Claims:
I/WE Claim,
[1] A process of Chemical recycling of PET bottles flakes comprises of FLAKE FEEDING HOPPER(1), WASHING TANK (5), FRICTION WASHER(7), Renaya Reactor1(10) (Preglcolysis Reactor), Renaya Reactor 2(11) (Glycolysis Reactor), FILTRATION REACTOR(14) & SAND FILTER(17), ANALYSIS TANK(18), OLIGOMER STORAGE TANK(19); wherein a process for chemical recycling of PET (Polyethylene terephthalate) bottle flakes through depolymerization process comprises of following steps: -
[a] flakes are agitator washed in WASHING TANK (5); wherein PET flakes are mixed with ethylene glycol heated at a temperature ranging from 50 to 100 degrees centigrade, is fed via GLYCOL PUMP(4), to remove the surfactant or any other surface impurities which have not being removed before; the washed PET flakes are then carried to the FRICTION WASHER(7) to remove the excess ethylene glycol which is transferred to GLYCOL BUFFER TANK(8);
[b] pre-glycolysis process takes place in Renaya Reactor 1(10) where washed flakes and 20-40% ethylene glycol are mixed; wherein 90% depolymerization takes place at 200-210 degree Celsius where glycol vapors absorbed by the PET flakes breaks its viscosity, thus melting it and depolymerisation process starts;
[c] the melted product from the Renaya Reactor 1(10) is transferred to Renaya Reactor 2(11); wherein 0-10 % ethylene glycol is mixed and it is heated at 200-210 degree Celsius for complete depolymerization, the resultant product would be monomers & oligomers;
[d] the melted product is transferred to FILTRATION REACTOR(14) wherein Hyflo slurry is injected from HY FLOW TANK (15) into the reactor(14) and the product is agitator mixed;
[e] the FILTRATION PUMP(16) transfers the melted product to SAND FILTER(17) wherein the mixed product moves in zigzag manner; Hyflo slurry forms a layer on the filter screens; and filter screen allows only oligomers & monomers to pass;
[f] color pigments are used to correct the final color value of oligomers & monomers in ANALYSIS TANK(18).
[2] A process of chemical recycling of PET bottles flakes as claimed in claim 1, wherein PET flakes are fed to the Flakes WASHING TANK (5) with the help of Horizontal SCREW CONVEYOR(2).
[3] A process of chemical recycling of PET bottles flakes as claimed in claim 1, wherein glass transition temperature in WASHING TANK (5) is between 50-100 Degree Celsius.
[4] A process of chemical recycling of PET bottles flakes as claimed in claim 1, wherein washed flakes are transferred to the FRICTION WASHER(7) with the help of an Inclined SCREW CONVEYOR(6).
[5] A process of chemical recycling of PET bottles flakes as claimed in claim 1, wherein washed & dry flakes are fed into Renaya Reactor 1(10) with the help of Inclined SCREW CONVEYOR(9).
[6] A process of chemical recycling of PET bottles flakes as claimed in claim 1, wherein Renaya Reactor 1(10) is horizontally designed with two partitions, the first partition has an agitator with baffles and second partition is to control overflow from first partition.
[7] A process of chemical recycling of PET bottles flakes as claimed in claim 1, wherein Renaya Reactor 2(11) is vertically designed with agitation to complete 100% depolymerization and increase the mass transfer.
[8] A process of chemical recycling of PET bottles flakes as claimed in claim 1, wherein the product of Renaya Reactor 2(11) is transferred to the FILTRATION REACTOR(14) with the help of GLYCOLYSIS PUMP(13) .
[9] A process of chemical recycling of PET bottles flakes as claimed in claim 1, wherein Hyflo slurry is injected from HY FLOW TANK(15) into a FILTRATION REACTOR(14) and agitator mixed in FILTRATION REACTOR(14).
[10] A process of chemical recycling of PET bottles flakes as claimed in claim 1, wherein the product of FILTRATION REACTOR(14) with Hyflo slurry is transferred to SAND FILTER(17) via FILTRATION PUMP(16).
[11] A process of chemical recycling of PET bottles flakes as claimed in claim 1, wherein SAND FILTER(17) is designed to restrict the flow of the product so, layers of Hyflo slurry are formed resulting in effective filtration.
[12] A process of chemical recycling of PET bottles flakes as claimed in claim 1, wherein the product of SAND FILTER(17) is transferred to the ANALYSIS TANK(18).
[13] A process of chemical recycling of PET bottles flakes as claimed in claim 1, wherein toners are added into an ANALYSIS TANK(18) for and agitators are provided for proper mixing and to create homogeneity.
[14] A process of chemical recycling of PET bottles flakes as claimed in claim 1, wherein the product of ANALYSIS TANK(18) is transferred to OLIGOMER STORAGE TANK(19) and then for further processing via OLIGOMER PUMP(20). , Description:Title of the Invention:-
Chemical recycling of PET bottles flakes.
Background of the Invention:-
Plastics are inexpensive and durable materials, which can be used to manufacture a variety of products that find use in a wide range of applications, so that the production of plastics has increased dramatically over the last decades. About 40% of these plastics are used for single-use disposable applications, such as packaging, agricultural films, and disposable consumer items, or for short-lived products that are discarded within a year of manufacture. Because of the durability & Non Biodegradability of the polymers involved, substantial quantities of plastics are piling up in landfill sites and in natural habitats worldwide, generating increasing environmental problems. Even degradable and biodegradable plastics may persist for decades depending on local environmental factors, like levels of ultraviolet light exposure, temperature, presence of suitable microorganisms, etc.

One solution to reduce environmental and economic impacts correlated with the accumulation of plastic is closed-loop recycling, wherein plastic material is reprocessed / recycled to manufacture new products. For example, one of the most common types of closed-loop recycling is polyethylene terephthalate (PET) recycling. PET wastes are subjected to successive treatments leading to food-contact-approved recycled PET (rPET), which is collected, sorted, pressed into bales, crushed, washed, chopped into flakes, melted and extruded in pellets and offered for sale. Then this recycled PET may be used to create fabrics for the clothing industry or new packaging such as bottles, blister packs, etc.

However, plastic wastes are generally collected all together, so that plastic bales contain a mixture of different plastics, the composition of which may vary from source to source, and the proportions of which may vary from bale to bale. Consequently, recycling processes require preliminary selection to sort out the plastic products according to their composition, size, resin type, color, functional additives used, etc.

Our invention is a revolutionary technology capable of transforming waste PET plastic back into sustainable polyesters. Products made from these sustainable polyesters have the same quality as those manufactured from petrochemicals (virgin material).

Our invention can be used to manufacture PET based products, not just filament yarns, our invention is able to convert used plastic bottles back into sustainable PET granules which can, in turn, be used to manufacture new bottles, packing film and textiles. Our invention is highly scalable. Compared to virgin PET granules the recycled PET Granules are indistinguishable, other than for lesser processing cost than virgin PET made from PTA and MEG.
Field of the Invention:-

The present invention provides a novel process for PET (Polyethylene terephthalate) bottle flakes chemical recycling through depolymerization process. Our invention converts PET flakes made from used PET bottles into oligomers & monomers. The oligomers & monomers can then be used as feedstock to manufacture recycled PET granules.
Description of Related Art:-

Patent: -JPH11302443A

Titled: -Recycling of pet bottle
Disclosure: - To provide a process to prepare again polyester articles of high purity by converting spent PET bottles recovered from the city into dimethyl terephthalate and ethylene glycol as main raw materials for the preparation of polyester articles. SOLUTION: A highly pure polyester polymer is obtained from PET bottle wastes by a process comprising steps; a monomer preparing step wherein recovered PET bottles subjected to necessary pretreatments such as sorting out foreign matters, crushing, washing and the like to give polyester flakes or polyester pellets, which purified ethylene glycol is added, flowed by depolymerization to give crude polyester monomers, to which subsequently purified methanol is added to effect transesterification followed by separation by crystallization, melting and purification by distillation to give purified dimethyl terephthalate and purified ethylene glycol, which are reacted together to give highly pure polyester monomers, and a polymer formation step wherein a highly pure polyester polymer is obtained by melt polymerization of the obtained highly pure polyester monomers.
Problem: -In cited invention, To obtain pure polyester monomers, purified methanol to give purified dimethyl terephthalate and purified ethylene glycol, which are then reacted together to give highly pure polyester monomers.
Solution: -While our invention does not use methanol to give ethylene glycol. In our process ethylene glycol is directly fed with PET flakes at a certain temperature to obtain pure oligomers and monomers.

Patent: -US7462649B2

Titled: -Method for recycling pet bottle
Disclosure: -A through process comprising depolymerization reaction of used PET bottles with EG, recovering DMT by ester interchange reaction with MeOH, obtaining terephthalic acid by hydrolysis of the recovered DMT, and manufacturing a PET polymer which can be used for manufacturing PET bottles again by using the terephthalic acid.
Problem: - In the cited invention, the process is to obtain DMT by means of reaction with MeOH and then finally via hydrolysis recovering terephthalic acid.
Solution: - Our process is for depolymerization of polymer with addition of MEG and our final product is Oligomer & Monomer

Summary of the Invention:-
The present invention relates to an improved process for PET (Polyethylene terephthalate) bottle flakes chemical recycling through depolymerization process The improved process requires Washing, Glycolysis, Filtration & optimization. In our invention the input is PET flakes and output is Oligomers & Monomers

Our invention’s process is divided in 5 parts:
Friction washing of flakes i.e., washing of PET flakes with Hot MEG (Mono Ethylene Glycol).
Pre-Glycolysis., melting of PET flakes in the presence of Ethyl Glycol for depolymerization reaction in RenayaReactor 1(10).
Glycolysis i.e., completes depolymerization reaction in presence of Ethyl Glycol in RenayaReactor 2(11).
Filtration of oligomer & Monomers in two parts (1st part FILTRATION REACTOR(14), 2nd Part SAND FILTER(17) ).
ANALYSIS TANK(18) i.e., adding toners for optimizing the product.

Initially Pet bottle flakes from flakes HOPPER(1) are fed in flakes WASHING TANK (5) via Horizontal SCREW CONVEYOR(2). In flakes WASHING TANK (5), the flakes are agitator washed with hot ethylene glycol fed via GLYCOL PUMP(4) at 50-100 Degree Celsius temperature to remove the surfactant or any other surface impurities (which has not been removed before), the washed flakes are then carried to the FRICTION WASHER(7) with the help of inclined screw conveyor(6) to remove the excess ethylene glycol and transfer the excess glycol to GLYCOL BUFFER TANK(8)

The washed flakes then with the help of Inclined SCREW CONVEYOR(9) are fed into the RenayaReactor 1(10), in RenayaReactor 1(10), 20-40% ethylene glycol is added and the temperature of RenayaReactor 1(10) is raised at 200-210 Degree Celsius, this creates chemical reaction between PET flakes & ethylene glycol, the glycol vapors are absorbed by the PET flakes which breaks its intrinsic viscosity, therefore the flakes starts melting and 90% of depolymerization is completed in this reactor(10). For complete depolymerization the product is then transferred to Renaya Reactor 2(11).

For complete depolymerization, the product from Renaya Reactor 1(10) is then processed in the RenayaReactor 2(11) with 0%-10% ethyl glycol injection at the temperature of 200-210 Degree Celsius; this completes the chemical reaction between PET Flakes and ethylene glycol which gives the resultant product Monomer & oligomer. Monomers & oligomers now need to be filtered, so the product is then transferred via GLYCOLYSIS PUMP(13) to the filtration tank(14).

For filtration, Hyflo slurry is injected from HY FLOW TANK(15) into the FILTRATION REACTOR(14) and agitator mixed with the product. Then the product is transferred via FILTRATION PUMP(16) to SAND FILTER(17)s . As Hyflo slurry sticks on the surface of the SAND FILTER(17)s and resists the flow of monomers & oligomers, and as a result the obtained product is free from all suspended impurities, all the suspended impurities in the monomers & oligomers is removed here and only filtered monomer & oligomer is passed through Hyflo slurry sticked filter screens in SAND FILTER(17).

The filtered product is then transferred to the ANALYSIS TANK(18), where color pigments are used to correct the color, after that it is transferred to OLIGOMER STORAGE TANK(19) and then for further processing via OLIGOMER PUMP(20).

Description of the drawings:
As shown in figure1 the PET bottle flakes are fed into the hopper(1) and then it is fed with the help of Horizontal SCREW CONVEYOR(2) for flake washing with hot ethylene glycol. Glycol is fed via GLYCOL PUMP(4) and processed at 50-100 Degree Celsius temperature to remove the surfactant or any other surface impurities which has not being removed before, the washed PET flakes are carried to the FRICTION WASHER(7) with the help of Inclined SCREW CONVEYOR(6) to remove the excess ethylene glycol and transfer the excess glycol to GLYCOL BUFFER TANK(8).
The washed flakes then with the help of Inclined SCREW CONVEYOR(9) goes to the RenayaReactor 1(10), and in RenayaReactor 1(10) 20-40% ethylene glycol is added and its temperature is raised at 200-210 Degree Celsius, by doing this the glycol vapors absorbed by the PET flakes breaks its viscosity and melting process starts here, 90% of depolymerization is completed in this reactor.
For complete depolymerization, the product from Renaya Reactor 1(10) is then processed to the RenayaReactor 2(11) with 0%-10% ethyl glycol injection at the same temperature of 200-210 Degree Celsius. Depolymerization reaction completed here and the resultant product is monomers & oligomers. The converted monomers & oligomers now need to be filtered, so the product is then transferred via GLYCOLYSIS PUMP(13) to the FILTRATION REACTOR(14). For filtration, Hyflo slurry is injected from HY FLOW TANK(15) into the filtration tank(14) and agitator mixed with the product then it is transferred via FILTRATION PUMP(16) to SAND FILTER(17). As Hyflo slurry sticks on the surface of the SAND FILTER(17)s and resists the flow of monomers & oligomers, and as a result the obtained product is free from all suspended impurities.
The filtered product is then transferred to the ANALYSIS TANK(18), where color pigments are used to correct the final color, after that the product is transferred to OLIGOMER STORAGE TANK(19) and then for further processing via OLIGOMER PUMP(20) .
Detailed Description of the Invention:-
The present invention provides a novel process for PET (Polyethylene terephthalate) bottle flakes chemical recycling through depolymerization process. The process comprises washing, Glycolysis, filtration and product optimization.

Diagram

As shown in diagram in our invention the process involves, Flakes hopper(1), flakes WASHING TANK (5), FRICTION WASHER(7), RenayaReactor1(10), RenayaReactor2(11), FILTRATION REACTOR(14), SAND FILTER(17), ANALYSIS TANK(18)s

The description of the process is as below:

As shown in the diagram the PET flakes in the hopper(1) are fed to the Flakes WASHING TANK (5) with the help of a Horizontal SCREW CONVEYOR(2). Washing of flakes is very necessary to remove non PET impurities in PET flakes and clean the surface of the flakes from surfactant, adhesives or any other surface impurities. Pre- washing is done by hot ethylene glycol fed via GLYCOL PUMP(4) at a temperature of 50-100 degree Celsius, in the WASHING TANK (5) hot ethylene glycol and pet bottle flakes are mixed through agitator, wherein PET flakes hold for 15-20 minute time before transferring to the next process. Due to the temperature, glycol mixing & agitation, the surface of flakes is cleaned from all surface impurities. The washed flakes are then transferred to the FRICTION WASHER(7) by the help of an Inclined SCREW CONVEYOR(6).

The basic function of the FRICTION WASHER(7) in our invention is to remove the contaminated glycol from the flakes which got carried away with the Inclined SCREW CONVEYOR(6) of the WASHING TANK (5). The removed dirty glycol is then passed through a screen separator and the excess glycol is transferred to GLYCOL BUFFER TANK(8).

The washed & dry flakes are then fed into Renaya Reactor 1(10) with the help of Inclined SCREW CONVEYOR(9). Depolymerization starts in the Renaya Reactor 1(10). The washed PET flakes are transferred to the horizontally designed RenayaReactor 1(10), in this reactor, 20-40% of glycol is injected to the reactor, and reactor temperature is raised to 200-210 Degree Celsius. The horizontal reactor has two partitions, one partition has an agitator with baffles, and the hot glycol vapors are absorbed by the PET flakes which reduces the intrinsic viscosity of the flakes resulting in melting of PET flakes. The overflow from the first partition is transferred to the second partition. Partitions are to increase the residence time of flakes, so that the PET flakes can easily react with hot glycol, during this depolymerization reaction strength of flakes is reduced and about 90% of depolymerization takes place in this reactor.

Depolymerization reaction
(C10H8O4)n +C2H6O2=C12H14O6 (PET Polymer + Ethyl Glycol) = Monomer

To convert the product into a complete oligomer & monomer, the partially depolymerized product of Renaya Reactor 1(10) is transferred to the Renaya Reactor 2(11). The vertical design of the Renaya Reactor 2(11) is in such a way that the partially depolymerized melt can be completely converted into oligomers & monomers. The Ethyl Glycol is injected in this reactor at 0%-10%. This reactor has got agitation to complete the chemical reaction and increase the mass transfer. After the complete reaction in Renaya Reactor 2(11) the melt is now converted into monomers & oligomers.

The product of Renaya Reactor 2(11) is then transferred to the FILTRATION REACTOR(14) via GLYCOLYSIS PUMP(13) . The conversion of PET flakes into monomers & oligomers is completed, now we have to filter the monomers & oligomers, to remove the suspended impurities present in the monomers &oligomers while processing the depolymerization reaction.

The filtration process starts with, Hyflo slurry injecting into the FILTRATION REACTOR(14) from HY FLOW TANK(15). The FILTRATION REACTOR(14) is equipped with an agitator for mixing and to avoid sedimentation of the Hyflo slurry at the bottom of the tank. The unfiltered monomers & oligomers along with Hyflo slurry are transferred via FILTRATION PUMP(16) to the SAND FILTER(17). The Hyflo slurry sticks on the SAND FILTER(17) & pre-coats the SAND FILTER(17) to increase the efficiency of the filtration; this reduces pore size of the SAND FILTER(17) for better filtration. The product is passed through sticked Hyflo layered filter screens in SAND FILTER(17)s; the purpose of providing Hyflo slurry is to restrict the flow of the unfiltered monomers & oligomers, so the molecules of unfiltered monomers & oligomers move in zigzag manner through the layer of Hyflo slurry. Due to zig zag movement & reduced pore size the suspended particles are restricted and the pure filtered monomer & oligomer is passed through. Thus the final product is free from all suspended impurities.

After the filtration process the filtered monomers & oligomers are transferred to the analysis tank(18) , here color correction is done.

Color pigments like red toner/blue toner are used to increase/decrease the color value of a product as per requirement. Agitators are provided for proper mixing and to create homogeneity. After the dosing of these colors, the sample is tested, and if the product satisfies all technical parameters it is transferred to OLIGOMER STORAGE TANK(19) and then for further processing via OLIGOMER PUMP(20).