Single-use filter elements, methods for treating air, and uses of divinylbenzene polymers or copolymers

Abstract

The present disclosure relates to a single-use filter component for removing NO2 in an air treatment system, the component comprising a polymer composition as an air filtration medium, the polymer composition comprising a plurality of free vinyl groups, the component comprising an optical sensor configured to allow an end user to inspect the air filtration medium and determine when the filter is used based on a color change from white to yellow or to notify the end user of the color change. The present disclosure further relates to a single-use filter component for simultaneously removing NO2 in an air treatment system, the component comprising a HEPA filter formed from a polymer composition comprising a plurality of free vinyl groups. The present disclosure further relates to an air treatment system, a method for treating air, and the use of a polymer or copolymer of divinylbenzene to form an air filtration medium.

Description

[Technical Field]

[0001] The present invention provides a single-use filter element. More specifically, the present invention provides a single-use filter element for removing NO2 in an air treatment system. The present invention also provides an air treatment system including the above-mentioned single-use filter element. Specifically, the single-use filter element includes a polymer composition as an air filtration medium, the polymer composition including a plurality of free vinyl groups. The present invention further provides a method for treating air, the method including passing NO2-containing air through the above-mentioned single-use filter. The present invention also provides the use of a divinylbenzene polymer or copolymer to form an air filtration medium, more specifically, at least 7.0% of the carbon atoms in the divinylbenzene polymer or copolymer are vinyl carbon atoms. The present invention is particularly applicable to air conditioning systems, including both home air purifiers and industrial HVAC systems, as well as products such as masks.

[0002] Air pollution is an ever-growing concern in modern society and is well-known to have significant adverse effects on the environment and ultimately on human health. Data from the World Health Organization (WHO) indicate that nine out of ten people breathe air containing high levels of pollutants above WHO guideline limits, and ambient air pollution is estimated to cause more than four million premature deaths worldwide each year. Pollution is particularly problematic in densely populated urban environments, where pollution from industrial processes (such as power generation, agriculture, and waste incineration), along with significant amounts of pollution emitted from vehicles during fuel combustion, can create hot spots of extremely high levels of environmental pollutants that are harmful to health. However, air pollution in the home is another concern, especially in developing countries. Domestic air pollution can occur during household activities such as cooking or burning fuels such as wood and coal.

[0003] Air pollutants include both gaseous and particulate (airborne) pollutants. Particulate matter (PM) is typically very small solid or liquid particles, often solid carbon particles (PM) with diameters less than 10 microns. 10 ), and fine particles with a diameter of less than 2.5 microns (PM 2.5 ), and ultrafine particles (PM) with a diameter of less than 0.1 microns 0.1 ) Common sources include combustion engines and the burning of fuels such as wood and coal. Along with particulate pollutants, gaseous pollutants known to have adverse health effects include nitrogen dioxide (NO2), nitric oxide (NO), ozone (O3), sulfur dioxide (SO2), and carbon monoxide (CO).

[0004] Despite long-standing knowledge of the problems associated with gaseous pollutants, the majority of filters used in air purification focus on capturing particulate matter. Typically, filters are made from different layers of porous media, sometimes with different thicknesses depending on the end use and the minimum size of the particulate matter to be filtered. The layers are often made from glass fiber or polymers.

[0005] Along with particulate matter, NO2 is a prominent pollutant resulting from road emissions, i.e., from the combustion of fuel in combustion engines. Road traffic is a major outdoor source of nitrogen dioxide. Therefore, people living near busy roads are particularly exposed to and affected by NO2 pollution. In addition, NO2 can also result from internal sources, such as cooking and heating. Long-term exposure to NO2 can cause a decline in lung function. There is evidence that even short-term exposure to NO2 can increase the risk of bronchitis and asthma. NO2 can cause inflammation of the airways and increase susceptibility to respiratory infections and allergens.

[0006] However, there is a need to control ambient NO2 levels, and as a result, there remains a need for effective air filters that can filter harmful gaseous pollutants such as NO2.

[0007] It is known that filters may further contain adsorbents or catalysts to remove gaseous pollutants such as volatile organic compounds, carbon monoxide, and nitrogen dioxide. A common adsorbent / catalyst is activated carbon, and in recent decades, much research has been done on factors affecting NO adsorption on activated carbon. However, over time, the amount of nitrogen dioxide slip can easily increase. Furthermore, activated carbon can reduce nitrogen dioxide to produce another pollutant, nitrogen monoxide (nitric oxide). Activated carbon does not bind either NO or NO strongly and therefore does not absorb them sufficiently to remove pollutants from the air. Naturally, it is preferable to filter nitrogen dioxide from the air without producing other nitrogen oxides, primarily nitric oxide. Because air pollutants are generally invisible to the naked eye, at least at background levels, end users cannot visually determine when the adsorbent is underperforming or has become worn out, given that activated carbon remains essentially black. Some commercially available air purifiers are equipped with sensors that alert users to increased concentrations of pollutants in the ambient air. Many other materials, such as zeolites, metal organic frameworks (MOFs), and metal oxides such as Al2O3 and TiO2 (doped and undoped), have been investigated for their adsorption capabilities, but none have the efficiency required for use in air filters to remove NO2. Nevertheless, some air purifiers include some additional materials, such as zeolites or alumina, along with activated carbon.

[0008] It has been known for decades that polymers can react with gaseous pollutants such as NO. For example, Jellinek and Flagsman, Journal of Polymer Science, Part A-1, Vol. 7, pp. 1153-1168 (1969), studied the reaction of nitrogen dioxide with polystyrene film. Shortly thereafter, Grubner et al., in "Collection of Nitrogen Dioxide by Porous Polymer Beads," American Industrial Hygiene Association Journal, 33:4, pp. 201-206, studied the reactivity of nitrogen dioxide with Porapak® Q. Porapak® Q is a crosslinked polymer of ethylvinylbenzene and divinylbenzene primarily used in HPLC columns. WO 2017 / 160646 A1 discloses an air filter containing a polymer adsorbent for reactive gases. The reactive gas is disclosed to be hydrogen fluoride, fluorine, hydrogen bromide, bromine, hydrogen chloride, chlorine, sulfuric acid, sulfurous acid, hydrogen sulfide, sulfur dioxide, nitric acid, nitrous acid, nitrogen dioxide, or a mixture thereof. The polymeric adsorbent comprises the reaction product of (i) a precursor polymer material comprising the polymerization product of a polymerizable composition containing 8-65 wt% maleic anhydride, 30-85 wt% divinylbenzene, and 0-40 wt% styrene-type monomers, and (ii) a nitrogen-containing compound selected from ammonia or compounds having at least one primary or secondary amino group. This disclosure focuses on the removal of sulfur dioxide (SO2), a reactive gas resulting from reaction with amino groups present in the polymeric adsorbent.

[0009] Therefore, there is a need in the art for a component for use in an air treatment system that is effective in removing NO from the air and that allows the end user to easily determine when the sorbent material is worn out and needs to be replaced.The present inventors have developed the present invention with the objective of overcoming the problems in the prior art.

[0010] Accordingly, in a first aspect, there is provided a single-use filter component for removing NO2 in an air treatment system, the component comprising a polymer composition as an air filtration medium, the polymer composition comprising a plurality of free vinyl groups; A single-use filter component is provided, wherein the component includes an optical sensor configured to allow an end user to inspect the air filtration media and determine when the filter is used up based on a color change from white to yellow or to notify the end user of the color change.

[0011] The present disclosure will now be further described. In the following sections, different aspects / embodiments of the present disclosure are defined in more detail. Each aspect / embodiment so defined can be combined with any other aspect / embodiment or aspects / embodiments, unless expressly indicated otherwise. In particular, any feature indicated as being preferred or advantageous can be combined with any other feature or features indicated as being preferred or advantageous.

[0012] The present invention relates to a single-use filter component for removing NO2 in an air treatment system. "Single-use" means that the filter component is intended to be used without filter regeneration and can be replaced with a replacement component when the filter component reaches the end of its working life, which can be determined as described herein. Furthermore, "single-use" should not be interpreted as being limited to one use, but rather to one lifespan. Thus, a "single-use" filter may still have the ability to adsorb NO2 after being used by an end user. For example, an air conditioning system or air purifier may be turned on and off multiple times to actively pass air through the "single-use" filter component.

[0013] The component is part of an air treatment system. Preferably, the component is a replaceable part of the air treatment system. In other words, the component of the present invention may be removed by an end user, for example, in an air purifier, when the filter component becomes used and is replaced with a new filter component. In another example, a mask, such as a respirator, may include a removable filter component. Alternatively, the component may be integrated with the air treatment system. Typically, this is preferred when the air treatment system is disposable, given the cost of disposing of the entire system. For example, the air treatment system may be a disposable mask that includes an integrally formed, single-use filter component.

[0014] The filter components described herein are suitable for removing NO2 when installed in an air treatment system, which refers to any type of apparatus or device in which the filter component can be presented to an air stream being treated for the removal of NO2.

[0015] The filter component includes a polymer composition as an air filtration medium. Specifically, the polymer composition includes a plurality of free vinyl groups. The inventors have discovered that a filter component including an air filtration medium formed from a polymer composition including a plurality of free vinyl groups exhibits advantageous selectivity for adsorbing NO2 from air. Specifically, the inventors believe that NO2 reacts with the free vinyl groups and can therefore be considered chemisorbed. By "free vinyl groups," we mean that the polymer composition includes R-CH=CH2 groups. The polymer composition can be obtained by reacting monomers containing ethylenic groups (i.e., those containing a carbon-carbon double bond), such as vinyl groups, in an addition polymerization reaction to form a single-bonded carbon chain backbone. Thus, free vinyl groups are unreacted groups. As described herein, the inventors have discovered that divinylbenzene is a particularly preferred monomer that can be polymerized to produce a polymer in which a portion of the vinyl groups do not react to polymerize or crosslink.

[0016] The components of the present invention allow end users to inspect the air filtration media and determine when the filter is worn out. The end user can determine when the filter is worn out based on a color change from white to yellow. Alternatively, the components include an optical sensor configured to notify the end user of the color change and, therefore, the need to replace the filter. The optical sensor can be configured, for example, to provide an output when a specific wavelength of reflected light is observed (i.e., yellow light sufficient to indicate a decrease in NO2 removal performance).

[0017] Thus, the filter component may take any form known in the art, provided that the component includes a means for allowing an end user to notice a color change. In one embodiment, the component may include a frame, such as a perimeter frame, or a housing. The component may take the form of a cartridge, preferably made from injection-molded rigid plastic. Such a cartridge may be designed to fit into an air filtration system, such as an air conditioner. In either case, the component may contain the air filtration media and include a removable opening that allows a user to directly view the air filtration media. Preferably, the opening in the component may be a screen or mesh sufficient to contain the air filtration media but including gaps that allow visual inspection. In another embodiment, the component may include an optically transparent portion, such as a transparent window, that allows inspection of the air filtration media held within the component. In such an embodiment, rather than an end user actively inspecting for color changes, an external optical sensor may be used to detect such color changes and notify the end user. Such an external optical sensor may form part of the air treatment system in which the filter component is installed, rather than the filter component itself.

[0018] The present inventors have discovered that by providing a polymer composition having multiple free vinyl groups as an air filtration medium, nitrogen dioxide can react with the vinyl groups to produce a yellow product. As a result, the inventors have found that by increasing the number of vinyl groups in the polymer, the color change becomes more pronounced and the amount of NO2 that can be adsorbed simultaneously is significantly improved. Therefore, the present invention does not require a separate colorimetric indicator, such as a pH indicator, e.g., methyl red; preferably, the polymer composition does not contain such a separate colorimetric indicator. In other words, the color change from white to yellow results entirely from the chemisorption of NO2 onto the polymer composition as a result of the reaction between the multiple free vinyl groups and NO2.

[0019] In an alternative preferred embodiment, the component includes an optical sensor that can detect a color change from white to yellow and notify a user when a sufficient color threshold is reached. This is particularly preferred for air conditioning and air purification systems that may be installed in locations that are more difficult for users to reach, for example in industrial HVAC systems.

[0020] If the component allows for visual inspection by a user, the component preferably includes a yellow marker to allow the end user to compare with the air filtration media and thereby determine when the filter is used. Thus, the filter component of the present invention allows the end user to replace the filter containing the air filtration media with a new filter component once the color of the air filtration media matches the marker, and / or otherwise dispose of the used filter, such as if the filter is part of a disposable mask.

[0021] As will be appreciated, the exact point at which the color change indicates that the filter has exhausted its NO2 removal performance will depend on the filtration medium selected. If the polymer has more free vinyl groups per unit weight, the final color intensity may be a darker yellow than a polymer with fewer free vinyl groups. Therefore, those skilled in the art can easily select the desired endpoint based on the selected polymer through routine testing. For example, the polymer can be tested to observe when the NO2 level in the treated test gas begins to increase, and the color of the polymer can then be set to provide an endpoint or exchange point.

[0022] In one embodiment, the component further includes activated carbon downstream of the polymer composition. Activated carbon is a preferred additional material for filter components, particularly in air conditioning systems, because it can be used to adsorb other pollutants, such as volatile organic compounds, fragrances, gaseous household chemicals, and many other gases. The inventors have discovered that by providing activated carbon downstream of the polymer composition, NO can be selectively adsorbed before contact with the activated carbon, where it would otherwise be reduced to form NO. As will be understood, "downstream" refers to the location of the activated carbon relative to the direction in which the air being treated moves through the filter during use. "Downstream" is used to refer to a later location of the air being treated, such that the air first passes through the polymer composition and then the activated carbon. This configuration minimizes or prevents NO production on the activated carbon, freeing up the activated carbon's ability to treat pollutants other than NO.

[0023] Preferably, the air filtration media is provided in the form of a plurality of beads held within a component. The beads are substantially spherical and preferably have an average particle size (d) in the range of 100 μm to 1600 μm, preferably 300 μm to 1200 μm. 50 ) The beads may be held, for example, between a mesh screen.

[0024] Preferably, the air filtration media has a filtration rate of at least 600 m 2 / g. Such a high surface area allows for efficient extraction of NO2 from air, a pollutant typically present in relatively low concentrations (e.g., less than 1 ppm in ambient air). Surface area may also be referred to as BET specific surface area as the total surface area of the porous polymer per unit mass (or volume); such measurements are conventional in the art and are typically measured by nitrogen adsorption. Preferably, the surface area is at least 700 m 2 / g, more preferably 750 to 2000m 2 / g.

[0025] In one embodiment, the polymer composition may be supported on a fiber. For example, the polymer composition may be supported on a scrim, which is a woven fabric typically made from cotton. The polymer composition may also be supported on wool, a material that can simultaneously adsorb the pollutant formaldehyde.

[0026] In another embodiment, the polymer composition itself may be provided in the form of a woven or nonwoven fabric, and fibers may be formed from the polymer composition. Preferably, the polymer composition is meltblown to form a nonwoven sheet as an air filtration medium. Even more preferably, the polymer composition may be provided in the form of a HEPA filter. HEPA filters are well known in the art and are required to filter at least 99.95%, preferably greater than 99.97%, of particles with a diameter of 0.3 μm or greater. Thus, HEPA filters can adsorb gaseous NO2 from the air while simultaneously physically capturing and filtering particles larger than 0.3 μm, including microorganisms such as bacteria and viruses, dust, and aerosols. To prevent backpressure buildup, HEPA filters must be replaced over time. The simultaneous color change resulting from the reaction with NO2 helps indicate to the user when the filter is worn out and needs to be replaced.

[0027] Since existing filters may already contain a HEPA filter upstream of the activated carbon filter, it is highly desirable to provide the NO2-treated polymer itself as a HEPA filter, since there are no additional components to increase backpressure. This is particularly important in air conditioning systems where backpressure limitation is important.

[0028] A further aspect of the present invention provides a single-use filter component for simultaneously removing NO2 in an air treatment system, the component comprising a HEPA filter formed from a polymer composition containing a plurality of free vinyl groups. HEPA filters are well known and are typically replaced periodically, often without inspection, based on the expected lifespan of the filter in a given application. Thus, the filter of the further aspect serves to simultaneously remove NO2 from the air being filtered. Given that HEPA filters are often replaced periodically to ensure effective particulate filtration, users do not need to inspect the color change resulting from NO2 adsorption.

[0029] The polymer composition comprises a plurality of free vinyl groups. As described herein, the present inventors have discovered that the presence of free and unreacted vinyl groups can be used to react with NO to efficiently remove NO from the air while simultaneously changing the color of the polymer composition from white to yellow. The presence of free vinyl groups in the polymer composition, as described herein, 13 C solid-state nuclear magnetic resonance ( 13 C solid state nuclear magnetic resonance, 13 This can be readily determined by C SSNMR spectroscopy.

[0030] It is particularly preferred that the polymer composition be a hydrocarbon, i.e., composed of hydrogen and carbon. In other words, the polymer composition is preferably the polymerization product of a hydrocarbon precursor. Hydrocarbon polymers without additional functional groups make the polymer relatively inert to many pollutants and hydrophobic, making them particularly suitable for selective adsorption of NO2. To incorporate free vinyl groups into the final polymer, at least one precursor preferably contains two vinyl groups, such that one vinyl group is incorporated into the polymer backbone during polymerization and the other remains unpolymerized and thus free. Divinylbenzene is therefore a particularly preferred precursor, i.e., a particularly preferred monomer for polymerization. Therefore, the polymer composition preferably comprises a polymer or copolymer of divinylbenzene. Even more preferably, the polymer composition consists of a polymer or copolymer of divinylbenzene. Divinylbenzene generally refers to a mixture of the para and meta isomers of divinylbenzene, since this is the most commonly commercially available form.

[0031] Divinylbenzene (DVB) polymers and copolymers are known and are frequently used as porous polymer adsorbents in chromatography. Divinylbenzene polymers and copolymers can range from mesoporous to microporous, with particularly high surface areas allowing efficient air-polymer interaction. While DVB polymers and copolymers are known, DVB with two vinyl groups is used during polymerization as a crosslinker to link two polymer chains during polymer growth, rather than providing free vinyl groups. Therefore, the resulting polymer may lack free vinyl groups. A common copolymer is that obtained from the polymerization of styrene with divinylbenzene (i.e., styrene-divinylbenzene).

[0032] The present inventors have discovered that it is possible to increase the number of free vinyl groups in the resulting polymer or copolymer by polymerizing a monomer containing at least two vinyl groups and / or by increasing the concentration of such a monomer in the polymerizable composition prior to polymerization. Accordingly, the polymer composition is preferably the polymerization product of a polymerizable composition containing at least 60% by weight of a monomer containing at least two vinyl groups. Even more preferably, the polymerizable composition contains at least 70%, at least 80%, at least 85%, or at least 90% by weight of a monomer containing at least two vinyl groups. Accordingly, when the polymer composition comprises or consists of a polymer or copolymer of divinylbenzene, the polymer composition is the polymerization product of a polymerizable composition containing at least 60%, at least 70%, at least 80%, at least 85%, or at least 90% by weight of divinylbenzene. Preferably, the polymer composition comprises a polymer of divinylbenzene, i.e., essentially the polymerization product of divinylbenzene. However, divinylbenzene with a purity approaching 100% can be difficult to obtain and relatively expensive. For this reason, at least 80% by weight of divinylbenzene is particularly preferred for forming a copolymer of divinylbenzene. In another embodiment, a monomer having at least three vinyl groups (e.g., trivinylbenzene) can be used for polymerization. However, divinylbenzene is generally readily commercially available and is also a relatively inexpensive monomer for polymerization, thus reducing the cost of single-use filter components.

[0033] Preferably, the polymer composition comprises a copolymer of divinylbenzene and an optionally substituted styrene, typically styrene and / or alkyl-substituted styrene, preferably styrene and / or ethylstyrene (i.e., ethylvinylbenzene). Similarly to divinylbenzene, alkylstyrene and ethylstyrene generally refer to mixtures of para- and meta-alkylstyrene and para- and meta-ethylstyrene, respectively. Thus, the polymer composition is preferably the polymerization product of a polymerizable composition consisting essentially of divinylbenzene and an optionally substituted styrene, preferably styrene and / or ethylstyrene. Because divinylbenzene precursors are often available only with relatively low purity, such as at least 50% by weight, such compositions are commercially available as "divinylbenzene." Divinylbenzene is often commercially produced by thermal dehydrogenation of the isomeric diethylbenzene. Pursuant to the desire to increase the number of free vinyl groups, commercially available divinylbenzenes having a purity of at least 80% by weight are particularly suitable, since the remaining 20% by weight is typically a mixture of styrene, ethylstyrene, and unavoidable impurities. In commercially available divinylbenzene, some unavoidable impurities such as naphthalene may remain from the cyclization of orthodivinylbenzene, but substantially all of the naphthalene can be easily separated.

[0034] In another embodiment, the polymer composition may comprise a copolymer of a methacrylate (such as methyl methacrylate), divinylbenzene, and optionally styrene and / or alkylstyrene, as described above. Such a polymer composition may be obtained from the polymerization of commercially available divinylbenzene with methacrylate.

[0035] Divinylbenzene copolymers suitable for use as air filtration media according to the present invention include Lewatit® VP OC 1065 (a copolymer of amine-functionalized styrene and DVB), available from Lanxess®, and Diaion® HP20, available from Mitsubishi Chemical Corporation, which is a copolymer of DVB and styrene. Porapak® Q is a copolymer of ethylvinylbenzene and divinylbenzene. In a particularly preferred embodiment, the polymer composition is PuroSorb® PAD1200, available from Purolite®, which is a copolymer obtainable from the polymerization of commercially available divinylbenzene and its associated impurities, such as ethylstyrene. PAD1200 provides a particularly large amount of free vinyl groups due to the incomplete polymerization of a large amount of divinylbenzene in the polymerizable composition used.

[0036] The polymer compositions for use in the present invention provide a plurality of free vinyl groups for reaction with NO from an air stream containing NO. The number of free vinyl groups is: 13 The concentration of vinyl groups in the polymer composition can be quantified by C SSNMR spectroscopy. Regardless of the precursors and / or monomers used to form the polymer composition, it is preferred that at least 5.0% of the carbon atoms in the polymer composition are vinyl carbon atoms, preferably at least 5.5%, at least 6.0%, at least 6.5%, at least 7.0%, and even more preferably at least 7.5% of the carbon atoms are vinyl carbon atoms. Such a concentration of vinyl groups provides the desired strong color change from white to yellow, and as the number of vinyl carbon atoms decreases below about 5.0%, the color change and adsorption capacity for NO2 become progressively weaker.

[0037] When the polymer composition comprises a polymer or copolymer of divinylbenzene, the inventors have found that the free vinyl groups 13It was found that a peak was generated at about 112 ppm (corresponding to the unsubstituted carbon of the vinyl group, i.e., -CH=CH2) in the C SSNMR spectrum. In any case, the peak generated from the vinyl group was 13 It can be easily identified by comparing the C SSNMR spectrum with that of the polymer resulting from reaction with bromine. Bromine (Br2) reacts with free vinyl groups, 13 The vinyl carbon peak disappears from the aromatic region of the C SSNMR spectrum. The relative intensities of the vinyl carbon peaks can then be used to quantify the total vinyl content of the polymer composition (the intensity value is doubled to account for the two carbon atoms in the vinyl group). We found that PAD1200 contains approximately 3.8% unsubstituted vinyl carbon atoms relative to the total number of carbon atoms in the polymer composition, corresponding to approximately 7.6% vinyl carbon atoms in the polymer composition. We found that Porapak® Q is a copolymer of a higher amount of ethylstyrene compared to PAD1200, as evidenced by larger peaks in the aliphatic region of the spectrum (approximately 15 ppm and 29 ppm). Porapak® Q produces an unsubstituted vinyl carbon peak at approximately 112 ppm with an intensity of approximately 3.2% (corresponding to a vinyl carbon content of approximately 6.4%).

[0038] 13 C SSNMR spectra were recorded at a static magnetic field strength (ν( 1 H) = 600 MHz). 13 For C, the probe is tuned to 150.94 MHz, with 20.5 ppm alanine CH3 as the reference. The powdered sample may be loaded into a zirconia MAS rotor with a Kel-F cap, providing a sample mass before and after weighing. The sample mass may be approximately 30 mg to approximately 60 mg. The rotor may be spun using purified compressed air at room temperature. The number of scans may be 1024, and D1 may be set to 30.0 s. 13Such parameters for C SSNMR spectroscopy are typical in the art.

[0039] As can be seen, the molecular formula C 10 H 10 Divinylbenzene, having the formula (I), contains four vinyl carbon atoms, two of which form part of the polymer backbone for incorporation into the final polymer. Thus, the maximum free vinyl content of pure divinylbenzene, in which only one vinyl group is polymerized, is 20.0%. Thus, a polymer or copolymer of divinylbenzene containing at least 7.0% vinyl carbon atoms results from at least 35% of the second vinyl group remaining unreacted during polymerization. As the level of crosslinking increases during polymerization due to the polymerization of two vinyl groups of the same monomer, conformational restrictions prevent further polymerization of the second vinyl group of adjacent monomer units, leaving free vinyl groups in the resulting polymer. Thus, as described herein, the polymer composition preferably comprises at least 60%, at least 70%, at least 80%, at least 85%, or at least 90% by weight of a copolymer formed from a monomer having at least two vinyl groups, most preferably divinylbenzene.

[0040] According to a further aspect, there is provided an air treatment system including the single-use filter described herein. Preferably, the air treatment system is an automotive air conditioning system. This is particularly useful because the filter is used in systems that encounter high levels of NO2, and where the system is inspected and replaced periodically over its useful life.

[0041] When the filter component becomes spent, as determined by a user observing a color change of the polymer composition to yellow, the filter component may be replaced. Alternatively, the optical sensor may be configured to alert the user to the color change. In such an embodiment, a warning light in the vehicle's dashboard control panel may be used to alert the user to the color change of the filter and, therefore, that the filter is spent and needs to be replaced. Alternatively, in an embodiment in which the polymer is in the form of a HEPA filter, the filter may simply be replaced as part of routine servicing of the vehicle's air conditioning system.

[0042] According to a further aspect, there is also provided a method of treating air to remove NO2, the method comprising passing NO2-containing air through a single-use filter described herein.

[0043] In yet a further aspect, there is provided a use of a polymer or copolymer of divinylbenzene to form an air filtration medium, wherein at least 7.0% of the carbon atoms of the polymer or copolymer of divinylbenzene are 13 The vinyl carbon atom is a carbon atom as determined by C SSNMR. Commercially available polymers and copolymers of divinylbenzene are known and are sold for use in applications such as the purification of biological materials such as small peptides and proteins, wastewater treatment, decolorization of chemicals, sugar solutions and / or stevia, or chromatography columns. The present inventors have determined that such polymers and copolymers are particularly suitable for forming air filtration media suitable for removing NO from air. [Brief explanation of the drawings]

[0044] The invention will now be further described with reference to the following non-limiting figures. [Figure 1] 1 is a plot of NO2 slip and NO production as a function of time comparing a commercial activated carbon with polymer PAD610. [Figure 2]1 represents the structure of a styrene-divinylbenzene copolymer that has no free vinyl groups. [Figure 3] 1 shows the structure of an ethylstyrene-divinylbenzene copolymer having multiple free vinyl groups.

[0045] Figure 1 compares the polymer compositions described herein suitable for use in single-use filter components with commercially available activated carbon compositions for use in home air purifiers. Figure 1 shows the results obtained when air having approximately 40% relative humidity and 400 ppb of NO was passed through the test samples at room temperature (22°C). Figure 1 shows a rapid increase in NO slip from the activated carbon, while the polymer PAD610 (a polymethacrylic polymer crosslinked with DVB and containing multiple free vinyl groups) maintains a low level of NO slip for more than 90 hours. Advantageously, the polymer compositions do not produce appreciable levels of NO production, while NO production closely tracks the amount of NO slip in the activated carbon, rising rapidly to above 40 ppb.

[0046] Figure 2 shows the structure of a styrene-divinylbenzene copolymer that has no free vinyl groups. Divinylbenzene serves to crosslink the polymer backbone of the polymerized styrene. Figure 3, on the other hand, shows the structure of a copolymer of ethylstyrene and divinylbenzene, such as may be obtained by polymerization of commercially available divinylbenzene, which has a purity of at least 80% by weight, the remainder being essentially ethylstyrene. While the structure shown in Figure 3 includes para-substituted benzene rings, it will be understood that the copolymer may contain a mixture of meta- and para-substitutions. The copolymer shown in Figure 3, which may be obtained by polymerization of commercially available divinylbenzene, exhibited significantly more crosslinking than the comparative copolymer in Figure 2. As crosslinking increases during polymerization, some of the vinyl groups remain unpolymerized and become free in the resulting polymer.

[0047] As used herein, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Use of the term "comprising" is intended to be interpreted as including such features but not excluding other features, and is intended to include options of features necessarily limited to those recited. In other words, unless the context clearly dictates otherwise, this term also includes the limitations "consisting essentially of" (intended to mean that certain additional components may be present provided they do not materially affect the essential properties of the recited features) and "consisting of" (intended to mean that when components are expressed as percentages by their proportions, these add up to 100%, while accounting for any unavoidable impurities, but that other features may not be included).

[0048] The foregoing detailed description has been provided for purposes of illustration and example, and is not intended to limit the scope of the appended claims. Many variations of the presently preferred embodiments set forth herein will be apparent to those skilled in the art and remain within the scope of the appended claims and their equivalents.

Claims

1. NO in air handling systems ２ 1. A single-use filter component for removing airborne particles, the component comprising a polymer composition as an air filtration medium, the polymer composition comprising a plurality of free vinyl groups; a reaction of the free vinyl groups in the polymer composition with NO2 results in chemisorption of NO2 onto the polymer composition and a color change of the polymer composition from white to yellow, the polymer composition comprising a polymer or copolymer of divinylbenzene, the free vinyl groups being groups that have not reacted in a polymerization reaction of the divinylbenzene; A single-use filter component that allows an end user to determine when a filter is used by a color change of the polymer composition from white to yellow, or the component includes an optical sensor configured to notify the end user of the color change.

2. 10. The single-use filter component of claim 1, wherein the component includes at least an optically transparent portion to allow inspection of the air filtration media held within the component.

3. 10. The single-use filter component of claim 1, wherein the air filtration media is provided in the form of a plurality of beads held within the component.

4. 10. The single-use filter component of claim 1, wherein the air filtration media is provided in the form of a woven or nonwoven fabric.

5. 5. The single-use filter component of claim 4, wherein the air filtration media is provided in the form of a HEPA filter.

6. The air filtration media has a thickness of at least 600 m ２ 10. The single-use filter component of claim 1 having a surface area of 1 / g.

7. 10. The single-use filter component of claim 1, further comprising a yellow marker for allowing the end user to compare to the air filtration media and thereby determine when the filter is exhausted.

8. 10. The single-use filter component of claim 1, wherein the polymer composition is a polymerization product of a polymerizable composition comprising at least 80% by weight of divinylbenzene.

9. At least 7.0% of the carbon atoms of said polymer composition are １３ 10. The single-use filter component of claim 1, wherein C is a vinyl carbon atom as determined by SSNMR.

10. 10. The single-use filter component of claim 1, wherein the component further comprises activated carbon downstream of the polymer composition.

11. 10. An air treatment system comprising the single-use filter component of claim 1.

12. An automotive air conditioning system comprising the single-use filter component of claim 1.

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