Synthetic leather casting paper and synthetic leather manufacturing method

Abstract

To provide process paper for synthetic leather that can produce synthetic leather with a deep matte appearance and deeper black hue.SOLUTION: A process paper 100 for synthetic leather comprises a base material 10 and a release agent layer 30 provided on the base material 10, wherein a surface 30S on the release agent layer 30 that is opposite to the base material 10 side satisfies (1) and (2) as follows: (1) specular glossiness, in accordance with JIS Z 8741: 1997, is between 0.1% and 5.0% at a 20° gloss value, and (2) ΔRz, a value given from a maximum height roughness Rz value minus a 10-point average roughness Rzjis value, in accordance with JIS B 0601: 2001, is 0 or more and 5.0 or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a casting paper for synthetic leather, a method for producing synthetic leather, and synthetic leather. [Background technology]

[0002] Synthetic leather is produced using a synthetic leather casting paper, which has a substrate and a release agent layer.

[0003] Examples of methods for producing synthetic leather include the following. First, a coating liquid containing a synthetic resin such as a urethane resin or a vinyl chloride resin as a main component is applied onto the release agent layer of the synthetic leather casting paper, and the applied coating liquid is dried to form a resin layer. If necessary, a base fabric is further laminated onto the resin layer via an adhesive to form a laminate with the synthetic leather. Finally, the synthetic leather is produced by peeling the synthetic leather casting paper from the resin layer of the laminate. In this method for producing synthetic leather, the surface condition of the release agent layer of the synthetic leather casting paper is transferred to the surface of the synthetic leather.

[0004] For example, Patent Document 1 discloses a release paper for producing synthetic leather, which comprises a paper base layer, an ionizing radiation-cured resin layer provided on the paper base layer, and a release agent layer formed on the ionizing radiation-cured resin layer. The release paper for producing synthetic leather described in Patent Document 1 contains, as an essential component, phenolic particles having an average particle size of 1 μm or more and 30 μm or less in an amount of 10% by mass or more and 80% by mass or less in the dried ionizing radiation-cured resin layer.

[0005] Patent Document 2 discloses a release paper for producing synthetic leather, which comprises a paper base layer, a filling layer provided on the paper base layer, and a release agent layer formed on the filling layer. The filling layer of the release paper for producing synthetic leather described in Patent Document 2 contains, as essential components, a thermoplastic resin or a thermosetting resin, and a silicone composite powder.

[0006] Patent Document 3 discloses a release sheet (processing paper) used in the production of resin articles such as synthetic leather. The release sheet described in Patent Document 3 has a base layer and a resin layer disposed on one side of the base layer. The resin layer in the release sheet described in Patent Document 3 has an irregular uneven structure on the side opposite to the base layer, and the uneven structure has an arithmetic mean roughness (Sa) of 0.2 μm or more and 0.6 μm or less and a shortest autocorrelation length (Sal) of 60 μm or more and 200 μm or less. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-172279 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-251253 [Patent Document 3] Japanese Patent Application Publication No. 2019-218658 Summary of the Invention [Problem to be solved by the invention]

[0008] In recent years, consumer preferences have become more diverse, and there is a demand for synthetic leather with a deep matte appearance and a texture with a deeper black hue, as a more luxurious synthetic leather. A texture with a deep matte appearance and a deep black hue is a deep black texture that is less likely to exhibit gloss. Therefore, in order to obtain synthetic leather with a more luxurious feel, there is room for further improvement in the surface properties of the release agent layer of casting paper for synthetic leather.

[0009] An object of the present invention is to provide a casting paper for synthetic leather that can be used to produce synthetic leather with a deep matte appearance and a deeper black color, thereby providing a synthetic leather with a more luxurious feel.An object of the present invention is to provide a method for producing synthetic leather with a deep matte appearance and a deeper black color, thereby providing a synthetic leather with a more luxurious feel.An object of the present invention is to provide synthetic leather with a deep matte appearance and a deeper black color, thereby providing a synthetic leather with a more luxurious feel. [Means for solving the problem]

[0010] According to one aspect of the present invention, there is provided a casting paper for synthetic leather, which comprises a substrate and a release agent layer provided on the substrate, and the surface of the release agent layer opposite to the substrate satisfies the following (1) and (2): (1) The specular gloss, in accordance with JIS Z 8741:1997, is 0.1% or more and 5.0% or less in 20° gloss value. (2) ΔRz, which is the value obtained by subtracting the ten-point average roughness Rzjis from the maximum height roughness Rz in accordance with JIS B 0601:2001, is 0 μm or more and 5.0 μm or less.

[0011] In the casting paper for synthetic leather according to one aspect of the present invention, it is preferable that the surface of the release agent layer further satisfies the following (3). (3) The arithmetic mean height Sa, measured in accordance with ISO 25178, is 1 μm or more.

[0012] In the casting paper for synthetic leather according to one aspect of the present invention, the release agent layer preferably contains (A) a binder resin and (B) a filler.

[0013] In the casting paper for synthetic leather according to one aspect of the present invention, it is preferable that the (A) binder resin contains polyvinyl alcohol, and the (B) filler contains starch particles.

[0014] In the casting paper for synthetic leather according to one embodiment of the present invention, it is preferable that the (A) binder resin contains at least one mixed resin selected from a mixed resin of a silicone-modified acrylic resin and a melamine resin, and a mixed resin of a silicone-modified alkyd resin and a melamine resin, and the (B) filler contains silica particles.

[0015] According to one aspect of the present invention, there is provided a method for producing synthetic leather, comprising the steps of: applying a coating liquid containing a synthetic resin onto the release agent layer of the synthetic leather casting paper according to the above-described aspect of the present invention; drying the applied coating liquid to form synthetic leather containing the synthetic resin; and peeling the synthetic leather casting paper from the synthetic leather after drying.

[0016] According to one aspect of the present invention, there is provided synthetic leather obtained by the method for producing synthetic leather according to the above-mentioned aspect of the present invention, wherein the surface of the synthetic leather satisfies the following (4): (4) The specular gloss, in accordance with JIS Z 8741:1997, is 0.1% or more and 5.0% or less in 20° gloss value.

[0017] According to one aspect of the present invention, it is preferable that the surface of the synthetic leather satisfies the following (5). (5) L conforming to JIS Z 8781-4:2013 * a * b * Lightness L in the color system * The value is 6.0 or less. [Effects of the Invention]

[0018] According to one aspect of the present invention, it is possible to provide a casting paper for synthetic leather that can be used to produce synthetic leather with a luxurious feel, having a deep matte appearance and a deeper black color. According to one aspect of the present invention, a method for producing synthetic leather having a deep matte appearance and a deeper black color can be provided as a synthetic leather with a luxurious feel. According to one aspect of the present invention, a synthetic leather having a luxurious feel and a deep matte appearance and a deeper black color can be provided. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a cross-sectional view schematically illustrating an example of a process sheet according to an embodiment of the present invention. [Figure 2] FIG. 3 is a cross-sectional view schematically illustrating another example of a process sheet according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] <Processing paper for synthetic leather> A preferred embodiment of a casting paper for synthetic leather, which is an example of the present invention, will be described below.

[0021] The synthetic leather casting paper according to this embodiment comprises a substrate and a release agent layer provided on the substrate, and the surface of the release agent layer opposite to the substrate satisfies the following (1) and (2): (1) The specular gloss, in accordance with JIS Z 8741:1997, is 0.1% or more and 5.0% or less in 20° gloss value. (2) ΔRz, which is the value obtained by subtracting the ten-point average roughness Rzjis from the maximum height roughness Rz in accordance with JIS B 0601:2001, is 0 μm or more and 5.0 μm or less. In the following description, the surface of the release agent layer opposite to the substrate side may be simply referred to as the surface of the release agent layer.

[0022] The synthetic leather casting paper according to this embodiment satisfies the above-mentioned (1), so that the surface of the release agent layer has appropriate irregularities. Therefore, by using the synthetic leather casting paper according to this embodiment, whose surface of the release agent layer satisfies the above-mentioned (1), it is possible to obtain synthetic leather with a deep matte appearance.

[0023] Furthermore, when the synthetic leather casting paper according to this embodiment satisfies the above-mentioned (2), the difference between the maximum height and the average height of the irregularities on the surface of the release agent layer becomes small, and the degree of irregularities on the surface of the release agent layer becomes nearly uniform. Therefore, by using the synthetic leather casting paper according to this embodiment, whose release agent layer surface satisfies the above-mentioned (2), synthetic leather with a deeper black color can be obtained.

[0024] Therefore, by using the casting paper for synthetic leather according to this embodiment, which satisfies both the above (1) and (2), a synthetic leather with a more luxurious feel can be obtained that combines the properties of a deep matte appearance and a deeper black color. Note that in this specification, the "deeper black color" may also be referred to as "jet blackness."

[0025] The synthetic leather casting paper according to this embodiment will be described with reference to the drawings. FIG. 1 is a cross-sectional view schematically illustrating an example of the synthetic leather casting paper according to this embodiment. As shown in FIG. 1, the synthetic leather casting paper 100 comprises a substrate 10 and a release agent layer 30. The surface 10S of the substrate 10 on which the release agent layer 30 is provided is a rough surface with fine irregularities. The release agent layer 30 is provided directly on and in contact with the surface 10S on the rough side of the substrate 10. The release agent layer 30 is formed from a release agent composition 35 containing a binder resin 31 and a filler 33. The surface 30S of the release agent layer 30 satisfies both of the above-mentioned (1) and (2).

[0026] FIG. 2 is a cross-sectional view schematically illustrating another example of the synthetic leather casting paper according to this embodiment. As shown in FIG. 2, the synthetic leather casting paper 200 includes a substrate 20 and a release agent layer 40. The surface 20S of the substrate 20 on which the release agent layer 40 is provided is smoother than the surface 10S of the substrate 10 shown in FIG. 1, which is a rough surface having fine irregularities. The release agent layer 40 is provided directly on and in contact with the smooth surface 20S of the substrate 20. The release agent layer 40 is formed from a release agent composition 46 containing a binder resin 42 and a filler 44. The surface 40S of the release agent layer 40 satisfies both of the above-mentioned (1) and (2).

[0027] An example of the casting paper for synthetic leather according to this embodiment has been described above with reference to Figures 1 and 2, but the casting paper for synthetic leather according to this embodiment is not limited to this. The casting paper for synthetic leather according to this embodiment can take various forms as long as the surface of the release agent layer satisfies both of the above-mentioned (1) and (2).

[0028] For example, the synthetic leather casting paper may have a substrate and a release agent layer in direct contact with each other. The synthetic leather casting paper may also have an intermediate layer between the substrate and the release agent layer. Examples of the intermediate layer include an adhesive layer. For example, the release agent layer may or may not contain a filler.

[0029] [Surface characteristics of release agent layer] The surface characteristics of the release agent layer of the casting paper for synthetic leather according to this embodiment will be described. The surface of the release agent layer of the synthetic leather casting paper according to this embodiment simultaneously satisfies the above-mentioned (1) and (2). For example, by combining the selection of the type of substrate and the adjustment of the composition of the release agent composition used to form the release agent layer, a surface of the release agent layer simultaneously satisfying the above-mentioned (1) and (2) can be obtained. The substrate may be a substrate having a rough surface with fine irregularities, or a substrate having a smooth surface with minimal fine irregularities. When the release agent composition contains, for example, (A) a binder resin and (B) a filler, the dispersion state of the filler in the release agent composition may be adjusted. The dispersion state of the filler in the release agent composition can be adjusted by selecting the combination of (A) the binder resin and (B) the filler. Note that, in this specification, surface characteristics related to the index of surface roughness may sometimes be referred to as surface texture.

[0030] (Specular gloss) In the casting paper for synthetic leather according to this embodiment, the specular gloss of the surface of the release agent layer is 0.1% or more and 5.0% or less in 20° gloss value. In the casting paper for synthetic leather according to this embodiment, the specular gloss is measured in accordance with JIS Z 8741:1997.

[0031] In the synthetic leather casting paper according to this embodiment, the specular gloss of the surface of the release agent layer is preferably 0.1% or more, more preferably 0.3% or more, and even more preferably 0.5% or more, in 20° gloss value. In the synthetic leather casting paper according to this embodiment, the specular gloss of the surface of the release agent layer is preferably 3.0% or less, more preferably 2.5% or less, even more preferably 2.0% or less, and even more preferably 1.5% or less, in 20° gloss value. If the specular gloss of the surface of the release agent layer of the synthetic leather casting paper according to this embodiment is in the above-mentioned range in terms of 20° gloss value, the synthetic leather according to this embodiment will be more likely to have a deep matte appearance and jet black color.

[0032] In the synthetic leather casting paper according to this embodiment, the specular gloss of the surface of the release agent layer is preferably 0.1% or more, more preferably 0.3% or more, even more preferably 0.5% or more, and even more preferably 1.0% or more, in 60° gloss value. In the synthetic leather casting paper according to this embodiment, the specular gloss of the surface of the release agent layer is preferably 5.0% or less, more preferably 4.0% or less, even more preferably 3.0% or less, and even more preferably 2.5% or less, in 60° gloss value. If the specular gloss of the surface of the release agent layer of the synthetic leather casting paper according to this embodiment is in the above-mentioned range in terms of 60° gloss value, the synthetic leather according to this embodiment will be more likely to have a deep matte appearance and jet black color.

[0033] (ΔRz) In the synthetic leather casting paper according to this embodiment, the ΔRz on the surface of the release agent layer is 0 μm or more and 5.0 μm or less. The smaller the ΔRz value, the more uniform the unevenness of the surface of the release agent layer. ΔRz is expressed as the difference between the maximum height roughness Rz value measured in accordance with JIS B 0601:2001 and the ten-point average roughness Rzjis value measured in accordance with JIS B 0601:2001, and is expressed by the following mathematical formula 1: ΔRz=Rz-Rzjis (Equation 1)

[0034] In the casting paper for synthetic leather according to this embodiment, the ΔRz of the surface of the release agent layer is preferably 4.5 μm or less, more preferably 4.0 μm or less, and even more preferably 3.5 μm or less. In the casting paper for synthetic leather according to this embodiment, ΔRz of the surface of the release agent layer may be, for example, 0.1 μm or more, or 0.3 μm or more. In the casting paper for synthetic leather according to this embodiment, if ΔRz on the surface of the release agent layer is equal to or less than the above upper limit, the synthetic leather according to this embodiment is more likely to have a deep matte appearance and jet black color.

[0035] (Rz) In the casting paper for synthetic leather according to this embodiment, the Rz of the surface of the release agent layer is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more. In the casting paper for synthetic leather according to this embodiment, the Rz of the surface of the release agent layer is preferably 25 μm or less, more preferably 20 μm or less, and even more preferably 18 μm or less.

[0036] (Rzjis) In the casting paper for synthetic leather according to this embodiment, Rzjis on the surface of the release agent layer is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more. In the casting paper for synthetic leather according to this embodiment, Rzjis on the surface of the release agent layer is preferably 20 μm or less, more preferably 18 μm or less, and even more preferably 16 μm or less.

[0037] In the casting paper for synthetic leather according to the present embodiment, if Rz and Rzjis on the surface of the release agent layer are within the above-mentioned ranges, the synthetic leather according to the present embodiment is more likely to have a deep matte appearance and jet black color.

[0038] (Sa) It is preferable that the surface of the release agent layer of the casting paper for synthetic leather according to this embodiment satisfies the following (3). (3) The arithmetic mean height Sa, measured in accordance with ISO 25178, is 1 μm or more. When the surface of the release agent layer of the casting paper for synthetic leather according to this embodiment satisfies the requirement (3), the synthetic leather according to this embodiment is more likely to have a deep matte appearance and a jet black color. The arithmetic mean roughness Sa represents the average of the absolute values ​​of the height differences of each point relative to the average plane of the surface, and is a parameter that serves as an index of surface roughness. The arithmetic mean height Sa is preferably 1.5 μm or more, more preferably 2.0 μm or more, and even more preferably 3.0 μm or more. The upper limit of the arithmetic mean height Sa is not particularly limited, and is, for example, preferably 6.0 μm or less, more preferably 5.0 μm or less, and even more preferably 4.0 μm or less.

[0039] (Ra) The surface of the release agent layer of the synthetic leather casting paper according to this embodiment preferably has an arithmetic mean roughness Ra of 0.3 μm or more, more preferably 0.4 μm or more, and even more preferably 0.5 μm or more, as measured in accordance with JIS B 0601:2001. The synthetic leather casting paper according to this embodiment preferably has an arithmetic mean roughness Ra, measured in accordance with JIS B 0601:2001, of 6 μm or less, more preferably 5 μm or less, and even more preferably 4 μm or less. In the casting paper for synthetic leather according to the present embodiment, if the arithmetic mean roughness Ra on the surface of the release agent layer is equal to or less than the above upper limit, the synthetic leather according to the present embodiment is more likely to have a deep matte appearance and jet black color. The arithmetic mean roughness Ra represents the average value of the average height difference from the mean surface, and is a parameter that serves as an index of line roughness.

[0040] Next, the materials constituting each layer will be described.

[0041] [1] Base material The substrate of the casting paper for synthetic leather is not particularly limited as long as it can support the release agent layer described below. In addition, the substrate is not particularly limited as long as it satisfies the above (1) and (2).

[0042] Examples of the substrate include a paper substrate and a resin film. The substrate may be, for example, a laminated paper comprising a paper substrate and a laminate layer. The laminate layer is formed by laminating a thermoplastic resin onto the paper substrate. Examples of the thermoplastic resin in the laminate layer include polyolefin resins, and examples of the polyolefin resin include polyethylene. Examples of the paper substrate include fine paper, medium-quality paper, glassine paper, art paper, clay-coated paper, and cast-coated paper.

[0043] Examples of resin films include polyester films and polyolefin films. Examples of polyester films include polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, etc. Examples of polyolefin films include polyethylene, polypropylene, polymethylpentene, etc. The resin film may be a single layer, or may be a multilayer film made up of two or more layers of the same or different resin films.

[0044] Among these substrates, the substrate is preferably a paper substrate from the viewpoints of strength and easy availability.

[0045] The thickness of the substrate is not particularly limited, and is preferably, for example, 5 μm or more, more preferably 10 μm or more, and is preferably, for example, 300 μm or less, more preferably 200 μm or less.

[0046] [2] Release layer The release agent layer is formed from a release agent composition. The composition of the release agent composition is not particularly limited as long as the surface of the release agent layer satisfies the above-mentioned (1) and (2). In order to facilitate the surface of the release agent layer satisfying the above-mentioned (1) and (2), the release agent composition preferably contains (A) a binder resin and (B) a filler. Furthermore, the release agent composition may further contain (C) a release agent, if necessary.

[0047] ((A) Binder resin) The binder resin is not particularly limited, and a resin used in a release agent composition for forming a release agent layer of a casting paper can be used. The binder resin may be a resin that exhibits release properties by itself, or a resin that does not exhibit release properties by itself. The binder resin may be used alone or in combination of two or more types.

[0048] When the binder resin is a binder resin that does not exhibit releasability, examples of the binder resin that does not exhibit releasability include polyvinyl alcohol; hydroxyl group-containing acrylic acid ester copolymer; urethane resin; alkyd resin; amino resin; epoxy resin; phenolic resin; and melamine resin.

[0049] When a binder resin that does not exhibit releasability is used as the binder resin, the binder resin that does not exhibit releasability may be a water-soluble resin such as polyvinyl alcohol. When a water-soluble resin is used as the binder resin, polyvinyl alcohol is preferably used as the binder resin from the viewpoint of releasability, as well as from the viewpoint of improving affinity and dispersibility with fillers and additives. By using polyvinyl alcohol as the binder resin, releasability can be easily maintained even when synthetic leather is repeatedly formed into a film. Hereinafter, polyvinyl alcohol may be referred to as PVA.

[0050] When PVA is used as the binder resin, the type of PVA is not particularly limited. PVA is obtained by saponifying polyvinyl acetate. The degree of saponification of PVA is expressed as a percentage of the number of hydroxyl groups relative to the total number of acetate groups and hydroxyl groups in PVA. The degree of saponification and degree of polymerization of PVA are not particularly limited. The degree of saponification of PVA may be 87% or more, or 98% or more. The degree of saponification of PVA may be 100% or less, or 99% or less. The degree of polymerization of PVA may be 500 or more, or 1700 or more. The degree of polymerization of PVA may be 2400 or less, or 600 or less. Among these, from the viewpoint of the sealing effect of the release agent, it is preferable that the PVA has a degree of saponification of 98% or more and a degree of polymerization of 500 or more. One type of PVA may be used alone, or two or more types may be used in combination.

[0051] When the binder resin itself exhibits releasability, for example, a low-polarity resin can be used. Examples of the low-polarity binder resin exhibiting releasability include polyorganosiloxane, fluoropolymer, polyolefin such as polyethylene, polypropylene, and polymethylpentene, and diene polymers such as polybutadiene and polyisoprene.

[0052] Further, binder resins exhibiting such releasability include binder resins that have been chemically modified to impart releasability. In the case of binder resins that have been chemically modified to impart releasability, examples of the resin components that are chemically modified in the binder resins that have been imparted with releasability include polyvinyl alcohol; hydroxyl group-containing acrylic acid ester copolymers; urethane resins; alkyd resins; amino resins; epoxy resins; phenolic resins; and melamine resins. The binder resins exhibiting releasability may also be water-insoluble resins.

[0053] In resins that have been chemically modified to impart release properties, examples of chemically modifying components include polyorganosiloxanes or organosiloxane oligomers having functional groups, fluorocarbon compounds having functional groups, and long-chain alkyl compounds having functional groups. Among these, long-chain alkyl compounds include compounds having an alkyl group with 12 or more carbon atoms, specifically, for example, lauryl groups, palmityl groups, and stearyl groups. Examples of functional groups of the compound to be chemically modified include a hydroxyl group, an amino group, a carboxyl group, an epoxy group, an isocyanate group, a (meth)acryloyl group, a thiol group, and an alkoxysilyl group.

[0054] Resins that have been chemically modified to provide release properties are usually referred to as silicone-modified resins, fluoro-modified resins, or long-chain alkyl-modified resins. Examples of silicone-modified resins include alkyd resins chemically modified with polyorganosiloxane (so-called silicone-modified alkyd resins) and acrylic resins chemically modified with polyorganosiloxane (so-called silicone-modified acrylic resins). Among these, by using silicone-modified resins, the modified components remain on the surface of the release agent layer even when synthetic leather is repeatedly formed into films, making it easier to maintain release properties.

[0055] As the binder resin, a binder resin exhibiting releasability and a binder resin not exhibiting releasability may be used in combination. In this case, from the viewpoint of improving the affinity and dispersibility with the addition of fillers, etc., and improving the releasability, the binder resin is preferably at least one mixed resin selected from, for example, a mixed resin of a silicone-modified acrylic resin and a melamine resin, and a mixed resin of a silicone-modified alkyd resin and a melamine resin. Since the binder resin contains a melamine resin as a curing agent component, the release agent layer is cured, improving the releasability. Hereinafter, a mixed resin of a silicone-modified acrylic resin and a melamine may be referred to as a silicone-modified acrylic resin / melamine. Furthermore, a mixed resin of a silicone-modified alkyd resin and a melamine may be referred to as a silicone-modified alkyd resin / melamine.

[0056] ((B) Filler) The filler is not particularly limited as long as the surface of the release agent layer satisfies the above-mentioned (1) and (2). Examples of filler materials include inorganic particles such as silica particles, alumina particles, titanium oxide particles, zinc oxide particles, calcium carbonate particles, magnesium hydroxide particles, aluminum hydroxide particles, kaolin particles, talc particles, and clay particles; and organic particles such as urea resin and starch particles. Among these, it is preferable to use silica particles as the inorganic particles and starch particles as the organic particles, in order to make it easier for the surface of the release agent layer to satisfy the above-mentioned (1) and (2).

[0057] The shape of the filler is not particularly limited and may be spherical or irregular. In order to make it easier for the surface of the release agent layer to satisfy the above-mentioned (1) and (2), the shape of the filler is preferably irregular.

[0058] When the filler is, for example, silica particles, the silica particles may be, for example, spherical silica particles or irregular silica particles. In order to easily satisfy the above-mentioned (1) and (2), the silica particles are preferably irregular silica particles. The irregular silica particles may be silica particles obtained by crushing or pulverizing silica aggregates, or may be particles formed by secondary aggregation of primary particles by a wet method such as a precipitation method or a gel method. The silica particles may have their surfaces modified with organic groups, functional groups, or the like in terms of dispersibility in the release agent composition.

[0059] When the filler is, for example, starch particles, the starch particles are not particularly limited. The shape of the starch particles may be, for example, spherical or may have an irregular shape characteristic of natural starch. Examples of starch particles include starch particles derived from corn, potato, rice, tapioca, etc. Also included are modified starch particles such as esterified, etherified, and acetylated. Among these, starch particles are preferred, and acetylated starch particles derived from rice are more preferred, in order to easily satisfy the above-mentioned (1) and (2).

[0060] The average particle size of the filler is the median particle size (D50) of particle sizes as viewed from the fine particle side at 50% cumulative volume. The average particle size (D50) can be measured using a laser diffraction particle size distribution analyzer, with the release agent composition containing the filler as the measurement target. The average particle size (D50) of the filler is preferably 1 μm or more, more preferably 2 μm or more, and even more preferably 3 μm or more. The average particle size (D50) of the filler is preferably 10 μm or less, more preferably 8 μm or less, and even more preferably 7 μm or less. When the average particle size (D50) of the filler is 1 μm or more, the surface of the release agent layer is more likely to satisfy the above-mentioned (1) and (2). When the average particle size (D50) of the filler is 10 μm or less, the releasability of the synthetic leather formed on the release agent layer is more likely to be improved.

[0061] ((C) Release Agent) A release agent is preferably used when the binder resin itself does not exhibit releasability. Examples of the release agent include a release-type low-molecular-weight or oligomeric component. Specific examples of the release agent include wax (hydrocarbon compound); polyorganosiloxane or organosiloxane oligomer; fluorocarbon; and long-chain alkyl compounds, as well as polyether adducts and polyester adducts of these release-type low-molecular-weight or oligomeric components. One type of release agent may be used alone, or two or more types may be used in combination.

[0062] The release agent composition may further contain additives in addition to the binder resin, filler, and optionally the release agent, such as a curing agent, a crosslinking agent, a reaction initiator, and a catalyst.

[0063] The stripping composition is preferably used in the form of a solution containing an organic solvent or a dispersion liquid using water as a dispersion medium. Examples of organic solvents include toluene, xylene, hexane, heptane, methanol, ethanol, isopropanol, isobutanol, n-butanol, acetone, methyl ethyl ketone, tetrahydrofuran, etc. The organic solvents may be used alone or in combination of two or more.

[0064] From the viewpoints of coatability and drying property, the nonvolatile content of the release agent composition solution is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 20% by mass or more. From the same viewpoints, the nonvolatile content of the release agent composition solution is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less.

[0065] In order to facilitate the surface of the release agent layer satisfying the above-mentioned (1) and (2), it is preferable that the combination of (A) binder resin and (B) filler is such that the binder resin contains polyvinyl alcohol and the filler contains starch particles.

[0066] The ratio of polyvinyl alcohol as the binder resin and starch particles as the filler in the release agent composition that forms the release agent layer is preferably such that the filler content is 65 parts by mass or more, more preferably 70 parts by mass or more, even more preferably 75 parts by mass or more, and even more preferably 80 parts by mass or more, per 100 parts by mass of the binder resin. The ratio of polyvinyl alcohol as the binder resin and starch particles as the filler in the release agent composition that forms the release agent layer is preferably 135 parts by mass or less, more preferably 130 parts by mass or less, even more preferably 125 parts by mass or less, and even more preferably 120 parts by mass or less, per 100 parts by mass of the binder resin.

[0067] In addition, in order to facilitate the surface of the release agent layer satisfying the above-mentioned (1) and (2), it is also preferable that the combination of (A) binder resin and (B) filler is such that the binder resin contains at least one mixed resin selected from a mixed resin of a silicone-modified acrylic resin and a melamine resin, and a mixed resin of a silicone-modified alkyd resin and a melamine resin, and the filler contains silica particles.

[0068] The ratio of at least one mixed resin selected from a mixed resin of a silicone-modified acrylic resin and a melamine resin and a mixed resin of a silicone-modified alkyd resin and a melamine resin as a binder resin in the release agent composition that forms the release agent layer to silica particles as a filler is preferably such that the filler content is 15 parts by mass or more, and more preferably 20 parts by mass or more, per 100 parts by mass of the binder resin. The ratio of at least one mixed resin selected from a mixed resin of a silicone-modified acrylic resin and a melamine resin and a mixed resin of a silicone-modified alkyd resin and a melamine resin as a binder resin in the release agent composition that forms the release agent layer to silica particles as a filler is preferably such that the filler content is 40 parts by mass or less, and more preferably 35 parts by mass or less, per 100 parts by mass of the binder resin.

[0069] [Manufacturing method for casting paper for synthetic leather] The method for producing the casting paper for synthetic leather is not particularly limited. A method for producing casting paper for synthetic leather includes, for example, a step of preparing a release agent composition and a step of applying the release agent composition to a substrate to form a coating film. Specifically, the following method can be mentioned. First, a release agent composition for forming the release agent layer is prepared, and then the release agent composition is applied to a substrate and heated to form a coating film, thereby providing the release agent layer on the substrate. Examples of methods for applying the release agent composition include spin coating, spray coating, bar coating, knife coating, roll coating, roll knife coating, blade coating, die coating, gravure coating, and air knife coating.

[0070] Further, for example, the following method can be mentioned. First, a release agent composition for forming the release agent layer containing a thermosetting component is prepared as the release agent composition for forming the release agent layer. Next, the release agent composition is applied onto a substrate, and then heated to dry and cure, thereby providing a release agent layer on the substrate. Further, the following method can be mentioned. First, a release agent composition for forming the release agent layer containing a component having a functional group that reacts with active energy rays is prepared as the release agent composition. Next, the release agent composition is applied onto a substrate, and then the coating film is cured by irradiation with active energy rays, thereby providing a release agent layer on the substrate. Note that the coating film may be cured by using a combination of heating and irradiation with active energy rays. Examples of active energy rays include ultraviolet rays and electron beams.

[0071] The temperature to which the coating film formed on the substrate is heated is preferably 80°C or higher and 250°C or lower, and more preferably 100°C or higher and 230°C or lower. The time for heating the coating film formed on the substrate is preferably 15 seconds or more and 5 minutes or less, and more preferably 20 seconds or more and 3 minutes or less. The coating film formed on the substrate may be cured by heating during drying, or by other means than heating, such as irradiation with active energy rays.

[0072] For example, by adjusting the selection of the substrate, the composition of the release agent composition, etc. in the course of the above-mentioned manufacturing method, it is possible to obtain a synthetic leather casting paper in which the surface of the release agent layer satisfies the above-mentioned properties (1) and (2).

[0073] <Manufacturing method for synthetic leather> Next, a method for producing synthetic leather, which is one preferred embodiment of the present invention, will be described.

[0074] The synthetic leather casting paper according to the present embodiment is used in the synthetic leather manufacturing process. Examples of a method for manufacturing synthetic leather using the synthetic leather casting paper according to the present embodiment include a method having the following steps.

[0075] The method for producing synthetic leather according to this embodiment includes the steps of applying a coating liquid containing a synthetic resin onto a release agent layer in the synthetic leather casting paper according to this embodiment (step 1), drying the applied coating liquid to form synthetic leather containing synthetic resin (step 2), and peeling the synthetic leather casting paper from the synthetic leather after drying (step 3). Step 2 may be a step of drying the applied coating liquid to form a synthetic resin layer, applying an adhesive to the synthetic resin layer, and then laminating a base fabric and aging the resulting product. In this case, step 3 may be a step of peeling the synthetic leather casting paper together with the base fabric from the synthetic leather after aging.

[0076] In the method for producing synthetic leather according to this embodiment, examples of the synthetic resin contained in the synthetic resin-containing coating liquid include urethane resin, vinyl chloride resin, and polyamide resin. From the viewpoint of the texture and durability of synthetic leather, the synthetic resin is preferably a urethane resin. Furthermore, from the viewpoint of obtaining a synthetic leather with a high jet black color, the synthetic resin-containing coating liquid is preferably colored black. In the coating liquid, the synthetic resin itself may be colored black, or the coating liquid containing the synthetic resin may be colored black.

[0077] Specifically, a coating liquid containing a black urethane resin is applied onto the release agent layer of the synthetic leather casting paper according to this embodiment. Examples of application methods include bar coating, knife coating, roll coating, roll knife coating, blade coating, and die coating. The applied coating liquid is then dried to form a urethane resin layer, after which a base fabric is attached via an adhesive and aged. Finally, the urethane resin layer is peeled off from the synthetic leather casting paper together with the base fabric to produce synthetic leather.

[0078] The synthetic leather casting paper according to this embodiment preferably has a peel strength from the resin layer of the synthetic leather of 30 mN / 30 mm or more and 3,000 mN / 30 mm or less, more preferably 50 mN / 30 mm or more and 2,000 mN / 30 mm or less, even more preferably 60 mN / 30 mm or more and 1,000 mN / 30 mm or less, even more preferably 70 mN / 30 mm or more and 500 mN / 30 mm or less, and even more preferably 90 mN / 30 mm or more and 200 mN / 30 mm or less.

[0079] When the peel strength of the release agent layer from the resin layer of the synthetic leather is equal to or greater than the above-mentioned lower limit, the resin layer of the synthetic leather can be prevented from accidentally peeling off from the release agent layer.When the peel strength of the release agent layer from the resin layer of the synthetic leather is equal to or less than the above-mentioned upper limit, the casting paper for synthetic leather can be stably peeled off from the synthetic leather even after repeated use of the casting paper for synthetic leather, and synthetic leather having the desired deep matte finish and jet black color can be produced.

[0080] <Synthetic leather> Next, a synthetic leather, which is one example of a preferred embodiment of the present invention, will be described.

[0081] The synthetic leather according to this embodiment is obtained by using the synthetic leather casting paper according to this embodiment and by the synthetic leather manufacturing method according to this embodiment. The surface of the synthetic leather according to this embodiment satisfies the following (4). Furthermore, it is preferable that the surface of the synthetic leather according to this embodiment satisfies the following (5). (4) The specular gloss, in accordance with JIS Z 8741:1997, is 0.1% or more and 5.0% or less in 20° gloss value. (5) L conforming to JIS Z 8781-4:2013 * a * b * Lightness L in the color system * The value is 6.0 or less.

[0082] The surface of the synthetic leather according to this embodiment satisfies the above (4), and thus has a deep matte appearance and a jet black color. In particular, when the above (4) and (5) are satisfied, and the lightness L * When the value is 6.0 or less, the surface of the synthetic leather tends to have a more jet black color without losing its matte finish, and therefore the synthetic leather according to this embodiment has a luxurious feel.

[0083] (Specular gloss) The specular gloss of the surface of the synthetic leather according to this embodiment is preferably 0% or more, more preferably 0.1% or more, in terms of 20° gloss value. The specular gloss of the surface of the synthetic leather according to this embodiment is preferably 1.0% or less, more preferably 0.5% or less, and even more preferably 0.3% or less, in 20° gloss value.

[0084] (Lightness L * value) The surface brightness L of the synthetic leather according to this embodiment *Preferably, the value is 5.0 or less, more preferably 4.5 or less, even more preferably 4.0 or less, even more preferably 3.5 or less, and even more preferably 3.0 or less. The surface brightness L of the synthetic leather according to this embodiment * The lower the value, the more jet black the leather. * The value may be, for example, 0 or greater, or 0.1 or greater.

[0085] The synthetic leather produced using the synthetic leather casting paper according to this embodiment can be used for various purposes, such as shoes, bags, sofas, school bags, and interior materials for vehicles.

[0086] The present invention is not limited to the above-described embodiment, and may include modifications and improvements within the scope of achieving the object of the present invention. [Example]

[0087] Examples will be described below, but the present invention is not limited to these examples in any way.

[0088] The following raw materials were prepared as raw materials for producing the casting paper for synthetic leather of each Example and Comparative Example.

[0089] (binder resin) "PVA": A mixture of 50 parts by mass of PVA (Kuraray Poval 22-98, manufactured by Kuraray Co., Ltd.) and 50 parts by mass of PVA (Kuraray Poval 5-98, manufactured by Kuraray Co., Ltd.). "Silicone-modified acrylic resin / melamine": A mixed resin of silicone-modified acrylic resin and melamine (X-62-9088, manufactured by Shin-Etsu Chemical Co., Ltd.). "Silicone-modified alkyd resin / melamine": A mixed resin of silicone-modified alkyd resin and melamine (Tesfine 309, manufactured by Showa Denko).

[0090] (filler) "Starch particles": Acetylated rice-derived starch particles (Matsutani Kikyou, manufactured by Matsutani Chemical Industry Co., Ltd.) The average particle diameter (D50) of these starch particles was 4.1 μm. "Silica particles A": amorphous silica particles (Sylysia 420 manufactured by Fuji Silysia Chemical Ltd.) The average particle diameter (D50) of the silica particles A was 3.1 μm. "Silica particles B": amorphous silica particles (Silisia 470 manufactured by Fuji Silysia Chemical Ltd.) The average particle diameter (D50) of silica particles B was 14.1 μm. The average particle size (D50) of the filler is a value obtained by measuring the median value of the volumetric particle size distribution (D50 in the volumetric particle size distribution) using a laser diffraction particle size distribution analyzer (product name "Mastersizer 3000" manufactured by Malvern Panalytical).

[0091] (Removal agent) Emulsion silicone KM-3951 (Shin-Etsu Chemical Co., Ltd.)

[0092] (base material) "Substrate A": Matte Plus Genshi 155.5G (one-sided clay-coated paper, manufactured by Nippon Paper Industries Co., Ltd.). Thickness: 194 μm. The surface characteristics of the clay-coated surface of Substrate A are rougher than the surface characteristics of the cast-coated surface of Substrate B. Furthermore, no release agent layer is provided on either the clay-coated surface or the base paper surface of Substrate A. "Substrate B": Espritcoat E (ST) 165G (one-sided cast-coated paper, manufactured by Nippon Paper Industries Co., Ltd.) thickness 194 μm. The surface characteristics of the cast-coated surface of substrate B are smoother than those of the clay-coated surface of substrate A. Furthermore, substrate B does not have a release agent layer on either the cast-coated surface or the base paper surface.

[0093] Example 1 [Production of casting paper for synthetic leather]

[0094] Starch particles were dispersed in 100 parts by mass of PVA to a solid content of 80 parts by mass, and 43.5 parts by mass of a release agent was added in terms of solid content, followed by dilution with water to 18% by mass to prepare release agent composition coating solution A. Release agent composition coating solution A contains the aforementioned release agent (emulsion silicone KM-3951). The coating amount after drying was 5 g / m on the rough surface (clay coated surface) of the above-mentioned substrate A. 2 The release agent composition coating solution A was applied using a Mayer bar so that the coating temperature was as follows: After coating, the coating solution was dried at 180°C for 1 minute to prepare a casting paper for synthetic leather.

[0095] [Making synthetic leather] (Preparation of Black Polyurethane Resin Layer Coating Solution) A black polyurethane resin layer coating liquid having a solids ratio (mass ratio) of thermoplastic polyurethane resin to black pigment of 100:6.4 was prepared by mixing and stirring 100 parts by mass (solids concentration: 35% by mass) of thermoplastic polyurethane resin (trade name: CRISBON 7367SL, manufactured by DIC Corporation), 15 parts by mass (solids concentration: 15% by mass) of black pigment (trade name: UST-3794black, manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.), 30 parts by mass of methyl ethyl ketone, and 10 parts by mass of dimethylformamide.

[0096] (Preparation of adhesive layer coating liquid) An adhesive layer coating liquid was prepared by mixing and stirring 100 parts by mass of polyurethane resin (trade name: CRISBON 4010, manufactured by DIC Corporation) (solid content concentration: 50% by mass), 3 parts by mass of amine catalyst (trade name: CRISBON Accel HM, manufactured by DIC Corporation) (solid content concentration 100% by mass), 5 parts by mass of dimethylformamide, and 10 parts by mass of toluene. Prior to use of the adhesive layer coating liquid, 10 parts by mass of polyisocyanate crosslinking agent (trade name: BURNOCK D-750, manufactured by DIC Corporation) (solid content concentration: 75% by mass) was mixed and stirred, and then the adhesive layer coating liquid was used.

[0097] (Production of synthetic leather) A black polyurethane resin layer coating solution was applied to the release agent layer surface of the synthetic leather casting paper using an applicator so that the film thickness after drying would be 15 μm, and then dried at 100°C for 3 minutes. An adhesive layer coating solution of polyurethane resin (CRISBON 4010, manufactured by DIC Corporation) was applied to the dried black polyurethane resin layer using an applicator so that the film thickness in a wet state would be 75 μm. A wet base fabric was laminated onto the applied adhesive layer coating solution and pressed with a hand roller, and then dried at 100°C for 5 minutes. The mixture was then left to stand at room temperature for 24 hours. After standing, the interface between the release agent layer of the synthetic leather casting paper and the black polyurethane resin layer was peeled off to produce synthetic leather.

[0098] <Example 2> Casting paper for synthetic leather and synthetic leather were prepared in the same manner as in Example 1, except that in the aforementioned release agent composition coating solution A, starch particles were dispersed so that the solid content ratio was 100 parts by mass relative to 100 parts by mass of PVA.

[0099] Example 3 Casting paper for synthetic leather and synthetic leather were prepared in the same manner as in Example 1, except that in the release agent composition coating solution A, starch particles were dispersed in an amount of 120 parts by mass, in terms of solid content, relative to 100 parts by mass of PVA.

[0100] Example 4 [Production of casting paper for synthetic leather] Silica particles A were dispersed in a toluene solution containing 100 parts by mass of silicone-modified acrylic resin / melamine to a solid content ratio of 30 parts by mass and added to prepare release agent composition coating solution B. Note that release agent composition coating solution B does not contain the aforementioned release agent (silicone emulsion KM-3951). The coated amount after drying was 5 g / m on the smooth surface (cast coated surface) of substrate B. 2 The release agent composition coating solution B was applied using a Mayer bar so that the coating temperature was as follows: After coating, the sheet was dried at 180°C in two steps: an initial drying step and a post-drying step immediately thereafter, to prepare a casting paper for synthetic leather.

[0101] [Making synthetic leather] The synthetic leather of Example 4 was produced in the same manner as in Example 1, except that the casting paper for synthetic leather of Example 4 was used instead of the casting paper for synthetic leather of Example 1.

[0102] <Example 5> A casting paper for synthetic leather and synthetic leather were produced in the same manner as in Example 4, except that in the release agent composition coating liquid B, a silicone-modified alkyd resin / melamine was used as the binder resin.

[0103] <Comparative Example 1> Casting paper for synthetic leather and synthetic leather were prepared in the same manner as in Example 1, except that in the aforementioned release agent composition coating solution A, starch particles were dispersed so that the solid content ratio was 60 parts by mass per 100 parts by mass of PVA.

[0104] <Comparative Example 2> A casting paper for synthetic leather and synthetic leather were produced in the same manner as in Example 1, except that in the release agent composition coating solution A, the starch particles were changed to silica particles B.

[0105] <Comparative Example 3> A casting paper for synthetic leather and a synthetic leather were produced in the same manner as in Example 5, except that in the above-mentioned release agent composition coating solution B, the silica particles A were changed to the silica particles B and the content was changed to 13 parts by mass.

[0106] <Comparative Example 4> A casting paper for synthetic leather and synthetic leather were produced in the same manner as in Example 5, except that the content of silica particles A in the release agent composition coating liquid B was changed to 5 parts by mass.

[0107] [Evaluation of surface properties] The specular gloss and surface properties of the surface of the release agent layer of the synthetic leather casting paper prepared in each example, and the surface of the synthetic leather obtained using the synthetic leather casting paper prepared in each example, were evaluated according to the measurement methods shown below. The measurement results are shown in Table 2. For the synthetic leather obtained in each example, in addition to the specular gloss and surface properties other than the arithmetic surface height Sa, L * a * b * Lightness L in the color system * was measured.

[0108] (Specular gloss) Using a gloss meter (VG7000, manufactured by Nippon Denshoku Industries Co., Ltd.), the specular gloss of the surface of the release agent layer of the synthetic leather casting paper and the surface of the synthetic leather was measured at angles of 20° and 60°. The specular gloss was measured in accordance with "JIS Z8741-1997 Specular Gloss Measurement Method."

[0109] (Ra, Rz, Rzjis, ΔRz) Using a contact surface roughness meter (SV3000S4, manufactured by Mitutoyo Corporation), the arithmetic mean roughness Ra, maximum height roughness Rz, and ten-point mean roughness Rzjis were measured in accordance with JIS B0601: 2001. ΔRz was calculated by subtracting the Rzjis value from the Rz value.

[0110] (Sa) Using a shape measuring laser microscope (VK-9700, manufactured by Keyence Corporation), the arithmetic mean height Sa was measured in accordance with ISO 25178. This measuring device is a non-contact type measuring device.

[0111] (L * ) Using a colorimeter (Colorcom System, manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.), lightness L* in the L*a*b* color system was measured in accordance with JIS Z 8781-4:2013.

[0112] [Table 1]

[0113] [Table 2] [Explanation of symbols]

[0114] 100, 200...casting paper for synthetic leather, 10, 20...substrate, 10S...surface (surface of substrate), 20S...surface (surface of substrate), 30, 40...release agent layer, 30S...surface (surface of release agent layer), 40S...surface (surface of release agent layer), 31, 42...binder resin, 33, 44...filler, 35, 46...release agent composition.

Claims

1. A substrate and a release agent layer provided on the substrate, the release agent layer contains (A) a binder resin and (B) a filler, the binder resin (A) contains polyvinyl alcohol, The (B) filler contains starch particles, the surface of the release agent layer opposite to the substrate satisfies the following (1) and (2): Process paper for synthetic leather. (1) The specular gloss, in accordance with JIS Z 8741:1997, is 0.1% or more and 5.0% or less in terms of 20° gloss value. (2) ΔRz, which is the value obtained by subtracting the ten-point average roughness Rzjis from the maximum height roughness Rz in accordance with JIS B 0601:2001, is 0 μm or more and 5.0 μm or less.

2. The surface of the release agent layer further satisfies the following (3): The casting paper for synthetic leather according to claim 1. (3) The arithmetic mean height Sa measured in accordance with ISO 25178 is 1 μm or more.

3. a step of applying a coating liquid containing a synthetic resin onto the release agent layer of the casting paper for synthetic leather according to claim 1 or 2; a step of drying the applied coating liquid to form a synthetic leather containing the synthetic resin; After drying, peeling the synthetic leather casting paper from the synthetic leather. Synthetic leather manufacturing method.

4. The surface of the synthetic leather satisfies the following (4): The method for producing the synthetic leather according to claim 3. (4) The specular gloss, in accordance with JIS Z 8741:1997, is 0.1% or more and 5.0% or less in terms of 20° gloss value.

5. The surface of the synthetic leather satisfies the following (5): The method for producing the synthetic leather according to claim 4. (5) L conforming to JIS Z 8781-4:2013 ＊ a ＊ b ＊ Lightness L in the color system ＊ The value is 6.0 or less.

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