Abstract: A process for separating nitrogen which comprises, with a nitrogen gas separation apparatus of a pressure-swing adsorption type, a gas transfer step between an adsorber having completed an adsorption step with another adsorber having completed a regeneration step. The gas transfer step further comprising discharging part of the gas being transferred out of the system. This process provides, with compact equipment, high-purity product nitrogen with a purity of at least 99.99%, which has been considered difficult to obtain with conventional pressure-swing adsorption apparatuses.

Abstract: Rapidly shrinking fibers hardly soluble in water and capable of shrinking in water at 20.degree. C. by not less than 30% in not longer than 10 seconds are obtained, for example, by spinning, drawing and heat-treating a carboxy-modified polyvinyl alcohol under specific conditions. Yarns made from a fiber of this kind in conjunction with a fiber slowing shrinking in water as well as nonwoven fabrics made by incorporating yarns containing said rapidly shrinking fibers in nonwoven fabric shrinkable upon absorption of water are suited as means of tightly fitting edge portions of disposable diapers to the thigh.

Abstract: Rapidly shrinking fibers hardly soluble in water and capable of shrinking in water at 20.degree. C. by not less than 30% in not longer than 10 seconds are obtained, for example, by spinning, drawing and heat-treating a carboxy-modified polyvinyl alcohol under specific conditions. Yarns made from a fiber of this kind in conjunction with a fiber slowing shrinking in water as well as nonwoven fabrics made by incorporating yarns containing said rapidly shrinking fibers in nonwoven fabric shrinkable upon absorption of water are suited as means of tightly fitting edge portions of disposable diapers to the thigh.

Abstract: A fine-denier, high-tenacity, water-resistant polyvinyl alcohol fiber is produced by dissolving a polyvinyl alcohol having an average degree of polymerization between 1,200 and 3,000, boric acid or a salt thereof in a proportion of 0.5 to 5 weight percent relative to said polyvinyl alcohol and an acid for adjusting a final spinning solution to pH 5 or less in water to prepare an aqueous solution containing 8 to 14 weight percent of said polyvinyl alcohol, discharging said aqueous solution as said spinning dope from a spinneret nozzle having an average orifice diameter of 0.02 to 0.04 millimeters into a bath comprising an aqueous solution containing alkali and dehydrating salt at a bath draft within a range of 10 to -60 percent, and finally stretching the resulting tow at least 10-fold. The fine-denier fiber thus obtained has a marked reinforcing effect on various materials, particularly inorganic hydraulic materials such as cement.

Abstract: In a process for producing fiber-reinforced hydraulically setting extruding materials, the process which comprises, not adding the reinforcing fiber in the form of single fibers to the starting materials, but employing it as collected yarns by collecting the single fibers with a collecting agent, uniformly dispersing them in the starting materials, then releasing the collected condition of said dispersed collected yarns and splitting into single fibers by swelling and dissolution of the collecting agent and by the shear force by a screw etc., thereby the dispersion is improved.The single fibers having a great aspect ratio which have been released from the collected condtion are uniformly dispersed in the extruding material, and a remarkable reinforcing effect is obtained.

Abstract: Polyvinyl alcohol synthetic fibers are used as reinforcing materials for hydraulically setting materials, and by selecting the aspect ratio of the polyvinyl alcohol fiber and the dispersing agent for said fiber, adequate dispersion is made possible even with the fiber of 2 denier or less, thereby a higher reinforcing effect may be achieved.The polyvinyl alcohol fiber is obtained by depositing 0.1-3.0% by weight based on the fiber of an oxidized polyethylene having an acid value of 5-150, and has a single yarn fineness of 0.5-2 denier, a length of 3-8 mm and an aspect ratio of 200-800, and the hydraulically setting material contains 0.1-4% by weight of said fiber.