LEATHER THREAD: This invention is a sewing thread for a leather product composed of fibers attached with a highly water absorbing powdery material on the surface of the fibers, in a ratio of 5 weight % or more based on the weight of the fibers, and a leather product, with excellent water-proof property, prepared by using the same thread.
A sewing thread for the leather products in this invention is the sewing thread composed of fibers attached with a highly water absorbing powdery material on the surface of the fibers in the ratio of 5 weight % or more based on the fiber weight.
Here, as the fibers constituting the sewing thread for the leather products in this invention (hereinafter called as "sewing thread"), although there is no specific limitation provided that it is a conventionally known fiber such as a natural fiber, a synthetic fiber, etc., the fibers preferably have a certain degree of strength at the seams to meet the object of this invention. For this purpose, it is preferable for the fibers used in this invention to be excellent in strength such as a tensile strength, a loop strength, a knot strength, etc. Concretely, for example, by expressing with a tensile strength of a single fiber, it is 2 g/denier or higher, preferably 2.5 g/denier or higher, and in case of using as a bundle of fibers, the tensile strength of the fiber bundle is 1.8 g/denier or higher, preferably 2.2 g/denier or higher. As raw materials of the fibers, concretely, synthetic fibers such as a polyester, a polyamide, etc., are cited. Among them, the polyester is preferred, and a polyethylene erephtahalate is especially preferable.
Also, although the shape of the fibers constituting the sewing thread in this invention is not specifically limited, for example, shapes such as a long fiber, a spun fiber, a braid, a cord, a rope, a cable, etc., are cited. Further, it is preferable for the long fiber to be treated with an interlacing treatment by using an interlace nozzle or a taslan nozzle, or a false twisting treatment. These fibers can be used as the single fiber, or by bundling plural numbers of fibers, but it is preferable to use as a bundle of fibers since the highly water absorbing powdery material can be mingled among each of the fibers. In this case, total denier of the fiber bundle is 6000-13000 denier, preferably 8000-11000 denier. The denier of the single fiber is preferably small so as to attach the highly water absorbing powdery material on the surface of the fibers, and to disperse and mingle the highly water absorbing powdery material to the whole parts of the sewing thread, and is concretely 10 denier or lower, preferably 5 denier or lower. Also, it is allowed to use the fibers by combining single fibers having different deniers and/or different shapes.
As the highly water absorbing powdery material used in this invention, there is no specific limitation provided that it is a powdery material of a cross-linked polymeric material having a water absorbing property, concretely, for example, a cross-linked polymeric material of water soluble vinyl monomers such as (meth)acrylamide, (meth)acrylic acid. 2-acrylamide-2-methylpropane sulfonic acid, vinyl sulfonic acid, styrene sulfonic acid, etc., and a grafted starch, a cyanoethylated starch, a carboxymethylated starch, etc., are cited. Preferably, a cross-linked polymeric material of a water soluble vinyl monomer, and more preferably, a copolymer obtained by copolymerizing an anionic monomer with the cross-linked polymeric material of the water soluble vinyl monomer are used. By copolymerizing the anionic monoer, it is possible to improve the water absorbing property of the obtained copolymer. As the anionic monomers, for example, it is preferable to use a substance obtained by neutralizing acid monomers such as (meth)acrylic acid, 2-acrylamide-2-methylpropane sulfonic acid, vinylsulfonic acid, styrenesulfonic acid, etc., with an alkali metal salt of sodium ion, potassium ion, etc., or with ammonium ion, etc., to attain 50-100 mol % of the degree of neutralization.
As for a method for polymerization to obtain the highly water absorbing powdery material in this invention, a conventionally known method can be used, for example, the powdery material can be obtained by adding a solution obtained by dissolving the anionic monomer with water and neutralizing, into a petroleum-based aliphatic hydrocarbon solvent added with a surfactant, a polymerization initiator, a cross-liking agent, etc., under a nitrogen atmosphere, further substituting the atmosphere of the solution with nitrogen, reacting for several hours, removing the petroleum-based resinous hydrocarbon solvent and water after the completion of the reaction, and drying the obtained polymer. Here, as the petroleum-based resinous hydrocarbon solvent, normal hexane, ligroin, benzene, toluene, xylene, naphthene, etc., are cited.
As the highly water absorbing powdery material in this invention, it is preferable to have 0.1-100 μm of mean particle diameter under a dried condition, and 0.2-20 μm thereof is more preferable. The water absorption rate of the highly water absorbing powdery material itself is 20 fold or more in volume increasing ratio thereof, preferably 100 fold or more, and more preferably 200-500 fold.
The sewing thread in this invention is the above fiber attached with the highly water absorbing powdery material on the surface thereof The attached amount of the highly water absorbing powdery material is 5 weight % or more, preferably 5-70 weight %, more preferably 7-25 weight % based on the fiber weight. In case that the attached amount is less than 5 weight %, the dynamic water absorbing rate of a soccer ball prepared by using the sewing thread of this invention is high and the effect of this invention can not be attained. Also, the more effect of this invention can be obtained by the more the attached amount, but in case that the attached amount is larger than 70 weight %, the falling off of the highly water absorbing powdery material attached to the fiber becomes large amount and effectless. Also, in considering the practical effect and economical property on using the highly water absorbing powdery material with the sewing thread for the soccer ball, the attached amount of the highly water absorbing powdery material is most preferably 7-25 weight % based on the fiber weight.
As the attached state of the highly water soluble powdery material, it is preferable for the powdery material to be attached uniformly on the fiber surface, and as to the fiber bundle, the material is preferably dispersed and mingled into the inside of the fiber bundle. In this way, by the fact that the highly water absorbing powdery material is dispersed and mingled into the inside of the fiber bundle, in the case that the highly water absorbing powdery material makes a contact with water, the highly water absorbing powdery material swells, the swollen highly water absorbing powdery material is restrained among the each of the fibers to yield a packing effect, as a result, the seams are effectively blocked and it is also possible to perform a packing in accordance with the deformation of the holes in the seams.
As for the attaching method of the highly water absorbing powdery material, a conventionally known methods such as a method of immersing the fibers in a dispersion liquid containing the highly water absorbing powdery material, a method of spraying the highly water absorbing powdery material to the fibers, etc., can be used. Concretely, for example, the fiber attached with the powdery material is obtained by immersing the fiber in a dispersion liquid containing the highly water absorbing powdery material by 10-55 weight %, preferably by 20-45 weight % based on the weight of the dispersion liquid at a room temperature for 0.5 sec to 1 minute, dispersing and mingling the highly water absorbing powdery material into even the inside of the fiber bundles, squeezing suitably so as to attain a prescribed attached amount and then drying. As the dispersion solution, although there is no specific limitation provided that it is a non-solvent for the highly water absorbing powdery material, concretely, it is preferable to use the mixed solvent of water with the petroleum-base resinous hydrocarbon solvent used in the polymerization of the highly water absorbing powdery material as it is.
Further, in the dispersion liquid containing the highly water absorbing powdery material, it is preferable to add an adhesive. As the adhesive, a vinyl acetate resin, a urethane-based resin, an acrylic resin, a nitrile rubber-based resin, chloroprene-based resin, a polyester-based resin, etc., are cited. As a solvent for the adhesives, an aqueous solvent, an organic solvent, etc., are used and the aqueous solvent is preferably used. The using amount of the adhesive is 20 weight % or less, preferably 3-15 weight % based on the weight of the highly water absorbing powdery material.
The attachment of the highly water absorbing powdery material can be performed before or after the formation of the fibers as the fiber bundles, or before or after the performance of the interlacing or false twisting treatment of the single fiber.
The sewing thread for the leather products thus obtained, has excellent strength at the seams and water absorbing property. Also by sewing up the leather panels by using the above sewing thread for the leather products, leather products having an excellent water proof property can be obtained.
As the leather panels sewn up by using the sewing thread of this invention, there is no specific limitation provided that they are made of a leather, and a natural leather, a leather made from vinyl chloride, a synthetic leather, an artificial leather, etc., are cited. Among them, in order to exhibit the effect of the sewing thread in this invention efficiently and obtain the leather products having an excellent water proof property, it is preferable to use a leather having an excellent water proof property such as the synthetic leather and the artificial leather. Also, it is preferable to have a water proof treatment on these leathers themselves.
Here, as the synthetic leather, it means, for example, an article obtained by impregnating a urethane polymer solution or emulsion liquid to a fabric composed of fibers of a polyester or a nylon, coagulating, drying and coating a urethane resin on the surface thereof, and as the artificial leather, it means, for example, an article obtained by impregnating a urethane polymer solution or emulsion liquid to a nonwoven fabric composed of fibers of a polyester or a nylon, coagulating, drying and coating a urethane resin on the surface thereof.
The leather panels are prepared by cutting these -leathers according to the objective products. As the leather products obtained by sewing up these leather panels, there is no specific limitation, but for example, sport goods, interior goods, clothings, etc., are cited. Among them, as the products in which the effect of the sewing thread of this invention is exhibited most, sport goods used in a rainy weather, especially a ball for the ball game such as the soccer ball, the rugby ball, etc., and more specifically the soccer ball are preferably cited. That is, by using the sewing thread in this invention for the production of the soccer ball, it becomes possible to prevent the rain water from being absorbed to the inside of the soccer ball, i.e., into the nonwoven fabric constituting the artificial leather by absorbing the rain water with the highly water absorbing powdery material attached to the sewing thread in this invention and swelling the highly water absorbing powdery material to close the holes of the seams. The soccer ball obtained by using the sewing thread in this invention, has a high water proof property, and it becomes possible to reduce a water absorption rate thereof, especially a dynamic water absorption rate widely and to make the dynamic water absorption rate as 5% or less, preferably 2% or less.
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