JP7573371B2 - Skin material and method for producing the same - Google Patents

Description

This disclosure relates to a skin material and a method for manufacturing the skin material.

2. Description of the Related Art Leather-like sheets are being used in place of natural leather or fiber sheets for automobile interior parts such as instrument panels, door trims, and seats.
Such leather-like sheets have an uneven surface, i.e., a grain pattern, to provide an attractive appearance.

Methods for imparting a grained pattern to a leather-like sheet include the "embossing method," in which an embossed pattern is imparted to a flat surface by pressing, and the "release paper method," in which a polymer liquid is applied to release paper that has already been embossed with a pattern, and then dried to transfer the embossed pattern of the release paper.

The embossing method is widely used due to its features such as few restrictions on the surface to be treated, the ability to freely adjust the pattern, the ability to obtain a uniform texture, and low cost.

For example, Patent Document 1 describes a leather-like sheet having a specific surface layer on the surface of a specific base layer and an embossed pattern, the surface layer of which contains specific fine particles.

Japanese Patent Application Publication No. 4-333674

Even if the surface of a leather-like sheet embossed using the embossing method has a relatively good embossing condition overall, the reproduction of subtle irregularities in the details is insufficient and the surface tends to lack sharpness.

Furthermore, when the embossing conditions are made strong in order to fully reproduce the fine irregularities, problems arise such as loss of texture and reduced productivity.
It has been difficult to achieve embossing that reproduces fine concaves and convexes sharply without impairing the texture of the leather-like sheet.

It is speculated that it would be difficult to achieve a high transfer rate of the grain pattern using the embossing method in the leather sheet material of Patent Document 1.

The inventors of the present disclosure have focused on the storage modulus of the skin layer from the perspective of achieving a high transfer rate and conducted extensive research. As a result, they discovered that the lower the storage modulus of the skin layer in a specific temperature range, the higher the transfer rate of the grain pattern by the embossing method, which led to the completion of the present invention.

The problem that one embodiment of the present disclosure aims to solve is to provide a skin material that has an excellent transfer rate of a grain pattern using an embossing method, and a method for manufacturing the skin material.

Specific means for solving the above problems include the following aspects.
<1> A skin material including a skin layer having a storage modulus of 1.0 MPa or less in a temperature range of 160°C to 170°C.
<2> The skin material according to <1>, wherein the skin layer contains polyurethane.
<3> The skin material according to <1> or <2>, wherein the content of the crosslinking agent in the skin layer is 3 parts by mass or less per 100 parts by mass of the base resin in the skin layer.
<4> The skin material according to any one of <1> to <3>, wherein the content of the crosslinking agent in the skin layer is 0 parts by mass per 100 parts by mass of the base resin in the skin layer.
<5> The skin material according to any one of <1> to <4>, wherein the skin layer has irregularities on at least one surface.
<6> The skin material according to any one of <1> to <5>, wherein the skin layer has a thickness of 10 μm to 300 μm.
<7> The skin material according to any one of <1> to <6>, wherein the skin layer, the adhesive layer, and the base fabric are disposed in this order in a thickness direction of the skin layer.
<8> A method for producing the skin material according to <7>,
forming a skin layer having a storage modulus of 1.0 MPa or less in a temperature range of 160° C. to 170° C. using a composition for forming a skin layer;
forming an adhesive layer on one of the skin layer or the base fabric;
a step of adhering the surface layer and the base fabric via the adhesive layer;
and bringing an embossing roll into contact with the surface of the skin layer opposite the adhesive layer to perform embossing to form recesses.

According to one embodiment of the present disclosure, it is possible to provide a skin material that has an excellent transfer rate of a grain pattern by the embossing method, and a method for manufacturing the skin material.

FIG. 1 is a schematic cross-sectional view showing one embodiment of a layer structure of a skin material according to the present disclosure. FIG. 2 is a schematic cross-sectional view showing one embodiment of a layer structure of a skin material of the present disclosure having a concave-convex pattern formed thereon. FIG. 2 is a schematic diagram showing one embodiment of embossing for a skin material.

In the present disclosure, a numerical range indicated using "to" means a range that includes the numerical values before and after "to" as the minimum and maximum values, respectively.
In the numerical ranges described in the present disclosure, the upper or lower limit value described in a certain numerical range may be replaced with the upper or lower limit value of another numerical range described in the present disclosure. In addition, in the numerical ranges described in the present disclosure, the upper or lower limit value described in a certain numerical range may be replaced with a value shown in the examples.
In the present disclosure, combinations of two or more preferred aspects are more preferred aspects.
In the present disclosure, when there are multiple substances corresponding to each component, the amount of each component means the total amount of multiple substances, unless otherwise specified.
In the present disclosure, the term "step" refers not only to an independent step, but also to a step that cannot be clearly distinguished from other steps, as long as the purpose of the step is achieved.

<Skin material>
The skin material of the present disclosure includes a skin layer having a storage modulus of 1.0 MPa or less in a temperature range of 160°C to 170°C.
This allows the covering material of the present disclosure to have an excellent transfer rate of the grain pattern when embossed.

First, an embodiment of a skin material according to the present disclosure will be described with reference to the drawings. Note that the same reference numerals in the following drawings represent the same components.
Fig. 1 is a schematic cross-sectional view showing one embodiment of the layer structure of a laminate 10A for forming a skin material of the present disclosure. The embodiment shown in Fig. 1 shows an example of a simple layer structure of the skin material of the present disclosure.
In the embodiment shown in Fig. 1, a laminate 10A for forming a skin material has an adhesive layer 14 and a skin layer 16 containing a urethane resin, in this order, on a base fabric 12. By embossing this laminate 10A to form a concave-convex pattern, a skin material 10 of the present disclosure having recesses 18 on the skin layer 16 side shown in Fig. 2 is obtained.
As shown in FIG. 2, the skin material 10 has an adhesive layer 14 and a skin layer 16 containing a urethane resin on a base fabric 12 in this order, and has a recess 18 on the skin layer 16 side.
In addition, the recess 18 may be deep enough to extend beyond the interface between the adhesive layer 14 and the base fabric 12 and reach the inside of the base fabric 12.

The skin material of the present disclosure may include the skin layer described above, and may also include a skin layer, an adhesive layer, and a base fabric, which will be described in detail below.
The skin material of the present disclosure may have a skin layer, an adhesive layer, and a base fabric disposed in this order in the thickness direction of the skin layer.
The skin material of the present disclosure may also have other layers that are typically provided in skin materials, as long as the effects of the present disclosure are not impaired. The other layers will be described later.

<Epidermis layer>
(Storage Modulus)
The skin layer in the present disclosure has a storage modulus of 1.0 MPa or less in a temperature range of 160°C to 170°C.
From the viewpoint of achieving an excellent transfer rate of the grain pattern by the embossing method, the surface layer in the present disclosure preferably has a storage modulus in the temperature range of 160°C to 170°C of 0.8 MPa or less, more preferably 0.7 MPa or less, and even more preferably 0.6 MPa or less.
From the viewpoint of processability by embossing, the skin layer in the present disclosure preferably has a storage modulus in the temperature range of 160° C. to 170° C. of 0.003 MPa or more, and more preferably 0.005 MPa or more.
The storage modulus is measured in accordance with JIS K 7244 (1998).

The skin layer in the skin material of the present disclosure may contain a resin.
Examples of the resin include urethane resin (also simply referred to as polyurethane in this specification), polyvinyl chloride resin, acrylic resin, and ester resin.
Among the above, from the viewpoints of good durability and elasticity, and good processability when forming recesses, it is preferable that the surface layer in the present disclosure contains polyurethane.
The resin used to form the surface layer may be one type alone or a combination of two or more types of resins. Depending on the purpose, the resins listed above may be appropriately selected and combined for use.

Examples of polyurethanes used to form the surface layer include polycarbonate-based polyurethanes, polyether-based polyurethanes, polyester-based polyurethanes, and modified products thereof.
When the skin material of the present disclosure is used for applications requiring long-term durability, such as automobile interior materials and chairs, the skin layer in the skin material of the present disclosure preferably contains a polycarbonate-based polyurethane.

In this disclosure, the resin is preferably contained in an amount of 90% by mass or more, and more preferably 95% by mass or more, based on the total mass of the surface layer.

(Crosslinking Agent)
The skin layer in the skin material of the present disclosure may contain a crosslinking agent.
The inclusion of a crosslinking agent can improve the strength of the skin layer. However, on the other hand, if the skin layer contains a large amount of crosslinking agent, it tends to be difficult to achieve a storage modulus of 1.0 MPa or less in the temperature range of 160° C. to 170° C.
Therefore, although the skin layer may contain a crosslinking agent, it is preferred to keep the amount of the crosslinking agent to a relatively small amount.
Specifically, in the skin material of the present disclosure, the content of the crosslinking agent in the skin layer is preferably 3 parts by mass or less, more preferably 1 part by mass or less, and even more preferably 0.1 part by mass or less, per 100 parts by mass of the base resin in the skin layer.
In the present disclosure, the resin that serves as the main component in the skin layer means a resin that is contained in an amount of 60 mass % or more with respect to the total mass of the skin layer.

In addition, the skin material of the present disclosure preferably contains 0 parts by mass of crosslinking agent in the skin layer per 100 parts by mass of the resin that is the main component in the skin layer. In other words, the skin material of the present disclosure preferably does not contain a crosslinking agent in the skin layer.

Crosslinking agents that can be used in this disclosure include oxazolines, carbodiimides, diisocyanates, etc.

(Other ingredients)
The skin layer may further contain other components in addition to those mentioned above.
Examples of other components include colorants, fillers, stabilizers, flame retardants, synthetic resins other than those mentioned above, and gelation accelerators.

The surface layer may contain a colorant. By containing a colorant in the surface layer, a desired hue can be imparted to the surface material, and the surface material can have excellent design.
When the surface layer contains a colorant, the colorant is not particularly limited, and a suitable colorant such as a dye or pigment can be used. From the viewpoint of better durability and light resistance, a pigment is preferred.
Examples of colorants include inorganic pigments such as titanium white (titanium dioxide), zinc white, ultramarine, cobalt blue, red iron oxide, vermilion, chrome yellow, titanium yellow, and carbon black; organic pigments or dyes such as quinacridone, permanent red 4R, isoindolinone, Hansa Yellow A, phthalocyanine blue, indanthrene blue RS, and aniline black; metal pigments selected from the group consisting of foil powder of metals such as aluminum and brass; and pearlescent (pearl) pigments selected from the group consisting of foil powder of titanium dioxide-coated mica and basic lead carbonate.
When a pigment is used as the colorant, a pigment dispersant such as a surfactant or a polymer dispersant may be used in combination.

The skin layer may contain a filler. Examples of the filler include inorganic fillers such as calcium carbonate, silica (silicon dioxide), alumina (aluminum oxide), mica, talc, barium sulfate, etc. The skin layer may contain only one type of filler, or may contain two or more types of fillers.
The skin layer may contain a stabilizer, which improves the heat resistance of the skin layer.
Examples of the stabilizer include fatty acid metal salts such as magnesium stearate, aluminum stearate, calcium stearate, barium stearate, zinc stearate, calcium laurate, barium laurate, and zinc laurate, sodium compounds such as phenol and naphthol, metal salts such as zinc and barium, organic tin compounds such as dibutyltin dilaurate and dibutyltin dimaleate, and phosphorous esters such as diethyl phosphite, dibutyl phosphite, dioctyl phosphite, diphenyl isodecyl phosphite, tricresyl phosphite, triphenyl phosphite, tris(nonylphenyl)phosphite, and triisooctyl phosphite. The surface layer may contain only one type of stabilizer, or two or more types.
The surface layer may contain a flame retardant. When the surface layer contains a flame retardant, the surface material can be given flame retardancy. As the flame retardant, a known inorganic or organic flame retardant can be appropriately selected and used. The surface layer may contain only one type of flame retardant, or may contain two or more types of flame retardants.
The surface layer may contain other synthetic resins than the above-mentioned resins such as polyurethane for the purpose of improving the film properties, etc. When the surface layer contains other resins, the content of the other resins is preferably 10 parts by mass or less relative to 100 parts by mass of the total solid content of the surface layer.

(Formation of the epidermis layer)
The method for forming the surface layer is not particularly limited, and the surface layer can be formed by preparing a composition for forming a surface layer containing the above-mentioned components and forming it into a sheet by a calendar method, a paste processing method, a melt extrusion method, etc. Alternatively, the surface layer can be formed by applying the composition for forming a surface layer directly onto a release substrate.

The skin layer preferably includes irregularities on at least one surface.
For example, fine projections and recesses can be formed on the surface of the skin layer by embossing the surface of the skin layer using an embossing roll.

There are no particular limitations on the thickness of the skin layer, but from the viewpoint of good flexibility, feel, etc., the thickness of the skin layer in this disclosure is preferably 10 μm to 300 μm, more preferably 20 μm to 200 μm, and even more preferably 20 μm to 80 μm.

<Adhesive Layer>
The skin material of the present disclosure may further have an adhesive layer between the base fabric and the skin layer.
The adhesive layer is provided for the purpose of, for example, improving the adhesion between layers.
The adhesive layer can be formed, for example, by applying an adhesive to the back surface of the skin layer (the surface of the skin layer on the adhesive layer side) and drying the adhesive. The adhesive may be laminated by a transfer method or a coating method.
The adhesive used to form the adhesive layer that is provided as desired is not particularly limited and is appropriately selected according to the purpose. The resin that can be used to form the adhesive layer may be selected from polyurethane, polyvinyl acetate, polyvinyl chloride, polyvinylidene chloride, polystyrene, etc., based on the required performance. From the viewpoint of the track record of use in vehicle interior materials, polyurethane and polyvinyl chloride are preferable. More specifically, for example, (1) urethane-based emulsion adhesive, (2) vinyl chloride-based adhesive, (3) two-component curing polyester-based adhesive, (4) two-component curing urethane adhesive, etc. are preferably used.
Usually, when laminating the base fabric and the surface layer, an adhesive layer can be formed by applying an adhesive to the back surface of the surface layer.
The skin material may have only one adhesive layer, or may have two or more adhesive layers as required.
As described above, the adhesive can be applied by any of the known methods such as the transfer method and the coating method.
In addition, when the adhesive layer is formed by a transfer method, a protective sheet may be provided on the surface of the adhesive layer in order to protect the surface of the adhesive layer that has been previously prepared. As the protective sheet, a resin film, a release-treated paper, a resin-laminated paper, etc. can be appropriately used.

The thickness of the adhesive layer is preferably 5 μm to 100 μm, more preferably 20 μm to 90 μm, and even more preferably 40 μm to 80 μm.

<Base fabric>
The base fabric for the skin material of the present disclosure is not particularly limited as long as it has the necessary strength and durability, and may be appropriately selected from known base fabrics depending on the purpose. The base fabric may be any of knitted fabric, woven fabric, and nonwoven fabric.
When the skin material is applied to a molded article having projections and recesses, it is preferable to use a knitted fabric, woven fabric, or the like having a certain degree of elasticity, and from the viewpoint of good feel and shape conformability, it is more preferable to use a knitted fabric.
When the base fabric is used as a cover material for a vehicle seat, for example, knitted fabrics such as knitted fabrics and modified knitted fabrics may be used from the viewpoints of stretchability and ease of thickness control.
Also, a three-dimensional structured base fabric having a gap between the outer fabric and the inner fabric, a three-dimensional nonwoven fabric, etc. may be used.

Examples of the material of the fibers (yarns) used for knitting and weaving the base fabric include polyester, rayon, hemp, cotton, vinyl chloride, vinylidene chloride, aramid, acrylic, phenol, and carbon-based fibers, and may be blended fibers containing these fibers.
From the viewpoint of embossing processability, etc., the base fabric is preferably a knitted fabric containing at least one type of fiber selected from the group consisting of polyester fibers, rayon fibers, vinyl chloride fibers, vinylidene chloride fibers, aramid fibers, and acrylic fibers, and among these, it is more preferable that the base fabric contains polyester fibers in terms of durability and cost as a vehicle interior material.
As the base fabric, in addition to the knitted fabric, for example, a base fabric for synthetic leather using a punch roman knit described in JP-A-2013-72141 can be used.
The thickness of the base fabric is appropriately selected depending on the intended use of the skin material, but is preferably in a range that provides excellent feel and does not reduce flexibility, for example, in the range of 0.15 mm to 10.0 mm, and more preferably in the range of 0.3 mm to 1.5 mm.

The surface of the base fabric facing the surface layer may be brushed as necessary. The base fabric may also be a pile knit fabric with pile formed on the surface of the base fabric facing the surface layer. By having the surface of the base fabric brushed or with pile, the adhesion to adjacent layers (e.g., adhesive layers, etc.) is further improved.

<Other layers>
The skin material of the present disclosure may have layers other than the skin layer and the adhesive layer, depending on the purpose.
The other layer may be, for example, a surface treatment layer.

<Surface treatment layer>
The skin material may further have a surface treatment layer on the surface of the skin layer opposite to the adhesive layer side.
By providing the surface treatment layer to the skin material, it is possible to impart any desired good feel to the skin material, to further improve the appearance, and to further improve the durability.
The surface treatment layer contains at least a resin, and when provided for the purpose of further improving the feel, may contain organic particles as a feel improver, a colorant for improving design, etc., as desired.
Furthermore, the surface treatment layer formed as desired on the outermost surface of the skin material may be colored or printed, or may have natural leather-like unevenness, typically a grained pattern, depending on the purpose.

Resins that can be contained in the surface treatment layer include polyurethane, acrylic resin, fluororesin, polyvinyl chloride resin, etc., and from the viewpoint of good feel, it is preferable to use polyurethane as the main material. Here, the "main material" means the resin with the highest content ratio when multiple types of resins are used in combination.
The polyurethane used in the surface treatment layer is preferably a water-based polyurethane.
Examples of the acrylic resin used in the surface treatment layer include polymers or copolymers of methacrylic acid or methacrylic acid esters, such as polymethyl methacrylate (PMMA), and copolymers of alkyl methacrylate, alkyl acrylate, and styrene.

By including organic particles as a filler in the surface treatment layer, it is possible to impart a moist and warm feel to the skin material, compared to the case where amorphous inorganic fillers that have conventionally been used as matting agents are used.
Examples of the organic particles include organic resin particles such as urethane beads and acrylic beads, and protein-based fillers such as collagen particles.
From the viewpoint of improving the feel, the shape of the organic particles is preferably spherical or nearly spherical, for example, with a ratio of the major axis to the minor axis of 1.5 or less, and the average particle size is preferably in the range of 1 μm to 20 μm, more preferably in the range of 5 μm to 10 μm. By having the particle size in the above range, falling off of the particles from the surface treatment layer and adverse effects on the appearance can be suppressed, and a good appearance and excellent texture can be maintained for a long period of time.
The average particle size of the organic particles is measured using an automatic particle size measuring device (model: CAPA-300) manufactured by Horiba, Ltd., by a light transmission centrifugal sedimentation method using water as a dispersion medium at a disk rotation speed of 3000 rpm (revolutions per minute), and the value measured by the method of measuring the volume-based median diameter is used.
The organic particles may be used alone or in combination of two or more kinds.

The surface treatment layer may contain a colorant to impart design, if necessary. The general-purpose colorants listed for the surface layer can be used as the colorant, and the preferred amounts of addition are also the same.
For the purpose of further improving the abrasion resistance, a surface treatment layer containing a crosslinked structure can also be formed.

The thickness of the surface treatment layer is preferably in the range of 2 μm to 10 μm, and more preferably in the range of 2 μm to 5 μm.

The skin material of the present disclosure reproduces the fine irregularities created by the embossing process, making it suitable for use in a variety of applications that require design, such as vehicle interior materials.

<Production method of skin material>
The method for producing the skin material of the present disclosure is not particularly limited, but the following mode A is preferred.

<Aspect A>
The method for producing a skin material according to aspect A is a method for producing a skin material according to the present disclosure, and includes the steps of: using a composition for forming a skin layer to form a skin layer having a storage modulus of 1.0 MPa or less in a temperature range of 160° C. to 170° C. (step (I)); forming an adhesive layer on one side of the skin layer (step (II)); adhering a base fabric to the side of the adhesive layer opposite the skin layer side (step (III)); and bringing an embossing roll into contact with the side of the skin layer opposite the adhesive layer to perform embossing to form recesses (step (IV)).

(Step (I))
Step (I) is a step of forming a skin layer having a storage modulus of 1.0 MPa or less in a temperature range of 160° C. to 170° C. using a composition for forming a skin layer.
The method for forming the surface layer may be any method, including a calendar method, a paste processing method, a melt extrusion method, and the like.
Preferably, a method of applying a previously prepared composition for forming a skin layer containing a urethane resin to the surface of a suitable release substrate by a known coating method such as using a knife coater, etc. In this case, by using a release substrate having a fine uneven pattern on its surface, the fine uneven pattern can be transferred to the surface of the skin layer.
The composition may also be formed into a sheet by a calendar method to form the skin layer.

The composition for forming the skin layer can contain the resin, crosslinking agent, colorant, and other components described in the skin layer section above, and the preferred aspects of each component are the same as those described in the skin layer section above.

The preferred range of storage modulus values in the temperature range of 160°C to 170°C is the same as the preferred range of values described for the storage modulus in the skin layer section above.

(Step (II))
Step (II) is a step of forming an adhesive layer on either the surface layer or the base fabric obtained in step (I).
The adhesive layer can be formed, for example, by applying an adhesive to the back surface of the skin layer or to the base fabric. In particular, it is preferable to apply an adhesive to the back surface of the skin layer and dry it to form the adhesive layer.
The adhesive used to form the adhesive layer that is provided if desired is as described in the section on the adhesive layer.
Methods for applying the adhesive include a transfer method and a coating method.
An adhesive is applied to the back surface of the skin layer or to the base fabric, and the applied adhesive layer is heated and dried to form an adhesive layer on the back surface of the skin layer or on the base fabric.

(Step (III))
Step (III) is a step of bonding the surface layer and the base fabric via an adhesive layer.
In step (II), if an adhesive layer is formed on the skin layer, a base fabric may be adhered to the side of the adhesive layer opposite the skin layer side, and if an adhesive layer is formed on the base fabric, the skin layer may be adhered to the side of the adhesive layer opposite the base fabric side.
The side of the base fabric that contacts the adhesive layer may be subjected to a nap raising treatment by a conventional method.
The adhesive for forming the adhesive layer, the preferred thickness of the adhesive layer, etc. are as described above.

(Step (IV))
Step (IV) is a step of embossing the surface of the laminate to which the base fabric obtained in step (III) is adhered, opposite the adhesive layer of the skin layer, by contacting the surface with an embossing roll to form recesses.
FIG. 3 is a schematic diagram showing one embodiment of embossing for forming irregularities in the laminate 10A for forming the skin obtained in step (III) to obtain the skin.
As shown in FIG. 3 , the laminate 10A for forming the skin material is heated and pressed between an embossing roll 24 for shaping and a backup roll 26 in an embossing machine having a pair of embossing rolls, so that a concave-convex pattern is formed in the laminate 10A and the skin material 10 is obtained.
The embossing method may be a method in which the surface layer side of the laminate is heated with a heater or the like, and then a shape is imparted with an embossing roll, or a flat embossing plate may be used. Also, the embossing roll or embossing plate itself may be heated to impart a shape.
During the embossing process, a desired gap can be provided between the laminate for forming the skin material and the embossing roll or embossing plate depending on the required design and thickness.

The processing conditions in the embossing machine are appropriately selected depending on the purpose.
For example, in the case of embossing using an embossing roll, the heating temperature of the surface of the skin layer that comes into contact with the embossing roll is preferably in the range of 90° C. to 210° C., more preferably in the range of 130° C. to 170° C. The heater of the embossing roll may be adjusted so that the surface temperature falls within the above range.
The pressure during embossing is preferably 0.1 kgf/cm ² to 50 kgf/cm ² , more preferably 0.5 kgf/cm ² to 20 kgf/cm ² , further preferably 1.0 kgf/cm ² to 10 kgf/cm ² , and particularly preferably 1.0 kgf/cm ² to 5.0 kgf/cm ^2. Note that 1 kgf/cm ² can be converted to 9.80665×10 kPa in SI units.

The processing speed during embossing is preferably 0.5 m/min to 20 m/min, more preferably 1 m/min to 10 m/min, and even more preferably 1.5 m/min to 5 m/min.
For example, in the case of embossing using an embossing plate, the heating temperature is preferably in the range of 90° C. to 210° C., more preferably 130° C. to 170° C., as the surface temperature on the urethane skin side of the laminate. The heater of the embossing plate may be adjusted so that the surface temperature falls within the above range.
The pressing time is preferably from 10 to 90 seconds, more preferably from 15 to 80 seconds, and even more preferably from 20 to 70 seconds.
Through step (IV), the skin material of the present disclosure having a fine uneven pattern can be obtained.

(Step (V))
Step (V) is a step of forming a surface treatment layer (e.g., a feel-improving layer) on the surface of the skin layer (the surface of the skin layer opposite the adhesive layer side) in order to improve the feel and appearance.
The step (V) is carried out by applying a composition for forming a surface treatment layer containing a resin onto the surface of the skin layer.
The composition for forming a surface treatment layer can be applied by appropriately applying a known method.
The surface treatment layer may be formed by a method appropriately selected from the following: coating by gravure printing, coating by a coating device such as a reverse coater or a direct coater, etc. Among these, the gravure printing method is preferred from the viewpoint of forming a more uniform layer.
The details of the surface treatment layer are as described above.

In the manufacturing method of the present disclosure, a step of imparting a design to further improve the appearance can be carried out, if necessary.
After completing the above steps (I) to (IV) or any other steps described above that are carried out as desired, a step of imparting a design can be carried out.
An example of a process for imparting a design is a process for forming a grain pattern on the surface by pressing an embossing roll engraved with a grain pattern, which is a fine, leather-like uneven pattern, against the skin layer or an optionally provided surface treatment layer while the surface is heated.

The skin material of the present disclosure obtained by the manufacturing method of the present disclosure can have a skin layer with good flexibility and feel, or a surface treatment layer with good feel, in which the fine unevenness caused by embossing is sharply reproduced on the outermost surface. For this reason, it is suitable for use as a skin material for molded bodies with complex shapes, and for decorative applications of molded bodies with excellent design and durability such as abrasion resistance.

The skin material of the present disclosure can be manufactured by a simple method such as the manufacturing method of the present disclosure described above, and has excellent appearance and durability, maintains a fine uneven pattern for a long period of time, and is flexible, making it suitable for use in a variety of fields, including automotive interior materials, railway car and aircraft interior parts, furniture, footwear such as shoes, bags, interior and exterior components for building decoration, and clothing coverings or linings.

The present disclosure will be described in further detail below with reference to examples, but the invention of the present disclosure is not limited to these examples.
The molecular weight of the resin contained in the surface layer obtained in each of the Examples and Comparative Examples was measured in the same manner as described above.

Example 1
JK-831N (polycarbonate-based polyurethane, manufactured by Meisei Chemical Industry Co., Ltd.) was diluted with water in an amount to give a solid content of 16% by mass to prepare a composition for forming a surface layer.
The obtained composition for forming a surface skin layer was applied to a release paper with a knife coater at a coating amount of 250 g/ ^m2 to form a surface skin layer having a thickness of 40 μm on the surface of the release paper. (Step (I))

A composition for forming an adhesive layer was prepared by adding 5 parts by mass of dimethylformamide (DMF) to 100 parts by mass of polyurethane (product name: TA205, manufactured by DIC Corporation) and 10 parts by mass of a crosslinking agent (product name: Burnock DN950, manufactured by DIC Corporation). The obtained composition for forming an adhesive layer was coated in an amount of 150 g/ ^m2 to form a 60 μm thick adhesive layer on the surface layer, thereby obtaining a laminate. (Step (II))

The laminate of the skin layer and adhesive layer obtained in step (II) was attached to a base fabric that had been prepared in advance. (Step (III))

In this manner, a laminate for forming a skin material having a thickness of 1.0 mm and comprising the base fabric, the adhesive layer, and the skin layer in this order was obtained.
The release paper was peeled off from the resulting laminate for forming the skin material, and the laminate was then embossed.
The heater of the embossing machine was adjusted so that the surface temperature on the skin layer side was 160° C., and embossing was performed at a pressure of 2 kgf/cm ² and a processing speed of 2 m/min to obtain the skin material of Example 1 having a fine three-dimensional shape and pattern. (Step (IV))

Example 2
A skin material of Example 2 was obtained in the same manner as in Example 1, except that the polyurethane in step I in Example 1 was changed to D-4080 (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.).

Example 3
A skin material of Example 3 was obtained in the same manner as in Example 1, except that the polyurethane in step I in Example 1 was changed to WLS-210 (manufactured by DIC Corporation).

Example 4
The skin material of Example 4 was obtained in the same manner as in Example 1, except that in step I in Example 1, K-2010 (manufactured by Nippon Shokubai Co., Ltd.) was further added as a crosslinking agent in an amount of 3 parts by mass per 100 parts by mass of the polyurethane, which was the base resin.

Comparative Example 1
The skin material of Comparative Example 1 was obtained in the same manner as in Example 1, except that in step I in Example 1, K-2010 (manufactured by Nippon Shokubai Co., Ltd.) was further added as a crosslinking agent in an amount of 6 parts by mass per 100 parts by mass of the polyurethane, which was the base resin.

Comparative Example 2
A skin material of Comparative Example 2 was obtained in the same manner as in Example 1, except that in step I in Example 1, V-02 (manufactured by Nisshinbo Chemical Inc.) was further added as a crosslinking agent in an amount of 6 parts by mass per 100 parts by mass of the polyurethane, which was the base resin.

Comparative Example 3
A skin material of Comparative Example 3 was obtained in the same manner as in Example 3, except that in step I in Example 3, V-02 (manufactured by Nisshinbo Chemical Inc.) was further added as a crosslinking agent in an amount of 4 parts by mass per 100 parts by mass of the polyurethane, which was the base resin.

<Evaluation>
(Storage Modulus)
In each of the Examples and Comparative Examples, the storage modulus of the skin layer was measured by the following method.
The skin material obtained in each Example or Comparative Example was cut to obtain only the skin layer. The storage modulus of the obtained skin layer was measured at 160° C. and 170° C. in accordance with JIS K 7244 (1998). The results are shown in Table 1.

(Transferability)
The obtained skin material test samples were visually observed, and the state of transfer of the embossing die used in the embossing process was evaluated according to the following evaluation criteria. The results are shown in Table 1.
～Evaluation criteria～
The evaluation criteria are as follows: Among the evaluation results below, A and B are at levels that are not problematic in practical use.
A: The corners of the recesses have a sharp R shape of the embossed mold and are clearly transferred.
B: The shape of the embossed mold is transferred, but the corners of the recesses have a gentle R shape.
C: The shape of the embossed mold is hardly transferred.

As shown in Table 1, in Examples 1 to 3 in which the skin layer did not contain a crosslinking agent, and in Example 4 in which the content of the crosslinking agent was 3 parts by mass, the storage modulus in the temperature range of 160°C to 170°C was 1.0 MPa or less, and the squeeze transferability was excellent.
Among them, Example 1, in which the storage modulus was 0.15 MPa or less, was more excellent in the grain transferability.
On the other hand, Comparative Examples 1 to 3, in which the storage modulus exceeded 1.0 MPa, were inferior in the grain transferability.

REFERENCE SIGNS LIST 10: Skin material 10A: Laminate for forming skin material 12: Base fabric 14: Adhesive layer 16: Skin layer 18: Recess 24: Embossing roll 26: Backup roll

Claims (6)

a skin layer having a storage modulus of 0.003 MPa or more and 0.6 MPa or less in a temperature range of 160°C to 170°C, which is an embossing temperature ;
An adhesive layer and a base fabric,
The skin layer includes irregularities on at least one surface,
the skin layer comprises polyurethane;
the adhesive layer comprises at least one selected from the group consisting of polyurethane, polyvinyl acetate, polyvinyl chloride, polyvinylidene chloride, and polystyrene;
A skin material, wherein the fibers used for knitting or weaving the base fabric include at least one fiber selected from the group consisting of polyester, rayon, hemp, cotton, vinyl chloride, vinylidene chloride, aramid, acrylic, phenol, and carbon-based fibers, or a blended fiber containing the above fiber . 2. The skin material according to claim 1 , wherein the content of the crosslinking agent in the skin layer is 3 parts by mass or less per 100 parts by mass of the base resin in the skin layer. 3. The skin material according to claim 1 , wherein the content of the crosslinking agent in the skin layer is 0 part by mass per 100 parts by mass of the base resin in the skin layer. The skin material according to any one of claims 1 to 3 , wherein the thickness of the skin layer is 10 µm to 300 µm. The skin material according to any one of claims 1 to 4 , wherein the skin layer, the adhesive layer, and the base fabric are disposed in this order in the thickness direction of the skin layer. A method for producing the skin material according to claim 5 , comprising the steps of:
forming a surface layer having a storage modulus of 0.003 MPa or more and 0.6 MPa or less in a temperature range of 160°C to 170°C , which is an embossing temperature , using a composition for forming a surface layer;
forming an adhesive layer on one of the skin layer or the base fabric;
a step of adhering the surface layer and the base fabric via the adhesive layer;
and bringing an embossing roll into contact with the surface of the skin layer opposite the adhesive layer to perform embossing to form recesses.