Resin recovery method

Abstract

This invention provides a resin recovery method that can suppress the decrease in molecular weight. [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 solution; and cutting the concentrated solution. In the resin recovery method, when heating and concentrating the solution, the solution is concentrated at a temperature at which the resin contained in the concentrated solution is melted, and the resin contained in the concentrated solution that is cut is melted.

Description

Technical Field

[0001] The present invention relates to a method for recovering a resin from a 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. In order to achieve this, research and development on the recycling of waste plastic materials have been conducted.

[0003] Patent Document 1 describes a method in which a polyamide molding containing glass fibers is dissolved by adding an aqueous phosphoric acid solution having a concentration of 70% by weight or more and heating while stirring, and then separating the polyamide solution from the glass fibers.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] \ However, when using the method described in Patent Document 1, the molecular weight of the recycled polyamide decreases.

[0006] An object of the present invention is to provide a method for recovering a resin capable of suppressing a decrease in molecular weight.

Means for Solving the Problems

[0007] (1) A method for recovering a resin from a fiber reinforced resin, comprising a step of dissolving the resin contained in the fiber reinforced resin in ethylene glycol, a step of performing solid-liquid separation on the solution in which the resin is dissolved in ethylene glycol and the fibers, and a step of heating and concentrating the solution to obtain a concentrated solution. A method for recovering resin, comprising the step of cutting the concentrated liquid, wherein when the solution is heated and concentrated, the solution is concentrated at a temperature at which the resin contained in the concentrated liquid is melted, and the resin contained in the concentrated liquid to be cut is melted.

[0008] (2) The resin recovery method according to (1), wherein when the solution is heated and concentrated, the solution is concentrated at a temperature of 150°C or higher and 300°C or lower.

[0009] (3) The resin recovery method according to (1) or (2), wherein the solution is heated and concentrated while stirring.

[0010] (4) A method for recovering resin according to any one of (1) to (3), wherein the pressure is reduced when the solution is heated and concentrated.

[0011] (5) A method for recovering resin according to any one of (1) to (4), wherein when the solution is heated and concentrated, the solution is heated and concentrated to obtain a first concentrated solution, and the first concentrated solution is heated and concentrated to obtain a second concentrated solution, wherein the first concentrated solution has an ethylene glycol concentration of 8% by mass or more and 23% by mass or less, and the second concentrated solution 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, it is possible to provide a method for recovering resin that can suppress the decrease in molecular weight. [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 concentrate is obtained by heating and concentrating the solution. The concentration of ethylene glycol in the concentrate 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 concentration temperature is the temperature at which the resin contained in the concentrate is melted. As will be described later, since the resin contained in the concentrate to be cut is melted, heat loss is suppressed. The heating and concentration temperature is preferably 150°C or more and 300°C or less. If the heating and concentration temperature is 150°C or higher, the resin dissolves more easily in ethylene glycol, and if it is 300°C or lower, the decrease in the molecular weight of the resin is suppressed.

[0019] When concentrating the solution by heating, it is preferable to stir. This shortens the heating concentration time. Also, when concentrating the solution by heating, it is preferable to reduce the pressure. This shortens the heating concentration time. At this time, the degree of reduced pressure is not particularly limited, but for example, it is 20 kPa or more and 100 kPa or less.

[0020] When concentrating the solution by heating, after concentrating the solution by heating to obtain a first concentrated solution, the first concentrated solution is concentrated by heating to obtain a second concentrated solution. It is preferable that the concentration of ethylene glycol in the first concentrated solution is 8% by mass or more and 23% by mass or less, and it is preferable that the concentration of ethylene glycol in the second concentrated solution is 2% by mass or more and 5% by mass or less. This suppresses bumping when cutting the second concentrated solution in water. The degree of reduced pressure when obtaining the first concentrated solution is not particularly limited, but for example, it is 20 kPa or more and less than 80 kPa. Also, the degree of reduced pressure when obtaining the second concentrated solution is not particularly limited, but for example, it is 80 kPa or more and 100 kPa or less.

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

[0022] When concentrating the solution by heating, it is preferable to use a concentrating kettle. Thereby, ethylene glycol distilled off from the solution can be recovered.

[0023] (Cutting step) The concentrated solution is cut to obtain a recycled resin. The resin contained in the concentrated solution to be cut is molten. Here, since the heating concentration temperature is the temperature at which the resin contained in the concentrated solution is molten, heat loss is suppressed. The temperature of the concentrated solution to be cut is not particularly limited as long as the resin can be molten, but for example, it is 150°C or more and 300°C or less.

[0024] 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.

[0025] It is preferable to cut the concentrated liquid in water. Thereby, 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 it is possible to cut the concentrated liquid in water, but for example, it is 50°C or higher and 60°C or lower.

[0026] When cutting the concentrated liquid in water, it is preferable to use a pelletizer of the underwater cutting method. Thereby, the ethylene glycol eluted into the water can be recovered.

[0027] As described above, the embodiments of the present invention have been explained, 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.

Examples

[0028] Hereinafter, examples of the present invention will be described, but the present invention is not limited to the examples.

[0029] [Example 1] (Dissolution step) Waste of glass fiber reinforced nylon 6 (crushed intake manifold; number average molecular weight (Mn) of nylon 6 is 12,000) and ethylene glycol were mixed so that the mass ratio of nylon to ethylene glycol was 1:3 (50 kg:150 kg), and then heated under reflux at 170°C for 1 hour to dissolve nylon 6 in ethylene glycol to obtain a mixed solution. Here, the mass ratio of nylon 6 to glass fiber in the glass fiber reinforced nylon 6 is 70:30.

[0030] (Solid-liquid separation step) The mixed solution with a liquid temperature of 170°C was filtered through a filter with a mesh size of 20 μm to perform solid-liquid separation into an ethylene glycol solution of nylon 6 and glass fiber.

[0031] (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).

[0032] 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 used as a high-viscosity stirring blade, until the concentration of ethylene glycol reached 3.0% by mass, yielding 51.5 kg of the second concentrate. At this point, the nylon 6 contained in the second concentrate was molten.

[0033] (cutting process) Using a gear pump, the second concentrated liquid was supplied to a submersible 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 number-average molecular weight (Mn) of 9800, 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, The process includes cutting the concentrated liquid, When heating and concentrating the aforementioned solution, the solution is concentrated at a temperature at which the resin contained in the concentrated liquid is melted. A method for recovering resin, wherein the resin contained in the concentrated liquid to be cut is molten.

2. The method for recovering resin according to claim 1, wherein when the solution is heated and concentrated, the solution is concentrated at a temperature of 150°C or higher and 300°C or lower.

3. The method for recovering resin according to claim 1 or 2, wherein the solution is heated and concentrated while being stirred.

4. A method for recovering resin according to claim 1 or 2, wherein the pressure is reduced when the solution is heated and concentrated.

5. When heating and concentrating the aforementioned solution, after heating and concentrating the solution to obtain a first concentrated solution, the first concentrated solution is heated and concentrated to obtain a second concentrated solution. 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 1 or 2, wherein the second concentrated liquid has an ethylene glycol concentration of 2% by mass or more and 5% by mass or less.