JP3002731B1 - Plastic mixed waste treatment method - Google Patents

Abstract

Kind Code: A1 Abstract: A treatment method for purifying chlorine-containing resin, which requires little pretreatment and discharges no harmful substances to the environment, is a plastic mixed waste mixed with chlorine-containing resin. provide. A plastic mixed waste and an alkaline solution are contained in a reaction vessel, and the contents in the reaction vessel are heated to 180 ° C.
Heat to the following temperature and stir.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating plastic waste, and more particularly, to a method for treating plastic waste using an alkaline solution.

[0002]

2. Description of the Related Art The production of plastic raw materials in Japan reaches about 14.66 million tons per year. Of these, plastics containing chlorine, such as polyvinyl chloride and polyvinylidene chloride, account for about 21%. At present, products produced from these chlorine-containing plastic raw materials are widely used for a wide range of applications. For example, polyvinyl chloride is widely used for industrial and general purposes because it is an inexpensive resin and has excellent workability and mechanical properties. Also,
Polyester resin or polyethylene terephthalate (PE
Plastics such as T) are also used in large amounts for a wide range of applications.

As described above, plastics have a very wide range of applications and are used in large quantities. On the other hand, with the increase in plastic production, waste of plastic products is increasing year by year, and has become a major social problem. ing. Plastic products that are no longer needed are usually collected at once and become a mixed waste of various plastics.

At present, plastic waste disposal includes (1) landfill, (2) recycling, (3) incineration, and (4)
Thermal decomposition oil conversion, (5) conversion to solid fuel, and (6) conversion to blast furnace raw material.

[0005] The "landfill" of (1) typically includes a sea surface landfill and a lowland landfill. However, at present, it is difficult to secure a new landfill. Also, plastic does not rot. Therefore, the ground where plastic waste is landfilled is unstable. In addition, plastic waste will be collected in the future due to the enforcement of the Containers and Packaging Recycling Law and the Home Appliance Recycling Law.

[0006] The "recycling process" of (2) is a processing method in which only high-quality plastic waste is separated and collected, and processed into a desired product. Thus, in the recycling process, it is necessary to determine whether each of the plastic wastes is suitable for the recycling process. Therefore, it is very inefficient to apply this to plastic mixed waste. As described above, in the processing method by the regeneration processing,
All plastic waste cannot be treated and is inefficient.

In contrast to the physical treatment methods (1) and (2), the treatment methods (3) to (6) decompose the plastic itself. Since the plastic containing chlorine is mixed in the mixed plastic waste, hydrochloric acid is generated during decomposition. Therefore, the waste treatment equipment deteriorates rapidly because it is exposed to hydrochloric acid at a high temperature. Further, when the chlorine-containing resin is decomposed, a small amount of an organic chlorine compound may be generated. Such an organic chlorine compound is not preferable for the environment, and causes a problem of environmental pollution. In particular, most of the above-mentioned chlorine-containing resins are mixed with a plasticizer in order to impart plasticity. For example, at present, plasticizers for polyvinyl chloride are consumed most in quantity. During plastic degradation, this plasticizer behaves as an environmental hormone and can cause problems during processing. what if,
Even if the chlorine-containing resin is a waste that is not mixed, an inorganic chlorine compound such as sodium chloride can be inevitably mixed. Therefore, such inorganic chlorine compounds
Since organic chlorine compounds can be generated during incineration or thermal decomposition of waste, there is a problem of environmental pollution.

[0008] In the thermal decomposition oil conversion of (4), the operation of equipment and the quality of products are greatly affected depending on the waste mixed. In particular, water, pet materials, metals, and the like need to be removed from the waste at the stage of pretreatment. It is no exaggeration to say that moisture cannot be avoided in wastes. Therefore, a drying step is required in order to adjust the moisture content of the waste to an appropriate value. As for pet materials, beverage pet containers are separated and collected by manual selection. However, pet containers for foods and detergents can be inevitably mixed. These pet materials are
When the equipment is operating, it is a cause of blockage of piping and the like. Metals are collected from waste by an eddy current generator. As described above, in the case of thermal decomposition oiling, etc., it is necessary to go through a plurality of pretreatment steps in order to remove pet materials, metals, moisture, etc., and it is difficult to remove all of these in the pretreatment. It is.

[0009]

An object of the present invention is to decompose and extract a plasticizer or the like in a plastic mixed waste mixed with a chlorine-containing resin without generating and discharging harmful substances. And to provide a processing method for obtaining a purified plastic.

[0010]

According to the present invention, a plastic mixed waste mixed with a chlorine-containing resin and an alkaline solution are accommodated in a reaction vessel, and the contents in the reaction vessel are heated to 180 ° C. A step of heating at the following temperature to selectively decompose and extract a plasticizer from the chlorine-containing resin.

Further, according to the present invention, almost no pretreatment is required, and preferably, only the plastic mixed waste is crushed in advance.

According to the present invention, the alkaline solution is preferably a caustic aqueous solution. In particular,
The concentration of the aqueous caustic solution is preferably 20 to 50% by weight.

Further, the ratio of the plastic mixed waste to the alkaline solution is preferably 1 to 8% by weight.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the plastic mixed waste to be treated can be waste mixed with plastic and discharged from ordinary households and / or various industries.

According to the present invention, it is not always necessary to remove moisture, metal, and the like from the plastic mixed waste in advance, and the mixed waste may be left as it is. Conventionally, in a process such as thermal decomposition oiling, the separated pet material may be kept mixed. Thus, in the present invention, moisture, metal,
A plurality of pretreatment steps for removing pet materials and the like can be omitted.

According to the present invention, it is preferable that the plastic mixed waste is crushed in advance by a cutter or the like. As for the degree of crushing, the finer the crushing, the more efficiently the contact reaction with the alkaline solution described below can be performed. 3m to get
It is desirable to crush to about m or more. More preferably, the maximum length of the crushed plastic is from 5 mm to 15 mm.
mm. With such a degree of crushing, a contact reaction with an alkaline solution described later can be sufficiently performed. In the present invention, a pretreatment such as removal of pet material and metal and removal of water as in the above-described conventional technique is not particularly required, and a simple pretreatment such as crushing as described above is preferable. Of course, when the individual sizes of the plastics are small in advance, it is needless to say that the plastics need not be crushed.

Next, preferably, the crushed plastic mixed waste and the alkaline solution are accommodated in a reaction vessel.

In the present invention, since an alkaline solution is used, it is preferable that the reaction vessel is alkali-resistant. In addition, since heating is performed as described below, it is more preferable that the material be alkali-resistant and heat-resistant.

According to the present invention, it is preferable to use caustic as the alkali. Caustic alkali shows strong alkalinity as an aqueous solution. By using such a strong base as a catalyst, hydrolysis extraction of the plasticizer contained in the chlorine-containing resin and hydrolysis of the pet material can be efficiently advanced. Also, by using caustic,
Phthalic acid generated by hydrolysis from a plasticizer or pet material can be precipitated as sodium phthalate or potassium phthalate. Therefore, these precipitated phthalates can be easily recovered. The phthalate recovered from the alkaline solution can be purified purely by any suitable method known in the art. The purified phthalate can be reused as a desired chemical raw material. Ethylene glycol produced by the decomposition of pet material can also be recovered from the alkaline solution, purified, and reused as a chemical raw material or raw fuel.

In the present invention, it is important from the viewpoint of processing efficiency to promptly perform a selective decomposition and extraction reaction of a plasticizer from a chlorine-containing resin and to rapidly perform a decomposition reaction of a pet material. If the concentration of the alkaline solution is reduced, the above-mentioned reaction rate is reduced, so that it is not efficient. On the other hand, when the concentration of the alkaline solution is increased, the decomposition and extraction of the plasticizer and the decomposition of the pet material can proceed promptly, but chlorine can also be extracted from the chlorine-containing resin. In view of these, in the present invention, in the case of the above-mentioned preferred embodiment using caustic alkali, the concentration is preferably 20% by weight to 50% by weight. By the way, caustic alkali can be usually obtained at the above preferable concentration (usually around 48% by weight). Moreover, such preferred concentrations of caustic solutions cannot be solidified at room temperature and are therefore easier to handle in the present invention. Further, in the case of the preferable caustic alkali concentration as described above, the steam pressure cannot be increased during the heating described later. Therefore, when a closed container is used, it is not necessary to use a pressure-resistant container.

The alkaline solution as described above and preferably the crushed plastic mixed waste are each in a predetermined amount,
Place in a reaction vessel. In addition, at the time of accommodation, it is preferable from the viewpoint of safety that the atmosphere in the reaction vessel be an inert gas atmosphere.

In the present invention, since the reaction is a solid-liquid contact reaction, an appropriate solid-liquid ratio is desirable for promoting the reaction. Here, in the present specification, the solid-liquid ratio indicates a ratio of the weight of the solid to the weight of the liquid. In the present invention, the solid-liquid ratio is desirably a large value from the viewpoint of processing efficiency.
However, since the specific gravity of the plastic is smaller than that of the alkaline solution, the amount floating on the alkaline solution increases depending on the amount of the plastic. Therefore,
Solid-liquid contact cannot be performed sufficiently. Conversely, if the solid-liquid ratio is made smaller, solid-liquid contact can be sufficiently performed and the reaction can proceed promptly, but it is not efficient. In the present invention, taking these factors into consideration, the solid-liquid ratio is set to 1
Preferably, it is between 8% and 8% by weight. In the present invention, the alkali functions as a catalyst when hydrolyzing the plasticizer and the pet material contained in the chlorine-containing resin. In a preferred embodiment using caustic alkali, it also has a function of precipitating phthalic acid, which is generated by decomposition from a plasticizer or pet material, as a phthalate. Therefore, in the case of a preferred embodiment using caustic alkali in particular, it is necessary to consider the required amount of alkali. However, if the solid-liquid ratio is as described above, the amount of alkali can sufficiently function during the catalyst and precipitation reaction.

Thereafter, the contents contained in the reaction vessel are heated to a temperature of 180 ° C. or less. In the present invention, in order to selectively decompose and extract the plasticizer contained in the chlorine-containing resin by the contact reaction with the alkaline solution, the reaction temperature is almost zero, and almost no chlorine is extracted. It is important that the temperature is such that it can be extracted. The reaction temperature can proceed from room temperature, but if the temperature is low, the decomposition rate of the plasticizer and the decomposition rate of the pet material are low, so it is not efficient, but most chlorine is extracted from the chlorine-containing resin. Without decomposing, the plasticizer can be selectively decomposed and extracted. Also, as the reaction temperature,
When the temperature exceeds 180 ° C., chlorine extraction is also started from the chlorine-containing resin, so that the plasticizer cannot be selectively decomposed and extracted from the chlorine-containing resin. According to the present invention, in consideration of these, the reaction temperature may be from room temperature to 180 ° C, but is preferably from 100 ° C to 18 ° C.
Desirably, the temperature is 0 ° C.

The contents contained in the reaction vessel are heated to a predetermined temperature which can be achieved by heating the reaction vessel or the like, and then maintained for a predetermined time, whereby the plasticizer contained in the chlorine-containing resin is heated. And pet materials can be decomposed and phthalic acid can be sufficiently extracted. In the case of the preferred embodiment using sodium hydroxide, the phthalic acid can be sufficiently extracted within about 5 hours as a holding time by using the above-mentioned preferable concentration, solid-liquid ratio and reaction temperature.
That is, the selective decomposition and extraction of the plasticizer contained in the chlorine-containing resin and the decomposition of the pet material can be sufficiently performed.

In the present invention, the specific gravity of the plastic is smaller than that of the alkaline solution. Therefore, when the plastic and the alkaline solution are at rest or the reaction vessel is left at rest, the plastic and the alkaline solution may not sufficiently come into contact with each other, and the reaction may not proceed quickly. Therefore, in order to make the reaction proceed efficiently, it is desirable that the plastic and the alkaline solution are brought into contact as much as possible. In the present invention, it is preferable to increase the chance of contact between the plastic in the reaction vessel and the alkaline solution by using a shaking device or a stirring device. As an example, when using a stirring device such as an electromagnetic rotary blade, it depends on the stirring performance of the stirring blade and the like,
It is preferable to set the stirring rotation speed to about 400 rpm to 1000 rpm. By such means such as stirring, the solid-liquid contact reaction can be sufficiently improved.

According to the present invention, as described above, from the chlorine-containing resin that can be mixed with the plastic mixed waste,
The plasticizer can be selectively decomposed and extracted. In addition, additives that can be contained in polyethylene, polystyrene, polypropylene, and the like that can be mixed in chlorine-containing resin and plastic mixed waste can be simultaneously extracted. A chlorine-based resin containing no plasticizer can be purified and reused as a raw material for a desired chlorine-based resin product. Further, a chlorine-based resin containing no plasticizer can be used as a raw material for thermal decomposition oiling, and can be oiled without generating an organic chlorine compound. In a preferred embodiment using a caustic alkali, phthalic acid generated by decomposition of a plasticizer precipitates in an alkaline solution as a phthalate and can be easily recovered, and this phthalate is reused as a chemical raw material. Can be used. Furthermore, at the same time as the decomposition extraction of the plasticizer from the chlorine-containing resin, the pet material that can be mixed with the plastic mixed waste can also be decomposed at the same time. In a preferred embodiment using caustic alkali, phthalic acid (terephthalic acid) generated by decomposition can be easily recovered from an alkaline solution as a phthalate, and this phthalate can be reused as a chemical raw material or the like. Can be. Furthermore, by decomposition of pet material,
Since ethylene glycol is also produced, it can also be reused as a chemical raw material or raw fuel.

[0027]

EXAMPLES Examples of the present invention will be described below together with comparative examples. In the following Examples and Comparative Examples, plastic mixed waste containing a chlorine-containing resin separated from general waste was used as a sample.

Example 1 First, a plastic mixed waste was crushed by a crushing cutter for 10 minutes.
Crushed to about mm. 15 pieces of crushed mixed plastic
g were separated and stored in a reaction vessel. As a reaction vessel, an autoclave made of SUS304 having an inner volume of 1 L (liter) was used. Then, 500 mL (milliliter) of a 50% by weight aqueous sodium hydroxide solution was accommodated in the reaction vessel, and the solid-liquid ratio was adjusted to 3% by weight. The atmosphere in the reaction vessel was a nitrogen gas atmosphere.

Next, the reaction vessel was heated and the contents were
The temperature was raised to a temperature of 0 ° C. Then, the contents were stirred at a rotation speed of 1000 rpm by an electromagnetic induction type rotating blade, and the temperature was maintained for 2, 3 and 5 hours. Thereafter, the autoclave was cooled to room temperature. After cooling, the contents were taken out of the reaction vessel, passed through a glass filter, and the filtrate was diluted. The diluted filtrate was passed through a cation exchange column to remove sodium ions. The phthalic acid and chlorine in the liquid from which sodium ions had been removed were quantified by ion chromatography. Dionex (Dionex) as an ion chromatography device
DX100 manufactured by the company was used.

Example 2 In Example 2, the same sample as in Example 1 was used. Exactly the same as Example 1 except that the reaction temperature was 180 ° C., and the holding time was 0 hour (that is, immediately after the temperature of the contents in the reaction vessel reached 180 ° C., the temperature was lowered) and 3 hours. Phthalic acid and chlorine were quantified by a simple method.

COMPARATIVE EXAMPLE 1 Using the same sample as in Example 1, except that the reaction temperature was 200 ° C. and the holding time was 5 hours, the same procedure as in Example 1 was carried out. Chlorine was quantified.

Reaction temperature 150 ° C. (Example 1), 180 ° C.
When the amount of dephthalic acid removed with respect to the retention time at (Example 2) and 200 ° C. (Comparative Example 1) was examined, the characteristic diagram shown in FIG. 1 was obtained. Here, the amount of dephthalic acid indicates the ratio of the weight of dephthalic acid to the weight of the sample when stored.

As is clear from FIG. 1, the first embodiment (15
0 ° C.), Example 2 (180 ° C.) and Comparative Example 1 (200 ° C.).
C), the amount of dephthalic acid was about 0.15% by weight at any holding time. Therefore, it was found that the amount of dephthalic acid had reached a plateau, and it was confirmed that the phthalic acid contained in the sample was sufficiently extracted.

Further, the dechlorination rate in Example 1 (150 ° C.) and Example 2 (180 ° C.), that is, the ratio of the dechlorination amount to the total chlorine amount contained in the sample at the time of storage was determined. As a result, the dechlorination rate was
2.6%. On the other hand, as a result of obtaining the dechlorination rate in Comparative Example 1, the value was as high as 15%.

As described above, in Example 1 (150 ° C.) and Example 2 (180 ° C.), phthalic acid was sufficiently and selectively extracted with almost no extraction of chlorine. I understood. On the other hand, the reaction temperature 20
At 0 ° C., although dephthalic acid could be sufficiently performed, it was found that the dephthalic acid could not be selectively performed because of the high dechlorination rate.

Example 3 The same plastic mixed waste as the sample used in Example 1 was finely crushed to about 5 mm by a crushing cutter. From the mixed plastic waste thus crushed, 1.0 g was separated and placed in a reaction vessel having an internal volume of 35 mL (milliliter). As the reaction vessel, a stainless steel sealed vessel whose inside surface was treated with a fluororesin was used. Subsequently, 10 mL of a 50% by weight aqueous sodium hydroxide solution was accommodated in the reaction vessel, and the solid-liquid ratio was adjusted to 1% by weight. Thereafter, the atmosphere in the reaction vessel was changed to a nitrogen gas atmosphere, and the reaction vessel was sealed.

Next, the reaction vessel was immersed in an oil bath which had been heated to 180 ° C. in advance and held for a predetermined time. The holding time was 5 hours. During the temperature holding, the reaction vessel was shaken, and the contents in the reaction vessel were stirred.
As a shaking device, YAMATO (Yamato) M
Using H-10 OIL BATH SHAKER, the contents in the reaction vessel were stirred at a shaking frequency of 120 times / minute.

Thereafter, the reaction vessel was pulled out of the oil bath and cooled to room temperature. After cooling, the contents were taken out of the reaction vessel. Thereafter, the procedure was performed in the same manner as in Example 1, and phthalic acid and chlorine were quantified.

The amount of dephthalic acid and the dechlorination rate by the treatment in Example 3 were examined. As a result, the amount of dephthalic acid was about 0.5.
The dechlorination rate was 15% by weight and the dechlorination rate was 2.6%, and the same results as in Examples 1 and 2 were obtained.

From the above, it was found that in Examples 1, 2 and 3, phthalic acid could be sufficiently and selectively extracted without almost extracting chlorine.

[0041]

As described above, according to the present invention, preferably, only the plastic mixed waste is crushed as a pretreatment, and the plasticizer contained in the chlorine-containing resin is removed by the contact reaction with the alkaline solution. Selectively decompose and extract,
It can be purified as a plastic containing no plasticizer. In addition, phthalic acid generated by decomposition of the plasticizer can be recovered and reused as a chemical raw material or the like. At the same time, the pet material can also be decomposed and the decomposition products can be reused as chemical raw materials and the like.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the temperature holding time at reaction temperatures of 150, 180 and 200 ° C. and the amount of dephthalic acid.

Continuation of the front page (56) References JP-A-10-330532 (JP, A) JP-A-9-291290 (JP, A) JP-A-8-259728 (JP, A) JP-B-51-42640 (JP) , B2) (58) Field surveyed (Int. Cl. ⁷ , DB name) C08J 11/02 B09B 3/00 C10G 1/10

Claims (5)

(57) [Claims] 1. A step of accommodating a plastic mixed waste mixed with a chlorine-containing resin and an alkaline solution in a reaction vessel, and heating the contents in the reaction vessel at a temperature of 180 ° C. or less to form the content. A process for selectively decomposing and extracting a plasticizer from a chlorine-based resin. 2. The method according to claim 1, wherein the plastic mixed waste is crushed in advance so that the maximum length is 5 to 15 mm. 3. The processing method according to claim 1, wherein the alkaline solution is an aqueous caustic solution. 4. The concentration of the aqueous caustic alkali solution is 20
The method according to claim 3, wherein the amount is from 50 to 50% by weight. 5. The treatment method according to claim 1, wherein a ratio of the plastic mixed waste to the alkaline solution is 1 to 8% by weight.