JP4005301B2 - Method for recovering active ingredients from polyester waste - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of recovering effective components from polyester waste, more particularly, from polyester waste consisting essentially of poly ethylene terephthalate and plant fiber, and dimethyl terephthalate and ethylene glycol as effective ingredient The present invention relates to an efficient separation and recovery method.
[0002]
[Prior art]
Since polyalkylene terephthalate is excellent in chemical stability, it is produced and used in large quantities in food fields such as life-related materials such as fibers, films and resins, drinking water, bottles for carbonated beverages and the like.
[0003]
However, fiber, film, resin product waste, and non-standard polyalkylene terephthalate (hereinafter sometimes simply referred to as “polyester waste”), which are generated in large quantities with increasing production and usage. Treatment costs are not only related to product costs, but these treatments are now a major social problem, and various proposals have been made regarding recycling methods.
[0004]
However, material recycling, which converts polyester waste to a lower quality grade by melt molding, has greatly improved the so-called “disposable” situation, but the quality of the resulting recycled product is further reduced when recycled again. Therefore, its use is limited, and it is difficult to finally avoid discarding polyalkylene terephthalate.
[0005]
Thermal recycling is also carried out using polyester waste as fuel. This method has the advantage of reusing the combustion heat of the polyester waste, but it is nothing but the burning of the polyester waste, so there are problems of loss of the polyalkylene terephthalate raw material and generation of carbon dioxide, saving resources and It is not preferable from the viewpoint of global environmental conservation.
[0006]
On the other hand, chemical recycling, in which polyester waste is converted and recovered into its constituent components, and polyalkylene terephthalate is produced again by a polymerization reaction and reused, has been studied for the above two types of recycling methods.
[0007]
That is, the recovered polyester waste is reacted with methanol (hereinafter may be abbreviated as MeOH), and chemical recycling to recover dimethyl terephthalate (hereinafter may be abbreviated as DMT) and alkylene glycol. Since the compound is basically reused without any loss, it is possible to reuse the originally intended resource.
[0008]
However, polyester waste discharged from the distribution industry and households is usually discarded in the form of fibers (naturally blended with cotton and hemp) in addition to resins and films, as well as fiber waste. There are many cases.
[0009]
The mixed natural fiber may be decomposed in the process of heating / reaction of polyester waste, resulting in damage to equipment, generation of malodor, and other problems. In addition, degradation products may significantly reduce the quality of recovered DMT and alkylene glycol. For this reason, in the chemical recycling, in order to effectively use the polyester waste, it is necessary to separate the natural fibers contained therein.
[0010]
Conventionally, as a method for recovering polyester waste, a method of depolymerizing polyalkylene terephthalate with ethylene glycol (hereinafter sometimes abbreviated as EG) and then transesterifying with MeOH to obtain DMT is glycolysis. It is widely known as a transesterification reaction method and is also practiced industrially.
[0011]
However, the thermal decomposition temperature of natural fibers is as low as about 130 ° C. for animal fibers and about 200 ° C. for plant fibers. The chemical recycling of polyalkylene terephthalate containing fibers has been difficult to apply. For this reason, a method (US Pat. No. 5,866,622) for dissolving and separating polyester in an aromatic ester such as dimethyl terephthalate, methyl paratoluate, dimethyl isophthalate, etc. has been proposed. There is a problem, and polyester waste containing substantially natural fibers is usually separated from other polyester waste by pretreatment, and chemical recycling is not performed at present.
[0012]
[Problems to be solved by the invention]
An object of the present invention is to solve the problems the prior art has had point, from polyester waste consisting essentially of the plant fiber and poly ethylene terephthalate to establish a method to efficiently recover the DMT and EG There is.
[0013]
[Means for Solving the Problems]
As a result of intensive studies in view of the above-described prior art, the present inventors have used a catalyst, and if polyester waste is depolymerized with EG at a temperature that does not cause problems such as thermal decomposition of plant fibers, it will be mixed. The present invention has been completed by finding that the plant fibers can be left as solids and can be easily separated and recovered.
[0014]
That is, the object of the present invention is to
A method of separating and recovering effective components from polyester waste consisting essentially of the plant fiber and poly ethylene terephthalate, and sequentially passed through the waste steps below (a) ~ (c) characterized by separating and recovering dimethyl terephthalate and ethylene glycol as an active ingredient, the active ingredient a method for recovering from polyester waste.
(A) A step of introducing polyester waste into ethylene glycol containing a depolymerization catalyst at a temperature of 110 to 190 ° C.
(B) Step (a) After passing, the step of taking out the plant fiber by solid-liquid separation in a solid state.
(C) A step of adding and adding a transesterification catalyst and methanol to the residue of step (b) to conduct a transesterification reaction to obtain dimethyl terephthalate and ethylene glycol, and then separating and recovering both.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
The polyester waste present invention is targeted, a mixture consisting essentially of the plant fiber and poly ethylene terephthalate, wherein the term "substantially", the vegetable fiber and poly ethylene terephthalate is, When the total polyester waste is less than 50 wt%, it means that the method of the present invention is not intended.
[0016]
In the recovery method of the present invention, it is necessary to sequentially pass the polyester waste through the steps (a) to (c) described above. Hereinafter, each step will be described.
[0017]
In the step (a), a temperature of the polyester waste 110 to 19 0 ° C., it is necessary to put into EG containing a depolymerization catalyst. Here, when the temperature of the EG is less than 110 ° C., the depolymerization time becomes very long and it is not efficient. On the other hand, exceeding 19 0 ° C. When becomes significant thermal decomposition of the vegetable fiber, and reducing the quality of the recovered product. A preferred range of temperature is, if it contains vegetable fibers as a plant fiber is 140 to 190 ° C.. In addition, about the addition amount of a catalyst, since it will become economical if it is too much, what is necessary is just about 0.1 to 10 weight% on the basis of a polyester waste, and it heat-holds on these conditions for 1 to 10 hours .
[0018]
Furthermore, the weight ratio of the EG and poly ethylene terephthalate supplied to the step (a) is preferably set to 0.5 to 20, when the ratio is in this range, regardless of the shape of the polyester waste In addition, the depolymerization time does not change significantly, and the purification cost of EG that is finally reused can be reduced. The weight ratio is preferably 1-5.
[0019]
For the contact between polyester waste and EG and the temperature rise of polyester waste, the melting time can be shortened by using operations such as stirring in the melting tank and circulation of the liquid in the tank by an external pump. Although an effect can also be obtained, excessive stirring or the like is a waste of power, so it is sufficient that the liquid in the tank is flowing.
[0020]
Next, in the step (b), it is necessary to solid-liquid separate the polyester waste that has passed the step (a). The polyester waste forms a slurry state, and various solid-liquid separation devices can be used for solid-liquid separation of the slurry, and the purpose is to remove foreign matter when there is little mixing of plant fibers. A filter may be used.
[0021]
The polyester waste obtained by the operation in the step (b) may be concentrated in a liquid containing this oligomer until the weight ratio of EG and polyester waste is 0.5 to 2.0 on the raw material charge ratio basis. preferable.
[0022]
As a means for concentrating the oligomer-containing EG solution, it can be easily carried out by distillation operation, which must be carried out under reduced pressure, and the boiling point of EG used and the thermal decomposition temperature of the plant fiber are 140 ° C. it becomes significant above, considering that come crowded leaks vegetable fibers become fine particles by solid-liquid separation operation such 1.33~100k P a, of preferably 1.33~6.7k P a It is preferable to perform a vacuum distillation operation.
[0023]
Finally, in step (c), the ester exchange reaction catalyst and MeOH are added and added to the solution obtained by concentrating the oligomer to the separation liquid in step (b), preferably to the above-mentioned ratio, to perform the ester exchange reaction. After obtaining DMT and EG, both are separated and recovered.
[0024]
In the transesterification reaction, 200 to 400% by weight of MeOH is charged based on the polyester waste, and at the same time, 1 to 10% by weight of the transesterification reaction catalyst is charged based on the polyester waste. The reaction may proceed at a transesterification reaction tank pressure near atmospheric pressure and a transesterification reaction temperature of 65 to 85 ° C.
[0025]
The transesterification reaction is completed in 0.5 to 5 hours, and becomes a slurry of DMT, MeOH, and EG in a solid state. In recovering DMT from the slurry, a solid-liquid separator can be applied as a conventional means, but any method may be adopted.
[0026]
A small amount of DMT is dissolved in MeOH and EG to form a slurry state. The slurry is cooled and then supplied to a solid-liquid separator. Since the cake of DMT obtained by the solid-liquid separation operation contains MeOH and EG as mother liquors, the cake is put into fresh MeOH, stirred, and slurried again to wash the DMT. The obtained slurry is supplied again to the solid-liquid separator, and separated into a DMT cake and a mother liquor MeOH.
[0027]
The number of repetitions of this washing operation is uniquely determined by the required quality of the DMT to be recovered, but usually it may be performed 2 to 4 times. Further, as a conventional means, the mother liquor MeOH in each washing step can be circulated. Further, the washing operation may be performed continuously or batchwise.
[0028]
The mixed solution of EG and MeOH solid-liquid separated from DMT contains dissolved DMT, depolymerization catalyst and transesterification catalyst. EG and MeOH are separated and purified separately for use in the process again. The This purification operation is preferably carried out by distillation, but need not be limited to the distillation operation. In the case of performing distillation, MeOH having a low boiling point is first distilled off, the liquid remaining at the bottom of the column is supplied to the next distillation column, and EG is distilled off. At this time, since DMT dissolved in EG, a catalyst, and an oligomer having 1 to 3 repeating units are present at the bottom of the tower, the bottom liquid is used for the purpose of reducing the amount of catalyst used and improving the recovery rate of active ingredients. A part of may be returned to the depolymerization tank.
[0029]
In addition, since there is a possibility that a small amount of solid matter such as dust and sand contained in the polyester waste is mixed in the DMT collected by the solid-liquid separation operation described above, depending on the required quality of the DMT, If necessary, it may be purified by distillation under reduced pressure, and a part of the column bottom liquid in the purification operation may be returned to the depolymerization tank.
[0030]
Hereinafter, the recovery method of the present invention will be described more specifically with reference to a flow chart (FIG. 1) showing an embodiment of the recovery method of the present invention.
[0031]
First, ground poly ethylene terephthalate, charged depolymerization catalyst, a depolymerization vessel EG in (figure 1) simultaneously depolymerizing polyester waste.
[0032]
Plant fibers that do not dissolve in EG in the depolymerization tank (1 in the figure) can be separated by a solid-liquid separation device (2 in the figure) and removed out of the system as a solid. The solid matter is further washed by EG in the washing tank (3 in the figure), and the deposit on the surface of the solid is circulated to the depolymerization tank (1 in the figure), and the solid matter is separated as plant fibers. can do. Here, the residence time of the depolymerization tank may be 1 to 10 hours, and the internal temperature may be 110 to 190 ° C.
[0033]
Then, the ethylene terephthalate depolymerization reaction has ended, and the EG and polyester waste feed weight ratio 0.5 to 2. EG is distilled and distilled off in a distillation / concentration tank (4 in the figure) so that it becomes 0, and the distilled EG can be circulated and supplied to the depolymerization tank (1 in the figure).
[0034]
Then, the concentrated polyester waste depolymerization solution is supplied to a transesterification reaction tank (5 in the figure), and further, the polyester waste depolymerization solution is converted into DMT and EG by supplying a transesterification reaction catalyst and MeOH. Convert to At this time, the transesterification reaction tank internal temperature is preferably 65 to 85 ° C. and normal pressure, and the residence time is preferably 0.5 to 5 hours.
[0035]
The produced DMT and EG are cooled together with excess MeOH, then supplied to a solid-liquid separator (6 in the figure), and separated into DMT cake, EG, and MeOH liquid. Here, since the DMT cake contains MeOH as a mother liquor, it is slurried again with MeOH (not shown) and solid-liquid separated again.
[0036]
Further, the DMT cake washed twice is supplied to the DMT distillation column (7 in the figure), and the purified DMT is recovered. The residue at the bottom of the distillation column (7 in the figure) is partially returned to the depolymerization tank (1 in the figure), and the remainder is discarded outside the system.
[0037]
On the other hand, the mixed solution of EG and MeOH separated by the solid-liquid separator (6 in the figure) is supplied to the MeOH distillation column (8 in the figure) to distill off MeOH. This distilled MeOH can be used as a part of MeOH supplied to the transesterification reaction tank (5 in the figure).
[0038]
Further, the residue at the bottom of the MeOH distillation column (8 in the figure) is supplied to the EG distillation column (9 in the figure) to distill off the EG. A part of the distilled EG is used as EG supplied to the depolymerization tank (1 in the figure), and the remaining EG is recovered and taken out of the system.
[0039]
A part of the kettle remaining in the distillation column (9 in the figure) is returned to the depolymerization tank (1 in the figure), and the remainder is taken out of the system as waste.
[0040]
By performing the above operation, it is possible to from polyester waste consisting essentially of the plant fiber and poly ethylene terephthalate, easily be recovered and DMT and EG as an active ingredient.
[0041]
【Example】
Hereinafter, the content of the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto. In addition, each numerical value in an Example was calculated | required with the following method. In the examples, “parts” means “parts by weight” unless otherwise specified.
[0042]
(1) Dimethyl terephthalate, monohydroxyethyl terephthalate, bishydroxyethyl terephthalate content (%):
DMT contained after the depolymerization, DMT contained in the liquid before and after distillation, monohydroxyethyl terephthalate (hereinafter sometimes abbreviated as MHET) contained in the distillation residue. Bishydroxyethyl terephthalate (hereinafter sometimes abbreviated as BHET) was quantified by gas chromatography (HP-5890 manufactured by Hewlett-Packard Company, capillary column: TC-1701 manufactured by GL Sciences Inc.).
[0043]
(2) EG content (%):
The amount of EG contained after depolymerization and the EG contained in the liquid before and after distillation were gas chromatographed (GC-7A manufactured by Shimadzu Corporation, packed column filler: polyethylene glycol 6000 manufactured by GL Sciences, Inc. Used).
[0044]
(3) Oligomer weight average molecular weight:
Partly depolymerized, using polyalkylene terephthalate in a molten state as a sample, using tetrahydrofuran as the mobile phase in liquid chromatography (L-4000, manufactured by Hitachi, Ltd.), hexafluoro-2-propanol and chloroform as the solvent for the sample The molecular weight was determined by a calibration curve prepared using standard polystyrene using the above mixed solvent.
[0045]
[Example 1]
9.79.7 parts of EG were put into a separable flask, and 48.2 parts of a fiber blended fabric (commercial product (65% polyester, 35% cotton) cut) and 1.5 parts of sodium carbonate were added and stirred. The temperature was kept at 185 ° C. for 4 hours.
[0046]
The above-mentioned EG solution was put into a filtration device using a 100-mesh wire mesh whose surroundings were heated to 170 ° C. as a filter medium, and filtration was performed while hot. The plant fiber remaining on the filter was washed with 90 parts of EG heated to 170 ° C., and the washing solution was received in another receiver.
[0047]
The EG solution obtained in hot filtration was concentrated by vacuum distillation 6.7k P a, were recovered 309 parts of EG as a fraction.
[0048]
To this concentrate, 5.55 parts of sodium carbonate and 136.2 parts of MeOH were added as a transesterification catalyst. The liquid temperature was maintained at 75 ° C. for 1 hour under stirring at normal pressure, and a transesterification reaction was carried out.
[0049]
The resulting mixture of DMT, EG and MeOH was cooled to 40 ° C. and filtered through a glass 3G-4 filter. DMT recovered on the filter was put into 180 parts of MeOH, washed with stirring at 40 ° C., and filtered again with a glass filter. This operation was repeated twice.
[0050]
It charged DMT was captured on the filter into a distillation apparatus, was recovered 17.1 parts to distill DMT as a fraction by vacuum distillation pressure 6.7k P a. Based on the polyester charged, 54.5% by weight of DMT was recovered. Moreover, there was no problem in the quality of distilled DMT.
[0051]
[Comparative Example 1]
When the same operation as in Example 1 was carried out except that the depolymerization temperature was 230 ° C., the obtained DMT was colored and apparently a problem in quality was recognized.
[0052]
【The invention's effect】
According to the method of the present invention, the polyester waste consisting essentially of the plant fiber and poly ethylene terephthalate, it is possible to easily recover the DMT and EG.
[Brief description of the drawings]
FIG. 1 is a flow diagram schematically illustrating one embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Depolymerization tank 2 Solid-liquid separation apparatus 3 Washing tank 4 Distillation / concentration tank 5 Transesterification reaction tank 6 Solid-liquid separation apparatus 7 DMT distillation tower 8 MeOH distillation tower 9 EG distillation tower 10 Crushed polyester waste 11 Depolymerization catalyst 12 MeOH
13 Transesterification catalyst 14 Recovered DMT
15 Collected EG
16 Plant fiber solids 17 Waste 18 Waste

Claims (13)

A method of separating and recovering effective components from polyester waste consisting essentially of the plant fiber and poly ethylene terephthalate, and sequentially passed through the waste steps below (a) ~ (c) characterized by separating and recovering dimethyl terephthalate and ethylene glycol as an active ingredient, the active ingredient a method for recovering from polyester waste.
(A) A step of introducing polyester waste into ethylene glycol containing a depolymerization catalyst at a temperature of 110 to 190 ° C.
(B) Step (a) After passing, the step of taking out the plant fiber by solid-liquid separation in a solid state.
(C) A step of adding and adding a transesterification catalyst and methanol to the residue obtained in step (b) to conduct transesterification to obtain dimethyl terephthalate and ethylene glycol, and then separating and recovering both.   The separation and recovery method according to claim 1, wherein the separation and recovery in the step (c) is performed by distillation or solid-liquid separation operation. As depolymerization catalyst used in step (a), the alkali metal carbonates, alkaline earth metal carbonates, acetic acid manganese, with at least one compound selected from the group consisting of zinc acetate, and the amount added The separation and recovery method according to claim 1, wherein 0.1 to 10% is based on the weight of polyester waste. Ethylene glycol amount used in step (a), the the 0.5 to 20 times by weight based on the poly ethylene terephthalate, separation and recovery process of claim 1. The separation and recovery method according to claim 1, wherein the solid matter separated in step (b) is further washed with ethylene glycol to separate and remove the active ingredient adhering to the plant fiber.   The residue after taking out the solid in the step (b) is distilled and concentrated, and the distilled ethylene glycol is recycled and reused in the step (a), and the residue is sent to the next step. Separation and recovery method. The distillation, concentration operation, the weight of the polyester waste charged to the depolymerization vessel, the weight ratio of ethylene glycol 0.5-2. The collection | recovery method of Claim 6 performed so that it may become the range of 0 . The distillation, concentration operation under pressures of 1.33~100k P a, separation and recovery process of claim 6 wherein. The separation and recovery method according to claim 1, wherein the plant fiber is cotton. The separation and recovery method according to claim 1, wherein the plant fiber is hemp.   A method for reusing an active ingredient, wherein the recovered dimethyl terephthalate according to claim 1 is used as a raw material for producing terephthalic acid.   A method for reusing an active ingredient, wherein the recovered dimethyl terephthalate according to claim 1 is used as a raw material for producing bis (β-hydroxyethyl) terephthalate.   A method for reusing an active ingredient, wherein the recovered dimethyl terephthalate according to claim 1 is used as a raw material for polyester production.

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