1. Field of the Invention
The present invention relates generally to rayon fibers, and more particularly to rayon fibers with ion-generating characteristics and a method for manufacturing such fibers.
2. Description of the Related Art
Ceramics that radiate far infrared rays, when adhered to clothing, are known to promote blood flow. However, due to the relatively low temperatures of the human body (40.degree. C. or lower), it is difficult for a person's body heat to bring the ceramics to a temperature that is high enough to radiate high levels of far infrared rays. As a result, the effect on the body is minimal. In addition, there were no rayon fibers with antibiotic, deodorant, and far infrared radiation characteristics until a few years ago. Prior to then, washing and dry cleaning often did not remove dirt, smells, and germs from clothing made from mixes of rayon fiber, cotton, and/or synthetic fibers, in particular underwear, sheets, futon covers used at hospitals and other medical facilities, and kitchen utensils. Thus, such materials were non-hygenic. Also, since they did not radiate far infrared rays, they could not raise the temperature of the skin surface and did not promote blood circulation.
Various solutions to these problems have been proposed. One example, disclosed in Japanese Patent Publication Heisei 2-169764 Official Bulletin, is a rayon fiber that has electrotreated fibers with 3-4% tourmaline by weight adhered or impregnated thereon, the tourmaline particles having a diameter of 2 .mu.m or less. Another example, disclosed in Patent Publication Heisei 4-327207 Official Bulletin, is a rayon fiber impregnated with or having adhered thereon ultra fine tourmaline particles as a ceramic. In this process, the tourmaline particles are mixed with alkali cellulose, carbon disulfide, and caustic soda. The mixture is vacuum kneaded, ripened, and then spun into rayon fibers. Tourmaline is believed to provide a stable electrical charge effect that electrically stimulates the electropotential of the skin surface. The tourmaline radiates stimulating far infrared rays to the skin surface and, through a multiplying effect, improves the body's metabolism and blood circulation.
Also, Patent Publications Heisei 3-215266 Official Bulletin and Heisei 5-98506 Official Bulletin teach public compound ceramics with deodorant and antibiotic characteristics. These ceramics comprise fine magnesia particles used as the base and one of alumina, silica, zinc oxide, titanium, zeolite, serpentine, hornblende, oyastone, or the like mixed in as the additive. These references also teach methods of manufacturing these compound ceramics as well as fibers containing these ceramics.
Rayon fiber is commonly manufactured from cellulose, an inert carbohydrate found in cell walls of plants, wood, cotton, and other materials. In one method, purified cellulose is treated with caustic soda (sodium hydroxide) to form alkali cellulose. After the alkali cellulose has aged, carbon disulfide is added to form cellulose xanthate, which is dissolved in sodium hydroxide. This viscous solution, known as viscose, is forced through spinnerettes, thimble-like devices with tiny holes through which the viscose is pumped to form the rayon fibers. Emerging from the holes, jets of viscose enter a coagulating bath of acids and salts, in which they are reconverted to cellulose and coagulated to form a solid filament. The filament may be manipulated and modified during the manufacturing process to control luster, strength, elongation, filament size, and cross section.
Processes for manufacturing clothing with ceramics having ion-generating characteristics typically involve both dry and wet pulverization of ceramics to create a powder. This dispersion of ceramics (e.g., tourmaline powder) in water is added to alkaline cellulose in a kneader together with carbon disulfide and caustic soda, forming viscose. The viscose, containing the ceramics, is then spun to form rayon fiber.