Grainy imitation leather sheet

Abstract

A grainy imitation leather sheet comprises a fiber substrate and a resin layer laminated on one side of the aforementioned fiber substrate. The resin layer includes at least a skin layer, which comprises polyurethane, a nonionic compound with an HLB value of 10-16, and a water-soluble polymer. It has a surface free energy, as determined by the OWRK method, of a polar component of 25-40 mJ / m² and a dispersed component of 30-40 mJ / m².

Description

Technical Field

[0001] This invention relates to a grained imitation leather sheet that combines high wettability, high water resistance, and high secondary adhesion. Prior Technology

[0002] As materials for shoes, bags, or clothing, grain-like imitation leather sheets, such as artificial leather or synthetic leather, with a grain-like resin layer are known. Typical grain-like imitation leather sheets have a fiber substrate and a resin layer containing polyurethane laminated on the fiber substrate.

[0003] In recent years, in the manufacture of grainy imitation leather sheets, in order to reduce the environmental impact, there has been a demand for a manufacturing method that uses an aqueous polyurethane emulsion or other aqueous polyurethane solution that can be dispersed in an aqueous medium, which reduces the amount of organic solvents used. For example, Patent Document 1 discloses a grainy artificial leather that has a grainy layer formed by an aqueous polyurethane resin dispersion on at least one side of a matrix layer made of a three-dimensional entangled nonwoven fabric and a polymer elastomer provided by an aqueous resin dispersion.

[0004] Furthermore, Patent Document 2 below discloses a method for manufacturing a porous structure for imitation leather sheet, characterized in that a mixture comprising at least one of the following groups, in addition to (A) an aqueous thermoplastic binder and (B) a carbamate prepolymer terminal isocyanate end-capping agent, is applied to a substrate, and then the porous body is formed by heating with steam, high frequency heating or high frequency induction heating, and then dried.

[0005] However, when processing grained imitation leather sheets into secondary products such as shoes, bags, or clothing, the surface treatment or secondary adhesion of the grained resin layer is required. The surface treatment of grained imitation leather sheets refers to, for example, applying a treatment liquid containing pigments, matting agents, antibacterial agents, etc., to the surface of the resin layer using gravure coating or similar methods to adjust its surface properties. Furthermore, the secondary adhesion of grained imitation leather sheets refers to the adhesion when other materials are bonded to the surface of the grained resin layer with an adhesive.

[0006] Polyurethane used to form a granular resin layer, when an aqueous polyaminoformate formed by using aqueous polyaminoformate, mostly contains aqueous polyaminoformates with relatively high hydrophobicity in order to maintain the preservation stability of the aqueous polyaminoformate liquid. When such an aqueous polyaminoformate liquid comprising a relatively highly hydrophobic aqueous polyaminoformate liquid is used to form a granular resin layer, there is a problem of low wettability for highly polar aqueous treatment liquids as the surface of the resin layer also becomes more hydrophobic.

[0007] To solve such a problem, for example, the following patent literature 3 reveals a leather-like sheet material, which is formed by forming an epidermal layer containing aqueous polyaminoformate on a deformed sheet by coating and drying with an aminoformate resin composition. Moreover, patent literature 3 reveals that by adjusting the ratio of hydrophilic to hydrophobic components, the polarity of the aqueous polyaminoformate is improved, maintaining the water resistance while improving the secondary sequestration. [Previous technical literature] [Patent Literature]

[0008] Patent Literature 1: Bulletin of Japan Special Kai 2003-155672 Patent literature 2: Japan Special Bulletin 2002-249987 Patent Literature 3: International Publication Booklet No. 2012 / 017724 Contents of the invention

[0009] [Invention of topics to solve]

[0010] In order to manufacture grain-like leather-like sheets with high water resistance, a resin layer containing polyurethane with high water resistance is mostly used. In the imitation leather sheets as revealed in patent literature 3 , the polarity becomes difficult to improve sufficiently when the water resistance of the surface of the resin layer is improved. Therefore, in the case of imitation leather sheets as revealed in patent literature 3, which further improves water resistance, it is considered that the sufficiently high wettability to aqueous liquids required for surface treatment with high polarity treatment liquids cannot be obtained. Also, in order to further improve the wettability of the surface of the resin layer, the water resistance is considered to be reduced when increasing the ratio of hydrophilic components in the polyurethane. In this way, the wettability and water resistance of the surface of the resin layer are in a trade-off relationship.

[0011] Also, for grained imitation leather sheets, as described above, sometimes high secondary adhesion is required. Previous resin layers containing aqueous polyurethane had low secondary connectivity even with high wettability.

[0012] Thus, it is impossible to obtain a grainy imitation leather sheet that combines high wettability to aqueous liquids, high water resistance, and high re-adhesion.

[0013] The purpose of this invention is to provide a grainy imitation leather sheet that combines high wettability to aqueous liquids, high water resistance, and high re-adhesion. [Methods used to solve problems]

[0014] One embodiment of the present invention is a grainy imitation leather sheet, comprising a fiber substrate and a resin layer deposited on one side of the fiber substrate, the resin layer including at least a skin layer. Furthermore, the skin layer comprises polyurethane, a nonionic compound with an HLB value of 10-16, and a water-soluble polymer, and the skin layer has a surface free energy of 25-40 mJ / m² for the polar component and 30-40 mJ / m² for the dispersed component, as determined by the Owens-Wendt-Rabel-Kaelble method (hereinafter also referred to as the OWRK method). According to such a grainy imitation leather sheet, a grainy imitation leather sheet with a resin layer surface possessing both high wettability, high water resistance, and high secondary adhesion can be obtained. Moreover, such polyurethane is typically an aqueous polyurethane dispersible in an aqueous medium.

[0015] Furthermore, polyurethanes with surface free energy of 5~20 mJ / m² for polar components and 30~40 mJ / m² for dispersed components as determined by the OWRK method are more suitable from the perspective of obtaining granular imitation leather sheets that combine high wettability, high water resistance and high secondary adhesion.

[0016] In addition, nonionic compounds that include at least one of the groups comprising polysiloxane compounds and acetylene glycol compounds are preferred from the point that even a small amount of addition can significantly improve the surface free energy.

[0017] Furthermore, those with a skin layer containing 0.8 to 5.0% by mass of nonionic compounds are preferable from the perspective of not reducing water resistance or secondary adhesion and easily maintaining sufficient wettability.

[0018] Furthermore, water-soluble polymers with a number average molecular weight of 10,000 to 150,000, and containing 1.0 to 10% by mass of water-soluble polymers, are preferable from the perspective of not reducing water resistance and easily maintaining high secondary adhesion.

[0019] In addition, a continuous membrane with a thickness of 10~100μm and no pores is preferable, as it has no depressions on the surface of the epidermis, resulting in a more aesthetically pleasing appearance.

[0020] Furthermore, the resin layer includes at least an adhesive layer with a thickness of 30 to 120 μm, which includes a polyurethane adhesive layer for bonding to the fiber substrate, and is preferable from the point of view that the resin layer can be strongly bonded to the fiber substrate. [Effects of the Invention]

[0021] According to the present invention, a grainy imitation leather sheet can be obtained, which has both high wettability to aqueous liquids, high water resistance, and high secondary adhesion. Simple Explanation of the Diagram

[0022] Figure 1 is a schematic cross-sectional view illustrating one example of the implementation of a grainy imitation leather sheet 10. Implementation

[0023] [The form in which the invention is carried out]

[0024] The present invention will now be described in detail with reference to one embodiment of a grainy imitation leather sheet.

[0025] Referring to FIG1, one embodiment of the grainy imitation leather sheet 10 includes a fiber substrate 1 and a resin layer 2 deposited on one surface of the fiber substrate 1. The resin layer 2 includes a skin layer 2a, an intermediate layer 2b, and an adhesive layer 2c.

[0026] The adhesive layer 2c is a polyurethane layer used to bond the resin layer 2 to the fiber substrate 1. Furthermore, the intermediate layer 2b, located between the skin layer 2a and the adhesive layer 2c, is a polyurethane layer selected for purposes such as adjusting surface texture.

[0027] Furthermore, the skin layer 2a is preferably disposed on the outermost layer of the resin layer, and is a polyurethane as the main body layer for imparting high wettability, high water resistance and high secondary adhesion to the surface of the resin layer. Specifically, the skin layer 2a comprises at least polyurethane, a nonionic compound with an HLB value of 10 to 16 and a water-soluble polymer, and is a polyurethane as the main body layer having a surface free energy of 25 to 40 mJ / m² for polar components and 30 to 40 mJ / m² for dispersed components as determined by the OWRK method.

[0028] The grained imitation leather sheet of this embodiment, as exemplified by grained imitation leather sheet 10, has a resin layer deposited on one side of a fiber substrate. This resin layer includes at least a skin layer, which comprises at least polyurethane, a nonionic compound with an HLB value of 10-16, and a water-soluble polymer. This resin layer imparts a grained appearance to the grained imitation leather sheet. Furthermore, the resin layer may, as required, include, as described above, an adhesive layer for bonding the skin layer to the fiber substrate, or an intermediate layer for adjusting the surface texture, or other layers.

[0029] The fiber substrate is a woven fabric, a knitted fabric, a non-woven fabric, or a combination of these fiber entanglements. Among these, non-woven fabric is particularly preferred from the perspective of maintaining a soft texture. Furthermore, the fiber substrate may also contain a polymeric elastomer impregnated into the voids of the fiber entanglement.

[0030] There are no particular restrictions on the types of resins that form fibers. Specifically, examples include aromatic polyesters such as polyethylene terephthalate (PET), phthalic acid-modified polyethylene terephthalate, sulfonated isophthalic acid-modified polyethylene terephthalate, polybutylene terephthalate, and polyhexamethylene terephthalate; fatty acid polyesters such as polylactic acid, polyethylene succinate, polybutylene succinate, polybutylene adipate, and polyhydroxybutyrate-polyhydroxyvalerate copolymer; nylons such as nylon 6, nylon 66, nylon 10, nylon 11, nylon 12, and nylon 6-12; polyolefins such as polypropylene, polyethylene, polybutene, polymethylpentene, and chlorinated polyolefins; modified polyvinyl alcohol such as modified polyvinyl alcohol containing 25-70 moles of ethylene units; and elastomers such as polyurethane elastomers, polyamide elastomers, and polyester elastomers. Among these, PET, phthalic acid-modified polyethylene terephthalate, polylactic acid, nylon 6, nylon 12, nylon 6-12, copolymers of nylon, and polypropylene are particularly preferred in terms of their superior spinning properties and the resulting artificial leather. These resins can be used individually or in combination of two or more.

[0031] Furthermore, there is no particular limitation on the fineness of the fibers forming the fiber substrate, but from the point of obtaining a soft texture, it is particularly desirable to have extremely fine fibers with an average fineness of 0.001 to 0.5 dtex.

[0032] Furthermore, the fiber substrate may contain a polymeric elastomer impregnated into the voids of the fiber entanglement. Specific examples of polymeric elastomers impregnated into the voids of the fiber entanglement include polyurethane, acrylonitrile-based elastomers, olefin-based elastomers, polyester-based elastomers, polyamide-based elastomers, and acrylic elastomers. Among these, cross-linked waterborne polyurethane obtained by solidifying a polyurethane emulsion is particularly preferred from the viewpoint of reducing the amount of organic solvent used.

[0033] The proportion of polymeric elastomer in the fiber substrate is not particularly limited, but it is preferably 5-60% by mass, more preferably 8-40% by mass. Furthermore, the thickness of the fiber substrate is not particularly limited, but it is preferably 0.2-3.0 mm.

[0034] The grained imitation leather sheet of this embodiment, as exemplified by grained imitation leather sheet 10, has a resin layer deposited on one side of a fiber substrate. This resin layer includes at least a skin layer, which comprises at least polyurethane, a nonionic compound with an HLB value of 10-16, and a water-soluble polymer. This resin layer imparts a grained appearance to the grained imitation leather sheet. Furthermore, the resin layer may, as required, include, as described above, an adhesive layer for bonding the skin layer to the fiber substrate, or an intermediate layer for adjusting the surface texture, or other layers.

[0035] In this embodiment, the polyurethane is preferably an aqueous polyurethane dispersion derived from an emulsion or dispersion of polyurethane or its prepolymer dispersed in water or an aqueous medium primarily composed of water. Aqueous polyurethane is distinct from solvent-based polyurethane solutions derived from polyurethane solutions dissolved in organic solvents. For example, aqueous polyurethane is obtained by reacting an urethane raw material containing a high molecular weight polyol, an organic polyisocyanate, a chain extender, and, where desired, a multifunctional compound.

[0036] Specific examples of high molecular weight polyols include polyether polyols and their copolymers such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and poly(methyltetramethylene glycol); polyester polyols and their copolymers such as polybutylene adipate diol, polybutylene sebacate diol, polyhexamethylene adipate diol, poly(3-methyl-1,5-pentylene adipate) diol, poly(3-methyl-1,5-pentylene sebacate) diol, and polycaprolactone diol; polycarbonate polyols and their copolymers such as polyhexamethylene carbonate diol, poly(3-methyl-1,5-pentylene carbonate) diol, polypentamethylene carbonate diol, and polytetramethylene carbonate diol; and polyester carbonate polyols. Furthermore, depending on the need, polyfunctional alcohols such as trifunctional or tetrafunctional alcohols or short-chain alcohols such as ethylene glycol can also be used in combination. These can be used alone or in combination of two or more.

[0037] Furthermore, specific examples of organic polyisocyanates include non-yellowing diisocyanates such as aliphatic or alicyclic diisocyanates like hexamethylene diisocyanate, isoflavone diisocyanate, norcamphene diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate; and aromatic diisocyanates such as 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, and phenyl dimethyl diisocyanate. Additionally, polyfunctional isocyanates such as trifunctional isocyanates may be used in combination as needed. These can be used alone or in combination of two or more.

[0038] Specific examples of chain-stretching agents include hydrazine, ethylenediamine, propylenediamine, hexamethylenediamine, nonamethylenediamine, phenylenediamine, isophoronediamine, and piperazine. Diamines such as diazinonedioic acid and diazinonedioic acid; triamines such as diethylenetriamine; tetraamines such as triethylenetetramine; diols such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,4-bis(β-hydroxyethoxy)benzene, and 1,4-cyclohexanediol; triols such as trimethylolpropane; pentaols such as pentaerythritol; and amino alcohols such as aminoethyl alcohol and aminopropyl alcohol. These can be used alone or in combination of two or more.

[0039] Examples of crosslinking agents include difunctional polyisocyanate compounds that form crosslinking structures with hydroxyl or amine groups; polyfunctional isocyanate compounds such as biuret type, addition type, and isotricyanate type; and crosslinking agents having carbodiimide groups that form crosslinking structures with carboxyl groups. Compounds of zolyl, epoxy, cyclic carbonate, aziridinyl, or hydrazine derivatives or acehydrazine derivatives, etc. These can be used alone or in combination of two or more. When using a crosslinking agent, the preferred blending ratio of the crosslinking agent relative to the aqueous polyurethane is 2-20% by mass.

[0040] Preferably, the outermost skin layer, which is configured as the outermost layer of the resin layer, comprises at least polyurethane, a nonionic compound with an HLB value of 10-16, and a water-soluble polymer, and has a surface free energy of 25-40 mJ / m² for the polar component and 30-40 mJ / m² for the dispersed component as determined by the OWRK method. Preferably, the skin layer contains at least 90% by mass of water-based polyurethane, particularly at least 95% by mass of water-based polyurethane.

[0041] Here, surface free energy refers to the surface tension, which is composed of the sum of intermolecular forces held by the solid. Furthermore, the polar and dispersion components of the surface free energy analyzed by the Owens-Wendt-Rabel-Kaelble method (OWRK method) are each components of the intermolecular forces analyzed by the OWRK method. The polar component reflects the orientation forces of the solid, while the dispersion component reflects the dispersion forces of the solid.

[0042] The skin layer of this embodiment has a surface free energy of 25~40 mJ / m² for the polar component and 30~40 mJ / m² for the dispersed component, as determined by the OWRK method. Due to the presence of such polar and dispersed components in the surface free energy of the skin layer, a grained imitation leather sheet with excellent balance between water resistance and wettability can be obtained.

[0043] When the polar component of the surface free energy of the epidermis is less than 25 mJ / m², wettability tends to decrease. Furthermore, when the polar component of the surface free energy of the epidermis exceeds 40 mJ / m², secondary adhesion tends to decrease. When the dispersed component of the surface free energy of the epidermis is less than 30 mJ / m², secondary adhesion tends to decrease. Additionally, when the dispersed component of the surface free energy of the epidermis exceeds 40 mJ / m², wettability tends to decrease.

[0044] A skin layer with such surface free energy can be obtained by adjusting the type of polyurethane contained in the skin layer or by adding nonionic compounds and water-soluble polymers with an HLB value of 10 to 16 to adjust the surface free energy of the skin layer, or by adding them in a certain proportion.

[0045] The polyurethane contained in the epidermis is preferably an aqueous polyurethane having a surface free energy of 3-25 mJ / m², more preferably 10-20 mJ / m², and a dispersion component of 30-40 mJ / m². Here, the surface free energy of the polyurethane refers to the surface free energy of a polyurethane that does not contain nonionic compounds and water-soluble polymers with an HLB value of 10-16.

[0046] The polar and dispersive components of the surface free energy of polyurethane can be varied by adjusting the ratio of hydrophilic to hydrophobic components in the soft segments of the polyol units derived from polyurethane.

[0047] Specifically, when the ratio of hydrophilic components in the polymer polyol is increased, the polar component increases; when the ratio of hydrophobic components is increased, the dispersing component increases. Furthermore, when the polar component of the surface free energy of polyurethane is large, the polar component of the surface free energy of the epidermis also increases; when the dispersing component is large, the dispersing component of the surface free energy of the epidermis also increases.

[0048] The hydrophilic component of the soft segment originates from the repeating structure of a polymeric polyol unit with 1 to 3 carbon atoms after the ester bond is removed. Specific examples of such hydrophilic polymeric polyols include 2-carbon polymeric polyols such as polyethylene glycol and 3-carbon polymeric polyols such as polypropylene glycol.

[0049] The hydrophobic component of the soft segment originates from the repeating structure of a polymeric polyol unit with 4 to 6 carbon atoms after the ester bond is removed. Specific examples of such hydrophobic polymeric polyols include polytetramethylene glycol (4 carbon atoms), polypentamethylene glycol (5 carbon atoms), and polyhexamethylene carbonate glycol (6 carbon atoms).

[0050] For the surface free energy polarity of polyurethane adjusted as described above, considering both water resistance and excellent secondary adhesion, a value of 3~25 mJ / m² is preferred, and more preferably 10~20 mJ / m². If the surface free energy polarity of the polyurethane is too low, the polarity of the skin layer also decreases, reducing the adhesion of adhesives or thermoplastic urethane resins, and tending to decrease secondary adhesion. Conversely, if the surface free energy polarity of the polyurethane increases, the polarity of the skin layer also increases, resulting in higher secondary adhesion, but tending to decrease water resistance.

[0051] Furthermore, polyurethanes with a surface free energy dispersion of 30-40 mJ / m² are preferable from the perspective of balancing excellent water resistance and secondary adhesion. If the surface free energy dispersion of the polyurethane is too small, there is a tendency for reduced secondary adhesion.

[0052] Specific examples of such polyurethanes include waterborne polyurethanes contained in DIC-manufactured Hydran ULK-190 or Hydran ULK-003, which are polyurethane emulsions.

[0053] The epidermal layer contains nonionic compounds with an HLB value of 10–16. The HLB value (Hydrophilic-Lipophilic Balance) indicates the degree of affinity of a surfactant for water and oil. HLB values ​​range from 0 to 20; the closer to 0, the higher the lipophilicity, and the closer to 20, the higher the hydrophilicity. By incorporating nonionic compounds with an HLB value of 10–16 into the epidermal layer, the surface free energy of the epidermal layer is increased, thereby improving the wettability required for surface treatment. The HLB value is calculated, for example, using the Griffin method: HLB value = 20 × (total molecular weight of the hydrophilic portion / total molecular weight).

[0054] By incorporating nonionic compounds with HLB values ​​of 10 to 16 into the epidermis, the polar components of the epidermal surface can be increased, thereby improving wettability. On the other hand, even with the incorporation of nonionic compounds with HLB values ​​of 10 to 16 into the epidermis, secondary adhesion is difficult to improve.

[0055] When the HLB value of a nonionic compound is less than 10, the polar component of the surface free energy of the epidermis is difficult to increase sufficiently due to the low hydrophilicity of the nonionic compound. Conversely, when the HLB value of a nonionic compound exceeds 16, the water resistance of the epidermis tends to decrease due to the high hydrophilicity of the nonionic compound.

[0056] Specific examples of nonionic compounds with an HLB value of 10 to 16 include polysiloxanes such as polyether-modified polydimethylsiloxanes, acetylene glycol compounds, polyoxyethylene alkyl ether compounds, polyoxyethylene alkyl allyl ether compounds, polyoxyethylene-polyoxypropylene block copolymer compounds, and fluorine compounds such as organofluorine compounds, all of which have an HLB value of 10 to 16. These can be used alone or in combination of two or more. Among these, polysiloxane compounds or acetylene glycol compounds are preferred, and polyether-modified polydimethylsiloxane compounds are more preferred, considering that adding a small amount can significantly increase the surface free energy.

[0057] The preferred content of nonionic compounds with an HLB value of 10-16 in the epidermal layer is 0.8-5.0% by mass, more preferably 1.2-4.0% by mass. If the content of nonionic compounds with an HLB value of 10-16 is too low, the surface free energy of the epidermal layer may not be sufficiently enhanced, leading to insufficient wettability. Conversely, if the content of nonionic compounds with an HLB value of 10-16 is too high, the nonionic compounds may be incorporated into the surface of the epidermal layer, potentially reducing water resistance or secondary adhesion.

[0058] Furthermore, the epidermis contains water-soluble polymers. Due to their high polarity and surface free energy, these polymers readily penetrate the molecular network of the water-based polyurethane in the epidermis. Therefore, increasing the polarity of the epidermis enhances secondary adhesion.

[0059] Furthermore, as mentioned above, increasing the proportion of hydrophilic components in the soft segments of polyurethane can increase the polar component of the polyurethane. However, excessively increasing the polar component by increasing the proportion of hydrophilic components in the soft segments of polyurethane can lead to a decrease in water resistance because polyurethane easily swells in water. In the skin layer of this embodiment, by incorporating a water-soluble polymer, the polar component of the polyurethane is not made too large, thus avoiding a decrease in water resistance, and secondary adhesion can be selectively improved.

[0060] Water-soluble polymers refer to polymers that, when mixed with water, can produce a solution of 10g or more dissolved in 1L of water. Specific examples include polyurethane-modified polyoxyethylene, polyethylene glycol, polyvinyl alcohol, and polyvinylpyrrolidone. These can be used alone or in combination of two or more. Among these, polyurethane-modified polyoxyethylene is particularly suitable because its strong interaction with water-based polyurethanes allows it to easily penetrate the network of polyurethane molecules in the epidermis, thus increasing the polar components of the epidermis.

[0061] The number average molecular weight of the water-soluble polymer is 10,000 or higher, preferably 10,000 to 150,000, and more preferably 30,000 to 120,000. When the number average molecular weight is too low, the improvement effect on secondary adhesion tends to be smaller. Conversely, when the number average molecular weight is too high, water resistance tends to decrease.

[0062] The preferred proportion of water-soluble polymer in the epidermal layer is 1.0 to 10% by mass, more preferably 2.0 to 8.0% by mass. If the proportion of water-soluble polymer is too low, there is a tendency for the polar components of the surface free energy of the epidermal layer to not increase sufficiently. Conversely, if the proportion of water-soluble polymer is too high, there is a concern that the water resistance of the epidermal layer may decrease.

[0063] Within the skin layer, without impairing the effects of the present invention, additives such as defoamers, leveling agents, thickeners, pigments, dyes, matting agents, organic solvents, and resin beads may be included as needed.

[0064] There is no particular limitation on the thickness of the epidermis, but it is preferably 10~100μm, more preferably 10~50μm. The thickness of the epidermis can be calculated, for example, from cross-sectional images obtained by scanning electron microscopy (SEM).

[0065] Furthermore, a continuous membrane without pores is preferable, as it results in a more aesthetically pleasing appearance due to the absence of depressions on its surface. When the epidermis has pores, depressions can form on its surface during secondary processing, leading to undesirable appearance.

[0066] The grainy imitation leather sheet of this embodiment contains at least a skin layer as described above, and may further include, as needed, an adhesive layer for bonding the skin layer to the fiber substrate or a layer containing other resins, such as an intermediate layer, for adjusting the texture of the surface.

[0067] Next, an example of a method for manufacturing the grained imitation leather sheet of this embodiment will be described. The method for manufacturing the grained imitation leather sheet of this embodiment is the same as that for conventional methods for manufacturing grained imitation leather sheets, except that the resin layer that imparts the grained appearance contains the epidermal layer as described above.

[0068] For example, a fiber substrate as described above is prepared, and a resin layer is formed to impart a granular appearance to one side of the fiber substrate. Specifically, for example, a dry surface-forming method can be used, in which a film of a resin layer formed on release paper is attached to the surface of the fiber substrate, and the fiber substrate is laminated to the resin layer by peeling off the release paper.

[0069] Specifically, a coating liquid for forming the epidermis is first applied to the release paper, and then dried to form a film that becomes the epidermis.

[0070] The coating system for the surface layer is a mixture of aqueous polyurethane emulsions or dispersions containing aqueous polyurethane, nonionic compounds with an HLB value of 10-16, water-soluble polymers, and crosslinking agents or additives as needed. It is preferable to use water-soluble polymers and nonionic compounds with an HLB value of 10-16 in liquid form, such as aqueous solutions or oils, for ease of mixing.

[0071] There is no particular limitation on the concentration of the solid component of the aqueous polyurethane in the aqueous polyurethane solution, but it is preferably about 20-60% by mass. Similarly, there is no particular limitation on the concentration of the solid component of the aqueous solution of the water-soluble polymer, but it is preferably about 20-60% by mass.

[0072] Then, a coating solution for the skin layer is applied to the release paper and dried. The drying conditions are not particularly limited, but drying at 70-130°C for 1-10 minutes is preferred. In this way, a film forming the skin layer is created on the release paper.

[0073] Then, a film forming an intermediate layer or adhesive layer is formed on the surface of the film that forms the skin layer on the release paper. There are no particular limitations on the resin system used to form the intermediate layer or adhesive layer, but polyurethane is preferred from the perspective of excellent adhesion to other layers. Furthermore, waterborne polyurethane is particularly preferred from the perspective of reducing the amount of organic solvent used.

[0074] The polyurethane used in the adhesive layer can be a solvent-based polyurethane dissolved in organic solvents, or it can be an aqueous polyurethane. However, from the perspective of reducing organic solvents, an aqueous polyurethane is preferred. Furthermore, in order to improve adhesion to the substrate, a crosslinking agent is preferably incorporated into the adhesive layer.

[0075] The crosslinking agent for the polyurethane used as the adhesive layer can be any well-known polyurethane crosslinking agent without particular limitation. Specifically, examples include epoxy compounds, aziridine compounds, carbodiimide compounds, organic polyisocyanate compounds, etc. Azoline compounds, melamine-formamide compounds, urea hydroxymethyl compounds, etc. These can be used alone or in combination of two or more.

[0076] Furthermore, the intermediate layer is a layer configured as needed to adjust the thickness of the granular resin layer of the granular imitation leather sheet. The polyurethane used in the intermediate layer can be a solvent-based polyurethane dissolved in organic solvents, or it can be an aqueous polyurethane. However, from the perspective of reducing organic solvents, an aqueous polyurethane is preferred.

[0077] The adhesive layer is formed by coating an adhesive layer solution onto the surface of a film forming the skin layer on the release paper and then drying it. Similarly, the intermediate layer is formed by coating an intermediate layer solution onto the surface of a film forming the skin layer on the release paper and then drying it. Furthermore, when an intermediate layer is formed, an adhesive layer is formed by coating an adhesive layer solution onto the surface of a film layered with both the skin layer and the intermediate layer on the release paper and then drying it. Each layer can be a single layer or a plurality of layers composed of solutions with different compositions. The films forming the intermediate layer and the adhesive layer are formed in the same manner as the films forming the skin layer.

[0078] The thickness of the intermediate layer is not particularly limited, but it is preferably 10~50μm, more preferably about 20~40μm. Similarly, the thickness of the next layer is not particularly limited, but it is preferably 30~130μm, more preferably about 50~100μm.

[0079] Then, the resulting stack (adhesive layer / outer layer / release paper, or adhesive layer / intermediate layer / outer layer / release paper) is deposited onto the surface of the fiber substrate through the adhesive layer, and a resin layer is bonded onto the surface of the fiber substrate by applying pressure with a gap roller or the like. Furthermore, if necessary, cross-linking of the polyurethane contained in the adhesive layer can be promoted by curing at 40-90°C for approximately 1-3 days. By peeling the release paper off the thus obtained stack, a grained imitation leather sheet is obtained.

[0080] The resulting grainy imitation leather sheet exhibits excellent processability for secondary products such as shoes, bags, and clothing. Specifically, when a treatment solution containing pigments, matting agents, and antibacterial agents is applied to the surface of the resin layer using methods such as gravure coating, it displays excellent wetting properties with highly polar aqueous treatment solutions. Furthermore, when other materials are bonded to the surface of the resin layer with adhesives, it exhibits particularly excellent adhesion to adhesives containing water-based polyurethane or hot-melt polyurethane adhesives. [Example]

[0081] The present invention will now be described in more detail by way of examples. Furthermore, the scope of the present invention is not limited to the examples. Hereinafter, parts and percentages are based on mass unless otherwise specified.

[0082] First, the evaluation methods used in the embodiments are summarized and explained below.

[0083] [Calculation of the polar and dispersed components of the surface free energy of polyurethane and its epidermis] Using pure water and methylene chloride as test solutions, the polar and dispersed components of the surface free energy of polyurethane and the epidermis were analyzed by the OWRK method. Specifically, regarding the surface free energy of polyurethane, a polyurethane emulsion flows into a mold of a specific size with release paper having a smooth surface, and by drying the emulsion, a polyurethane film with a thickness of about 50 mm is formed. Then, 1 μL of pure water and diiodomethane were dropped onto the surface of the polyurethane film using a syringe, and the contact angles of each droplet were measured using a contact angle meter (CA-DT manufactured by Kyowa Interface Science Co., Ltd.). Furthermore, the ambient temperature for the measurement was 25°C and 50% RH. Then, according to OWRK analysis, the following equation (1) is used to solve the simultaneous equations and calculate the polar component γp and the dispersion component γd of the surface free energy of the polyurethane film surface. 1+cosθ=2[(γ d·γ L d) / γ L 2] 1 / 2+2[(γ p·γ L p) / γ L 2] 1 / 2···Formula (1) The symbols in equation (1) represent the following. •γd: Dispersion component of surface free energy of polyurethane film surface (mJ / m2) • γp: Polar component of the surface free energy of polyurethane film (mJ / m2) ·θ: Contact angle (°) of each test solution • γ L d: Dispersed component of surface free energy of each test solution (mJ / m 2) (water: 21.8 mJ / m 2, diiodomethane: 49.5 mJ / m 2) • γ Lp: Polar component of surface free energy of each test solution (mJ / m²) (water: 51.0 mJ / m², diiodomethane: 1.3 mJ / m²) γL: Surface free energy of the test solution Similarly, a coating solution for forming the epidermis of a grainy imitation leather sheet was used to form a film. The contact angles of the epidermis surface with pure water and diiodomethane were measured. According to OWRK analysis, the polar component γp and the dispersed component γd of the surface free energy of the epidermis of the grainy imitation leather sheet were calculated using Equation (1).

[0084] [Number-average molecular weight of water-soluble polymers] The number average molecular weight was determined by gel permeation chromatography (GPC) under the following conditions and was used as a conversion value for standard polystyrene. (GPC measurement conditions) Device: "CBM-20A", manufactured by Shimadzu Corporation. Mobile phase: N,N-dimethylformamide (flow rate: 1 mL / min) Tubing string: Shodex KD-806M Detector: Differential refractometer Measurement temperature: 40℃ Standard material: Polystyrene, manufactured by Tosoh Corporation Injection volume: 50μL Sample concentration: 2mg / 2cc

[0085] [Water resistance of the epidermis] Cut 3cm x 3cm film sheets from the outer layer of the grain-like imitation leather sheet. Then, immerse the film sheets in water at 25°C for 24 hours, and then remove the film sheets. Then, measure the weight of the film sheets after wiping off any excess water, and calculate the weight swelling rate (%) according to the following formula. Weight swelling percentage (%) = {(weight after swelling – weight before impregnation) / weight before impregnation} × 100 Water resistance is determined based on the obtained weight swelling rate value according to the following evaluation criteria. Advantages: Weight swelling rate less than 5% Good: Weight swelling percentage is 5% or more and less than 15%. Inferior: Weight swelling rate is above 15%

[0086] [Wetness of the surface of the epidermis] According to JIS K6768, the wettability of the surface of the epidermis of a grained imitation leather sheet was determined. Specifically, a wettability test solution (wetting tension test solution manufactured by Kanto Chemical Co., Ltd.: 65 mJ / m²) was applied to the surface of the epidermis of the grained imitation leather sheet using a wireless bar coater with a wet film thickness of 12 μm. Then, a liquid film that did not break for more than 5 seconds was rated as "high", a liquid film that broke for more than 2 seconds but less than 5 seconds was rated as "medium", and a liquid film that broke for less than 2 seconds was rated as "low".

[0087] [Secondary adhesion of the epidermal surface] Prepare grained imitation leather sheets, hot melt adhesive tape, and plain woven fabric, each cut into strips 150mm long and 30mm wide. Furthermore, use 200μm thick thermoplastic urethane hot melt adhesive tape (NASA-T manufactured by Sambu Fine Chemical). Also, the plain woven fabric has a unit area of ​​1.3g / m². Then, on the surface of the grainy imitation leather sheet, a stack of hot melt adhesive tape and plain woven fabric, sequentially layered, is pressed together at 130°C and 6 kgf / cm² for 30 seconds to create a test piece. Furthermore, only one end is designated as the unbonded section, with a 30mm longitudinal region extending from the end, followed by the remaining 120mm longitudinal region.

[0088] Then, a tensile testing machine was used to determine the peel strength of the hot melt adhesive tape bonded to the surface of the grained imitation leather sheet. Specifically, the unbonded end of the obtained test piece of grained imitation leather sheet and the unbonded end of the plain weave fabric were clamped in the upper and lower jaws of the tensile testing machine, and the peel strength between the hot melt adhesive tape and the surface of the imitation leather layer was determined at a test rate of 50 mm / min. Then, when the peel strength is 3.0 kg / cm or higher and the epidermis is damaged during peeling, it is judged as "excellent"; when the peel strength is 3.0 kg / cm or higher but the epidermis is not damaged, it is judged as "good"; and when the peel strength is less than 3.0 kg / cm, it is judged as "inferior".

[0089] Furthermore, the raw materials used in this embodiment will be summarized and described below.

[0090] (Polyurethane emulsion for the epidermis) • Polyurethane A emulsion: A polyether-based polyurethane emulsion with 35% solids content (Hydran ULK-190, manufactured by DIC). • Polyurethane B emulsion: A polyether-based polyurethane emulsion with 30% solids content (Hydran ULK-003, manufactured by DIC). • Polyurethane C emulsion: A polyester / polyether polyurethane emulsion with 45% solids content (Hydran CRS-086, manufactured by DIC). • Polyurethane D emulsion: An anionic, self-emulsifying polycarbonate-based polyurethane emulsion with 40% solids content (100% modulus 3.0 MPa) • Polyurethane E emulsion: A polycarbonate-based polyurethane emulsion with 30% solids content (Hydran WLS-290SG DIC (manufactured by Hydran) Co., Ltd.)

[0091] (The next layer uses a polyurethane emulsion) • A polyether-based polyurethane emulsion with 55% solids content (Hydran WLA-451TA, manufactured by DIC).

[0092] (Nonionic compounds) • Nonionic compound E: Polysiloxane with HLB value = 12 (polyether-modified polydimethylsiloxane, polysiloxane oil KF-351A manufactured by Shin-Etsu Chemical Industry Co., Ltd.) • Nonionic compound F: Polysiloxane compound with HLB value = 10 (polyether-modified polydimethylsiloxane, polysiloxane oil KF-353 manufactured by Shin-Etsu Chemical Industry Co., Ltd.) • Nonionic compound G: Polysiloxane compound with HLB value = 16 (polyether-modified polydimethylsiloxane, polysiloxane oil KF-354L manufactured by Shin-Etsu Chemical Industry Co., Ltd.) • Nonionic compound H:HLB value = 7 polysiloxane (polyether modified polydimethylsiloxane, polysiloxane oil KF-352A manufactured by Shin-Etsu Chemical Industry Co., Ltd.) • Nonionic compound I: Ethynyl glycol-based nonionic surfactant with an HLB value of 13 (Surfynol 465 manufactured by Nissin Chemical Industries, Ltd.) • Nonionic compound X: Polyoxyethylene alkyl ether nonionic compound with HLB value of 18 (NIKKOL BC-23 manufactured by Nikko Chemical Co., Ltd.)

[0093] (Aqueous solution of water-soluble polymer) • Aqueous solution of water-soluble polymer J: Aqueous solution of polyether polyol-based urethane polymer (polyurethane-modified polyoxyethylene) with a quantity average molecular weight of 68,000 (solid content 47.6%, Adekanol UH-541VF, ADEKA (stock)) • Aqueous solution of water-soluble polymer K: Polyethylene glycol (manufactured by Fujifilm and Koichi Pharmaceutical Co., Ltd.) with a quantity average molecular weight of 20,000 is diluted to an aqueous solution with a solid content of 50%. • Aqueous solution of water-soluble polymer L: Polyethylene oxide (Alkox L-11 of Mingcheng Chemical Industry Co., Ltd.) with a quantity average molecular weight of 110,000 was diluted to an aqueous solution with a solid content of 50%. • Aqueous solution of water-soluble polymer M: Polyethylene glycol (manufactured by Fujifilm and Hikari Pure Chemical Industries, Ltd.) with a quantity average molecular weight of 8,000 is diluted to an aqueous solution with a solid content of 50%. • Aqueous solution of water-soluble polymer Y: Polyethylene glycol (manufactured by Fujifilm and Hikari Pure Chemical Industries Co., Ltd.) with a quantity average molecular weight of 500,000 was diluted to an aqueous solution with a solid content of 50%.

[0094] (Fiber-based substrate) Nonwoven fabric containing polyethylene terephthalate (PET) fibers with an average fineness of 0.1 dtex and polyurethane impregnated onto the nonwoven fabric, with a PET / polyurethane ratio of 90 / 10, a unit area weight of 530 g / m², and a thickness of 1 mm.

[0095] [Example 1] The above-mentioned raw materials are mixed in a manner that makes solid components as follows to prepare a coating liquid for the epidermis and a coating liquid for the adhesive layer. (Epidermal coating) • Polyurethane A 100 parts (95.5%) (parts by weight (%), the same applies below) • Nonionic compound E 1.4 parts (1.3%) • Water-soluble polymer J 3.4 parts (3.2%) (Next layer: coating liquid) • Adhesive layer: 100 parts polyurethane · Crosslinking agent 17 parts · 0.5 parts leveling agent • 0.5 parts of thickener

[0096] Then, a skin layer coating liquid with a WET adhesion amount of 120 g / m² is applied to the release surface of the release paper, and dried in a dryer at 90°C for 5 minutes to form a skin layer film. Next, an adhesive layer coating liquid with a WET adhesion amount of 130 g / m² is applied to the surface of the skin layer film, and dried in a dryer at 90°C for 5 minutes to form an adhesive layer film. Then, the laminate of the skin layer film and the adhesive layer film formed on the release paper is overlapped onto the surface of the fiber substrate with the adhesive layer films facing each other, and pressure is applied using a flatbed hot press to bond the fiber substrate and the laminate. The pressure is applied at a temperature of 100°C, a pressure of 5 kgf / cm, and a duration of 10 seconds. After pressure application, further curing is performed at 70°C for 72 hours to crosslink the polyurethane adhesive used in the adhesive layer.

[0097] Then, the release paper is peeled off from the resulting laminate to obtain the grainy imitation leather sheet of Example 1, which has a fiber substrate and a resin layer including a skin layer laminated on one side of the fiber substrate. The resulting grainy imitation leather sheet has a skin layer with a thickness of 50 μm, a thickness of 0.1 mm, and a unit area weight of 640 g / m². Then, each evaluation is performed according to the evaluation method described above. The results are shown in Table 1 below.

[0098] [Table 1] Example number Surface layer of grainy imitation leather sheet Waterborne polyurethane Nonionic surfactants Water-soluble polymers Evaluation results polar components (mJ / m²) Dispersed components (mJ / m²) type polar components (mJ / m²) Dispersed components (mJ / m²) type HLB value type content (parts by weight) type content (parts by weight) Number average molecular weight Wettability Water resistance Secondary adhesion Example 1 39.6 33.8 A 16.0 35.8 E 12 Polysiloxane 1.4 J 3.4 68000 high excellent excellent Example 2 37.2 35.2 A 16.0 35.8 E 12 Polysiloxane 1.4 K 3.4 20000 high excellent good Example 3 37.8 34.4 A 16.0 35.8 E 12 Polysiloxane 1.4 L 3.4 110000 high good excellent Example 4 27.3 34.1 A 16.0 35.8 E 12 Polysiloxane 0.8 J 3.4 68000 middle excellent excellent Example 5 37.8 34.1 A 16.0 35.8 E 12 Polysiloxane 4.5 J 3.4 68000 high good excellent Example 6 28.2 35.9 A 16.0 35.8 F 10 Polysiloxane 1.4 J 3.4 68000 middle excellent excellent Example 7 38.1 35.8 A 16.0 35.8 G 16 Polysiloxane 1.4 J 3.4 68000 high good excellent Example 8 35.7 35.3 A 16.0 35.8 I 13 Acetylene diol system 1.4 J 3.4 68000 high excellent excellent Example 9 36.7 34.6 A 16.0 35.8 E 12 Polysiloxane 1.4 J 1.5 68000 high excellent good Example 10 38.2 35.2 A 16.0 35.8 E 12 Polysiloxane 1.4 J 9.5 68000 high good excellent Example 11 30.5 36.5 B 3.6 36.3 E 12 Polysiloxane 2.5 J 3.4 68000 high excellent good Example 12 38.6 35.7 C 21.1 35.8 E 12 Polysiloxane 1.4 J 3.4 68000 high good excellent Example 13 33.6 36.1 A 16.0 35.8 E 12 Polysiloxane 1.4 J 0.7 68000 high excellent good Example 14 38.7 33.3 A 16.0 35.8 E 12 Polysiloxane 1.4 M 9.5 8000 high excellent good Comparative Example 1 20.3 36.6 A 16.0 35.8 E 12 Polysiloxane 0.6 J 3.4 68000 Low excellent excellent Comparative Example 2 19.7 38.7 A 16.0 35.8 H 7 Polysiloxane 5.0 J 3.4 68000 Low excellent excellent Comparative Example 3 22.3 26.3 D 8.6 23.6 E 12 Polysiloxane 1.4 J 9.5 68000 Low excellent inferior Comparative Example 4 16.3 36.2 A 16.0 35.8 - - - - - - - Low excellent inferior Comparative Example 5 18 36.8 A 16.0 35.8 - - - - J 3.4 68000 Low excellent excellent Comparative Example 6 17.2 36.2 A 16.0 35.8 E 12 Polysiloxane 0.6 - - - Low excellent excellent Comparative Example 7 twenty two 36.8 A 16.0 35.8 X 18 Polyoxyethylene alkyl ether system 1.4 J 3.4 68000 high inferior inferior Comparative Example 8 24.3 35.4 A 16.0 35.8 E 12 Polysiloxane 1.4 Y 3.4 500000 high inferior inferior Comparative Example 9 42 33 A 16.0 35.8 E 12 Polysiloxane 4.5 J 9.5 68000 high inferior inferior Comparative Example 10 21.2 42 E 5.5 41.1 H 7 Polysiloxane 5 J 3.4 68000 Low excellent inferior

[0099] [Example 2] In addition to using a coating liquid for the epidermis prepared in a manner that produces a solid composition as described below, a grained imitation leather sheet was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1. • Polyurethane A 100 parts (95.5%) • Nonionic compound E 1.4 parts (1.3%) • Water-soluble polymer K 3.4 parts (3.2%)

[0100] [Example 3] In addition to using a coating liquid for the epidermis prepared in a manner that produces a solid composition as described below, a grained imitation leather sheet was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1. • Polyurethane A 100 parts (95.5%) • Nonionic compound E 1.4 parts (1.3%) • Water-soluble polymer L 3.4 parts (3.2%)

[0101] [Example 4] In addition to using a coating liquid for the epidermis prepared in a manner that produces a solid composition as described below, a grained imitation leather sheet was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1. • Polyurethane A 100 parts (95.9%) • 0.8 parts (0.8%) of nonionic compound E • Water-soluble polymer J 3.4 parts (3.3%)

[0102] [Example 5] In addition to using a coating liquid for the epidermis prepared in a manner that produces a solid composition as described below, a grained imitation leather sheet was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1. • Polyurethane A 100 parts (92.6%) • Nonionic compound E 4.5 parts (4.2%) • Water-soluble polymer J 3.4 parts (3.2%)

[0103] [Example 6] In addition to using a coating liquid for the epidermis prepared in a manner that produces a solid composition as described below, a grained imitation leather sheet was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1. • Polyurethane A 100 parts (95.5%) • Nonionic compound F 1.4 parts (1.3%) • Water-soluble polymer J 3.4 parts (3.2%)

[0104] [Example 7] In addition to using a coating liquid for the epidermis prepared in a manner that produces a solid composition as described below, a grained imitation leather sheet was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1. • Polyurethane A 100 parts (95.5%) • Nonionic compound G 1.4 parts (1.3%) • Water-soluble polymer J 3.4 parts (3.2%)

[0105] [Example 8] In addition to using a coating liquid for the epidermis prepared in a manner that produces a solid composition as described below, a grained imitation leather sheet was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1. • Polyurethane A 100 parts (95.5%) • Nonionic compound I 1.4 parts (1.3%) • Water-soluble polymer J 3.4 parts (3.2%)

[0106] [Example 9] In addition to using a coating liquid for the epidermis prepared in a manner that produces a solid composition as described below, a grained imitation leather sheet was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1. • Polyurethane A 100 parts (97.1%) • Nonionic compound E 1.4 parts (1.4%) • Water-soluble polymer J 1.5 parts (1.5%)

[0107] [Example 10] In addition to using a coating liquid for the epidermis prepared in a manner that produces a solid composition as described below, a grained imitation leather sheet was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1. • Polyurethane A 100 parts (90.1%) • Nonionic compound E 1.4 parts (1.3%) • Water-soluble polymer J 9.5 parts (8.6%)

[0108] [Example 11] In addition to using a coating liquid for the epidermis prepared in a manner that produces a solid composition as described below, a grained imitation leather sheet was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1. • Polyurethane B 100 parts (94.4%) • Nonionic compound E 2.5 parts (2.4%) • Water-soluble polymer J 3.4 parts (3.2%)

[0109] [Example 12] In addition to using a coating liquid for the epidermis prepared in a manner that produces a solid composition as described below, a grained imitation leather sheet was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1. · Polyurethane C 100 parts (95.5%) • Nonionic compound E 1.4 parts (1.3%) • Water-soluble polymer J 3.4 parts (3.2%)

[0110] [Example 13] In addition to using a coating liquid for the epidermis prepared in a manner that produces a solid composition as described below, a grained imitation leather sheet was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1. • Polyurethane A 100 parts (97.9%) • Nonionic compound E 1.4 parts (1.4%) • Water-soluble polymer J 0.7 parts (0.7%)

[0111] [Example 14] In addition to using a coating liquid for the epidermis prepared in a manner that produces a solid composition as described below, a grained imitation leather sheet was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1. • Polyurethane A 100 parts (90.2%) • Nonionic compound E 1.4 parts (1.2%) • Water-soluble polymer M 9.5 parts (8.6%)

[0112] [Comparative Example 1] In addition to using a coating liquid for the epidermis prepared in a manner that produces a solid composition as described below, a grained imitation leather sheet was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1. • Polyurethane A 100 parts (96.1%) • 0.6 parts (0.6%) of nonionic compound E • Water-soluble polymer J 3.4 parts (3.3%)

[0113] [Comparative Example 2] In addition to using a coating liquid for the epidermis prepared in a manner that produces a solid composition as described below, a grained imitation leather sheet was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1. • Polyurethane A 100 parts (92.3%) • Nonionic compound H 5.0 parts (4.6%) • Water-soluble polymer J 3.4 parts (3.1%)

[0114] [Comparative Example 3] In addition to using a coating liquid for the epidermis prepared in a manner that produces a solid composition as described below, a grained imitation leather sheet was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1. • Polyurethane D 100 parts (90.1%) • Nonionic compound E 1.4 parts (1.3%) • Water-soluble polymer J 9.5 parts (8.6%)

[0115] [Comparative Example 4] In addition to using a coating liquid for the epidermis prepared in a manner that produces a solid composition as described below, a grained imitation leather sheet was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1. · Polyurethane A 100 parts (100%)

[0116] [Comparative Example 5] In addition to using a coating liquid for the epidermis prepared in a manner that produces a solid composition as described below, a grained imitation leather sheet was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1. • Polyurethane A 100 parts (96.7%) • Water-soluble polymer J 3.4 parts (3.3%)

[0117] [Comparative Example 6] In addition to using a coating liquid for the epidermis prepared in a manner that produces a solid composition as described below, a grained imitation leather sheet was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1. • Polyurethane A 100 parts (99.4%) • 0.6 parts (0.6%) of nonionic compound E

[0118] [Comparative Example 7] In addition to using a coating liquid for the epidermis prepared in a manner that produces a solid composition as described below, a grained imitation leather sheet was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1. • Polyurethane A 100 parts (95.5%) • Nonionic compound X 1.4 parts (1.3%) • Water-soluble polymer J 3.4 parts (3.2%)

[0119] [Comparative Example 8] In addition to using a coating liquid for the epidermis prepared in a manner that produces a solid composition as described below, a grained imitation leather sheet was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1. • Polyurethane A 100 parts (95.5%) • Nonionic compound E 1.4 parts (1.3%) • Water-soluble polymer Y 3.4 parts (3.2%)

[0120] [Comparative Example 9] In addition to using a coating liquid for the epidermis prepared in a manner that produces a solid composition as described below, a grained imitation leather sheet was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1. • Polyurethane A 100 parts (87.8%) • Nonionic compound E 4.5 parts (3.9%) • Water-soluble polymer J 9.5 parts (8.3%)

[0121] [Comparative Example 10] In addition to using a coating liquid for the epidermis prepared in a manner that produces a solid composition as described below, a grained imitation leather sheet was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1. · Polyurethane E 100 parts (92.3%) ·Nonionic compound H 5 parts (4.6%) • Water-soluble polymer J 3.4 parts (3.1%)

[0122] Referring to Table 1, the grainy imitation leather sheets obtained in Examples 1 to 14 of the present invention, which contain a skin layer comprising polyurethane, a nonionic compound with an HLB value of 10 to 16 and a water-soluble polymer, a polar component of 25 to 40 mJ / m² and a dispersion component of 30 to 40 mJ / m², all exhibit wettability of "medium" or higher, water resistance of "good" or higher, and secondary adhesion of "good" or higher.

[0123] On the other hand, the grainy imitation leather sheet obtained in Comparative Example 1, which had a low proportion of nonionic compounds and a polar component of less than 25 mJ / m², exhibited low wettability. Furthermore, the grainy imitation leather sheet obtained in Comparative Example 2, which used nonionic compounds with an HLB value of less than 10, also exhibited low wettability even with an increased proportion of nonionic compounds due to a polar component of less than 25 mJ / m². Moreover, the grainy imitation leather sheet obtained in Comparative Example 3, which used waterborne polyurethane with low polar and dispersed components, also exhibited low wettability and poor secondary adhesion, even with extensive blending of water-soluble polymers, due to a polar component of less than 25 mJ / m² and a dispersed component of less than 30 mJ / m².

[0124] Furthermore, the granular imitation leather sheet obtained in Comparative Example 4, which contains no nonionic compounds and water-soluble polymers and has a polar component of less than 25 mJ / m², has excellent water resistance but low wettability and poor secondary adhesion.

[0125] In addition, compared with the grainy imitation leather sheet obtained in Comparative Example 4, the grainy imitation leather sheet obtained in Comparative Example 5, which only incorporates water-soluble polymers in the epidermis layer, also has low wettability despite improved secondary adhesion due to the polar component being less than 25 mJ / m2.

[0126] Furthermore, compared to the grainy imitation leather sheet obtained in Comparative Example 4, the grainy imitation leather sheet obtained in Comparative Example 6, which only incorporates nonionic compounds in the epidermis layer, also exhibits improved secondary adhesion but low wettability due to the polar component being less than 25 mJ / m².

[0127] Furthermore, the grainy imitation leather sheet obtained in Comparative Example 7, which used a nonionic compound with an HLB value exceeding 16 in the epidermis layer, also exhibited improved wettability but reduced water resistance and secondary adhesion due to its polar component being less than 25 mJ / m². Similarly, the grainy imitation leather sheet obtained in Comparative Example 8, which used a water-soluble polymer with a high number-average molecular weight, also showed improved wettability but reduced water resistance and secondary adhesion due to its polar component being less than 25 mJ / m².

[0128] Furthermore, the grainy imitation leather sheet obtained in Comparative Example 9, which blends a nonionic compound with an HLB value of 12 and a water-soluble polymer in a high proportion, exhibits improved wettability but reduced water resistance and secondary adhesion due to the polar component exceeding 40 mJ / m². Similarly, the grainy imitation leather sheet obtained in Comparative Example 10, which uses a waterborne polyurethane with a high dispersion component, also exhibits improved water resistance but reduced wettability and secondary adhesion due to the dispersion component exceeding 40 mJ / m².

[0129] 1: Fiber substrate 2: Resin layer 2a: Epidermis 2b: Intermediate layer 2c: Next layer 10: Grainy imitation leather sheet

Claims

1. A grainy imitation leather sheet comprising a fiber substrate and a resin layer laminated on one side of the fiber substrate, the resin layer comprising at least a skin layer, the skin layer comprising polyurethane, a nonionic compound with an HLB value of 10 to 16 and a water-soluble polymer, and the skin layer having a surface free energy of 25 to 40 mJ / m² for polar components and 30 to 40 mJ / m² for dispersed components as determined by the Owens-Wendt-Rabel-Kaelble method.

2. The grainy imitation leather sheet of claim 1, wherein the polyurethane has a surface free energy of 5 to 20 mJ / m² for polar components and 30 to 40 mJ / m² for dispersed components as determined by the Owens-Wendt-Rabel-Kaelble method.

3. The grainy imitation leather sheet of claim 1, wherein the polyurethane is an aqueous polyurethane.

4. The grainy imitation leather sheet as claimed in claim 2, wherein the polyurethane is an aqueous polyurethane.

5. The grainy imitation leather sheet of claim 1, wherein the nonionic compound comprises at least one of a polysiloxane compound and an acetylene glycol compound.

6. The grained imitation leather sheet of claim 1, wherein the outer layer contains 0.8 to 5.0% by mass of the nonionic compound.

7. The grainy imitation leather sheet of claim 1, wherein the water-soluble polymer has a number average molecular weight of 10,000 to 150,000.

8. The grainy imitation leather sheet of claim 1, wherein the outer layer comprises 1.0 to 10% by mass of the water-soluble polymer.

9. The grainy imitation leather sheet of claim 1, wherein the water-soluble polymer comprises polyurethane-modified polyoxyethylene.

10. The grained imitation leather sheet of any one of claims 1 to 9, wherein the outer layer is a non-porous continuous film with a thickness of 10 to 100 μm.

11. The grainy imitation leather sheet of claim 10, wherein the resin layer comprises an adhesive layer of 30 to 120 μm thickness that is used to attach a fiber substrate, the adhesive layer comprising polyurethane.

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