A method for preparing reconstituted tobacco leaf having electromagnetic induction heating function

Abstract

The present application belongs to the field of reconstituted tobacco preparation, and particularly relates to a preparation method of reconstituted tobacco with electromagnetic induction heating function. The preparation method comprises the following steps: A, preparing sodium citrate stabilized silver nano colloidal solution; B, preparing silver nanoparticle-mint alcohol composite crystal; C, mixing smoking agent, adhesive, silver nanoparticle-mint alcohol composite crystal, and then adding tobacco powder to obtain a mixture; D, quickly and uniformly mixing the mixture with water to prepare slurry; E, casting the slurry as the slurry of the thick slurry method reconstituted tobacco process for once drying; F, re-drying the reconstituted tobacco obtained in step D after pressing. The present application uses slurry with silver nanoparticles to prepare reconstituted tobacco, so that the reconstituted tobacco has electromagnetic characteristics and can be stably heated and smoked. The silver nanoparticles as receptors are uniformly distributed in the reconstituted tobacco, which can make the heating uniform. This avoids the problem of local uneven heat after the existing reconstituted tobacco is heated by the central receptor.

Description

Technical Field

[0001] This invention belongs to the field of reconstituted tobacco preparation, specifically relating to a method for preparing reconstituted tobacco with electromagnetic induction heating function. Background Technology

[0002] When people smoke tobacco products, their respiratory cells suffer varying degrees of damage due to direct exposure to the smoke. Tobacco companies have been working to reduce this damage by processing tobacco to minimize its harmfulness. Various methods have been developed, among which heating reconstituted tobacco leaves without burning them is a particularly effective approach.

[0003] Existing heating methods include resistance heating and electromagnetic induction heating. Electromagnetic induction heating involves inserting a sensor at the center of the cigarette's smoking section. The sensor generates heat due to eddy currents induced by the electromagnetic field within the heating device. However, this method leads to uneven heating; tobacco near the sensor is overheated, while tobacco further away is underheated.

[0004] This application is submitted in order to address the aforementioned issues. Summary of the Invention

[0005] This application provides a method for preparing reconstituted tobacco leaves with electromagnetic induction heating function, the preparation method comprising the following steps:

[0006] A. Prepare a 0.01-0.02M silver nitrate aqueous solution, stir, and control the temperature at 0-5℃. Then add 0.5-2wt% sodium citrate aqueous solution to the silver nitrate aqueous solution, and then slowly add 0.01-0.3M sodium borohydride aqueous solution dropwise, so that the molar ratio of silver ions to sodium borohydride is 1:(1.3-1.7). After the addition is complete, continue stirring for 20-40 minutes, and let it stand at room temperature for 1.5-2.5 hours to obtain sodium citrate-stabilized silver nanosol, which can be stored at 4℃ in the dark for later use.

[0007] The volume ratio of the silver nitrate aqueous solution, the sodium citrate aqueous solution, and the sodium borohydride aqueous solution is 100:(5-15):(70-80);

[0008] B. Dissolve menthol in ethanol to obtain a menthol ethanol solution; then, add the sodium citrate-stabilized silver nanoparticle sol obtained in step A into the menthol ethanol solution, disperse it evenly by ultrasonication, and crystallize it at low temperature of -10℃ to 0℃ for 2 to 4 hours. After filtration, dry it below 40℃ to remove residual ethanol to obtain silver nanoparticle-menthol composite crystals.

[0009] The concentration of the menthol ethanol solution is 0.1-0.3 g / mL, and the volume ratio of sodium citrate-stabilized silver nanoparticles to the menthol ethanol solution is 1:(1-3).

[0010] C. Mix the smoke-generating agent with the adhesive to obtain a mixed solution. Then, mix the silver nanoparticle-menthol composite crystals obtained in step B with the mixed solution. Then, add raw materials containing tobacco powder and plant fiber to obtain a mixture.

[0011] D. Quickly and uniformly mix the mixture with water to prepare a slurry with a water content of 75-85%;

[0012] E. The slurry obtained in step D is used as the slurry for the thick slurry reconstituted tobacco process. After casting, it is dried once to make the moisture content of the reconstituted tobacco 12%.

[0013] F. After pressing the reconstituted tobacco leaves obtained in step D with a pressure roller, dry them again so that the moisture content of the reconstituted tobacco leaves is 9-10% and the linear pressure of the pressure roller is 100-200 N / cm.

[0014] Preferably, the mixing time in step D is controlled to be 10s~60s.

[0015] Preferably, in step C, the smoke-generating agent is glycerol and / or propylene glycol.

[0016] Preferably, in step E, the primary drying process employs a combination of steel belt heating and hot air drying, with the steel belt temperature at 5-95°C and the hot air temperature at 75-85°C.

[0017] Preferably, in step E, the secondary drying is carried out by hot air drying at a temperature of 60-70°C.

[0018] The second aspect of this application provides a heated cigarette with electromagnetic induction heating function, wherein the tobacco segment of the heated cigarette contains reconstituted tobacco obtained by the preparation method described in the first aspect.

[0019] The beneficial effects of this invention are:

[0020] 1. This invention uses a slurry containing silver nanoparticles to prepare reconstituted tobacco leaves, giving them electromagnetic properties that allow for stable heating and tobacco production. The silver nanoparticles, acting as receptors, are uniformly distributed within the reconstituted tobacco leaves, ensuring even heating. This avoids the problem of uneven heat distribution in existing reconstituted tobacco leaves, where heating occurs through a central receptor.

[0021] 2. This invention first uses sodium citrate to surface-modify and electrostatically stabilize silver nanoparticles, preventing their aggregation. Then, it uses low-temperature crystallization with menthol to embed the stabilized silver nanoparticles entirely within the crystal, forming a solid composite crystal. This structure completely solves the problem of pure silver nanosol easily becoming free, migrating, and detaching during the preparation of reconstituted tobacco leaves, ensuring that the electromagnetic heating functional particles are firmly fixed in the tobacco leaf matrix, while also guaranteeing heating uniformity and product structural stability.

[0022] Menthol is encapsulated in crystals, making it less volatile during tobacco drying and rolling. It slowly releases a cool aroma when burning, enhancing the smoking experience.

[0023] Silver nanoparticles not only provide electromagnetic heating, but also have antibacterial and antifungal properties, inhibiting the growth of mold and bacteria during the storage of reconstituted tobacco leaves, extending shelf life, and reducing mold growth.

[0024] 3. Traditional thick slurry casting relies on gravity casting, resulting in fibers that are prone to longitudinal orientation, loose structure, low strength (especially weak in the transverse direction), and easy cracking / dusting. The pressure-driven slurry forming process of this application uses pressure rollers for secondary pressing, enabling the reconstituted tobacco leaves to achieve fiber rearrangement and interweaving under pressure, with dense particle packing, reduced porosity, increased density, uniform adhesive penetration, stronger interfacial bonding, and more uniform wet film thickness with fewer defects. During subsequent drying, the reconstituted tobacco leaves are less prone to cracking. Detailed Implementation

[0025] The present invention will be described below with reference to specific embodiments, but the implementation of the present invention is not limited thereto. Experimental methods not specifically described in the embodiments generally use conventional conditions and conditions described in the manual, or conditions recommended by the manufacturer. The general equipment, materials, reagents, etc., used are all commercially available unless otherwise specified. The raw materials used in the following embodiments and comparative examples are all commercially available.

[0026] Example 1

[0027] First, reconstituted tobacco leaves containing silver nanoparticles were prepared as follows:

[0028] Step 1: Preparation of silver nanoparticle-menthol composite crystals

[0029] A. Prepare 100 mL of 0.01 M silver nitrate aqueous solution and place it in a three-necked flask. Stir magnetically at 300 rpm for 15 minutes, then place the three-necked flask in an ice-water bath and control the temperature at 0℃.

[0030] Add 10 mL of 1 wt% sodium citrate solution to a three-necked flask. Sodium citrate acts as a stabilizer to prevent the agglomeration of silver nanoparticles.

[0031] Then, 75 mL of 0.02 M sodium borohydride (NaBH4) aqueous solution was slowly added dropwise to a three-necked flask at a rate of 1 drop / second. The solution changed from colorless to bright yellow, and then to brownish-yellow. The molar ratio of silver ions to sodium borohydride was 1:1.5. Stirring was continued for 30 min, followed by aging at room temperature for 2 h to obtain sodium citrate-stabilized silver nanosol. The concentration of silver nanoparticles was approximately 1 mM, with a particle size of 10-20 nm. The sodium citrate-stabilized silver nanosol was stored at 4 °C in the dark for later use.

[0032] In this process, sodium borohydride acts as a strong reducing agent, reducing silver ions to elemental silver nanoparticles at low temperatures. Sodium citrate, as a surface ligand, adsorbs onto the particle surface, providing electrostatic or steric hindrance to inhibit particle aggregation and control particle size. Low temperatures of 0-5 degrees Celsius slow down the reduction rate, preventing rapid particle growth and aggregation, and ensuring uniform particle size. Slowly adding the reducing agent prevents excessively high local concentrations, which could lead to uneven particle morphology and size.

[0033] B. The above-mentioned sodium citrate-stabilized silver nano-sol was added to a menthol ethanol solution and ultrasonically dispersed evenly. Then, it was crystallized at -10℃ for 2 hours. After sieving the crystals, they were dried in an oven at 30℃ to remove residual ethanol and a small amount of water, thus obtaining silver nanoparticle-menthol composite crystals.

[0034] The ultrasonic power was 600 W, the frequency was 40 kHz, and the ultrasonic time was 10 minutes. The menthol ethanol solution was prepared by dissolving menthol in anhydrous ethanol, and the concentration of menthol was 0.1 g / mL. The volume ratio of sodium citrate-stabilized silver nanoparticles to the menthol ethanol solution was 1:2.

[0035] During this process, the solubility of menthol decreases rapidly at low temperatures and crystallizes in a directional manner, encapsulating and embedding the dispersed silver nanoparticles inside the crystals, thereby fixing the silver nanoparticles and preventing powder from falling off.

[0036] Preserving silver nanoparticles as silver nanoparticle-menthol composite crystals is beneficial for the fixation of silver nanoparticles in reconstituted tobacco.

[0037] Step 2, the method for preparing reconstituted tobacco using the slurry method is as follows:

[0038] Mixing: The following components are mixed evenly according to their respective weight proportions to obtain the raw materials: 62 kg tobacco powder, 5 kg silver nanoparticle-menthol composite crystals, 3 kg guar gum, 6 kg propylene glycol, and 9 kg glycerin.

[0039] The mixing method is as follows: First, take all of the propylene glycol and glycerol from the formula and mix them in a compound solvent at room temperature. Then, add guar gum and continue stirring until the guar gum is completely swollen and dispersed without any gel or lumps, thus obtaining a guar gum alcohol sol. Next, mix the silver nanoparticle-menthol composite crystals with the guar gum alcohol sol, and then add tobacco powder to obtain a mixture. In the above process, the alcohol phase environment of propylene glycol and glycerol is used to encapsulate the composite crystals, isolating them from the large amount of free water introduced by subsequent water addition, delaying the dissolution and release of menthol, and preventing the silver nanoparticles from agglomerating upon contact with water, thus providing protection for subsequent mixing and pulping.

[0040] Pulping: 340 kg of water was added to the mixture at a mass ratio of 1:4 to prepare a slurry with a water content of 80%. During this process, the mixture and water were rapidly and uniformly mixed for 10-60 seconds. In this embodiment, a high-speed dispersing paddle was used with a stirring speed of 800 r / min and a mixing time of 20 seconds. Then, casting was immediately performed to ensure that the silver nanoparticle-menthol composite crystals were not mostly dissolved / swollen by the water.

[0041] Casting: After adding the above slurry to the casting box, the slurry is evenly cast onto the steel belt. This step uses standard operating procedures. For example, the steel belt speed is 8 m / min, and the scraper gap is 0.5 mm.

[0042] Primary drying: A combination of steel belt heating and hot air drying is used. The steel belt surface temperature is 90℃, the hot air temperature is 80℃, and the reconstituted tobacco leaves are dried until the moisture content is 12%.

[0043] Pressure molding: The reconstituted tobacco leaves, after being dried once, are pressed by a pair of pressure rollers with a linear pressure of 150 N / cm. Under this pressure, the reconstituted tobacco leaves are not crushed or the pulp is squeezed out.

[0044] Secondary drying: The reconstituted tobacco leaves are conveyed by a fiber mesh belt to a drying zone with hot air at 60°C for drying. After drying, the moisture content of the reconstituted tobacco leaves is 10%, and then they are rolled up and stored.

[0045] Comparative Example 1

[0046] The difference from Example 1 is that the sodium citrate-stabilized silver nanosol obtained in step A of step one is used directly to replace the silver nanoparticle-menthol composite crystals in step two, while the other steps remain unchanged, to obtain reconstituted tobacco leaves.

[0047] Comparative Example 2

[0048] The difference from Example 1 is that step two, pressure molding, is omitted, while other steps remain unchanged.

[0049] The tensile strength and dust loss rate of the reconstituted tobacco leaves from Example 1, Comparative Example 1, and Comparative Example 2 were tested, and the results are shown in Table 1 below.

[0050] Comparative Example 3

[0051] Tobacco powder, silver nanoparticle-menthol composite crystals, guar gum, propylene glycol, and glycerin were weighed in the same proportions as in Example 1 and added to a mixing tank along with 340 kg of water. The mixture was stirred at 400 r / min for 20 min until the materials were evenly mixed to prepare a slurry with a moisture content of 80%, which was then immediately cast.

[0052] Tensile strength was determined according to the national standard GB / T 12914-2018 (Determination of Tensile Strength of Paper and Paperboard - Constant Rate Tensile Method (20 mm / min)). Dust shedding rate was determined according to the method in Example 1 of patent CN110398438B; the mass loss rate was the dust shedding rate. Samples were tested after equilibration at (20±2)℃ and (60±2)%RH for 48 hours. Three groups were selected for each test, and the average result was taken.

[0053] Table 1

[0054]

[0055] As can be seen from Table 1:

[0056] Compared to Example 1, in Comparative Example 1, silver nanosol stabilized by sodium citrate was used instead of silver nanoparticle-menthol composite crystals. The silver particles were not fixed by crystals, which led to an increase in the dust loss rate of the reconstituted tobacco product.

[0057] Compared to Example 1, Comparative Example 2 lacked a pressure molding step, resulting in a decrease in the tensile strength of the reconstituted tobacco leaves and a slight increase in the dust loss rate.

[0058] Compared to Example 1, Comparative Example 3, without the pre-coating protection of alcoholic liquid, resulted in a significant loss of menthol and aggregation of silver nanoparticle-menthol composite crystals after prolonged immersion and stirring, ultimately increasing the dust loss rate of the reconstituted tobacco product.

[0059] This indicates that the method in Example 1 of this application significantly improves the tensile strength of reconstituted tobacco leaves and reduces the powder loss rate of silver particles.

Claims

1. A method for preparing reconstituted tobacco leaves with electromagnetic induction heating function, characterized in that, The preparation method includes the following steps: A. Prepare a 0.01-0.02M silver nitrate aqueous solution, stir, and control the temperature at 0-5℃. Then add 0.5-2wt% sodium citrate aqueous solution to the silver nitrate aqueous solution, and then slowly add 0.01-0.3M sodium borohydride aqueous solution dropwise, so that the molar ratio of silver ions to sodium borohydride is 1:(1.3-1.7). After the addition is complete, continue stirring for 20-40 minutes, and let it stand at room temperature for 1.5-2.5 hours to obtain sodium citrate-stabilized silver nanosol. The volume ratio of the silver nitrate aqueous solution, the sodium citrate aqueous solution, and the sodium borohydride aqueous solution is 100:(5-15):(70-80); B. Dissolve menthol in ethanol to obtain a menthol ethanol solution; then add the sodium citrate-stabilized silver nanoparticle sol obtained in step A into the menthol ethanol solution, disperse it evenly by ultrasonication, and crystallize it at low temperature at -10℃~0℃ for 2~4 h. After filtration, dry it at 10-40℃ to remove residual ethanol to obtain silver nanoparticle-menthol composite crystals. The concentration of the menthol ethanol solution is 0.1-0.3 g / mL, and the volume ratio of sodium citrate-stabilized silver nanoparticles to the menthol ethanol solution is 1:(1-3). C. Mix the smoke-generating agent with the adhesive to obtain a mixed solution; then, mix the silver nanoparticle-menthol composite crystals obtained in step B with the mixed solution, and then add raw materials containing tobacco powder and plant fiber to obtain a mixture; D. Quickly and uniformly mix the mixture with water to prepare a slurry with a water content of 75-85%; E. The slurry obtained in step D is used as the slurry for the thick slurry reconstituted tobacco process. After casting, it is dried once to make the moisture content of the reconstituted tobacco 12%. F. After pressing the reconstituted tobacco leaves obtained in step D with a pressure roller, dry them again so that the moisture content of the reconstituted tobacco leaves is 9-10% and the linear pressure of the pressure roller is 100-200 N / cm.

2. The preparation method according to claim 1, characterized in that, In step E, the primary drying process employs a combination of steel belt heating and hot air drying, with the steel belt temperature at 5-95℃ and the hot air temperature at 75-85℃.

3. The preparation method according to claim 1, characterized in that, In step E, the secondary drying is carried out using hot air drying at a temperature of 60-70℃.

4. A heated cigarette with electromagnetic induction heating function, characterized in that, The tobacco segment of the heated cigarette contains reconstituted tobacco obtained by the preparation method according to claims 1-3.

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