Synthetic leather

Abstract

To provide a synthetic leather having good elongation characteristics and durability (particularly, low-temperature flexibility and heat resistance (low-temperature flexibility after heat resistance and elongation characteristics after heat resistance)) while using a raw material composed of a plant-derived component.SOLUTION: A synthetic leather according to an embodiment includes a fibrous substrate and a skin layer provided on the fibrous substrate and made of a polyurethane resin. The fibrous substrate includes a knitted fabric and a polyether-based polyurethane resin applied to the knitted fabric. The knitted fabric has a basis weight of 150g / m2 or more, and the content of the cotton fiber in the knitted fabric is 75 mass% or more. The adhesion amount of the polyether-based polyurethane resin to the knitted fabric is 10% by mass or more. The polyether-based polyurethane resin fills the spaces between the fibers constituting the yarns of the knitted fabric and is hardly present between the yarns. The content of the plant-derived component in the synthetic leather is 40% by mass or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to synthetic leather. [Background technology]

[0002] In recent years, in light of environmental issues, there has been a demand for synthetic leather made from plant-derived components. For example, Patent Document 1 describes a synthetic imitation leather made from a base fabric constituting a core and a surface layer. It describes that at least the surface layer is made of a bio-polyurethane resin, and that the content of plant-derived components is 28 to 95% by mass relative to 100% by mass of the bio-polyurethane resin. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-226047 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to increase the proportion of plant-derived components in synthetic leather, it is preferable that not only the resin layer but also the fibrous substrate be made from plant-derived components, such as natural fibers such as cotton, or resins made from bio-based components. However, in this case, there is a problem of poor durability (particularly mechanical strength and heat resistance). In Patent Document 1, when using a woven fabric impregnated with a bio-polyurethane resin, a nonwoven fabric impregnated with a bio-polyurethane resin, or a fibrous substrate with a microporous layer of a bio-polyurethane resin formed thereon, it is difficult to improve durability. Another problem is poor elongation properties.

[0005] The present invention has been made in light of the above-mentioned circumstances, and its object is to provide synthetic leather that uses raw materials composed of plant-derived components and that has good elongation properties and durability (particularly low-temperature flexibility and heat resistance (low-temperature flexibility after heat resistance and elongation properties after heat resistance)). [Means for solving the problem]

[0006] The present invention includes the embodiments shown below. [1] A fabric comprising a fibrous base material and a surface layer made of a polyurethane resin provided on the fibrous base material, the fibrous base material including a knitted fabric and a polyether-based polyurethane resin applied to the knitted fabric, and the knitted fabric having a basis weight of 150 g / m 2 The above synthetic leather is characterized in that the cotton fiber content in the knitted fabric is 75% by mass or more, the amount of the polyether-based polyurethane resin attached to the knitted fabric is 10% by mass or more, the polyether-based polyurethane resin fills the spaces between the fibers constituting the yarns of the knitted fabric and is barely present between the yarns, and the plant-derived component content in the synthetic leather is 40% by mass or more. [2] The synthetic leather according to [1], wherein the amount of the polyether polyurethane resin attached to the knitted fabric is 15 to 30% by mass. [3] The synthetic leather according to [1] or [2], wherein the knitted fabric is a circular knitted fabric. [4] The synthetic leather according to [3], wherein the knitting structure of the circular knitted fabric is mock lody. [5] The synthetic leather according to any one of [1] to [4], wherein the cotton fiber is a compact yarn. [6] The synthetic leather according to any one of [1] to [5], wherein the density of the fibrous base material is 25 to 50 courses / 25.4 mm, or 30 to 40 wells / 25.4 mm. [Effects of the Invention]

[0007] According to an embodiment of the present invention, synthetic leather can be provided that uses raw materials composed of plant-derived components and that has good elongation properties and durability (particularly low-temperature flexibility and heat resistance (low-temperature flexibility after heat resistance and elongation properties after heat resistance)). [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view of a synthetic leather according to an embodiment. FIG. [Figure 2] FIG. 10 is a cross-sectional view of a synthetic leather according to another embodiment. [Figure 3] 1A and 1B are cross-sectional photographs of a fibrous base material according to one embodiment, where (a) is a 40x magnification and (b) is a 100x magnification. [Figure 4] 1A and 1B are cross-sectional photographs of a knitted fabric according to one embodiment, where (a) is a 40x magnification and (b) is a 100x magnification. [Figure 5] FIG. 2 is a cross-sectional schematic diagram showing a polyether-based polyurethane resin present between threads. [Figure 6] 1A and 1B are cross-sectional photographs of a fibrous base material according to one embodiment, where (a) is the original image and (b) is an image clearly showing the polyether-based polyurethane resin present between the threads. [Figure 7] FIG. 1 is a tissue diagram of the mock lodi tissue of Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0009] The synthetic leather according to this embodiment includes a fibrous base material and a surface layer made of a polyurethane resin provided on the fibrous base material.

[0010] 1 is a cross-sectional view schematically illustrating the cross-sectional structure of synthetic leather 1 according to one embodiment. Synthetic leather 1 has a skin layer 3 laminated on one side of a fibrous base material 2. In this example, a polyether-based polyurethane resin (not shown) is applied to the entire fibrous base material 2.

[0011] Fig. 2 is a schematic diagram showing the cross-sectional structure of synthetic leather 10 according to another embodiment. This synthetic leather 10 differs from the synthetic leather 1 shown in Fig. 1 in that a skin layer 3 is provided on a fibrous base material 2 via an adhesive layer 4, and that a surface treatment layer 5 is provided on the skin layer 3. Therefore, in the example shown in Fig. 2, the adhesive layer 4, the skin layer 3, and the surface treatment layer 5 are laminated in this order on one surface of the fibrous base material 2.

[0012] In the examples of Figures 1 and 2, the front surface of the synthetic leather 1, 10 (i.e., the front surface of the skin layer 3 or the surface treatment layer 5) is flat, but in consideration of the design, it may be provided with irregularities such as a leather-like grain pattern in a conventional manner. Here, the front surface of the synthetic leather refers to the surface (design surface) of the front or back of the synthetic leather that is visible when in use. Specifically, the surface of the synthetic leather is the front surface of the skin layer or the surface treatment layer.

[0013] FIG. 3 is a cross-sectional photograph of a fibrous substrate according to one embodiment (after the polyether-based polyurethane resin has been applied to the knitted fabric), and FIG. 4 is a cross-sectional photograph of the knitted fabric before the resin has been applied. Before the resin is applied as shown in FIG. 4, there are large spaces between the fibers that make up the yarn and between the yarns. On the other hand, after the resin is applied as shown in FIG. 3, the resin has filled the spaces between the fibers that make up the yarn, bonding the fibers together, but there is almost no resin between the yarns. That is, in FIG. 3, the polyether-based polyurethane resin is present in a state where it fills the spaces between the fibers that make up the yarn and is almost not present between the yarns.

[0014] Here, "filling the spaces between the fibers that make up the yarn, but being barely present between the yarns" refers to a state in which the fibers that make up the yarn are bonded with resin, resin is present on the fiber surfaces, and some of the yarn surfaces are covered with resin, but there is barely any resin between the yarns, and multiple yarns are not bonded together with resin. By having the polyether-based polyurethane resin fill the spaces between the fibers that make up the yarn, durability (retention of elongation properties after heat aging and low-temperature flexibility performance) is improved. Because the polyether-based polyurethane resin is barely present between the yarns, a decrease in the elongation properties of the knitted fabric is suppressed, making it easier to obtain good elongation properties.

[0015] In this embodiment, "there is almost no resin between the threads" means that when the cross section of the synthetic leather is observed, the proportion of resin present between the threads, i.e., the portion of the outer periphery of the cross section of the thread that is bonded to other threads via resin, is less than 25%.

[0016] The proportion of resin present between adjacent threads is measured as follows: A vertical cross section of synthetic leather is observed at 100x magnification using a microscope (for example, VHX-200 / 100F manufactured by Keyence Corporation), and the outer periphery (A) of the cross section of the thread and the length of the portion (B) of the cross section of the thread that is bonded to other threads via resin are measured at 10 random locations, and the proportion of the portion of the outer periphery of the cross section of the thread that is bonded to other threads via resin is calculated using the following formula, and the average value is calculated. Ratio of resin present between threads (%) = B / A x 100

[0017] FIG. 5 is a cross-sectional schematic diagram showing polyether-based polyurethane resin present between threads. In FIG. 5, thread 7 is formed from a plurality of fibers 6. A polyether-based polyurethane resin (not shown) is filled between the fibers 6. In part of the outer periphery 8(A) of the cross section of the thread, there is a portion 9 where multiple threads are bonded together with resin. In FIG. 5, the portion (B) of the outer periphery 8(A) of the cross section of the thread where multiple threads are bonded together with resin is shown by a solid line, and the portion where the surface of the thread is coated with resin but where multiple threads are not bonded together with resin is shown by a dotted line.

[0018] Fig. 6 shows a cross-sectional photograph of a fibrous substrate according to one embodiment (after the polyether-based polyurethane resin has been applied to the knitted fabric). Fig. 6(b) shows the portions of Fig. 6(a) where multiple threads are bonded together with the resin by solid lines, and the portions where the surfaces of the threads are coated with the resin but where the multiple threads are not bonded together with the resin by dotted lines.

[0019] The fibrous base material used in this embodiment comprises a knitted fabric and a polyether polyurethane resin applied to the knitted fabric.

[0020] Knitted fabrics have a loop structure that makes them more stretchable than woven or nonwoven fabrics, so the synthetic leather obtained by using knitted fabrics tends to have good stretch properties.

[0021] The knitted fabric is not particularly limited, and examples thereof include circular knitting, flat knitting, tricot, double raschel, etc. Among these, circular knitting is preferred from the viewpoint of elongation properties.

[0022] As the circular knitting structure, conventionally known knitting structures can be used. Among circular knitting structures, double knitting is preferred from the viewpoint of elongation properties. Examples of circular knitting double knitting structures include mock rody, brushed, smooth (interlock), punch roma, ripple, Milano rib, and jacquard. Among these, mock rody is preferred because it can achieve a good balance between elongation properties and strength by knitting so that one yarn appears alternately in the front and back ground structures.

[0023] The knitted fabric may be colored with a dye or pigment, or may be uncolored.

[0024] It is essential to use cotton fiber as the fiber material constituting the knitted fabric. The cotton fiber content in the knitted fabric is 75% by mass or more. This increases the content of plant-derived components in the resulting synthetic leather, resulting in a synthetic leather with a high bio content. The cotton fiber content is preferably 100% by mass.

[0025] As the fiber material constituting the knitted fabric, fibers other than cotton fibers can be used in combination by techniques such as blending, co-mingling, twisting, and interknitting so that the cotton fiber content in the knitted fabric is 75% by mass or more. Examples of fiber materials other than cotton fibers include natural fibers other than cotton fibers, regenerated fibers, and synthetic fibers. These can be used alone or in combination of two or more. Among these, synthetic fibers are preferred, and polyester fibers are more preferred, from the viewpoints of durability, particularly mechanical strength and heat resistance.

[0026] The thickness of the cotton fiber yarn is not particularly limited, but is preferably 15 to 30, and more preferably 15 to 26. When the thickness of the cotton fiber yarn is equal to or greater than the lower limit, knitting properties are good. When the thickness of the cotton fiber yarn is equal to or less than the upper limit, tear strength is good.

[0027] The cotton fiber is not particularly limited, and any of carded yarn, combed yarn, and compact yarn may be used. Among these, compact yarn with low fluff is preferred. Low fluff causes gaps between the yarns in the resulting knitted fabric. This makes it easier to impart the polyether polyurethane resin with the desired state and to obtain good elongation properties.

[0028] The thickness (total fineness) of the yarns of fibers other than cotton fibers is not particularly limited, but is preferably 150 to 170 dtex (35 to 39 cotton count).

[0029] The density of the knitted fabric is not particularly limited, but is preferably 25 to 50 courses / 25.4 mm, 30 to 40 welts / 25.4 mm, and more preferably 30 to 39 courses / 25.4 mm, 31 to 33 welts / 25.4 mm. When the density of the knitted fabric is equal to or greater than the lower limit, the tensile strength and tear strength are good. When the density of the knitted fabric is equal to or less than the upper limit, voids are formed between the yarns of the resulting knitted fabric, making it easier to impart the polyether-based polyurethane resin to the desired state and to obtain good elongation properties.

[0030] The weight of the knitted fabric is 150g / m 2 That is all. By making the basis weight of the knitted fabric equal to or greater than the lower limit, the content of plant-derived components in the resulting synthetic leather can be increased, resulting in a synthetic leather with a high bio content. In addition, good durability (particularly, retention of low-temperature flexibility after heat aging) can be easily obtained. The basis weight of the knitted fabric is preferably 250 to 450 g / m 2 is.

[0031] The thickness of the knitted fabric is not particularly limited, but is preferably 0.5 to 1.5 mm. When the thickness of the knitted fabric is equal to or greater than the lower limit, the tensile strength and tear strength are good. When the thickness of the knitted fabric is equal to or less than the upper limit, good elongation properties are easily obtained.

[0032] The thickness of the knitted fabric is measured as follows: A vertical cross section of the knitted fabric is observed at 100x magnification using a microscope (for example, VHX-200 / 100F manufactured by Keyence Corporation), the thickness of the knitted fabric is measured at any 10 points, and the average value is calculated.

[0033] The knitted fabric is provided with a polyether polyurethane resin.

[0034] The polyether polyurethane resin is preferably applied to the entire knitted fabric in the thickness direction in order to impart durability.

[0035] It is essential that the resin applied to the knitted fabric be a polyether-based polyurethane resin. The ether bonds in polyether-based polyurethane resins have relatively low cohesive strength, resulting in high flexibility of the resin. Therefore, the use of polyether-based polyurethane resins improves durability (particularly, the retention of low-temperature flexibility and elongation properties after heat aging). While polyurethane resins other than polyether-based polyurethane resins can be used in combination within a range that does not impair the effects of the present invention, it is preferable to use only polyether-based polyurethane resins from the viewpoint of durability.

[0036] The form of the polyether-based polyurethane resin is not particularly limited, but is preferably a water-based one-component type from the viewpoint of ease of imparting the resin to the desired state described above.

[0037] The Tg (glass transition temperature) of the polyether polyurethane resin is not particularly limited, but from the viewpoint of elongation characteristics and low-temperature flexibility, it is preferably −50° C. or lower. The glass transition temperature can be measured by a known method using a differential scanning calorimeter or the like.

[0038] From the viewpoint of bio content, the polyether polyurethane resin is preferably a resin made from raw materials comprising conventionally known plant-derived components.

[0039] Various additives such as catalysts, matting agents, smoothing agents (e.g., silicone oils), surfactants, fillers, leveling agents, thickeners, crosslinking agents, and penetrating agents may be added to the polyether-based polyurethane resin within a range that does not impair the effects of this embodiment.

[0040] The amount of polyether polyurethane resin attached to the knitted fabric is 10% by mass or more. When the amount of polyether polyurethane resin attached is equal to or greater than the lower limit, durability (particularly, retention of low-temperature flexibility and elongation properties after heat aging) becomes good. The amount of polyether polyurethane resin attached is preferably 15 to 30% by mass.

[0041] The density of the fibrous substrate is not particularly limited, and is preferably 25 to 50 coarse / 25.4 mm, 30 to 40 well / 25.4 mm, and more preferably 30 to 39 coarse / 25.4 mm, 31 to 33 well / 25.4 mm. When the density of the fibrous substrate is equal to or greater than the lower limit, the tear strength and tensile strength are good. When the density of the fibrous substrate is equal to or less than the upper limit, good elongation properties are easily obtained.

[0042] The basis weight of the fibrous base material is not particularly limited, and is 275 to 550 g / m 2 When the basis weight of the fibrous base material is equal to or greater than the lower limit, the tensile strength and tear strength are good. When the basis weight of the fibrous base material is equal to or less than the upper limit, the elongation characteristics and finishability (easy laying) are good.

[0043] The thickness of the fibrous substrate is not particularly limited, but is preferably 0.5 to 1.5 mm. When the thickness of the fibrous substrate is equal to or greater than the lower limit, the tensile strength and tear strength are good. When the thickness of the fibrous substrate is equal to or less than the upper limit, good elongation properties are easily obtained.

[0044] The thickness of the fibrous substrate is measured as follows: A vertical cross section of the synthetic leather is observed at 100x magnification using a microscope (for example, VHX-200 / 100F manufactured by Keyence Corporation), the thickness of the fibrous substrate is measured at any 10 points, and the average value is calculated.

[0045] The synthetic leather according to this embodiment has a surface layer made of polyurethane resin provided on the fibrous base material.

[0046] The polyurethane resin constituting the surface layer is not particularly limited, and any conventionally known polyurethane resin can be used. Among them, polycarbonate-based polyurethane resins are preferred from the viewpoints of hydrolysis resistance and chemical resistance.

[0047] The form of the polyurethane resin is not particularly limited, and may be solventless, hot melt, solvent-based, or water-based, and further may be one-component or two-component curing, and may be selected appropriately depending on the purpose and application.

[0048] From the viewpoint of bio content, the polyurethane resin is preferably a resin made from raw materials comprising conventionally known plant-derived components.

[0049] The surface layer may contain various additives, such as colorants (pigments, dyes), matting agents, smoothing agents, surfactants, fillers, leveling agents, thickeners, etc., as needed, within the range that does not impair the effects of the present invention. These may be used alone or in combination.

[0050] The thickness of the skin layer is not particularly limited, but is preferably 20 to 50 μm, and more preferably 25 to 40 μm. When the thickness of the skin layer is equal to or greater than the lower limit, the abrasion resistance and chemical resistance of the resulting synthetic leather can be improved. When the thickness of the skin layer is equal to or less than the upper limit, the texture of the resulting synthetic leather can be improved.

[0051] The thickness of the skin layer is measured as follows: A vertical cross section of the synthetic leather is observed at 100x magnification using a microscope (for example, VHX-200 / 100F manufactured by Keyence Corporation), the thickness of the entire resin layer is measured at any 10 points, and the average value is calculated.

[0052] The basis weight of the surface layer is not particularly limited, but is, for example, 20 to 50 g / m 2 is preferably 25 to 40 g / m 2 When the basis weight of the surface layer is equal to or greater than the lower limit, the abrasion resistance and chemical resistance of the resulting synthetic leather can be improved. When the basis weight of the surface layer is equal to or less than the upper limit, the texture of the resulting synthetic leather can be improved.

[0053] In this embodiment, other resin layers may be provided in addition to the surface layer, as needed, such as a surface treatment layer, an adhesive layer, a foam layer, and an anchor coat layer.

[0054] The resin constituting the other resin layer is not particularly limited, and any conventionally known resin can be used. Polyurethane resins are preferred, and polycarbonate-based polyurethane resins are more preferred among them from the viewpoints of hydrolysis resistance and chemical resistance.

[0055] From the viewpoint of bio-content, the resin constituting the other resin layer is preferably a resin made from raw materials comprising conventionally known plant-derived components.

[0056] The thickness of the entire resin layer consisting of the surface layer and other resin layers is not particularly limited, but is preferably 192.5 to 435 μm. When the thickness of the entire resin layer is equal to or greater than the lower limit, good abrasion resistance, chemical resistance, and low-temperature flexibility are easily obtained. When the thickness of the entire resin layer is equal to or less than the upper limit, good texture and finish (easy application to seats, instrument panels, door materials, steering wheels, etc., and good appearance) are easily obtained.

[0057] The thickness of the entire resin layer is measured as follows: A vertical cross section of the synthetic leather is observed at 100x magnification using a microscope (for example, VHX-200 / 100F manufactured by Keyence Corporation), the thickness of the entire resin layer is measured at any 10 points, and the average value is calculated.

[0058] The basis weight of the entire resin layer consisting of the surface layer and other resin layers is not particularly limited, and is 192.5 to 435 g / m 2 It is preferable that the weight per unit area of ​​the entire resin layer is equal to or greater than the lower limit, which makes it easy to obtain good abrasion resistance, chemical resistance, and low-temperature flexibility. When the weight per unit area of ​​the entire resin layer is equal to or less than the upper limit, it makes it easy to obtain good texture and finish (easy to apply to seats, instrument panels, door materials, steering wheels, etc., and provides a good appearance).

[0059] The synthetic leather according to this embodiment has a plant-derived component content of 40% by mass or more. By ensuring that the plant-derived component content in the synthetic leather is equal to or greater than the lower limit, it is possible to provide synthetic leather with a high bio content. The plant-derived component content in the synthetic leather is preferably 50% by mass or more.

[0060] The content of plant-derived components in synthetic leather is measured as follows: It is calculated by measuring the bio-based content in accordance with ASTM D6866.

[0061] The synthetic leather according to this embodiment has a modulus of 25 N / mm at 10% elongation. 2 It is preferably equal to or less than 20 N / mm 2 or less, and more preferably 15 N / mm 2 When the synthetic leather has a modulus value at 10% elongation of not more than the upper limit, it has good elongation properties. When used for vehicle seats, it is easy to achieve a good finish (easy application to seats, instrument panels, door materials, steering wheels, etc., and the upholstery looks good).

[0062] The synthetic leather according to this embodiment preferably retains 50% or more, and more preferably 60% or more, of its modulus at 10% elongation before and after 500 hours of heat aging at 120° C. When the modulus retention at 10% elongation is equal to or greater than the lower limit, it is easy to obtain good durability (especially retention of elongation properties after heat aging) even when cotton fibers are used as the fibrous base material.

[0063] The weight of the synthetic leather according to this embodiment is 467.5 to 985 g / m 2 It is preferable that the weight per unit area of ​​the synthetic leather is equal to or greater than the lower limit, thereby improving the tensile strength. When the weight per unit area of ​​the synthetic leather is equal to or less than the upper limit, it is easy to obtain good elongation properties and finish (easy application to seats, instrument panels, door materials, steering wheels, etc., and good appearance).

[0064] Next, a method for producing the synthetic leather according to the present embodiment will be described. The production method is not particularly limited, and the same production method as that used for conventionally known synthetic leathers can be used. The production method according to one embodiment includes the following steps: (1) A step of applying a polyether-based polyurethane resin to a knitted fabric to prepare a fibrous base material; (2) applying a resin composition liquid for forming a surface layer onto a releasable substrate to form a surface layer; (3) bonding the surface layer and the fibrous substrate together; and (4) peeling off the release substrate; It includes:

[0065] In the above-mentioned step (1) of preparing a fibrous substrate, a polyether-based polyurethane resin composition liquid (hereinafter sometimes simply referred to as a resin composition liquid) is applied to a knitted fabric. The polyether-based polyurethane resin composition liquid may contain a solvent such as a highly polar solvent, if necessary. From the viewpoint of environmental load, water is preferably used as the solvent.

[0066] The viscosity of the resin composition liquid is not particularly limited, but is preferably 100 to 500 mPa·s. When the viscosity is equal to or greater than the lower limit, separation of the resin composition liquid can be suppressed. When the viscosity is equal to or less than the upper limit, penetration of the resin is good, and it is easy to impart the polyether-based polyurethane resin to the desired state.

[0067] The method for applying the resin composition liquid to the knitted fabric can be any of various conventionally known methods, and is not particularly limited. Examples include padding, dipping, coating, spraying, and textile printing. Among these, padding is preferred from the viewpoint of easily applying the polyether-based polyurethane resin in the desired state.

[0068] When padding is used as a method for applying the resin composition liquid to the knitted fabric, the pickup rate is not particularly limited, but is preferably 20 to 120 mass %. When the pickup rate is in this range, the polyether polyurethane resin can be applied in the desired state.

[0069] After applying the resin composition liquid to the knitted fabric, a heat treatment is carried out as necessary. The heat treatment is carried out to evaporate the solvent in the resin composition liquid and dry the resin. Furthermore, when a catalyst or crosslinking agent that causes a crosslinking reaction by heat treatment is used, or when a two-component curing resin is used, the heat treatment is carried out to promote the reaction and form a coating with sufficient strength. The heat treatment temperature may be, for example, 130 to 190°C or 150 to 170°C. The heat treatment time may be 1 to 3 minutes or 2 to 3 minutes.

[0070] In the step (2) of forming the surface layer, the surface layer is formed on a releasable substrate.

[0071] The method for applying the resin composition liquid for the surface layer to the releasable substrate can be any of various conventionally known methods, and is not particularly limited. Examples include methods using a reverse roll coater, a spray coater, a knife coater, a comma coater, a roll coater, a die coater, etc. Among these, application using a knife coater or a comma coater is preferred because it allows the formation of a uniform thin film layer.

[0072] The releasable substrate is not particularly limited, and may be a substrate that has releasability to polyurethane resins or a substrate that has been subjected to a release treatment. Examples include release paper, release-treated cloth, water-repellent cloth, olefin sheets or films made of polyethylene resins or polypropylene resins, fluororesin sheets or films, and plastic films with release paper. The releasable substrate may have an uneven pattern. By using such a releasable substrate, an uneven pattern such as a grain pattern can be formed on the surface of the synthetic leather to impart design features.

[0073] The coating thickness of the resin liquid for the surface skin layer may be appropriately set depending on the thickness of the surface skin layer, and is preferably 100 to 250 μm, more preferably 125 to 200 μm. By setting the coating thickness within this range, the surface skin layer will have a thickness of preferably 20 to 50 μm, more preferably 25 to 40 μm.

[0074] After applying the resin composition liquid for the surface layer to the releasable substrate, a heat treatment is carried out as necessary. The heat treatment is carried out to evaporate the solvent in the resin composition liquid for the surface layer and dry the resin. When using a catalyst or crosslinking agent that causes a crosslinking reaction by heat treatment or when using a two-component curing resin, the heat treatment is carried out to promote the reaction and form a coating with sufficient strength. The heat treatment temperature may be, for example, 50 to 120°C or 70 to 90°C. The heat treatment time may be 1 to 3 minutes or 2 to 3 minutes.

[0075] In the step (3) of bonding the surface layer and the fibrous substrate, the surface layer and the fibrous substrate are laminated together. Examples of lamination methods include conventionally known methods such as transfer, heat fusion, thermocompression, and adhesion using an adhesive. When an adhesive is used, a resin composition liquid for the adhesive layer may be applied to the surface layer, and then the fibrous substrate may be laminated. The method for applying the resin composition liquid for the adhesive layer may be the same as the method for applying the resin composition liquid for the surface layer.

[0076] In the step (4) of peeling off the releasable substrate, the releasable substrate is peeled off from the surface layer. By peeling off the releasable substrate, the synthetic leather according to the present embodiment is obtained. However, the method for producing the synthetic leather according to the present embodiment is not limited to the above method.

[0077] In addition, when forming an anchor coat layer, after forming a surface layer on a releasable substrate, the surface layer may be coated with the resin liquid for the anchor coat layer before coating with the resin liquid for the adhesive layer. After that, the resin liquid for the adhesive layer may be coated and then bonded to a fibrous substrate, or the fibrous substrate may be directly bonded to the anchor coat layer without coating with the resin liquid for the adhesive layer.

[0078] When forming a foam layer, after forming a surface layer on a releasable substrate, a foam layer resin liquid may be applied to the surface layer before applying an adhesive layer resin composition liquid. Then, the adhesive layer resin composition liquid may be applied, followed by lamination to a fibrous substrate. Alternatively, after forming a surface layer on a releasable substrate, a foam layer resin liquid may be applied to the surface layer before applying an anchor coat layer resin liquid. Then, an anchor coat layer may be formed by applying an anchor coat layer resin liquid, followed by further application of an adhesive layer resin composition liquid, followed by lamination to a fibrous substrate. Alternatively, the fibrous substrate may be directly laminated to the anchor coat layer without applying an adhesive layer resin composition liquid.

[0079] When the surface treatment layer is formed, the releasable substrate is peeled off from the surface skin layer, and then a resin liquid for the surface treatment layer is applied to the front surface of the surface skin layer to form the surface treatment layer.

[0080] The methods for applying the resin liquid for the anchor coat layer, the resin liquid for the foam layer, and the resin liquid for the surface treatment layer, and the heat treatment after application can be the same as those for forming the surface skin layer.

[0081] The synthetic leather according to this embodiment uses a knitted fabric to which a polyether-based polyurethane resin has been applied as a fibrous substrate, the knitted fabric containing 75% by mass or more of cotton fibers, and the polyether-based polyurethane resin fills the spaces between the fibers constituting the yarns of the knitted fabric, but is present in a state where it is almost not present between the yarns. This results in excellent elongation properties and durability (particularly low-temperature flexibility and heat resistance (low-temperature flexibility after heat resistance and elongation properties after heat resistance)) despite using raw materials composed of plant-derived components.

[0082] The synthetic leather according to this embodiment may be used for any purpose, including interior materials for various vehicles, such as automobile seats, ceiling materials, dashboards, door linings, and steering wheels, as well as interior applications such as coverings for sofas and chairs, and fashion applications such as bags and shoes.

[0083] The various numerical ranges described in this specification can be arbitrarily combined with their upper and lower limits, and all such combinations are considered to be preferred numerical ranges described in this specification. Furthermore, a numerical range described as "X to Y" means from X to Y. [Example]

[0084] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0085] Each evaluation item was performed according to the following method.

[0086] [Elongation properties: Modulus value at 10% elongation] Three dumbbell-shaped (JIS K6251:2023 6.2 Dumbbell No. 1) test pieces were taken from the synthetic leather in the longitudinal direction (well direction). The test pieces were attached to the grips of a tensile tester (Autograph AG-IS model, manufactured by Shimadzu Corporation) at a room temperature of 20±2°C and a humidity of 65±5%RH, with a grip width of 25 mm and a grip spacing of 40 mm, and pulled at a pulling speed of 300 m / min. The stress when the stroke distance reached 4 mm was measured, and the 10% modulus value was calculated using the following formula. The average value of the three points was taken as the modulus value of the synthetic leather at 10% elongation. When the modulus value at 10% elongation was 25 N / mm 2 If the value was less than this, it was determined that the elongation characteristics were excellent. 10% modulus value (N / mm 2 ) = Stress (N) when stroke distance reaches 4 mm / Cross-sectional area of ​​test piece (mm 2 )

[0087] [Low temperature flexibility] Five test pieces measuring 45 mm wide and 70 mm long were taken from the synthetic leather in the longitudinal direction (well direction). The test pieces were bent 30,000 times at a speed of 100 times / min at -30°C in a low-temperature bending test using a flexometer according to JIS K6557-8:2017. After 30,000 bendings, the backside of the test piece was visually observed. Test pieces in which no breaks were observed in the backing fabric were marked with a circle, and those in which breaks were observed were marked with an ×. Of the five tests, a test piece was considered to have passed if it received 3 or more circle marks.

[0088] [Durability: Preparation of test specimens] A sample measuring 300 mm in width and 400 mm in length was taken from the longitudinal direction (well direction). The sample was heat-treated by being left to stand in a dryer adjusted to 120°C for 500 hours to obtain a sample after the heat aging test.

[0089] [Durability: Elongation characteristics after heat aging test] Using the samples after the heat aging test, the modulus value at 10% elongation of the synthetic leather after the heat aging test was determined in the same manner as in [Elongation properties: Modulus value at 10% elongation] above. A synthetic leather that retained 50% or more of the modulus value at 10% elongation of the synthetic leather before the heat aging test was deemed to have passed.

[0090] [Durability: Low temperature flexibility after heat aging test] Using the samples after the heat aging test, the low-temperature flexibility of the synthetic leather after the heat aging test was evaluated in the same manner as in the above [Low-temperature flexibility]. Of the five measurements, a sample was considered to have passed if it received 3 or more ○ marks.

[0091] [Example 1] <Formulation 1: Resin composition liquid for surface layer> Polyurethane resin (polycarbonate-based polyurethane resin): 100 parts by weight (Dainichiseika Color & Chemicals Mfg. Co., Ltd., Lezamin NE-8850, solid content 30% by mass) Pigment (carbon black): 20 parts by weight (Manufactured by DIC Corporation, DILAC BLACK L-8283S, solid content 25% by mass) ·DMF: 50 parts by mass Preparation method: The viscosity was adjusted with DMF to 3,000 mPa·s (BII type viscometer (BHII type), manufactured by Toki Sangyo Co., Ltd., rotor: No. 4, 12 rpm, 23°C).

[0092] <Formulation 2: Resin composition liquid for adhesive layer> (1) Production Example 1: Polyisocyanate Solution Polyol component: Polycarbonate polyol: 20 parts by weight (Ube Industries, Ltd., ETERNACOLL UH-200, solid content 100% by mass) Diisocyanate component: XDI type: 9.02 parts by mass (Mitsui Chemicals, Takenate 500, solid content 100% by mass) Preparation method: The above ingredients were mixed and heated from 25 to 80° C. at a rate of 1° C. / min. The mixture was stirred at 80° C. for 60 minutes to complete the urethane reaction, yielding a polyisocyanate solution. (2) Preparation Example 2: Polyol Solution Main ingredient: Polycarbonate polyol: 30 parts by weight (Ube Industries, Ltd., ETERNACOLL UH-100, solid content 100 parts by mass) Catalyst: Amine catalyst: 2 parts by mass (TEDA-L33, manufactured by Tosoh Corporation, solid content 33% by mass) Flame retardant: Phosphorus-based flame retardant: 20 parts by weight (Pekoflam STC powder, manufactured by Clariant Japan Co., Ltd., solid content 100% by mass) ·DMF: 90 parts by mass Preparation method: The viscosity was adjusted with DMF to 10,000 mPa·s (BII type viscometer (BHII type), rotor: No. 4, 12 rpm, 23°C). (3) 29.02 parts by mass of the polyisocyanate solution of Production Example 1 and 152 parts by mass of the polyol solution of Production Example 2 were weighed, stirred, and mixed to obtain a resin composition liquid for adhesive layer. The viscosity of the resin composition liquid for adhesive layer was 10,000 mPa s (BII type viscometer (BHII type), manufactured by Toki Sangyo Co., Ltd., rotor: No. 4, 12 rpm, 23°C).

[0093] <Formulation 3: Resin composition liquid for surface treatment layer> Polyurethane resin (polycarbonate-based polyurethane resin): 90 parts by weight (Manufactured by DIC Corporation, Hydran WLS-250, solid content 35% by mass) Matting agent: Silica-containing water-based polycarbonate polyurethane resin: 10 parts by weight (Dow Chemical Japan, HYDRHOLAC UD-2, solid content 26.5% by mass) Crosslinking agent: Isocyanate-based crosslinking agent (HDI-based): 1 part by weight (LANXESS AQUADERM XL 50, solid content 50% by mass) Leveling agent: Silicone leveling agent: 1 part by weight (LANXESS AQUADERM Fluid H, solid content 100% by mass) ·Water: 20 parts by mass Preparation method: The above chemicals were mixed and stirred to prepare a resin composition for surface treatment layer. The viscosity of the obtained resin composition for surface treatment layer was 200 mPa s (BII type viscometer (BHII type), manufactured by Toki Sangyo Co., Ltd., rotor: No. 1, 12 rpm, 23°C).

[0094] <Formulation 4-1: Polyether-based polyurethane resin composition liquid> Polyether polyurethane resin: 90 parts by weight (Manufactured by DIC Corporation, Hydran WLS-120AR, water-based one-component type, solid content 50% by mass) Crosslinking agent: Isocyanate-based crosslinking agent (HDI-based): 4 parts by weight (LANXESS AQUADERM XL 50, solid content 50% by mass) ·Water: 300 parts by mass Preparation method: The above chemicals were mixed and stirred to prepare a polyether-based polyurethane resin composition liquid. The viscosity of the obtained polyether-based polyurethane resin composition liquid was 300 mPa·s (BII type viscometer (BHII type), manufactured by Toki Sangyo Co., Ltd., rotor: No. 1, 12 rpm, 23°C).

[0095] <Fiber base material> Using an 18G circular knitting machine, 26 count cotton yarn (compact yarn) was used as the lead yarn for all of the face yarns (Y2, Y5), connecting yarns (Y1, Y4), and back yarns (Y3, Y6), and a circular knit fabric was knitted in the mock lodie knit structure shown in Figure 7. Next, it was dyed with a black disperse dye at 130°C for 30 minutes in a dyeing machine. The resulting circular knit fabric was washed and dried, and then heat-treated in a heat setter to achieve the desired density. As a result, a knitted fabric (weight per unit area: 320 g / m 2 The knitted fabric had a thickness of 1.2 mm, a density of 38 courses / 25.4 mm, and 33 wales / 25.4 mm, and the cotton fiber content in the knitted fabric was 100% by mass. The knitted fabric had a flat front surface and a checkered uneven surface on the back surface.

[0096] The resulting knitted fabric was coated with a polyether-based polyurethane resin composition liquid of formulation 4-1 shown in Table 1 in an amount (wet) of 384 g / m 2 (pickup rate 120%), and padding treatment was performed. Next, the machine width (setter pin width) was adjusted to the desired density, and the fibrous base material was obtained by heat treatment at 130 ° C for 5 minutes in a dryer. The obtained fibrous base material had a basis weight of 370 g / m 2 The knitted fabric had a thickness of 1.2 mm, a density of 38 courses / 25.4 mm, and 33 wales / 25.4 mm, and the amount of polyether polyurethane resin attached to the knitted fabric was 15.6% by mass.

[0097] <Production of synthetic leather> The resin composition liquid for the surface layer prepared according to the above-mentioned Formulation 1 was applied to a release paper (R-51, manufactured by Lintec Corporation) having a leather-like grain pattern in the form of a sheet using a comma coater so that the coating thickness (wet) was 180 μm, and the sheet was then heat-treated in a dryer at 80°C for 2 minutes to form a surface layer. The surface layer had a basis weight (dry coating amount) of 30 g / m. 2 and the thickness was 30 μm.

[0098] Next, the resin composition liquid for adhesive layer prepared according to the above-mentioned Formulation 2 was applied in the form of a sheet to the surface of the skin layer formed on the release paper using a comma coater so that the coating thickness (wet) was 320 μm, and while the resin composition liquid for adhesive layer was still viscous, it was attached to the above-mentioned fibrous substrate (the front side of the knitted fabric) and subjected to a force of 49 N / m using a mangle. 2 The sheet was then pressed under a load of 160 g / m. The release paper was then peeled off to obtain a laminate consisting of a surface layer, an adhesive layer, and a fibrous substrate. The adhesive layer was a foamed layer, and the basis weight (dry adhesion amount) was 160 g / m. 2 and the thickness was 160 μm.

[0099] Next, the resin composition liquid for the surface treatment layer prepared according to the above-mentioned Formulation 3 was applied to the surface of the skin layer after peeling off the release paper using a roll coater in a wet coating amount of 21.5 g / m 2 The mixture was then heat-treated in a dryer at 80°C for 2 minutes to form a surface treatment layer, thereby obtaining the synthetic leather of Example 1. The surface treatment layer had a basis weight (dry coating amount) of 7.5 g / m2 The thickness was 7.5 μm. The weight (dry coating weight) of the entire resin layer was 197.5 g / m 2 and the thickness was 197.5 μm.

[0100] [Example 2] The synthetic leather of Example 2 was obtained in the same manner as in Example 1, except that the surface yarns (Y2, Y5) used in the knitted fabric were changed to 167 dtex / 48 f polyester textured yarns.

[0101] [Example 3, Comparative Example 1] The synthetic leathers of Example 3 and Comparative Example 1 were obtained in the same manner as in Example 1, except that the basis weight and density of the fibrous base material were changed as shown in Tables 2 and 3, and the amount of polyether-based polyurethane resin attached to the knitted fabric was changed as shown in Tables 2 and 3.

[0102] Comparative Example 2 A synthetic leather of Comparative Example 2 was obtained in the same manner as in Example 1, except that the polyether-based polyester resin composition liquid was changed to formulation 4-3 (polycarbonate-based polyurethane resin composition liquid) shown in Table 1.

[0103] [Example 4, Comparative Examples 3 to 5] The polyether-based polyester resin composition liquid was changed to formulation 4-2 and formulations 4-4 to 4-6 shown in Table 1, and the amount of polyether-based polyurethane resin adhered to the knitted fabric was changed to those shown in Tables 2 and 3. The rest of the procedure was the same as in Example 1, and synthetic leathers of Example 4 and Comparative Examples 3 to 5 were obtained.

[0104] Details and evaluation of the obtained synthetic leather are shown in Tables 2 and 3. The "adhesion amount" in "impregnated resin" in Tables 2 and 3 is the amount of polyether polyurethane resin adhered to the knitted fabric. The "resin adhesion amount" in "fibrous substrate" of "synthetic leather" in Tables 2 and 3 is the amount of resin (converted to solid content) imparted to the knitted fabric by the resin composition liquid shown in Table 1. Furthermore, the "density (courses / well)" in "fibrous substrate" of "synthetic leather" is the value for synthetic leather. Furthermore, in "synthetic leather" in Tables 2 and 3, "thickness (mm)", "basis weight (g / m 2) is the value for synthetic leather.

[0105] [Table 1]

[0106] Details of each component in Table 1 are as follows: Polyether polyurethane resin: Water-based one-component polyether polyurethane resin (DIC Corporation, Hydran WLS-120AR, solids content 50% by mass, Tg -50°C or less) Polycarbonate-based polyurethane resin: Water-based one-component polycarbonate-based polyurethane resin (DIC Corporation, Hydran WLS-110AR, solids content 50% by mass, Tg above -50°C) Isocyanate-based crosslinking agent: Isocyanate-based crosslinking agent (HDI type) (AQUADERM XL 50, manufactured by LANXESS KK, solid content 50% by mass)

[0107] [Table 2]

[0108] [Table 3]

[0109] The results are shown in Tables 2 and 3. In the synthetic leather of Comparative Example 1, the weight of the knitted fabric was 150 g / m 2 Because the content of plant-derived components in the synthetic leather was less than 40% by mass, it was a synthetic leather with a low bio content.

[0110] The synthetic leather of Comparative Example 2 was poor in durability (low-temperature flexibility and low-temperature flexibility after heat aging) because it used a knitted fabric in which a polycarbonate-based polyurethane resin was added to the fibrous base material.

[0111] The synthetic leathers of Comparative Examples 3 and 5 had poor durability (low-temperature flexibility and elongation after heat aging) because the amount of polyether-based polyurethane resin attached to the knitted fabric was less than 10% by mass. The synthetic leather of Comparative Example 4 had poor elongation because the amount of polyether-based polyurethane resin attached to the knitted fabric was as high as 37.5% by mass and the polyether-based polyurethane resin was present between the yarns.

[0112] In contrast, the synthetic leathers of Examples 1 to 4 were excellent in elongation properties and durability (low-temperature flexibility after heat aging, elongation properties after heat aging, and low-temperature flexibility). [Explanation of symbols]

[0113] 1, 10...synthetic leather, 2...fibrous base material, 3...surface layer, 4...adhesive layer, 5...surface treatment layer

Claims

1. A synthetic leather comprising a fibrous base material and a surface layer made of a polyurethane resin provided on the fibrous base material, the fibrous base material includes a knitted fabric and a polyether-based polyurethane resin applied to the knitted fabric, The knitted fabric has a basis weight of 150 g / m ２ That's all, The content of cotton fiber in the knitted fabric is 75% by mass or more, the amount of the polyether-based polyurethane resin adhering to the knitted fabric is 10% by mass or more; the polyether-based polyurethane resin fills spaces between fibers constituting the yarns of the knitted fabric, and is hardly present between the yarns; A synthetic leather in which the content of plant-derived components in the synthetic leather is 40% by mass or more.

2. 2. The synthetic leather according to claim 1, wherein the amount of the polyether-based polyurethane resin attached to the knitted fabric is 15 to 30% by mass.

3. 3. The synthetic leather according to claim 1, wherein the knitted fabric is a circular knitted fabric.

4. The synthetic leather according to claim 3, wherein the knitting structure of the circular knitted fabric is mock lody.

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