KR102339830B1 - Manufacturing of high-viscosity recycled PET chips using low-viscosity PET flakes - Google Patents

Abstract

The present invention relates to a method for manufacturing recycled PET chips with high intrinsic viscosity (IV) and high purity suitable as raw materials for high value-added products without an existing energy-consuming solid-state polymerization process by using recycled PET bottle flakes, which comprises a recycled PET bottle crushing process, a screening process, a pre-drying process for mixing a first thickener, a dehumidifying process, an extrusion process for mixing a second thickener, and a chip forming and surface crystallizing process. The present invention can produce a variety of high value-added products by recycling used low-grade PET flakes into high-grade PET flakes, thereby providing an industrial effect of increasing a recycling rate and a commercially advantageous effect.

Description

Manufacturing of high-viscosity recycled PET chips using low-viscosity PET flakes

The present invention relates to a method for manufacturing a recycled PET chip having a high intrinsic viscosity (IV) and high purity by using recycled PET flakes having a low intrinsic viscosity (IV).

Polyethylene terephthalate (PET) has excellent physical and chemical properties and is used in various applications such as fibers, films, tire cords, and beverage containers. Since the demand for bottles, which is a substitute for glass containers and hazardous plastic containers, is steadily increasing, these PET bottles are treated as household waste unless they are used for other purposes after use. will be left

Currently, PET bottle flakes from crushed PET bottles are used for recycling, but recycled PET bottle flakes have low intrinsic viscosity (IV) (0.72 dl/g) and low purity, mainly polyester short fibers and PET packaging materials. It is used for products with low added value, such as sheets.

In addition, the existing method of manufacturing recycled PET chips with high intrinsic viscosity (IV) for the production of higher added-value products is made through solid state polymerization, but there is a problem in energy consumption.

In relation to the recycling of used PET bottles, for example, in the prior art, in Patent Document 1, the crushed PET bottle is put into water, and the PET bottle is separated from the components of the cap or cap retainer with different specific gravity, the label and the bottom of the empty bottle. Obtaining step, adding the separated PET pulverized product to white kerosene or light oil and stirring during heating to remove the label and label-attaching adhesive component contained in the PET pulverized product; A method for recovering and regenerating PET from an empty PET bottle is disclosed, comprising the step of removing residual solvent attached to the pulverized PET product during stirring by adding normal hexane. A selection step of dismantling the compressed and injected PET bottle in the step, separating foreign substances attached to the PET bottle and at the same time sorting and separating by color of the PET bottle, and after the selection is completed in the screening step, pulverizing to a predetermined size to form PET chips A washing step of removing foreign substances, label bonds, and chemicals from the PET chips pulverized in the pulverization step using cold water and hot water, and drying to remove moisture and foreign substances remaining on the PET chips washed in the washing step. Although the prior art discloses a PET bottle regeneration method characterized in that it consists of a dust collector for collecting and removing contaminants generated in the screening step, pulverizing step, washing step, and drying step, the prior art simply selects the used PET bottle. It is a technology that is only a degree of technology, and there is no implication regarding the technology of using recycled PET bottle flakes to regenerate them into products with higher added value.

And in Patent Document 3, intrinsic viscosity (IV) is as high as 0.95 dl/g, and the distribution range is mainly from 0.60 to 0.80 dl/g, collecting a wide PET material, mixing the collected materials, and mixing them with a large number of non-uniform flakes reshaping into a heterogeneous IV material mixture comprising molded and chunky fragments and direct solid state polymerization (SSP) of the heterogeneous mixture to form a heterogeneous material having an average IV of at least 0.90 dl/g; A method for producing a PET material suitable for use in the production of a high-performance plastic strap is to manufacture a high-performance PET strap using recycled PET bottle flakes having a rather high intrinsic viscosity (IV). One compound selected from carbonylbiscaprolactam (CBC), 1,4-phenylenebisoxazoline (p-BOX) and 1,3-phenylenebisoxazoline (m-BOX) is melted on a polyester chip Disclosed is a method for producing a high-viscosity and high-strength industrial polyester fiber characterized in that 0.25 to 1.00% by weight is added based on the total weight of the spinning resin in the spinning process.

The inventor of the present application is a recycling technology of recycled PET bottle flakes with high added value compared to the existing recycling technology. High viscosity uniquely suitable as a raw material for high value-added products from recycled PET bottle flakes with low intrinsic viscosity (IV) and low purity. A method for manufacturing a recycled PET chip having a viscosity (IV) and high purity was developed, and the present invention was completed.

KR 10-0578766 B1 KR 10-0895529 B1 KR 10-0257284 B1 KR 10-1429686 B1

The problem to be solved in the present invention relates to the provision of a method for manufacturing a high-viscosity recycled PET chip using low-viscosity recycled PET flakes, and more specifically, a solid-state polymerization process that consumes a lot of energy using recycled PET bottle flakes. An object of the present invention is to provide a method for manufacturing a recycled PET chip with high viscosity and intrinsic viscosity (IV) and high purity suitable as a raw material for products with high added value.

As a means of solving the problem according to the present invention, the manufacturing method of high-viscosity recycled PET chips using low-viscosity recycled PET flakes is a method of collecting and pulverizing low-grade recycled PET with low intrinsic viscosity (IV). After that, the first thickener is blended, heated and dried to a certain moisture content, and then foreign substances are removed from the PET polymer in the molten state obtained by blending the second thickener and melt-extruding at the melting temperature, cutting to obtain PET chips, and then crystallizing to obtain unique It consists in making a recycled PET chip with a higher viscosity (IV).

One embodiment according to the manufacturing method of the high-viscosity recycled PET chip using the low-viscosity recycled PET flakes of the present invention is a). A pulverization process of pulverizing recycled PET with low intrinsic viscosity (IV) to obtain 3 to 5 mm PET flakes, b). A transparent flake sorting process of sorting transparent PET flakes by an optical flake sorter from the pulverized PET flakes of the pulverization process, c). A pre-drying process to obtain a PET reaction mixture by mixing the first thickener with the transparent PET flakes selected in the screening process and drying for a certain period of time until the moisture content reaches 1000 ppm while heating at 120 to 140° C., d). After the pre-drying process, the PET reaction mixture is heated at 160 to 170° C. for a certain period of time to dehumidify to a moisture content of less than 50 ppm to obtain a PET dried product, e). After extrusion, an extrusion process of separating foreign substances from the extrusion melt to obtain a high-purity PET melt; and f). A molding process of cutting the PET melt in the extrusion process to a certain diameter and molding it into PET chips and g). It consists of including a recycling PET chip manufacturing process in which PET chips are made with higher intrinsic viscosity (IV) and high purity by crystallizing the surface using residual heat of PET chips while staying for a certain period of time.

The low-grade recycled PET with a low intrinsic viscosity (IV) of the present invention generally consists of recycled PET bottles having an intrinsic viscosity (IV) of about 0.7 dl/g, and the colored PET bottles and other plastics are separated in the sorting process. It consists of removing and using only transparent recycled PET.

In the present invention, a recycled PET chip having an intrinsic viscosity (IV) suitable as a raw material for a desired product by mixing different series of thickeners from the recycled PET bottle having an intrinsic viscosity (IV) of about 0.7 dl/g in two steps. It consists of manufacturing a high-purity recycled PET chip having an intrinsic viscosity (IV) of 0.72 to 0.9 dl/g.

The recycled PET chip manufacturing method according to the present invention has an energy-saving effect because it manufactures high-viscosity recycled PET chips from low-viscosity PET bottle flakes without the conventional energy-consuming solid-state polymerization process. It has the characteristic of manufacturing recycled PET chips with intrinsic viscosity (IV) suitable as a raw material for a desired product by mixing a thickener.

In addition, since the surface of the regenerated chip is crystallized using residual heat after forming the regenerated chip, there is an effect that there is no need to add a surface crystallization process when the regenerated chip is used as a raw material.

1 is a view schematically showing a manufacturing process of a high-viscosity recycled PET chip using low-viscosity recycled PET bottle flakes according to the present invention;

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

1 is a view schematically showing the manufacturing process of a high-viscosity recycled PET chip using low-viscosity recycling PET bottle flakes according to the present invention. do.

A method of manufacturing a high-viscosity recycled PET chip using low-viscosity recycled PET flakes according to the present invention is a). A pulverization process of pulverizing recycled PET with low intrinsic viscosity (IV) to obtain 3 to 5 mm PET flakes, b). A transparent flake sorting process of sorting transparent PET flakes by an optical flake sorter from the pulverized PET flakes of the pulverization process, c). A pre-drying process to obtain a PET reaction mixture by mixing the first thickener with the transparent PET flakes selected in the screening process and drying for a certain period of time until the moisture content reaches 1000 ppm while heating at 120 to 140° C., d). After the pre-drying process, the PET reaction mixture is heated at 160 to 170° C. for a certain period of time to dehumidify to a moisture content of less than 50 ppm to obtain a PET dried product, e). After melt extrusion, an extrusion process of separating foreign substances from the extrusion melt to obtain a high-purity PET melt, and f). A molding process of cutting the PET melt in the extrusion process to a certain diameter and molding it into PET chips, g). It consists of including a recycling PET chip manufacturing process of manufacturing PET chips with higher intrinsic viscosity (IV) and high purity by crystallizing the surface using residual heat of the PET chips while staying in the PET chips for a certain period of time.

Said a) according to the invention. The crushing process is a process of pulverizing recycled PET with low intrinsic viscosity (IV) into flakes, and the recycled PET consists of collected recycled PET bottles, etc. having an intrinsic viscosity (IV) of about 0.7 dl/g.

The pulverization process consists of pulverizing recycled PET into 3 to 5 mm PET flakes, and pulverizing them into 3 to 5 mm fine particles to increase the surface area of the PET flakes to increase drying efficiency in the subsequent pre-drying process, and This is done for a uniform reaction.

b) according to the invention. The sorting process consists of separating and removing colored flakes or other plastics mixed in the pulverized PET flakes and sorting only the transparent PET flakes.

The sorting process selects only transparent PET flakes from the pulverized PET flakes using an optical flake sorter, and the optical flake sorter employs an NIR CCD camera to sort only transparent PET flakes, so it is possible to manufacture high-purity recycled PET chips.

c) according to the invention. The pre-drying process is a process to obtain a PET reaction mixture by primarily removing moisture from the PET flakes and blending the first thickener. so that the reaction is uniform.

As a specific example of the pre-drying process, as shown in FIG. 1 , the selected PET flakes and the first thickener are put into the friction dryer 1, and the dryer temperature is 140° C., and the stirrer speed is 120 to 50 RPM. It consists of drying to a moisture content of 1000ppm by continuously injecting heated air at 140℃ and staying there for about 2 hours.

The first thickener may be any compound as long as the thickening reaction occurs without melting near 140° C., which is the dryer temperature, and 165° C., which is the dryer temperature, which will be described later in the preparation process. Preferably, a carbodiimide-based thickener is blended, and the carbodiimide-based thickener is a known and known compound, for example, carbodiimide, polycarbodiimide, etc., and the first thickener has an intrinsic viscosity suitable for the intended product. According to (IV), the mixing ratio is appropriately adjusted and added in an amount of 0.25 to 0.75% by weight based on the total weight of the PET reaction mixture.

Said d) according to the invention. The dehumidification process is a process to obtain a PET dried product by drying and dehumidifying the PET reaction mixture so that the water content of the PET reaction mixture is less than 50 ppm in order to prevent hydrolysis of the PET flakes in the reaction mixture of the PET flakes and the first thickener.

In the dehumidification process, as shown in the drawing, the PET reaction mixture is put into the drying hopper 2, and the moisture is removed from the dehumidifier 3 under the conditions of a dryer temperature of 165° C., a dew point of -60 to -40° C., and a residence time of about 5 hours. It consists of drying and dehumidifying the PET reaction mixture so that the moisture content of the PET reaction mixture is less than 50 ppm while injecting high-temperature hot air from which has been removed into the hopper.

e) according to the invention. The extrusion process is a process to obtain a PET melt by mixing the second thickener with the dried and dehumidified PET dried product with a moisture content of less than 50 ppm, melt extrusion at a melting temperature, and then physically removing foreign substances from the melt extrudate.

The second thickener injected in the extrusion process has a lower melting temperature than the first thickener, so it is a compound that cannot be used because it is melted near the dryer temperature of 140 °C and the dryer temperature of 165 °C in the preparation process to be described later.

If the second thickener is added together with the first thickener when the first thickener is added, it is melted in the dryer, making it impossible to operate the pre-drying process and the dehumidifying process. Preferably, the second thickener is a compound well known as an oxazoline-based thickener, for example, oxazoline, 1,3-phenylene bisoxazoline, etc., and is a thickener of a different series from the first thickener, and the PET melt It is blended in an amount of 0.1 to 0.75% by weight based on the total weight.

In the present invention, a high-viscosity recycled PET chip having a uniform viscosity can be manufactured by dividing the first thickener and the second thickener with a time lag, and from this, the quality of the desired product is also improved.

In addition, with respect to the blending of the first thickener in the pre-drying process, the blending ratio of the second thickener in the extrusion process is appropriately adjusted to obtain the desired product, for example, BCF yarn (intrinsic viscosity 0.72dl/g), PET sheet (intrinsic viscosity 0.73dl/g) g), PET container (intrinsic viscosity 0.75 ~ 0.8dl/g), construction materials (intrinsic viscosity 0.8dl/g), carbonated container (intrinsic viscosity 0.85dl/g), high tenacity yarn (intrinsic viscosity 0.90dl/g), etc. It is possible to manufacture recycled PET chips having an intrinsic viscosity (IV) of 0.72 to 0.90 dl/g, which is suitable for manufacturing products.

In the extrusion process, as shown in the drawing, dry and dehumidified PET dried and dehumidified to a moisture content of less than 50 ppm and a second thickener are added to the extruder 4, a melting temperature of 275 to 280° C., a maximum melting pressure of 110 bar, and melt extrusion. It consists of passing the molten extrudate through a stainless steel filter of 20 microns at a vacuum degree of 10 mbar to remove foreign substances to obtain a high-purity PET melt.

f) according to the invention. The molding process is a process of cutting the PET melt in the extrusion process while cooling it and molding it into a PET chip of a certain shape.

In the forming process, as shown in the figure, the PET melt discharged from the filter 5 is circulated by the pelletizer 6 under the conditions of a die plate temperature of 320° C. and a blade rotation speed of 3200 RPM in 90° C. water with a diameter of 2.8 mm. It consists of cutting and molding into spherical PET chips.

g) according to the invention. The recycling PET chip manufacturing process uses the residual heat of the PET chip manufactured in the molding process to crystallize the surface of the PET chip to produce a high-purity recycled PET chip having an intrinsic viscosity (IV) of 0.72 to 0.90 dl/g, Since the PET chip manufactured in the molding process must have residual heat of 140° C. or higher for surface crystallization, the temperature conditions of the molding process must be appropriately controlled for crystallization.

In the recycling PET chip manufacturing process, as shown in the figure, the PET chip molded into a chip shape passes through an inline crystallizer 7 equipped with a vibrating conveyor while staying for about 15 minutes. It has a crystallinity of 40% or more. .

The reason for crystallizing the surface of the recycled PET chip is that energy can be saved by omitting the surface crystallization, which is essential when drying PET at a customer company that uses the PET chip as a final raw material.

If the raw materials that have not been crystallized on the surface are dried immediately, the raw materials become agglomerated, making it impossible to transport or input the raw materials, so the drying process is essential.

As described above, the method for manufacturing high-viscosity recycled PET chips using low-viscosity recycled PET flakes according to the present invention is a solid-state polymerization reaction that consumes a lot of energy from low-grade recycled PET with low intrinsic viscosity (IV) (0.70dl/g). It can be seen that it is an industrially very advantageous invention because it is possible to manufacture a recycled PET chip with high intrinsic viscosity (0.72 to 0.90 dl/g) suitable for the production of high value-added products without it.

In addition, in the method for manufacturing high-viscosity recycled PET chips using low-viscosity recycled PET bottle flakes according to the present invention, the mixing ratio of the second thickener in the extrusion process is appropriately adjusted with respect to the first thickener blend in the pre-drying process. It has the advantage of being able to manufacture a recycled PET chip having an intrinsic viscosity (IV) suitable for manufacturing.

Claims (6)

a). A grinding process to obtain 3 ~ 5 mm PET flakes by grinding recycled PET with an intrinsic viscosity (IV) of 0.70 dl/g;
b). A transparent flake sorting process of sorting transparent PET flakes by an optical flake sorter from the pulverized PET flakes of the pulverization process;
c). In the transparent PET flakes selected in the screening process, 0.25 to 0.75 wt% of a carbodiimide-based thickener as the first thickener is blended based on the total weight of the PET reaction mixture, and when the moisture content reaches 1000 ppm while heating at 120 to 140 ° C. A pre-drying process to obtain a PET reaction mixture by drying for a certain period of time until
d). After the preliminary drying process, the PET reaction mixture is heated to 160 ~ 170 ℃ for a certain period of time to dehumidify the moisture content to less than 50ppm to obtain a PET dried product;
e). Mix 0.1 to 0.75 wt% of an oxazoline-based thickener as a second thickener based on the total weight of the PET melt in the PET dried material in the dehumidification process, and melt extrusion at a melting temperature of 275 to 280°C and a maximum melt pressure of 110 bar. Then, an extrusion process to obtain a high-purity PET melt by separating foreign substances from the extrusion melt;
f). A molding process of cutting the PET melt of the extrusion process to a certain diameter and molding it into a PET chip of a certain shape;
g). Recycling PET chip manufacturing process for producing PET chips with intrinsic viscosity (IV) of 0.72 to 0.90 dl/g and high purity by crystallizing the surface using residual heat of PET chips while staying for a certain period of time A method of manufacturing high-viscosity recycled PET chips using low-viscosity recycled PET flakes. The method according to claim 1, wherein, in the sorting process, only transparent PET flakes are selected by employing a NIR CCD camera as an optical flake sorter. delete delete The low point of claim 2, wherein the molding process is performed by cutting and molding a spherical PET chip having a diameter of 2.8 mm in circulating water at 90°C, while controlling the PET chip to retain residual heat of 140°C or higher. A method for manufacturing high-viscosity recycled PET chips using recycled PET flakes. The high-viscosity recycled PET using low-viscosity recycled PET flakes according to claim 5, wherein the recycling PET chip manufacturing process crystallizes the surface of the PET chip while staying for a certain time using residual heat of the spherical PET chip manufactured in the molding process. Chip manufacturing method.

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