Stock material or miscellaneous articles – Structurally defined web or sheet – Continuous and nonuniform or irregular surface on layer or...
Patent
1992-12-07
1994-09-27
Ryan, Patrick J.
Stock material or miscellaneous articles
Structurally defined web or sheet
Continuous and nonuniform or irregular surface on layer or...
428143, 428147, 428221, 428245, 428332, 428340, 428391, 385100, 385109, 385115, B32B 2510, B32B 2000
Patent
active
053506170
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a water shieldable material having superior water shieldability. More particularly, the present invention relates to a water shieldable material having superior water shieldability for water having a lower ionicity as well as water having a high ionicity such as a sea-water, for which it is generally difficult to attain superior water shieldability, and is capable of effectively being used as a water shielding tape for a hold winding layer of, in particular, an electrical wire cable or an optical fiber cable. The present invention relates further to a cable using the water shielding material.
PRIOR ART
In recent years, cables such as optical fiber cables embedded in the ground have frequently been used. Accordingly, characteristics required as a filler, such as, covering buffer properties preventing the core of a communication cable from external force, an easy filling ability depending on workability when manufacturing the cable or the like are required of the cable, and in addition to superior water shieldability. The water shieldability is a property of absorbing rapidly water flowing in a longitudinal direction of the cable and shielding the water by a swell thereof, when a jacket of the cable is broken and the water flows into the cable.
The T-letter method and L-letter method have been used as methods of testing the water shieldability. The T-letter method is a method of testing water flowing in the longitudinal direction when an external force is applied to the jacket of the cable and water flows through holes or crocks generated by the external force into the cable. The L-letter method is a method of testing water flowing in the longitudinal direction from a cross section of the cable cut by an external force. In both methods, the water shieldability is evaluated by a length expressed in mm and after the water has flowed into the cable for 24 hours. When the value representing the length is small, it is determined that the cable has superior water shieldability, and it is required that the cable has superior value of the water shieldability in the T-letter method and the L-letter method.
Japanese Unexamined Patent Publication (Kokai) No. 63-6055 discloses a composite material having a water swelling ability and comprised of a substrate of a polyvinylpyrrolidine group binder, a dried film of which has water-solubility and a water-soluble polymer coated on the substrate. This composite material, however, cannot be practically used because, since the binder is water-soluble, the water-shieldable tape curls when there is a change in humidity due to dimensional changes caused by the substrate and the coating layer absorbing moisture, and the tape becomes sticky when absorbing moisture. Further this composite material has inferior workability when manufacturing and applying the cable because of the high level of hardness of the film thereof.
Japanese Unexamined Patent Publication (Kokai) No. 1-240547 discloses a water shieldable material obtained by coating a surface of a woven fabric and a nonwoven sheet with a rubber group binder and a high ion water absorption composition. This type water shieldable material made of a water absorption polymer composed of particles having a small diameter has an inferior water shieldability value as measured by the L-letter method because the water absorption polymer does not drop away from the surface of the nonwoven fabric and thus the polymer swells on the surface of the nonwoven fabric, and this type of water shieldable material made of a water absorption polymer composed of particles having a large diameter has an inferior water shieldability value as measured by the T-type method because the density of the coating layer composed of the rubber group binder and the water absorption polymer is small. Accordingly, when, for example, water shielding inside an optical fiber cable takes place using this water shieldable material, it is necessary to wind the water shieldable material on the outside of the cable and in
REFERENCES:
patent: 4802732 (1989-02-01), Fukuma et al.
Derwent Publications Ltd., London, GB; AN 90-380880 (51) & JP-A-2 276 840 (Tokai Rubber Ind KK) Nov. 13, 1990.
Derwent Publications Ltd., London GB; AN 89-321387 (44) & JP-A-1 240 547 (Nippon Teleg. & Teleph. KK) Sep. 26, 1989.
Communication dated Apr. 7, 1993 from the European Patent Office in Application 919 032 82.1; Supplementary European Search Report and Annex.
Fujisawa Noriaki
Kukita Shigezou
Kuwabara Tsuneo
Sakai Yasuro
Ryan Patrick J.
Weisberger Richard C.
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