KR20120128480A - Recycled polyester using waste polyester and manufacturing method thereof - Google Patents

Abstract

PURPOSE: A manufacturing method of recycled polyester using waste polyester is provided to increase productivity of recycled polyester and to improve physical properties such as color of recycled polyester by reducing time for depolymerization. CONSTITUTION: A depolymerizing method of waste polyester flakes to bis-2-hydroxethylterephthalate comprises: a step of obtaining a primary mixture by mixing waste polyester flake with ethylene glycol as a solvent and catalyst; a step of melting the waste polyester flake in the primary mixture; and a step of generating bis-2-hydroxyethylterephthalate by adding zinc acetate as a catalyst into the melt primary mixture and depolymerizing the same.

Description

Recycled polyester using waste polyester and manufacturing method thereof {RECYCLED POLYESTER USING WASTE POLYESTER AND MANUFACTURING METHOD THEREOF}

The present invention depolymerized waste polyester using ethylene glycol and zinc acetate as depolymerization catalyst to produce bis-2-hydroxyethyl terephthalate (BHET) as an intermediate, and produced bis-2-hydroxy. The present invention relates to a recycled polyester using waste polyester and a method for producing the same, wherein the ethyl terephthalate (BHET) is condensed again to obtain a recycled polyester having the same or similar physical properties of the new polyester.

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 much more volume.Incineration generates various harmful gases, which cause smog, and they do not decompose even when landfilled. 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 advanced foreign countries, research on the recovery and recycling of useful resources from wastes has already been carried out in a number of ways with long-term planning. Public opinion on environmental pollution has begun to emerge in Korea, and a plan for economic recovery and recycling of waste resources has been established, and related research is being progressed.

Among general synthetic resins, polyester is the most widely used synthetic resin in fibers, films, food containers, etc., and waste polyester generated during the manufacturing 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. The waste polyester is recovered by terephthalic acid (TPA), dimethyl terephthalate (DMT) and ethylene glycol (ethlyene glycol: EG), which are raw materials through depolymerization using waste polyester as a catalyst. 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, and recovers terephthalic acid, dimethyl. 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.

In addition, in general, the depolymerization is carried out by mixing the melted polyester with ethylene glycol to melt the depolymerization, but the conventional depolymerization using the ethylene glycol as a catalyst and solvent is required to depolymerize (about 2 hours or more) As a result, the productivity is lowered, and there is a problem of deterioration of color due to long depolymerization.

The present invention has been invented to solve the above problems, by collecting the discarded waste polyester to recover the good bis-2-hydroxyethyl terephthalate from the waste polyester through depolymerization, recovered Bis-2 -By using hydroxyethyl terephthalate to produce regenerated polyester through polycondensation reaction, the time required for depolymerization can be shortened to increase productivity of regenerated polyester and to improve physical properties such as color of regenerated polyester. It is an object of the present invention to provide a recycled polyester using a waste polyester that can be designed and a method for producing the same.

It is also an object of the present invention to provide a newly produced polyester produced by a general production method and a recycled polyester having no difference in physical properties and a method for producing the same.

According to one embodiment of the present invention, in the depolymerization method of depolymerizing waste polyester flakes with bis-2-hydroxyethyl terephthalate (BHET), (1) ethylene glycol as a catalyst and solvent ( EG; mixing with ethylene glycol) to obtain a first mixture; (2) a melting step of melting the waste polyester flakes in the first mixture; And (3) depolymerization by adding zinc acetate as a catalyst to the melted first mixture to depolymerize to produce bis-2-hydroxyethyl terephthalate (BHET). Depolymerization method is provided.

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

The melting step may consist of heating the first mixture melted in a nitrogen gas atmosphere under a pressure of 1.5 to 2.5kg / ㎠ at a temperature of 210 to 240 ℃ for 3 to 4 hours while stirring at a rate of 10 to 50rpm have.

In the depolymerization step, the zinc acetate may be used in an amount of 50 to 200 ppm based on 1 kg of the waste polyester flakes.

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.

After the depolymerization step, a bis-2-hydroxyethyl terephthalate produced in the depolymerization step may be further filtered to remove the foreign matter.

According to another embodiment of the present invention, depolymerized waste polyester flakes with bis-2-hydroxyethyl terephthalate (BHET), followed by polycondensation of the bis-2-hydroxyethyl terephthalate to regenerated polyester. In the method of producing a regenerated polyester, (1) mixing the waste polyester flakes with ethylene glycol (EG; ethylene glycol) as a catalyst and a solvent to obtain a first mixture; (2) a melting step of melting the waste polyester flakes in the first mixture; (3) depolymerization by adding zinc acetate as a catalyst to the melted first mixture and depolymerizing to produce bis-2-hydroxyethyl terephthalate (BHET); And (4) polycondensation step of polycondensing the bis-2-hydroxyethyl terephthalate. Provided is a method for producing recycled polyester using waste polyester, characterized in that it comprises a.

The polycondensation step may be performed by heating the bis-2-hydroxyethyl terephthalate at 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 polycondensation step may be performed by adding a polycondensation catalyst to the bis-2-hydroxyethyl terephthalate.

Antimony oxide (Sb ₂ O ₃ ) may be used as the polycondensation catalyst.

The antimony oxide may be used in an amount of 50 to 600 ppm based on 1 kg of the waste polyester flakes.

In the polycondensation step, a heat stabilizer may be added to the bis-2-hydroxyethyl terephthalate.

Phosphoric acid (H ₃ PO ₄ ) may be used as the heat stabilizer.

The phosphoric acid may be used in an amount of 100 to 400 ppm based on the total amount of bis-2-hydroxyethyl terephthalate.

In the polycondensation 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 another embodiment of the present invention, bis-2-hydroxyethyl terephthalate is prepared according to the above depolymerization method.

The bis-2-hydroxyethyl terephthalate may have a color of Lab in a color scheme of L * of 93.1 to 94.9, and b * of 4.4 to 3.3.

According to another embodiment of the present invention, there is provided a regenerated polyester, characterized in that it is produced according to the method for producing a regenerated polyester.

The regenerated polyester provides a regenerated polyester characterized in that it has physical properties of intrinsic viscosity (IV) 0.65 to 0.70 dl / g, melting point (Tm) 240 to 260 ° C.

The regenerated polyester provides a regenerated polyester, characterized in that the color L * is 40 to 70, b * is 2 to 8.

In addition, the regenerated polyester is characterized in that the moisture content is 1wt% or less.

According to the present invention, it is possible to recover the high quality bis-2-hydroxyethyl terephthalate with good color by enabling depolymerization for a significantly shorter time compared to the conventional depolymerization method of waste polyester. Recycled polyester can be prepared by polycondensing the recovered bis-2-hydroxyethyl terephthalate, and the recycled polyester has excellent physical properties that are inferior to that of general polyester, and thus can be used in various industrial fields. .

In addition, by recycling waste 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 of, or approximation to, the numerical values of 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 polyester by glycolysis using ethylene glycol, followed by polycondensation. It is about how to get it.

The depolymerization method of waste polyester according to the present invention is a depolymerization method of depolymerizing waste polyester flakes with bis-2-hydroxyethyl terephthalate (BHET), wherein (1) ethylene as a catalyst and a solvent Mixing step of obtaining a first mixture by mixing with glycol (EG; ethylene glycol); (2) a melting step of melting the waste polyester flakes in the first mixture; And (3) depolymerization by adding zinc acetate as a catalyst to the melted first mixture to depolymerize to produce bis-2-hydroxyethyl terephthalate (BHET).

The mixing step of (1) consists of mixing the waste polyester flakes with ethylene glycol (EG; ethylene glycol) as a catalyst and a solvent to obtain a first mixture. The waste polyester flakes are those obtained by removing metal components, synthetic resins of different components, etc. from the collected waste polyester, and pulverizing them into flakes having a size in the range of 1 to 20 mm using a grinder or the like. Preferably, the waste polyester flakes may be finely pulverized to a size in the range of 1 to 5 mm to be easily melted, but the present invention is limited to the flake shape as described above or the range of the size of the bar as described above. no.

The melting step of (2) consists of allowing the waste polyester flakes in the first mixture to react well with ethylene glycol as a catalyst and solvent as described above, and also to promote depolymerization by zinc acetate described below.

The depolymerization step of (3) consists of adding zinc acetate as a catalyst to the molten first mixture to depolymerize to produce bis-2-hydroxyethyl terephthalate (BHET).

In the depolymerization step, the ethylene glycol decomposes the polyester into bis-2-hydroxyethyl terephthalate by depolymerization by a transesterification reaction with the waste polyester. The reaction rate of the depolymerization of the present invention depends on the temperature, catalyst, feedstock granularity and the amount of glycol. The final monomer composition is also 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 particular, in the present invention, unlike the conventional depolymerization using only ethylene glycol as a catalyst, by using zinc acetate in addition to ethylene glycol as a catalyst to reduce the time required for depolymerization of the oligomer obtained at the same time to increase the recovery rate of waste polyester It is characterized by one point that improves color.

In the depolymerization, in particular, the first mixture formed by mixing the waste polyester flake and ethylene glycol (EG) in a molar ratio of 1.0: 0.1 to 2.0 was pressurized to 1.5 to 2.5 kg / cm 2 using nitrogen (N ₂ ) gas, 210 After melting for 3 to 4 hours while stirring at a rate of 10 to 50rpm at 240 ℃, zinc acetate was added to the molten first mixture in an amount of 50 to 200ppm based on 1kg of the waste polyester flakes Pressurized at 2.0 to 2.5 kg / cm 2 using nitrogen gas, and depolymerized for 50 to 119 minutes, preferably 60 to 90 minutes, while stirring at a speed of 30 to 70 rpm at 225 to 260 ° C.

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

The mixed waste polyester flakes and ethylene glycol (EG) are pressurized to 1.5 to 2.5 kg / cm 2 using nitrogen (N ₂ ) gas and the continuous polyester flakes start melting at about 210 ° C. by continuous heating. While continuously rising to 230 to 240 ℃ about as the temperature rises slower melting is actively proceeded. 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 polyester flakes and ethylene glycol (EG) is about 3 to 4 hours, the melting is completed, after the melting of the waste polyester flakes is completed, the zinc acetate is added, and nitrogen gas Pressurized to 2.0 to 2.5 kg / cm 2, the stirring speed was increased to 20 to 60 rpm, the temperature was raised to 225 to 260 ° C., and the waste polyester flakes were subjected to transesterification reaction with ethylene glycol under the catalyst of zinc acetate. The depolymerization is promoted to allow bis-2-hydroxyethyl terephthalate to be produced.

In the depolymerization process under the zinc acetate catalyst, 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 ℃.

In the depolymerization step, the zinc acetate may be used in an amount of 50 to 200 ppm based on 1 kg of the waste polyester flakes, and when used in less than 50 ppm, there may be a problem in that it is not sufficient to expect an effect as a catalyst. On the contrary, when it exceeds 200 ppm, the b value (b *) increases rapidly in the color of the obtained bis-2-hydroxyethyl terephthalate and the regenerated polyester produced using the same, resulting in poor color. There may be a problem.

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 a recycled polyester in the polycondensation process performed. 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 understood by those skilled in the art that the selection of an appropriate filter and the appropriate degree of pressurization can be selected in consideration of the source of waste polyester and the degree of contamination of the waste polyester.

Bis-2-hydroxyethyl terephthalate can be obtained by the depolymerization method according to the present invention as described above, wherein the bis-2-hydroxyethyl terephthalate is Lab color system, L * is 93.1 To 94.9, b * may be from 4.4 to 3.3, which is brighter than the depolymerization of conventional waste polyester using only ethylene glycol as catalyst and the color of the regenerated polyester thus obtained (raising L value), And it is closer to yellow (reduction of b value) has the advantage of better in terms of color.

In the method for producing recycled polyester using waste polyester according to the present invention, after depolymerizing waste polyester flakes with bis-2-hydroxyethyl terephthalate (BHET), the bis-2-hydroxyethyl terephthalate is prepared. A method for producing a recycled polyester by polycondensation, the method comprising: (1) mixing a waste polyester flake with ethylene glycol (EG) as a catalyst and solvent to obtain a first mixture; (2) a melting step of melting the waste polyester flakes in the first mixture; (3) depolymerization by adding zinc acetate as a catalyst to the melted first mixture and depolymerizing to produce bis-2-hydroxyethyl terephthalate (BHET); And (4) a polycondensation step of polycondensing the bis-2-hydroxyethyl terephthalate.

The mixing step of (1), the melting step of (2), and the depolymerization step of (3) are the same as or similar to those described above, and thus repeated description will be avoided.

Further, the polycondensation step of (4) consists of polycondensing the bis-2-hydroxyethyl terephthalate obtained in the depolymerization step. The polycondensation step is a step of producing a polyester with the bis-2-hydroxyethyl terephthalate, and the bis-2-hydroxyethyl terephthalate in a vacuum to 30 to the same or similar to the process for producing a general polyester It may consist of heating to a temperature range of 245 to 290 ° C for 60 to 240 minutes while stirring at 90 rpm.

The vacuum state may be adjusted to be about 1.5 mbar or less at about 285 ° C. by performing the step as the polycondensation process starts and the temperature rises.

In the polycondensation process, antimony oxide (Sb ₂ O ₃ ), titanium oxide, dibutyl tin dilaurate and the like 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 polycondensation 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 polycondensation 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 polycondensation 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 various sizes according to 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.

The recycled polyester is provided by the method for producing recycled polyester using waste polyester according to the present invention as described above. The regenerated polyester has physical properties of intrinsic viscosity (IV) 0.65 to 0.70 dl / g, melting point (Tm) of 240 to 260 ° C, and the regenerated polyester (shape of chip) has a color of L * of 40 to 70, b * Is 2 to 8, and a moisture product of 1 wt% or less can make a polyester product of excellent physical properties. However, it can be understood by those skilled in the art that the intrinsic viscosity of the regenerated polyester can be arbitrarily adjusted according to the progress of the polymerization as in the case of the new polyester.

Examples of the method for producing the recycled polyester fiber of the present invention are shown below, but not limited thereto.

Comparative example  One

The collected waste polyesters are sorted to have an average size of 2.5 mm and pulverized into flakes. The pulverized waste flakes and ethylene glycol (EG) are mixed in a molar ratio of 1.0: 0.25, and nitrogen gas is used. And pressurized to 2.0 kg / cm 2, and stirred at a rate of 18 rpm at about 235 ° C. to continue heating for about 2 hours until the spent polyester flakes were 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 degree of polymerization of the oligomers according to the results of depolymerization was measured and shown in Table 1 below. The degree of polymerization of the oligomer was calculated by quantitative analysis of the hydroxyl group (OH group) at the terminal of bis-2-hydroxyethyl terephthalate. Depolymerization time was measured as the time to complete the depolymerization process when the temperature rises in the mixed melting process.

Example  1 to 3

50 ppm (Example 1), 100 ppm (Example 2) and 200 ppm (Example 3) of zinc acetate as a depolymerization catalyst after the waste polyester flakes were melted in Comparative Example 1 based on 1 kg of the waste polyester flakes. Bis-2-hydroxyethyl terephthalate was obtained in the form of oligomer by the same procedure as in Comparative Example 1 except that the amount was added in the amount of. The polymerization degree of the oligomer according to the result of depolymerization was measured and shown in Table 1 below. It was.

Classification (Amount of Catalyst (ppm)) Depolymerization time (hours) Oligomeric Polymerization Degree Comparative Example 1 (0 ppm) 2 4.4 Example 1 (50 ppm) One 4.1 Example 2 (100 ppm) One 3.9 Example 3 (200 ppm) One 4.2 The amount of catalyst means an amount added based on 1 kg of waste polyester flakes.
Zinc acetate is used as a catalyst.

As shown in Table 1, Examples 1 to 3 to which zinc acetate was added as a depolymerization catalyst according to the present invention are depolymerized to a similar level even by depolymerization of a much shorter time (about 1/2 level) than Comparative Example 1. I could confirm that.

Example  4 to 5

As shown in Table 2, except that different depolymerization time (Example 2 is 1 hour, Example 4 is 1.5 hours, Example 5 is 2 hours) was carried out in the same manner as in Example 2 2-hydroxyethyl terephthalate was obtained in the form of oligomer, and the degree of polymerization of the oligomer according to the result of depolymerization was measured and shown in Table 2 below. In addition, the color tone measurement results (including Comparative Example 1) according to the Lab color system are shown together in Table 2 below. The color was measured by measuring the values of L * and b * in accordance with ASTM E398-90 and E805-93.

division Depolymerization time
(time) Oligomer
Degree of polymerization Hue L Tint b Comparative Example 1 2 4.4 93 4.5 Example 2 One 3.9 94.5 3.4 Example 4 1.5 4.7 94.2 3.5 Example 5 2 4.6 94.1 3.8  Zinc acetate is used as a catalyst.

As shown in Table 2, when zinc acetate was added as the depolymerization catalyst according to the present invention, it was confirmed that depolymerization did not occur particularly even if the depolymerization time was prolonged. It was confirmed that the increase (a difference of significance is not considered), which may be attributed to the promotion of the reverse reaction as well as the forward reaction by lowering the activation energy of the reaction can be seen in the characteristics of the general catalyst. In addition, it was confirmed that the color tone also became brighter with a shorter time (L component, but it was judged to have little difference), and closer to lighter yellow (b component, but judged to have little difference).

Example  6

As shown in Table 3 below, except that the depolymerization time was fixed at 1 hour (Comparative Example 1 was 2 hours) and the depolymerization temperature was changed (Example 2 was 250 ° C. and Example 6 was 230 ° C.). Was carried out in the same manner as in Example 2 to obtain a bis-2-hydroxyethyl terephthalate in the oligomer form, it is shown in Table 3 by measuring the polymerization degree of the oligomer according to the result of the depolymerization. In addition, the color tone measurement results (including Comparative Example 1) according to the Lab color system are shown together in Table 3 below.

division Depolymerization temperature
(℃) Oligomer
Degree of polymerization Hue L Tint b Comparative Example 1 250 4.4 93 4.5 Example 2 250 3.9 94.5 3.4 Example 6 230 3.7 94.9 3.3  Zinc acetate is used as a catalyst.

As shown in Table 3, when zinc acetate was added as the depolymerization catalyst according to the present invention, it was confirmed that depolymerization did not occur particularly well even when the depolymerization temperature was lowered, and it was confirmed that there was no significant difference in color tone.

Example  7

The bis-2-hydroxyethyl terephthalate as an oligomer obtained in Example 2 was removed foreign matter through a filter, and the bis-2-hydroxyethyl terephthalate (BHET) was continuously heated in a vacuum state to give 285 It was made to rise to ℃ and stirred at 60rpm, polycondensation for 60 minutes to produce a polyester to prepare a recycled polyester chip.

In the polycondensation process, H ₃ PO ₄ was added to 150 ppm based on 1 kg of the waste polyester flakes at a reaction temperature of 260 ° C., Sb ₂ O based on 1 kg of the waste polyester flakes at a reaction temperature of 265 ° C. 300 ppm of ₃ was added.

* Property and color experiment

The recycled polyester chip prepared in Example 7 was measured by the conventional method to measure the physical properties of intrinsic viscosity (IV), acid value (-COOH), melting point (Tm), and the color of the recycled polyester chip. The values of L * and b * were measured by the methods of E398-90 and E805-93 of ASTM.

As a control, the physical properties and colors of the new polyester fiber chip (Comparative Example 2) were measured in the same manner as above.

The measured values are shown in Table 4 below.

division IV
(㎗ / g) -COOH
(ed / ton) Tm (占 폚) L * b * Depolymerization time
(minute) Example 7 0.715 36.3 242.8 44.8 7.6 60 Comparative Example 2 0.664 47.2 252.9 55.0 11.4 -

As shown in Table 4, it can be seen that the physical properties of the recycled polyester chip produced by the waste polyester chip manufacturing method according to the present invention is not significantly different from the embodiment chip.

Therefore, by using zinc acetate in addition to the existing ethylene glycol as the depolymerization catalyst, the depolymerization time can be shortened by almost half, thereby reducing the energy used for regeneration of the waste polyester and increasing productivity. Nevertheless, it is possible to obtain bis-2-hydroxyethyl terephthalate having the same or better color and lower polymerization degree, which can be used to produce regenerated polyester chips as compared to newer polyester chips. It was confirmed that it can have an equivalent degree of physical properties, it was confirmed that can be effectively recycled waste polyester.

The present invention can be used in the industry of producing and processing polyester, and can be used in the textile industry and the like using such polyester.

Claims (12)

In the depolymerization method of depolymerizing waste polyester flakes with bis-2-hydroxyethyl terephthalate (BHET),
(1) a mixing step of mixing the waste polyester flakes with ethylene glycol (EG) as a catalyst and solvent to obtain a first mixture;
(2) a melting step of melting the waste polyester flakes in the first mixture; And
(3) depolymerization by adding zinc acetate as a catalyst to the melted first mixture and depolymerizing to produce bis-2-hydroxyethyl terephthalate (BHET);
Depolymerization method of waste polyester, characterized in that comprises a. The method of claim 1,
The depolymerization method of waste polyester, characterized in that the first mixture in the mixing step is made by mixing the waste polyester flakes and ethylene glycol (EG) in a molar ratio of 1.0: 0.1 to 2.0. The method of claim 1,
The melting step consists of heating the molten first mixture in a nitrogen gas atmosphere under a pressure of 1.5 to 2.5kg / ㎠ at a temperature of 210 to 240 ℃ for 3 to 4 hours while stirring at a rate of 10 to 50rpm Depolymerization method of waste polyester characterized in that. The method of claim 1,
In the depolymerization step, the zinc acetate is used in an amount of 50 to 200 ppm based on 1 kg of the waste polyester flakes. The method of claim 1,
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. A method for depolymerization of waste polyester, characterized by heating to a range. The method of claim 1,
After the depolymerization step, the depolymerization method of waste polyester, characterized in that further comprising the step of filtering the bis-2-hydroxyethyl terephthalate produced in the depolymerization step to remove foreign matters. In the manufacturing method of the recycled polyester which depolymerizes waste polyester flakes with bis-2-hydroxyethyl terephthalate (BHET), and then polycondenses the said bis-2-hydroxyethyl terephthalate to produce regenerated polyester. ,
(1) a mixing step of mixing the waste polyester flakes with ethylene glycol (EG) as a catalyst and solvent to obtain a first mixture;
(2) a melting step of melting the waste polyester flakes in the first mixture;
(3) depolymerization by adding zinc acetate as a catalyst to the melted first mixture and depolymerizing to produce bis-2-hydroxyethyl terephthalate (BHET); And
(4) a polycondensation step of polycondensing the bis-2-hydroxyethyl terephthalate;
Method for producing a recycled polyester using waste polyester, characterized in that consisting of. The method of claim 7, wherein
The polycondensation step using the waste polyester, characterized in that the bis-2-hydroxyethyl terephthalate is heated to a temperature range of 245 to 290 ℃ for 60 to 240 minutes while stirring at 30 to 90 rpm in a vacuum state Method for producing recycled polyester. Bis-2-hydroxyethyl terephthalate according to any one of the preceding claims. The method of claim 9,
The bis-2-hydroxyethyl terephthalate is bis-2-hydroxyethyl terephthalate, characterized in that the color of the lab L * 93.1 to 94.9, b * is 4.4 to 3.3. 10. A recycled polyester that is prepared according to any of claims 7-8. The method of claim 11,
The regenerated polyester has a physical property of intrinsic viscosity (IV) 0.65 to 0.70 dl / g, melting point (Tm) 240 to 260 ℃.