JP2790336B2 - Manufacturing method of non-woven fabric suitable for manufacturing artificial leather - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to a method for producing a nonwoven fabric for producing a nonwoven fabric having reduced needle marks and improved anisotropy specific to a needle punched nonwoven fabric. More specifically, the present invention relates to a method for producing a nonwoven fabric having a smooth surface which is excellent in balance between physical properties in the vertical and horizontal directions and is suitable for producing artificial leather with less occurrence of so-called surface morrow.

[Prior art]

Conventionally, a needle punched nonwoven fabric has been widely used as a base fabric for producing artificial leather. However, on the surface of the needle-punched non-woven fabric, there is a so-called needle mark in which a mark through which the needle penetrates has a hole shape or a fiber bundle protrudes in a feather shape. In the internal structure of the needle-punched nonwoven fabric, the fibers are mainly bundled and pushed in the thickness direction in the portion where the needle penetrates (so-called needle strain), and the fiber is mainly in the portion where the needle does not penetrate. It has a structure lying in the thickness direction. When such a needle-punched nonwoven fabric is used for the base layer and processed into artificial leather, irregularities and pinholes due to needle marks are generated on the surface of the artificial leather. Fine irregularities called so-called surface morro or fishing morrow are generated on the surface, and the commercial value is remarkably reduced. It is known to perform a hot press treatment with a heated roller or belt, or with a cooling roller after heating under tension, for smoothing irregularities on the surface of the nonwoven fabric and fixing feathers. Methods to reduce the effect of the Neidor strain include reducing the number of needle barbers, increasing the number of punches extremely, dispersing the Neidole strain by treating the needle-punched nonwoven surface with high-speed fluid flow, Methods of mixing fibers and performing a shrinkage treatment after needle punching are known. Furthermore, a method of subjecting a nonwoven fabric to a kind of kneading treatment to loosen the needle stock is also known (Japanese Patent Publication No. 53-19700). When the nonwoven fabric is used for the base layer of artificial leather, the base layer is oriented in a vertical direction in each manufacturing process such as impregnation of an elastic polymer, coagulation, extraction of a part of a fiber component, provision of a sponge layer and a surface layer, embossing and buffing. The artificial leather obtained tends to have strong anisotropy in the vertical and horizontal directions. As a method of improving this anisotropy, a method of stretching in the width direction during needle punching (Japanese Patent Publication No. 58-31422),
A method of performing a widening process at the time of solidifying and impregnating an elastic polymer into a nonwoven fabric
A method of inserting a knitted fabric between nonwoven webs and performing needle punching (Japanese Patent Publication No. 55-13040) is known.

[Problems to be solved by the invention]

In the conventional surface smoothing treatment by resin fixing or heat fusion, it is difficult to reduce the influence of the needle stock, even if the surface feathers can be fixed and smoothed. Even if the conditions of the nidol punch were changed or the shrinkage treatment was performed, the needle strain itself remained almost unchanged in the nonwoven fabric, and the effect was not sufficiently satisfactory. In addition, the method of kneading and unraveling a needle-punched nonwoven fabric through a pair of rollers or belts having a surface speed difference is expected to be effective, but in a nonwoven fabric subjected to high-speed punching, the needle stock is stretched in the vertical direction. Therefore, a sufficient effect cannot be expected only by rubbing in the longitudinal direction, and the roller slips on the surface of the non-woven fabric, so that feathers are often generated. As a method of improving the physical property difference of the artificial leather in the vertical and horizontal directions, in the artificial leather manufacturing process, in a process that is easy to expand in the vertical direction such as during the impregnation and coagulation of an elastic polymer, a method in which the width is fixed or fixed with a tenter etc. Although the effect can be expected sufficiently, there is a problem that the device becomes complicated and expensive. The present invention provides a method for producing a nonwoven fabric suitable for producing artificial leather having a small difference in physical properties in the vertical and horizontal directions with less generation of surface morrow due to the needle stock without using an expensive special device. is there.

[Means for Solving the Problems]

The present invention widens a needle-punched nonwoven fabric containing a heat-fusible fiber by 5 to 25% at a temperature at which the heat-fusible fiber does not fuse, releases the tension, and then widens to a width not exceeding the widening width. And a heat treatment at a temperature at which at least a part of the heat-fusible fiber is fused, followed by pressing with a cooling roller to smooth the surface, thereby producing a nonwoven fabric suitable for artificial leather production. . The heat-fusible fiber used in the present invention is, for example, at least one selected from the group consisting of thermoplastic synthetic fibers such as polyester fibers, polyamide fibers, and polyolefin fibers, and the following ultrafine fiber-generating fibers and core-sheath composite fibers. Can be used, but when two or more of these are mixed, the fiber having the lower melting point or softening point becomes the heat-fusible fiber. From the viewpoint of the flexibility and surface smoothness of the obtained artificial leather, it is preferable to use an ultrafine fiber-generating fiber containing the following heat-fusible component. That is, the heat-fusible component is a polymer that has a melting point or softening point lower by at least 10 ° C. than the ultrafine fiber component and decomposes with a solvent-soluble or decomposer, for example,
At least one selected from the group consisting of polyethylene or ethylene copolymer, ethylene-vinyl acetate copolymer or partially saponified product thereof, polystyrene or styrene copolymer, polyester, polyamide, polyvinyl chloride or vinyl chloride copolymer; It is a polymer. The ultrafine fiber component is a polymer having a different solvent or decomposer from the heat-fusible component, for example, polyester such as polyethylene terephthalate or ethylene terephthalate copolymer, polybutylene terephthalate or butylene terephthalate copolymer, or nylon-6. And at least one polymer selected from the group consisting of polyamides such as nylon-66, nylon-610, nylon-12, polyamides containing aromatic rings, polypropylene, saponified ethylene-vinyl acetate copolymer, and polyvinyl alcohol. . Ultrafine fiber-generating fibers such as sea-island cross-sectional structural fibers, bimetal cross-sectional structural fibers, microfibril bundle-bonded cross-sectional structural fibers, or core-sheath type fibers by melt spinning using these heat-fusible components and ultrafine fiber components. Spun into conjugate fiber. Part of the surface of the ultrafine fiber-generating fiber or the core-sheath fiber must be covered with a heat-fusible component. The nonwoven fabric of the present invention uses at least one kind of fiber selected from the group of the above heat-fusible fibers, but it is not necessary that all the fibers are heat-fusible fibers, and polyacrylonitrile fibers, polyvinyl alcohol fibers, regenerated cellulose fibers , Cotton, hemp,
At least one kind of fiber selected from the group of natural fibers such as silk and wool can be used as a mixture. The fibers are defibrated with a card and formed into a random web or a cross-wrap web through a webber, and the obtained fiber web is laminated to a desired weight and thickness. Weight of the laminated fiber web is generally in the range of 100 to 2000 g / m ^2. Next, the fiber web is needle-punched by a conventionally known method to perform a fiber entanglement treatment to obtain a needle-punched nonwoven fabric. The number of punches is usually in the range of 200 to 2500 punches / cm ² , and it is preferable that the fibers are sufficiently entangled in terms of stretchability and fullness. In the present invention, a widening process is performed before gluing the nonwoven fabric or impregnating the elastic polymer. The state in which the fibers constituting the nonwoven fabric are not fixed by the sizing agent or the elastic polymer, that is,
It is important to carry out the widening process in a state where the fibers can move with each other. The widening ratio is preferably 5 to 25%. If it is less than 5%, a sufficient effect cannot be obtained, and if it is more than 25%, the nonwoven fabric becomes thinner or spots are easily formed, which is not preferable. Also,
Heat treatment in the widened state is also preferable for improving the surface morro, but heat treatment in a high temperature condition where the fiber thread is fused is not preferable so that the subsequent release of tension sufficiently rearranges the fiber of the needle stock. . The stretched nonwoven fabric is once released from tension and the fibers are rearranged so that the nonwoven fabric structure becomes more stable. Next, the fibers are heat-treated at a temperature at which a part of the fibers is heat-sealed while being widened to a width smaller than the previous widening width,
Pressing with a cooling roller smoothes the surface and fixes the feathers. If the widening width is wider than the above widening width, the fibers in the needle stock are undesirably tensioned.
In the heat treatment, the entire nonwoven fabric may be heated by a hot air oven or the like, or the surface layer on the side to be brought into contact with a heat roller and smoothed may be mainly heated. In the latter case, a more sublime nonwoven is obtained. The surface-smoothed nonwoven fabric is impregnated with a solution or dispersion of an elastic polymer, and is further applied to the surface as necessary, and after coagulating to a porous state, in the case of ultrafine fiber-generating fibers, the heat-welding component is dissolved with a solvent. By decomposing with a dissolving or dispersing agent to form a sheet-like material in which microfibers and a porous elastic polymer are mixed,
In the case of a core-sheath type fiber or a normal fiber, at least a part of the heat-fusible component is dissolved or decomposed and removed with a solvent or a decomposer for the heat-fusible component to form a sheet.
Alternatively, after gluing and fixing to the nonwoven fabric, at least a part of the heat-fusible component is dissolved or decomposed and removed, and then modified into ultrafine fibers or at least a part of the heat-fused portion is decomposed, and then a solution of an elastic polymer or The dispersion is impregnated and, if necessary, further applied to the surface, solidified porously and at least part of the paste is removed to form a sheet. The obtained sheet-like material is subjected to coloring, surface finishing, embossing, napping, softening treatment, and the like as necessary to obtain artificial leather.

[Action]

In the non-woven fabric immediately after the needle punch, the fibers constituting the non-woven fabric, particularly the fibers drawn into the needle stock, are in a considerably strained state. Further, the needle stock is elongated in the vertical direction due to a relative speed difference between the web and the needle, and is in a vertically long state. By widening the nonwoven fabric in this state by 5 to 25% in the horizontal direction, the needle stock is expanded in the horizontal direction, and the fibers constituting the stock are in a state of easy movement, and the fibers constituting the stock are further strained. Therefore, some slippage occurs and the entanglement is loosened. Then, when the tension is released, the width of the entire nonwoven fabric shrinks, but the width after the shrinkage becomes slightly wider than before the widening. At this time, the fibers constituting the strain are rearranged at a more stable position than the state where the entanglement is loose. Furthermore, the fiber constituting the strain is expanded by narrowing it to a width smaller than the initial width, and the fiber constituting the plant is loosened by heat fixing, and the fiber constituting the nonwoven fabric is heat-sealed and fixed in a state where the horizontal orientation is increased as a whole. Is done. Therefore, the elongation in the vertical direction is small and the physical properties in the vertical and horizontal directions are balanced even when the width is not specifically regulated in the step of impregnating and solidifying the elastic polymer. This difference in physical properties can be adjusted by a combination of the initial widening ratio and the widening ratio during heat fixing. In addition, since the fiber inside the needle stock is in a loosened state and the orientation in the thickness direction is reduced,
Even if a surface layer is applied and processed into artificial leather, there is no surface morrow due to the needle strain.

【Example】

Next, specific embodiments of the present invention will be described, but the present invention is not limited to these embodiments.
The parts and percentages in the examples relate to weight unless otherwise specified. Example 1 A cross-wrap web was prepared using an ultrafine fiber-generating fiber composed of 50 parts of polyethylene and 50 parts of polyester, and punched to a punch density of 1000 punches / cm ² to obtain a basis weight of 650 g / m 2.
^2. A three-dimensional entangled nonwoven fabric having an average thickness of 4.06 mm was obtained. This non-woven fabric is widened by 18% at room temperature and then loosened once, then heat-treated in a heating furnace at 140 ° C while expanding the width by 17% compared to the width before widening, and passed between cooling press rollers to make the surface feathers Was fused and fixed, and the thickness was adjusted to 2.0 mm. Next, this nonwoven fabric was impregnated with a solution of polyurethane in dimethylformamide (DMF) (concentration: 7%), drained with a doctor knife, and then coated on the surface with a 20% concentration of a polyurethane solution at a solid content of 100 g / m ² , and wet-processed. Solidified. Further, the polyethylene was extracted and removed with toluene to obtain a leather-like sheet. The surface of the obtained leather-like sheet was a smooth surface with almost no feather defects. In addition, even if it was pulled vertically, horizontally or diagonally, no generation of morro was observed. In addition, the lateral strength of this leather-like sheet is 58 kg / 2.5 cm, 20
% Tensile strength was 7 kg / 2.5 cm Comparative Example 2 Using the ultrafine fiber-generating fiber of Example 1, a leather-like sheet was obtained in the same manner as in Example 1 except that the width was not increased by 18%. The surface of the leather-like sheet had almost no fuzz defects, but had irregularities on the entire surface, which were considered to be due to needle marks. The lateral strength of this leather-like sheet is 48kg / 2.5cm, 20%
Strength was 4 kg / 2.5 cm. Example 2 and Comparative Example ² A random web having an average basis weight of 120 g / cm ² was produced by mixing and weaving 70% of polyester fiber and 30% of a core-sheath composite fiber having polyethylene as a sheath component. Five random webs were laminated and needle-punched at a punch density of 850 punches / cm ² to obtain a needle-punched nonwoven fabric having an average basis weight of 480 g / m ² and a thickness of 3.20 mm. This non-woven fabric was widened by 20% in an atmosphere of 40 ° C, and the tension was released.
Was growing. Next, in a heating furnace at 130 ° C., at the same time as the heat treatment, the sheet is widened by 19% compared to the width before the above-mentioned widening, and then pressed by a cooling press roller to a thickness of 1.58 mm,
The surface fuzz was fixed and smoothed. Next, a polyurethane resin was impregnated and applied by the same method as in Example 1 and wet coagulated. On the coated surface of the obtained sheet-like material, generation of fuzz defects was hardly observed, the surface morro was good, and the strength ratio in the vertical and horizontal directions was 1.02. On the other hand, for comparison, a sheet-like material produced in the same manner as in the present example without performing only the initial widening treatment had few feather defects on the surface, but had remarkable surface morrow, and had a longitudinal-lateral strength ratio of 1.36.

【The invention's effect】

The artificial leather processed by the nonwoven fabric of the present invention has the following features. The generation of surface morro at the time of elongation is reduced, and it can be processed into a higher value-added secondary product. The difference in the vertical and horizontal physical properties is improved. Therefore, there is no need to use a complicated and expensive tenter as a manufacturing facility.

Claims (1)

(57) [Claims] 1. A needle-punched nonwoven fabric containing heat-fusible fibers is widened by 5 to 25% at a temperature at which the heat-fusible fibers are not fused, and after the tension is released, the width does not exceed the widening width of the previous one. A method for producing a nonwoven fabric suitable for producing artificial leather, characterized by widening and heat-treating at a temperature at which at least a part of the heat-fusible fiber is fused, followed by pressing with a cooling roller to smooth the surface.