Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D39/00—Filtering material for liquid or gaseous fluids
  • B01D39/14—Other self-supporting filtering material ; Other filtering material
  • B01D39/16—Other self-supporting filtering material ; Other filtering material of organic material, e.g. synthetic fibres
  • B01D39/1669—Cellular material
  • B01D39/1676—Cellular material of synthetic origin
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2239/00—Aspects relating to filtering material for liquid or gaseous fluids
  • B01D2239/04—Additives and treatments of the filtering material
  • B01D2239/0407—Additives and treatments of the filtering material comprising particulate additives, e.g. adsorbents

Definitions

• This invention relates to air filters in general, and more particularly to air filters of the sort which purge unwanted substances from air, i.e. to air filters which remove unwanted substances from air and/or neutralize unwanted substances in air.
• Air filters are used to purge unwanted substances from air.
• air filters are commonly used in laboratories to purge unwanted substances from the air in fumehoods before the air is vented from the fumehood, e.g., to the atmosphere or to the ambient air of the laboratory.
• the air filter typically uses activated carbon granules to purge unwanted substances from the air.
• Activated carbon is generally preferred for use in air filters because the activated carbon is very effective in purging solvents from air.
• the use of activated carbon granules is generally highly
• the activated carbon granules are easily handled, and since they naturally pack into an enclosure with spaces therebetween so as to combine high surface area contact with excellent air flow.
• the activated carbon granules are disposed in a simple filter frame, captured between two
• opposing screens e.g., meshes, grills, etc. which pass air therethrough but retain the activated carbon granules therebetween.
• activated carbon granules are extremely effective in purging solvents from the air, they are largely ineffective in purging acids from the air.
• special additives e.g., rare earth metals, organic metal catalysts, etc.
• these additives tend to reduce the effective surface area of the activated carbon granules, thereby reducing filter capacity.
• these acid- purging additives are generally only modestly
• a novel air filter which comprises at least two stages, an acid- purging stage and a solvent-purging stage.
• the acid- purging stage generally comprises an air-permeable skeleton having an acid-neutralizing substance mounted thereto.
• the solvent-purging stage generally
• an air filter for purging unwanted substances from air comprising:
• an air filter for purging unwanted substances from air comprising:
• an acid-purging stage wherein the acid-purging stage comprises an air-permeable skeleton which has an acid-neutralizing substance mounted thereto, wherein the air-permeable skeleton comprises fiberglass fibers and the acid-neutralizing substance comprises sodium bicarbonate, and further wherein the sodium
• the bicarbonate is secured to the fiberglass fibers using an adhesive; and a solvent-purging stage, wherein the solvent- purging stage comprises solvent-purging granules captured between two air-permeable screens, and further wherein the solvent-purging granules comprise activated carbon granules.
• an air filter for purging unwanted substances from air comprising:
• the acid-purging stage comprises an air-permeable skeleton which has an acid-neutralizing substance mounted thereto, wherein the air-permeable skeleton comprises open cell
• polyurethane foam and the acid-neutralizing substance comprises sodium bicarbonate, and further wherein the sodium bicarbonate is secured to the open cell
• a solvent-purging stage wherein the solvent- purging stage comprises solvent-purging granules captured between two air-permeable screens, and further wherein the solvent-purging granules comprise activated carbon granules.
• the method for purging unwanted substances from air comprising:
• the air filter comprising:
• the air filter comprising:
• an acid-purging stage wherein the acid- purging stage comprises an air-permeable skeleton which has an acid-neutralizing substance mounted thereto, wherein the air-permeable skeleton comprises fiberglass fibers and the acid-neutralizing substance comprises sodium bicarbonate, and further wherein the sodium bicarbonate is secured to the fiberglass fibers using an adhesive; and
• solvent-purging stage comprises solvent-purging granules captured between two air-permeable screens, and further wherein the solvent-purging granules comprise activated carbon granules;
• the air filter comprising:
• an acid-purging stage wherein the acid- purging stage comprises an air-permeable skeleton which has an acid-neutralizing substance mounted thereto, wherein the air-permeable skeleton comprises open cell polyurethane foam and the acid-neutralizing substance comprises sodium bicarbonate, and further wherein the sodium bicarbonate is secured to the open cell polyurethane foam using an adhesive; and
• solvent-purging stage comprises solvent-purging granules captured between two air-permeable screens, and further wherein the solvent-purging granules comprise activated carbon granules;
• an air filter for purging unwanted substances from air comprising:
• At least one reactant attached to the filtration media at least one reactant attached to the filtration media .
• an air filter comprising:
• a filtration media and at least one reactant attached to the filtration media;
• Fig. 1 is a schematic view showing a novel air filter formed in accordance with the present
• Fig. 1A is a schematic view showing another novel air filter formed in accordance with the present invention
• Figs. 2-4 are schematic views showing how the acid-purging stage of the novel air filter can be fabricated.
• Fig. 5 is a schematic view showing further details of the solvent-purging stage of the novel air filter
• Fig. 6 is a photograph showing a piece of open cell polyurethane (PU) foam before impregnation with citric acid crystals;
• Fig. 7 is a photograph of a piece of open cell polyurethane (PU) foam after the open cell
• polyurethane (PU) foam has been impregnated with granular citric acid crystals.
• Air filter 5 generally comprises two stages, an acid-purging stage 10
• Acid-purging stage 10 generally comprises an air- permeable skeleton 20 having an acid-neutralizing substance 25 mounted thereto.
• acid- purging stage 10 comprises fibers (e.g., fiberglass fibers) which have sodium bicarbonate adhered thereto.
• acid-purging stage 10 In another preferred form of the invention, and looking now at Fig. 1A, acid-purging stage 10
• an open cell foam e.g., open cell
• polyurethane foam with sodium bicarbonate adhered thereto .
• Solvent-purging stage 15 generally comprises solvent-purging granules 30 packed between two
• the solvent-purging granules comprise activated carbon granules .
• acid-neutralizing substance 25 e.g., sodium bicarbonate
• solvent-purging granules 30 e.g., activated carbon granules
• acid-purging stage 10 generally comprises an air-permeable skeleton 20 having an acid-neutralizing substance 25 mounted thereto .
• acid-purging stage 10 comprises fiberglass fibers which have sodium bicarbonate adhered thereto.
• Sodium bicarbonate is extremely effective in neutralizing acids, and is relatively inexpensive, but its powder-like consistency makes it difficult to use in an air filter, where high surface area contact is required.
• the present invention solves this difficulty, and makes it practical to use sodium bicarbonate in an air filter, by providing a new and improved method for supporting the sodium bicarbonate in an acid-purging stage.
• acid-purging stage 10 preferably comprises an air- permeable mass of fiberglass fibers which together create the air-permeable skeleton 20.
• fiberglass fibers are highly resistant to acids and bases, and easily pass air therethrough with nominal pressure loss. Looking next at Fig. 3, the fiberglass fibers are coated with an adhesive 40. Then, and looking now at Fig. 4, sodium bicarbonate powder is deposited on the fiberglass fibers, with adhesive 40 binding the sodium bicarbonate powder to the
• the sodium bicarbonate is interspersed throughout, and adheres to, air- permeable skeleton 20, so that air passing therethrough makes excellent surface area contact with the sodium bicarbonate, whereupon the sodium
• bicarbonate can neutralize acids in the air.
• acid-purging stage 10 can comprise an air-permeable skeleton 20 made with a structure and/or a material other than, or in addition to, fiberglass fibers (e.g., polyurethane fibers, an open cell foam, etc.), and/or acid-purging stage 20 can comprise an acid-neutralizing substance 25 other than, or in addition to, sodium bicarbonate (e.g., sodium bicarbonate),
• hydroxide potassium hydroxide, sodium carbonate, calcium carbonate, calcium bicarbonate, calcium hydroxide, etc.
• acid-purging stage 10 comprises an open cell foam with an acid-neutralizing substance adhered thereto.
• acid-purging stage 10 preferably comprises open cell polyurethane foam (preferably having a pore characteristic of 20 PPI, i.e., 20 pores per inch), having sodium bicarbonate adhered thereto.
• This open cell polyurethane foam is highly resistant to acids and bases, and easily passes air therethrough with nominal pressure loss.
• solvent-purging stage 15 generally comprises solvent-purging granules 30 packed between two opposing screens (e.g., meshes, grills, etc.) 35.
• the solvent-purging granules comprise activated carbon granules captured between two opposing screens (e.g., meshes, grills, etc.) which pass air therethrough but retain the activated carbon granules therebetween.
• novel air filter 5 comprises a filter frame 45 having mounted therein two filter stages, the acid-purging stage 10 followed by the solvent-purging stage 15.
• Acid-purging stage 10 comprises the air-permeable skeleton 20 (preferably fiberglass fibers or an open cell polyurethane foam) which has the acid- neutralizing substance 25 (preferably sodium
• Solvent-purging stage 15 comprises the solvent-purging granules 30
• the novel air filter of the present invention is capable of purging both acids and solvents from the air passing through the filter.
• the acid-purging stage of the present invention is optimized by, preferably, using highly effective and relatively inexpensive sodium bicarbonate, supported on an air-permeable skeleton structure (e.g., fiberglass fibers, an open cell polyurethane foam, etc.), to neutralize acid.
• an air-permeable skeleton structure e.g., fiberglass fibers, an open cell polyurethane foam, etc.
• the use of sodium bicarbonate in the air filter also eliminates the toxicity concerns which can be present when using the rare earth metals and organic metal catalysts of the prior art.
• the solvent-purging stage of the present invention is optimized by, preferably, using highly effective activated carbon granules to purge solvents from air, but without the addition of the aforementioned acid-purging rare earth metals and organic metal catalysts which can reduce the solvent- purging capacity thereof.
• acid-purging stage 10 precedes solvent-purging stage 15 in the air flow, i.e., air moving through the air filter moves through acid-purging stage 10 before it moves through solvent- purging stage 15.
• the acid-neutralizing stage can follow the solvent-purging stage, i.e., air moving through the air filter can move through the solvent- purging stage before it moves through the acid-purging stage .
• the present invention is unique in a number of ways, including (i) the two- stage composite construction of the air filter, which combines an acid-purging stage with a solvent-purging stage, (ii) the use of sodium bicarbonate in an air filter, and (iii) the manner in which the sodium bicarbonate is supported within the air filter (e.g., on an air permeable skeleton such as fiberglass fibers, open cell polyurethane foam, etc.) .
• the present invention purges acids from the air without requiring the use of toxic additives .
• the present invention purges unwanted acids from the air without diminishing the capacity of the air filter to purge solvents from the air.
• the present invention utilizes an
• the present invention provides for the binding of powders to fibers and/or open cell foam which can be industrialized in an inexpensive manner.
• Ammonia is one of the most troublesome chemicals present in a laboratory. Among other things, ammonia is highly volatile, has a very low olfactory limit, and is highly detrimental to human health. At the same time, ammonia is also one of the 12 most common chemicals found in a laboratory. For this reason, it is important that there be effective methods and apparatus for protecting laboratory personnel (e.g., chemists, etc.) from the harmful effects of ammonia.
• filtration fumehoods are commonly used by laboratory personnel to protect themselves from ammonia.
• a filtration fumehood also known as a recirculatory fumehood and/or as a filtering fumehood
• activated carbon filters are impregnated with a chemical specifically chosen for its reaction with ammonia (e.g., sulfuric acid, ZnCl 2 , etc.) . It is necessary to impregnate the activated carbon filters with a reactant because "classical" (i.e., non- impregnated) activated carbon filters do not
• the impregnated activated carbon filter is effectively limited to neutralizing ammonia (and highly related chemicals) .
• each filter is effectively limited to handling a short list of chemicals.
• the users of filtration fumehoods must select a particular impregnated activated carbon filter for their fumehood in accordance with the chemicals that they will be handling in the fumehood, e.g., an activated carbon filter impregnated with sulfuric acid for use when handling ammonia, an activated carbon filter impregnated with potassium carbonate for use when handling inorganic acids, etc.
• This can be problematic, since it may require a filter change when different materials are to be handled in the fumehood
• the present invention comprises the provision and use of a new filtration media for chemical
• the new filtration media comprises an open cell foam, a reactant (e.g., citric acid for neutralizing ammonia) disposed on the surface of the open cell foam, and glue for holding the reactant (e.g., citric acid) on the surface of the open cell foam.
• a reactant e.g., citric acid for neutralizing ammonia
• glue for holding the reactant (e.g., citric acid) on the surface of the open cell foam.
• the open cell foam is preferably formed out of polyurethane (PU) , polyethylene (PE) , silicone, rubber, polyvinylchloride (PVC) or other material which is resistant to the effects of the target chemical which is to be purged (e.g., ammonia) .
• the open cell foam has a pore size which (a) allows the open cell foam to present a large surface area, and (b) is capable of easily passing air therethrough without imposing a significant pressure drop on the flow of air through the filter, e.g., the open cell foam may have a pore size of 20 pores per inch (PPI) .
• the reactant is impregnated on the surfaces of the open cell foam so that the reactant is presented to air passing through the open cell foam, whereby to allow the reactant to efficiently react with the target chemical in the air and thereby neutralize the target chemical by virtue of the chemical reaction of the reactant with the target chemical.
• the target chemical is ammonia
• the reactant is citric acid
• the citric acid is in granular form, and the citric acid crystals (small grain) are sprinkled directly on the surface of the open cell foam, without requiring that the citric acid be placed in a liquid solution for deployment on the open cell foam (direct sprinkling of citric acid crystals consumes less energy (because it does not require drying) , and allows the deposition of a greater quantity of citric acid on the open cell foam) .
• the citric acid crystals have an average grain size majority comprised between 25 ASTM Mesh and 50 ASTM Mesh.
• Glue is used to maintain the reactant (e.g., the citric acid crystals) on the surface of the open cell foam.
• the glue is selected so that the glue does not interact with the open cell foam, and/or with the reactant (e.g., the citric acid), and/or with the target chemical (e.g., ammonia) which is to be
• the glue comprises polyvinyl acetate or ethylene vinyl acetate copolymers or acrylic copolymers or other emulsions.
• the glue is applied (e.g., by brushing, spraying, etc.) to the open cell foam first, and then the reactant (e.g., citric acid crystals) is applied (e.g., by sprinkling, blowing, etc.) on the surface of the glue-bearing open cell foam.
• the reactant e.g., citric acid crystals
• Fig. 6 is a photograph showing a piece of open cell polyurethane (PU) foam 50 before
• Fig. 7 is a photograph of a piece of open cell
• the target chemical e.g., ammonia
• the reactant e.g., the citric acid
• ammonia vapors and citric acid it is a classical acid-base reaction which leads to the creation of an ammonium citrate salt.
• This ammonium citrate salt is solid and is retained on the surface of the open cell foam by virtue of the glue which binds the citric acid crystals to the surface of the open cell foam.
• the new filter using a reactant other than citric acid, for purging ammonia vapors and/or other target chemicals from air.
• a reactant other than citric acid for purging ammonia vapors and/or other target chemicals from air.
• citric acid oxalic acid, tartric acid, maleic acid, ascorbic acid, succinic acid, anhydrous phosphoric acid, etc.
• the reactant i.e., citric acid or an alternative acid
• the reactant carried by the open cell foam is solid at normal temperature and pressure.
• the open cell foam of the present invention can carry multiple reactants for purging multiple target chemicals from the air. Thus, with the present invention, it is not necessary for the filter to be restricted to use for just one target chemical .
• ammonia/other target chemical purging filter of the present invention can be used alone (e.g., for purging ammonia and/or other target chemicals), or it can be used in combination with other filtration media to further enlarge the range of target chemicals which can be purged from air.
• the novel ammonia/other target chemical purging filter of the present invention can be used as one stage of a multi ⁇ stage filter, wherein another stage of the multi-stage filter may comprise an activated carbon filter (which may or may not be impregnated with a reactant) .
• novel ammonia/other target chemical purging filter of the present invention may form one stage of a three- stage filter, i.e., the three-stage filter may
• an acid-purging stage e.g., comprising an open cell foam carrying sodium bicarbonate
• solvent-purging stage comprising activated carbon granules
• ammonia-purging stage comprising an open cell foam carrying citric acid (or an alternative reactant) .
• ammonia-purging stage is preferably placed before the solvent-purging stage, and may be placed before the acid-purging stage if desired.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Adhesives Or Adhesive Processes (AREA)
• Filtering Materials (AREA)
• Disinfection, Sterilisation Or Deodorisation Of Air (AREA)
• Solid-Sorbent Or Filter-Aiding Compositions (AREA)

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Citations (6)

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• 2013
  • 2013-03-11 WO PCT/US2013/030194 patent/WO2013134765A1/en not_active Ceased
  • 2013-03-11 JP JP2014561183A patent/JP2015516184A/ja active Pending
• 2018
  • 2018-05-24 JP JP2018099542A patent/JP6673978B2/ja active Active

Patent Citations (6)

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