JP2002167341A - Method of recovering effective components from polyester fiber wastes - Google Patents

Abstract

PROBLEM TO BE SOLVED: To establish an efficient and economical method capable of obtaining a recovered monomer with high purity by improving handleability of fiber wastes in a method of recovering effective components from impurity-containing polyester fiber wastes. SOLUTION: The simple and economical method of obtaining the recovered monomer with high purity comprises adding a reaction process provided with a process to remove impurities by a physical and chemical method, after a pretreatment process of removing fiber wastes judged other than polyester fibers by examination using a judging device and then improving handleability by applying pulverization and granulation to fiber wastes which pass several tests.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a polyester fiber waste containing impurities, which is subjected to a pretreatment such as discrimination by a discriminator, pulverization, granulation and the like, and then subjected to a chemical reaction treatment to obtain high-purity as an active ingredient. The present invention relates to a method for simply and efficiently recovering a bishydroxyl terephthalate or terephthalic acid component and an alkylene glycol.

[0002]

2. Description of the Related Art Polyester, for example, polyethylene terephthalate, has been widely used as a fiber, film, resin, etc. due to its excellent properties. Effective utilization has become a major problem not only in terms of cost but also in terms of environmental issues, and various proposals have been made as a method of treating it through material recycling, thermal recycling, and chemical recycling.

[0003] Among them, in the material recycling, polyester resin scraps such as PET bottles are collected mainly by local governments and actively recycled, but it is extremely difficult to adopt the recycling method for fiber scraps. There is no such embodiment.

[0004] Thermal recycling for converting polyester waste into fuel has the advantage of reusing the combustion heat of the polyester waste, but it has nothing but the relatively low calorific value of burning a large amount of polyester waste. Therefore, there is a problem that the polyester raw material is lost, which is not preferable in terms of resource saving.

On the other hand, in the chemical recycling, since the polyester waste is regenerated into a raw material monomer, there is little deterioration in quality due to the regeneration, and the method is suitable for closed loop recycling. Most of the chemical recycling targets resin waste and film waste. As a method of recycling polyester fiber waste, for example, Japanese Patent Application Laid-Open No. 48-61447 discloses that polyester waste is converted into excess ethylene glycol (hereinafter sometimes abbreviated as EG).
Bis-β-hydroxy terephthalate (hereinafter sometimes abbreviated as BHET)
Has been proposed to obtain a regenerated polyester by direct polycondensation of polyester. However, in this method, in the depolymerization step, polyester waste and EG are put into the depolymerization reaction system at a time and depolymerized, so that the added polyester is used. Debris solidifies inside the reactor and cannot be stirred.

[0006] Therefore, the depolymerization system becomes non-uniform and the depolymerization time is prolonged. In addition, the amount of EG used is not only economically disadvantageous but also impurities such as diethylene glycol are produced as by-products in the reaction product. Significantly reduces the physical properties of the resulting polyester, especially the softening point,
There were drawbacks such as that only low quality polyester could be obtained. In such conventional techniques, a technique for efficiently treating polyester fiber waste has not been completed.

[0007] When fibers outside the polyester production process are to be collected, it is sometimes impossible to avoid mixing fibers different from polyester such as polyethylene, polypropylene, nylon and cotton. Further, even if the material is a polyester, those containing a dye are decomposed during a series of reactions such as depolymerization and dispersed in the recovered monomer to significantly deteriorate the quality. There have been no examples that mention the quality of the recovered monomer when these impurities are mixed.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art, to improve the handling properties in the subsequent reaction step in the pretreatment step, and to remove impurities in the reaction step. An object of the present invention is to establish an efficient and economical method for recovering an active ingredient, which can provide a high-purity recovered monomer from fiber waste containing impurities by providing a facility for removing the same.

[0009]

Means for Solving the Problems As a result of diligent studies, the present inventors have found that in the pretreatment step, the fibers other than the polyester as the active ingredient are eliminated by an appropriate discriminator, and then the reaction proceeds efficiently. For this purpose, the fiber waste that has passed the discrimination test is pulverized to an appropriate size, then granulated and solidified. The present inventors have found a method for recovering an active ingredient that efficiently obtains the present invention, and have completed the present invention.

That is, an object of the present invention is to analyze a polyester fiber waste by a discriminator and determine that the fiber is a fiber different from the polyester. If the fibrous waste is pulverized to 30 to 150 mm, the fibrous waste is first pulverized to 30 to 150 mm, and then the pulverized material is further pulverized to 2 to 50 mm. Is solidified into a cylindrical solid having a diameter of 2 to 20 mm and a length of 2 to 60 mm by a granulator to a bulk density of 0.10 to 1.0 g / cm ^3, and then the solid is pneumatically transported to form a solid as described below. By combining the pretreatment step of transporting to the reaction step and the following reaction steps (a) to (f), it can be achieved by a method of recovering a high-purity active ingredient from polyester fiber waste. (A) a depolymerization reaction step in which the crude polyester obtained through the pretreatment step is introduced into an alkylene glycol containing a depolymerization catalyst to obtain bis-β-hydroxyterephthalate (BHET); (b) the depolymerization reaction A foreign matter removing step of removing different plastics such as polyethylene, polystyrene, polypropylene, polyvinyl chloride and the like other than polyester during or after the reaction of the step; (c) a filtration separation step of filtering and separating undissolved components after the depolymerization reaction (D) a BHET concentration step of subjecting a mixture of BHET and alkylene glycol obtained through the filtration and sorting step to distillation and evaporation to distill and evaporate the alkylene glycol to obtain concentrated BHET; (e) the BHET concentration step In the mixture of crude BHET and crude alkylene glycol obtained in (F) purified dimethyl terephthalate and purified alkylene glycol from a mixture of crude dimethyl terephthalate and crude methanol and crude alkylene glycol obtained in the transesterification reaction step; A purification step for separating and recovering glycol;

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In the method for recovering active ingredients of the present invention, fibers different from polyester, for example, nylon, polyethylene, polypropylene, cotton, etc. cannot be active ingredients. Eliminate at the stage. That is, the fiber waste is analyzed by a discriminating device such as a near-infrared spectrometer, and if the fiber waste shows an absorption pattern different from that of polyester, the fiber waste is not transported to the next step and is eliminated at that stage. Only fiber waste that has passed the inspection by the near-infrared analysis is transported to the next step.

The fiber waste that has passed the inspection by the near-infrared analysis is desirably granulated and solidified in terms of handling properties in the reaction step after the pretreatment step or pneumatic transport properties after the pretreatment step. . However, it is extremely difficult to directly feed yarn waste having a continuous structure into a granulator, and it is necessary to first pulverize the fiber waste into an appropriate size. The size of the pulverized product is preferably 2 to 50 mm.
If the crushed diameter is large, a problem that solidification becomes insufficient in the next granulation step occurs. As an embodiment of the pulverization, it is preferable to use a two-stage pulverizer in order to improve the pulverization processing capacity. That is, the polyester fiber waste is roughly pulverized to 30 to 150 mm by a primary pulverizer, and then pulverized to 2 to 50 mm by a secondary pulverizer. If the size of the pulverized material is directly specified to be 2 to 50 mm in the primary pulverizer, the load applied to the pulverizer becomes excessive, which is inefficient.

Next, the pulverized material is put into a granulator, and the pulverized material is solidified into a cylindrical solid. The size of the diameter is preferably 2 to 20 mm, more preferably 4 to 6 mm.
The length is preferably 2 to 60 mm. The granulation method is a method in which the pulverized material is pushed into a hole having a defined size, and a part of the surface is melted by frictional heat of the polyester surface generated at that time and solidified as a binder, but the diameter is large. As a result, the surface of the solidified product is not sufficiently solidified due to the influence of a small frictional heat.

If the solidification is insufficient as described above, in the subsequent pneumatic transportation process, the solids collapse due to the collision with the pipes, so that a bridge is easily formed in the storage tank at the destination, and the discharge from the storage tank is reduced. Extremely difficult. Further, in the granulation method, the glass transition point of the polyester or more,
It is necessary to operate at temperatures below the melting point. That is, as a granulation method, there is also a method in which the fiber waste is heated to a temperature equal to or higher than the melting point of the polyester, completely melted, and then cooled and solidified. In the granulation method, impurities such as nylon are decomposed and collected. Deterioration of monomer quality.

Further, if the solidification is completely solidified in the inside of the solid in the granulation method, there is also a problem that the reaction rate is greatly reduced due to the deterioration of the contact efficiency between the solvent and the solid in the reaction step. Therefore, in the present invention, a granulation method in which only a part of the surface of the fiber waste is melted and solidified at an operating temperature equal to or higher than the glass transition point of the polyester and equal to or lower than the melting point is adopted. This granulation method has made it possible to improve the handling properties while suppressing the decomposition of impurities and the reduction of the reaction rate.

When granulation and solidification are not performed, the bulk density of the pulverized product is about 0.10 g / cm ^{3. In} this case, when the pulverized product is put into a reactor in a subsequent reaction step, it becomes very bulky. In addition, the pulverized material absorbs the solvent alkylene glycol, which makes it very difficult to stir in the reaction tank. Bulk specific gravity with the granulating or solids are in terms of smoothly advancing increases but the final bulk density reaction 0.10~1.0g / cm ^3, and preferably is increased to 0.40 g / cm ³ or more It is necessary to improve handling. From the above viewpoints, granulation and solidification after grinding play a very important role in the present invention.

After the granulation and solidification, the solid is transported to the reaction step by air transport. In addition, a series of pretreatment steps can be performed automatically, including saving the manpower including feeding the polyester waste into a crusher. Hereinafter, each of the reaction steps will be described.

In the step (a), the polyester fiber solid which has passed through the pretreatment step is subjected to a depolymerization reaction in a known depolymerization catalyst, in an excess of alkylene glycol at a known catalyst concentration of 120 to 210 ° C. . Here, when the temperature of the alkylene glycol is lower than 120 ° C., the depolymerization time becomes extremely long, and the efficiency becomes inefficient. Meanwhile, 2
When the temperature exceeds 00 ° C., thermal decomposition of the oil agent and the like contained in the fiber waste becomes remarkable, and nitrogen compounds and the like generated by the decomposition are dispersed in the recovered monomer, making it difficult to separate in the subsequent purification step. The temperature is preferably between 140 and 190C. Existing chemical recycling technology requires operation at high temperatures, making it difficult to cope with mixing of oils.

When the polyester fiber waste used in the present invention is colored by a dye, the dye may be decomposed in the reaction step to reduce the molecular weight, and may be dispersed in the recovered monomer to significantly lower the quality. Therefore, when handling the colored fiber waste, it is effective to incorporate a step of discharging the dye before the step (a). In this step, the granulated solid containing the dye is put into a solvent such as water, alkylene glycol, dimethylformamide, para-xylene, or 2-heptanone.
Heat at 90 ° C. to extract the dye. The discharging method may be a batch method or a continuous extraction method such as a countercurrent multistage extraction method. The solid after dye extraction is washed with alkylene glycol, and then transported to the step (b) in the same manner as fiber waste without dye.

Further, when nylon which cannot be eliminated at the stage of receiving is mixed, the nylon is decomposed in the reaction step and mixed as a nitrogen compound such as ε-caprolactam into the recovered monomer, which makes separation difficult. Therefore, it is effective to incorporate a step of dissolving and removing the nylon before the step (a) in the solidified material containing nylon. In this step, a solid containing nylon is put into a solvent such as alkylene glycol, and heated to 100 to 190 to dissolve and remove nylon. This step may be performed in the discharge printing step.

In the step (b), different fibers from the polyester such as polyethylene and polypropylene, which could not be excluded in the discrimination test in the pretreatment step, are floated and separated in the depolymerization reaction layer. Since the specific fibers have a lower specific gravity than the alkylene glycol which is a solvent for the depolymerization reaction and float on the liquid surface, they are separated into layers as a eutectic mixed floating mass of different fibers, and then the eutectic mixing is performed. The suspended matter layer is removed from the depolymerization and removed.

In the step (c), after the depolymerization reaction, different fibers such as cotton which cannot be excluded in the discrimination test in the pretreatment step are filtered and sorted. The object of the foreign fiber to be removed in the step (c) is a component having a higher specific gravity than the alkylene glycol and cannot be separated by the removal method in the step (b). At the time of passing through the step (c), the polyester is converted into bis-β-hydroxy terephthalate (hereinafter sometimes abbreviated as BHET), and the reaction solution is a mixture of BHET and alkylene glycol.

In step (d), the mixture of BHET and alkylene glycol passed through step (c) is converted from the mixture of alkylene glycol and polyester fiber waste to allow the transesterification reaction in step (e) to proceed efficiently. The alkylene glycol is distilled off until the weight ratio becomes 0.5 to 2.0 times based on the raw material charge ratio. The alkylene glycol distilled off at this time is recycled to the step (a) again.

In step (e), the mixture of BHET and alkylene glycol from which alkylene glycol has been distilled off in step (d) is subjected to a transesterification reaction with methanol in the presence of a known ester exchange catalyst and a known concentration, followed by centrifugation. Solid-liquid separation is performed by solid-liquid separation means such as separation.

In step (f), the crude dimethyl terephthalate and crude alkylene glycol obtained in step (e) are purified by a purification method such as distillation to obtain high-purity purified dimethyl terephthalate and purified alkylene glycol.
At this time, the impurities that have passed through the reaction step are captured at the bottom of the column, and thus the recovered monomers contain no impurities and have high purity.

[0026]

EXAMPLES Hereinafter, the content of the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. Incidentally, a spectrophotometer (trade name; Plascan) manufactured by Opto Giken was used as the near-infrared analyzer.

Example 1 An absorption spectrum of 100 kg of polyester fiber waste containing no dye generated from the polyester production process was measured by a near-infrared spectrometer, and the absorption pattern was consistent with that of the polyester resin. The whole amount of the fiber waste is put into a primary pulverizer, and the primary pulverization is performed by setting the screen diameter of the pulverizer to 75 mm. 2
The secondary pulverization was performed at a setting of 0 mm. Thereafter, the pulverized product was put into a granulator operated under the conditions of a diameter of 4 mm, a length of 45 mm, and an internal temperature of the granulator of 170 ° C., solidified, and then transported to the reaction step by air transport. Incidentally, the bulk density of the solid product transported to the reaction step was 0.40 g / cm ³ .

In the reaction step, 100 kg of the solidified product was charged into a mixture of 400 kg of ethylene glycol (hereinafter abbreviated as EG) and 3 kg of sodium carbonate which had been heated to 185 ° C. in advance, and reacted at normal pressure for 4 hours. .

After completion of the reaction, the mixture of BHET and EG is sent to the distillation column, and the temperature at the bottom of the column is 140 to 150 ° C., and the pressure is 13.
300 kg of EG was distilled off under the condition of 3 kPa. Then E
3 kg of sodium carbonate and 200 kg of methanol were added to 200 kg of a mixture of BHET and EG after G was distilled off,
The reaction was carried out at normal pressure at 75 to 80 ° C. for 1 hour.

After completion of the reaction, the reaction solution is cooled to 40 ° C.
By centrifugation, solid-liquid separation was carried out into a cake mainly composed of crude dimethyl terephthalate and a filtrate mainly composed of methanol and crude EG. The crude dimethyl terephthalate is then pressured to 6.
7 kPa, tower bottom temperature 180-200 ° C, crude EG at pressure 1
Purification was performed by distillation under the conditions of 3.3 kPa and a tower bottom temperature of 140 to 150 ° C., and finally dimethyl terephthalate and ethylene glycol were obtained at a yield of 85%. The recovered dimethyl terephthalate is comparable to commercially available products in terms of appearance, acid value, melting color, and sulfated ash, and the recovered ethylene glycol is comparable to commercially available products in diethylene glycol concentration, water content, and melting color. In all cases, recovered monomers of high purity were obtained.

[Comparative Example 1] In Example 1, primary grinding was performed with the screen diameter of the primary grinding machine set to 75 mm, and the mixture was subjected to a granulator without performing secondary grinding. Insufficiently, the storage tank after pneumatic transportation in the next process was not discharged in a bridge, and the line stopped.

[0032]

As described above, in the pretreatment step, the handleability in the subsequent reaction step is improved, and in the reaction step, equipment for removing impurities is provided, so that a high-purity recovered monomer can be obtained from fiber waste containing impurities. It is possible to establish an efficient and economical method for recovering active ingredients.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C07C 69/82 C07C 69/82 A C08J 11/22 C08J 11/22 // B29K 67:00 B29K 67:00 C08L 67:00 C08L 67:00 (72) Inventor Kazuhiro Sato 77 Kitayoshida-cho, Matsuyama-shi, Ehime Pref. AC41 AC48 AC91 FE11 FG24 KA03

Claims (7)

[Claims] 1. When a polyester fiber waste is analyzed by a discriminator and discriminated as a fiber different from polyester, the fiber waste is excluded and is not transported to the next step. Puts the fiber waste in a lump into a pulverizer and first removes the fiber waste from 30 to 1
After pulverizing to 50 mm, the pulverized product is further 2 to 50 mm
After the pulverized material is solidified into a cylindrical solid having a diameter of 2 to 20 mm and a length of 2 to 60 mm by a granulator to a bulk density of 0.10 to 1.0 g / cm ³ , A method for recovering a high-purity active ingredient from polyester fiber waste by combining a pretreatment step of transporting a substance to a reaction step described below by pneumatic transportation and the following reaction steps (a) to (f). (A) a depolymerization reaction step in which the crude polyester obtained through the pretreatment step is introduced into an alkylene glycol containing a depolymerization catalyst to obtain bis-β-hydroxyterephthalate (BHET); (b) the depolymerization reaction A foreign matter removing step of removing different plastics such as polyethylene, polystyrene, polypropylene, polyvinyl chloride and the like other than polyester during or after the reaction of the step; (c) a filtration separation step of filtering and separating undissolved components after the depolymerization reaction (D) a BHET concentration step of subjecting a mixture of BHET and alkylene glycol obtained through the filtration and sorting step to distillation and evaporation to distill and evaporate the alkylene glycol to obtain concentrated BHET; (e) the BHET concentration step In a mixture of the crude BHET and the crude alkylene glycol obtained in (F) purified dimethyl terephthalate and purified alkylene glycol from a mixture of crude dimethyl terephthalate and crude methanol and crude alkylene glycol obtained in the transesterification reaction step; A purification step of separating and recovering glycol; 2. The method according to claim 1, wherein the polyester is polyethylene terephthalate. 3. The method according to claim 1, wherein a near-infrared spectrometer is used for the discriminating device. 4. The active ingredient according to claim 1, wherein in the granulation method in the pretreatment step, a granulation method in which a part of the polyester is melted by operating in a temperature range from the glass transition point to the melting point of the polyester. Collection method. 5. The method of claim 1, wherein the pretreatment step employs an automatic transfer device to save labor. 6. When a dye is contained in the crude polyester solid obtained in the pretreatment step, the solid
2. The method for recovering an active ingredient according to claim 1, wherein the method is carried out at a temperature of 00 to 190 [deg.] C. into a solvent and the process proceeds to a reaction process via a discharge process for extracting a dye. 7. If the crude polyester solid obtained in the pretreatment step contains nylon, the solid is put into a solvent at 100 to 190 ° C. to dissolve and remove the nylon, and then react. The method for recovering an active ingredient according to claim 1, wherein the method proceeds to a step.