Reuse of bioplastics in polymerisation

Abstract

The present invention relates to a process for reusing a polymer composition comprising at least one biodegradable polyester, starch and / or additives, comprising the steps of: (1) contacting said biodegradable polymer composition with a first solvent comprising from 50 to 100% by weight of cyclopentanone, obtaining a liquid fraction comprising at least one biodegradable polyester and a solid fraction comprising insoluble starch and / or additives; (2) separating said liquid fraction comprising at least one polyester from said solid fraction; (3) at least partially removing said first solvent from said liquid fraction; (4) reusing the polyester obtained from said liquid fraction in a polymerisation or thermoplastic transformation process, thereby obtaining a biodegradable polymer composition. Biodegradable polyesters obtained by means of the said reutilisation process, biodegradable polymer compositions comprising them, and biodegradable articles obtained therefrom constitute further objects of the invention.

Description

[0001] REUSE OF BIOPLASTICS IN POLYMERISATION

[0002] DESCRIPTION

[0003] The present invention relates to the chemical recycling of waste bioplastics, and in particular to the processing of biodegradable compositions comprising biopolymers for the selective recovery of polyesters suitable for reuse in polymerisation reactions. It also relates to a polymerisation process for obtaining biodegradable polyesters from polyesters selectively recovered from biodegradable plastics

[0004] The term biopolymers generally refers to biodegradable and / or bio-based polymers. Biodegradable polymers are defined as polymers that are able to degrade once they have reached the end of their primary use and be organically recycled by nourishing microorganisms without generating an accumulation of waste in the environment. Bio-based polymers are defined as those obtained from natural or renewable resources, that is from sources that, by their very nature, can be regenerated within the time scale of a human lifetime.

[0005] In view of the current widespread use of bioplastics as an alternative to conventional plastics, a further increase in sustainability could be achieved by increasing the possibility of reusing the polymers or monomers of which they are made. This would minimise the use of land and the production of CO2 that are needed for the preparation of their monomers.

[0006] For this reason, new ways of recycling / reuse for biopolymers are also being considered alongside the recycling of conventional plastics.

[0007] While non-biodegradable bio-based polymers can be recycled in the recycling plants already used for their fossil-based counterparts, biodegradable polymers require specific alternative solutions depending on the characteristics of the polymers themselves.

[0008] The main technologies for the recycling of biopolymers currently include sorting, mechanical recycling, chemical recycling and depolymerisation by enzymes, which can be applied to postindustrial or post-consumer waste.

[0009] For example, there are known processes for the mechanical recycling of biopolymers, in particular from post-industrial waste, using shredding, grinding and melting operations, through which the materials are reused as such. However, renewable biopolymers such as polyhydroxyalkanoates and natural polymers are particularly sensitive to temperature and the presence of moisture. This can lead to degradation and stickiness problems during processing. Such problems are also encountered in chemical recycling processes, which involve chemical depolymerisation (or chemolysis), for example by hydrolysis or alcoholysis reactions, or thermal depolymerisation to recover the precursors needed for the production of new polymers. Furthermore, biodegradable items such as packaging films, bags and printed or thermoformed items for the food service industry may consist of one or more different biodegradable compositions, arranged for example in single or multiple layers, comprising different categories of biodegradable polymers, such as (aliphatic and / or aliphatic-aromatic) diacid-diol polyesters, polyhydroxy alkanoates, polymers of natural origin, together with fillers and / or other additives; such articles may also contain adhesives and inks. Such heterogeneity makes the recycling of biodegradable compositions even more complex, as processing conditions must be adjusted with regard to the chemical and physical characteristics of the individual components and any resulting degradation phenomena. The application of recovery processes to post-consumer products is further complicated by the presence of contaminants deriving from use and the disposal chain.

[0010] Thus the literature contains hardly any description of the chemical recycling of bioplastic formulations containing starch or fillers, and the chemolysis processes developed hitherto for, for example, PET are not compatible with the presence of starch or contaminants.

[0011] For example, the process described in EP 0 742 251 Bl allows PET to be recovered from polymer blends resulting from the recycling of plastics by first selectively separating the PVC and then the PET. This process, in addition to not allowing for the adequate removal of starch, involves multiple washes with different organic solvents.

[0012] There is therefore a need for processes with a low environmental impact which make it possible to recycle biodegradable products of a heterogeneous composition, even when very thick, avoiding treatment through industrial composting and favouring their recovery through an ad hoc system that directs them to mechanical recycling or re-polymerisation reactions.

[0013] In order to meet this need the Applicant has now developed a process that is able to treat complex matrices and thus implement the chemical recycling process even when biopolymer mixtures and additives that are incompatible with the polymerisation process are present. This process involves the recovery of one or more biodegradable polyesters from waste bioplastics including starch or additives by treatment with a solvent containing at least 50% cyclopentanone, followed by a simple solid / liquid separation.

[0014] It has in fact been found that this solvent selectively solubilises the biodegradable polyesters present (whether diacid-diol or hydroxyacid type), which can be separated from the waste bioplastic and reused in polymerisation reactions or in mechanical recycling, leaving a solid residue comprising starch and any insoluble additives such as fillers and / or other impurities. The solvent can also be easily recovered and recycled in the process through simple evaporation. Polyesters can also be obtained in a further purified form for example by precipitation with environmentally-friendly polar non-solvents such as water or alcohols.

[0015] It is therefore an object of the present invention to provide a process for recycling a polymer composition comprising at least one biodegradable polyester and at least one polymer of natural origin and / or additives, comprising the steps of:

[0016] 1) contacting said polymer composition with a first solvent comprising 50-100% by weight of cyclopentanone, resulting in a liquid fraction comprising at least one biodegradable polyester and a solid fraction comprising said polymer of natural origin and / or additives and any insoluble impurities.

[0017] 2) separating said liquid fraction comprising at least one biodegradable polyester from said solid fraction (resulting in a solid residue);

[0018] 3) at least partly removing said first solvent from said liquid fraction;

[0019] 4) reusing the polyester obtained in step 3) in a polymerisation or thermoplastic conversion process, resulting in a biodegradable polymer composition.

[0020] The process is described in more detail below.

[0021] The polymer composition fed to the process according to the invention contains one or more biodegradable polyesters and one or more further components chosen from a polymer of natural origin (preferably starch) and additives.

[0022] By biodegradable polyesters are meant both polyhydroxy alkanoates and diacid-diol polyesters. The latter are chosen from aliphatic polyesters, aromatic polyesters, aliphatic / aromatic polyesters or mixtures thereof.

[0023] The polyhydroxyalkanoates are preferably selected from the group consisting of the lactic acid polyesters, poly-s-caprolactone, polyhydroxybutyrate (PHB), polyhydroxybutyrate-valerate (PHBV), polyhydroxybutyrate-propanoate polyhydroxybutyrate -hexanoate (PHBH), polyhydroxybutyrate-decanoate, polyhydroxybutyrate-dodecanoate, polyhydroxybutyratehexadecanoate, polyhydro xybutyrate-octadecanoate, poly-3-hydroxybutyrate-4- hydroxybutyrate or mixtures thereof.

[0024] Preferably, the polyhydroxyalkanoate in the starting composition comprises at least 70% by weight of one or more lactic acid polyesters.

[0025] In a preferred embodiment, said lactic acid polyesters are selected from the group consisting of poly L-lactic acid, poly D-lactic acid, poly D-L lactic acid stereo complex, copolymers comprising more than 50% in moles of said lactic acid polyesters or mixtures thereof.

[0026] Particularly preferred are lactic acid polyesters containing at least 95% by weight of repeating units derived from L-lactic or D-lactic acid or combinations thereof. In a particularly preferred embodiment, the lactic acid polyester comprises at least 95% by weight of units derived from L-lactic acid, < 5% by weight of repetitive units derived from D- lactic acid and has a melting temperature in the range 135-175°C.

[0027] Said diacid-diol polyester is chosen from aliphatic polyesters, aromatic polyesters, aliphatic / aromatic polyesters or mixtures thereof; preferably it is an aliphatic / aromatic polyester and / or an aliphatic polyester.

[0028] In the case of an aliphatic / aromatic polyester, this preferably comprises: a) a dicarboxylic component comprising al) units derived from at least one aromatic dicarboxylic acid and a2) units derived from at least one saturated or unsaturated (preferably saturated) aliphatic dicarboxylic acid, b) a diol component comprising units derived from at least one saturated or unsaturated (preferably saturated) aliphatic diol.

[0029] The aromatic dicarboxylic acids of component al) are preferably selected from aromatic dicarboxylic acids of the phthalic acid type, preferably terephthalic acid or isophthalic acid, more preferably terephthalic acid and heterocyclic aromatic dicarboxylic compounds, preferably 2,5-furandicarboxylic acid, 2,4-furandicarboxylic acid, 2,3 -furandicarboxylic acid, 3,4-furandicarboxylic acid, more preferably 2,5-furandicarboxylic acid, their esters, salts and mixtures thereof.

[0030] In a preferred embodiment, the aromatic dicarboxylic acids comprise:

[0031] - 1 to 99%, preferably 5 to 95% and more preferably 10 to 80%, in moles of terephthalic acid, its esters or salts;

[0032] - 99 to 1%, preferably 95 to 5% and more preferably 90 to 20%, in moles of 2,5- furandicarboxylic acid its esters or salts.

[0033] The aliphatic dicarboxylic acids of component a2) are preferably selected from saturated C2- C24, preferably C4-C13, more preferably C4-C11, dicarboxylic acids, their C1-C24, more preferably C1-C4, alkyl esters, their salts and mixtures thereof. Preferably, the saturated aliphatic dicarboxylic acids are selected from: succinic acid, 2-ethylsuccinic acid, glutaric acid, 2-methylglutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecandioic acid, dodecandioic acid, brassylic acid and their Cl-24 alkyl esters. In a preferred embodiment of the present invention the saturated aliphatic dicarboxylic acids comprise succinic acid, adipic acid, azelaic acid, sebacic acid or mixtures thereof.

[0034] Any unsaturated aliphatic dicarboxylic acids in component a2) are preferably selected from itaconic acid, fumaric acid, maleic acid, 4-methylene-pimelic acid, 3,4-bis(methylene) nonandioic acid, 5-methylene-nonandioic acid, their C1-C24, preferably C1-C4, alkyl esters, their salts and mixtures thereof. In a preferred embodiment of the present invention, the unsaturated aliphatic dicarboxylic acids consist of itaconic acid or comprise mixtures comprising at least 50% in moles, preferably more than 60% in moles, more preferably more than 65% in moles of itaconic acid its C1-C24, preferably C1-C4, esters.

[0035] With regard to the saturated aliphatic diols in component b), these are preferably selected from 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6- hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11- undecanediol, 1,12-dodecanediol 1,13-tridecanediol, 1,4-cyclohexanedimethanol, neopentylglycol, 2-methyl- 1,3-propanediol, dianhydrosorbitol, dianhydromannitol, dianhydroiditol, cyclohexanediol, cyclohexanmethanediol, dialkylene glycols and polyalkylene glycols such as polyethylene glycol, polypropylene glycol and mixtures thereof. Preferably, the diol component comprises at least 50% in moles of one or more diols chosen from 1,2- ethanediol, 1,3-propanediol, 1,4-butanediol. More preferably, the diol component comprises, or consists of, 1,4-butanediol.

[0036] As regards any unsaturated aliphatic diols of component b, these are preferably selected from cis 2-buten-l,4-diol, trans 2-buten-l,4-diol, 2-butyn-l,4-diol, cis 2-penten-l,5-diol, trans 2- penten-l,5-diol, 2-pentyn-l,5-diol, cis 2-hexen-l,6-diol, trans 2-hexen-l,6-diol, 2-hexyn-l,6- diol, cis 3-hexen-l,6-diol, trans 3-hexen-l,6-diol, 3-hexyn-l,6-diol.

[0037] In the case of an aliphatic polyester, this preferably comprises: c) a dicarboxylic component comprising units derived from at least one saturated or unsaturated aliphatic dicarboxylic acid, d) a diol component comprising units derived from at least one saturated or unsaturated aliphatic diol.

[0038] The saturated aliphatic dicarboxylic acids in component c) are preferably present in amounts of 95 to 100% in moles with respect to the total dicarboxylic component; they are preferably chosen from saturated C2-C24, preferably C4-C13, more preferably C4-C11, dicarboxylic acids, their C1-C24, preferably C1-C4, alkyl esters, their salts and mixtures thereof. Preferably the saturated aliphatic dicarboxylic acids are chosen from succinic acid, 2-ethylsuccinic acid, glutaric acid, 2-methylglutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid, hexadecanedioic acid, octadecanedioic acid and Cl -24 alkyl esters thereof. Preferably the dicarboxylic component comprises, or consists of, units derived from succinic acid. Any unsaturated aliphatic dicarboxylic acids in component c) are present in an amount preferably from 0 to 5% in moles relative to the total dicarboxylic component; they are preferably chosen from itaconic acid, fumaric acid, maleic acid, 4-methyl-pimelic acid, 3,4-bis (methylene) nonandioic acid, 5-methylene-nonandioic acid, their C1-C24, preferably C1-C4, alkyl esters, their salts and mixtures thereof. In a preferred embodiment of the present invention the unsaturated aliphatic dicarboxylic acids comprise itaconic acid or comprise mixtures comprising at least 50% in moles, preferably more than 60% in moles, more preferably more than 65% in moles, of itaconic acid and its C1-C24, preferably C1-C4, esters.

[0039] As far as the saturated aliphatic diols in component d) are concerned, these are preferably present in quantities of 95 to 100% in moles with respect to the total diol component; they are preferably chosen from 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5- pentanediol, 1,6-hexanediol, 1,7 -heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11 -undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,4-cyclohexanediol neopentylglycol, 2-methyl- 1,3-propanediol, dianhydrosorbitol, dianhydromannitol, dianhydroiditol, cyclohexanediol, cyclohexanmethanediol, dialkylene glycols and polyalkylene glycols having a molecular weight of 100-4000, such as for example polyethylene glycol, polypropylene glycol and mixtures thereof. Preferably the diol component comprises at least 50% in moles of one or more diols chosen from 1,2-ethanediol, 1,3-propanediol, 1,4-butanediol.

[0040] More preferably the diol component comprises or consists of 1,4-butanediol.

[0041] As far as the unsaturated aliphatic diols in component d) are concerned, these are preferably present in quantities of 0 to 5% in moles with respect to the total diol component; they are preferably selected from cis 2-buten-l,4-diol, trans 2-buten-l,4-diol, 2-butyn-l,4-diol, cis 2- penten-l,5-diol, trans 2-penten-l,5-diol, 2-pentyn-l,5-diol, cis 2-hexen-l,6-diol, trans 2-hexen- 1,6-diol, 2-hexyn-l,6-diol, cis 3-hexen-l,6-diol, trans 3-hexen-l,6-diol, 3-hexyn-l,6-diol.

[0042] In a particularly preferred embodiment, the biodegradable composition fed to the process according to the present invention comprises one or more diacid-diol polyesters selected from the group consisting of: poly( 1,4-butylene succinate), poly( 1,4-butylene succinate-co-1,4- butylene adipate), poly(l,4-butylene succinate-co-l,4-butylene azelate), poly(l,4-butylene adipate-co- 1,4-butylene terephthalate), poly(l,4-butylene succinate-co-l,4-butylene terephthalate), poly( 1,4-butylene azelate-co- 1,4-butylene terephthalate), poly( 1,4-butylene brassylate-co- 1 ,4-butylene terephthalate), poly( 1 ,4-butylene sebacate-co- 1 ,4-butylene terephthalate), poly( 1 ,4-butylene adipate-co- 1 ,4-butylene sebacate-co- 1 ,4-butylene terephthalate), poly(l,4-butylene azelate-co- 1 ,4-butylene sebacate-co- 1 ,4-butylene terephthalate), poly(l,4-butylene adipate-co- 1 ,4-butylene azelate-co- 1 ,4-butylene terephthalate), poly(l,4-butylene succinate-co- 1 ,4-butylene sebacate-co- 1 ,4-butylene terephthalate), poly(l,4-butylene adipate-co- 1 ,4-butylene succinate-co- 1 ,4-butylene terephthalate), poly(l,4-butylene azelate-co- 1 ,4-butylene succinate-co- 1 ,4-butylene terephthalate), poly(l,4-butylene adipate-l,4-butylene azelate-co- 1,4-butylene succinate-co- 1,4- butylene terephthalate), poly( 1,4-butylene adipate-l,4-butylene sebacate-co- 1,4-butylene succinate-co- 1,4-butylene terephthalate), poly( 1,4-butylene adipate-l,4-butylene azelate-co-

[0043] 1,4-butylene sebacate-co- 1,4-butylene succinate-co- 1,4-butylene terephthalate) and mixtures thereof.

[0044] The aliphatic and / or aliphatic / aromatic polyesters (known as diacid-diol polyesters) of the biodegradable composition undergoing the process according to the present invention may further comprise repetitive units derived from at least one hydroxy acid in an amount of, for example, between 0 and 49%, preferably between 0 and 30% in moles, relative to the total moles of the dicarboxylic component. Examples of convenient hydroxy acids are glycolic acid, hydroxybutyric acid, hydroxycaproic acid, hydroxy valeric acid, 7-hydroxyheptanoic acid, 8- hydroxycaproic acid, 9-hydroxynonanoic acid, lactic acid or lactide.

[0045] Long molecules with two non-terminal functional groups may also be present, typically in quantities of no more than 10% in moles to the total moles of the dicarboxylic component. Examples are dimer acids, ricinoleic acid and acids with epoxy functional groups, and also polyoxyethylenes with molecular weights between 200 and 10000.

[0046] Diamines, amino acids, and amino-alcohols may also be present in percentages of up to 30% in moles with respect to the total moles of the dicarboxylic component.

[0047] One or more polyfunctional molecules may also be present, typically in quantities of between 0.01 and 3% in moles to the total moles of the dicarboxylic component. Examples of these molecules are glycerol, pentaerythritol, trimethylolpropane, citric acid, dipentaerythritol, monoanhydrosorbitol, monohydromannitol, acid triglycerides, polyglycerols, etc.

[0048] According to one aspect of the invention, the biodegradable composition subjected to the process comprises at least one polyhydroxy alkanoate and at least one polyester from diacid- diol, in any proportion; for example, it comprises mixtures comprising from 1 to 99% by weight, preferably from 10% to 70% by weight, of polyhydroxyalkanoate, and from 99 to 1%, preferably from 30% to 60% by weight, of polyester from diacid-diol relative to the total weight of the mixture.

[0049] According to one aspect, the biodegradable composition subjected to the process further comprises from 0 to 5% by weight, preferably from 0.01 to 0.45% by weight, relative to the total composition, of a cross-linking agent and / or chain extender having two or more functional groups, preferably chosen from peroxide groups, epoxy groups and isocyanate groups.

[0050] Examples of compounds having two or more functional groups containing isocyanate groups are p-phenylene diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4- diphenylmethane diisocyanate, l,3-phenylene-4-chloro diisocyanate, 1,5 -naphthalene diisocyanate, 4,4-diphenylene diisocyanate, 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate, 3-methyl-4,4'-diphenylmethane diisocyanate, diphenyl ester diisocyanate, 2,4-cyclohexane diisocyanate, 2,3 -cyclohexane diisocyanate l-methyl-2,4-cyclohexyl diisocyanate, 1-methyl- 2,6-cyclohexyl diisocyanate, bis-(cyclohexyl isocyanate) methane, 2,4,6-toluene triisocyanate, 2,4,4-diphenylether triisocyanate, polymethylene-polyphenyl-polyisocyanates, methylene diphenyl diisocyanate triphenylmethane triisocyanate, 3,3'-ditolylen-4,4-diisocyanate, 4,4'- methylene-bis-(2-methylphenyl isocyanate), hexamethylene diisocyanate, 1,3-cyclohexylene diisocyanate, 1,2-cyclohexylene diisocyanate and mixtures thereof.

[0051] Examples of compounds having two or more functional groups carrying peroxide groups are benzoyl peroxide, lauroyl peroxide, isononanoyl peroxide, di-(t-butylperoxyisopropyl)benzene, t-butyl peroxide, dicumyl peroxide, alpha, alpha-di(t-butylperoxy)diisopropylbenzene, 2,5- dimethyl-2,5-di(t-butylperoxy)hexane, t-butyl cumyl peroxide, di-t-butyl peroxide, 2,5- dimethyl-2,5-di(t-butylperoxy)hex-3-yne, di(4-t-butylcyclohexyl)peroxydicarbonate, dicetyl peroxydicarbonate, dimiristyl peroxydicarbonate, 3,6,9-trimethyl-3,6,9-trimethyl-l,4,7- triperoxonane, di(2-ethylhexyl)peroxydicarbonate and mixtures thereof.

[0052] Examples of compounds with two or more functional groups carrying epoxy groups are polyepoxides from epoxidised oils and / or styrene-glycidyl ether-methyl methacrylate and / or glycidyl ether-methyl methacrylate.

[0053] The polymer composition subjected to the process according to the present invention also optionally includes one or more polymers of natural origin.

[0054] Said polymer of natural origin is advantageously selected from starch, chitin, chitosan, alginates, proteins such as gluten, zein, casein, collagen, gelatin, natural gums, cellulose (also in nanofibrils) and pectin. Starch is preferred.

[0055] The term starch is used here to refer to all types of starch, that is: flour, native starch, hydrolysed starch, destructured starch, gelatinised starch, plasticised starch, thermoplastic starch, biofillers comprising complexed starch or mixtures of these. Typically present in biodegradable compositions are starches such as potato, maize, tapioca and pea starch. Included in the definition are starches that can be easily deconstructed and have high initial molecular weights, such as potato or maize starch. The starch may be present both as such and in a chemically modified form, such as in the form of starch esters with a degree of substitution between 0.2 and 2.5, hydroxypropyl starch, and starch modified with fatty chains.

[0056] By unstructured starch, reference is made here to the teachings contained in Patents EP-0 118240 and EP-0327505, meaning starch processed in such a way that it does not substantially show the so-called “maltese crosses” under the optical microscope in polarised light and the so-called “ghosts” under the optical microscope in phase contrast.

[0057] Where the biodegradable composition includes unstructured starch, it typically also includes 1-40% by weight, relative to the weight of the starch, of one or more plasticisers chosen from water and polyols having 2 to 22 carbon atoms. As far as water is concerned, this may also be the water naturally present in starch. Among the polyols, polyols having 1 to 20 hydroxyl groups and / or containing 2 to 6 carbon atoms, their ethers, thioethers and organic and inorganic esters are preferred. Examples of polyols are glycerol, diglycerol, poly glycerol, pentaerythritol, ethoxylated poly glycerol, ethylene glycol, polyethylene glycol, 1,2-propanediol, 1,3- propanediol, 1,4-butanediol, neopentylglycol, sorbitol, sorbitol monoacetate, sorbitol diacetate, sorbitol monoethoxylate, sorbitol diethoxylate, and mixtures thereof. Examples of mixtures include between 2 and 90% by weight glycerol.

[0058] The polymer composition processed according to the present invention also optionally comprises one or more additional polymers other than the polyhydroxyalkanoates, diacid-diol polyesters and polymers of natural origin listed above.

[0059] These additional polymers are, for example, selected from the group consisting of vinyl polymers, aromatic diacid diol polyesters, polyamides, polyurethanes, polyureas, polycarbonates and mixtures thereof.

[0060] Examples of vinyl polymers include: polyethylene, polypropylene and their copolymers, polyvinyl alcohol and its copolymers such as butenediol / vinyl alcohol copolymer, polyvinyl acetate, polyethylene vinyl acetate and polyethylene vinyl alcohol, polystyrene, chlorinated vinyl polymers, poly acrylates.

[0061] Chlorinated vinyl polymers include polyvinyl chloride, polyvinylidene chloride, polyethylene chloride, poly(vinyl chloride - vinyl acetate), poly(vinyl chloride - ethylene), poly(vinyl chloride - propylene), poly(vinyl chloride - styrene), poly(vinyl chloride - isobutylene) as well as copolymers in which polyvinyl chloride accounts for more than 50% in moles. Such copolymers may be random, block or alternating.

[0062] With regard to the polyamides that may be present in the biodegradable composition undergoing the process according to the present invention, these are selected, for example, from the group consisting of polyamide 6 and 6,6, polyamide 9 and 9,9, polyamide 10 and 10,10, polyamide 11 and 11,11, polyamide 12 and 12,12 and their combinations of the 6 / 9, 6 / 10, 6 / 11, 6 / 12 type, mixtures thereof and copolymers both random and block.

[0063] The polycarbonates that may be present are, for example, selected from the group consisting of polyalkylene carbonates, preferably polyethylene carbonates, polypropylene carbonates, polybutylene carbonates, mixtures thereof and both random and block copolymers.

[0064] Among the polyethers, examples are those selected from the group consisting of polyethylene glycols, polypropylene glycols, polybutylene glycols, their copolymers and mixtures thereof. As far as diacid diol polyesters other than those described above are concerned, these for example comprise a dicarboxylic component comprising, with respect to the total dicarboxylic component, 100% in moles of units derived from at least one aromatic dicarboxylic acid and a diol component comprising units derived from at least one saturated or unsaturated aliphatic diol.

[0065] Preferably, said aromatic dicarboxylic acids and aliphatic diols are selected from those described above for the aliphatic-aromatic polyester of the composition according to the present invention.

[0066] In addition to the aforementioned components, the biodegradable composition according to the present invention optionally also contains one or more additives selected from the group consisting of fillers, plasticisers, UV stabilisers, lubricants, nucleating agents, surfactants, antistatic agents, pigments, flame retardant agents, compatibilising agents, lignin, organic acids, antioxidants, anti-mould agents, waxes, process aids. Inks and adhesives may also be present. Said fillers are preferably selected from kaolin, wollastonite, barytes, clay, talc, calcium and magnesium carbonates, iron and lead carbonates, aluminium hydroxide, diatomaceous earth, aluminium sulfate, barium sulfate, silica, mica, titanium dioxide and mixtures thereof.

[0067] Such fillers, such as talc, calcium carbonate or mixtures thereof, are typically present in the form of particles with an arithmetic mean diameter greater than 1 micron, measured along the major axis of the particle.

[0068] With regard to the plasticisers, in addition to the plasticisers preferably used for the preparation of de- structured starch described above, there may be one or more plasticisers selected from the group consisting of phthalates, such as, for example, diisononyl phthalate, trimellitates, such as, for example, trimellitic acid esters with C4-C20 mono-alcohols preferably selected from the group consisting of n-octanol and n-decanol, and aliphatic esters of mono- and dicarboxylic acids with linear or branched C2-C8 alkenes, for example neopentylglycol. When present, the selected plasticisers are preferably present up to 10% by weight, relative to the total weight of the composition.

[0069] The lubricants are for example zinc stearate, calcium stearate, aluminium stearate and acetyl stearate. Preferably, the composition according to the present invention comprises up to 1% by weight of lubricants, more preferably up to 0.5% by weight, relative to the total weight of the composition.

[0070] Examples of nucleating agents include saccharin sodium salt, calcium silicate, sodium benzoate, calcium titanate, boron nitride, isotactic polypropylene, low molecular weight PLA. Process aids include, for example, slip agents. By slip agents are meant, for example, biodegradable fatty acid amides such as oleamide, erucamide, ethylene-bis-stearylamide, fatty acid esters such as glycerol oleates or glycerol stearates, saponified fatty acids such as stearates. Pigments may also be present, for example titanium dioxide, clays, copper phthalocyanine, titanium dioxide, silicates, iron oxides and hydroxides, carbon black, and magnesium oxide. Examples of compatibilising agents are di- and / or poly-functional compounds bearing isocyanate, peroxide, carbodiimide, isocyanurate, oxazoline, epoxy, anhydride or divinyl ether groups and mixtures thereof.

[0071] These additives are preferably present in quantities of up to 10% by weight and more preferably up to 6% and even more preferably up to 2% by weight, relative to the total weight of the composition.

[0072] For the purposes of the present invention, biodegradable polyester or biodegradable composition means a polyester or polymer composition that is biodegradable according to EN 13432.

[0073] The biodegradable composition subjected to process step 1) according to the present invention preferably originates from post-industrial waste (i.e. waste from industrial production, processing or manufacturing processes) and / or from post-consumer waste, for example from the plastics waste stream after appropriate sorting operations.

[0074] The process therefore enables biodegradable compositions originating from, for example, flexible biodegradable items, such as packaging films, bags, and rigid items, such as moulded or thermoformed foodservice items, either from industrial waste or end-of-life, to be recycled. Generally the flexible biodegradable articles are predominantly made of polymer compositions comprising starch, whereas rigid biodegradable articles are predominantly made of polymer compositions comprising fillers. The recycling process according to the invention is particularly advantageous when applied to waste polymer compositions from closed-loop collection chains (e.g. waste collection at the point of sale or consumption).

[0075] Said wastes are optionally subjected to one or more preliminary operations to remove organic or inorganic debris and residues, to obtain a homogeneous composition and enlarge the surface area to facilitate subsequent process step 1).

[0076] Said preliminary operations are advantageously selected from the group consisting of washing, screening, separation, comminution and conditioning.

[0077] Washing, for example, allows any residual non-plastic materials to be separated out and is carried out in one or more successive operations, for example in a tank or by means of a water jet on a belt. Basic solutions can also be used, for example to remove adhesive labels from the waste.

[0078] Separation or sorting operations may be carried out for example manually, by density, by optical, magnetic or electrostatic systems, by dissolution or flotation.

[0079] Comminution operations include for example shredding or crushing, grinding, pelletising, and are intended to reduce the size of the waste material and bring it to a homogenous size, facilitating subsequent process step 1).

[0080] A size of less than 5 cm, less than 2 cm or less than 1 cm is preferred.

[0081] Conditioning may comprise drying or drying operations, for example in a flow of air.

[0082] The order of these preliminary operations depends on the origin and type of polymer composition fed to the process.

[0083] According to a first embodiment of the present invention, in step 1) of the process there is fed a biodegradable composition, the polymer component of which consists of, or mainly comprises, one or more aliphatic and / or aliphatic / aromatic (preferably aliphatic / aromatic) diacid diol polyesters and starch.

[0084] According to a second embodiment of the present invention, in step 1) of the process there is fed a biodegradable composition consisting of, or mainly comprising, one or more aliphatic and / or aliphatic-aromatic diacid polyesters and one or more fillers.

[0085] According to a third embodiment of the present invention, in step 1) of the process there is fed a biodegradable composition consisting of, or mainly comprising, one or more polyhydroxy alkanoates, one or more aliphatic and / or aliphatic-aromatic (preferably aliphatic / aromatic) diacid diol polyesters and starch.

[0086] According to a fourth embodiment of the present invention, a biodegradable composition comprising, or mainly comprising, one or more polyhydroxyalkanoates, one or more diacid diol polyesters of the aliphatic and / or aliphatic-aromatic and one or more fillers and / or other additives is fed to step 1) of the process.

[0087] In step 1) of the process according to the present invention, the polymer composition described above is brought into contact with a first solvent comprising from 50% to 100% by weight of cyclopentanone, resulting in a liquid fraction comprising at least one polyester and a solid fraction comprising starch and / or additives and any insoluble impurities.

[0088] According to a first aspect, said first solvent essentially comprises cyclopentanone; preferably this comprises at least 60%, at least 70%, at least 80%, at least 90% by weight of cyclopentanone. Since cyclopentanone is a by-product of the polymerisation of adipic acid, the process is particularly advantageous when the polymer composition fed thereto comprises aliphatic or aliphatic-aromatic polyesters whose aliphatic component comprises adipic acid. In such a case, the cyclopentanone can in fact be obtained directly from the waste products of the polymerisation process in step 4), with a net saving in terms of cost and the environmental sustainability of the recycling process.

[0089] This makes it possible not only to avoid the disposal of polymerisation reaction effluents, the components of which are thus fully utilised, but also to reduce and simplify the purification operations that would otherwise be required for recovery of the individual components to be used as solvents.

[0090] According to another aspect, said first solvent comprises at least 50% of cyclopentanone and up to 40% by weight, more preferably 10 to 25% by weight, of linear, cyclic or branched, saturated or unsaturated aliphatic alcohols.

[0091] In other words, the amount by weight of aliphatic alcohols with respect to cyclopentanone is preferably less than 1:1, more preferably less than 1:1.5, more preferably less than 1:2.

[0092] Saturated and unsaturated linear aliphatic alcohols, with preferably a C2-C8, more preferably C2-C4 chain are preferred, C4 chain alcohols being most preferred. In combination, or alternatively, aliphatic C2-C6, more preferably C2-C4, chain diols are preferred, C4 chain diols being most preferred.

[0093] Examples of preferred alcohols and diols are ethanol, propanol, propan-2-ol, 1 -butanol, butan- 2-ol, 3-buten-l-ol, 1 -pentanol, 3-pentanol, hexanol, 1,2-ethanediol, 1,2-propanediol, 1,3- propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, cyclohexanediol, dialkylene glycols, 2-buten-l,4-diol, 2-penten-l,5-diol, 2-hexen-l,6-diol, 3- hexen-l,6-diol and mixtures thereof. Most preferred are 1 -butanol, 3-buten-l-ol, 1,4- butanediol, propanol, propan-2-ol. According to another aspect, said first solvent advantageously comprises up to 15%, preferably up to 10%, more preferably up to 7%, even more preferably up to 5% by weight of water. Advantageously, the said first solvent comprises at least 0.5% by weight of water, more advantageously at least 1 % by weight of water, with respect to the weight of the solvent. According to a preferred embodiment, said first solvent includes i. 50-100% cyclopentanone by weight, ii. 0-40% by weight, preferably 5-30% by weight, even more preferably 10-25% by weight of alcohols, diols or their mixtures, and iii. 0-15% by weight, preferably 0.5%-10% by weight, of water.

[0094] According to another aspect, said first solvent includes other components that are miscible with cyclopentanone. Examples are ketones or cyclic ethers such as tetrahydrofuran (THF).

[0095] According to a particularly preferred aspect, said first solvent is a mixture comprising one or more saturated and / or unsaturated aliphatic C2-C4 alcohols, THF and water, in addition to cyclopentanone. Said mixture has been found to be surprisingly selective in the solubilisation of diacid-diol polyesters, possibly in a mixture with hydroxy-acid polyesters, removing them from the biodegradable compositions comprising them even when non-biodegradable polymers such as polyolefins are present. Said mixture may also advantageously be obtained as a byproduct of the polymerisation of diacid-diol polyesters comprising adipic acid and butanediol. One example of a preferred mixture includes cyclopentanone (50-65% by weight), 3-buten-l- ol (15-25% by weight), 1-butanol (5-10% by weight), isopropanol (3-7% by weight), water (2- 5% by weight) and THF (1-5% by weight).

[0096] In step 1) of the process according to the present invention, said polymer composition is brought into contact with said first solvent in such quantities as to achieve a mass / volume ratio of preferably less than 25%, more preferably 2% to 20%, to facilitate solubilisation of the polyester present in the biodegradable composition.

[0097] Said step 1) is preferably carried out at a temperature between 50°C and the boiling temperature of the solution at the working pressure, which is preferably between atmospheric pressure and 2-3 bar.

[0098] The duration of step 1) will vary mainly according to the temperature and pressure conditions used and the manner of contact between the solvent and the polymer composition, for example from a few minutes under drastic conditions to 3 hours under milder conditions.

[0099] Working at atmospheric pressure, it is preferable to operate at a temperature above 60°C, above 80°C and even more preferably of 100°C or above, for between 30 and 90 minutes Step 1) is therefore preferably performed in equipment suitable for facilitating solubilisation of the polyester from the polymer composition. For example, reactors allowing effective mixing and adequate heat exchange surfaces will preferably be used.

[0100] At the end of step 1) a liquid fraction comprising at least one polyester and a solid fraction comprising starch and / or additives and any insoluble impurities are obtained in the form of a mixture or suspension.

[0101] The product from step 1) that is fed to step 2) is characterised by a viscosity of preferably from 1 to 2000 mPa.s, more preferably from 5 to 1000 mPa.s, even more preferably from 10 to 750 mPa.s, measured at a concentration of 10% by weight / volume and at 50°C, applying a shear rate of 25 s-1 and operating with a rheometer with a flat-plate configuration having a diameter D=50 mm and a gap of 1 mm.

[0102] Said solid fraction is separated from said liquid fraction in step 2) of the process, from which it constitutes a solid residue.

[0103] Said solid residue advantageously undergoes one or more washes with solvent, preferably under the conditions in step 1), which is then repeated one or more times.

[0104] The separation in step 2) is performed by any solid / liquid separation technique known to those skilled in the art, after possible cooling of the mixture according to the technique selected, for example at a temperature below 70°C or 50°C.

[0105] The separation operations in process step 2) are for example chosen from the group consisting of filtering, centrifuging or settling. Filtering comprises for example microfiltering and ultrafiltering; centrifuging is preferred.

[0106] Said separation operations are preferably conducted using continuous or discontinuous vertical or horizontal axis machines (for example centrifuges, settlers).

[0107] Once separated from the waste bioplastics, the polyesters separated into the liquid fraction during step 2) of the process according to the invention are then obtained by simple removal of the solvent during step 3), or undergo optional purification steps.

[0108] They are subsequently reused, either alone or mixed with other monomers, in step 4) for the production of biodegradable plastics.

[0109] They are in fact suitable for use as such in thermoplastic transformation processes to obtain biodegradable articles, or, after undergoing further optional fractioning or depolymerisation processes, in polymerisation processes to produce a biodegradable polyester.

[0110] The operations of removing solvent during step 3) are carried out using techniques known to those skilled in the art. For example, one or more operations chosen from adsorption, reverse osmosis, crystallisation, evaporation, distillation are performed. Multi-effect evaporators, potentially with mechanical or thermal recompression, and low residence time devices such as falling or scraped films, are particularly suitable.

[0111] According to a preferred aspect, before removal of the first solvent during step 3) or preferably after partial removal of said first solvent, the process according to the invention comprises an optional step of adding a second solvent (or non-solvent) in which said polyester is insoluble. By the term “insoluble” is meant a solubility of the polyester of less than 2% by weight / volume in said second solvent, measured by contacting the polyester with the solvent (with a solvent:polyester ratio of 1:10 by weight) at 25 °C for 24 hours in the presence of a soluble fraction having a Number Average Molecular Weight < 10000 g / mol, preferably < 5000 g / mol. Said second solvent (or non-solvent) is preferably chosen from water, preferably C2-C4 saturated or unsaturated aliphatic alcohols, and mixtures thereof. It is advantageously used in a ratio of 1:2 to 10:1 by volume with respect to the first solvent if the second solvent is water or includes water; in a ratio of 1:1 to 10:1 by volume with respect to the first solvent if the second solvent is an aliphatic alcohol.

[0112] Said second solvent causes the polyester to precipitate out, and it is advantageously separated from the solvent mixture during step 3) through at least one solid / liquid separation operation, keeping any additives and / or impurities such as inks and adhesives in solution. The thus purified polyester is more suitable for subsequent use in polymerisation.

[0113] Preferably the polyester is obtained in solid form at the end of step 3) and is dried (i.e. has a residual solvent content advantageously below 1% by weight).

[0114] After removal of the solvent or solvents present, the polyester is fed to step 4) for reuse in a polymerisation or thermoplastic transformation process. The process according to the invention thus allows a biodegradable polyester or biodegradable polymer composition to be obtained again.

[0115] The polyester obtained in step 3) advantageously undergoes an optional depolymerisation step before being sent to step 4).

[0116] Said optional depolymerisation step can be carried out by solvolysis, for example by glycolysis or hydrolysis processes. Advantageously, the reuse in polymerisation in process step 4) takes place by means of the process described in patent application WO 2022 / 013309 Al, in particular by means of hydrolysis, separation and repolymerisation steps.

[0117] The depolymerisation product optionally obtained comprises a mixture of the monomers of the polyesters present in the initial biodegradable composition, for example hydroxy acids, dicarboxylic acids and diols selected from those described above as components of the polyester in the initial biodegradable composition, and / or oligomers thereof. Said monomers are advantageously selected from the group consisting of: adipic acid, azelaic acid, sebacic acid, succinic acid, terephthalic acid, furandicarboxylic acid, lactic acid, 3- hydroxybutyric acid, 3 -hydroxy valeric acid and 3 -hydroxyhexanoic acid, 1,2-ethanediol, 1,3- propanediol, 1,4-butanediol.

[0118] Within the meaning of the present invention the term “oligomer” means each set of repeating units in the polymer chain (i.e. hydroxyacid units and / or diacid-diol units) having a molecular weight of less than 5000, preferably less than 2000.

[0119] According to one aspect of the invention, during step 4) mixtures of monomers and / or oligomers obtained downstream of one of the above-mentioned polyester depolymerisation processes are fed to said polymerisation reactions in an amount from 1% to 100% by weight, preferably from 2% to 50% by weight and more preferably from 5% to 30% by weight, relative to the weight of the mixture subjected to polymerisation, resulting in a biodegradable polyester. A further object of the present invention is therefore a process for preparing a biodegradable polyester comprising feeding at least one biodegradable polyester selectively recovered from a polymer composition, and / or oligomers and / or monomers thereof, in particular a mixture of oligomers and / or monomers of the polyester obtained according to steps 1 to 3 of the process in claim 1 to a polymerisation reaction (esterification and / or polycondensation) in an amount 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 weight of the mixture undergoing polymerisation.

[0120] Within the meaning of the present invention the weight of the polymerised mixture is calculated without taking into account any solvent (for example water) present.

[0121] The amount of hydroxy acids or their oligomers in the polymerisation mixture is advantageously between 0% and 25% by weight, preferably between 2 and 15% by weight, relative to the total weight of the polymerisation mixture.

[0122] According to one aspect, the amount of hydroxyacid or its oligomers that may be present in the polymerisation mixture is kept within the range indicated by one of the removal operations described for step 3), or by fractional extraction or precipitation.

[0123] According to another aspect, the amount of monomers and / or oligomers is kept within the range indicated by adding further virgin or recycled monomers to the polymerisation mixture.

[0124] The polymerisation according to the invention is carried out according to any of the processes known in the state of the art. In particular, it may advantageously be carried out by polycondensation. Examples of synthesis processes that may advantageously be used for the preparation of polyesters are described in international patent application WO 2016 / 050963. The polymerisation reaction according to the invention preferably comprises: (i) Preparation of an oligomer product through an esterification and / or transesterification reaction of a mixture comprising: a) a dicarboxylic component comprising: al) 0-80% in moles, relative to the total dicarboxylic component, of units derived from at least one aromatic dicarboxylic acid and / or its ester, salt or derivative, and a2) 20-100% in moles, with respect to the total dicarboxylic component, of units derived from at least one aliphatic dicarboxylic acid and / or its ester, salt or derivative, and b) a diol component, c) a hydroxy acid component in an amount of 0% to 25% by weight, preferably 2% to 15% by weight, of the total weight of said mixture,

[0125] (ii) polycondensation of the oligomer product obtained from step (i), and

[0126] (iii) granulation of the polyester obtained from step (ii).

[0127] The aromatic dicarboxylic acids, aliphatic dicarboxylic acids and diols are preferably selected from those described above as being components of the polyesters in the biodegradable starting composition.

[0128] Advantageously, the polymerisation reaction may be performed in the presence of a suitable catalyst. Examples of suitable catalysts are organometallic tin compounds, for example stannoic acid derivatives, titanium compounds, for example ortho-butyl titanate, aluminium compounds, for example Al-triisopropyl, Antimony and Zinc and Zirconium compounds and mixtures thereof.

[0129] Said polymerisation is advantageously preceded by complete removal of water from the polymerisation mixture to avoid interference in the esterification step.

[0130] During polymerisation, branching agents, compatibilising or stabilising agents such as those described above are advantageously added as components of the biodegradable starting composition.

[0131] The polymerisation product obtained is a biodegradable polyester and can in turn be subjected to reactive extrusion for the preparation of biodegradable polymer compositions.

[0132] The invention therefore also relates to the polymers obtained by the process described above. According to a different aspect, the invention relates to a biodegradable polymer composition comprising said polymers and optionally further biodegradable polymers and additives known in the art, for example chosen from those described above for the biodegradable composition subjected to the depolymerisation process

[0133] Said biodegradable polymer composition obtained according to the invention can advantageously be used in, for example, blown film, cast extrusion, thermoforming and injection moulding processes, resulting in biodegradable articles with application in, for example, the packaging, foodservice or agro-textile sectors.

[0134] According to another aspect, the invention thus relates to biodegradable articles comprising said biodegradable polymer composition.

[0135] Examples of articles comprising the composition according to the present invention are:

[0136] - films, both mono and bi-oriented, and multi-layer films with other polymer materials;

[0137] - films for use in the agricultural sector as mulching sheets;

[0138] - fabric for use in the agricultural sector as agro-textile cloth;

[0139] - films for use in the hygiene sector such as for nappies, liners for sanitary towels, etc.

[0140] - stretch film also cling film for food, for baling in agriculture and for wrapping waste;

[0141] - bags and liners for organic collection such as food waste and grass cuttings;

[0142] - fruit and vegetable bags and shopping bags;

[0143] - coatings obtained using the extrusion coating technique;

[0144] - multilayer laminates with layers of paper, plastics, aluminium, metallised films;

[0145] - expanded or expandable granules for the production of formed parts by sintering;

[0146] - expanded and semi-expanded products including expanded blocks formed from pre-expanded particles;

[0147] - expanded sheets, thermoformed expanded sheets, containers made from them for food packaging;

[0148] - composites with gelatinised, de-structured and / or complexed starch, natural starch, flours, other fillers of natural, vegetable or inorganic origin as fillers;

[0149] - articles produced by thermoforming such as containers, trays, plates, beverage dispensing capsules and printed circuit boards for electronics.

[0150] - fibres, microfibres, composite fibres, textiles and non-wovens for health, hygiene, agriculture and clothing.

[0151] EXAMPLES

[0152] Example 1

[0153] 15.06 g of material for recycling consisting of a biodegradable waste composition comprising 57% by weight of PBAT (i.e. poly(l,4-butylene adipate-co-l,4-butylene terephthalate)), 9% by weight of PLA, 2% by weight of soluble additives and 32% by weight of starch was placed in a 500 ml flask at atmospheric pressure in contact with a solvent (achieving a 10% m / v recycling material / solvent ratio) and heated to 110°C. This temperature was maintained for 1 hour (step 1). The solvent was a mixture comprising cyclopentanone (59% by weight), 3-buten-l-ol (20% by weight), 1-butanol (7% by weight), isopropanol (5% by weight), water (4% by weight) and THF (2% by weight).

[0154] At the end of step 1, the reactor was allowed to cool to 30°C and the resulting mixture was centrifuged at 1800 RCF until complete separation (approx. 30 seconds; step 2). The supernatant liquid fraction was removed and 150 g of a second solvent (or non-solvent) consisting of water was added, resulting in quantitative precipitation of the polyester.

[0155] The separated polyester then underwent a second solid / liquid separation operation by centrifuging at 1800 RCF for 30 minutes.

[0156] The residual solvent was removed by drying at 90°C for 24 hours (step 3).

[0157] The polyester thus obtained was then reused in polymerisation as a partial replacement for the virgin raw materials according to the procedure described below (step 4).

[0158] 26.8g of terephthalic acid, 26.6g of adipic acid, 46.4g of 1,4-butanediol and 0.018g of an 80% solution of diisopropyl triethanolamine titanate in 2-propanol (Tyzor TE, corresponding to 21ppm by weight of Ti with respect to the amount of PBAT theoretically obtainable by converting the feedstocks loaded) were loaded into a 1 -litre glass conical reactor equipped with mechanical stirring, a nitrogen inlet and a distillation column (equipped with a condenser and condensate collection flask).

[0159] The reactor temperature was gradually raised to 230°C over a period of 120 minutes and then kept constant until at least 95% of theoretical conversion had been achieved.

[0160] The distillation column and water condenser were replaced with an air condenser connected to a mechanical pump, and 8g of polyester recovered from step 3 and 0.075g of tetra n-butyl titanate (corresponding to 120ppm by weight of Ti with respect to the theoretical amount of polyester obtainable) were added to the reactor, the temperature was raised to 240°C over the course of 30 minutes and at the same time the pressure was reduced to below 2 mbar.

[0161] The polymerisation reaction was continued for 3 hours and 30 minutes, finally obtaining a product with an MFR = 10.3 g / lOmin (190°C / 2.16kg on product dried at 90°C for 1 hour), terminal acidity 25 meq / Kg (potentiometric titration).

[0162] Example 2

[0163] 15.03 g of material for recycling consisting of a biodegradable composition derived from industrial waste comprising 57% by weight of PBAT (i.e. poly(l,4-butylene adipate-co-1,4- butylene terephthalate)), 9% by weight of PLA, 2% by weight of soluble additives and 32% by weight of starch was placed in a 500ml flask at atmospheric pressure, in contact with a solvent in a 10% m / v recycling material / solvent ratio and heated to 110°C. This temperature was maintained for 1 hour (step 1).

[0164] The solvent was a mixture of cyclopentanone (91% by weight) and water (9% by weight).

[0165] At the end of step 1 the reactor was allowed to cool to 30°C and the resulting mixture was centrifuged at 1800 RCF until complete separation (approx. 30 minutes; step 2). The supernatant liquid fraction was removed and 150 g water was added, resulting in quantitative precipitation of the polyester.

[0166] The separated polyester then underwent a second solid / liquid separation operation by centrifuging at 1800 RCF for 30 minutes.

[0167] The residual solvent was removed by drying at 90°C for 24 hours (step 3).

[0168] The polyester thus obtained was suitable for direct reuse in polymerisation as a partial replacement for virgin raw materials.

Claims

CLAIMS1. Process for recycling a polymer composition comprising at least one biodegradable polyester and at least one natural polymer and / or additives, comprising the steps of:1) contacting said polymer composition with a first solvent comprising 50-100% by weight of cyclopentanone, resulting in a liquid fraction comprising at least one biodegradable polyester and a solid fraction comprising at least one natural polymer and / or insoluble additives;2) separating said liquid fraction comprising at least one biodegradable polyester from said solid fraction;3) at least partly removing said first solvent from said liquid fraction;4) reusing the polyester obtained from said liquid fraction in a polymerisation or thermoplastic transformation process, resulting in a biodegradable polymer composition.

2. Process according to claim 1 in which said polymer composition comprises at least one polyhydroxyalkanoate and at least one aliphatic or aliphatic-aromatic diacid-diol polyester.

3. Process according to either of claims 1-2 in which said first solvent further comprises 0- 40% by weight, preferably 0-30% by weight, even more preferably 10-25% by weight, of alcohols, diols or mixtures thereof.

4. Process according to any one of claims 1 to 3 in which said first solvent comprises a quantity of water less than or equal to 10% by weight.

5. Process according to any one of claims 1 to 4 comprising, before step 3) of removing the first solvent, or preferably between step 3) and step 4) of reusing the polyester, a further step of adding a second solvent in which said polyester is insoluble, the polyester being obtained in solid form at the end of step 3).

6. Process according to claim 5 in which said second solvent is chosen from water and C2- C4 aliphatic alcohols.

7. Process according to any one of claims 1-6 in which said first solvent is a mixture comprising cyclopentanone, one or more saturated and / or unsaturated aliphatic alcohols, tetrahydrofuran and water.

8. Process according to claim 7 in which said mixture is a by-product of the polymerisation of diacid-diol polyesters comprising adipic acid and aliphatic diols.

9. Process according to any one of claims 1-8 in which the polyester fed to step 4) is dried.

10. Process according to any one of claims 1 -9 in which the polyester obtained from the liquid fraction is reused in step 4) in a polymerisation process, said process comprising, before step 4), an optional depolymerisation step, preferably by solvolysis.

11. Process according to any one of claims 1-10 in which a mixture comprising monomers and / or oligomers of the polyester obtained according to steps 1-3) of the process in claim 1 is fed to said polymerisation process in step 4) in an amount of from 1% to 100% by weight, preferably from 2% to 50% by weight and more preferably from 5% to 30% by weight, relative to the weight of the mixture subjected to polymerisation.

12. Polymer obtained by the recycling process according to claim 1.

13. Biodegradable polymer composition comprising the polymer according to claim 12.

14. Biodegradable articles comprising said polymer according to claim 12 or said biodegradable polymer composition according to claim 13.