JP2024150970A - Resin recovery method and device - Google Patents

Abstract

[Problem] To provide an efficient method for recovering resin. [Solution] The method for recovering resin includes pouring a solution in which the resin component to be recovered is dissolved in a solvent into a transport path, precipitating the resin component from the solution in the transport path while transporting the solution along the transport path, and separating and recovering the precipitate from the solvent. [Selected Figure] Figure 2

Description

The present invention relates to a method and device for recovering resin.

In recent years, there has been active development of recycling technologies for recovering resin materials from resin molded products as recycled raw materials. Resin molded products are used in a variety of fields, including food, beverages, pharmaceuticals, medical products, chemicals, cosmetics, toiletries, and industrial products, and such resin molded products are often the subject of recycling. For example, Patent Document 1 discloses a method for recovering recycled raw materials of polyamide-based resin from a film containing polyamide-based resin.

Specifically, in Patent Document 1, a piece of film containing polyamide-based resin is immersed in a dissolving liquid in a melting furnace. The valve is then opened, and the dissolving liquid containing the dissolved polyamide-based resin is discharged from the melting furnace and stored in a furnace for the next process. In the next process, the temperature of the furnace is adjusted to cause the polyamide-based resin to precipitate in the furnace, after which the valve is opened and the precipitated polyamide-based resin is collected all at once.

JP 2022-114533 A

As described above, in Patent Document 1, the process of precipitating the resin component from the solution is carried out in a batch manner. However, such a batch-type process has various disadvantages. For example, the production volume per hour may decrease. In addition, large-scale equipment may be required, which may increase capital investment and the floor space required for installing the equipment. In addition, the energy efficiency of the entire process is poor, and running costs tend to be high. Furthermore, quality differences occur between batches, which can make lot management complicated.

The object of the present invention is to provide an efficient method and device for recovering resin.

Item 1. Pouring a solution in which a resin component to be recovered is dissolved in a solvent into a transport path;
While transporting the solution along the transport path, a resin component is precipitated from the solution within the transport path;
and separating and recovering the precipitate from the solvent.

Item 2. The solution is a solution produced by immersing a film containing two or more resin components in a solvent that dissolves a portion of the two or more resin components.
Item 2. A method for recovering a resin according to item 1.

Item 3. A method for producing a recycled resin raw material, comprising processing a precipitate recovered by the resin recovery method according to item 1 or 2 to produce a granular or powdery recycled resin raw material.

Item 4. A method for producing a film, comprising producing a film using the recycled resin raw material produced by the production method according to item 3.

Item 5. A transport path for transporting a solution in which the resin component to be recovered is dissolved in a solvent;
a separation section that separates a resin component precipitated from the solution in the transport path from the solvent while the solution is transported along the transport path;
A resin recovery device comprising:

According to the present invention, resin components can be efficiently recovered.

1 is a diagram showing a schematic diagram of a system including a resin recovery device according to an embodiment of the present invention and various devices arranged around it; FIG. 2 is a diagram showing the configuration of the dissolution device and the recovery device in FIG. 1 .

The following describes a resin recovery method and device according to one embodiment of the present invention, with reference to the drawings.

＜1. Overview＞
FIG. 1 shows a schematic diagram of a system including a resin recovery device 2 according to an embodiment of the present invention and various devices 1, 3, and 4 arranged around the device. This system is a recycling system that recovers a resin material from a resin film F1 and regenerates a recycled resin film F5 from the recovered resin material. In this system, a dissolving device 1 upstream of the recovery device 2 is a device that generates a solution 12 in which the resin components to be recovered contained in the film F1 are dissolved. The solution 12 is generated by immersing the film F1 in a solvent 11. The recovery device 2 is a device that generates a precipitate F2 of the resin components to be recovered from the solution 12 supplied from the dissolving device 1, and separates and recovers the precipitate. A manufacturing device 3 downstream of the recovery device 2 produces a recycled resin raw material F4 from the precipitate F2 recovered by the recovery device 2. A manufacturing device 4 further downstream of the manufacturing device 3 produces a recycled film F5 using the recycled resin raw material F4 produced by the manufacturing device 3.

2. Details of each device
The devices 1 to 4 in FIG. 1 will now be described in detail.

<2-1. Melting device＞
2 is a diagram showing the configuration of the dissolving device 1 and the recovery device 2. The dissolving device 1 includes a tank 10 into which a solvent 11 is supplied. The film F1 is an item to be recycled, and may be a used product, an unused product, a waste product in the manufacturing process, an intermediate product in the waste process, etc. The film F1 to be processed is preferably a crushed piece of the above-mentioned article, and can be produced by appropriately using a known crusher, shredder, cutter, etc. Size (area) of each crushed piece is preferably 500 mm2 or ^less , more preferably 300 mm2 or ^less , even more preferably 200 ^mm2 or less, and particularly preferably 100 ^mm2 or less.

Film F1 may contain one type of resin component, or may contain two or more types of resin components. Film F1 may be a single-layer film or a laminate film. Film F1 may also contain components other than the resin component. Film F1 may contain metal components such as aluminum, coloring components such as ink, antiblocking agents, additives, etc. Examples of additives include heat stabilizers, antioxidants, ultraviolet absorbers, light stabilizers, lubricants, antistatic agents, flame retardants, antibacterial agents, and fluorescent whitening agents.

The film F1 is immersed in the solvent 11 contained in the tank 10. The solvent 11 dissolves one or more types of resin components contained in the film F1. The resin components dissolved in the solvent 11 are the resin components to be recovered by the recovery device 2. The solvent 11 may selectively dissolve a portion of the resin components contained in the film F1, or may dissolve all of them. However, a typical or preferred example of a situation in which the present invention is applied is a situation in which the film F1 contains two or more types of resin components and the solvent 11 dissolves a portion of them. In this example, among the multiple types of resin components contained in the film F1, a portion of the resin components to be recovered can be separated and recovered from the other resin components.

Examples of the types of resin components contained in film F1 include polyamide-based resins, polystyrene-based resins, polyolefin-based resins, and polyester-based resins. Examples of polyamide-based resins include aliphatic polyamides such as nylon 6-based resins, nylon 66-based resins, and nylon 12-based resins, aromatic polyamides, amorphous polyamides, and polyamide elastomers. Examples of polystyrene-based resins include styrene-butadiene copolymers, styrene-isoprene copolymers, styrene-isoprene-butadiene copolymers, styrene-acrylic copolymers, acrylonitrile-butadiene-styrene copolymers, and acrylonitrile-styrene copolymers. Examples of polyolefin-based resins include polypropylene-based, polyethylene-based, and cyclic polyolefin-based resins. Examples of polyester-based resins include polyethylene terephthalate and polyethylene naphthalate.

When the resin component to be recovered by the recovery device 2 is a polyamide-based resin, preferred examples of the solvent 11 include ethylene glycol-based aliphatic cyclic alcohols, aliphatic alcohols, ethylene glycol (EG), propylene glycol, butanediol, and pentanediol. When the resin component to be recovered by the recovery device 2 is a polystyrene-based resin or a polyolefin-based resin, preferred examples of the solvent 11 include cyclic terpene solvents such as limonene and pinene, aromatic solvents such as xylene, toluene, ethylbenzene, benzene, and mesitylene, cyclic ether solvents such as tetrahydrofuran and 2-methyltetrahydrofuran, and cyclic aliphatic solvents such as cyclohexane, methylcyclohexane, and ethylcyclohexane. When the resin component to be recovered by the recovery device 2 is a polyester-based resin, preferred examples of the solvent 11 include aprotic polar solvents such as N-methyl-2-pyrrolidone (NMP) and dimethylformamide.

The dissolving device 1 may be equipped with a heating device and/or stirring device (not shown). By using such devices, the solvent 11 containing the film F1 can be appropriately heated and/or stirred, thereby efficiently dissolving the resin components to be recovered.

As a result, a solution 12 in which the resin components to be recovered by the recovery device 2 are dissolved in the solvent 11 is generated in the tank 10. The solution 12 is sent from the dissolving device 1 to the recovery device 2. In this embodiment, the flow rate of the solution 12 is controlled, and the solution 12 is sent to the recovery device 2 by a predetermined amount per unit time. The predetermined amount may be a constant amount or a variable amount. In other words, the flow rate may always be constant or may be variable. In the latter case, the flow rate may be zero. In any case, the solution 12 is sent from the dissolving device 1 to the recovery device 2 in a continuous manner, not in a batch manner. There are no particular limitations on the method for achieving this, but for example, a method of controlling the opening of a valve that opens and closes the outlet of the tank 10 for discharging the solution 12 can be considered. Alternatively, a feeder with a flow control function may be attached to the dissolving device 1 or between the dissolving device 1 and the recovery device 2.

In addition, a residue F3 consisting of insoluble components of the film F1 that did not dissolve in the solvent 11 may remain in the tank 10. In this case, the solution 12 is separated from the residue F3 by a separation section 13 such as a filter arranged in the tank 10, and then sent to the recovery device 2. Meanwhile, the residue F3 is appropriately discharged from the dissolving device 1. For example, the residue F3 may be periodically removed from the tank 10. The residue F3 thus recovered may then be reused as a recycled raw material. The residue F3 may be composed only of a resin component, or may contain components other than the resin component in addition to the resin component. Alternatively, the residue F3 may not contain a resin component.

<2-2. Recovery device>
As shown in FIG. 2, the recovery device 2 includes a conveying device 20. The conveying device 20 has a conveying path 21. In this embodiment, the solution 12 is poured from the dissolving device 1 to an upstream position of the conveying path 21 at a predetermined amount (which may be a constant amount or a variable amount) per unit time. The conveying device 20 conveys the solution 12 supplied from the dissolving device 1 in this manner to the downstream side along the conveying path 21. At this time, in this embodiment, the conveying speed of the solution 12 is controlled, and the solution 12 is conveyed in the conveying path 21 at a predetermined amount per unit time. Note that the predetermined amount here may be a constant amount or a variable amount. In other words, the conveying speed of the solution 12 may always be constant or may be varied. In the latter case, the conveying speed may be zero. In any case, the solution 12 is conveyed in a continuous manner, not in a batch manner. In the example of FIG. 2, the conveying device 20 is a screw conveyor, and has a screw 22 arranged in the conveying path 21 and extending coaxially with the conveying path 21. The conveying speed of the solution 12 is controlled by controlling the rotation speed of the screw 22. However, the method of conveying the solution 12 is not limited to this, and other methods, such as using a pressure pump in the conveying device 20, may be appropriately adopted.

While the solution 12 is transported along the transport path 21, a precipitate (crystal) F2 of the resin component to be recovered contained in the solution 12 precipitates from the solution 12 within the transport path 21. For example, the solution 12 is cooled while being transported along the transport path 21, causing the precipitate F2 to precipitate from the solution 12. Note that cooling here refers to lowering the temperature of the solution 12 based on the temperature at which it was supplied from the dissolving device 1. In other words, cooling here includes heating the solution 12 when the solution 12 is heated to a high temperature in the dissolving device 1.

In order to cool the solution 12, a temperature control device 23 such as a chiller or heater can be attached. In the example of FIG. 2, the temperature control device 23 is attached to the side wall that defines the transport path 21. However, if the solution 12 is cooled rapidly, the resin components may precipitate unevenly near the upstream of the transport path 21, causing the transport path 21 to become clogged. In this regard, the temperature control device 23 contributes to slowly cooling the solution 12, and allows the resin components to gradually precipitate along the transport path 21. In the example of FIG. 2, the temperature control device 23 is divided into multiple segments 23a to 23d along the transport direction, and the temperatures of these segments 23a to 23d can be set to become lower from upstream to downstream. This allows for more effective slow cooling.

The method of cooling the solution 12 is not limited to the above-mentioned method. For example, a constant temperature may be maintained along the transport path 21 without segmenting the temperature control device 23, or the resin component may be precipitated at room temperature without installing the temperature control device 23. Alternatively, the solution 12 may be cooled by blowing air. Furthermore, the method of precipitating the resin component from the solution 12 is not limited to the method of cooling the solution 12. For example, instead of or in addition to cooling the solution 12, a poor solvent may be added to the solution 12 being transported in the transport path 21, or the solution 12 being transported in the transport path 21 may be heated to evaporate the solvent 11.

As the precipitation of the resin component proceeds along the conveying path 21, the suspension of the solution 12 proceeds. For example, the solution 12 flowing on the upstream side of the conveying path 21 is a relatively low-viscosity, thin liquid. On the other hand, on the downstream side of the conveying path 21, the solution 12 may become a slurry due to solid particles of the resin component in the process of crystallization, and a relatively high-viscosity suspension may flow. Note that the solution 12 may already be somewhat suspended when it is introduced into the conveying path 21. Thus, the conveying device 20 is a device that conveys the solution 12 in which the resin component is dissolved, and at the same time, it is also a device that conveys the suspension in which the solid particles of the resin component are dispersed. The conveying device 20 also conveys precipitate F2 that has precipitated in the conveying path 21 and is floating or settling in the solution 12 or the suspension.

A separation section 25 is disposed in the downstream portion of the conveying path 21. The separation section 25 separates the precipitate F2 precipitated in the conveying path 21 from the solvent 11. Here, the precipitate F2 that has settled in the solution 12 or the suspension is collected, and the precipitate F2 that is floating in the solution 12 or the suspension is also extracted and collected. In the example of FIG. 2, the separation section 25 is a filter disposed in the conveying path 21 (hereinafter, the filter may also be given the symbol 25). The filter 25 is capable of performing solid-liquid separation, and has a mesh size that allows the solvent 11 (or the solution 12) to pass through but not the precipitate F2. As a result, the solvent 11 (or the remaining solution 12, if any) passes through the filter 25, and the precipitate F2 is collected in the filter 25, resulting in the separation of the two. The precipitate F2 collected by the filter 25 is then collected. The solvent 11 that has passed through the filter 25 is also then collected separately.

The precipitate F2 collected by the filter 25 is extruded from the conveying path 21 by, for example, the screw 22, and sent to the manufacturing device 3 for the recycled resin raw material F4. At this time, the precipitate F2 is preferably extruded from the conveying path 21 in a predetermined amount per unit time (which may be a constant amount or a variable amount). In other words, the precipitate F2 is preferably extruded in a continuous manner, not in a batch manner. The precipitate F2 is preferably then continuously conveyed to the manufacturing device 3 in a predetermined amount per unit time (which may be a constant amount or a variable amount). In addition, the solvent 11 separated from the precipitate F2 is also preferably sent out in a continuous manner from the conveying path 21 in a predetermined amount per unit time (which may be a constant amount or a variable amount).

The transport path 21 is preferably a substantially sealed path. In this case, it is possible to prevent the solution 12 and precipitate F2 from coming into contact with the atmosphere and being exposed to light such as ultraviolet light. Therefore, for example, oxidation and nitrogen oxidation of the resin components to be recovered are suppressed. As a result, it is possible to effectively prevent deterioration of the resin components to be recovered, and to recover, for example, a resin with good optical properties.

<2-3. Manufacturing equipment for recycled resin raw materials>
The manufacturing device 3 manufactures recycled resin raw material F4 from the precipitate F2 of the resin component recovered by the recovery device 2. More specifically, the manufacturing device 3 receives the precipitate F2 sent from the conveying device 20 and processes it into granular or powdered recycled resin raw material F4. The granular recycled resin raw material F4 is, for example, a granulated material or a pellet. A granulated material is not a raw material that is heated and melted and then solidified as in the case of pellets, but a mass obtained by compressing and solidifying a powdered raw material without heating and melting it. A granulated material is typically an opaque mass.

The precipitate F2 can be processed into powder, for example, by drying the precipitate F2. A known dryer can be used for drying, and for example, a hot air dryer such as a fluidized bed dryer, a far-infrared dryer, a microwave dryer, etc. can be preferably used.

The precipitate F2 can be processed into a granulated product, for example, using a known granulator. In this case, it is preferable to dry the precipitate F2 before granulation, or to dry the granulated product after granulation. A known dryer can be used for the drying here as well, and for example, a hot air dryer such as a fluidized bed dryer, a far-infrared dryer, a microwave dryer, etc. can be preferably used. The granulated product can also be dried while being granulated. The precipitate F2 can also be dried while being stirred in a vacuum state to produce a granulated product. The drying process can also be performed multiple times out of the three timings before, during, and after granulation.

The precipitate F2 can be processed into pellets, for example, using a known resin pellet manufacturing machine. For example, the precipitate F2 can be supplied to an extruder, heated and melted in the extruder, extruded through a die, and cut into an appropriate shape.

Recycled resin raw material F4 is made of the same material as precipitate F2, contains one or more types of resin components, and may also contain components other than resin. Note that recycled resin raw material F4 in the form of powder or granules is less susceptible to thermal degradation than recycled resin raw material F4 in the form of pellets, since it has not been subjected to excessive thermal history such as heating and melting during processing.

<2-4. Recycled film manufacturing equipment>
The manufacturing device 4 manufactures the recycled film F5 using the recycled resin raw material F4 manufactured by the manufacturing device 3. More specifically, the manufacturing device 4 manufactures the recycled film F5 using only the recycled resin raw material F4, or using other raw materials in addition to the recycled resin raw material F4. That is, the recycled resin raw material F4 can be used as a part or all of the raw material of the recycled film F5. The other raw materials may be resin, raw materials other than resin, or may contain both. As the other raw materials, virgin resin raw materials can be used. The recycled film F5 may be a single-layer film or a laminated film. In either case, a layer in which the recycled resin raw material F4 and other raw materials are mixed may be formed, or in the latter case, a layer containing the recycled resin raw material F4 and a layer made of other raw materials may be laminated. The recycled film F5 contains one or more types of resin components, and may further contain components other than resin.

The recycled film F5 can be manufactured using known film-forming methods. For example, the recycled resin raw material F4 may be fed into an extruder, heated and melted in the extruder, and then extruded through a die for extrusion molding. At this time, a laminated film can be manufactured by co-extrusion. After molding, the recycled film F5 is appropriately stretched.

<3. Application Examples>
Two application examples of the resin recovery method using the above-mentioned dissolving apparatus 1 and recovery apparatus 2 will be described below.

<3-1. Application example 1>
In the tank 10 of the dissolving device 1, ethylene glycol at 170°C is charged as the solvent 11, and 10 wt% of the film (crushed pieces) F1 containing polyamide resin as the resin component to be recovered is charged. Then, the solution 12 is charged from the tank 10 to the conveying path 21. At this time, the temperatures of the segments 23a to 23d of the temperature control device 23 are maintained at 180°C, 150°C, 120°C, and 100°C, respectively. As a result, as the solution 12 is conveyed along the conveying path 21, the polyamide resin contained in the solution 12 gradually precipitates and the suspension progresses. The polyamide resin dissolved in the solution 12 is cooled to about 100°C near the most downstream of the conveying path 21, and at this point it is almost completely precipitated. The precipitate F2 of the polyamide resin is collected by a filter 25 with a mesh size of 5 μm attached at the end of the conveying path 21, extruded from the conveying path 21 through a die, and sent further forward. On the other hand, ethylene glycol, which is the solvent 11, separated from the precipitate F2 by the filter 25, falls through the filter 25 and is separately recovered.

<3-2. Application example 2>
Cyclohexane at room temperature, which is the solvent 11, is poured into the tank 10 of the dissolving device 1, and 10 wt % of the film (crushed pieces) F1 containing polystyrene resin as the resin component to be recovered is poured into the tank 10. Then, the solution 12 is poured into the conveying path 21 from the tank 10. In this example, the temperature control device 23 is not operated. Instead, isopropanol (IPA), which is a poor solvent, is poured into the conveying path 21 in an amount equal to that of the solution 12. As a result, as the solution 12 is conveyed along the conveying path 21, the polystyrene resin contained in the solution 12 gradually precipitates and the suspension advances. The precipitate F2 of the polystyrene resin is collected by a filter 25 with a mesh size of 25 μm attached at the end of the conveying path 21, extruded from the conveying path 21 through a die, and further sent forward. Meanwhile, cyclohexane, which is the solvent 11, separated from the precipitate F2 by the filter 25, passes through the filter 25 and falls, and is separately collected.

＜4. Features＞
In the above embodiment, while the solution 12 containing the resin components to be recovered is transported along the transport path 21, the resin components are precipitated from the solution 12 within the transport path 21. That is, the process of precipitating the resin components from the solution 12 is carried out continuously rather than batchwise. This allows the resin components to be efficiently recovered. In turn, the recycled resin raw material F4 and further the recycled film F5 can be efficiently produced from the resin components thus recovered.

5. Modifications
Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the present invention. For example, the following modifications are possible.

＜5-1＞
In the above embodiment, an example is shown in which a recycled resin film F5 is recycled from a resin film F1. However, the recycling object to which the present invention can be applied is not limited to a film, and any resin molded product can be recycled from any resin molded product. In this case, the type of the original resin molded product and the recycled resin molded product may be different or the same.

＜5-2＞
As shown by the dotted line in FIG. 1, a circulation path 50 may be provided for returning the solvent 11 separated from the precipitate F2 and recovered in the recovery device 2 to the tank 10. The solvent 11 leaving the recovery device 2 is received at the upstream of the circulation path 50 and transported along the circulation path 50 to the tank 10, or to a supply source or supply path (not shown) that supplies the solvent 11 to the tank 10. The circulation path 50 connects the recovery device 2 to the tank 10, or to a supply source or supply path (not shown) that supplies the solvent 11 to the tank 10. The solvent 11 is preferably transported continuously from the recovery device 2 at a predetermined amount per unit time (which may be a constant amount or a variable amount) along the circulation path 50. It is preferable that the circulation path 50 is a substantially sealed path in order to effectively prevent deterioration of the solvent 11.

＜5-3＞
In the above embodiment, the solid-liquid separation process by the separation unit 25 is realized by a filter, but is not limited to this embodiment. For example, the solution 12 in the transport path 21 may be heated to a boiling point of the solvent 11 or higher to volatilize the solvent 11, thereby separating the precipitate F2 from the solvent 11. In this case, the above-mentioned temperature control device 23 can function as the separation unit 25, and may be operated to heat the solution 12 to a boiling point of the solvent 11 or higher. The precipitate F2 thus recovered is then pushed out of the transport path 21 by the screw 22 and recovered.

1 Dissolution device 10 Tank 11 Solvent 13 Separation section (filter)
12 Solution 2 Resin recovery device 20 Conveyor device 21 Conveyor path 22 Screw 23 Temperature control devices 23a to 23d Segments 25 Separation section (filter)
3 Recycled resin raw material manufacturing device 4 Film manufacturing device F1 Film F2 Precipitate F3 Residue F4 Recycled resin raw material F5 Recycled film

Claims (5)

pouring a solution in which the resin component to be recovered is dissolved in a solvent into a transport path;
conveying the solution along the conveying path while precipitating the resin component from the solution within the conveying path;
and separating and recovering the precipitate from the solvent. The solution is a solution produced by immersing a film containing two or more types of resin components in the solvent that dissolves a portion of the two or more types of resin components.
The method for recovering resin according to claim 1. A method for producing recycled resin raw material, comprising processing the precipitate recovered by the resin recovery method according to claim 1 or 2 to produce a granular or powdered recycled resin raw material. A method for producing a film, comprising producing a film using the recycled resin raw material produced by the production method according to claim 3. a transport path for transporting a solution in which the resin component to be recovered is dissolved in a solvent;
a separation unit that separates a precipitate of the resin component precipitated from the solution in the transport path from the solvent while the solution is transported along the transport path;
A resin recovery device comprising: