Search

CN-115968385-B - Reuse of bioplastic in polymerization

CN115968385BCN 115968385 BCN115968385 BCN 115968385BCN-115968385-B

Abstract

The present invention relates to a method for recycling biodegradable polymer compositions comprising a polyester mixture in a polymerization. The method comprises the steps of 1) reacting the polymer composition with water at a temperature above the melting temperature of at least one of the polyesters, obtaining a depolymerized product of monomers and/or oligomers thereof comprising the polyesters in a mixture, 2) separating a fraction comprising impurities and/or fillers from the depolymerized product, 3) subjecting the monomers and/or oligomers to polymerization in an amount of 1 to 100% by weight relative to the mixture subjected to polymerization, thereby obtaining a biodegradable polymer composition. Further objects of the invention are the polymers obtained by said recycling process, the biodegradable polymer compositions comprising said polymers, and the biodegradable articles obtained from said compositions.

Inventors

  • KATIA BASTIOLI
  • Luo Botuo.walailuo

Assignees

  • 诺瓦蒙特股份公司

Dates

Publication Date
20260505
Application Date
20210714
Priority Date
20200715

Claims (14)

  1. 1. A method of recycling a biodegradable polymer composition comprising a polyester mixture in a polymerization, the method comprising the steps of: 1) Reacting the polymer composition with water at a temperature above the melting point of at least one of the polyesters to produce a depolymerization product of monomers and/or oligomers thereof comprising the polyester in a mixture, 2) Separating a fraction comprising impurities and/or fillers from the depolymerized product, 3) Subjecting the monomer and/or the oligomer to polymerization in an amount of 1 to 100 wt% relative to the mixture subjected to polymerization, thereby producing a biodegradable polymer composition, Wherein in step 1) the polymer composition comprises at least one polyhydroxyalkanoate and at least one polyester from a diacid-diol, and the reaction is performed at a temperature above the melting temperature of the polyhydroxyalkanoate, and wherein additives from the starting polyester mixture are fed to polymerization step 3) together with monomers and/or oligomers in an amount of up to 5wt% relative to the mixture subjected to polymerization.
  2. 2. The process of claim 1, wherein step 1) is performed at a pressure above atmospheric pressure.
  3. 3. The method according to claim 1, wherein in step 3) the monomer and/or oligomer is subjected to polymerization in an amount of 2 to 50% by weight relative to the mixture subjected to polymerization.
  4. 4. The method according to claim 1, wherein in step 3) the monomer and/or oligomer is subjected to polymerization in an amount of 5 to 30% by weight relative to the mixture subjected to polymerization.
  5. 5. The process of claim 1, wherein the polymerization of step 3) is conducted to maintain the amount of hydroxy acid or oligomer thereof from 0 wt% to 25 wt% of the total weight of the polymerization mixture.
  6. 6. The process of any one of claims 1 to 5, wherein the polyester mixture comprises at least one aliphatic-aromatic diacid glycol polyester.
  7. 7. The process of any one of claims 1 to 5, wherein the polyester mixture comprises at least one aliphatic diacid diol polyester.
  8. 8. The method of any one of claims 1 to 5, wherein the biodegradable composition comprises one or more polyhydroxyalkanoates, one or more aliphatic diacid diol polyesters, one or more aliphatic-aromatic diacid diol polyesters, and one or more additional polymers comprising one or more vinyl polymers.
  9. 9. The method of any one of claims 1 to 5, wherein the biodegradable composition comprises one or more fillers.
  10. 10. The method of any one of claims 1 to 5, wherein the biodegradable polymer composition further comprises a polymer of natural origin.
  11. 11. The method of claim 10, comprising a pretreatment step of removing the naturally derived polymer from the biodegradable polymer composition comprising polyester mixture prior to step 1.
  12. 12. A polymer obtained by the recycling process according to claim 1.
  13. 13. A biodegradable polymer composition comprising the polymer of claim 12.
  14. 14. A biodegradable article comprising the polymer of claim 12 or the biodegradable polymer composition of claim 13.

Description

Reuse of bioplastic in polymerization The present invention relates to a process for polymerizing monomers and/or oligomers resulting from the depolymerization of bioplastic, in particular biodegradable compositions comprising biopolymers such as polyhydroxyalkanoates and diacid-diol polyesters. The term biopolymer generally refers to a polymer that is biodegradable and/or biobased. Biodegradable polymers are polymers that can be organically degraded and recovered by feeding microorganisms after they reach the end of their initial use without creating a waste accumulation in the environment. Bio-based polymers are defined as polymers obtained from natural or renewable sources, i.e. from sources which are renewable in their nature within the time scale of human life. In view of the widespread use of bioplastic as a substitute for conventional plastics, a further increase in sustainability can be achieved by increasing the possibility of reusing its monomers. This minimizes land use and renewable CO 2 production by converting waste into fertile humus with net carbon sink effect without risk of any persistent matter accumulating in the environment, thus creating a true recycling economy. In addition, some of the most commonly used bio-based polymers such as polylactic acid (PLA), while biodegradable under industrial or household composting conditions, may slowly degrade under normal conditions if handled in the form of thick articles. Thus, the massive processing and wasting of valuable raw materials may also have an environmental impact. For this reason, in addition to the recycling of conventional plastics, new methods of recycling/reusing biopolymers are also contemplated. While non-biodegradable bio-based polymers can be recovered in recovery plants already in use for their fossil-based counterparts, biodegradable polymers require alternatives and specific solutions depending on the nature of the polymer itself. The main recycling technologies currently used for biopolymers include sorting, mechanical recycling, chemical recycling and enzymatic depolymerization, which can be applied to post-industrial or post-consumer waste. For example, a method of mechanically recovering biopolymers, particularly biopolymers from industrial waste, by shredding, grinding and melting operations is known, in which the material is reused as such. However, biopolymers such as PLA and polyhydroxyalkanoates are generally particularly sensitive to the presence of temperature and moisture, which may be caused by the presence of other components. This can lead to degradation and problems with tackiness during processing. Such problems are also encountered in chemical recovery processes (e.g., by hydrolysis, alcoholysis, or thermal depolymerization reactions). For example, the process described in EP 2022 818 B1 involves hydrolyzing PLA articles in the solid state by exposure to water saturated steam at a temperature below the melting point of PLA, under the corresponding saturated steam pressure. This method requires careful control of temperature and pressure to avoid bringing the material into a molten state. Furthermore, biodegradable articles such as packaging films, bags and printed or thermoformed articles for the food service industry may be composed of one or more different biodegradable compositions, for example arranged in a single layer or in multiple layers, comprising other classes of biodegradable polymers such as diacid-diol polyesters (aliphatic and/or aliphatic-aromatic) and polymers of natural origin, together with fillers and/or other additives, in addition to polyhydroxyalkanoates such as PLA. Such heterogeneity makes recovery of the biodegradable composition even more complex, since the processing conditions must be adjusted taking into account the chemical and physical properties of the individual components and any degradation phenomena that occur. For these reasons, methods have been developed, for example, for recovering PLA from waste mixtures, wherein PLA is dissolved in a suitable solvent and separated from other solid polymers and undissolved components (e.g., by filtration or precipitation). This separation allows for subsequent chemical recovery of PLA (typically by hydrolysis, alcoholysis or thermal depolymerization) with or without the presence of a catalyst. For example, patent EP2 419 396 B1 and US 8,431,686 relate to a process in which PLA is extracted in a solvent and subsequently subjected to hydrolysis or alcoholysis, respectively, to produce lactic acid or lactate. However, these methods only allow recovery of lactic acid and its derivatives, i.e. only one type of monomer, and require the use of organic solvents. Thus, there is a need for a process that makes it possible to recover heterogeneous biodegradable compositions with low environmental impact by reusing the different components resulting from depolymerization of the heterogeneous biodegradable composition in a polymerization reactio