REUSE OF BIOPLASTICS IN POLYMERISATION

Abstract

The present invention relates to a process for the reuse in polymerization of a biodegradable polymeric composition re) comprising a mixture of polyesters. The process comprises the steps of: 1) reacting said polymeric composition with water at a temperature higher than the melting temperature of at least one of said polyesters, obtaining a depolymerization product comprising monomers of said polyesters and/or their oligomers in a mixture, 2) separating from said depolymerization product a fraction comprising impurities and/or fillers, 3) subjecting said monomers and/or oligomers to polymerization, in quantities from 1% to 100% by weight, with respect to the mixture subjected to polymerization, obtaining a polymeric composition biodegradable. Further objects of the invention are the polymers obtained by means of said reuse process, the biodegradable polymeric compositions that comprise said polymers and the biodegradable articles obtained from said composition

Claims

1. A process for reuse in polymerisation of a biodegradable polymer composition comprising a mixture of polyesters, said process comprising the steps of: 1) reacting said polymer composition with water at a temperature above the melting point of at least one of said polyesters, resulting in a depolymerisation product comprising monomers of said polyesters and/or oligomers thereof in a mixture, 2) separating out a fraction containing impurities and/or fillers from this depolymerisation product, 3) subjecting said monomers and/or oligomers to polymerisation, in amounts from 1% to 100% by weight, preferably from 2% to 50% by weight and more preferably from 5% to 30% by weight, with respect to the mixture subjected to polymerisation, resulting in a biodegradable polymer composition, wherein, in step 1), the said polymer composition comprises at least one polyhydroxyalkanoate and at least one polyester from diacid-diol, and the reaction is carried out at a temperature above the melting temperature of said polyhydroxyalkanoate and wherein additives from the starting mixture of polyesters are fed to polymerisation step 3), together with monomers and/or oligomers, in amounts of up to 5% by weight with respect to the mixture subjected to polymerisation.

2. The process according to claim 1, in which said step 3) of polymerization is carried out keeping the amount of hydroxy acid or its oligomers between 0% and 25% by weight of the total weight of the polymerisation mixture.

3. The process according to claim 1, in which said mixture of polyesters comprises at least one aliphatic-aromatic-type diacid diol polyester.

4. The process according to claim 1, in which said mixture of polyesters comprises at least one aliphatic-type diacid diol polyester.

5. The process according to claim 1, in which said biodegradable composition comprises one or more polyhydroxyalkanoates, one or more aliphatic-type diacid diol polyesters, one or more aliphatic-aromatic-type diacid diol polyesters, and one or more additional polymers comprising one or more vinyl polymers.

6. The process according to claim 1, in which said biodegradable composition comprises one or more fillers.

7. The process according to claim 1, in which said biodegradable polymer composition further comprises polymers of natural origin.

8. The process according to claim 1, prior to step 1, a pre-treatment step that removes said polymers of natural origin from said biodegradable polymer composition comprising a mixture of polyesters.

9. A polymer Polymers obtained by the reuse process according to claim 1.

10. A biodegradable polymer composition comprising the polymer according to claim 9.

11. A biodegradable article comprising said polymer according to claim 9 or said biodegradable polymer composition according to claim 10.

12. The process according to claim 2, in which said mixture of polyesters comprises at least one aliphatic-aromatic-type diacid diol polyester.

13. The process according to claim 2, in which said mixture of polyesters comprises at least one aliphatic-type diacid diol polyester.

14. The process according to claim 2, in which said biodegradable composition comprises one or more polyhydroxyalkanoates, one or more aliphatic-type diacid diol polyesters, one or more aliphatic-aromatic-type diacid diol polyesters, and one or more additional polymers comprising one or more vinyl polymers.

15. The process according to claim 3, in which said biodegradable composition comprises one or more polyhydroxyalkanoates, one or more aliphatic-type diacid diol polyesters, one or more aliphatic-aromatic-type diacid diol polyesters, and one or more additional polymers comprising one or more vinyl polymers.

16. The process according to claim 4, in which said biodegradable composition comprises one or more polyhydroxyalkanoates, one or more aliphatic-type diacid diol polyesters, one or more aliphatic-aromatic-type diacid diol polyesters, and one or more additional polymers comprising one or more vinyl polymers.

17. The process according to claim 2, in which said biodegradable composition comprises one or more fillers.

18. The process according to claim 3, in which said biodegradable composition comprises one or more fillers.

19. The process according to claim 4, in which said biodegradable composition comprises one or more fillers.

20. The process according to claim 5, in which said biodegradable composition comprises one or more fillers.

Description

EXAMPLES

Example 1

[0165] 102.5 g of a formulation consisting mainly of 78% w/w PBAT (i.e. poly(1,4-butylene adipate-co-1,4-butylene terephthalate)), 19.5% w/w PLA and 2.5% w/w talc was placed in a pressure reactor with 200 g water and heated to 200° C. This temperature was maintained for 2 hours (step 1).

[0166] After 2 hours the reactor was allowed to cool and the product was collected, heated to 60° C. to ensure complete solubility of the liberated adipic acid and then filtered under vacuum with paper using a Buchner to separate out the insoluble fraction (mainly comprising terephthalic acid and talc) (step 2).

[0167] The liquid phase, amounting to 270 g, contained mainly 1,4-butanediol, lactic acid, adipic acid, traces of dimers and linear trimers including lactate units, 1,4-butylene terephthalate and/or 1,4-butylene adipate.

[0168] HPLC-MS analysis performed using a Phenomenex Luna Omega C18 PS 100mm×2.1mm×1.6 μm column, using gradient elution with acetonitrile (A) and 0.1% formic acid in water (B), increasing the concentration of A from 5% to 95% and acquiring the signal with a mass spectrometer under positive ESI ionisation (for oligomers) and negative ESI ionisation (for acids and hydroxy acids) revealed the presence of lactic acid, adipic acid, butanediol and dimers and trimers containing lactate, 1,4-butylene adipate and/or 1,4-butylene terephthalate units. The analysis did not reveal any polymer chains with a molecular mass of more than 2,000, so it was assumed that depolymerisation was quantitative and that 25 g of lactic acid, 29.6 g of adipic acid and 34.4 g of 1,4-butanediol were present in the liquid phase as free acids or oligomers.

[0169] 372.6 g (2.2445 moles) of terephthalic acid, 299.4 g (2.0507 moles) of adipic acid, 645 g (7.1633 moles) of 1,4-butanediol, 0.66 g (0.007163 moles) of glycerol, 0,25 g of Tyzor TE and 270 g of solution obtained by filtering the depolymerisation product and containing about 89 g of depolymerisation products (corresponding to 6.3% by weight of the total weight of the polymerisation mixture) were placed in a 2-litre glass reactor equipped with a mechanical stirring system, a nitrogen inlet and a distillation line with a Vigreux-type column, water coolant and a collecting flask. The lactic acid reused in the mixture therefore constituted 5.8% in moles of the total acids and hydroxy acids used, corresponding to 1.8% by weight of the total weight of the polymerisation mixture.

[0170] The reactor was immersed in an oil bath and the temperature of the oil was gradually increased to approximately 250° C. over a period of 2 hours so that a melt temperature of approximately 235° C. was reached. The esterification reaction was carried out for 4 hours, at the end of which the melt was clear. The esterification product was found to be a white waxy solid similar to that obtained from a similar mixture without introduction of the depolymerisation product.

[0171] 170 g of the esterification product was placed in a 1000 ml glass conical reactor equipped with mechanical stirring, nitrogen inlet and vacuum line with a boil-over abatement system connected to a mechanical vacuum pump. The reactor was immersed in an oil bath and the esterification product (oligomer) was caused to melt under a flow of nitrogen. The oil temperature was raised to 240° C., then 0.18 g of catalyst mixture (30% w/w tetrabutyl titanate and 70% w/w tetrabutyl zirconate) was added and the vacuum was increased to less than 3 mbar over 30 minutes. The reaction was carried out at 240° C. and with a residual pressure of less than 3 mbar for 6 hours, resulting in a polyester with an MFR (190° C./2.16 kg) of 5.0 g/10 min, viscosity in solution of 1.04 dl/g (2 g/l, chloroform, 25° C.) and colour L*=67.9, colour a*=8.1 and colour b*=12.9 measured on the granule according to ASTM D6290.