Semiconductor device manufacturing: process – Forming bipolar transistor by formation or alteration of... – Self-aligned
Patent
1997-05-05
1998-11-24
Edwards, Newton
Semiconductor device manufacturing: process
Forming bipolar transistor by formation or alteration of...
Self-aligned
428394, D02G 300
Patent
active
058404236
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION
This invention relates to a polyvinyl alcohol (hereinafter abbreviated as "PVA")-based fiber which has excellent hot water resistance because it has been sufficiently crosslinked not only on the fiber surface but also inside of the fiber. In particular, this invention is concerned with a PVA-based fiber which, owing to sufficient crosslinkage even inside of the fiber, hardly causes the dissolution of PVA from the end surface of the fiber and at the same time has a sufficient strength, when subjected to dyeing treatment in a hot water bath at a high temperature, or when subjected to steam curing in a high-temperature autoclave to heighten the strength of a cement product to which the fiber has been added as a reinforcing fiber.
BACKGROUND ART
A PVA-based fiber has the highest strength and the highest modulus of elasticity among general-purpose fibers and also has good adhesiveness and alkali resistance so that it has attracted attentions particularly as a cement reinforcing material substitutable for asbestos. It is, however, poor in hot water resistance (which will be also called "wet heat resistance") so that its applications have so far been limited even if it is employed as general industrial materials or materials for clothes. For example, when the PVA-based fiber is used for a cement product as a cement reinforcing material, it is accompanied with the problem that it cannot be subjected to autoclave curing at high temperature conditions. In the case where a PVA-based fiber is employed as a reinforcing fiber for a cement product, it is now the common but inevitable practice to subject the product to autoclave curing under heating conditions at room temperature or a low temperature. The autoclaving at such a low temperature also involves problems such as insufficiency in the size stability and strength of the resulting cement product and requirement for long curing days.
When the PVA-based fiber is used for mixed fabric products with a polyester-based fiber, a dyeing method commonly employed for the dyeing of a polyester fiber, in which dyeing is carried out in an aqueous solution at a high temperature of from 120.degree. C. to 130.degree. C. using a disperse dye, cannot be applied because of inferior hot water resistance of the PVA-based fiber. So, the use of the PVA-based fiber for clothes has been limited largely also from this viewpoint.
A carbon fiber has been used in some cases for autoclave curing at high temperatures but it is accompanied with a problem that it has inferior adhesiveness with cement matrix and thus produces only poor reinforcement effect and at the same time is expensive.
Attempts have been made to improve the wet heat resistance of a PVA-based fiber. For example, Japanese Patent Application Publication No. Sho 30-7360/1955 or Japanese Patent Application Publication No. Sho 36-14565/1961 describes that a PVA-based fiber is made hydrophobic by the crosslinking reaction (formalization) of hydroxyl groups of PVA by using formalin and that the fiber available by this method has sufficient hot water resistance against dyeing or washing. Such a PVA-based fiber, however, has not hot water resistance high enough to meet the level required by the present invention, that is, hot water resistance high enough to withstand high-temperature autoclave curing and moreover, it has a disadvantage in low strength.
Japanese Patent Application Laid-Open No. Sho 63-120107/1988 discloses a process which comprises formalizing a high strength PVA-based fiber. The fiber obtained by this process has however a formalization degree as low as 5-15 mole % and only very small part of the amorphous region of the fiber has been rendered hydrophobic so that the fiber available by this method has not sufficient hot water resistance and therefore cannot be used at all as an industrial material exposed in repetition to wet heat for a long period of time or as a cement reinforcing material subjected to high-temperature autoclave curing.
In Japanese Patent Application Laid-Open No.
REFERENCES:
patent: 5229057 (1993-07-01), Ohmory et al.
patent: 5238995 (1993-08-01), Fukunishi et al.
patent: 5340650 (1994-08-01), Hirakawa et al.
patent: 5380588 (1995-01-01), Nishiyama et al.
patent: 5455114 (1995-10-01), Ohmory et al.
Ando Yusuke
Hitomi Yoshinori
Mayahara Mitsuro
Sano Hirofumi
Sano Tomoyuki
Edwards Newton
Kuraray Co. Ltd.
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