Method for recovering fiber component

Abstract

Provided is a method for recovering a fiber component comprising either polyester fibers or protein fibers, the method comprising; treating a fiber product containing the polyester fibers and the protein fibers with an alkylene glycol solution of an alkoxide or an aqueous solution containing a reducing agent. Further, it is preferable that the protein fibers are animal hair fibers and that the polyester fibers each include an alkylene benzenedicarboxylate as a main repeating unit. It is also preferable that the alkoxide is sodium methoxide and that the alkylene glycol is polyethylene glycol. The method makes it possible to recover protein fibers having good quality.

Description

Method for recovering fiber components

[0001] The present invention relates to a method for recovering fiber components from a fiber product containing polyester fibers and protein fibers.

[0002] Polyester is widely used in textile products due to its excellent properties, but the effective utilization of polyester textile products after use is a major issue, including environmental concerns. In particular, textile products using yarns in which polyester fibers are blended with protein fibers such as wool are widely used due to their ease of handling, but have the problem of difficulty in separating the polyester fibers from the protein fibers.

[0003] Therefore, for example, Patent Document 1 proposes a method for separating chemical fibers such as polyester fibers by treating them with hot water at a specified temperature and pressure. However, the separation was not sufficient by hot water treatment alone.

[0004] Furthermore, when chemical recycling, in which the polyester polymer is first depolymerized and then repolymerized, is adopted as a method for treating polyester fiber products after separation, there is a problem that foreign matter is easily mixed into fiber products that are blended with protein fibers such as wool, and discoloration of the resulting recycled polyester polymer cannot be suppressed.

[0005] On the other hand, when attempting to isolate only the protein fibers, there was a problem in that the scales on the surface of the fibers disappeared, significantly reducing the texture of the protein fibers.

[0006] Japanese Patent Application Laid-Open No. 2003-164827

[0007] The present invention provides a method for recovering any fiber component from a fiber product containing polyester fibers and protein fibers.

[0008] In order to solve the above problems, the following inventions are provided: 1. A method for recovering a fiber component, characterized in that a fiber product containing polyester fibers and protein fibers is treated with an alkylene glycol solution of an alkoxide or an aqueous solution containing a reducing agent, and either of the fiber components is recovered. 2. The method for recovering a fiber component as described above in 1, wherein the protein fibers are animal hair fibers. 3. The method for recovering a fiber component as described above in 1 or 2, wherein the polyester fibers are made of polyester having alkylene benzene dicarboxylate as the main repeating unit. 4. The method for recovering a fiber component as described above in any one of 1 to 3, wherein the protein fibers are fibers made of mammalian body hair, and the method comprises treating the fibers with an alkylene glycol solution of an alkoxide to obtain a treatment liquid containing protein fibers made of mammalian body hair and dissolved polyester components, and then recovering the protein fibers. 5. The method for recovering a fiber component as described above in any one of 1 to 4, wherein the alkoxide is sodium methoxide. 6. The method for recovering a fiber component as described above in any one of 1 to 5, wherein the alkylene glycol is polyethylene glycol. 7. The method for recovering a fiber component as described above in any one of 1 to 6, wherein the alkylene glycol solution of an alkoxide is a slurry. 8. The method for recovering a fiber component according to any one of 1 to 7 above, wherein the treatment temperature in the alkylene glycol solution is 20 to 40°C. 9. The method for recovering a fiber component according to any one of 1 to 8 above, wherein the treatment time in the alkylene glycol solution is 72 to 240 hours. 10. A protein fiber obtained by the method for recovering a fiber component according to any one of 1 to 9 above, characterized in that the fiber has scaly scales on the surface of the fiber. 11. The method for recovering a fiber component according to 1 above, wherein the temperature of the aqueous solution containing a reducing agent is 50 to 100°C, and a polyester fiber component is recovered. 12. The method for recovering a fiber component according to 11 above, wherein the polyester fiber has been dyed. 13. The method for recovering a fiber component according to 11 or 12 above, wherein the aqueous solution containing a reducing agent contains urea and a surfactant. 14. The method for recovering a fiber component according to any one of 11 to 13 above, wherein the recovered polyester fiber component is a bis(hydroxyalkyl) aromatic dicarboxylate.15. A method for producing a recycled polyester component, which comprises repolymerizing a polyester fiber component obtained by the recovery method according to any one of 11 to 14 above.

[0009] According to the present invention, there is provided a method for recovering any fiber component from a textile product containing polyester fibers and protein fibers.

[0010] Fig. 1 is a scanning electron micrograph at a magnification of 1500 times before the solvent contact treatment, and Fig. 2 is a scanning electron micrograph at a magnification of 1500 times after the solvent contact treatment.

[0011] The present invention will be described in detail below.

[0012] The method for recovering fiber components of the present invention essentially involves treating a textile product containing polyester fibers and protein fibers with an alkylene glycol solution of an alkoxide or an aqueous solution containing a reducing agent, and recovering one of the fiber components.

[0013] [Textile Products] The textile products used in the present invention include polyester fibers and protein fibers. Furthermore, it is preferable that the textile product be primarily composed of polyester fibers. Here, "primarily composed of polyester fibers" means that polyester fibers constitute the majority of the fibers constituting the textile product. The polyester fibers preferably account for 50% by weight or more, more preferably 70% by weight or more, and particularly 90% by weight or more, based on the weight of the textile product. Furthermore, the protein fiber content is preferably 50% by weight or less, more preferably 30% by weight, and particularly preferably in the range of 1 to 10% by weight. Furthermore, within the scope of the present invention, natural fibers such as cotton and silk, chemical fibers derived from natural materials such as rayon, cupra, acetate, and lyocell, and synthetic fibers other than polyester fibers, such as polyamide fibers, acrylic fibers, and urethane fibers, may also be included.

[0014] Examples of textile products containing such polyester fibers and protein fibers include various types of clothing such as suits, coats, sweaters, skirts, and dresses, which are made using yarns in which polyester fibers are blended with wool, a protein fiber. The present invention makes it possible to separate the polyester fibers and wool from fabrics made using such blended yarns in an economically and rational manner, and is particularly effective for fabrics made using polyester / wool blend fibers, which are consumed in large quantities.

[0015] [Polyester Fiber] The polyester fiber used in the present invention is a fiber made of a polycondensate synthesized by dehydration condensation of a polycarboxylic acid and a polyalcohol to form an ester bond. The polyester forming the fiber is a polymer having an ester bond and is generally classified into aliphatic polyester, semi-aromatic polyester, and wholly aromatic polyester.

[0016] The polycarboxylic acid constituting this polyester is preferably a dicarboxylic acid or an ester-forming derivative thereof, and more preferably an aromatic dicarboxylic acid such as terephthalic acid or 2,6-naphthalenedicarboxylic acid.

[0017] The polyalcohol, the other component constituting the polyester, is preferably a diol or an ester-forming derivative thereof. As the diol, an aliphatic glycol having 2 to 20 carbon atoms is preferably used. Examples of this aliphatic glycol include ethylene glycol (hereinafter sometimes abbreviated as EG), 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol. The aliphatic glycol may be an alicyclic glycol having 3 to 30 carbon atoms, and a specific example is 1,4-cyclohexanedimethanol.

[0018] In the present invention, a polyester obtained by combining such a polycarboxylic acid and a polyalcohol is used as one of the starting materials for forming a textile product.

[0019] Among these, it is preferable that the polyester is an aromatic polyester, more specifically, a polyester having alkylenebenzene dicarboxylate as the main repeating unit, and furthermore, it is preferable that the polyester is a polyester having polyalkylene terephthalate, particularly polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, or the like as the main component.

[0020] Furthermore, when the aromatic polyester is polyalkylene terephthalate (terephthalic acid: para position), it is also preferable that the polymer contains this as the main polymer component and other minor polymer components. Here, the main polyester component means 60% by weight or more of the weight of the polymer. The minor polymer component is preferably, for example, polyalkylene isophthalate (isophthalic acid: meta position).

[0021] In particular, when the polyester is a polyalkylene terephthalate, which is an aromatic polyester, a polyester obtained by copolymerizing terephthalic acid as a dicarboxylic acid component with isophthalic acid or 5-sodium sulfoisophthalic acid as a copolymer component is one of the preferred embodiments in view of its high dyeability and the physical properties obtained. The recovery method of the present invention is also effective when such polyester fibers are dyed with a disperse dye or the like.

[0022] [Protein Fibers] The textile product used in the present invention contains protein fibers in addition to the polyester fibers described above. Protein fibers are generally fibers having cystine bonds (S-S). Furthermore, so-called animal hair fibers made from mammalian body hair are preferred, and animal hair fibers having scaly scales (also called cuticle scales) on the surface are even more preferred. Examples of such fibers made from mammalian body hair include sheep's hair such as wool (also called sheep's wool), goat hair such as cashmere and mohair, llama hair such as llama hair, vicuna hair, and alpaca hair, camel hair, rabbit hair such as angora hair, and horse hair, among which wool is preferred.

[0023] [Fiber Component Recovery Step] In the present invention, a textile product containing the above-described polyester fibers and protein fibers is used as a starting material to recover either of the fiber components. More specifically, it is preferable to recover the polyester component that serves as a raw material for chemical recycling as the polyester fiber component, and the protein fiber component that can be recycled as is as the protein fiber component. The treatment method is treatment with an alkylene glycol solution of alkoxide (hereinafter sometimes referred to as "solvent contact treatment") or treatment with an aqueous solution containing a reducing agent (hereinafter sometimes referred to as "reducing aqueous solution treatment").

[0024] [Solvent Contact Treatment] This method involves treating a textile product in an alkylene glycol solution of an alkoxide, and recovering protein fibers as a fiber component.

[0025] That is, this recovery method is a process in which a textile product is brought into contact with an alkylene glycol solution of an alkoxide to obtain a treatment liquid containing fibers made from mammalian hair, which is a protein fiber, and dissolved polyester that does not have a fibrous shape.

[0026] Alkoxides are compounds in which the hydrogen of the hydroxy group of an alcohol is substituted with a metal, and examples include sodium methoxide, sodium ethoxide, potassium t-butoxide, etc. Among these, sodium methoxide is preferred in the present invention.

[0027] Alkylene glycols are obtained by polymerization or copolymerization of alkylene oxides such as ethylene oxide and propylene oxide, and because they have a high viscosity index and a low pour point, they can be used as a solution or slurry of the alkoxide. Among these, polyethylene glycol is preferably used in the present invention.

[0028] The amount of alkoxide contained in the alkylene glycol is preferably in the range of 0.1 to 50% by weight, more preferably 1 to 30% by weight, and particularly preferably 5 to 15% by weight, based on the total weight of the alkylene glycol. Because the solubility of alkoxide is low, the alkylene glycol solution is preferably in the form of a slurry. Furthermore, the alkylene glycol solution may be left to stand after immersion, but it is preferable to stir the solution under gentle conditions.

[0029] The temperature during the solvent contact treatment is preferably in the range of 20 to 40° C., more preferably 25 to 35° C., and particularly preferably 28 to 32° C. Furthermore, the time for this solvent contact treatment is preferably 12 hours or more, more preferably 24 to 1000 hours, and particularly preferably 72 to 240 hours.

[0030] [Recovery step] In this solvent contact treatment, the polyester component is removed from a textile product containing polyester fibers and protein fibers, and the protein fibers are recovered. In other words, this is a polyester removal step, which is a step of obtaining fibers made of mammalian body hair from the treatment solution. This can be done, for example, by filtration and washing.

[0031] The filtration temperature is preferably 20 to 40°C, more preferably 25 to 35°C, in order to avoid deterioration of the surface of the protein fibers. After filtration, it is preferable to further wash the fibers. For example, alkylene glycol or water can be used as the washing liquid. Washing can be performed by immersing the fibers in the washing liquid and then squeezing them, or by spraying the washing liquid. The washing temperature is preferably 20 to 40°C, more preferably 25 to 35°C, in order to avoid deterioration of the fiber surface, as in the entire process.

[0032] The fibers made from mammalian hair obtained by the above-mentioned solvent contact treatment have the same scales on the surface of the fibers as before the treatment. Furthermore, when dried, the scales are closed and the protein fibers do not felt and remain in good condition.

[0033] The protein fibers obtained by the solvent contact treatment of the present invention are fibers made from mammalian body hair, and are of superior quality compared to well-known methods such as polyester hydrolysis using an alkaline aqueous solution or polyester extraction using an organic solvent such as ethylene glycol. The scales are densely arranged on the fiber surface, and do not open outward to increase voids, and there is little entanglement between the fibers, nor does felting occur. There is almost no change in the state of the scaly scales present on the fiber surface between the protein fibers contained in the textile product before and after the treatment of the present invention, and the scales remain closed. Such high-quality protein fibers can be obtained by the recovery method of the present invention, making them easy to reuse as textile products.

[0034] [Reducing aqueous solution treatment] While the solvent contact treatment is a method for recovering protein fibers, the other reducing aqueous solution treatment is a method for treating a textile product with an aqueous solution containing a reducing agent to recover polyester fiber components as fiber components.

[0035] Furthermore, a preferred method is to use a textile product containing polyester fibers and protein fibers as a starting material, treat it in an aqueous solution containing a reducing agent at a temperature of 50 to 100°C, and then recover the polyester component.

[0036] Protein fibers such as wool are polymers crosslinked by cystine bonds (S-S), and in this aqueous reduction treatment, the cystine bonds are cleaved by treating the fiber with an aqueous solution containing a reducing agent, eliminating the hardly soluble portion and recovering the polyester component from the fiber product.Furthermore, it is preferable that the aqueous solution is at a high temperature.

[0037] The reducing agent is not particularly limited, but preferred examples include known reducing agents having a thiol group, such as thioglycolic acid, thioglycolic acid salts (ammonium thioglycolate, monoethanolamine thioglycolate, etc.), cysteamine, cysteamine salts (cysteamine hydrochloride, etc.), cysteine ​​(L-cysteine, DL-cysteine, etc.), cysteine ​​salts (L-cysteine ​​hydrochloride, DL-cysteine ​​hydrochloride, etc.), acetylcysteine ​​(N-acetyl-L-cysteine, etc.), glyceryl thioglycolate, thiolactic acid, thiolactate salts, and butyrolactone thiol. Other known reducing agents, such as sulfites (sodium sulfite, etc.), can also be used. It is particularly preferred to use sodium disulfite, sodium sulfite, sodium thioglycolate, cysteine, etc.

[0038] In this step, the reaction is preferably carried out in an aqueous solution at a temperature of 70 to 100°C, more preferably 90 to 100°C. The treatment time is preferably in the range of 0.5 to 10 hours, more preferably 1 to 3 hours. Furthermore, the treatment is preferably carried out while stirring.

[0039] In order to ensure that the reducing agent is thoroughly impregnated into the textile product, it is preferable that the aqueous treatment solution contains a surfactant such as urea or sodium dodecyl sulfate.

[0040] Thereafter, the water is evaporated in a dryer to produce a textile product mainly composed of polyester fibers, and the polyester component can be recovered as polyester itself by carrying out a washing process or the like.

[0041] Furthermore, by carrying out the treatment under such mild conditions in the aqueous reducing solution treatment of the present invention, it is possible to significantly suppress reaction inhibition in subsequent treatments, particularly in the depolymerization of polyester into its reaction intermediate, bis(hydroxyalkyl) benzenedicarboxylate, etc.

[0042] In the aqueous reducing solution treatment of the present invention, it is preferable to treat the recovered polyester component with an aromatic alcohol or a derivative thereof following the reducing agent treatment. Examples of aromatic alcohols or derivatives thereof include benzyl alcohol, benzaldehyde, and benzoic acid, with benzyl alcohol (hereinafter sometimes referred to as "BA") being particularly preferred.

[0043] In the present invention, following the treatment with the aqueous reducing agent solution, it is preferable to treat the textile product with such a solution of aromatic alcohol or a derivative thereof at a temperature ranging from the glass transition temperature of the polyester to the glass transition temperature of the polyester plus 100°C, and recover the polyester.

[0044] After immersion, the textile product is dehydrated. As a dehydration treatment after immersion, methods such as squeezing, dehydration by centrifugation, and Soxhlet extraction can be applied.

[0045] In particular, this treatment not only allows protein fibers to be removed more thoroughly, but is also effective in removing the dyed polyester fibers when the polyester fibers are dyed with a disperse dye or the like.

[0046] Furthermore, it is preferable to further depolymerize the polyester component obtained by the reducing aqueous solution treatment. Normally, if the reducing agent treatment is not carried out, the cystine bonds inhibit depolymerization, and only a colored polyester component of low purity is obtained. However, by carrying out the process of the present invention, it is possible to obtain a white polyester component of high purity.

[0047] That is, it is preferable to subsequently carry out a method in which the polyester component is depolymerized into a bis(hydroxyalkyl) aromatic dicarboxylate in an alkylene glycol containing a depolymerization catalyst.

[0048] The catalyst used in the depolymerization reaction in the depolymerization step is preferably a first transition metal catalyst. Among these, manganese oxide, manganese acetate, zinc oxide, and zinc acetate are preferred, and manganese acetate is particularly preferred. The catalyst is preferably used after being dissolved or suspended in alkylene glycol in advance.

[0049] Generally, depolymerized polyester products tend to gradually become more discolored due to long-term storage, but the products obtained by the recovery method and production method of the present invention are clearly less discolored.

[0050] The alkylene glycol (hereinafter sometimes abbreviated as AG) used in the depolymerization reaction in the depolymerization step is the same as the polyalcohol forming the skeletal structure of the polyester used in the textile product. For example, when the polyester is polyethylene terephthalate (PET), ethylene glycol (EG) can be used.

[0051] In the aqueous reduction solution treatment of the present invention, it is preferable to further carry out a purification step after the polyester component recovery step. The purification step includes crystallization or adsorption treatment, and it is more preferable to carry out both of them.

[0052] When solid-liquid separation is performed after crystallization, it is preferable to wash the crystallized product with water or alkylene glycol. The washing is preferably performed by treating the product in a Nutsche filter while spraying a washing liquid. By carrying out such treatment, the depolymerization catalyst dissolved in the alkylene glycol and other color-causing substances can be washed away, and a more highly purified aromatic dicarboxylate bis(hydroxyalkyl) can be obtained.

[0053] When the polyester component contained in the textile product is recovered as a bis(hydroxyalkyl) aromatic dicarboxylate as an intermediate substance of polyester by the above-mentioned recovery step (depolymerization), it can be particularly preferably used as an intermediate substance for producing recycled polyester polymer.

[0054] The polyester component obtained by the above-described recovery method of the present invention can be further repolymerized to produce recycled polyester.

[0055] The recycled polyester polymer obtained in this manner is a polymer with little yellowness, which is considered to be inferior in quality. The polyester recovery method of the present invention is less likely to produce colored by-products. Furthermore, it is believed that the addition of a subsequent crystallization step or other process facilitates dissociation of the catalyst from the intermediate, such as the aromatic dicarboxylate bis(hydroxyalkyl), making it less likely to remain as an impurity. This effect is particularly pronounced when depolymerization is performed using a low concentration of a manganese-based catalyst or a high concentration of a zinc-based catalyst.

[0056] In the recycled polyester polymer obtained by the present invention, protein fibers have been removed, and if the polyester fibers in the textile product are dyed, the dyes have also been removed.

[0057] The resulting recycled polyester polymer more preferably exhibits the following properties: ＊ , a ＊ , b ＊ As the hue in the color space colorimeter, b ＊ The value is preferably 8 or less. The obtained recycled polyester polymer preferably has a yellowness index (YI) of 15 or less. The obtained recycled polyester polymer preferably has a whiteness index (W) of 75 or more, more preferably 80 to 100. The obtained recycled polyester polymer preferably has an intrinsic viscosity (IV) of 0.30 to 1.50 dL / g, more preferably 0.40 to 1.30 dL / g, and particularly preferably 0.50 to 1.20 dL / g.

[0058] The present invention will be described in more detail below with reference to examples. The values ​​in the examples were determined by the following methods. "% owf" is an abbreviation for "% on the weight of fiber."

[0059] 1) Hue (L ＊ a ＊ b ＊, YI, W) A sample (5 g) was pressed between two metal plates to form a plate, which was then heated at 140°C for 2 hours to crystallize the sample to obtain a measurement sample. The measurement sample was measured for hue L according to JIS Z8781-4:2013 using a measurement device ("SE7700" manufactured by Nippon Denshoku Industries Co., Ltd.). ＊　 , a ＊　 , b ＊　 The values ​​were measured.

[0060] The yellowness index (YI) was calculated by the following formula (1), and the whiteness index (W) was calculated by the following formula (2). Yellowness index (YI): 0.34-71.7×a ＊ / L ＊ +178.78 x b ＊ / L ＊　 (1) Whiteness (W): 100-√{(100-L ＊ ) ２　 +a ＊２　 +b ＊２　} (2) The higher the yellowness index (YI) value, the stronger the yellowness, and the higher the whiteness index (W) value, the stronger the whiteness.

[0061] 2) Nitrogen (N) content: Measured using a total nitrogen / protein analyzer (Nitto Seiko Analytech Co., Ltd., "DTN-300V").

[0062] 3) Intrinsic Viscosity (IV) A fiber (polymer) sample was dissolved in 10 mL of a tetrachloroethane / phenol mixed solvent (volume ratio 1 / 1), and the intrinsic viscosity (dL / g) at 35° C. was measured.

[0063] Example 1 A fiber assembly consisting of 0.01 g of polyethylene terephthalate fiber and 0.1 g of wool fiber was immersed in 100 g of ethylene glycol and 10 g of sodium methoxide at room temperature for 120 hours (5 days).

[0064] The wool was recovered from the treatment solution obtained after immersion. All of the polyethylene terephthalate fibers had dissolved. The obtained wool was observed with a scanning electron microscope (SEM) 3D real surface view microscope ("VE-8800" manufactured by Keyence Corporation), and it was confirmed that the scales on the wool remained closed after treatment, just as they were before treatment, and that no felting had occurred. SEM photographs before and after treatment are shown in Figures 1 and 2.

[0065] Example 2 A wool-polyester blend fabric (textile product) consisting of 40 g of polyethylene terephthalate fiber and 360 g of wool fiber was immersed in 2000 g of ethylene glycol and 200 g of sodium methoxide at room temperature (25° C.) for 120 hours (5 days).

[0066] After immersion, the wool fibers were recovered from the treatment solution. All of the polyethylene terephthalate fibers were dissolved. The obtained wool fibers were observed with a scanning electron microscope (SEM) 3D real surface view microscope ("VE-8800" manufactured by Keyence Corporation). It was confirmed that the wool scales remained closed after the treatment, just as they were before the treatment, and that no felting had occurred.

[0067] Example 3: A fiber assembly consisting of 0.01 g of black-dyed polyethylene terephthalate fiber and 0.1 g of wool fiber was prepared as a textile product. The polyethylene terephthalate fiber was dyed using 0.87% owf of nitrogen-containing orange disperse dye, 0.4% owf of nitrogen-containing red disperse dye, and 4.7% owf of nitrogen-containing black disperse dye, resulting in a black fiber containing 0.38 wt% nitrogen (N). The wool fiber was animal hair fiber manufactured by Sunwell.

[0068] 0.11 g of this fabric was placed in a 0.5 L beaker, and 110 g of a mixed solution (100 g of ethylene glycol and 10 g of sodium methoxide) was added to the beaker. With the textile product immersed in the mixed solution, the internal temperature was adjusted to 30°C and the mixture was stirred at normal pressure for 120 hours (5 days) (solvent contact treatment).

[0069] The wool fibers were then removed from the beaker and squeezed to remove excess treatment liquid (liquid in which polyester fibers were dissolved in the mixed solution) (removal treatment). The treated wool product was dried in a vacuum dryer at 30°C for 8 hours, and the wool fibers were recovered.

[0070] The recovered wool fibers were observed with a SEM (scanning electron microscope) 3D real surface view microscope (VE-8800 manufactured by Keyence Corporation), and it was confirmed that the scales on the wool fibers were closed, just as they were before and after the treatment, and that they had not felted.

[0071] [Example 4] (Textile Product) A test textile product was prepared as a sample: a mixture of 380 g of polyethylene terephthalate (PET) fiber fabric and 20 g of wool fiber. The PET fiber was a yarn having an IV of 0.60 dL / g, a Tg of 70°C, a Tm of 255°C, a 24 dtex, a strength of 3.9 cN / dtex, and an elongation of 41%. The PET fiber was a black fiber dyed with 0.87% owf of nitrogen-containing orange dye, 0.4% owf of nitrogen-containing red dye, and 4.7% owf of nitrogen-containing black dye, which were disperse dyes, and contained 0.38 wt% nitrogen (N). The wool fiber was black-dyed animal hair fiber manufactured by Sunwell.

[0072] (Polyester component recovery method (1): Reduction treatment) 400 g of this textile product was placed in a 5-liter separable flask, and 3260 g of a mixed aqueous solution (2000 mL of water, 200 g of sodium disulfite, 960 g of urea, and 100 g of sodium dodecyl sulfate) that had been heated in a separate beaker until the internal temperature reached 90° C. was added to the separable flask containing the textile product. With the textile product immersed in the mixed aqueous solution, the internal temperature was adjusted to 90° C. and the mixture was stirred for 60 minutes (immersion treatment).

[0073] The textile was then removed from the separable flask and squeezed to remove excess treatment solution (a liquid in which wool fibers were dissolved in the mixed aqueous solution). Coloration was observed in the treatment solution, and the weight of the lightly decolorized textile after squeezing was 970 g.

[0074] The textile product was then dried in a dryer set at 100° C. under normal pressure for 8 hours to evaporate the water content.

[0075] The dried textile product was again placed in the separable flask, and 4,000 g of benzyl alcohol (BA) was added. The mixture was stirred for 30 minutes while the internal temperature was adjusted to 105°C. The fabric-like textile product was removed from the separable flask and squeezed to remove excess treatment solution. Coloration was observed in the treatment solution. The coloration of the dyed fabric had almost disappeared at this stage, leaving a white fabric. Furthermore, the wool fiber aggregates had disappeared, and only a fabric made of white PET fibers was observed.

[0076] After squeezing, the textile product was again placed in the separable flask, and the same steps of immersion in the solution and squeezing as above were repeated a total of six times.

[0077] Visual inspection showed that the textile product had turned white after the third treatment, but even after the fourth treatment, the squeezed treatment liquid was slightly colored, and it was only after the sixth treatment that the treatment liquid finally became transparent.

[0078] The treated textile product was dried in a vacuum dryer at 80°C for 8 hours, and a textile product made of white polyester with high whiteness was recovered as a polyester component. The weight of the treated textile product was 360g, and all of the wool had been removed.

[0079] The polyester component was recovered in the same manner as above, except that the temperature of the mixed aqueous solution (2000 ml of water, 200 g of sodium disulfite, 960 g of urea, and 100 g of sodium dodecyl sulfate) used to remove proteins from the textile product was changed from 90°C to 25°C. The color of the treatment solution after squeezing in the reduction treatment of the polyester component recovery method (1) above remained transparent, and the textile product itself clearly remained colored. Therefore, for this sample, the subsequent polyester component recovery treatment (2) described below was discontinued for the 25°C treatment, and only the 90°C treatment was subjected to the polyester component recovery treatment (2) described below.

[0080] (Polyester component recovery method (2): depolymerization treatment) The polyester in the textile product recovered by the above method was further depolymerized. First, 300 parts by weight of the above polyester, 1500 parts by weight of ethylene glycol (EG), and 0.38 parts by weight (100 mmol% based on the polyester) of manganese acetate (Mn acetate) as a depolymerization catalyst were placed in a 2-L separable flask and nitrogen was sealed inside. At this time, the Mn acetate was dissolved in EG beforehand and then added.

[0081] Thereafter, the separable flask containing the polyester was heated with a mantle heater to an internal temperature of 220°C, and depolymerization treatment was carried out for 4 hours at normal pressure with stirring, to obtain a BHET (bis(hydroxyethyl)benzenedicarboxylate) solution.

[0082] The BHET solution after depolymerization was brown. Therefore, this depolymerized solution was further filtered through a 200 μm mesh to remove the solid content remaining inside, and then slowly cooled to 70° C. After that, while stirring and cooling, a temperature-lowering treatment (1) from 70° C. to 40° C. was carried out for 10 minutes from 0 to 10 minutes, a temperature-lowering treatment (2) from 40° C. to 30° C. was carried out for 50 minutes from 10 to 60 minutes, and a temperature-lowering treatment (3) from 30° C. to 15° C. was carried out for 120 minutes from 60 to 180 minutes, and then stirring was carried out for 60 minutes while maintaining the internal temperature at 15° C. The internal temperature was lowered over a total of 4 hours, causing BHET crystals to precipitate, thereby obtaining a BHET / EG slurry.

[0083] The BHET / EG slurry was then subjected to a compression treatment using a filter press manufactured by Nippon Filter Equipment Co., Ltd. to separate the BHET and EG into solid and liquid. The BHET at this stage contained 35% by weight of EG based on the dry weight of BHET.

[0084] The BHET after the solid-liquid separation was then dried in a vacuum dryer at 50°C for 8 hours, and the dried BHET was recovered as a polyester component. The obtained BHET was white and free of any foreign matter.

[0085] (Repolymerization of Polyester) Then, 254 parts by weight of the obtained dry BHET was placed in a reaction vessel under normal pressure in a nitrogen atmosphere together with 0.007 part by weight of a phosphorus-based stabilizer and 0.07 part by weight of diantimony trioxide as a repolymerization catalyst.

[0086] The temperature inside the reactor was then raised to 285°C, and the pressure was gradually reduced under the following conditions: atmospheric pressure for 10 minutes, a pressure of 4 kPa for 10 minutes, and further a pressure of 0.4 kPa for 40 minutes. While products generated by the reaction, such as ethylene glycol, were distilled out of the reactor, a polycondensation reaction was carried out to obtain recycled polyester.

[0087] The colors and physical properties of the textile product before treatment, the recovered polyester component, and the recycled polyester after repolymerization are shown in Table 1.

[0088] [Example 5] The polyester component (BHET) was recovered in the same manner as in Example 4, except that the mixed aqueous solution used to remove proteins from the textile product was changed from sodium disulfite to cysteine, and the immersion treatment was performed in a mixed aqueous solution (2000 ml of water, 200 g of cysteine, 960 g of urea, and 100 g of sodium dodecyl sulfate). Polyester component recovery method (1): The color of the treatment liquid after squeezing in the reduction treatment was darker than in Example 1, and the textile product itself was a polyester fabric with a high whiteness. Furthermore, the polyester component (BHET) obtained after depolymerization of the polyester was also white.

[0089] This depolymerized polyester component (BHET) was subjected to a polycondensation reaction to obtain a recycled polyester in the same manner as in Example 4. The color and physical properties of the recycled polyester before treatment (textile product), the recovered polyester component, and after repolymerization are shown in Table 1.

[0090] [Example 6] The polyester component (BHET) was recovered in the same manner as in Example 4, except that the mixed aqueous solution used to remove proteins from the textile product was changed from sodium disulfite to cysteamine and the immersion treatment was performed in a mixed aqueous solution (2000 ml of water, 200 g of cysteamine, 960 g of urea, and 100 g of sodium dodecyl sulfate). Recovery of polyester component (1): The color of the treatment liquid after squeezing in the reduction treatment was darker than in Example 4, and the textile product itself was a polyester fabric with a high whiteness. Furthermore, the polyester component (BHET) obtained after depolymerization of the polyester was also white.

[0091] This depolymerized polyester component (BHET) was subjected to a polycondensation reaction to obtain a recycled polyester in the same manner as in Example 4. The recovered polyester component before treatment (textile product), and the color and physical properties of the recycled polyester after repolymerization are also shown in Table 1.

[0092] [Example 7] The polyester component (BHET) was recovered in the same manner as in Example 4, except that the mixed aqueous solution used to remove proteins from the textile product was changed from sodium disulfite to sodium thioglycolate, and the immersion treatment was performed in a mixed aqueous solution (2000 ml of water, 200 g of sodium thioglycolate, 960 g of urea, and 100 g of sodium dodecyl sulfate). Polyester component recovery method (1): The color of the treatment liquid after squeezing in the reduction treatment was darker than in Example 4, and the textile product itself was a polyester fabric with a high whiteness. Furthermore, the polyester component (BHET) obtained after depolymerization of the polyester was also white.

[0093] This depolymerized polyester component (BHET) was subjected to a polycondensation reaction to obtain a recycled polyester in the same manner as in Example 4. The color and physical properties of the recycled polyester before treatment (textile product), the recovered polyester component, and after repolymerization are shown in Table 1.

[0094] [Example 8] The polyester component (BHET) was recovered in the same manner as in Example 4, except that the mixed aqueous solution used to remove proteins from the textile product was changed from sodium disulfite to sodium sulfite, and the immersion treatment was performed in a mixed aqueous solution (2000 ml of water, 200 g of sodium sulfite, 960 g of urea, and 100 g of sodium dodecyl sulfate). Recovery of polyester component (1): The color of the treatment liquid after squeezing in the reduction treatment was darker than in Example 4, and the textile product itself was a polyester fabric with a high whiteness. Furthermore, the polyester component (BHET) obtained after depolymerization of the polyester was also white.

[0095] This depolymerized polyester component (BHET) was subjected to a polycondensation reaction to obtain a recycled polyester in the same manner as in Example 4. The color and physical properties of the recycled polyester before treatment (textile product), the recovered polyester component, and after repolymerization are shown in Table 1.

[0096]

[0097] Comparative Example 1 The mixed aqueous solution (2000 ml of water, 200 g of sodium disulfite, 960 g of urea, and 100 g of sodium dodecyl sulfate) used for removing proteins from textile products was changed to a benzyl alcohol (BA) treatment, and the mixture was stirred for 60 minutes while adjusting the internal temperature to 90° C. (immersion treatment). Thereafter, the mixture was subjected to BA treatment at 105° C. for 30 minutes six more times in the same manner as in Example 4, followed by depolymerization and recovery of the polyester component (BHET).

[0098] During the BA treatment, the wool turned brown, and it was confirmed that most of the wool solids remained even after the sixth BA treatment. Thereafter, repolymerization was carried out in the same manner as in Example 4. The color and physical properties of the recycled polyester before treatment (textile product), the recovered polyester component, and after repolymerization are shown in Table 2.

[0099]

[0100] The method of recovering either fiber component from a textile product containing polyester fibers and protein fibers of the present invention can be effectively used as a raw material for textile recycling. Furthermore, the obtained protein fibers and polyester polymer components are of high quality, which promotes the reuse of discarded textile products that have not previously been recycled into fibers, thereby contributing to reducing the environmental load.

Claims

1. A method for recovering fiber components, characterized by treating a fiber product containing polyester fibers and protein fibers with an alkylene glycol solution of an alkoxide or an aqueous solution containing a reducing agent, and recovering either of the fiber components.

2. The method for recovering fiber components according to claim 1, wherein the protein fiber is animal hair fiber.

3. The method for recovering fiber components according to claim 1, wherein the polyester fibers are made of polyester having alkylenebenzene dicarboxylate as the main repeating unit.

4. A method for recovering fiber components according to claim 1, wherein the protein fibers are fibers made from mammalian body hair, and the fibers are treated with an alkylene glycol solution of an alkoxide to produce a treatment solution containing the protein fibers made from mammalian body hair and a dissolved polyester component, and then the protein fibers are recovered.

5. The method for recovering fiber components according to claim 1, wherein the alkoxide is sodium methoxide.

6. The method for recovering fiber components according to claim 1, wherein the alkylene glycol is polyethylene glycol.

7. The method for recovering fiber components according to claim 1, wherein the alkylene glycol solution of the alkoxide is in the form of a slurry.

8. The method for recovering fiber components according to claim 1, wherein the temperature for treatment with the alkylene glycol solution is 20 to 40°C.

9. The method for recovering fiber components according to claim 1, wherein the treatment time with the alkylene glycol solution is 72 to 240 hours.

10. Protein fibers obtained by the method for recovering fiber components according to any one of claims 1 to 9, characterized in that the fibers have scaly scales on their surfaces.

11. The method for recovering a fiber component according to claim 1, wherein the treatment temperature in the aqueous solution containing a reducing agent is 50 to 100°C and polyester fiber components are recovered.

12. The method for recovering fiber components according to claim 11, wherein the polyester fibers are dyed.

13. The method for recovering fiber components according to claim 11, wherein the aqueous solution containing a reducing agent contains urea and a surfactant.

14. The method for recovering a fiber component according to claim 11, wherein the recovered polyester fiber component is a bis(hydroxyalkyl) aromatic dicarboxylate.

15. A method for producing a recycled polyester component, which comprises repolymerizing the polyester fiber component obtained by the recovery method according to any one of claims 11 to 14.

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