Silver-coated artificial leather, its manufacturing method, and method for separately recovering the surface layer of silver-coated artificial leather

Abstract

To provide grained artificial leather which includes an intermediate layer and a skin layer for coating the intermediate layer for forming a grain layer, and which can be separately collected by peeling only the skin layer from the intermediate layer just by simple processing.MEANS: A grained artificial leather includes: a fiber entangled body; an intermediate layer integrated with the fiber entangled body and containing foamed polyurethane; and a skin layer which is laminated on the intermediate layer and whose thickness is 4-20 μm. The skin layer at least includes a first region which contains silicone-modified polyurethane and organic polysiloxane, which comes into contact with the intermediate layer and whose thickness is equal to or greater than 4 μm.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a technique for realizing the recycling of materials for silver-coated artificial leather.

Background Art

[0002] Silver-coated artificial leather having an appearance similar to natural leather and used as a surface material for bags, clothing, shoes, etc. is known. As such silver-coated artificial leather, a silver-coated artificial leather including a fiber complex, an intermediate layer including a foamed polyurethane layer for forming a silver surface layer integrated with the fiber complex, and a skin layer coating the intermediate layer is known.

[0003] Due to the demand for resource recycling, separation and recovery of similar materials from waste have been conventionally carried out. Also in silver-coated artificial leather, it is preferable that the materials are separated and recovered for resource recycling. However, in silver-coated artificial leather formed by laminating and integrating a fiber complex, an intermediate layer including a foamed polyurethane layer, and a skin layer, it has been required that each layer be adhered with a high adhesive force so as not to peel from each other in the use environment.

[0004] For example, for the purpose of suppressing peeling of the skin layer, Patent Document 1 below discloses a silver-coated leather-like sheet including a fiber substrate and a polyurethane skin film laminated on the surface layer directly or via another polyurethane layer, and a silver-coated leather-like sheet in which the polyurethane skin film does not peel even after dropping mono(2-ethylhexyl) phthalate on the surface of the polyurethane skin film and leaving it at room temperature for 336 hours.

[0005] By the way, although it is not a technique for suppressing peeling of the skin layer, Patent Document 2 below discloses adding a silicone-based surfactant to an aqueous ink from the viewpoint of improving the storage stability of the aqueous ink and the abrasion resistance of the printed matter.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2019-151948 [Patent Document 2] Japanese Patent Application Laid-Open No. 2020-097683 [Summary of the Invention] [Problems to be Solved by the Invention]

[0007] As described above, in the conventional silver-coated artificial leather, each layer is adhered to each other with a high adhesive force so as not to peel off in the use environment, and there has been no idea of separating and recovering similar materials by separating each layer.

[0008] An object of the present invention is to provide a silver-coated artificial leather having an intermediate layer for forming a silver surface layer and an epidermal layer coating the intermediate layer, which can be separated and recovered only by peeling off only the epidermal layer from the intermediate layer by a simple hot water immersion treatment. [Means for Solving the Problems]

[0009] One aspect of the present invention includes a fiber complex, an intermediate layer including a foamed polyurethane integrated with the fiber complex, and an epidermal layer having a thickness of 4 to 20 μm laminated on the intermediate layer. The epidermal layer contains a silicone-modified polyurethane and an organic polysiloxane, and is a silver-coated artificial leather including at least a first region of 4 μm or more in contact with the intermediate layer. Such silver-coated artificial leather is adhered with a high adhesive force so that the intermediate layer and the epidermal layer do not peel off from each other in the general use environment of products using it. At the time of disposal, for example, only by a simple hot water immersion treatment such as immersing in hot water at 90°C for 24 hours, only the epidermal layer can be selectively peeled off from the intermediate layer (hereinafter, this property is also referred to as hot water peelability). Therefore, according to such silver-coated artificial leather, only the epidermal layer can be selectively peeled off and separated and recovered.

[0010] In addition, it is preferable that the first region contains 3.0 mass% or more of silicon atoms because it is easy to obtain a silver-coated artificial leather having sufficiently excellent hot water peelability.

[0011] In addition, it is preferable that the epidermal layer further includes a second region that coats the first region because it is excellent in the degree of freedom of adjusting color and surface physical properties.

[0012] Another aspect of the present invention includes a step of preparing a base material including a fiber complex and an intermediate layer including a foamed polyurethane integrated with the fiber complex, and applying an ink containing a silicone-modified polyurethane and an organic polysiloxane to the surface of the intermediate layer by gravure coating and then drying it to form an epidermal layer including at least a first region of 4 μm or more. This is a method for manufacturing a silver-coated artificial leather.

[0013] Another aspect of the present invention includes a step of preparing any of the above silver-coated artificial leathers, and a step of immersing the silver-coated artificial leather in hot water to peel off the epidermal layer. This is a method for separately recovering the epidermal layer of a silver-coated artificial leather. According to such a method, only the epidermal layer can be peeled off from the intermediate layer forming the silver surface layer and separately recovered.

Advantages of the Invention

[0014] According to the present invention, in a silver-coated artificial leather including an intermediate layer for forming a silver surface layer and an epidermal layer coating the intermediate layer, a silver-coated artificial leather capable of peeling off and separately recovering only the epidermal layer from the intermediate layer by only a simple hot water immersion treatment can be obtained.

Brief Description of the Drawings

[0015]

Figure 1

Embodiments for Carrying Out the Invention

[0016] Hereinafter, an embodiment of the silver-tone artificial leather according to the present invention will be described. The silver-tone artificial leather of this embodiment includes a fiber complex, an intermediate layer including a foamed polyurethane integrated with the fiber complex, and an epidermal layer having a thickness of 4 to 20 μm laminated on the intermediate layer. The epidermal layer is a silver-tone artificial leather including at least a first region of 4 μm or more in thickness in contact with the intermediate layer and containing a silicone-modified polyurethane and an organopolysiloxane. Hereinafter, the silver-tone artificial leather of this embodiment will be described in detail with reference to the drawings and its typical manufacturing method.

[0017] FIG. 1 shows a schematic cross-sectional view of the silver-tone artificial leather 10. In FIG. 1, 1 is a fiber complex, 2 is an intermediate layer containing a foamed polyurethane, and 3 is an epidermal layer having a thickness of 4 to 20 μm laminated on the intermediate layer and including at least a first region of 4 μm or more in thickness in contact with the intermediate layer and containing a silicone-modified polyurethane and an organopolysiloxane. In the silver-tone artificial leather 10 of this embodiment, the intermediate layer 2 includes a laminated region 2a laminated on the fiber complex 1 and an impregnated region 2b impregnated and applied to the fiber complex 1. The intermediate layer 2 has a foamed structure having pores v. Further, on the outer surface of the silver-tone artificial leather, for example, embossed patterns may be formed by embossing rolls.

[0018] Hereinafter, an example of the manufacturing method of the silver-tone artificial leather according to this embodiment will be described.

[0019] In the manufacturing method of the silver-tone artificial leather of this embodiment, first, a base material including a fiber complex and a foamed polyurethane layer serving as an intermediate layer integrated with the fiber complex is prepared. For example, the base material is manufactured as follows.

[0020] The fiber structure of the fiber complex is not particularly limited, and examples thereof include non-woven fabrics, woven fabrics, knitted fabrics, or complexes combining them, and preferably non-woven fabrics or complexes of non-woven fabrics and woven fabrics.

[0021] The resin forming the fiber complex is not particularly limited. Specifically, for example, nylon resins such as 6-nylon, 66-nylon, 610-nylon, 10-nylon, 11-nylon, 12-nylon, 612-nylon; aromatic polyester resins such as polyethylene terephthalate (PET), modified polyethylene terephthalate, polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polytriethylene terephthalate, polyhexamethylene terephthalate, polypropylene terephthalate, polyethylene naphthalate, and aliphatic polyester resins such as polylactic acid, polyethylene succinate, polybutylene succinate, polybutylene succinate adipate, polyhydroxybutyrate-polyhydroxyvalerate copolymer, etc. polyester resins; polyolefin resins such as polypropylene, polyethylene, polybutene, polymethylpentene, chlorine-based polyolefin, ethylene vinyl acetate copolymer, styrene ethylene copolymer; modified polyvinyl alcohol-based resins formed from modified polyvinyl alcohol containing 25 to 70 mol% of ethylene units; and crystalline elastomers such as polyurethane-based elastomers, polyamide-based elastomers, polyester-based elastomers, etc. Among these, nylon resins and aromatic polyester resins are preferred because of their excellent balance of various properties.

[0022] Also, the fineness and form of the fiber are not particularly limited. For example, it may be regular fiber with an average fineness exceeding 1 dtex, or ultrafine fiber with an average fineness less than 1 dtex, preferably ultrafine fiber of 0.0001 to 0.1 dtex. Also, the form of the fiber may be solid fiber, or fiber having pores such as hollow fiber or bell pepper-shaped fiber. The average fineness is determined as the average value calculated using the density of the resin forming the fiber from 15 fiber diameters randomly selected by magnifying 3000 times with a scanning electron microscope (SEM) a cross-section parallel to the thickness direction of the silver-coated artificial leather.

[0023] Also, the thickness of the fiber complex is not particularly limited, but for example, it is preferably about 0.3 to 3 mm, more preferably about 0.5 to 1.5 mm.

[0024] The base material comprises a fiber complex and a foamed polyurethane layer integrated with the fiber complex.

[0025] Such a base material can be obtained, for example, by impregnating a fiber complex with a polyurethane solution containing polyurethane that solidifies wet in the fiber complex, and then further applying the same polyurethane solution to the surface of the fiber complex, and then immersing it in a coagulating liquid such as water or a mixed solvent of water and DMF, etc., to wet-solidify the polyurethane layer containing foamed polyurethane.

[0026] Alternatively, instead of forming a polyurethane layer containing foamed polyurethane integrated with the fiber complex using the wet-solidification method, a so-called dry foaming surface-forming method can be used to integrate the polyurethane layer containing foamed polyurethane with the fiber complex. Specifically, a method of forming a polyurethane layer containing foamed polyurethane on a release paper and adhering the polyurethane layer containing foamed polyurethane formed on the release paper to the fiber complex may be used. In this embodiment, as a representative example, a method of integrating a foamed polyurethane layer with a fiber complex using the wet-solidification method will be described in detail.

[0027] The type of polyurethane forming the foamed polyurethane is not particularly limited, and specific examples thereof include, for example, polyester-based polyurethane, polycarbonate-based polyurethane, polyester-polycarbonate-based polyurethane, polyether-based polyurethane, etc. These may be used alone or in combination of two or more.

[0028] In addition, the foamed polyurethane layer may contain additives such as a coagulation regulator, an antioxidant, a light-resistant agent, an antibacterial agent, etc., in addition to a colorant such as a pigment, as long as the effects of the present invention are not impaired.

[0029] As the solvent contained in the polyurethane solution, for example, a mixed solvent obtained by mixing N,N-dimethylformamide (DMF), cyclohexanone (CHN), tetrahydrofuran (THF), methyl ethyl ketone (MEK), acetone (Ac), dioxane, isopropyl alcohol, toluene, water, etc. is preferably used.

[0030] In the base material, the fiber complex is impregnated with the polyurethane solution in advance, and further, after applying the polyurethane solution to the surface of the fiber complex and then immersing it in the coagulating liquid to solidify it, the foamed polyurethane impregnated inside the fiber complex is integrated with the fiber complex to form an impregnated region, and a laminated region containing the foamed polyurethane laminated on the impregnated region, and a polyurethane layer containing the foamed polyurethane integrated with the fiber complex is formed.

[0031] The thickness of the intermediate layer formed from the polyurethane layer containing the foamed polyurethane is not particularly limited, but is preferably 100 to 600 μm, more preferably 200 to 400 μm. Also, among the intermediate layers, the thickness of the laminated region laminated on the impregnated region is preferably 50 to 500 μm, more preferably 100 to 300 μm. Further, the total thickness of the base material is preferably 800 to 3000 μm, more preferably 1200 to 2000 μm.

[0032] Also, the expansion ratio of the foamed polyurethane, defined as (volume of the foamed polyurethane) / (solid volume of the polyurethane excluding the pores of the foamed polyurethane), is preferably 1.5 to 5 times, more preferably 3 to 4 times, from the viewpoint of excellent hot water peelability. When the expansion ratio of the foamed polyurethane is too low, in the hot water immersion treatment described later, the hot water hardly reaches the surface in contact with the intermediate layer, and the time required for peeling becomes long, etc., and the hot water peelability tends to decrease. Also, when the expansion ratio is too high, the mechanical properties tend to decrease, such as a decrease in wear resistance.

[0033] The mass ratio of the fiber to the foamed polyurethane (fiber / foamed polyurethane) forming the fiber complex constituting the silver-coated artificial leather is preferably 40 / 60 to 70 / 30, more preferably 50 / 50 to 60 / 40, from the viewpoint of excellent balance between texture and form stability. When the ratio of the foamed polyurethane is too high, it tends to have a rubbery texture, and when the ratio of the fiber is too high, the form stability tends to decrease.

[0034] Next, an ink containing a silicone-modified polyurethane and an organopolysiloxane (hereinafter, also simply referred to as the first ink) is gravure-coated on the surface of the foamed polyurethane layer serving as the intermediate layer of the substrate thus prepared, and then dried, thereby forming a first region of 4 μm or more included in the skin layer and in contact with, preferably directly in contact with, the intermediate layer.

[0035] The first ink applied to form the first region contains a silicone-modified polycarbonate-based polyurethane, an organic solvent that dissolves the polyurethane, and an organopolysiloxane blended as an additive.

[0036] The polyurethane forming the first region contains a silicone-modified polyurethane, and it is particularly preferable that the silicone-modified polyurethane be the main component. Specifically, for example, the first region preferably contains 60% by mass or more, more preferably 80% by mass or more, and particularly preferably 90% by mass or more of the silicone-modified polyurethane.

[0037] The silicone-modified polyurethane is a polyurethane in which a siloxane bond is introduced into the main chain or side chain of the polyurethane. The silicone-modified polyurethane is produced, for example, by reacting a polyol, a chain extender, an active hydrogen group-containing organopolysiloxane, and a polyisocyanate using a known method for producing a polyurethane.

[0038] In addition, as the silicone-modified polyurethane, depending on the difference in the polyol component, silicone-modified polycarbonate-based polyurethane, silicone-modified polyester-based polyurethane, silicone-modified polyether-based polyurethane, etc. can be mentioned. Among these, silicone-modified polycarbonate-based polyurethane is preferable because of its particularly excellent durability.

[0039] The first region may contain a silicone-unmodified polyurethane other than the silicone-modified polyurethane as long as the effects of the present invention are not impaired. Specific examples of the silicone-unmodified polyurethane include polycarbonate-based polyurethane, polyester-based polyurethane, polyester-polycarbonate-based polyurethane, polyether-based polyurethane, etc. that are not silicone-modified. These may be used alone or in combination of two or more.

[0040] And the first region contains an organopolysiloxane in addition to the silicone-modified polyurethane. The organopolysiloxane is a silicone compound having a siloxane bond in the polymer main chain, and is preferably in an oil form. Specific examples of the organopolysiloxane include, for example, polydimethylsiloxane, or an organomodified polysiloxane in which one of the two methyl groups of the siloxane unit (-Si-O-) of polydimethylsiloxane is substituted with another chemical structure, or a terminal organomodified polysiloxane in which another chemical structure is added to one end or both ends of polydimethylsiloxane. Examples of the other chemical structure include a polyether group, a phenyl group, a polyester group, an alkyl group or an aralkyl group having 2 to 9 carbon atoms, etc. Specifically, for example, polyether-modified polydimethylsiloxane, phenyl-modified polydimethylsiloxane, polyester-modified polydimethylsiloxane, aralkyl-modified polydimethylsiloxane, etc. can be mentioned.

[0041] In addition, the first region may contain additives such as colorants such as pigments, light-resistant agents, antioxidants, antibacterial agents, and dispersants as long as the effects of the present invention are not impaired. In particular, the first region is preferably colored with a pigment.

[0042] The content ratio of the silicone-modified polyurethane contained in the first region is preferably such that the silicon atom content ratio contained in the first region is 1.0% by mass or more, more preferably 2.0% by mass or more, from the viewpoint of excellent hot water peelability.

[0043] Also, the content ratio of the organopolysiloxane contained in the first region is preferably such that the silicon atom content ratio contained in the first region is 0.5% by mass or more, more preferably 1.0% by mass or more, particularly preferably 2.0% by mass or more, from the viewpoint of excellent hot water peelability.

[0044] Also, as the total content ratio of the silicon atoms contained in the first region, a ratio of 3.0% by mass or more, more preferably 3.5% by mass or more, particularly preferably 4.0% by mass or more is preferable from the viewpoint of excellent hot water peelability.

[0045] As the solvent contained in the first ink, for example, a mixed solvent obtained by mixing N,N-dimethylformamide (DMF), cyclohexanone (CHN), tetrahydrofuran (THF), methyl ethyl ketone (MEK), acetone (Ac), dioxane, isopropyl alcohol, toluene, water, etc. is preferably used.

[0046] Also, the concentration of the silicone-modified polyurethane contained in the first ink is not particularly limited, but is preferably about 5 to 15% by mass.

[0047] The coating method of the first ink is not particularly limited, but from the viewpoint of easy control of the film thickness, a method of gravure coating the first ink on the surface of the intermediate layer using a gravure roll can be mentioned. As the gravure roll, it is preferable that the size of the cells engraved on the surface of the gravure roll is 65 to 180 mesh, more preferably 100 to 130 mesh, from the viewpoint of being able to uniformly apply an appropriate amount of ink. Also, the gravure coating may be performed in multiple stages so as to ensure a uniform film thickness.

[0048] The coating amount of the first ink is 10 to 40 g / m per single coating 2 , and more preferably 15 to 30 g / m 2 , and particularly preferably 20 to 25 g / m 2 . By repeating the coating, the thickness of the first region is adjusted. The total coating amount of the first ink for forming the first region is 50 to 250 g / m 2 , and more preferably 100 to 200 g / m 2 , and particularly preferably 120 to 150 g / m 2 . By applying the first ink to the surface of the intermediate layer in such a coating amount and drying the solvent, a first region of 4 μm or more in contact with the intermediate layer is formed. The drying conditions are appropriately adjusted according to the type of the solvent and the like. For example, conditions for drying in about 5 to 30 seconds in a hot air dryer set at 100 to 120 °C can be mentioned.

[0049] The thickness of the first region thus formed is 4 μm or more, preferably 5 μm or more, and more preferably 6 μm or more. The upper limit is 20 μm, which is the upper limit of the thickness of the epidermal layer. When the thickness of the first region is less than 4 μm, the hot water peelability deteriorates.

[0050] In addition, the epidermal layer may further include a second region that coats the first region, if necessary. By further containing such a second region, it is preferable in terms of improving the degree of freedom in adjusting the color and surface physical properties.

[0051] The second region is formed by gravure coating an ink containing the same ink as the first region or an ink containing a polyurethane different from the first region that does not contain silicone-modified polyurethane or organopolysiloxane, or an ink containing a resin other than polyurethane (hereinafter, also simply referred to as the second ink) on the surface of the first region and then drying it. The method for forming the second region is formed by the same method except that the second ink is used instead of the first ink.

[0052] Similarly, the second region may also contain additives such as colorants such as pigments, lightfast agents, antioxidants, antibacterial agents, and dispersants, as long as the effects of the present invention are not impaired. In particular, it is preferable that the second region is also colored with a pigment.

[0053] The total thickness of the epidermal layer including at least the first region is 4 to 20 μm, preferably 4 to 15 μm, and more preferably 8 to 15 μm. When the total thickness of the epidermal layer is less than 4 μm, the effects such as protecting the surface and imparting abrasion resistance tend to be insufficient. When it exceeds 20 μm, the texture becomes hard, the flex resistance decreases, and the embossing moldability by embossing decreases.

[0054] In this way, a silver-tone artificial leather having an intermediate layer and an epidermal layer that form a silver surface layer is obtained. In such silver-tone artificial leather, after forming the epidermal layer, an embossed pattern may be imparted to the surface thereof by embossing with an embossing roll having a heated texture, for example. The shape of the texture on the surface of the embossing roll is not particularly limited, but for example, an embossing roll having a height difference between unevenness of about 20 to 100 μm is preferably used. Also, the surface temperature of the embossing roll is appropriately selected such that the shape of the texture can be appropriately transferred and a temperature at which small openings with a small diameter tend to remain. Specifically, for example, it is preferably 150 to 190 °C, and more preferably 160 to 180 °C.

[0055] Such silver-tone artificial leather is a silver-tone artificial leather having an intermediate layer and an epidermal layer that form a silver surface layer, and is a silver-tone artificial leather that can be separated and recovered by peeling only the epidermal layer by immersion in hot water.

[0056] Specifically, for example, when immersed in hot water at 90°C, only the epidermal layer can be selectively peeled off from the intermediate layer. Specifically, when immersed in hot water at 90°C, it is preferably completely peeled off in 12 hours, further preferably in 8 hours, and particularly preferably in 4 hours. Note that peeling means that, for example, voids are formed in at least a part between the intermediate layer and the epidermal layer, and the epidermal layer can be easily peeled off with a light force from that part. The higher the temperature of the hot water, the shorter the time required for peeling, so it is appropriately selected, but it is preferably 80°C or higher, further preferably 90°C or higher. Also, it may be treated with steam.

[0057] On the other hand, in the general use environment of such silver-coated artificial leather, the epidermal layer does not peel off and maintains a strong adhesive force to the intermediate layer. Specifically, in an accelerated test under high temperature and high humidity conditions, for example, it does not peel off even when left in a constant temperature and humidity chamber at 90°C and 80% RH for 4 weeks.

[0058] By peeling the epidermal layer in this way, the epidermal layer can be separated and recovered. The recovered epidermal layer can also be reused as a raw material for ink by redissolving it, etc. Note that since the peeled epidermal layer is peeled off only by immersion in hot water, it can be recovered without causing deterioration such as a significant decrease in the molecular weight of polyurethane. For example, when the molecular weight of the polyurethane of the recovered epidermal layer in terms of polystyrene is measured by GPC, the deterioration can be suppressed so that the retention rate of the weight average molecular weight is 80% or more. Therefore, it can be reused as a material for forming the epidermal layer when manufacturing silver-coated artificial leather.

[0059] The silver-coated artificial leather of the present embodiment described above is preferably used as a surface material for products that come into contact with the human body, such as clothing materials, shoe upper materials, and lining materials for backpacks.

Example

[0060] Hereinafter, the present invention will be described more specifically with reference to examples. Note that the scope of the present invention is not limited to these examples in any way.

[0061] [Example 1] A sea-island composite fiber composed of 45 parts by mass of 6-nylon (sea component) and 55 parts by mass of polystyrene (island component) was melt-spun, drawn 3 times, provided with a fiber finishing agent, subjected to mechanical crimping, and then dried to produce crimped fibers.

[0062] The obtained crimped fibers were cut into 51 mm to obtain 3 dtex staples, and a web was formed. Then, needle punching of about 500 punches / cm was alternately performed on both sides of the web to obtain a nonwoven fabric of the sea-island composite fiber. The basis weight of the obtained nonwoven fabric of the sea-island composite fiber was 350 g / m 2 , and the apparent specific gravity was 0.17. 2

[0063] Then, the nonwoven fabric of the sea-island composite fiber was treated with a 4% aqueous solution of polyvinyl alcohol, compressed and fixed to a thickness of about 1.3 mm, and the surface was buffed to be smoothed. Then, the smoothed nonwoven fabric of the sea-island composite fiber was impregnated with a polyurethane solution mainly containing a polyester-based polyurethane. Further, the same polyurethane solution was applied to the surface in an amount of 100 g / m in terms of solid content, and then immersed in a mixed solution of DMF / water to wet-coagulate porous foamed polyurethane. The polyurethane solution was a solution having a concentration of 13% by mass mainly containing a polyester-based polyurethane and using dimethylformamide (hereinafter referred to as DMF) as a solvent. 2

[0064] Then, the nonwoven fabric of the sea-island composite fiber provided with the foamed polyurethane was immersed in hot toluene to elute and remove the island component, thereby converting the sea-island composite fiber into a hollow fiber. In this way, a base material including a nonwoven fabric and a foamed polyurethane layer integrated with the nonwoven fabric was obtained. According to observation by a microscope, the thickness of the foamed polyurethane layer was 300 μm. Further, the foaming ratio of the foamed polyurethane layer was 3.7 times.

[0065] On one hand, 11% by mass of silicone-modified polycarbonate-based polyurethane containing a red pigment was added to a polyurethane solution containing DMF as a solvent, and 10% by mass of one-end polyether-modified polydimethylsiloxane was added to the polyurethane solid content to prepare a first ink. The content ratio of silicon atoms contained in the first region formed by evaporating and drying the first ink was 4.7% by mass. The content ratio of silicon atoms contained in the first region was measured using a fluorescence X-ray apparatus ZSX Primun-μ (manufactured by Rigaku Corporation) with a film prepared by spreading 1.0 g of the ink on an aluminum dish and drying it at 120 °C for 2 hours under vacuum as a sample.

[0066] Then, the first ink was applied to the surface of the foamed polyurethane layer using a 150-mesh gravure roll so that the thickness after drying was about 16 μm to form an epidermal layer. This epidermal layer is entirely the first region and includes a 16-μm first region. And, 18 convex portions with an average depth of 60 μm per mm 2 An embossed pattern including an uneven surface was formed by performing die pressing at a temperature of 170 °C, a pressure of 15 kg / cm, and a processing speed of 1.5 m / min using an embossing roll having fine uneven patterns on the entire surface. In this way, artificial leather with a silver finish was manufactured.

[0067] The thickness (film thickness) of the epidermal layer was measured as follows. Three locations of the cross-section randomly selected from the obtained artificial leather with a silver finish were observed at 400 times magnification with a scanning electron microscope (SEM) to take images. Then, in the three images, the thickness of the epidermal layer and the thickness of the first region were measured five times at 50-μm intervals, and the average of the thicknesses of the epidermal layer in each image was obtained. Then, the average value of the averages of the thicknesses of the epidermal layer obtained from the three images was further calculated. The average value of the thickness of the epidermal layer obtained in this way was taken as the thickness of the epidermal layer.

[0068] Then, a 7 cm (vertical) × 4.5 cm (horizontal) piece was cut out from the obtained silver-colored artificial leather to prepare a test piece. The obtained test piece was immersed in hot water at 90°C contained in a wide-mouth bottle and left in a dryer at 90°C for 24 hours. Then, after 24 hours, the silver-colored artificial leather was taken out from the hot water and judged according to the following criteria. A: The epidermis layer was completely peeled off from the intermediate layer. B: There were gaps between the epidermis layer and the intermediate layer partially, and it was easily peeled off when pinched with fingers and pulled. C: The intermediate layer and the epidermis layer were not peeled off at all.

[0069] In addition, the obtained silver-colored artificial leather was left in a thermo-hygrostat at 90°C and 80% RH, taken out after 4 weeks, and judged according to the following criteria. A: The intermediate layer and the epidermis layer were not peeled off at all. B: Peeling was observed between the intermediate layer and the epidermis layer.

[0070] The results are shown in Table 1.

[0071]

Table 1

[0072] [Example 2] Instead of applying the ink so that the thickness after drying became about 16 μm, the silver-colored artificial leather was manufactured and evaluated in the same manner as in Example 1 except that the ink was applied so that the thickness after drying became about 8 μm. The results are shown in Table 1.

[0073] [Example 3] Instead of impregnating the non-woven fabric of the sea-island composite fiber with a polyurethane solution mainly containing polyester-based polyurethane, the silver-colored artificial leather was manufactured and evaluated in the same manner as in Example 1 except that it was impregnated with a polyurethane solution mainly containing a polyurethane containing a polymer polyol unit in which polycarbonate diol and polyester diol were mixed at a molar ratio of 60:40. The results are shown in Table 1.

[0074] [Example 4] A silver-coated artificial leather was produced and evaluated in the same manner as in Example 1, except that the ratio of the one-end polyether-modified polydimethylsiloxane to the polyurethane solid content contained in the first ink was changed from 10% by mass to 3% by mass. The results are shown in Table 1.

[0075] [Example 5] A first region was formed on the surface of the foamed polyurethane layer in the same manner as in Example 1, except that the ratio of the one-end polyether-modified polydimethylsiloxane to the polyurethane solid content contained in the first ink was changed from 10% by mass to 4% by mass, and the film thickness after drying was adjusted to 4 μm from 16 μm. Then, the same ink as the first ink prepared in Example 1 was used as the second ink on the surface of the first region, and the second ink was applied so that the thickness after drying became 4 μm and dried to form the second region. A silver-coated artificial leather was produced and evaluated in the same manner as in Example 1 except for the above. The results are shown in Table 1.

[0076] [Example 6] A first region was formed on the surface of the foamed polyurethane layer in the same manner as in Example 1, except that the ratio of the one-end polyether-modified polydimethylsiloxane to the polyurethane solid content contained in the first ink was changed from 10% by mass to 23% by mass, and the film thickness after drying was adjusted to 4 μm from 16 μm. Then, the same ink as the first ink prepared in Example 1 was used as the second ink on the surface of the first region, and the second ink was applied so that the thickness after drying became 8 μm and dried to form the second region. A silver-coated artificial leather was produced and evaluated in the same manner as in Example 1 except for the above. The results are shown in Table 1.

[0077] [Example 7] Instead of the one - terminal polyether - modified polydimethylsiloxane contained in the first ink, unmodified polydimethylsiloxane was blended, and a first region was formed on the surface of the foamed polyurethane layer in the same manner as in Example 1 except that the film thickness after drying was adjusted from 16 μm to 8 μm. Then, the same ink as the first ink prepared in Example 1 was used as the second ink, and the second ink was applied to the surface of the first region so that the thickness after drying would be 8 μm, and the second region was formed by drying. A silver - tinted artificial leather was produced and evaluated in the same manner as in Example 1 except for the above. The results are shown in Table 1.

[0078] [Example 8] The same ink as the first ink prepared in Example 1 was used as the second ink, and the second ink was applied to the surface of the first region so that the thickness after drying would be 4 μm, and the second region was formed by drying. A silver - tinted artificial leather was produced and evaluated in the same manner as in Example 1 except for the above. The results are shown in Table 1.

[0079] [Comparative Example 1] The silicone - modified polycarbonate - based polyurethane contained in the first ink was changed to unmodified polycarbonate - based polyurethane, and a first ink not containing one - terminal polyether - modified polydimethylsiloxane was used to form a first region with a film thickness of 8 μm after drying. Then, the same ink as the first ink prepared in Example 1 was used as the second ink, and the second ink was applied to the surface of the first region so that the thickness after drying would be 4 μm, and the second region was formed by drying. A silver - tinted artificial leather was produced and evaluated in the same manner as in Example 1 except for the above. The results are shown in Table 1.

[0080] [Comparative Example 2] A first ink not containing one - terminal polyether - modified polydimethylsiloxane was used to form a first region with a film thickness of 16 μm after drying. A silver - tinted artificial leather was produced and evaluated in the same manner as in Example 1 except for the above. The results are shown in Table 1.

[0081] Referring to Table 1, the silver-coated artificial leathers obtained in Examples 1 to 8, each having an epidermal layer including a first region with a thickness of 4 μm or more directly contacting the intermediate layer and containing silicone-modified polyurethane and organopolysiloxane, had their epidermal layers peeled off when immersed in hot water at 90°C for 24 hours. In Example 4 where the silicon atom content ratio was 2.8% by mass, it did not peel off naturally but peeled off by pulling with a slight force. On the other hand, the silver-coated artificial leather of Comparative Example 1, which does not contain silicone-modified polyurethane and organopolysiloxane and does not contain silicon atoms, did not have its epidermal layer peeled off even when immersed in hot water at 90°C for 24 hours. Also, the silver-coated artificial leather of Comparative Example 2, which contains silicone-modified polyurethane but does not contain organopolysiloxane and has a low silicon atom content ratio, did not have its epidermal layer peeled off even when immersed in hot water at 90°C for 24 hours.

Explanation of Symbols

[0082] 1 Fiber complex 2 Intermediate layer 2a Laminated region laminated on fiber complex 1 2b Impregnated region impregnated in fiber complex 1 3 Epidermal layer 10 Silver-coated artificial leather v Void

Claims

1. A silver-toned artificial leather comprising a fiber complex, an intermediate layer containing a foamed polyurethane integrated with the fiber complex, and an epidermal layer having a thickness of 4 to 20 μm laminated on the intermediate layer, wherein the epidermal layer includes at least a first region having a thickness of 4 μm or more in contact with the intermediate layer and containing a silicone-modified polyurethane and an organic polysiloxane.

2. The silver-toned artificial leather according to Claim 1, wherein the first region contains 3.0% by mass or more of silicon atoms.

3. The silver-toned artificial leather according to Claim 1 or 2, wherein the epidermal layer is peeled from the intermediate layer when immersed in hot water at 90° C. for 24 hours.

4. The silver-toned artificial leather according to any one of Claims 1 to 3, wherein the epidermal layer further includes a second region coating the first region.

5. A step of preparing a base material including a fiber complex and an intermediate layer containing a foamed polyurethane integrated with the fiber complex; a step of forming an epidermal layer including at least a first region having a thickness of 4 μm or more by gravure coating an ink containing a silicone-modified polyurethane and an organic polysiloxane on the surface of the intermediate layer and then drying. A method for producing a silver-toned artificial leather, characterized by comprising:

6. A step of preparing the silver-toned artificial leather according to any one of Claims 1 to 4; a step of separating and recovering the epidermal layer of the silver-toned artificial leather by immersing the silver-toned artificial leather in hot water to peel the epidermal layer from the intermediate layer. A method for separately recovering the epidermal layer of a silver-toned artificial leather, characterized by comprising:

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