Patent Publication Number: US-10322303-B2

Title: PM 2.5 mask

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims all benefits accruing under 35 U.S.C. § 119 from China Patent Application No. 201420392742.9, filed on Jul. 16, 2014, in the China Intellectual Property Office, the contents of which are hereby incorporated by reference. 
     BACKGROUND 
     1. Technical Field 
     The disclosure generally relates to protective masks. 
     2. Description of Related Art 
     PM 2.5 refers to particles with notional diameter of less than 2.5 μm. Compared with large diameter particles, PM 2.5 has small particle size, large surface area, and high activity. PM 2.5 easily adsorbs toxic substances, such as heavy metals and microorganisms. Additionally, PM 2.5 can stay a long time in the air. Thus the air pollution is more serious with an increasing concentration of PM 2.5 in the air. Breathing PM 2.5 is very unhealthy. 
     PM 2.5 masks can be used to protect people from PM 2.5. Conventional PM 2.5 masks are mostly made of multilayer non-woven fabric, which has many defects, such as large thickness, large mass, and poor filtration. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Implementations of the present technology will now be described, by way of example only, with reference to the attached figures. 
         FIG. 1  is a sectional schematic view of one embodiment of a PM 2.5 mask. 
         FIG. 2  is a scanning electron microscope (SEM) image of a carbon nanotube structure. 
         FIG. 3  is a transmission electron microscope (TEM) image of a carbon nanotube structure. 
         FIG. 4  is an SEM image of a drawn carbon nanotube film. 
         FIG. 5  is an SEM image of a flocculated carbon nanotube film. 
         FIG. 6  is an SEM image of a pressed carbon nanotube film. 
         FIG. 7  is an SEM image of a twisted carbon nanotube wire. 
         FIG. 8  is an SEM image of an untwisted carbon nanotube wire. 
     
    
    
     DETAILED DESCRIPTION 
     It will be appreciated that for simplicity and clarity of illustration, where appropriate, reference numerals have been repeated among the different figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein can be practiced without these specific details. In other instances, methods, procedures, and components have not been described in detail so as not to obscure the related relevant feature being described. Also, the description is not to be considered as limiting the scope of the embodiments described herein. The drawings are not necessarily to scale and the proportions of certain parts have been exaggerated to better illustrate details and features of the present disclosure. 
     Several definitions that apply throughout this disclosure will now be presented. 
     The term “substantially” is defined to be essentially conforming to the particular dimension, shape or other feayure that the term modifies, such that the component need not be exact. For example, “substantially cylindrical” means that the object resembles a cylinder, but can have one or more deviations from a true cylinder. The term “comprising,” when utilized, means “including, but not necessarily limited to”; it specifically indicates open-ended inclusion or membership in the so-described combination, group, series and the like. The expression “PM 2.5” can refer to particles of solid matter with a notional diameter of less than 2.5 μm or to a device to function against particles of such size. 
       FIG. 1  illustrates one embodiment of a PM 2.5 mask  100 , which includes a mask body  10 , a filter layer  20 , and two ties  30 . The mask body  10  includes an inner layer and an outer layer, a gap is formed between the inner layer and the outer layer. In another embodiment, the mask body  10  is a multilayered structure. The filter layer  20  is located in the gap, and can filter out PM 2.5. Each tie  30  is located on opposite sides of the mask body  10 . The two ties  30  are used to fix the PM 2.5 mask  100  on the ears of a wearer. An opening (not shown) is located on one side of the mask body  10 , and is used to replace the filter layer  20 . Two ends of the opening are connected via a connector. 
     A material of the mask body  10  can be a thin and gas-permeable material. The material can be cotton, silk, gauze, non-woven fabric, hemp, fiber, nylon, spandex, polyester, polyacrylonitrile, or the like. In one embodiment, the material of the mask body  10  is a material modified with air anions. Air anions of the material modified with air anions can reduce an activity of microorganisms and bacteria in the air, thereby inhibiting survival of the microorganisms and bacteria. The air anions of the material modified with air anions can also neutralize polluted micro-particles with positive ions in the air, to purify the air. 
     In one embodiment, the mask body  10  is a one-piece structure. In another embodiment, the mask body  10  includes at least two layers sewn or bonded together. The mask body  10  can be circular-arc, semi-spherical, proculiform, rectangular, or other shape. In one embodiment, the mask body  10  is rectangular, and the material of the mask body  10  is non-woven fabric. 
     The connector allows the opening to be opened or closed repeatedly. The connector can be velcro, zipper, button, snap, pin, or the like. In one embodiment, the PM 2.5 mask  100  does not include an opening and a connector. 
     In one embodiment, the two ties  30  are flexible. In one embodiment, the PM 2.5 mask  100  includes only one tie  30 , the two ends of the tie  30  being located on opposite sides of the mask body  10 . In another embodiment, the PM 2.5 mask  100  does not include a tie  30 , the PM 2.5 mask  100  is pasted or otherwise adhered on the wearer&#39;s skin. 
     Referring to  FIGS. 2 and 3 , the filter layer  20  includes a carbon nanotube structure. The carbon nanotube structure includes a plurality of carbon nanotubes without impurities. In one embodiment, the filter layer  20  is a pure carbon nanotube structure and consists of just carbon nanotubes. The carbon nanotube structure includes a plurality of carbon nanotube films stacked and crossed with each other. The carbon nanotube structure includes a plurality of micropores. A diameter of a micropore of the plurality of micropores is larger than 1 micrometer and less than 2.5 micrometers. 
     Each of the plurality of carbon nanotube films can be a drawn carbon nanotube film, a flocculated carbon nanotube film, or a pressed carbon nanotube film. 
       FIG. 4  illustrates that the drawn carbon nanotube film includes a number of carbon nanotubes that are arranged substantially parallel to a surface of the drawn carbon nanotube film. A large number of the carbon nanotubes in the drawn carbon nanotube film can be oriented along a preferred direction, meaning that a large number of the carbon nanotubes in the drawn carbon nanotube film are arranged substantially along the same direction. An end of one carbon nanotube is joined to an end of an adjacent carbon nanotube arranged substantially along the same direction by van der Waals force, to form a free-standing film. The term ‘free-standing’ includes films that do not have to be supported by a substrate. The drawn carbon nanotube film can be formed by drawing from a carbon nanotube array. Examples of a drawn carbon nanotube film are taught by U.S. Pat. No. 7,045,108 to Jiang et al., and US patent application US 2008/0170982 to Zhang et al. A width of the drawn carbon nanotube film relates to the carbon nanotube array from which the drawn carbon nanotube film is drawn. A thickness of the carbon nanotube drawn film can range from about 0.5 nanometers to about 100 micrometers. 
     A minority of carbon nanotubes in the drawn carbon nanotube film may be randomly aligned. However, the number of randomly aligned carbon nanotubes is very small and does not affect the overall oriented alignment of the majority of carbon nanotubes in the drawn carbon nanotube film. The majority of the carbon nanotubes in the drawn carbon nanotube film substantially aligned along the same direction may not be exactly straight, and can be curved to a certain degree, or are not exactly aligned along the overall aligned direction, and can deviate from the overall aligned direction by a certain degree. Therefore, partial contacts can exist between the randomly aligned carbon nanotubes and adjacent carbon nanotubes. The drawn carbon nanotube film includes a plurality of successively oriented carbon nanotube segments joined end-to-end by van der Waals force. Each carbon nanotube segment includes a plurality of carbon nanotubes substantially parallel to each other, combined together by van der Waals force. 
       FIG. 5  illustrates a flocculated carbon nanotube film which can include a number of carbon nanotubes entangled with each other. The carbon nanotubes can be substantially uniformly distributed in the flocculated carbon nanotube film. The flocculated carbon nanotube film can be formed by flocculating the carbon nanotube array. Examples of the flocculated carbon nanotube film are taught by U.S. Pat. No. 8,846,144 to Wang et al. 
       FIG. 6  illustrates a pressed carbon nanotube film which can include a number of disordered carbon nanotubes arranged along a same or different directions. Adjacent carbon nanotubes are attracted to each other and combined by van der Waals force. A planar pressure head can be used to press the carbon nanotubes array along a direction perpendicular to a substrate, thereby a pressed carbon nanotube film having a plurality of isotropically arranged carbon nanotubes can be obtained. A roller-shaped pressure head can be used to press the carbon nanotubes array along a fixed direction, thereby a pressed carbon nanotube film having a plurality of carbon nanotubes aligned along a fixed direction is obtained. The roller-shaped pressure head can also be used to press the array of carbon nanotubes along different directions, thereby a pressed carbon nanotube film having a plurality of carbon nanotubes aligned along different directions is obtained. Examples of pressed carbon nanotube films are taught by US PGPub. 20080299031A1 to Liu et al. 
     Adjacent carbon nanotube films of the plurality of carbon nanotube films can be combined simply by van der Waals force. In some embodiments, the number of films of the plurality of carbon nanotube films is in a range from about four to about eight. When the number of carbon nanotube films is too small, the diameter of the micropores will be large, which is not appropriate for trapping PM 2.5. When the number of carbon nanotube films is too large, the breathability of the PM 2.5 mask  100  will be reduced. 
     When a large number of the carbon nanotubes in each carbon nanotube film of the carbon nanotube structure is oriented along a preferred orientation, an angle between the aligned directions of the carbon nanotubes in two adjacent carbon nanotube films can range from about 0 degrees to about 90 degrees. 
     In one embodiment, the carbon nanotube structure consists of four drawn carbon nanotube films stacked and crossed with each other, the angle between the aligned directions of the carbon nanotubes in adjacent drawn carbon nanotube films is about 90 degrees, and the diameter of the micropores is about 1.5 micrometers. 
     In one embodiment, the carbon nanotube structure includes a plurality of carbon nanotube wires. The carbon nanotube wires can be parallel to each other, braided together, or twisted together to form a carbon nanotube film. In one embodiment, the plurality of carbon nanotube wires are arranged along a same direction, a gap being defined between adjacent carbon nanotube wires. 
     The carbon nanotube wire can be an untwisted carbon nanotube wire or a twisted carbon nanotube wire. 
       FIG. 7  illustrates that the untwisted carbon nanotube wire includes a plurality of carbon nanotubes substantially oriented along a length of the untwisted carbon nanotube wire. The untwisted carbon nanotube wire can be formed by treating a drawn carbon nanotube film with a volatile organic solvent. The drawn carbon nanotube film can be formed by drawing a film from a carbon nanotube array; the drawn carbon nanotube film being a free-standing structure. The drawn carbon nanotube film includes a plurality of carbon nanotube segments joined end-to-end by van der Waals force. Each carbon nanotube segment includes a plurality of carbon nanotubes substantially parallel to each other, and combined by van der Waals force. A length of the untwisted carbon nanotube wire can be set as desired. A diameter of the untwisted carbon nanotube wire can range from about 0.5 nanometers to about 100 micrometers. The drawn carbon nanotube film is treated by applying an organic solvent to the drawn carbon nanotube film so as to soak the entire surface of the drawn carbon nanotube film. After being soaked by the organic solvent, adjacent parallel carbon nanotubes in the drawn carbon nanotube film will bundle together when the organic solvent volatilizes, due to the surface tension of the organic solvent, thus the drawn carbon nanotube film will shrink into the untwisted carbon nanotube wire. The organic solvent can be volatile organic solvents, such as ethanol, methanol, acetone, dichloroethane, or chloroform. Compared with the drawn carbon nanotube film, a specific surface area of the untwisted carbon nanotube wire is decreased, and a viscosity of the untwisted carbon nanotube wire is increased. 
       FIG. 8  illustrates that the twisted carbon nanotube wire includes a plurality of carbon nanotubes spirally arranged along an axial direction of the twisted carbon nanotube wire. The twisted carbon nanotube wire is formed by twisting a carbon nanotube film. In one embodiment, the twisted carbon nanotube wire is treated by applying an organic solvent to the twisted carbon nanotube film. After being soaked by the organic solvent, adjacent parallel carbon nanotubes in the carbon nanotube wire will bundle together as the organic solvent volatilizes, due to the surface tension of the organic solvent. A specific surface area of the twisted carbon nanotube wire is decreased, and a viscosity of the twisted carbon nanotube wire is increased. 
     Examples of carbon nanotube wire are taught by U.S. Pat. No. 7,045,108 to Jiang et al., and US patent application U.S. Pat. No. 8,602,765 to Jiang et al. 
     In one embodiment, the PM 2.5 mask  100  further includes an absorbent layer. The absorbent layer is located in the gap of the mask body  10 . The absorbent layer absorbs atmospheric water vapor. 
     In one embodiment, the PM 2.5 mask  100  further includes a supporter located in the mask body  10 . The absorbent layer is used to form a large cavity in the PM 2.5 mask to expand the effective flow area, thereby reducing the respiratory effort of wearers. A material of the supporter can be plastic or metal. 
     When the carbon nanotube structure includes four to eight carbon nanotube films stacked and crossed with each other, the diameter of the micropores in the carbon nanotube structure is larger than 1 micrometer and less than 2.5 micrometers. The PM 2.5 mask not only has excellent breathability but can filter PM 2.5 efficiently. 
     The PM 2.5 mask has excellent bend resistance and very little weight due to the excellent mechanical properties and light weight of the carbon nanotube structure. 
     A specific surface area of the carbon nanotubes is about 170 m 2 /g, the carbon nanotube structure can filter out toxic gases from the air, thus the PM 2.5 mask can purify air without additional adsorption layers. 
     The carbon nanotubes have low specific surface area, and are combined by van der Waals force. Thus, the carbon nanotube structure has viscosity and can be adhered directly on the mask body  10  without an adhesive. Additionally, the carbon nanotube structure uses this property of adherence to adhere to impurities which are difficult to filter. 
     It is to be understood that the above-described embodiments are intended to illustrate rather than limit the present disclosure. Variations may be made to the embodiments without departing from the spirit of the present disclosure as claimed. Elements associated with any of the above embodiments are envisioned to be associated with any other embodiments. The above-described embodiments illustrate the scope of the present disclosure but do not restrict the scope of the present disclosure.