Method for separating plastic and cellulose from blended fabric

Abstract

Disclosed is a method for separating a plastic and cellulose from a blended fabric, the method comprising: bringing a blended fabric of cellulose and the plastic into contact with a treatment liquid that has a cellulose dissolving power and comprises only an ionic liquid which has a melting point of 100°C or less, or a treatment liquid that contains the ionic liquid and an organic solvent so as to dissolve the cellulose in the blended fabric into the treatment liquid; and subsequently separating a residual fabric that contains the plastic and the treatment liquid that contains the cellulose from each other, thereby separating the cellulose and the plastic in a recyclable state. By using this method, cellulose and the plastic can be separated from a blended fabric of the cellulose and the plastic in a recyclable state. In addition, the plastic can be separated therefrom, while maintaining the form of a fabric.

Description

Method for separating plastics and cellulose from blended fabrics

[0001] The present invention relates to a method for separating plastics and cellulose from a blended fabric, and more specifically, to a method for separating plastics and cellulose from a blended fabric using an ionic liquid capable of dissolving cellulose, in which the cellulose in the blended fabric is dissolved in the ionic liquid while the plastic component is separated from the blended fabric while maintaining the form of the fabric.

[0002] Cellulose, which is expected to be a biofuel, is difficult to dissolve or extract using water or organic solvents, and existing technologies that treat it with strong acids at high temperatures and pressures require a large amount of energy. Therefore, in recent years, technologies that use ionic liquids, which can dissolve cellulose under mild conditions, to dissolve, isolate, purify, decompose, and modify cellulose have attracted attention.

[0003] While cellulose has the advantages of being highly hygroscopic, durable, and heat-resistant, it also has the disadvantages of being prone to wrinkling and shrinking. To overcome these disadvantages and further improve the functionality of the fibers, blended fabrics combining cellulose with other plastics such as polyester are often used. In recent years, various recycling methods have been developed for recovering cellulose, plastics, or their decomposition products from such blended fabrics.

[0004] For example, Patent Document 1 discloses a fiber separation method in which blended fibers are introduced into an ionic liquid that dissolves specific fibers, and an extraction step is carried out to extract the specific fibers contained in the blended fibers into the ionic liquid. In an example of the method, a technique is disclosed in which blended fibers containing cellulose are introduced into an ionic liquid (1-butyl-3-methyl-pyridinium chloride) that dissolves cellulose fibers, and a heat treatment is carried out at a temperature equal to or higher than the melting point of the ionic liquid, thereby extracting the cellulose fibers into the ionic liquid.

[0005] Patent Document 2 discloses a process for recovering polyester components and non-polyester component products from an article composed of a polyester mixture, and in an example, discloses a technique for recovering polyester from a blended fiber of PET and cotton using an autoclave under a constant pressure.

[0006] The methods of Patent Documents 1 and 2 can extract only cellulose or only plastic from a blended fabric, but no simple method has been known to date for separating both cellulose and plastic components from a blended fabric in a recyclable state, while the plastic retains its fabric shape.

[0007] JP 2012-254400 A JP 2017-504694 A

[0008] The present invention has been made in view of the above circumstances, and aims to provide a method for separating plastic and cellulose from a blended fabric, which separates each component from the blended fabric of cellulose and plastic in a recyclable state, and with the plastic retaining the shape of the fabric.

[0009] As a result of extensive research into achieving the above object, the inventors discovered that the above problem could be solved by treating a blended fabric of cellulose and plastic with a specific ionic liquid, and thus completed the present invention.

[0010] That is, the present invention provides: 1. a method for separating plastic-cellulose from a blended fabric, comprising contacting a blended fabric of cellulose and plastic with a treatment solution consisting solely of an ionic liquid capable of dissolving cellulose and having a melting point of 100°C or less, or a treatment solution containing the ionic liquid and an organic solvent, dissolving the cellulose in the blended fabric in the treatment solution, and then separating the remaining fabric containing plastic from the treatment solution containing cellulose, thereby separating the cellulose and the plastic in a recyclable state; 2. the method for separating plastic-cellulose from a blended fabric of 1, wherein the ionic liquid is composed of a cationic component and an anionic component not containing a halogen atom; 3. the method for separating plastic-cellulose from a blended fabric of 1, wherein the blended fabric is contacted with the treatment solution under heating; 4. the method for separating plastic-cellulose from a blended fabric of 3, wherein the blended fabric is contacted with the treatment solution under heating at 40 to 120°C; 5. the method for separating plastic-cellulose from a blended fabric of 1, wherein the blended fabric is contacted with the treatment solution under pressure; 6. 5. The method for separating plastics and cellulose from a blended fabric of 5, in which the blended fabric is brought into contact with a treatment liquid under a pressure of 0.1 MPa or more but less than 1.0 MPa, 7. The method for separating plastics and cellulose from a blended fabric of 1, in which the blended fabric is brought into contact with a treatment liquid under heat and pressure, 8. The method for separating plastics and cellulose from a blended fabric of 7, in which the blended fabric is brought into contact with a treatment liquid under heating at 40 to 120°C and a pressure of 0.1 MPa or more but less than 1.0 MPa, 9. The method for separating plastics and cellulose from a blended fabric of any of 1 to 8, in which the contact is carried out by immersing the blended fabric in the treatment liquid, 10. The method for separating plastics and cellulose from a blended fabric of 9, in which the blended fabric and the treatment liquid are stirred forward and backward, 11. 9. A method for separating plastics and cellulose from a blended fabric, which comprises immersing the blended fabric in the treatment liquid, dissolving the cellulose in the blended fabric in the treatment liquid, and then lifting up the remaining fabric containing the plastics to separate it from the treatment liquid containing the cellulose; 12. A method for regenerating cellulose, which comprises a step of mixing the treatment liquid containing cellulose obtained by the method for separating plastics and cellulose from a blended fabric in 11 with a solvent that does not dissolve cellulose,13. A method for regenerating cellulose according to 12, comprising a step of separating the regenerated cellulose from a mixed solution of the ionic liquid and the solvent; and 14. A method for recovering an ionic liquid, comprising a step of distilling off the solvent from the mixed solution from which the regenerated cellulose has been separated by the method for regenerating cellulose according to 13.

[0011] According to the present invention, by treating a blended fabric in the form of a fabric with a specific ionic liquid, cellulose and plastic components can be separated in a simple manner in a recyclable state, with the plastic remaining in the form of a fabric. That is, cellulose can be recovered from the ionic liquid solution of cellulose separated by the separation method of the present invention, and the remaining plastic can be extracted in the form of a fabric and recovered by washing. Furthermore, the ionic liquid used in the separation method of the present invention can be reused (recycled) after cellulose recovery by, for example, distilling off the solvent, as needed.

[0012] FIG. 1 is a diagram showing an IR chart of the blended fabric used in the examples before treatment with an ionic liquid. FIG. 2 is a diagram showing an IR chart of the fabric evaluated as "△" after treatment with the same ionic liquid. FIG. 3 is a diagram showing an IR chart of the fabric evaluated as "◯" after treatment with the same ionic liquid. FIG. 4 is a diagram showing a photograph of cellulose recovered in Example 13. FIG. 5 is a diagram showing an IR chart of the cellulose recovered in Example 13. FIG. 6 is a diagram showing a photograph of cellulose recovered in Comparative Example 1. FIG. 7 is a diagram showing an IR chart of the cellulose recovered in Comparative Example 1.

[0013] The present invention will be described in more detail below. The method for separating plastic and cellulose from a blended fabric according to the present invention is characterized in that a blended fabric of cellulose and plastic is contacted with a treatment liquid consisting solely of an ionic liquid capable of dissolving cellulose and having a melting point of 100°C or less, or a treatment liquid containing the ionic liquid and an organic solvent, and the cellulose in the blended fabric is dissolved in the treatment liquid, and then the remaining fabric containing plastic is separated from the treatment liquid containing cellulose, and the cellulose and plastic are separated in a recyclable state.

[0014] The blended fabric can be appropriately selected from known blends, and specific examples include various blends such as cotton / polyester, cotton / nylon, cotton / polyester / polyurethane, cotton / nylon / polyurethane, rayon / polyester, rayon / nylon, and rayon / acrylic / polyester, but the method of the present invention can be suitably used for cotton / polyester blended fabrics. The blending ratio of plastic to cellulose in the blended fabric can also be arbitrary, and the mass ratio, for example, plastic:cellulose is about 10:90 to 90:10, preferably 20:80 to 80:20, more preferably 30:70 to 70:30, and even more preferably 35:65 to 65:35.

[0015] The ionic liquid used to treat the blended fabric may be any ionic liquid capable of dissolving cellulose and having a melting point of 100°C or less. It may be selected from various conventionally known ionic liquids, such as quaternary ammonium salt, imidazolium salt, pyridinium salt, quaternary phosphonium salt, choline, sulfonium salt, and neutralized salt ionic liquids. However, from the viewpoint of separating cellulose and plastic in a recyclable state, which is a feature of the present invention, ionic liquids composed of a cationic component and an anionic component that does not contain halogen atoms are preferred. Here, "having the ability to dissolve cellulose" means that 1 part by weight of crystalline cellulose, Avicel (registered trademark), is added to 100 parts by weight of ionic liquid, and after 24 hours, the Avicel is dissolved while stirring at 100°C. In other words, no undissolved Avicel is visible to the naked eye.

[0016] In particular, imidazolium salt-type ionic liquids and neutralized salt-type ionic liquids are preferred in the present invention. Examples of the cation component of the imidazolium salt-type ionic liquid include 1-ethyl-3-methylimidazolium ion, 1-butyl-3-methylimidazolium ion, and 1-hexyl-3-methylimidazolium ion.

[0017] Neutralized salt-type ionic liquids are ionic liquids consisting of salts obtained by acid-base neutralization reactions (see Ionic Liquids - The Frontline and Future of Development, pp. 19-21, CMC Publishing Co., Ltd. (2003)), and have cations formed by the addition of protons. The neutralized salt-type ionic liquid used in the present invention may be any ionic liquid consisting of a salt obtained by acid-base neutralization reactions, and there are no particular restrictions on the cationic components that make up the ionic liquid. However, from the viewpoint of having good cellulose dissolving ability, those represented by the following formula (1) or (2) are more preferred.

[0018]

[0019] As described above, the anion component is preferably one that does not contain a halogen atom, and is preferably an anion of an organic acid. Examples of the organic acid include carboxylic acids such as formic acid and acetic acid; and sulfonic acids such as methanesulfonic acid and p-toluenesulfonic acid. Carboxylic acids are preferred, and acetic acid is more preferred.

[0020] In the present invention, suitable ionic liquids include, but are not limited to, 1-ethyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium acetate, 1,8-diazabicyclo[5.4.0]-7-undecene (DBU) acetate, and 1,5-diazabicyclo[4.3.0]-5-nonene (DBN) acetate.

[0021] The method of the present invention includes a step of contacting the above-mentioned blended fabric with a treatment solution consisting of the above-mentioned ionic liquid alone or a treatment solution containing an ionic liquid and an organic solvent. In this case, the organic solvent may be any organic solvent that is compatible with the ionic liquid and does not dissolve the plastics that make up the blended fabric. Examples of the organic solvent include alcohols such as methanol and ethanol; chain ethers such as dibutyl ether, 1,2-dimethoxyethane, 1,2-ethoxymethoxyethane, methyl diglyme, methyl triglyme, methyl tetraglyme, ethyl glyme, ethyl diglyme, butyl diglyme, ethyl cellosolve, ethyl carbitol, butyl cellosolve, and butyl carbitol; heterocyclic ethers such as tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, and 4,4-dimethyl-1,3-dioxane; γ-butyrolactone, γ-valerolactone, δ-valerolactone, 3-methyl-1,3-oxolane, and 3-methyl-1,3-oxolane. lactones such as oxazolidin-2-one and 3-ethyl-1,3-oxazolidin-2-one; amides such as N-methylformamide, N,N-dimethylformamide, N-methylacetamide and N-methylpyrrolidinone; carbonates such as diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, propylene carbonate, ethylene carbonate and butylene carbonate; imidazolines such as 1,3-dimethyl-2-imidazolidinone; nitriles such as acetonitrile and propionitrile; esters such as methyl acetate and ethyl acetate; ketones such as acetone and methyl isobutyl ketone, dimethyl sulfoxide (hereinafter referred to as DMSO), and the like can be used alone or in combination of two or more.

[0022] A specific example of a suitable combination is one in which the blended fabric contains synthetic fibers (plastic fibers) such as polyester fibers and cotton fibers, the ionic liquid is composed of a cationic component and an anionic component that does not contain halogen atoms, and the treatment liquid contains the ionic liquid and DMSO. With this combination, plastic and cellulose can be separated from the blended fabric with higher separation accuracy.

[0023] When a treatment liquid containing an ionic liquid and an organic solvent is used, the content of the organic solvent in the treatment liquid is preferably 1 to 70 mass %, more preferably 2 to 60 mass %, and even more preferably 5 to 50 mass %.

[0024] There is no particular limitation on the method for contacting the blended fabric with the treatment liquid, and the blended fabric may be immersed in the treatment liquid or the treatment liquid may be applied to or impregnated into the blended fabric, but the method of immersing the blended fabric in the treatment liquid is simple and preferable.

[0025] The temperature during contact may be within a temperature range in which the treatment solution remains liquid, but from the viewpoint of improving treatment efficiency, heating is preferred, with heating at 40 to 120°C being more preferred, and 50 to 90°C being even more preferred. The pressure during contact is optional, and may be normal pressure or pressurized. From the viewpoint of balancing safety and ease of operation, normal pressure is preferred, but since pressurized conditions improve treatment efficiency compared to normal pressure, contact may be carried out under pressurized conditions as necessary. When contact is carried out under pressurized conditions, from the viewpoints of treatment efficiency, safety, and workability, the pressure is preferably 0.1 MPa or more and less than 1.0 MPa, and more preferably 0.4 to 0.9 MPa. Note that either heating or pressurization during contact may be carried out, or both may be carried out.

[0026] In the method of the present invention, a blended fabric is brought into contact with a treatment solution, such as by immersion, to dissolve the cellulose in the blended fabric in the treatment solution, and then the treatment solution containing the dissolved cellulose is separated from the remaining fabric containing plastic. Furthermore, a method of stirring in one direction during contact is also acceptable, but a forward / reverse stirring method, such as that used in a washing machine that reverses rotation after a certain period of time, is preferred. This allows the cellulose to more easily escape from the fibrous plastic in solution, allowing for complete separation in a shorter period of time, enabling immediate transfer to the spinning or extrusion process. Any method can be used to separate the treatment solution from the remaining fabric containing plastic. However, when the blended fabric is immersed in the treatment solution, a preferred method is to simply pull the remaining fabric containing plastic out of the treatment solution and separate it.

[0027] The plastic component of the remaining separated cloth is removed in cloth form, washed with water or an organic solvent such as methanol or DMSO, and then dried and recovered. This allows the plastic component to be separated from the cellulose component while maintaining the form of the cloth. As a washing liquid, an organic solvent is preferred because water can cause cellulose to immediately precipitate in cloth form from the liquid adhering to the cloth, and DMSO is more preferred because it does not easily precipitate cellulose. A two-stage washing method in which washing with DMSO is followed by washing with water or methanol, which have a lower boiling point, may also be employed. When performing this two-stage washing, if priority is given to ensuring that cellulose is not precipitated, it is also possible to use a mixture of DMSO and an ionic liquid instead of DMSO.

[0028] On the other hand, the treatment solution containing cellulose separated by the above method can be mixed with a solvent (poor solvent) that does not dissolve cellulose, thereby precipitating and regenerating the cellulose contained therein. Water is a preferred poor solvent. The regenerated cellulose can be separated from the mixed solution of the ionic liquid and the poor solvent by known methods such as filtration. As shown in the examples below, the regenerated cellulose obtained by the method of the present invention is in a state that allows it to be reused as cellulose without decomposition or deterioration.

[0029] Furthermore, the ionic liquid can be recovered by removing the poor solvent from the mixed solvent of the ionic liquid and the poor solvent after separating the regenerated cellulose by a known method such as distillation. The recovered ionic liquid can be recycled and, for example, can be reused in the method of the present invention or used for other common applications of ionic liquids.

[0030] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples. The materials used in the following examples are as follows. (1) Blended fabric: A cotton / polyester blended fabric (cotton:polyester = 35:65 (mass ratio)) manufactured by Nisshinbo Textile Inc. was cut into 3 cm square pieces and used. (2) Ionic liquid: (a) 1-ethyl-3-methylimidazolium acetate (EMI·AcO, manufactured by Kanto Chemical Co., Inc.) (b) 1-butyl-3-methylimidazolium acetate (BMI·AcO, manufactured by Tokyo Chemical Industry Co., Ltd.) (c) 1,8-diazabicyclo[5.4.0]-7-undecene (DBU) acetate (DBUH·AcO) (d) 1,5-diazabicyclo[4.3.0]-5-nonene (DBN) acetate (DBNH·AcO) (c) and (d) are neutralized salt-type ionic liquids, (c) is a mixture of DBU (manufactured by San-Apro Co., Ltd.) and acetic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in a molar ratio of 1:1, and (d) is a mixture of DBN (manufactured by Tokyo Chemical Industry Co., Ltd.) and acetic acid in a molar ratio of 1:1, both of which were synthesized in-house. Furthermore, for (a) EMI·AcO, a mixture to which 10% by mass of dimethyl sulfoxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) had been added in advance was also investigated.

[0031] [1] Separation of Polyester-Cellulose from Blended Fabric at Room Temperature and Normal Pressure [Example 1] The blended fabric was placed in a sample bottle (50 ml) containing at least 20 ml of the ionic liquid BMI·AcO and pressed with tweezers until the entire blended fabric was completely submerged in the ionic liquid. The lid was then placed on the bottle and left at room temperature for a predetermined time. After the predetermined time had elapsed, the fabric was removed with tweezers and placed in a tray of water. While the fabric was still in the water, a toothbrush was used to remove the swollen gel-like cellulose-containing ionic liquid and excess ionic liquid adhering to the fabric. During this process, cotton-like regenerated cellulose precipitated from the removed swollen gel-like cellulose-containing ionic liquid. After sufficient removal of the adhering matter, the fabric was transferred to a tray containing methanol. While still immersed in methanol, the surface of the fabric was rubbed with a toothbrush to remove any regenerated cotton or other material that had been brought in from the water. The fabric was then removed from the methanol and air-dried. The resulting fabric was evaluated according to the following criteria. ×: Clearly in the process of swelling △: Swollen gel cannot be removed with a toothbrush 〇: Swollen gel can be removed with a toothbrush ◎: Swollen gel peels off from the surface without using a toothbrush

[0032] [2] Separation of polyester-cellulose from blended fabric at 100°C and normal pressure [Examples 2 to 5] The blended fabric was placed in a sample bottle (50 ml) containing at least 20 ml of each ionic liquid, and pressed with tweezers until the entire blended fabric was completely submerged in the ionic liquid. The sample tube was then placed in an oil bath set to 100°C with the lid closed, and fixed in a position where the level of the ionic liquid in the sample tube was below the level of the silicone oil in the oil bath. After leaving the sample for a predetermined time, the same treatment as in Example 1 was carried out, and the sample was evaluated according to the above criteria.

[0033] [3] Separation of Polyester-Cellulose from Blended Fabric Under Pressure of Less Than 1 MPa [Examples 6 to 11] Pressure studies under pressure of less than 1 MPa were carried out using an autoclave (TEM-V300, Taiatsu Glass Industry Co., Ltd.). A 500 ml glass pressure-resistant container was used, and at least 120 ml of each ionic liquid was added in advance (up to the point where the thermocouple could be touched). The container was then set in the designated position in the autoclave. The blended fabric was then placed in the ionic liquid and pressed with tweezers until the entire blended fabric was completely submerged in the ionic liquid. The autoclave was then closed and sealed. If heated, nitrogen gas was introduced after the set temperature was reached and the pressure was increased to the designated pressure. After leaving the container for a designated period of time, the pressure was released, the autoclave lid was removed, and the fabric was removed from the pressure-resistant container using tweezers. The same treatment as in Example 1 was then carried out and the results were evaluated according to the above criteria.

[0034] [4] Separation of Polyester-Cellulose from Blended Fabric at 100°C and Under a Pressure of Less than 5 MPa [Example 12] A 5 MPa pressure was examined using an induction-heated microautoclave (SSN-400, Shikoku Rika Co., Ltd.). 30 ml of ionic liquid EMI·AcO was placed in a metal pressure-resistant container for the SSN-400, and the blended fabric was then placed in the ionic liquid and pressed with tweezers until the entire blended fabric was completely submerged in the ionic liquid. The pressure-resistant container was then sealed, nitrogen gas was introduced, and the pressure was increased to 5 MPa. The pressure-resistant container was then attached to the SSN-400 body and heated to the set temperature (100°C). After reaching the set temperature, the container was left for a predetermined period of time. After a predetermined time had elapsed, heating was stopped, and once the temperature had dropped to 40°C or below, the pressure-resistant container was removed from the main body. After the pressure was released, the lid of the pressure-resistant container was opened, and the cloth was removed from the pressure-resistant container using tweezers. The cloth was then treated in the same manner as in Example 1 and evaluated according to the above criteria.

[0035] The evaluation results of the fabrics obtained in each of the above examples are shown in Table 1. In addition, IR charts measured by the ATR method using an infrared spectrometer (IR Affinity-1S, Shimadzu Corporation) for the blended fabric before treatment are shown in Figure 1, for the fabrics evaluated as △ after treatment are shown in Figure 2, and for the fabrics evaluated as ◯ after treatment are shown in Figure 3.

[0036]

[0037] As shown in Table 1, the ionic liquid used in the examples achieved a rating of ○ within 12 hours when heated to 100°C even at normal pressure, meaning that only the cellulose in the blended fabric was dissolved and removed cleanly while maintaining its fabric shape. Furthermore, not only the ionic liquid but also the one to which dimethyl sulfoxide was added achieved a rating of ○, demonstrating that the present invention can also be implemented using a mixture of ionic liquid and organic solvent.

[0038] Furthermore, comparing Figures 1 and 2, the peaks of the polyester component seen in Figure 1 are almost not seen in Figure 2, indicating that the cellulose-containing ionic liquid component is attached to the surface and has not been removed. Conversely, the peaks derived from the cellulose component shown in Figure 1 are not seen in Figure 3, and the IR chart is of the polyester component only, indicating that the cellulose component has been completely removed from the blended fabric.

[0039] (Recovery of cellulose from cellulose-containing ionic liquid) [Example 13] After removing the blended fabric rated "good" by the above method, cellulose was dissolved in the ionic liquid, and by adding this to water, cellulose could be precipitated because ionic liquids are easily dissolved in water. A photograph of the recovered cellulose is shown in Figure 4. An IR chart of this recovered cellulose is shown in Figure 5. Figure 5 is an IR chart of a typical cellulose.

[0040] Comparative Example 1: A dissolution study was conducted on the 3 cm square blended fabric at normal pressure using 1-butyl-3-methyl-pyridinium chloride (Tokyo Chemical Industry Co., Ltd.) described in Japanese Patent No. 5824766. Because 1-butyl-3-methyl-pyridinium chloride is a solid at room temperature with a melting point of 111°C, the dissolution study was conducted in the same manner except that the temperature in step 2) above was changed to 120°C. Dissolution took one hour, yielding a fabric with cellulose removed to the same extent as a sample with a rating of 0, but the solution was dark brown to black in color. After removing the fabric, the 1-butyl-3-methyl-pyridinium chloride solution was poured into water, resulting in the precipitation of a black water-insoluble material. This material was recovered by filtration and dried to obtain a black granular recovered material. A photograph of this recovered material is shown in Figure 6, and its IR chart is shown in Figure 7. As can be seen from Figures 6 and 7, the appearance and IR chart of the recovered material differ from those of Example 13, indicating that clean, recyclable cellulose was not recovered.

[0041] [4] Separation of Polyester-Cellulose from Blended Fabric Using Forward and Reverse Stirring Method [Examples 14-17] Studies using different stirring methods were conducted under normal pressure using a stirrer (BLh300Ft, Shinto Scientific Co., Ltd.) and a 300 ml separable flask. The overall experimental conditions were as follows. Four pieces of blended fabric cut into 5 cm square pieces were placed in the separable flask (lower part) containing 200 g of reaction solution (ionic liquid only or ionic liquid:DMSO mixture (80:20 mass ratio)). After confirming that the entire blended fabric was completely immersed in the reaction solution, the separable flask (lower part) was attached to the separable flask (upper part) equipped with a thermometer and stirring blades, and then immersed in an oil bath. The stirring method was set to automatic forward rotation (unidirectional rotation) or automatic forward / reverse rotation (reversal every 5 seconds), and the oil bath was turned on to begin heating. The oil bath temperature was set so that the reaction solution temperature (internal temperature) in the reaction flask was 80°C. After the internal temperature reached 80°C and a predetermined time had passed, the cloth was removed and placed in a tray containing water. While the cloth was still in the water, a toothbrush was used to remove the swollen gel-like cellulose-containing ionic liquid and excess ionic liquid that had adhered to the cloth. After sufficient removal of the adhering matter, the cloth was transferred to a tray containing methanol, and while still immersed in methanol, the surface of the cloth was rubbed again with a toothbrush to remove recycled cotton and other materials that had been brought in from the water. The cloth was then removed from the methanol and air-dried, and the resulting cloth was evaluated according to the following criteria: ×: Clearly in the process of swelling △: Swollen gel could not be removed with a toothbrush ○: Swollen gel could be removed with a toothbrush ◎: Swollen gel peeled off from the surface without using a toothbrush

[0042] The individual conditions for Examples 14 to 17 are shown below. [Example 14] Reaction solution: DBUH·AcO Stirring: Automatic forward rotation (unidirectional rotation) [Example 15] Reaction solution: DBUH·AcO Stirring: Automatic forward / reverse stirring [Example 16] Reaction solution: DBUH·AcO-dimethyl sulfoxide mixed solution (weight ratio 80:20) Stirring: Automatic forward rotation (unidirectional rotation) [Example 17] Reaction solution: DBUH·AcO-dimethyl sulfoxide mixed solution (weight ratio 80:20) Stirring: Automatic forward / reverse stirring

[0043] The results of Examples 14 to 17 are shown in Table 2.

[0044]

[0045] A comparison of Examples 14 and 15, and Examples 16 and 17 in Table 2 shows that forward and reverse stirring significantly improves the cellulose dissolution rate. In Examples 14 and 16, the cloth wrapped around the stirring shaft and stirring blades during cellulose dissolution, and sometimes even became integrated, making it difficult to remove the cloth one by one. In contrast, in Examples 15 and 17, the cloths floated individually even during cellulose dissolution. This suggests that the reaction rate improved because the liquid was able to come into contact with the entire surface of the cloth throughout the reaction time under forward and reverse stirring conditions. Even with unidirectional rotation, as cellulose dissolution progressed, the wrapping or integration eventually dissolved, and the cloths became loose, making them easy to remove.

Claims

1. A method for separating plastic and cellulose from a blended fabric, comprising contacting a blended fabric of cellulose and plastic with a treatment liquid consisting solely of an ionic liquid having the ability to dissolve cellulose and a melting point of 100°C or less, or a treatment liquid containing said ionic liquid and an organic solvent, dissolving the cellulose in the blended fabric in said treatment liquid, and then separating the remaining fabric containing plastic from the treatment liquid containing cellulose, and separating the cellulose and the plastic in a recyclable state.

2. The method for separating plastic-cellulose from a blended fabric according to claim 1, wherein the ionic liquid is composed of a cationic component and an anionic component that does not contain a halogen atom.

3. The method for separating plastics and cellulose from a blended fabric according to claim 1, wherein the blended fabric is contacted with a treating solution under heating.

4. The method for separating plastics and cellulose from a blended fabric according to claim 3, wherein the blended fabric is brought into contact with the treating solution under heating at 40 to 120°C.

5. The method for separating plastic-cellulose from a blended fabric according to claim 1, wherein the blended fabric is contacted with the treating solution under pressure.

6. The method for separating plastics and cellulose from a blended fabric according to claim 5, wherein the blended fabric is contacted with the treatment liquid under a pressure of 0.1 MPa or more but less than 1.0 MPa.

7. The method for separating plastic-cellulose from a blended fabric according to claim 1, wherein the blended fabric is contacted with a treating solution under heat and pressure.

8. A method for separating plastics and cellulose from a blended fabric according to claim 7, wherein the blended fabric is contacted with a treatment liquid under heating at 40 to 120° C. and under a pressure of 0.1 MPa or more and less than 1.0 MPa.

9. The method for separating plastic-cellulose from a blended fabric according to any one of claims 1 to 8, wherein said contacting is carried out by immersing said blended fabric in said treatment liquid.

10. The method for separating plastic-cellulose from a blended fabric according to claim 9, wherein said blended fabric and said treatment solution are mixed in opposite directions.

11. A method for separating plastics and cellulose from a blended fabric according to claim 9, comprising the steps of immersing the blended fabric in the treatment liquid, dissolving the cellulose in the blended fabric in the treatment liquid, and then lifting the remaining fabric containing the plastics as is to separate it from the treatment liquid containing the cellulose.

12. A method for regenerating cellulose, comprising the step of mixing a treatment liquid containing the cellulose obtained by the method for separating plastics and cellulose from a blended fabric according to claim 11 with a solvent that does not dissolve cellulose, thereby regenerating cellulose.

13. The method for regenerating cellulose according to claim 12, further comprising a step of separating the regenerated cellulose from the mixed solution of the ionic liquid and the solvent.

14. A method for recovering an ionic liquid, comprising the step of distilling off the solvent from a mixed solution from which the regenerated cellulose has been separated by the method for regenerating cellulose according to claim 13.

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