Coated porous substrate formation by solution coating

A method for making an openly microporous filtration membrane wherein a copolymeric perfluorocarbon in an equivalent weight range of from about 900 to about 1500 coats an openly microporous filtration substrate comprising the steps of:

• solvating the perfluorocarbon copolymer in a dispersion media selected from a group consisting of:
• chlorotrifluoroethylene, perfluorooctanoic acid, perfluorodecanoic acid, perfluorotributylamine, perfluorotrialkylamine, perfluoro-1-methyldecalin, decafluorobiphenyl, pentafluorophenol, pentafluorobenzoic acid, N-butylacetamide, tetrahydrothiophene-1,1-dioxide, N,N-dimethylacetamide, N,N-diethylacetamide, N,N-dimethylpropionamide, N,N-dibutylformamide, N,N-dipropylacetamide, N,N-dimethylformamide, 1-methyl-2-pyrrolidinone, and mixtures thereof to form a true solution of the perfluorocarbon copolymer in the dispersion media;
• applying the dispersion to the openly microporous filtration substrate until substantially all surfaces of the microporous substrate are coated;
• and removing the dispersion media.

A method for making an openly microporous substrate having an applied coating of a perfluorocarbon copolymer, the perfluorocarbon copolymer coating substantially all surfaces of the openly microporous substrate;

• and the copolymeric perfluorocarbon being a copolymer of two monomers, one monomer being selected from a group consisting of vinyl fluoride, hexafluoropropylene, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, perfluoro (alkylvinyl ether), tetrafluoroethylene and mixtures thereof, the second monomer being selected from a group of monomers containing at least one of a pendant SO.sub.2 F based functional group and a pendant COF based functional group, the second monomer being represented by the generic formula CF.sub.2 .dbd.CFR.sub.1 SO.sub.2 F or CF.sub.2 .dbd.CFR.sub.1 COF, with R.sub.1 being a bifunctional perfluorinated radical comprising generally 1 to 8 carbon atoms, the carbon atom adjacent the SO.sub.2 F or COF based group having at least one attached fluorine, and the copolymeric perfluorocarbon having an equivalent weight of at least about 900, but not greater than about 1500, comprising the steps of:
• dissolving the copolymeric perfluorocarbon in a quantity of a solvent at a temperature not greater than about 300.degree. C. to achieve a true solution of at least 2 percent by weight of the copolymeric perfluorocarbon in the solvent;
• the solvent being selected from a group consisting of:
• chlorotriffluoroethylene, perfluorooctanoic acid, perfluorodecanoic acid, perfluorotributylamine, perfluorotrialkylamine, perfluoro-1-methyldecaline, decafluorobiphenyl, pentafluorophenol, pentafluorobenzoic acid, N-butylacetamide, tetrahydrothiophene-1,1-dioxide, N,N-dimethylacetamide, N,N-diethylacetamide, N,N-dimethylpropionamide, N,N-dibutylformamide, N,N-dipropylacetamide, N,N-dimethylformamide, 1-methyl-2-pyrrolidinone, and mixtures thereof, applying the true solution to substantially all surfaces of the openly microporous substrate;
• and removing the solvent using at least one of heat and vacuum.

A method for making a microporous filter having a substrate formed of coadhered particles of a thermoplastic and having an average pore size of not more than 2 microns, the filter having an applied coating of a perfluorocarbon copolymer, the perfluorocarbon copolymer coating substantially all surfaces of the microporous filter, the copolymeric perfluorocarbon being a copolymer of two monomers, one monomer being selected from a group consisting of vinyl fluoride, hexafluoropropylene, vinylidene fluoride, trifluoroethylene, chlorotrifluoroethylene, perfluoro (alkylvinyl ether), tetrafluoroethylene and mixtures thereof, the second monomer being selected from a group of monomers containing at least one of a pendant SO.sub.2 F based functional group and a pendant COF based functional group, the second monomer being represented by the generic formula CF.sub.2 .dbd.CFR.sub.1 SO.sub.2 F or CF.sub.2 .dbd.CFR.sub.1 COF, with R.sub.1 being a bifunctional perfluorinated radical comprising generally 1 to 8 carbon atoms, the carbon atom adjacent the SO.sub.2 F or COF based group having at least one attached fluorine, and the copolymeric perfluorocarbon having an equivalent weight of at least about 900, but not greater than about 1500, comprising the steps of:

• dissolving the copolymeric perfluorocarbon in a quantity of a solvent at a temperature not greater than about 300.degree. C. to achieve a true solution of at least 2 percent by weight of the copolymeric perfluorocarbon in the solvent;
• the solvent being selected from a group consisting of:
• chlorotrifluoroethylene, perfluorooctanoic acid, perfluorodecanoic acid, perfluorotributylamine, perfluorotrialkylamine, perfluoro-1-methyldecalin, decafluorobiphenyl, pentafluorophenol, pentafluorobenzoic acid, N-butylacetamide, tetrahydrothiophene-1,1-dioxide, N,N-dimethylacetamide, N,N-diethylacetamide, N,N-dimethylpropionamide, N,N-dibutylformamide, N,N-dipropylacetamide, N,N-dimethylformamide, 1-methyl-2-pyrrolidinone, and mixtures thereof, applying the true solution to substantially all surfaces of the microporous filter by immersion of the filter in the true solution and applying one of pressure and vacuum at a temperature at least greater than room temperature but not greater than about 200.degree. C.;
• and removing the solvent using at least one of heat not exceeding 200.degree. C. and vacuum.