Porous sheet
AssigneeKao Soap Co., Ltd.
InventorsMitsuru Tokuyama, Kenji Ohki, Masayuki Sagae, Kaoru Tsujii
Life of this patent
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Abstract
A porous sheet is disclosed that comprises a thin, flexible sheet made of thermoplastic resin having solid particles distributed therein. Small spaces are formed around the particles, such that abrasion or buffing of the opposite surfaces of the sheet causes the formation of a multitude of fine pores that extend through the sheet, making the sheet vapor-permeable but liquid-impermeable.
Claims10
A liquid-impermeable, vapor-permeable, thin, flexible, porous sheet made from a composition comprising a blend of thermoplastic resin and solid filler particles, said thermoplastic resin forming a matrix in which said filler particles are dispersed, said solid filler particles extending to the opposite surfaces of said sheet, said thermoplastic resin matrix being spaced from the surfaces of said solid filler particles thereby to provide apertures surrounding said solid filler particles, the portions of said thermoplastic matrix on the opposite surfaces of said sheet that overlie the outermost portions of said solid filler particles having been removed by abrasion or buffing so that said outermost portions of said solid filler particles are uncovered and exposed and said apertures form passages that extend between and penetrate through said opposite surfaces of said sheet, said passages being of a small size so that liquid cannot substantially permeate through said sheet and vapor can permeate through said sheet.
A process for manufacturing a liquid-impermeable, vapor-permeable, thin, flexible, porous sheet, which comprises the steps of:
- blending thermoplastic resin and solid filler particles to form a molding composition;
- molding said composition to form a thin, flexible sheet wherein said thermoplastic resin forms a matrix in which said filler particles are dispersed with said solid filler particles extending to the opposite surfaces of said sheet and with said thermoplastic resin matrix being spaced from the surfaces of said solid filler particles thereby to provide apertures surrounding said solid filler particles;
- then abrading or buffing the opposite surfaces of said sheet to remove the portions of said thermoplastic matrix on the opposite surfaces of said sheet that overlie the outermost portions of said solid filler particles so that said outermost portions of said solid filler particles are uncovered and exposed and said apertures form passages that extend between and penetrate through said opposite surfaces of said sheet, said passages being of a small size so that liquid cannot substantially permeate through said sheet and vapor can permeate through said sheet.
Dependencies are inferred from the claim text.