GB2105759A - Porous media to separate gases, liquid droplets and/or solid particles from gases or vapors and coalesce entrained droplets - Google Patents

Abstract

Fluid-permeable gas-vapor treating mats are provided and comprise a sheet or elongated web formed from a mixture of: (a) glass fibers, (b) finely divided activated carbon, (c) a fiber-forming terephthalate polyester in an amount of 5 to 10% by weight, of the finished mat, (d) micro-bits of certain expanded, thermoplastic styrene-polymers, expanded polyolefins or flexible foamed polyurethanes, said microbits comprising from 2 to 50% by weight of the finished mat, (e) from 2 to 10% by weight, based on the finished mat, of a compatible organic binder, and (f) cobeat of wet-lapped cotton fibers, and any of said micro-bits, said cobeat agent being distributed throughout the mat, and comprising from 2 to 30% by weight of the finished mat. n

Description

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GB 2 105 759 A 1

SPECIFICATION

Porous media to separate gases, liquid droplets and/or solid particles from gases or vapors and coalesce entrained droplets

5 This invention relates to porous media, briefly called gas-vapor mats or gas-vapor filtering or treating mats, having good tensile strength and porosity to provide maintained good flow-through rates but yet being sufficiently dense to enable 10 filtering finely divided solid particles and/or entrained liquid droplets from aerosols or gasses and/or vapor streams, as well as coalescing liquid droplets entrained in them, and also capable of separating some gases from such streams. 15 A web of merely glass fibers such as Owens-Corning De 636 bound with polyvinyl alcohol (98% hydrolyzed) was made but its use has been rather restricted. For example, it has been used as a battery plate separator and as the base for roof 20 covering to be coated over with tar. However, no such web of glass fiber and polyvinyl alcohol (i.e. called PVA) has been known for use in any such treatment of fluids as described above.

For many years various industries have been 25 concerned with troublesome solid particles or fine droplets of liquids, or harmful gases released into working areas and often passing through vents or smoke stacks into the outside atmosphere, thus provoking bothersome environmental problems. 30 In some cases, it has been merely dust particles from working with inorganic materials such as recovering minerals from ores or grinding and polishing operations.

In other cases involved are liquid droplets 35 entrained from chemical operations such as electroplating, spray coating of one kind or another or production of certain synthetic resins. In still other situations it may be harmful gases, for example, sulfur dioxide carried into the 40 atmosphere as from burning of high sulfur content fuel oils or bituminous coals. Production of a polyphenylene oxidepolystyrene alloy polymer involves release in part of resin fines or pellets, dust particles and of oily plasticizer droplets 45 entrained apparently as an aerosol into the air.

Some attempts to overcome some of these problems have been made by using (i) a filter medium such as a mat of glass fibers held together by a phenol formaldehyde resin binder, 50 or (ii) glass wool air filters in window openings or other outlets. However, generally these filter media are bulky and yet not dense enough to restrain the finer particles or gases, thus still allowing undesirable fluid passage through them 55 and thereby still to pass out to the atmosphere. Then also some of these mats, among other shortcomings, have an undesirably limited tensile strength resulting in too frequent breaks requiring interrupting their use in undue time-consuming 60 repair.

Other attempts include use of electric charging precipitators, such as the long known Cottrell electric precipitators, but these are costly to install, operate and maintain, and do not restrain merely gases, for example, sulfur dioxide.

These disadvantages are overcome by the gas-vapor filter or treating mats of the invention. Then too, these mats of the invention show enhanced porosity and tensile strength over the above described glass fibers and PVA webs of the prior art used as battery separators and in roof covering sheets.

The present invention provides a fluid-permeable gas-vapor treating mat which comprises a sheet of elongated web formed from a mixture of:

(a) glass fibers from 6.35 millimeters long to below a length at which said fibers are prone to roping, and from 3 to 12 microns in diameter.

(b) finely divided activated carbon, in an amount below that at which more than insignificant dusting of carbon from the finished mat would occur.

(c) a fiber-forming terephthalate polyester in an amount of 5 to 10% by weight, of the finished mat,

(d) micro-bits(as herein defined) of a polymer which is non-brittle in its initial expanded form, and is selected from an expanded, thermoplastic styrene-polymer, and an expanded polyolefin, selected from polyethylene, polypropylene, polybutene and polymethylpentene, or micro-bits (as herein defined) of a flexible foamed polyurethane, said micro-bits comprising from 2 to 50% by weight of the finished mat,

(e) from 2 to 10% by weight, based on the finished mat, of a compatible organic binder, insoluble in cold water and soluble in hot water and inert to the glass fibers and micro-bits, and

(f) cobeat of wet-lapped cotton fibers, and any of said micro-bits, said cobeat agent being distributed throughout the mat, and comprising from 2 to 30% by weight of the finished mat.

Said finished mat will generally have a tensile strength from 0.9 to 5.3 kilograms per centimeter and a porosity from 150 to 915 liters per square decimeter per minute at a pressure differential of 2.54 centimeters of water (gauge).

in one preferred embodiment, the binding agent is polyvinyl alcohol, at least 98%

hydrolyzed.

The micro-bits component of the gas-vapor treating mats of the invention are micro-bits of a polymer which is non-brittle in expanded form and selected from an expanded, thermoplastic styrene-polymer or lower polyolefin, or of a flexible foamed polyurethane likewise non-brittle in expanded form. The micro-bits of an expanded, thermoplastic styrene-polymer or lower polyolefin are defined and more fully described as produced from an expanded, thermoplastic polymer selected from a styrene-polymer and a polyolefin from polyethylene to polymethylpentene, each being non-brittle in expanded form and characterized by being in the form of micro-bits which are (a) from 40 to 325 microns long and from 20 to 325 microns wide, (b) from substantially completely to entirely completely

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free of intact cells of the expanded polymer bit-pieces from which they were produced, (c) substantially without any uniformity in outline of the individual micro-bits particles, and (d) in 5 density from 85 percent of, to substantially the same as, the specific unexpanded polymer from which there was provided the aforesaid expanded polymer.

These micro-bits of an expanded, 10 thermoplastic styrene-polymer or a lower polyolefin are produced from so-called bit-pieces of any of the expanded thermoplastic, non-brittle in expanded form styrene-polymers or lower poly-olefins as starting material. By "bit-pieces" is 1 5 meant any of the discrete free-flowing forms of any of these styrene-polymers and lower poly-olefins, such as (i) the various sizes of granules made by cutting the respective extruded polymer into fairly small lengths usually called pellets or 20 crystal (as with a styrene-polymer) or pellets or cubes of a polyethylene-polystyrene alloy, (ii) the various sizes of styrene-polymer beads obtained from suspension polymerization or otherwise as by molding the particles obtained by 25 disintegrating any of these different polymer forms, (iii) the so-called "grind" including the coarsely ground molded polymer or waste or other scrap such polymer of various sizes, e.g. 3.175 millimeter (i.e. ml) thick, 6.35 ml wide, and 9.535 30 ml long, and (iv) any other small sized shapes of any of them.

The preparation and properties of flexible polyurethane foams are described, for example, in the "Handbook of Foamed Plastics", Bender, Rene 35 J. Section X, pp. 173—236, Lake Publishing Corporation, Libertyville, Illinois, U.S.A. (1955), "Polyurethanes: Chemistry and Technology", Saunders & Frisch, Chapter VII, Part II, Interscience Publishers, New York, N.Y., U.S.A. 40 (1964), and "The Development and Use of

Polyurethane Foams", Doyle, E.N. pp. 233—256, McGraw Hill Book Company, New York, N.Y., U.S.A. (1971).

The flexible polyurethane foams useful to 45 provide foamed polyurethane micro-bits preferably should be no greater than 72.14 grams per liter in density, and show excellent recovery after 75% deflection with approximately less than 1% loss in height (as determined by American Society of 50 Testing Materials D-1 564-64T).

The flexible foam polyurethanes are not obtained in the foregoing same bit-pieces forms as are the styrene-polymers and lower polyolefins, but rather in continuous foamed 55 blocks as a result of the reaction that provides the polyurethane. Accordingly, the foamed polyurethane blocks first are shredded into bit-pieces (for example, similar to how they may be prepared for use in stuffing into various articles). 60 The foamed polyurethane micro-bits are herein defined and more fully described as comprising broken and interconnected strand portions from adjacent cells of the flexible foam, which strand portions show substantially total absence of 65 intact cells and cell windows and are tripodal particles with generally uneven length legs, the strand portions having hook-like projections, indentations and flutes resulting from destruction of the cells and cell windows of the starting flexible foam.

The micro-bits of any expanded thermoplastic, non-brittle in expanded form styrene-polymer or lower polyolefin or flexible foamed polyurethane are prepared by disintegrating the respective starting expanded polymer bit-pieces in a comminuting machine. One such machine is that produced by Fitzpatrick Company (of 832 Industrial Drive, Elmhurst, Illinois 60120 U.S.A.) according to their Bulletin No. 152 copyright 1968 using the broached fixed blades (identified thereby by "Code DS225") to replace the blades or other comminuting elements, mounted for rotation in the comminuting chamber model DAS06, both shown on that Bulletin's page 5. That chamber is liquid-tightly capped, for example, by a cover such as shown in their Code M44D6 or Code MA44D6 (upper half of page 3 of their Bulletin 152).

That model DAS06 comminuting chamber is rectangular in horizontal cross-section and has a pair of opposed parallel entirely vertical walls integrally joined at each of their opposite ends by a separate one of a pair of opposed vertically arcuate walls each with its convex face exposed to the exterior.

Sixteen identical, slat-shaped comminuting arms are separately removably but fixedly carried with their snugly adjacent to one another bases encircled about, and keyed to, the operating shaft and intermediate its free outer mounting ends. These arms extend radially out from the shaft (e.g. 127 m m from its axis to the outer end of each arm) with the first of each consecutive four of them extending horizontally toward one arcuate wall, the second of each four extending vertically, the third four of them extending toward the other arcuate wall, and the fourth four of them extending vertically downward.

Each arm is rectangular in cross-section in a plane running through the entire length of the shaft's axis and of that arm, and of each arm 180° removed from it. The outer end of each arm meets at right angles with its two wider sides (5.4 mm width) and its narrow or impact side (9.525 mm wide) facing the direction of rotation. That narrow side also meets at right angles with the two wider sides which are parallel to one another for most of their width and with the trailing third of their surfaces tapering to one another and terminating in the knife edge of their trailing end.

Each free exposed end of the shaft extends through its respective stuffing box in its neighbouring one of the two parallel vertical walls on through a bearing carried on a respective trunnion affixed to the machine's foundation and spaced outwardly away from the respective wall. A driving pulley is mounted on each end of the shaft extending outwardly from its respective mounting trunnion.

The bottom of the comminuting chamber is an

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exchangeable dish-shaped, arcuate screen curved convexly downward with an inside radius (from the axis of the operating shaft) equal to the length of a comminuting arm plus 0.762 mm clearance.

5 The screen's overall rectangular peripheral opening has such dimensions and shape as to enable it to be removably fitted in a liquid-tight engagement with the bottom of the four walls of the comminuting chamber.

10 The screen has staggered rows of, for example circular holes varying in diameter as from 0.102 to 3.175 mm and closely spaced to one another with sufficient space between them for the screen to hold up underworking conditions.

15 Except for its starting material feed hopper inlet at one side of it, the rest of the chamber's cover is arcuate and convex upwardly with a radius (from the axis of the operating shaft) sufficient for the rotating arms to have a 0.762 mm 20 clearance from the inwardly facing surfaces of a plurality (e.g. three) pre-breaker bars (about 20.32 cm long and 6.35 mm wide) protruding for 3.175 mm along their entire length into the interior of the comminuting chamber, and 25 extending spaced apart from one another and parallel to the axis of the operating shaft.

The selected driving pulley on the operating shaft is connected by driving belts extending from a motor shaft drive pulley and can be operated at 30 speeds embracing the range of from 4700 to 8000 r.p.m., and more effectively from 5000 to 7500 r.p.m.

The mats according to the invention, which can be called gas-vapor adsorption, filtering or 35 treating mats, include (i) the glass fibers, (ii) the micro-bits, and (iii) the organic binding agent, generally together with an amount of finely divided activated carbon (as primary gas-adsorbing agent) below that at which undesirable 40 dusting off of carbon particles can occur, a sufficient amount of the cobeat to serve to restrain the carbon particles against dusting off, and an amount of a fiber-forming terephthalate polyester sufficient to hold the mat's tensile 45 strength within its earlier above recited range without undesirable lowering of the mat's porosity. For example, satisfactory adsorption filtering and treating mats have been obtained by adding to the three primary constituents (i), (ii) 50 and (iii), finely divided activated carbon to a maximum of 25%, 5 to 10% of polyester fibers, and from 2% to 30% of cobeat, said percentages being based on the total weight of the finished mat.

55 Any of the gas-adsorbing activated carbons from their various sources, for example, charcoal, coal, petroleum distillation residue or pecan nut shells can be used.

The gas-vapor adsorption treating mats are 60 prepared by a combination of steps comprising preparing a cobeat suspension of wet lap cotton fibers and micro-bits in water (as described further below) and separately as suspension of micro-bits in water in the proportion recited 65 further below.

Then a furnish supply suspension is prepared by admixing in water an amount of the cobeat suspension within a given range and adding a quantity of a fiber-forming polyethylene 70 terephthalate polyester in a quantity to partake in providing the finished mat with tensile strength within an effective range without adversely affecting its porosity. Then finely divided activated carbon is admixed within the range up to a 75 maximum of about 25% of the planned total solids of the finished mat, and an aqueous suspension of the micro-bits is added in an amount to provide in the finished mat from 10% to 30% of micro-bits.

80 The remaining addition admixed is a suspension of glass fibers, micro-bits and binding agent, each within its respective range and so proportioned to the other solids for the finished mat to have the planned tensile strength and 85 porosity. The finally resulting suspension from all of these included constituents is fed to the furnish box within the rate of feed recited for the mats lacking the carbon and polyester, and there similarly diluted with water and then fed onto the 90 Fourdrenier screen and dried as with the other mats.

In each of the procedures preparing a mat wherein an organic binding agent is used, it is beneficial to add that agent to the suspension 95 (being prepared) within the last minute or so of the agitation before the suspension is to be fed to the (machine) supply chest and also that the web leaving the Fourdrenier screen initially is subjected to radiant heat from a relatively close 100 source at a temperature in the range of from

600°C to 700°C. That rapidly causes solution of the organic binding agent in the water carried by the mat and enhances the drying of the organic binding agent at the intersections of the water-105 insoluble constituents.

The mats of this invention are effective for removal and/or recovery of various gases or vapors, either inorganic or organic, for example, sulfur dioxide, chlorinated alkanes such as carbon 110 tetrachloride and other chlorinated alkanes, and benzene and phenol.

Gas-vapor treating mats comprising glass fibers, micro-bits and binding agent, but omitting the polyester and activated carbon used 115 according to the present invention, are described in my British Patent Application No. 7904618 (published No. 201 5056 A), from which this Application is divided.

Claims (3)

1. Claims

   120 1 ■ A fluid-permeable gas-vapor treating mat which comprises a sheet or elongated web formed from a mixture of:

   (a) glass fibers from 6.35 millimeters long to below a length at which said fibers are prone to

   125 roping, and from 3 to 12 microns in diameter,

   (b) finely divided activated carbon, in an amount below that at which more than insignificant dusting of carbon from the finished mat would occur,

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   (c) a fiber-forming terephthalate polyester in an amount of 5 to 10% by weight, of the finished mat,

   (d) micro-bits (as herein defined) of a polymer 5 which is non-brittle in its initial expanded form,

   and is selected from an expanded, thermoplastic styrene-polymer, and an expanded polyolefin, selected from polyethylene, polypropylene, polybutene and polymethylpentene, or micro-bits 10 (as herein defined) of a flexible foamed polyurethane, said micro-bits comprising from 2 to 50% by weight of the finished mat,

   (e) from 2 to 10% by weight, based on the finished mat, of a compatible organic binder,

   ■ 15 insoluble in cold water and soluble in hot water and inert to the glass fibers and micro-bits, and

   (f) cobeat of wet-lapped cotton fibers, and any of said micro-bits, said cobeat agent being distributed throughout the mat, comprising from

   20 2 to 30% by weight of the finished mat.
2. 2. A gas-vapor treating mat as claimed in claim 1 wherein the polyester is polyethylene terephthalate.
3. 3. A gas-vapor treating mat as claimed in claim 1 or 2 wherein the amount of finely-divided active carbon is not more than 25% by weight, based on total solids in the mat.

   Printed for Her Majesty's Stationery Office by the Courier Press, Leamington Spa, 1983. Published by the Patent Office, 25 Southampton Buildings, London, WC2A 1AY, from which copies may be obtained

   3. A gas-vapor treating mat as claimed in claim 25 1 or 2 wherein the amount of finely-divided active carbon is up to 25% by weight, based on total solids in the mat.

   4. A gas-vapor treating mat as claimed in any preceding claim wherein the micro-bits are those 30 of a styrene-polymer.

   5. A gas-vapor treating mat as claimed in claim 4, wherein the styrene-polymer is polystyrene.

   6. A gas-vapor treating mat as claimed in any of claims 1 to 3, wherein the micro-bits are those

   35 of a polyurethane.

   7. A gas-vapor treating mat as claimed in any of claims 1 to 3, wherein the micro-bits are those of a lower polyolefin.

   8. A gas-vapor treating mat as claimed in claim 40 1 wherein the polyolefin is polyethylene.

   9. A gas-vapor treating mat as claimed in any preceding claim, wherein the organic binder is polyvinyl alcohol at least 98% hydrolyzed.

   10. A gas-vapor treating mat as claimed in 45 claim 1 and substantially as hereinbefore described.

   New Claims or Amendments to Claims filed on 3 Sept 82

   Superseded claims 3 50 New or Amended Claims:—