WO2023073864A1

WO2023073864A1 - Method for producing high purity polyethylene or polypropylene

Info

Publication number: WO2023073864A1
Application number: PCT/JP2021/039834
Authority: WO
Inventors: 和敏池永
Original assignee: 学校法人君が淵学園
Priority date: 2021-10-28
Filing date: 2021-10-28
Publication date: 2023-05-04
Also published as: JPWO2023073864A1

Abstract

One embodiment of the present invention relates to a method for producing high purity polyethylene or polypropylene in which the polyethylene or polypropylene purity is higher than in a waste plastic. The method includes an extraction step for extracting polyethylene or polypropylene from the waste plastic which contains polyethylene or polypropylene, using a high boiling point solvent having a boiling point of 145°C or higher at 1 atm as an extraction solvent.

Description

Production method for producing high-purity polyethylene or polypropylene

One embodiment of the present invention relates to a manufacturing method for manufacturing high-purity polyethylene or polypropylene.

Many plastics composed of multiple components have been developed for the purpose of long-term storage of products such as foodstuffs and daily necessities, and as container and packaging materials for products that respond to diverse lifestyles. It is disposed of as a mixture or laminate containing plastics.

In recent years, with the enactment of the so-called Containers and Packaging Recycling Law (the Law Concerning the Promotion of Sorted Collection and Recycling of Containers and Packaging), it is desired to use recycled materials by recycling waste containers and packaging based on the Containers and Packaging Recycling Law. ing. In addition, with the recent increase in awareness of the protection of the natural environment, waste plastic materials from general plastic products other than containers and packaging waste based on the Containers and Packaging Recycling Law are being reused as recycled materials. Demand for recycling is also increasing.

It is extremely important to effectively recycle plastics containing multiple components that have been discarded as described above. For this recycling, it is required to separate the waste plastics and highly purify the prescribed plastics. there is

Waste plastics that are simply mixed with single-component plastics cannot be sorted by general physical sorting methods such as specific gravity separation in water or optical sorting using Raman light. However, it is difficult to separate composite plastics containing multiple components. In addition, optical sorting methods rarely sort PET bottles smaller than the cap size, so there is a limit to physical sorting methods.

In order to solve the above problems, in recent years, methods have been developed for separately collecting composite plastic materials consisting of multiple components (for example, Patent Documents 1 and 2).

JP 2018-187808 A JP 2015-21054 A

However, the high-purity products obtained by conventional separation and high-purification methods, such as the methods described in Patent Documents 1 and 2, do not have sufficient purity for the intended plastic.

One embodiment of the present invention provides a method for producing high-purity PE or PE from waste plastic containing polyethylene (hereinafter also referred to as "PE") or polypropylene (hereinafter also referred to as "PP").

As a result of earnestly examining methods for solving the above problems, the inventors of the present invention have found that the above problems can be solved according to the following configuration examples, and have completed the present invention.
A configuration example of the present invention is as follows.

[1] An extraction step of extracting polyethylene or polypropylene from waste plastic containing polyethylene or polypropylene using a high-boiling solvent with a boiling point of 145 ° C. or higher at 1 atm as an extraction solvent.
A production method for producing high-purity polyethylene or polypropylene in which the purity of the polyethylene or polypropylene is higher than that of the waste plastic.

[2] The production method according to [1], wherein the high-boiling solvent is an aromatic compound.

[3] The production method according to [1] or [2], wherein the high-boiling solvent is at least one selected from cumene, mesitylene and trimethylbenzene.

[4] In the extraction step, a poor solvent for polyethylene or polypropylene is added to the solution obtained by dissolving the polyethylene or polypropylene in the waste plastic in the extraction solvent, and the polyethylene or polypropylene is precipitated and recovered. The manufacturing method according to any one of [1] to [3], comprising

[5] The production method according to [4], wherein the poor solvent is at least one selected from methanol, ethanol, isopropanol, acetone, ethyl acetate, tetrahydrofuran and chloroform.

According to one embodiment of the present invention, high-purity PE or PE can be easily produced from waste plastic containing PE or PP.
Therefore, according to one embodiment of the present invention, waste plastics (PE or PP) can be smoothly reused, contributing to the construction of a recycling-oriented society.

FIG. 1 is a flowchart showing an example of a production method for producing high-purity polyethylene or polypropylene according to one embodiment of the present invention.

<<Manufacturing method for producing high-purity polyethylene or polypropylene>>
A production method for producing high-purity polyethylene or polypropylene according to one embodiment of the present invention (hereinafter also referred to as “this production method”) uses a high-boiling solvent having a boiling point of 145 ° C. or higher at 1 atm as an extraction solvent, PE or an extraction step of extracting PE or PP from waste plastic containing PP,
It is a production method for producing high-purity PE or PP in which the purity of PE or PP is higher than that of the waste plastic.
Hereinafter, the high-purity PE or PP produced by this production method is also simply referred to as "high-purity product".

<Extraction process>
The extraction step is a step of extracting PE or PP from waste plastic containing PE or PP using a high boiling point solvent having a boiling point of 145° C. or higher at 1 atm as an extraction solvent.

The extraction solvent is not particularly limited as long as it is a high-boiling solvent having a boiling point of 145° C. or higher at 1 atm.
The boiling point at 1 atm of the high boiling point solvent is preferably 150° C. or higher and preferably 200° C. or lower.
By using an extraction solvent having a boiling point within the above range, a highly purified product of higher purity can be easily obtained. In addition, it is preferable to use an extraction solvent having a boiling point within the above range because it is possible to keep the vapor concentration in the working environment sufficiently low.
The extraction solvent used in the extraction step may be one kind or two or more kinds.

The high-boiling-point solvent is preferably an aromatic compound, and at least one selected from cumene, mesitylene and trimethylbenzene, from the viewpoint that a highly purified product of higher purity can be easily obtained. Cumene and mesitylene are more preferable, and mesitylene is particularly preferable, from the viewpoint of availability.

The waste plastic is not particularly limited as long as it includes PE or PP, and specific examples include bid items from the Japan Containers and Packaging Recycling Association, items collected by local governments, plastic raw material manufacturers (unused (deteriorated) items) ), plastic molding manufacturers (including unused (deteriorated) raw materials, molding defects, molding residues), collected products from plastic product users (e.g. convenience stores, supermarkets, shopping stores), waste plastic intermediate processing companies , recovered products from industrial waste disposal companies, unsorted waste plastics such as recovered marine plastics; and waste plastics sorted by intermediate processing companies.
Among these, as the waste plastic, pre-sorted waste plastic is preferable, and waste plastic sorted by optical sorting is more preferable. The waste plastic separated by the optical sorting may be PE or PP that has been agglomerated by a conventionally known method, or may be PE or PP in the form of a film before being agglomerated.

In general, intermediate processing companies for waste plastics use optical sorting machines such as Raman spectroscopy to separate recovered plastics larger than PET bottle caps from PE, PP, polystyrene (PS), and polyethylene terephthalate (PET). ) and vinyl chloride resin. The purity of PE or PP separated in this way is about 80% at most, which is the limit of the sorter (the balance includes, for example, PS, PET, vinyl chloride resin, and aluminum). .
Then, the separated PE or PP is washed with water and dried with hot air at about 80 ° C. to reduce the volume, resulting in agglomerate PE (agglomerate PE) or agglomerate PP (agglomerate PP). called.

It should be noted that the waste plastic used in this manufacturing method may be PE or PP with a higher purity (80% or more) than PE or PP sorted by normal sorting. In other words, this production method may be a production method for producing PE or PP obtained by further purifying high-purity PE or PP.

The extraction step is not particularly limited, and preferably includes a step 1 of dissolving PE or PP in the raw material waste plastic in the extraction solvent to obtain a solution containing PE or PP.
The above step 1 is preferably a heating reflux step from the viewpoint that a highly purified product of higher purity can be easily obtained.
Such a heating-refluxing step is preferably performed while stirring.
A conventionally known extractor such as a Soxhlet extractor may be used for the heating under reflux. Since the temperature at the time of contact with the extraction solvent tends to decrease and the extraction capacity tends to decrease, such a method requiring reheating tends not to be suitable.

The reflux temperature in the heating and refluxing step may be appropriately set according to the extraction solvent to be used.
A specific example of the reflux temperature is a temperature near the boiling point of the extraction solvent, preferably 145 to 200° C., more preferably 150° C., from the viewpoint that a highly purified product of higher purity can be easily obtained. ~200°C.
In step 1, the temperature at which the waste plastic and the extraction solvent are brought into contact is preferably within this reflux temperature range.

A conventionally known heating method can be employed for the heating method in the heating and refluxing step. Examples include dielectric heating, hot air heating, and heating by fire (flame). Among these, microwave heating is preferable because the heating time can be shortened and the step 1 can be shortened.

The heating and refluxing step may be performed under pressure. In this case, for example, a closed container may be used.
By performing the heating and refluxing step under pressure, the reflux temperature in the heating and refluxing step can be lowered and the reflux time can be shortened.
The pressurization includes, for example, a pressure such that the pressure in the system is atmospheric pressure to 5 MPa. When the heating/refluxing step is performed under such a pressure, the heating/refluxing may be performed at a reflux temperature corresponding to the pressure.

The time for the heating and refluxing step is not particularly limited, and may be appropriately set according to the amount of polyethylene and polypropylene in the waste plastic to be dissolved.

In the step 1, the components dissolved in the extraction solvent can be permeated to obtain an extraction solvent in which PE or PP is dissolved, and the PE or PP can be removed without permeating the components insoluble in the extraction solvent. It is preferable to carry out step 1 (contact the waste plastic with the extraction solvent) so that it can be separated from the dissolved extraction solvent.
Specifically, the waste plastic is placed in a bag made of cotton, paper, or the like that is permeable to components dissolved in the extraction solvent and impermeable to components insoluble in the extraction solvent, and the waste plastic placed in the bag is used. Performing step 1, using a filter made of paper, cotton, activated carbon, celite, etc., which allows the components dissolved in the extraction solvent to pass through and does not allow the components insoluble in the extraction solvent to pass through, the components dissolved in the extraction solvent. For example, step 1 can be carried out by permeating and dissolving in the extraction solvent and separating components insoluble in the extraction solvent.
By performing such step 1, the components insoluble in the extraction solvent can be easily separated.

The extraction step preferably includes step 2 of separating and recovering PE or PP from the solution containing PE or PP obtained in step 1.
The step 2 is not particularly limited, and conventionally known methods can be employed. Specifically, a poor solvent for PE or PP is added to the solution containing PE or PP obtained in step 1. to precipitate and recover PE or PP.

The poor solvent is not particularly limited as long as it has a low solubility for PE or PP, but a solvent with a low boiling point is preferable.
The low boiling point includes solvents having a boiling point at 1 atm of preferably 90° C. or lower, more preferably 70° C. or lower.
Examples of the poor solvent include methanol, ethanol, isopropanol, acetone, ethyl acetate, tetrahydrofuran, and chloroform. Among these, acetone is preferable because it can easily obtain PE or PP of higher purity.
One type of the poor solvent may be used, or two or more types may be used.

The method for recovering the precipitated PE or PP is also not particularly limited, and conventionally known methods can be employed, but a preferred example is filtration (including hot filtration).

The extraction solvent and poor solvent are preferably recovered and reused.
Examples of the method for recovering the extraction solvent and the poor solvent include a method of distilling and purifying the filtrate obtained by the filtration.

Each of the above steps may be performed using a batch-type device (system), a semi-batch-type device (system), or a continuous-type device (system). may

<Highly purified product>
The highly purified product is not particularly limited as long as the PE or PP has a higher purity than the waste plastic used in the production method.
According to this production method, for example, when agglomerate PE or agglomerate PP having a PE or PP purity of 80% is used as the waste plastic, the PE or PP purity is preferably 90% or more, more preferably 95%. The above plastic (highly purified product) can be obtained.
The purity of PE or PP in the obtained highly purified product can be measured by nuclear magnetic resonance spectroscopy or the method described in Japanese Patent No. 6574081, for example.

The highly purified product can be used, for example, in films (sheets), plastic materials for cars, trains, airplanes, ships, etc., molded bodies such as pallets, bottle containers other than drinking water, and packaging films. Since the highly purified product has a higher purity of PE or PP than conventional agglomerate PE, PP, etc., it can be used for film forming, etc., which could not be done with conventional waste plastics.
Moreover, the highly purified product can be used by mixing with virgin PE, PP, or the like, if necessary.

Next, one embodiment of the present invention will be described in more detail with examples, but the present invention is not limited by these.

[Example 1]
In a 200 mL eggplant-shaped flask equipped with a reflux condenser, a stirrer and 1.04 g of Agrome PP (manufactured by Ecoport Kyushu Co., Ltd., waste plastic whose purity was adjusted to about 80% by mass by a continuous optical sorting device) and 86.0 g of cumene as an extraction solvent were added, and heated under reflux for 1 hour with stirring at a reflux temperature of 155° C. (near the boiling point of cumene) using a hot stirrer. Then, 55.3 g of methanol as a poor solvent was added to the eggplant-shaped flask after heating under reflux to precipitate PP.
Suction filtration was carried out to collect the precipitated plastic. The mass of the filtered residue after drying (recovered plastic containing PP as the main component) was 0.94 g, and the extraction residue remaining in the cotton bag was 0.02 g. Therefore, the extraction rate was 98%.
From the filtrate obtained by the suction filtration, methanol and cumene were distilled off under reduced pressure and recovered using a cooling device (solvent recovery rate: 80%). The residue in the filtrate after recovering the solvent (hereinafter also referred to as "filtrate residue") was 0.08 g.

When the purity of PP and PE in the recovered plastic was measured by the method for measuring the purity of plastics described in Patent No. 6574081, the purity was 89.5%.

[Example 2]
In Example 1, the same operation as in Example 1 was performed except that the amount of agglomerate PP used was changed to 0.98 g and the type of poor solvent was changed to acetone.
The mass of the filtered material after drying (recovered plastic containing PP as a main component) was 0.76 g, and the extraction residue was 0.03 g, so the extraction rate was 96%.
Also, the solvent recovery rate was 87%, and the filtrate residue was 0.19 g.

When the purity of PP and PE in the recovered plastic was measured by the method for measuring the purity of plastics described in Japanese Patent No. 6574081, the purity was 98.5%.
Further, infrared spectrophotometric analysis revealed that the extraction residue was mainly PET.

[Example 3]
In Example 1, the same operation as in Example 1 was performed except that the amount of agglomerate PP used was changed to 1.09 g, the extraction solvent was changed to mesitylene, and the reflux temperature was changed to 164°C.
The mass of the filtered material after drying (recovered plastic containing PP as a main component) was 0.95 g, and the extraction residue was 0.06 g, so the extraction rate was 94%.
Also, the solvent recovery rate was 72%, and the filtrate residue was 0.08 g.

[Example 4]
In Example 3, the same operation as in Example 3 was performed except that the amount of agglomerate PP used was changed to 1.02 g, the amount of mesitylene used was changed to 87.0 g, and the type of poor solvent was changed to acetone. did
The mass of the filtered material after drying (recovered plastic containing PP as a main component) was 0.85 g, and the extraction residue was 0.03 g, so the extraction rate was 97%.
Also, the solvent recovery rate was 83%, and the filtrate residue was 0.14 g.

[Example 5]
Example 4 except that in Example 4, Agrome PE (manufactured by Ecoport Kyushu Co., Ltd., waste plastic with a PE purity of about 80% by mass by a continuous optical sorting device) was used instead of Agrome PP. performed the same operation.
The mass of the filtered material after drying (recovered plastic containing PE as a main component) was 0.84 g, and the extraction residue was 0.07 g, so the extraction rate was 92%.
Also, the solvent recovery rate was 88%, and the filtrate residue was 0.06 g.

[Example 6]
In Example 4, instead of 1.02 g of agglomerate PP, waste PP (manufactured by Ecoport Kyushu Co., Ltd., a film before agglomerating waste plastic with a PP purity of about 80% by mass by a continuous optical sorting device) was used. The same operation as in Example 4 was performed except that 0.00 g was used.
The mass of the filtered material after drying (recovered plastic containing PP as a main component) was 0.84 g, and the extraction residue was 0.08 g, so the extraction rate was 91%.
Also, the solvent recovery rate was 80%, and the filtrate residue was 0.08 g.

[Example 7]
In Example 5, instead of 0.97 g of agglomerate PE, waste PE (manufactured by Ecoport Kyushu Co., Ltd., a film before agglomeration of waste plastic with a PE purity of about 80% by mass by a continuous optical sorting device) was used. The same operation as in Example 5 was performed except that .03 g was used.
The mass of the filtered material after drying (recovered plastic containing PE as a main component) was 0.93 g, and the extraction residue was 0.04 g, so the extraction rate was 96%.
Also, the solvent recovery rate was 87%, and the filtrate residue was 0.06 g.

[Comparative Example 1]
In Example 1, the amount of agglomerate PP used was changed to 1.15 g, 86.6 g of toluene was used instead of 86.0 g of cumene, and the reflux temperature was changed to 110°C (a temperature near the boiling point of toluene). Except for this, the same operation as in Example 1 was performed.
The mass of the filtered material (recovered plastic) after drying was 0.32 g, and the extraction residue was 0.79 g, so the extraction rate was 32%.
Also, the solvent recovery rate was 56%, and the filtrate residue was 0.04 g.

Claims

An extraction step of extracting polyethylene or polypropylene from waste plastics containing polyethylene or polypropylene using a high-boiling solvent with a boiling point of 145 ° C. or higher at 1 atm as an extraction solvent.
A production method for producing high-purity polyethylene or polypropylene in which the purity of the polyethylene or polypropylene is higher than that of the waste plastic.
The production method according to claim 1, wherein the high-boiling solvent is an aromatic compound.
The production method according to claim 1 or 2, wherein the high-boiling solvent is at least one selected from cumene, mesitylene and trimethylbenzene.
The extraction step includes a step of precipitating and recovering polyethylene or polypropylene by adding a poor solvent for polyethylene or polypropylene to a solution obtained by dissolving polyethylene or polypropylene in the waste plastic in the extraction solvent. The production method according to any one of claims 1 to 3.
The production method according to claim 4, wherein the poor solvent is at least one selected from methanol, ethanol, isopropanol, acetone, ethyl acetate, tetrahydrofuran and chloroform.