Resin recovery method

Abstract

This invention provides a resin recovery method that can reduce the amount of residual ethylene glycol. [Solution] The resin recovery method is a method for recovering resin from fiber-reinforced resin. The resin recovery method includes the steps of: dissolving the resin contained in the fiber-reinforced resin in ethylene glycol; solid-liquid separation of the solution in which the resin is dissolved in ethylene glycol and the fibers; heating and concentrating the solution to obtain a concentrated liquid; and cutting the concentrated liquid in water.

Description

Technical Field

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[0001] The present invention relates to a method for recovering resin from fiber-reinforced resin.

Background Art

[0002] In recent years, efforts to significantly reduce the generation of waste have been actively carried out through waste prevention, reduction, recycling, and reuse. Toward this realization, research and development on the recycling of waste plastic materials have been conducted.

[0003] Patent Document 1 describes a recycling method for a fiber-reinforced resin composite material obtained by mixing fibers with resin to increase strength. The recycling method for the fiber-reinforced resin composite material separates fibers from waste materials of the fiber-reinforced resin composite material using a solvent with high solubility of the resin, and separates and recovers the resin and the solvent from the dissolved solution after fiber separation.

Prior Art Documents

Patent Documents

[0004] <00岁00019>

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the recycling method for the fiber-reinforced resin composite material described in Patent Document 1, when ethylene glycol is used as the solvent, the residual amount of ethylene glycol in the recovered resin increases.

[0006] An object of the present invention is to provide a method for recovering resin capable of reducing the residual amount of ethylene glycol.

Means for Solving the Problems

[0007] <00000°36>(1) A method for recovering resin, comprising the steps of: dissolving the resin contained in the fiber-reinforced resin in ethylene glycol; separating the solution in which the resin is dissolved in ethylene glycol from the fibers; heating and concentrating the solution to obtain a concentrated liquid; and cutting the concentrated liquid in water.

[0008] (2) The method for recovering resin according to (1), wherein the resin contained in the concentrated liquid that is cut in water is melted.

[0009] (3) A method for recovering resin according to (1) or (2), wherein a concentration vessel is used when heating and concentrating the solution, an underwater cutting type pelletizer is used when cutting the concentrated liquid underwater, and the concentration vessel and the pelletizer are airtightly connected.

[0010] (4) A method for recovering resin according to any one of (1) to (3), wherein when the solution is heated and concentrated, the solution is heated and concentrated while stirring to obtain a first concentrated solution, and the first concentrated solution is heated and concentrated while stirring to obtain a second concentrated solution, and the stirring force for stirring the first concentrated solution is greater than the stirring force for stirring the solution.

[0011] (5) The resin recovery method according to (4), wherein the first concentrated liquid has an ethylene glycol concentration of 8% by mass or more and 23% by mass or less, and the second concentrated liquid has an ethylene glycol concentration of 2% by mass or more and 5% by mass or less. [Effects of the Invention]

[0012] According to the present invention, a method for recovering resin that can reduce the amount of residual ethylene glycol can be provided. [Modes for carrying out the invention]

[0013] Embodiments of the present invention will be described below.

[0014] The resin recovery method of this embodiment is a method for recovering resin from fiber-reinforced resin. The fiber-reinforced resin is not particularly limited, but examples include crushed material from an intake manifold. The fibers constituting the fiber-reinforced resin are not particularly limited, but examples include glass fibers and carbon fibers. The resin constituting the fiber-reinforced resin is not particularly limited as long as it can be dissolved in ethylene glycol, but examples include polyamides such as nylon 6 and nylon 66.

[0015] The following describes each step in the resin recovery method of this embodiment.

[0016] (melting process) First, the resin contained in the fiber-reinforced resin is dissolved in ethylene glycol. The method for dissolving the resin contained in the fiber-reinforced resin in ethylene glycol is not particularly limited, but one example is to mix the fiber-reinforced resin and ethylene glycol and heat under reflux. At this time, the heating reflux temperature is not particularly limited as long as it is below the boiling point of ethylene glycol, but for example, it is between 150°C and 170°C.

[0017] (solid-liquid separation process) The resin is dissolved in ethylene glycol, and the fibers are separated into a solid-liquid solution and fibers. The method of solid-liquid separation is not particularly limited, but examples include filtration and centrifugal separation.

[0018] (heating concentration process) A concentrated solution is obtained by heating and concentrating the solution. The concentration of ethylene glycol in the concentrated solution is not particularly limited, but for example, it is 2% by mass or more and 5% by mass or less. At this time, the heating and concentrating temperature is preferably the temperature at which the resin contained in the concentrated solution is melted. As will be described later, heat loss is suppressed when the resin contained in the concentrated solution to be cut is melted. It is preferable to stir the solution when heating and concentrating it. This shortens the heating and concentrating time. It is also preferable to reduce the pressure when heating and concentrating the solution. This shortens the heating and concentrating time. At this time, the degree of pressure reduction is not particularly limited, but for example, it is 20kPa or more and 100kPa or less. It is preferable to use a concentration kettle when heating and concentrating the solution. This increases the recovery rate of ethylene glycol contained in the solution.

[0019] When heating and concentrating the solution, it is preferable to heat and concentrate the solution while stirring to obtain a first concentrate, and then heat and concentrate the first concentrate while stirring to obtain a second concentrate, with the stirring force for the first concentrate being greater than the stirring force for the solution. This suppresses bumping when cutting the second concentrate in water. At this time, it is preferable that the concentration of ethylene glycol in the first concentrate is 8% by mass or more and 23% by mass or less, and the concentration of ethylene glycol in the second concentrate is 2% by mass or more and 5% by mass or less.

[0020] The heating and concentration temperature when obtaining the second concentrate is not particularly limited, but for example, it is between 150°C and 300°C. The degree of reduced pressure when obtaining the second concentrate is not particularly limited, but for example, it is between 80kPa and 100kPa. The heating and concentration temperature when obtaining the first concentrate is not particularly limited, but for example, it is between 150°C and 300°C. The degree of reduced pressure when obtaining the first concentrate is not particularly limited, but for example, it is between 20kPa and less than 80kPa.

[0021] Since the second concentrated liquid has a higher viscosity than the first concentrated liquid, when obtaining the first concentrated liquid, a stirring blade for low viscosity (for example, a max blend blade) is used as necessary, and when obtaining the second concentrated liquid, it is preferable to use a stirring blade for high viscosity (for example, a helical ribbon blade). Thereby, the production stability when producing a concentrated liquid by heating and concentrating a solution is improved.

[0022] (Cutting step) The concentrated liquid is cut in water to obtain a recycled resin. As a result, since the ethylene glycol contained in the concentrated liquid elutes into the water, the residual amount of ethylene glycol in the recycled resin is reduced. The temperature of the water is not particularly limited as long as the concentrated liquid can be cut in water, but for example, it is 50°C or higher and 60°C or lower. When cutting the concentrated liquid in water, it is preferable to use a underwater cutting type pelletizer and that the concentrating kettle and the pelletizer are airtightly connected. Thereby, the recovery rate of ethylene glycol contained in the concentrated liquid increases.

[0023] The residual amount of ethylene glycol in the recycled resin is not particularly limited, but for example, it is 1% by mass or less. The form of the recycled resin is not particularly limited, but for example, pellets can be mentioned.

[0024] It is preferable that the resin contained in the concentrated liquid cut in water is melted. As a result, since the water temperature in the vicinity of the concentrated liquid becomes high, the ethylene glycol contained in the concentrated liquid is likely to elute. The temperature of the concentrated liquid cut in water is not particularly limited, but for example, it is 150°C or higher and 300°C or lower.

[0025] In addition, when the recycled resin is treated with subcritical water by a known method, monomers are recovered. At this time, if the residual amount of ethylene glycol in the recycled resin is not reduced, the yield of monomers decreases.

[0026] As described above, the embodiments of the present invention have been described, but the present invention is not limited to the above embodiments, and the above embodiments may be appropriately modified within the scope of the gist of the present invention.

Example

[0027] The following describes embodiments of the present invention, but the present invention is not limited to these embodiments.

[0028] [Example 1] (melting process) Waste glass fiber reinforced nylon 6 (crushed intake manifold material) and ethylene glycol were mixed so that the mass ratio of nylon to ethylene glycol was 1:3 (50 kg:150 kg). The mixture was then heated under reflux at 170°C for 1 hour to dissolve the nylon 6 in the ethylene glycol and obtain a mixed solution. Here, the mass ratio of nylon 6 to glass fibers in glass fiber reinforced nylon 6 is 70:30.

[0029] (Solid-liquid separation process) The mixture, at a temperature of 170°C, was filtered through a filter with a mesh size of 20 μm to separate the nylon 6 ethylene glycol solution from the glass fibers.

[0030] (heating concentration process) 200 kg of ethylene glycol solution of nylon 6 was transferred to the first concentration vessel. Under conditions of a temperature of 170°C and a reduced pressure of 20 kPa, the ethylene glycol was distilled off while stirring with a Maxblend blade until the concentration of ethylene glycol reached 8.0% by mass, yielding 54 kg of the first concentrate. During this process, as the concentration of the ethylene glycol solution of nylon 6 progressed, the temperature rose to 280°C. Here, 280°C is a temperature above the melting point of nylon 6 (220°C).

[0031] After transferring 54 kg of the first concentrate to the second concentrate vessel, the ethylene glycol was distilled off under conditions of a temperature of 280°C and a reduced pressure of 80 kPa, while stirring with a helical ribbon impeller, until the concentration of ethylene glycol reached 3.0% by mass, yielding 51.5 kg of the second concentrate. At this time, the stirring force of the helical ribbon impeller was greater than that of the Maxblend impeller. Also, the nylon 6 contained in the second concentrate was molten.

[0032] (cutting process) Using a gear pump, the second concentrated liquid was supplied to a submersible cutting type pelletizer under the following conditions to cut the second concentrated liquid and obtain recycled nylon 6 pellets. At this time, the nylon 6 contained in the second concentrated liquid being cut was molten. The recycled nylon 6 pellets had a residual ethylene glycol content of 1.0% by mass or less and a diameter of 3.2 mm. Furthermore, there was no bumping during the cutting of the second concentrated liquid. Supply rate of the second concentrated solution: 10 kg / h Dice heater temperature: 280℃ Rotary blade rotation speed: 3000 rpm

Claims

1. A method for recovering resin from fiber-reinforced resin, A step of dissolving the resin contained in the fiber-reinforced resin in ethylene glycol, The process involves separating the solution in which the resin is dissolved in ethylene glycol from the fibers into solid and liquid components. A step of heating and concentrating the aforementioned solution to obtain a concentrated solution, A method for recovering resin, comprising the step of cutting the concentrated liquid underwater.

2. The resin recovery method according to claim 1, wherein the resin contained in the concentrated liquid that is cut in water is melted.

3. When heating and concentrating the aforementioned solution, a concentration kettle is used. When cutting the aforementioned concentrated liquid underwater, an underwater cutting type pelletizer is used. The resin recovery method according to claim 1 or 2, wherein the concentration vessel and the pelletizer are airtightly connected.

4. When heating and concentrating the aforementioned solution, the solution is heated and concentrated while stirring to obtain a first concentrated solution, and then the first concentrated solution is heated and concentrated while stirring to obtain a second concentrated solution. The resin recovery method according to claim 1 or 2, wherein the stirring force for stirring the first concentrated liquid is greater than the stirring force for stirring the solution.

5. The first concentrated liquid has an ethylene glycol concentration of 8% by mass or more and 23% by mass or less. The resin recovery method according to claim 4, wherein the second concentrated liquid has an ethylene glycol concentration of 2% by mass or more and 5% by mass or less.