EP2287395A1

EP2287395A1 - Leather-like sheet having excellent grip performance and artificial leather product using the same

Info

Publication number: EP2287395A1
Application number: EP09729392A
Authority: EP
Inventors: Tetsuya Ashida; Yoshiki Nobuto; Yoshimi Yamaguchi; Norio Makiyama; Hisao Yoneda; Kyoichi Fujimoto; Kozo Hayashi
Original assignee: Kuraray Co Ltd
Current assignee: Kuraray Co Ltd
Priority date: 2008-04-10
Filing date: 2009-04-07
Publication date: 2011-02-23
Anticipated expiration: 2029-04-07
Also published as: JP5452477B2; JPWO2009125758A1; EP2287395B1; WO2009125758A1; EP2287395A4

Abstract

A leather-like sheet including a fibrous substrate and non-modified or modified hollow nanosilica particles which adhere to at least a part of the surface thereof. The leather-like sheet has a good grippability in both dry and wet conditions, particularly, an improved grippability in wet conditions.

Description

TECHNICAL FIELD

The present invention relates to grain-finished leather-like sheets with a good grippability in a wet condition, suede-finished leather-like sheets with a good grippability in both dry and wet conditions having a unique touch, leather-like sheets having a intermediate appearance (semi grain-finished appearance) between a nubuck appearance and a grain-finished appearance, and artificial leather product made thereof.

BACKGROUND ART

Game balls, hand gloves, soles of shoes, floorings, etc. are required to have, in addition to a good grippability in dry condition, a good grippability when their surfaces are wet with sweat, water, etc. To make the surface of a substrate such as metals, plastics, woods, fibers and papers hard to slip, Patent Document 1 proposes to cover the surface of the substrate with a coating composition containing a polyurethane resin having hydroxyl groups, a liquid rubber having hydroxyl groups, inorganic or organic fillers, and an isocyanate prepolymer. However, the substrate covered with the coating composition has an insufficient wet grippability (grippability in wet condition), because it comes easy to slip as the water absorption or water adhesion is increased. In addition, Patent Document 1 addresses nothing about a wet grippability.
To reduce the water absorption and moisture permeability of a synthetic leather, Patent Document 2 proposes to produce the synthetic leather using a synthetic rubber elastomer, blended with gelatin. In the production method taught by Patent Document 2, the synthetic rubber elastomer blended with gelatin is made into a sheet or film form, the surface thereof is made into a foamed structure by a thermal foaming, a part of the surface skin layer is removed, and then, the surface is made porous by removing gelatin with a hot water. However, the synthetic leather of Patent Document 2 has a high surface tackiness and a low abrasion resistance. In addition, Patent Document 2 addresses nothing about a wet grippability,
Patent Document 3 discloses a leather-like sheet for halls having a porous surface layer in which microholes with a diameter of 5 to 100 µm are formed in a density of 300 to 10,000/cm². The microholes communicate with voids inside the leather-like sheet and have a penetrant inside thereof. Patent Document 3 teaches that the leather-like sheet has a good sweat absorbability and absorbs sweat quickly thereby to exhibit a good non-slip property. However, the proposed leather-like sheet is easy to be abraded because of a large pore diameter and becomes easy to slip if the surface is wetted with the sweat which is not absorbed.
Patent Document 4 discloses a game ball covered with a synthetic leather. The synthetic leather cover has a pebbled outer surface on which many pebbles and many valleys between pebbles are produced. On the side wall of each pebble, many holes are provided. However, the holes on the side wall of the pebble are easily clogged with soil to reduce the sweat absorbability, resulting in the reduction of the grippability.
Patent Document 5 discloses a leather-like sheet for balls having a porous pebbled surface in which microholes are formed on the surface of pebbles but substantially not formed on the surface of valleys, However, the porous surface is easily abraded and the holes are easily soiled.
Patent Document 6 describes a surface material for balls having a pebbled surface in which a coating layer of an elastic polymer is provided on the top of each pebble and pores with a diameter of 0.5 to 50 µm are formed on the side wall of each pebble in a density of 1000/cm² or more. However, the valleys are easily soiled and the touch is poor because the top of each pebble is coated with the elastic polymer.
Patent Document 7 describes a leather-like sheet having a pebbled, porous elastic polymer layer on its surface in which open pores with a diameter of 10 to 500 nm are formed on the top surface of each pebble in a density of 1000/cm² or more. However, the porous surface is necessarily inferior to a non-porous surface in the surface abrasion resistance. In addition, the proposed technique cannot be applied to a substrate having a smooth surface.
Patent Document 8 discloses a composition for forming a heat-insulating layer containing a binder resin, hollow particles, and a solvent or dispersion medium. However, the hollow particles have a particle size of 0.3 to 300 µm which is far larger than nanosize. In the working examples of Patent Document 8, the heat-insulating- sheet is produced by applying the composition on a nonwoven fabric made of acrylic fibers. The composition contains hollow particles ("Microsphere F-80E" manufactured by Matsumoto Yushi-Seiyaku Co., Ltd.) having a particle size of 10 to 30 µm and a shell made of a copolymer of vinylidene chloride, acrylonitrile, etc. However, Patent Document 8 describes or addresses nothing about the use of hollow nanosilica particles with nanosize which will be mentioned below and the improvement of the wet grippability of a leather-like sheet by the use of the hollow nanosilica particles.
Patent Document 9 discloses a technique to increase the reactivity of hollow nanosilica particles for improving the dispersibility of the particles in an organic resin, etc. In the proposed technique, the secondary aggregation of the particles is reduced by modifying the surface with various kinds of functional groups. However, Patent Document 9 discloses nothing about the details of the surface modification.
Also proposed are a nonskid hand glove in which a foamed coating of a rubber or a thermoplastic resin is formed on the substrate of the glove made of knitted elastic fibers and non-elastic fibers (Patent Document 10) and a method of applying a non-slipping resin such as a styrene-isoprene block copolymer and a hydrogenated product thereof onto a raised surface using a patterned gravure roll (Patent Document 11). However, in both the proposals, the writing effect and high-quality touch characteristic of the raised surface are lost.

Patent Document 1: JP 7-30285B
Patent Document 2: JP 63-152483A
Patent Document 3: JP 2000-328465A
Patent Document 4: US 6,024,661
Patent Document 5: JP 2004-300656A
Patent Document 6: JP 2004-277961A
Patent Document 7: WO 2008/001716
Patent Document 8: JP 2001-220552A
Patent Document 9: JP 2007-99607A
Patent Document 10; JP 2008-075201A
Patent Document 11: JP 2001-214376A

DISCLOSURE OF THE INVENTION

As described above, the wet grippability of the known leather-like sheets is still insufficient and the improvement thereof is required. In the known techniques, the improvement of the wet grippability is attempted by enhancing the water absorption and the moisture absorption by making the surface or pebbles on the surface porous. However, the wet grippability is still insufficient and the surface abrasion resistance is necessarily reduced when the surface is made porous. Thus, in view of the above state of the art, the object of the present invention is to provide a leather-like sheet having an improved wet grippability.
In addition, as described above, the known techniques fail to realize a good grippability required in sport gloves and working gloves without loosing the elegant raised appearance, the brilliant, dense colors of the raised surface and the writing effect. Particularly, in both grain-finished and suede-finished leather-like sheets, the wet grippability is insufficient and the improvement thereof is not considered. The object of the present invention is to provide a suede-finished leather-like sheet and a semi-grain-finished leather-like sheet which combine a good grippability in both dry and wet conditions required in sport gloves and working gloves, an elegant appearance and a soft touch.
As a result of extensive research in view of achieving the above objects, the inventors have found that the hollow nanosilica particles which have been known to be excellent in the corrosion resistance, heat insulation, electric insulation, delustering effect and feel are also effective for improving the wet grippability. It has been further found that the hollow nanosilica particles (surface-modified particles) which have the surface modified with at least one compound selected from the group consisting of a compound having isocyanate group, a compound having alkyl group, a compound having aryl group and a compound having UV-sensitive functional group are particularly effective for improving the wet grippability.
It has been still further found that the wet grippability is drastically improved when the hollow nanosilica particles are allowed to be present on the raised surface. It has been still further found that the surface-modified particles can be allowed to be present on the surface of fibers uniformly without adversely affecting the elegant raised appearance and the writing effect of the raised portion and the improving effect of the surface-modified particles on the grippability is long-lasting.
Thus, the present invention provides a leather-like sheet comprising a fibrous substrate and a grain-finished portion covering 10% or more of the surface of the fibrous substrate, wherein the grain-finished portion comprises a surface layer and an optional coating layer, and the surface layer comprises non-modified, hollow nanosilica particles having a primary particle size of 50 to 150 nm and an elastic polymer, or comprises modified hollow nanosilica particles and an optional elastic polymer.
The present invention further provides a leather-like sheet which comprises a fiber entangled body comprising bundles of microfine fibers each having an average fineness of 0.3 dtex or less, an elastic polymer inside the fibers entangled body and raised fibers of the microfine fibers on a surface of the leather-like sheet, a surface of the raised fibers on at least one surface of the leather-like sheet being provided with hollow nanosilica particles having a primary particle size of 50 to 150 nm.
The present invention still further provides an artificial leather product wherein at least a portion of a surface thereof is formed by the leather-like sheet mentioned above.
At least a portion of the surface of the leather-like sheet of the present invention is a grain-finished portion. The grain-finished portion is composed of a surface layer and an optional coating layer under the surface layer. The surface layer is made of the non-modified hollow nanosilica particles and the elastic polymer, or made of the modified hollow nanosilica particles and an optional elastic polymer. Since the surface layer contains the non-modified or modified hollow nanosilica particles, the leather-like sheet of the invention has a good grippability in both dry and wet conditions even when the surface is not made porous. In addition, since the surface is not needed to be porous, the surface strength such as a surface abrasion resistance is higher than a porous surface.
In another embodiment of the present invention, the hollow nanosilica particles are attached to the surfaces of the raised fibers and bundles of fibers on the surface of the leather-like sheet without using a binder. Therefore, the leather-like sheet combines a soft hand, a good dry and wet grippability and a unique touch without deteriorating the elegance or appearance and colors of a suede-finished leather-like sheet. By shortening the raised fibers on the surface and coating an elastic polymer so as to lay down a part of the raised fibers, a leather-like sheet having a nubuck appearance and touch can be produced.
In a still another embodiment, the leather-like sheet of the present invention is a semi-grain-finished leather-like sheet wherein a coated portion and a raised portion are mixedly present on the surface. Since the raised portion is provided with the hollow nanosilica particles, the semi-grain-finished leather-like sheet retains a high-quality appearance without deteriorating the writing effect of the raised portion and has a good grippability in both dry and wet conditions and a unique touch.

BRIEF DESCRIPTION OF DRAWINGS

Fig. 1 is a schematic cross-sectional view illustrating an example of the pebble-valley structure optionally formed on the leather-like sheet of the present invention. Pebble tops are shown by horizontal straight lines.
Fig. 2 is a schematic cross-sectional view illustrating an example of the secondary pebble-valley structure optionally formed on the leather-like sheet of the present invention. Pebble tops of the secondary pebble-valley structure are shown by horizontal straight lines.
Fig. 3 is a schematic cross-sectional view illustrating the depth (D) of the valley,
Fig. 4 is a schematic cross-sectional view illustrating the boundary (B) between a valley having a semicircular cross section and a flat portion.
Fig. 5 is a schematic cross-sectional view illustrating the boundary (B) between a valley having a trapezoid cross section and a flat portion.
Fig. 6 is a schematic plan view illustrating examples of the secondary pebble-valley structure. The portions of dark shading are valleys of the secondary pebble-valley structure.

BEST MODE FOR CARRYING OUT THE INVENTION

(1) Grain-Finished Leather-Like Sheet

The leather-like sheet of the present invention includes a fibrous substrate and a grain-finished portion which covers 10% or more of the surface of the fibrous substrate. The grain-finished portion is composed of a surface layer and an optional coating layer. In an embodiment of the present invention, the surface layer contains hollow nanosilica particles (not surface-modified) and an elastic polymer. In another embodiment, the surface layer contains an elastic polymer and hollow nanosilica particles (surface- modified particles) which are surface-modified with at least one compound selected from the group consisting of a compound having isocyanate group, a compound having alkyl group, a compound having aryl group and a compound having UV-sensitive functional group. In still another embodiment, the surface layer contains the surface -modified particles, but does not contain the elastic polymer,
The fibrous substrate is preferably a knitted or woven fabric, a nonwoven fabric or a fiber entangled body (three-dimensionally entangled fabric). The fibrous substrate is preferably impregnated with an elastic polymer, and a fiber entangled body impregnated with an elastic polymer is more preferably used as the fibrous substrate. By impregnating an elastic polymer into the inside of the fiber entangled body, the properties such as strength of the fibrous substrate is enhanced, and simultaneously, the feeling resembling natural leathers is easy to obtain. The elastic polymer impregnated into the inside of the fiber entangled body is more preferably in a spongy form (porous form). The impregnated elastic polymer in a spongy form provides a grain-finished leather-like sheet and a semi-grain-finished or suede-finished leather-like sheet mentioned below with a soft and dense feeling as well as a cushioning property while maintaining their light weights.
The fibers for constituting the knitted or woven fabric, the nonwoven fabric and the fiber entangled body are selected from natural fibers, synthetic fibers and semi-synthetic fibers each being known in the art. Known cellulose-based fibers, acryl-based fibers, polyester-based fibers and polyamide-based fibers, alone or in combination of two or more, are preferably used industrially in view of the quality uniformity and costs. Although not particularly limited, microfine fibers are preferably used in the present invention because a soft feeling well resembling natural leathers is achieved, and the surface area of fibers to hold the hollow nanosilica particles is extremely increased in a semi-grain-finished or suede-finished leather-like sheet. The average fineness of microfine fibers is preferably 0.3 dtex or less, more preferably 0.0001 to 0.3 dtex, and still more preferably 0.0001 to 0.1 dtex.
The microfine fibers mentioned above may be produced by (a) directly spinning the microfine fibers having an intended average fineness or (b) first spinning microfine fiber-forming fibers having a fineness larger than the intended fineness, and then, converting the microfine fiber-forming fibers to microfine fibers having the intended average fineness. If the mass per unit area of the fibrous substrate exceeds 200 g/m², the fibrous substrate may be difficult to continuously produce from microfine fibers because of the elongation due to tension and the reduction in the thickness. Therefore, the method (b) in which the microfine fiber-forming fibers are converted to the microfine fibers in a later stage of the production is preferred.
Generally in the method (b), the microfine fiber-forming fibers are produced by composite-spinning or mix-spinning two or more kinds of thermoplastic polymers which are incompatible with each other and the microfine fiber-forming fibers are converted to the microfine fibers by removing at least one polymer component from the microfine fiber-forming fibers by extraction or decomposition, or by splitting the microfine fiber-forming fibers along the interface between the polymer components. Examples of the microfine fiber-forming fiber containing a removable polymer component include sea-island fiber and multi-layered fiber. By removing the sea component polymer from the sea-island fibers by extraction or decomposition or by removing at least one layered polymer component from the multi-layered fibers by extraction or decomposition, bundles of microfine fibers made of the island component (polymer component to be not removed) are obtained. The solvent for the removal by extraction or decomposition may be a solvent which dissolves the sea component polymer but does not dissolve the island component (polymer component to be not removed), and water, toluene, etc. may be practically used. Examples of the microfine fiber-forming fiber which is split or divided along the interface between the polymer components include radial-layered fiber and multi-layered fiber. This type of microfine fiber-forming fiber is split or divided along the interface between different kinds of layered polymers by a physical or chemical treatment and converted to bundles of microfine fibers.
The island component polymer for the sea-island fibers or multi-layered fibers is preferably selected from melt-spinnable polymers which have a sufficient fiber property such as strength and have a melt viscosity and a surface tension each being larger than those of the sea component under the spinning conditions. Examples of the island component polymers include polyamide such as nylon-6, nylon-66, nylon-610 and pylon-612; copolymers mainly composed of such polyamide; polyester such as polyethylene terephthalate, polypropylene terephthalate, polytrimethylene terephthalate, and polybutylene terephthalate; and copolymers mainly composed of such polyester.
The sea component polymer for the sea-island fibers or multi-layered fibers preferably have a melt viscosity lower than that of the island component polymer and a solubility in solvent or a decomposability by a decomposer larger than those of the island component polymer. Examples thereof include polyethylene, modified polyethylene, polypropylene, polystyrene, modified polystyrene, ethylene-propylene copolymers, ethylene-vinyl acetate copolymers, styrene-ethylene copolymers, styrene-acryl copolymers, modified polyester, and polyvinyl alcohol resins. The sea-island fibers are converted to the microfine fibers by extracting the sea component polymer with an organic solvent. A water-soluble, thermoplastic polyvinyl alcohol (water-soluble PVA) is preferably used because the microfine fibers are obtained using water or an aqueous solution at predetermined temperature and pH without using an organic solvent.
The viscosity average polymerization degree (hereinafter merely referred to as "polymerization degree") of the water-soluble PVA is preferably 200 to 500, more preferably 230 to 470, and still more preferably 250 to 450. If being 200 or more, the melt viscosity is moderate, and the water-soluble PVA is easily made into a composite with the island component polymer. If being 500 or less, the melt viscosity is not excessively high and the extrusion from a spinning nozzle is easy. By using the water-soluble PVA having a polymerization degree of 500 or less, i.e., a low-polymerization degree PVA, the dissolution to a hot water becomes quick. The polymerization degree (P) of the water-soluble PVA is measured according to JIS-K6726, in which the water-soluble PVA is re-saponified and purified, and then, an intrinsic viscosity [η] is measured in water of 30 °C. The polymerization degree (P) is calculated from the following equation: $P = {([η] 10^{3} / 8.29)}^{(1 / 0.62)} .$
The saponification degree of the water-soluble PVA is preferably 90 to 99,99 mol %, more preferably 93 to 99.98 mol %, still more preferably 94 to 99.97 mol %, and particularly preferably 96 to 99.96 mol %. If being 90 mol % or more, the melt spinning is performed without causing thermal decomposition and gelation because of a good heat stability and the biodegradability is good. Also, the water solubility is not reduced when modified with a copolymerizable monomer which will be described below, and the conversion to microfine fibers becomes easy. PVA having a saponification degree exceeding 99.99 mol % is difficult to produce stably.
The melting point of the water-soluble PVA (Tm) is preferably 160 to 230 °C, more preferably 170 to 227 °C, still more preferably 175 to 224 °C, and particularly preferably 180 to 220 °C If being 160 °C or higher, the fiber tenacity is prevented from being reduced due to the lowering of crystallizability and the fiber formation is prevented from becoming difficult because of the deteriorated heat stability. If being 230 °C or lower, sea-island long fibers can be stably produced because the melt spinning can be performed at temperatures lower than the decomposition temperature of PVA. The measuring method of the melting point will be described below.
The water-soluble PVA is produced by saponifying a resin mainly constituted by vinyl ester units, Examples of vinyl monomers for the vinyl ester units include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laureate, vinyl stearate, vinyl benzoate, vinyl pivalate and vinyl versatate, with vinyl acetate being preferred in view of easy production of the water-soluble PVA.
The water-soluble PVA may be homo PVA or modified PVA introduced with co-monomer units, with the modified PVA being preferred in view of a good melt spinnability, water solubility and fiber properties. In view of a good copolymerizability, melt spinnability and water solubility of fibers, preferred examples of the cc-monomers are α-olefins having 4 or less carbon atoms such as ethylene, propylene, 1-butene and isobutene; and vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether and n-butyl vinyl ether. The content of the comonomer units derived from α-olefins and/or vinyl ethers is preferably 1 to 20 mol %, more preferably 4 to 15 mol %, and still more preferably 6 to 13 mol % based on the constitutional units of the modified PVA. Particularly preferred is ethylene-modified PVA, because the fiber properties are enhanced when the comonomer unit is ethylene. The content of the ethylene units is preferably 4 to 15 mol % and more preferably 6 to 13 mol %.
The water-soluble PVA can be produced by a known method such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. Preferred are bulk polymerization and solution polymerization which are carried out in the absence or presence of a solvent such as alcohol. Examples of the solvent for the solution polymerization include lower alcohols such as methyl alcohol, ethyl alcohol and propyl alcohol. The copolymerization is performed in the presence of a known initiator, for example, an azo initiator or peroxide initiator such as a,a'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethyl-varelonitrile), benzoyl peroxide, and n-propyl peroxycarbonate. The polymerization temperature is not critical and a range of from 0 to 150 °C is recommended.
To suitably converting the microfine fiber-forming fibers, i.e., the sea-island fibers to the microfine fibers having an average fineness of 0.3 dtex or less, the sea/island volume ratio is preferably 15/85 to 70/30, more preferably 30/70 to 70/30, still more preferably 30/70 to 60/40, and particularly preferably 40/60 to 60/40. If the content of the sea component is 15% or more, the amount of the component to be removed by the dissolution in a solvent or the decomposition by a decomposer is sufficient, and a leather-like sheet with a sufficient flexibility is obtained. Therefore, the use of a treating agent such as a softening agent in an excessively large amount is avoided. The use of an excessively large amount of the treating agent is unfavorable, because various problems, for example, the reduction of mechanical properties such as a tear strength, the adverse affect of other treating agents, the adverse affect on touch, and the deterioration of durability are caused. If the content of the sea component is 70% or less, the amount of fibers made of the island component to be obtained after the removal of the sea component by the dissolution or decomposition is sufficient, to enhance the mechanical properties of the leather-like sheet to be obtained. In addition, since the amount of the component to be removed by the dissolution or decomposition is not so large, problems of the variation in quality due to the insufficient removal and the waste treatment of a large amount of the recovered removable component are not caused. Thus, the ratio within the above range is industrially preferred also in view of the productivity such as production speed and production cost. The microfine fiber-forming fibers are produced by a mix-spinning method in which the sea component polymer and the island component polymer are mixed in a predetermined ratio under melting and the molten mixture is supplied to a composite-spinning spinneret by an extruder, or a composite-spinning method in which the polymers are supplied to a composite-spinning spinneret in a predetermined ratio from different melting lines. The spinning temperature (temperature of spinneret) is selected depending upon the combination of the island component polymer and the sea component polymer to be used, and generally, about 180 to 350°C for the combination of polymers suitable for the present invention. The average fineness of the microfine fiber-forming fibers in an entangled nonwoven fabric is preferably 1 to 10 dtex in view of the denseness and strength of the entangled nonwoven fabric and the feeling and bulkiness after impregnation of the resin to be mentioned below. The number of island component polymers (number of islands) dispersed throughout the sea component polymer on a cross section of the microfine fiber-forming fibers is preferably 10 to 10000 and more preferably 150 to 10000 when produced by the mix-spinning method, and preferably 10 to 1000 when produced by the composite-spinning method. Within the above ranges, the cross-sectional shape of fibers during the melt spinning is stable and the spinning is continued stably (good spinnability), the composite fibers are stably drawn, the strength of the composite fibers is good, and the microfine fibers are formed easily by extracting the sea component.
In the production of known artificial leathers, microfine fiber-forming long fibers are cut into staples having a desired length and the staples are made into a fiber web. In the present invention, sea-island long fibers (microfine fiber-forming long fibers) may be made into a fiber web by a spun bonding method without cutting. In the present invention, the method of producing the fiber web is not particularly limited and any of known methods such as a carding method, a paper making method, a spun bonding method and a melt blown method may be employed.
Then, the fiber web is made into a fiber entangled body (three-dimensionally entangled fabric) by an entangling treatment. The entangling treatment may be carried out by a known method such as a needle punching method and a spun lacing method singly or in combination. In a particularly preferred method, spun microfine fiber-forming long fibers are drawn by about 1.5 to 5 times, mechanically crimped, and then cut into staple fibers having a length of about 3 to 7 cm; the staple fibers are carded and made into a fiber web having a desired density through a webber; and the obtained fiber webs are lapped into layers having a desired weight and then needle-punched using needles having one or more barbs in a density of about 300 to 4000 punch/cm² to entangle the fibers in the thickness direction. The mass per unit area of the fiber entangled body is varied according to the desired mass per unit area of final products, and preferably 200 to 1000 g/m² in view of the process passing properties and the workability in the subsequent steps.
Then, the fiber entangled body thus obtained is, if necessary, impregnated with a solution or dispersion of an elastic polymer by a known method such as a dip nip method, a knife coat method, a bar coat method, a roll coat method and a spray coat method. The impregnated elastic polymer is then coagulated by a dry method or a wet method. By coagulating the impregnated elastic polymer into a spongy form having a number of voids by selecting the coagulation conditions, the effect mentioned above is obtained. The elastic polymer is selected from known polymers which have been generally used in the production of leather-like sheets. Preferred examples thereof include polyurethane resin, polyester elastomer, rubber resin, polyvinyl chloride resin, polyacrylic acid resin, polyamide acid resin, silicone resin, modified products thereof, and copolymers or mixtures thereof.
To impregnate the elastic polymer into the fiber entangled body, an aqueous dispersion or organic solution thereof is preferably used. If using the aqueous dispersion, the impregnated elastic polymer is gelated at 50 to 150 °C (dry method) or solidified (dry coagulation method). If using the organic solution, the impregnated elastic polymer is coagulated by the dry method or wet methods. The elastic polymer can be coagulated into a porous form by suitably selecting the coagulation conditions. To coagulate the elastic polymer into a porous form, the coagulation by a wet method (wet coagulation method) is preferably used in the present invention, in which the fiber entangled body impregnated with the organic solution is immersed in a treating bath containing a poor solvent for the elastic polymer, to allow the elastic polymer to coagulate into a porous form. Water is preferably used as the poor solvent for the elastic polymer. For example, when polyurethane is used as the elastic polymer, a mixed treating bath of water and a good solvent for the elastic polymer such as dimethylformamide (DMF) is preferably used. By suitably selecting the fixing ratio, the state of coagulation, i.e., the size, number and shape of the voids to be formed are preferably controlled. If using the aqueous dispersion, it is preferred to additionally use a heat-sensitive gelling agent, because a uniform coagulation in the thickness direction is obtained by the dry method alone or in combination with steaming or far infrared heating. If using the organic solvent, more uniform voids are obtained by combinedly using a coagulation modifier. Examples of the organic solvent include dimethylformamide, dimethylacetamide, and dimethyl sulfoxide. By coagulating the impregnated elastic polymer into a porous form in the fiber entangled body, especially in the three-dimensionally entangled fabric, a leather-like sheet having a hand resembling natural leathers, particularly having properties suitable as the raw materials for game balls, hand gloves, insoles of shoes, sock liners of shoes, foot beds of sandals, and upholstery of vehicle seats is obtained.
In the present invention, polyurethane resins are preferably used as the elastic polymer in view of the hand of the composite body (fibrous substrate) made of the microfine fiber entangled body and the elastic polymer and the balance between properties. Examples of the polyurethane resin include various types of polyurethanes which are obtained by the reaction of at least one kind of polymer diol having an average molecular weight of 500 to 3000, at least one kind of organic diisocyanate and at least one kind of chain extender in a predetermined molar ratio. Examples of the polymer diol include polyester diol, polyether diol, polyester ether diol, polylactone diol, and polycarbonate diol. Examples of the organic diisocyanate include aromatic, alicyclic, or aliphatic organic diisocyanates such as tolylene diisocyanate, xylylene diisocyanate, phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate. Examples of the chain extender include low molecular weight compounds having at least two active hydrogen atoms such as diol, diamine, hydroxylamine, hydrazine, and hydrazide. The polyurethane may be a mixture of two or more kinds of polyurethane or may be a polymer composition added with a polymer such as synthetic rubber, polyester elastomer, and polyvinyl chloride.
The microfine fiber-forming fibers mentioned above are converted to bundles of microfine fibers after the impregnation of the solution or dispersion of the elastic polymer and the subsequent coagulation, or before the impregnation and coagulation. In the present invention, the conversion to microfine fibers is preferably conducted after the coagulation of the elastic polymer. Particularly, when the sea-island fibers are used, interstices are left between the bundles of microfine fibers and the elastic polymer after the removal of the sea component polymer. Therefore, the bundles of microfine fibers are loosely bound by the elastic polymer to provide a leather-like sheet with a softer hand. In contrast, when the conversion to microfine fibers is conducted before the impregnation and coagulation of the elastic polymer, the bundles of microfine fibers are strongly bound by the elastic polymer. Therefore, the hand of the leather-like sheet to be obtained tends to be harder. However, this method is preferred when a leather-like sheet with a higher content of fibers and a firm hand with dense feel are desired, because the tendency to make the feel hard can be reduced by reducing the content of the elastic polymer in the fiber entangled body. The average fineness of the bundles of microfine fibers is preferably 1 to 10 dtex.
The thickness of the fibrous substrate used in the present invention is not particularly limited and selected according to the intended use, for example, the kind and required properties of game ball and the hand favored by game players if intended to be used as a surface material of game balls, and preferably 0.4 to 3.0 mm. If being 0.4 mm or more, the mechanical properties such as tensile strength, tear strength and abrasion resistance which are bare requirements of the material for balls, the cover material of grip portion of racket, handle, and handrail, and the material for sport gloves are ensured. If being 3.0 mm or less, an excessively large weight of the final products using the leather-like sheet is avoided.
If intended to use as the material for gloves, the thickness is selected according to the kinds of gloves, required properties and hand favored by game players and not particularly limited. Generally, the thickness is preferably 0.2 to 1.2 mm and more preferably 0.3 to 0.9 mm, because a good fit to hand is easily obtained.
If intended to use as the material for insole of shoes, sock liner of shoes and foot bed of sandals, the thickness varies depending upon the use, purpose or structure of shoes and the material to be combined, and preferably 0.3 to 1.5 mm and more preferably 0.5 to 1.3 mm in view of the strength, cushion and touch under wearing.
If intended to use as the material for upholstery of sofas and vehicle seats, the in-plane strength and the surface strength are important. Although depending upon the room where sofas are placed, the concept in car design and drivers, the thickness is preferably 0.5 to 2.0 mm and more preferably 0.7 to 1.8 mm.
The mass ratio of the microfine fibers and the elastic polymer in the fibrous substrate is selected according to the properties and hand to be required and not critical in obtaining the effect of the present invention, and generally 35/65 to 90/10. If using as the material for game balls and gloves, the mass ratio is preferably 35/65 to 65/35 and more preferably 40/60 to 60/40 when the conversion to microfine fibers is conducted after the impregnation and coagulation of the elastic polymer, or preferably 65/35 to 95/5 and more preferably 60/40 to 90/10 when the conversion to microfine fibers is conducted before the impregnation and coagulation of the elastic polymer. In case of producing a semi-grain-finished leather-like sheet, the mass ratio is preferably 50/50 to 80/20 and more preferably 60/40 to 70/30.
A coating layer of an elastic polymer (not containing non-modified or modified hollow nanosilica particles) may be formed on the surface of the fibrous substrate as a part of the grain-finished portion. Various methods may be used to coat the surface of the fibrous substrate with an elastic polymer. For example, a dispersion, solution or melt of the elastic polymer is continuously applied to the surface of the substrate while adjusting the applied amount by a clearance between the surface of the fibrous substrate and a knife, bar or roll, and then the applied elastic polymer is coagulated into a film form by a dry method, In the present invention, the improving effect of the non-modified or modified hollow nanosilica particles on the wet grippability is sufficiently obtained even if the coating layer is non-porous. Therefore, the coating layer is not necessarily required to be porous, but if necessary, the coating layer may be made porous by coagulating the elastic polymer by a wet method. The details of the dry coagulation and wet coagulation are mentioned above. If the fibrous substrate is composed of the fiber entangled body and the elastic polymer, it is preferred to coagulate both the elastic polymer impregnated into the fibrous substrate and the elastic polymer for forming the coating layer simultaneously, because the drying after the coagulation can be done by a single step and a leather-like sheet in which the fibrous substrate and the coating layer are well united is easily obtained.
In another method of forming the coating layer on the surface of the fibrous substrate, a given amount of a dispersion or solution of the elastic polymer is applied to a transfer/release sheet such as film and release paper, the applied elastic polymer is coagulated into a film form or porous form in the same manner as above, the resultant film is dried and adhered to the fibrous substrate via an adhesive or by re-dissolving the surface thereof with a treating liquid containing a solvent for the elastic polymer, and then the transfer/release sheet is removed. In a still another method, a given amount of a dispersion or solution of the elastic polymer is applied to a transfer/release sheet in the same manner as above, the applied sheet is superposed on the fibrous substrate before or during the coagulation, and the coating layer is allowed-to unite with the fibrous substrate simultaneously with the coagulation.
The elastic polymer for forming the coating layer is preferably a resin having a certain degree of grippability rather than a slippery resin.
Examples thereof include synthetic rubber, polyester elastomer, polyvinyl chloride resin, and polyurethane resin. Like the elastic polymer to be impregnated into the fiber entangled body, the polyurethane resin is preferably used in view of the balance between the elasticity, softness and abrasion resistance.
The polyurethane resin for forming the coating layer is selected from the above polyurethane resins for impregnating into the fiber entangled body If necessary, a mixture of two or more kinds of the polyurethane resins may be used and a polymer composition mainly composed of polyurethane added with a polymer such as synthetic rubber, polyester elastomer and polyvinyl chloride may be also usable. In view of the resistance to hydrolysis and elasticity, a polyurethane resin having the polymer diol component mainly composed of a polyether-based polymer diol such as polytetramethylene glycol is preferably used.
The solution or dispersion of the elastic polymer for forming the coating layer may be added with an additive such as a colorant, a light resistant agent and a dispersant alone or in combination of two or more according to the final use of the product. Other additives such as a foaling agent for controlling the shape of porous form used in the dry foaming and a coagulation regulator used in the wet coagulation may be added alone or in combination of two or more according to the necessity.
The thickness of the coating layer is not particularly limited and selected according to the intended use, for example, the kind and required properties of game ball and the hand favored by game players if intended to be used as a surface material of game balls, and preferably 0.03 to 0.5 mm and more preferably 0.1 to 0.3 mm. If being 0.03 mm or more, the mechanical properties such as tensile strength, tear strength and abrasion resistance which are bare requirements of the material for game balls and the cover material of grip portion of racket, handle, and handrail are ensured. If being 0.5 mm or less, an excessively large weight of the products such as game ball, racket and handle is avoided.
It is important for maintaining the grippability to cover 10% or more of the surface of the fibrous substrate with the grain-finished portion. So, it is also preferred to cover 10% or more of the surface of the fibrous substrate with the coating layer. If the grain-finished portion covers less than 10% of the surface of the fibrous substrate, it is difficult to obtain a sufficient grippability in both dry and wet conditions. To cover 10% or more of the surface of the fibrous substrate with the coating layer, a known coating method is employed. The term "10% or more of the surface of the fibrous substrate is covered with the grain-finished portion" means that the area of the surface layer is 10% or more of the surface area of the leather-like sheet.
Then, to the surface of the fibrous substrate, or to the surface of the coating layer or both the surface of the coating layer and the exposed surface of the fibrous substrate if the coating layer is formed, a dispersion composed of the non-modified hollow nanosilica particles, the elastic polymer and a solvent or a dispersion composed of the modified hollow nanosilica particles, a solvent and optionally the elastic polymer is applied and dried to form the surface layer of the grain-finished portion. To cover the intended portion of the surface of the fibrous substrate with the grain-finished portion, know methods may be employed alone or in combination. For example, an excessive amount of the dispersion for forming the surface layer is applied to the fibrous substrate while controlling the applied amount to the required amount by the clearance between the fibrous substrate and a knife, bar or roll, and the applied dispersion is allowed to coagulate or solidify by a dry or wet method. Alternatively, a measured amount of dispersion is applied to the surface of the fibrous substrate by using a gravure coater, a comma coater or a spray coater and then coagulated or solidified by a dry or wet method. In the present invention, the sufficient improving effect on the wet grippability due to the non-modified or modified hollow nanosilica particles is obtained even if the grain-finished portion is non-porous. Therefore, although the grain-finished portion is not necessarily needed to be porous, the dispersion may be coagulated into a porous form by a wet method, if necessary. If the fibrous substrate is a composite body made of the fiber entangled body and the elastic polymer, it is preferred, particularly in obtaining the material for game balls, to coagulate both the elastic polymer impregnated into the fibrous substrate and the elastic polymer for forming the grain-finished portion simultaneously, because the drying after the coagulation can be done in a single step and a leather-like sheet in which the fibrous substrate and the grain-finished portion are well united is easily obtained.
When the dispersion containing the elastic polymer, other methods may be employed to form the grain-finished portion on the fibrous substrate, which include a method in which the dispersion is applied to a transfer/release sheet such as film and release paper while regulating the applied amount by a knife coater, etc., the applied elastic polymer is coagulated into a film form or porous form in the dry method or wet method mentioned above, and then the resultant film is dried, solidified and adhered to the fibrous substrate via an adhesive or via the elastic polymer on the surface thereof re-dissolved with a treating liquid containing a solvent for the elastic polymer; a method in which a transfer/release sheet applied with the dispersion is superposed on the fibrous substrate before the coagulation and solidification of the dispersion. In each method, by finally removing the transfer/release sheet, the grain-finished portion which is transferred with a pebbled pattern or a mirror surface formed on the transfer/release sheet is obtained (transfer/release method).
The elastic polymer for forming the grain-finished portion is preferably a resin having a certain degree of grippability rather than a slippery resin. Examples thereof include synthetic rubber, polyester elastomer, polyvinyl chloride resin, and polyurethane resin. Like the elastic polymer to be impregnated into the fiber entangled body, the polyurethane resin is preferably used in view of the balance between the elasticity, softness and abrasion resistance.
The polyurethane resin for forming the grain-finished portion is selected from the above polyurethane resins for impregnating into the fiber entangled body. If necessary a mixture of two or more kinds of the polyurethane resins may be used and a polymer composition mainly composed of polyurethane added with a polymer such as synthetic rubber, polyester elastomer and polyvinyl chloride may be also usable. In view of the resistance to hydrolysis and elasticity, a polyurethane resin having the polymer diol component mainly composed of a polyether-based polymer diol such as polytetramethylene glycol is preferably used.
The dispersion of the non-modified or modified hollow nanosilica particles and the elastic polymer to be applied to the fibrous substrate may be added with an additive such as a colorant, a light resistant agent and a dispersant alone or in combination of two or more according to the final use of the product. Other additives such as a foaming agent for controlling the shape of porous form used in the dry foaming and a coagulation regulator used in the wet coagulation may be added alone or in combination of two or more according to the necessity.
The grain-finished portion is formed on the surface of the fibrous substrate, in addition to by a methods of applying the dispersion of the non-modified or modified hollow nanosilica particles and elastic polymer and a transfer/release method using the dispersion each being mentioned above, by a method in which a coating layer of the elastic polymer (not contain the non-modified or modified hollow nanosilica particles) is first formed and then a coating liquid containing the non-modified or modified hollow nanosilica particles and the elastic polymer is applied to the surface of the coating layer to form a surface layer of the non-modified or modified hollow nanosilica particles and the elastic polymer By this method, a surface layer containing the non-modified or modified hollow nanosilica particles only in the outermost surface of the grain-finished portion is formed.
When the grain-finished portion is composed of only a layer containing the non-modified or modified hollow nanosilica particles and the elastic polymer (surface layer), the thickness of the grain-finished portion is not particularly limited and selected according to the intended use, for example, the kind and required properties of game ball and the hand favored by game players if intended to be used as a surface material of game balls, and preferably 0.05 to 0.5 mm more preferably 0.1 to 0.3 mm. If being 0.05 mm or more, the mechanical properties such as abrasion resistance which are bare requirements of the material for game balls and the cover material of grip portion of racket, handle, and handrail are ensured. If being 0.5 mm or less, an excessively large weight of the products such as game ball, racket and handle is avoided.
When the grain-finished portion is composed of the surface layer containing the non-modified or modified hollow nanosilica particles and the elastic polymer and the coating layer, the thickness of the surface layer is preferably 0.001 to 0.1 mm and more preferably 0.003 to 0.08 mm, the thickness of the coating layer is preferably 0.03 to 0.5 mm and more preferably 0.08 to 0.3 mm. The total thickness of the surface layer and the coating layer is preferably 0.05 to 0.5 mm and more preferably 0.1 to 0.3 mm.
When the grain-finished portion is composed of the surface layer containing the non-modified or modified hollow nanosilica particles but not containing the elastic polymer and the coating layer, the thickness of the surface layer is preferably 0.00003 to 0.008 mm and more preferably 0.00005 to 0.005 mm and the total thickness of the surface layer and the coating layer is 0.05 to 0.5 mm and more preferably 0.1 to 0.3 mm.
In addition to the requirements by the final use, the balance between the thickness of the fibrous substrate and the thickness of the whole leather-like sheet should be considered when determining the preferred thickness of the grain-finished portion. From the inventors' experience, the thickness ratio of the grain-finished portion and the fibrous substrate is preferably 0.01:99.9 to 60:40. If the ratio of the grain-finished portion is 0.01 or more, the grain-finished portion is sufficiently perceived by touch. If the ratio is less than 60, a rubbery feel of the leather-like sheet attributable to the grain-finished portion is avoided.
A pebbled pattern (pebble-valley pattern) may be formed on the surface layer and the coating layer of the grain-finished portion. A preferred pebbled pattern and a method of forming it will be described below. The grain-finished portion may be colored. The coloring treatment may be conducted either before or after forming the pebbled pattern. For example, if the pebbled pattern is formed by an emboss roll, the coloring treatment may be made before or after the embossing treatment. However, since the embossing treatment is usually accompanied with heating and possibly discolors the surface layer and the coating layer, it is preferred to take a measures to prevent the discoloration due to heating prior to the embossing treatment. Pigments are most preferably used as the colorant in view of heat resistance, light resistance and fastness to abrasion. The coloring treatment is performed by a gravure method, a dyeing method, a reverse coat method or a direct coat method, with a gravure method being most preferred in view of productivity and costs.
When the coating layer is formed on a part or whole part of the surface of the fibrous substrate, the surface layer of the grain-finished portion is formed by applying a dispersion containing the non-modified or modified hollow nanosilica particles, the elastic polymer (binder) and a solvent to the surface of the coating layer or both the surface of the coating layer and the exposed surface of the fibrous substrate and drying the applied dispersion.
The hollow nanosilica particles are highly dispersible silica particles having a densified silica shell with a balloon structure (hollow structure) and are produced by, for example, the methods described in JP 2005-263550A and JP 2006-256921A . The primary particle size of the hollow nanosilica particles is 50 to 150 nm, the thickness of the silica shell is 5 to 15 nm when measured under a transmission electron microscope (TEM), the specific surface area measured by BET method is 150 to 300 m²/g, the pore volume by a mercury porosimetry is 9000 to 13000 mm³/g, the bulk density is 0.03 to 0.07 g/mL, and the shell pore size is 5 nm or less (less than the direct observation limit under TEM) and preferably 2 nm or less when measured by BET method.
As described above, the hollow nanosilica particles may be surface-modified particles having the surface modified with a surface modifier. The surface modified particles are obtained, for example, by the method described in Patent Document 9 in which a surface modifier is bonded to the hollow nanosilica particles via hydroxyl groups (-OH) on the surfaces thereof. Since the aggregation of primary particles is prevented by the surface modification the dispersibility of the particles in the dispersion medium is improved. The active groups of the elastic polymer in the fibrous substrate and/or the coating layer react with the isocyanate groups of the surface modifier. Therefore, the adhesion between the surface layer and the fibrous substrate and/or coating layer is enhanced even if the dispersion for forming the surface layer does not contain the elastic polymer (binder).
Examples of the surface modifier include isocyanate compounds, amine compounds, vinyl compounds, epoxy compounds, methacryloxy compounds, imide compound, compounds having alkyl group, compounds having aryl group, and compounds having UV-sensitive functional group. The UV-sensitive functional group is a functional group such as vinyl group, styryl group and acryl group which cause the reaction upon exposure to ultraviolet rays (UV). Preferred are the compounds having at least one group selected from isocyanate group, alkyl group, aryl group, and the UV-sensitive functional group. Particularly preferred are the isocyanate compounds because of a uniform dispersibility on the surface of the leather-like sheet, a long durable adhesion, a high reactivity with the polyamide resin, polyester resin and polyurethane resin which constitute the fibrous substrate, and its easy availability. As described in Patent Document 9, the surface-modified particles have been developed so as to improve the dispersibility of the hollow nanosilica particles. In contrast, the surface-modified particles contribute to the long-lasting grippability in the present invention. The surface-modified particles are commercially available from Grandex Co., Ltd. as "Nanotouch" (trademark).
The elastic polymer which is optionally contained in the dispersion for forming the surface layer is selected from the above elastic polymers for impregnating into the fibrous substrate, with the polyurethane resin mentioned above being preferred. Examples of the solvent for the dispersion include hydrocarbons such as n-hexane and cyclohexane; aliphatic alcohols such as methanol, ethanol and propanol; aromatic hydrocarbons such as toluene and xylene; ketones such as acetone; and amides such as dimethylformamide. These solvents may be used alone or in combination of two or more. Il the modifying group is not reactive to water, water may be used as the dispersion medium.
The solid content (total of the non-modined or modified hollow nanosilica particles and the elastic polymer) of the dispersion for forming the surface layer is preferably 5 to 20% by mass. If the elastic polymer is used, the content of the non-modified or modified hollow nanosilica particles is preferably 5 to 15 parts by mass per 100 parts by mass of the elastic polymers.
If the hollow nanosilica particles are not surface-modified, the dispersion is applied to the surface of the fibrous substrate and/or surface of the coating layer preferably in an amount (dry basis after removing the solvent, i.e, non-surface-modified particles) of 0.02 to 0.8 g/m². If the hollow nanosilica particles are surface-modified, the applied amount (dry basis after removing the solvent, i.e., surface-modified particles) is preferably 0.05 to 1 g/m² and more preferably 0.05 to 0.5g/m². The application is conducted by a gravure coat method, a reverse coat method or a direct coat method, with the gravure coat method being preferred, although not limited hereto. After the application, the solvent is removed by a known method thereby to obtain the leather-like sheet of the present invention in which the surface layer composed of the non-modified or modified hollow nanosilica particles and the elastic polymer is formed on the surface of the fibrous substrate and/or surface of the coating layer. With such a surface layer, the leather-like sheet of the present invention exhibits a good wet grippability even when the surface is not made porous. The effect of improving the wet grippability by the surface-modified particles is also obtained when the above dispersion is applied to the surface of a substrate such as wood, stone, metal, plastics, paper and natural leathers in place of the surface of the fibrous substrate or the coating layer.
In the present invention, it is preferred that 10% or more of the surface of the fibrous substrate is covered with the grain-finished portion. If 100% of the surface of the fibrous substrate is covered with the grain-finished portion, a grain-finished leather-like sheet is obtained, which is suitable as the surface material for game balls used in volleyball (indoor), beach volley ball, hand ball, soccer, rugby, and American football; the material for the sport gloves used in golf, baseball and marine sports; the material for insole and sock liner of shoes; the material for foot bed of sandals; the material for upholstery of vehicle seats; and the materials for other products requiring the wet grippability such as floorings, various kinds of grips and soles of shoes. The present invention will be described while taking the surface material of game balls such as volleyball as an example.
The game ball such as volleyball is basically structured from the inside, for example, by a tube (bladder usually made of rubber) which is inflatable with air, a cover layer (usually made of rubber), a reinforcing layer made of wound threads and a surface cover layer. The construction of the game ball of the present invention is not particularly limited as long as the surface cover layer is made of the leather-like sheet and the game ball may have any of known constructions. The surface material of game balls such as volleyball is basically the same as the leather-like sheet described above. Referring to Fig. 1, it is preferred to form a number of continuous pebbles and a number of discontinuous valleys on the surface of a resin layer 1 (the surface layer, the surface layer and coating layer, or the coating layer) which is formed on a fibrous substrate 2. The term "discontinuous valleys" means a number of isolated valleys (depressed portions) which are formed, for example, by pressing a flat sheet with a surface having a number of isolated pebbles disposed with intervals. The discontinuous valleys are formed by any of known methods as long as the desired valleys are stably formed, for example, by embossing the surface of the resin layer 1 with an emboss roll having a desired pebbled pattern, or by casting and solidifying a liquid containing the elastic polymer on a release paper having a desired pebbled pattern and laminating the obtained sheet of the elastic polymer to the surface of the fibrous substrate.
It is preferred that the vertical projection area of each valley is 1 to 5 mm², the average distance between the adjacent pair of valleys is 0.5 to 3 mm, and the valley depth is 50 to 500 µm. In the method using a release paper mentioned above, the depth of the valleys on the surface layer, the surface and coating layers or the coating layer is limited for the production limitation of the release paper. In addition, when a solution of the elastic polymer is applied to a release paper having discontinuous pebbles, the tendency of forming voids around the pebbles (corresponding to the valleys of surface layer, the surface and coating layers, or the coating layer) increases as the pebble depth increases. Therefore, such method is preferred for forming the valleys having a depth of less than 150 µm. In the method of embossing with a emboss roll, the dept is not so limited because the use of an emboss roll having pebbles with a depth corresponding to the valley depth to be formed is sufficient for the purpose. Therefore, in view of the industrial productivity, the pebble-valley pattern is preferably formed by the method using an emboss roll rather than the method using a release paper. In the method of forming the valleys using an emboss roll, the conditions such as the height of pebbles on the roll, the roll temperature, the embossing pressure and the embossing time may be suitably set. To obtain the valleys with a desired depth, the height of pebbles on the roll is preferably 80 to 700 µm, the roll temperature is preferably 150 to 180 °C, the embossing pressure (line pressure) is preferably 5 to 50 kg/cm, and the processing speed is preferably 0.5 to 5 m/min, although not particularly limited thereto. When a pebble-valley pattern is formed by an emboss roll, after the impregnation of the elastic polymer into the fiber entangled body, the same and/or different kinds of elastic polymer may be further impregnated and coagulated into a porous form, because the emboss processing is made successfully.
The game balls used in ball games such as volleyball game are required to have a surface structure which allows at least one valley to come into contact with the tips of fingers of a game player during handling a ball unconsciously. To ensure this, the valley depth is preferably 50 to 500 µm and more preferably 50 to 300 µm. If less than 50 µm, the ball comes to be slippery when wet with sweat or water to lose a toss controlling effect and make it difficult to obtain an intended flight curve of the serve. In addition, an aesthetically pleasing appearance is not obtained to decrease the commercial value. If exceeding 300 µm, the grippability when wet with sweat or water is increased and the toss control is enhanced. If exceeding 500 µm, the ball is gripped excessively by the tips of fingers to reduce the ball control. The "valley depth" referred to herein is an average of 10 distances (D) from the top surface of the pebbles on the coating layer to the deepest portion of the valleys as shown in Fig. 3, which are measured on a photograph of the cross-sectional taken along the thickness direction.
The vertical projection area of the valley on the surface of the resin layer 1 is preferably 1 to 5 mm² and more preferably 2 to 3 mm². If exceeding 5 mm², the toss control is deteriorated because the ball is gripped by the tips of fingers strongly. In addition, the abrasion resistance of the ball is reduced. If less than 1 mm², the ball is little gripped by fingers and becomes slippery when wet with sweat or water, thereby deteriorating the toss control. In addition, the ball is less aesthetic to reduce the commercial value. On a cross section passing the deepest portion of the valley on the surface of the resin layer 1, the boundary (B) between the valley and the flat portion is defined by the portion at which the angle between the perpendicular of the flat portion and the tangent of the valley surface is 45° as shown in Fig. 4, when the surface of the valley and the surface of the adjacent pebble is connected by a continuous curve. When the surface of the valley and the surface of the adjacent pebbles is connected in a broken line, the boundary (B) between the valley and the flat portion is defined by the broken portion as shown in Fig. 5. The vertical projection area of the valley" is defined by the vertical projection area of the region surrounded by the boundary onto the surface of the resin layer 1 (shown by X in Figs. 4 and 5),
The total of the vertical projection areas of the valleys is preferably 3 to 30% and more preferably to 25% of the total surface of the resin layer 1. If less than 3%, the toss control is poor and the intended flight path of the serve is difficult to obtain. In addition, the ball is less aesthetic to reduce the commercial value. If exceeding 30%, the toss control is deteriorated because the ball is gripped by the tips of fingers strongly. The cross-sectional shape of the valley of the resin layer 1 taken along the thickness direction is preferably bow, semicircle or trapezoid, and the three-dimensional shape is preferably hemisphere, frustum or prismoid. The shape of "hemisphere" is not necessarily needed to be an exact hemisphere and means that the shape is nearly hemisphere. The shape of "trapezoid" is also not necessarily needed to be an exact trapezoid and means that the shape is nearly trapezoid, for example, the base line may be straight or slightly convexed. The same is equally applied to the shapes of blow, semicircle, frustum and prismoid. By making the valleys hemisphere or trapezoid, an extremely delicate grip by the tips of fingers is obtained upon tossing the ball and a good ball control in the serve and other plays are obtained in a good balance.
The average distance between the valleys on the surface of the resin layer 1 is preferably 0.5 to 3 mm. If less than 0.5 mm, the soft feel, cushioning feel, touch and surface abrasion resistance are poor because the valleys are so close to each other to make the shape of pebbles partly excessively sharp. If exceeding 3 mm, the fitting feel and the grippability are poor. The average distance between the valleys is more preferably 1 to 2 mm. The average distance between the valleys is determined by randomly selecting 10 valleys from an electron microphotograph of the surface, measuring the shortest distance between a selected point on the circumference of the valley and the circumference of an adjacent valley, and averaging 10 measured values. A closed curve defined by the boundary B is taken as the circumference of the valley
On the pebbles (primary pebbles) on the surface of the resin layer 1, secondary valleys 5 having a depth which is less than that of the valleys (primary valleys) mentioned above and within a range of 10 to 100 µm and secondary pebbles 6 may be further formed (Fig. 2). The pattern of the secondary valley-pebble is not strictly limited. In view of obtaining a non-slip effect uniformly in any directions, however, it is preferred to array the valleys and pebbles into a grating pattern, a concentric circular pattern, a radial pattern, etc. (see Figs. 6a to 6h), in which the valleys and pebbles are arrayed along lines or curves extending in two or more direction, along lines and curves randomly arranged, or along a combination thereof. Like the primary valleys, the secondary valleys may be discontinuous. In view of obtaining a good grippability when wet with sweat and an aesthetically pleasing appearance, the secondary valleys preferably have a discontinuous shape like the primary valleys.
The depth of the secondary valleys is preferably less than the depth of the primary valleys and within a range of 10 to 100 µm, more preferably 20 to 70 µm. If being 10 µm or more, balls are easy to grip with tips of fingers and the toss control is good. If being 100 µm or less, the abrasion resistance and surface touch are good, and the adhesion of dirt can be prevented.
The secondary valleys are preferably discontinuous and the vertical projection area thereof is preferably 0.01 to 1 mm². The total vertical projection area of the secondary valleys is preferably 1 to 30% of the surface area of the resin layer 1. If being 0.01 to 1 mm², a smooth surface touch is obtained. If the secondary valleys are discontinuous and the ratio of the total vertical projection area thereof is 1 to 30%, balls are easy to well grip with the tips of fingers to further enhance the grippability. In addition, the straight flight of ball is improved and the intended flight path is easy to obtain particularly in the serve with a long flight distance. The ratio is preferably 3 to 20%. The secondary valley-pebble pattern is preferably formed on the top surface of pebble rather than side surface of pebble (see Fig. 2).
The secondary pebble-valley pattern is formed by a method in which the secondary pebble-valley pattern is formed simultaneously with the valleys using a release paper capable of forming both the valleys and the secondary pebble-valley pattern or a method in which the secondary pebble-valley pattern is embossed by an embossing treatment, with the method by the embossing treatment being preferred to the method using a release paper in view of industrial productivity. By suitably selecting the conditions such as the pebble height on an emboss roll, the emboss roll temperature, the emboss pressure and the embossing time, a desired secondary pebble-valley pattern is formed by using an emboss roll. These conditions are not particularly limited and, for example, the pebble height on an emboss roll is 80 to 700 µm, the roll temperature is 150 to 180 °C, the press pressure is 5 to 50 kg/cm, and the embossing time is 10 to 120 s. It is economically preferred to use an emboss roll capable of forming both the discontinuous valleys and the secondary pebble-valley pattern because the discontinuous valleys and the secondary pebble-valley pattern are formed simultaneously in a single embossing treatment.
Game balls, particularly volleyballs, which have a surface layer made of the leather-like sheet having a number of the discontinuous valleys mentioned above exhibit an extremely good ball control because the tips of ringers comes into good contact with the surface of ball when tossing it. In addition, the grippability in wet condition (when wet with sweat or water) is further improved by a synergetic effect of the secondary pebble-valley pattern and the surface layer holding the hollow nanosilica particles. Further, the ball control can be retained throughout the game, because the serve is prevented from moving out of the flight path and the flying speed is gradually reduced. Still further, the game balls have an aesthetically pleasing appearance. The leather-like sheet of the present invention which is produced by forming a surface layer or both a coating layer and a surface layer on the surface of the fibrous substrate and then forming a pebble-valley pattern on the surface layer or the leather-like sheet which is produced by forming a pebble-valley pattern on the surface of a coating layer and then forming a surface layer using a dispersion of the hollow nanosilica particles as mentioned above is particularly preferred as the surface material of a ball such as volleyball and beach volleyball which is hit directly by a hand. (2) Suede-Finished or Semi-Grain-Finished Leather-Like Sheet
The suede-finished leather-like sheet of the present invention is composed of the fiber entangled body (fibrous substrate) and the raised microfine fibers on the surface thereof. The fiber entangled body is made of bundles of microfine fibers having an average fineness of 0.3 dtex or less and an elastic polymer impregnated into the inside of the fiber entangled body. The raised surface (both the surface of the fibrous substrate on which the raised fibers are formed and the surface of the raised microfine fibers) holds the hollow nanosilica particles. On at least one surface of the fibrous substrate of the semi-grain-finished leather-like sheet of the present invention, a coating portion and a raised portion composed of the fibers constituting the fibrous substrate are mixedly present. The raised portion (both the surface of the fibrous substrate on which the raised fibers are formed and the surface of the raised microfme fibers) holds the hollow nanosilica particles.
In the production of the suede-finished or semi-grain-finished leather-like sheet, the fibrous substrate is made into a raised sheet having the raised microfine fibers by raising at least one surface thereof. The length of the raised fibers may be adjusted by changing the buffing or blushing conditions such as a grain size of sandpaper for buffing treatment, a buffing speed and a pressure of pressing sandpaper onto the surface of the fibrous substrate. The raised microfine fibers may be formed on one or both entire surfaces of the sheet or may be spotted on a part of one or both surfaces as long as the suede or nubuck appearance and touch are obtained.
To obtain bent wrinkles and feel more closely resembling natural leathers, the raised fiber sheet may be in the following structures: a structure having top and back surfaces different in fiber finenesses which is obtained by superposing two or more nonwoven fabrics made of fibers with different finenesses and then impregnating the elastic polymer into the superposed body; a multi-layered structure in which sheets obtained in the same manner except for the difference in finenesses are bonded by an adhesive; and a waterproof structure in which at least one layer of two or more layered laminate, except for the surface layer, is made of a waterproof film. To obtain a desired appearance, the raised fiber sheet may be colored with a colorant such as dye and pigment. To obtain a desired feel and function, the raised fiber sheet may be added, alone or in combination, with known treating agents such as a softener, a slime agent, a water repellent, a hydrophilic agent, a light-resistant agent, an antioxidant, a stainproofing agent, a fire retardant, an antimicrobial agent, an antifungal agent, and a fragrant agent. The treating agents may be added after the stage of adding the hollow nanosilica particles as long as the grippability aimed in the present invention is not adversely affected.
The pebble-valley pattern may be formed by embossing before or after adding the hollow nanosilica particles. By such embossing, a dichromatic appearance or an appearance provided with patterns, figures or stripes of blood vessels found in natural leathers is obtained and the feel of raised fibers can be changed, to give a variety of leather-like sheets.
Then, the hollow nanosilica particles are applied to the surface of the raised fiber sheet. The hollow nanosilica particles may be surface-modified. The details of the non-modified and modified hollow nanosilica particles are described above.
The non-modified or modified hollow nanosilica particles are applied to the raised surface or the raised portion of the raised fiber sheet by a selective applying method such as a gravure coat method, a spray coat method, a knife coat method and a bar coat method or by an impregnation/drying method for applying the particles to the whole layer in the thickness direction of the fibrous substrate, each using a dispersion thereof in a dispersion medium such as water and organic solvent selected from an aliphatic alcohol such as methanol and ethanol, an aliphatic hydrocarbon such as n-hexane, an aromatic hydrocarbon such as toluene and xylene, and a ketone such as acetone, methyl ethyl ketone (MEK) and methyl isobutyl ketone (MIBK). The application method is not strictly limited thereto, and an application method using an gravure roll is preferably used in the production of sport gloves and working gloves which need the surface grippability much more, because the application amount is easily controlled and the production is stable. A 30 to 300 mesh gravure roll is generally used and a 50 to 200 mesh gravure roll is preferably used because of a good transfer to the raised surface of the raised fiber sheet. A coarse mesh roll capable of transferring a necessary application amount at once may be used to obtain a desired grippability, and a finer mesh roll which transfers a necessary application amount in several portions may be used when an elegant feel of the raised surface is further intended. Thus, the application method is selected according to necessity.
The solid concentration of the dispersion of the non-modified or modified hollow nanosilica particles is preferable 1 to 10% by mass. If the solid concentration is excessively low, an excess amount of dispersion penetrates into the inside of the suede-finished leather-like sheet. If the solid concentration is excessively high, the adhered amount of the hollow nanosilica particles increases, thereby likely deteriorating the appearance of raised fibers and the feel or rapidly reducing the amount of primary particles of the non-modified or modified hollow nanosilica particles during the application operation. Thus, the adhered state of the hollow nanosilica particles intended in the present invention is difficult to obtain if outside the preferred concentration range. The application amount to the raised surface is preferably 0.02 to 0.8 g/m² and more preferably 0.05 to 0.5 g/m² on dry basis (after removal of solvent), because a soft feel and a good grippability in both dry and wet conditions are obtained without deteriorating an elegant feel of raised fibers and a color shade. After the application, the solvent is removed by a known method to obtain the suede-finished leather-like sheet having a raised surface holding the non-modified or modified hollow nanosilica particles. The application amount described above is the amount per one surface. When both surfaces of the suede-finished leather-like sheet are applied with the non-modified or modified hollow nanosilica particles, each surface is preferably applied in an amount of 0.02 to 0.8 g/m². The applied amounts to both surfaces may be the same or different.
The non-modified or modified hollow nanosilica particles are applied to the fibrous substrate after or before raising the surface by the method described above. Generally, the efficiency is good when applied after raising because the applied non-modified or modified hollow nanosilica particles are all maintained on the surface of the leather-like sheet. However, the non-modified or modified hollow nanosilica particles may be applied in any stages of the production as long as the applied particles are retained in final product. The production of the leather-like sheet optionally includes a step of applying the elastic polymer to the surface for forming the coating portion, a step of embossing the surface, etc. The non-modified or modified hollow nanosilica particles may be applied in any stages of the production including these optional steps.
The suede-finished leather-like sheet thus obtained is suitably used as a material having a good grippability and a high quality appearance and touch particularly as a material for the production of port gloves, working gloves, sport shoes and sandals, and additionally, suitable as a material for furniture utilizing the unique touch of the present invention, other types of gloves and shoes and sock liner of shoes.
The semi-grain-finished leather-like sheet of the present invention has the coating portion on the fibrous substrate, i.e. the portion made of the elastic polymer on the surface of the fibrous substrate which substantially covers the fibrous substrate. The words "substantially cover" means that the raised fibers and raised bundles of fibers each having a writing effect do not penetrate though and do not project out of the coating portion of the elastic polymer on the fibrous substrate. Therefore, lying fibers or bundles of fibers (raised fibers and raised bundles of fibers each having no writing effect) may be present on the surface of coating portion. Such a substantially covered structure is obtained by various method, for example, by gravure-printing or spray-coating a dispersion, solution or melt of the elastic polymer on the surface of the fibrous substrate. The gravure printing is generally carried out by using 50 to 200 mesh gravure roll, although not limited thereto. A roll with various designs may be used for application.
The elastic polymer for forming the coating portion is preferably a resin having a certain degree of grippability rather than a slippery resin. Examples thereof include synthetic rubber, polyester elastomer, polyvinyl chloride resin, and polyurethane resign. Like the elastic polymer to be impregnated into the fiber entangled body, the polyurethane resin is preferably used in view of the balance between the plasticity softness and abrasion resistance.
The polyurethane resin for forming the coating portion may be the same as or different from the polyurethane resins mentioned above for impregnating into the fiber entangled body. Preferably, the polyurethane for the coating portion and the polyurethane for impregnating into the fiber entangled body are selected from the same kind of polyurethane resins in view of coherence. If necessary, a mixture of two or more kinds of the polyurethane resins may be used and a polymer composition mainly composed of polyurethane added with a polymer such as synthetic rubber, polyester elastomer and polyvinyl chloride may be also usable. In view of the resistance to hydrolysis and elasticity, a polyurethane resin having the polymer diol component mainly composed of a polyether-based polymer diol such as polytetramethylene glycol is preferably used.
10 obtain a desired appearance, the elastic polymer for forming the coating portion may be colored with a colorant such as dye and pigment. The obtain a desired feel and function, the elastic polymer may be added, alone or in combination, with known treating agents such as a slime agent, a water repellent, a hydrophilic agent, a light-resistant agent, an antioxidant, a stainproofing agent, a fire retardant, an antimicrobial agent, an antifungal agent, and a fragrant agent. In addition, the elastic polymer may be included with the hollow nanosilica particles and/or the surface-modified particles described above.
The present invention includes the following four types of coating portions (1) to (4). The grippability aimed in the present invention can be obtained in any types as long as the raised portion holds the non-modified or modified hollow nanosilica particles. Preferred are the coating portions (2), (3) and (4) because a synergetic effect is obtained.

(1) The coating portion contains the elastic polymer with substantially no non-modified and modified hollow nanosilica particles.
(2) The coating portion contains the elastic polymer and the non-modified hollow nanosilica particles.
(3) The coating portion contains the elastic polymer and the modified hollow nanosilica particles.
(4) The modified hollow nanosilica particles adhere to at least a part of the surface of the coating portion made of the elastic polymer.

Each type of the coating portion will be described below in detail.
In the coating portion (1), the aimed grippability is attributable to the frictional resistance of the raised portion of the fibrous substrate, and the area ratio (A/B) of the coating portion (A) and the raised portion (B) is preferably 10/90 to 60/40 and more preferably 20/80 to 50/50. If exceeding 60/40, the grippability may be unfavorably reduced. If less than 10/90, the suede-finished appearance is obtained in place of the aimed semi-grain-finished appearance.
In the coating portions (2) and (3), the aimed grippability is attributable to both the raised portion and the coating portion, and the area ratio (A/B) is preferably 10/90 to 90/10 and more preferably 20/80 to 80/20. If being outside the above range, the semi-grain-finished appearance is not obtained. If less than 10/90, the suede-finished appearance is resulted. If exceeding 90/10, the writing effect is lost to make the appearance grain-finished.
The coating portion (1), (2) or (3) is formed by applying a solution of the elastic polymer optionally containing the dispersed non-modified or modified hollow nanosilica particles to the fibrous substrate having raised fibers to which the non-modified or modified hollow nanosilica particles adhere. The coating portion (1), (2) or (3) may be embossed, if necessary. If being embossed, the step of applying the elastic polymer and the step of embossing may be carried out in this order or reverse order.
The concentration of the solid component (total of the non-modified or modified hollow nanosilica particles and the elastic polymer) of the solution of the elastic polymer containing the dispersed non-modified or modified hallow nanosilica particles for forming the coating portion (2) or (3) is preferably 5 to 20% by mass. The content of the non-modified or modified hollow nanosilica particles is preferably 5 to 15 parts by mass per 100 parts by mass of the elastic polymer.
In the coating portion (4), the surface-modified hollow nanosilica particles adhere to at least a part of its surface. If not surface-modified, the adhesion strength between the elastic polymer and the hollow nanosilica particles is low and the hollow nanosilica particles fall off from the product made from the leather-like sheet during its use, thereby reducing the synergetic effect of improving the grippability. The aimed grippability is, as in the case of the coating portions (2) and (3), attributable both the raised portion and the coating portion and the area ratio (A/B) is preferably 10/90 to 90/10 and more preferably 20/80 to 80/20. If being outside the above range, the semi-grain-finished appearance is not obtained. If less than 10/90, the suede-finished appearance is resulted. If exceeding 90/10, the writing effect is lost to make the appearance grain-finished.
As in the case of forming the coating portions (1) to (3), the coating portion (4) is formed by applying the elastic polymer to the raised fiber sheet having the surface-modified hollow nanosilica particles and then applying the surface-modified hollow nanosilica particles. If necessary, the coating portion (4) may be embossed. If being embossed, the step of applying the elastic polymer and the step of embossing may be carried out in this order or reverse border.
The coating portion (4) is also formed by a step (a) of forming the raised fibers on the fibrous substrate, a step (b) of applying the elastic polymer, an optional step (c) of embossing, and a step of applying the surface-modified hollow nanosilica particles to the surface of the obtained leather-like sheet. The steps (a), (b), and (c) may be conducted in any of the following orders: (a) → (b) → (c), (a) → (c) → (b), (b) → (a) → (c), (b) → (c) → (a), (c) → (a) → (b), and (c) → (b) → (a). By changing the order, various appearances are obtained, for example, an appearance with highlighted embossed pattern, a dichromatic appearance having the elastic polymer only on the pebbles in the embossed pattern and an appearance having the raised fibers on the pebbles and no raised fibers on the valleys. Thus, the type of coating portion can be varied according to the needs of customers.
Examples of the solvent for the solution of the elastic polymer for forming the coating portion include cyclohexane, ketone such as acetone, amide such as dimethylformamide, and toluene. Theses solvents may be used alone or in combination of two or more.
The semi-grain-finished leather-like sheet thus obtained is suitably used as the material having a grippability and a high quality appearance having a writing effect and touch, for examples, the material for producing sport gloves, working gloves and foot beds of sport shoes and sandals.

EXAMPLES

The present invention will be decried in more detail with reference to the examples. However, it should be noted that the scope of the present invention is not limited thereto. The "part(s)" and "%" used in the examples is based on the mass unless otherwise noted. Each evaluation was carried out by the following method.

(1) Grippability of Volleyball in Wet Condition

Ten players exercised in volleyball (indoor) in mummer for a long period of time to evaluate the grippability when handling the ball with hands and fingers wet with sweat. The evaluation was made according to the following ratings A to C. Most frequent rating of ten players was employed as the evaluation result of wet grippability.

A: Sufficient grippability without slip of hand.
B: Little slip of hand but insufficient grippability.
C: Frequent slip of hand and lack of grippability.

(2) Grippability of Sandal in Wet Condition

Sandals having a foot bed made of a leather-like sheet were produced. Then testers wore sandals on their bare feet and made a walking test. The walking test was done on the sandals in dry condition and on the sandals in wet condition after immersing the sandals in water for one minute to allow water to soak into the leather-like sheet sufficiently. The results were evaluated by the following ratings A to C. Most frequent rating of ten testers was employed as the evaluation result of grippability.

A: Easy to walk with sufficient grip without slip of feet.
B: Little slip of feet but insufficient grippability
C: Hard to walk because of frequent slip of feet.

(3) Percentage of Covering (area ratio of coating portion)

On an electron photomicrograph (x 100) of the surface of leather-like sheet, the elastic polymer visually perceived was colored and the area ratio of the colored portion was determined.

EXAMPLE 1

Sea-island fibers having a fineness of 15 dtex were produced by melt-spinning 50 parts of polyethylene (sea component) and 50 parts of 6-nylon (island component) from a single melting line. The sea-island fibers were drawn by 2.5 times, crimped and cut into 51-mm length. The obtained staples were carded and made into a fiber web by a crosslap webber. The fiber webs were superposed and needle-punched to obtain a fiber entangled body having a mass per unit area of 650 g/m².
The fiber entangled body was impregnated with a 13% dimethylformamide (DMF) solution of a polyester-based polyurethane (100% modulus: 100 kg/cm²) which had been produced by the polymerization of polyethylene propylene adipate, 4,4"-diphenylmethane diisocyanate, (MDI) and ethylene glycol (EG). Immediately thereafter, a 26% DMF solution of the same polyester-based polyurethane was applied to the surface of the fiber entangled body in an amount of 40 g/m² and allowed to soak into the inside thereof. The surface was further applied with a 20% DMF solution of a polycarbonate-based polyurethane (100% modulus: 40 kg/cm²) in an amount of 75 g/m² _. The fiber entangled body impregnated with the polyurethane was immersed in a coagulation bath (40 °C) of DMF/water = 30/70 for 30 min to coagulate the polyurethane into a porous form. After washing with water, the sea-island fibers were converted to microfine fibers having an average fineness of 0.01 dtex by extracting the polyethylene with toluene, to obtain a fibrous substrate having a thickness of 1.6 mm which was composed of bundles of 6-nylon microfine fibers and a porous polyurethane.
A 10% solution of a polyester-based polyurethane containing a blue pigment was applied to the surface of the fibrous substrate using a gravure roll, to form a coating layer having a porous layer and a non-porous layer in a total thickness of about 200 µm. Then an embossing treatment was conducted at a roll temperature of 170 °C, a press pressure of 8 kg/ern and a treating speed of 1 m/min using an emboss roll having trapezoid pebbles having a height of 0.5 mm and a vertical projection area of 4 mm². The discontinuous valleys formed on the surface of the coating layer had a similar valley depth and the average thereof was 200 µm. The vertical projection areas of the valleys are also nearly the same and the average thereof was 2 mm². The average distance between the valleys was 2.5 mm and the total of the vertical projection areas was 9% of the surface area of the coating layer,
A uniform dispersion (dispersion medium: cyclohexanone/acetone/DMF mixed solvent (50/40/10)) containing hollow nanosilica particles (primary particle size: 50 to 150 nm, thickness of the silica shell: 5 to 15 nm, shell pore size: 2 nm or less (BET method)) in an amount of 10% of a polycarbonate-based polyurethane (binder) solid component was prepared. The dispersion was diluted with the same dispersion medium to half the concentration. The diluted dispersion was applied to the surface of the pebble-valley pattern on the coating layer using a 150-mesh gravure roll (applied amount: 1.5 g/m² in total of the hollow nanosilica particles and the binder) to form a non-porous surface layer.
Volleyballs were produced by a known method using the obtained leather-like sheet as the surface material. The evaluation result on the wet grippability of the obtained volleyballs was A.

EXAMPLE 2

In the same manner as in Example 1, a fibrous substrate having a thickness of 1.6 mm which was composed of bundles of 6-nylon microfine fibers and a porous polyurethane was obtained.
A 10% solution of a polyester-based polyurethane containing a blue pigment was applied to the surface of the fibrous substrate using a gravure roll, to form a coating layer having a thickness of about 5 µm. Then an embossing treatment was conducted at a roll temperature of 170 °C, a press pressure of 8 kg/cm and a treating speed of 1 m/min using an emboss roll having trapezoid pebbles having a height of 0.5 mm and a vertical projection area of 4 mm². The discontinuous valleys formed on the surface of the coating layer had a similar valley depth and the average thereof was 200 µm. The vertical projection areas of the valleys are also nearly the same and the average thereof was 2 mm². The average distance between the valleys was 2.5 mm and the total of the vertical projection areas was 9% of the surface area of the coating layer.
A uniform dispersion (dispersion medium: cyclohexanone/acetone/DMF mixed solvent (50/40/10)) containing surface-modified particles ("Nanotouch" (trademark) manufactured by Grandex Co., Ltd.) in an amount of 10% of a polycarbonate-based polyurethane (binder) solid component was prepared. Nanotouch is a product obtained by surface-modifying the hollow nanosilica particles (primary particle size: 50 to 150 nm, thickness of the silica shell: 5 to 15 nm, shell pore size: 2 nm or less (BET method)) with isocyanate group. The dispersion was diluted with the same dispersion medium to half the concentration. The diluted dispersion was applied to the surface of the pebble-valley pattern on the coating layer using a 150-mesh gravure roll (applied amount: 1.5 g/m² in total of the hollow nanosilica particles and the binder) to form a surface layer.
Volleyballs were produced by a known method using the obtained leather-like sheet as the surface material. The evaluation result on the wet grippability of the obtained volleyballs was A.

EXAMPLE 3

A leather-like sheet was produced in the same manner as in Example 2 expect for diluting a uniform dispersion (dispersion medium: methyl ethyl ketone) containing 10% of surface-modified particles ("Nanotouch" (trademark) manufactured by Grandex Co., Ltd.), which is a product obtained by surface-modifying the hollow nanosilica particles (primary particle size: 50 to 150 nm, thickness of the silica shell: 5 to 15 nm, shell pore size: 2 nm or less (BET method)) with isocyanate group, with methyl ethyl ketone to 1/10 concentration.
Volleyballs were produced by a known method using the obtained leather-like sheet as the surface material. The evaluation result on the wet grippability of the obtained volleyballs was A.

EXAMPLE 4

A mixture of nylon-6 chips and low density polyethylene chips in a mass ratio of 50:50 was extruded from an extruder to melt-spin sea-island mix-spun fibers having a polyethylene sea component. The sea-island fibers were drawn, crimped and cut to obtain 4-dtex staples having a 51-mm length. The staples were carded and the obtained webs were superposed by a crosslapper. The superposed web was needle-punched in a density of 700 punch/cm² using a needle punching machine to obtain an entangled nonwoven fabric. The entangled nonwoven fabric was impregnated with a dimethylformamide (DMF) solution of a polyurethane resin (based on poly- 3-methylpentane adipate/polyethylene glycol copolymer) and then immersed in a water/DMF mixed bath to wet-coagulate the polyurethane resin. The treated fabric was then introduced into a bath of toluene heated to 85 to 95°C and the sea component polyethylene in the sea-island fibers was extracted away by repeating the immersion-squeezing operation several times. When polyethylene was no longer extracted, the entangled nonwoven fabric was squeezed and then immediately introduced into hot water at about 100 to 120°C to completely remove the remaining toluene azeotropically. After impregnating a softener, the fabric was dried in a steam drier at about 130 to 150 °C, to obtain a fibrous substrate having a mass per unit area of 170 g/m², a thickness of 0.45 mm, and a nylon microfine fibers-polyurethane resin ratio of 75/25. The average fineness of the nylon microfine fibers in the obtained fibrous substrate was 0.007 dtex. One surface of the fibrous substrate was buffed with a sand paper and dyed dark gray with a metal complex acid dye using a wince dyeing machine, to obtain a dark gray suede-finished leather-like sheet having a raised surface of the nylon microfine fibers.
Using surface-modified hollow nanosilica particles which had been obtained by surface-modifying the hollow nanosilica particles (primary particle size: 50 to 150 nm, thickness of the silica shell: 5 to 15 nm, shell pore size: 2 nm or less (BEST method)) with isocyanate group, a uniform MEK dispersion containing 2% of the surface-modified hollow nanosilica particles was prepared. The dispersion was applied to the surface of the suede-finished leather-like sheet using a 150-mesh gravure roll (applied amount (solid basis): 0-2 g/m² of hollow nanosilica particles), and the sheet was dried in a steam dryer at about 110 to 130 °C, to obtain a suede-finished leather-like sheet in which the hollow nanosilica particles adhered so as to cover a part of the raised surface of the microfine fibers.
The obtained suede-finished leather like sheet had a softness and elegant appearance of raised fibers resembling natural suede leathers and was easy to grip with hands in both dry and wet conditions. In the present invention the grippability in dry condition is evaluated after allowing a suede-finished leather-like sheet to stand in a standard condition (temperature: 20°C, humidity: 45%) for 24 h or longer, and the grippability in wet condition is evaluated after immersing a suede-finished leather-like sheet in distilled water for 10 min and wiping away the excess water on the sheet with a filtering paper.
Using a 3 cm × 12 cm piece of the suede-finished leather-like sheet, the surface to which the hollow nanosilica particles adhered was measured for the coefficient of dynamic friction using Friction Tester KES-SE (manufactured by Kato Tech Co., Ltd.) under a load of 25 g and a friction speed of 1mm/s. The result is shown in Table 1 by the average of three measured values.

EXAMPLE 5

Ethylene-modified polyvinyl alcohol (ethylene unit content: 8.5 mol%, polymerization degree: 380, saponification degree: 98,7 mol%) for the sea component polymer and isophthalic acid-modified polyethylene terephthalate, (isophthalic acid unit content: 6.0 mol%) for the island component polymer were separately melted. Then, the molten polymers were fed into a composite-spinning spinneret which was provided with a number of nozzles arranged in parallel so as to spin 25-island sea-island fibers. The molten polymers were fed into the spinneret in a pressure balance so as to regulate the areal ratio of the sea component polymer and the island component polymer on the cross section to sea/island = 25/75 and the fed polymers were extruded from nozzles at a spinneret temperature of 290 °C. The extruded polymers were made thinner by pulling using an air jet-nozzle type sucking apparatus while controlling air jet so as to obtain an average spinning speed of 3600 m/min, thereby spinning sea-island fibers having an average fineness of 2.4 dtex. The sea-island fibers were continuously collected on a net while sucking from the back side. The pile amount of the sea-island fibers was controlled by changing the moving speed of net. The sea-island fibers collected on the net were pressed by an emboss roll kept at 80 °C, to obtain a long fiber web having an average mass per unit area of 30 g/m².
After spraying a mixed oil agent of a mineral slip oil and an antistatic agent, the long fiber web was continuously lapped by a crosslapper to obtain a layered long fiber web with 14 layers. The layered long fiber web was needle-punched from both sides in a total density of 1700 punch/cm² while allowing the barbs to pass through the web in the thickness direction to three-dimensionally entangle the fibers, thereby obtaining a fiber entangled body made of sea-island fibers.
After uniformly applying water to both the surfaces, the fiber entangled body was wet-heat shrunk by allowing it to continuously pass through an atmosphere of 75°C and 95% relative humidity in a retention time of 4 min while under pension and frictional stress-free conditions in both the length and width direction. Then, the fiber entangled body was dried by pressing between metal rolls at 120 °C while simultaneously compressing and smoothening the surface. Thereafter, the whole of the fiber entangled body was dried in an atmosphere at 120 °C, to obtain a densified fiber entangled body having a mass per unit area of 1125 g/m².
An aqueous dispersion (solid concentration: 11% by mass) of a polyurethane composition mainly composed of polycarbonate/ether-based polyurethane was impregnated into the obtained fiber entangled body, which was then pressed by a metal roll so as to regulate the impregnated amount to 50 parts by mass per 100 parts by mass of the fiber entangled body. The fiber entangled body was heated to a surface temperature of 80 °C for one minute by an infrared heater to heat-coagulate the polyurethane composition. The fiber entangled body thus treated was dried in an atmosphere of 120 °C and immediately thereafter cured in an atmosphere of 150 °C for 2 min, to allow the polyurethane composition to be present in the spaces between the sea-island fibers. Then, the fiber entangled body was treated in a jet dyeing machine by hot water at 90 °C for 20 min to remove the modified polyvinyl alcohol in the sea-island fibers by extraction and then dried at 120 °C, to obtain a fibrous substrate having a thickness of 1.4 mm which includes a fiber entangled body made of bundles of microfine long fibers of the modified polyethylene terephthalate and the polyurethane composition inside the fiber entangled body
The fibrous substrate was sliced into two parts along it surface. The non-sliced surface was buffed with a sand paper to raise the fibers and order the raised fibers, to form the raised fibers of the modified polyethylene terephthalate microfine fibers, followed by the dyeing treatment with a disperse dye in a jet dyeing machine and a finishing treatment of ordering raised fibers by brushing, thereby obtaining a dark gray suede finished leather-like sheet having a thickness of 0,6 mm.
Using the hollow nanosilica particles primary particle size: 50 to 150 nm, thickness of the silica shell: 5 to 15 nm, shell pore size: 2 nm or less (BET method)), a uniform aqueous dispersion containing 2% of the hollow nanosilica particles was prepared. The dispersion was applied to the surface of the suede-finished leather-like sheet using a 150-mesa gravure roll (applied amount: 0.2 g/m² of hollow nanosilica particles), and the sheet was dried in a steam dryer at about 110 to 130 °C, to obtain a suede-finished leather-like sheet in which the hollow nanosilica particles adhered to the surface of fibers.
The obtained suede-finished leather-like sheet had a softness and an elegant appearance of raised fibers resembling natural suede leathers and was easy to grip with hands in both dry and wet conditions.

COMPARATIVE EXAMPLE 1

A dark gray raised fiber sheet was produced in the same manner as in Example 4. The obtained raised fiber sheet was evaluated in the same manner as in Example 4 except for applying nothing to the surface thereof. Like Example 4, the obtained raised fiber sheet had a softness and an elegant appearance of raised fibers resembling natural suede leathers. However, the grippability with hands was insufficient for the intended use in both dry and wet conditions. The coefficient of dynamic friction measured in the same manner as in Example 4 is shown in Table 1.

COMPARATIVE EXAMPLE 2

Using the same type of the hollow nanosilica particles as used in Example 4, a uniform dispersion (dispersion medium:

cyclohexane/acetone/DMF mixed solvent (50/40/10)) containing the hollow nanosilica particles in an amount of 5% of the polycarbonate-based polyurethane (binder) solid component was prepared. Using a 150-mesh gravure roll, the dispersion was applied to the surface of the dark gray raised fiber sheet which has obtained in the same manner as in Example 4 (applied amount: 0.2 g/m² of the hollow nanosilica particles and the binder in total), and the sheet was dried in a steam dryer at about 110 to 130 °C, to obtain a leather-like sheet in which the hollow nanosilica particles adhered to the surface thereof.

The obtained leather-like sheet had a good grippability in both dry and wet conditions, however, lacked the flexibility, had a rigid feel and did not have a raised fiber feel at all. Thus the obtained leather-like sheet was quite different from the suede-finished leather-like sheet having a good appearance and touch intended in the present invention.

Table 1

	Coefficient of Dynamic Friction
	dry condition	wet condition
Example 4	2.75	2.92
Example 5	-	-
Comparative Example 1	1.61	1.89

COMPARATIVE EXAMPLE 3

A suede-finished leather-like sheet was produced in the same manner as in Example 4 except that hollow nanosilica particles having a primary particle size of 300 µm were adhered to the surface of the suede-finished leather-like sheet which had obtained in the same manner as in Example 4. The obtained suede-finished leather-like sheet had an elegant writing effect. Sandals produced using the suede-finished leather-like sheet was evaluated for the grippability. Although the grippability was good in dry condition immediately after beginning the test, the grippability gradually reduced when began to sweat. The result of evaluation was B for the dry condition test and C for the wet condition test.

COMPARATIVE EXAMPLE 4

A suede-finished leather-like sheet was produced in the same manner as in Example 4 except that non-hollow nanosilica particles having a primary particle size of 100 µm were adhered to the surface of the suede-finished leather-like sheet which had obtained in the same manner as in Example 4. The obtained suede-finished leather-like sheet had an elegant writing effect. Sandals produced using the suede-finished leather-like sheet were evaluated for the grippability. Although the grippability was good in dry condition immediately after beginning the test, the grippability gradually reduced when began to sweat. The result of evaluation was B for the dry condition test and C for the wet condition test.

PRODUCTION EXAMPLE 1

Sea-island fibers having a fineness of 15 dtex were produced by melt-spinning 50 parts of polyethylene (sea component) and 50 parts of 6-nylon (island component) from a single melting line. The sea-island fibers were drawn by 2.5 times, crimped and cut into 51-mm length. The obtained staples were carded and made into a fiber web by a crosslap robber. The fiber webs were superposed and needle-punched to obtain a fiber entangled body having a mass per unit area or 320 g/m².
The fiber entangled body was impregnated with a 13% dimethylformamide (DMF) solution of a polyester-based polyurethane (100% modulus: 100 kg/cm²) which had been produced by the polymerization of polyethylene propylene adipate, 4,4"-diphenylmethane diisocyanate (MDI) and ethylene glycol (EG). The fiber entangled body impregnated with the polyurethane was immersed in a coagulation bath (40 °C) of DMF/water = 30/70 for 30 min to coagulate the polyurethane into a porous form. After washing with water, the sea-island fibers were converted to microfine fibers having an average fineness of 0.01 dtex by extracting the polyethylene with toluene, to obtain a fibrous substrate having a thickness of 0.8 mm which was composed of bundles of 6-nylon microfine fibers and a porous polyurethane. The obtained fibrous substrate was dyed ocher yellow with a metal complex dye using a wince dyeing machine.

PRODUCTION EXAMPLE 2

A sea-island fiber web was produced by melting 40 parts of a thermoplastic polyvinyl alcohol (sea component) and 60 parts of polyethylene terephthalate (island component) in different extruders, introducing the molten polymers to a composite-spinning nozzle, and blowing the spun fibers from the nozzle onto a collection net while drawling the fibers by air jet. The fineness of the fibers constituting the web was 3 dtex. The obtained fiber web was lapped and needle-punched to obtain a fiber entangled body having a mass per unit area of 400 g/m². Upon extracting the polyvinyl alcohol from the fiber entangled body with hot water at 90 °C, the fiber entangled body shrunk slightly to obtain a fiber entangled body having a mass per unit area of 320 g/m².
An aqueous emulsion of polyether-based polyurethane ("Evafanol Apt-48" (tradename) manufactured by Nicca Chemical Co., Ltd.) was diluted with water to a solid concentration of 5%. The diluted aqueous emulsion was impregnated into the fiber entangled body and squeezed out. The pickup (pick-up amount of the emulsion in the fiber entangled body) was 60%. After drying, a fibrous substrate having a thickness of 0.8 mm which was composed of microfine fibers having an average fineness of 0.1 dtex and the impregnates polyurethane was obtained. The obtained fibrous substrate was dyed ocher yellow with a disperse dye using a circular dyeing machine.

EXAMPLE 6

The fibrous substrate produced in Production Example 1 was raised on its one surface by a #400 sand paper to obtain a raised fiber sheet.
Using surface-modified particles which had obtained by surface-modifying the hollow nanosilica particles (primary particles size: 50 to 150nm, thickness of the silica shell: 5 to 15 nm shell pore size: 2nm or less (BET method)) with isocyanate group in the manner described in Patent Document 7, a uniform MEK dispersion containing 2% of the surface-modified particles was prepared. The dispersion was applied to the surface of the raised fiber sheet using a 150-mesh gravure roll (applied amount: 0.2 g/m² of the hollow nanosilica particles), and the sheet was dried in a hot-air dryer maintained at 130 °C, to obtain a raised fiber sheet in which the hollow nanosilica particles adhered to the raised portion.
Separately, a uniform solution (solvent: cyclohexanone/acetone/DMF mixed solvent (50/40/10)) containing 3% of the polyester-based polyurethane of the same type as impregnated into the sheet was prepared. The solution was applied to the raised fiber sheet using a gravure roll having an elliptical dot pattern (major axis: 2 mm, minor axis: 1 mm) to obtain a semi-grain-finished leather-like sheet having a grain-finished portion and a raised portion on its surface.
The surface of the obtained semi-grain-finished leather-like sheet was covered with the grain-finished portion by 30% and the raised portion had a fine and an elegant writing effect. Sandals produced using the semi-grain-finished leather-like sheet was evaluated for the grippability. The results were A in both the dry condition test and the wet condition test.

EXAMPLE 7

The fibrous substrate produced in Production Example 1 was raised on its one surface by a #400 sand paper to obtain a raised fiber sheet. Separately, using the non-modified hollow nanosilica particles (primary particle size: 50 to 150nm, thickness of the silica shell: 5 to 15 nm, shell pore size: 2nm or less (BET method)), a uniform MEK dispersion containing 2% of the noun-modified particles was prepared. The dispersion was applied to the surface of the raised fiber sheet using a 150-mesh gravure roll (applied amount: 0.2 g/m² of the hollow nanosilica particles), and the sheet was dried in a hot-air dryer maintained at 130 °C, to obtain a raised fiber sheet in which the hollow nanosilica particles adhered to the raised portion. Then, the raised surface was embossed with an emboss roll to obtain a raised fiber sheet having a surface with an embossed pattern like a basketball configuration.
Using the polyester-based polyurethane of the same type as used in Example 6 as the binder, a uniform dispersion (dispersion medium: cyclohexanone/acetone/DMF mixed solvent (50/40/10)) containing the hollow nanosilica particles in an amount of 10% of the binder and having a solid content of 3% was prepared. The dispersion was applied to the raised fiber sheet using a 150-mesh gravure roll to obtain a semi-grain-finished leather-like sheet.
The obtained semi-grain-finished leather-like sheet was covered with the polyurethane grain-finished portion only on the pebbles of the embossed pattern, and 50% of the surface was covered with the grain-finished portion. The raised fibers having a writing effect remained in the valleys of the embossed pattern. Sandals produced using the semi-grain-finished leather-like sheet was evaluated for the grippability. The results were A in both the dry condition test and the wet condition test.

EXAMPLE 8

Using the polyester-based polyurethane of the same type as used in Example 6 as the binder, a uniform dispersion (dispersion medium: cyclohexanone/acetone/DMF mixed solvent (50/40/10)) containing the isocyanate-modified hollow nanosilica particles in an amount of 10% of the binder and having a solid content of 3% was prepare. Using a 150-mesh gravure roll, the dispersion was applied to the raised fiber sheet produced in Example 7 which had the hollow nanosilica particles adhered to the raised portion and the surface with an embossed pattern like a basketball configuration, to obtain a semi-gram-finished leather-like sheet.
The obtained semi-grain-finished leather-like sheet was covered with the polyurethane grain-finished portion only on the pebbles of the embossed pattern and 50% of the surface was covered with the grain-finished portion. The raised fibers having a writing effect remained in the valleys of the embossed pattern. Sandals produced using the semi-grain-fnished leather-like sheet was evaluated for the grippability. The results were A in both the dry condition test and the wet condition test.

EXAMPLE 9

Using a 150-mesh gravure roll, a uniform solution (solvent: cyclohexanone/acetone/DMF mixed solvent (50/40/10)) containing 3% of the polyester-based polyurethane of the same type as impregnated into the sheet was applied to one surface of the fibrous substrate produced in Production Example 1. After drying, the surface was embossed with an emboss roll having an emboss pattern imitating the grain skin of adult cow cowhide. Then, the pebbles of the embossed pattern were raised by a #600 sand paper to obtain a semi-grain-finished raised fiber sheet.
Separately, a uniform MEK dispersion containing 2% of the surface-modified particles of the same type as used in Example 6 was prepared. The dispersion was applied to the surface of the semi-grain-finished raised fiber sheet using a 150-mesh gravure roll (applied amount: 0.2 g/m² of the hollow nanosilica particles), and the sheet was dried in a hot-air dryer maintained at 130 °C, to obtain a semi-grain-finished leather-like sheet.
The surface of the leather-like sheet was covered with the grain-finished portion by 60%, and the surface-modified particles adhered to both the grain-finished portion and the raised portion, to give a fine and an elegant writing effect. Sandals produced using the leather-like sheet was evaluated for the grippability. The results were A in both the dry condition test and the wet condition test.

EXAMPLE 10

Using the polyester-based polyurethane of the same type as used in Example 6 as the binder, a uniform dispersion (dispersion medium: cyclohexanone/acetone/DMF mixed solvent (50/40/10)) containing the hollow nanosilica particles in an amount of 10% of the binder and having a solid content of 3% was prepared. Using a 150-mesh gravure roll, the dispersion was applied to the raised fiber sheet produced in Example 8 which had a surface with an embossed pattern like a basketball configuration, to obtain a semi-grain-finished leather-like sheet having a surface on which the grain-finished portion and the raised portion were mixedly present.
The obtained semi-grain-finished leather-like sheet was covered with the polyurethane grain-finished portion only on the pebbles of the embossed pattern and 50% of the surface was covered with the grain-finished portion. The raised fibers having a writing effect remained in the valleys of the embossed pattern. Sandals produced using the semi-grain-finished leather-like sheet was evaluated for the grippability. The results were A in both the dry condition test and the wet condition test.

EXAMPLE 11

A semi-grain-finished leather-like sheet having a surface on which the grain-finished portion and the raised portion were mixedly present was produced in the same manner as in Example 9 except for using the fibrous substrate produced in Production Example 2.
The obtained leather-like sheet was covered with the grain-finished portion by 55% of its surface and had an elegant writing effect. Sandals produced using the semi-grain-finished leather-like sheet were evaluated for the grippability. The results were A in both the dry condition test and the wet condition test.

COMPARATIVE EXAMPLE 5

A semi-grain-nnished leather-like sheet was produced in the same manner as in Example 6 except that the hollow nanosilica particles were not adhered to the raised fiber sheet. The obtained semi-grain-finished leather-like sheet was covered with the grain-finished portion by 30% of its surface and had an elegant writing effect. Sandals produced using the semi-grain-finished leather-like sheet were evaluated for the grippability. Although the grippability was good in dry condition immediately after beginning the test, the grippability gradually reduced when began to sweat. The result of evaluation was B for the dry condition test and C for the wet condition test.

COMPARATIVE EXAMPLE 6

A leather-like sheet was produced in the same manner as in Example 2 by forming a coating layer on the surface of a fibrous substrate and then forming discontinuous valleys on the surface of the coating layer.
Using the polycarbonate-based polyurethane of the same type as used in Example 2 as the binder, a uniform dispersion containing hollow silica particles having a primary particle size of 300 µm in an amount 10% of the binder was prepared in the same manner as in Example 2. By applying the dispersion, a surface layer was formed on the leather-like sheet.
Using the obtained leather-like sheet as the surface material, volleyballs were produced by a known method. The evaluated grippability of the volleyballs in wet condition was B.

COMPARATIVE EXAMPLE 7

A leather-like sheet was produced in the same manner as in Example 2 by forming a coating layer on the surface of a fibrous substrate and then forming discontinuous valleys on the surface of the coating layer.
Using the polycarbonate-based polyurethane of the same type as used in Example 2 as the binder, a uniform dispersion containing non-hollow silica particles having a primary particle size of 100 nm in an amount 10% of the binder was prepared in the same manner as in Example 2. By applying the dispersion, a surface layer was formed on the leather-like sheet.
Using the obtained leather-like sheet as the surface material volleyballs were produced by a known method. The evaluated grippability of the volleyballs in wet condition was B.

COMPARATIVE EXAMPLE 8

A leather-like sheet was produced in the same manner as in Example 2 by forming a coating layer on the surface of a fibrous substrate and then forming discontinuous valleys on the surface of the coating layer.
Using the polycarbonate-based polyurethane of the same type as used in Example 2 as the binder, a uniform dispersion containing non-hollow silica particles having a primary particle size of 20 nm in an amount 10% of the binder was prepared in the same manner as in Example 2. By applying the dispersion, a surface layer was formed on the leather-like sheet.
Using the obtained leather-like sheet as the surface material, volleyballs were produced by a known method. The evaluated grippability of the volleyballs in wet condition was B.

INDUSTRIAL APPLICABILITY

Because of a good wet grippability, the grain-finished leather-like sheet of the present invention is suitable as the material for the products requiring a grippability in wet condition, for example, the material for game balls, gloves, insole of shoes, seats, floorings, sole of shoes, various grips, etc.
The suede-finished leather-like sheet of the present invention has an appearance resembling a dense and elegant appearance of natural suede leathers and an appearance resembling a raised fiber appearance of natural nubuck leathers. The suede-finished leather-like sheet further has a good color developability and a soft, bulky and dense feel as well as a good grippability in both dry and wet conditions. The suede-finished leather-like sheet is suitably used in various applications, for example, sport gloves such as golf glove, baseball batting glove, horse riding glove, marine sport glove and driving glove for automobile, motorbike and bicycle; working gloves for use in processing working, agricultural working, lifesaving working and military use; and other applications such as a surface material for the grip of racket, a seat material for horse-riding pants, a surface material for vehicle seats, a material for clothes and shoes, a material for insole of sport shoes, a material for foot bed of sandals, etc.
The semi-grain-finished leather-like sheet of the present invention has a semi-grain-finished appearance exhibiting a dense and elegant writing effect and a good grippability in both dry and wet conditions. The semi-gram-finished leather-like sheet is suitably used in various applications, for example, sport gloves such as golf glove and baseball batting glove, working gloves such as processing working glove as well as sport shoes, foot bed of sandals, grip of tennis racket and golf club, etc.

Claims

A leather-like sheet comprising a fibrous substrate and a grain-finished portion covering 10% or more of a surface of the fibrous substrate,
wherein the grain-finished portion comprises a surface layer and an optional coating layer, and the surface layer comprises non-modified hollow nanosilica particles having a primary particle size of 50 to 150 nm and an elastic polymer, or comprises modified hollow nanosilica particles and an optional elastic polymer, and
wherein the modified hollow nanosilica particles are particles which are surface-modified with at least one compound selected from the group consisting of a compound having isocyanate group, a compound having alkyl group, a compound having aryl group and a compound having UV-sensitive functional group.
The leather-like sheet according to claim 1, wherein the non-modified or modified hollow nanosilica particles have a thickness of silica shell of 5 to 15 nm and a shell pore size of 5 nm or less.
The leather-like sheet according to claim 1 or 2, wherein the surface of the fibrous substrate is completely covered with the grain-finished portions.
The leather-like sheet according to any one of claims 1 to 3, wherein the fibrous substrate is exposed in a portion of the surface of the fibrous substrate which is not covered with the grain-finished portions, and the fibers constituting the fibrous substrate are raised.
The leather-like sheet according to any one of claims 1 to 4, wherein the fibrous substrate comprises a fiber entangled body made of bundles of microfine fibers having an average fineness of 0.0001 to 0.3 dtex and a porous elastic polymer.
The leather-like sheet according to claim 5, wherein the mass ratio of the microfine fibers and the elastic polymer is 35/65 to 90/10.
The leather-like sheet according to any one of claims 1 to 6, wherein the grain-finished portion is non-porous.
The leather-like sheet according to any one of claims 1 to 7, wherein the coating layer contains the elastic polymer but does not contain the non-modified hollow nanosilica particles and the modified hollow nanosilica particles.
The leather-like sheet according to claim 8, wherein the coating layer is non-porous.
The leather-like sheet according to claim 8, wherein the coating layer and the surface layer are non-porous.
The leather-like sheet according to claim 8, wherein the coating layer is porous and the surface layer is non-porous.
The leather-like sheet according to any one of claims 1 to 11, wherein continuous pebbles and discontinuous valleys are formed on the grain-Rnished portions.
The leather-like sheet according to any one of claims 1 to 12, wherein continuous pebbles and discontinuous valleys are formed on the coating layer.
The leather-like sheet according to any one of claims 1 to 13, wherein the non-modified hollow nanosilica particles are present in an amount of 0.02 to 0.8 g/m².
The leather-like sheet according to any one of claims 1 to 13, wherein the surface-modified hollow nanosilica particles are present in an amount of 0.05 to 1 g/m².
An artificial leather product wherein at least a part of a surface thereof is made from the leather-like sheet as defined in any one of claims 1 to 15.
The artificial leather product according to claim 16 which is a game ball.
The artificial leather product according to claim 17, wherein the game ball is volleyball.
A suede-finished leather-like sheet which comprises a fibrous substrate comprising a fiber entangled body made of bundles of microfine fibers having an average fineness of 0.3 dtex or less and an elastic polymer inside the fiber entangled body and comprises raised fibers of the microfine fibers formed on a surface of the fibrous substrate, wherein non-modified or modified hollow nanosilica particles having a primary particle size of 50 to 150 nm are present on at least the surface having the raised fibers.
The suede-finished leather-like sheet according to claim 19, wherein the modified hollow nanosilica particles are particles which are surface-modified with at least one compound selected from the group consisting of a compound having isocyanate group, a compound having alkyl group, a compound having aryl group and a compound having UV-sensitive functional group.
The suede-finished leather-like sheet according to claim 19 or 20, wherein the non-modified or modified hollow nanosilica particles have a thickness of silica shell of 5 to 15 nm and a shell pore size of 5 nm or less.
The suede-finished leather-like sheet according to any one of claims 19 to 22, wherein the non-modified or modified hollow nanosilica particles are present in an amount of 0.02 to 0.8 g/m².
The suede-finished leather-like sheet according to any one of claims 19 to 22, wherein at least a part of the non-modified or modified hollow nanosilica particles cover at least a part of the raised surface comprising the microfine fibers.
An artificial leather product wherein at least a part of a surface thereof is made from the suede-finished leather-like sheet as defined in any one of claims 19 to 23.
A sport glove or working glove produced by using the artificial leather product as defined in claim 24.
Sport shoes or sandals produced by using the artificial leather product as defined in claim 24.
A leather-like sheet comprising a fibrous substrate wherein a coating portion and a raised portion comprising fibers constituting the fibrous substrate are mixedly present on a surface of the fibrous substrate, and wherein non-modified or modified hollow nanosilica particles having a primary particle size of 50 to 150 nm adhere to the raised portion.
The leather-like sheet according to claim 27, wherein the modified hollow nanosilica particles are particles which are surface-modified with at least one compound selected from the group consisting of a compound having isocyanate group, a compound having alkyl group, a compound having aryl group and a compound having UV-sensitive functional group.
The leather-like sheet according to claim 27 or 28, wherein the non-modified or modified hollow nanosilica particles have a thickness of silica shell of 5 to 15 nm and a shell pore size of 5 nm or less.
The leather-like sheet according to any one of claims 27 to 29, wherein the coating portion does not contain the non-modified hollow nanosilica particles and the modified hollow nanosilica particles, and an area ratio of the coating portion and the raised portion is 10/90 to 60/40.
The leather-like sheet according to any one of claims 27 to 29, wherein the coating portion comprises an elastic polymer and the non-modified hollow nanosilica particles having a primary particle size of 50 to 150 nm, and the area ratio of the coating portion and the raised portion each being formed on the fibrous substrate surface is 10/90 to 90/10.
The leather-like sheet according to any one of claims 27 to 29, wherein the coating portion comprises an elastic polymer and the modified hollow nanosilica particles having a primary particle size of 50 to 150 non and surface-modified with at least one compound selected from the group consisting of a compound having isocyanate group, a compound having alkyl group, a compound having aryl group and a compound having UV-sensitive functional group, and wherein the area ratio of the coating portion and the raised portion each being formed on the fibrous substrate surface is 10/90 to 90/10.
The leather-like sheet according to any one of claims 27 to 29, wherein at least a part of a surfaces of the coating portion has the modified hollow nanosilica particles having a primary particle size of 50 to 150 nm and surface-modified with at least one compound selected from the group consisting of a compound having isocyanate group, a compound having alkyl group, a compound having aryl group and a compound having UV-sensitive functional group, and wherein the area ratio of the coating portion and the raised portion each being formed on the fibrous substrate surface is 10/90 to 90/10.
The leather-like sheet according to any one of claims 27 to 34, wherein the fibrous substrate is a fiber entangled body comprising bundles of microfine fibers having an average fineness of 0.0001 to 0.3 dtex.
The leather-like sheet according to any one of claims 27 to 34, wherein the fibrous substrate is composed of a fiber entangled body comprising bundles of microfine fibers having an average fineness of 0.0001 to 0.3 dtex and an elastic polymer in the fiber entangled body.
The leather-like sheet according to claim 35, wherein a mass ratio of the microfine fibers and the elastic polymer is 35/65 to 90/10.
An artificial leather product wherein at least a part of a surface thereof is made from the leather-like sheet as defined in any one of claims 27 to 36.
Sport glove, working glove, sport shoes or sandals produced by using the artificial leather product as defined in claim 37.