Kuraray Co., Ltd.

Masaki Okazaki

Akio Mizobe

Tsuneo Genba

Shigeru Sasaki

Mitsuo Matsumoto

Fumio Sanda

Junichi Yoshinaka

Mitsuro Mayahara

Isao Sakuragi

Disposable moldings comprising a polymer (A) having a repeating structure unit in the main chain represented by the formula (I) ##STR1## wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4, R.sup.5 and R.sup.6 are respectively a hydrogen atom or a lower alkyl, and a polymer composition comprising the polymer (A). The moldings of the present invention disintegrate themselves due to decomposition of the polymer (A) in atmosphere, soil or water and do not cause any environmental pollution.

Disposable moldings and polymer compositions for their production

A synthetic fiber suited for use as a reinforcement for cement mortar or concrete as derived from monofilaments having a tensile strength of not less than 80 kg/mm.sup.2, Young's modulus of not less than 2,300 kg/mm.sup.2, a flat cross section in which the minor axis-to-major axis ratio is 1:2 to 1:10, and a fineness of 1,000-9,000 denier, and being cut to a fiber length such that the aspect ratio (the value obtained by dividing the fiber length by the diameter of a circle equivalent in area to the cross section of the fiber) amounts to 20-150, in particular a polyvinyl alcohol fiber having the above-mentioned characteristic features, shows good dispersibility in cement mortar and produces very good reinforcing effect. Materials of construction which are excellent in workability and postcure strength can be obtained by incorporating the above-mentioned fiber to cement and the like.

Synthetic fiber for use in reinforcing cement mortar or concrete and

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.

Method for production of high-tenacity, fine-denier polyvinyl alcohol

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.

Process for producing hydraulically setting extruding materials

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.

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Okayama, Japan

Masaki Okazaki