Recovery method for polyurethane for artificial leather and recovery method for base material fiber

Abstract

To provide a recovery method for highly productive polyurethane for artificial leather and a recovery method for base material fibers, which are applicable to many artificial leathers.SOLUTION: An artificial leather is a grain artificial leather having a skin layer on a base material consisting of a high density nonwoven fabric with density of 0.19 to 0.35 g / cm3 and wet coagulated polyurethane. The high density nonwoven fabric contains synthetic fibers. A recovery method for polyurethane for artificial leather impregnates the artificial leather in a first DMF bath at 40°C to 100°C for 0.2 to 20 minutes, and subsequently, dissolves or separates the skin layer from the grain artificial leather, and impregnates the artificial leather in a second DMF bath at 40°C to 100°C for 0.2 to 20 minutes, and applies nipping processing. A recovery method for base material fibers recovers a synthetic fiber component used in the base material of the artificial leather after removing polyurethane from the artificial leather. It is preferable that fineness of the artificial fibers constituting the high density nonwoven fabric is 0.5 to 4.0 dtex, the high density nonwoven fabric consists of shrinkable fibers and non-shrinkable fibers, and the shrinkable fibers are polyester fibers. It is preferable that temperature of the second DMF bath is higher than the temperature of the first DMF bath, nipping is performed multiple times, and the method to separate the skin layer from the grain artificial leather peels off the skin layer by using a scraper between the skin layer and the base material.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for recovering polyurethane for artificial leather and a method for recovering base fibers, and more particularly to a method for efficiently recovering polyurethane and fibers in non-woven fabrics.

Background Art

[0002] Artificial leather composed of non-woven fabric and a polymer elastomer is widely and generally used because of its excellent texture and physical properties. However, since it is a composite in which various fibers constituting the non-woven fabric and a polymer elastomer mainly composed of polyurethane are strongly bonded, it has been difficult to efficiently recover them.

[0003] Therefore, for example, Patent Document 1 discloses artificial leather containing silicone-modified polyurethane and organopolysiloxane that are easily dissolved in hot water. However, such a method has a problem that not only the durability of the artificial leather itself is reduced, but also the artificial leather to be recovered is limited and cannot be a general-purpose method.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Provided are a method for recovering polyurethane for artificial leather and a method for recovering base fibers, which are applicable to many artificial leathers and have high productivity.

Means for Solving the Problems

[0006] The method for recovering polyurethane for artificial leather of the present invention has a density of 0.19 to 0.35 g / cm 3It is a silver-coated artificial leather having an epidermal layer on a base material composed of a high-density nonwoven fabric in the range of and wet-set polyurethane. After immersing the artificial leather containing synthetic fibers in a first DMF bath at 40°C to 100°C for 0.2 minutes to 20 minutes, the epidermal layer is dissolved or separated from the silver-coated artificial leather, and then it is immersed in a second DMF bath at 40°C to 100°C for 0.2 minutes to 20 minutes and nip-treated.

[0007] Furthermore, it is preferable that the fineness of the fibers constituting the high-density nonwoven fabric is 0.5 to 4.0 dtex, the high-density nonwoven fabric is composed of shrinkable fibers and non-shrinkable fibers, and the shrinkable fibers are polyester fibers. Also, it is preferable that the temperature of the second DMF bath is higher than that of the first DMF bath, the number of nip treatments is plural, and the method of separating the epidermal layer from the silver-coated artificial leather is a method of peeling off the epidermal layer by applying a scrapper between the epidermal layer and the base material.

[0008] Another method for recovering the base material fibers of the present invention is a silver-coated artificial leather having an epidermal layer on a base material composed of a high-density nonwoven fabric in the range of 0.19 to 0.35 g / cm3 and wet-set polyurethane. After immersing the silver-coated artificial leather containing synthetic fibers in a first DMF bath at 40°C to 100°C for 0.2 minutes to 20 minutes, the epidermal layer is dissolved or separated from the silver-coated artificial leather, and then it is immersed in a second DMF bath at 40°C to 100°C for 0.2 minutes to 20 minutes, nip-treated, and after removing the polyurethane from the artificial leather, the synthetic fiber component used in the base material of the artificial leather is recovered. Furthermore, the present invention includes a recycling method for recovering polyurethane for artificial leather and base material fibers by the above recovery method.

Advantages of the Invention

[0009] According to the present invention, a method for recovering polyurethane for artificial leather and base material fibers with high productivity is provided while being applicable to many artificial leathers.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, the present invention will be described in detail. The method for recovering polyurethane for artificial leather of the present invention is a silver-coated artificial leather having an epidermal layer on a base material composed of a high-density non-woven fabric with a density in the range of 0.19 to 0.35 g / cm 3 and wet-set polyurethane. The artificial leather containing synthetic fibers in the high-density non-woven fabric is immersed in a first DMF bath at 40°C to 100°C for 0.2 minutes to 20 minutes, and then the epidermal layer is dissolved or separated from the silver-coated artificial leather. Subsequently, it is immersed in a second DMF bath at 40°C to 100°C for 0.2 minutes to 20 minutes and subjected to nip treatment.

[0011] Here, the artificial leather targeted by the recovery method of the present invention is a silver-coated artificial leather having an epidermal layer on a base material composed of a high-density non-woven fabric and wet-set polyurethane. The base material of the artificial leather is composed of fibers and resin. In the present invention, the fibers constituting the base material are high-density non-woven fabrics, and the resin constituting the base material is wet-set polyurethane. And the high-density non-woven fabric contains synthetic fibers as its constituent fibers.

[0012] Here, the fibers used for the base layer serving as the base material of the artificial leather contain synthetic fibers such as polyamide and polyester, and may further include regenerated fibers such as rayon and acetate, or single or mixed fibers such as natural fibers. More preferable synthetic fibers include polyamide fibers such as nylon 6, nylon 66, and nylon 12, and polyester fibers such as polyethylene terephthalate and polybutylene terephthalate. Also, in order to obtain a soft texture, it is also preferable to use synthetic fibers made of ultra-fine fibers.

[0013] And in the present invention, those fibers have a density of 0.19 to 0.35 g / cm 3It is essential to form a high-density non-woven fabric within a specific density range, and it further contains synthetic fibers. To obtain a high-density non-woven fabric, the needle punching conditions, calendar conditions during finishing, etc. can be made strict to increase the density of the non-woven fabric. In particular, a combination of shrinkable fibers and non-shrinkable fibers is preferred. By adopting such a combination, it becomes possible to obtain a non-woven fabric with a balance between a soft texture and high density.

[0014] As the shrinkable fibers, it is preferable to use fibers with hot water shrinkability, which enables the production of non-woven fabrics with stable quality. As the fibers with hot water shrinkability, polyester fibers with low water absorption are particularly preferred. Here, the non-shrinkable fibers only need to have a shrinkage rate smaller than that of the shrinkable fibers in the process. Due to the difference in the shrinkage rates of two or more types of fibers, it becomes possible to obtain a high-density non-woven fabric with excellent texture and minute voids. The difference in shrinkage rate is preferably 15 - 60%. Also, the ratio of shrinkable fibers to non-shrinkable fibers is preferably in the range of 40:60 - 90:10, and particularly preferably in the range of 50:50 - 85:15.

[0015] The fineness of the fibers constituting such a high-density non-woven fabric is preferably in the range of 0.5 - 4.0 dtex. More preferably, it is in the range of 0.7 - 3.5 dtex, and particularly preferably in the range of 0.8 - 3.0 dtex.

[0016] The high-density non-woven fabric for artificial leather with silver used in the present invention is a high-density non-woven fabric made by means such as carding, web-forming, layering, needle punching, shrinkage treatment, calendar treatment, etc. using fibers with the above-described configuration.

[0017] The artificial leather used in the present invention is composed of the above-described high-density non-woven fabric and a base material made of wet coagulation polyurethane as its components. Wet coagulation polyurethane is a polyurethane that is immersed in a liquid such as water (wet treatment) to remove the solvent and form pores.

[0018] More specifically, for example, it is preferable to use a wet coagulated polyurethane having a porous structure, which is obtained by coagulating polyurethane dissolved in DMF by dipping it in water. As the type of polyurethane, various urethane resins such as polycarbonate-based, ether-based, ester-based, and ester-ether-based can be preferably used. Further, when durability is emphasized, a polycarbonate-based polyurethane resin can be used, and it can be appropriately selected according to the intended use. Also, the 100% elongation stress of the polyurethane is preferably in the range of 1 to 60 MPa, and particularly preferably in the range of 1.5 to 45 MPa. The polyurethane used here is preferably soluble in DMF.

[0019] The artificial leather used in the present invention is a so-called silvered artificial leather in which an epidermis layer exists on a base material composed of the above-mentioned high-density non-woven fabric and wet coagulated polyurethane. As the epidermis layer, not only a wet coat layer made of wet coagulated polyurethane but also a dry coat layer obtained by lamination or the like may be used, and it is also preferable that the surface thereof is further surface-coated by gravure coating or the like.

[0020] Here, the wet coat layer is formed by coating the wet coagulated polyurethane used in the above-mentioned base material preparation on the surface of the base material and coagulating it in water together with the polyurethane in the base material to form a porous polyurethane coat layer serving as the epidermis layer on the surface.

[0021] The dry coat layer is formed by, for example, forming a polyurethane coat layer on release paper, laminating it with a base material composed of a non-woven fabric and polyurethane, and forming a coat layer serving as an epidermis layer on the surface. At this time, in order to enhance the adhesiveness between the epidermis layer and the base material, it is preferable that the dry coat layer has two or more layers. A film layer containing no cross-linking agent is laminated on the side closer to the release paper, and a binder layer containing a cross-linking agent is laminated on the film layer. The release paper with the film layer and the binder layer laminated thereon is laminated on the base material and aged to strengthen the adhesion. Then, it is also preferable to remove the release paper to obtain a silver-coated artificial leather having an epidermis layer on the base material. Here, the film layer and the binder layer may each be formed of a plurality of layers. Further, this dry coat layer may be formed on the wet coat layer described above, or a resin such as another polyurethane may be gravure-coated on their surfaces.

[0022] The method for recovering the polyurethane for artificial leather of the present invention is a method in which such silver-coated artificial leather is immersed in a first DMF bath at 40°C to 100°C for 0.2 minutes to 20 minutes, then the epidermis layer is dissolved or separated from the silver-coated artificial leather, and then immersed in a second DMF bath at 40°C to 100°C for 0.2 minutes to 20 minutes and nip-treated.

[0023] The base material serving as the base of the artificial leather used in the present invention is such that the wet-solidified polyurethane is solidified in a porous state in a high-density non-woven fabric. And in addition to being in a porous state, in the high-density non-woven fabric, the polyurethane is further dispersed by a large number of fibers, so it is in a state that is extremely easily dissolved in DMF. At this time, the product of the major axis and the minor axis of the polyurethane in the base material is preferably 1000 μm 2 or less, and more preferably, the product of the major axis and the minor axis is in the range of 200 to 800 μm. 2

[0024] And as the first DMF bath used for polyurethane recovery, its temperature needs to be in the range of 40°C to 100°C, more preferably in the range of 50°C to 95°C, and particularly preferably in the range of 60°C to 90°C. The immersion time needs to be in the range of 0.2 minutes to 20 minutes, more preferably in the range of 1 to 18 minutes, and particularly preferably in the range of 2 to 16 minutes. As the immersion time, a plurality of DMF baths may be used as long as the total time is as described above.

[0025] In the recovery method of the present invention, after immersion in the first DMF bath, the epidermal layer is dissolved or separated from the silver-coated artificial leather. When the epidermal layer is a wet polyurethane coating layer or a gravure coating layer, it is mainly subjected to a dissolution treatment. When the epidermal layer contains a binder layer crosslinked thereto, it is preferable to use a separation treatment in combination.

[0026] As a method for separating the epidermal layer from the silver-coated artificial leather, it is preferable that it is a method of physically separating by scraping off with a scrapper between the epidermal layer and the substrate. The substrate of the artificial leather of this method contains wet-solidified polyurethane, but usually, the wet-solidified polyurethane also oozes out and solidifies on the surface of the high-density non-woven fabric. Therefore, not only when there is a coating layer of wet-solidified polyurethane, but also when a dry polyurethane crosslinked on the substrate is laminated, it becomes possible to easily separate the epidermal layer.

[0027] And in the recovery method of the present invention, after dissolving or separating the epidermal layer from the silver-coated artificial leather as described above, it is subsequently immersed in a second DMF bath at 40°C to 100°C for 0.2 minutes to 20 minutes and subjected to nip treatment.

[0028] As the second DMF bath used for polyurethane recovery, its temperature needs to be in the range of 40°C to 100°C, more preferably in the range of 50°C to 95°C, and particularly preferably in the range of 60°C to 90°C. Also, the temperature of the second DMF bath may be higher than that of the first DMF bath. The immersion time in the second DMF bath needs to be in the range of 0.2 minutes to 20 minutes, more preferably in the range of 1 to 18 minutes, and particularly preferably in the range of 2 to 16 minutes. Also, as the immersion time, a plurality of DMF baths may be used so that the total time before the nip becomes as described above.

[0029] Furthermore, in the recovery method of the present invention, it is also preferable that the number of nips in the DMF bath immersion and nip treatment is plural. Particularly preferably, it is a plurality of immersions and nip treatments, 2 to 5 times. The polyurethane for artificial leather recovered as a DMF solution in this way can be distilled to recover high-purity DMF, and then the distillation residue can be dried to obtain reusable polyurethane. This recycled polyurethane can be effectively utilized, for example, by mixing it with a polyurethane DMF solution for immersion.

[0030] And another recovery method of the base material fiber of the present invention is a silver-coated artificial leather having an epidermal layer on a base material composed of a high-density non-woven fabric with a density in the range of 0.19 to 0.35 g / cm 3 and wet-solidified polyurethane. The silver-coated artificial leather containing synthetic fibers in the high-density non-woven fabric is immersed in a first DMF bath at 40°C to 100°C for 0.2 minutes to 20 minutes, then the epidermal layer is dissolved or separated from the silver-coated artificial leather, and then immersed in a second DMF bath at 40°C to 100°C for 0.2 minutes to 20 minutes, followed by nip treatment. After removing the polyurethane from the artificial leather, the synthetic fiber component used in the base material of the artificial leather is recovered.

[0031] After recovering polyurethane by the method of the present invention, the nonwoven fabric contains almost no polyurethane and can be usefully used as a raw material for synthetic fiber recycling. As the synthetic fiber, polyester fiber and polyamide fiber are typical as mentioned above. In particular, when the synthetic fiber constituting the nonwoven fabric is a polyester fiber such as polyethylene terephthalate, recycling can be performed with higher efficiency. Furthermore, the present invention includes a recycling method for recovering polyurethane for artificial leather and base fibers by the above recovery method.

Example

[0032] The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to these examples. In addition, parts and % in the examples and comparative examples are based on weight unless otherwise specified. Each measured value in the examples was measured by the following method.

[0033] (1) Peel strength Leaving 20 mm at each end of a test piece of artificial leather (width: 25 mm, length: 90 mm), an adhesive is applied. A PVC sheet of the same size (width: 25 mm, length: 90 mm) is bonded to the applied surface in alignment with the artificial leather, and the adhesive is cured. Each of the artificial leather and the PVC sheet without the adhesive applied was pulled at a speed of 50 mm / min with a tensile testing machine, and the strength was measured.

[0034] (2) Tensile strength Samples were prepared in accordance with JIS K 6557-2, placed on a tensile testing machine, torn at a speed of 50 mm / min, and the maximum load until cutting was read.

[0035] (3) Polyurethane voids in the base material An image of the base material cross-section of the obtained artificial leather 1 was taken with a scanning electron microscope (SEM) at a magnification of 200 times, and for 20 voids, the product of the major axis and minor axis of polyurethane was determined, and the average value was taken as the area of "polyurethane voids in the base material".

[0036] (Example 1) (Manufacture of Artificial Leather 1) 80 wt% of polyester shrinkage fibers made of polyethylene terephthalate (hereinafter referred to as "PET") with a single fiber fineness of 2.2 dtex and a length of 51 mm and 20 wt% of polyester non-shrinkage fibers made of PET with the same fineness and length were mixed, and a web was created through a carding machine. Subsequently, needle punching was performed to mechanically entangle the fibers, and they were immersed in warm water at 70°C for 2 minutes, followed by shrinkage with a shrinkage rate of 33% per unit area. After drying, the basis weight was 315 g / m 2 , thickness 1.47 mm, apparent density 0.214 g / cm 3 of high-density non-woven fabric 1 was obtained. The shrinkage rate difference between the polyester shrinkage fibers and the polyester non-shrinkage fibers was 40%.

[0037] The obtained high-density non-woven fabric 1 was immersed in a 12 wt% concentration wet coagulation ester-ether-based polyurethane (100% modulus 11 MPa)-DMF solution. After scraping off the excess solution on the surface of the high-density non-woven fabric and squeezing it at 90% of the high-density non-woven fabric thickness, before the compression of the substrate composed of the non-woven fabric and polyurethane recovered, a 20 wt% concentration wet coagulation ester-ether-based polyurethane (100% modulus 6.8 MPa)-DMF solution was coated on one side surface to a basis weight of 900 g / m 2 , and then immersed in a coagulation bath containing 5% DMF in water to wet coagulate the polyurethane in the substrate and the coating layer respectively to form a porous polyurethane.

[0038] Thereafter, DMF was thoroughly washed and removed in water and dried at 120°C to obtain a sheet in which the polyurethane in the substrate and the coating layer formed pores. A process of applying a treatment liquid (paint) in which a pigment was dispersed to the surface of the sheet having pores made of polyurethane with a 7.5 wt% polyurethane-containing DMF-IPA-MEK solution using a gravure roll and drying was repeated 5 times to obtain artificial leather 1.

[0039] The obtained artificial leather 1 had a basis weight of 585 g / m 2(Breakdown: 50 wt% fiber, 45 wt% impregnated and coated polyurethane, 5 wt% gravure polyurethane), with a thickness of 1.60 mm. As a result of analyzing an image at a magnification of 200 times of the substrate cross-section of the obtained artificial leather 1 with a scanning electron microscope (SEM), the product of the major axis and minor axis of the polyurethane was 600 μm 2 (average value of 20 measurements). (Recovery of polyurethane and substrate fibers) The artificial leather 1 obtained in Example 1 was cut into 10 cm × 10 cm, immersed in 400 ml of an 80 °C DMF solution for 1 minute, then the artificial leather 1 was taken out and the coating layer made of porous polyurethane was removed by scraping it off with a scraper.

[0040] The remaining substrate made of polyurethane-nonwoven fabric was immersed again in an 80 °C DMF solution for 1 minute, then the substrate was taken out, nipped with a mangle with a nip pressure of 25 N / cm 2 and a gap of 0 mm to remove the DMF in which the polyurethane was dissolved from the substrate. Then, after repeating the immersion in this DMF solution and nipping with a mangle twice, it was washed thoroughly with normal-temperature ion-exchanged water and dried at 110 °C for 20 minutes, and the fibers derived from the high-density nonwoven fabric were taken out, and the substrate fibers were recovered as PET raw materials for recycling. The remaining amount of polyurethane in the obtained PET raw material was 0.3 wt%.

[0041] On the other hand, the polyurethane coating layer removed with a scraper was also immersed in an 80 °C DMF solution, stirred for 10 minutes with a stirrer to dissolve it, and mixed with the DMF in which the polyurethane extracted from the substrate was dissolved. The DMF in which this polyurethane was dissolved was distilled, and the fraction with a boiling point of 153 °C was recovered as recycled DMF and reused. As a result of drying the distillation residue obtained in this distillation process at 200 °C, recycled polyurethane with a solid content concentration of 98 wt% and a polyurethane concentration of 90 wt% was obtained.

[0042] Furthermore, this recycled polyurethane was finely crushed and mixed into a polyurethane-DMF solution for impregnating high-density nonwoven fabric so that it was 5 wt% based on the solid content of the original polyurethane. Then, in the same procedure as for the artificial leather 1, a recycled artificial leather was obtained using the high-density nonwoven fabric 1 and polyurethane for impregnation and the coating layer. Although the physical properties of the obtained recycled artificial leather were slightly inferior to those of the artificial leather 1, it retained high physical properties of 90% in tensile strength and 85% in peel strength.

[0043] (Example 2) Using the artificial leather 1 obtained in Example 1, however, different from Example 1, as a method for extracting polyurethane, the immersion time of the coating layer made of polyurethane porous into the DMF solution before removal with a scraper was changed from 1 minute to 10 minutes, the immersion time of the base material into the DMF solution after removal of the coating layer was changed from 1 minute to 30 minutes, and the number of repetitions of the immersion-nip of the base material was changed from 2 times to 5 times. Polyurethane and base material fibers were recovered from the artificial leather 1 in the same manner as in Example 1. As a result, the residual amount of polyurethane in the PET raw material for recycling was 0.2 wt%, and more polyurethane was extracted than in Example 1.

[0044] (Example 3) Using the artificial leather 1 obtained in Example 1, however, as a method for extracting polyurethane, polyurethane and base material fibers were recovered from the artificial leather 1 in the same manner as in Example 1 except that the temperature of the used DMF solution was changed from 80 °C to 60 °C. The residual amount of polyurethane in the PET raw material for recycling when polyurethane was extracted was 0.4 wt%, and it was found that polyurethane could be extracted sufficiently.

[0045] (Comparative Example 1) Using the artificial leather 1 obtained in Example 1, however, as a method for extracting polyurethane, polyurethane was recovered from the artificial leather 1 in the same manner as in Example 1 except that the temperature of the used DMF was changed from 80 °C to 25 °C. The residual amount of polyurethane in the PET raw material for recycling when polyurethane was extracted was 24 wt%, and the extraction of polyurethane was insufficient.

[0046] (Example 4) Using the artificial leather 1 obtained in Example 1 as well, however, as a method for extracting polyurethane, the temperature of the DMF used was changed from 80°C to 60°C, the immersion time before removing the coating layer made of polyurethane porous with a scraper was changed from 1 minute to 0.5 minute, and the immersion times for the substrate twice after removing the coating layer were also changed from 1 minute to 0.5 minute. In the same manner as in Example 1, polyurethane and the substrate fibers were recovered from the artificial leather 1. The remaining amount of polyurethane in the PET raw material for recycling when extracting polyurethane was 0.5 wt%, and it was found that polyurethane could be sufficiently extracted.

[0047] (Example 5) (Manufacture of artificial leather 2) The ratio of the fibers of the high-density nonwoven fabric 1 used in Example 1 was changed from 80 wt% of shrinkable fibers and 20 wt% of non-shrinkable fibers to 50 wt% of shrinkable fibers and 50 wt% of non-shrinkable fibers, with a shrinkage rate of 25% per unit area and a basis weight of 280 g / m 2 , a thickness of 1.47 mm, and an apparent density of 0.19 g / cm 3 to obtain a nonwoven fabric 2.

[0048] Using the obtained nonwoven fabric 2 in the same manner as in Example 1, artificial leather 2 was obtained. The obtained artificial leather 2 had a basis weight of 540 g / m 2 , and a thickness of 1.55 mm. The observation result of the cross-section SEM of the obtained artificial leather 2 showed that the product of the major axis and minor axis of the polyurethane was 900 μm 2 .

[0049] (Extraction of polyurethane) Using the artificial leather 2 obtained above, polyurethane and the substrate fibers were recovered in the same manner as in Example 1. The remaining amount of polyurethane in the PET raw material for recycling when extracting polyurethane was 8.0%, and although the remaining amount of polyurethane was slightly high, it was found that polyurethane could be sufficiently extracted.

[0050] (Example 6) (Manufacture of artificial leather 3) Using polyester non-shrinking fibers made of polyethylene terephthalate (hereinafter referred to as "PET") with a single-filament fineness of 2.2 dtex and a length of 51 mm, a web was created through a carding machine, and the number of needle punching operations was increased to mechanically increase the degree of entanglement of the fibers. After drying, the basis weight was 325 g / m 2 , the thickness was 1.25 mm, and the apparent density was 0.26 g / cm 3 of high-density nonwoven fabric 3 was obtained.

[0051] Using the obtained high-density nonwoven fabric 3 in the same manner as in Example 1, artificial leather 3 was obtained. The obtained artificial leather 3 had a basis weight of 585 g / m 2 , and the thickness was 1.48 mm. The observation result of the cross-section SEM of the obtained artificial leather 3 showed that the product of the major axis and minor axis of the polyurethane was 400 μm 2 .

[0052] (Recovery of Polyurethane and Substrate Fibers) The polyurethane and substrate fibers of the artificial leather 3 obtained above were recovered in the same manner as in Example 1. The residual amount of polyurethane in the PET raw material for recycling when the polyurethane was extracted was 0.3%, indicating that the polyurethane could be sufficiently extracted.

[0053] (Example 7) (Manufacture of Artificial Leather 4) Similar to the high-density nonwoven fabric 1 in Example 1, 80 wt% of polyester shrinkable fibers and 20 wt% of polyester non-shrinkable fibers were used, but the supply amount to the process was changed, and after drying, the basis weight was 290 g / m 2 , the thickness was 1.22 mm, and the apparent density was 0.238 g / cm 3 of high-density nonwoven fabric 4 was obtained. The obtained high-density nonwoven fabric 4 was immersed in a 7 wt% concentration polyurethane-DMF solution for wet coagulation, and coated with a 21 wt% concentration polyurethane-DMF solution to a basis weight of 1200 g / m 2 In the same manner as in Example 1 except for coating, a sheet in which the polyurethane in the substrate and the coating layer was porous was obtained.

[0054] Furthermore, a three-layer laminate layer of a skin layer, an intermediate layer, and an adhesive layer was laminated on the release paper, and a base material having a coating layer on the surface was bonded to obtain artificial leather 4 having a three-layer laminate layer. Each of the laminate layers is a paint obtained by dissolving polyurethane in a DMF-MEK solution and dispersing a pigment. Furthermore, a polyurethane containing a crosslinking agent was used for the adhesive layer. The obtained artificial leather 4 had a basis weight of 530 g / m 2 and a thickness of 1.30 mm. Also, as a result of SEM observation of the cross-section of artificial leather 4, the product of the major axis and minor axis of the polyurethane in the base material was 500 μm 2 .

[0055] The obtained artificial leather 4 was recovered for polyurethane and base material fibers in the same manner as in Example 1. However, when extracting the polyurethane, the crosslinked laminate adhesive layer did not dissolve in DMF and was physically peeled off (removed) with a scraper, and only the other polyurethane components were recovered. Also, the residual amount of polyurethane in the recycled PET raw material was 0.6 wt%, and the polyurethane could be sufficiently extracted.

[0056] (Comparative Example 2) (Manufacture of artificial leather 5) Using polyester non-shrinking fibers made of PET with a single-filament fineness of 2.2 dtex and a length of 51 mm, a web was created through a carding machine, entangled by needle punching, and after drying, the basis weight was 320 g / m 2 , the thickness was 1.78 mm, and the apparent density was 0.18 g / cm 3 to obtain a non-woven fabric 5.

[0057] The obtained non-woven fabric 5 was used in the same manner as in Example 1 to obtain artificial leather 5. The obtained artificial leather 5 had a basis weight of 591 g / m 2 and a thickness of 1.85 mm. As a result of SEM observation of the cross-section of the obtained artificial leather 5, the product of the major axis and minor axis of the polyurethane was 1200 μm 2 .

[0058] (Extraction of polyurethane) As a result of extracting polyurethane from the artificial leather 5 obtained above in the same manner as in Example 1, the residual amount of polyurethane in the PET raw material for recycling was 18 wt%, and the extraction of polyurethane was insufficient.

[0059] (Comparative Example 3) (Production of artificial leather 6) Using a polyester non-shrinking fiber made of PET with a single fiber fineness of 2.2 dtex and a length of 51 mm, a web was created through a carding machine, entangled by changing the needle punching conditions, and after drying, the basis weight was 285 g / m 2 , thickness 1.73 mm, apparent density 0.16 g / cm 3 of non-woven fabric 6 was obtained.

[0060] The obtained non-woven fabric 6 was used in the same manner as in Example 1 to obtain artificial leather 6. The obtained artificial leather 6 had a basis weight of 570 g / m 2 , thickness 1.81 mm. The observation result of the cross-sectional SEM of the obtained artificial leather 6 showed that the product of the major axis and minor axis of the polyurethane was 1600 μm 2 .

[0061] (Extraction of polyurethane) As a result of extracting polyurethane from the artificial leather 6 obtained above in the same manner as in Example 1, the residual amount of polyurethane in the PET raw material for recycling was 23 wt%, and the extraction of polyurethane was insufficient.

[0062] (Comparative Example 4) Using the non-woven fabric 5 obtained in Comparative Example 2, however, after entangling the fibers, calendar processing was performed with a calendar facility having a surface temperature set to 120 °C, and the basis weight was 319 g / m 2 , thickness 0.85 mm, apparent density 0.38 g / cm 3 of high-density non-woven fabric 7 was obtained. However, when attempting to immerse this high-density non-woven fabric 7 in a 12 wt% concentration wet coagulation polyurethane-DMF solution, it was not sufficiently impregnated, and a high-quality artificial leather could not be obtained.

Claims

1. A silver-coated artificial leather having a skin layer on a base material composed of a high-density nonwoven fabric with a density in the range of 0.19 to 0.35 g / cm ３ and a wet-set polyurethane. The artificial leather containing synthetic fibers in the high-density nonwoven fabric is immersed in a first DMF bath at 40°C to 100°C for 0.2 minutes to 20 minutes, and then the skin layer is dissolved or separated from the silver-coated artificial leather. Subsequently, it is immersed in a second DMF bath at 40°C to 100°C for 0.2 minutes to 20 minutes and subjected to nip treatment. A method for recovering polyurethane for artificial leather, characterized by the above steps.

2. The method for recovering polyurethane for artificial leather according to claim 1, wherein the fineness of the fibers constituting the high-density nonwoven fabric is 0.5 to 4.0 dtex.

3. The method for recovering polyurethane for artificial leather according to claim 1, wherein the high-density nonwoven fabric is composed of shrinkable fibers and non-shrinkable fibers.

4. The method for recovering polyurethane for artificial leather according to claim 3, wherein the shrinkable fibers are polyester fibers.

5. The method for recovering polyurethane for artificial leather according to claim 1, wherein the temperature of the second DMF bath is higher than that of the first DMF bath.

6. The method for recovering polyurethane for artificial leather according to claim 1, wherein the number of nip passes is plural.

7. The method for recovering polyurethane for artificial leather according to claim 1, wherein the method for separating the skin layer from the silver-coated artificial leather is a method of scraping the skin layer with a scrapper between the skin layer and the base material to peel off the skin layer.

8. A silver-coated artificial leather having a skin layer on a substrate composed of a high-density nonwoven fabric with a density in the range of 0.19 to 0.35 g / cm and a wet-set polyurethane, wherein the high-density nonwoven fabric contains synthetic fibers. After immersing the silver-coated artificial leather in a first DMF bath at 40°C to 100°C for 0.2 minutes to 20 minutes, the skin layer is dissolved or separated from the silver-coated artificial leather, and then continuously immersed in a second DMF bath at 40°C to 100°C for 0.2 minutes to 20 minutes, followed by nip treatment. After removing the polyurethane from the artificial leather, a method for recovering the synthetic fiber components used in the substrate of the artificial leather to recover the substrate fibers. ３ ​

9. A recycling method for recovering polyurethane for artificial leather and base material fibers by the recovery methods according to claim 1 and claim 8.