Patent Application
20190177910
The present invention relates to a nubuck-like fabric including a flexible sheet that is formed by application of a resin to a woven or knitted fabric. The present invention also relates to a method of manufacturing the nubuck-like fabric.
A tactile feel and texture that are close to those of natural leather are demanded in a nubuck-like fabric. The natural leather is internally formed with a moderate number of voids, thus structurally having a distinctive tactile feel (a smooth, soft, and supple feel called “moist feel”) and a distinctive texture (nap). It is conceivable that even the nubuck-like fabric can have a moist feel and nap that are closer to those of the natural leather by having a structure (with voids) similar to that of the natural leather. On the other hand, the natural leather has a drawback that it abrades easily, so that superior abrasion resistance that cannot be achieved by the natural leather is demanded of the nubuck-like fabric. To this end, a suitable material needs to be selected for the nubuck-like fabric.
Generally known methods of manufacturing nubuck-like fabrics (artificial leathers) include a wet method in which a fiber sheet impregnated with a solvent-based polyurethane resin is immersed in a solidification liquid for solidification of the solvent-based polyurethane resin and a dry method in which a fiber sheet impregnated with a water based polyurethane resin is dried in a gas phase for solidification of the water based polyurethane resin.
There is, for example, a nubuck-like artificial leather that has been developed to include a resin applied to a base material by a dry method (refer to PTL 1, for example). The nubuck-like artificial leather described in PTL 1 delivers on a moist feel and nap that are close to those of the natural leather and also has high abrasion resistance.
PTL 1: WO 2017/043322 A
The nubuck-like artificial leather described in PTL 1 uses a nonwoven fabric, not a woven or knitted fabric (hereinafter called “woven/knitted fabric” as a general term) for a base material. Compared with the nonwoven fabric, the woven/knitted fabric is not uniformly dense with filaments because the filaments are unevenly distributed among stitches or others, and therefore, use of the dry method has been difficult to achieve uniform application of a resin. When a woven/knitted fabric has been used for a base material, the wet method has been used conventionally for application of a resin to the woven/knitted fabric. However, the use of the wet method for the application of the resin to the woven/knitted fabric easily causes the resin to excessively adhere to filament surfaces and to be excessively present among filaments, so that a finished nubuck-like artificial leather structurally has the filaments buried in the resin. With such a structure, expression of a moist feel and nap that are close to those of the natural leather is difficult.
In view of the above problem, an object of the present invention is to provide a nubuck-like fabric that has a nubuck-like distinctive moist feel and nubuck-like distinctive nap that are close to those of the natural leather and also has superior abrasion resistance with a woven or knitted fabric used for a base material. Another object of the present invention is to provide a method of manufacturing the nubuck-like fabric.
As a solution to the above problem, a nubuck-like fabric according to the present invention includes a flexible sheet formed by application of a resin to a woven/knitted fabric,
wherein the flexible sheet includes:
In the above nubuck-like fabric, the flexible sheet formed by the application of the resin to the woven/knitted fabric includes the filled portion that includes the filaments and the resin, and the non-filled portion including the spaces, thus internally having a porous structure. Such a structure is similar to that of the natural leather. The above nubuck-like fabric thus can deliver on a moist feel and nap that are close to those of the natural leather with the woven/knitted fabric used for a base material. Moreover, because of presence of the non-filled portion in the flexible sheet, there is no excessive adhesion of the resin to the woven/knitted fabric, which is used for the base material, so that the nubuck-like distinctive moist feel and the nubuck-like distinctive nap that can be obtained are close to those of the natural leather. In the filled portion of the flexible sheet, the filaments are reinforced by the resin, so that a resulting fabric product has greater strength than the natural leather has and thus has superior abrasion resistance.
In the nubuck-like fabric according to the present invention, it is preferable that the flexible sheet also include a nap part at its surface.
By including the nap part at the surface, this nubuck-like fabric can deliver on nubuck-like distinctive nap that is closer to that of the natural leather.
In the previous nubuck-like fabric according to the present invention, the nap part has a thickness preferably ranging from 0.01 to 0.4 mm, inclusive.
With this nubuck-like fabric, the thickness of the nap part is set in the suitable range, so that nubuck-like distinctive nap that can be achieved is even closer to that of the natural leather.
In the nubuck-like fabric according to the present invention, the spaces in the non-filled portion preferably include voids that are surrounded by the filaments.
In this nubuck-like fabric, the spaces in the non-filled portion include the voids surrounded by the filaments. This means that these voids are moderately distributed in the flexible sheet and are fixed. Consequently, the porous structure including the voids is held steady, and a resulting fabric product has superior abrasion resistance.
In the previous nubuck-like fabric according to the present invention, the filled portion preferably includes, in a multifilament yarn forming the woven/knitted fabric, a multifilament-yarn composite where the filaments and the resin hold together, and in a unit area of a section of the flexible sheet, a rate of occupancy Gy (%) by the voids is defined by Formula (1):
Gy(%)={C1/(A1+B1+C1)}×100 (1)
where A1 is a sectional area of the filaments included in the multifilament-yarn composite, B1 is a sectional area of the resin included in the multifilament-yarn composite, and C1 is a sectional area of the voids surrounded by the filaments that are held together by the resin in the multifilament-yarn composite. It is preferable that the rate of occupancy Gy (%) by the voids satisfy Formula (2):
Gy (%)≤15 (2)
In this nubuck-like fabric, the rate of occupancy Gy (%) by the voids that is defined by Formula (1) satisfies Formula (2), so that a nubuck-like distinctive moist feel that can be achieved is comparable to that of the natural leather.
In the previous nubuck-like fabric according to the present invention, the flexible sheet preferably includes a nap part at its surface, the filled portion also preferably includes, at a base of the nap part, a film-shaped nap composite where the filaments and the resin hold together, and in a unit area of the section of the flexible sheet, a rate of occupancy Gs (%) by the voids is defined by Formula (3):
Gs (%)={C2/(A2+B2+C2)}×100 (3)
where A2 is a sectional area of the filaments included in the nap composite, B2 is a sectional area of the resin included in the nap composite, and C2 is a sectional area of the voids surrounded by the filaments that are held together by the resin in the nap composite. It is preferable that the rate of occupancy Gs (%) by the voids satisfy Formula (4):
Gs/Gy>1 (4)
In this nubuck-like fabric, the rate of occupancy Gs (%) by the voids that is defined by Formula (3) satisfies Formula (4), so that the nap composite formed near the surface structurally includes a relatively large number of voids. This means that a nubuck-like distinctive moist feel that can be achieved is closer to that of the natural leather.
In the nubuck-like fabric according to the present invention, the spaces in the non-filled portion preferably include fissures formed by separation of the filaments.
In this nubuck-like fabric, the spaces in the non-filled portion include the fissures that are formed by the separation of the filaments. This means that the filled portion formed can be film-shaped where the filled portion adjoins the fissures.
In the nubuck-like fabric according to the present invention, each of the filaments preferably has a filament linear density ranging from 0.1 to 0.7 dtex, inclusive.
The filaments used in this nubuck-like fabric each have the suitable filament linear density. As such, nap that can be achieved is especially satisfactory with necessary and sufficient abrasion resistance being maintained.
In the nubuck-like fabric according to the present invention, the resin is preferably at least one selected from the group consisting of a polyurethane resin, a silicone resin, and an acrylic resin.
In this nubuck-like fabric, the suitable resin is used, thus imparting suitable softness to a resulting fabric product that also has superior abrasion resistance.
As a solution to the above problem, a method of manufacturing a nubuck-like fabric according to the present invention includes:
a napping step of raising a nap on a surface of a woven/knitted fabric to form the nap on the surface;
a pressing step of pressing the woven/knitted fabric at the surface formed with the nap to form a base material;
a resin application step of impregnating the base material with a resin; and
a drying step of drying the base material impregnated with the resin with moist heat.
According to the above method of manufacturing the nubuck-like fabric, the napping step and the pressing step are carried out before the resin application step is carried out, whereby the nap formed on the surface of the woven/knitted fabric can be denser to hold the resin. Moreover, carrying out the drying with moist heat in the drying step enables a flexible sheet to internally form a porous structure including a filled portion that includes filaments and the resin, and a non-filled portion including spaces. Such a structure is similar to that of the natural leather, so that a fabric thus obtained can deliver on a nubuck-like distinctive moist feel and nubuck-like distinctive nap that are close to those of the natural leather. In the flexible sheet, the filaments are reinforced by the resin, so that a resulting fabric product has greater strength than the natural leather has and thus has superior abrasion resistance.
In the nubuck-like fabric manufacturing method according to the present invention, a masking step of applying a water-soluble composition to a surface of the base material is preferably carried out subsequently to the pressing step.
According to this nubuck-like fabric manufacturing method, with the masking step carried out, the resin can be prevented from excessively soaking into the nap, thus allowing the nubuck-like fabric to have a nap part having a suitable thickness.
In the nubuck-like fabric manufacturing method according to the present invention, a dressing step of raising the nap on the surface of the base material including the resin is preferably carried out subsequently to the drying step to arrange the nap.
According to this nubuck-like fabric manufacturing method, with the dressing step carried out, a nubuck-like distinctive moist feel and nubuck-like distinctive nap that can be achieved are closer to those of the natural leather.
In the previous nubuck-like fabric manufacturing method according to the present invention, a crumpling step is preferably carried out subsequently to the dressing step.
According to this nubuck-like fabric manufacturing method, with the crumpling step carried out, a hardened texture resulting from the drying can be turned into a softened texture, so that the nubuck-like fabric is given softness and thus can deliver on a nubuck-like distinctive moist feel and nubuck-like distinctive nap that are even closer to those of the natural leather.
With reference to the accompanying drawings, a detailed description is hereinafter provided of a nubuck-like fabric and a method of manufacturing the nubuck-like fabric according to the present invention. It is to be noted that the following structure is not intended to be restrictive of the present invention.
The base material is obtained when a woven/knitted fabric formed of a multifilament yarn including filaments 10 has its nap raised. A side on which the nap is raised is considered as a right face of the base material. Usable examples of the woven/knitted fabric for the base material include knitted fabrics such as a tricot knitted fabric, a double raschel knitted fabric, and the circular knitted fabric, and woven fabrics obtained by, for example, a plain weave, a twill weave, and a satin weave. The base material has a weight per area that is preferably adjusted to range from 150 to 1,000 g/m2, inclusive. With the weight per area of the base material being in this range, a necessary and sufficient amount of resin 20 can be easily applied. With the weight per area of the base material being less than 150 g/m2, the resin 20 easily slips through the filaments 10 of the base material. With the weight per area of the base material being more than 1,000 g/m2, it is difficult to allow the resin 20 to be held among the filaments 10 of the base material through sufficient impregnation. The base material has a thickness L that is preferably set to range from 0.5 to 3.7 mm, inclusive. With the thickness L of the base material being in this range, a resulting fabric that can be obtained as a final product has a superior texture and superior workability. With the thickness L of the base material being less than 0.5 mm, a resulting fabric as a final product is less likely to have a nubuck-like distinctive moist feel and nubuck-like distinctive nap and can possibly be paper-textured. With the thickness L of the base material being greater than 3.7 mm, a resulting fabric as an industrial material can possibly have deteriorated workability, thus leading to a manufacturing problem such as sewing difficulties. Examples that can be used for the filaments 10 used in the base material include synthetic fibers such as a polyester fiber, a nylon fiber, an acrylic fiber, a vinylon fiber, and an urethane fiber, semisynthetic fibers such as an acetate fiber, a triacetate fiber, and a promix fiber, regenerated fibers such as a rayon fiber, a cupra fiber, and a polynosic fiber, and natural fibers such as a cotton fiber, a silk fiber, and a hemp fiber. One of these fibers may be used alone, or two or more of these fibers may be used in combination as a fiber blend. In terms of versatility and durabilities (mechanical strength, thermal resistance, and light resistance), the synthetic fibers are preferable materials for the filaments 10. The polyester fiber is a more preferable material for the filaments 10 because of its superior strength.
Usable examples of the resin 20 include polyurethane resins, silicone resins, and acrylic resins. Among these resins, the polyurethane resins are preferable for use. The polyurethane resins are generally classified into non-water based polyurethane resins (solvent-based polyurethane resins) and water based polyurethane resins. Although a suitable polyurethane resin used for manufacturing the nubuck-like fabric 100 of the present invention is water based because a dry method is used, also the non-water based polyurethane resins that are used in conventional wet methods are usable. It is to be noted that the nubuck-like fabric manufacturing method using the dry method according to the present invention is described later in detail in [Method of manufacturing nubuck-like fabric]. Given examples of the polyurethane resins include a polyether polyurethane resin, a polyester polyurethane resin, and a polycarbonate polyurethane resin. One of these polyurethane resins may be used alone, or two or more of these polyurethane resins may be used in combination as a blend. The polycarbonate polyurethane resin is preferable in terms of abrasion resistance. Based on how the polyurethane resins cure, there are a one-component type, a two-component curing type, and a moisture curing type as given examples. Among these types, the one-component type polyurethane resin that is water based is suitable in terms of reduced environmental loading and reduced work load. Based on dispersion, the water based one-component type polyurethane resin is of a self-emulsifying type or a forced emulsifying type. It is to be noted that each of the above polyurethane resins can include various additives such as a catalyst, a crosslinking agent, a smoothing agent, a gelation promoter, a filler, a wax, a light resistance improver, a foaming agent, a thermoplastic resin, a thermosetting resin, a dye, a pigment, a flame retardant, a conductivity imparting agent, an antistatic agent, a moisture permeability improver, a water repellent agent, an oil-repellent agent, a hollow foam, a water absorbent, protein powder, a moisture absorbent, a deodorant, a foam stabilizer, an antifoaming agent, an antifungal agent, an antiseptic agent, a pigment dispersant, an inert gas, an antiblocking agent, a hydrolysis inhibitor, a delustering agent, a tactile feel improver, and a thickener.
An amount of impregnation of the base material with the resin 20 with respect to the weight per area of the base material is adjusted to range preferably from 7 to 50% by weight, inclusive and more preferably from 10 to 30% by weight, inclusive in terms of solid content. With the amount of impregnation with the resin 20 being in the above range, a ratio of the filaments 10 to the resin 20 becomes suitable, thus enabling formation of a structure similar to that of natural leather. With the amount of impregnation with the resin 20 being less than 7% by weight, bonding strength is not enough for the filaments 10. This makes formation of voids 30a (described later) difficult, and a resulting fabric as a final product is less likely to have a nubuck-like distinctive moist feel. With the amount of impregnation with the resin 20 being more than 50% by weight, there can possibly be a rubber-like sticky feel and spoiled nap.
The nubuck-like fabric 100 according to the present invention is formed to be structurally similar to the natural leather, which is a porous material. Specifically, the flexible sheet 100′ forming the nubuck-like fabric 100 is formed with, at its surface, the nap part 50 standing up from the multifilament yarn, and many microscopic spaces are formed in the flexible sheet 100′. In this specification, an area including these microscopic spaces is specified as a non-filled portion 30. The flexible sheet 100′ has the resin 20 filled among the filaments 10, so that the filaments 10 are held together by the resin 20, forming a filled portion 40 where the filaments 10 are integral with the resin 20. The filled portion 40 includes a multifilament-yarn composite 40a and a nap composite 40b. The multifilament-yarn composite 40a is a structure in the multifilament yarn and is where the filaments 10 and the resin 20 hold together. The nap composite 40b is a film-shaped structure where the filaments 10 and the resin 20 hold together and is formed near a base of the nap part 50, thus being closer to the surface of the flexible sheet 100′ than the multifilament-yarn composite 40a is. The spaces in the non-filled portion 30 include the voids 30a and fissures 30b. The voids 30a are surrounded by the filaments 10 that are held together by the resin 20 in the multifilament-yarn composite 40a and the nap composite 40b, while the fissures 30b are formed by separation of the filaments 10 into the multifilament-yarn composite 40a and the nap composite 40b. With such a structure formed, relative positions of the filaments 10 are substantially fixed in the flexible sheet 100′. Consequently, the voids 30a surrounded by the filaments 10 are each allowed to retain its form and are fixed in the flexible sheet 100′.
As illustrated in
The nubuck-like characteristics that are imparted to the fabric, such as “moist feel”, “nap”, and “abrasion resistance”, are affected by (I) a thickness of the nap part 50 lying down on the flexible sheet 100′, (II) a rate of occupancy by the voids in the multifilament-yarn composite 40a, and (III) a ratio of a rate of occupancy by the voids in the nap composite 40b to the rate of occupancy by the voids in the multifilament-yarn composite 40a (this ratio is hereinafter referred to as “void proportion ratio”).
With the thickness d1 of the nap part 50 being set in a suitable range in a sectional image of the flexible sheet 100′ that is taken using an electron microscope with the nap part 50 lying down, expression of nubuck-like distinctive nap can be achieved. In the nubuck-like fabric 100 according to the present invention, the thickness d1 of the nap part 50 is set to range preferably from 0.01 to 0.4 mm, inclusive and more preferably from 0.05 to 0.2 mm, inclusive. With the present invention's nubuck-like fabric 100 having the thickness d1 set in the above range, the nap part 50 imparts nap that is comparable to that of the natural leather to the flexible sheet 100′. The thickness d1 that is less than 0.01 mm is less likely to effect nap. With the thickness d1 being greater than 0.4 mm, a tactile feel can possibly be different from that of the natural leather. It is to be noted that when the thickness d1 of the nap part 50 is measured in each of three sections of the nubuck-like fabric 100, namely, a section parallel to a knitted or woven direction of the base material, a section intersecting the knitted or woven direction at 45°, and a section orthogonal to the knitted or woven direction, after five sweeping strokes are made in such a direction as to lay down the filaments with the foundation brush (SA-15-P8, T427 manufactured by Daiso Industries Co., Ltd.) that is brought perpendicularly into contact with the nap part 50 positioned at the surface of the nubuck-like fabric 100, the smallest value measured may only have to be in the above range.
In a unit area of a sectional image of the flexible sheet 100′ that is taken with the electron microscope, the rate of occupancy Gy (%) by the voids in the multifilament-yarn composite 40a is defined by Formula (1):
Gy (%)={C1/(A1+B1+C1)}×100 (1)
In Formula (1), A1 is a sectional area of the filaments 10 included in the multifilament-yarn composite 40a, B1 is a sectional area of the resin 20 included in the multifilament-yarn composite 40a, and C1 is a sectional area of the voids 30a surrounded by the filaments 10 that are held together by the resin 20 in the multifilament-yarn composite 40a. With the rate of occupancy Gy (%) by the voids in the multifilament-yarn composite 40a being set in a suitable range, expression of a nubuck-like distinctive moist feel can be achieved.
In the nubuck-like fabric 100 according to the present invention, the rate of occupancy Gy by the voids preferably satisfies Formula (2):
Gy (%)≤15 (2)
The rate of occupancy Gy by the voids can be changed through adjustment of the amount of impregnation of the filaments 10 (base material) with the resin 20. With the present invention's nubuck-like fabric 100 satisfying Formula (2), improved abrasion resistance of the flexible sheet 100′ is effected by the multifilament-yarn composite 40a and the nap composite 40b while the voids 30a impart to the flexible sheet 100′ the nubuck-like distinctive moist feel that is comparable to that of the natural leather. With the rate of occupancy Gy by the voids being higher than 15%, there is a decline in strength that easily causes abrasion, and any sufficiently moist feel is difficult to impart.
In a unit area of the sectional image of the flexible sheet 100′ that is taken with the electron microscope, the rate of occupancy Gs (%) by the voids in the nap composite 40b is defined by Formula (3):
Gs (%)={C2/(A2+B2+C2)}×100 (3)
In Formula (3), A2 is a sectional area of the filaments 10 included in the nap composite 40b, B2 is a sectional area of the resin 20 included in the nap composite 40b, and C2 is a sectional area of the voids 30a surrounded by the filaments 10 that are held together by the resin 20 in the nap composite 40b. With the void proportion ratio (Gs/Gy) of the rate of occupancy Gs (%) by the voids in the nap composite 40b to the rate of occupancy Gy (%) by the voids in the multifilament-yarn composite 40a being in a suitable range, expression of a nubuck-like distinctive moist feel can be achieved.
In the nubuck-like fabric 100 according to the present invention, the void proportion ratio (Gs/Gy) preferably satisfies Formula (4):
Gs/Gy>1 (4)
The rate of occupancy Gs by the voids can be changed through adjustment of the amount of impregnation of the filaments 10 (base material) with the resin 20. The present invention's nubuck-like fabric 100 satisfying Formula (4) can deliver on the nubuck-like distinctive moist feel close to that of the natural leather because the nap composite 40b formed near the surface structurally includes relatively many of the voids 30a. With the void proportion ratio (Gs/Gy) being less than 1, any sufficiently moist feel is difficult to impart.
By including the nap composite 40b, the nubuck-like fabric 100 according to the present invention does not have the multifilament yarn of the base material exposed at its surface, so that its surface has a lower coefficient of friction (MIU). Specifically, when the coefficient of friction of the surface of the nubuck-like fabric 100 is measured in each of three directions, namely, the knitted or woven direction of the base material, a direction intersecting the knitted or woven direction at 45°, and a direction orthogonal to the knitted or woven direction, it is preferable that the smallest value measured range from 0.15 to 0.45, inclusive. A surface of the natural leather has a coefficient of friction approximately ranging from 0.1 to 0.3. With the surface of the nubuck-like fabric 100 having the coefficient of friction ranging from 0.15 to 0.45, inclusive, expression of a nubuck-like distinctive moist feel close to that of the natural leather can be achieved. With the coefficient of friction being less than 0.15, there can possibly be lack of abrasion resistance. With the coefficient of friction being greater than 0.45, there can be an insufficiently moist feel.
In the nubuck-like fabric 100 according to the present invention, a thickness d2 of the nap composite 40b is set to range preferably from 0.01 to 0.2 mm, inclusive and more preferably from 0.05 to 0.1 mm, inclusive. With the present invention's nubuck-like fabric 100 having the thickness d2 set in the above range, improved abrasion resistance can be achieved. With the thickness d2 being less than 0.01 mm, the nap composite 40b can possibly be ruined with ease through abrasion. With the thickness d2 being greater than 0.2 mm, a resulting nubuck-like fabric 100 is stiffer and can possibly have a tactile feel different from that of the natural leather.
Selecting or setting a suitable size of each of the filaments 10 is effective in achieving a well-balanced combination of the moist feel, the nap, and the abrasion resistance for the nubuck-like fabric 100 according to the present invention. Each of the filaments 10 has such a thickness that its filament linear density ranges preferably from 0.1 to 0.7 dtex, inclusive and more preferably from 0.1 to 0.5 dtex, inclusive. With the present invention's nubuck-like fabric 100 having the filaments 10 that each have the thickness in the above range in terms of filament linear density, satisfactory nap can be achieved with necessary and sufficient abrasion resistance being maintained. With the filament linear density being less than 0.1 dtex, sufficient abrasion resistance is difficult to ensure. With the filament linear density being more than 0.7 dtex, a nubuck-like distinctive moist feel and nubuck-like distinctive nap are difficult to achieve. It is to be noted that a blend of fibers of multiple kinds and different sizes may be used for the filaments 10 as long as the above condition is satisfied.
When viewed in a thickness-wise section, the present invention's nubuck-like fabric 100 having the above structure includes the nap part 50 formed at its surface and also includes the filled portion 40 that includes the filaments 10 and the resin 20, and the non-filled portion 30 including the spaces. Thus, the nubuck-like fabric 100 internally has the porous structure including the voids 30a and the fissures 30b, and this porous structure is similar to that of the natural leather, which is the porous material. With such a structure being formed in at least one of a section parallel to the knitted or woven direction of the base material of the nubuck-like fabric 100, a section intersecting the knitted or woven direction at 45°, or a section orthogonal to the knitted or woven direction, the nubuck-like fabric 100 according to the present invention can deliver on a nubuck-like distinctive moist feel and nubuck-like distinctive nap that are close to those of the natural leather.
The base material, which is a base of the nubuck-like fabric, is prepared first. The base material is made through the napping step (S1) in which a nap is raised on a surface of a woven/knitted fabric having a weight per area of 150 to 1,000 g/m2, inclusive to form the nap on the surface of the woven/knitted fabric and the pressing step (S2) in which the woven/knitted fabric is thermally pressed at the surface. In the napping step, a roller wound with card clothing or sandpaper (emery), for example can be used (in a card clothing raising machine, an emery raising machine, or the like) to raise the nap. When the roller is used to raise the nap, the woven/knitted fabric is brought into contact with a roller surface while being moved in a rotation direction of the roller (in a longitudinal direction of the woven/knitted fabric). A raised condition of the nap of the woven/knitted fabric can be adjusted here by changes that are made to various conditions such as a type of the card clothing or the sandpaper, rotational speed of the roller, contact pressure between the woven/knitted fabric and the roller, and frequency of contact between the woven/knitted fabric and the roller. The napping step to carry out can be, instead of being the nap raising using the roller, a publicly known method such as adoption of a woven or knitted fabric structure that has a nap, or flocking. The pressing step is carried out using, for example, an embossing roller engraved with a crimping pattern. In this way, the woven/knitted fabric's surface formed with the nap can be denser with more filaments, and the nubuck-like fabric as the final product has an easily formed nap composite.
Carried out next on an as needed basis is the masking step (S3) in which a water-soluble composition is applied to a right face of the base material. The masking step to carry out is, for example, application of the water-soluble composition such as carboxymethyl cellulose, hydroxyethyl cellulose or hydroxypropyl methylcellulose to the right face of the base material by, for example, screen printing, or application of a water repellent agent to the right face of the base material by, for example, screen printing. Among these methods, the application of the water-soluble composition to the right face of the base material is suitable because of ease of work and a good finish that is provided for the nubuck-like fabric as the final product. Adjustment of an amount of the water-soluble composition to apply enables a limited extent of impregnation of the nap with the resin in the resin application step and desired thicknesses of a nap part and the nap composite of the nubuck-like fabric as the final product.
Carried out next is the resin application step (S4) in which the base material is impregnated with the resin. The resin application step to carry out is, for example, a mangle-pad method in which the base material is immersed in a resin solution including the resin and is then passed through a mangle to be wrung or a method of coating the base material with a resin solution with a spray coater, a gravure coater, a reverse coater, a doctor blade coater, or the like. Among these methods, the mangle-pad method is suitable because the base material can be uniformly impregnated with the resin. A condition of impregnation with the resin is set such that the base material having the weight per area of 150 to 1,000 g/m2, inclusive is given 30 to 300 g/m2 of the resin in terms of solid content. Consequently, adhesion of the resin takes place among the filaments of a multifilament yarn in the base material as well as in the nap where density of the filaments has been increased in the pressing step, although a closest portion of the nap to the surface does not have the resin adhered because of the water-soluble composition applied in the masking step. The amount of the resin to apply with respect to the weight of the base material is adjusted to range from 7 to 50% by weight, inclusive and preferably from 10 to 30% by weight, inclusive in terms of resin solid content.
Carried out next is the drying step (S5) in which the base material impregnated with the resin is dried with moist heat. In the drying step, a high temperature steamer, a high pressure steamer, or the like is used. The drying with moist heat is preferable because the resin can be solidified without fail even at a depth of the base material. The base material that has been dried with the moist heat can be processed to form a fabric product having superior strength and superior abrasion resistance. A drying condition for the base material is set such that a drying temperature ranges preferably from 80 to 150° C., inclusive and more preferably from 100 to 130° C., inclusive. With the drying temperature being in the above range, the filaments can be provided with the resin with migration of the resin suppressed, and the nap composite and a multifilament-yarn composite can be formed. With the drying temperature being lower than 80° C., the resin is insufficiently dried (cured) and thus migrates. As such, it is difficult to provide the resin to designated positions of the filaments. With the drying temperature being higher than 150° C., a nubuck-like fabric as a final product easily has a less moist feel and nap that is coarse and hard. Drying time is set to range preferably from 50 to 1,200 s, inclusive and more preferably from 100 to 600 s, inclusive. With the drying time being in the above range, the filaments can be provided with the resin with migration of the resin suppressed, and the nap composite and the multifilament-yarn composite can be formed. With the drying time being less than 50 s, the resin is insufficiently dried (cured) and thus migrates. As such, it is difficult to provide the resin to the designated positions of the filaments. With the drying time being more than 1,200 s, a nubuck-like fabric as a final product easily has a less moist feel and nap that is coarse and hard. The base material that has undergone the drying step has the filaments that are hardened while being held together by the resin in the multifilament yarn and near a base of the nap part, and thus is a flexible sheet that can be used even as it is as a nubuck-like fabric. This flexible sheet is internally formed with many voids surrounded by the filaments. In other words, the nubuck-like fabric according to the present invention is formed to have the voids that are moderately distributed in the flexible sheet, thus being structurally similar to the natural leather.
Carried out next is the dressing step (S6) in which the nap is raised on the right face of the base material including the resin. This dressing step is an optional step that is carried out as required so that the nap that has been disarranged by the drying can be arranged. With the dressing step carried out, a finished nubuck-like fabric has a surface having a suitable coefficient of friction (MIU) and thus can deliver on a nubuck-like distinctive moist feel and nubuck-like distinctive nap that are closer to those of the natural leather. The coefficient of friction of the surface of the nubuck-like fabric ranges preferably from 0.15 to 0.45, inclusive and more preferably from 0.20 to 0.40, inclusive. With the coefficient of friction being less than 0.15, there can be lack of abrasion resistance. With the coefficient of friction being greater than 0.45, there can be an insufficiently moist feel.
The crumpling step (S7) is carried out last for texture adjustment. This crumpling step is an optional step that is carried out as required so that a hardened texture resulting from the drying can be turned into a softened texture. Given examples of a device that is used in the crumpling step include a milling machine in which a drum loaded with a fabric is rotated to fling down the fabric for imparting softness and a vibration staking machine in which a surface of a fabric is stabbed with a plurality of pins to be given softness and smoothness. One of these machines may be used alone, or these machines may be used in combination.
A description is hereinafter provided of examples in which respective nubuck-like fabrics were made to each have a structure according to the present invention. For comparison with the fabrics of the present invention, fabrics each not having the structure according to the present invention were made in comparative examples, respectively.
An interlaced yarn including a PET splittable grey yarn (84 dtex/25 f) and a PET grey yarn (33 dtex/12 f) was used to form a circular knitted base fabric of blister structure. The base fabric had a weight per area of 466.6 g/m2 and a thickness of 1.1 mm. This base fabric was used as a base of a flexible sheet of the nubuck-like fabric. The base fabric first underwent the napping step (in which #600 sandpaper was used to raise a nap one thousand times per minute), thereafter was dyed with a disperse dye and underwent the napping step again (in which the #600 sandpaper was used to raise the nap one thousand times per minute). Carried out thereafter was the pressing step in which an embossing roller engraved with a pore-like crimping pattern was used for thermal pressing (at 100° C. with 150 kg/mm and 3 m/min), whereby a base material was obtained. The base material underwent the masking step (in which a water solution including 16% by weight of carboxymethyl cellulose was applied to a right face of the base material with a 1350-mesh drawing screen with a wet coating amount being 46 g/m2 and then underwent 60° C. heat treatment for 10 min). Thereafter, the base material underwent the resin application step in which the mangle-pad method was used to impregnate the base material with a polyurethane resin solution. In the resin application step, the polyurethane resin solution used included 20% by weight of a water based polyurethane resin (“SAD8⋅2” manufactured by DKS Co. Ltd.), and the amount of impregnation of the base material with respect to the weight per area of the base material was adjusted to 16% by weight in terms of solid content. Following the impregnation with the polyurethane resin, the drying step, namely, the drying with moist heat was carried out (at 130° C. for 10 min with 95% RH), whereby the flexible sheet having the polyurethane resin applied to the base fabric (knitted fabric) was formed. In this flexible sheet, the amount of the polyurethane resin applied was 74.7 g/m2 in terms of solid content. The dressing step (in which the #600 sandpaper was used to raise the nap one thousand times per minute) and the crumpling step (in which a vibration staking machine manufactured by Cartigliano S.p.A. under the product name of “3H3200A” was used with a working speed of 3 m/min and with a stabbing depth being 3.0 mm) were carried out last, whereby the nubuck-like fabric of Example 1 was obtained.
A circular knitted base fabric that was the same as the one used for the nubuck-like fabric of Example 1 was used as a base of a flexible sheet of the nubuck-like fabric. In manufacturing of the nubuck-like fabric, the polyurethane resin solution to use in the resin application step was switched to a polyurethane resin solution including 40% by weight of the water based polyurethane resin (“SAD8⋅2” manufactured by DKS Co. Ltd.), and the amount of impregnation of a base material with respect to the weight per area of the base material was adjusted to 32% by weight in terms of solid content. The amount of the polyurethane resin applied was adjusted to 149.3 g/m2 in terms of solid content. The steps carried out in Example 2 were otherwise the same as in Example 1, whereby the nubuck-like fabric of Example 2 was obtained.
To form a base fabric of weft backed satin weave, a PET 2H textured yarn (84 dtex/25 f) was used for a warp, an interlaced yarn including four PET splittable grey yarns (each with 84 dtex/25 f) and two PET grey yarns (each with 33 dtex/12 f) was used for a weft 1, and a PET 1H textured yarn (330 dtex/96 f) was used as a weft 2. The base fabric had a weight per area of 314 g/m2 and a thickness of 1.0 mm. This base fabric was used as a base of a flexible sheet of the nubuck-like fabric. In manufacturing of the nubuck-like fabric, the amount of the polyurethane resin applied in the resin application step was adjusted to 50.2 g/m2 in terms of solid content. The steps carried out in Example 3 were otherwise the same as in Example 1, whereby the nubuck-like fabric of Example 3 was obtained.
To form a tricot base fabric, a PET grey yarn (84 dtex/24 f) was used as a front ground yarn, a PET 1H textured yarn (84 dtex/144 f) was used as a connecting yarn, and an interlaced yarn including a PET splittable grey yarn (84 dtex/25 f) and a PET grey yarn (44 dtex/12 f) was used as a back ground yarn. The base fabric had a weight per area of 394.1 g/m2 and a thickness of 1.3 mm. This base fabric was used as a base of a flexible sheet of the nubuck-like fabric. In manufacturing of the nubuck-like fabric, the amount of the polyurethane resin applied in the resin application step was adjusted to 63.1 g/m2 in terms of solid content. The steps carried out in Example 4 were otherwise the same as in Example 1, whereby the nubuck-like fabric of Example 4 was obtained.
A circular knitted base fabric that was the same as the one used for the nubuck-like fabric of Example 1 was used as a base of a flexible sheet of the nubuck-like fabric. In manufacturing of the nubuck-like fabric, the pressing step was followed by the resin application step, and no masking step was carried out. The steps carried out in Example 5 were otherwise the same as in Example 1, whereby the nubuck-like fabric of Example 5 was obtained.
A circular knitted base fabric that was the same as the one used for the nubuck-like fabric of Example 1 was used as a base of the fabric. The base fabric first underwent the napping step (in which #600 sandpaper was used to raise a nap one thousand times per minute), thereafter was dyed with the disperse dye and underwent the napping step again (in which the #600 sandpaper was used to raise the nap one thousand times per minute). Thereafter, heat setting was carried out (at 150° C. for 1 min), whereby the fabric of Comparative Example 1 was obtained. In other words, the fabric of Comparative Example 1 was such that the same base fabric as in the nubuck-like fabric of Example 1 was not impregnated with the polyurethane resin solution and underwent the heat setting.
To forma base fabric of warp backed satin weave, a twisted yarn formed of two PET 1H textured yarns (each with 84 dtex/96 f) was used for a warp, a PET 2H textured yarn (167 dtex/48 f) was used for a weft 1, and a PET 1H textured yarn (330 dtex/96 f) was used for a weft 2. The base fabric had a weight per area of 501.2 g/m2 and a thickness of 1.3 mm. This base fabric was used as a base of the fabric. In manufacturing of the fabric, heat setting was carried out first (at 150° C. for 1 min) and was followed by the resin application step. In the resin application step, a polyurethane resin solution was applied to a surface of the base fabric by blade coating (so that the amount of a polyurethane resin applied was 30 g/m2 in terms of solid content). The used polyurethane resin solution included 29.6% by weight of the water based polyurethane resin (“SAT18D” manufactured by DKS Co. Ltd.). Subsequently to the application of the polyurethane resin, drying with dry heat was carried out (at 130° C. for 10 min). Carried out last was the pressing step in which the embossing roller engraved with the pore-like crimping pattern was used for thermal pressing (at 100° C. with 150 kg/mm and 3 m/min), whereby the fabric of Comparative Example 2 was obtained.
To identify characteristics of each of the above fabrics, various measurements and an evaluation were carried out next, and a relationship between fabric structure and the characteristics was examined for each of the fabrics. Measurement items and an evaluation item are as follows.
Respective images of three sections of each of the fabrics were taken using the scanning electron microscope (S-3000N manufactured by Hitachi High-Technologies Corporation) with a magnification of 1,000× after five sweeping strokes were made in such a direction as to lay down filaments with the foundation brush (SA-15-P8, T427 manufactured by Daiso Industries Co., Ltd.) that was brought perpendicularly into contact with a nap part positioned at a surface. Those three sections were a section parallel to a knitted or woven direction of the base fabric, a section intersecting the knitted or woven direction at 45°, and a section orthogonal to the knitted or woven direction. A thickness of the nap part was determined in each of those three sectional SEM images, and the smallest value determined was considered as the thickness (mm) of the nap part of the fabric. Moreover, a thickness of a nap composite was determined in each of those three sectional SEM images, and the smallest value determined was considered as the thickness (mm) of the nap composite of the fabric.
Respective images of sections of each of the fabrics were taken using the scanning electron microscope (S-3000N manufactured by Hitachi High-Technologies Corporation) with the magnification of 1,000×. Those sections were a section orthogonal to the knitted or woven direction and a section parallel to the knitted or woven direction. Image analysis was carried out to determine a total area of the filaments, a total area of the resin, and a total area of voids in the nap composite shown in each of the SEM images. When an area of the nap composite in each of the SEM images is 100, a proportion of the total area of the filaments, a proportion of the total area of the resin, and a proportion of the total area of the voids were respectively considered as a rate of occupancy (%) by the filaments, a rate of occupancy (%) by the resin, and a rate of occupancy (%) by the voids in the nap composite. The rate of occupancy (%) by the filaments, the rate of occupancy (%) by the resin, and the rate of occupancy (%) by the voids in the nap composite respectively correspond to, in a unit area, a sectional area A2 of the filaments included in the nap composite, a sectional area B2 of the resin included in the nap composite, and a sectional area C2 of the voids surrounded by the filaments that are held together by the resin in the nap composite. Moreover, image analysis was carried out to determine a total area of the filaments, a total area of the resin, and a total area of voids in a multifilament-yarn composite shown in each of the SEM images. When an area of the multifilament-yarn composite in each of the SEM images is 100, a proportion of the total area of the filaments, a proportion of the total area of the resin, and a proportion of the total area of the voids were respectively considered as a rate of occupancy (%) by the filaments, a rate of occupancy (%) by the resin, and a rate of occupancy (%) by the voids in the multifilament-yarn composite. The rate of occupancy (%) by the filaments, the rate of occupancy (%) by the resin, and the rate of occupancy (%) by the voids in the multifilament-yarn composite respectively correspond to, in a unit area, a sectional area A1 of the filaments included in the multifilament-yarn composite, a sectional area B1 of the resin included in the multifilament-yarn composite, and a sectional area C1 of the voids surrounded by the filaments that are held together by the resin in the multifilament-yarn composite. Furthermore, a void proportion ratio that is a ratio of the rate of occupancy (%) by the voids in the nap composite to the rate of occupancy (%) by the voids in the multifilament-yarn composite was calculated for each of the fabrics. The rate of occupancy by the filaments, the rate of occupancy by the resin, and the rate of occupancy by the voids in each of the nap composite and the multifilament-yarn composite were calculated at each of two spots in the section orthogonal to the knitted or woven direction and at each of two spots in the section parallel to the knitted or woven direction (four spots in total), and those values obtained by averaging were adopted as the rate of occupancy by the filaments, the rate of occupancy by the resin, and the rate of occupancy by the voids in each of the nap composite and the multifilament-yarn composite.
An automatic surface tester (KES-FB4-AUTO-A manufactured by Kato Tech Co., Ltd.) was used to measure a coefficient of friction (MIU) of each of the fabric surfaces in each of three directions, namely, the knitted or woven direction of the base fabric, a direction intersecting the knitted or woven direction at 45°, and a direction orthogonal to the knitted or woven direction. Among the values measured in the three directions, the smallest value was adopted as the coefficient of friction of the fabric surface.
A mark produced on each of the fabric surfaces by impression of a finger was visually evaluated based on the following criteria.
◯: The produced finger mark was similar to a finger mark produced on the natural leather
X: No finger mark similar to the finger mark produced on the natural leather was produced
Results of the measurements and the evaluation are shown below in Table 1.
The nubuck-like fabrics of Examples 1 to 5 each had the thickness of the nap part in the range of 0.01 to 0.4 mm and the thickness of the nap composite in the range of 0.01 to 0.2 mm. Because of the nap part of appropriate thickness and the nap composite of appropriate thickness, each of the finger marks obtained was similar to that produced on the natural leather. Moreover, the nubuck-like fabrics of Examples 1 to 5 each had the void proportion ratio (Gs/Gy) of more than 1. In other words, the number of voids identified in the nap composite that was formed near the fabric surface was relatively large. In addition, the nubuck-like fabrics of Examples 1 to 5 each had the coefficient of friction of less than 0.4, enabling the finger marks similar to the finger mark produced on the natural leather. Consequently, the nubuck-like fabrics of Examples 1 to 5 each had expression of a nubuck-like distinctive moist feel and nubuck-like distinctive nap that were close to those of the natural leather, and their tactile feels were satisfactory.
On the other hand, the fabric of Comparative Example 1 that had no polyurethane resin applied was formed with neither the nap composite nor the multifilament-yarn composite, had the coefficient of friction of more than 0.4 and had no expression of a nubuck-like distinctive moist feel. The fabric of Comparative Example 2 was formed with no nap part, so that the finger mark obtained was not similar to that produced on the natural leather. Although the fabric of Comparative Example 2 was formed with the nap composite, no multifilament-yarn composite was formed, and the voids identified were distributed differently from those of the nubuck-like fabrics of Examples 1 to 5 with no expression of a nubuck-like distinctive moist feel and nubuck-like distinctive nap.
Each of the nubuck-like fabrics according to the present invention had an observed structure in which the relatively large number of voids were included in the nap composite formed near the surface. Such a structure conceivably delivered on the nubuck-like distinctive moist feel and the nubuck-like distinctive nap that were close to those of the natural leather.
A nubuck-like fabric and a method of manufacturing the nubuck-like fabric according to the present invention can be used for various leather goods including seats for cars, aircraft, and ships, sofas, furniture, bags, and shoes.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-235340 | Dec 2017 | JP | national |
