KR102599800B1 - Manufacturing method of recycled PET chip using waste PET - Google Patents

Abstract

The present invention improves purity through a purification process by selecting and melting only transparent waste PET from low-grade waste PET with low intrinsic viscosity (IV) (0.72 dl/g), and produces high intrinsic viscosity (IV) (8 ~ 1.02dl/g) Regarding the manufacturing method of recycled PET chips.
The manufacturing method of the present invention includes selecting only transparent waste PET bottles, pulverizing them into flakes, grinding them again in a wet manner at low temperature, and then centrifuging to obtain only pure transparent waste PET bottles, a selection process and a purification process by melting, It consists of crystallization and solid-state polymerization processes to prevent hydrolysis due to moisture, and a process to manufacture recycled PET chips.
The present invention has the effect of producing high-quality recycled PET chips through solid-state polymerization by improving purity through multiple selection processes and refining processes by melting, so that higher quality PET molded products can be produced, and various products with high added value can be produced. It is suitable for manufacturing and has a very commercially advantageous advantage.

Description

Manufacturing method of recycled PET chip using waste PET}

The present invention relates to a method of manufacturing recycled PET chips using waste PET, and more specifically, to a method of manufacturing high-quality recycled PET chips with improved purity and intrinsic viscosity of transparent waste PET from waste PET waste.

Polyethylene terephthalate (PET) has large crystallinity and a high melting point, so it is used in a variety of applications such as fibers, films, beverage containers, and injection molding materials. PET is light in weight, has high strength, does not break, has excellent transparency, and is resistant to gases. Due to its characteristics of low transmittance and high light transmittance, it is widely used as a substitute for glass containers as beverage containers for carbonated drinks, bottled water, and juice drinks.

Since PET is a thermoplastic resin, used waste PET can be recycled by melting. Current waste PET recycling technologies include mechanical recycling, chemical recycling, and energy recovery through incineration. Chemical recycling is a high-quality recycling method. The product can be obtained, but there are problems such as difficult technical access, high costs such as treatment facilities, and recycling methods such as energy recovery through incineration have the problem of polluting the environment because harmful compounds such as dioxin are generated during incineration. The appropriate method would be to use a mechanical recycling method that costs less and does not cause pollution problems.

In order to produce high-quality recycled PET from waste PET waste, it is important to select pure waste PET from waste PET waste regardless of whether it is a chemical recycling method or a mechanical recycling method. Since the selection of waste PET is not appropriate, heterogeneous synthetic resins are produced. Alternatively, if labels attached to waste PET waste are mixed, the physical properties deteriorate due to a decrease in molecular weight due to hydrolysis during the molding process of recycled PET, causing problems in the quality of recycled PET products.

For example, in the prior art related to the recycling method of waste PET, Patent Document 1 includes the steps of collecting PET material with a high intrinsic viscosity (IV) of 0.95 dl/g and a wide distribution range of mainly 0.60 to 0.80 dl/g; mixing the collected materials and reforming them into a heterogeneous IV material mixture comprising substantially a plurality of heterogeneous flake-like and chunk-like fragments and subjecting the heterogeneous mixture to direct solid state polymerization (SSP) such that the average IV is 0.90 dl. A method of manufacturing a PET material suitable for use in the manufacture of a high-performance plastic strap, which includes the step of forming a dissimilar material having a weight of more than /g, involves manufacturing a high-performance PET strap using recycled PET bottle flakes with a somewhat high intrinsic viscosity (IV), and the patented method is Document 2 includes an input step of injecting compressed PET bottles, a sorting step of dismantling the compressed PET bottles and injecting them in the input step, separating foreign substances attached to the PET bottles, and sorting the PET bottles by color, and the sorting step. A pulverizing step in which PET chips are formed by pulverizing them to a certain size after the selection is completed, a washing step in which foreign substances, label bonds, and chemicals are removed from the PET chips pulverized in the pulverizing step using cold water and hot water, and the washing step. A PET bottle recycling method comprising a drying step for removing moisture and foreign substances remaining in the washed PET chips, and a dust collection section for collecting and removing contaminants generated in the selecting, grinding, washing, and drying steps. It is starting.

Additionally, Patent Document 3 discloses a process for producing flakes by pulverizing waste polyester products; A process of drying the flakes so that the residual moisture content is 0.1% by weight or less; And a process for preparing a recycled polyester melt by melting the dried flakes, wherein the process of drying the flakes is performed at a temperature of 60 to 200 ° C. for 1 to 24 hours. A method for producing a recycled polyester polymer. is starting.

The inventor of the present invention developed a method for manufacturing high-quality recycled PET chips from waste PET waste by improving purity and viscosity using transparent waste PET selection and purification and mechanical recycling technology, and completed the present invention.

KR 10-0257284 B1 KR 10-0895529 B1 KR 10-1417193 B1

The problem to be solved in the present invention is to provide a method for manufacturing high-quality recycled PET chips that improve the purity of waste PET (polyethylene terephthalate; PET) by precise selection and melting of transparent waste PET and improve intrinsic viscosity through solid-state polymerization. In more detail, the purity is increased by precise selection and melting purification of transparent waste PET only from low-grade waste PET with low intrinsic viscosity (IV) (0.72 dl/g), and the intrinsic viscosity (IV The purpose is to provide a method of manufacturing recycled PET chips with high (8 ~ 1 dl/g).

As a means of solving the problem according to the present invention, the method of manufacturing recycled PET chips using waste PET is to select only transparent waste PET from the collected waste PET waste, crush it into flakes, and crush it again in a wet manner at low temperature, A plurality of selection processes to obtain only pure transparent waste PET by centrifugation, a purification process by melting, a crystallization process to prevent hydrolysis, a solid phase polymerization process, and a process of melting and extruding the solid polymer to produce recycled PET chips. It is made up of

One embodiment of the method for manufacturing recycled PET chips using waste PET of the present invention is a). A sorting process that selects only transparent waste PET from the collected waste PET and then compresses the transparent waste PET, b). The first sorting process c) crushes the compressed waste PET into flakes and then separates only the transparent PET flakes. The second sorting process, d), where transparent waste PET flakes are wet-grinded and the grinded product is centrifuged to remove foreign substances and obtain transparent waste PET flakes. Drying process to dehumidify and dry transparent waste PET pulverized material, e). A refining process, f), in which the dried transparent waste PET pulverized material is melt-extruded at the melting temperature, filtered and cooled in the molten state, and then pulverized into flakes to produce recycled PET flakes. Crystallization process to crystallize recycled PET flakes, g). Solid-state polymerization process and h) for solid-state polymerization of crystallized recycled PET flakes. It consists of a recycled PET chip manufacturing process in which the solid polymer is extruded under melting temperature conditions, cut, and molded into chips.

Another more specific embodiment according to the manufacturing method of recycled PET chips using waste PET of the present invention is a). A sorting process that removes contaminants from the collected waste PET, selects only the transparent waste PET, and then compresses the selected transparent waste PET, b). The first sorting process c) crushes the compressed waste PET into flakes with a size of 5 to 10 mm and then separates only the transparent PET flakes. Second selection process, d), where transparent waste PET flakes are wet-grinded at 5 to 10°C and centrifuged to obtain transparent waste PET flakes. Drying process of dehumidifying and drying transparent waste PET pulverized material to a residual moisture of 0.1% by weight or less, e). A refining process to produce recycled PET flakes by melt-extruding the dried waste PET pulverized material at the melting temperature, filtering the molten state, cooling, and pulverizing it into flakes with a size of 3 to 5 mm, f). Crystallization process in which recycled PET flakes are crystallized at 140 ~ 165℃ for a certain period of time, g). a solid-state polymerization process in which crystallized recycled PET flakes are filled with nitrogen gas under vacuum conditions and subjected to solid-state polymerization at 180 to 220°C; and h) a recycled PET chip manufacturing process in which the solid polymer is extruded under melting temperature conditions, cut, and formed into PET chips. It consists of including:

The manufacturing method of recycled PET chips according to the present invention improves purity and produces recycled PET pellets with a high intrinsic viscosity (IV) of 8 to 1 dl/g, so it can be used in PET containers, building materials, and carbonate receptors that require high intrinsic viscosity. It is suitable for manufacturing a variety of products with high added value, such as high-strength polyester long fibers.

The manufacturing method of recycled PET chips using waste PET according to the present invention has the effect of improving purity through a plurality of selection processes and a purification process by melting and then manufacturing high-quality recycled PET pellets through solid-state polymerization. It has a very commercial advantage as it can produce high-quality PET molded products and is suitable for manufacturing a variety of products with high added value.

Figure 1 is a diagram schematically showing the manufacturing process of high-quality recycled PET chips using waste PET of the present invention.

Hereinafter, the present invention will be described in more detail for carrying out the present invention, but the present invention is not limited by the contents described below.

The attached Figure 1 is a diagram schematically showing the manufacturing process of high-quality recycled PET chips using waste PET of the present invention. The present invention will be described in detail with reference to Figure 1.

The manufacturing method of recycled PET chips using waste PET according to the present invention is a). A sorting process that selects only transparent waste PET from the collected waste PET and then compresses the transparent waste PET, b). The first sorting process c) crushes the compressed waste PET into flakes and then separates only the transparent PET flakes. The second sorting process, d), where transparent waste PET flakes are wet-grinded and the grinded product is centrifuged to remove foreign substances and obtain transparent waste PET flakes. Drying process to dehumidify and dry transparent waste PET pulverized material, e). A refining process in which the dried transparent waste PET pulverized material is melt-extruded at the melting temperature, filtered and cooled in the molten state, and then pulverized into flakes to produce recycled PET flakes, f). Crystallization process to crystallize recycled PET flakes, g). It includes a solid-state polymerization process of solid-state polymerization of crystallized recycled PET flakes, and h) a recycled PET chip manufacturing process of extruding and cutting the solid-state polymer at a melting temperature and forming it into chips.

The sorting process according to the present invention is a process of selecting transparent waste PET from the collected waste PET, removing contaminants, labels, etc., and compressing to obtain only transparent waste PET. The collected waste PET is disposed of in various forms. It is a product, and although it is not particularly limited, it is desirable to collect waste PET bottles, which are advantageous for recovery and sorting operations.

The selection of transparent waste PET in the above sorting process uses an optical sorter to separate and remove colored waste PET that is difficult to distinguish with the naked eye, select only transparent waste PET, and press the selected transparent waste PET to increase grinding efficiency. .

The first selection process according to the present invention is a process of obtaining transparent waste PET flakes by cutting, crushing, and washing compressed transparent waste PET into flakes. The selection process minimizes changes in physical properties of PET during the recycling process and improves purity. It is a process that is done.

In the first selection process, the compressed transparent waste PET bottle is cut and crushed into waste PET flakes of 5 to 10 mm in size, and then the waste PET flakes are placed in a washing tank equipped with a heating means and washed with hot water at 70 to 80 ° C. Then, it is screened to separate only transparent waste PET flakes.

Through the first selection process, labels, adhesives, etc. attached to transparent waste PET are separated by hot water and float to the top of the washing tank, so the washing water is passed through to remove floating matter, and the particles are smaller than waste PET flakes and heavy metals, etc. Foreign substances are separated by screen work and separated into only transparent waste PET flakes.

The secondary sorting process according to the present invention is a secondary sorting process in which transparent waste PET flakes are centrifuged by wet grinding at low temperature to obtain transparent waste PET flakes. Using a wet grinder, 5 It consists of pulverizing at ~10°C to a size smaller than the flakes of the first selection process.

The wet grinder of the second sifting process is widely used in the technical field to which the present invention belongs, and the adhesive attached to the transparent waste PET flakes increases in hardness at low temperatures and can be separated more easily. Wet pulverized material pulverized into particles smaller than flakes is sedimented by centrifugation to obtain transparent waste PET pulverized material.

The drying process according to the present invention is a process of removing moisture from transparent waste PET pulverized material in order to prevent the decrease in the degree of polymerization of PET due to hydrolysis, resulting in a decrease in the physical properties of PET, and removing residual moisture using a dehumidifier, etc. It consists of dehumidifying and drying to less than 0.1% by weight.

In the purification process according to the present invention, in order to improve the purity of the final product, recycled PET pellets, the dried transparent waste PET pellets are melt-extruded, filtered in the molten state to remove foreign substances contained in the melt, and cooled to room temperature. This is a preliminary recycling process to obtain recycled PET flakes with improved purity by crushing the extruded product cut to a certain size into flakes of a certain size.

In the purification process, dried transparent waste PET pulverized material is melted and extruded using an extruder at a melt temperature of 275 to 280°C and a maximum pressure of 110 bar, and the molten PET is passed through a 20 micron stainless steel filter at a vacuum degree of 10 mbar to be contained in the melt. This consists of removing the contained foreign substances to obtain high-purity recycled PET extrudate, cooling it to room temperature, cutting it into pieces, and pulverizing it into flakes to obtain recycled PET.

In addition, it is desirable to expand the polymerization area of the recycled PET in order to improve reaction efficiency in the subsequent crystallization process and solid-state polymerization process, and it is preferable to obtain recycled PET flakes by pulverizing them into flakes with a size of 3 to 5 mm.

The crystallization process according to the present invention is a process of preheating and drying the recycled PET flakes to crystallize them. The crystallization time may vary depending on the input amount of recycled PET flakes and the crystallization temperature, but is generally 1 ~ 1 at 140 ~ 165 ℃. It consists of crystallization for about 2 hours.

The crystallization process employs a rotary-type crystallization facility or a crystallization facility that crystallizes while flowing in a heating hopper equipped with a high-speed stirrer. The solid-state polymerization reaction can be performed simply after preheating for the solid-state polymerization reaction without a crystallization process. In this case, sticking of raw materials may occur, which has an undesirable effect on the efficiency of the solid-state polymerization reaction.

The solid-state polymerization process according to the present invention is a process for producing recycled PET with high intrinsic viscosity (IV) through solid-state polymerization reaction, and solid-state polymerization of crystallized recycled PET flakes is carried out under vacuum and nitrogen atmosphere at a reaction temperature of 200 to 210°C. It is done by doing what you are told.

The solid-state polymerization process consists of maintaining the reaction temperature of the recycled PET flakes in a reactor at 200 to 210°C, introducing nitrogen into the reactor at a vacuum of less than 5 mbar and a flow rate of 2000 L/hr, and performing solid-state polymerization under a nitrogen atmosphere.

In addition, the solid phase polymerization process consists of allowing the reaction product to remain in the lower part of the reactor under stirring for 5 to 6 hours after the solid phase polymerization reaction is completed. The reaction product is allowed to remain for 5 to 6 hours under stirring after the solid phase polymerization reaction is completed. Prevents the bridging phenomenon of PET flakes and facilitates discharge.

The recycled PET chip manufacturing process according to the present invention is a process of manufacturing recycled PET chips by melt-extruding and cutting the solid polymer discharged after completion of the solid polymerization process, and melt-extruding the solid polymer at a melt temperature of 280°C. Then, it is cut to produce recycled PET chips with an intrinsic viscosity (IV) of 0.8 to 1.dl/g.

The recycled PET chip with an intrinsic viscosity (IV) of 0.8 to 1.dl/g manufactured according to the method of the present invention is suitable for the production of high-strength polyester long fibers that require high intrinsic viscosity in addition to general PET containers, for example. , It is suitable for manufacturing products with high added value such as building materials (intrinsic viscosity 0.8dl/g), carbonate receptors (intrinsic viscosity 0.85dl/g), and high-strength yarn (intrinsic viscosity 0.90dl/g), which is very commercially advantageous. .

Claims (5)

a). A sorting process that selects only transparent waste PET from the collected waste PET and then compresses the transparent waste PET,
b). The first sorting process involves cutting and pulverizing the compressed waste PET into flakes with a size of 5 to 10 mm, washing the waste PET flakes with hot water at 70 to 80°C, and then screening to select only transparent waste PET flakes;
c). A second sorting process in which transparent waste PET flakes are wet-grinded at 5 to 10°C to a smaller size than the PET flakes in the first sorting process and centrifuged to obtain transparent waste PET flakes,
d). Drying process of dehumidifying and drying transparent waste PET pulverized material so that the residual moisture is less than 0.1% by weight,
e). A refining process in which dried transparent waste PET pulverized material is melt-extruded at the melting temperature, filtered in the molten state, cooled to room temperature, cut to a certain size, and then pulverized into flakes of 3 to 5 mm in size to produce recycled PET flakes;
f). A crystallization process in which recycled PET flakes are crystallized at 140 to 165°C for 1 to 2 hours,
g). A solid-state polymerization process in which crystallized recycled PET flakes are solid-phase polymerized under a nitrogen atmosphere by adding them to a reactor at a reaction temperature of 200 to 210°C under a vacuum of less than 5 mbar and nitrogen at a flow rate of 2000 ℓ/hr.
h). A method for manufacturing high-quality recycled PET chips using waste PET, comprising a recycled PET chip manufacturing process of extruding and cutting solid polymers at melt temperature conditions and forming them into PET chips. delete delete According to claim 1, the purification process involves melting and extruding dried transparent waste PET pulverized material at a melting temperature of 275 to 280°C, and then filtering the molten state through a 20 micron stainless steel filter. Manufacturing method of recycled PET chips. delete