Treatment agent for fiber recycling and method for fiber recycling

Abstract

This treatment agent for fiber recycling comprises an ionic liquid formed from a cation having nitrogen atoms or phosphorus atoms and an anion.

Description

Treatment Agent for Fiber Recycling and Fiber Recycling Method

[0001] The present invention relates to a treatment agent for fiber recycling and a fiber recycling method.

[0002] Fiber products are discarded in large quantities every day as cuttings in the sewing process or as used clothes, etc., and there is a strong demand for recycling. However, for blended fibers spun from two or more different fibers, fibers with a resin-coated surface (laminated), and fiber products using these, it is necessary to devise methods during chemical recycling to isolate the fibers.

[0003] For example, Patent Document 1 discloses a technique for selectively removing a cellulose-based polymer, which is a natural material, from blended fibers by heat-treating the blended fibers, an acid anhydride or carboxylic acid, and a solvent in the presence of an acid catalyst, and separating the synthetic fibers; Patent Document 2 discloses a method for recycling a nylon fiber processed with polyurethane by heat-treating it with an organic solvent to remove the polyurethane component and then depolymerizing the nylon fiber from which the polyurethane component has been removed to recover lactam; Patent Document 3 discloses a method for recovering a nylon 6 product from which the above polyurethane has been separated and removed by heating a nylon 6 product containing a polyether-based polyurethane together with a cyclic amide compound solvent.

[0004] JP-A-2006-316191 JP-A-2008-31127 JP-A-2011-88943

[0005] However, the method of Patent Document 1 can only be applied to blended fibers containing cellulose-based polymers, and moreover, since the cellulose-based polymers are decomposed, the cellulose-based polymers cannot be recovered. The methods of Patent Documents 2 and 3 have problems in that they use organic solvents with a low flash point and a large environmental load, which may damage the safety of the working environment and have a large environmental load for recycling.

[0006] The present invention is intended to solve the above problems, and an object thereof is to provide a treatment agent for fiber recycling enabling safe and low-environmental-load recycling, and a fiber recycling method using the treatment agent for fiber recycling.

[0007] The present inventors have diligently studied to solve the above problems and have arrived at the present invention. Specifically, the present invention comprises a treatment agent for fiber recycling comprising an ionic liquid consisting of a cation containing a nitrogen atom or a phosphorus atom and an anion; and a method for recycling fibers comprising the step of bringing fibers into contact with the treatment agent for fiber recycling.

[0008] According to the present invention, it is possible to provide a treatment agent for textile recycling that enables safe and environmentally friendly recycling, and a method for recycling textiles using the treatment agent.

[0009] The present invention is described in detail below. The textile recycling treatment agent of the present invention (hereinafter also simply referred to as the "treatment agent") contains an ionic liquid consisting of a cation containing a nitrogen atom or a phosphorus atom and an anion. An ionic liquid is a salt composed of a combination of a cation and anion that is in liquid form. In the present invention, an ionic liquid refers to a salt composed of a combination of a cation and anion that has a melting point of 45°C or less at 1 atmosphere. The melting point is a value determined by differential scanning calorimetry (DSC) by raising the temperature from -150°C to 100°C at 10°C / min and measuring the change in heat relative to the reference. In the present invention, the melting point of the ionic liquid is preferably 25°C or less. In the present invention, the ionic liquid is preferably a liquid at 1 atmosphere and 25°C.

[0010] The cations constituting ionic liquids contain either a nitrogen atom or a phosphorus atom. Examples of cations containing a nitrogen atom include quaternary ammonium cations (tetraethylammonium cation, tributylmethylammonium cation, etc.), pyrrolidinium cations (1-butyl-1-methylpyrrolidinium cation, etc.), pyridinium cations (1-butyl-3-methylpyridinium cation, etc.), piperidinium cations (1-butyl-1-methylpiperidinium cation, etc.), and imidazolium cations (cations represented by the general formula (1) below). Examples of cations containing a phosphorus atom include phosphonium cations (methyltributylphosphonium cation, trihexyltetradecylphosphonium cation, etc.). Among these, imidazolium cations are preferred from the viewpoint of solubility in polyurethanes and cellulose fibers.

[0011] The cation is preferably a cation represented by the following general formula (1).

[0012]

[0013] In general formula (1), R １ ~R ５ Each of these independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. The alkyl group may be linear or branched.

[0014] Examples of cations represented by the general formula (1) include 1-methylimidazolium, 1-ethylimidazolium, 1-propylimidazolium, 1-butylimidazolium, 1,3-dimethylimidazolium, 1-ethyl-3-methylimidazolium, 1,3-diethylimidazolium, 1-propyl-3-methylimidazolium, and 1-butyl-3-methylimidazolium. Of these, 1-ethyl-3-methylimidazolium cation is preferred from the viewpoint of stability and fiber dissolution efficiency.

[0015] The anions constituting the ionic liquid are not particularly limited, but from the viewpoint of stability and fiber dissolution efficiency, it is preferable that the pKa of their conjugate acid is 0.3 to 4.8. pKa represents the acid dissociation constant pKa of a substance in water. The pKa of the conjugate acid of the anion in this invention is a value calculated using the following software package 1, based on a database of Hammett substituent constants and known literature values. Software package 1: Advanced Chemistry Development (ACD / Labs) Software V8.14 for Solaris (1994-2007 ACD / Labs).

[0016] An anion's conjugate acid is a substance produced when an anion accepts a proton. Examples of conjugate acids with a pKa of 0.3 to 4.8 include acetic acid [pKa: 4.8], decanoic acid [pKa: 4.8], formic acid [pKa: 3.8], glycolic acid [pKa: 3.8], methoxyacetic acid [pKa: 3.6], fluoroacetic acid [pKa: 2.6], and difluoroacetic acid [pKa: 1.3]. Of these, acetic acid is preferred from the viewpoint of stability and fiber dissolution efficiency.

[0017] As the ionic liquid, 1-ethyl-3-methylimidazolium acetate is preferred.

[0018] The fiber recycling treatment agent of the present invention may contain two or more ionic liquids.

[0019] In the present invention, the fibers to be recycled include blended fibers containing at least two types of fibers, and fibers whose surface is coated with resin. Among the fibers included in the blended fibers, cellulose fibers or polyurethane fibers are preferred due to their good solubility in ionic liquids. Examples of cellulose fibers include cotton and hemp. Polyurethane fibers are more preferred because they can be recovered after dissolution. Furthermore, a high crosslinking density (500 mol / m³) is preferred. ３(As described above) Polyurethane fibers have low solubility in ionic liquids and are therefore undesirable for textile products such as clothing, and are not used in general textile products. Furthermore, as fibers included in blended fibers, nylon fibers or polyester fibers are preferred because they are poorly soluble in ionic liquids and easy to recover. Among nylon fibers, 6-nylon (nylon 6) is preferred.

[0020] Examples of blended fibers include blends of nylon fibers and polyurethane fibers, blends of nylon fibers and cotton fibers, blends of polyester fibers and polyurethane fibers, and blends of polyester fibers and cotton fibers. It is preferable to use a fiber recycling treatment agent containing 1-ethyl-3-methylimidazolium acetate on these blended fibers.

[0021] Examples of fibers with a resin-coated surface include nylon fibers laminated with polyurethane resin, nylon fibers laminated with acrylic resin, polyester fibers laminated with polyurethane resin, and polyester fibers laminated with acrylic resin.

[0022] The present invention relates to a method for recycling fibers (hereinafter also simply referred to as the "recycling method"), which includes a step of bringing fibers into contact with a treatment agent of the present invention. The method of bringing the fibers into contact with the treatment agent is not particularly limited and includes methods such as immersing the fibers in the treatment agent, spraying the treatment agent onto the fibers, and washing the fibers with the treatment agent. Through the above steps, specific fibers and resins contained in the fibers are dissolved, making fiber recycling easier. "Fiber recycling" means recovering (isolating) at least one type of fiber from the fibers.

[0023] In one embodiment, the recycling method of the present invention is a blended fiber containing a first fiber and a second fiber, and includes a step of dissolving the second fiber.

[0024] Examples of blended fibers include those containing at least two of the aforementioned fibers. The first fiber in the blended fiber may be nylon or polyester fiber, while the second fiber may be cellulose or polyurethane fiber.

[0025] To simplify the explanation, the following description will primarily focus on the case where the blended fiber consists of only two types of fibers (a first fiber and a second fiber). Even when the blended fiber contains three or more types of fibers, recycling can be carried out by selecting appropriate conditions.

[0026] In the step of dissolving the second fiber, the weight ratio of the treatment agent to the blended fiber is not particularly limited as long as it can dissolve the second fiber in the blended fiber, but from the viewpoint of dissolution efficiency, it is preferable that the treatment agent:blended fiber = 90:10 to 99:1. The time for which the blended fiber and the treatment agent are in contact is also not particularly limited as long as it is long enough to dissolve the second fiber.

[0027] The process of dissolving the second fiber may include a step of heating the fiber recycling treatment agent. To facilitate the dissolution of the second fiber, it is preferable to include a step of heating the mixture of the blended fiber and the treatment agent in the process of dissolving the second fiber. In the above heating step, from the viewpoint of dissolution efficiency, the heating temperature is preferably 50 to 100°C and the heating time is preferably 3 to 5 hours.

[0028] After the step of dissolving the second fibers, the treatment agent containing the dissolved second fibers and the undissolved fibers (first fibers) are obtained. The process may further include a step of isolating the first fibers after the step of dissolving the second fibers. The method for isolating the first fibers is not particularly limited and may include filtration or centrifugation.

[0029] The process may include a step of isolating the second fibers after the step of dissolving the second fibers. The method for isolating the second fibers is not particularly limited, but for example, the second fibers may be precipitated by cooling the treatment agent in which the second fibers have been dissolved, and then recovered by filtration or centrifugation. The recovered second fibers can be reused. The temperature of the treatment agent during cooling is not particularly limited as long as the second fibers can be isolated. If the treatment agent is heated in the step of dissolving the second fibers, the treatment agent may be cooled to a temperature lower than the heating temperature, for example, around 25 to 40°C.

[0030] The treatment agent used after isolating the second fiber can be used again in fiber recycling methods.

[0031] In one embodiment, the recycling method of the present invention includes a step of dissolving the resin, wherein the fiber is a third fiber whose surface is coated with a resin. Examples of fibers include the aforementioned fiber whose surface is coated with a resin. Examples of resins include polyurethane resin and acrylic resin. Examples of third fibers include nylon fiber and polyester fiber.

[0032] The conditions in the resin dissolution process, such as the weight ratio of the treatment agent to the fibers and the contact time between the fibers and the treatment agent, should be appropriately selected to ensure the resin is dissolved. Similar to the blended fiber recycling method described above, the resin dissolution process may include a step of heating the treatment agent. It is preferable to include a step of heating the mixture of fibers and treatment agent in the resin dissolution process. The heating conditions should be appropriately selected.

[0033] The process may further include a step of isolating a third fiber after the step of dissolving the resin. The isolation method can be selected as appropriate.

[0034] The process may include a step of isolating the resin after the step of dissolving the resin. The isolation method is not particularly limited; for example, the resin may be precipitated by cooling the treatment agent in which the resin has been dissolved, and then recovered by filtration or centrifugation. The treatment agent after the resin has been isolated can be used again in the fiber recycling method.

[0035] This specification discloses the following:

[0036] The present disclosure (1) is a treatment agent for fiber recycling, which contains an ionic liquid composed of a cation containing a nitrogen atom or a phosphorus atom and an anion.

[0037] The present disclosure (2) is the treatment agent for fiber recycling according to the present disclosure (1), wherein the pKa of the conjugate acid of the anion is 0.3 to 4.8.

[0038] The present disclosure (3) is the treatment agent for fiber recycling according to the present disclosure (1) or (2), wherein the cation is a cation represented by the following general formula (1). [[ID=X]] [In the general formula (1), R １ [[ID=Y]] ~ R ５ each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. ]

[0039] The present disclosure (4) is a fiber recycling method including a step of bringing a fiber into contact with the treatment agent for fiber recycling according to any one of the present disclosures (1) to (3).

[0040] The present disclosure (5) is the fiber recycling method according to the present disclosure (4), wherein the fiber is a blended fiber containing a first fiber and a second fiber, and includes a step of dissolving the second fiber.

[0041] The present disclosure (6) is the fiber recycling method according to the present disclosure (5), further including a step of isolating the first fiber after the step of dissolving the second fiber.

[0042] The present disclosure (7) is the fiber recycling method according to the present disclosure (5) or (6), further including a step of isolating the second fiber after the step of dissolving the second fiber.

[0043] The present disclosure (8) is the fiber recycling method according to any one of the present disclosures (5) to (7), including a step of heating the treatment agent for fiber recycling in the step of dissolving the second fiber.

[0044] The present disclosure (9) is the fiber recycling method according to the present disclosure (7) or (8), including a step of cooling the treatment agent for fiber recycling in the step of isolating the second fiber

[0045] The present disclosure (10) is a method for recycling fibers according to the present disclosure (4), wherein the fiber is a third fiber whose surface is coated with a resin, and the method includes a step of dissolving the resin.

[0046] The present invention will be further described below with reference to examples and comparative examples, but the present invention is not limited thereto.

[0047] The following ionic liquids were used as treatment agents for fiber recycling in the examples and comparative examples: • Ionic liquid (1): 1-ethyl-3-methylimidazolium acetate (conjugate acid of the anion: acetic acid [pKa: 4.8]) [manufactured by Tokyo Chemical Industry Co., Ltd.] • Ionic liquid (2): 1-ethyl-3-methylimidazolium tetrafluoroborate (conjugate acid of the anion: tetrafluoroboric acid [pKa: -0.4]) [manufactured by Tokyo Chemical Industry Co., Ltd.] • Ionic liquid (3): 1-butyl-3-methylimidazolium acetate (conjugate acid of the anion: acetic acid [pKa: 4.8]) [manufactured by Tokyo Chemical Industry Co., Ltd.] • Ionic liquid (4): trihexyltetradecylphosphonium decanoate (conjugate acid of the anion: decanoic acid [pKa: 4.8]) [manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.] • Ionic liquid (5): Trihexyltetradecylphosphonium chloride (conjugate acid of the anion is hydrochloric acid [pKa: -6.0]) [Manufactured by Fujifilm Wako Pure Chemical Corporation] • Ionic liquid (6): Tributylmethylammonium bis(trifluoromethanesulfonyl)imide (conjugate acid of the anion is bis(trifluoromethanesulfonyl)imide [pKa: -10.4]) [Manufactured by Fujifilm Wako Pure Chemical Corporation]

[0048] <Example 1> 48.5 g of ionic liquid (1) was weighed into a beaker, and 1.501 g of plain-woven white cloth made of a 6-nylon / polyurethane blend yarn of 90 / 10 was added to the ionic liquid. The mixture was then heated and stirred at 70°C for 4 hours using a hot stirrer. Next, the white cloth was removed with tweezers, washed with 100 ml of ionic liquid (1), and then washed again with 100 ml of water. The removed white cloth was dried in a dryer set to 105°C for 1 hour, and then its weight was measured. The weight of the dried white cloth was 1.355 g, which was approximately 90% by weight of the white cloth before it was added. This result suggests that, since the blend yarn used in the white cloth is composed of 90% by weight of 6-nylon and 10% by weight of polyurethane, the polyurethane was extracted into the ionic liquid, and only the 6-nylon was separated as a solid component. The removal rate of polyurethane contained in the white cloth was determined by dividing the weight loss of the white cloth by the weight of polyurethane originally contained in the white cloth. Polyurethane removal rate (%) = [(Initial weight of white cloth - Weight of white cloth after drying) / (Initial weight of white cloth × 10 / 100)] × 100

[0049] <Example 2> The same procedure as in Example 1 was followed, except that the plain weave white cloth made of a 6-nylon / polyurethane=90 / 10 blend yarn was replaced with 1.502 g of plain weave white cloth made of a polyester / cotton=50 / 50 blend yarn. The weight of the white cloth after drying was 0.763 g.

[0050] <Example 3> The same procedure as in Example 1 was followed, except that ionic liquid (1) was replaced with ionic liquid (2) and 1.490 g of white cloth was used. The weight of the white cloth after drying was 1.423 g.

[0051] <Example 4> The same procedure as in Example 1 was followed, except that ionic liquid (1) was replaced with ionic liquid (3) and 1.510 g of white cloth was used. The weight of the white cloth after drying was 1.364 g.

[0052] <Example 5> The same procedure as in Example 1 was followed, except that ionic liquid (1) was replaced with ionic liquid (4) and 1.508 g of white cloth was used. The weight of the white cloth after drying was 1.408 g.

[0053] <Example 6> The same procedure as in Example 1 was followed, except that ionic liquid (1) was replaced with ionic liquid (5) and 1.511 g of white cloth was used. The weight of the white cloth after drying was 1.449 g.

[0054] <Example 7> The same procedure as in Example 1 was followed, except that ionic liquid (1) was replaced with ionic liquid (6) and 1.488 g of white cloth was used. The weight of the white cloth after drying was 1.423 g.

[0055] <Comparative Example 1> The same procedure as in Example 1 was followed, except that the ionic liquid was changed to N,N-dimethylformamide (DMF) and 1.495 g of white cloth was used. The weight of the white cloth after drying was 1.348 g.

[0056] <Comparative Example 2> The same procedure as in Example 1 was followed, except that the ionic liquid was changed to N-methyl-2-pyrrolidone (NMP) and 1.510 g of white cloth was used. The weight of the white cloth after drying was 1.362 g.

[0057] <Recovery of Fibers Dissolved in Ionic Liquid> In Example 1, after removing the white cloth, a plain-woven white cloth made of the same 6-nylon / polyurethane=90 / 10 blended yarn was added to the ionic liquid and heated and stirred at 70°C for 4 hours using a hot stirrer. The same operation of adding white cloth and heating and stirring was repeated until the weight change of the white cloth stopped (until the ionic liquid was saturated). After that, the ionic liquid was allowed to cool to room temperature (25°C). The cooled ionic liquid was filtered by suction filtration, the solid was washed with water, and then dried in a dryer set to 105°C for 1 hour to recover the fibers. The weight of the recovered fibers (polyurethane) was measured and divided by the weight of the fibers dissolved in the ionic liquid (total weight change of all white cloth) to calculate the fiber (polyurethane) recovery rate.

[0058] For Examples 2-7 and Comparative Examples 1 and 2, the recovery rate of fibers dissolved in the ionic liquid was calculated in the same manner. In Example 2, even when the ionic liquid was cooled, the dissolved cotton did not precipitate and could not be recovered. Similarly, in Comparative Examples 1 and 2, even when the organic solvent was cooled, only the viscosity increased, and the dissolved polyurethane did not precipitate and could not be recovered.

[0059] <Measurement of Flash Point> In Examples 1 to 7 and Comparative Examples 1 and 2, the flash points of the ionic liquid and organic solvent used as treatment agents for fiber recycling were measured using the Cleveland open-type filter according to JIS K 2265-4:2007. The results for each example and comparative example are shown in Tables 1-1 and 1-2.

[0060]

[0061]

[0062] The results in Tables 1-1 and 1-2 show that recycling can be achieved using ionic liquids, which have a flash point higher than 150°C and allow for easier assurance of the working environment safety, in the same way as when using organic solvents such as DMF and NMP.

[0063] According to the present invention, products made from fibers can be easily recycled.

Claims

1. A treatment agent for fiber recycling comprising an ionic liquid consisting of a cation containing a nitrogen atom or a phosphorus atom and an anion.

2. The textile recycling treatment agent according to claim 1, wherein the pKa of the conjugate acid of the anion is 0.3 to 4.

8.

3. The treatment agent for fiber recycling according to claim 1, wherein the cation is a cation represented by the following general formula (1). [In general formula (1), R １ ~R ５ Each of these independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

4. A method for recycling fibers, comprising the step of bringing fibers into contact with the fiber recycling treatment agent described in claim 1.

5. The fiber recycling method according to claim 4, wherein the fiber is a blended fiber containing a first fiber and a second fiber, and the method includes a step of dissolving the second fiber.

6. The fiber recycling method according to claim 5, further comprising the step of isolating the first fiber after the step of dissolving the second fiber.

7. A method for recycling fibers according to claim 5 or 6, further comprising the step of isolating the second fibers after the step of dissolving the second fibers.

8. The method for recycling fibers according to claim 5 or 6, further comprising the step of heating the fiber recycling treatment agent in the step of dissolving the second fiber.

9. The fiber recycling method according to claim 7, further comprising the step of cooling the fiber recycling treatment agent in the step of isolating the second fiber.

10. The fiber recycling method according to claim 4, wherein the fiber is a third fiber whose surface is coated with resin, and the method includes a step of dissolving the resin.

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