RU2794734C1 - Method for manufacturing biodegradable pet chips - Google Patents

Abstract

FIELD: chemical industry.

SUBSTANCE: invention is related specifically to methods for production of biodegradable PET chips. The method includes supplying purified terephthalic acid (PTA) and initial or recycled monoethylene glycol (MEG) in a given amount to a slurry tank (302), transferring the resulting mixture to an esterification reactor (304) for esterification to obtain the monomer, transferring monomers from an esterification reactor to a reactor polymerization (306), feeding one or more polycatalysts to the polymerization reactor, and polymerizing the monomers in the polymerization reactor. A water-insoluble composition based on an enzyme, which is a natural protein molecule, is fed at the stage of supplying PTA, or MEG, or a polycatalyst, or a combination thereof. The water-soluble enzyme composition is provided at any stage or combination thereof, including post-polymerization steps, but excluding the esterification step. After granulation, a predetermined amount of biodegradable PET chips is moved at a predetermined frequency through the fluidized bed mold chamber, the chips are transferred in batches from the fluidized bed chamber to a reactor of predetermined capacity, and the chips are cooled using a refrigerator.

EFFECT: provision of a method for production of ready-to-use biodegradable PET that does not require mixing with additives at the stage of production of the final product.

18 cl, 4 dwg

Description

FIELD OF TECHNOLOGY TO WHICH THE INVENTION RELATES

The present invention generally relates to biodegradable PET polymer raw materials. In particular, the present invention relates to a process for the production of biodegradable polyethylene terephthalate or PET chips for use in the manufacture of biodegradable polyester packaging such as film/laminate bags, bottles, trays, or any other product.

BACKGROUND OF THE INVENTION

Plastics are usually high molecular weight organic polymers. They are usually synthetic and produced by polymerization, most often derived from petrochemicals. Plastics are inexpensive, durable and easy to work with compared to other options, which are used to produce a variety of components that find use in a wide range of applications. As a consequence, the production of plastics has increased dramatically over the past few decades. For example, polyethylene terephthalate, or PET, is a widely used thermoplastic polymer for the production of polymeric products such as films, bottles, etc. Due to the durability of polymer products, which are highly resistant to degradation (due to high molecular weight, hydrophobicity and crystallinity), despite being recyclable, due to poor collection, significant amounts of single-use plastic accumulate in landfills and in natural habitat, causing growing environmental problems around the world. To address these problems, various physical, chemical and/or biochemical approaches have been developed to reduce the biodegradability of polymeric products and increase their rate of biodegradation. For example, additives have been added to combine/blend with non-biodegradable polymer resins at the stage of manufacturing the final polymer product by the user to make the polymer product biodegradable.

However, the mixing of additives during the production of the final product to obtain a biodegradable polymer product seems to be satisfactory, but the mixing of the additives during the production of the final product, especially for large-scale production of packaging and other products made from polyester or PET chips with special properties, including minimum IV and homogeneous dispersion, requires additional complex observations, expertise, tests and quality control. This prevents adaptation of the additive mixing process at the stage of production of the final product to obtain a biodegradable product. Thus, there is a need for a biodegradable PET chip for making biodegradable PET polymer products ready for use in making biodegradable polymer products without mixing such an additive at the end product manufacturing stage.

SUMMARY OF THE INVENTION

The present invention describes a method for producing biodegradable PET chips, comprising the steps of supplying purified terephthalic acid (PTA) in a predetermined amount to a slurry tank; supplying primary and/or recycled monoethylene glycol (MEG) in a predetermined amount to the slurry tank; transferring the slurry tank combination to an esterification reactor to esterify the combination in the reactor at a temperature above 250° C. at which monomers are released; transfer of monomers from the esterification reactor to the polymerization reactor; providing polycatalysts, such as, but not limited to, a Ti-based catalyst, Sb ₂ O ₃ , or any other suitable catalysts, or a combination thereof, to the polymerization reactor; and polymerizing the monomers in a polymerization reactor at a temperature above 280°C, where the enzyme-based composition is provided either at the PTA / MEG stage, or at the polycatalyst stage, or at other stages, or in combinations thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

In FIG. 1 is a flow diagram of a process (100) for producing biodegradable film-grade polyethylene terephthalate chips in accordance with an embodiment of the present invention.

Fig. 2 is a flow diagram of a process (200) for producing injection molded and biodegradable bottle grade polyethylene terephthalate chips in accordance with an embodiment of the present invention.

Fig. 3 is a schematic illustration of a method (100) for producing biodegradable polyethylene terephthalate chips according to an embodiment of the present invention.

In FIG. 4 schematically shows a process (200) for producing biodegradable polyethylene terephthalate chips in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

While the present invention has been described in connection with what is currently considered the most practical and preferred embodiment, it should be understood that various arrangements and alternative embodiments are intended to be included within the scope of the appended claims. The present invention generally describes a biodegradable PET polymer raw material and, in particular, a process for the production of biodegradable polyethylene terephthalate film or PET chips for use in biodegradable polyester film/laminate packaging. The biodegradability of the PET chip is induced by the enzyme-based composition present either on the surface or throughout the thickness of the chip provided in one of the steps or combinations thereof in the process. Enzymes in an enzyme-based formula are naturally occurring protein molecules that act as highly efficient catalysts for biochemical reactions, helping the chemical reaction to proceed quickly and efficiently. Studies show that the enzymes present in the enzyme-based composition attract bacteria to the surface of the polymer product and colonize the surface of the plastic, forming a biofilm and thus accumulating bacteria on the surface of the polymer product. As soon as the bacteria colonize on the surface of the product, they secrete acids and/or enzymes that break down the polymer chains. Bacteria use biodegradable polymer as a component in the absence of nutrients for bacteria. The composition of the enzyme-based composition may include, but is not limited to, naturally occurring peptides/enzymes/proteins derived from dietary biological sources such as plants or vegetables, etc. Exemplary enzyme based compositions are described in Indian Patent Application No. 3104/MU M/2015 and 20161 1028054 and US9925707/EP3162841, however, any other similar/modified composition can also be used without deviating from the scope of the present invention. With reference to FIG. 1, 2, 3 and 4 will now describe various embodiments of the present invention. In FIG. 1 is a flow diagram of a process (100) for producing biodegradable polyethylene terephthalate chips in accordance with an embodiment of the present invention. The method (100) for producing biodegradable PET chips includes the step (102) of supplying a predetermined amount of purified terephthalic acid (PTA) to a slurry tank (302). The predetermined amount of PTA may be 68% by weight; however, another suitable amount of PTA may be provided based on requirements without departing from the scope of the present invention. The method (100) further includes the step (104) of supplying virgin or recycled monoethylene glycol (MEG) in a predetermined amount to the slurry tank (302). The predetermined amount of MEG is typically 31% by weight; however, another suitable amount of MEG may be provided based on requirements without departing from the scope of the present invention. The method (100) further includes the step (106) of transferring the slurry tank combination (302) to the esterification reactor (304) to esterify the combination in the reactor (304) which releases the monomer. The esterification takes place in the esterification reactor (304) at a temperature above 250° C. under a pressure of 2.5 bar, releasing monomers and water vapour. In step (106), the success of the esterification is confirmed if 95% by weight of steam-derived distilled water is removed from the esterification reactor (304). The method (100) further includes the step (108) of transferring the monomers from the esterification reactor (304) to the polymerization reactor (306). The polymerization reactor (306) may have a capacity of 20 m ³ ; however, a reactor (306) of a different capacity may also be used without departing from the scope of the present invention. The method (100) further includes the step (110) of supplying polycatalysts to the polymerization reactor (306) to impart desired properties to the resulting polymer. The polycatalysts can be, without limitation, a Ti, Sb ₂ O ₃ based catalyst, or any other suitable catalysts known in the art, or a combination thereof. The method (100) further includes a step (112) for polymerizing the monomers in a polymerization reactor (306). The polymerization of the monomers occurs by holding the monomers in the reactor (306) for 1.5-3 hours under vacuum at a temperature above 280°C. In step (112) of method (100), the polymerization of monomers takes place in the polymerization reactor (306) in the aforementioned predetermined temperature range to produce PET polymers. The resulting polyethylene terephthalate polymers (polymerized monomers) are forced by the pressure of inert gases such as nitrogen (N ₂ ) from the top of the polymerization reactor (306) to push through the specification spinneret (308) for strands configured for the polymerization reactor (306). In one example, a strand die (308) specification includes a plurality of holes, such as, but not limited to, 95 holes, each having a diameter of approximately 8 mm, but other specification die (308) strands can also be used without deviating from scope of the present invention. The strands exiting the spinneret (308) are stretched to a predetermined length, such as but not limited to 1.5 meters. The drawn strands are cooled in line by spraying chilled demineralized (DM) water onto the drawn strands or by other suitable cooling mechanism such as, but not limited to, automatic feeding of the strands under water. The cooled PET polymer filaments are then granulated into predetermined chips such as but not limited to 4×4×3 mm inline using a roller granulator or other suitable granulator. The enzyme-based composition, as previously discussed above, is provided with either PTA at (102) or MEG at (104) or a polycatalyst step (110) or other steps or combinations thereof to cause biodegradability of the polymer chips, which must be obtained using method (100). Biodegradable PET chips can also be produced by providing an enzyme-based composition in any of the steps or combinations thereof of the above-described method (100) for producing PET chips if the composition is not water-soluble. Alternatively, the composition may be provided in steps/steps only or combinations thereof, with the exception of the esterification step, for the production of biodegradable PET chips. Biodegradable PET chips can also be produced by adding an enzyme-based aqueous composition to the cooling water of an underwater stacker and then cutting the strands into chips. The dried chips are coated with an enzyme-based composition on the surface of the chips. Biodegradable PET chips can also be produced by placing an additional mixing zone in the process (100) to feed and mix the enzyme composition before pushing the molten PET polymer into the strand die (308) and then cooling and cutting the strands into chips having dispersed composition based on enzymes. The granular biodegradable PET chips are transferred to a dryer (310) to evaporate the water from the PET chips before being packaged for further use, such as for making plastic films. As used herein, the term PET polymer of textile or fiber grade, film and bottle grade is intended to describe PET which can be described as having an intrinsic viscosity in the range of 0.64-0.75,0.6-0.66 and 0.57- 0.64, respectively. In order to suit the use of various grades of PET resin, it is desirable for PET to have the following characteristics. The above method (100) produces biodegradable polyethylene terephthalate chips with film characteristics having an IV (intrinsic viscosity) of 0.6 to 0.66, which can be used to make a polyethylene terephthalate polymer film laminate for various suitable packaging applications. Injection molding and biodegradable PET chips are produced using the method (200) shown in FIG. 2, according to the embodiment of the present invention, known as solid state polycondensation (SSP), according to the above method (100) after the granulation step of the above method (100) to increase IV (intrinsic viscosity) suitable for injection molding, blow molding , extrusion, etc. The method (200) includes the step (202) of conveying a predetermined amount of biodegradable PET chips at a predetermined frequency through at least one pre-crystallizer or fluid bed chambers of the mold (402, 404). In one example, a predetermined amount of biodegradable chips can be transferred at a rate of 1.5 T/h, however any other amount or frequency can also be used without departing from the scope of the present invention. In the fluidized bed chambers (402, 404), air or nitrogen gas at 150° C.-170° C. is used to heat the PET chips before being transferred to the SSP reactor (406) as described in the next step (204). The method (200) further includes the step (204) of transferring the chips from the fluidized bed chamber(s) (402, 404) to the SSP reactor (406) of a given capacity for a given batch residence time. In one example, the capacity of the SSP (406) reactor is 30 tons, but other suitable capacity SSP (406) can also be used. In one example, the residence time in the SSP reactor (406) may be in the range of 10-20 hours, however the residence time may vary depending on the desired IV (intrinsic viscosity) of the resulting PET chips. During the stay in the SSP reactor (406), one or more by-products such as, but not limited to, aldehyde, MEG, etc., are released from the SSP reactor (406), which must be extracted during the residence time. Inert gas such as nitrogen (N ₂ ) from the bottom of the SSP reactor (406) at 180°C ~ 200°C passes into the SSP reactor (406) to recover by-products, leaving only biodegradable injection molding and PET chips bottles with the desired IV (intrinsic viscosity). The method (200) further includes the step (206) of cooling the chips withdrawn periodically in a calculated amount and frequency from the bottom of the SSP reactor (406) using a suitable cooler (408) providing the desired residence time for each batch withdrawn from the SSP reactor (406). The produced biodegradable injection-molded PET bottle chips are then ready to be packaged for further use such as making plastic bottles or other suitable products.

For bottle-grade biodegradable PET chips only, in step (102) of the process (100) for producing film biodegradable PET chips, a predetermined amount of purified isophthalic acid (IPA) is provided along with PTA, giving a total weight of IPA and PTA of about 68%. The predetermined amount of IPA may be 2% by weight and PTA may be 66% by weight, resulting in a total of 68% by weight; however, other suitable amounts of IPA and PTA may be provided based on requirements without departing from the scope of the present invention. In various other embodiments, in addition to adding the enzyme-based composition in the above steps or without it, ingredients such as, but not limited to, PTA, MEG, polycatalyst, etc. may be premixed with at least one of the ingredients in a predetermined amount of the enzyme composition. While the present invention has been described in connection with what is currently considered the most practical and preferred embodiment, it should be understood that various devices and alternative embodiments are intended to be included within the scope of the appended claims.

Claims (27)

1. Method (100) for the production of biodegradable PET chips, including the following steps: a) supplying purified terephthalic acid (PTA) in a predetermined amount to the slurry tank (302) in step (102); b) supplying primary or recycled monoethylene glycol (MEG) in a predetermined amount to the slurry tank (302) in step (104); c) transferring the mixture present in the slurry tank (302) to the esterification reactor (304) to esterify the combination in the reactor (304) which releases the monomer in the esterification step (106); d) transferring the monomers from the esterification reactor (304) to the polymerization reactor (306) in step (108); e) feeding one or more polycatalysts to the polymerization reactor (306) to impart the desired properties to the polymer to be obtained in step (110); And f) polymerization of the monomers in the polymerization reactor (306) in step (112), where the composition based on the enzyme, which is a natural protein molecule, is fed either to the PTA feeding step (102), or to the MEG feeding step (104), or to the step polycatalyst (110) or the other steps above or combinations thereof if the composition is insoluble in water, otherwise the composition is provided at any step or combination thereof except for the esterification step (106). 2. Method (100) for producing biodegradable PET chips according to claim 1, characterized in that the predetermined amount of PTA is 68% by weight. 3. Method (100) for producing biodegradable PET chips according to claim 1, characterized in that the predetermined amount of MEG is 31% by weight. 4. Method (100) for producing biodegradable PET chips according to claim 1, wherein the polycatalysts are at least one of Ti, Sb ₂ O ₃ based catalysts or any other suitable catalysts. 5. The method (100) for producing biodegradable PET chips according to claim 1, characterized in that the PET polymers obtained by polymerization are pushed out by the pressure of inert gases from the top of the polymerization reactor (306) to transfer the polymers to the spinneret for strands (308). 6. Method (100) for producing biodegradable PET chips according to claim 5, characterized in that the inert gas is nitrogen (N ₂ ). 7. Method (100) for the production of biodegradable PET chips according to claim 5, characterized in that the spinneret (308) of the strands creates strands of polymers obtained by polymerization, which are stretched to a predetermined length. 8. Method (100) for producing biodegradable PET chips according to claim 7, characterized in that the predetermined length of the threads is 1.5 meters. 9. The method (100) for producing biodegradable PET chips according to claim 7, wherein the drawn strands are cooled in-line by spraying chilled demineralized (DM) water onto the drawn strands or other suitable cooling mechanism. 10. Method (100) for producing biodegradable PET chips according to claim 9, characterized in that another suitable cooling mechanism is automatic filament feeding under water. 11. The method (100) for producing biodegradable PET chips according to claim 7, wherein the cooled PET polymer filaments are then granulated into pre-shaped chips on a conveyor using a roller granulator, an underwater granulator, or other suitable granulator. 12. Method (100) for the production of biodegradable PET chips according to claims 1 and 7, characterized in that the enzyme-based composition is fed into the cooling water of an underwater stacker and then the threads are cut into chips. 13. The method (100) for producing biodegradable PET chips according to claim 1, characterized in that it includes an additional mixing zone to provide the enzyme-based composition before pushing the PET polymer in the molten phase into the spinneret (308) for the strands, followed by cooling and cutting strand on shavings. 14. The method (100) for producing biodegradable PET chips according to claim 7, characterized in that the biodegradable PET chips are transferred to a dryer (310) to evaporate water from the PET chips before packaging for further use. 15. Method (200) for the production of biodegradable PET chips, comprising the following steps: a) moving a predetermined amount of biodegradable PET chips at a predetermined frequency through at least one chamber of the precrystallizer or fluidized bed mold (402, 404), in accordance with the method (100) of claims 11-13, after the granulation steps, then, to increase its own viscosity, suitable for injection molding, blow molding, extrusion, etc. at step (202): b) transferring the chips in batches at step (204) from the fluidized bed chamber(s) (402, 404) to an SSP reactor (406) of a given capacity for a given residence time; and c) cooling the chips withdrawn periodically in the calculated quantity and frequency from the bottom of the SSP reactor (406) using a suitable cooler (408) providing the desired residence time for each batch taken from the SSP reactor (406) in step (206) . 16. The method (200) for producing biodegradable PET chips according to any one of the preceding claims, comprising the steps of providing a predetermined amount of purified isophthalic acid (IPA) along with PTA. 17. The method (200) for producing biodegradable PET chips according to claim 16, wherein the predetermined amount of IPA is 2% by weight. 18. The method (200) for producing biodegradable PET chips according to claim 16, wherein the predetermined amount of PTA is 66% by weight.

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