Artificial leather for ball

Abstract

An artificial leather for a ball, comprising: a base layer containing a fiber entangled body and a polyurethane elastic body; and a polyurethane porous layer having a plurality of protrusions on a surface thereof, wherein at least one or the entirety of the protrusions have a groove.

Description

Artificial leather for balls

[0001] This invention relates to artificial leather for balls.

[0002] Traditionally, numerous artificial leathers have been proposed as surface materials and anti-slip materials for balls where grip is required.

[0003] For example, Patent Document 1 describes a coating composition for imparting slip resistance to a substrate surface, comprising a polyurethane resin having hydroxyl groups in its molecule, a liquid rubber having hydroxyl groups in its molecule, an inorganic or organic filler, and an isocyanate prepolymer. However, when a coating layer formed from the above composition is used in applications where it frequently comes into contact with human hands, it absorbs sweat from the hands, softens, and changes in tactile feel. In particular, when used as a surface material for a basketball, which is used continuously for long periods and comes into contact with a large amount of sweat generated during play, the anti-slip performance deteriorates significantly due to sweat absorption.

[0004] Patent Document 2 describes an anti-slip material obtained by slicing a foamed sheet-like material, which is made by impregnating a needle-punched nonwoven fabric with a rubber-like viscoelastic resin and solidifying it, leaving air bubble marks on the sliced ​​surface. Patent Document 3 describes a synthetic leather in which a porous structure is formed on the surface of the molded product, obtained by mixing gelatin into a synthetic rubber elastic material, heating and foaming it, removing a portion of the surface skin layer of the resulting molded product, and then removing the gelatin with hot water. However, the surface of such synthetic leather has high tackiness and low apparent density, resulting in low abrasion resistance, and was not suitable for use in ball applications. However, the anti-slip material described in Patent Document 2 and the synthetic leather described in Patent Document 3 have low surface strength and are easily abraded, and were not suitable for use in ball applications such as basketballs.

[0005] Patent Document 4 describes a structure comprising a fiber entanglement body, a porous substrate layer consisting of a porous elastic body and a penetrant present in the space of the fiber entanglement body, and a porous surface layer formed on its surface, wherein the surface of the porous surface layer has 300 to 10,000 open pores (microholes) with an average diameter of 5 to 100 μm per cm. ２ A leather-like sheet is described in which a penetrating agent exists inside the aforementioned open pores. However, because such a leather-like sheet has many large open pores across its entire surface, the apparent density of the surface is low, making it prone to wear. Therefore, when such a leather-like sheet is used for balls, there is a problem that the uneven surface shape collapses after prolonged use. In addition, the recessed areas are prone to getting dirty, and once the recessed areas become dirty, the dirt is difficult to remove. Furthermore, the penetrating agent present in the open pores dissolves due to sweat during play, causing the ball surface to become slippery.

[0006] Patent Document 5 describes a sweat-absorbing game ball in which a wet-coated polyurethane coating layer is laminated onto the surface of a polyurethane-containing fiber material, and the surface of the coating layer has multiple protrusions and valleys between the protrusions, with the sides of the protrusions having multiple open holes. However, such a ball had the problem that the sides of the protrusions were prone to getting dirty after prolonged use, and once dirty, the dirt was difficult to remove. Furthermore, when dirty, the sweat-absorbing effect decreased, and the tactile feel, which was similar to that of natural leather, also deteriorated.

[0007] Patent Document 6 describes a leather-like sheet for balls, comprising a fiber entanglement body and a porous surface layer having an uneven shape laminated on its surface. The porous surface layer has microholes (open pores) with an average diameter of 5 to 100 μm on the surface of the protrusions, while the concave surfaces are substantially free of open pores. It is described that these open pores are formed by buffing the surface of the protrusions with sandpaper or a pin cloth, or by dissolving the surface with a solvent. However, the open pores formed by this method are large in diameter, resulting in a low apparent surface density, which makes them prone to wear during ball games. Furthermore, this wear can cause the open pores to enlarge or disappear, leading to reduced sweat absorption and decreased ball grip.

[0008] Patent Document 7 describes a ball surface material in which a coating layer made of a porous polymer elastic material having an uneven surface is formed on the surface of a base layer, wherein the side surface of the protrusions has 1000 open holes of about 0.5 to 50 μm per cm. ２ The above-mentioned ball surface materials are disclosed. It is described that such open holes are formed by first surface-treating the porous polymer elastic material of the surface layer with an organic solvent to create holes before embossing, then embossing with a mold having a surface unevenness of 0.1 mm or more, and then applying a coating layer made of polymer elastic material to the top surface of the protrusions. However, balls with an uneven surface having multiple large holes only on the sides of such protrusions have the problem that the sides are easily soiled, and the soiled areas are difficult to remove. Furthermore, when soiled, the grip performance decreases.

[0009] As a method to solve these problems, Patent Document 8 describes a leather-like sheet containing a substrate containing a fiber entanglement and a porous elastic resin layer laminated on the surface of the substrate, wherein the leather-like sheet has an uneven surface on the side where the porous elastic resin layer is formed, and the uneven surface has convex portions having a top surface and side surfaces and concave portions having valley bottom surfaces connected to the side surfaces, and the top surface of the convex portions has 1000 open holes / mm with a diameter of 10 to 500 nm ２A leather-like sheet characterized by having the above features is described. Furthermore, Patent Document 9 describes a coating layer formed on the surface of a fibrous base material having substantially continuous protrusions and adjacent hemispherical recesses, wherein the height difference between the protrusions and recesses is 50 to 1000 μm, and the vertical projected area of ​​the adjacent recesses is 3 to 30 mm. ２ The invention also describes a ball made of a sheet having an average spacing of 0.5 to 3 mm between recesses, and further having secondary irregularities formed on its surface that are less deep than the depth of the recesses and 10 to 100 μm in thickness.

[0010] Japanese Patent Publication No. 1-129073, Japanese Utility Model Publication No. 63-197475, Japanese Patent Publication No. 63-152483, Japanese Patent Publication No. 2000-328465, U.S. Patent No. 6024661 Specification, Japanese Patent Publication No. 2004-300656, Japanese Patent Publication No. 2004-277961, International Publication No. 2008 / 001716, Japanese Patent Publication No. 2009-5899

[0011] While the leather-like sheet described in Patent Document 8 and the ball described in Reference Document 9 offer some degree of grip, their grip when the surface is wet is not sufficient, and further improvements are needed. The present invention has been made in view of this situation, and aims to provide an artificial leather for balls that offers excellent grip when the surface is wet.

[0012] As a result of various studies, the inventors of the present invention have found that the above problem can be solved by having at least some of the multiple protrusions of the porous polyurethane layer have grooves, and have arrived at the present invention. That is, the present invention encompasses the following inventions.

[0013] [1] Artificial leather for a ball comprising a base layer containing a fiber entanglement body and a polyurethane elastic body, and a polyurethane porous layer having a plurality of protrusions on its surface, wherein at least a portion of the plurality of protrusions has grooves. [2] The artificial leather for a ball according to [1], wherein the grooves include grooves (a) extending in a first direction in a plan view of the polyurethane porous layer and grooves (b) at an angle to groove (a). [3] The artificial leather for a ball according to [2], wherein the angle between groove (a) and groove (b) is 60 to 90°. [4] The artificial leather for a ball according to [2] or [3], wherein the protrusions have protrusions (A) and protrusions (B), where protrusion (A) has groove (a) and protrusion (B) has groove (b). [5] The artificial leather for a ball according to [4], wherein the protrusions (A) and protrusions (B) are arranged alternately. [6] The artificial leather for balls according to [4] or [5] above, wherein the height of the protrusion (A) is 100 to 400 μm, and the height of the protrusion (B) is 10 to 50 μm lower than the height of the protrusion (A). [7] The artificial leather for balls according to any one of [2] to [6] above, wherein the depth of the groove (a) is 1 to 20 μm, and the depth of the groove (b) is 20 to 60 μm. [8] The artificial leather for balls according to any one of [2] to [7] above, wherein the width of the groove (a) is 10 to 200 μm, and the width of the groove (b) is 10 to 200 μm. [9] The area of ​​the protrusion (A) in plan view is 2 to 4 mm ２ The area of ​​the convex portion (B) in plan view is 1 to 2 mm ２Artificial leather for balls as described in any of [4] to [8] above.

[10] Artificial leather for balls as described in any of [4] to [9] above, wherein each of the protrusions (A) has 3 to 6 of the grooves (a), and each of the protrusions (B) has 3 to 6 of the grooves (b).

[11] Artificial leather for balls as described in any of [4] to

[10] above, wherein the shape of the protrusions (A) and the protrusions (B) in plan view is at least one selected from a square, a rectangle, a rounded square, and a rounded rectangle.

[12] Artificial leather for balls as described in any of [4] to

[11] above, wherein the shape of the cross-section of the protrusions (A) and the protrusions (B) is at least one selected from a square, a rectangle, a trapezoid, and a semicircle.

[13] The artificial leather for balls according to any one of [4] to

[12] above, wherein the top surface of the protrusion (A) has open holes with a diameter of 10 to 500 nm.

[14] The number of open holes is 1000 per mm ２ The artificial leather for balls described in

[13] above, having the above characteristics.

[15] The artificial leather for balls described in any of [1] to

[14] above, having a maximum static friction coefficient and dynamic friction coefficient with silicone resin of 0.50 or more.

[16] The artificial leather for balls described in any of [1] to

[15] above, satisfying the following formula (1): (Friction coefficient when wet / Friction coefficient when dry) × 100 ≥ 80 (%) (1)

[0014] According to the present invention, it is possible to provide an artificial leather for balls that has excellent grip when the surface is wet.

[0015] The first image shows the surface of the artificial leather for the ball obtained in Example 1, taken at 30x magnification using a "Digital Microscope VHX-8000" (manufactured by Keyence Corporation). The second image shows the surface of the artificial leather for the ball obtained in Comparative Example 1, taken at 50x magnification using a "Digital Microscope VHX-8000" (manufactured by Keyence Corporation).

[0016] The following describes the artificial leather for balls according to an embodiment of the present invention (hereinafter sometimes referred to as "artificial leather for balls of this embodiment").

[0017] [Artificial Leather for Balls] The artificial leather for balls of this embodiment comprises a base layer containing a fiber entanglement compound and a polyurethane elastic body, and a polyurethane porous layer having a plurality of protrusions on its surface, wherein at least a portion of the plurality of protrusions have grooves. In the artificial leather for balls of this embodiment, because the protrusions have grooves, when a large amount of moisture such as sweat adheres to the artificial leather for balls, the moisture flows along the grooves. As a result, the amount of moisture on the surface of the artificial leather for balls that comes into contact with the hand is reduced, so the surface of the artificial leather for balls has excellent grip even when wet. In the artificial leather for balls of this embodiment, the back surface of the polyurethane porous layer (the surface opposite to the surface with the plurality of protrusions) is located on the base layer side, and therefore the plurality of protrusions are exposed. The polyurethane porous layer and the base layer may be joined via an adhesive or the like, or they may be directly joined, but it is preferable that the polyurethane porous layer and the base layer are directly joined.

[0018] <Base Layer> The base layer of this embodiment includes a fiber entanglement and a polyurethane elastic body. The thickness of the base layer is preferably 0.4 to 3.0 mm, more preferably 0.8 to 2.0 mm, and even more preferably 1.3 to 1.8 mm, from the viewpoint of obtaining a ball with an excellent balance of mechanical properties, weight, texture, etc.

[0019] [Fiber Entanglement] The fiber entanglement of this embodiment is a fiber entanglement that includes a nonwoven fabric formed from fibers. "Fiber entanglement including a nonwoven fabric" refers to a form in which the fiber entanglement consists of a nonwoven fabric, a form in which a nonwoven fabric and a woven or knitted fabric are intertwined and integrated, and a form in which a nonwoven fabric and a base material other than a woven or knitted fabric are intertwined and integrated. Conventional known natural fibers, synthetic fibers, semi-synthetic fibers, etc., can be used as the fibers that form the fiber entanglement. Specifically, examples include cellulose fibers, acrylic fibers, polyester fibers, polyamide fibers, etc. Among these, polyamide fibers are preferred from the viewpoint of obtaining an artificial leather for balls that has superior grip when the surface is wet (hereinafter also simply referred to as "superior grip when wet"). These may be used individually or in combination of two or more types.

[0020] The fibers forming the fiber complex are preferably ultra-fine fibers that can achieve a softer texture closer to natural leather. From the viewpoint of easily obtaining a softer texture closer to natural leather, the average fineness of the fibers is preferably 0.3 dtex or less, more preferably 0.0001 to 0.1 dtex.

[0021] The basis weight of the fiber complex is preferably 200 to 1000 g / m ２ and more preferably 300 to 800 g / m. ２ When the basis weight is within the above range, the elasticity of the fiber complex becomes better, and it becomes easier to form desired convex portions on the surface of the polyurethane porous layer.

[0022] [Polyurethane elastomer] By including a polyurethane elastomer in the base layer, the ball made of the artificial leather for balls of the present embodiment has good touch and resilience. Also, when used in the production of sewn-type balls, the sewing property is also good. Any polyurethane elastomer that has been conventionally used for artificial leather for balls can be adopted, and specific examples include polyurethane elastomers. As the polyurethane elastomer, at least one polymer polyol having an average molecular weight of 500 to 3000 selected from polyester diol, polyether diol, polyether ester diol, polycarbonate diol, polycarbonate ether diol, polycarbonate ester diol, etc., and 4,4'-diphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, etc., at least one polyisocyanate selected from aromatic, alicyclic, aliphatic diisocyanates, etc. are combined as the main components, and further at least one low molecular compound having two or more active hydrogen atoms such as ethylene glycol, ethylenediamine, etc. are combined in a predetermined molar ratio, and these are polymerized by a melt polymerization method, a bulk polymerization method, a solution polymerization method, etc. in one step or multiple steps. The content of the polymer polyol component in the polyurethane elastomer is preferably 15 to 90% by mass.

[0023] The artificial leather for balls obtained by adopting a polyurethane elastomer as the polyurethane elastic body has excellent balance in texture and mechanical properties. Furthermore, if the type is appropriately selected, it will also have excellent balance including durability. The base layer may contain a mixture of different types of polyurethane elastic bodies.

[0024] From the viewpoint of obtaining an artificial leather base material with excellent texture, the content of the polyurethane elastic body in the base layer is preferably 5 to 45% by mass, more preferably 7 to 40% by mass, and even more preferably 8 to 30% by mass.

[0025] The base layer may or may not contain components other than the fiber complex and the polyurethane elastic body. Examples of such other components include various additives that can be added to the polyurethane elastic body liquid used when impregnating the polyurethane elastic body. The content of the above other components is preferably 0.5 to 10.0% by mass, more preferably 1.0 to 5.0% by mass, and even more preferably 1.5 to 3.0% by mass.

[0026] <Polyurethane porous layer> The polyurethane porous layer of this embodiment has a plurality of convex portions on the surface, and at least a part of the plurality of convex portions has grooves. The polyurethane porous layer contains a polyurethane elastic body. The polyurethane porous layer may contain a polymer elastic body other than the polyurethane elastic body. Examples of the polymer elastic body other than the polyurethane elastic body include synthetic rubber, polyester elastomer, polyvinyl chloride resin, etc. A specific example of the polyurethane elastic body is a polyurethane elastomer, and a preferred embodiment is the same as the above [Polyurethane elastic body]. From the viewpoint of the balance between wear resistance and grip, the 100% elongation stress of the polyurethane elastomer is preferably a low modulus of 20 to 100 kgf / cm ２ If the 100% elongation stress is 20 kgf / cm ２ or more, the wear resistance will be better, and if the 100% elongation stress is 100 kgf / cm ２ or less, the grip will be better. The 100% elongation stress of the polyurethane elastomer is more preferably 30 to 90 kgf / cm ２, more preferably 40 to 80 kgf / cm ２ It is.

[0027] The polyurethane porous layer may contain additives such as a coloring agent, a light-resistant agent, and a dispersant. Further, as other additives, in order to control the shape of the pores, a foaming agent in the case of dry foaming, a coagulation regulator in the case of wet coagulation, etc. may be included.

[0028] The thickness of the polyurethane porous layer can be arbitrarily selected according to the required physical properties, the texture preferred by the players using the ball, etc., and is not particularly limited, but is preferably 50 to 600 μm, more preferably 100 to 500 μm, and even more preferably 200 to 400 μm. If the thickness of the polyurethane porous layer is 50 μm or more, the grip property when wet becomes better, and a softer texture closer to natural leather is obtained. Further, if the thickness of the polyurethane porous layer is 600 μm or less, even if it wears, the convex portions are less likely to peel off.

[0029] [Convex portion] At least a part of the convex portion of this embodiment has a groove. The groove of the convex portion preferably includes a groove (a) extending in a first direction in a plan view of the polyurethane porous layer and a groove (b) forming an angle with the groove (a) from the viewpoint of obtaining a synthetic leather for balls with excellent grip property when wet. Here, the first direction is the direction in which the groove (a) extends.

[0030] (Groove (a) and groove (b)) The groove of the synthetic leather for balls of this embodiment includes a groove (a) extending in a first direction in a plan view of the polyene porous layer and a groove (b) forming an angle with the groove (a), and it is more preferable that the angle formed by the groove (a) and the groove (b) is 60 to 90°. Here, when the groove (a) and the groove (b) are not orthogonal, they form an acute angle and an obtuse angle, and in this specification, the angle formed by the groove (a) and the groove (b) refers to the acute angle. With such a configuration, no matter what direction it is, by catching a finger in the groove, a strong gripping feeling is easily obtained.

[0031] The depth of groove (a) is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more, from the viewpoint of obtaining an artificial leather for balls with superior grip when wet, and preferably 20 μm or less, more preferably 17 μm or less, and even more preferably 15 μm or less, from the viewpoint of abrasion resistance. That is, the depth of groove (a) is preferably 1 to 20 μm, more preferably 3 to 17 μm, and even more preferably 5 to 15 μm.

[0032] The depth of groove (b) is preferably 20 μm or more, more preferably 25 μm or more, and even more preferably 30 μm or more, from the viewpoint of obtaining an artificial leather for balls with superior grip when wet, and preferably 60 μm or less, more preferably 55 μm or less, and even more preferably 50 μm or less, from the viewpoint of abrasion resistance. That is, the depth of groove (b) is preferably 20 to 60 μm, more preferably 25 to 55 μm, and even more preferably 30 to 50 μm.

[0033] In one embodiment of the present invention, it is preferable that the depth of groove (a) is 1 to 20 μm and the depth of groove (b) is 20 to 60 μm. When the depths of groove (a) and groove (b) are different in this way, moisture such as sweat accumulates in the deeper groove (groove (b)), resulting in superior grip even when wet.

[0034] The width of groove (a) is preferably 10 μm or more, more preferably 20 μm or more, and even more preferably 30 μm or more, from the viewpoint of obtaining an artificial leather for balls with superior grip when wet, and preferably 200 μm or less, more preferably 150 μm or less, and even more preferably 100 μm or less, from the viewpoint of obtaining an artificial leather for balls with superior grip when dry. That is, the width of groove (a) is preferably 10 to 200 μm, more preferably 20 to 150 μm, and even more preferably 30 to 100 μm.

[0035] The width of groove (b) is preferably 10 μm or more, more preferably 20 μm or more, and even more preferably 30 μm or more, from the viewpoint of obtaining an artificial leather for balls with superior grip when wet, and preferably 200 μm or less, more preferably 150 μm or less, and even more preferably 100 μm or less, from the viewpoint of obtaining an artificial leather for balls with superior grip when dry. That is, the width of groove (b) is preferably 10 to 200 μm, more preferably 20 to 150 μm, and even more preferably 30 to 100 μm.

[0036] In one embodiment of the present invention, it is preferable that the width of groove (a) is 10 to 200 μm and the width of groove (b) is 10 to 200 μm. When the widths of groove (a) and groove (b) are within the above range, sweat can easily enter the grooves and the protrusions can easily be gripped by the fingers.

[0037] (Protrusions (A) and (B)) In this embodiment, the artificial leather for the ball preferably has protrusions, namely protrusions (A) and protrusions (B), namely protrusions (A) having grooves (a) and protrusions (B) having grooves (b). Such a configuration of the artificial leather for the ball results in superior grip when wet. Furthermore, from the viewpoint of obtaining an artificial leather for the ball with superior grip when wet, it is preferable that the protrusions (A) and (B) are arranged alternately.

[0038] From the viewpoint of obtaining an artificial leather for balls that has superior grip when wet, the height of the protrusion (A) is preferably 100 μm or more, more preferably 150 μm or more, and even more preferably 180 μm or more. From the viewpoint of widening the contact area with the fingers when holding the ball, it is preferably 400 μm or less, more preferably 300 μm or less, and even more preferably 250 μm or less. That is, the height of the protrusion (A) is preferably 100 to 400 μm, more preferably 150 to 300 μm, and even more preferably 180 to 250 μm.

[0039] The height of the protrusion (B) is preferably 10 to 50 μm lower than the height of the protrusion (A), more preferably 11 to 40 μm lower, and even more preferably 12 to 30 μm lower. If the height of the protrusion (B) is 10 μm or more lower than the height of the protrusion (A), moisture such as sweat and water can easily penetrate the lower part (protrusion (B)). In this case, the coefficient of friction between the hand and the artificial leather for the ball decreases, but the grip of the fingers becomes easier to feel. For these reasons, the grip performance in wet conditions is improved. If the height of the protrusion (B) is 50 μm or less lower than the height of the protrusion (A), the contact area between the hand and the artificial leather for the ball becomes appropriate, the grip of the fingers is felt appropriately, and the impact received by the hand can be reduced. In one embodiment of the present invention, it is preferable that the artificial leather for the ball of this embodiment has a height of 100 to 400 μm for the protrusion (A) and a height of 10 to 50 μm lower for the protrusion (B) than for the protrusion (A).

[0040] From the viewpoint of obtaining a ball-use artificial leather with superior grip when wet, the area of ​​the convex portion (A) in plan view is preferably 2 to 4 mm. ２ , more preferably 2.2 to 3.9 mm ２ More preferably 2.4 to 3.8 mm ２ Therefore, from the viewpoint of obtaining an artificial leather for balls that has superior grip when wet, the area of ​​the convex portion (B) in plan view is preferably 1 to 2 mm. ２ , more preferably 1.2 to 1.9 mm ２ More preferably 1.3 to 1.8 mm ２ In one aspect of the present invention, the artificial leather for the ball of this embodiment has a planar area of ​​the convex portion (A) of 2 to 4 mm. ２ Therefore, the area of ​​the convex portion (B) in plan view is 1 to 2 mm ２ It is preferable that this is the case. If the area of ​​the convex part (A) in a plan view and the area of ​​the convex part (B) in a plan view are within the above range, it will look like a typical basketball even if the height difference between the convex part (A) and the convex part (B) is small.

[0041] The shape of the convex portion (A) and the convex portion (B) in plan view is not particularly limited, but from the viewpoint of obtaining an artificial leather for balls that has superior grip when wet, it is preferably a square, rectangle, rounded square, or rounded rectangle, and more preferably a square or rectangle.

[0042] The cross-sectional shapes of the protrusions (A) and (B) are not particularly limited, but from the viewpoint of obtaining artificial leather for balls that has superior grip when wet, they are preferably square, rectangular, trapezoidal, semicircular, or sector-shaped, and more preferably sector-shaped.

[0043] When a protrusion (A) has a groove (a) and a protrusion (B) has a groove (b), the number of grooves (a) per protrusion (A) and the number of grooves (b) per protrusion (B) may be one, but it is preferable that there be multiple grooves, and more preferably three to six grooves, for each. In other words, it is preferable that the artificial leather for the ball has multiple grooves (a) per protrusion (A) and multiple grooves (b) per protrusion (B), and more preferably that there are three to six grooves (a) per protrusion (A) and three to six grooves (b) per protrusion (B). The number of grooves (a) per protrusion (A) and the number of grooves (b) per protrusion (B) may be the same or different. If the number of grooves (a) and grooves (b) are both two or more, when moisture such as sweat adheres to the ball's artificial leather, the moisture flows more easily along the grooves, reducing the amount of moisture on the surface of the ball's artificial leather that comes into contact with the hand. As a result, the ball's artificial leather becomes more grippy. Also, if the number of grooves (a) and grooves (b) are both six or less, the grip of the fingers becomes easier to feel.

[0044] When a protrusion (A) has a groove (a) and a protrusion (B) has a groove (b), it is preferable that the height of protrusion (A) is 150 to 400 μm, the height of protrusion (B) is 10 to 50 μm lower than that of protrusion (A), the depth of groove (a) is 1 to 20 μm, and the depth of groove (b) is 20 to 60 μm. In this way, the taller protrusion (A) has a shallower groove to increase the contact area with the finger, and the shorter protrusion (B) has a deeper groove. This allows moisture such as sweat to concentrate on the shorter protrusion (B), and further, this moisture flows along groove (b), resulting in improved grip when wet.

[0045] From the viewpoint of obtaining a ball-specific artificial leather with superior grip when wet, it is preferable that the top surface of the convex portion (A) has open pores with a diameter of 10 to 500 nm. In this specification, the top surface of the convex portion (A) is the plane that includes the vicinity of the top of the convex portion (A) on the surface of the polyurethane porous layer. Since the top surface of the convex portion (A) is not necessarily a horizontal surface, it may not be possible to strictly define the top surface of the convex portion (A). In such cases, the top surface of the convex portion (A) can be said to be the surface that comes into contact with the palm when the palm of the hand is placed on the surface of the ball-specific artificial leather. Furthermore, in the case of a ball using ball-specific artificial leather, it is the surface that comes into contact with the palms of both hands when the ball is supported by the palms of both hands.

[0046] From the perspective of obtaining a ball-specific synthetic leather with superior grip when wet, the ball-specific synthetic leather has 1,000 open pores with a diameter of 10 to 500 nm on the top surface of the convex portion (A) at a rate of 1,000 pores / mm². ２ It is preferable to have the above. 1000 open holes / mm ２ With the above characteristics, sweat generated from the palm can be absorbed through the microscopic pores, improving grip when wet and making it easier to obtain a feel similar to natural leather. Furthermore, if the pores are at the nano-level, the abrasion resistance of the surface will not decrease. Balls using the above-described artificial leather for balls as the surface material can maintain superior grip even when used continuously for long periods and in contact with large amounts of sweat generated during play, as sweat is less likely to remain on the surface due to its excellent sweat absorption properties.

[0047] From the viewpoint of obtaining a ball-use artificial leather with superior grip when wet, the number of open holes is preferably 1000 / mm ２ The above is a more efficient 1500 pieces / mm ２ The above is true, and there is no particular upper limit, but from the viewpoint of wear resistance, it is preferably 5000 pieces / mm ２ More preferably 10,000 pieces / mm ２ The following applies: The number of open holes is preferably 1,000 to 5,000 per mm. ２ More precisely, 1500 to 10000 pieces / mm ２ That is the case.

[0048] The diameter of the open holes is preferably 10 to 500 nm, more preferably 30 to 300 nm, and even more preferably 50 to 200 nm. When the diameter of the open holes is within the above range, sufficient abrasion resistance can be ensured, grip performance in wet conditions is improved, and a touch and slipperiness similar to natural leather that adheres to the fingertips can be maintained. It is preferable that only open holes with a diameter of 10 to 500 nm exist on the top surface of the convex portion (A), but open holes of sizes outside this range may also exist as long as they do not impair the effects of the present invention.

[0049] Open pores can be formed by selecting the polyurethane resin and coagulation regulator, adjusting the composition and temperature of the coagulation bath when forming the porous polyurethane layer, and their shape, size, and number can also be adjusted.

[0050] It is preferable that a crack exists at the boundary between the convex portion (A) and the convex portion (B). When a crack exists at the boundary between the convex portion (A) and the convex portion (B) and fibers are exposed through the crack, moisture adhering to the surface of the artificial leather for the ball is more easily absorbed by capillary action, resulting in superior grip when wet.

[0051] The artificial leather for the ball in this embodiment may have a surface treatment, such as coloring, applied to the surface of the polyurethane porous layer. If the artificial leather for the ball has protrusions (A) and open holes on the top surface of the protrusions (A), it is preferable that the surface treatment does not hinder the absorption of moisture, etc., by the open holes. The surface treatment method is preferably a method of coloring by dispersing pigment in the polyurethane porous layer.

[0052] The artificial leather for the ball in this embodiment may or may not have a layer on the surface of the protrusions consisting of an auxiliary agent such as a grip-enhancing agent like rosin resin or liquid rubber, a softener, a penetrating agent, or a water-repellent agent. However, if the top surface of the protrusion (A) has an open hole, it is preferable that the artificial leather for the ball does not have a layer consisting of the aforementioned auxiliary agent.

[0053] The artificial leather for balls of this embodiment is suitable as a surface material for balls such as basketballs, American footballs, rugby balls, and handballs.

[0054] <Physical Properties of Artificial Leather for Balls> Since the artificial leather for balls of this embodiment is used for balls, it is preferable that it has excellent abrasion resistance. From the viewpoint of abrasion resistance, the artificial leather for balls preferably has a maximum static friction coefficient and dynamic friction coefficient with the silicone resin when dry of 0.50 or higher, more preferably 0.52 or higher, and even more preferably 0.54 or higher. In this specification, "maximum static friction coefficient and dynamic friction coefficient with the silicone resin when dry" refers to the value measured when no moisture visible to the eye is attached to the surface of the artificial leather for balls, at a temperature of 20°C and a relative humidity of 50%.

[0055] Furthermore, the artificial leather for the ball in this embodiment preferably satisfies the following formula (1) from the viewpoint of abrasion resistance: (coefficient of friction when wet / coefficient of friction when dry) × 100 ≥ 80 (%) (1) In this specification, "when wet" of the artificial leather for the ball in (1) above refers to the state in which water is sprayed three times from a height of 10 cm at a 45° angle onto the surface of the artificial leather for the ball using a spray bottle that dispenses 1 ml of water per push.

[0056] [Method for Manufacturing Artificial Leather for Balls] In order to obtain an artificial leather for balls with superior grip when wet, the artificial leather for balls according to this embodiment is preferably manufactured by a manufacturing method comprising the following steps (1) to (3). Step (1): Step to obtain a base layer. Step (2): Step to form a polyurethane porous layer on the surface of the base layer. Step (3): Step to provide protrusions on the surface of the polyurethane porous layer.

[0057] <Step (1)> Step (1) is the step of obtaining a base layer. The fibers that form the fibrous entanglement contained in the base layer are preferably ultrafine fibers that can achieve a flexible texture closer to that of natural leather.

[0058] Ultrafine fibers can be obtained by performing an ultrafine fiber-generating treatment on ultrafine fiber-generating fibers such as sea-island type fibers (continuous two-layer type fibers), multilayer laminated type fibers, and petal-shaped laminated type fibers. Among these, from the viewpoint of ease of manufacture, the method of obtaining ultrafine fibers by performing an ultrafine fiber-generating treatment on sea-island type fibers is preferred.

[0059] Sea-island fibers can be obtained by compounding or mixing two or more incompatible thermoplastic resins and spinning them. The island component resin, which is included in sea-island fibers and later becomes an ultrafine fiber, can be used without particular limitation as long as it is melt-spinnable, has a melt viscosity higher than that of the sea component resin under melt-spinning conditions, has high surface tension, and can fully exhibit fiber properties such as polymer strength. Suitable island component resins include, for example, polyamide polymers such as nylon-6, nylon-66, nylon-610, nylon-612, and copolymers mainly composed of these; polyester polymers such as polyethylene terephthalate, polypropylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, and copolymers mainly composed of these.

[0060] The marine component resins contained in sea-island type fibers that are removed by extraction or decomposition are not particularly limited and can be used as long as they are melt-spinned, have a lower melt viscosity than the island component polymer under melt-spinning conditions, have higher solubility in a predetermined solvent or decomposition properties in a predetermined decomposition agent than the island component resin, and have low compatibility with the island component resin. Examples of marine component resins include olefin resins such as polyethylene, polypropylene, ethylene propylene copolymer, and ethylene vinyl acetate copolymer, as well as resins that are soluble in organic solvents and can be dissolved and removed by organic solvents, such as polystyrene, styrene acrylic copolymer, and styrene ethylene copolymer. In addition, resins that can be removed using only water without the use of solvents, such as polyvinyl alcohol resins, water-soluble polyester resins, easily alkali-degradable modified polyester resins, polyacrylamide resins, and carboxymethylcellulose resins, are also used.

[0061] The volume ratio of sea components to island components in sea-island type fibers is not particularly limited, but from the viewpoint of easily obtaining ultrafine fibers, it is preferable that sea component:island component = 30:70 to 70:30 (volume %). When the sea component is 30 volume percent or more, it becomes easier to obtain artificial leather for balls with sufficient flexibility without excessive use of fiber treatment agents such as softeners. By avoiding excessive use of fiber treatment agents, it is possible to suppress a decrease in mechanical properties such as tear strength, a decrease in touchability, and a decrease in durability of the artificial leather for balls. When the sea component is 70 volume percent or less, it becomes easier to obtain sufficiently ultrafine fibers with excellent mechanical properties. In addition, it is possible to suppress non-uniformity of the physical properties of the artificial leather for balls due to insufficient removal of sea components. Furthermore, when the volume ratio of sea components to island components in sea-island type fibers is within the above range, the spinning stability of the sea-island type fibers is less likely to decrease, and it is easier to ensure good industrial productivity.

[0062] As a method for spinning sea-island type fibers, conventionally known melt spinning methods for forming sea-island type fibers can be used without particular limitation. A specific example is a melt spinning method in which multiple molten resins with different components are simultaneously extruded from different spindles, the extruded materials from the multiple spindles are compounded in a molten state, and undrawn fibers are obtained by cooling while being drawn. The melt-spun undrawn fibers may be subjected to post-processing such as oiling, drawing, and crimping.

[0063] Next, the marine polymer component of the obtained sea-island type fiber can be subjected to an ultrafine fiber treatment by dissolving and removing it in a solvent or by decomposing and removing it in a decomposition solution, thereby obtaining ultrafine fibers made of island component resin.

[0064] The ultrafine fiber treatment can be performed in the following cases (1) to (4): (1) after manufacturing sea-island type fibers; (2) after manufacturing a web of sea-island type fibers; (3) after manufacturing a web of sea-island type fibers, and then intertwining the web three-dimensionally to manufacture a three-dimensional entangled nonwoven fabric; (4) after manufacturing a web of sea-island type fibers, and then intertwining the web three-dimensionally to manufacture a three-dimensional entangled nonwoven fabric, and then impregnating the three-dimensional entangled nonwoven fabric with a polyurethane elastic material to obtain a three-dimensional entangled nonwoven fabric containing a polyurethane elastic material. Among these, it is preferable to perform the treatment in case (4) from the viewpoint that a flexible and soft-textured artificial leather can be produced by creating a space between the ultrafine fibers and the polyurethane elastic material. The following describes a method for manufacturing artificial leather for balls by "(4) manufacturing a web of sea-island type fibers, then intertwining the web three-dimensionally to produce a three-dimensional entangled nonwoven fabric, impregnating the three-dimensional entangled nonwoven fabric with a polyurethane elastic material to obtain a three-dimensional entangled nonwoven fabric containing a polyurethane elastic material," followed by an ultrafine fiber treatment.

[0065] After manufacturing sea-island fibers, a web is produced. The sea-island fibers used in the production of the web may be short fibers or long fibers, and the choice depends on the method of web formation. The method of producing the web is not particularly limited, and conventional methods known for producing nonwoven fabrics, such as the carding method, papermaking method, and spunbond method, can be used without any particular limitations.

[0066] Next, the obtained webs are laminated in multiple layers to a predetermined weight, and a three-dimensional entangled nonwoven fabric is manufactured by three-dimensionally entangling them using a needle punching method, spunlace method, or the like. From the viewpoint of achieving a weight and density suitable for use as artificial leather for balls, the three-dimensional entangled nonwoven fabric is preferably manufactured by the following method: Spinned sea-island type fibers are stretched to 1.5 to 5 times their original length, and then mechanically crimped. Subsequently, they are cut into short fibers of about 3 to 7 cm. The obtained short fibers are defibrated with a card, and then passed through a webber to manufacture a web. The obtained webs are laminated to a desired weight, and then punched at 300 to 4000 punches / cm using a needle having one or more barbs. ２ By using needle punching, a three-dimensional entangled nonwoven fabric is obtained in which the fibers are intertwined in the thickness direction.

[0067] After manufacturing a three-dimensional entangled nonwoven fabric, a polyurethane elastomer is impregnated into the three-dimensional entangled nonwoven fabric to obtain a three-dimensional entangled nonwoven fabric containing the polyurethane elastomer. The timing of impregnation with the polyurethane elastomer may be after the ultrafine fiberization treatment. Methods for obtaining a three-dimensional entangled nonwoven fabric containing the polyurethane elastomer include a wet method using a polyurethane elastomer solution to solidify the polyurethane elastomer in a solidification bath, and a dry method using a polyurethane elastomer aqueous dispersion with a foaming agent dispersed in it to dry and solidify the polyurethane elastomer. Among these, the method of solidifying the polyurethane elastomer in a solidification bath using a wet method with a polyurethane elastomer solution is preferred. The polyurethane elastomer solution is an organic solvent solution of the polyurethane elastomer, and the polyurethane aqueous dispersion is an aqueous dispersion of the polyurethane elastomer obtained by suspending or emulsifying the polyurethane elastomer in an aqueous medium.

[0068] The method for solidifying a polyurethane elastic material in a solidification bath using the wet method described above specifically involves immersing a three-dimensional entangled nonwoven fabric in a polyurethane elastic material solution to impregnate the three-dimensional entangled nonwoven fabric with the polyurethane elastic material, and then immersing the impregnated three-dimensional entangled nonwoven fabric in a solidification bath to solidify the polyurethane elastic material in a porous state, followed by drying. The solidification bath contains a poor solvent for the polyurethane elastic material. By solidifying the polyurethane elastic material in this manner, it is possible to make the polyurethane elastic material porous.

[0069] The solvent for the polyurethane elastic solution is not particularly limited as long as it is a solvent capable of dissolving polyurethane. Specifically, dimethylformamide (DMF) can be preferably used because it can form a suitable porous structure.

[0070] The concentration of the polyurethane elastic material in the polyurethane elastic material solution is preferably 10 to 25% by mass, more preferably 12 to 20% by mass, in terms of solid content, from the viewpoint of efficiently permeating the polyurethane elastic material into the three-dimensional entangled nonwoven fabric and from the viewpoint of easily obtaining an artificial leather for balls with a superior texture.

[0071] The polyurethane elastic body solution may contain additives such as colorants, lightfasteners, and dispersants, as well as solidification modifiers to control the shape of the porous structure, as needed. From the viewpoint of obtaining more uniform voids, it is preferable that the polyurethane elastic body solution contains a solidification modifier.

[0072] A mixture of water, a poor solvent for polyurethane, and DMF, a good solvent, is preferably used as the solidification bath. By adjusting the mixing ratio, the shape and number of voids formed can be controlled. The mixing ratio of good solvent to poor solvent in the solidification bath is preferably good solvent / poor solvent = 0 / 100 to 40 / 60 (by mass). The temperature of the solidification bath is preferably 50°C or lower, more preferably 40°C or lower. When the temperature of the solidification bath is 50°C or lower, the solidification rate becomes appropriate, and it is possible to suppress the porous structure from becoming too dense and the porous structure from becoming difficult to form.

[0073] After obtaining a three-dimensional entangled nonwoven fabric containing a polyurethane elastic body, a substrate layer containing fiber entanglements and a polyurethane elastic body is obtained by subjecting the sea-island type fibers to an ultrafine fiber treatment. In this case, since the sea component is removed, voids are created between the ultrafine fibers and the polyurethane elastic body, and the restraint of the ultrafine fibers by the polyurethane elastic body is weakened, making it easier to obtain a soft-textured artificial leather for balls. However, if the polyurethane elastic body is impregnated after the ultrafine fiber treatment, the ultrafine fibers are strongly restrained by the polyurethane elastic body, which may result in a hard-textured artificial leather for balls. In such cases, it is possible to make the artificial leather for balls somewhat softer by lowering the ratio of polyurethane elastic body in the substrate layer. When the objective is to obtain an artificial leather for balls with a full-bodied texture obtained when the ratio of ultrafine fibers is high, it is preferable to manufacture it in this manner.

[0074] The dry method for drying and solidifying a polyurethane elastomer includes (I) a method in which a polyurethane elastomer aqueous dispersion containing a foaming agent is applied to a three-dimensional entangled nonwoven fabric and then heated and dried, and (II) a method in which the three-dimensional entangled nonwoven fabric is immersed in a polyurethane elastomer aqueous dispersion to impregnate the three-dimensional entangled nonwoven fabric with polyurethane elastomer and then dried. In the case of method (II), if the polyurethane elastomer is impregnated into the three-dimensional entangled nonwoven fabric and dried as is, the polyurethane elastomer may migrate to the surface layer of the three-dimensional entangled nonwoven fabric, resulting in an inability to obtain a substrate with a uniform polyurethane elastomer content. Therefore, in method (II), it is preferable to add a heat-sensitive gelling agent to the polymer elastomer aqueous dispersion. By adding a heat-sensitive gelling agent, the polymer elastomer aqueous dispersion gels due to the heat during heating and drying, suppressing the migration of the polyurethane elastomer. In this case, by combining methods such as steaming or far-infrared heating, the polymer elastomer can be solidified more uniformly in the thickness direction.

[0075] In the method of drying and solidifying a polyurethane elastic body by a dry method, a base layer containing a fiber entanglement and a polyurethane elastic body can be obtained by performing an ultrafine fiberization treatment in the same manner as in the method of solidifying a polyurethane elastic body in a solidification bath by a wet method.

[0076] When a three-dimensional entangled nonwoven fabric containing a polyurethane elastic material is subjected to a microfiber treatment, the mass ratio of microfibers to polymer elastic material in the base layer (microfibers / polymer elastic material) is preferably 35 / 65 to 65 / 35. Furthermore, when a polyurethane elastic material is impregnated after the microfiber treatment, the mass ratio of microfibers to polymer elastic material in the base layer (microfibers / polymer elastic material) is preferably 65 / 35 to 95 / 5. By setting the mass ratio within the above range, it becomes easier to obtain artificial leather for balls that has a texture similar to natural leather, which is generally preferred as a material for balls.

[0077] <Step (2)> Step (2) is a step in which a polyurethane porous layer is formed on the surface of the substrate layer. The following (i) to (v) are examples of methods for forming the polyurethane porous layer: (i) A method of forming by wet application, in which a polyurethane elastic body solution or polyurethane elastic body aqueous dispersion is applied to the surface of the substrate layer to a predetermined thickness. (ii) A method of forming by dry application, in which a polyurethane elastic body solution or polyurethane elastic body aqueous dispersion is applied to the surface of the substrate layer to a predetermined thickness. (iii) A method of forming by wet application, in which a polyurethane elastic body solution or polyurethane elastic body aqueous dispersion is applied to a sheet such as a film or release paper, a polyurethane porous layer film is formed by wet application, and then the polyurethane porous layer film is bonded to the substrate layer via an adhesive, or a treatment solution containing a solvent capable of dissolving polymer elastic bodies is applied to the polyurethane porous layer film to redissolve the polyurethane porous layer and bond it to the substrate layer, and then the sheet is peeled off. (iv) A method of forming a polyurethane porous layer film by applying a polyurethane elastic body solution or polyurethane elastic body aqueous dispersion to a sheet such as a film or release paper, forming a polyurethane porous layer film by a dry method, then bonding the polyurethane porous layer film to a base layer via an adhesive, or applying a treatment solution containing a solvent capable of dissolving the polymer elastic body to the polyurethane porous layer film to redissolve the polyurethane porous layer and bond it to the base layer, and then peeling off the sheet. (v) A method of forming a polyurethane porous layer by applying a predetermined amount of polyurethane elastic body solution or polyurethane elastic body aqueous dispersion to a transfer release sheet, etc., then bonding it to a base layer before solidifying the polyurethane elastic body, or during the solidification of the polyurethane elastic body, and then solidifying it. Among these, from the viewpoint of obtaining an artificial leather for balls with superior grip when wet, it is preferable to form the polyurethane porous layer by (i) (hereinafter also referred to as the wet method).

[0078] The wet method involves applying a polyurethane elastic body solution to the surface of a substrate layer, then immersing it in a solidification bath containing a poor solvent for the polyurethane elastic body to solidify it in a porous state, and subsequently drying it.

[0079] In the wet process, methods for applying a polyurethane elastic solution or polyurethane elastic aqueous dispersion to the substrate layer surface include, for example, applying it using a knife coater, bar coater, roll coater, etc.

[0080] The solvent for the polyurethane elastic body solution is preferably dimethylformamide (DMF) from the viewpoint of easily forming open pores of a desired number and size.

[0081] The concentration of the polyurethane elastic material in the polyurethane elastic material solution varies depending on the type of polyurethane elastic material, but is preferably 10 to 30% by mass, more preferably 12 to 24% by mass, in terms of solid content. Within this range, it is easier to achieve both grip and abrasion resistance. Furthermore, within this range, the viscosity of the polyurethane elastic material solution becomes easy to handle, making it easier to apply to the desired thickness.

[0082] The polyurethane elastic body solution may contain additives such as colorants, lightfasteners, and dispersants, as well as coagulation modifiers to control the shape and size of the porous structure (open pores), as needed. From the viewpoint of obtaining more uniform voids, it is preferable that the polyurethane elastic body solution contains a coagulation modifier.

[0083] A mixture of water, a poor solvent for polyurethane, and DMF, a good solvent, is preferably used as the solidification bath. By adjusting the mixing ratio, the shape, size, and number of voids formed can be controlled. The mixing ratio of good solvent to poor solvent in the solidification bath is preferably good solvent / poor solvent = 0 / 100 to 40 / 60 (by mass). Within this range, it becomes easier to form open pores that communicate with the surface of the substrate layer. Having such interconnected open pores results in a ball-type artificial leather with superior water absorption and grip when wet.

[0084] The temperature of the coagulation bath is preferably 50°C or lower, more preferably 40°C or lower. A coagulation bath temperature of 50°C or lower allows for an appropriate coagulation rate, preventing the porous structure from becoming too dense and making it difficult to form. It also facilitates the formation of protrusions.

[0085] When the polyurethane elastic material contained in the base layer and the polyurethane elastic material forming the porous polyurethane layer are of the same type, it is preferable to perform the solidification of the polyurethane elastic material in step (1) and the solidification of the polyurethane elastic material in step (2) simultaneously. By performing solidification simultaneously, drying after solidification is completed in one step, resulting in improved production efficiency and further enhancing the adhesion between the base layer and the porous polyurethane layer.

[0086] The thickness of the porous polyurethane layer before the protrusions are added to the surface is preferably 50 to 700 μm, more preferably 75 to 600 μm, and even more preferably 100 to 500 μm. If the thickness of the porous polyurethane layer before the protrusions are added to the surface is 50 μm or more, it becomes easier to form a large number of fine open holes, resulting in good embossability when adding the protrusions. Also, if the thickness of the porous polyurethane layer before the protrusions are added to the surface is 700 μm or less, it is possible to suppress the open holes from being stretched too large or tearing when adding the protrusions.

[0087] <Step (3)> Step (3) is a step in which protrusions are added to the surface of the porous polyurethane layer.

[0088] Methods for creating raised areas include using an embossing roll with recesses, transferring a raised shape using a flat embossing plate, and transferring a raised area using release paper with raised areas. Among these, the method using an embossing roll with recesses is preferred from the viewpoint of being able to form raised areas with large height differences, easily obtaining artificial leather for balls with a good texture, and productivity.

[0089] From the viewpoint of obtaining artificial leather for balls with superior grip when wet, it is preferable that the embossing roll has recesses with a greater difference in height than the thickness of the polyurethane porous layer before the protrusions are applied to the surface. When such an embossing roll is used, the recesses on the surface of the embossing roll (hereinafter also referred to as the "protrusion-forming portion") are less likely to come into contact with the portion of the polyurethane porous layer surface where the protrusions are formed. As a result, when forming the protrusions, it is possible to prevent the closure of open holes present in the portion of the polyurethane porous layer surface where the protrusions are formed. In addition, when embossing with the embossing roll, the difference in pressing force between the portion where the protrusions are formed and the other portion (the portion where the protrusions are not formed), and the resulting temperature difference, can melt or soften the surface of the other portion, making it easier to close the open holes in the other portion. When the open holes in the other portion are closed, the closed portion becomes darker in color than the protrusion portion, resulting in a two-tone effect and making it easier to obtain a three-dimensional effect. Furthermore, using such an embossing roll prevents excessive pressure from being applied to the sides of the protrusions, thus suppressing the enlargement of the openings on the sides of the protrusions and preventing them from being stretched and torn.

[0090] The average height difference of the convex portion of the embossing roll varies depending on the thickness of the polyurethane porous layer, but is preferably 250 to 1000 μm, and more preferably 500 to 700 μm.

[0091] When embossing with an embossing roll, the roll surface temperature is preferably 150 to 180°C, and the press pressure is preferably 5 to 50 kgf / cm². ２ More preferably 7 to 50 kgf / cm² ２ More preferably 8 to 50 kgf / cm² ２ The processing time is preferably 10 to 120 seconds. Furthermore, if the fibrous entanglement contained in the substrate layer is embossed so that it becomes concave by pressing or the like, it is preferable because it provides a polyurethane porous layer on the surface, contains fibrous entanglement in the inner layer, and yields a convex portion with open holes and other portions without open holes.

[0092] After step (3), the surface of the polyurethane porous layer may be subjected to a surface treatment such as coloring. If the artificial leather for the ball has protrusions (A) and open holes on the top surface of the protrusions (A), it is preferable that the surface treatment does not hinder the absorption of moisture, etc., by the open holes. The surface treatment method is preferably a method of coloring by dispersing pigment in the polyurethane porous layer.

[0093] Furthermore, after step (3), a layer consisting of a grip-enhancing agent such as rosin resin or liquid rubber, a softener, a penetrating agent, a water-repellent agent, or other auxiliary agents may be formed on the surface of the protrusions, or it may not be formed.

[0094] The present invention will be described in more detail below with reference to examples. However, the scope of the present invention is not limited in any way by the content of the examples.

[0095] [Measurement and Evaluation Methods] Various physical properties were measured using the following methods. The results are shown in Table 1.

[0096] <Height of protrusions and depth of grooves> Using a "One-Shot 3D Shape Measuring Machine VR-3000" (manufactured by Keyence Corporation), the surface of the artificial leather for the ball was photographed at 25x magnification with a low-magnification camera. In the photographs, five arbitrary points were selected for each of the protrusions (A) and (B), and a profile was created by drawing a vertical line through the center of the protrusion and perpendicular to the groove. Then, the valleys at both ends of the protrusion were connected with a straight line, and the distance to the highest point of the protrusion was defined as the height of the protrusion. The average of the heights of the five protrusions was defined as the height of the protrusion. For the depth of the groove, the shoulders of the groove were connected with a straight line, and the distance to the deepest point of the groove was determined. After calculating the average depth of the grooves present in one protrusion, the average of the average depths of the grooves in the five protrusions was defined as the depth of the groove.

[0097] <Area of ​​the protrusions> The surface of the artificial leather for the ball was photographed at 50x magnification using a "Digital Microscope VHX-8000" (manufactured by Keyence Corporation). For each of the photographed protrusions (A) and (B), five arbitrary locations were selected, and the area in a plan view was calculated from their contours. The grooves were also included in the area of ​​the protrusions.

[0098] <Angle between grooves> Using a "Digital Microscope VHX-8000" (manufactured by Keyence Corporation), the surface of the artificial leather for the ball was photographed at 50x magnification. In the photographs taken so that groove (a) and groove (b) were in the same field of view, straight lines were drawn at five arbitrary locations, extending to adjacent grooves (a) and groove (b), respectively. The angle between these two lines, which was 90° or less, was measured, and the average of the angles at the five locations was taken as the angle between groove (a) and groove (b).

[0099] <Diameter and number of open holes> The surface of the artificial leather for the ball was photographed using a scanning electron microscope at a magnification of 1000x. Ten protrusions (A) were arbitrarily selected from the obtained photographs, and the number of open holes present on the top surface of each protrusion (A) was counted, and the diameter and number of holes were measured per 1 mm. ２ The number of open holes with a diameter of 10 to 500 nm was calculated. In addition, ten protrusions (A) were arbitrarily selected from the obtained photographs, and the area of ​​the open holes observed on the top surface of each protrusion (A) was calculated using image analysis software. Subsequently, a virtual circle having an area equal to the area of ​​each open hole was assumed, and the diameter of this virtual circle was defined as the equivalent area circle diameter, and the average value of this equivalent area circle diameter was defined as the diameter of the open holes.

[0100] <Dry Friction Coefficient> The dry friction coefficient of the ball's artificial leather was measured using the following method, with reference to JIS K7125:1999. The ball's artificial leather was cut to a width of 6.3 cm and a length of 12 cm to form a test piece. The test piece was conditioned for 24 hours at a temperature of 20°C and a relative humidity of 65%. A 6.3 cm square, 200 g metal sliding piece was then attached to the test piece by wrapping it around the piece and securing it with tape. Next, a 1 mm thick silicone pad (artificial skin material for tattoo practice, manufactured by Ruicoo) was placed on a load cell. The test piece with the sliding piece attached was positioned so that its surface was in contact with the silicone pad. The frictional force was measured using a load cell when the test piece with the sliding piece attached was moved 10 cm on the silicone pad at a speed of 10 cm / min. The frictional force was measured as the average value while the test specimen was in motion. The frictional force applied when moving the test specimen from a stationary position and the frictional force applied to the moving test specimen were measured. From the obtained frictional forces, the static friction coefficient and the kinetic friction coefficient were calculated in accordance with JIS K7125:1999, and these were defined as the dry friction coefficient.

[0101] <Wet Friction Coefficient> In the <Dry Friction Coefficient> above, the friction force was measured in the same manner as before, except that after placing the silicone pad on the load cell, deionized water was sprayed onto the surface of the silicone pad at three locations from a height of 10 cm at a 45° angle using a spray bottle with a discharge volume of 1 ml per push, so that the pad was evenly wet. From the obtained friction force, the friction coefficient was calculated in accordance with JIS K7125:1999 and this was defined as the wet friction coefficient.

[0102] <Thickness of the Polyurethane Porous Layer> An arbitrary protrusion was selected from the ball's artificial leather, and the ball's artificial leather was cut from the top surface side to the base layer side, passing through approximately the center of the top surface of the protrusion. The cross-section of the ball's artificial leather was photographed at 200x magnification using a "Digital Microscope VHX-8000" (manufactured by Keyence Corporation), and the vertical distance between the base layer and the top surface of the protrusion was measured at the position where the vertical distance between the base layer and the top surface of the protrusion was greatest. Five measurements were taken for two different protrusions, and the average of the five vertical distances was taken as the thickness of the polyurethane porous layer.

[0103] [Example 1] A continuous two-layer (sea-island) type mixed spun fiber, in which the island component was 6-nylon and the sea component was low-density polyethylene (island component / sea component = 50 / 50 (mass ratio)), was melt-spun. The obtained fibers were stretched, crimped, and cut to obtain staples with a 5dtex and a fiber length of 51 mm. After passing the obtained staples through a card, a web was made using the cross-wrapper method, and the webs were stacked and laminated. Next, 980 punches / cm were performed using a single-barb felt needle. ２ By needle-punching the laminated web at a needle-punching density, a basis weight of 640 g / m² is achieved. ２ A three-dimensional entangled nonwoven fabric was obtained.

[0104] The obtained three-dimensional entangled nonwoven fabric was heat-dried and then pressed to smooth its surface. The smoothed three-dimensional entangled nonwoven fabric was then immersed for 10 minutes in a polyester-polyurethane DMF solution containing 17.5% by mass of polyester-polyurethane, and then immersed for 30 minutes in a 30% by mass aqueous solution of DMF to obtain a three-dimensional entangled nonwoven fabric containing sponge-like solidified polyurethane. The polyurethane-containing three-dimensional entangled nonwoven fabric was then washed with hot water, and the polyethylene in the continuous two-layer (sea-island) type mixed spun fibers was dissolved and removed in toluene at 90°C to obtain a fiber entanglement body containing ultrafine 6-nylon fibers with an average fineness of approximately 0.007 dtex and a base layer containing a porous polyurethane elastic body.

[0105] On the surface of the obtained substrate layer, a DMF solution (20% solids by mass) containing brown pigment and polyether-based polyurethane ("MP-145," manufactured by Dainippon Ink and Chemicals, Inc.) was applied at a rate of 470 g / m². ２ The material was applied. Subsequently, it was immersed in water for 12 minutes to solidify the polyether-based polyurethane, and then dried to form a 250 μm thick porous polyurethane layer.

[0106] The composite surface, in which a porous polyurethane layer is formed on a substrate layer, is embossed from the polyurethane porous layer side using an embossing roll, with a roll surface temperature of 170°C and a press pressure of 10 kgf / cm². ２Embossing was performed under the condition of a processing time of 30 seconds to obtain artificial leather for balls. Figure 1 shows an image of the surface of the obtained artificial leather for balls, taken at a magnification of 30x using a digital microscope "VHX-6000" (manufactured by Keyence Corporation).

[0107] [Comparative Example 1] Artificial leather for balls was obtained in the same manner as in Example 1, except that a different embossing roll was used than the one used in Example 1. Figure 2 shows an image of the surface of the obtained artificial leather for balls, taken at a magnification of 50x using a digital microscope "VHX-8000" (manufactured by Keyence Corporation).

[0108]

[0109] As shown in Table 1, the artificial leather for balls of the present invention, in which at least a portion of the protrusions have grooves, exhibits excellent grip when wet. On the other hand, the artificial leather for balls obtained in Comparative Example 1, which does not have grooves in the protrusions, exhibits inferior grip when wet.

Claims

1. An artificial leather for a ball comprising a base layer containing a fiber entanglement and a polyurethane elastic body, and a polyurethane porous layer having a plurality of protrusions on its surface, wherein at least a portion of the plurality of protrusions has grooves.

2. The artificial leather for a ball according to claim 1, wherein the groove includes a groove (a) extending in a first direction in a plan view of the polyurethane porous layer and a groove (b) at an angle to groove (a).

3. The artificial leather for a ball according to claim 2, wherein the angle between groove (a) and groove (b) is 60 to 90°.

4. The artificial leather for a ball according to claim 2, wherein the protrusion has a protrusion (A) and a protrusion (B), the protrusion (A) has the groove (a), and the protrusion (B) has the groove (b).

5. The artificial leather for a ball according to claim 4, wherein the protrusions (A) and (B) are arranged alternately.

6. The artificial leather for a ball according to claim 4, wherein the height of the protrusion (A) is 100 to 400 μm, and the height of the protrusion (B) is 10 to 50 μm lower than that of the protrusion (A).

7. The artificial leather for a ball according to claim 2, wherein the depth of groove (a) is 1 to 20 μm, and the depth of groove (b) is 20 to 60 μm.

8. The artificial leather for a ball according to claim 2, wherein the width of groove (a) is 10 to 200 μm, and the width of groove (b) is 10 to 200 μm.

9. The area of ​​the convex portion (A) in plan view is 2 to 4 mm ２ The area of ​​the convex portion (B) in plan view is 1 to 2 mm ２ The artificial leather for a ball as described in claim 4.

10. The artificial leather for a ball according to claim 4, wherein each of the protrusions (A) has 3 to 6 of the grooves (a), and each of the protrusions (B) has 3 to 6 of the grooves (b).

11. The artificial leather for a ball according to claim 4, wherein the shape of the convex portion (A) and the convex portion (B) in plan view is at least one selected from a square, a rectangle, a rounded square, and a rounded rectangle.

12. The artificial leather for a ball according to claim 4, wherein the cross-sectional shape of the convex portion (A) and the convex portion (B) is at least one selected from a square, a rectangle, a trapezoid, and a semicircle.

13. The artificial leather for a ball according to claim 4, wherein the top surface of the convex portion (A) has an open hole with a diameter of 10 to 500 nm.

14. The number of open holes is 1000 / mm ２ The artificial leather for a ball according to claim 13, having the above characteristics.

15. The artificial leather for a ball according to claim 1 or 2, wherein the maximum static friction coefficient and dynamic friction coefficient with the silicone resin are 0.50 or higher.

16. The artificial leather for a ball according to claim 1 or 2, satisfying the following formula (1). (Coefficient of friction in wet conditions / Coefficient of friction in dry conditions) × 100 ≥ 80 (%) (1)

Images