METHOD FOR DETERMINING THE ADDITIVE CONTENT IN TOBACCO PAPER FOR ELECTRIC CIGARETTES

Description

[0001] The present invention relates to a method for measuring an additive content in a tobacco paper for electronic cigarettes.

[0002] Glycerin (E422) is an additive used as a humectant in tobacco products. In cigarette and pipe tobacco, the humectant is primarily used to extend the product's storage life and prevent it from drying out. In shisha tobacco, higher amounts of humectant are added to the tobacco to prevent the tobacco from burning and to produce the densest vapor possible. Glycerin is also used as a vaporizer in electronic cigarettes, where it produces a dense white vapor when heated.

[0003] During the production of a certain type of electronic cigarette, glycerin, binders, flavorings, tobacco, and other aerosol-forming additives are mixed into a paste. This paste is rolled and dried, creating what is known as tobacco paper. This tobacco paper is then crimped, for example, in a crimper, and processed into a strand. A defined amount of glycerin is added during the production of the paste. However, an undefined amount can be lost during the drying process. Subsequent control of the glycerin content is therefore very important for quality assurance of the final product.

[0004] DE 10 2007 041 429 A1 discloses a method for measuring a moisture content value F of dielectric materials using at least one microwave resonator. A shift in the resonance frequency A is evaluated for at least two resonance modes with mutually different resonance frequencies, and a density-independent moisture content value is calculated from the measured resonance frequency shifts. It is known to measure the resonance frequency shifts for widely separated resonance frequencies. One resonance frequency is measured at a frequency below 1 GHz, while the other resonance frequency shift is measured at a frequency above 7 GHz.

[0005] WO 2017 / 080982 A1 discloses a device and a method for determining the proportion of at least one additive in a tobacco-containing substance. To determine the proportions of tobacco and water, two measured variables are obtained from an alternating electromagnetic field. It is further explained that to determine the proportion of at least one further additive, a further measured variable must be obtained by measuring with a second alternating electromagnetic field at a second measuring frequency. By measuring the measured variables, for example the magnitude and phase of the alternating electromagnetic fields or resonance shift and resonance broadening, at two different measuring frequencies independently of one another, a total of four measured variables are available from which conclusions can be drawn about the weight proportions of tobacco, water, and the at least one additive.It should also be noted that, in principle, three measured variables are sufficient to determine tobacco, water, and an additive, but four measured variables further increase the accuracy of the measurement. This approach, known from the prior art, consists in advantageously determining the moisture content and the weight fractions of the tobacco and the additive from the at least four measured variables in a data processing device as the best solution of an overdetermined system of equations, for example, with minimum squares of error. The weight fractions of additives can be determined in addition to the moisture content and the weight fraction of the tobacco.

[0006] The invention is based on the object of providing a method for measuring the additive content in a tobacco paper which provides the most accurate values ​​possible using simple means.

[0007] According to the invention, the object is achieved by the method having the features of claim 1. Advantageous embodiments form the subject matter of the subclaims.

[0008] The method according to the invention is intended to measure the additive content in tobacco paper for electronic cigarettes as accurately as possible. The additive content is determined in volume % or weight %. The tobacco paper is produced from a pasty mass of additives, water, flavorings, and tobacco, whereby the pasty mass is preferably dried after a rolling step to form a single-ply tobacco paper. During the drying process, an unpredictable amount of additives and water escapes, so that a measurement must be taken to determine the additive content of the tobacco paper. The measurement is carried out using at least one microwave resonator with two resonance modes at two different resonance frequencies.The smaller of the two resonance frequencies lies in a frequency range of less than 1 GHz, the larger of the two resonance frequencies has values ​​of more than 2 GHz, whereby the lower range can lie in a lower microwave range of 800 MHz. For each of the two resonance frequencies, a density-independent moisture value is calculated, with the additive content being determined depending on the two density-independent moisture values. The density-independent moisture value is preferably a density-independent moisture angle. The respective density-independent moisture value is characterized by the fact that it is independent of the density and indicative of a moisture content in the material being measured. Unlike the prior art, instead of four measured values ​​being combined to form a system of equations, the values ​​obtained from the two resonance modes are processed to form density-independent moisture values.By determining the additive content independently of the tobacco content using a density-independent parameter such as the moisture content angle, significantly more accurate values ​​can be achieved. In physical terms, this means that the evaluation of state variables that are represented as intensive state variables yields significantly better results than the evaluation of extensive state variables.

[0009] Glycerin is the preferred additive in the tobacco processing industry. Especially with glycerin, the density-independent moisture values ​​provide very accurate results.

[0010] In a preferred embodiment, the glycerol content g is determined linearly from both humidity angles and an offset value. It is important for the glycerol content g that both humidity values, i.e., both the resonance frequency in the high-frequency range and the resonance frequency in the microwave range, contribute to the glycerol content.

[0011] In a similarly preferred further development, a moisture content for the tobacco paper is measured based on the moisture content at the higher frequency. It is important to note that the measurement of the moisture content of the tobacco paper depends only on the density-independent moisture content at the higher frequency, and any contributions from the lower resonance frequency can be neglected. This behavior is not observed when measuring the glycerol content, as this depends on both moisture values.

[0012] In a preferred embodiment, the at least one microwave resonator is designed as a planar sensor. The planar sensor has a field emerging from the resonator body that interacts with the measurement object. When using a planar sensor, the tobacco paper is filtered over a flat sensor surface and transported through a measurement field.

[0013] In addition to planar sensors, gap sensors can also be provided in which the tobacco paper is transported through a gap through a resonator cavity.

[0014] In one possible embodiment, the measurement can be performed directly on the single-ply tobacco paper. However, it has been found that the measurement can also be performed on the tobacco paper wound into a reel. In principle, it is also possible to perform both measurements consecutively. Alternatively or additionally, the measurement can also be performed during or directly after the drying step. The measurement can be performed after the drying process has been completed or at a defined time during the drying process.

[0015] In a preferred embodiment, it is possible to measure the glycerol content of the tobacco paper before it is further processed into a strand, i.e. before it enters the crimper.

[0016] The measuring method according to the invention is highly reliable and can control the addition of water and / or glycerin to the slurry depending on the measured moisture values. In this way, a desired value for the glycerin and moisture content can be adjusted.

[0017] In a preferred embodiment, the humidity value is a humidity angle. The humidity angle is determined as the quotient of the resonance frequency shift and the broadening of the half-width. The resonance frequency shift compares the frequency changes in Hertz between an empty and a filled resonator. The half-width of the resonance curve with an unfilled resonator is also considered. Instead of the half-width, it is also possible to consider other variables caused by the damping of the resonance, such as the amplitude of the resonance curve. It has proven advantageous to determine the humidity angle as the arc tangent of the density-independent quotient of the resonance frequency shift and the broadening of the half-width.

[0018] The method according to the invention is explained in more detail below using an exemplary embodiment. The figures show: Figure 1 shows a schematic view of locations for glycerol measurement in the primary, Figure 2 shows possible locations for glycerol measurement in the crimper, Figure 3 shows the measured values ​​for the humidity angle of two modes as a function of moisture and glycerol content, and Figure 4 shows results of the glycerol measurement.

[0019] Figure 1shows a very schematic view of a mixer 10 in which glycerin is mixed with water, binding agents, flavorings, other aerosol-forming additives, and tobacco to form a slurry for use in electronic cigarettes. The exemplary embodiment is based on glycerin, but other additives with or without glycerin can be used and measured in the same way. The ingredients are added in precisely defined proportions and processed in the mixer to form a homogeneous mixture in the form of a slurry. The slurry thus formed is rolled in a rolling machine 12 and fed as flat material to the dryer 14. The drying process takes place in the dryer 14, during which an undefined amount of water and glycerin is lost from the tobacco paper. The dried tobacco paper is rolled up into a reel 16.Possible measuring stations MP for monitoring moisture and measuring glycerin content are located, for example, in dryer 14, on the route of the dried tobacco paper from dryer 14 to reel 16, and directly at reel 16. The obtained values ​​for the glycerin content and / or moisture content can be fed back to mixer 10 to adjust the glycerin content to a desired value. Control of the moisture content is also possible. The measured values ​​can also be used to adjust the drying process parameters to the desired values ​​for moisture and glycerin.

[0020] Figure 2shows a schematic view of how tobacco paper 18 is unwound from the reel 16 along the transport direction T. The tobacco paper is fed to a crimper 20 via transport rollers 18. Paper 22 for strand wrapping is also fed to the crimper 20 to be formed into a strand in the area 24. The possible measuring stations MP are located along the path from the reel to the crimper 20, where additional paper is fed to form the strand.

[0021] Figure 3 shows the moisture content values ​​(moisture content in %) plotted against the humidity angle Φ for two frequencies of 0.9 GHz and 5.6 GHz. The humidity angle Φ is calculated as the arctangent of the quotient of B / A, where A describes the resonance frequency shift and B the broadening of the resonance curve.

[0022] The measurements were performed at different glycerol and moisture contents. The second measurement was taken on the same material for the higher frequency.

[0023] The measurement at 5.6 GHz shows that the humidity angles Φ are independent of the glycerol content of the samples and depend only on their moisture content. This results from the proportionality of humidity angle and moisture content at different glycerol contents. Therefore, the Figure 3 The regression line shown can be used as a calibration for a glycerol-independent moisture measurement.

[0024] The measurement at 0.9 GHz, however, shows that the measured moisture angles Φ depend on both the moisture and glycerol content. Samples with the same glycerol content are identified in the figure by separate linear regressions. To compensate for the influence of varying material moisture content, the moisture angles Φ of both frequencies must be considered when measuring the glycerol content.

[0025] Figure 4 shows the result of the evaluation, with the reference value for the glycerol content plotted against the measured glycerol value. The calculation is performed using the humidity angles Φ of both frequencies in the calibration equation shown below. The good agreement of the values ​​with the best-fit line is clearly visible, with the measured values ​​deviating from the reference values ​​by only a few percent.

[0026] For the humidity measurement, the measured value of the resonance mode with the high frequency Φ H is used. An approach for the humidity value u is: u = a 1 • Φ H + a 2 where a 1 , a 2 represent calibration coefficients. Once the calibration coefficients are determined, the humidity value can be determined directly from the measured humidity angle Φ H .

[0027] To determine the glycerol content, the humidity angle of both modes is used: g = b 1 • Φ L + b 2 • Φ H + b 3 where b 1 , b 2 , and b 3 are the calibration coefficients. It is important to note that both moisture angles are considered mass-independent variables in the determination of the glycerol content, thus making the measurement of moisture and glycerol content independent of the mass of the sample. The mass fraction of the sample, determined as in the prior art using a potentially overdetermined system of equations, impairs the measurement accuracy. The additional determination of the tobacco content cannot be performed with the inventive approach, which relies on mass-independent measurement variables.

Claims

1. Method for measuring the additive content in tobacco paper for electric cigarettes, which is produced from a pulpy mass of additives, water, flavorings, and tobacco, wherein the pulpy mass is dried to form a single-layer tobacco paper, characterized in that the tobacco paper is measured with at least one microwave resonator with two resonance modes with two resonance frequencies (fL, fH) is measured, wherein the smaller of the two resonance frequencies (fL) lies in the frequency range of less than 1 GHz and the larger of the two resonance frequencies lies in the microwave range of more than 2 GHz, a density-independent moisture value (ΦL,H) is calculated for each of the two resonance modes, and the glycerol content (g) is determined as a function of the two moisture values (ΦL,H).

2. Method according to claim 1, characterized in that the additive consists completely or partially of glycerin.

3. Method according to claim 1 or 2, characterized in that the additive content (g) depends linearly on both density-independent moisture values (ΦL,H) and an offset value.

4. Method according to one of claims 1 to 3, characterized in that a moisture content for the tobacco paper is measured as a function of the density-independent moisture value (ΦH) at the higher frequency.

5. Method according to one of claims 1 to 4, characterized in that the additive content (g) is determined independently of the mass of the tobacco paper.

6. Method according to one of claims 1 to 5, characterized in that the at least one microwave resonator has a planar sensor.

7. Method according to one of claims 1 to 6, characterized in that the at least one microwave resonator has a gap sensor.

8. Method according to one of claims 1 to 7, characterized in that the measurement is performed on the single-layer tobacco paper.

9. Method according to one of claims 1 to 8, characterized in that the measurement is performed on the tobacco paper wound into a bobbin.

10. Method according to one of claims 1 to 9, characterized in that the measurement is performed in or directly after the dryer.

11. Method according to one of claims 1 to 10, characterized in that the measurement is carried out before a crimping device.

12. Method according to one of claims 1 to 11, characterized in that the addition of water and / or glycerin to the pulpy mass is carried out depending on at least one of the density-independent moisture values.

13. Method according to one of claims 1 to 12, characterized in that a moisture value (Φ) is provided as the moisture value, which is determined as the quotient of the broadening of the half-value width (B) and the resonance frequency shift (A), wherein empty and filled resonators are compared with each other.

14. Method according to one of claims 1 to 12, characterized in that the moisture value is a moisture value (Φ), which is the arctangent of the quotient of the spread of the half-value width (B) and the resonance frequency shift (A).