How to recycle cotton blend textile products

Abstract

To provide a recycling method capable of easily separating a cotton-mixed fiber product containing synthetic fibers and cotton into the synthetic fibers and the cotton, and recycling the cotton-mixed fiber product. A method for recycling cotton blended fiber products containing synthetic fibers and cotton, comprising the steps of: (1) Step 1 of pulverizing the cotton blend fiber product to prepare pulverized fiber; and (2) adding the pulverized fibers to a dispersion medium to prepare a dispersion liquid, and allowing the dispersion liquid to stand; A recycling method comprising the steps of:

Description

[Technical Field]

[0001] The present invention relates to a method for recycling cotton blend textile products. [Background technology]

[0002] In recent years, efforts have been made to recycle waste textile products (hereinafter referred to as "waste textiles"), which are discarded materials that are not used for finished products, such as textile products discarded in daily life and defective products at textile production sites, from the perspective of effective utilization of waste resources and waste reduction. One of the main recycling methods for waste textiles is material recycling, which reuses them as materials. In particular, the recycling of cotton fiber, which is derived from plants and has excellent biodegradability, has attracted attention. In this recycling, naturally derived cellulose fiber, which has excellent biodegradability, is kneaded into plastic products, imparting biodegradability to the products. This type of material recycling is a highly sustainable recycling method because it directly contributes to resource circulation.

[0003] Fiber-reinforced composite materials containing cellulose in plastic products are known (see Patent Document 1). However, in Patent Document 1, the cellulose is cellulose nanofiber (CNF) derived from pulp, which is a primary resource, and does not contribute to resource circulation. Furthermore, many textile products are consumed, and many are discarded after consumption; cotton textile products in particular are incinerated or buried. Patent Document 1 has the problem of not considering the possibility of obtaining cotton textile products through recycling.

[0004] Therefore, there is a need for the development of a recycling method that can easily separate cotton-blend fiber products containing synthetic fibers and cotton into the synthetic fibers and cotton, and that can recycle the cotton-blend fiber products. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6360954 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a recycling method that can easily separate a cotton-blend fiber product containing synthetic fibers and cotton into the synthetic fibers and cotton, and can recycle the cotton-blend fiber product. [Means for solving the problem]

[0007] As a result of extensive research, the inventors have discovered that a recycling method comprising (1) step 1 of pulverizing a cotton-blended fiber product to prepare pulverized fibers, and (2) step 2 of adding the pulverized fibers to a dispersion medium to prepare a dispersion and allowing the dispersion to stand still, can easily separate the synthetic fibers and cotton in the dispersion by allowing it to stand still, and have completed the present invention.

[0008] That is, the present invention relates to the following recycling method. 1. A method for recycling cotton blended textile products containing synthetic fibers and cotton, comprising: (1) Step 1 of pulverizing the cotton blend fiber product to prepare pulverized fiber; and (2) adding the pulverized fibers to a dispersion medium to prepare a dispersion liquid, and allowing the dispersion liquid to stand; A recycling method comprising the steps of: 2. The recycling method according to item 1 or 2, wherein the specific gravity of the dispersion medium is 0.96 to 1.60. 3. The recycling method according to any one of items 1 to 3, wherein the synthetic fibers contain at least one resin selected from the group consisting of polyester-based resins, polypropylene-based resins, acrylic-based resins, acetate-based resins, nylon-based resins, and cellulose-based resins. 4. The recycling method according to any one of items 1 to 3, wherein the dispersion medium contains at least one selected from the group consisting of alkali metal salts and alkaline earth metal salts. 5. The recycling method according to any one of items 1 to 4, wherein the content of the pulverized fibers in the dispersion is 0.1 to 15 parts by mass, based on 100 parts by mass of the dispersion medium. 6. The recycling method according to any one of items 1 to 5, wherein the average fiber length of the pulverized fibers is 100 μm or more and 1000 μm or less. 7. The recycling method according to any one of items 1 to 6, wherein the temperature of the dispersion in step 2 is 4 to 50°C. [Effects of the Invention]

[0009] The recycling method of the present invention can easily separate cotton-mixed fiber products containing synthetic fibers and cotton into the synthetic fibers and cotton, and therefore can recycle cotton-mixed fiber products. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a photograph of a dispersion liquid after primary separation in Example 1. [Figure 2] 1 is a photograph of a dispersion liquid after secondary separation in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0011] The recycling method of the present invention will be described in detail below.

[0012] The recycling method of the present invention is a method for recycling cotton-blend fiber products containing synthetic fibers and cotton, and includes: (1) Step 1 of pulverizing the cotton-blend fiber product to prepare pulverized fibers; and (2) Step 2 of adding the pulverized fibers to a dispersion medium to prepare a dispersion and allowing the dispersion to stand. In the recycling method of the present invention, the pulverized fibers prepared in Step 1 are added to a dispersion medium to form a dispersion, and by allowing the dispersion to stand, the synthetic fibers and cotton in the pulverized fibers separate in the dispersion due to the difference in their specific gravities relative to the dispersion, and the synthetic fibers and cotton can be easily separated by allowing the dispersion to stand.

[0013] (synthetic fiber) The cotton-mixed textile products that are the materials to be treated in the recycling method of the present invention contain synthetic fibers. The resin contained in the synthetic fibers is not particularly limited, but synthetic fibers containing thermoplastic resins are often used in cotton-mixed textile products.

[0014] The thermoplastic resin is not particularly limited, and examples thereof include polyester-based resins, polypropylene-based resins, acrylic-based resins, acetate-based resins, nylon-based resins, cellulose-based resins, polyethylene-based resins, polyvinyl chloride-based resins, polystyrene-based resins, acrylonitrile-butadiene-styrene-based resins, acrylonitrile-styrene-based resins, polymethyl(meth)acrylate-based resins, etc. Among these, polyester-based resins, polypropylene-based resins, acrylic-based resins, acetate-based resins, nylon-based resins, and cellulose-based resins are preferred, and synthetic fibers containing polyester-based resins and polypropylene-based resins are often used in cotton-blend textile products such as clothing, and in particular, synthetic fibers containing polyester-based resins such as polyethylene terephthalate are most commonly used.

[0015] The cotton-mixed fiber product, which is the object of the recycling method of the present invention, contains cotton. The type of cotton is not particularly limited, and any known cotton may be used. By pulverizing the cotton, the pulverized fibers contain finely divided cellulose fibers.

[0016] The mass ratio of synthetic fiber to cotton in a cotton-blend fiber product is not particularly limited. In a cotton-blend fiber product, the mass ratio of synthetic fiber to cotton is preferably 98:2 to 30:70, more preferably 95:7 to 40:60, even more preferably 93:7 to 50:50, particularly preferably 80:20 to 55:45, and most preferably 70:30 to 60:40. Furthermore, when a synthetic fiber containing polyethylene terephthalate is used as the synthetic fiber contained in a cotton-blend fiber product, the mass ratio of synthetic fiber to cotton in the cotton-blend fiber product is often 65:35.

[0017] The cotton-mixed fiber product to be treated in the present invention is not particularly limited as long as it contains the above-mentioned synthetic fiber and cotton, and can be a wide range of materials, such as clothing, towel products, used clothing, etc. In particular, cotton-mixed fiber products derived from waste materials such as used clothing can be preferably used.

[0018] (Process 1) Step 1 is a step of pulverizing a cotton blended fiber product to prepare pulverized fibers. The cotton blended fiber product described above is subjected to Step 1.

[0019] The method for pulverizing the cotton blended fiber product is not particularly limited, and the product can be pulverized by a known method. As such a pulverization method, mechanical pulverization is preferably used, for example, a method of cutting with a cutting machine, a method of coarsely pulverizing with a fiberizer, etc.

[0020] The average fiber length of the pulverized fibers is preferably 100 μm or more, more preferably 150 μm or more, and even more preferably 200 μm or more. The average fiber length of the pulverized fibers is preferably 1000 μm or less, more preferably 500 μm or less, and even more preferably 300 μm or less. When the lower limit of the average fiber length range is within the above range, the pulverized fibers can have a length suitable for recycling. When the upper limit of the average fiber length is within the above range, entanglement between the pulverized fibers is suppressed in step 2, making it easier to separate the pulverized fibers in the dispersion.

[0021] In this specification, the average fiber length of the pulverized fibers can be measured by processing a micrograph using image processing software ImageJ.

[0022] The average fiber diameter of the pulverized fibers is not particularly limited, but is preferably about the same as the fiber diameter of cotton fibers, specifically 10 to 30 μm.

[0023] In this specification, the average fiber diameter of the pulverized fibers can be measured by processing a micrograph using image processing software ImageJ.

[0024] In step 1 described above, the cotton blended fiber product is pulverized to prepare pulverized fibers.

[0025] (Process 2) In step 2, the pulverized fibers are added to a dispersion medium to prepare a dispersion liquid, and the dispersion liquid is allowed to stand. The pulverized fibers used are the pulverized fibers prepared in step 1 above.

[0026] The dispersion medium is not particularly limited as long as it can disperse the pulverized fibers. However, the specific gravity of the dispersion medium used in step 2 is preferably 0.96 to 1.60, more preferably 1.00 to 1.58, even more preferably 1.10 to 1.57, particularly preferably 1.20 to 1.55, most preferably 1.36 to 1.53, and most preferably 1.40 to 1.49. Cotton-blended fiber products recycled by the recycling method of the present invention contain synthetic fibers and cotton. The synthetic fibers often contained in such cotton-blended fiber products are synthetic fibers containing polyester resins and have a specific gravity of 1.38. Cotton has a specific gravity of 1.54. Therefore, in the present invention, by setting the specific gravity of the dispersion medium within the above range, the synthetic fibers and cotton can be more easily separated by allowing the dispersion to stand, as described below.

[0027] The dispersion medium preferably contains an alkali metal salt and / or an alkaline earth metal salt (hereinafter also referred to as "salts"). When the dispersion medium contains a salt, it becomes easier to adjust the specific gravity of the dispersion liquid to the above range.

[0028] The salts are not particularly limited as long as they are water-soluble, and examples thereof include chloride salts, bromide salts, iodide salts, etc. More specifically, examples thereof include NaCl, KCl, MgCl, CaCl, CaBr, etc. Among these, CaCl is preferred because it is easier to adjust the specific gravity of the dispersion medium to the above range.

[0029] The dispersion medium is preferably an aqueous solution in which salts are dissolved in water. The blending ratio of salts to water in the dispersion medium is preferably salts:water=80:20 to 30:70 by mass, more preferably 70:30 to 40:60. By having the blending ratio of salts to water in the above range, it becomes easy to adjust the specific gravity of the dispersion liquid to the above range.

[0030] The content of pulverized fibers in the dispersion is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, even more preferably 5 parts by mass or less, and particularly preferably 3 parts by mass or less, based on 100 parts by mass of the dispersion medium. The content of pulverized fibers in the dispersion is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, even more preferably 0.5 parts by mass or more, and particularly preferably 1 part by mass or more, based on 100 parts by mass of the dispersion medium. By setting the upper limit of the pulverized fiber content in the dispersion within the above range, the synthetic fibers and cotton can be separated more efficiently by leaving the dispersion to stand. By setting the lower limit of the pulverized fiber content in the dispersion within the above range, a large amount of synthetic fibers and cotton can be separated at once, further improving processing efficiency.

[0031] The dispersion medium may contain other components in addition to the above salts and water, such as surfactants and defoamers.

[0032] The surfactant is not particularly limited, and any conventional surfactant used in aqueous solutions can be used. Examples of such surfactants include nonionic surfactants, anionic surfactants, and cationic surfactants. The surfactant is a component that acts as a degassing agent, and by including a surfactant in the dispersion medium, air bubbles adhering to the pulverized fibers can be removed, making it easier to separate the synthetic fibers from the cotton.

[0033] As the nonionic surfactant, glycerin, sorbitol, etc. can be used.

[0034] As the anionic surfactant, a linear alkylbenzene sulfonate or the like can be used.

[0035] As the cationic surfactant, a quaternary ammonium salt or the like can be used.

[0036] The upper limit of the surfactant content in the dispersion medium is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 1% by mass or less, based on 100% by mass of the dispersion medium. The lower limit of the surfactant content is not particularly limited and may be 0%, 0.1%, 0.5% by mass, etc.

[0037] The defoaming agent is not particularly limited, and any conventional defoaming agent used in aqueous solutions can be used. Examples of such defoaming agents include silicon-based defoaming agents, quaternary ammonium salts, and the like. By including a defoaming agent in the dispersion medium, air bubbles adhering to the pulverized fibers can be removed, making it easier to separate the synthetic fibers from the cotton.

[0038] The upper limit of the content of the defoaming agent in the dispersion medium is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 1% by mass or less, based on 100% by mass of the dispersion medium. The lower limit of the surfactant is not particularly limited, and may be 0%, 0.1%, 0.5% by mass, etc.

[0039] In step 2, after preparing a dispersion by adding the pulverized fibers to a dispersion medium, the dispersion may be irradiated with ultrasonic waves. By irradiating the dispersion with ultrasonic waves, air bubbles adhering to the pulverized fibers can be removed, making it easier to separate the synthetic fibers from the cotton.

[0040] In step 2, after preparing a dispersion by adding the pulverized fibers to a dispersion medium, the dispersion may be depressurized and subjected to vacuum degassing. By subjecting the dispersion to vacuum degassing, air bubbles adhering to the pulverized fibers can be removed, making it easier to separate the synthetic fibers from the cotton.

[0041] In step 2, the dispersion is allowed to stand. The standing time is preferably 1 to 48 hours, more preferably 1.5 to 24 hours, and even more preferably 2 to 12 hours. When the lower limit of the standing time is within the above range, the synthetic fibers and cotton are more easily separated in the dispersion. When the upper limit of the standing time is within the above range, the working efficiency is further improved.

[0042] The temperature of the dispersion when allowed to stand is preferably 4 to 50°C, more preferably 10 to 40°C, and even more preferably 20 to 30°C. When the temperature of the dispersion is within the above range, there is no need to heat the dispersion, which improves cost efficiency and makes it easier for the resin and cotton to separate in the dispersion. Furthermore, when the lower limit of the temperature of the dispersion is within the above range, precipitation of salts such as calcium chloride in the dispersion can be suppressed.

[0043] In step 2, the upper dispersion is allowed to stand, causing the synthetic fibers to rise to the top layer and the cotton to settle to the bottom layer. In step 2, the synthetic fibers and cotton may be collected, filtered, washed, and then dried. The drying temperature is not particularly limited, but is preferably 50 to 200°C, and more preferably 80 to 120°C.

[0044] In the recycling method of the present invention, after step 1, step 2 can be performed two or more times. By performing step 2 two or more times, synthetic fibers can be separated at a higher concentration. In the recycling method of the present invention, when step 2 is performed, the synthetic fibers rise to the top layer in the dispersion liquid upon standing, and cotton settles to the bottom layer. The top layer can be collected and added to the dispersion medium to prepare a new dispersion and then allowed to stand.

[0045] When step 2 is performed two or more times, the specific gravity of the dispersion medium used in the first step is preferably 1.10 to 1.60, more preferably 1.20 to 1.53, and even more preferably 1.30 to 1.49. The specific gravity of the dispersion medium used in the second or subsequent steps is preferably 1.10 to 1.50, more preferably 1.20 to 1.50, and even more preferably 1.30 to 1.49. Cotton-blended fiber products recycled by the recycling method of the present invention contain synthetic fibers and cotton. The synthetic fibers often contained in such cotton-blended fiber products are synthetic fibers containing polyester resins and have a specific gravity of 1.38. Cotton has a specific gravity of 1.54. Therefore, by setting the specific gravity of the dispersion medium used in the first step and the specific gravity of the dispersion medium used in the second or subsequent steps within the above ranges, the synthetic fibers are separated in the first step and the cotton is separated in the second or subsequent steps, which makes it even easier to separate the synthetic fibers and cotton.

[0046] By the above-described step 2, the dispersion is allowed to stand, and the synthetic fibers rise to the top layer in the dispersion, while the cotton settles to the bottom layer, allowing them to be separated.

[0047] The recycling method of the present invention can be used to recycle various cotton-blend fiber products containing synthetic fibers and cotton. The recycling method of the present invention is particularly useful for cotton-blend fiber products that use polyethylene terephthalate as the synthetic fiber and have a mass ratio of polyethylene terephthalate to cotton of 65:35. [Example]

[0048] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0049] Example 1 (1) Fiber crushing A fabric product with a mass ratio of polyester fiber to cotton fiber of 65:35 was finely pulverized in a grinder to prepare a powder of pulverized fibers. The average fiber length of the pulverized fibers was 257 μm.

[0050] (2) Preparation of dispersion medium Calcium chloride and water were mixed in a mass ratio of 60:40 and stirred to prepare an aqueous solution with a specific gravity of 1.48. This aqueous solution was designated as dispersion medium 1. Calcium chloride and water were mixed in a mass ratio of 55:45 and stirred to prepare an aqueous solution with a specific gravity of 1.43. This aqueous solution was designated as dispersion medium 2.

[0051] (3) Preparation of primary dispersion (primary suspension) 2 g of the ground fiber was added to 100 ml of dispersion medium 1, and 0.1 g of TWEEN (registered trademark) 80 was added as a surfactant while stirring to prepare a suspension.

[0052] (4) Primary standing The suspension prepared in (3) above was allowed to stand for 4 hours at a temperature of 30° C. After 4 hours, some of the fibers rose to the surface of the liquid, and some of the fibers settled.

[0053] (5) Preparation of secondary dispersion (secondary suspension) The fibers that had risen to the surface of the liquid were collected, filtered and washed with filter paper, and added to the dispersion medium 2. 0.1 g of TWEEN (registered trademark) 80 was added as a surfactant while stirring to prepare a suspension.

[0054] (6) Secondary standing The suspension prepared in (5) above was allowed to stand for 4 hours at a temperature of 30° C. After 4 hours, some of the fibers rose to the surface of the liquid, and some of the fibers settled.

[0055] (7) Powder recovery The fibers that floated to the surface of the liquid were collected, filtered and washed with filter paper, then dried in a dryer at a temperature of 80°C, and the filtered powder was collected.

[0056] (analysis) The ratio of cotton fiber to polyester fiber was measured for the filtered and washed fibers obtained in the primary separation using the dissolution method of JIS L 1030-2-3. The filtered powder had a polyester fiber content of 80% by mass and a cotton fiber content of 20% by mass.

[0057] The filtered powder obtained by the secondary separation was measured for the ratio of cotton fiber to polyester fiber by the dissolution method of JIS L 1030-2-3. The filtered powder had a polyester fiber content of 93% by mass and a cotton fiber content of 7% by mass.

Claims

1. A method for recycling cotton blended fiber products containing synthetic fibers and cotton, comprising: (1) Step 1 of pulverizing the cotton blend fiber product to prepare pulverized fibers; (2) adding the pulverized fibers to a dispersion medium to prepare a dispersion liquid, and allowing the dispersion liquid to stand; A recycling method comprising the steps of:

2. 2. The recycling method according to claim 1, wherein the specific gravity of the dispersion medium is 0.96 to 1.

60.

3. 2. The recycling method according to claim 1, wherein the synthetic fibers contain at least one resin selected from the group consisting of polyester-based resin, polypropylene-based resin, acrylic-based resin, and nylon-based resin.

4. 2. The recycling method according to claim 1, wherein the dispersion medium contains at least one selected from the group consisting of alkali metal salts and alkaline earth metal salts.

5. 2. The recycling method according to claim 1, wherein the content of the pulverized fibers in the dispersion is 15 parts by mass or less, based on 100 parts by mass of the dispersion medium.

6. 2. The recycling method according to claim 1, wherein the average fiber length of the pulverized fibers is 100 μm or more and 1000 μm or less.

7. 2. The recycling method according to claim 1, wherein the temperature of the dispersion in the step 2 is 4 to 50°C.

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