Patent Publication Number: US-2019183184-A1

Title: Electronic smoking article

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a Divisional application of U.S. application Ser. No. 14/332,823, filed Jul. 16, 2014, which claims priority under 35 U.S.C. § 119(e) to U.S. provisional Application No. 61/856,923, filed on Jul. 22, 2013, the entire content of each of which is incorporated herein by reference thereto. 
    
    
     WORKING ENVIRONMENT 
     Electronic smoking articles include a liquid supply containing a liquid aerosol formulation and a heater. The liquid aerosol formulation can include aerosol formers such as propylene glycol and/or glycerin. It is known that heating glycerin and/or propylene glycol beyond the temperatures required to volatilize the liquid aerosol formulation produces carbonyls. 
     Heaters formed of alloys including iron tend to corrode and rust over time, producing iron oxide. Iron oxide tends to catalyze reactions with glycerin and/or propylene glycol such that carbonyls and/or carbon monoxide are produced at temperatures below the temperature required to volatilize the liquid aerosol formulation in electronic smoking articles. Abatement of the production of carbonyls and/or carbon monoxide at lower temperatures is desirable. 
     SUMMARY OF SELECTED FEATURES 
     An electronic smoking article, such as an electronic cigarette comprises a heater and a liquid aerosol formulation. The liquid aerosol formulation comprises at least one aerosol former, optionally water, optionally nicotine, and phosphoric acid. The phosphoric acid is included in an amount sufficient to substantially abate corrosion of the heater. The heater element can be a wire heater, such as a wire coil formed of a material including iron. 
     In an embodiment, a method of abating formation of one or more of carbonyls, formaldehyde and carbon monoxide during smoking of an electronic smoking article includes forming a liquid aerosol formulation including phosphoric acid in an amount sufficient to substantially abate corrosion of the heater. 
     In another embodiment, a liquid aerosol formulation of an electronic smoking article includes at least one aerosol former, optionally water, nicotine, and phosphoric acid in an amount sufficient to substantially abate corrosion of an iron-containing heater of an electronic smoking article. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top planar view of an electronic smoking article in the form of an electronic cigarette according to a first embodiment. 
         FIG. 2  is a side cross-sectional view of the electronic smoking generating article shown in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     Heaters formed of metal alloys including iron tend to corrode and rust over time, producing iron oxide. During heating of a liquid aerosol formulation including at least one aerosol former, the iron oxide tends to catalyze reactions with glycerin and/or propylene glycol such that carbonyls and/or carbon monoxide are produced at temperatures below the temperature required to volatilize the liquid aerosol formulation. An electronic smoking article which abates corrosion of heaters formed of metal alloys including iron is described herein. 
     As used herein, the term “electronic smoking article” is inclusive of all types of electronic smoking articles, regardless of form, size or shape, including electronic cigarettes, electronic cigars, electronic pipes, electronic hookahs and the like. The liquid aerosol formulation can include nicotine or be nicotine free. Moreover, the liquid aerosol formulation can include tobacco flavors or instead, or in combination include other suitable flavors. 
     Preferably, the electronic smoking article comprises a heater formed of a metal alloy including iron and a liquid supply region (or liquid supply) (or reservoir) containing a liquid aerosol formulation including at least one aerosol former and food grade phosphoric acid. Preferably, the phosphoric acid is included in the liquid aerosol formulation in an amount sufficient to substantially prevent corrosion of a heater and avoid formation of one or more of formaldehyde, carbonyls and carbon monoxide resulting from catalytic reactions between iron oxide and the at least one aerosol former. 
     The liquid aerosol formulation disclosed herein forms an aerosol when heated in an electronic smoking article as shown in  FIGS. 1 and 2 . The electronic smoking article  60  comprises a replaceable cartridge (or first section)  70  and a reusable fixture (or second section)  72 , which are coupled together at a threaded joint  74  or by other convenience such as a snug-fit, snap-fit, detent, clamp and/or clasp. 
     As shown in  FIG. 2 , the first section  70  can house a mouth-end insert  20 , a heater  319 , a flexible, filamentary wick  328  and a reservoir  314  as discussed in further detail below. 
     The second section  72  can house a power supply  12 , control circuitry  11 , and optionally a puff sensor  16 . The threaded portion  74  of the second section  72  can be connected to a battery charger when not connected to the first section  70  for use so as to charge the battery. 
     Preferably, the first section  70  and the second section  72  include an outer cylindrical housing  22  extending in a longitudinal direction along the length of the electronic smoking article  60 . Moreover, in one embodiment, the reservoir  314  of the first section  70  is refillable such that the first section  70  is reusable. In another embodiment, the first section  70  can also be replaceable so as to avoid the need for cleaning the heater  319 . 
     In the preferred embodiment, the electronic smoking article  60  includes a heater  319  and a filamentary wick  328  as shown in  FIG. 2 . The first section  70  includes an outer tube (or casing)  22  extending in a longitudinal direction and an inner tube (or chimney)  362  coaxially positioned within the outer tube  22 . Preferably, a nose portion  361  of an upstream gasket (or seal)  320  is fitted into an upstream end portion  365  of the inner tube  362 , while at the same time, an outer perimeter  367  of the gasket  320  provides a liquid-tight seal with an interior surface  397  of the outer casing  22 . The upstream gasket  320  also includes a central, longitudinal air passage  315 , which opens into an interior of the inner tube  362  that defines a central channel  321 . A transverse channel  333  at an upstream portion of the gasket  320  intersects and communicates with the central, longitudinal air passage  315  of the gasket  320 . This channel  333  assures communication between the central, longitudinal air passage  315  and a space  335  defined between the gasket  320  and a threaded connection  74 . 
     Preferably, a nose portion  393  of a downstream gasket  310  is fitted into a downstream end portion  381  of the inner tube  362 . An outer perimeter  382  of the gasket  310  provides a substantially liquid-tight seal with an interior surface  397  of the outer casing  22 . The downstream gasket  310  includes a central channel  384  disposed between the central passage  321  of the inner tube  362  and the mouth end insert  20 . 
     In this embodiment, the reservoir  314  is contained in an annulus between an inner tube  362  and an outer casing  22  and between the upstream gasket  320  and the downstream gasket  310 . Thus, the reservoir  314  at least partially surrounds the central air passage  321 . The reservoir  314  comprises the liquid aerosol formulation and optionally a liquid storage medium (not shown) operable to store the liquid aerosol formulation therein. 
     Preferably, the liquid storage medium is a fibrous material comprising cotton, polyethylene, polyester, rayon and combinations thereof. Preferably, the fibers have a diameter ranging in size from about 6 microns to about 15 microns (e.g., about 8 microns to about 12 microns or about 9 microns to about 11 microns). In the alternative, the reservoir  314  may comprise a filled tank lacking a fibrous storage medium and containing only liquid aerosol formulation. 
     Also preferably, the liquid aerosol formulation has a boiling point suitable for use in the electronic electronic smoking article  60 , such as an electronic cigarette. If the boiling point is too high, the heater  319  will not be able to vaporize liquid in the filamentary wick  328 . However, if the boiling point is too low, the liquid may vaporize even when the heater  319  is not being activated. 
     Preferably, the heater  319  extends through the central air passage  321  of the inner tube  362 . The heater  319  is in contact with the filamentary wick  328 , which preferably extends between opposing sections of the reservoir  314  so as to deliver the liquid aerosol formulation from the reservoir  314  to the heater  319 . 
     Preferably, the filamentary wick  328  preferably comprises filaments having a capacity to draw a liquid, more preferably a bundle of glass (or ceramic) filaments and most preferably a bundle comprising a group of windings of glass filaments, preferably three of such windings, all which arrangements are capable of drawing liquid via capillary action via interstitial spacings between the filaments. Preferably, the filamentary wick  328  is flexible and includes three strands, each strand including a plurality of filaments. 
     Preferably, the electronic smoking article  60  also includes at least one air inlet  440  arranged upstream of the heater  319 . In the preferred embodiment, the at least one air inlet  440  includes one or two air inlets. Alternatively, there may be three, four, five or more air inlets. Altering the size and number of air inlets  440  can also aid in establishing the resistance to draw of the electronic smoking article  60 . 
     The power supply  12  can include a battery arranged in the electronic smoking article  60 . The power supply  12  is operable to apply voltage across the heater  319  associated with the filamentary wick  328 . Thus, the heater  319  volatilizes the liquid aerosol formulation according to a power cycle of either a predetermined time period, such as a 2 to 10 second period. 
     Preferably, electrical contacts between the heater  319  and the electrical leads  26  are highly conductive and temperature resistant while the heater  319  is highly resistive so that heat generation occurs primarily along the heater  319  and not at the contacts. 
     The battery can be a Lithium-ion battery or one of its variants, for example a Lithium-ion polymer battery. Alternatively, the battery may be a Nickel-metal hydride battery, a Nickel cadmium battery, a Lithium-manganese battery, a Lithium-cobalt battery or a fuel cell. In that case, preferably, the electronic smoking article  60  is usable by a smoker (vaporer) until the energy in the power supply is depleted. Alternatively, the power supply  12  may be rechargeable and include circuitry allowing the battery to be chargeable by an external charging device. In that case, preferably the circuitry, when charged, provides power for a pre-determined number of puffs, after which the circuitry must be re-connected to an external charging device. 
     Preferably, the electronic smoking article  60  of each embodiment also includes control circuitry which can be on a printed circuit board  11 . The control circuitry  11  can also include a heater activation light  27  that is operable to glow when the heater  319  is activated. Preferably, the heater activation light  27  comprises at least one LED and is at an upstream end  28  of the electronic smoking article  60  so that the heater activation light  27  illuminates a cap which takes on the appearance of a burning coal during a puff. Moreover, the heater activation light  27  can be arranged to be visible to the smoker. In addition, the heater activation light  27  can be utilized for smoking article system diagnostics. The light  27  can also be configured such that the smoker can activate and/or deactivate the light  27  when desired, such that the light  27  would not activate during smoking (vaping) if desired. 
     The time-period of the electric current supply to the heater  319  may be pre-set depending on the amount of liquid desired to be vaporized. The control circuitry  11  can be programmable and can include an application specific integrated circuit (ASIC). In other embodiments, the control circuitry  11  can include a microprocessor programmed to carry out functions. 
     As shown in  FIG. 2 , the electronic smoking article  60  further includes a mouth-end insert  20  having at least two off-axis, preferably diverging outlets  21 . Preferably, the mouth-end insert  20  includes at least two diverging outlets  21 . (e.g, 3, 4, 5, or preferably 6 to 8 outlets or more). Preferably, the outlets  21  of the mouth-end insert  20  are located at ends of off-axis passages  23  and are angled outwardly in relation to the longitudinal direction of the electronic smoking article  60  (i.e., divergently). As used herein, the term “off-axis” denotes at an angle to the longitudinal direction of the electronic smoking article. Also preferably, the mouth-end insert (or flow guide)  20  includes outlets uniformly distributed around the mouth-end insert  20  so as to substantially uniformly distribute aerosol in a smoker&#39;s mouth during use. Thus, as the aerosol passes into a smoker&#39;s mouth, the aerosol enters the mouth and moves in different directions so as to provide a full mouth feel as compared to electronic smoking articles having an on-axis single orifice which directs the aerosol to a single location in a smoker&#39;s mouth. 
     In addition, the outlets  21  and off-axis passages  23  are arranged such that droplets of unaerosolized liquid aerosol formulation carried in the aerosol impact interior surfaces of the mouth-end insert  20  and/or interior surfaces of the off-axis passages  23  such that the droplets are removed or broken apart. In the preferred embodiment, the outlets  21  of the mouth-end insert  20  are located at the ends of the off-axis passages  23  and are angled at 5 to 60° with respect to the central longitudinal axis of the electronic smoking article  60  so as to more completely distribute aerosol throughout a mouth of a smoker during use and to remove droplets. 
     Preferably, each outlet  21  has a diameter of about 0.015 inch to about 0.090 inch (e.g., about 0.020 inch to about 0.040 inch or about 0.028 inch to about 0.038 inch). The size of the outlets  21  and off-axis passages  23  along with the number of outlets  21  can be selected to adjust the resistance to draw (RTD) of the electronic smoking article  60 , if desired. 
     In a preferred embodiment, the electronic smoking article  60  is about the same size as a conventional smoking article. In some embodiments, the electronic smoking article  60  can be about 80 mm to about 110 mm long, preferably about 80 mm to about 100 mm long and about 7 mm to about 8 mm in diameter. For example, in an embodiment, the electronic smoking article is about 84 mm long and has a diameter of about 7.8 mm. 
     The outer cylindrical housing  22  of the electronic smoking article  60  may be formed of any suitable material or combination of materials. Preferably, the outer cylindrical housing  22  is formed at least partially of metal and is part of the electrical circuit. The outer cylindrical housing  22  can be any suitable color and/or can include graphics or other indicia printed thereon. Although the housing is described herein as cylindrical, other forms and shapes are contemplated. 
     Preferably, at least one adhesive-backed label is applied to the outer housing  22 . The label completely circumscribes the electronic smoking article  60  and can be colored and/or textured to provide the look and/or feel of a traditional cigarette. The label can include holes therein which are sized and positioned so as to prevent blocking of the air inlets  440 . 
     In the preferred embodiment, the heater  319  is a wire coil heater formed of a metal alloy including iron Examples of suitable electrically resistive materials for use in making the heater  319  include titanium, zirconium, tantalum and metals from the platinum group. Examples of suitable metal alloys include stainless steel, nickel-, cobalt-, chromium-, aluminium- titanium- zirconium-, hafnium-, niobium-, molybdenum-, tantalum-, tungsten-, tin-, gallium-, manganese- and iron-containing alloys, and super-alloys based on nickel, iron, cobalt, stainless steel. For example, the heater can be formed of iron aluminide and other composite materials, the electrically resistive material may optionally be embedded in, encapsulated or coated with an insulating material or vice-versa, depending on the kinetics of energy transfer and the external physicochemical properties required. In a preferred embodiment, the heater  319  may be constructed of iron-aluminide (e.g., FeAl or Fe 3 Al) or a nickel-chromium-iron. 
     During use, a heater coil including even a small amount of iron (e.g., a wire coil formed of a nickel-chromium-iron alloy) may undergo corrosion, which is identified by visible pitting, discoloration and surface oxygen. While not wishing to be bound by theory, it is believed that the corroded heater  319  reacts with aerosol formers in the reservoir  314  to form carbonyls, formaldehyde, and carbon monoxide during smoking. 
     It has been found that the addition of food grade phosphoric acid to the liquid aerosol formulation substantially abates potential corrosion of the iron-containing heater  319  and formation of iron oxide. Since formation of iron oxide is abated, iron oxide is not available to catalyze reactions with aerosol formers resulting in the formation of carbonyls and carbon monoxide in the aerosol. Thus, in a preferred embodiment, the liquid aerosol formulation includes at least one aerosol former, optionally water, optionally nicotine, and phosphoric acid in an amount sufficient to substantially prevent corrosion of the heater  319 . 
     In the preferred embodiment, food grade phosphoric acid is added to the liquid aerosol formulation in an amount sufficient to substantially abate corrosion of the iron containing heater so as to reduce the amount of carbonyls and carbon monoxide formed during smoking as compared to liquid aerosol formulations excluding phosphoric acid. Preferably, the phosphoric acid is added in an amount ranging from about 0.1% to about 5% (e.g., about 0.2% to about 5%, about 0.5% to about 4%, about 0.75% to about 3%, or about 1% to about 2%). Preferably, the phosphoric acid is included in amount which is insufficient to alter the pH of the liquid aerosol formulation. While not wishing to be bound by theory, it is believed that acidic liquid aerosol formulations may promote charring of the heater, which can clog the heater and/or filamentary wick resulting in lower aerosol delivery and is therefore to be avoided or minimized. 
     Also preferably, the at least one aerosol former is selected from the group consisting of propylene glycol, glycerin and combinations thereof. Preferably, the at least one aerosol former is included in an amount ranging from about 40% by weight based on the weight of the liquid formulation to about 90% by weight based on the weight of the liquid formulation (e.g., about 50% to about 80%, about 55% to about 75% or about 60% to about 70%). Moreover, in one embodiment, the liquid formulation can include propylene glycol and glycerin included in a ratio of about 3:2. 
     Preferably, the liquid formulation also includes water. Water can be included in an amount ranging from about 5% by weight based on the weight of the liquid formulation to about 40% by weight based on the weight of the liquid formulation, more preferably in an amount ranging from about 10% by weight based on the weight of the liquid formulation to about 15% by weight based on the weight of the liquid formulation. 
     The liquid aerosol formulation optionally includes at least one flavorant in an amount up to about 15% by weight (e.g., about 0.2% to about 15%, about 1% to about 12%, about 2% to about 10%, or about 5% to about 8%). The at least one flavorant can be a natural flavorant or an artificial flavorant. Preferably, the at least one flavorant is selected from the group consisting of tobacco flavor, menthol, wintergreen, peppermint, herb flavors, fruit flavors, nut flavors, liquor flavors, and combinations thereof. 
     Preferably, the liquid aerosol formulation also includes nicotine. The nicotine is included in the liquid aerosol formulation in an amount ranging from about 1% by weight to about 10% by weight (e.g., about 2% to about 9%, about 2% to about 8%, about 2% to about 6%). In an alternative embodiment, the liquid aerosol formulation can be nicotine-free. 
     When the word “about” is used in this specification in connection with a numerical value, it is intended that the associated numerical value include a tolerance of ±10% around the stated numerical value. Moreover, when reference is made to percentages in this specification, it is intended that those percentages are based on weight, i.e., weight percentages. The expression “up to” includes amounts of zero to the expressed upper limit and all values therebetween. When ranges are specified, the range includes all values therebetween such as increments of 0.1%. 
     Moreover, when the words “generally” and “substantially” are used in connection with geometric shapes, it is intended that precision of the geometric shape is not required but that latitude for the shape is within the scope of the disclosure. When used with geometric terms, the words “generally” and “substantially” are intended to encompass not only features which meet the strict definitions but also features which fairly approximate the strict definitions. 
     It will now be apparent that a new, improved, and nonobvious electronic smoking article, liquid aerosol formulation and method has been described in this specification with sufficient particularity as to be understood by one of ordinary skill in the art. Moreover, it will be apparent to those skilled in the art that numerous modifications, variations, substitutions, and equivalents exist for features of the electronic smoking article, liquid aerosol formulation and method which do not materially depart from the spirit and scope of the invention. Accordingly, it is expressly intended that all such modifications, variations, substitutions, and equivalents which fall within the spirit and scope of the invention as defined by the appended claims shall be embraced by the appended claims.