Open-pore sintered glasses for use in electronic cigarettes

Abstract

A sintered body for use as a liquid reservoir in an electronic cigarette, medication administering devices, in thermally heated evaporators for fragrant substances is provided. The sintered body is made of open-pore sintered glass and has a porosity of greater than 50 vol %. The average pore size is in a range from 1 to 450 μm. The glass of the sintered body has a transition temperature T.sub.g of at least 450° C.

Claims

1. A sintered body for use as a liquid reservoir, comprising an open-pore sintered glass having a porosity of >50 vol % and an average pore size in a range from 90 to 450 μm, wherein the open-pore sintered glass comprises glass having a transition temperature of at least 450° C., wherein the open-pore sintered glass has a specific surface area that is at least 0.8 m.sup.2/g and smaller than 20 m.sup.2/g.

2. The sintered body as claimed in claim 1, wherein the open-pore sintered glass is configured for a use selected from the group consisting of an electronic cigarette, a medication administering device, and a thermally heated evaporator for a fragrant substance.

3. The sintered body as claimed in claim 1, wherein the open-pore sintered glass has a mass and adsorbs propylene glycol in an amount of at least 50% of the mass at a temperature of 20° C. and in an adsorption time of 3 hours.

4. The sintered body as claimed in claim 3, wherein the open-pore sintered glass is configured so that not more than 15 wt % of previously adsorbed propylene glycol is desorbed during a desorption time of 100 hours, and wherein the open-pore sintered glass desorbs at least 50% of the previously adsorbed propylene glycol at a temperature of 300° C. and a desorption time of 5 minutes.

5. The sintered body as claimed in claim 1, wherein the transition temperature is greater than 600° C.

6. The sintered body as claimed in claim 1, wherein the glass has a coefficient of linear thermal expansion a in a range from 2.5 ppm/K to 10.5 ppm/K.

7. The sintered body as claimed in claim 1, wherein the average pore size is in a range from 90 μm to 350 μm.

8. The sintered body as claimed in claim 1, wherein the porosity is at greater than 80 vol %.

9. The sintered body as claimed in claim 1, wherein the glass is selected from the group consisting of a borosilicate glass, an aluminosilicate glass, an aluminoborosilicate glass, and a soda-lime glass.

10. The sintered body as claimed in claim 1, wherein the glass comprises (in wt % on an oxide basis): TABLE-US-00009 SiO.sub.2 70 to 75 wt %; Na.sub.2O + K.sub.2O 12 to 16 wt %; CaO 8 to 11 wt %; MgO 0 to 5 wt %; and Al.sub.2O.sub.3 0 to 2 wt %.

11. The sintered body as claimed claim 1, wherein the glass comprises (in wt % on an oxide basis): TABLE-US-00010 SiO.sub.2 70 to 85 wt %; B.sub.2O.sub.3 5 to 15 wt %; Alkali oxides 3 to 7 wt %; Alkaline earth oxides 0 to 4 wt %; and Al.sub.2O.sub.3 2 to 5 wt %.

12. The sintered body as claimed in claim 1, wherein the glass comprises (in wt % on an oxide basis): TABLE-US-00011 SiO.sub.2 50 to 75 wt %; Na.sub.2O 0 to 15 wt %; K.sub.2O 2 to 14 wt %; Al.sub.2O.sub.3 0 to 15 wt %; MgO 0 to 4 wt %; CaO 3 to 12 wt %; BaO 0 to 15 wt %; ZnO 0 to 5 wt %; and TiO.sub.2 0 to 2 wt %.

13. The sintered body as claimed in claim 1, wherein the glass comprises (in wt % on an oxide basis): TABLE-US-00012 SiO.sub.2 30 to 85 wt %; B.sub.2O.sub.3 0.5 to 20 wt %; Al.sub.2O.sub.3 0 to 15 wt %; Na.sub.2O 3 to 15 wt %; K.sub.2O 2.5 to 15 wt %; ZnO 0 to 12 wt %; MgO 2 to 10 wt %; BaO 0 to 10 wt %; TiO.sub.2 0 to 10 wt %; and CaO 0 to 8 wt %.

14. The sintered body as claimed in claim 1, wherein the specific surface area is smaller than 10 m.sup.2/g.

15. The sintered body as claimed in claim 1, wherein the open-pore sintered glass is configured for a use selected from the group consisting of an electronic cigarette and a thermally heated evaporator for a fragrant substance.

16. A sintered body for use as a liquid reservoir, comprising an open-pore sintered glass having a porosity of >50 vol % and an average pore size in a range from 1 to 450 μm, wherein the open-pore sintered glass comprises glass having a transition temperature of at least 450° C., wherein the glass comprises (in wt % on an oxide basis): TABLE-US-00013 SiO.sub.2 50 to 60 wt %; B.sub.2O.sub.3 8 to 12 wt %; Al.sub.2O.sub.3 8 to 12 wt %; and BaO 20 to 30 wt %.

17. The sintered body as claimed in claim 1, wherein the glass comprises (in wt % on an oxide basis): TABLE-US-00014 SiO.sub.2 75 to 85 wt %; B.sub.2O.sub.3 8 to 18 wt %; Al.sub.2O.sub.3 0.5 to 4.5 wt %; Na.sub.2O 1.5 to 5.5 wt %; and K.sub.2O 0 to 2 wt %.

18. A sintered body for use as a liquid reservoir, comprising an open-pore sintered glass having a porosity of >50 vol % and an average pore size in a range from 1 to 450 μm, wherein the open-pore sintered glass comprises glass having a transition temperature of at least 450° C., wherein the glass comprises (in wt % on an oxide basis): TABLE-US-00015 SiO.sub.2 58 to 65 wt %; B.sub.2O.sub.3 6 to 10.5 wt %; Al.sub.2O.sub.3 14 to 25 wt %; MgO 0 to 5 wt %; CaO 0 to 9 wt %; BaO 0 to 8 wt %; SrO 0 to 8 wt %; ZnO 0 to 2 wt %; and a total of MgO, CaO, and BaO is 8 to 18 wt %.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will now be explained in more detail by way of exemplary embodiments and FIGS. 1 to 9, wherein:

(2) FIGS. 1a and 1b are SEM images of one embodiment of the sintered body according to the invention;

(3) FIGS. 2a and 2b are SEM images of sintered glasses with different pore sizes as comparative examples;

(4) FIGS. 3a and 3b are SEM images of sintered glasses with different pore sizes as comparative examples;

(5) FIG. 4 is an SEM image of a liquid reservoir made of an organic polymeric material as a second comparative example;

(6) FIG. 5 is a graphical diagram showing the adsorption capacity of the exemplary embodiment and various comparative examples;

(7) FIG. 6 is a graphical diagram of the desorption of one embodiment of a liquid reservoir according to the invention and a polymeric comparative example at 20° C.;

(8) FIG. 7 is a graphical diagram of the desorption of one embodiment of a liquid reservoir according to the invention and the comparative examples at 300° C.;

(9) FIG. 8 is a schematic view of the configuration of an electronic cigarette; and

(10) FIG. 9 is a schematic view of the configuration of one embodiment of the evaporator unit in which the heating element is directly arranged on the liquid reservoir.

DETAILED DESCRIPTION

(11) Table 1 shows six different exemplary embodiments of a sintered body according to the invention. The individual exemplary embodiments differ in terms of the composition of the sintered glass.

(12) TABLE-US-00008 TABLE 1 COMPOSITION AND PROPERTIES OF EXAMPLES 1 TO 6 Composition Exam- Exam- Exam- Exam- Exam- Exam- [wt %] ple 1 ple 2 ple 3 ple 4 ple 5 ple 6 SiO.sub.2 69 80 61 55 72.8 74.3 B.sub.2O.sub.3 1 13 10 10 Al.sub.2O.sub.3 4 2.5 18 10 0.2 1.3 Na.sub.2O 13 3.5 13.9 13.2 K.sub.2O 3 1 0.1 0.3 BaO 2 3.3 25 CaO 5 4.8 9.0 10.7 MgO 3 2.8 4.0 0.2 α.sub.(20-300) 9.1 3.25 3.2 4.0 9.5 9.0 [ppm/K] Density 2.5 2.2 2.43 2.80 [g/cm.sup.3] Tg [° C.] 525 525 717 665 564 573

(13) FIGS. 1a and 1b are SEM images (scanning electron micrographs) of an exemplary embodiment of the sintered body. The sintered body exhibits a very porous structure, both at the surface and at the breaking edge. Pores 1 are between 90 and 330 μm in size. In addition to the large open pores, the sintered body also has very small closed pores 2. For producing the exemplary embodiment of FIG. 1, NaCl was used as a salt.

(14) FIGS. 2a to 3b are SEM images of two different porous sintered glasses with different pore sizes. FIGS. 2a and 2b show SEM images of a porous sintered glass which has a multitude of very small pores. Pores 3 are only a few nanometers in size. The sintered glass of FIGS. 3a and 3b consists of many relatively large sintered glass grains 4. The intermediate spaces 5 between the individual glass grains 4 are very large here.

(15) FIG. 4 shows an SEM image of a liquid reservoir made of an organic polymer. The storage medium consists of entangled polymeric fibers 6. Thus, the liquid reservoir has a nonwoven structure. Between the individual fibers 6 there are many cavities 7 which can take up a carrier liquid.

(16) FIG. 5 illustrates the uptake capacity of liquid reservoirs. For this purpose, the different liquid reservoirs were soaked in propylene glycol for 3 hours, and then the mass increase was determined. Exemplary embodiment 10 corresponds to the sintered glass shown in FIG. 1. Comparative example 11 is the sintered glass of FIG. 3 with the pores of only a few nanometers in size. Comparative example 8 is the polymeric nonwoven of FIG. 4. Comparative example 9 is a sintered ceramic. Comparative example 12 has very large pores.

(17) It will be apparent from FIG. 5, that a ceramic structure 9 can only take up a small amount of propylene glycol and is therefore not suitable as a liquid reservoir for use in electronic cigarettes and/or in medication administering devices and/or in thermally heated evaporators for fragrant substances.

(18) In sintered glasses, uptake capacity depends on the pore size. Sintered glasses with very small pores 11 cannot take up enough propylene glycol, whereas in sintered glasses with excessively large pores 12 the specific surface area is too small to fully adsorb the uptaken propylene glycol. Therefore, a large proportion of the uptaken propylene glycol will flows out of the pores again. By contrast, the pores of exemplary embodiment 10 are large enough to take up enough propylene glycol and small enough to provide a sufficiently large specific surface area on which the propylene glycol can be adsorbed.

(19) In addition to exemplary embodiment 10, the liquid reservoir of polymeric material 8 also exhibits high uptake capacity.

(20) FIG. 6 illustrates the results of a desorption test at 20° C. for the exemplary embodiment 10 and the polymeric liquid reservoir 8. For this purpose, the samples 8 and 10 soaked with propylene glycol were stored at a temperature of 20° C., and the mass loss of propylene glycol was measured as a function of time. Even after a period of 5 days, both the exemplary embodiment and the polymeric liquid reservoir show a loss of propylene glycol of less than 20 wt % of the previously uptaken propylene glycol.

(21) FIG. 7 illustrates desorption of propylene glycol at 300° C. For this purpose, the samples 8 to 12 were first soaked with propylene glycol and then dried at 300° C. in a furnace for 5, 10, 20, and 40 minutes. The mass loss of propylene glycol was determined with a balance. After 10 minutes, all samples had released the major proportion of propylene glycol. In exemplary embodiment 10, 50% of the propylene glycol had evaporated already after 5 minutes. While the polymeric sample 8 had melted as soon as after 5 minutes at 300° C., the exemplary embodiment withstands the high temperature load.

(22) It will be obvious from FIGS. 5 to 7 that the liquid reservoir according to the invention is outstandingly suitable for use in an electronic cigarette and/or in medication administering devices and/or thermally heated evaporators for fragrant substances.

(23) The underlying adsorption and desorption tests shown here are exemplary. Alternative determinations of the uptake and release capacity are manifold, e.g. quantitative tracking of coloring/discoloring of a body in contact with dyed propylene glycol.

(24) FIG. 8 illustrates an electronic cigarette 21 according to the invention. Cigarette 21 comprises a tip 23 and a mouthpiece 25 on which the user drags to inhale the aerosol generated in the cigarette by means of an evaporator 22. According to a preferred embodiment of the invention, mouthpiece 25 is removable from tip 23.

(25) Cigarette 21 comprises an electrical energy storage 27 in order to provide the electrical energy for evaporating the organic liquid in evaporator 22. In the illustrated embodiment, the electrical energy storage 27 is accommodated in the tip 23 of cigarette 21. Medication administering devices may have a similar configuration.

(26) Electronic cigarette 21 further comprises a control unit 31 which controls the heating power for evaporator 22. In particular, the control unit 31 may be configured to check whether a user is inhaling and, depending thereon, to regulate the heating power of evaporator 22. Furthermore, a light-emitting diode 29 may be disposed in the tip 23, which is also controlled by control unit 31. When the control unit 31 detects that the user is dragging on cigarette 21, it can control the light-emitting diode 29 so that the light-emitting diode 29 lights up. Thus, a visual effect is achieved corresponding to the glowing when dragging on a conventional cigarette.

(27) The evaporator unit 22 according to the invention includes a liquid reservoir 24 comprising a sintered body 28 and organic carrier liquid 10 adsorbed in the sintered body 28. The sintered body 28 has a specific surface area preferably in a range from 0.5 square meters per gram to a maximum of 10 square meters per gram. A specific surface area in this range leads to a high uptake capacity for carrier liquid 30 and at the same time still sufficient mechanical and thermal stability.

(28) For heating the liquid reservoir 24 and thus for evaporating the organic carrier liquid 30 with constituents dissolved therein, such as nicotine, fragrant substances, and/or flavoring substances, the evaporator unit 22 comprises an electrically heatable heating element 26. Heating element 26 is supplied with power by electrical energy storage 27, controlled by control unit 31. By heating to an operating temperature of greater than 100° C., the organic carrier liquid 30 adsorbed in the sintered body 28, in particular a high-boiling alcohol such as glycerol or propylene glycol, can be evaporated. The sintered body 28 has a porosity of more than 50 vol % in order to be able to take up a large amount of carrier liquid and to be able to release the carrier liquid with the dissolved flavoring substances and/or stimulants, such as in particular nicotine, over a sufficiently long time.

(29) The glass used for the sintered body 28 preferably has a coefficient of linear thermal expansion α in a range from 2.5 ppm/K (i.e. 2.5.Math.10.sup.−6K.sup.−1) to 10.5 ppm/K, preferably in a range from 3.0 ppm/K to 10.0 ppm/K. Transition temperatures T.sub.g of greater than 450° C., in particular greater than 500° C. are particularly preferred. Suitable glasses are disclosed herein.

(30) FIG. 9 shows an exemplary embodiment of an evaporator unit 22 in which the heating element 26 is disposed directly on the sintered body 28. In particular, the heating element 26 is firmly connected to the sintered body 28. Such a connection can in particular be achieved if the heating element 26 is provided in the form of a sheet resistor. For this purpose, an electrically conductive sheet resistor type coating patterned in the form of a conductive path is applied onto the sintered body 28. A coating that is directly applied to the sintered body 28 as a heating element 26 is advantageous in order to achieve good thermal contact which provides for fast heating, inter alia. In the present illustrated example, enlarged contacts 261, 262 are provided in the conductive coating, at which the sheet resistor can be electrically contacted. The electrical connection can be established to mating contacts in the mouthpiece 25 when the liquid reservoir 24 is inserted, for example.