EP0077633A1
Expired / Lapsed
EP
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Filter media
Assignee: Pall Corp
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Filing: 1982-10-12
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Granted: —
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Expires: 2002-10-12
Abstract
Abstract Filter media comprised of charge modified, resin coated inorganic microfibers are prepared by mixing inorganic microfibers with an aqueous solution of a water soluble, noncolloidal cationic thermosetting binder resin to form a dispersion, following which a precipitating agent is added to precipitate the binder resin and coat the microfibers. The coated microfibers may be used in the dispersed or suspended form as a filter aid. Preferably they are formed into a filter sheet which is then dried and cured to form a filter sheet of narrowly distributed pore size, pore sizes as small as one-half micron, and having a positive zeta potential in alkaline media. Glass is the preferred microfiber and polyamine-epichlorohydrins the preferred resins. By providing the normally negative zeta potential microfibers with a positive zeta potential the binder resins used to coat the microfibers substantially enhance particulate removal capabilities of the microfiber filter sheet.
Inventors
- 👤 David Boris Pall
- 👤 Thomas Charles Gsell
- 👤 Irving Brian Joffee
- 👤 Peter John Degen
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-02 15:24
CPC Classifications
B; B01; B01D; B01D39/00; B01D39/14; B01D39/20; B01D39/2003; B01D39/2017; B01D39/2024; B01D2239/00; B01D2239/04; B01D2239/0471
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
85 words
A process for forming a fibrous filter medium exhibiting a positive zeta potential in alkaline media with the aid of a binder resin or polymer characterised by the steps of (1) mixing inorganic microfibers normally having a negative zeta potential with an aqueous solution of a water-soluble, non-colloidal, cationic, thermo-setting binder resin or polymer to form a microfiber dispersion; and (2) adding a precipitating agent to said dispersion to precipitate said binder resin or polymer and coat said microfibers with said binder resin or polymer.
Claim 2
Dependent Claim
85 words
A process for forming a fibrous filter medium exhibiting a positive zeta potential in alkaline media with the aid of a binder resin or polymer characterised by the steps of (1) mixing inorganic microfibers normally having a negative zeta potential with an aqueous solution of a water-soluble, non-colloidal, cationic, thermo-setting binder resin or polymer to form a microfiber dispersion; and (2) adding a precipitating agent to said dispersion to precipitate said binder resin or polymer and coat said microfibers with said binder resin or polymer.
Claim 3
Dependent Claim
16 words
The process of claim 1 characterised in that the microfibers are glass, titanate or mixtures thereof.
Claim 4
Dependent Claim
28 words
The process of claim 1 characterised in that said binder resin or polymer is an epoxide-based water soluble resin, for example a polyamido/polyamino-epichlorohydrin resin, or a polyamine-epichlorohydrin resin.
Claim 5
Dependent Claim
26 words
The process of any one of claims 1 to 3 characterised in that said binder resin or polymer has a substantial number of quaternary ammonium groups.
Claim 6
Dependent Claim
23 words
The process of claim 1 characterised in that the pH of said dispersion prior to the addition of said precipitating agent is alkaline.
Claim 7
Dependent Claim
38 words
The process of any one of claims 1 to 5 characterised in that the weight ratio of said binder resin or polymer to said microfibers present in said dispersion is in the range from 1:100 to . 40:100.
Claim 8
Dependent Claim
40 words
The process of any one 6f claims 1 to 6 characterised in that the weight ratio of said binder resin or polymer to said precipitating agent is in the range of from 100:1 to 1:1, preferably from 10:1 to 1:1
Claim 9
Dependent Claim
53 words
The process of any one of claims 1 to 7 characterised in that said aqueous solution of a water soluble, non- colloidal cationic thermosetting binder resin or polymer prior to mixing with said microfibers, has a concentration of from about 1 to about 10 weight per cent of said binder resin or polymer.
Claim 10
Dependent Claim
42 words
The process of any one of claims 1 to 8, characterised in that the precipitating agent is added to said dispersion as an aqueous solution or dispersion preferably having a concentration in the range of from 0.01 to 4.00 weight per cent.
Claim 11
Dependent Claim
26 words
The process of any one of claims 1 to 9, characterised in that said precipitating agent is a synthetic, water-soluble or dispersible polymer containing anionic groups.
Claim 12
Dependent Claim
38 words
The process of any one of claims 1 to 10, characterised in that the inorganic microfibers are mixed with water to form an initial dispersion prior to the said mixing with the aqueous binder resin or polymer solution.
Claim 13
Dependent Claim
22 words
The process of any one of claims 1 to 11, characterised in that the coated microfibers are formed into a filter sheet.
Claim 14
Dependent Claim
124 words
The process of claim 12, characterised in that the sheet formation is effected by forming a layer or mat of the coated microfibers on a foraminous surface, drawing a vacuum through said surface to remove water from the mat, drying the mat and curing the binder resin or polymer to form a self-supporting sheet. 14 . A fibrous filter medium exhibiting a positive zeta potential and coated with a binder resin or polymer, characterised by inorganic microfibers normally having a negative zeta potential substantially uniformly coated with a precipitated cured, cationic, non-colloidal, thermoset binder resin or polymer, said binder resin or polymer being present in an amount sufficient to impart said positive zeta potential to said filter medium and to bond said microfibers together.
Claim 15
Dependent Claim
24 words
1 5 . The filter medium of claim 14 characterised in that said microfibers are glass, titanate, or a mixture of glass and titanate.
Claim 16
Dependent Claim
30 words
The filter medium of claim 14 or claim 15, characterised in that said binder resin or polymer is an epoxide-based resin, for example a polyamido/polyamino-epichlorohydrin resin, or a polyamine-epichlorohydrin resin.
Claim 17
Dependent Claim
41 words
The filter medium of claim 14, claim 15 or claim 16 characterised in that the weight ratio of said binder resin or polymer to said microfibers is in the range of from 1: 100 to 40:100, preferably from 5:100 to 30:100.
Claim 18
Dependent Claim
35 words
The filter medium of any one of claims 14 to 17 , characterised in that said filter sheet has actual pore sizes ranging from about 0.5 to about 50 micrometers, preferably 20 micrometers or less.
Claim 19
Dependent Claim
36 words
19: The filter medium of any one of claims 1 4 to 18, characterised in that said microfibers are staple fibers and have a mean diameter in the range of from 0.1 to about 10 micrometers.
Claim 20
Dependent Claim
29 words
The filter medium of any one of claims 14 to 19, characterised in that the medium has an effective particulate removal capability smaller than the actual membrane pore size.
Claim 21
Independent Claim
45 words
A method for the filtration of particulates from a fluid medium comprising passing said medium through the filter medium of any one of claims 11 to 17, said particulates preferably having a negative charge and a size ranging from about 0.001 to about 50 micrometers.
Claim 22
Independent Claim
204 words
A method cf making a supported, inorganic, microfiber filter sheet, said supported inorganic microfiber filter sheet having (1) a binder resin or polymer coating the microfibers, and (2) a positive zeta potential in alkaline media, said method being characterised by the steps of: (a) applying to a fibrous substrate web an aqueous solution of an adhesive resin compatible with said binder resin or polymer coating the microfibers; (b) applying a precipitating agent for said adhesive resin to said substrate web; (c) introducing said precipitating agent into the fibrous matrix of said substrate web to mix with said aqueous solution of an adhesive resin and cause said adhesive resin to precipitate and coat the fibers of said substrate web; (d) depositing on said substrate web an aqueous slurry or inorganic microfibers coated with said binder resin or polymer; (e) drawing the water from said aqueous slurry through said substrate web and forming said inorganic microfibers into a sheet on the surface of said substrate web; and (f) drying said sheet and said substrate web and curing said first adhesive resin and said binder resin or polymer to provide adhesive interfiber bonding between said inorganic microfibers of said sheet and said fibers of said substrate web.
Claim 23
Independent Claim
204 words
A method cf making a supported, inorganic, microfiber filter sheet, said supported inorganic microfiber filter sheet having (1) a binder resin or polymer coating the microfibers, and (2) a positive zeta potential in alkaline media, said method being characterised by the steps of: (a) applying to a fibrous substrate web an aqueous solution of an adhesive resin compatible with said binder resin or polymer coating the microfibers; (b) applying a precipitating agent for said adhesive resin to said substrate web; (c) introducing said precipitating agent into the fibrous matrix of said substrate web to mix with said aqueous solution of an adhesive resin and cause said adhesive resin to precipitate and coat the fibers of said substrate web; (d) depositing on said substrate web an aqueous slurry or inorganic microfibers coated with said binder resin or polymer; (e) drawing the water from said aqueous slurry through said substrate web and forming said inorganic microfibers into a sheet on the surface of said substrate web; and (f) drying said sheet and said substrate web and curing said first adhesive resin and said binder resin or polymer to provide adhesive interfiber bonding between said inorganic microfibers of said sheet and said fibers of said substrate web.
Claim 24
Dependent Claim
13 words
A supported inorganic microfiber filter sheet made by the method of claim 22.
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