Heat-conducting glue for reconstituted tobacco as well as preparation method and application of heat-conducting glue

Abstract

The invention relates to the field of tobaccos, in particular to reconstituted tobacco heat-conducting glue and a preparation method and application thereof. The natural polymer adhesive and the metal heat-conducting filler are combined, the viscosity of the adhesive and the particle size of the metal filler are adjusted and limited, or the metal filler is subjected to heating and surface modification treatment, and the adhesive and the metal filler are simply blended, so that the heat-conducting adhesive with high stability, high safety and good heat-conducting property can be obtained. The reconstituted tobacco is prepared by using the heat-conducting glue, the heat-conducting filler is uniformly distributed in the reconstituted tobacco, and the heat-conducting property of the reconstituted tobacco is good. Therefore, the method has the advantages of being low in cost, easy to operate, high in safety and the like, and the prepared reconstituted tobacco is good in heat conduction performance and has wide application potential in the field of heated cigarettes.

Description

Technical Field

[0001] The invention belongs to the field of tobacco manufacturing, and particularly relates to a heat-conducting adhesive for reconstituted tobacco leaves, a preparation method and an application thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] The rapid development of new tobacco products may trigger a revolution in the tobacco industry. Major tobacco companies around the world have been deploying new tobacco products. Heat-not-burning (HnB) tobacco products, also known as heated cigarettes, belong to the category of tobacco products and are the new tobacco products closest to traditional cigarettes. Heated cigarettes have the characteristics of "heating tobacco or tobacco extracts instead of burning tobacco", which reduces the harmful components produced by high-temperature combustion and cracking of tobacco, and greatly reduces the release of chemical components in mainstream smoke.

[0004] When smoking heated cigarettes, whether using peripheral heating or internal core heating, due to the low thermal conductivity of the tobacco itself and the limitations of the area of ​​the heating components, the heat conduction is not uniform, and the precipitation of volatile components of tobacco in different areas is inconsistent. The temperature of the tobacco material close to the heat source is higher, and the atomization medium, aroma components and external flavors and fragrances contained in the tobacco material can be better atomized and volatilized, while the temperature of the tobacco material far from the heat source is lower, and these volatile substances contained in the tobacco material cannot be effectively atomized and volatilized.

[0005] Reconstituted tobacco is the smoking substrate for heated cigarettes. It is usually a sheet-shaped substrate formed by mixing tobacco powder, stem powder, smoke agent, water, CMC and other fillers, rolling (scraping) and drying. However, due to the inherent low thermal conductivity of tobacco materials and other additives, as well as the porous and fluffy microstructure of reconstituted tobacco, the thermal conductivity of reconstituted tobacco is low. Due to the loose structure of reconstituted tobacco, it is difficult to improve the thermal conductivity of reconstituted tobacco itself.

[0006] In the prior art, the thermal conductivity of reconstituted tobacco is mainly improved by adding thermal conductive fillers. Thermal conductive fillers can be divided into metals, ceramic nitrides, carbon and carbides, and metal oxides. Metal particles have high thermal conductivity, but their density and hardness are usually very high. During the processing of reconstituted tobacco, flocculation will occur, and metal particles are prone to oxidation or reaction with reconstituted tobacco components; ceramic nitrides also have high thermal conductivity and stable properties, but their hardness is too high, which will damage the cutting equipment during the processing and slicing of reconstituted tobacco leaves; carbon materials such as graphene and carbon nanotubes have the highest thermal conductivity at present, but reconstituted tobacco leaves need to be heated at 350°C, which is easy to produce carbon-containing oxide impurities, affecting the quality of reconstituted tobacco leaves. Secondly, additives such as graphene and carbon nanotubes may precipitate from reconstituted tobacco leaves and enter the human mouth and lungs with smoke. Moreover, carbon materials will make the color of reconstituted tobacco leaves black, affecting the appearance quality of the product.

[0007] In the prior art, thermally conductive fillers are usually directly mixed with tobacco powder to make reconstituted tobacco leaves. The thermally conductive fillers are easily dispersed unevenly, resulting in poor thermal conductivity, and the fillers are easily precipitated, causing harm to the human body; or the thermally conductive fillers are dissolved in a solvent to make a slurry, and then the slurry is coated on the surface of the tobacco. Since the thermally conductive fillers only exist on the surface of the tobacco, the improvement of the thermal conductivity of the tobacco is limited. Summary of the invention

[0008] In order to solve the above problems, the present invention provides a preparation method of reconstituted tobacco leaf thermal conductive adhesive and its application. The present invention develops a low-cost, simple-operation, and high-safety method to improve the thermal conductivity of reconstituted tobacco leaves, which is of great significance for improving the quality of heated cigarettes.

[0009] In order to achieve the above object, the present invention adopts the following technical solution:

[0010] The first aspect of the present invention provides a method for preparing a thermally conductive adhesive for reconstituted tobacco, comprising:

[0011] The adhesive matrix, the thermal conductive filler or the modified thermal conductive filler, the thickener and the solvent are uniformly mixed to obtain a thermal conductive adhesive;

[0012] The preparation method of the modified thermally conductive filler is as follows: heat-treating the thermally conductive filler, and then treating it with sodium bicarbonate and a silane coupling agent in sequence to obtain the modified thermally conductive filler.

[0013] In some embodiments, the adhesive matrix is ​​a natural polymer adhesive;

[0014] In some embodiments, the adhesive is selected from at least one of starch adhesive, xanthan gum, and carboxymethyl cellulose;

[0015] In some embodiments, the mass fraction of the adhesive colloid is between 1% and 10%;

[0016] In some embodiments, the viscosity of the adhesive ranges from 2000 to 5000 mPa·s.

[0017] In some embodiments, the thickener is selected from at least one of guar gum, xanthan gum, gelatin, soy protein, chitosan, and sodium alginate;

[0018] In some embodiments, the solvent is selected from at least one of glycerol, propylene glycol, ethanol, and water.

[0019] In some embodiments, the thermally conductive filler is a metal oxide, and the mass fraction of the thermally conductive filler in the adhesive is between 1% and 30%;

[0020] In some embodiments, the thermally conductive filler is selected from at least one of aluminum oxide, zinc oxide, magnesium oxide, and titanium oxide;

[0021] In some embodiments, the thermally conductive filler has a particle size of 200-500 mesh.

[0022] In some embodiments, the heat treatment temperature is 150-500°C.

[0023] In some embodiments, the specific steps of sequentially treating with sodium bicarbonate and a silane coupling agent include:

[0024] The metal oxide is mixed with a sodium bicarbonate solution with a mass fraction of 5 to 10%, stirred for 10 to 30 minutes, then allowed to stand for precipitation, filtered, and dried; the dried metal oxide is immersed in a silane coupling agent solution, reacted for 1 to 3 hours under anhydrous nitrogen conditions at 60 to 100° C., filtered, washed, and dried to obtain a metal oxide modified thermal conductive filler.

[0025] In some embodiments, the silane coupling agent is selected from at least one of aminopropyltriethoxysilane, methyltrichlorosilane, and γ-glycidyloxypropyltrimethoxysilane;

[0026] In some embodiments, the mass fraction of the silane coupling agent is 1-3%.

[0027] The second aspect of the present invention provides a thermally conductive adhesive for reconstituted tobacco prepared by the above method.

[0028] The third aspect of the present invention provides the use of the above-mentioned thermally conductive adhesive in the preparation of reconstituted tobacco leaves. The reconstituted tobacco leaves are prepared by a two-step method. First, the thermally conductive adhesive is synthesized, and then tobacco powder, stem powder, smoke-generating agent, wood pulp fiber, and water are mixed evenly to obtain a tobacco raw material mixture. Finally, the thermally conductive adhesive and the tobacco raw material mixture are mixed evenly, and the mixture is rolled or scraped and dried to obtain reconstituted tobacco leaves.

[0029] Beneficial Effects of the Invention

[0030] (1) The present invention uses natural polymer adhesive as the heat-conducting adhesive colloid, which can avoid the harmfulness and impurities caused by the use of organic synthetic adhesives, thereby improving the safety and sensory quality of heated cigarettes.

[0031] (2) The present invention adjusts the viscosity of the adhesive colloid within a certain range, and utilizes the viscosity of the colloid to evenly disperse the thermally conductive filler in the adhesive without agglomeration or sedimentation, thereby improving the dispersion uniformity of the thermally conductive filler.

[0032] (3) The present invention uses metal oxide as a thermal conductive filler, which has high thermal conductivity, high thermal stability, high safety and low density. The particle size of the metal oxide particles is between 200 and 500 meshes, which can prevent the thermal conductivity from being reduced due to a large particle size, and can also prevent the metal oxide with a particle size too small from precipitating from the reconstituted tobacco leaves and entering the human mouth and lungs with the smoke, thereby improving safety.

[0033] (4) The present invention pre-treats the metal oxide by heating, thereby removing impurities on the surface of the metal oxide and releasing impurities in advance, thereby avoiding the generation of odor during the use of the heated cigarette and affecting the sensory quality.

[0034] (5) The present invention can remove impurities on the surface of the metal oxide and improve the compatibility of the metal oxide with the adhesive by modifying the surface of the metal oxide, thereby preventing the metal oxide from agglomerating and settling in the adhesive, and improving the effect of the metal oxide on enhancing the thermal conductivity of the reconstituted tobacco leaves.

[0035] (6) Traditional processes mostly use a one-step method to prepare high thermal conductivity reconstituted tobacco, that is, directly adding thermal conductive fillers to reconstituted tobacco raw materials, and obtaining reconstituted tobacco through steps such as mixing, rolling, and drying. Since the density of thermal conductive fillers is greater than that of tobacco powder, they are easy to settle and agglomerate in the raw materials, resulting in poor uniformity. The present invention uses a two-step method to prepare high thermal conductivity reconstituted tobacco, that is, first synthesizing a thermal conductive adhesive, then mixing the thermal conductive adhesive with tobacco raw materials, and obtaining reconstituted tobacco through steps such as rolling, drying, etc., thereby improving the uniformity of the thermal conductive filler in the reconstituted tobacco.

[0036] (7) The preparation method of the thermal conductive adhesive of the present invention is simple, the thermal conductive adhesive is easy to use, and the cost of the adhesive colloid and the metal oxide is low, which greatly improves the economic benefits of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention, and the exemplary embodiments of the present invention and their description are used to explain the present invention and do not constitute improper limitations on the present invention.

[0038] Figure 1 .SEM image of reconstituted tobacco leaves filled with 10% mass fraction alumina thermal conductive adhesive;

[0039] Figure 2 .Chart showing the change in thermal coefficient of reconstituted tobacco leaves filled with different mass fractions of alumina thermal conductive adhesive. DETAILED DESCRIPTION

[0040] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0041] The present invention will be further described in detail below in conjunction with specific embodiments. It should be noted that the specific embodiments are intended to explain the present invention rather than to limit it.

[0042] In the following examples and comparative examples, all raw materials and reagents are commercially available products.

[0043] Example 1

[0044] a) Preparation of thermal conductive adhesive

[0045] 1. Select 300 mesh alumina, heat it at 200°C for 30 minutes, and after cooling, immerse it in a 10% mass fraction sodium bicarbonate solution and stir it for 30 minutes, and take it out after drying; 2. Prepare a solution of aminopropyl triethoxysilane and anhydrous ethanol at a ratio of 1:50, soak the alumina in it, heat it to 75°C in a water bath, keep it at a constant temperature for 3 hours, filter it, wash it with anhydrous ethanol, and dry it to obtain a surface-modified alumina thermal conductive filler; 3. Mix starch glue: water: modified alumina at a ratio of 1.0:2.0:0.6 to ensure that the thermal conductive material and the colloid are fully mixed and uniform; 4. Add solvent, and gradually add water and glycerin to the mixed thermal conductive material and colloid as needed to adjust the viscosity and fluidity of the colloid to ensure that the viscosity is 5000mPa·s; 5. Thoroughly mix and stir the thermal conductive material, colloid and solvent for 30 minutes until a uniform mixture is obtained.

[0046] b) Preparation of Reconstituted Tobacco Raw Material Mixture

[0047] The tobacco powder, stem powder, wood pulp fiber, CMC, glycerin, propylene glycol and water and other fillers are mixed in a ratio of 15:5:1:1:4:1:73, and stirred evenly to obtain a thick slurry of tobacco raw materials.

[0048] c) Preparation of reconstituted tobacco substrate

[0049] The prepared thermal conductive adhesive is added to the thick slurry in different proportions, and stirred evenly to obtain a reconstituted tobacco thick slurry.

[0050] d) Scraping and forming

[0051] The prepared reconstituted tobacco leaf slurry is scraped onto a substrate to form a slurry thin layer with a certain thickness.

[0052] e) Drying

[0053] The thick slurry thin layer is dried to obtain thick slurry method reconstituted tobacco leaves.

[0054] like Figure 2 As shown, after adding alumina thermal conductive adhesive, the thermal conductivity of the reconstituted tobacco leaves is greatly improved, and with the increase of alumina content, the thermal conductivity gradually increases. When 5wt% alumina is added, the thermal conductivity of the reconstituted tobacco leaves is increased by 29.2%.

[0055] Example 2

[0056] a) Preparation of thermal conductive adhesive

[0057] 1. Select 400 mesh magnesium oxide, heat it at 250°C for 1 hour, cool it to room temperature, heat it and immerse it in a 5% mass fraction sodium bicarbonate solution and stir it for 10 minutes, and take it out after drying; 2. Methyltrichlorosilane and anhydrous ethanol are prepared into a solution at a ratio of 1:100, and magnesium oxide is immersed in it. It is heated to 60°C in a water bath, kept at a constant temperature for 1 hour, filtered, washed and dried with anhydrous ethanol to obtain a surface-modified aluminum oxide thermal conductive filler; 3. Starch glue: water: modified magnesium oxide are mixed at a ratio of 1.0:2.0:1.0 to ensure that the thermal conductive material and the colloid are fully mixed and uniform; 4. Add solvent, and gradually add water and glycerin to the mixed thermal conductive material and colloid as needed to adjust the viscosity and fluidity of the colloid to ensure that the viscosity is 4000mPa·s; 5. The thermal conductive material, colloid and solvent are thoroughly mixed and stirred for 10 minutes until a uniform mixture is obtained.

[0058] b) Preparation of Reconstituted Tobacco Raw Material Mixture

[0059] The tobacco powder, stem powder and wood pulp fiber are mixed in a ratio of 7:3:2, and stirred thoroughly to obtain a tobacco raw material mixture.

[0060] c) Preparation of reconstituted tobacco substrate

[0061] The thermal conductive adhesive, tobacco raw material mixture, glycerin, propylene glycol and water are uniformly mixed in a certain proportion, wherein the proportion of tobacco raw material mixture, glycerin, propylene glycol and water is 64:12.8:3.2:16, and magnesium oxide accounts for 5% of the total mass fraction. The mixture is stirred evenly to obtain a reconstructed tobacco leaf matrix.

[0062] d) Roller pressing

[0063] The prepared reconstituted tobacco leaf matrix is ​​subjected to multi-stage rolling to form a thin sheet with a certain thickness.

[0064] e) Drying

[0065] The slices are dried to obtain roller-pressed reconstituted tobacco leaves.

[0066] After testing, it was found that the thermal conductivity of recycled tobacco leaves was improved by 24.5% after adding magnesium oxide thermal conductive adhesive.

[0067] Embodiment 3:

[0068] a) Preparation of thermal conductive adhesive

[0069] 1. Mix starch glue: water: alumina (300 mesh) according to 1.0:2.0:0.6 to ensure that the thermal conductive material and the colloid are fully mixed; 2. Add solvent. As needed, gradually add water and glycerin to the mixed thermal conductive material and colloid to adjust the viscosity and fluidity of the colloid to ensure that the viscosity is 5000mPa·s; 3. Thoroughly mix and stir the thermal conductive material, colloid and solvent for 30 minutes until a uniform mixture is obtained.

[0070] b) Preparation of Reconstituted Tobacco Raw Material Mixture

[0071] The tobacco powder, stem powder, wood pulp fiber, CMC, glycerin, propylene glycol and water and other fillers are mixed in a ratio of 15:5:1:1:4:1:73, and stirred evenly to obtain a thick slurry of tobacco raw materials.

[0072] c) Preparation of reconstituted tobacco substrate

[0073] The prepared thermal conductive adhesive is added to the thick slurry in different proportions, and stirred evenly to obtain a reconstituted tobacco thick slurry.

[0074] d) Scraping and forming

[0075] The prepared reconstituted tobacco leaf slurry is scraped onto a substrate to form a slurry thin layer with a certain thickness.

[0076] e) Drying

[0077] The thick slurry thin layer is dried to obtain thick slurry method reconstituted tobacco leaves.

[0078] According to tests, when 5wt% of alumina is added, the thermal conductivity of reconstituted tobacco leaves is improved by 23.4%.

[0079] Comparative Example 1

[0080] The difference from Example 1 is that the aluminum oxide is not heated. The sensory quality of the prepared heated cigarette products was evaluated, and some smokers felt that the smoke of the heated cigarette products prepared in Comparative Example 1 contained slight metallic impurities, which had a negative impact on the sensory quality. No metallic impurities were felt in the product of Example 1.

[0081] Comparative Example 2:

[0082] The difference from Example 1 is that the particle size of aluminum oxide is 100 mesh. Some metal particles of Comparative Example 2 settle in the adhesive. When 5wt% of aluminum oxide is added, the thermal conductivity of Comparative Example 2 is improved by 22.6%.

[0083] Comparative Example 3:

[0084] The ratio of raw materials is the same as that of Example 1, except that Comparative Example 3 adopts a one-step method to prepare reconstituted tobacco, that is, aluminum oxide, adhesive, tobacco powder and other reconstituted tobacco raw materials are directly blended, stirred evenly, and then rolled and dried to obtain reconstituted tobacco. The results show that aluminum oxide is unevenly dispersed in the reconstituted tobacco and agglomerates occur. When 5wt% of aluminum oxide is added, the thermal conductivity of Comparative Example 3 is improved by 19.4%.

[0085] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a thermally conductive adhesive for reconstituted tobacco, characterized in that: include: The adhesive matrix, the thermal conductive filler or the modified thermal conductive filler, the thickener and the solvent are uniformly mixed to obtain a thermal conductive adhesive; The preparation method of the modified thermally conductive filler is as follows: heat-treating the thermally conductive filler, and then treating it with sodium bicarbonate and a silane coupling agent in sequence to obtain the modified thermally conductive filler.

2. The method for preparing the thermally conductive adhesive for reconstituted tobacco according to claim 1, characterized in that: The adhesive matrix is ​​a natural polymer adhesive; Or, the adhesive is selected from at least one of starch adhesive, xanthan gum, and carboxymethyl cellulose; Or, the mass fraction of the adhesive colloid is between 1% and 10%; Alternatively, the viscosity of the adhesive is in the range of 2000 to 5000 mPa·s.

3. The method for preparing the thermally conductive adhesive for reconstituted tobacco according to claim 1, characterized in that: The thickener is selected from at least one of guar gum, xanthan gum, gelatin, soy protein, chitosan and sodium alginate.

4. The method for preparing the thermally conductive adhesive for reconstituted tobacco according to claim 1, characterized in that: The solvent is selected from at least one of glycerol, propylene glycol, ethanol and water.

5. The method for preparing the thermally conductive adhesive for reconstituted tobacco according to claim 1, characterized in that: The thermally conductive filler is a metal oxide; Or, the thermally conductive filler is selected from at least one of aluminum oxide, zinc oxide, magnesium oxide, and titanium oxide; Or, the particle size of the thermal conductive filler is 200-500 mesh; Alternatively, the mass fraction of the thermally conductive filler in the adhesive is between 1% and 30%.

6. The method for preparing the thermally conductive adhesive for reconstituted tobacco according to claim 1, characterized in that: The heat treatment temperature is 150-500°C.

7. The method for preparing the thermally conductive adhesive for reconstituted tobacco according to claim 1, characterized in that: The specific steps of sequentially treating with sodium bicarbonate and a silane coupling agent include: The metal oxide is mixed with a sodium bicarbonate solution with a mass fraction of 5 to 10%, stirred for 10 to 30 minutes, then allowed to stand for precipitation, filtered, and dried; the dried metal oxide is immersed in a silane coupling agent solution, reacted for 1 to 3 hours under anhydrous nitrogen conditions at 60 to 100° C., filtered, washed, and dried to obtain a metal oxide modified thermal conductive filler.

8. The method for preparing the thermally conductive adhesive for reconstituted tobacco according to claim 1, characterized in that: The silane coupling agent is selected from at least one of aminopropyltriethoxysilane, methyltrichlorosilane and γ-glycidyloxypropyltrimethoxysilane; Alternatively, the mass fraction of the silane coupling agent is 1-3%.

9. Thermally conductive adhesive for reconstituted tobacco prepared by the method according to any one of claims 1 to 8.

10. Use of the thermally conductive adhesive according to claim 9 in preparing reconstituted tobacco, characterized in that: The reconstituted tobacco leaf is prepared by a two-step method. First, a thermal conductive adhesive is synthesized. Then, tobacco powder, stem powder, smoke generating agent, wood pulp fiber and water are mixed evenly to obtain a tobacco raw material mixture. Finally, the thermal conductive adhesive and the tobacco raw material mixture are mixed evenly, and the mixture is rolled or scraped and dried to obtain a reconstituted tobacco leaf.

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