METHOD FOR DEPOLYMERISING OXYGENATED POLYMER MATERIALS BY NUCLEOPHILIC CATALYSIS

Abstract

The present invention relates to a method for depolymerising oxygenated polymer materials, in particular by nucleophilic catalysis and to the use of said method in the recycling of plastic materials and the preparation of aromatic and aliphatic compounds that can be used as fuel, synthesis intermediates, raw materials in the construction sector, and in the petrochemical, electrical, electronic, textile, aeronautical, pharmaceutical, cosmetic and agrochemical industry. The present invention also relates to a method for manufacturing fuels, electronic components, plastic polymers, rubber, medicines, vitamins, cosmetics, perfumes, food products, synthetic yarns and fibres, synthetic leathers, glues, pesticides, fertilisers comprising (i) a step of depolymerisation of oxygenated polymer materials according to the method of the invention and optionally (ii) a step of hydrolysis, and optionally (iii) a step of functionalisation and/or defunctionalisation.

Claims

1. A method for depolymerising oxygenated polymers by selective cleaving of oxygen-carbon bonds of ester functions (—CO—O—) and carbonate functions (—O—CO—O—), characterised in that wherein it comprises a step of putting into contact said oxygenated polymers with a hydrosilane compound of formula (I) ##STR00022## wherein R.sup.1, R.sup.2 and R.sup.3 represent, independently from one another, a hydrogen atom, a halogen atom, a hydroxyl group, an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, an aryloxy group, a silyl group, a siloxy group, an aryl group, an amino group, said alkyl, alkenyl, alkynyl, alkoxy, silyl, siloxy, aryl and amino groups being optionally substituted, or R.sup.1 is such as defined above and R.sup.2 and R.sup.3, taken together with the silicon atom to which they are linked to form an optionally substituted silyl heterocycle; in presence of a Lewis base type catalyst, said Lewis base type catalyst being an alcoholate of formula (II)
(R.sup.6—O.sup.−).sub.wM.sup.w+  (II) wherein w is 1, 2, 3, 4, and 5; R.sup.6 is an alkyl comprising 1 to 6 carbon atoms, an alkenyl comprising 2 to 6 carbon atoms, an alkynyl comprising 2 to 6 carbon atoms or a monocyclic or polycyclic aryl typically bi- or tri-cyclic comprising 6 to 20 carbon atoms; and M is a metal chosen from among Li, Na, K, Cs or Rb, Cu, Mg, Zn, Ca, Sr, Ba, Pb, Al, Sb, La, Zr, Si, Ti, Sn, Hf, Ge, V; or a compound allowing to release a fluoride (F.sup.−) of formula (III):
Y.sup.2+—(F.sup.−).sub.z  (III) wherein z is 1, 2, 3, 4; Y is an alkyl ammonium of which the alkyl comprises 1 to 6 carbon atoms, an alkenyl ammonium of which the alkenyl comprises 2 to 6 carbon atoms, an alkynyl ammonium of which the alkynyl comprises 2 to 6 carbon atoms, or an aryl comprising 6 to 10 carbon atoms; a quinine ammonium, or Y is a metal chosen from among Li, Na, K, Cs, Rb, Cu, Zn, Ca, Ba, Al, Zr, Sn; a fluorosilicate chosen from among: hexafluorosilicates SiF.sub.6.sup.2− with an alkaline counterion chosen from among Li, Na, K and Cs; or fluorosilicates of formula (R.sup.7).sub.3SiF.sub.2.sup.− with an alkyl ammonium counterion of formula N(R.sup.10).sub.4.sup.+ or a sulfonium counterion of formula S(R.sup.11).sub.3.sup.+; with R.sup.7 being an alkyl comprising 1 to 6 carbon atoms chosen from among methyl, ethyl, propyl, butyl, pentyl or hexyl and their branched isomers; or an aryl comprising 6 to 10 carbon atoms chosen from among phenyl, benzyl or naphthyl; R.sup.10 being a hydrogen atom; a methyl, an ethyl, a propyl, a butyl, and their branched isomers; R.sup.11 being a hydrogen atom; a methyl, an ethyl, a propyl, a butyl, and their branched isomers or primary, secondary or tertiary amines; a primary or secondary amide, a guanidine derivative chosen from among bicyclic sodium or potassium guanidinates, in particular sodium or potassium salt of the anion of 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (or Hhpp), guanidine, 1,5,7-triazabicyclo[4.4.0]dec-5-ene (or TBD); a carbenic heterocycle of general formula (IV): ##STR00023## wherein R.sup.8 and R.sup.9 represent, independently from one another, an alkyl comprising 1 to 6 carbon atoms, an alkenyl comprising 2 to 6 carbon atoms, an alkynyl comprising 2 to 6 carbon atoms or a bi- or tri-cyclic aryl comprising 6 to 20 carbon atoms; a carbonate of formula (V)
M′.sub.2CO.sub.3  (V) wherein M′ is a metal chosen from among Li, Na, K, Cs or Rb.

2. The method according to claim 1, wherein the oxygenated polymers are chosen from among saturated or unsaturated polyesters chosen from among polylactic acid (PLA), polycaprolactone (PCL), polyhydroxyalkanoate (PHA), polyhydroxyvalerate (PHV), polyethylene adipate (PEA), polybutylene succinate (PBS), poly(3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), polydioxanone (PDO); polycarbonates chosen from among PC-BPA, polypropylene carbonate (PPC), polyethylene carbonate (PEC), poly(hexamethylene carbonate), allyl diglycol carbonate (ADC) or CR-39; or hydrolysable tannins chosen from among gallotannins, ellagitannins, or suberin.

3. The method according to claim 1, wherein the oxygenated polymers are chosen from among polyesters chosen from among PET, PCL, PDO or PLA; polycarbonates chosen from among PC-BPA or PPC; hydrolysable tannins chosen from among gallotannins, ellagitannins, or suberin.

4. The method according to claim 1, wherein the Lewis base type catalyst is an alcoholate of formula (II), wherein R.sup.6 is a linear or branched alkyl comprising 1 to 6 carbon atoms, chosen from among methyl, ethyl, propyl, butyl, pentyl or hexyl and their branched isomers and M is Li, Na, K or Rb.

5. The method according to claim 1, wherein the Lewis base type catalyst is an alcoholate of formula (II) chosen from among CH.sub.3—OLi, CH.sub.3—ONa, CH.sub.3—OK, CH.sub.3—ORb, CH.sub.3CH.sub.2—OK, (CH.sub.3—O).sub.3Al, (PhO).sub.3Al, (iPrO).sub.3Al or tBu-OK.

6. The method according to claim 1, wherein the Lewis base type catalyst is a compound of formula (III), wherein Y is an alkyl ammonium of which the alkyl comprises 1 to 6 carbon atoms, chosen from among methyl, ethyl, propyl, butyl, pentyl or hexyl and their branched isomers.

7. The method according to claim 1, wherein the Lewis base type catalyst is a compound of formula (III), chosen from among CsF, TMAF (tetramethylammonium fluoride) or TBAF (tetrabutylammonium fluoride).

8. The method according to claim 1, wherein the Lewis base type catalyst is a fluorosilicate chosen from among fluorosilicate ammonium (K.sub.2SiF.sub.6) or difluorotriphenylsilicate tetrabutylammonium [(n-Bu).sub.4N.sup.+(Ph).sub.3SiF.sub.2.sup.−] also called TBAT.

9. The method according to claim 1, wherein the Lewis base type catalyst is a carbenic heterocycle of formula (IV) chosen from among 2,6-di(1,3-diisopropyl)imidazolium carbene, 1,3-bis(1-adamantanyl)imidazolium carbene or 1,3-bis(2,6-diisopropylphenyl)imidazolinium carbene.

10. The method according to claim 1, wherein the hydrosilane compound implemented is a hydrosilane compound of formula (I) wherein R.sup.1, R.sup.2 and R.sup.3 represent, independently from one another, a hydrogen atom; a hydroxyl group, an alkyl group chosen from among methyl, ethyl, propyl, butyl, and their branched isomers; an alkoxy group of which the alkyl radical is chosen from among methyl, ethyl, propyl, butyl and their branched isomers; an alkoxy group of which the alkyl radical is chosen from among methyl, ethyl, propyl, butyl and their branched isomers; an aryl group chosen from among phenyl and benzyl; an aryloxy group of which the aryl radical is chosen from among phenyl and benzyl; a siloxy group (—O—Si(X′).sub.3) of which each X, independently from one another, is chosen from among a hydrogen atom, an alkyl group chosen from among methyl, ethyl, propyl, an aryl group chosen from among phenyl and benzyl, a polymeric organosilane of general formulas ##STR00024## wherein X′ is such as defined above and n is an integer comprised between 1 and 20000, advantageously between 1 and 5000, more advantageously between 1 and 1000; said alkyl, alkoxy, aryl, aryloxy, siloxy and aryl groups being optionally substituted.

11. The method according to claim 1, wherein the hydrosilane compound implemented is a hydrosilane compound of formula (I), wherein R.sup.1, R.sup.2 and R.sup.3 represent, independently from one another, a hydrogen atom; an alkyl group chosen from among methyl, ethyl, propyl and its branched isomer; an aryl group chosen from among benzyl and phenyl; a siloxy group chosen from among polydimethylsiloxane (PDMS), polymethylhydroxysiloxane (PMHS) and tetramethyldisiloxane (TMDS).

12. The method according to claim 1, wherein the molar ratio between the hydrosilane compound of formula (I) and the oxygenated polymer is comprised between 0.1 and 20.

13. The method according to claim 1, wherein the catalyst quantity is from 0.001 to 0.9 molar equivalent, limits included, with respect to the initial molar number of the starting oxygenated polymer.

14. A method for recycling plastic materials or mixtures of plastic materials containing at least one oxygenated polymer characterised in that it comprises (i) a step of depolymerising oxygenated polymer materials according to claim 1, optionally (ii) a step of hydrolysis and optionally (iii) a step of functionalisation and/or defunctionalisation.

15. A method for preparing non-aromatic (or aliphatic) compounds, saturated or unsaturated, mono-, di- and/or tri-oxygenated, or mono-, di-, and/or tri-cyclic aromatic compounds, of which each cycle is optionally mono-, di-, and/or tri-oxygenated, characterised in that it comprises (i) a step of depolymerising oxygenated polymer materials according to claim 1, optionally (ii) a step of hydrolysis to form the corresponding non-silyl compounds and optionally (iii) a step of functionalisation and/or defunctionalisation.

16. A method for manufacturing fuels, electronic components, plastic polymers, rubber, medicaments, vitamins, cosmetic products, perfumes, food products, yarns and synthetic fibres, synthetic leathers, glues, pesticides, fertilisers, comprising (i) a step of depolymerising oxygenated polymer materials according to claim 1, and optionally (ii) a step of hydrolysis to form the non-aromatic (or aliphatic) compounds, saturated or unsaturated, mono-, di- and/or tri-oxygenated and/or mono-, di-, and/or tri-cyclic aromatic compounds, of which each cycle is mono-, di- and/or tri-oxygenated, optionally (iii) a step of functionalisation and/or defunctionalisation.

Description

[0208] Other advantages and features of the present invention will appear upon reading the examples below, given in an illustrative and non-limiting manner and figures appended, wherein:

[0209] FIG. 1 represents the reduction of oxygenated polymers with Lewis acid catalysts that are BCF (B(C.sub.6F.sub.5).sub.3) and the iridium complex according to Cantat et al (WO2016/098021, Feghali et al. Chem Sus Chem, 2015, 8, 980-984 et Monsigny et al. ACS Sustainable Chem. Eng., 2018, 6, 10481-10488).

[0210] FIG. 2 represents the use of Lewis acid-type catalyst to reduce biomass. (a) The reduction of cellulose with the B(C.sub.6F.sub.5).sub.3 catalyst (Gagné et al., Angew. Chem. Int. Ed. 2014, 53, 1646-1649) and (b) the reduction of lignin with the B(C.sub.6F.sub.5).sub.3 and [Ir] catalysts according to Cantat. (Cantat et al. WO2016005836Al, Feghali et al. Energy Environ. Sci., 2015, 8, 2734-2743, Monsigny et al. Green Chem., 2018, 20, 1981-1986).

[0211] FIG. 3 represents the reduction of aryl ether bonds in lignin models (i.e. oxygen carbon bond between two aromatics in a molecule mimicking a bond present in a lignin polymer) with potassium terbutanolate (KOtBu) non-catalytically (2-3 equivalents) (Gruber et al., Chem. Sci., 2013, 4, 1640).

[0212] FIG. 4 is a schematic representation comparing the depolymerisation of PLA by the depolymerisation method of the invention (c) with the methods of the state of the art (Cantat et al. WO2016/098021 and Chem Sus Chem, 2015, 8, 980-984 (a); Monsigny et al. ACS Sustainable Chem. Eng., 2018, 6, 10481-10488 (b)). [0213] (a) Cantat et al. WO2016/098021, the mixture of triethylsilane (Et.sub.3SiH, 3.3 equivalents) and PLA (1 equivalent) in the presence of BCF (5 mol %), as catalyst leads to the production of silyl alcohol corresponding to the monomers of the PLA (PG-Si for silylated propylene glycol), but also to a significant quantity of propane. [0214] (b) Monsigny et al. ACS Sustainable Chem. Eng., 2018, 6, 10481-10488, under similar conditions with an iridium-based catalyst [Ir] leads to a mixture of products: PG-Si is still the main compound, but unlike the reaction with BCF, the main by-product is silylated propanol and not propane. [0215] (c) Finally, in the method of the invention, the use of TBAF which is a Lewis base, as catalyst, does not allow the cleavage of simple bonds σ-C—O such as alcohols and ethers. The depolymerisation reaction of the PLA in the presence of trimethoxysilane which here also serves as solvent leads to the quantitative formation of the sole product PG-Si.

EXAMPLES

[0216] In the examples below, only the most commonly used polymers (for example, PCL, PET, PC-BPA and PLA) have been tested. On the other hand, the quantity of hydrosilane of general formula (I) necessary to realize the depolymerisation is largely dependent on the type of polymeric material used to obtain silylated alcohols (—OSiR.sup.1R.sup.2R.sup.3). It must be noted that, by approximation, and in order to calculate the molar yield of depolymerisation reactions, the starting material is considered to be exclusively formed from the polymer studied.

[0217] The yields obtained are of the order of 68 to 99 mol % with respect to the mole number of monomer in the starting polymer. The conversions have been calculated by being based on spectroscopic analyses (.sup.1H NMR and .sup.13C NMR) by using a Bruker DPX 200 MHz spectrometer, and by adding an internal standard (mesitylene or diphenylmethane). The yields have been obtained using gaseous phase chromatography by using as standard, the same compound previously synthesised (external calibration curve). The mass spectrometry data have been collected on a Shimadzu GCMS-QP2010 Ultra gas chromatograph mass spectrometer device equipped with a Supelco SLB™-ms molten silica capillary column (30 m×0.25 mm×0.25 μm). The qualitative analyses of gas have been carried out using gaseous phase chromatography on a Shimadzu GC-2010 device equipped with a Carboxen™ 1006 PLOT capillary column (30 m×0.53 mm).

General Experimental Depolymerisation Protocol

[0218] 1. Under argon or nitrogen inert atmosphere, the hydrosilane of general formula (I), the oxygenated polymer and the solvent (if necessary) are stirred in a Schlenk tube. The hydrosilane concentration in the reactional mixture varies from 1.0-6.0 mol.Math.L.sup.−1 (concentration calculated based on half of the final volume of solvent introduced). [0219] 2. Then, the catalyst is added to the reactional mixture (1 to 0.001 molar equivalents calculated with respect to the number of moles of polymer material initially added). The solution is stirred and the Schlenk tube is left open in order to discharge the gases produced by the reaction. [0220] 3. After the end of adding the solution and stopping the gaseous emission, the Schlenk tube is closed and is left to stir. In the case where the starting material is insoluble, the solubilisation is carried out during the reaction time, given the end products are soluble in the solvents used. The following reaction is carried out by .sup.1H NMR and by GC-MS. [0221] 4. Once the reaction has ended (reaction time of 1 minute to 24 hours), the solvent, as well as the volatile compounds are evaporated using a Schlenk line (10.sup.−2 mbar). The oil obtained is purified using a silica gel chromatography by using an elution gradient of 100:0% up to 0:100% of pentane:CH.sub.2Cl.sub.2. [0222] 5. The products can be hydrolysed by using NaOH (10%) in methanol, to provide the corresponding hydrolysed product. The hydrolysis reaction lasts from 1 minute to 16 hours. The end product is obtained after purification on chromatographic column by using an elution gradient of 100:0% up to 0:100% of CH.sub.2Cl.sub.2:AcOEt.

[0223] A set of results is presented below, giving examples of depolymerising synthetic and semi-synthetic oxygenated polymer materials.

[0224] The catalysts tested are TBAT, TBAF and KOtBu.

[0225] The hydrosilanes used are PhSiH.sub.3, (MeO).sub.3SiH, (EtO).sub.3SiH TMDS and PMHS. The oxygenated polymer materials used are PLA, PC-BPA, PCL, PET and PDO. The PET used is a commercial PET sampled from Evian bottles.

Example 1: Depolymerisation of PC-BPA with trimethoxysilane ((MeO).SUB.3.SiH) with KOtBu

[0226] ##STR00009##

[0227] Commercial PC-BPA (123.2 mg; 0.5 mmol; 1 molar equivalent) and trimethoxysilane (244 mg; 2 mmol; 4 molar equivalent) have been added to 1.5 mL of THF. The KOtBu catalyst (0.05 molar equivalent) is added while stirring. After 6 hours of room temperature reaction (20±5° C.), the solvent is evaporated under vacuum. The product obtained IIa is purified by using the same conditions as that described in the general operating method. Coming from this purification, the product IIa is obtained with a very high purity with a yield of 97% with respect to the starting material introduced.

[0228] The hydrolysis of the product IIa in corresponding dehydroxylated product can be carried out directly by adding to the reactional mixture, 10 ml of a NaOH solution (10%) in a methanol/water mixture by adding it at 25° C. for 2 hours. The hydrolysed product (BPA) is obtained with a yield of 88%, as white solid, after purification on chromatographic column, by using the conditions described in the general operating method.

Example 2: depolymerisation of PC-BPA with trimethoxysilane ((MeO).SUB.3.SiH) with TBAT

[0229] ##STR00010##

[0230] The same operating method used for the depolymerisation of PC-BPA by (MeO).sub.3SiH with KOtBu in example 1 is used for the depolymerisation with TBAT (0.05 molar equivalent). In this case, 123.2 mg of PC-BPA (0.5 mmol; 1 molar equivalent) are used with 244 mg of trimethoxysilane (244 mg; 2 mmol; 4 molar equivalent) and 0.05 molar equivalent of TBAT (13.5 mg, 0.025 mmol, 5 mol %). After 6 hours of reaction, the conversion is total in IIa. The purification of the products is carried out by following the same operating method described in example 1.

[0231] The hydrolysis of the product IIa leads to the obtaining of BPA (white solid, 92% yield).

Example 3: Depolymerisation of PC-BPA with Trimethoxysilane ((MeO).SUB.3.SiH) with TBAF (1M in THF)

[0232] ##STR00011##

[0233] The same operating method used for the depolymerisation of PC-BPA by (MeO).sub.3SiH with KOtBu in example 1 is used for the depolymerisation with TBAF (1M in THF). In this case, 123.2 mg of PC-BPA (0.5 mmol; 1 molar equivalent) are used with trimethoxysilane (244 mg; 2 mmol; 4 molar equivalent) and 504 of TBAF (0.05 mmol; 0.1 molar equivalent). After 12 hours of reaction, the conversion is total in IIa.

[0234] The purification of the products is carried out by following the same operating method described in example 1. The hydrolysis of the product IIa leads to the obtaining of BPA (white solid, 92% yield).

Example 4: depolymerisation of PC-BPA with triethoxysilane ((Et.SUB.0.).SUB.3.SiH) with TBAF (1M in THF)

[0235] ##STR00012##

[0236] The same operating method used for the depolymerisation of PC-BPA by (MeO).sub.3SiH with TBAF in example 3 is used for the depolymerisation with triethoxysilane. In this case, 123.2 mg of PC-BPA (0.5 mmol; 1 molar equivalent) are used with 4 molar equivalent of triethoxysilane (328 mg; 2 mmol); and 504 of TBAF (0.05 mmol; 0.1 molar equivalent). After 12 hours of reaction, the conversion is total in IIa. The purification of the products is carried out by following the same operating method described in example 1.

[0237] The hydrolysis of the product IIb leads to the obtaining of BPA (white solid, 92% yield).

Example 5: Depolymerisation of PC-BPA with TMDS with TBAF (1M in THF)

[0238] ##STR00013##

[0239] The same operating method used for the depolymerisation of PC-BPA by (MeO).sub.3SiH with TBAF in example 3 is used for the depolymerisation with TMDS. In this case, 123.2 mg of PC-BPA (0.5 mmol; 1 molar equivalent) are used with (266.7 mg; 2.0 mmol; 4 molar equivalent) of TMDS and (504; 0.05 mmol; 0.1 molar equivalent) of TBAF 0.1 molar equivalent. After 12 hours of reaction, the conversion is total in silylated monomer.

[0240] The hydrolysis of silylated monomers is therefore done directly in the reactional medium and leads to the obtaining of BPA (white solid, 92% yield).

Example 6: Depolymerisation of PC-BPA with PMHS with TBAF (1M in THF)

[0241] ##STR00014##

[0242] The same operating method used for the depolymerisation of PC-BPA by (MeO).sub.3SiH with TBAF in example 3 is used for the depolymerisation with PMHS. In this case, 123.2 mg of PC-BPA (0.5 mmol; 1 molar equivalent) are used with 330.7 mg of PMHS (5.5 mmol; 11 molar equivalent) and 504 of TBAF (0.05 mmol; 0.1 molar equivalent).

[0243] After 12 hours, the hydrolysis of silylated monomers is done directly in the reactional medium and leads to the obtaining of BPA (white solid, 68% yield).

Example 7: Depolymerisation of PET by Using TMDS with TBAF (1M in THF)

[0244] ##STR00015##

[0245] The same operating method used for the depolymerisation of PC-BPA by (MeO).sub.3SiH with TBAF in example 3 is used for the depolymerisation with PMHS. In this case, 96.1 mg of PET (0.5 mmol; 1 molar equivalent) are used with TMDS (400.0 mg; 3.0 mmol; 6 molar equivalent) and 0.1 molar equivalent of TBAF (50 μL; 0.05 mmol; 0.1 molar equivalent). After 72 hours at 60° C., the hydrolysis of the silylated product is done directly in the reactional medium and leads to the obtaining of BDM (white solid, 85% yield).

Example 8: Depolymerisation of PCL by Using TMDS with TBAF (1M in THF)

[0246] ##STR00016##

[0247] The same operating method used for the depolymerisation of PC-BPA by (MeO).sub.3SiH with TBAF in example 3 is used for the depolymerisation with PMHS. In this case, (58.2 mg; 0.5 mmol; 1 molar equivalent) of PCL are used with 266.7 mg of TMDS (2.0 mmol; 4 molar equivalent) and 504 of TBAF (0.05 mmol; 0.1 molar equivalent). After 12 hours at room temperature (20±5° C.), the hydrolysis of the silylated product is done directly in the reactional medium and leads to the obtaining of 1,6-hexanediol (white solid, 89% yield).

Example 9: Depolymerisation of PLA by Using TMDS with TBAF (1M in THF)

[0248] ##STR00017##

[0249] The same operating method used for the depolymerisation of PC-BPA by (MeO).sub.3SiH with TBAF in example 3 is used for the depolymerisation with PMHS. In this case, (37.0 mg; 0.5 mmol; 1 molar equivalent) of PLA are used with 266.7 mg of TMDS (2.0 mmol; 4 molar equivalent) and 504 of TBAF (0.05 mmol; 0.1 molar equivalent). After 48 hours at 60° C., the hydrolysis of the silylated product is done directly in the reactional medium and leads to the obtaining of propylene glycol (white oil, 93% yield).

Example 10: Depolymerisation of PDO by Using TMDS with TBAF (1M in THF)

[0250] ##STR00018##

[0251] The same operating method used for the depolymerisation of PC-BPA by (MeO).sub.3SiH with TBAF in example 3 is used for the depolymerisation with PMHS. In this case, 52.2 mg of PDO (0.5 mmol; 1 molar equivalent) are used with 266.7 mg of TMDS (2.0 mmol; 4 molar equivalent) and 504 of TBAF (0.05 mmol; 0.1 molar equivalent). After 12 hours at room temperature (20±5° C.), the hydrolysis of the silylated diethyleneglycol is done directly in the reactional medium and leads to the obtaining of diethyleneglycol DEG (colourless oil, 89% yield).

Example 11

[0252] ##STR00019##

[0253] The same operating method used for the depolymerisation of PC-BPA by (MeO).sub.3SiH with TBAF in example 3 is used for the depolymerisation with PCL with (MeO).sub.3SiH. In this case, (52.2 mg; 0.5 mmol; 1 molar equivalent) of PCL are used with (244 mg; 2 mmol; 4 molar equivalent) of (MeO).sub.3SiH and 2.8 mg; (0.025 mmol; 5 mol %) of TBAF without solvent. After 6 hours at 70° C., the purification of the silylated product is carried out by following the same operating method described in example 1 and is obtained at 98%.

Characterisation of the Molecules Obtained:

[0254] ##STR00020##

[0255] .sup.1H NMR (200 MHz, THF-d.sub.8, Me.sub.4Si) δ (ppm)=7.10 (4H, m, Ar-H), 6.86 (4H, m, Ar—H), 3.58 (18H, s, MeOSi), 1.61 (6H, s, CH.sub.3—)

[0256] .sup.13C NMR (50 MHz, THF-d.sub.8, Me.sub.4Si): δ (ppm)=151.1, 144.4, 127.5, 118.4, 50.6, 32.7, 30.5.

##STR00021##

[0257] .sup.1H NMR (200 MHz, THF-d.sub.8, Me.sub.4Si) δ (ppm)=3.73 (4H, t.sup.3J=6 Hz, O—CH.sub.2), 1.55 (4H, m, O—CH.sub.2—CH.sub.2—CH.sub.2), 1.40 (4H, m, O—CH.sub.2—CH.sub.2—CH.sub.2—).

[0258] .sup.13C NMR (50 MHz, THF-d.sub.8, Me.sub.4Si): δ (ppm)=63.0, 50.2, 32.3, 25.3.

[0259] The abbreviations used are specified below:

PC-BPA=Polycarbonate bisphenol A

PCL=Poly(caprolactone)

PDO=Poly(dioxanone)

[0260] PET=Poly(ethylene terephthalate)
PVC=Poly(vinyl chloride)
DEG=Diethylene glycol
EG=Ethylene glycol
PG=Propylene glycol
BDM=Benzene dimethanol
TPA=terephthalic acid

PLLA=Poly(L-lactide)

[0261] PLA=Polylactic acid

BPA=Bisphenol A

PS=Polystyrene