JP2008031388A - Chemical recycling method of resin finished nylon 6 fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an effective chemical recycle method of nylon 6 fibers attached with resin components by removing only resin components by heat treatment with a lactam, followed by depolymerization of the nylon 6 fibers removed of the resin components to recover lactam. <P>SOLUTION: The chemical recycle method of nylon 6 fibers attached with resin components comprises (A) a process of heating the nylon 6 fibers attached with the resin components to elute the resin components into a lactam (process a), (B) a process of taking out the nylon 6 fibers in the organic solvent (process b), (C) a process of recovering the lactam by depolymerization of the nylon 6 fiber removed of the resin components (process c) and (D) a process of recovering the lactam from the lactam layer containing the resin components (process d). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for removing a resin from resin-processed nylon 6 fibers such as rain clothes, winter clothes, and air bags. The present invention relates to a chemical recycling method using this method, and more specifically, a resin-processed nylon 6 The present invention relates to a method for recovering caprolactam by depolymerizing nylon 6 fiber from which a resin component has been removed from the fiber.

  Nylon fibers represented by nylon 6 fibers are widely used as clothing and industrial materials, and are known as fibers that can be easily recycled. As a method of recycling nylon 6 fiber, thermal recycling method that incinerates and recovers it as thermal energy, material recycling that is remolded and reused after being melted, chemically depolymerized and returned to the raw material of nylon, There is chemical recycling that is reused for nylon production.

  Among these, chemical recycling decomposes nylon into raw materials and can be used for a wide range of applications including reuse as nylon raw materials. Therefore, it can be said that this is an industrially useful recycling method. However, in recent years, nylon fibers that have been surface-treated with various polyurethanes have various uses, such as fabrics that have been treated with polyurethane to impart moisture permeability and waterproofness to the surface of nylon fibers, such as rain clothes, winter clothes, and ski wear. The amount used is increasing year by year. Further, a fabric in which a nylon fiber surface is coated with a silicone resin to provide airtightness is used for an air bag or the like, and the amount of use is increasing year by year. Most of these resin-processed nylon 6 fibers are discarded after use, and most of them are treated by methods such as incineration and embedding in the ground. Therefore, it has become important to recycle discarded nylon fibers that have been processed into resin.

  Nylon products containing components other than nylon include various components such as resin-treated surfaces and those containing cellulosic fibers and glass fibers, reducing the recovery rate of raw materials obtained in chemical recycling. It is difficult to efficiently recover lactam by chemical recycling, such as reducing purity, and many methods have been proposed.

  As a method for chemically recycling nylon fibers, for example, in Patent Document 1, in the presence of a phosphoric acid catalyst, a cloth product made of nylon and a material of clothing accessories are substantially unified with nylon 6, and depolymerized, A method for recovering ε-caprolactam has been proposed. Patent Document 2 discloses that a composite composed of nylon 6 and cellulosic fibers is heated to 30 to 70 ° C. in a phosphoric acid aqueous solution having a concentration of 65% by mass or more and 77% by mass or less to dissolve dissolved nylon 6 and insoluble. A method of separating nylon cellulosic fibers and recovering nylon 6 has been proposed. In Patent Document 3, an acidic substance is added to nylon 6 waste containing non-melted material such as glass fiber, and the non-melted material is separated by heat treatment at 220 to 400 ° C. to lower the solution viscosity. A method has been proposed for obtaining lactam in high yield by depolymerization. Patent Document 4 proposes a method of crystallizing ε-caprolactam obtained by directly depolymerizing a thermoplastic material mainly composed of nylon 6. Patent Document 5 proposes a method of depolymerizing nylon 6 and extracting and recovering caprolactam with an alkylphenolic compound.

  However, although the method of Patent Document 1 is chemical recycling of nylon fiber garment products, it is a method of substantially recovering lactam by depolymerization of nylon 6 single component. Further, Patent Documents 2 and 3 are methods of chemically recycling a composite containing another component mainly composed of nylon 6, but non-melted materials such as cellulose-based fibers and glass fibers to be combined are acidic substances. This is a method of recovering lactam by depolymerizing nylon 6 after dissolving nylon 6 by directly heat-treating with phosphoric acid or acidic aqueous solution to remove non-melted material. Patent Document 4 is a method of directly depolymerizing a thermoplastic material mainly composed of nylon 6 and chemically recycling it. Since the recovered lactam contains a large amount of impurities, hydrocarbons, chlorinated hydrocarbons and alcohols are used. Recrystallization purification is required with an organic solvent such as, which is not only complicated, but also reduces the lactam recovery rate and increases the amount of residue that becomes waste. Patent Document 5 is also a method of directly depolymerizing a mixture containing nylon 6 and chemically recycling it. However, since a lot of impurities are contained in the recovered lactam, it is necessary to extract and purify the lactam with a phenolic compound. It is complicated.

When the technology described in these documents is applied to chemical recycling of nylon 6 fibers processed with resin such as polyurethane (for example, nylon fibers impregnated and coated with urethane resin or the like to impart functions such as water repellency, waterproofing and moisture permeability). It has been found by the present inventors that various problems may occur. For example, polyurethane and silicone resins are chemically unstable when heated in an acidic aqueous solution. Therefore, when nylon fibers that are still attached to these resins are decomposed under depolymerization conditions, the purity of the recovered caprolactam is reduced. In addition to lowering the viscosity, there is a possibility of causing a problem such as an increase in the viscosity of the defatted raw material and a deactivation of the catalyst, thereby reducing the caprolactam recovery rate. Therefore, none of the techniques in the above documents are satisfactory from the viewpoint of practical chemical recycling.
JP 07-310204 A JP 09-241416 A JP 2001-294571 A Japanese Patent Laid-Open No. 08-048666 Japanese National Patent Publication No. 11-508913

Therefore, in the present invention, when chemically recycling resin-processed nylon 6 fibers, it is possible to achieve high purity and high yield by a simple operation without any problem of caprolactam purity degradation or degradation of caprolactam recovery rate due to decomposition of resin components. The task is to recover caprolactam.

As a result of intensive studies to solve the problems, the present inventor is to heat-treat the resin-processed nylon 6 fiber with a caprolactam solution as a raw material, take out the nylon 6 fiber, and then depolymerize to recover caprolactam. Thus, it was found that efficient chemical recycling can be performed, and the present invention was completed.

  That is, the present invention includes a step of heat-treating a resin-processed nylon 6 fiber in a caprolactam solution to elute the resin component in an organic solvent (step a), and a step of taking out the nylon 6 fiber in the caprolactam solution (step b). ), A method for chemical recycling of nylon 6 fibers after resin processing, which includes a step (c step) of depolymerizing nylon 6 fibers from which resin components obtained in step b have been removed to recover caprolactam. Since the polyurethane component and the silicone resin component are chemically unstable in the heated state of the acidic aqueous solution, the polyurethane component and the silicone resin component are decomposed under the depolymerization condition, causing a decrease in caprolactam purity and reducing the caprolactam recovery rate. The method has been found to be particularly effective for resin processed nylon 6 fibers.

  The present invention also includes a step of heat-treating the resin-processed nylon 6 fiber in a caprolactam solution, which is a raw material of the nylon 6 fiber, and eluting the resin component in the caprolactam solution (step a), in the caprolactam solution A method of removing the resin component from the resin-processed nylon 6 fiber, which comprises a step (b step) of taking out the nylon 6 fiber.

  According to the present invention, the resin can be removed from the resin-processed nylon 6 fiber by a simple method. In addition, by using the above method in chemical recycling of resin-processed nylon 6 fiber, caprolactam can be recovered with a high yield and the amount of residue can be reduced. Moreover, since a high-purity caprolactam with a smaller amount of impurities can be recovered, the quality required as, for example, a nylon raw material can be obtained industrially advantageously without complicated purification.

  The present invention is a method in which a nylon 6 fiber subjected to resin processing is heat-treated in a caprolactam solution which is a raw material of the nylon 6 fiber, the resin component is eluted in an organic solvent, and the nylon 6 fiber in the caprolactam solution is taken out. Furthermore, the method is a chemical recycling method for resin-processed nylon 6 fibers, characterized in that caprolactam is recovered by depolymerizing the nylon 6 fibers from which the resin component has been removed.

  Furthermore, it is a chemical recycling method for resin-processed nylon 6 fibers, wherein caprolactam is recovered from a caprolactam solution from which the resin component is eluted.

<Nylon 6 fiber>
In the present invention, the nylon 6 fiber to be used is not particularly limited, but it is preferably a single composition, that is, a homopolymer, but not to impair the effects of the present invention, for example, all monomers As long as it is 50 mol% or less, preferably 10 mol% or less, more preferably 5 mol% or less, other copolymerization components may be copolymerized. When depolymerization is performed using an acidic catalyst such as phosphoric acid as the depolymerization catalyst, the catalyst may be deactivated by the diamin component of the copolymer component, but a catalyst equivalent to the catalyst amount deactivated by the diamine component is added. By doing so, the depolymerization reaction can be performed without problems. These nylon 6 fibers may be added with a polymerization degree adjusting agent, a terminal group adjusting agent and the like. Examples of copolymer components include diamine components such as hexanemethylenediamine, 1,4-diaminobutane, p-phenylenediamine, and p-xylylenediamine, and dicarboxylic acids such as adipic acid, sebacic acid, succinic acid, terephthalic acid, and isophthalic acid. An amino acid component, such as an acid component or laurolactam, etc. can be mentioned. Examples of the polymerization degree adjusting agent and the end group adjusting agent include acetic acid and benzoic acid.

<Resin-processed nylon 6 fiber>
The resin used for resin processing of the nylon 6 fiber referred to in the present invention is not particularly limited as long as it is removed by an organic solvent to be described later, and the processing method is substantially attached to, infiltrated and integrated with the nylon fiber. As long as it is made into a resin, it may be a resin processed by any processing method. Examples of the resin used include polyurethane resins and silicone resins. In addition, examples of processing methods include coating, film processing, laminating, etc., such as those in which a molten resin or a resin solution is infiltrated and adhered, adhered or infiltrated to the fiber surface, or sheets and films laminated. Including. Such processing is generally performed to impart functions to fabrics using various resins in order to improve functions such as water repellency, waterproofing, moisture permeability, and airtightness. The fiber may be in the form of a fabric, clothing, industrial material, fabric other than clothing, or the like.

  The resin-processed nylon 6 fiber used in the present invention includes nylon 6 fiber, preferably nylon 6 fiber product containing 50% by mass or more, industrial waste generated in the manufacturing process of nylon 6 fiber product, or nylon 6 Used waste products and the like. For example, industrial, clothing, indoor / outdoor fiber structures, or fiber scraps thereof may be used.

  More specifically, fiber products using fibers imparted with functions such as moisture permeable waterproofness and airtightness improvement by resin processing such as polyurethane or silicone resin, such as rain clothes, winter clothes, ski wear, swimwear, uniforms, etc. , Clothing such as innerwear, stockings, knitwear, indoor products such as curtains and carpets, industrial products such as fishing nets and marine ropes, outdoor products such as ropes, nets, tire cords, belts and seats, airbags, etc. Examples of functional materials and fiber waste include polymer yarn waste generated in the manufacturing process, fabric crush waste, defective product waste, and used products. Said nylon 6 fiber may use the thing of the said form independently, and is good also as a raw material combining these.

<Nylon 6 fiber processed with polyurethane>
The polyurethane component used for polyurethane processing of the nylon 6 fiber in the present invention is not particularly limited as long as it is removed by the raw material caprolactam solution, and the processing method substantially adheres to the nylon 6 fiber. -As long as it is infiltrated and integrated, a polyurethane component processed by any processing method may be used. The polyurethane component used is a polyurethane component that is chemically unstable when heated in an acidic aqueous solution, and therefore decomposes under depolymerization conditions, causing deactivation of the depolymerization catalyst and reduction in caprolactam purity. In this case, the effect of the present invention is effectively exhibited. The processing methods include coating, film processing, laminating, etc., and the polyurethane component is substantially attached, infiltrated, and integrated by infiltrating molten polyurethane or polyurethane solution, etc., and adhering, adhering to or infiltrating the fiber surface. Including those that have been made into. Such processing is generally performed in order to impart a moisture-permeable and waterproof function to the fabric.

  The urethane component is not particularly limited as long as it is a resin having a urethane bond, and examples thereof include those produced using a polyisocyanate compound and a polyether, or a polyol such as polyester, an auxiliary agent and a catalyst.

  Examples of the nylon 6 product processed with polyurethane include a nylon 6 fiber product coated with “ENTANT” (registered trademark) (manufactured by Toray Industries, Inc.).

<Nylon 6 fiber processed with silicone resin>
The silicone resin component used for processing the nylon 6 fiber in the present invention is not particularly limited as long as it is removed by a solution of caprolactam as a raw material, and the processing method is substantially nylon 6 fiber. Any silicone resin component processed by any processing method may be used as long as it adheres, permeates and is integrated with the resin, and examples thereof include methyl vinyl silicone resin.

<Process a>
In the present invention, first, a resin-processed nylon 6 fiber is heat-treated with a raw material caprolactam solution (herein, “caprolactam solution” refers to a solution in which caprolactam is melted) to elute resin components. A process (a process) is performed. In step a, the resin-processed nylon 6 fiber and the raw material caprolactam solution are mixed and stirred while heating. Here, it is essential that the heating temperature is not less than the melting point of the raw material caprolactam and less than the melting point of the nylon 6 fiber, but is usually 80 to 180 ° C, preferably 90 to 160 ° C. Within this range, the resin component can be easily eluted from the resin-processed nylon 6 fiber into the raw material caprolactam solution, and the nylon 6 fiber is not melted. Specifically, the decomposition of the polyurethane component and the silicone resin component can be suppressed, and the workability is also good. The resin elution step may be any of reduced pressure, normal pressure, and increased pressure.

  The resin-processed nylon 6 fiber used in this process can be used in any form, but when the collected clothing is recycled, buttons and chucks made of a different type of resin from the metal fittings and nylon 6 fiber in advance, other From the viewpoint of improving workability, it is preferable that other materials such as cellulose fibers that are insoluble in the caprolactam solution, which is an accessory part, are removed.

The size of the resin-processed nylon 6 fiber to be introduced into the caprolactam solution is not particularly specified, but if it is too large to efficiently remove the resin component, stirring is difficult and the contact efficiency with the organic solvent is poor, Even if it is too small, the separation operation of taking out the nylon 6 fiber in the subsequent process becomes complicated, and therefore it is preferable that the nylon 6 fiber is cut into an appropriate size according to the equipment.
The amount of caprolactam used to elute the resin component is 0.1 to 200 times the mass of the nylon 6 fiber component. Preferably, it is 0.5 to 50 times by mass, more preferably 1 to 10 times by mass. When the amount of caprolactam used is small, the removal rate of the resin component is slow, and when it is large, the cost is high and it is economically disadvantageous. Caprolactam used for elution of the resin component may be used together with one or more different solvents such as water.

  The stirring time for eluting the resin component varies depending on the type of resin, nylon 6 fiber size and equipment, etc., but considering production efficiency, it is usually 0.1 to 20 hours, preferably 0.1 to 10 hours, more preferably 0.1 to 5 hours.

<Process b>
The nylon 6 fiber from which the resin component has been removed in step a is taken out from the caprolactam solution in step b. The method of taking out may be taken out by pulling up the nylon 6 fiber from the caprolactam solution charged with nylon 6 fiber, or the nylon 6 fiber may be taken out by removing the caprolactam solution from the system charged with nylon 6 fiber. Although it does not matter, a filtration operation or a centrifugal drainage operation can be adopted because of the simplicity of the operation.

  Here, it is preferable that the amount of the resin component remaining on the nylon 6 fiber after elution is small, but there is no problem if the resin component that substantially adheres to the nylon 6 fiber is small. When the amount of the eluted resin component is large, it may be rinsed again using caprolactam, or rinsed with water or other solvent, but it is preferable to rinse with caprolactam. The amount of the solvent to be used is usually 0.1 to 200 times the mass of the nylon fiber, although it depends on the amount of the organic solvent adhered from the resin component. Preferably, it is 0.5 to 50 times by mass, more preferably 1 to 10 times by mass.

  In the present invention, in order to elute and remove the resin component adhering to the fiber using caprolactam which is a raw material of nylon 6 fiber, the resin component is removed from the nylon 6 fiber in this step b, and then a process such as drying is performed. It is possible to use for the next c process as it is, without passing. In the case of using caprolactam in the case of rinsing off as described above, the same rinsing operation can be performed, and then it can be used as it is in the next step c without reducing the steps such as drying. In the case where the solvent remains, if the solvent remains, the subsequent step is adversely affected, and it is preferable to perform the step of rinsing with caprolactam after performing the step of drying or caprolactam.

<Process c>
The nylon 6 fiber from which the resin component thus removed has been removed is subjected to step c and depolymerized to recover caprolactam. These nylon 6 fibers from which the resin component has been removed in step b may be depolymerized by themselves, or may be depolymerized together with other nylon 6 fiber scraps, etc. It can also be depolymerized together with caprolactam oligomers and the like contained in the water extracted by polymerization.

<Depolymerization>
The depolymerization method performed in the present invention may be any method. Normally, nylon 6 fiber is depolymerized by heating, and a catalyst may be used, and it may be in the absence of water (dry type) or in the presence (wet type).

  The depolymerization pressure may be any of reduced pressure, normal pressure, and increased pressure. The depolymerization temperature is usually 100 to 400 ° C, preferably 200 to 350 ° C, more preferably 220 to 300 ° C. When the temperature is low, the nylon 6 fiber does not melt and the depolymerization rate becomes slow. High temperatures cause unnecessary nylon 6 fiber degradation, leading to a reduction in the purity of the recovered caprolactam.

  When a catalyst is used, an acid or base catalyst is usually used. Examples of the acid catalyst include phosphoric acid, boric acid, sulfuric acid, organic acid, organic sulfonic acid, solid acid, and salts thereof, and examples of the base catalyst include alkali hydroxide, alkali salt, alkaline earth hydroxide, alkali Examples include earth salts, organic bases, solid bases and the like. Preferably, phosphoric acid, boric acid, organic acid, alkali hydroxide, alkali salt, etc. are mentioned. More preferably, phosphoric acid, sodium phosphate, potassium phosphate, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate and the like can be mentioned.

  The usage-amount of a catalyst is 0.01-50 mass% normally with respect to a nylon 6 fiber component. Preferably, the content is 0.1 to 20% by mass, and more preferably 0.5 to 10% by mass. When the amount of the catalyst used is small, the reaction rate is slow, and when it is large, the side reaction increases and the cost of the catalyst is increased, which is economically disadvantageous.

  The amount of water used for wet depolymerization is 0.1 to 50 times the mass of the nylon 6 fiber component. Preferably, it is 0.5 to 20 times by mass, more preferably 1 to 10 times by mass. When the amount of water used is small, the reaction rate is slow, and when it is large, the concentration of the recovered caprolactam aqueous solution is low, which is disadvantageous in obtaining caprolactam.

<Caprolactam recovery method>
When dry depolymerization is performed, the produced caprolactam is distilled from the reactor by vacuum distillation to obtain recovered caprolactam. After the depolymerization reaction is completed, caprolactam may be taken out by distillation under reduced pressure, or may be taken out continuously as the reaction proceeds.

  When wet depolymerization is performed, the produced caprolactam is distilled from the reactor together with water to obtain a recovered caprolactam aqueous solution. After completion of the depolymerization reaction, the caprolactam aqueous solution may be taken out by distillation, or may be taken out continuously as the reaction proceeds. Preferably, water is continuously supplied to the reactor, and the produced caprolactam aqueous solution is continuously removed from the reactor. More preferably, water vapor is continuously supplied to the reaction apparatus at normal pressure, and the produced caprolactam aqueous solution is continuously removed from the reaction apparatus.

  Since the nylon 6 fiber from which the resin component has been removed in step a has substantially high nylon purity, depolymerization in step c can yield high yield and high-purity caprolactam. The obtained caprolactam aqueous solution can recover sufficiently high-purity caprolactam by separating it from water by distillation. Further, when a high-purity caprolactam is required, it can be subjected to precision distillation according to the purpose or combined with a purification method such as recrystallization.

<Process d>
Caprolactam is recovered in the d step from the caprolactam solution containing the resin after the nylon 6 fiber is taken out in the b step. Caprolactam can also be recovered from the cleaning solution used when rinsing the resin component remaining on the nylon 6 fiber in step b. The recovery method depends on the type of caprolactam and eluted resin, but can be recovered almost quantitatively by distillation under reduced pressure above the melting point of caprolactam. The caprolactam recovered here can be used again as caprolactam for eluting the resin component in step a.
Further, when the resin elution amount in the caprolactam solution is small, the caprolactam solution can be repeatedly used for resin elution in step a without purification by distillation.

<How to check caprolactam quality>
The quality of caprolactam obtained by the depolymerization performed in the present invention was confirmed by capillary gas chromatography and HPLC purity. That is, as a method for confirming purity by capillary gas chromatography, analysis is performed by capillary gas chromatography equipped with a strong polar column (TC-FFAP, 60 m, 0.25 mm, 0.25 μm) (manufactured by GL Sciences Inc.), The GC purity was confirmed by the peak area of caprolactam. Moreover, as a method for confirming purity by HPLC, analysis was performed by HPLC equipped with a reverse phase column (TSK-GEL, ODS-120T, 4.6 mm × 25.0 cm) (manufactured by Tosoh Corporation), and HPLC was determined by the peak area of caprolactam. The purity was confirmed.

Example 1
(Step a)
After 300 g of nylon 6 fiber fabric coated with porous polyurethane (“ENTANT” (registered trademark) (manufactured by Toray Industries, Inc.)) is cut into a square of about 10 cm, 5 L of Separa is prepared with 3.0 kg of caprolactam having a GC purity of 99.98%. The mixture was placed in a bull flask, immersed in a 120 ° C. silicone oil bath, a condenser and a stirrer were set, stirred for about 1 minute every about 15 minutes, and heat-treated for 3 hours.

(Step b)
The nylon 6 fiber fabric is taken out from the separable flask after completion of the heat treatment in step a and washed with 1.0 kg of water twice to remove the eluted polyurethane component, and then warm air at 60 ° C. It dried with the dryer and obtained 210 g of nylon 6 fiber fabrics. It was observed with the naked eye that the polyurethane component was removed from the obtained nylon 6 fiber fabric.

(Step c)
210 g of nylon 6 fiber fabric from which the polyurethane component dried in step b was removed and 8.4 g of 75 wt% aqueous phosphoric acid as a depolymerization catalyst were charged into a depolymerization apparatus and heated to 260 ° C. in a nitrogen atmosphere. Nitrogen was stopped, superheated steam was blown into the depolymerizer at an introduction rate of 250 g / hour, and the caprolactam water vapor continuously distilled from the depolymerizer was cooled at 260 ° C. for 6 hours. The resulting depolymerization operation was carried out.

  After water was distilled off from the obtained aqueous caprolactam solution at about 70 ° C. and 3.3 kPa under reduced pressure, it was transferred to a 500 ml Houben flask, 3.7 g of 40 wt% aqueous sodium hydroxide solution was added, and about 100 The solution was concentrated in a silicone oil bath at a reduced pressure of 3.3 kPa at 3.3 ° C. Next, vacuum distillation in which caprolactam was distilled off in a silicon oil bath under a reduced pressure condition of about 160 ° C. and 0.7 kPa was carried out to obtain 166 g of caprolactam having a GC purity of 99.98% and an HPLC purity of 93.14%.

(D process)
After removing water from the washing solution obtained by washing the nylon 6 fiber fabric in step b with an evaporator at about 70 ° C. and 3.3 kPa under reduced pressure, the nylon 6 fiber fabric was taken out in step b and then separable flask. The caprolactam solution from which the polyurethane component was eluted was mixed, transferred to a 2 L Houben flask, and subjected to vacuum distillation twice to distill caprolactam in a silicone oil bath under a reduced pressure of about 160 ° C. and 0.7 kPa. Then, 2.94 kg of caprolactam having a GC purity of 99.98% was recovered (caprolactam recovery rate of 98%).

Example 2
(Step a)
After cutting 30 g of nylon 6 fiber fabric coated with porous polyurethane (“ENTANT” (registered trademark) (manufactured by Toray Industries, Inc.)) into about 10 cm square, the GC purity obtained in the d step of Example 1 was 99.98%. Into a 500 ml separable flask together with 300 g of caprolactam, immersed in a 120 ° C. silicone oil bath, a condenser and a stirrer were set, stirred for about 1 minute every about 15 minutes, and heat-treated for 3 hours.

(Step b)
After removing the fabric from the separable flask after the heat treatment in step a and washing it with 500 ml of water twice in the same manner, the polyurethane is dried with a hot air dryer at 60 ° C. and can be observed with the naked eye. The removed nylon 6 fiber fabric 21g was obtained.

(D process)
After concentrating the water-washed solution obtained by washing the fabric of step b with an evaporator at about 70 ° C. and 3.3 kPa under reduced pressure, it is mixed with the caprolactam layer containing polyurethane in the separable flask after removing the fabric of step b, and 500 ml The flask was transferred to a Houben flask and subjected to vacuum distillation in which caprolactam was distilled off in a silicone oil bath under a reduced pressure condition of about 160 ° C. and 0.7 kPa to recover 294 g of caprolactam having a GC purity of 99.98%. (Caprolactam recovery rate 98%)
Example 3
Except for changing 300 g of caprolactam having a GC purity of 99.98% to 353 g of 85 mass% caprolactam aqueous solution, the steps a and b of Example 2 were carried out, and 21 g of a nylon 6 fiber fabric from which polyurethane that could be observed with the naked eye was removed was removed. Obtained.

Example 4
Except for changing to a heating temperature of 100 ° C. and a heating time of 5 hours, the steps a and b of Example 2 were carried out to obtain 21 g of a nylon 6 fiber fabric from which polyurethane that could be observed with the naked eye was removed.

Example 5
Except for changing to a heating temperature of 140 ° C. and a heating time of 2 hours, steps a and b of Example 2 were carried out to obtain 21 g of a nylon 6 fiber fabric from which polyurethane that could be observed with the naked eye was removed.

Example 6
In the same manner as in Example 1, after heat treatment in step a, the fabric was taken out from the separable flask and filtered under reduced pressure while maintaining at 80 ° C. or higher so that caprolactam was not crystallized. The amount of caprolactam deposited was 155 g. The isolated fabric was subjected to a depolymerization operation in the same manner as in step c of Example 1. After removing water from the obtained caprolactam aqueous solution by an evaporator under a reduced pressure of about 70 ° C. and 3.3 kPa using an evaporator, it was transferred to a 500 ml Houben flask, 3.7 g of 40 wt% aqueous sodium hydroxide solution was added, and about 100 The solution was concentrated in a silicone oil bath under a reduced pressure condition of 3.3 kPa. Next, vacuum distillation in which caprolactam was distilled off in a silicon oil bath under reduced pressure conditions of about 160 ° C. and 0.7 kPa was performed to obtain 320 g of caprolactam having a GC purity of 99.58%.

Example 7
30g of nylon 6 fiber fabric for airbag processed with methyl vinyl silicone resin is cut into about 10cm square, then charged into a 3L separable flask with 1.0kg of caprolactam with 99.98% GC purity, and 160 ° C silicone oil It was immersed in a bath, a condenser and a stirrer were set, and the mixture was stirred for about 1 minute every about 15 minutes, and heat-treated for 3 hours. Nylon from which silicone resin has been removed as a result of removing fabric from the separable flask after heat treatment and washing twice with 1.0 kg of water, followed by drying with a 60 ° C hot air dryer. 27 g of 6-fiber fabric was obtained.

Comparative Example 1
The nylon 6 fiber fabric 210g from which polyurethane was removed was changed to 210 g of nylon 6 fiber fabric to which polyurethane was adhered, and only step c of Example 1 was performed. 94 g of caprolactam having a GC purity of 99.02% and an HPLC purity of 36.0% was obtained.

Comparative Example 2
The c process of Example 1 was carried out except that the nylon 6 fiber fabric from which the polyurethane was removed was changed to a nylon 6 fiber fabric prior to polyurethane adhesion to which polyurethane did not adhere, and 167 g of caprolactam having a GC purity of 99.98% was obtained. Obtained.

Comparative Example 3
After cutting 300 g of nylon 6 fiber fabric with no polyurethane attached into a 10 cm square in the same manner as in Step a of Example 1, it was charged into a 5 L separable flask together with 3.0 kg of caprolactam having a GC purity of 99.98%. It was immersed in a silicone oil bath at 0 ° C., a condenser and a stirrer were set, and the mixture was stirred for about 1 minute every about 15 minutes, and heat-treated for 3 hours. Next, the nylon 6 fiber fabric was taken out from the separable flask and washed twice with 1.0 kg of water, and then dried with a hot air dryer at 60 ° C. As a result, 300 g of nylon 6 fiber fabric was obtained. It was confirmed that the nylon 6 fiber fabric did not dissolve in the lactam.

  According to the present invention, lactam as a raw material can be obtained from nylon 6 fiber to which a resin component is adhered by an industrially advantageous method.

Claims (5)

Resin-processed nylon 6 fiber is heat-treated in a caprolactam solution to elute the resin component into the caprolactam solution (step a), a step of taking out the nylon 6 fiber in the caprolactam solution (step b), step b A method for chemically recycling resin-processed nylon 6 fibers, comprising the step of recovering caprolactam by depolymerizing the nylon 6 fibers from which the resin component obtained in step 1 has been removed (step c). The method for chemical recycling of resin-processed nylon 6 fibers according to claim 1, wherein the heat treatment temperature in step a is 80 to 180 ° C. 3. The method for chemical recycling of resin-processed nylon fibers according to claim 1, wherein the resin used for resin processing is a polyurethane-based resin or a silicone resin. The resin-processed nylon 6 fiber is heat-treated in a caprolactam solution that is a raw material of the nylon 6 fiber to elute the resin component into the caprolactam solution (step a), and the nylon 6 fiber in the caprolactam solution is taken out. Step (b step), step of recovering caprolactam by depolymerizing the nylon 6 fiber from which the resin component has been removed in step b (step c), step of recovering caprolactam from the caprolactam solution in which the resin component is eluted in step a ( The method of chemical recycling of resin-processed nylon 6 fibers according to any one of claims 1 to 3, characterized in that it comprises a step d). The resin-processed nylon 6 fiber is heat-treated in a caprolactam solution that is a raw material of the nylon 6 fiber to elute the resin component into the caprolactam solution (step a), and the nylon 6 fiber in the caprolactam solution is taken out. A method for removing a resin component from a resin-processed nylon 6 fiber, comprising a step (b step).