Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Patent
1994-07-08
1996-05-28
Cannon, James C.
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
427246, 427354, 427412, 428253, 428262, 428283, 4283155, 4283159, 428421, B05D 300, B32B 512, B32B 2712, B32B 2718
Patent
active
055209980
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a waterproof sheet having both a high water pressure resistance and a high moisture permeability and a method for producing the same.
BACKGROUND ART
A conventional moisture-permeable waterproof sheet is mainly produced by coating a fabric with a solution of polyurethane in a water-soluble solvent, and wet coagulating the polyurethane. Rain or other types of water cannot permeate the porous polyurethane film formed thereon when the solvent is removed with water, but moisture (water vapor) can permeate it.
However, when the porosity of the waterproof fabric is increased (the number of pores are increased and the pore size becomes large) to improve the permeability, the water pressure resistance thereof does not fail to fall, and the waterproof sheet is not waterproof. Conversely, when the water pressure resistance thereof is improved (the number of pores is decreased and the pore size becomes small), the moisture permeability thereof is lowered. Accordingly, the improvement of the moisture permeability conflicts with that of the water pressure resistance.
DISCLOSURE OF INVENTION
An object of the present invention is to overcome the contradiction described above, and develop a waterproof sheet having both a high water pressure resistance and a high moisture permeability. The present invention is intended to provide a novel waterproof fabric having both a water-pressure resistance as high as at least 5,000 mm and a moisture permeability as high as at least 8,000 g/m.sup.2.24 hr.
The present invention provides a highly water-pressure-resistant and highly moisture-permeable waterproof sheet comprising a fabric and a wet coagulated polyurethane film thereon, said wet coagulated polyurethane film containing from 0.5 to 20% by weight, based on the solid component of the polyurethane, of a dispersed clay organic composite prepared by introducing a quaternary ammonium ion into the interlayers of a expandable phillosilicate, and said waterproof sheet having a water pressure resistance of at least 5,000 mm and a moisture permeability of at least 8,000 g/m.sup.2.24 hr.
The waterproof sheet of the present invention mentioned above is prepared by a process comprising dissolving a polyurethane into a solvent containing mainly a nitrogen-containing polar solvent, dispersing from 0.5 to 20% by weight, based on the solid component of the polyurethane, of a organophilic clay complex prepared by introducing a quaternary ammonium ion into the interlayers of a expandable phillosilicate in the solution, coating a fabric with the resultant solution, immersing the coated fabric in a coagulation bath whereby the polyurethane is coagulated, washing the resultant fabric, and drying it.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a SEM photograph of a cross section of a waterproof sheet obtained in an example of the present invention.
FIG. 2 is a SEM photograph of a cross section of a waterproof sheet in a comparative example of the present invention.
FIG. 3 is a SEM photograph of the polyurethane film surface of a waterproof sheet obtained in an example of the present invention.
FIG. 4 is a SEM photograph of the polyurethane film surface of a waterproof sheet obtained in a comparative example of the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
The highly water-pressure-resistant and highly moisture-permeable sheet of the present invention will be explained in detail in accordance with the steps of the production thereof.
Polyurethanes used in the present invention include conventional polyester polyurethanes, polyether polyurethanes, polycarbonate polyurethanes, or modified polyurethanes prepared by copolymerizing with a polyamino acid, silicone, fluoromonomer, etc., or polyurethane elastomers obtained by optionally blending these polyurethanes. Such a polymer is dissolved in a water-soluble solvent mainly containing a nitrogen-containing polar solvent in an amount of 15 to 30% by weight, and the resultant solution is used as a solution of polyurethane in a nitrog
REFERENCES:
patent: 5204403 (1993-04-01), Furuta et al.
Huruya Takenori
Kondo Hisao
Nakano Toshiaki
Nishizakura Kouichi
Sekimoto Takahiro
Cannon James C.
Toray Industries Inc.
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