Process for producing permeable membranes
First Claim
1. A process for producing a permeable membrane, which comprises mixing, in a molten state, (A) 90 to 30 parts by weight of at least one thermoplastic linear organic synthetic resin having stretchability with (B) 10 to 70 parts by weight of at least one compound having partial compatibility with the synthetic resin (A) and selected from the group consisting of synthetic polymers or oligomers containing at least 20 carbon atoms, natural organic polymeric compounds containing at least 20 carbon atoms, fatty acids containing at least 16 carbon atoms, and esters or salts of said fatty acids, the total amount of components (A) and (B) being 100 parts by weight;
- fabricating the resultant molten mixture into a film or sheet in which components (A) and (B) are present in a partly mutually dissolved state;
treating said film or sheet with a solvent which is a good solvent for component (B) but a poor solvent for component (A), for a time sufficient to remove 50 to 100% by weight of component (B) from said film or sheet;
drying the thus treated film or sheet until the amount of said solvent in or adhering to said film or sheet is not more than 10% by weight based on the total weight of said solvent and said film or sheet; and
stretching the dried film or sheet 50 to 1500% monoaxially or biaxially to form a network of continuous pores in the film or sheet.
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Abstract
A process for preparing permeable membranes which comprises kneading in the molten state two different kinds of thermoplastic synthetic resins which are partly compatible with each other, fabricating the molten mixture into a sheet, film or hollow article, treating the fabricated article with a solvent which is a good solvent for one of the component resins but is a poor solvent for the other to dissolve and remove the former resin, drying the fabricated article, and then stretching it. In place of the resin to be removed by the solvent, rubbers or oligomers having partial compatibility with the resin which remains undissolved can be used.
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Citations
4 Claims
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1. A process for producing a permeable membrane, which comprises mixing, in a molten state, (A) 90 to 30 parts by weight of at least one thermoplastic linear organic synthetic resin having stretchability with (B) 10 to 70 parts by weight of at least one compound having partial compatibility with the synthetic resin (A) and selected from the group consisting of synthetic polymers or oligomers containing at least 20 carbon atoms, natural organic polymeric compounds containing at least 20 carbon atoms, fatty acids containing at least 16 carbon atoms, and esters or salts of said fatty acids, the total amount of components (A) and (B) being 100 parts by weight;
- fabricating the resultant molten mixture into a film or sheet in which components (A) and (B) are present in a partly mutually dissolved state;
treating said film or sheet with a solvent which is a good solvent for component (B) but a poor solvent for component (A), for a time sufficient to remove 50 to 100% by weight of component (B) from said film or sheet;
drying the thus treated film or sheet until the amount of said solvent in or adhering to said film or sheet is not more than 10% by weight based on the total weight of said solvent and said film or sheet; and
stretching the dried film or sheet 50 to 1500% monoaxially or biaxially to form a network of continuous pores in the film or sheet. - View Dependent Claims (2, 3, 4)
- fabricating the resultant molten mixture into a film or sheet in which components (A) and (B) are present in a partly mutually dissolved state;
Specification