How to regenerate blended fibers

Abstract

This invention provides a method for regenerating blended fibers that can improve the recovery rate of terephthalic acid. [Solution] The method for regenerating blended fibers includes the step of depolymerizing a blend of polyester fibers and wool in a solution in which a strong base is dissolved in a solvent to obtain a first reaction solution. The solvent contains tetrahydrofuran and methanol, and the ratio of methanol to the total amount of tetrahydrofuran and methanol is 20% by volume or more and 40% by volume or less.

Description

Technical Field

[0001] The present invention relates to a method for recycling blend fibers containing polyester fibers and wool.

Background Art

[0002] In recent years, efforts to significantly reduce the generation of waste have been actively pursued through waste prevention, reduction, recycling, and reuse. In order to achieve this, research and development on the recycling of blend fibers have been carried out.

[0003] Patent Document 1 describes a method for recycling waste blend fiber products containing polyester fibers and cotton staple fibers. At this time, the polyester fibers are depolymerized in a basic aqueous solution under a controlled environment to obtain treated fiber products containing cotton staple fibers.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the method described in Patent Document 1, when recycling blend fibers containing polyester fibers and wool, the recovery rate of terephthalic acid, which is a constituent unit of polyester fibers, cannot be improved.

[0006] An object of the present invention is to provide a method for recycling blend fibers capable of improving the recovery rate of terephthalic acid.

Means for Solving the Problems

[0007] (1) A method for regenerating blended fibers, comprising the step of depolymerizing a blend of polyester fibers and wool in a solution in which a strong base is dissolved in the solvent to obtain a first reaction solution, wherein the solvent comprises tetrahydrofuran and methanol, and the ratio of methanol to the total amount of tetrahydrofuran and methanol is 20% by volume or more and 40% by volume or less.

[0008] (2) A method for regenerating blended fibers, comprising the steps of: depolymerizing a blend of polyester fibers and wool in an aqueous solution of a strong base to obtain a second reaction solution; filtering the second reaction solution to obtain a filtrate; and depolymerizing the filtrate in a solution in which a strong base is dissolved in a solvent to obtain a first reaction solution, wherein the solvent comprises tetrahydrofuran and methanol, and the ratio of methanol to the total amount of tetrahydrofuran and methanol is 20% by volume or more and 40% by volume or less.

[0009] (3) A method for regenerating blended fibers according to (1) or (2), further comprising the steps of: distilling off the solvent from the first reaction solution to obtain a solid; adding water and an organic solvent to the solid and filtering to obtain a filtrate; separating the filtrate to obtain an aqueous layer; and adding a strong acid to the aqueous layer to generate a precipitate.

[0010] (4) The method for regenerating blended fibers according to (3), further comprising the step of adding a strong acid to the aqueous layer to produce a precipitate and immersing the precipitate in methanol. [Effects of the Invention]

[0011] According to the present invention, a method for regenerating blended fibers that can improve the recovery rate of terephthalic acid can be provided. [Brief explanation of the drawing]

[0012] [Figure 1] This is the infrared transmission spectrum of the precipitate from Example 1. [Figure 2] This is the infrared transmission spectrum of the precipitate from Example 2. [Modes for carrying out the invention]

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

[0014] [First embodiment of a method for regenerating blended fibers] The method for regenerating blended fibers according to this embodiment includes a step of obtaining a first reaction solution by depolymerizing a blended fiber containing polyester fibers and wool in a solution in which a strong base is dissolved in the solvent. At this time, the solvent contains tetrahydrofuran and methanol. The ratio of methanol to the total amount of tetrahydrofuran and methanol is 20% by volume or more and 40% by volume or less, and preferably 25% by volume or more and 40% by volume or less. Since the ratio of methanol to the total amount of tetrahydrofuran and methanol is 20% by volume or more, the depolymerization of wool is suppressed, and since it is 40% by volume or less, the depolymerization of polyester fibers is promoted and the depolymerization of wool is suppressed. As a result, the recovery rate of terephthalic acid, which is a constituent unit of polyester fibers, is improved.

[0015] Strong bases are not particularly limited as long as they can depolymerize polyester fibers, but examples include sodium hydroxide, potassium hydroxide, barium hydroxide, strontium hydroxide, and lithium hydroxide.

[0016] The depolymerization temperature is not particularly limited, but for example, it is between 20°C and 30°C.

[0017] Alternatively, water may be added after the blended fibers have been depolymerized.

[0018] The method for regenerating blended fibers in this embodiment may further include the steps of: removing the solvent from the first reaction solution to obtain a solid; adding water and an organic solvent to the solid and filtering to obtain a filtrate; separating the filtrate to obtain an aqueous layer; and adding a strong acid to the aqueous layer to generate a precipitate.

[0019] The organic solvent is not particularly limited as long as it can purify the terephthalate which is the depolymerization product. For example, ethyl acetate can be mentioned.

[0020] The strong acid is not particularly limited as long as it can precipitate terephthalic acid. For example, sulfuric acid can be mentioned.

[0021] The blend fiber may further contain fibers other than polyester fiber and wool. The fibers other than polyester fiber and wool are not particularly limited. For example, cotton, acrylic fiber, polyamide fiber, urethane fiber, rayon can be mentioned.

[0022] When the blend resin contains polyamide fiber, the method for regenerating the blend fiber of the present embodiment preferably further includes a step of immersing the precipitate formed by adding a strong acid to the aqueous layer in methanol. Thereby, the polyamide fiber contained in the precipitate is dissolved and removed in methanol.

[0023] [Second aspect of the method for regenerating blend fiber] The method for regenerating the blend fiber of the present embodiment includes a step of depolymerizing a blend fiber containing polyester fiber and wool in an aqueous solution of a strong base to obtain a second reaction solution, and a step of filtering the second reaction solution to obtain a filtrate. Thereby, wool is removed from the blend fiber.

[0024] The strong base is not particularly limited as long as it can depolymerize wool. For example, sodium hydroxide, potassium hydroxide, barium hydroxide, strontium hydroxide, lithium hydroxide can be mentioned.

[0025] The depolymerization temperature is not particularly limited. For example, it is 20°C or higher and 65°C or lower.

[0026] The method for regenerating blended fibers in this embodiment further includes a step of obtaining a first reaction solution by depolymerizing the filtrate in a solution in which a strong base is dissolved in the solvent. At this time, the solvent contains tetrahydrofuran and methanol. The ratio of methanol to the total amount of tetrahydrofuran and methanol is 20% by volume or more and 40% by volume or less, and preferably 25% by volume or more and 40% by volume or less. Since the ratio of methanol to the total amount of tetrahydrofuran and methanol is 20% by volume or more, the depolymerization of wool is suppressed, and since it is 40% by volume or less, the depolymerization of polyester fibers is promoted and the depolymerization of wool is suppressed. As a result, the recovery rate of terephthalic acid, which is a constituent unit of polyester fibers, is improved.

[0027] Strong bases are not particularly limited as long as they can depolymerize polyester fibers, but examples include sodium hydroxide, potassium hydroxide, barium hydroxide, strontium hydroxide, and lithium hydroxide.

[0028] The depolymerization temperature is not particularly limited, but for example, it is between 20°C and 30°C.

[0029] Alternatively, water may be added after the blended fibers have been depolymerized.

[0030] The method for regenerating blended fibers in this embodiment may further include the steps of: removing the solvent from the first reaction solution to obtain a solid; adding water and an organic solvent to the solid and filtering to obtain a filtrate; separating the filtrate to obtain an aqueous layer; and adding a strong acid to the aqueous layer to generate a precipitate.

[0031] The organic solvent is not particularly limited as long as it is possible to purify the depolymerization product, terephthalate, but ethyl acetate is an example.

[0032] The strong acid is not particularly limited as long as it can precipitate terephthalic acid, but sulfuric acid is an example.

[0033] The blended fibers may further contain fibers other than polyester fibers and wool. Examples of fibers other than polyester fibers and wool are, but are not limited to, cotton, acrylic fibers, polyamide fibers, urethane fibers, and rayon.

[0034] When the blended resin contains polyamide fibers, the method for regenerating the blended fibers according to this embodiment is: Preferably, the process further includes a step of adding a strong acid to the aqueous layer to form a precipitate, which is then immersed in methanol. This allows the polyamide fibers contained in the precipitate to dissolve and be removed in methanol.

[0035] Although embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and the above embodiments may be modified as appropriate within the scope of the spirit of the present invention. [Examples]

[0036] The following describes embodiments of the present invention, but the present invention is not limited to these embodiments.

[0037] [Infrared transmission spectrum] The infrared transmission spectrum of the precipitate was measured using an infrared spectrophotometer (IR).

[0038] [Example 1] (Blended fibers) A blend of 3.99 g of fibers was regenerated, consisting of 1.89 g of cotton, 1.24 g of polyester fiber, 0.34 g of acrylic fiber, 0.30 g of wool, and polyamide fibers consisting of 0.07 g of nylon, 0.04 g of urethane fiber, and 0.11 g of rayon. Here, the polyester fiber consists of terephthalic acid units and ethylene glycol units.

[0039] (Depolymerization) In a solution of 2 g sodium hydroxide dissolved in 100 mL of water, 3.99 g of blended fibers were reacted under reflux at 60°C for 5 hours. The mixture was then filtered under reduced pressure to obtain a filtrate and 3.70 g of filtrate material. Next, 30 mL of 1 mol / L aqueous sulfuric acid solution was added to the filtrate to generate a precipitate. After filtering under reduced pressure, the mixture was dried overnight at 80°C to obtain 0.05 g of precipitate.

[0040] Figure 1 shows the infrared transmission spectrum of the precipitate. The infrared transmission spectrum of the wool is also shown in Figure 1.

[0041] Figure 1 shows that the precipitate is essentially a depolymer of wool that does not contain polyester.

[0042] (Depolymerization) 2 g of sodium hydroxide was dissolved in a mixed solvent consisting of 25 mL of methanol and 75 mL of tetrahydrofuran. 3.70 g of the filtrate was reacted in this solution at room temperature for 5 hours, then 100 mL of water was added and the mixture was stirred overnight to obtain the reaction solution.

[0043] (Solvent removal) Using an evaporator, the solvent was removed from the reaction mixture by distillation while heating at 45°C to obtain the solid component.

[0044] (extraction) After adding 150 mL of water and 150 mL of ethyl acetate to the solids and stirring, the mixture was filtered under reduced pressure to obtain 2.50 g of filtrate and filtrate. Next, the filtrate was separated using a separatory funnel, and the ethyl acetate layer was removed to obtain the aqueous layer. Then, 150 mL of ethyl acetate was added to the aqueous layer, and the separation and removal of the ethyl acetate layer was repeated twice using a separatory funnel to obtain the aqueous layer. Next, 30 mL of 1 mol / L sulfuric acid aqueous solution was added to the aqueous layer to generate precipitate, and the mixture was filtered under reduced pressure to obtain the filtrate.

[0045] (Post-processing) The filtrate was immersed in 70 mL of methanol for 30 minutes, then filtered under reduced pressure to obtain filtrate and 1.01 g of filtrate. At this time, liquid chromatography-mass spectrometry (LC-MS) identified the filtrate as terephthalic acid, and the recovery rate of terephthalic acid was 94%.

[0046] [Example 2] (Blended fibers) 4.03 g of a blended fiber (mass ratio 7:3) of polyester fiber and wool was regenerated as a blended fiber. Here, the polyester fiber consists of terephthalic acid units and ethylene glycol units.

[0047] (Depolymerization) In a solution of 2 g sodium hydroxide dissolved in 100 mL of water, 4.03 g of blended fibers were reacted under reflux at 60°C for 5 hours. The mixture was then filtered under reduced pressure to obtain 2.99 g of filtrate and filtrate. Next, 30 mL of 1 mol / L aqueous sulfuric acid solution was added to the filtrate to form a precipitate. After filtering under reduced pressure, the mixture was dried overnight at 80°C to obtain 0.07 g of precipitate.

[0048] Figure 2 shows the infrared transmission spectrum of the precipitate. The infrared transmission spectrum of the wool is also shown in Figure 2.

[0049] Figure 2 shows that the precipitate is essentially a depolymer of wool that does not contain polyester.

[0050] (Depolymerization) 2 g of sodium hydroxide was dissolved in a mixed solvent consisting of 25 mL of methanol and 75 mL of tetrahydrofuran. 2.99 g of the filtrate was reacted in this solution at room temperature for 5 hours, then 100 mL of water was added and the mixture was stirred overnight to obtain the reaction solution.

[0051] (Solvent removal) Using an evaporator, the solvent was removed from the reaction mixture by distillation while heating at 45°C to obtain the solid component.

[0052] (extraction) After adding 150 mL of water and 150 mL of ethyl acetate to the solids and stirring, the mixture was filtered under reduced pressure to obtain 0.95 g of filtrate and filtrate. Next, using a separatory funnel, the filtrate was separated, and the ethyl acetate layer was removed to obtain an aqueous layer. Then, 150 mL of ethyl acetate was added to the aqueous layer, and the separation and removal of the ethyl acetate layer was repeated twice using a separatory funnel to obtain an aqueous layer. Next, 30 mL of 1 mol / L aqueous sulfuric acid solution was added to the aqueous layer to generate a precipitate, and the mixture was filtered under reduced pressure to obtain 2.44 g of filtrate. At this time, liquid chromatography-mass spectrometry (LC-MS) identified the filtrate as terephthalic acid, and the recovery rate of terephthalic acid was 100%.

[0053] [Example 3] (Blended fibers) 4.00 g of a blended fiber (mass ratio 7:3) of polyester fiber and wool was regenerated as a blended fiber. Here, the polyester fiber contains terephthalic acid units and ethylene glycol units. (Depolymerization) 2 g of sodium hydroxide was dissolved in a mixed solvent consisting of 25 mL of methanol and 75 mL of tetrahydrofuran. 4.00 g of blended fiber was reacted in this solution at room temperature for 5 hours, then 150 mL of water was added and the mixture was stirred overnight to obtain the reaction solution.

[0054] (Solvent removal) Using an evaporator, the solvent was removed from the reaction mixture by distillation while heating at 45°C to obtain the solid component.

[0055] (extraction) After adding 150 mL of water and 150 mL of ethyl acetate to the solids and stirring, the mixture was filtered under reduced pressure to obtain 1.05 g of filtrate and filtrate. Next, using a separatory funnel, the filtrate was separated, and the ethyl acetate layer was removed to obtain an aqueous layer. Then, 150 mL of ethyl acetate was added to the aqueous layer, and the separation and removal of the ethyl acetate layer was repeated twice using a separatory funnel to obtain an aqueous layer. Next, 30 mL of 1 mol / L sulfuric acid aqueous solution was added to the aqueous layer to generate a precipitate, and the mixture was filtered under reduced pressure to obtain 2.60 g of filtrate. At this time, liquid chromatography-mass spectrometry (LC-MS) identified the filtrate as terephthalic acid, and the recovery rate of terephthalic acid was 100%.

Claims

1. The process includes a step of depolymerizing a blend of polyester fibers and wool in a solution in which a strong base is dissolved in a solvent to obtain a first reaction solution. A method for regenerating blended fibers, wherein the solvent comprises tetrahydrofuran and methanol, and the ratio of methanol to the total amount of tetrahydrofuran and methanol is 20% by volume or more and 40% by volume or less.

2. A step of obtaining a second reaction solution by depolymerizing a blend of polyester fibers and wool in an aqueous solution of a strong base, The process involves filtering the second reaction solution to obtain a filtrate, The process includes the step of depolymerizing the filtrate in a solution in which a strong base is dissolved in a solvent to obtain a first reaction solution. A method for regenerating blended fibers, wherein the solvent comprises tetrahydrofuran and methanol, and the ratio of methanol to the total amount of tetrahydrofuran and methanol is 20% by volume or more and 40% by volume or less.

3. A step of removing the solvent from the first reaction solution to obtain a solid component, A step of adding water and an organic solvent to the solid content and filtering to obtain a filtrate, The process of separating the filtrate to obtain an aqueous layer, A method for regenerating blended fibers according to claim 1 or 2, further comprising the step of adding a strong acid to the aqueous layer to generate a precipitate.

4. The aforementioned blended fiber further comprises polyamide fiber, The method for regenerating blended fibers according to claim 3, further comprising the step of adding a strong acid to the aqueous layer and immersing the precipitate formed therein in methanol.

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