JPH10195233A - Fractionation of plastic waste product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for fractionating plastic waste products into plastic components 15 soluble in a fractionating solvent and plastic components which is not soluble therein by using the fractionating solvent. SOLUTION: This method for fractionating a plastic waste product comprises (i) a dissolving step for dissolving a part of plastic contained in a waste product in a fractionating solvent by bringing the waste product into the fractionating solvent, (ii) a first solid-liquid separating step for separating a dissolved product obtained in the dissolving step into the fractionating solvent containing dissolved plastic and undissolved plastic, (iii) a cleaning step for cleaning. undissolved plastic obtained in the first solid-liquid separation step by using a fresh fractionating solvent as a cleaning solution and dissolving the dissolved plastic attached onto the undissolved plastic surface in the fractionating solvent and (iv) a circulating step for circulating the fractionating solvent containing the dissolved plastic after cleaning obtained in the cleaning step.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for separating plastic waste.

[0002]

2. Description of the Related Art PE (polyethylene), PP (polypropylene), PS (polystyrene), PVC (polyvinyl chloride), PET (polyethylene terephthalate) and A
BS resin (acrylonitrile / butadiene / styrene copolymer) is widely used as a general-purpose plastic. Therefore, the majority of plastic waste consists of these plastics. At present, most of plastic waste is incinerated or landfilled without being reused, but such treatment is not desirable in terms of resource saving. Until now, various methods have been proposed for reusing plastic waste. One of the typical methods is a method of thermally decomposing oil into oil (pyrolysis oiling method). ing. In this method, a plastic waste is heated to a high temperature of about 450 ° C. to generate a cracked oil. In the thermal cracking and oiling method, when the plastic waste as the raw material to be treated is composed of only hydrocarbon-based plastics such as PE, PP, and PS, problems such as blockage troubles and corrosion of equipment and piping occur. And can be easily implemented. However, if the raw materials to be processed are PE, PP, P
Hydrocarbon plastics such as S, PVC, PET, AB
When it is made of a mixture with a different hydrocarbon-based plastic such as S resin, various problems occur, and it is difficult to safely and stably carry out the method. For example, when PVC is mixed, hydrogen chloride having a high corrosiveness is generated, and causes corrosion of equipment and piping. When PET is mixed, phthalic acids are generated by its thermal decomposition, and this causes a piping blockage trouble. When ABS resin is mixed, toxic hydrogen cyanide is generated by its thermal decomposition. In this way, when plastic waste is pyrolyzed to oil, the waste
It is desirable to remove the different hydrocarbon-based plastics in advance, but at present, there is no known industrially advantageous method for separating hydrocarbon-based plastics from different hydrocarbon-based plastics. Many difficulties have arisen in the practical use of a method for thermally cracking plastic waste containing hydrogen-based plastics and different hydrocarbon-based plastics.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for separating plastic waste into a plastic component which is soluble in the separation solvent and a plastic component which is insoluble by using the separation solvent.

[0004]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have completed the present invention. That is, according to the present invention, in the method for separating plastic waste, (i) dissolving a part of the plastics contained in the waste in the separation solvent by contacting the waste with a separation solvent. (Ii) a first solid-liquid separation step of separating the dissolved product obtained in the dissolving step into a separation solvent containing dissolved plastic and an undissolved plastic; and (iii) a first solid-liquid separation step. A washing step of washing the obtained undissolved plastic using a fresh fractionating solvent as a washing liquid, and dissolving the dissolved plastic adhering to the undissolved plastic surface in the fractionating solvent, (iv) the washing obtained in the washing step And a circulating step of circulating a fractionated solvent containing the dissolved plastic later to the dissolving step.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Plastic waste used as a raw material to be treated in the present invention is composed of a plastic component soluble in a separation solvent and a plastic component insoluble in the separation solvent. Representative examples of such plastic wastes include those composed of hydrocarbon-based plastics and different hydrocarbon-based plastics. Hydrocarbon plastics include polyolefin plastics such as PE and PP and aromatic plastics such as PS,
The different hydrocarbon plastics include PVC, PET and A
BS resin and the like are included. All of these plastics are general-purpose plastics that are produced in large quantities, and the bulk of plastic waste consists of these plastics. Of course, the plastic waste in this case can contain a hydrocarbon-based plastic and a different hydrocarbon-based plastic other than the above-mentioned plastics, but the ratio is usually 30% by weight or less. In general plastic waste, the proportion of hydrocarbon plastic is usually 50% by weight or more, and sometimes 75% by weight.
% By weight or more.

[0006] The fractionating solvent used in the present invention has a dissolving property that dissolves some plastics in plastic waste and does not dissolve other plastics. For example, for a plastic waste consisting of the hydrocarbon-based plastic and the different hydrocarbon-based plastic, one that selectively dissolves only the hydrocarbon-based plastic and does not substantially dissolve the different hydrocarbon-based plastic is selected. As such a fractionating solvent, a liquid hydrocarbon mixture containing an aromatic hydrocarbon and a paraffinic hydrocarbon can be used. Such a mixed solvent has the advantage of being inexpensive because it can be easily prepared using a product oil obtained by pyrolyzing a hydrocarbon-based plastic contained in plastic waste.

As the separation solvent used in the present invention, an appropriate solvent is selected and used according to the plastic component to be separated. The separation solvent comprises a hydrocarbon plastic and a different hydrocarbon plastic which are general plastic waste. As the separation solvent for separating the plastic waste into the two components, a liquid hydrocarbon mixture containing an aromatic hydrocarbon and a paraffinic hydrocarbon can be preferably used as described above. Hereinafter, the fractionation solvent comprising the liquid hydrocarbon mixture in this case will be described in detail.
The ratio of the aromatic hydrocarbon contained in this fractionation solvent is:
It is 5 to 70%, preferably 8 to 65%. When the proportion of the aromatic hydrocarbon exceeds the above range, a substantial amount of the different hydrocarbon-based plastic, particularly PVC, will be dissolved. On the other hand, when the proportion is less than the above range, the hydrocarbon-based plastic, particularly PS Substantially does not dissolve. The proportion of the paraffinic hydrocarbon is 5 to 85%, preferably 10 to 80%. When the proportion of the paraffin-based hydrocarbon exceeds the above range, the hydrocarbon-based plastic, particularly PS, substantially does not dissolve, while when the proportion is less than the range, the different hydrocarbon-based plastic,
In particular, a substantial amount of PVC becomes soluble. The proportion of the olefinic hydrocarbon in the mixture is the remaining amount obtained by subtracting the aromatic hydrocarbon and the paraffinic hydrocarbon in the mixture, and is usually 0 to 25%.

In the present specification, the proportions of the aromatic hydrocarbon, paraffinic hydrocarbon and olefinic hydrocarbon with respect to the fractionation solvent are different from the usual weight%,
It was determined based on a ¹³ C-NMR spectrum,
The apparatus for measuring the ¹³ C-NMR spectrum, the measurement conditions, the assignment of the spectrum, and the method for obtaining the ratio of each component are as follows.

(1) Apparatus The nuclear magnetic resonance spectroscopy (hereinafter referred to as NMR) apparatus used for the measurement is a GX270-FTNMR apparatus manufactured by JEOL Ltd. (2) Measurement conditions The sample was deuterated chloroform (CDCl ₃ : 99.96a manufactured by ISOTECINC.) As a solvent and an NMR lock agent.
dissolved in tom% D), 3 with respect to ¹³ C-NMR measurement
The concentration was 0 wt%. Chemical shift is 5 mmφ using tetramethylsilane (TMS) as an internal standard (0.0 ppm).
The measurement was performed at a rotation speed of 15 Hz using a Pyrex sample tube. The main measurement conditions are ¹³ C-NMR, ¹ H decoupling measurement with gate (NNE) eliminating nuclear Overhauser effect (NOE) for quantitative measurement.
Was performed, and the pulse repetition time was 6.9 seconds, the data point was 32 K, and the number of integrations was 4000. (3) Assignment of spectrum and determination of percentage of each hydrocarbon component ¹³ C-NMR spectrum is described in Eberhand, Breifmaier., And Wolfgang Voelter.
on-13 NMRSpectroscopy ”, VCH Verlagsgesellschaft
mbH, (1987), and the integrals were calculated to calculate the integrals of each bond type carbon (paraffin hydrocarbon: Cp, olefin hydrocarbon: Co, aromatic hydrocarbon: Ca). Percentages were determined. Chemical shift of paraffinic hydrocarbon (Cp): 14.2
46.2 ppm Chemical shift of olefinic hydrocarbon (Co): 111.
5-114.2 ppm, 137.0-145.0 ppm Chemical shift of aromatic hydrocarbon (Ca): 125.5-
136.9 ppm In the method of calculating the percentage of each hydrocarbon component based on the ¹³ C-NMR spectrum, the aromatic hydrocarbon having a paraffinic hydrocarbon group bonded thereto is composed of a paraffinic hydrocarbon and an aromatic hydrocarbon. The aromatic hydrocarbon to which the olefinic hydrocarbon group is bonded is calculated by dividing into an olefinic hydrocarbon and an aromatic hydrocarbon.

Next, the present invention will be described with reference to the drawings. FIG. 1 is a flow sheet 1 for separating plastic waste (hereinafter simply referred to as waste) according to the present invention.
Here is an example. In FIG. 1, 1 indicates a dissolving step, 2 indicates a first solid-liquid separating step, 3 indicates a washing step, and 4 indicates a second solid-liquid separating step. In order to separate the plastic waste according to the flow sheet shown in FIG. 1, first, the crushed waste is supplied to the melting step 1 through the line 10, and the waste is supplied from the second solid-liquid separation step through the line 14. And the waste is brought into contact with the separation solvent to selectively dissolve a part of the waste in the separation solvent. Dissolution process 1
Is carried out using a dissolution tank with a stirrer. The contact temperature between the waste and the separation solvent in this dissolution process is
The temperature at which the soluble plastic dissolves in the separation solvent,
Usually, heating conditions are employed. For example, when the waste consists of a hydrocarbon plastic and a different hydrocarbon plastic, the contact temperature is 50 to 200 ° C., preferably 8 to 200 ° C.
0-180 ° C. The pressure in the dissolving step may be a pressure sufficient to maintain at least a part of the fractionated solvent in a liquid phase under the heating condition, and is usually 0 to 5 kg / cm.
² G, preferably 0 to ² kg / cm ² G. The contact time is the time required for the plastic to dissolve,
Usually, it is 1 minute or more, preferably 3 to 30 minutes. The use ratio of the fractionated solvent is 50 to 10 per 100 parts by weight of the waste.
00 parts by weight, preferably 100 to 500 parts by weight. The concentration of the plastic dissolved in the separation solvent obtained in the dissolving step in the solution is 5 to 50% by weight, preferably 10 to 50% by weight.
４０40% by weight. The concentration of the dissolved plastic can be adjusted by the supply amount of the fractionating solvent.

The dissolved product obtained in the dissolving step 1 is sent through a line 11 to a first solid-liquid separating step 2, where it is subjected to solid-liquid separation. By this solid-liquid separation, the separation solvent containing the dissolved plastic and the undissolved plastic are separated,
The former is withdrawn through line 16 and the latter with line 12
And is supplied to the cleaning step 3. The fractionated solvent containing the dissolved plastic is sent to a subsequent processing step, for example, a decomposition step for decomposing the plastic. First
The solid-liquid separation step 2 is performed using a solid-liquid separation device such as a filtration device. The undissolved plastic obtained in the first solid-liquid separation step 2 has a surface to which the dissolved plastic adheres, exhibits surface tackiness, and is poor in handleability. 3 where it is washed.

The washing step 3 is performed using a washing tank having a stirrer. As a cleaning liquid in the cleaning step 3, a fresh fractionated solvent is used, which is supplied through a line 17. The washing temperature in the washing step 3 is 50 to 200 ° C, preferably 80 to 180 ° C. The amount of the separation solvent used as the cleaning liquid varies depending on the amount of the dissolved plastic adhered to the surface of the undissolved plastic that is the object to be cleaned, and is not uniquely defined. The concentration of the dissolved plastic contained in the solution is 10% by weight or less, preferably 1 to 5%.
The amount is such that it will be wt%. By the washing treatment in this washing step, substantially the entire amount (90% by weight or more) of the dissolved plastic adhered to the surface of the undissolved plastic is dissolved and removed in the separation solvent. The washing product is sent to the second solid-liquid separation step 4 through the line 13.

In the second solid-liquid separation step 4, undissolved plastic as an object to be washed and a separation solvent as a washing liquid are separated. This second solid-liquid separation step can be performed using a solid-liquid separation device such as a filtration device. The fractionation solvent containing the plastic obtained in the second solid-liquid separation step is circulated through the line 14 to the dissolution step 1.
On the other hand, undissolved plastic is recovered through line 18. As described above, the concentration of the dissolved plastic in the solution circulated in the dissolving step 1 is 10% by weight or less, preferably 1 to 5% by weight. If the plastic concentration in the solution is higher than the above range, the dissolving power of the solution (fractionating solvent) is impaired, which is not preferable. When the fractionated solvent containing the plastic obtained in the second solid-liquid separation step 4 is circulated for use in the dissolution step 1, this fractionated solvent can be directly circulated to the dissolution step 1 via a pipe, but once the storage tank And then circulated to the dissolution step 1.

The method shown in FIG. 1 is a continuous type, a batch type,
Alternatively, it can be implemented by any method combining these. When the dissolving step 1 is performed in a continuous manner, the step can be performed in a plurality of stages. In order to perform this in two stages, two dissolving tanks are prepared, waste and a separation solvent are supplied to the first tank, and the dissolving operation described above is performed. And then proceed to the melting operation. This will make the second tank more
Since the distribution of the waste in the tank having a longer residence time in the dissolving step becomes larger, the efficiency of dissolving the waste increases. For example, in the case of one stage, the dissolution rate of waste is 60-70.
%, In the case of two stages, a dissolution rate of 90 to 95% can be obtained even if the average residence time in the dissolution step 1 is the same. That is, when the dissolving step 1 is performed in a continuous manner, by performing it in a plurality of stages, the contact time between the waste and the separation solvent is averaged, so that the dissolving efficiency can be increased.

When only the dissolving step 1 is performed in a batch mode and the subsequent steps are performed in a continuous mode, it is necessary to provide two or more dissolving tanks. In the example in which two dissolving tanks are provided, while the dissolving operation is performed in the first dissolving tank, the dissolved product is continuously extracted from the second dissolving tank and sent to the first solid-liquid separation step 2, Subsequent steps can be performed in a continuous manner.

FIG. 2 shows another example of a flow sheet for implementing the method of the present invention. In FIG. 2, reference numeral 1 denotes a dissolving step, and 5 denotes a joining step of a washing step and a solid-liquid separation step.
In order to separate the waste according to the flow sheet shown in FIG. 2, the waste is supplied to the dissolving step 1 through the line 10 and the separation solvent circulated through the line 14 is supplied to the dissolving step 1; By contacting the waste with the separation solvent,
Part of the waste is selectively dissolved in the fractionation solvent. This dissolving step 1 can be carried out in the same manner as the dissolving step 1 shown in connection with FIG.

The dissolved product obtained in the dissolving step 1 passes through a line 11 and is combined with a washing step and a solid-liquid separation step.
Sent to This bonding step 5 is a step having a solid-liquid separation function and a function of washing the separated solid surface, and is performed using a centrifugal filter or a cake filter equipped with a liquid spray device. The dissolved product introduced into the bonding step 5 is first separated into a fractionated solvent containing the dissolved plastic and an undissolved plastic, and the fractionated solvent containing the dissolved plastic is recovered through the line 16. Next, on the surface of the cake-like undissolved plastic after the completion of the solid-liquid separation, a fresh separation solvent is sprayed as a cleaning liquid through the line 17 to dissolve and remove the dissolved plastic adhered to the undissolved plastic surface in the separation solvent. I do. This cleaning removes substantially all of the dissolved plastic adhering to the undissolved plastic surface. The amount of fresh fractionated solvent used as a washing solution is such that the concentration of dissolved plastic contained in the fractionated solvent is 10% by weight or less in the total solution,
Preferably, the amount is 1 to 5% by weight. The separation solvent (wash waste liquid) containing the dissolved plastic obtained by this washing treatment is circulated to the dissolution step 1 through the line 14 and used as the separation solvent. On the other hand, the undissolved plastic that has been washed is collected through the line 18.

In the method shown in FIG. 2, the dissolving step 1 and the connecting step 5 of the washing step and the solid-liquid separating step can be performed using one apparatus. Among the conventionally known filtration devices, a so-called multifunctional filtration device having a solid-liquid stirring function, a solid-liquid separation function (filtration function), a filter cake washing function, a washing cake drying function, and the like is known. By using such an apparatus, the steps 1 and 5 can be performed by one apparatus.

[0019]

Next, the present invention will be described in more detail with reference to examples.

Reference Example 1 As a plastic waste model, PE: 35% by weight,
A plastic mixture consisting of 30% by weight of PP, 20% by weight of PS, 5% by weight of PVC, 5% by weight of PET and 5% by weight of ABS resin was crushed into strips. Next, Table 1
10 g of the crushed material was added to 100 g of each of the various solvents shown in (1) and heated at 130 ° C. for 30 minutes with stirring to conduct a plastic dissolution test. Table 2 shows the results. In Table 2, when the plastic component was dissolved in the solvent, it was indicated by "O", and when it was not dissolved, it was indicated by "X".

The specific contents of the pyrolysis oil shown in Table 1 are as follows. Pyrolysis oil A: Pyrolysis oil of PE Pyrolysis oil B: Mixed oil of pyrolysis oil of PS and pyrolysis oil of PE (mixing weight ratio = 0.95 / 0.05) Pyrolysis oil C: PE Mixed oil of pyrolyzed oil, pyrolyzed oil of PP and pyrolyzed oil of PS (mixing weight ratio = 1/1/1) Pyrolyzed oil D: Fraction of boiling point of pyrolyzed oil of PE below 280 ° C Oil E: a fraction having a boiling point of 150 to 350 ° C. of pyrolysis oil C Pyrolysis oil F: a fraction having a boiling point of 280 ° C. or lower of pyrolysis oil C Pyrolysis oil G: A fraction having a boiling point of 280 ° C. or lower of pyrolysis oil of PE Oil of a fraction having a boiling point of 280 ° C. or less of the pyrolysis oil of PP and a fraction having a boiling point of 280 ° C. or less of the pyrolysis oil of PS (mixing weight ratio = 8/8/84) A mixed oil of a fraction having a boiling point of 280 ° C. or less of the pyrolysis oil, a fraction having a boiling point of 280 ° C. or less of the pyrolysis oil of PP, and a fraction having a boiling point of 280 ° C. or less of the pyrolysis oil of PS (Weight ratio = 44/45/11)

[0022]

[Table 1]

[0023]

[Table 2]

The following can be seen from the results shown in Table 1 above. (1) Xylene is at least one kind of plastic A selected from PE, PP, PS and ABS, and PVC
It can be used as a separation solvent for selectively dissolving the plastic A contained in the waste consisting of at least one kind of plastic B selected from PET and PET. (2) Toluene is at least one kind of plastic A selected from PS and ABS, and PE, PP, PVC
It can be used as a separation solvent for selectively dissolving the plastic A contained in the waste consisting of at least one kind of plastic B selected from PET and PET. (3) Pyrolysis oil A comprises at least one kind of plastic A selected from PE and PP, and PS, PVC, PE
It can be used as a fractionation solvent for selectively dissolving the plastic A contained in the waste consisting of at least one type of plastic B selected from T and ABS. (4) Pyrolysis oil D comprises at least one kind of plastic A selected from PE and PP, and PS, PVC, PE
It can be used as a fractionation solvent for selectively dissolving the plastic A contained in the waste consisting of at least one type of plastic B selected from T and ABS. (5) Pyrolysis oils B, C, EH are PE, PT and PS
At least one kind of plastic A selected from
It can be used as a fractionation solvent for selectively dissolving the plastic A contained therein from the waste consisting of at least one type of plastic B selected from PVC, PET and ABS. That is, these pyrolysis oils are suitable as a separation solvent for separating waste consisting of hydrocarbon plastics and different hydrocarbon plastics into these two components.

Reference Example 2 Among the plastic mixtures shown in Reference Example 1, a hydrocarbon-based plastic mixture (PE: 41% by weight, PP: 35)
(% By weight, PS: 24% by weight) was dissolved in 100 g of the solvent F to form a solution, and this solution was thermally decomposed at 400 ° C. and normal pressure to obtain a cracked oil. next,
The cracked oil was distilled to obtain a fraction A having a boiling point of 100 to 400 ° C. Next, a dissolution test of the plastic mixture was performed in the same manner as in Reference Example 1 except that this fraction A was used as a fractionating solvent. As a result, it was confirmed that PE, PP and PS were all dissolved. In addition, it was confirmed that PVC, PET, and ABS resin were substantially insoluble and retained solid in the solvent. Further, when the proportions of aromatic hydrocarbons, paraffinic hydrocarbons and olefinic hydrocarbons contained in the fraction A were examined based on the ¹³ C-NMR spectrum, it was found that aromatic hydrocarbons: 3
The results were 5%, 50% paraffinic hydrocarbons and 15% olefinic hydrocarbons.

Example 1 A crushed product of a plastic mixture shown as a plastic waste model in Reference Example 1 was subjected to a separation treatment according to the flow sheet shown in FIG. 1, and then the separated plastic was subjected to a decomposition treatment. Distillation was performed. A: Separation Step (1) Dissolution Step As the separation solvent, the fraction A of Reference Example 2 containing the hydrocarbon-based plastic obtained in the washing step described below at a concentration of 1.5% by weight was used. In this case, the melting treatment temperature of the raw plastic mixture is 130 ° C., the melting treatment pressure is normal pressure, and the treatment time is 30 minutes. The amount of the raw material plastic mixture used was 100 parts by weight, and the amount of the fractionated solvent was 2 parts.
59 parts by weight. By the dissolution treatment, 100% by weight of the hydrocarbon-based plastic in the raw plastic mixture
Was dissolved and removed in the fractionation solvent. (2) First Solid-Liquid Separation Step The dissolution treatment product obtained in the dissolution step was filtered with a filter to obtain 329 parts of a solution and 15 parts by weight of a solid, different hydrocarbon-based plastic. The hydrocarbon-based plastic contained in the solution was 85 parts by weight, and the concentration in the solution was 2 parts by weight.
It was 6% by weight. (3) Washing step To 159 parts by weight of the solid foreign hydrocarbon-based plastic obtained above, 259 parts by weight of the fraction A shown in Reference Example 2 were added.
The plastic was washed with stirring. In this case, the washing temperature was 130 ° C., and the washing time was 30 minutes. (4) Second solid-liquid separation step The washing treatment product is filtered with a filter, and the solution 259 is removed.
Parts by weight and 15 parts by weight of a solid, different hydrocarbon plastic were obtained. Hydrocarbon plastic contained in solution is 4
And its concentration in the solution was 1.5% by weight. This solution was circulated to the dissolving step and used as a fractionation solvent. The solid hetero-hydrocarbon plastic obtained in this step was excellent in handleability without surface tackiness. B: Decomposition Step 100 parts by weight of the solution containing the hydrocarbon-based plastic obtained in the first solid-liquid separation step is subjected to a thermal decomposition treatment at a temperature of 400 ° C. and normal pressure for 30 minutes to obtain 98 parts by weight of a decomposition product oil. Obtained. C: Fractionation fractionation step for fractionated solvent The cracked product oil obtained in the cracking step B is distilled to have a boiling point of 400
0.7 parts by weight of a heavy oil fraction having a boiling point of 150 ° C. or lower and 5.4 parts by weight of a light oil fraction having a boiling point of 150 ° C. or lower. The light oil fraction thus obtained was analyzed by ¹³ C-NMR to find that the aromatic hydrocarbon: 35
%, Paraffinic hydrocarbons: 50% and olefinic hydrocarbons: 15%. Using this light oil fraction as a fractionating solvent, the plastic mixture was dissolved in the same manner as in the above-mentioned dissolving step. However, it was confirmed that it was kept in a solid state.

[0027]

According to the method for separating plastic waste of the present invention, a plastic component soluble in a separation solvent and a plastic component insoluble in the separation solvent can be efficiently separated. In addition, in the case of the present invention, the plastic component insoluble in the separation solvent is subjected to a washing treatment with a fresh separation solvent, so that the dissolved plastic component does not substantially adhere to the component. Therefore, it is possible to effectively prevent the loss of the dissolved plastic component at the time of separation between the dissolved plastic component and the insoluble plastic component, and the obtained separated solvent-insoluble plastic component has no adhesion of the dissolved plastic component on the surface. Therefore, it has no surface tackiness and is very easy to handle. Furthermore, in the present invention, since the solution after washing the plastic is circulated to the dissolving step and used as a fractionating solvent, the economics of the entire process is extremely high.

[Brief description of the drawings]

FIG. 1 shows an example of a flow sheet when the method for separating plastic waste according to the present invention is carried out.

FIG. 2 shows another example of a flow sheet when the method for separating plastic waste according to the present invention is carried out.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Dissolution process 2 1st solid-liquid separation process 3 Washing process 4 2nd solid-liquid separation process 5 Combination process of a washing process and a solid-liquid separation process

Continued on the front page (72) Inventor Kenji Nomi 2-1-1, Tsurumichuo, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture Inside Chiyoda Chemical Works (72) Inventor Masafumi Narita 2--12, Tsurumichuo, Tsurumi-ku, Yokohama-shi, Kanagawa No. 1 Chiyoda Chemical Construction Co., Ltd. (72) Inventor Hideki Sugiyama 2-2-1 Tsurumi Chuo, Tsurumi-ku, Yokohama, Kanagawa Prefecture No. 1 Chiyoda Chemical Construction Co., Ltd.

Claims (1)

[Claims] 1. A method for separating plastic waste, comprising: (i) a step of bringing the waste into contact with a separation solvent to dissolve a part of the plastics contained in the waste in the separation solvent; ii) a first solid-liquid separation step of separating the dissolved product obtained in the dissolving step into a fractionating solvent containing dissolved plastic and undissolved plastic; (iii) a first solid-liquid separation step obtained A washing step of washing the undissolved plastic using a fresh fractionating solvent as a washing liquid and dissolving the dissolved plastic adhering to the undissolved plastic surface in the fractionated solvent; (iv) dissolution after washing obtained in the washing step A circulating step of circulating a fractionating solvent containing plastic to the dissolving step.