antioxidants, such as phenolic types, rheology modifiers, such as hydrophobic or hydrophilic fumed silica, and adhesion promoters, such as malonic acid, fumaric acid, chlorinated rubber, vinyl chloride / vinyl acetate copolymers, vinyl chloride / vinyl acetate / maleic acid terpolymers. Other additives may be used to enhance the performance of the composition or blend, such as other resins, including but not limited to coumarone-indene or terpene-phenolic which may help increase the tackiness of the adhesive when hot and slow the recrystallization time. All of the additives described above may be used in an effective amount customary for these substances.Additives and fillers may for example be used to influence the conductivity of the layer (LA), in particular in case the composite is used for applications in electromobility. The layer (LA) can be electrically conductive or insulating.Suitable additives may for example be additives to improve the thermal conductivity of the layer (LA). Suitable additives may for example be surface modified aluminum tri-hydroxides, preferably is an alkyl-silane treated aluminium trihydroxide (ATH). Such surface modified aluminum tri-hydroxides are in principle known and for example disclosed in WO9932554.Preferably ATH is a coarse ATH. The size distribution of the surface modified ATH may be mon-omodal, bimodal or multimodal. In a preferred embodiment the size distribution of the ATH is bi-modal or trimodal to allow a dense packing of the filler in the binder matrix. Preferably the surface modified ATH has a particle size D90 of preferably 50 to 200 m, more preferable 60 to 150 m and especially preferred 80 to 120 pm. In an especially preferred embodiment the surface modified ATH has at least a bimodal size distribution of 30 to 70 wt.-% of a surface modified ATH having a size of 1-20 pm and 30 to 70 wt.-% of a surface modified ATH having a D90 size of 40 to 200 pm, each based on the total weight of the surface modified ATH.According to the present invention, at least two parts are bonded but the composite may comprise further parts. The parts may comprise different materials and may also vary in shape and size. According to the present invention, it is also possible that the at least two parts comprise the same material. At least two parts are bonded to form an article. According to the present invention, the article may also comprise further parts or components.The first part or component of the bonded article may comprise a polymer, a metal, leather, wood, a ceramic material, a textile material, glass, rubber, cement, minerals, for example a crepe rubber, a natural leather, a synthetic leather, a polyurethane (for example a polyurethane foam and / or a thermoplastic polyurethane TPU), a thermoplastic rubber, a styrene butadiene rubber, a polyvinyl acetate, a polyamide (PA), a polyvinyl chloride, a polystyrene, an acrylonitrile butadiene styrene, a polyethylene terephthalate (PET), a polybutylene terephthalate, a textile, a fabric, a thermo-plastic polyurethane knit fiber and a combination thereof. According to a further embodiment, the present invention also relates to the composite as disclosed above, wherein the first part (P1) comprises a foamed polymer, a compact polymer, polymer fibers, a metal, leather, wood, a ceramic material, a textile material, glass, rubber, cement, minerals or mixtures thereof.The second part or component may comprise the same or a different material. According to a further embodiment, the present invention also relates to the composite as disclosed above, wherein the second part (P2) comprises a foamed polymer, a compact polymer, polymer fibers, a metal, leather, wood, a ceramic material, a textile material, glass rubber, cement, minerals or mixtures thereof.According to the present invention, it is also possible that one or more surfaces of part (P1) and / or part (P2) are at least partially covered with a layer (LC) which may for example comprise a polymer selected from a polyurethane, a polychloroprene, a latex, a polystyrene, a polyamide, a polyolefin, a polyacrylate, a polyester, a polyether, a copolymer thereof, and any combination thereof, an epoxy resin, or a silicon based polymer. In the context of the presentinvention, it is also possible that the layer (LA) and the layer (LC) are in contact with each other and the layer (LC) may be placed between part (P1) and layer (LA) and / or between part (P2) and layer (LA).According to a further aspect, the present invention is also directed to a process for preparing a composite as disclosed above, the process comprising(I) providing a first part (P1);(ii) applying a composition suitable to form an adhesive layer (LA) comprising a polyurethane (PU-1) which comprises functional groups (FG-1) which are labile at a pH value below 5 at a temperature of more than 40°C, and are stable at a pH of 7 at a temperature of 80°C for at least 24 h, preferably for at least 72 h, to at least one surface of the first part (P1);(ill) joining the second part (P2) with the first part (P 1).According to step (II), a composition suitable to form an adhesive layer (LA) comprising a polyurethane (PU-1) which comprises functional groups (FG-1) which are lable at a pH value below 5 at a temperature of more than 40°C, and are stable at a pH of 7 at a temperature of 80°C for at least 24 h, preferably for at least 72 h is applied to at least one surface of the first part (P1).According to step (ill), the second part (P2) is joined with the first part (P1) to obtain the composite. The second part (P2) is at least partially connected with the adhesive layer (LA).The one or two component adhesive can by applied manually or automatically by e.g., cartridges or process well known to a skill person.Suitable methods for the application of layer (LA) or a composition suitable to form layer (LA) include for example dots and beads application, spray, web coating, brush and trowel, curtain coating, film application, cartridge based hand gun. The layer (LA) can be applied for example using an automated or machine assisted process, e.g. using an automatic sprayer, dot coater, gravure printer or via pneumatic gun.According to a further embodiment, the present invention also relates to the process as disclosed above, wherein the adhesive layer (LA) is prepared from one or multi component polyurethane based adhesive. Suitable are one component adhesives, for example as 1 K moisture cured polyurethane prepolymers, but also two component adhesives, such as 2K polyurethane systems. The adhesive layer (LA) can be also prepared as thermoplastic polyurethane composition, or from solution using organic solvent or further customary additives.According to the present invention, the layer (LA) is applied in an amount and a way that allows bonding of the parts to form an article. The application amount of the layer (LA) is preferably in the range from 10 g / m2to 1500 g / m2, preferred from 20 to 1000 g / m2, more preferred from 50 to 500 g / m2, particularly preferred from 100 to 450 g / m2.The process of the present invention may also comprise further steps, such as for example treatment steps of a surface. Surface treatment may for example include a surface treatment such as a physical treatment, a chemical treatment, a solvent treatment, or any combination thereof. Physical treatments can include treating a surface with an abrasive to increase a surface roughness. Chemical treatments can include etching a surface with acid. Solvent treatments can include contacting a surface with a solvent to remove contaminants from the surface. Preferably, the treating step does not include a primer treatment (i.e. coating with a primer solution before application of the adhesive).According to a further aspect, the present invention is also directed to a composite obtained or obtainable according to the process according to the present invention.Parts of the composite are for example an extruded part, an injection molded part, a pressed part, a foamed part, a cable sheath, a hose, a profiled element, a drive belt, a fiber material, a nonwoven, a film, a molded part, a sole, a sporting good, a part of footwear, a plug, a housing, or a damping element for the electrical industry, for the automobile industry, for machine construction, for 3D printing, for medicine, or for consumer goods, batteries, articles for e- mobility.It has been found that the articles according to the present invention can be disassembled using suitable mild conditions which makes them easier to recycle. According to the present invention, it is possible to disassemble the article and obtain the individual components allowing to separate these components and recycle them. This way, mixing of different components can be reduced or avoided. Furthermore, the individual components obtained may also be reused.According to a further embodiment, the present invention also relates to the process as disclosed above, wherein the composite is separated into its parts by applying debonding conditions (CD), preferably wherein the debonding conditions (CD) treatment with an acidic solution or treatment with an acidic solution and heat. According to the present invention, it is also possible to combine treatment with an acidic solution or treatment with an acidic solution and heat with a mechanical treatment.In principle, the debonding conditions may also include other conditions depending on the chemical nature of the functional groups (FG-1). In case the functional groups (FG-1) are imine groups, the debonding conditions may for example also include the treatment with an amine at a pH of about 10. In case the functional groups (FG-1) are acetal groups, the debonding conditions may also include the treatment with an alcohol in combination with the treatment with an acidic solution.Typically, debonding conditions (CD) comprise a treatment at a pH below 5, preferably below 4, in particular below 2 or below 1. Suitable debonding conditions may include a debonding temperature and debonding pressure. The debonding can be conducted by treating the article at elevated temperature, for example in an oven or with a solution and depending on the chemical nature of a given material at a temperature in the range of from 20 °C to 160°C, preferably in a range from 50 °C to 120°C, preferably in a range from 60°C to 100°C. The debonding can be conducted by treating the article at elevated temperature for a time period of 1 second to 24 hours, preferentially 1 hour to 10 hours.Typically, debonding could be carried out at a temperature in the range from 20 °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. Typically debonding is carried out in air, in water environment, steam environment, or dry environment. According to the present invention, debonding may be carried out at a temperature in the range from 20 °C to 160 °C, in air, in water environment, steam environment, or dry environment. According to the present invention, debonding may be carried out at a temperature in the range from 20 °C to 160 °C in organic solvents, e.g., alcohols, THF, acetone, toluene, ethyl acetate, or amines. Furthermore, surfactants and other additives may be used to facilitate debonding process.The heat can be supplied via heating in an oven, treatment with heated air, treatment with heated water, heated aqueous solutions including further additives such as for example surfactants, or steam or can be generated using radiation such as for example microwave and / or radiofrequency radiation according to the present invention. According to the present invention, also combinations of these methods can be used.According to a further aspect, the present invention is also directed to a process for recycling a composite obtained according to a process as disclosed above or a composite according to the present invention, at least comprising the step(x) treating the composite with a solution at a pH in the range of 0 to 5.Specifically, the process comprises: contacting the composite with an acid solution and allowing at least a portion of the adhesive layer to decompose.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, acetone, ethyl acetate or further solvents. The solution also may comprise surfactants.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 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. More preferable acids are phosphoric acid, citric acid and hydrochloric acid.While it is desirable to submerge the entire composite into the acid solution, there are embodiments where only a part of the composite is contacted with the acid solution. In these embodiments, the remaining portion of the adhesive layer (i.e. the portion that does not contact the acid solution) will not be decomposed.According to the present invention it is also possible that a layer of the residual adhesive remains on the debonded components which may be used in a further process without a recycling step. Preferably, no residual adhesive remains on the surfaces of the debonded components. This has the advantage that residual adhesive does not interfere in the recycling of the debonded components. The residual adhesive can be removed by additional washing with organic solvents, such as Me-THF, iso-propanol and ethyl acetate or mixtures thereof, and thus ensure proper recycling of the debonded substrates.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; or ii) polymer, preferably polymer A1 , polymer composition, preferably polymer composition A1 , or polymer product, preferably polymer product A1; 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; orvii) 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, ab-sorbing, 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 whichthe 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. (Methacrylates 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 AT', 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 AT', 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 A1 ”, as used herein, comprises any product comprising the polymer A1 and / or polymer composition A1 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 A1, polymer composition, preferably polymer composition A1 or polymer product, preferably polymer product A1 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 agrochemi-cal 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 ingredientsand / 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, Apo-carotenoids, 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 product(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 polyurethane 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 compositions” 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 polymeric dispersant(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 paragraph

[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.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 . Composite comprising a first part (P1) which is at least partially connected with an adhesive layer (LA) and a second part (P2) which is at least partially connected with the adhesive layer (LA), wherein the adhesive layer comprises a polyurethane (PU-1) which comprises functional groups (FG-1) which are labile at a pH value below 5 at a temperature of 20°C, preferably of more than 40°C, and are stable at a pH of 7 at a temperature of 80°C for at least 24 h, preferably for at least 72 h.2. The composite according to embodiment 1, wherein the functional groups (FG-1) are labile at a pH value in the range of below 2 at a temperature in the range of from 60°C to 100°.3. The composite according to any one of embodiments 1 or 2, wherein groups (FG-1) are selected from acetal groups and imine groups.4. The composite according to any one of embodiments 1 to 3, wherein the content of functional groups (FG-1) per gram of the polyurethane is in the range of from 0.1 mmol / g to 9 mmol / g.The composite according to any one of embodiments 1 to 4, wherein the first part (P1) comprises a foamed polymer, a compact polymer, polymer fibers, a metal, leather, wood, a ceramic material, a textile material, glass, rubber, cement, minerals and combinations thereof. The composite according to any one of embodiments 1 to 5, wherein the second part (P2) comprises a foamed polymer, a compact polymer, polymer fibers, a metal, leather, wood, a ceramic material, a textile material, glass rubber, cement, minerals and combinations thereof. Process for preparing a composite according to any one of embodiments 1 to 6, the process comprising(I) providing a first part (P1);(II) applying a composition suitable to form an adhesive layer (LA) comprising a polyurethane (PU-1 ) which comprises functional groups (FG-1) which are labile at a pH value below 5 at a temperature of more than 40°C and are stable at a pH of 7 at a temperature of 80°C for at least 24 h, preferably for at least 72 h, to at least one surface of the first part (P1);(ill) joining the second part (P2) with the first part (P 1). The process according to embodiment 7, wherein the adhesive layer (LA) is prepared from a one or multi component polyurethane based adhesive. The process according to embodiment 7 or 8, wherein the functional groups (FG-1) are labile at a pH value in the range of below 2 at a temperature in the range of from 60°C to 100°. The process according to any one of embodiments 7 to 9, wherein groups (FG-1) are selected from acetal groups and imine groups. The process according to any one of embodiments 7 to 10, wherein the content of functional groups (FG-1) per gram of the polyurethane is in the range of from 0.1 mmol / g to 9 mmol / g. The process according to any one of embodiments 7 to 11, wherein the first part (P1) comprises a foamed polymer, a compact polymer, polymer fibers, a metal, leather, wood, a ceramic material, a textile material, glass, rubber, cement, minerals and combinations thereof. The process according to any one of embodiments 7 to 12, wherein the second part (P2) comprises a foamed polymer, a compact polymer, polymer fibers, a metal, leather, wood, a ceramic material, a textile material, glass rubber, cement, minerals and combinations thereof. A composite obtained or obtainable according to a process according to any one of embodiments 7 to 13.The process according to any one of embodiments 7 to 13, wherein the composite is separated into its parts by applying debonding conditions (CD), preferably wherein the debonding conditions (CD) comprise treatment with an acidic solution or treatment with an acidic solution and heat. The process according to embodiment 15, wherein the debonding conditions (CD) comprise a treatment at a pH below 5 at a temperature in the range of from 40 °C to 160°C. The process according to embodiment 15, wherein the debonding conditions (CD) for the adhesive layer (LA) comprising a polyurethane (PU-1 ) with the functional group (FG-1) selected from imine groups, comprise a treatment at a pH above 10 in presence of amines at temperature in the range of from 20 °C to 160°C Process, preferably according to any one of the embodiments 7 to 13, comprising the step: converting the composite obtainable by or obtained by the process according to any one of embodiments 7 to 13 or a chemical material obtainable by or obtained by the process according to any one of embodiments 7 to 13 to obtain a product. Process according to embodiment 18, wherein the product is selected from:I) building block or monomer; or ii) polymer, preferably polymer A1 , polymer composition, preferably polymer composition A1 , or polymer product, preferably polymer product A1; or ill) 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 Process according to any one of embodiments 18 or 19,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 / 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 embodiment chain of custody models, preferably based on mass balance, preferably the International Sustainability and Carbon Certification (ISCC) standard.21. Composite comprising a first part (P1) which is at least partially connected with an adhesive layer (LA) and a second part (P2) which is at least partially connected with the adhesive layer (LA), wherein the adhesive layer comprises a polyurethane (PU-1) which comprises functional groups (FG-1) which are labile at a pH value below 5 at a temperature of 20°C, preferably of more than 40°C, and are stable at a pH of 7 at a temperature of 80°C for at least 24 h, preferably for at least 72 h, wherein groups (FG-1) are selected from acetal groups and imine groups.22. The composite according to embodiment 21, wherein the functional groups (FG-1) are labile at a pH value in the range of below 2 at a temperature in the range of from 60°C to 100°.23. The composite according to any one of embodiments 21 or 22, wherein groups (FG-1) are selected from acetal groups.24. The composite according to any one of embodiments 21 to 23, wherein the content of functional groups (FG- 1) per gram of the polyurethane is in the range of from 0.1 mmol / g to 9 mmol / g.25. The composite according to any one of embodiments 21 to 24, wherein the first part (P1) comprises a foamed polymer, a compact polymer, polymer fibers, a metal, leather, wood, a ceramic material, a textile material, glass, rubber, cement, minerals and combinations thereof.26. The composite according to any one of embodiments 21 to 25, wherein the second part (P2) comprises a foamed polymer, a compact polymer, polymer fibers, a metal, leather, wood, a ceramic material, a textile material, glass rubber, cement, minerals and combinations thereof.27. Process for preparing a composite according to any one of embodiments 21 to 26, the process comprising (I) providing a first part (P1);(ii) applying a composition suitable to form an adhesive layer (LA) comprising a polyurethane (PU-1 ) which comprises functional groups (FG-1) which are labile at a pH value below 5 at a temperature of more than 40°C and are stable at a pH of 7 at a temperature of 80°C for at least 24 h, preferably for at least 72 h, to at least one surface of the first part (P1);(iii) joining the second part (P2) with the first part (P 1).28. The process according to embodiment 27, wherein the adhesive layer (LA) is prepared from a one or multi component polyurethane based adhesive.29. A composite obtained or obtainable according to a process according to any one of embodiments 27 or 28.30. The process according to any one of embodiments 27 or 28, wherein the composite is separated into its parts by applying debonding conditions (CD), preferably wherein the debonding conditions (CD) comprise treatment with an acidic solution or treatment with an acidic solution and heat.31 . The process according to embodiment 30, wherein the debonding conditions (CD) comprise a treatment at a pH below 5 at a temperature in the range of from 20 °C to 160°C.32. The process according to embodiment 30, wherein the debonding conditions (CD) for the adhesive layer (LA) comprising a polyurethane (PU-1) with the functional group (FG-1) selected from imine groups, comprise a treatment at a pH above 10 in presence of amines at temperature in the range of from 20 °C to 160°C.33. Composite comprising a first part (P1) which is at least partially connected with an adhesive layer (LA) and a second part (P2) which is at least partially connected with the adhesive layer (LA), wherein the adhesive layer comprises a polyurethane (PU-1) which comprises functional groups (FG-1) which are labile at a pH value below 5 at a temperature of 20°C, preferably of more than 40°C, and are stable at a pH of 7 at a temperature of 80°C for at least 24 h, preferably for at least 72 h, wherein groups (FG-1) are selected from acetal groups, wherein the polyurethane (PU-1) comprising functional groups (FG-1) is prepared using a polyol composition which comprises a polyacetal polyol comprising at least one functional group of the general structure (I):wherein R1 and R2 is selected from hydrogen, aliphatic or cycloaliphatic carbon chains with a length between 1-20 carbons, aromatic groups, and groups ending in functional groups such as hydroxyl groups.34. The composite according to embodiment , wherein he polyacetal polyol used ac comprises at least one functional group of the general structure (la) or (lb):35. Composite comprising a first part (P1) which is at least partially connected with an adhesive layer (LA) and a second part (P2) which is at least partially connected with the adhesive layer (LA), wherein the adhesive layer comprises a polyurethane (PU-1) which comprises functional groups (FG-1) which are labile at a pH value below 5 at a temperature of 20°C, preferably of more than 40°C, and are stable at a pH of 7 at a temperature of 80°C for at least 24 h, preferably for at least 72 h, wherein groups (FG-1) are selected from imine groups, wherein the polyurethane (PU-1) comprising functional groups (FG-1) is prepared using Vanillin or a derivative thereof and at least one amine A having at least one amino group or by the reaction of hydroxymethylfurfural or a derivative thereof and at least one amine A having at least one amino group.36. The composite according to any one of embodiments 33 to 35, wherein the functional groups (FG-1) are labile at a pH value in the range of below 2 at a temperature in the range of from 60°C to 100°.37. The composite according to any one of embodiments 33 to 36, wherein the content of functional groups (FG-1) per gram of the polyurethane is in the range of from 0.1 mmol / g to 9 mmol / g.38. The composite according to any one of embodiments 33 to 37, wherein the first part (P1) comprises a foamed polymer, a compact polymer, polymer fibers, a metal, leather, wood, a ceramic material, a textile material, glass, rubber, cement, minerals and combinations thereof.39. The composite according to any one of embodiments 33 to 38, wherein the second part (P2) comprises a foamed polymer, a compact polymer, polymer fibers, a metal, leather, wood, a ceramic material, a textile material, glass rubber, cement, minerals and combinations thereof.40. Process for preparing a composite according to any one of embodiments 33 to 39, the process comprising(I) providing a first part (P1);(II) applying a composition suitable to form an adhesive layer (LA) comprising a polyurethane (PU-1) which comprises functional groups (FG-1) which are labile at a pH value below 5 at a temperature ofmore than 40°C and are stable at a pH of 7 at a temperature of 80°C for at least 24 h, preferably for at least 72 h, to at least one surface of the first part (P1);(ill) joining the second part (P2) with the first part (P1 ).41 . The process according to embodiment 40, wherein the adhesive layer (LA) is prepared from a one or multi component polyurethane based adhesive.42. A composite obtained or obtainable according to a process according to any one of embodiments 40 or 41 .43. The process according to any one of embodiments 40 or 41 , wherein the composite is separated into its parts by applying debonding conditions (CD), preferably wherein the debonding conditions (CD) comprise treatment with an acidic solution or treatment with an acidic solution and heat.44. The process according to embodiment 43, wherein the debonding conditions (CD) comprise a treatment at a pH below 5 at a temperature in the range of from 20 °C to 160°C.45. The process according to embodiment 43, wherein the debonding conditions (CD) for the adhesive layer (LA) comprising a polyurethane (PU-1) with the functional group (FG-1) selected from imine groups, comprise a treatment at a pH above 10 in presence of amines at temperature in the range of from 20 °C to 160°C.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. MaterialsVanillin (99%), ethylene carbonate, 1 ,6-Hexanediol (H16, 99%), Jeffamine® D230 (Polypropylene glycol) bis(2- aminopropyl ether), Mn~230), Jeffamine® ED900 (O,O'-Bis(2-aminopropyl) polypropylene glycol-block-poly- ethylene glycol-block-polypropylene glycol, Mn~900, CAS No: 65605-36-9), Jeffamine® D2000 (Polypropylene glycol) bis(2-aminopropyl ether), Mn~2000), paraformaldehyde (for synthesis), 1 ,4-Diazabicyclo[2.2.2]octane (DABCO, >99%), ortho-phosphoric acid (H3PO4, 99%), 1 M HCI solution and citric acid (>99.5%) were procured from Merck and utilized without further purification. Siral 70 was provided by SASOL (Germany). 1 ,4-Butanediol (99%) and paraldehyde (98%) were purchased from TCI Europe. Na2CO3 (anhydrous, 99.5%) was purchased from Acros Organics. Deuterated CDCI3 was obtained from Cambridge Isotope Laboratories. Ethyl acetate and n-hexane were procured from Biosolve B.V. and used without further purification. 1 ,4-Butanediol divinyl ether (B14 DVE), K10 montmorillonite clay, Methylene diphenyl diisocyanate (MDI, Lupranat® ME), Lupranol®1005 / 1 (polypropylene glycol with an average molecular weight of 4000 and OH number of 28 mg KOH / g), Lupranol® 1000 / 1 (polypropylene glycol with an average molecular weight of 2000 and OH number of 55 mg KOH / g) and Lupranol® 2095 (trifunctional reactive polyether polyol containing primary hydroxyl groups with OH number of 35 mg KOH / g) were obtained from BASF (Germany) and used as received. The amine functionality of Jeffamine® D230, Jeffamine® ED900 and Jeffamine® D2000 was determined to be 1 .7, 1 .4 and 1 .2, respectively using titrimetric1H NMR analysis.Beechwood test bars (2.5 x 10 cm) were sourced from Rocholtt, Germany. PET foil (thickness: 0.4 mm) was procured from Rayher Hobby GmbH. Polyester-polyol-based PU foam and PET textile were provided by BASF. MethodsTo determine the isocyanate content of the prepolymer, a Metrohm 916 Ti-Touch titrator was employed following the ASTM D5155-19 standard method.Lap-shear tests were conducted in accordance with ISO 4587 I DIN EN 1465 standard, at a strain rate of 5 mm / min, utilizing a pre-force of 10 N. The adhesion tests were performed using beechwood test bars (2.5 x 10 cm, obtained from Rocholtt, Germany).The following methods were used to determine the properties of the acetal containing polyols: hydroxyl number was determined according to method EN ISO 4629-1 :2016 and is given in mg KOH / g. Acid number was determined according to DIN EN ISO 2114 and is given in mg KOH / g. Adhesion specimen preparation~100 mg of isocyanate prepolymer was evenly spread onto a substrate of interest measuring 1 cm x 1 cm, which could be either PU foam or PET foil. Next, a PET textile measuring 1 cm x 1 cm was affixed onto the adhesive-coated substrate. A pressure was applied to the adhesive assembly by pressing with a 700 g load for one day. Following this, the applied adhesive was allowed to cure for one week at a temperature of 23°C and a RH of 60%.For lap-shear measurements, the beechwood test bars were bonded together with a specimen overlap of 25 mm x 25 mm, ensuring that the thickness of the adhesive layer remained ~ 100 pm by employing a spacer. A pressure was applied to the adhesive assembly by pressing with a 1 kg load for one day. Subsequently, the adhesive between the glued wood samples were cured using the same procedure. Debonding the substratesGlued substrates with a 1x1 cm2adhesion surface (either PU foam-PET textile or PET foil-PET textile) were exposed to aqueous solutions of 1 M H3P04, 1 M citric acid, or 1 M HCI at 80°C. For PU foam-PET textile samples, 30 ml of the solution was used, and for PET foil-PET textile samples, 10 ml was used. Debonding was monitored at half-hour intervals over 10 hours.5. Cleaning the substratesAfter debonding, the substrates were washed with Me-THF or ethyl acetate to remove any residual material, completing the recycling process.6. Synthesis6.1 Synthesis of HEV (4-(2-hydroxyethoxy)-3-methoxybenzaldehyde)Vanillin (30.0 g, 197 mmol), ethylene carbonate (17.7 g, 201 mmol), and Na2COa (420 mg, 3.94 mmol) were placed in a 2-neck flask equipped with a magnetic stir bar and reflux condenser. The mixture was flushed with Ar for 30 min, then heated to 165 °C for 3 h under Ar atmosphere. After the reaction, the mixture was dissolved in chloroform and washed twice with DI water, followed by two additional washes with brine twice to remove ethylene carbonate and sodium carbonate. The organic layer was subsequently dried over MgSC and the solvent was evaporated. Finally, HEV was purified by flash column chromatography on silica gel employing an eluent mixture of ethyl acetate / hexane (70 / 30). The resulting material, HEV, was obtained as a white solid, yielding 24.5 grams.6.2 Synthesis of imine-containing polyolsHEV was mixed with Jeffamine derivative. The reaction was conducted at 60 °C under a reduced pressure of 15 mbar for 2 h using a rotary evaporator. Subsequently, the resulting material underwent drying for 12 h under vacuum at 40 °C. b. Imine polyol 1 (IP 1)Above mentioned general procedure was used to synthesize IP 1 with HEV (4.71 g) and Jeffamine D2000 (40.0 g). The resulting polyol was obtained as a clear liquid.c. Imine polyol 2 (IP 2)Above mentioned general procedure was used to synthesize IP 2 with HEV (16.79 g) and Jeffamine ED900 (55 g). The resulting polyol was obtained as a clear liquid. d. Imine polyol 3 (IP 3)Above mentioned general procedure was used to synthesize IP 3 with HEV (3.10 g) and Jeffamine D230 (2.14 g) in 20 ml THF. After evaporation of THF, the resulting polyol was obtained as a highly viscous liquid.6.3 Synthesis of acetal-containing polyols a. Acetal polyol 1 (AP 1)1 ,4-Butanediol (B14) and 1 ,4-butanediol divinyl ether (B14 DVE) were dried for at least 48 h over molecular sieves prior to use. Dry 1 ,4-butanediol (259 g, 2.87 mol) and K10 catalyst (7.35 g, 1.2 wt%) were added into a 1 I three-neck round bottom flask equipped with an argon inlet, a mechanical stirrer, a thermocouple, and an addition funnel. The reaction mixture was heated to 30 °C and the mechanical stirrer was set to 450 rpm to fully suspend the catalytic particles in the reaction mixture. B14 DVE (350 g, 2.46 mol) was placed in the addition funnel and dropped into the reaction mixture in approximately 0.5 h. The internal reaction temperature was kept constant at 30 °C for 2 hours. After which, the reaction mixture was filtered to remove the solid catalyst and the filtrate was then dried with a rotary evaporator at 65 °C and 18 mbar for 2 h, after which a clear colorless liquid was obtained with an OH value of 114 mg KOH / g and an acid value below 0.1 mg KOH / g. b. Acetal polyol 2 (AP 2) )1 ,4-Butanediol (B14) and 1 ,4-butanediol divinyl ether (B14 DVE) were dried for at least 48 h over molecular sieves prior to use. Dry 1 ,4-butanediol (195 g, 2.16 mol) and K10 catalyst (6.0 g, 1.2 wt%) were added into a 1 I three-neck round bottom flask equipped with an argon inlet, a mechanical stirrer, a thermocouple, and an addition funnel. The reaction mixture was heated to 30 °C and the mechanical stirrer was set to 450 rpm to fully suspend the catalytic particles in the reaction mixture. B14 DVE (300 g, 2.11 mol) was placed in the addition funnel and dropped into the reaction mixture in approximately 0.5 h. The internal reaction temperature was kept constant at 30 °C for 3 hours. After which, the reaction mixture was filtered to remove the solid catalyst and the filtrate was then dried with a rotary evaporator at 65 °C and 18 mbar for 2 h, after which a clear colorless liquid was obtained with an OH value of 54 mg KOH / g and an acid value below 0.1 mg KOH / g.c. Acetal polyol 3 (AP 3)1 ,6-Hexanediol (H16) was melted in an oven at 80 °C. H16 (352 g 2.98 mol) and Siral 70 (21 g) were added to a 1 I one neck flask fitted with a water-cooled short path vacuum condenser and a receiving flask. Paraformaldehyde (85 g, 2.83 mol) was then added, and the oil bath temperature was set to 110 °C. The mixture was vigorously stirred and vacuum was applied. After 2.5 h, the reaction mixture was cooled, diluted with acetone to reduce viscosity and vacuum filtered to remove the solid catalyst. The filtrate was then dried for 2 h at 80 °C and 1 mbar. The resulting material is a clear, colorless polyacetal polyol which slowly crystalizes at room temperature, with an OH value of 120 mg KOH / g and an acid value below 0.1 mg KOH / g. d. Acetal polyol 4 (AP 4))1 ,6-Hexanediol (H16) was melted in an oven at 80 °C. H16 (100.3 g 0.85 mol) and Siral 70 (7.81 g) were added to a 500 ml three-neck flask fitted with a Dean-Stark condenser and an argon inlet. The reaction mixture was heated to 65 °C using an oil bath, and a 1 :1 hexane / pentane mixture was added until continuous reflux was observed. Paraldehyde (115 g, 0.87 mol) was then added in 5 batches, with 90-minute intervals between additions. After 24 h, the reaction mixture was cooled, diluted with acetone to reduce viscosity and vacuum filtered to remove the solid catalyst. The filtrate was subsequently dried at 80 °C and 1 mbar for 2 hours. The resulting material is a clear, colorless polyacetal polyol with an OH value of 131 mg KOH / g and an acid value below 0.1 mg KOH / g.6.4 Synthesis of linear iso-prepolymers for 1 K PU adhesives a. General synthesis of reference and imine containing iso-prepolymers (reference 1 (R 1), example 1 (E 1), example 2 (E 2)):The polyols and imines were mixed with DABCO catalyst at 80 °C under an argon flow, following the formulation provided in the table with the specified raw materials. Subsequently, MDI was added to the mixture. The reaction was performed for 3 hours at 80 °C under argon. Following the reaction, the experimental NCO content was determined. b. General synthesis of acetal containing iso-prepolymers (example 3 (E 3), example 4 (E 4), example 5 (E 5)):PPG 4000 is mixed with 65 mg of DABCO. The mixture was heated to 80°C under Ar flow. Above it, MDI (7.15 g) is added. The reaction was continued for 3 h. After that, polyacetal polyol was added according to the formulation below. The reaction was kept stirring for 3 more hours at the same temperature. Following the reaction, the experimental NCO content was determined.Table 1. Raw materials used to synthesize linear 1K PU prepolymers.6.5 Synthesis of crosslinked iso-prepolymers for 1 K PU adhesives a. General synthesis of reference and imine containing iso-prepolymers (reference 2 (R 2), reference 3 (R 3), example 6 (E 6), example 7 (E 7), example 8 (E 8), example 9 (E 9), example 10 (E 10)):The polyols and imine of interest were mixed with DABCO catalyst at 80 °C under an argon flow, following the formulation provided in the table with the specified raw materials. Subsequently, MDI was added to the mixture. The reaction was performed for 3 hours at 80 °C under argon. Following the reaction, the experimental NCO content was determined. b. General synthesis of acetal containing iso-prepolymers (example 11 (E 11), example 12 (E 12), example 13 (E 13), example 14 (E 14)):Lupranol 1005 / 1 and Lupranol 2095 are mixed with 65 mg of DABCO. The mixture was heated to 80 °C under Ar flow. Above it, MDI (7.15 g) is added. The reaction was continued for 3 h. After that, polyacetal polyol of interest was added according to the formulation below. The reaction was kept stirring for 3 more hours at the same temperature. Following the reaction, the experimental NCO content was determined.Table 2. Raw materials used to synthesize crosslinked 1K PU prepolymers.7. Results Table 3. NCO content and tack-free time of the prepolymers, lap-shear strength of cured adhesives (1 week, RT, 60% RH).Table 4A. Time required for debonding of glued PU foam-PET textile substrates under different conditions.Identical conditions were employed for the debonding at 80 °C with a constant stirring rate at 200 rpm. - represents no debonding after 24 h under specified conditions, n.m.: experiment was not performed. Table 4B. Time required for debonding of glued PU foam-PET textile substrates under different conditions (A more detailed study).dentical conditions were emp oyed for the debonding at 80 °C with a constant stirring rate at 200 rpm. - represents no debonding after 24 h under specified conditions, n.m.: experiment was not performed.Table 5. Time required for debonding of glued PET foil-PET textile substrates under different conditions.Identical conditions were employed for the debonding at 80 °C with a constant stirring rate at 200 rpm. - represents no debonding after 24 h under specified conditions, n.m.: experiment was not performed.After debonding of example 8 and example 11 -glued substrates, additional washing with organic solvents, such as chloroform, dichloromethane, dimethylformamide, THF, Me-THF and ethyl acetate, more preferably environmentally benign solvents such as Me-THF and ethyl acetate was performed to remove residual adhesive and obtain adhesive-free surfaces of substrates and thus ensure proper recycling of the debonded substrates.Literature citedS. Kirchhecker et al. (Green Chem., 2021 , 23, 957-965)WO 2018 / 156689US 9,683,152EP 23186236.8EP 22216457.6

Claims

Claims1 . Composite comprising a first part (P1) which is at least partially connected with an adhesive layer (LA) and a second part (P2) which is at least partially connected with the adhesive layer (LA), wherein the adhesive layer comprises a polyurethane (PU-1) which comprises functional groups (FG-1) which are labile at a pH value below 5 at a temperature of 20°C, preferably of more than 40°C, and are stable at a pH of 7 at a temperature of 80°C for at least 24 h, preferably for at least 72 h, wherein groups (FG-1) are selected from acetal groups and imine groups.

2. The composite according to claim 1, wherein the functional groups (FG-1) are labile at a pH value in the range of below 2 at a temperature in the range of from 60°C to 100°.

3. The composite according to any one of claims 1 or 2, wherein groups (FG-1) are selected from acetal groups.

4. The composite according to any one of claims 1 to 3, wherein the content of functional groups (FG-1) per gram of the polyurethane is in the range of from 0.1 mmol / g to 9 mmol / g.

5. The composite according to any one of claims 1 to 4, wherein the first part (P1) comprises a foamed polymer, a compact polymer, polymer fibers, a metal, leather, wood, a ceramic material, a textile material, glass, rubber, cement, minerals and combinations thereof.

6. The composite according to any one of claims 1 to 5, wherein the second part (P2) comprises a foamed polymer, a compact polymer, polymer fibers, a metal, leather, wood, a ceramic material, a textile material, glass rubber, cement, minerals and combinations thereof.

7. Process for preparing a composite according to any one of claims 1 to 6, the process comprising(i) providing a first part (P1);(ii) applying a composition suitable to form an adhesive layer (LA) comprising a polyurethane (PU-1) which comprises functional groups (FG-1) which are labile at a pH value below 5 at a temperature of more than 40°C and are stable at a pH of 7 at a temperature of 80°C for at least 24 h, preferably for at least 72 h, to at least one surface of the first part (P1);(iii) joining the second part (P2) with the first part (P1), wherein groups (FG-1) are selected from acetal groups and imine groups.

8. The process according to claim 7, wherein the adhesive layer (LA) is prepared from a one or multi component polyurethane based adhesive.

9. A composite obtained or obtainable according to a process according to any one of claims 7 or 8.

10. The process according to any one of claims 7 or 8, wherein the composite is separated into its parts by applying debonding conditions (CD), preferably wherein the debonding conditions (CD) comprise treatment with an acidic solution or treatment with an acidic solution and heat.11 . The process according to claim 10, wherein the debonding conditions (CD) comprise a treatment at a pH below 5 at a temperature in the range of from 20 °C to 160°C.

12. The process according to claim 10, wherein the debonding conditions (CD) for the adhesive layer (LA) comprising a polyurethane (PU-1 ) with the functional group (FG-1) selected from imine groups, comprise a treatment at a pH above 10 in presence of amines at temperature in the range of from 20 °C to 160°C.

13. Process, preferably according to any one of the claims 7 to 8, comprising the step: converting the composite obtainable by or obtained by the process according to any one of claims 7 to 8 or a chemical material obtainable by or obtained by the process according to any one of claims 7 to 8 to obtain a product.

14. Process according to claim 13, wherein the product is selected from:I) building block or monomer; or ii) polymer, preferably polymer A1 , polymer composition, preferably polymer composition A1 , or polymer product, preferably polymer product A1; or ill) 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; orviii) 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 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.

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