Synthetic leather and method for producing same

Abstract

[Problem] To provide synthetic leather having abrasion resistance and flame retardancy suitable for industrial materials such as vehicle interior materials and interior materials, especially for seats, the synthetic leather causing no problem of delamination between different types of resin in a resin layer.　[Solution] This synthetic leather comprises a laminate including a fibrous base material and a synthetic resin layer provided on the fibrous base material, wherein the synthetic resin layer includes a plurality of thermoplastic resin composition layers having different compositions, and at least a mixed composition layer is included at a boundary surface of adjacent layers of the plurality of thermoplastic resin composition layers, with the compositions of the adjacent thermoplastic resin composition layers being mixed in the mixed composition layer.　

Description

Synthetic leather and its manufacturing method

[0001] The present invention relates to synthetic leather, and more particularly to synthetic leather suitable for industrial materials such as vehicle interior trims and interior materials.

[0002] Conventional synthetic leathers are often constructed by laminating multiple resin layers with different properties onto a fibrous substrate in order to simultaneously satisfy multiple different required properties. For example, physical properties such as abrasion resistance, mechanical properties, and flame retardancy may conflict with physical properties such as flexibility, cushioning, and texture, making it difficult to achieve sufficient levels of both properties simultaneously in a single resin layer. On the other hand, laminating multiple resin layers with different properties creates interfaces between the resin layers, which can easily lead to delamination.

[0003] For example, Patent Document 1 discloses a synthetic leather in which a porous layer made of a moisture-curing polyurethane resin and a non-porous layer made of a polyurethane resin are laminated in this order on one side of a fibrous substrate. According to the disclosure of this document, a synthetic leather can be obtained that has high flame retardancy without compromising design, appearance quality, or texture, and is highly safe for the environment and the human body. However, since the synthetic leather in this document is constructed by laminating multiple resin layers in order, there are interfaces between the multiple resin layers, making it prone to interlayer delamination.

[0004] Patent Document 2 discloses a synthetic leather comprising a substrate layer made of a nonwoven fabric or woven or knitted fabric, an adhesive layer laminated on the substrate layer, and a skin layer laminated on the adhesive layer, the adhesive layer containing a flame retardant. A porous layer is also provided between the substrate layer and the adhesive layer. However, this method exclusively employs a method in which the skin layer is formed on a release paper, an adhesive layer is further formed on the skin layer, and a porous layer is formed on the substrate layer, and the two are then bonded together, which creates a high possibility of an interface between the adhesive layer and the porous layer that is prone to delamination.

[0005] Patent Document 3 discloses a method of producing a laminate that is less susceptible to delamination by co-extruding a foamable polyurethane resin composition and a thermoplastic elastomer in a molten state to form a two-layer structure, and laminating this with a fibrous substrate to produce a laminate that can be used for synthetic leather, etc. However, this method does not aim to simultaneously satisfy multiple different required properties, and therefore does not disclose a method of laminating multiple resin layers having different properties while making use of each of those properties.

[0006] JP-A-2009-19304 Patent No. 5731086 JP-A 10-193430

[0007] The present invention has been made in view of the above-mentioned current situation, and aims to provide a synthetic leather that has improved strength and durability by providing a plurality of resin composition layers having different physical properties, thereby making it possible to simultaneously satisfy a plurality of different required characteristics, while preventing delamination between the resin compositions.

[0008] That is, the present invention relates to the following synthetic leather and a method for producing the same: (1) A synthetic leather consisting of a laminate including a fibrous substrate and a synthetic resin layer provided on the fibrous substrate, characterized in that the synthetic resin layer includes a plurality of thermoplastic resin composition layers having different compositions, and at least a mixed-composition layer, in which the compositions of the adjacent thermoplastic resin layers are mixed, is included at the interface between the plurality of thermoplastic resin composition layers.

[0009] (2) The synthetic leather according to (1), wherein the synthetic resin layer comprises at least a substrate-side thermoplastic resin composition layer present on the surface in contact with the fibrous substrate and a surface-side thermoplastic resin composition layer present on the surface opposite to the surface in contact with the fibrous substrate, and the surface-side thermoplastic resin composition layer is composed of a thermoplastic polycarbonate-based polyurethane resin composition.

[0010] (3) The synthetic leather according to (1), wherein the synthetic resin layer comprises at least a substrate-side thermoplastic resin composition layer present on the surface in contact with the fibrous substrate and a surface-side thermoplastic resin composition layer present on the surface opposite to the surface in contact with the fibrous substrate, and the substrate-side thermoplastic resin composition layer is composed of a thermoplastic polyether-based polyurethane resin composition.

[0011] (4) The synthetic leather according to (3), wherein the substrate-side thermoplastic resin composition layer contains bubbles, and the volume fraction of the bubbles in the substrate-side thermoplastic resin composition layer is 10 to 60%.

[0012] (5) The synthetic leather according to (1), wherein the laminate constituting the synthetic leather further has a surface treatment layer containing a silicone compound on the surface opposite to the fibrous substrate.

[0013] (6) A method for producing a synthetic leather according to (1), comprising the steps of: joining and laminating melts of a plurality of thermoplastic resin compositions having different compositions supplied from a plurality of extruders before a T-die; extruding the joined and laminated melts from the T-die by a co-extrusion method to form a synthetic resin layer; and laminating the synthetic resin layer and a fibrous substrate.

[0014] (7) The method for producing a synthetic leather according to (6), characterized in that the step of forming the synthetic resin layer comprises extruding a melt of the thermoplastic resin composition for the substrate side from one extruder and a melt of the thermoplastic resin composition for the surface side from another extruder, supplying both melts to a feed block, joining and laminating them in the feed block, and then supplying the joined laminated melt to a co-extrusion T-die connected to the feed block. －１ and a viscosity at a melting temperature of 185°C of 500 to 10,000 Pa·s.

[0015] According to the present invention, it is possible to provide synthetic leather that contains a plurality of thermoplastic resin composition layers with different compositions in a synthetic resin layer, yet has excellent peel strength between the thermoplastic resin composition layers, and can simultaneously satisfy various conflicting required properties. For example, until now, it has been difficult to simultaneously satisfy abrasion resistance and flexibility, low-temperature flexibility, flame retardancy, low cost, etc., because these properties are in conflict with each other. However, according to the present invention, it is possible to obtain synthetic leather that has high abrasion resistance and also has excellent flexibility, low-temperature flexibility, flame retardancy, low cost, etc.

[0016] 1 is a schematic diagram showing the cross-sectional structure of the synthetic leather of the present invention.

[0017] 1. Synthetic Leather The synthetic leather of the present invention comprises at least a fibrous substrate and a synthetic resin layer. (1) Fibrous Substrate The fibrous substrate used in the present invention is not particularly limited, and examples include fibrous fabrics such as woven fabrics, knitted fabrics, and nonwoven fabrics, as well as natural leather (including split leather). The fibrous fabric may be one that has been coated or impregnated with a conventionally known solvent-based or solventless polymer compound and then dry- or wet-coagulated. The term "solventless" as used herein includes aqueous systems.

[0018] Examples of the polymer compound include polyurethane resin and vinyl chloride resin. The type of fiber in the fiber fabric is not particularly limited, and examples thereof include conventionally known fibers such as natural fibers, regenerated fibers, semi-synthetic fibers, and synthetic fibers, and two or more of these may be combined.

[0019] Among these, knitted fabrics made of synthetic fibers, particularly polyester fibers, are preferably used as the fibrous substrate from the viewpoints of strength and processability. The single yarn fineness is not particularly limited, but is preferably 0.1 to 20 dtex. The fibrous substrate may be colored with a dye or pigment.

[0020] The thickness of the fibrous substrate is not particularly limited and may be set appropriately depending on the application. In the case of a knitted fabric made of synthetic fibers, the thickness is preferably about 0.7 to 1.2 μm. The mass per unit area of ​​the fibrous substrate is also not particularly limited, but from the viewpoint of abrasion resistance, it is preferably 150 to 350 g / m ２ is preferable, and more preferably 260 to 320 g / m２ is.

[0021] (2) Synthetic Resin Layer The synthetic resin layer of the present invention is a laminate containing two or more layers made of thermoplastic resin compositions with different properties. Here, the properties include color, abrasion resistance, tensile strength, tear strength, low-temperature bending resistance, flexibility, heat resistance, light resistance, hydrolysis resistance, oil resistance, chemical resistance, flame retardancy, etc., which are required for synthetic leather. In the present invention, by including two or more thermoplastic resin composition layers with different properties in a synthetic resin layer composed of multiple layers, various required properties can be simultaneously satisfied.

[0022] The fact that the properties of the plurality of thermoplastic resin composition layers are different from one another usually means that the plurality of thermoplastic resin composition layers have different compositions.

[0023] Here, the differences in composition may include differences in the thermoplastic resins themselves that form the matrix, differences in the additives blended therein, differences in the blending ratio of the thermoplastic resin and the additives, differences in the presence or absence of bubbles or differences in the volume fraction of bubbles, etc.

[0024] In the present invention, two or more thermoplastic resin composition layers having different compositions and properties are contained in a synthetic resin layer, and various required properties can be simultaneously satisfied. In addition, as will be described later, the present invention has the characteristic that delamination does not occur between the multiple thermoplastic resin composition layers having different properties.

[0025] <Layer structure of synthetic resin layer> The synthetic resin layer of the present invention includes two or more thermoplastic resin composition layers having different compositions, and further includes at least a mixed composition layer at the interface between these multiple thermoplastic resin composition layers, in which the compositions of the adjacent multiple thermoplastic resin layers are mixed.

[0026] In the present invention, in contrast to a mixed composition layer in which the compositions of adjacent thermoplastic resin layers are mixed, the plurality of thermoplastic resin composition layers themselves may be referred to as single composition layers, and therefore the synthetic resin layer of the present invention includes a single composition layer and a mixed composition layer.

[0027] As an example, in the case of a synthetic resin layer containing two thermoplastic resin composition layers having different compositions, if the two layers are designated as Layer A and Layer B, Layer A and Layer B each exist independently in the layer structure within the synthetic resin layer, while a mixed composition layer in which the compositions of Layer A and Layer B are mixed exists in the layer portion corresponding to the boundary surface (lamination boundary) where Layer A and Layer B are adjacent.

[0028] Therefore, the mixed composition layer is sandwiched between layers A and B, and the compositions of layers A and B are mixed. Preferably, the portion closer to layer A has a composition closer to layer A, and the portion closer to layer B has a composition closer to layer B. It is more preferable that the mixing ratio of the compositions of layers A and B changes continuously in the thickness direction.

[0029] Near the boundary surface with layer A, the composition of the mixed composition layer becomes extremely close to that of layer A, and near the boundary surface with layer B, the composition of the mixed composition layer becomes extremely close to that of layer B. For this reason, layers A and B are connected via a mixed composition layer whose composition changes continuously in the thickness direction, and as a result, there is no clear layer boundary surface between layer A, the mixed composition layer, and layer B.

[0030] For example, if layer A contains additive a and layer B contains additive b, the mixed composition layer contains additive a and additive b, and the concentration of additive a increases in the thickness direction from layer B to layer A, and the concentration of additive b increases in the thickness direction from layer A to layer B.

[0031] By blurring the interface between the layers in this way, the peel strength between layers A and B is increased, making it less likely for delamination to occur. By giving layers A and B different properties, it is possible to create a synthetic leather that is highly durable and less likely to delaminate, while simultaneously satisfying different required properties.

[0032] The above-mentioned examples of the A layer and B layer are merely examples, and the present invention may include three or more layers of a single composition, or two or more layers of a mixed composition.

[0033] In the present invention, the synthetic resin layer is provided on a fibrous substrate, and one side of the synthetic resin layer is in contact with the fibrous substrate. Among the multiple thermoplastic resin composition layers constituting the synthetic resin layer, the thermoplastic resin composition layer that is a single-composition layer present on the side in contact with the fibrous substrate is referred to as the substrate-side resin layer.

[0034] A single-composition layer is also present on the other side of the synthetic resin layer (the surface side opposite to the surface in contact with the fibrous substrate). Of the multiple thermoplastic resin composition layers constituting the synthetic resin layer, the single-composition thermoplastic resin composition layer present on the surface side opposite to the surface in contact with the fibrous substrate is referred to as the surface-side resin layer. Therefore, the synthetic resin layer includes at least a substrate-side resin layer and a surface-side resin layer as single-composition layers.

[0035] The layer structure of the synthetic resin layer includes at least a substrate-side resin layer (single-composition layer), a surface-side resin layer (single-composition layer), and a mixed-composition layer, but may also include other thermoplastic resin composition layers.

[0036] Such a single-composition layer can be provided at any position between the substrate-side resin layer and the surface-side resin layer, and can impart new physical properties to the synthetic leather. When providing such a new single-composition layer, a new mixed-composition layer can be formed between the new single-composition layer and another single-composition layer adjacent to it. By forming a mixed-composition layer between adjacent single-composition layers, interlayer delamination can be made less likely to occur.

[0037] The synthetic resin layer preferably has a three-layer structure including a substrate-side resin layer, a surface-side resin layer, and a mixed composition layer formed between the substrate-side resin layer and the surface-side resin layer.

[0038] When the synthetic resin layer has a three-layer structure as described above, the mixed-composition layer is sandwiched between two single-composition layers (a substrate-side resin layer and a surface-side resin layer) of different compositions, and the compositions of both layers are mixed. Preferably, the mixed-composition layer has a composition close to the substrate-side resin layer on the side closer to the surface-side resin layer, and a composition close to the surface-side resin layer on the side closer to the surface-side resin layer on the side closer to the surface-side resin layer. More preferably, the mixing ratio of the respective compositions of the substrate-side resin layer and the surface-side resin layer changes continuously in the thickness direction.

[0039] The composition of the mixed composition layer is as close as possible to that of the substrate-side resin layer near the interface with the substrate-side resin layer, and the composition of the mixed composition layer is as close as possible to that of the surface-side resin layer near the interface with the surface-side resin layer. This ensures that the two single-composition layers are connected via the mixed composition layer whose composition changes continuously in the thickness direction, and as a result, it is desirable that there is no clear layer boundary surface between the substrate-side resin layer, the mixed composition layer, and the surface-side resin layer.

[0040] By blurring the laminated boundary between the multiple layers in this way, the peel strength between the substrate-side resin layer and the surface-side resin layer is increased, making delamination less likely to occur. By giving the substrate-side resin layer and the surface-side resin layer different properties, it is possible to produce a synthetic leather that is highly durable and less likely to delaminate while simultaneously satisfying different required properties.

[0041] <Layer Thickness> The thickness of the synthetic resin layer is not particularly limited, but is preferably 50 μm or more, more preferably 100 μm or more, for the entire synthetic resin layer. The upper limit of the thickness of the synthetic resin layer is not particularly limited, but is preferably 500 μm or less, more preferably 400 μm or less. If the thickness is 50 μm or more, sufficient abrasion resistance tends to be obtained. If the thickness is 500 μm or less, there is no risk of the texture becoming rough and hard.

[0042] The thickness of the substrate-side resin layer constituting the synthetic resin layer is not particularly limited, but assuming that no mixed composition layer is formed and the lamination boundary between the substrate-side resin layer and the single-composition layer adjacent to the substrate-side resin layer is clearly defined, the target thickness of the substrate-side resin layer is preferably 40 μm or more, more preferably 90 μm or more. The upper limit of the target thickness of the substrate-side resin layer is not particularly limited, but is preferably 400 μm or less, more preferably 300 μm or less.

[0043] The thickness of the surface-side resin layer constituting the synthetic resin layer is not particularly limited, but assuming that a mixed-composition layer is not formed and a laminate boundary surface between the substrate-side resin layer and the single-composition layer adjacent to the substrate-side resin layer is clear, the target thickness of the surface-side resin layer is preferably 10 μm or more, more preferably 20 μm or more. The upper limit of the target thickness of the surface-side resin layer is not particularly limited, but is preferably 100 μm or less, more preferably 80 μm or less.

[0044] When a mixed composition layer is formed between two single-composition layers, the thickness of the mixed composition layer is affected by the target thickness of the thinner of the two single-composition layers on both sides. For example, a mixed composition layer of approximately the same thickness as the thinner single-composition layer may be formed. For example, when a mixed composition layer is formed between two single-composition layers, a surface-side resin layer and a substrate-side resin layer, the thickness of the mixed composition layer may be affected by the target thickness of the thinner surface-side resin layer. If the target thickness of the surface-side resin layer is set to 40 μm and the target thickness of the substrate-side resin layer is set to 200 μm, the resulting synthetic resin layer may be approximately 20 μm for the surface-side resin layer, 40 μm for the mixed composition layer, and 180 μm for the substrate-side resin layer. However, this is just one example, and the present invention is not limited thereto.

[0045] The thickness of the mixed composition layer can be determined by cutting the synthetic resin layer in the thickness direction with a razor blade, observing the cross section under a microscope, and visually checking.

[0046] <Matrix Resin> The matrix resin of the thermoplastic resin composition constituting the synthetic resin layer is not particularly limited, and any conventionally known thermoplastic resin can be used. Examples include thermoplastic polyurethane resins such as polyether-based polyurethane resins, polyester-based polyurethane resins, and polycarbonate-based polyurethane resins; and elastomers such as polyester elastomer resins, polyamide elastomer resins, polyether elastomer resins, polystyrene-based elastomer resins, polyolefin-based elastomer resins, and polyvinyl chloride-based elastomers. These can be used alone or in combination of two or more.

[0047] Among these, thermoplastic polyurethane resins are preferably used, with thermoplastic polycarbonate-based polyurethane resins being preferred from the viewpoint of abrasion resistance, and thermoplastic polyether-based polyurethane resins being preferred from the viewpoints of texture, low-temperature flexibility, and hydrolysis resistance.

[0048] Any thermoplastic polyurethane resin that can be melted by heating can be used as the thermoplastic polyurethane resin. Generally, a thermoplastic polyurethane resin obtained by reacting a polymer diol, an organic diisocyanate, and a chain extender is used. Among these, a thermoplastic polyurethane resin obtained by reacting a polymer diol having a number average molecular weight of preferably 800 to 8,000, more preferably 900 to 6,000, with an organic diisocyanate and a chain extender is preferably used. The number average molecular weight can be determined by gel permeation chromatography (GPC) using polystyrene as a standard substance.

[0049] Examples of polymer diols preferably used in the production of thermoplastic polyurethane resins include polyester diols, polyether diols, polycarbonate diols, polyester polycarbonate diols, and polyester polyether diols, and one or more of these can be used. Among these, it is preferable to use polycarbonate diols and / or polyether diols as the polymer diols. When polycarbonate diols are used as the polymer diols, thermoplastic polycarbonate-based polyurethane resins can be obtained, and when polyether diols are used as the polymer diols, thermoplastic polyether-based polyurethane resins can be obtained.

[0050] Examples of polycarbonate diols used in the production of thermoplastic polyurethane resins include polycarbonate diols obtained by reacting a low-molecular-weight diol component with a carbonate compound such as a dialkyl carbonate, an alkylene carbonate, a diaryl carbonate, etc. Examples of dialkyl carbonates include dimethyl carbonate and diethyl carbonate, examples of alkylene carbonates include ethylene carbonate, and examples of diaryl carbonates include diphenyl carbonate.

[0051] Examples of the low molecular weight diol component include aliphatic diols such as ethylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 2-methyl-1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol; and alicyclic diols such as cyclohexanedimethanol and cyclohexanediol. One or more of these may be used.

[0052] Examples of polyether diols used in the production of thermoplastic polyurethane resins include polyethylene glycol, polypropylene glycol, and polytetramethylene glycol, and one or more of these can be used.

[0053] The type of organic diisocyanate used in the production of thermoplastic polyurethane resin is not particularly limited, and any of the organic diisocyanates conventionally used in the production of polyurethanes can be used. Among these, one or more of aromatic diisocyanates, alicyclic diisocyanates, and aliphatic diisocyanates having a molecular weight of 500 or less are preferably used as the organic diisocyanate.

[0054] The usable aliphatic or alicyclic diisocyanates are preferably those having a carbon number of 4 to 30. Examples of the aliphatic diisocyanate include tetramethylene diisocyanate, 1,5-pentamethylene diisocyanate (PDI), 1,6-hexamethylene diisocyanate (HDI), 2,2,4- (or 2,4,4-) trimethyl-1,6-hexamethylene diisocyanate, and lysine diisocyanate.

[0055] Examples of alicyclic diisocyanates include isophorone diisocyanate, hydrogenated xylene diisocyanate, hydrogenated diphenylmethane diisocyanate, norbornane diisocyanate, 1,4-diisocyanate cyclohexane, 1,3-bis(diisocyanate methyl) cyclohexane, and 4,4'-dicyclohexylmethane diisocyanate.

[0056] Examples of aromatic diisocyanates include 1,3-xylene diisocyanate, 1,4-xylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, diphenylmethane diisocyanate, phenylene diisocyanate, dimethyldiphenylmethane diisocyanate, triphenylmethane triisocyanate, naphthalene diisocyanate, and polymethylene polyphenyl polyisocyanate.

[0057] These diisocyanates may be used alone or in combination. More preferred examples include 1,5-pentamethylene diisocyanate (PDI), 1,6-hexamethylene diisocyanate (HDI), isophorone diisocyanate, 1,3-xylene diisocyanate, 1,4-xylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, and diphenylmethane diisocyanate. Among these, 1,6-hexamethylene diisocyanate is preferred due to its weather resistance and ease of industrial availability. Furthermore, considering the impact on the environment, it is preferable to use environmentally friendly 1,5-pentamethylene diisocyanate, which is a plant-derived isocyanate.

[0058] The type of chain extender used in the production of the thermoplastic polyurethane resin is not particularly limited, and any of the conventionally used chain extenders can be used. Among these, a low-molecular-weight compound having two or more active hydrogen atoms in the molecule capable of reacting with an isocyanate group and a molecular weight of 300 or less is preferably used as the chain extender. Examples of such chain extenders include diols such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,4-bis(β-hydroxyethoxy)benzene, 1,4-cyclohexanediol, bis-(β-hydroxyethyl)terephthalate, and xylylene glycol; diamines such as hydrazine, ethylenediamine, propylenediamine, xylylenediamine, isophoronediamine, piperazine and its derivatives, phenylenediamine, tolylenediamine, xylylenediamine, dihydrazine adipate, and dihydrazine isophthalate; and aminoalcohols such as aminoethyl alcohol and aminopropyl alcohol. These may be used alone or in combination. Among these, aliphatic diols having 2 to 10 carbon atoms are preferably used because the polyurethane foam layer obtained therefrom, and in turn the laminate, has good mechanical properties, and 1,4-butanediol is particularly preferably used.

[0059] In the present invention, a thermoplastic polyurethane resin obtained by reacting the above-mentioned polymeric diol, organic diisocyanate, and chain extender is preferably used. The method for producing the thermoplastic polyurethane resin is not particularly limited, and it can be produced by a prepolymer method or a one-shot method using a known urethane reaction technique using a polymeric diol, organic diisocyanate, chain extender, and other components as necessary. Among these, a method of melt polymerization substantially in the absence of a solvent, particularly a method of continuous melt polymerization using a multi-screw extruder, is preferably used.

[0060] In the present invention, it is preferable to use a thermoplastic polyurethane resin having a hardness in the range of 55 to 95, more preferably 65 to 90, in terms of JIS-A hardness, since this makes it possible to obtain a polyurethane foam layer, and thus a laminate, which is excellent in mechanical strength and flexibility.

[0061] <Additives> Additives can be selected and blended into the thermoplastic resin composition constituting the synthetic resin layer according to the desired properties. The type of additive is not particularly limited, and known additives such as colorants such as color pigments and extender pigments, flame retardants, air bubble generators, biomass fillers, crosslinking agents, heat stabilizers, conductivity imparting agents, antistatic agents, moisture permeability improvers, water repellents, oil repellents, water absorbents, moisture absorbents, deodorizers, pigment dispersants, and hydrolysis inhibitors can be added as needed.

[0062] The synthetic resin layer of the present invention preferably contains a flame retardant. The flame retardant is not particularly limited, and for example, phosphorus-based flame retardants, bromine-based flame retardants, antimony trioxide-based flame retardants, etc. can be used alone or in combination of two or more. Among the flame retardants, antimony trioxide-based flame retardants have poor flame retarding effect when used alone, and halogen-based flame retardants are concerned about their accumulation in the environment and toxicity to living organisms, so phosphorus-based flame retardants are more preferably used.

[0063] Examples of phosphorus-based flame retardants include diorganylphosphinates, ammonium polyphosphates, aluminum phosphates, phosphate esters, guanidine phosphates, and organic phosphine oxides, and these may be used alone or in combination of two or more.

[0064] The synthetic resin layer of the present invention may contain a colorant, such as carbon black, titanium oxide, phthalocyanine blue, phthalocyanine green, red iron oxide, or yellow iron oxide.

[0065] <Bubbles> The synthetic resin layer of the present invention preferably contains bubbles. Specifically, the synthetic resin layer of the present invention preferably has a thermoplastic resin composition layer containing bubbles. The presence of bubbles allows for the production of synthetic leather that is flexible and has an excellent texture. The size of the bubbles (the average diameter of the bubbles or the average length of the longest part of the cross-sectional shape) is not particularly limited, but is preferably 10 μm or more, more preferably 20 μm or more. The upper limit of the bubble size is not particularly limited, but is preferably 300 μm or less, more preferably 200 μm or less. A size of 10 μm or more tends to provide sufficient flexibility. A size of 300 μm or less tends to provide sufficient abrasion resistance. Note that the bubble size in the present invention refers to the size of the bubbles in the entire synthetic resin layer, including the single-composition layer and the mixed-composition layer, and can be determined by cutting the synthetic resin layer with a razor blade or the like, photographing the cross-section with a microscope, and measuring the length using image processing software.

[0066] Methods for incorporating bubbles into a thermoplastic resin composition layer include, but are not limited to, mixing hollow particles into the thermoplastic resin composition, or mixing a thermoexpandable microcapsule that vaporizes the encapsulated substance at the molding temperature to generate bubbles, or a thermally decomposable foaming agent that decomposes at the molding temperature to generate bubbles, into the thermoplastic resin composition before molding, and foaming the resin layer during molding. Hereinafter, these will be referred to as "bubble-generating agents."

[0067] The volume fraction of bubbles in the synthetic resin layer of the present invention is not particularly limited, but is preferably 10% or more, more preferably 20% or more. The upper limit of the volume fraction of bubbles is not particularly limited, but is preferably 60% or less, more preferably 50% or less. A volume fraction of 10% or more tends to provide sufficient flexibility, while a volume fraction of 60% or less tends to provide sufficient abrasion resistance. The volume fraction of bubbles is a value calculated based on the sum of the volume of the thermoplastic resin composition layer containing the bubble-generating agent and the volume of the mixed composition layer up to the midpoint. The volume fraction of bubbles can be determined by cutting the synthetic resin layer with a razor blade, photographing the cross section with a microscope, and calculating the sum of the area of ​​the thermoplastic resin composition layer containing the bubble-generating agent and the area of ​​the mixed composition layer up to the midpoint in the thickness direction using image processing software, and the area of ​​the bubbles, and then using the following formula:

[0068] (Equation 1) [Volume ratio of bubbles (%)] = ([Area of ​​bubbles] ÷ [Sum of area of ​​thermoplastic resin layer and area of ​​mixed composition layer up to the midpoint in the thickness direction]) × 100

[0069] The synthetic resin layer of the present invention preferably includes a thermoplastic resin composition layer containing thermally expandable microcapsules as a bubble generator. Thermally expandable microcapsules are minute plastic spheres containing hydrocarbons that vaporize at approximately the molding temperature within a shell of a thermoplastic polymer such as vinylidene chloride resin or acrylonitrile resin. Preferred examples of thermally expandable microcapsules include the "Advancell EM" series manufactured by Sekisui Chemical Co., Ltd., the "Matsumoto Microsphere F" and "Matsumoto Microsphere FN" series manufactured by Matsumoto Yushi Seiyaku Co., Ltd., and the "Kureha Microsphere H" and "Kureha Microsphere S" series manufactured by Kureha Corporation.

[0070] The synthetic resin layer of the present invention preferably includes a thermoplastic resin composition layer containing a thermally decomposable foaming agent as a bubble-generating agent. Specific preferred examples of the thermally decomposable foaming agent include azodicarbonamide-based foaming agents, 4,4'-oxybis(benzenesulfonylhydrazide)-based foaming agents, and sodium bicarbonate-based foaming agents.

[0071] The synthetic resin layer of the present invention preferably includes a thermoplastic resin composition layer containing hollow particles as a bubble-generating agent. Specific examples of preferred hollow particles include plastic microballoons, hollow glass beads, hollow polymer beads, and shirasu balloons.

[0072] Among the various types of bubble generators mentioned above, those containing a thermoplastic resin composition containing thermally expandable microcapsules are particularly preferred in terms of appearance quality and physical properties, especially abrasion resistance, because the bubbles do not connect with each other and become large, and the large bubbles do not cause surface irregularities or holes in the resin layer.

[0073] In the present invention, the single composition layer constituting the synthetic resin layer preferably includes a thermoplastic polycarbonate-based polyurethane resin composition layer having a thermoplastic polycarbonate-based polyurethane resin as a matrix resin, and / or a thermoplastic polyether-based polyurethane resin composition layer having a thermoplastic polyether-based polyurethane resin as a matrix resin.

[0074] At least the surface-side resin layer is preferably composed of a thermoplastic polycarbonate-based polyurethane resin as a matrix resin. The presence of a layer containing a thermoplastic polycarbonate-based polyurethane resin, which has excellent abrasion resistance, as a single-component layer on the surface of the synthetic resin layer opposite the fibrous substrate side results in a synthetic leather with excellent abrasion resistance. Furthermore, from the viewpoint of weather resistance, it is preferable to use a polyurethane resin that uses an aliphatic diisocyanate as the diisocyanate component for the surface-side resin layer.

[0075] The target thickness of the surface-side resin layer, which is a single-composition layer made of a thermoplastic polycarbonate-based polyurethane resin composition, is not particularly limited, but is preferably 10 μm or more, more preferably 20 μm or more. The upper limit is not particularly limited, but is preferably 100 μm or less, more preferably 80 μm or less. A thickness of 10 μm or more tends to provide sufficient abrasion resistance. A thickness of 100 μm or less does not cause the texture to become rough and hard.

[0076] The surface-side resin layer may contain flame retardants, colorants, heat stabilizers, conductivity imparting agents, antistatic agents, moisture permeability improvers, water repellents, oil repellents, water absorbents, moisture absorbents, deodorizers, pigment dispersants, hydrolysis inhibitors, etc. In addition to the thermoplastic polycarbonate-based polyurethane resin as the matrix resin, resin components such as thermoplastic polyether-based polyurethane resins, thermoplastic polyester-based polyurethane resins, polyethylene resins, and polypropylene resins may also be contained. The surface-side resin layer is preferably a non-porous layer.

[0077] At least the substrate-side resin layer is preferably composed of a thermoplastic polyether-based polyurethane resin as a matrix resin. The presence of a layer containing a thermoplastic polyether-based polyurethane resin, which has excellent flexibility, as a single-component layer on the fibrous substrate side of the synthetic resin layer allows for the production of synthetic leather with excellent texture, low-temperature flexibility, and hydrolysis resistance. Furthermore, for the substrate-side resin layer, which does not necessarily require emphasis on weather resistance, it is preferable to use a polyurethane resin that uses an aromatic diisocyanate, which has excellent physical properties, as a diisocyanate component.

[0078] The target thickness of the substrate-side resin layer, which is a single-composition layer made of a thermoplastic polyether-based polyurethane resin composition, is not particularly limited, but is preferably 40 μm or more, more preferably 90 μm or more. The upper limit is not particularly limited, but is preferably 400 μm or less, more preferably 300 μm or less. A thickness of 40 μm or more tends to provide sufficient flexibility. A thickness of 400 μm or less does not cause the texture to become rough and hard.

[0079] The substrate-side resin layer preferably contains a flame retardant. The amount of the flame retardant contained in the substrate-side resin layer as a single-composition layer is not particularly limited, but is preferably 10 g / m ２ More preferably, 20 g / m ２ The upper limit is not particularly limited, but it is preferably 100 g / m ２ or less, more preferably 80 g / m ２ The blending amount is 10 g / m or less. ２ If it is more than 100 g / m, sufficient flame retardancy can be obtained. ２If the thickness is less than this, there is no risk of the texture becoming rough and hard.

[0080] The substrate-side resin layer preferably contains bubbles. By containing bubbles, synthetic leather can be obtained that is flexible and has an excellent texture. The size of the bubbles (average diameter or average value of the length of the longest part as a cross-sectional shape) is preferably 10 μm or more, more preferably 20 μm or more. There is no particular upper limit to the size of the bubbles, but it is preferably 300 μm or less, more preferably 200 μm or less. When the size of the bubbles is 10 μm or more, sufficient flexibility tends to be obtained. When the size of the bubbles is 300 μm or less, sufficient abrasion resistance tends to be obtained.

[0081] The method for incorporating bubbles into the substrate-side resin layer is not particularly limited, but includes a method of blending a bubble-generating agent into the thermoplastic resin composition for the substrate-side resin layer. Specifically, examples include a method of mixing hollow particles into the thermoplastic resin composition, and a method of mixing a thermoexpandable microcapsule that vaporizes a substance contained therein at the molding temperature to generate bubbles, or a thermally decomposable foaming agent that decomposes at the molding temperature to generate bubbles, into the thermoplastic resin composition before molding, and foaming the resin layer during molding.

[0082] Examples of thermally expandable microcapsules include minute plastic spheres containing hydrocarbons that vaporize at about the molding temperature within a shell of a thermoplastic polymer such as the vinylidene chloride resin or acrylonitrile resin described above. When thermally expandable microcapsules are blended into the thermoplastic resin composition for the substrate-side resin layer, the blending ratio is preferably such that the volume fraction of bubbles after foaming relative to the substrate-side resin layer is 10 to 60% by volume.

[0083] Examples of hollow particles include plastic microballoons, etc. When hollow particles are mixed, the preferred blending amount is not particularly limited, but it is preferable to blend them so that the volume ratio of air bubbles after foaming to the substrate-side resin layer is 10 to 60% by volume.

[0084] Examples of the thermal decomposition type blowing agent include azodicarbonamide-based blowing agents, (4,4'-oxybis(benzenesulfonylhydrazide)-based blowing agents, sodium bicarbonate-based blowing agents, etc. When a blowing agent is mixed, since the amount of gas generated differs depending on the type of blowing agent, it is preferable to mix the blowing agent so that the volume ratio of bubbles after foaming to the substrate-side resin layer is 10 to 60% by volume.

[0085] The volume fraction of bubbles in the substrate-side resin layer is not particularly limited, but is preferably 10% or more, more preferably 20% or more. The upper limit of the volume fraction of bubbles is not particularly limited, but is preferably 60% or less, more preferably 50% or less. A volume fraction of 10% or more tends to provide sufficient flexibility, while a volume fraction of 60% or less tends to provide sufficient abrasion resistance.

[0086] The volume fraction of bubbles in the substrate-side resin layer is a value calculated based on the sum of the volume of the substrate-side resin layer containing the bubble-generating agent and the volume of the mixed composition layer up to the midpoint. The specific method for calculating the volume fraction of bubbles is as described above.

[0087] In addition to the flame retardant and bubble-generating agent described above, the substrate-side resin layer may contain colorants, heat stabilizers, conductivity-imparting agents, antistatic agents, moisture permeability improvers, water repellents, oil repellents, water absorbents, moisture absorbents, deodorizers, pigment dispersants, hydrolysis inhibitors, etc. Furthermore, in addition to the thermoplastic polyether-based polyurethane resin as the matrix resin, resin components such as thermoplastic polycarbonate-based polyurethane resins, thermoplastic polyester-based polyurethane resins, polyethylene resins, and polypropylene resins may be contained.

[0088] (3) Surface Treatment Layer The synthetic leather of the present invention preferably has a surface treatment layer containing a silicone compound on the surface of the synthetic resin layer opposite the fibrous substrate layer (on the surface-side thermoplastic resin composition layer). This further improves the abrasion resistance of the synthetic leather. The surface treatment layer is a general term for resin layers formed on the surface of the synthetic resin layer opposite the fibrous substrate layer and serving as the outermost layer to protect the synthetic resin layer. The surface treatment layer consists of at least one resin layer, but can also be composed of two or more resin layers of the same or different compositions.

[0089] The matrix resin constituting the surface treatment layer is not particularly limited, but from the viewpoint of abrasion resistance, polyurethane resin is preferred, and polycarbonate-based polyurethane resin is particularly preferred. The form of polyurethane resin may be solventless (solventless), hot melt, solvent-based or water-based, and may be one-component or two-component curing, and may be appropriately selected according to the specific application.

[0090] The resin material forming the surface treatment layer contains a silicone compound. Specific examples of the silicone compound include dimethyl silicone (i.e., polydimethylsiloxane), modified dimethyl silicone, and silicone-acrylic copolymer. The blending ratio of the silicone compound is not particularly limited, but is preferably 5 to 40 mass %, more preferably 10 to 20 mass %, of the total amount of the resin material forming the surface treatment layer.

[0091] The thickness of the surface treatment layer is not particularly limited, but is preferably 3 μm or more, more preferably 5 μm or more. The upper limit of the thickness is not particularly limited, but is preferably 30 μm or less, more preferably 15 μm or less. When the thickness is 3 μm or more, sufficient abrasion resistance tends to be obtained. When the thickness is 30 μm or less, there is no risk of the texture becoming rough and hard.

[0092] (4) Synthetic Leather As shown in Figure 1, the synthetic leather of the present invention comprises at least a fibrous substrate 1 and a synthetic resin layer 2 provided on the fibrous substrate, and preferably a surface treatment layer 3 can be further provided on the synthetic resin layer. That is, the layer structure of the synthetic leather of the present invention can be [fibrous substrate / synthetic resin layer], preferably [fibrous substrate / synthetic resin layer / surface treatment layer]. The synthetic resin layer 2 preferably has a layer structure of [substrate-side resin layer / mixed composition layer / surface-side resin layer], and as shown in Figure 1, the lamination boundary between each layer is not clear, and for example, the composition of the substrate-side resin layer and the surface-side resin layer is mixed, gradually changing in the thickness direction.

[0093] Including a breakdown of the specific layer structure of the synthetic resin layer, preferably, it is [fibrous substrate / substrate-side resin layer / mixed composition layer / surface-side resin layer], and more preferably, it is [fibrous substrate / substrate-side resin layer / mixed composition layer / surface-side resin layer / surface treatment layer].

[0094] The present invention is not limited to these layer configurations, and it is also possible to add a thermoplastic resin composition layer having a new composition to the synthetic resin layer in order to impart new physical properties, or to add a new skin layer as a surface treatment layer, as necessary.

[0095] 2. Method for Producing Synthetic Leather (1) Production of Synthetic Resin Layer The method for producing the synthetic leather of the present invention is not particularly limited, and any conventionally known method such as coextrusion or extrusion lamination can be used, but the synthetic resin layer of the present invention is preferably produced by coextrusion, more preferably by T-die coextrusion.

[0096] It is particularly preferred that the synthetic leather of the present invention be produced by a method comprising the steps of: joining and laminating melts of multiple thermoplastic resin compositions having different compositions supplied from multiple extruders before a T-die; extruding the joined and laminated melts from the T-die by a coextrusion method to form a synthetic resin layer; and laminating the synthetic resin layer and a fibrous base material.

[0097] More specifically, the process for forming the synthetic resin layer includes a process in which a melt (molten resin material) of the substrate-side thermoplastic resin composition is extruded from one extruder, a melt (molten resin material) of the surface-side thermoplastic resin composition is extruded from another extruder, the two melts are joined and laminated in a feed block, and then the joined laminated melt is supplied to a co-extrusion T-die connected to the feed block.

[0098] The melt-mixing temperature of the resin composition during co-extrusion can be appropriately determined depending on the type of matrix resin, the type and amount of additives, etc. In particular, when a polyurethane resin is used, it is desirable to perform melt-mixing at a temperature of 150 to 230°C.

[0099] For coextrusion, it is preferable to employ multilayer extrusion molding using a feedblock in which molten resin materials supplied from multiple extruders are laminated and joined in multiple layers before a T-die. Multiple thermoplastic resin compositions of different compositions that form the synthetic resin layer are melted in their respective extruders, and the resulting molten resin materials (melts) are fed to a feedblock where they are merged and laminated. The resulting merged laminated melt is then fed to a coextrusion T-die connected to the feedblock and molded into a multilayer film of the desired thickness to form the synthetic resin layer. By merging the molten resin materials of multiple thermoplastic resin compositions before the T-die, the laminate interfaces of the multiple thermoplastic resin composition layers that are formed mix together, forming a mixed composition layer.

[0100] The surface-side thermoplastic resin composition capable of forming the above-mentioned soluble resin material is preferably composed of a thermoplastic polycarbonate-based polyurethane resin as a matrix resin. Furthermore, from the viewpoint of weather resistance, it is preferable to use a polyurethane resin using an aliphatic diisocyanate as a diisocyanate component.

[0101] The substrate-side thermoplastic resin composition capable of forming the above-mentioned soluble resin material is preferably composed of a thermoplastic polyether-based polyurethane resin as a matrix resin, and more preferably a polyurethane resin using an aromatic diisocyanate as a diisocyanate component, which has excellent physical properties.

[0102] The thermoplastic resin composition on the substrate side preferably contains a flame retardant. The amount of the flame retardant added to the thermoplastic resin composition on the substrate side is not particularly limited, but is preferably 10 g / m ２ More preferably, 20 g / m ２ The upper limit is not particularly limited, but it is preferably 100 g / m ２ or less, more preferably 80 g / m ２ The blending amount is 10 g / m or less. ２ If it is more than 100 g / m, sufficient flame retardancy can be obtained. ２ If the thickness is less than this, there is no risk of the texture becoming rough and hard.

[0103] A bubble-generating agent can be blended into the substrate-side thermoplastic resin composition. Examples of the bubble-generating agent include hollow particles, thermally expandable microcapsules, and chemical foaming agents such as thermally decomposable foaming agents. These foam during molding, thereby allowing bubbles to be contained in the substrate-side resin layer that is formed. It is particularly preferable to blend a thermally expandable microcapsule into the substrate-side thermoplastic resin composition.

[0104] Examples of thermally expandable microcapsules include minute plastic spheres containing hydrocarbons that vaporize at about the molding temperature within a shell of a thermoplastic polymer such as the vinylidene chloride resin or acrylonitrile resin described above. When thermally expandable microcapsules are blended into the substrate-side thermoplastic resin composition, the blending ratio is preferably such that the volume fraction of bubbles after foaming is 10 to 60% by volume relative to the substrate-side resin layer.

[0105] Specific examples of the hollow particles and the thermal decomposition type foaming agent include those mentioned above. When these are mixed, the preferred blending amounts are not particularly limited, but it is preferable to blend them so that the volume fraction of bubbles after the substrate-side resin layer is formed and foamed is 10 to 60 volume %.

[0106] For the surface-side thermoplastic resin composition and the substrate-side thermoplastic resin composition, a shear rate of 100 sec －１ The viscosity of the molten resin material at a melting temperature of 185° C. is preferably 500 to 10,000 Pa s, and more preferably 500 to 5,000 Pa s. Methods for adjusting the viscosity of the molten resin material to this range include, but are not limited to, a method of adjusting the molecular weight of the thermoplastic resin raw material in advance.

[0107] The method for forming the desired mixed composition layer is not particularly limited, but particularly when a polyurethane resin is used, it is preferable that the compression ratio of the extruder screw (space volume of the feed section divided by space volume of the metering section) is 2 to 4, the length of the extruder screw divided by the diameter is 20 to 40, the melt mixing temperature of the extruder is 150 to 230°C, the viscosity of the molten resin material is 100 to 10,000 Pa·s at the melt mixing temperature and shear rate of the extruder, the screw rotation speed of the extruder is 1 to 40 rpm, and the shear rate is 10 to 1,000 sec －１ These include setting the temperature inside the feed block to 170 to 230°C, setting the lip width of the T-die to 0.1 to 2 mm, setting the total thickness of adjacent resin layers that form the mixed composition layer to 50 to 500 μm, and setting the thickness ratio of adjacent resin layers that form the mixed composition layer to 1:1 to 1:10. By appropriately combining these conditions, a desired mixed composition layer can be formed.

[0108] More preferably, in the method for forming a synthetic resin layer of the present invention, when a synthetic resin layer having a configuration of, for example, [substrate-side resin layer / mixed composition layer / surface-side resin layer] is formed as a multilayer film, the thermoplastic resin composition for the substrate-side resin layer is supplied to an extruder and melt-mixed, and the thermoplastic resin composition for the surface-side resin layer is supplied to another extruder and melt-mixed, and the resulting molten resin materials are separately supplied to a feed block, where they are joined and laminated.

[0109] In this case, the molten resin materials to be supplied to the feedblock can be supplied to the feedblock by setting a preferred thickness (target thickness) as the layer thickness that would be obtained if the materials were laminated in a T-die for coextrusion without going through the feedblock, and adjusting the screw rotation speed of the extruder based on that thickness. In this way, the joined laminated molten material can be supplied to the T-die for coextrusion and then molded into a multilayer film of the desired thickness to form a synthetic resin layer.

[0110] The preferred layer thickness that can be set as the target thickness is preferably 40 μm or more, more preferably 90 μm or more, for the substrate-side resin layer. The upper limit is not particularly limited, but is preferably 400 μm or less, more preferably 300 μm or less. The preferred layer thickness that can be set as the target thickness for the surface-side resin layer is preferably 10 μm or more, more preferably 20 μm or more. The upper limit is not particularly limited, but is preferably 100 μm or less, more preferably 80 μm or less.

[0111] (2) Lamination method of fibrous substrate In the preferred manufacturing method of the present invention, after the above-mentioned synthetic resin layer forming process, can laminate the obtained synthetic resin layer and fibrous substrate.Specifically, in the synthetic resin layer formed into a multilayer film shape by T-die, fibrous substrate is superposed on the side where the substrate-side resin layer is formed, and the synthetic resin layer is pressed by nip roll while it is still fluid.

[0112] By pressing the synthetic resin layer extruded from the T-die against the fibrous substrate with a nip roll while it is still in a fluid state before cooling and solidifying, the resin penetrates into the fibrous substrate, further increasing the peel strength. The nip roll is preferably heated to about 40 to 120°C. If the nip roll temperature is 40°C or higher, sufficient peel strength is obtained, and if it is 120°C or lower, there is a tendency for the fibrous substrate to be less susceptible to thermal degradation. In addition, the pressing force of the nip roll is preferably about 1 to 20 MPa.

[0113] (3) Lamination method of the surface treatment layer The method of forming the surface treatment layer is not particularly limited, but preferably, the resin composition liquid for the surface treatment layer is applied to the surface of the synthetic resin layer (the side opposite to the surface on which the fibrous base material is laminated) to a predetermined thickness using a reverse coater or the like, and then dried to form a surface treatment layer of a desired thickness. The amount of application is preferably such that the dry film thickness is 3 to 30 μm.

[0114] The present invention will be explained in more detail below with reference to examples. However, the present invention is not limited to the following examples, and it is of course possible to carry out the invention by making appropriate modifications within the scope of the above and below-described aims, and all such modifications are included in the technical scope of the present invention.

[0115] [Viscosity of molten resin material] Viscosity was measured using a capillary rheometer (trade name "ROSANDRH7", manufactured by NETZCH) at a shear rate of 100 sec －１ The viscosity at a melting temperature of 185°C was measured.

[0116] [Presence or Absence of Boundary Between Resin Compositions of Synthetic Resin Layers] The synthetic leathers obtained in the Examples and Comparative Examples were cut in the thickness direction with a razor blade and observed under a microscope. A case in which a layer thinner than the surface-side resin layer and darker in color than the substrate-side resin layer was present was marked with ○, and a case in which a layer thinner than the surface-side resin layer and darker in color than the substrate-side resin layer was not present and a clear boundary was visible was marked with ×.

[0117] [Peel strength between resin compositions of synthetic resin layers] Based on JIS L 1096B method (Scott method), a 30 × 120 mm test piece (synthetic leather) was attached to a testing machine in a bent state with a grip spacing of 20 mm and a load of 9.81 N, and the grip on one side was moved back and forth at a speed of 120 times / min over a distance of ±20 mm. After 1000 times, the presence or absence of peeling between the thermoplastic resin composition layers of the sample was visually evaluated, with a rating of ○ indicating no peeling and a rating of × indicating peeling. In the synthetic leather of the present invention, which is composed of a fibrous substrate, a synthetic resin layer, and a surface treatment layer, peeling may occur in this test between the fibrous substrate and the synthetic resin layer, between the surface-side resin layer within the synthetic resin layer and the substrate-side resin layer, and between the synthetic resin layer and the surface treatment layer. However, in this test, only the presence or absence of peeling between the surface-side resin layer within the synthetic resin layer and the substrate-side resin layer was evaluated. If there was no peeling between the surface-side resin layer within the synthetic resin layer and the substrate-side resin layer, it was evaluated as "no peeling (○)" regardless of the presence or absence of peeling between the fibrous substrate and the synthetic resin layer, and between the synthetic resin layer and the surface treatment layer. If there was peeling between the surface-side resin layer within the synthetic resin layer and the substrate-side resin layer, it was evaluated as "peeling (×)" regardless of the presence or absence of peeling between the fibrous substrate and the synthetic resin layer, and between the synthetic resin layer and the surface treatment layer.

[0118] [Volume Fraction of Bubbles] The synthetic leather was cut with a razor blade, and the cross section was photographed under a microscope. Image processing software was used to calculate the sum of the area of ​​the thermoplastic resin layer on the substrate side containing the bubble-generating agent and the area up to the midpoint in the thickness direction of the mixed composition layer, as well as the area of ​​the bubbles, and the volume fraction of bubbles was calculated using the following formula.

[0119] (Equation 3) [Volume ratio of bubbles (%)] = ([Area of ​​bubbles] ÷ [Sum of areas of thermoplastic resin layer and mixed composition layer up to the midpoint in the thickness direction]) × 100

[0120] [Example 1] <Fibrous substrate> A black tricot knit fabric (polyester fiber, mass per unit area: 290 g / m) was used as the substrate. ２ A film having a thickness of 900 μm was prepared.

[0121] <Formulation 1: Preparation of Flame Retardant Compound> 76.9 parts by mass of a polyether polyurethane resin (trade name "Rezamin P-2288", manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.) and 23.1 parts by mass of a flame retardant (diorganylphosphinate, trade name "EXOLIT OP-930", manufactured by Clariant) were mixed in a solid state and charged into a twin-screw kneader. The mixture was melt-kneaded at a temperature of 180°C, extruded into water in the form of strands, and cut with a pelletizer to obtain a flame retardant compound.

[0122] <Formulation 2: Preparation of Thermoplastic Polyether-Based Polyurethane Resin Composition> Pellets of the following components were placed in a polyethylene bag in a solid state and mixed by shaking: Flame retardant compound of Formulation 1: 99 parts by mass Thermally expandable microcapsule masterbatch (trade name "Advancell P501E2"; manufactured by Sekisui Chemical Co., Ltd.): 1 part by mass

[0123] <Formulation 3: Preparation of thermoplastic polycarbonate-based polyurethane resin composition> Pellets of the following components were placed in a polyethylene bag in a solid state and mixed by shaking. Polycarbonate polyurethane resin (trade name "Rezamin P-880", manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.): 83.2 parts by mass Color pigment masterbatch (trade name "Rezamin CPE-5 Black", manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.): 16.8 parts by mass

[0124] <Formulation 4: Resin composition liquid for surface treatment layer> The following components were charged into a beaker and mixed with a stirring blade: Water-based polycarbonate-based polyurethane resin (solid content 16.5% by mass): 90 parts by mass Water-based polycarbonate-based polyurethane resin (solid content 17% by mass): 10 parts by mass Carbodiimide-based crosslinking agent (solid content 40% by mass): 3 parts by mass Smoothing agent (aqueous dispersion of silicone-based compound, solid content 30% by mass): 9.6 parts by mass Leveling agent (trade name "AQUADERM Fluid H", manufactured by LANXESS Corporation, solid content 100% by mass): 1 part by mass

[0125] <Production of synthetic leather> Two single-screw extruders (25 mmφ and 35 mmφ) of a co-extrusion molding machine were prepared, and the thermoplastic resin composition of Formulation 2, which had been mixed in a solid state, was separately charged into the 35 mmφ single-screw extruder, and the thermoplastic resin composition of Formulation 3, which had been mixed in a solid state, was separately charged into the 25 mmφ single-screw extruder. The respective thermoplastic resin compositions were melt-mixed at a melt-mixing temperature of 195°C and extruded into a feed block.

[0126] At this time, the screw rotation speed of the extruder for the thermoplastic resin composition of Formulation 2 was adjusted to 6 rpm so that the target thickness of the thermoplastic resin composition layer of Formulation 2 after sheet molding would be 130 μm after foaming, and the screw rotation speed of the extruder for the thermoplastic resin composition of Formulation 3 was adjusted to 3 rpm so that the target thickness of the thermoplastic resin composition layer of Formulation 3 after sheet molding would be 70 μm. Here, the thermoplastic resin composition layer of Formulation 2 corresponds to the substrate-side resin layer, and the thermoplastic resin composition layer of Formulation 3 corresponds to the surface-side resin layer.

[0127] The extruded molten resin materials consisting of the thermoplastic resin compositions of Formulations 2 and 3 were then joined in a feed block immediately before the T-die. The T-die outlet thickness dimension was 0.3 mm, the T-die outlet width dimension was 300 mm, and the synthetic resin layer thickness was 0.20 mm.

[0128] Other conditions for melt mixing using the extruder were as follows: Screw length / diameter of 25 mmφ single-screw extruder: 30 Screw length / diameter of 35 mmφ single-screw extruder: 33 Viscosity of molten resin material of formulation 2: 2000 Pa·s Viscosity of molten resin material of formulation 3: 2000 Pa·s Temperature inside the feed block: 195°C

[0129] Next, the merged laminated melt, which was merged and laminated in the feed block, was fed to a coextrusion T-die connected to the feed block and extruded into a multilayer film to form a synthetic resin layer. By adjusting the screw rotation speed of the extruder, the thickness of the synthetic resin layer from the surface on the Formulation 2 side to the midpoint of the mixed portion of Formulation 2 and Formulation 3 was 130 μm, the thickness from the midpoint of the mixed portion of Formulation 2 and Formulation 3 to the surface on the Formulation 3 side of the synthetic resin layer was 70 μm, and the thickness of the mixed portion was 40 μm. The film thickness of the obtained synthetic resin layer was 200 μm. The midpoint of the mixed portion of Formulation 2 and Formulation 3 was determined visually by observing the cross section with a microscope.

[0130] Next, the fibrous substrate was placed on the surface of the molten synthetic resin layer on the formulation 2 side, and the grained surface of the grained release paper was placed on the surface of the synthetic resin layer on the formulation 3 side, and they were laminated using nip rolls at a temperature of 80°C, a pressure of 5 MPa, and a time of 1 second. After cooling, the release paper was peeled off to obtain a laminate consisting of the fibrous substrate and the synthetic resin layer.

[0131] Next, the resin composition liquid for surface treatment layer prepared according to the above-mentioned Formulation 4 was wet coated on the surface of the Formulation 3 side after peeling off the release paper using a reverse coater in an amount of 35 g / m ２ The mixture was applied to a sheet so as to have the following properties, and then treated in a dryer at 80° C. for 2 minutes to form a surface treatment layer having a dry coating thickness of 10 μm, thereby obtaining synthetic leather.

[0132] The synthetic leather thus obtained was evaluated for the presence or absence of an interface between the resin compositions of the synthetic resin layers, and no clear interface was found. Furthermore, the peel strength between the resin compositions of the synthetic resin layers was evaluated, and no peeling was found.

[0133] [Comparative Example 1] A black tricot knit fabric (polyester fiber, mass per unit area: 290 g / m) was used as the base material. ２ ) was prepared.

[0134] <Formulation 5: Resin composition liquid for resin layer (surface-side resin layer) opposite to fibrous substrate> The following components were mixed and stirred, and the viscosity was adjusted with dimethylformamide to 2000 mPa s (B-type viscometer, rotor: No. 3, 10 rpm, 23°C): 100 parts by mass of polycarbonate-based polyurethane resin (solid content 30% by mass): 20 parts by mass of dimethylformamide: 20 parts by mass of methyl ethyl ketone: 20 parts by mass of carbon black dispersion (carbon black 20% by mass): 20 parts by mass

[0135] Formulation 6: Resin composition liquid for surface treatment layer The following components were mixed and stirred to prepare a resin composition liquid for surface treatment. The viscosity of the obtained resin composition liquid for surface treatment was 1000 mPa·s (B-type viscometer, rotor: No. 3, 10 rpm, 23°C). Water-based polycarbonate-based polyurethane resin (solid content 16.5% by mass): 90 parts by mass Water-based polycarbonate-based polyurethane resin (solid content 17% by mass): 10 parts by mass Carbodiimide-based crosslinking agent (solid content 40% by mass): 3 parts by mass Smoothing agent (water dispersion of silicone-based compound, solid content 30% by mass): 9.6 parts by mass Leveling agent (trade name "AQUADERM Fluid H", manufactured by LANXESS Corporation, solid content 100% by mass, solid content 100% by mass): 1 part by mass Viscosity modifier (water dispersion of acrylic copolymer containing methacrylic acid as a copolymerization component, solid content 28% by mass): 1 part by mass

[0136] <Formulation 7: Resin composition liquid for substrate-side resin layer> The following components were mixed and stirred, and the viscosity was adjusted with dimethylformamide to 4500 mPa·s (B-type viscometer, rotor: No. 3, 10 rpm, 23°C): Polycarbonate-based polyurethane resin (solid content 70% by mass): 100 parts by mass Flame retardant (diorganylphosphinate, trade name "EXOLIT OP-930", manufactured by Clariant): 16.2 parts by mass

[0137] <Preparation of synthetic leather> The resin composition liquid for the surface-side resin layer prepared according to the above-mentioned formulation 5 was applied in sheet form to a release paper having a grained uneven pattern using an applicator (manufactured by Tester Sangyo Co., Ltd., SA-201, Baker-type applicator) so as to have a coating thickness of 220 μm, and the sheet was then treated in a dryer at 80° C. for 2 minutes to form a surface layer.

[0138] Next, the resin composition liquid for the substrate-side resin layer prepared according to Formulation 7 above was applied to the surface of the skin layer formed on release paper in a sheet form using an applicator (SA-201, Baker-type applicator, manufactured by Tester Sangyo Co., Ltd.) to a coating thickness of 200 μm, and then treated in a dryer for 1 minute at 100° C. The surface of the adhesive layer and the fibrous substrate were overlapped, and pressed in a laminator at room temperature under a pressure of 394.2 kPa for 4 seconds, after which the release paper was peeled off to obtain a laminate having a skin layer with a thickness of 40 μm.

[0139] Next, the resin composition liquid for the surface treatment layer prepared according to the above-mentioned Formulation 6 was applied to the surface of the skin layer after peeling off the release paper using a reverse coater (trade name "JUMBOSTAR-SR", manufactured by Ge.Ma.Ta.SpA) in a wet coating amount of 35 g / m ２ The mixture was applied to a sheet so as to have the following properties, and then treated in a dryer at 80° C. for 2 minutes to form a surface treatment layer having a thickness of 10 μm, thereby obtaining synthetic leather.

[0140] The synthetic leather thus obtained was evaluated for the presence or absence of an interface between the resin compositions in the synthetic resin layer. A clear interface was observed, and no mixed composition layer was formed. Furthermore, the peel strength between the resin compositions in the synthetic resin layer was evaluated, and peeling was observed.

[0141]

[0142] According to the present invention, it is possible to obtain synthetic leather that contains multiple thermoplastic resin composition layers with different compositions in a synthetic resin layer, yet has excellent peel strength between the thermoplastic resin composition layers, and can simultaneously satisfy various conflicting required properties. For example, it is possible to obtain synthetic leather that has high flame retardancy and also has excellent texture and flexibility due to the resin layers containing bubbles.

[0143] 1: Fibrous base material layer 2: Synthetic resin layer 3: Surface treatment layer

Claims

1. Synthetic leather consisting of a laminate including a fibrous base material and a synthetic resin layer provided on the fibrous base material, characterized in that the synthetic resin layer includes multiple thermoplastic resin composition layers with different compositions, and at least a mixed composition layer is included at the interface where the multiple thermoplastic resin composition layers are adjacent, in which the compositions of the adjacent multiple thermoplastic resin layers are mixed.

2. The synthetic leather according to claim 1, wherein the synthetic resin layer comprises at least a substrate-side thermoplastic resin composition layer present on the surface in contact with the fibrous substrate, and a surface-side thermoplastic resin composition layer present on the surface opposite to the surface in contact with the fibrous substrate, and the surface-side thermoplastic resin composition layer is composed of a thermoplastic polycarbonate-based polyurethane resin composition.

3. The synthetic leather according to claim 1, wherein the synthetic resin layer comprises at least a substrate-side thermoplastic resin composition layer present on the surface in contact with the fibrous substrate, and a surface-side thermoplastic resin composition layer present on the surface opposite to the surface in contact with the fibrous substrate, and the substrate-side thermoplastic resin composition layer is composed of a thermoplastic polyether-based polyurethane resin composition.

4. The synthetic leather according to claim 3, wherein the thermoplastic resin composition layer on the substrate side contains bubbles, and the volume fraction of the bubbles in the thermoplastic resin composition layer on the substrate side is 10 to 60%.

5. The synthetic leather according to claim 1, wherein the laminate constituting the synthetic leather further comprises a surface treatment layer containing a silicone compound on the surface opposite to the fibrous substrate.

6. A method for producing synthetic leather according to claim 1, comprising the steps of: joining and laminating melts of multiple thermoplastic resin compositions having different compositions supplied from multiple extruders before a T-die; extruding the joined and laminated melts from the T-die by a co-extrusion method to form a synthetic resin layer; and laminating the synthetic resin layer and a fibrous substrate.

7. A method for producing synthetic leather according to claim 6, characterized in that the step of forming the synthetic resin layer comprises extruding a melt of the thermoplastic resin composition for the substrate side from one extruder and a melt of the thermoplastic resin composition for the surface side from another extruder, supplying both melts to a feed block where they join and are laminated, and then supplying the joined laminated melt to a co-extrusion T-die connected to the feed block.

8. The shear rate of the melt is 100 sec －１ The method for producing synthetic leather according to claim 7, wherein the viscosity at a melting temperature of 185°C is 500 to 10,000 Pa·s.

Images