Base material for artificial leather and process for producing the same

Abstract

A substrate for artificial leather comprising a nonwoven fabric of bundles of microfine filaments. The substrate for artificial leather simultaneously satisfies the following requirements 1 to 4: (1) the bundle of microfine filaments comprises 8 to 70 microfine filaments having a cross-sectional shape of nearly circle; (2) the bundle of microfine filaments has a cross-sectional area of 170 to 700 m.sup.2 and a flatness of 4.0 or less; (3) on a cross section parallel to a thickness direction of the nonwoven fabric body, cross sections of the microfine fiber bundles exist in a density of 1500 to 3000/mm.sup.2; and (4) on a cross section parallel to a thickness direction of the nonwoven fabric body, gaps between the microfine fiber bundles have a size of 70 m or less. By satisfying the requirements, the substrate for artificial leather combines high level of sensuous qualities and high level of physical properties which have been considered to be mutually exclusive.

Claims

1. A substrate, comprising a nonwoven fabric comprising bundles of microfine filaments, wherein the nonwoven fabric is obtained by removing a sea component from sea-island filaments to convert the sea-island filaments to the bundles of the microfine filaments, such that: (1) each bundle of microfine filaments comprises 8 to 70 microfine filaments having a nearly circular cross-sectional shape; (2) each bundle of microfine filaments has a cross-sectional area of 170 to 700 m.sup.2 and a flatness of less than 3.0; (3) on a cross section parallel to a thickness direction of the nonwoven fabric, the number of bundles per area is 1500 to 3000/mm.sup.2; (4) on a cross section parallel to a thickness direction of the nonwoven fabric, gaps between the bundles of microfine filaments have a size of 70 m or less.

2. The substrate of claim 1, wherein on a cross section parallel to a thickness direction of the nonwoven fabric body, an average size of gaps between the bundles of microfine filaments in a region from a surface to a depth of 200 m is 10 to 40 m.

3. The substrate of claim 2, further comprising an elastic polymer.

4. A nap-finished artificial leather obtained by napping a surface of the substrate of claim 3.

5. A nap-finished artificial leather obtained by napping a surface of the substrate of claim 2.

6. The substrate of claim 1, further comprising an elastic polymer.

7. A nap-finished artificial leather obtained by napping a surface of the substrate of claim 6.

8. A nap-finished artificial leather obtained by napping a surface of the substrate of claim 1.

9. The substrate of claim 1, wherein the microfine filaments comprise a heat-shrinkable polymer.

10. A method of producing the substrate of claim 1, the method comprising, sequentially (a) to (d): (a) melt-spinning sea-island filaments having an island number of 8 to 70, a sea/island cross-sectional area ratio of 5:95 to 60:40 and a cross-sectional area of 70 to 350 m.sup.2 with a heat-shrinkable polymer as an island component and a water-soluble polymer as a sea component, and collecting the sea-island filaments, which have been spun, on a collecting surface in random orientations without cutting, thereby producing a sheet-form web of filaments; (b) after optionally superposing the web of filaments in layers, needle-punching the web of filaments from both sides thereof with at least needles with six barbs while allowing at least one barb to penetrate through the web of filaments, thereby three-dimensionally entangling the sea-island filaments to produce a nonwoven fabric body; (c) moist heat-treating the nonwoven fabric body to plasticize the sea component polymer and allow the heat-shrinkable polymer to shrink and then optionally pressing the nonwoven fabric under dry heating, thereby densifying the nonwoven fabric such that cross sections of the sea-island filaments exist 1000 to 3500/mm.sup.2 on a cross section parallel to a thickness direction of the nonwoven fabric body; and (d) removing the sea component from the sea-island filaments with water or an aqueous solution, thereby converting the sea-island filaments to bundles of microfine filaments.

11. The method of claim 10, further comprising, sequentially, (e) to (h) after (d): (e) applying a solution, aqueous dispersion, or melt, of an easily extractable polymer on at least one surface of the nonwoven fabric body and then coagulating the easily extractable polymer; (f) applying an aqueous dispersion of an elastic polymer on the same surface as the at least one surface of the nonwoven fabric body and then coagulating the elastic polymer; (g) removing the easily extractable polymer from the nonwoven fabric body; and (h) grinding the at least one surface applied with the elastic polymer under pressure to densify the nonwoven fabric body such that gaps between the bundles of microfine filaments in a region from the ground surface to a depth of 200 m on a cross section of the nonwoven fabric body parallel to its thickness direction have a size of 10 to 40 m in average.

12. The method of claim 11, further comprising (i) before or after (d): impregnating a solution or aqueous dispersion of an elastic polymer into the nonwoven fabric and then coagulating the elastic polymer.

13. The method of claim 10, further comprising (i) before or after (d); (i) impregnating a solution or aqueous dispersion of an elastic polymer into the nonwoven fabric and then coagulating the elastic polymer.

Description

EXAMPLES

(1) The present invention will be described in more detail with reference to the following examples. However, it should be noted that the scope of the present invention is not limited thereto. In the following, part(s) and % are based on mass unless otherwise noted. (1) Cross-Sectional Area of Sea-Island Fiber and Bundle of Microfine Filaments, Number of Bundled Fibers, and Flatness

(2) The cross-section taken parallel to the thickness direction of a sample was observed under a scanning electron microscope (magnification of about 100 to 300), and 20 sea-island fibers or bundles of microfine filaments which were oriented nearly perpendicular to the cross section were randomly and evenly selected from the observing field. The number of bundled fibers, the flatness and the projected size of each selected sea-island fiber and microfine fiber bundle were obtained, if needed, after magnifying 1000 to 3000 times. The flatness of fiber or bundle is defined as a ratio of the length of the longest portion in the cross section and the length in the direction perpendicular thereto. Generally, the longest portion mainly orients to the direction perpendicular to the thickness direction.

(3) Next, the cross-sectional area of each of selected 20 sea-island fibers or microfine fiber bundles were measured. The maximum and minimum cross-sectional areas were cut off and the remaining 18 cross-sectional areas were arithmetically averaged to obtain the cross-sectional areas of the sea-island fiber and the microfine fiber bundle.

(4) The cross-sectional area of the microfine fiber bundle is defined as the area of the region surrounded by the fibers in the periphery of bundle and the tangent line connecting the peripheral fibers. When the number of bundled fibers varied from bundle to bundle, the numbers of bundled fibers of sea-island fiber and microfine fiber bundle were determined in the same manner as in the cross-sectional area, i.e., the maximum and minimum numbers were cut off and the remaining 18 numbers were arithmetically averaged. (2) Existence Density of Sea-Island Fibers or Microfine Filaments on Cross Section of Substrate for Artificial Leather, Size of Gaps Between Microfine Fiber Bundles, and Average Size of Gaps

(5) A cross section of a sample taken parallel to the thickness direction was continuously observed under a scanning electron microscope (magnification of about 100 to 300) in a total observed area of about 0.3 to 0.5 mm.sup.2.

(6) The number of the cross sections of sea-island fibers or microfine fiber bundles in the observing field, which were deemed to be nearly perpendicular to the lengthwise direction of fibers or bundles, was counted. The total number was divided by the observed area to obtain the number of the cross sections of sea-island fibers or microfine fiber bundles existing per 1 mm.sup.2. This observation was made at least five portions of each sample and the smallest value was employed as the existence density of the sample.

(7) Next, the region not occupied by the cross sections of sea-island fibers or microfine fiber bundles on the same observing field was all deemed to be gaps, and the diameter of the largest circle drawn in gaps so as to be tangent to the cross sections of sea-island fibers or microfine fiber bundles was measured. When the gaps were open to form a broad region, two or more circles were drawn so as not to overlap with each other and the largest diameter of the drawn circles was measured. The size of gaps was not determined in the portion of the observing field where the bundles were closely adhered, except for the case where almost all the bundles were closely adhered throughout the observing field. The bundles apart from each other by the diameter of microfine fiber constituting the bundle or less were regarded as being closely adhered. The measured largest diameter of circles in the observing field was employed as the size of gaps between the microfine fiber bundles in the sample. In addition, the diameters of 20 gaps randomly and evenly selected from the observing filed were measured. The 18 values after cutting off the maximum and minimum values were arithmetically averaged to obtain the average size of gaps between the microfine fiber bundles. (3) Evaluation of Appearance of Nap-Finished Artificial Leather

(8) A nap-finished artificial leather was visually observed by 5 panelists selected form those skilled in artificial leather art and evaluated for its appearance according to the following ratings. The result is shown by the rating given by most of panelists.

(9) A: Extremely highly dense throughout napped surface and smooth touch with no roughness.

(10) B: Slightly less dense throughout napped surface or partially rough although relatively highly dense throughout napped surface, and relatively rough touch.

(11) C: Rough throughout napped surface and considerably rough touch. (4) Evaluation of Hand of Nap-Finished Artificial Leather

(12) A nap-finished artificial leather was made into a golf glove by sewing when the thickness was less than 0.8 mm, a jacket by sewing when the thickness was 0.8 to 1.2 mm, and a sofa by sewing when the thickness exceeded 1.2 mm. Each product was subjected to wear trial and evaluated for the hand of the nap-finished artificial leather by 5 panelists selected form those skilled in artificial leather art according to the following ratings. The result is shown by the rating given by most of panelists.

(13) A: Soft hand with fullness combined with sufficient dense feeling, and good fit feeling of product.

(14) B: Unsatisfied hand lacking in any of soft feeling, fullness and dense feeling, and insufficient fit feeling of product (same as general nap-finished artificial leather with respect to hand and fit feeling).

(15) C: Extremely poor in any or all of soft feeling, fullness and dense feeling, and poor fit feeling (inferior to general nap-finished artificial leather with respect to hand and fit feeling). (5) Evaluation of Surface Abrasion Resistance of Nap-Finished Artificial Leather

(16) The surface of a nap-finished artificial leather was abraded according to Martindale abrasion test of JIS L1096 under a load of 12 kPa and the number of abrasion of 50000 times. When the difference in mass (abrasion loss) before and after the test was 50 mg or less, the abrasion resistance was judged good. The variation of pilling on the surface of nap-finished artificial leather before and after the test was visually observed and evaluated by the following ratings. When the abrasion resistance was good and the pilling resistance was A or B, the surface abrasion resistance was judged good.

(17) A: No increase in pilling (decrease in pilling by cutting of napped fibers is allowable).

(18) B: Slight increase in piling but no increase in bard pilling.

(19) C: Noticeable increase in pilling and noticeable increase in hard pilling.

Example 1

(20) An ethylene-modified polyvinyl alcohol (ethylene unit: 8.5 mol %; polymerization degree: 380; saponification degree: 98.7 mol %) as the sea component polymer and isophthalic acid-modified polyethylene terephthalate (isophthalic acid unit: 6.0 mol %) as the island component polymer were separately melted. Then, the molten polymers were fed into a composite-spinning spinneret. The spinneret was provided with a number of nozzles arranged in parallel and capable of forming a cross section in which 25 islands of island component polymer having a uniform cross-sectional area were distributed in the sea component polymer. The molten polymers were fed into the spinneret in a pressure balance which regulated the average areal ratio of the sea component polymer and the island component polymer on the cross sections to sea/island=25/75 and the fed polymers were extruded from nozzles at a spinneret temperature of 250 C. The extruded polymers were made thinner by pilling using an air jet-nozzle type sucking apparatus by which the pressure of air jet was regulated so as to obtain an average spinning speed of 3600 m/min, thereby spinning sea-island fibers having an average cross-sectional area of 177 m.sup.2 (about 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. at a line pressure of 70 kg/cm, to obtain a web of filaments having an average mass per unit area of 30 g/m.sup.2. On a cross section parallel to the thickness direction of the obtained web of filaments, the cross sections of sea-island fibers existed in a density of 220 to 250/mm.sup.2. The shape of the web of filaments was stabilized enough to wind up.

(21) An oil agent mainly comprising a mineral oil-based lubricating oil agent additionally mixed with an antistatic agent was sprayed on to the surface of the embossed web of filaments. The web of filaments was then continuously lapped using a cross-lapper to obtain a 14-layered web of filaments. The layered web of filaments was three-dimensionally entangled by a needle punching method to obtain a nonwoven fabric having an existence density of sea-island fibers of 500/mm.sup.2. First, the lapped web of filaments was preliminarily entangled using needles A (needle gauge #40, 40 m barb depth, one barb, regular triangle cross section) from both sides thereof at a punching depth of allowing the barb to penetrate through the web in the thickness direction, to obtain a web of filaments which was entangled enough to keep the layers in position. Then, the lapped web of filaments was further entangled using needles B (needle gauge #42, 40 m barb depth, six barbs, regular triangle cross section) from both sides thereof at a punching depth of allowing three barbs to penetrate through the web in the thickness direction, thereby entangling the sea-island fibers in the thickness direction in a desired degree. The punching density by needles B was 1700 punch/cm.sup.2 in total of both sides.

(22) Immediately after uniformly spraying water of 18 C. on both sides, the nonwoven fabric is subject to the moist heat-shrinking treatment by continuously passing it through an atmosphere kept at 76 C. and a relative humidity of 95% over four minutes under conditions substantially free from tension and friction in both the lengthwise and widthwise directions, thereby uniformly compacting the space between the sea-island fibers. Thereafter, the nonwoven fabric was pressed between metal rolls kept at 120 C. for drying while compressing and flattening the surface, and then, the whole part of the nonwoven fabric was introduced into an atmosphere of 120 C. for drying, thereby obtaining a densified nonwoven fabric having a mass per unit area of 1125 g/m.sup.2. On a cross section parallel to the thickness direction of nonwoven fabric body, the existence density of sea-island fibers was 1900/mm.sup.2.

(23) The obtained nonwoven fabric was impregnated with an elastic polymer liquid, i.e., an aqueous dispersion (solid concentration: 11% by mass) of polyurethane composition mainly composed of a polycarbonate ether-based polyurethane. The nonwoven fabric was pressed between metal rolls so as to regulate the content of the elastic polymer liquid to 50 by mass per 100 by mass of nonwoven fabric body, and then, exposed to an infrared heater for one minute to heat the surface of the nonwoven fabric to 80 C., thereby heat-coagulating the elastic polymer. Finally, the nonwoven fabric was introduced into an atmosphere of 120 for drying, and immediately thereafter, introduced into an atmosphere of 150 C. for curing for two minutes, thereby allowing the polyurethane composition to exist in the space between the sea-island fibers. Then, the modified polyvinyl alcohol was removed from the sea-island fibers by extraction in a jet dyeing machine by hot water of 90 C. for 20 min and the nonwoven fabric was introduced into an atmosphere of 120 C. for drying, thereby obtaining a substrate for artificial leather of about 1.4 mm thick comprising a nonwoven fabric constituted by bundles of microfine filaments of polyethylene terephthalate and the polyurethane composition impregnated therein.

(24) On a cross section of the obtained substrate for artificial leather, the cross-sectional area of the bundles of microtine filaments ranged from 200 to 400 m.sup.2 and was 250 m.sup.2 in average and the fiber diameter was nearly uniform. Each bundle had 25 microfine filaments having a cross-sectional shape of nearly circle. The bundles were not so flattened in the thickness direction, and the flatness of bundle was 2.5 at the largest and less than 2.0 for most of the bundles. The projected size was 40 m. The existence density of bundles of microfine filaments on a cross section parallel to the thickness direction was 2500/mm.sup.2, the gaps between the microfine fiber bundles had a size of 52 m, and the average size of gaps was 35 m.

Example 2

(25) The substrate for artificial leather obtained in Example 1 was sliced to two parts in the thickness direction, and the divided surface was buffed with sandpaper to regulate the average thickness to 0.67 mm. The other surface not buffed was coated with a 6% aqueous solution of polyvinyl alcohol twice by a 55-mesh gravure roll, and then dried, and then, coated with an aqueous dispersion (solid concentration: 6% by mass) of polyurethane composition mainly composed of the same polycarbonate ether-based polyurethane as in Example 1 three times by a 75-mesh gravure roll and then dried. The surface coated with the polyurethane composition was napped by buffing using an endless sandpaper set on a buffing machine and the napped fibers were ordered, thereby forming naps of microfine fibers made of the modified polyethylene terephthalate. After dyeing with a disperse dye in a jet dyeing machine, the napped fibers were ordered by brushing, to form a beige nap-finished artificial leather. On the cross section of the nap-finished artificial leather, the existence density of microfine fiber bundles in the region from the napped surface to a depth of 200 m was 2700/mm.sup.2. The nap-finished artificial leather had the effects intended in the present invention, i.e., an extremely high denseness, an elegant nap appearance resembling that of natural nubuck leather as well as an excellent hand and surface abrasion resistance. The results of evaluation are shown in Table 1.

Comparative Example 1

(26) A web of filaments having a mass per unit area of 30 g/m.sup.2 stabilized by embossing was obtained in the same manner as in Example 1 except for using Nylon 6 as the island component polymer of the sea-island fibers for constituting the web of filaments and spinning the sea-island fibers under the condition of producing the fibers having an average cross-sectional area of 307 m.sup.2 (about 3.6 dtex). After providing the surface with the oil agent as in Example 1, the web of filaments was lapped by a crosslapper to obtain a layered web of filaments. The layered web of filaments was preliminarily entangled using needles A in the same manner as in Example 1, and then, entangled using needles C (needle gauge #42, 40 m barb depth, one barb, regular triangle cross section) from both sides thereof at a punching depth of allowing the barb to penetrate through the web in the thickness direction, thereby entangling the sea-island fibers in the thickness direction. The punching density was 3500 punch/cm.sup.2 in total of both sides. The obtained nonwoven fabric was subjected to the moist heat treatment and the press treatment in the same manner as in Example 1, to obtain a nonwoven fabric having a mass per unit area of 700 g/m.sup.2.

(27) The polyurethane composition was allowed to exist in the space between the sea-island fibers of the obtained nonwoven fabric in the same manner as in Example 1, and the modified polyvinyl alcohol was removed from the sea-island fibers by extraction, to obtain a substrate for artificial leather of about 1.4 mm thick comprising a nonwoven fabric constituted by bundles of microfine filaments of Nylon 6 and the polyurethane composition impregnated therein. The obtained substrate for artificial leather was made into a beige nap-finished artificial leather in the same manner as in Example 2 by slicing to two parts, buffing, forming napped fibers of Nylon 6 microfine fibers, dyeing with a metal complex acid dye in a jet dyeing machine to the same color as in Example 2, and finished by ordering. The obtained nap-finished artificial leather was insufficiently densified and merely had a coarse nap appearance which had been achieved by a known suede-finished artificial leather. The surface abrasion resistance was not so good and the hand was hard and bony. Thus, the properties obtained did not reach the level intended in the present invention. The results of evaluation are shown in Table 1.

Comparative Example 2

(28) A web of filaments having a mass per unit area of 30 g/m.sup.2 stabilized by embossing was obtained in the same manner as in Example 1 except for spinning the sea-island fibers for forming the web of filaments using a composite-spinning spinneret capable of forming a cross section in which 100 islands of island component polymer were distributed in the sea component polymer. After coating the surface with the oil agent as in Example 1, the obtained web of filaments was made into a layered web of filaments by a crosslapper and entangled by the needle punching as in Example 1. The obtained nonwoven fabric was hot-pressed without coating water, to obtain a nonwoven fabric having a mass per unit area of 970 g/m.sup.2.

(29) The polyurethane composition was allowed to exist in the space between the sea-island fibers of the obtained nonwoven fabric in the same manner as in Example 1, and the modified polyvinyl alcohol was removed from the sea-island fibers by extraction, to obtain a substrate for artificial leather of about 1.4 mm thick comprising a nonwoven fabric constituted by bundles of microfine filaments of modified polyethylene terephthalate and the polyurethane composition impregnated therein. The obtained substrate for artificial leather was made into a beige nap-finished artificial leather in the same manner as in Example 2 by slicing to two parts, buffing, forming napped fibers of modified polyethylene terephthalate microfine fibers, dyeing with a disperse dye, and finished by ordering. The obtained nap-finished artificial leather superficially looked densified. However, it is no more than that the bundles on the surface portion were flattened by the collapse in the thickness direction to increase the density. Many of the bundles has a flatness exceeding 3.0 and the largest flatness was 4.7. When the surface portion densified by flattened bundles was napped by buffing, the surface portion returned to an insufficiently densified state close to the sparse portion not densified. As a result, only coarse nap appearance which had been achieved by a known suede-finished artificial leather was obtained. In addition, since the central portion in the thickness direction was sparse and only the surface portion was excessively tightly compacted, the hand was hard as in the surface of corrugated paper. Thus, the properties obtained did not reach the level intended in the present invention. The results of evaluation are shown in Table 1. Although dyed in the same manner as in Example 2, the color was whitish without deepness and the appearance lacked quality of high grade, because the microfine fibers forming naps were extremely fine.

Comparative Example 3

(30) A web of filaments having a mass per unit area of 30 g/m.sup.2 stabilized by embossing was obtained in the same manner as in Example 1 except for spinning the sea-island fibers for forming the web of filaments using a composite-spinning spinneret capable of forming a cross section in which 64 islands of island component polymer were distributed in the sea component polymer under the condition of producing the fibers having an average cross-sectional area of 485 m.sup.2 (about 6.6 dtex). After providing the surface with the oil agent as in Example 1, the web of filaments was lapped by a crosslapper to obtain a layered web of filaments. The layered web of filaments was preliminarily entangled using needles A and then entangled using needles B in the same manner as in Example 1. The obtained nonwoven fabric was subjected to the moist heat treatment and the press treatment in the same manner as in Example 1, to obtain a nonwoven fabric having a mass per unit area of 990 g/m.sup.2.

(31) The polyurethane composition was allowed to exist in the space between the sea-island fibers of the obtained nonwoven fabric in the same manner as in Example 1, and the modified polyvinyl alcohol was removed from the sea-island fibers by extraction, to obtain a substrate for artificial leather of about 1.4 mm thick comprising a nonwoven fabric constituted by bundles of microfine filaments of modified polyethylene terephthalate and the polyurethane composition impregnated therein. The obtained substrate for artificial leather was made into a beige nap-finished artificial leather in the same manner as in Example 2 by slicing to two parts, buffing, forming napped fibers of modified polyethylene terephthalate microfine fibers, dyeing with a disperse dye, and finished by ordering. Since the number of bundles per unit cross-sectional area was sufficient, the obtained nap-finished artificial leather looked densified. However, since the bundles were largely flattened to have a flatness exceeding 4.0, the size of gaps between the bundles was significantly uneven and gaps having an extremely large size existed in places. Therefore, the obtained nap-finished artificial leather had coarse nap appearance which was no more than that achieved by a known suede-finished artificial leather. The loss of surface abrasion was small but the pilling occurred increasingly. In addition, the hand was slightly stiff and insufficient in bulky feeling. Thus, the properties obtained did not reach the level intended in the present invention. The results of evaluation is shown in Table 1.

Comparative Example 4

(32) A web of filaments having a mass per unit area of 30 g/m.sup.2 stabilized by embossing was obtained in the same manner as in Example 1 except for spinning the sea-island fibers for forming the web of filaments under the conditions of regulating the average areal ratio of the sea component polymer and the island component polymer on the cross section to sea/island=20/80 and the average cross-sectional area to 147 m.sup.2 (about 2.0 dtex). After providing the surface with the oil agent as in Example 1, the web of filaments was lapped by a crosslapper to obtain a layered web of filaments. The layered web of filaments was entangled in the same manner as in Example 1. The obtained nonwoven fabric was heat-shrunk by immersing in hot water of 70 C., and then, without drying the modified polyvinyl alcohol was removed from the sea-island fibers by extraction in hot water of 90 C., thereby obtaining a substrate for artificial leather having a mass per unit area of 845 g/m.sup.2 which comprised the bundles of microfine filaments of the modified polyethylene terephthalate but did not contain the polyurethane composition.

(33) The obtained substrate for artificial leather was made into a beige nap-finished artificial leather in the same manner as in Example 2 by slicing to two parts, buffing, forming napped fibers of modified polyethylene terephthalate microfine fibers, dyeing with a disperse dye, and finished by ordering. Although not impregnated with the polyurethane composition unlike other examples, the obtained nap-finished artificial leather had favorable hand with firm and dense feeling. However, a portion where the bundles were closely compacted and a portion where the bundles were slightly sparse existed mixedly on the cross section. When buffing such a substrate having the bundles unevenly distributed, a portion with dense naps and a portion with sparse naps, which may be caused by unevenly distributed bundles, existed mixedly on the napped surface. The existence density of bundles of microfine filaments on the cross section parallel to the thickness direction was 1400/mm.sup.2 even at the densified portion near the surface. The size of gaps between the microfine fiber bundles was 74 m and the average size of gaps in the region from the surface to a depth of 200 m was 42 m. As a result, the nap appearance was generally coarse and did not reach the level intended in the present invention. The results of evaluation are shown in Table 1.

Comparative Example 5

(34) The ethylene-modified polyvinyl alcohol (removable component) of the same type as used in Example 1 and the isophthalic acid-modified polyethylene terephthalate (fiber-forming component) of the same type as used in Example 1 were separately melted. Then, the molten polymers were fed into a composite-spinning spinneret capable of forming a layered cross section in which five layers of the removable component (corresponding to sea component polymer) and six layers of the fiber-forming component (corresponding to island component polymer) were alternately stacked. A web of filaments having a mass per unit area of 30 g/m.sup.2 stabilized by embossing was obtained in the same manner as in Example 1 except for feeding the molten polymers into the spinneret in a pressure balance which regulated the average areal ratio of the removable component and the fiber-forming component to 35/65 and spinning the composite fibers under the conditions of controlling the average cross-sectional area to 330 m (about 4.4 dtex). After providing the surface with the oil agent as in Example 1, the web of filaments was lapped by a crosslapper to obtain a layered web of filaments. The layered web of filaments was preliminarily entangled using needles A in the same manner as in Example 1, and then, entangled using needles D (needle gauge #32, 60 m barb depth, nine barbs, regular triangle cross section) from both sides thereof in a total punching density of 600 punch/cm.sup.2 at a punching depth of allowing the barbs to penetrate through the web in the thickness direction, thereby entangling the sea-island fibers in the thickness direction (If the punching density exceed 1000 punch/cm.sup.2, the trouble such as needle break occurs frequently). The layered web of filaments was further needle-punched using needles E (needle gauge #36, 80 m barb depth, one barb, regular triangle cross section) at a punching depth preventing the needles from penetrating through the web in the thickness direction in a punching density of 400 punch/cm.sup.2. After the needle punching by needles E, the nonwoven fabric was cross-sectionally observed. Many bundles were oriented in the thickness direction and the fiber ends formed by breaking were found in a density of 0.5 to 2.5/mm.sup.2 on the surface. The obtained nonwoven fabric was subjected to the moist heat treatment and the press treatment in the same manner as in Example 1, to obtain a nonwoven fabric having a mass per unit area of 650 g/m.sup.2.

(35) The polyurethane composition was allowed to exist in the space between the sea-island fibers of the obtained nonwoven fabric in the same manner as in Example 1, and the modified polyvinyl alcohol was removed from the sea-island fibers by extraction, to obtain a substrate for artificial leather of about 1.4 mm thick comprising a nonwoven fabric constituted by bundles of microfine filaments of modified polyethylene terephthalate and the polyurethane composition impregnated therein. The obtained substrate for artificial leather was made into a beige nap-finished artificial leather in the same manner as in Example 2 by slicing to two parts, buffing, forming napped fibers of modified polyethylene terephthalate microtine fibers, dyeing with a disperse dye, and finished by ordering. The obtained nap-finished artificial leather had a cross section which was clearly poor in the denseness of bundles as compared with Example 1. In addition, the size of gaps between the bundles was significantly uneven and gaps having an extremely large size existed in places. Therefore, the obtained nap-finished artificial leather had coarse nap appearance which was no more than that achieved by a known suede-finished artificial leather. The hand was extremely hard and bony. Thus, the properties obtained did not reach the level intended in the present invention. The results of evaluation are shown in Table 1.

(36) TABLE-US-00001 TABLE 1 Comparative Examples Example 2 1 2 3 4 5 Kind of composite sea- sea- sea- sea- sea- layered fiber island island island island island Island component modified Nylon 6 modified modified modified modified fiber (fiber-forming poly- poly- poly- poly- poly- component) ethylene ethylene ethylene ethylene ethylene terephthalate terephthalate terephthalate terephthalate terephthalate Sea component modified modified modified modified modified modified (removable polyvinyl polyvinyl polyvinyl polyvinyl polyvinyl polyvinyl component) alcohol alcohol alcohol alcohol alcohol alcohol Number of microfine 25 25 100 64 25 6 filaments Cross-sectional area 250 230 160 722 184 270 of bundles of microfine filaments (m.sup.2) Flatness of 2.5 2.9 4.7 4.3 2.6 3.8 microfine fiber bundles Number of cross 2500 1350 1900 1600 1400 450 section of bundles of microfine filaments (per mm.sup.2) Size of gaps (m) 52 78 74 82 74 107 Denseness and A B B C B C elegance of napped fibers Flexibility and A B C B A C bulky feeling of hand Surface abrasion A B C C C C resistance Abrasion loss (mg) 8 42 220 25 15 <1 Pilling A B A C C C

INDUSTRIAL APPLICABILITY

(37) The artificial leather obtained from the substrate for artificial leather of the invention combines good appearance, high surface strength and good hand and suitable for the production of clothes such as jacket, skirt, shirt and coat; shoes such as sport shoes, gentlemen's shoes and ladies' shoes; accessories such as belt; bags such as hand bag and children's backpack; furniture such as sofa and office chair; seats and interiors of vehicles such as passenger car, train, air plane and ship; and gloves such as sport glove, for example, golf glove, batting glove and baseball glove, driving glove and working glove.

(38) The nap-finished artificial leather obtained from the substrate for artificial leather of the invention has highly densified nap appearance resembling that of natural nubuck leather. The nap-finished artificial leather is excellent in color development, hand with both soft, bulky feeling and dense feeling, and surface abrasion resistance such as piling resistance, which are hitherto difficult to combine. The grain-finished artificial leather obtained from the substrate for artificial leather is highly flat and smooth and has appearance resembling the gain surface of natural leather having extremely fine bent wrinkles. The grain-finished artificial leather is also excellent in united feeling between substrate and grain layer, hand with soft and bulky feeling, and peeling strength due to adhesion, which are hitherto difficult to combine. These artificial leather are suitably applied to the use such as clothes, shoes, bags, furniture, car seats and sport gloves such as golf glove.