Stock material or miscellaneous articles – Layer or component removable to expose adhesive – Release layer
Reexamination Certificate
1997-07-25
2001-05-29
Cole, Elizabeth M. (Department: 1771)
Stock material or miscellaneous articles
Layer or component removable to expose adhesive
Release layer
C428S297700, C428S298100, C428S196000, C428S198000, C428S202000, C442S026000, C442S027000, C442S204000, C156S291000
Reexamination Certificate
active
06238761
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a unidirectional fiber sheet for reinforcing concrete support structures such as buildings, bridges and other civil architecture. More particularly, the present invention relates to a unidirectional fiber sheet which comprises an arranged fiber layer, a multi axial scrim and a release paper. The release paper is partially coated with an adhesive which temporarily secures the release paper to the arranged fiber layer and multi axial scrim. The adhesive coating covers about 3 to 80% of the surface area on one surface of the release paper.
BACKGROUND OF THE INVENTION
Buildings, bridges and other civil architecture, over a long period of time, can deteriorate. In other words, structural support members such as beams, pillars, walls, etc. can weaken over time. It is known in the art to use reinforced fabric material to repair weakened support structures. One method of reinforcing deteriorating civil architecture comprises the steps of coating the damaged portion of the structure with a primer, coating a room temperature curable resin over the primer, and adhering a reinforced fabric material over the room temperature curable resin layer. The weakened structure agglutinates with the reinforced fabric material by means of the room temperature curable resin so as to enhance the strength of the weakened structure.
Typically, the reinforced fabric material used in the above described processes is a unidirectional fiber sheet. Generally, such a unidirectional fiber sheet comprises an arranged fiber layer which is prepared from filament tows, a multi axial scrim having a net-like structure which supports the arranged fiber layer, and a release paper which is adhered to the arranged fiber layer and multi axial scrim.
In the above described process, after the unidirectional fiber sheet is applied over the layer of curable resin, the exterior surface of the unidirectional fiber sheet, i.e. the release paper surface, is rolled or patted to insure maximum contact between the unidirectional fiber sheet and the curable resin. Thereafter, the release paper is peeled away from the multi axial scrim. The capacity of this process to strengthen the deteriorating structure is limited by the amount of curable resin which permeates and impregnates the fiber sheet and scrim.
The inventors have observed that the degree to which the curable resin permeates and impregnates the fiber layer is effected by the adhesive coating by which the release paper is secured to the fiber layer and multi axial screen. In particular, the greater the release paper surface area which is covered with adhesive, the less curable resin will permeate and impregnate the arranged fiber layer. Generally, the viscosity of the adhesive is more than several millions centipoise (cps) and the viscosity of the curable resin is almost several ten thousands cps. As a result, the resin can hardly permeate the adhesive layer.
In prior art unidirectional fiber sheets, the entire surface of the release paper which abuts the surface of the fiber layer and multi axial scrim is coated with adhesive. The inventors have observed that when such prior art unidirectional fiber sheets employed, the curable resin does not adequately permeate the fiber layer and scrim. As a result, the agglutinating force between the structure and the unidirectional sheet is deficient and the reinforcing effect of the process less than optimal.
OBJECTS OF THE INVENTION
It is therefore desirable and an object of the present invention to provide a unidirectional fiber sheet which provides improved reinforcing effect by maximizing the permeation and impregnation of curable resin into the fiber sheet.
It is another object of the present invention to provide a unidirectional fiber sheet having a release paper that is sufficiently adhered to an arranged fiber layer and multi axial scrim during the application process, and that can be easily removed from the arranged fiber layer and multi axial scrim after application.
It is still a further object of the present invention to provide a method of preparing a unidirectional fiber sheet with the above properties.
SUMMARY OF THE INVENTION
Accordingly, the present invention provides a unidirectional fiber sheet which provides improved reinforcing effect by maximizing the permeation and impregnation of curable resin into the fiber sheet, and which also sufficiently adheres to the fiber layer while being easily removed from the fiber layer after application.
In one presently preferred embodiment of the present invention, the unidirectional fiber sheet comprises an arranged fiber layer, a multi axial scrim for supporting the arranged fiber layer, and a release paper partially coated with an adhesive so as to adhere to the arranged fiber layer and the multi axial scrim, wherein 3 to 80% of the surface area of the release paper is coated with the adhesive.
The adhesive is applied to the release paper in the form of stripes wherein the stripes may be positioned parallel or perpendicular to the filaments of the arranged fiber layer. The adhesive is a material selected from the group consisting of epoxy resin, unsaturated polyester resin, and polyurethane resin.
The arranged fiber layer is made of a fiber selected from the group consisting of carbon fiber, boron fiber, aramid fiber, glass fiber, polyethylene fiber, polyarylate fiber and steel fiber.
The multi axial scrim is preferably a tri-axial scrim. The multi axial scrim is made of a yarn which is selected from the group consisting of nylon, polyester, aromatic polyamide, carbon fiber and glass fiber.
Another aspect of the invention is the method of preparing the inventive unidirectional fiber sheet. In the preferred embodiment the method comprises the steps of: providing a release paper partially coated with an adhesive, wherein 3 to 80% of the surface area of the release paper is coated with the adhesive; and heat-pressing together an arranged fiber layer prepared from filament tows, a multi axial scrim having a net structure to support the arranged fiber layer, and the release paper.
REFERENCES:
patent: 2539420 (1951-01-01), Hazeltine et al.
patent: 4889234 (1989-12-01), Sorensen et al.
patent: 5-332031 (1993-12-01), None
patent: 8-142238 (1996-06-01), None
patent: 9-118760 (1997-05-01), None
Jeong Hoon-hee
Jeong Seong-roon
Kim Do-Hyun
Park Hern-jin
Cole Elizabeth M.
Sunkyong Industries Co., Ltd.
Woodcock Washburn Kurtz Mackiewicz & Norris
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