KR101306580B1 - Manufacturing method of recycled low melting polyester using waste low melting polyester - Google Patents

Abstract

The present invention depolymerized waste low melting polyester (WLMPET) using ethylene glycol as a depolymerization catalyst to produce bis-2-hydroxyethyl terephthalate (BHET) as an intermediate, and produced bis-2. Waste low-melting polyesters are subjected to polycondensation of hydroxyethyl terephthalate (BHET) to yield recycled low melting polyesters (RLMPET) with the same or similar properties of the new low melting polyesters. The present invention relates to a method for producing a regenerated low-melting polyester used, wherein the waste low-melting polyester is depolymerized with bis-2-hydroxyethyl terephthalate (BHET), and then the bis-2-hydroxyethyl terephthalate is condensed. In the method for producing a regenerated low melting polyester for producing a regenerated low melting polyester, (1) the waste low melting polyester Mixing step of mixing and; (ethylene glycol EG) to give a first mixture President and ethylene glycol as solvent; (2) a melting step of melting the waste low melting polyester in the first mixture; (3) depolymerization of the molten first mixture to produce bis-2-hydroxyethyl terephthalate (BHET); And (4) condensation polymerization step of condensation polymerization of the bis-2-hydroxyethyl terephthalate.

Description

Manufacturing Method of Regenerated Low Melting Polyester Using Waste Low Melting Point Polyester {MANUFACTURING METHOD OF RECYCLED LOW MELTING POLYESTER USING WASTE LOW MELTING POLYESTER}

The present invention depolymerized waste low melting polyester (WLMPET) using ethylene glycol as a depolymerization catalyst to produce bis-2-hydroxyethyl terephthalate (BHET) as an intermediate, and produced bis-2. Waste low-melting polyesters are subjected to polycondensation of hydroxyethyl terephthalate (BHET) to yield recycled low melting polyesters (RLMPET) with the same or similar properties of the new low melting polyesters. It relates to a method for producing a regenerated low melting polyester used.

As incomes rise and living standards rise, the amount of waste generated increases, causing serious environmental pollution. In particular, waste synthetic resins account for about 15% of household waste, but many of them are foam-molded or hollow-molded, and they occupy even more volume. There are disadvantages.

As part of environmentally-friendly policies, the use of degradable resins such as photodegradable resins and biodegradable resins is gradually increasing. However, photodegradable resins do not show the degrading effect when they are buried in the ground, and biodegradable resins have difficulty in generalization because they are 5 to 10 times more expensive than ordinary synthetic resins. This was not good and there was a limit to using it industrially.

Therefore, in terms of environmental protection and recycling of resources, there is increasing interest in recycling waste synthetic resins rather than using degradable resins. In the case of advanced foreign countries, studies on recovery and recycling of useful resources from wastes under long-term planning have been pursued in many ways. In Korea, public awareness of environmental pollution has begun to emerge, and an economic recovery and recycling plan has been established, and related research is progressing.

Among general synthetic resins, polyester is the most widely used synthetic resin in fibers, films, food containers, etc., and waste polyester generated during the manufacture of the above-mentioned articles, ie, fibers, films, food containers, etc. The recycling of waste such as waste polyester such as drinking water bottles is a big concern.

Solidified polyesters are thermally unstable, so it is almost impossible to reuse them after melting at temperatures above the melting point, so wastes must be recovered at lower temperatures. Waste polyesters are recovered by terephthalic acid (TPA), dimethyl terephthalate (DMT) and ethylene glycol (ethlyene glycol: EG), which are used as raw materials through depolymerization. And a method for preparing an intermediate product bis-2-hydroxyethyl terephthalate (BHET).

Among these methods, the method of recovering terephthalic acid, dimethyl terephthalate and ethylene glycol recovers terephthalic acid, dimethyl terephthalate and ethylene glycol by depolymerizing waste polyester, which is complicated and takes a long time to produce The method of producing recycled polyester using terephthalate and ethylene glycol has a disadvantage in that the procedure is complicated and takes a long time, compared to the method of producing recycled polyester with an intermediate product bis-2-hydroxyethyl terephthalate. have. Therefore, a method for producing regenerated polyester recovering the intermediate bis-2-hydroxyethyl terephthalate has been developed, but the regenerated polyester prepared from the recovered bis-2-hydroxyethyl terephthalate is recovered terephthalic acid, There was a problem that the physical properties or color is lower than the recycled polyester made of dimethyl terephthalate and ethylene glycol.

On the other hand, general synthetic fibers, in particular polyester fibers have a high melting point is rarely limited in use. In particular, when the fiber fabric itself is used as a wick or the like, and is used as an adhesive that is interposed between a tape-like fabric and press-bonded, the textile fabric itself may be thermally deteriorated by heating, and special equipment such as a high frequency sewing machine may be used. Because of the hassle that must be used, it is desired to adhere easily by a conventional simple hot press without using such special equipment.

Conventional low melting polyester short fibers have been widely used as hot melt binder fibers for the purpose of bonding different types of fibers in mutual fiber structures used in manufacturing mattresses, interior materials for automobiles, or various nonwoven fabrics. .

Therefore, the demand for low melting point in polyester resin is high and it is used for binder fiber, an adhesive agent, etc. Generally, copolymerized polyester is used for such a use.

For example, Japanese Patent Application Laid-open No. Hei 10-298271 uses adipic acid instead of terephthalic acid in the polymerization manufacturing process to improve crystallinity and heat resistance, and uses 1,4- as a diol component instead of ethylene glycol. Butanediol (BD) improves adhesiveness and provides fibers with low fiber strength even at high temperatures, but low melting point polyesters made using adipic acid have a melting point of less than 150 ° C. There was a problem in that it is difficult to prepare a polyester so that low melting point polyester of lower melting point cannot be prepared.

The present invention has been invented to solve the above problems, and the waste polyester is discarded, in particular, the waste low-melting point polyester during the production or cutting or other manufacturing process in the production line for producing a polyester product is collected To recover good quality bis-2-hydroxyethyl terephthalate through depolymerization, and use the recovered bis-2-hydroxyethyl terephthalate to obtain the same or similar physical properties It is an object of the present invention to provide a method for producing regenerated low melting polyester using waste low melting polyester to obtain a regenerated low melting polyester having.

Another object of the present invention is to provide a newly produced low melting point polyester produced by a general manufacturing method and a regenerated low melting point polyester having no difference in physical properties.

According to one embodiment of the invention, the depolymerized waste low-melting polyester with bis-2-hydroxyethyl terephthalate (BHET), and then polycondensing the bis-2-hydroxyethyl terephthalate to regenerate low melting point A method for producing a regenerated low melting point polyester for producing a polyester, comprising: (1) a mixing step of mixing a waste low melting point polyester with ethylene glycol (EG) as a catalyst and a solvent to obtain a first mixture; (2) a melting step of melting the waste low melting polyester in the first mixture; (3) depolymerization of the molten first mixture to produce bis-2-hydroxyethyl terephthalate (BHET); And (4) a condensation polymerization step of condensation polymerization of the bis-2-hydroxyethyl terephthalate. Provided is a method for producing a recycled low melting polyester using waste low melting polyester.

In the mixing step, the first mixture may be made by mixing the waste low melting point polyester and ethylene glycol (EG) in a molar ratio of 1.0: 0.1 to 2.0.

The depolymerization step is a temperature of 225 to 260 ° C. for 50 to 119 minutes while stirring the molten first mixture in a nitrogen gas atmosphere under a pressure of 2.0 to 2.5 kg / cm 2 at a speed of 30 to 70 rpm. Heating to a range.

The condensation polymerization step may be performed by heating the bis-2-hydroxyethyl terephthalate to a temperature range of 245 to 290 ° C. for 60 to 240 minutes while stirring at 30 to 90 rpm in a vacuum state.

According to another embodiment of the present invention, there is provided a regenerated low melting polyester, which is prepared according to the method for producing a regenerated low melting polyester.

According to the present invention, high-quality bis-2-hydroxyethyl terephthalate is recovered through depolymerization by collecting waste low melting point polyester generated in the production line for producing polyester products and during the cutting or other manufacturing process. And by using the recovered bis-2-hydroxyethyl terephthalate, it is possible to prepare a regenerated low melting point polyester having the same or similar physical properties of the new low melting point polyester through a condensation polymerization reaction, the regenerated low melting point poly Ester has excellent physical properties that are inferior to general new low melting point polyester, and thus can be used in various industrial fields.

In addition, by recycling waste low-melting polyester, which was difficult to dispose, there is an effect of saving resources and protecting the environment.

Hereinafter, preferred embodiments of the present invention will be described in detail. In describing the present invention, detailed descriptions of related well-known functions or configurations are omitted in order not to obscure the subject matter of the present invention.

The terms " about ", " substantially ", etc. used to the extent that they are used herein are intended to be taken to mean an approximation to or in the numerical value of the manufacturing and material tolerances inherent in the meanings mentioned, Accurate or absolute numbers are used to help prevent unauthorized exploitation by unauthorized intruders of the referenced disclosure.

Chemically recyclable polyesters include hydrolysis, which uses water to reduce monomers or oligomers, glycols such as ethylene glycol (EG) and propylene glycol (PG). And glycolysis using methanol, methanolysis using methanol, and the like.

Glycol glycolysis can be carried out in a batch or continuous process, is less expensive than methanolysis or hydrolysis, and can be applied to more applications than remelt injection.

Therefore, the present invention recovers bis-2-hydroxyethyl terephthalate (BHET) by depolymerizing waste low melting point polyester by glycolysis using ethylene glycol, and then condensation polymerization. A method for obtaining a regenerated low melting polyester.

In the method for producing regenerated low melting polyester using waste low melting polyester according to the present invention, after depolymerizing the waste low melting polyester with bis-2-hydroxyethyl terephthalate (BHET), the bis-2-hydrate In the method for producing a regenerated low melting polyester, which is polycondensation of oxyethyl terephthalate to produce a regenerated low melting polyester, (1) mixing a waste low melting polyester with ethylene glycol (EG; ethylene glycol) as a catalyst and a solvent Mixing to obtain a first mixture; (2) a melting step of melting the waste low melting polyester in the first mixture; (3) depolymerization of the molten first mixture to produce bis-2-hydroxyethyl terephthalate (BHET); And (4) condensation polymerization step of condensation polymerization of the bis-2-hydroxyethyl terephthalate.

The mixing step of (1) consists of mixing the waste low melting polyester with ethylene glycol as a catalyst and solvent to obtain a first mixture. The waste low melting point polyester is a metal waste, a synthetic resin of different components, etc. is removed from the collected waste low melting point polyester, and pulverized to a size in the range of 1 to 20 mm using a pulverizer. The low melting point waste polyester may be finely ground to a size in the range of 1 to 5 mm to be easily melted, but the present invention is not limited to the shape as described above or the range of the size as described above.

The melting step of (2) consists of allowing the waste low melting point polyester in the first mixture to react well with ethylene glycol as a catalyst and solvent as described above to promote depolymerization.

The depolymerization step of (3) consists of depolymerizing the molten first mixture to produce bis-2-hydroxyethyl terephthalate (BHET).

In the depolymerization step, the ethylene glycol decomposes the low melting polyester into bis-2-hydroxyethyl terephthalate by depolymerization by transesterification with the waste low melting polyester. The reaction rate of the depolymerization of the present invention depends on the temperature, catalyst, feedstock granularity and the amount of glycol. The composition of the final monomer is determined by the decomposition reaction time and the duration after depolymerization. Lower amounts of glycol require higher temperatures and longer reaction times, resulting in higher molecular weight oligomers.

In the depolymerization, the first mixture formed by mixing the waste low melting point polyester and ethylene glycol (EG) in a molar ratio of 1.0: 0.1 to 2.0 is pressurized to 1.5 to 2.5 kg / cm 2 using nitrogen (N ₂ ) gas, Melt for 3 to 4 hours while stirring at 210 to 240 ℃ at a rate of 10 to 50 rpm, pressurized to 2.0 to 2.5 kg / ㎠ using nitrogen gas, while stirring at a speed of 30 to 70 rpm at 225 to 260 ℃ Depolymerization for 50 to 119 minutes, preferably 100 to 140 minutes.

The mixing ratio of the waste low-melting polyester and ethylene glycol may have a problem that the reaction time is too long when ethylene glycol is mixed with less than 0.1 mol with respect to 1 mol of the waste low-melting polyester, on the contrary, exceeds 2.0 mol In this case, the amount of waste low-melting polyester administered to the depolymerization in the reaction container having a limited volume is reduced, resulting in low productivity, and relatively excessive energy is required for the depolymerization of the same amount of waste low-melting polyester. There may be a problem.

The mixed waste low melting point polyester and ethylene glycol (EG) are pressurized to 1.5 to 2.5 kg / cm 2 using nitrogen (N ₂ ) gas and the low melting point polyester starts melting at about 210 ° C. by continuous heating. When the temperature is continuously increased to 230 to 240 ° C., the temperature rise is slowed and the melting proceeds actively. When the melting proceeds to some extent, the mixture is stirred at 10 to 50 rpm to prevent the carbonization of the compound by concentrating thermal energy in one place.

After the melting time of the waste low melting polyester and ethylene glycol (EG) is about 3 to 4 hours, the melting is completed, after the melting of the waste low melting polyester is completed, using nitrogen gas 2.0 to 2.5 Pressurized at kg / cm 2, the stirring speed was raised to 20 to 60 rpm, and the temperature was raised to 225 to 260 ° C. to promote depolymerization of the waste low melting polyesters through the transesterification reaction of ethylene glycol under the catalyst of ethylene glycol. To produce bis-2-hydroxyethylterephthalate.

In the depolymerization process, the transesterification reaction is completed within a time range of about 50 to 119 minutes, so that the waste polyester is lost and only bis-2-hydroxyethyl terephthalate remains. The depolymerization process is most preferably performed for 60 to 90 minutes at 56 rpm at 255 ℃.

After the depolymerization step, a bis-2-hydroxyethyl terephthalate produced in the depolymerization step may be further filtered to remove the foreign matter. The filtering process is a process of removing bis-2-hydroxyethyl terephthalate generated by the depolymerization process through a filter to remove bis-2-hydroxyethyl terephthalate and removing bis-2-hydroxyethyl terephthalate after the filtering process. It is a process for reducing the productivity and the defective rate of the regenerated low melting polyester in the polycondensation step carried out. In the filtering process, the filter preferably uses a filter of about 300 to 1500 mesh, and may be pressurized to 1.5 to 3.0 kg / cm 2 to shorten the filtering process time, but the present invention is not limited thereto. It will be appreciated by those skilled in the art that the selection of an appropriate filter and the appropriate degree of pressurization can be selected in view of the source of the waste low melting point polyester and the degree of contamination of the waste low melting point polyester.

Bis-2-hydroxyethyl terephthalate can be obtained by the above depolymerization method according to the present invention as described above, and the bis-2-hydroxyethyl terephthalate is condensation-polymerized with polyester again to reduce regeneration. Melting point polyester can be obtained.

The condensation polymerization step of (4) comprises condensation polymerization of bis-2-hydroxyethyl terephthalate obtained in the depolymerization step. The polycondensation step is to produce a low melting point polyester with the bis-2-hydroxyethyl terephthalate. The bis-2-hydroxyethyl terephthalate may be vacuumed in the same or similar manner to a general polyester manufacturing step. 1 torr or less) mixed with ethylene glycol (EG) (mixing ratio (molar ratio) is a raw material PET: EG = 1: 0.25) while stirring the mixture at 30 to 90 rpm at a temperature range of 245 to 290 ℃ for 60 to 240 minutes It may consist of heating. At this time, the production of low-melting polyester is the waste polyester used as the raw material used in the depolymerization step as low-melting polyester to lower the melting point of the polyester and prevent the crystallization, for example, polyethylene glycol, etc. Due to the presence of such additives as polyethylene glycol, the regenerated polyester is also obtained as a low melting regenerated polyester, that is, a regenerated low melting point polyester.

The vacuum may be controlled to be 1.5 mbar or less at about 285 ° C. by stepwise as the condensation polymerization process starts and the temperature rises.

In the condensation polymerization process, antimony oxide (Sb ₂ O ₃ ), titanium oxide, dibutyl tin dilaurate, etc. may be used as the condensation catalyst, and antimony oxide may be preferably used. The antimony oxide may be used in an amount of 50 to 600 ppm based on the total amount of bis-2-hydroxyethyl terephthalate. When the amount of the antimony oxide used as the polycondensation catalyst is less than 50 ppm based on the total amount of bis-2-hydroxyethyl terephthalate, there may be a problem that the reaction rate is significantly lowered, on the contrary, exceeds 600 ppm. In this case, the reaction rate is too fast to increase the molecular weight distribution, and also may cause problems such as increasing the pack pressure by acting as a foreign material during spinning.

In addition, the condensation polymerization step may be performed by adding a thermal stabilizer to the bis-2-hydroxyethyl terephthalate. As the heat stabilizer, phosphoric acid (H ₃ PO ₄ ) may be preferably used. The thermal stabilizer is added for the thermal stability of the bis-2-hydroxyethyl terephthalate. The phosphoric acid may be used in an amount of 100 to 400 ppm based on the total amount of bis-2-hydroxyethyl terephthalate. When the amount of the phosphoric acid used as the thermal stabilizer is less than 100 ppm based on the total amount of bis-2-hydroxyethyl terephthalate, there may be a problem that the heat resistance of the final polymer is lowered, and in contrast, it exceeds 400 ppm. In this case, there may be a problem that acts as a foreign material during spinning to increase the pack pressure, and lower the reaction activity of the catalyst.

In the condensation polymerization step, titanium dioxide (TiO ₂ ) or silicon dioxide (SiO ₂ ) may be further added as a quencher in an amount of 0.01 to 3% by weight based on the total amount of bis-2-hydroxyethyl terephthalate.

According to the present invention, after the condensation polymerization step, a post-processing step such as a chip manufacturing step may be further included. The chip manufacturing step is a process of manufacturing a chip to facilitate the use of the recycled polyester produced by the polycondensation process, the size of the chip can be produced in a variety of sizes depending on the industrial field used, the production and Control of the size and shape of the chip, etc. will be readily understood by those skilled in the art.

A regenerated low melting point polyester is provided by the method for producing a regenerated low melting point polyester using the waste low melting point polyester according to the present invention as described above. The regenerated low melting point polyester has physical properties of intrinsic viscosity (IV) of 0.65 to 0.70 dl / g and a softening point of 140 to 160 ° C., and the regenerated low melting point polyester (in the form of a chip) has a color of L * of 40 to 60, b * Is 3 to 8, and it is possible to make polyester products of excellent physical properties with moisture content of 1 wt% or less. However, it can be understood by those skilled in the art that the intrinsic viscosity of the regenerated low melting polyester can be arbitrarily adjusted according to the degree of polymerization as in the case of the new low melting polyester.

Examples of the method for producing the regenerated low melting polyester fibers of the present invention are shown below, but not limited thereto.

Example  One

Waste low-melting polyesters include 598.0 kg (1 mole) of terephthalic acid, 256.0 kg (1 mole) of isophthalic acid, 403.3 kg (2.72 mole) of ethylene glycol and polyethylene glycol based on 1 ton of synthesized polyester (PET) The reaction mixture mixed with -4000 8.7 kg was subjected to esterification for 3.5 hours (210 minutes) at a reaction temperature of about 230 ° C. and a reaction pressure of about 2 kgf / cm 2. What was obtained by condensation polymerization for 3.5 hours (210 minutes) under a reaction temperature of 270 ° C. and a vacuum of less than 1 Torr was used. At this time, the additives include 150 ppm of phosphoric acid (H ₃ PO ₄ ) as a thermal stabilizer on the basis of 1 ton of PET produced, tin oxide (Sb ₂ O ₃ ) as a condensation catalyst in an amount of 300 ppm, and complementary colors. Cobalt acetate (Co (CH ₃ CO ₂ ) ₂ ) was used as an amount in an amount of 15 ppm, respectively.

The waste low melting polyester is pulverized to have an average size of 2.5 mm, and the pulverized waste low melting polyester and ethylene glycol (EG) are mixed in a molar ratio of 1.0: 0.25, using 2.0 kg of nitrogen gas. Pressurized to / cm 2 and stirred at a speed of 18 rpm at about 235 ° C continuously heated for about 2 hours until the waste low melting polyester is completely melted.

The molten mixture was pressurized to 2.5 kg / cm 2 using nitrogen gas, continuously heated to 255 ° C., and depolymerized with stirring at a speed of 56 rpm to obtain bis-2-hydroxyethyl terephthalate in oligomer form. The bis-2-hydroxyethyl terephthalate (BHET) is mixed with 0.25 mol of ethylene glycol on the basis of 1 mol of PET, continuously heated in a vacuum to raise to about 280 ℃, stirring at 60 rpm, 3.5 hours ( 210 minutes) to polycondensation to produce a regenerated low melting polyester, which was produced as a regenerated low melting polyester chip.

Table 1 shows the results of the component analysis and physical properties of the obtained regenerated low melting polyester and the low melting polyester as a new material. Here, the component analysis was carried out by nuclear magnetic resonance spectroscopy (NMR), where isophthalic acid is the mole percent of diacid added during PET polymerization, and diethylene glycol and polyethylene glycol respectively determine the total weight of PET. It is expressed in weight percent as a reference. In addition, physical and color experiments were performed as follows.

* Property and color experiment

The regenerated low melting polyester chip produced in Example 1 was measured by a conventional method such as glass transition temperature (Tg), softening point (℃), the color of the regenerated polyester chip is ASTM E398-90 The values of L * and b * were measured in the method of E805-93.

As a control, the physical properties and colors of the new low melting point polyester fiber chips (Comparative Example 1) were measured in the same manner as described above.

The measured values are shown in Table 1 below.

division IPA DEG PEG Tg
(℃) Softening point
(℃) Hue L Hue b Example 1 28.1 1.6 0.8 65.3 150 53.4 2.5 Comparative Example 1 27.8 2.3 0.7 66.4 150 45.2 5.2

As shown in Table 1, there is no significant difference in the content of IPA, DEG, PEG between the regenerated low melting polyester (Example 1) and the new low melting polyester (Comparative Example 1) according to the present invention in the component analysis results Appeared. These components are formulated as the main components exhibiting low melting point properties in the production of low melting point polyesters, and the regenerated low melting point polyester according to the present invention is characterized in that It is considered that it shows low melting point characteristics similar to that of new low-melting polyester, and the measurement results of glass transition temperature (Tg) and softening point (° C) also support this. Also, no significant difference was found in the experimental results of the color tone.

Therefore, it was confirmed that the waste low melting point polyester was depolymerized once, and then polycondensed again to be regenerated into a low melting point polyester to be used without difference from new materials.

The present invention can be used in the industry of producing and processing low melting point polyester, and can be used in the industry using such low melting point polyester.

Claims (5)

Regenerated low melting polyester which depolymerizes waste low melting point polyester with bis-2-hydroxyethyl terephthalate (BHET), and then polycondenses the bis-2-hydroxyethyl terephthalate to produce regenerated low melting point polyester. In the manufacturing method of
(1) a mixing step of mixing the waste low melting polyester with ethylene glycol (EG) as a catalyst and a solvent to obtain a first mixture;
(2) a melting step of melting the waste low melting polyester in the first mixture;
(3) depolymerization of the molten first mixture to produce bis-2-hydroxyethyl terephthalate (BHET); And
(4) condensation polymerization step of condensation polymerization of the bis-2-hydroxyethyl terephthalate;
Characterized by made, including;
In the mixing step, the first mixture is mixed with the waste low melting point polyester and ethylene glycol (EG) in a molar ratio of 1.0: 0.1 to 2.0,
The temperature of 225 to 260 ° C. for 50 to 119 minutes while stirring the first mixture melted in the depolymerization step in a nitrogen gas atmosphere under a pressure of 2.0 to 2.5 kg / cm 2 at a speed of 30 to 70 rpm. Consisting of heating to the range,
Wherein the condensation polymerization step comprises heating the bis-2-hydroxyethyl terephthalate to a temperature range of 245 to 290 ° C. for 60 to 240 minutes while stirring at 30 to 90 rpm in a vacuum state,
The regenerated low melting polyester prepared by the manufacturing method has physical properties of intrinsic viscosity (IV) 0.65 to 0.70 dl / g, softening point 140 to 160 ° C, and the regenerated low melting polyester (form of chip) has a color of L * 40-60, b * is 3-8, and the manufacturing method of the regenerated low melting polyester using the waste low melting polyester whose moisture content is 1 wt% or less.
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