JPH07126985A - Production of nubuck-like artificial leather - Google Patents

Abstract

PURPOSE:To obtain a good nubuck-like artificial leather having smooth, soft and sharp surface and chalk mark property and having short hair length, high fiber napping density and homogeneous napping state by eliminating rubber-like appearance and handle without requiring ultrafine treatment over two stages. CONSTITUTION:A web is formed from a conjugate fiber consisting of two or more kinds of high polymers and capable of processing into a ultrafine fiber and needle punching is applied in barb-through punching numbers of 500-3000/cm<2> in thickness direction of the web to prepare an entangled fibrous substrate and an elastic polymer is impregnated into the entangled fibrous substrate and the substrate is squeezed to 60-90% of the thickness of the substrate and solidified, and then, the conjugate fiber constituting the entangled fibrous substrate is formed into ultrafine shape and a liquid containing a solvent of an elastic polymer is applied to the unnapped surface of the entangled fibrous substrate to dissolve or swell a part for the elastic polymer, and the liquid is removed to solidify the substrate and a solvent-containing liquid treating face of the entangled fibrous substrate is subjected to buffing treatment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a nubuck-like artificial leather, and more specifically, it does not require a two-step fiber micronization treatment, and eliminates a rubber-like appearance and texture to provide a surface The present invention relates to a method for producing a nubuck-like artificial leather which is smooth, flexible, has sharp chalk marks, has short naps, has a high fiber nap density, and has excellent homogeneity.

[0002]

2. Description of the Related Art As a conventional method for producing artificial leather having a napped appearance, for example, a fiber assembly such as a woven fabric, a knitted fabric or a non-woven fabric is impregnated with a high molecular polymer and coagulated, and then the surface thereof is polished. The way is done.

Further, in order to control the appearance of the artificial leather, it is common practice to regulate the apparent density of the fiber aggregate, increase the impregnation amount of the elastic polymer, and control the buffing conditions.

However, in these methods, the napped fiber length becomes long, and a good appearance can be obtained as a suede or velour-like artificial leather, but an artificial leather having a dignified appearance as a nubuck tone with a short fiber length is obtained. I can't get it.

In order to solve this problem, as a method of shortening the napped fiber length, for example, Japanese Patent Laid-Open No. 3-161576.
Japanese Patent Laid-Open Publication No. 2004-242242 discloses a step of expressing the ultrafine fibers from the composite fibers in the surface layer portion, and then applying a polymer elastic body to coagulate them, and mainly to make the composite fibers in the inner layer into ultrafine fibers. A method consisting of a step process has been proposed.

[0006] However, in this method, the step of making the composite fiber extremely thin has two steps, the number of steps is increased and the operation becomes complicated, and the polymer elastic body is added after the fiber is made extremely thin. There is a problem that the polymer elastic body is firmly bonded to the ultrafine fibers in the outermost surface layer, and the appearance and the feel become rubber-like.

On the other hand, in JP-B-61-32432, a liquid which is a solvent for the elastic polymer and a non-solvent for the fibers is applied to the surface of the suede-like sheet to dissolve a part of the elastic polymer. Alternatively, it has been proposed to swell, then re-solidify, and then raise or shave. However, this method is intended to prevent the surface fluff of the napped sheet from falling off in a fiber napped suede with long naps on the napped surface, and a method for producing a nubuck-like artificial leather as in the present invention. Is completely different from.

[0008]

SUMMARY OF THE INVENTION Therefore, the present invention has two features.
It does not require ultrafine fiber processing over stages, yet eliminates rubber-like appearance and texture, has a smooth surface, is flexible, has a sharp chalk mark property, has short hair and high fiber nap density, It is an object of the present invention to provide a method for producing a good nubuck-like artificial leather having a uniform raised state.

[0009]

According to the present invention, as means for solving the above-mentioned problems, at least (a) 2
Forming a web from ultrafine fiber composite fibers comprising one or more high molecular weight polymers, and (b) in the thickness direction of the web, 50
Needle punching is performed at a barb-through punching number of 0 to 3000 / cm ² to prepare an entangled fibrous base material, and (c) the entangled fibrous base material is impregnated with an elastic polymer,
Squeeze to 60 to 90% of the thickness of the base material to solidify, (d) the composite fibers constituting the entangled fibrous base material are then extremely thinned, and (e) thereafter, the entangled fibrous material. A liquid containing a solvent for the elastic polymer is applied to the non-napped surface of the substrate to dissolve or swell a part of the elastic polymer, and then the liquid is removed and solidified, (f) the entanglement Provided is a method for producing a nubuck-like artificial leather, which comprises subjecting a solvent-containing liquid-treated surface of a fibrous base material to a buffing treatment.

In the method of the present invention, the ultrafine fiber composite fibers are composite fibers formed from two or more kinds of high molecular polymers having different properties by composite spinning, mixed spinning, etc., and at least one kind of composite fibers is used. Dissolving and removing high molecular weight polymers,
Alternatively, a material that can be made extremely fine by splitting due to physical or chemical action is used.

In particular, it is preferable to use a composite fiber composed of two or more kinds of high molecular weight polymers having different solvent solubility, and to dissolve and remove at least one high molecular weight polymer to make it ultrafine.

In the method of the present invention, specific examples of the high molecular weight polymer forming the ultrafine fibers include polyamides such as nylon 6, nylon 66 and nylon 12, and polyesters such as polyethylene terephthalate and polybutylene terephthalate.

Further, together with these ultrafine fiber-forming high molecular weight polymers, high molecular weight polymers having different properties (for example, solvent solubility) used as a dissolving / removing component and a binding component, in addition to the above polyamide and polyester, Examples thereof include polyethylene, polypropylene, high molecular weight polyethylene glycol, polystyrene and polyacrylate.

The composite fiber is applied to a known card, random webber, cross layer or the like to form a web.

The web thus obtained is subjected to needle punching at a barb penetration punching number of 500 to 3000 lines / cm ² , preferably 800 to 2000 lines / cm ² , in the thickness direction of the web. , Creating an entangled fibrous base material. Barb punch punching number 500 /
When it is less than cm ² , the entanglement of the entangled fibrous base material is insufficient, the strength is insufficient, and the choke mark property of the finished base material is also insufficient. On the other hand, if it is more than 3000 fibers / cm ² , the entangled fibrous base material is excessively subjected to needle punching, the damage becomes large, and the base material becomes unsatisfactory, which is not preferable.

Here, the number of barb penetrating punches is
When using a needle having at least one barb, the number of punches when punching is performed at a depth such that the barb located at the leading end penetrates in the thickness direction of the web is 1 cm ²
It is the value converted into the value per hit.

The entangled fibrous base material thus prepared by needle punching is impregnated with the elastic polymer and solidified.

Examples of the elastic polymer to be impregnated and solidified in the entangled fibrous base material include polyurethane elastomer, polyurea elastomer, polyurethane / polyurea elastomer, polyacrylic acid resin, acrylonitrile / butadiene elastomer, and styrene / butadiene elastomer. , Among others, polyurethane elastomers,
Polyurethane elastomers such as polyurea elastomer and polyurethane / polyurea elastomer are preferred. These polyurethane-based elastomers include at least one polymer glycol selected from polyether glycols, polyester glycols, polyester ether glycols, polycaprolactone glycols, polycarbonate glycols and the like having an average molecular weight of 500 to 4000 and 4,4′- Organic diisocyanates such as diphenylmethane diisocyanate, xylylene diisocyanate, tolylene diisocyanate, dicyclohexylmethane diisocyanate, and isophorone diisocyanate, and low-molecular glycols, diamines, hydrazine,
Alternatively, it is obtained by reacting with a chain extender selected from hydrazine derivatives such as organic acid hydrazide and amino acid hydrazide.

Further, in order to impregnate the entangled fibrous base material with the elastic polymer, the entangled fibrous base is usually used in the form of an organic solvent solution or dispersion (including an aqueous emulsion) of the elastic polymer. The material is impregnated, but its concentration is preferably 8 to 20%, particularly 12 to 1 in terms of softness as a nubuck-like artificial leather, denseness of the nubuck-like surface, fiber nap density, and the like.
8% is preferable. If the concentration is too low, the texture will be soft, but the napped feel of the surface will be rough and it will be difficult to obtain a nubuck-like appearance. On the other hand, if the concentration is too high, the appearance will be more dense and the napped hair will be closer to a nubuck-like short hair, but the texture will be hard.

In this manner, it is necessary to impregnate the entangled fibrous base material with the elastic polymer and then squeeze it to 60 to 90% of the base material thickness. Needless to say, if the elastic polymer forms a continuous layer on the surface of the base material, a sufficient surface napped fiber density cannot be obtained and a uniform nubuck-like artificial leather cannot be obtained due to the influence of thickness unevenness. Even if the layer is not formed, if the squeeze ratio exceeds 90% of the substrate thickness, the finally obtained sheet has long hair and the nubuck-like artificial leather intended by the present invention cannot be obtained. . On the other hand, if the squeeze ratio is less than 60% of the thickness of the base material, the amount of the elastic polymer contained in the base material is small, and the fluff becomes long, resulting in unevenness. In the present invention,
In particular, it is preferable to squeeze to 65 to 85% of the thickness of the base material, and the closer it is to this range, the shorter the fluff, the higher the surface fiber density, and the better the uniformity of the napped state.

The impregnated elastic polymer is then coagulated in the entangled fibrous base material. As a concrete method for coagulating the elastic polymer, any of known wet coagulation method and dry coagulation method may be used. Further, the solidified state of the elastic polymer in the entangled fibrous base material is preferably porous.

After the entangled fibrous base material is impregnated with the elastic polymer and coagulated, at least one high molecular polymer is dissolved and removed, or the composite is formed by a known method such as cleavage by physical or chemical action. Makes fibers very fine. Particularly, in the method of the present invention, it is preferable to use a composite fiber composed of two or more kinds of high molecular weight polymers having different solvent solubility, and to dissolve and remove at least one high molecular weight polymer to make it ultrafine. .

When the high-molecular polymer to be dissolved and removed is polyamide, a mixed solution of an alkali metal or an alkaline earth metal and a lower alcohol, formic acid or the like is used as a dissolution-removing agent, and in the case of polyester, sodium hydroxide is used. When the alkaline aqueous solution such as potassium hydroxide is polyethylene, polystyrene, polyacrylate or the like, benzene, toluene, xylene or the like is used.

The average fineness of the ultrafine fibers constituting the entangled fibrous base material after the ultrafine treatment is preferably 0.2 denier or less in order to obtain a homogeneous and textured surface appearance, and particularly preferably 0. It is 1 denier or less.

The non-napped surface of the entangled fibrous base material composed of the ultrafine fibers thus prepared, that is, the surface which has not been subjected to the raising treatment, is directly treated with the liquid containing the solvent for the elastic polymer. When treated with such a liquid after brushing,
The napped fiber length of the finally obtained sheet becomes long and the napped state of the surface becomes inhomogeneous, and the nubuck-like artificial leather intended by the present invention cannot be obtained.

As the liquid containing the solvent for the elastic polymer, a good solvent for the elastic polymer such as dimethylformamide, diethylformamide, dimethylacetamide, tetrahydrofuran or the like, or water, alcohol, methyl ethyl ketone and the above-mentioned elastic polymer are partially mixed. Those obtained are preferably used. Since the liquid containing the solvent for these elastic polymers needs to dissolve or swell a part of the elastic polymer, the solvent for the elastic polymer is at least 50% or more,
It is desirable to contain 70% or more.

The method of applying the liquid containing the solvent of the elastic polymer to the surface of the ultrafine entangled fibrous base material is not particularly limited, and examples thereof include coating with a gravure coater or spray coater, or release paper. And the like. A liquid containing a solvent of an elastic polymer is applied to the surface of a support such as, and contacted with the surface of the entangled fibrous base material before being dried to transfer the liquid. . In this step, it is preferable to apply the liquid while lightly nipping the base material with a gravure roll or the like.

Next, the liquid containing the solvent of the elastic polymer is removed.
And liquid removal treatment is performed to solidify the elastic polymer.
U A hot air dryer is used as this liquid removal treatment method.
Dry method and wet method of immersing in a liquid such as water.
However, the dry method uses a liquid containing the elastic polymer described above.
It is preferable because the amount can be reduced. Application of this liquid,
The liquid removal process is preferably repeated at least 2 to 6 times.
The higher the number of times, the higher the homogeneity, but more than 6 times
Then, the surface tends to become hard. Also entangled fiber
The amount of liquid applied to the non-napped surface of the quality substrate is
5-55 g / m ²Is preferred. The amount of liquid applied
5 g / m²The smaller the number, the longer the surface napped fiber length.
It becomes difficult to obtain the target nubuck-like artificial leather,
55 g / m ²If it exceeds, the surface will become hard and liquid will not be removed.
It will take time.

By this liquid application process and liquid removal process,
After the elastic polymer is dissolved or swelled, it is re-solidified to increase the bond between the ultrafine fibers and the elastic polymer on the surface of the entangled fibrous base material to press down the fiber, and by the buffing treatment described later, sharp chalk mark property It is possible to produce an excellent nubuck-like artificial leather having the following characteristics, short hair and uniform napped state.

Then, the surface of the entangled fibrous base material treated as described above is subjected to a buffing treatment. Before the buffing treatment, the surface is treated with a smooth or small embossing roll, a calender roll, a flat plate press or the like. May be. Buffing can be performed by a conventional method using sandpaper, a brush, a grindstone, or the like. However, if you do buffing with something that is too coarse or buffing for a long time, the treated surface will be rough and you will not be able to obtain the target nubuck-like artificial leather, so be careful I won't.

[0031]

In the method of the present invention, 500 to 3000 lines / cm ²
Since the fibers are sufficiently entangled by performing needle punching with the number of perforated barbs, the base material having sufficient strength, excellent choke mark properties, and no damage or fatigue can be obtained.

Further, the structure of the elastic polymer and the fiber is optimized by impregnating the entangled fibrous base material with the elastic polymer and squeezing to 60 to 90% of the thickness of the base material to solidify. When subjected to buffing treatment, a nubuck-like artificial leather having short naps, high surface fiber density, and excellent napped homogeneity can be obtained.

Further, after the ultrafine treatment, the non-napped surface of the substrate is treated with a liquid containing a solvent for the elastic polymer, so that the bond between the ultrafine fibers and the elastic polymer on the treated surface is enhanced. The surface is smooth and flexible due to the buffing process combined with the above requirements.
It is possible to produce an excellent nubuck-like artificial leather having sharp chalk marks, short hair, high surface fiber density, and uniform napped state.

Further, in the method of the present invention, the ultrathinning of the composite fiber is performed in one step, and the ultrathinning treatment in two steps is not required.

Moreover, since the entangled fibrous base material is impregnated with the elastic polymer and coagulated, the composite fiber is ultrafinely divided. Therefore, the prior art which is produced to give the elastic polymer after the fiber is ultrafinely formed. It is possible to completely eliminate the problem of (2), that is, the elastic polymer is firmly bonded to the ultrafine fibers in the outermost surface layer, and the appearance and the feel become rubber-like.

[0036]

The present invention will be described in detail below with reference to examples.

[Examples 1 to 3 and Comparative Examples 1 and 2] Nylon 6 and polyoxyethylene ether-modified low density polyethylene were chip-blended at a compounding ratio of 50:50, and were mixed and spun to have a fineness of 7 denier and a fiber length of 51 mm. A composite fiber was obtained. After the obtained composite fiber was made into a web by a card and a cross layer, the number of punched barbs was 120.
Needle punching at 0 / cm ² and 560 g /
It created the entangled fiber substrate material of m ^2.

This entangled fibrous base material was preheated in a hot air oven at 150 ° C. and then heated with a heating roll at 90 ° C. so that the apparent density was 0.3 g / cm ³ and the thickness was 1.87 mm. Pressed on.

Next, a polybutylene adipate having a molecular weight of 1800 is reacted with polytetramethylene ether glycol having a molecular weight of 2050, 4,4'-diphenylmethane diisocyanate and ethylene glycol, and the nitrogen content based on isocyanate is 4. 5% solution of polyurethane elastomer in dimethylformamide (concentration 15
%) Is impregnated into the pressed entangled fibrous base material, introduced onto a rotating smooth roll, and held down by a doctor blade made of Swedish steel, while changing the squeeze ratio with respect to the base material thickness as shown in Table 1. And squeezed. Then, soak in a 10% dimethylformamide aqueous solution,
Solidified. Then, wash thoroughly in 40 ° C warm water, and
After drying in a hot air oven at 20 ° C., the ratio of fiber to polyurethane elastomer is 88:12, 86 :, respectively.
The elastic polymer-impregnated base materials of 14, 81:19, 76:24, and 75:25 were obtained.

Next, dipping and nip were repeated on this base material in toluene at 80 ° C. to dissolve and remove polyethylene, and the composite fiber was ultrafine. After that, toluene contained in the base material is removed azeotropically in warm water at 90 ° C.
It was dried in a hot air dryer at 0 ° C. The average fineness of the obtained ultrafine fibers was 0.01 denier.

Then, dimethylformamide was added to the surface of the base material using a 200 mesh gravure coater.
After the operation of applying at a rate of g / m ² and drying with dry heat was repeated 6 times, the surface was lightly buffed with 400 mesh sandpaper.

The properties of the thus obtained sheet are as shown in Table 1, and when the squeeze rate was 60 to 90% (Examples 1 to 3), a good nubuck tone sheet was obtained.

[0043]

[Table 1]

In Table 1, ⊚ indicates extremely good, ∘ indicates good, Δ indicates slightly bad, and x indicates bad.

Example 4 Polyethylene terephthalate and low density polyethylene having a composition of 50:50 were melt extruded from two extruders, respectively, and were finely denier 4 pieces and fiber length 51 mm, which were laminated in 48 divisions by a composite spinneret. A hollow split type conjugate fiber was obtained. The obtained composite fiber was applied to a card and a cross layer to form a web, and needle punching was performed at a barb penetrating punching number of 2000 / cm ² to prepare an entangled fibrous base material of 560 g / m ² .

This entangled fibrous base material was preheated in a hot air oven at 150 ° C. and then heated with a heating roll at 90 ° C. so that the apparent density became 0.32 g / cm ³ and the thickness became 1.75 mm. Pressed on.

Next, a polyurethane elastomer dimethyl having a nitrogen content of 4.5% based on isocyanate obtained by reacting polytetramethylene ether glycol having a molecular weight of 2050, 4,4'-diphenylmethane diisocyanate and ethylene glycol. The above-mentioned pressed entangled fibrous base material was impregnated with a formamide solution (concentration: 13%) and squeezed to 70% of the base material thickness while pressing with a doctor blade. Substrate after squeeze 10
% Dimethylformamide aqueous solution for coagulation. Then, it was sufficiently washed in warm water at 40 ° C. to obtain an elastic polymer-impregnated base material having a fiber / polyurethane elastomer ratio of 78:21.

Then, it is treated in toluene at 80 ° C.,
The polyethylene was dissolved and removed, and the composite fiber was ultrafine. Then, toluene contained in the base material was azeotropically removed in hot water of 90 ° C, and dried in a hot air dryer of 120 ° C. The average fineness of the obtained ultrafine fibers was 0.08 denier.

Then, using a 200-mesh gravure coater on the surface of the substrate, 9 g / m ^{2 of} a dimethylformamide solution containing 5% of the above polyurethane elastomer was used.
After repeating the operation of coating at a ratio of 2 and drying with dry heat twice, the surface was lightly buffed with 400 mesh sandpaper.

The sheet thus obtained is a nubuck-like sheet having a very smooth and soft surface, a short napped fiber length, a high fiber napped density, a sharp chalk mark property and a uniform napped state. It was

[Comparative Example 3] In Example 2, the treatment was performed under the same conditions as in Example 2 except that dimethylformamide was not applied to the surface of the base material after the ultrathinning treatment. The obtained sheet had long surface napped fiber length, lacked sharp chalk mark properties, did not have a nubuck-like appearance, but rather had a suede-like appearance.

[Comparative Example 4] In Example 2, dimethylformamide was applied after buffing the surface of the base material after the ultrathinning treatment, but the napped fiber length became long and the napped state was inhomogeneous. Therefore, a good nubuck-like sheet could not be obtained.

[0053]

According to the manufacturing method of the present invention, a rubber-like appearance and texture are eliminated without the need for a two-step extra-thinning treatment, and the surface is smooth, flexible, and has a sharp chalk mark property. However, it is possible to manufacture a good nubuck-like artificial leather having short naps, a high fiber nap density, and a uniform nap state.

Claims (4)

[Claims] 1. A web is formed from at least (a) ultrafine fiber composite fibers composed of two or more high molecular weight polymers, and (b) 500 to 3000 strands / cm ^{2 in} the thickness direction of the web. Needle punching is performed by the number of punches through the barb to prepare an entangled fibrous base material, and (c) the entangled fibrous base material is impregnated with an elastic polymer, and the entangled fibrous base material has a thickness of 6
Squeeze to 0 to 90% to solidify, (d) after that, the composite fibers constituting the entangled fibrous base material are ultrafine,
(E) After that, a liquid containing a solvent for the elastic polymer is applied to the non-napped surface of the entangled fibrous base material to dissolve or swell a part of the elastic polymer, and then the liquid is removed. And (f) a solvent-containing liquid-treated surface of the entangled fibrous base material is subjected to a buffing treatment, thereby producing a nubuck-like artificial leather. 2. The nubuck-like artificial leather according to claim 1, wherein at least one high-molecular polymer is dissolved and removed from the conjugate fiber composed of two or more high-molecular polymers having different solvent solubility to make it ultrafine. Manufacturing method. 3. The method for producing a nubuck-like artificial leather according to claim 1, wherein the average fineness of the ultrafine fibers is 0.2 denier or less. 4. The nubuck-like artificial material according to claim 1, 2 or 3, wherein the amount of the liquid containing the solvent of the elastic polymer applied to the non-napped surface of the entangled fibrous base material is 5 to 55 g / m ^2. Leather manufacturing method.