Hollow sodium alginate gel beads, and preparation method and application thereof
Hollow sodium alginate gel spheres were prepared by a process of first curing and then foaming, which solved the problem of low flavor utilization and achieved efficient release and flavor retention of flavor in cigarettes. They are suitable for cigarette filter rods and meet the requirements of green chemical industry.
Patent Information
- Application Number
- CN202610437561.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-04-03
- Publication Date
- 2026-06-30
AI Technical Summary
In existing technologies, the utilization rate of fragrances is low and the fragrance retention is poor. Traditional fragrance application methods lead to pollution of the production environment and the fragrances have poor retention during cigarette storage and combustion.
Hollow sodium alginate gel spheres are prepared using a process of first curing and then foaming. A sodium alginate-sodium bicarbonate mixed solution is dripped into a calcium chloride solution using a syringe or injection pump to form gel spheres, which are then foamed with an acidic solution to form a hollow structure. After being loaded with tobacco flavoring, they are used in cigarette filter rods.
It improves the release efficiency and utilization rate of flavorings, enhances the aroma quality of cigarettes, avoids environmental pollution, has a simple preparation process, and uses readily available, non-toxic, and harmless raw materials, making it suitable for large-scale production.
Smart Images
Figure CN122298363A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of adsorption material technology, specifically relating to a hollow sodium alginate gel sphere, its preparation method, and its application. Background Technology
[0002] With the increasing popularity of healthy smoking concepts, the research and development of low-tar cigarettes has become an important direction for the tobacco industry. However, while reducing tar content, the aroma substances in the smoke will also decrease accordingly, affecting the consumer's smoking experience. To compensate for the loss of aroma, improve cigarette quality, and shape brand style, adding tobacco flavorings to cigarettes has become a necessary technical means.
[0003] Traditional methods of applying flavorings, such as spraying them directly onto tobacco, have several drawbacks. First, flavorings are volatile, leading to environmental pollution during production. Second, flavorings have poor retention during cigarette storage and combustion, resulting in waste. Therefore, developing novel flavoring carriers to load flavorings onto tobacco materials such as filter rods and cigarette paper, thereby achieving controlled flavoring release, is currently a hot research topic.
[0004] Loading fragrances onto porous materials is an effective controlled-release technique. Inorganic porous materials such as talc, silica, and activated carbon have been extensively studied. Gel materials, due to their hierarchical pore structure containing macropores, mesopores, and micropores, are considered ideal fragrance carriers. Among them, sodium alginate, as a widely available, non-toxic, and harmless natural polyanionic polysaccharide, has been widely used in the biopharmaceutical field for the sustained release of drugs.
[0005] However, the release requirements of tobacco flavorings differ significantly from those of sustained-release drugs. The effective release time of tobacco flavorings is concentrated within a few minutes of cigarette smoking. If the flavoring is adsorbed deep within the gel spheres, it is difficult to release it effectively during the short smoking time, resulting in low flavoring utilization. Summary of the Invention
[0006] In view of the problems of low fragrance utilization and poor fragrance retention in existing fragrance-carrying materials, the primary objective of this invention is to provide a simple, mild, low-cost, and environmentally friendly method for preparing hollow sodium alginate gel spheres.
[0007] To achieve the above objectives, this invention provides a method for preparing hollow sodium alginate gel spheres. This method employs a unique "pre-curing followed by foaming" process, specifically including the following steps: (1) Dissolve sodium alginate and sodium bicarbonate (a foaming agent) in water and stir until dissolved to obtain a sodium alginate-sodium bicarbonate mixed solution, wherein the concentration of sodium alginate is 1w%~2w and the concentration of sodium bicarbonate (a foaming agent) is 3w%~15w%. (2) The sodium alginate-sodium bicarbonate mixed solution is added dropwise to the calcium chloride solution to carry out a solidification reaction and form solid sodium alginate gel particles; The solid sodium alginate gel particles are immersed in an acidic solution to allow the foaming agent to react, resulting in hollow sodium alginate gel spheres.
[0008] In the preparation method provided by the present invention, in step (1), sodium alginate (concentration controlled at 1w%~2w%) is first added to water and dissolved fully under vigorous stirring; then, foaming agent sodium bicarbonate (concentration controlled at 3w%~15w%) is added and vigorous stirring is continued until it is completely dissolved to obtain a uniform mixed solution.
[0009] The preparation method provided by this invention, specifically step (2), involves injecting the mixed solution obtained in step (1) dropwise into a calcium chloride solution using a syringe or injection pump. At this time, sodium alginate undergoes a cross-linking reaction with calcium ions, rapidly solidifying to form gel spheres. Subsequently, the fully solidified gel spheres are retrieved and immersed in an acidic solution. The sodium bicarbonate encapsulated inside the gel spheres reacts chemically with the acid to generate carbon dioxide gas. The gas expands inside the gel spheres, thus forming a hollow structure.
[0010] Preferably, when using a syringe or injection pump for spraying, a flow rate of 15-30 mL / min is appropriate, more preferably 20-30 mL / min, and especially 25 mL / min is conducive to the high-quality formation of gel spheres.
[0011] More preferably, a syringe pump is used to spray the solution into the calcium chloride solution through an L-shaped 25G needle (1m from the liquid surface) at a flow rate of 15-30mL / min for solidification.
[0012] In the preparation method provided by this invention, in step (2), the concentration of the calcium chloride solution is 1~5 g / L, preferably 2~4 g / L, especially 2 g / L. At this concentration, it is beneficial for mild cross-linking and promotes subsequent acidic penetration and foaming, while controlling the mechanical strength of the gel.
[0013] The preparation method provided by this invention uses an acidic solution selected from one or more of citric acid solution, oxalic acid solution, malic acid solution, or acetic acid solution; preferably, the acidic solution is a citric acid solution; more preferably, the concentration of the citric acid solution is 10 g / L-500 g / L, further 200 g / L-100 g / L, 50 g / L-80 g / L, etc.; if the concentration of the citric acid solution is 50 g / L, 80 g / L, 100 g / L, etc., using the above-mentioned acidic solution is beneficial for the formation of an ideal hollow structure at the center of the gel particles.
[0014] A second objective of this invention is to provide hollow sodium alginate gel spheres prepared by the above method.
[0015] The hollow sodium alginate gel spheres prepared by the above-mentioned method provided by the present invention have an ideal structure. When used as a carrier for tobacco flavoring, they exhibit advantages such as large adsorption capacity, strong flavor retention capacity and high smoke transfer efficiency. They enable the flavoring to be mainly loaded in the hollow cavity and on the inner and outer surfaces, which can effectively avoid the ineffective loading of flavoring inside the bulk phase, thereby improving the release efficiency and utilization rate of flavoring during the smoking process.
[0016] The present invention also provides the application of hollow sodium alginate gel spheres prepared by any of the above methods in the adsorption and loading of tobacco flavorings.
[0017] Preferably, the tobacco flavoring is one or more of peppermint flavoring, orange flavoring and rose flavoring. More preferably, it is used to adsorb peppermint flavoring and add it to the cigarette filter rod, thereby giving the cigarette a cool smoking experience.
[0018] This invention further provides a method for loading tobacco flavorings using the aforementioned hollow sodium alginate gel spheres. Since tobacco flavorings often use propylene glycol as a solvent, a media exchange method is employed to achieve efficient loading. The specific operation steps are as follows: (i) The hollow sodium alginate gel spheres are subjected to a medium exchange with ethanol; (ii) The hollow sodium alginate gel balls after medium exchange are immersed in tobacco flavoring for loading.
[0019] Preferably, the coagulation bath liquid on the surface of the hollow sodium alginate gel balls is removed by centrifugation or other methods.
[0020] Preferably, step (i) involves immersing the hollow sodium alginate gel balls in ethanol of 90% or higher concentration at a volume ratio of 1:2 to 4, stirring, and then separating. This operation is repeated at least twice to obtain sodium alginate gel particles. At this point, the ethanol content in the sodium alginate gel medium is not less than 85%, thus ensuring the subsequent loading efficiency of the fragrance.
[0021] More preferably, the gel balls are immersed in 95% ethanol (the volume ratio of gel balls to ethanol is 1:3), stirred for 15 minutes, and then the ethanol is removed by spin-drying. To ensure that the water medium in the gel is fully replaced by the ethanol medium, this medium exchange step is repeated 3 times.
[0022] Using the above method, sodium alginate gel particles with a suitable bulk density (e.g., 45 g / 100 cm³) can be obtained.
[0023] Preferably, step (ii) involves immersing the sodium alginate gel particles in tobacco flavoring at a mass ratio of 1:0.5 to 1.5 for 20 to 40 minutes, followed by centrifugation after immersion.
[0024] Under suitable centrifugation conditions, such as using a centrifugal dryer with a centrifugal force of 500g-700g for 10-25 minutes, ideal centrifugation results can be obtained.
[0025] More preferably, the gel balls that have undergone media exchange are immersed in tobacco flavoring (mass ratio 1:1) for 30 minutes. After immersion, excess flavoring is removed from the surface of the gel balls using a centrifugal dryer (e.g., at 600g centrifugal force for 15 minutes). By employing the above technical solution, the present invention has the following significant beneficial effects: 1. The "curing before foaming" process proposed in this invention avoids the problems of gel sphere adhesion and breakage caused by simultaneous curing and foaming, ensuring the integrity and uniformity of the gel spheres. The entire preparation process is simple, the reaction conditions are mild, and it is easy to control and scale up for production.
[0026] 2. The raw materials used in this invention (sodium alginate, sodium bicarbonate, calcium chloride, citric acid, etc.) are all inexpensive, readily available, non-toxic, and harmless conventional chemicals. The production process is environmentally friendly and meets the requirements of green chemistry.
[0027] 3. The hollow structure prepared by this invention significantly increases the effective loading space of the fragrance, avoids the ineffective adsorption of the fragrance inside the gel phase, thereby improving the release efficiency and transfer rate of the fragrance during cigarette smoking, and effectively improving the aroma quality of cigarettes.
[0028] 4. The technology provided by this invention is highly operable, and the resulting aroma-carrying gel balls can be easily applied to cigarette filter rods and other tobacco materials, and has broad prospects for promotion and application. Attached Figure Description
[0029] Figure 1 The images shown are microscopic images of sodium alginate gel spheres prepared using different processes in Example 1, obtained by depth-of-field stacking using a Leica DVM6 ultra-depth-of-field video microscope.
[0030] Figure 2 These are microscopic images of sodium alginate gel spheres prepared by foaming with different types of acids in Example 2. They were obtained by depth-of-field stacking using a Leica DVM6 ultra-depth-of-field video microscope.
[0031] Figure 3 The images shown are microscopic images of sodium alginate gel spheres prepared with different amounts of sodium bicarbonate added in Example 3. They were obtained by depth-of-field stacking using a Leica DVM6 ultra-depth-of-field video microscope.
[0032] Figure 4 These are microscopic images of sodium alginate gel spheres prepared by foaming with different concentrations of citric acid in Example 4. They were obtained by depth-of-field stacking using a Leica DVM6 ultra-depth-of-field video microscope.
[0033] Figure 5 This is a macroscopic photograph of the sodium alginate gel particles prepared using an injection pump in Example 5.
[0034] Figure 6 A graph showing the relationship between the content of menthol in the mainstream cigarette smoke from different amounts of flavor-carrying gel balls added in Example 6.
[0035] Figure 7 This is a graph showing the transfer rate of menthol from the flavor-carrying gel balls to the mainstream smoke in different amounts in Example 6. Detailed Implementation
[0036] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.
[0037] Example 1 This embodiment provides a method for preparing hollow sodium alginate gel spheres, including the following steps: Weigh 0.5g of sodium alginate and dissolve it in 50mL of deionized water to obtain a clear sodium alginate solution. Then weigh 5g of sodium bicarbonate and add it to the above solution, stirring until it is completely dissolved.
[0038] Pre-curing followed by foaming process: Using a syringe, the mixed solution was added dropwise to a 2 g / L calcium chloride solution. It was observed that white gel spheres formed immediately upon addition, and the calcium chloride solution became cloudy. After the gel spheres had completely solidified, they were transferred to a 30 g / L citric acid solution. Numerous bubbles were observed to be generated from the inside of the gel spheres, causing them to float. The initially cloudy solution gradually became clear, yielding hollow sodium alginate gel spheres.
[0039] Comparative Example 1 Compared with Example 1, the only difference is in step (2), which is: the mixed solution is added drop by drop to the mixed solution containing 2g / L calcium chloride and 30g / L citric acid using a syringe.
[0040] like Figure 1 As shown, the sodium alginate gel spheres obtained using the "curing and foaming simultaneously" process described in Comparative Example 1 exhibit severe adhesion. This is because the pressure from the bubbles generated during foaming damages the not-yet-fully-cured gel surface, causing the uncured sodium alginate solution inside to flow out and adhere. In contrast, the gel spheres obtained using the "curing before foaming" process of Example 1 of this invention have regular shapes and good dispersibility.
[0041] Example 2 This embodiment provides a method for preparing hollow sodium alginate gel spheres, including the following steps: Weigh 0.5g of sodium alginate and 4g of sodium bicarbonate and dissolve them in 50mL of deionized water. Using the "curing before foaming" process shown in Example 1, the mixed solution was added dropwise to a 2g / L calcium chloride solution for curing. Then, the cured gel balls were transferred to solutions of citric acid, oxalic acid, malic acid, and acetic acid, each with a concentration of 30g / L, for foaming.
[0042] The results are attached. Figure 2 As shown: In oxalic acid solution, the gel spheres did not exhibit significant foaming, presumably because the generated calcium oxalate precipitate covered the surface of the gel spheres, hindering the penetration of acid into the interior. Foaming was observed in both malic acid and acetic acid solutions, but acetic acid has a strong, pungent odor and is unsuitable for tobacco materials; malic acid's foaming effect was less effective than citric acid.
[0043] Example 3 This embodiment provides a method for preparing hollow sodium alginate gel spheres, including the following steps: 0.5 g of sodium alginate was dissolved in 50 mL of deionized water. 0 g (control), 1.5 g (corresponding to 3% concentration), 2.5 g (5%), and 5 g (10%) of sodium bicarbonate were weighed and added to the above solution to prepare mixed solutions with different foaming agent contents. Using the "curing before foaming" process shown in Example 1, the solution was cured in a 2 g / L calcium chloride solution and then transferred to a 30 g / L citric acid solution for foaming.
[0044] The results are attached. Figure 3 As shown: the control group without sodium bicarbonate was a solid gel sphere. With increasing sodium bicarbonate content, the volume of the air bubbles inside the gel spheres gradually increased. When the addition reached 10%, an ideal hollow structure with a clearly defined single large air bubble was obtained, consistent with the experimental expectations.
[0045] Example 4 This embodiment provides a method for preparing hollow sodium alginate gel spheres, including the following steps: Weigh 0.5 g of sodium alginate and 5 g (10%) sodium bicarbonate and dissolve them in 50 mL of deionized water. Using the "curing before foaming" process described in Example 1, cure the gel balls in a 2 g / L calcium chloride solution. Then, transfer the cured gel balls to foaming solutions with concentrations of 10 g / L, 50 g / L, 100 g / L, 500 g / L, 1000 g / L, and saturated citric acid, respectively.
[0046] The results are attached. Figure 4As shown, when the concentration of citric acid is too high (e.g., 1000 g / L and above), the reaction becomes too vigorous, causing multiple small bubbles to form on a single gel sphere and potentially destroying the sphere's integrity. A good hollow structure can be obtained within a concentration range of 10 g / L to 500 g / L. Considering both economic cost and environmental factors, a citric acid concentration of around 50 g / L is the optimal choice.
[0047] Example 5 This embodiment provides a method for preparing hollow sodium alginate gel spheres, which differs from Example 1 only in that: A continuous preparation was performed using a syringe pump. 1 g of sodium bicarbonate and 0.75 g of sodium alginate were dissolved in 50 mL of deionized water. The resulting solution was transferred to the syringe pump and sprayed through an L-shaped 25G needle (1 m above the liquid surface) at different flow rates (1 mL / min to 35 mL / min) into a 2 g / L calcium chloride solution for solidification. Subsequently, the solution was transferred to a citric acid solution for foaming.
[0048] The results are attached. Figure 5 As shown, within a certain range, the faster the flow rate, the higher the production efficiency. Considering both production efficiency and the uniformity of gel particles, a flow rate of 25 mL / min is preferable.
[0049] Example 6 This embodiment provides a method for preparing hollow sodium alginate gel spheres, including the following steps: Weigh out sodium alginate and dissolve it in 50 mL of deionized water to obtain a clear sodium alginate solution. Then weigh out 5 g of sodium bicarbonate and add it to the above solution. Stir until it is completely dissolved. The concentration of sodium alginate is 1.5 w and the concentration of sodium bicarbonate is 10 w.
[0050] Curing followed by foaming process: Continuous preparation is carried out using an injection pump. The solution is sprayed into a 2 g / L calcium chloride solution at a rate of 25 mL / min through an L-shaped 25G needle (needle 1 m from the liquid surface) for curing. Then, it is transferred to a 50 g / L citric acid solution for foaming to obtain hollow sodium alginate gel spheres.
[0051] Example 7 This embodiment provides a method for loading tobacco flavorings onto hollow sodium alginate gel spheres, specifically including the following steps: (i) The hollow sodium alginate gel spheres prepared in Example 6 were subjected to medium exchange with ethanol. After 4 medium exchanges with 95% ethanol, the bulk density of the gel particles was measured to be 45 g / 100 cm³, which is much lower than that of solid sodium alginate gel spheres (80 g / 100 cm³). (ii) Weigh 5g of the particles and soak them in 5g of peppermint essence for 30 minutes (feed ratio is 1:1), then filter and treat with 600g centrifugal force for 15 minutes.
[0052] Gas chromatography-mass spectrometry (GC-MS) analysis showed that the menthol content in the loaded sodium alginate gel particles was 14.8%, which is equivalent to a peppermint flavor loading rate of 49.3%.
[0053] Examples 8-11 This embodiment 8-11 provides a method for loading tobacco flavorings using hollow sodium alginate gel spheres, specifically including the following steps: (i) The hollow sodium alginate gel spheres prepared in Example 6 were exchanged with ethanol for 1, 2, 3 and 4 times respectively with 95% ethanol medium; (ii) Weigh out 5g of the above particles and soak them in 5g of peppermint essence for 30 minutes (the ratio of feed to product is 1:1), then filter them and treat them with a centrifugal force of 600g for 15 minutes.
[0054] Gas chromatography-mass spectrometry (GC-MS) analysis showed that the menthol content in the hollow sodium alginate gel particles after media exchange 1, 2, 3, and 4 times was 1.5%, 5.6%, 13.9%, and 14.8%, respectively.
[0055] Experiment Example 1: Test of Fragrance Carrying Performance and Smoke Release Effect Smoke test: Gel beads loaded with 10 mg, 20 mg, 30 mg, 40 mg, and 50 mg of menthol (prepared in Example 7) were added to the filter rods of commercial cigarettes. Following GB / T 16447—2004 and GB / T 16450—2004 standards, the cigarettes were smoked using a 20-channel linear smoking machine, and Cambridge filters were used to capture the mainstream smoke. The menthol content in the mainstream smoke was quantitatively analyzed using GC-MS.
[0056] The results are attached. Figure 6 As shown, the menthol content in the mainstream flue gas has a good linear relationship with the amount of gel particles added to the filter rod, indicating that the carrier can stably and controllably release flavoring into the flue gas.
[0057] The menthol content was determined by gas chromatography-mass spectrometry (GC-MS), using an Agilent Technologies 7820A–5977B instrument. The 20-channel smoking machine, SM450, was manufactured by Cerulean, UK.
[0058] The results are attached. Figure 7As shown, the transfer rate of menthol decreased slightly with the increase of the amount of gel particles applied, but remained at a high level, proving that the hollow gel spheres prepared in this invention have excellent fragrance release performance.
[0059] The hollow sodium alginate gel spheres proposed in this invention have achieved ideal results in application, significantly outperforming other existing technologies. For example, Ding Sha et al. used mesoporous silica to support menthol, achieving a loading efficiency of only 7.94% (Journal of Kunming University of Science and Technology (Natural Science Edition), 2021, 46(1): 18-25), with no report on smoke transfer; Kong Haohui et al. used modified montmorillonite to support menthol, achieving a loading efficiency of 20%~25% and a smoke transfer rate of 0.567 mg / cig (Tobacco Science and Technology, 2019, 52(1): ). (73-78), and compared the application methods of menthol flavoring in the flavoring thread (smoke transfer amount of 0.208 mg / cig), flavor capsule (smoke transfer amount of 0.442~0.846 mg / cig), and tobacco spray (0.231~0.657 mg / cig, smoke transfer amount of 0.208 mg / cig); Liu Zhenlong evaluated the adsorption effect of various porous materials on menthol, including activated carbon (SY-1) with a loading efficiency of 21.0%, molecular sieve (MSM-41) with a loading efficiency of 26.0%, molecular sieve (SBA-1) with a loading efficiency of 21.0%, zeolite clay with a loading efficiency of 18.1%, and aluminosilicate with a loading efficiency of 4.9% (Research on Novel Porous Solid Cigarette Menthol Flavor Component Slow-Release Material [D]. Guangzhou: South China University of Technology, 2013), without evaluating smoke transfer. The hollow sodium alginate gel spheres provided by this invention have a peppermint flavor loading efficiency of up to 49.3% and a menthol transfer amount of 0.25 mg / cig in the smoke, which exceeds that of flavoring threads already in industrial application and achieves the effect of mature tobacco spraying application process. This proves that by designing a hollow structure, this invention can achieve a greater transfer of menthol in the smoke with a smaller peppermint flavor loading.
[0060] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.
Claims
1. A method for preparing hollow sodium alginate gel spheres, characterized in that, Includes the following steps: (1) Dissolve sodium alginate and sodium bicarbonate (a foaming agent) in water and stir until dissolved to obtain a sodium alginate-sodium bicarbonate mixed solution, wherein the concentration of sodium alginate is 1w%~2w and the concentration of sodium bicarbonate (a foaming agent) is 3w%~15w%. (2) The sodium alginate-sodium bicarbonate mixed solution is added dropwise to the calcium chloride solution to carry out a solidification reaction and form solid sodium alginate gel particles; The solid sodium alginate gel particles are immersed in an acidic solution to allow the foaming agent to react, resulting in hollow sodium alginate gel spheres.
2. The method according to claim 1, characterized in that, In step (2), the concentration of the calcium chloride solution is 1~5 g / L, preferably 2 g / L.
3. The method according to claim 1 or 2, characterized in that, In step (2), the acidic solution is selected from one or more of citric acid solution, oxalic acid solution, malic acid solution or acetic acid solution.
4. The method according to claim 3, characterized in that, The acidic solution is a citric acid solution; preferably, the concentration of the citric acid solution is from 10 g / L to 500 g / L; more preferably, the concentration of the citric acid solution is 50 g / L.
5. A hollow sodium alginate gel sphere, characterized in that, Prepared by the method described in any one of claims 1-4.
6. The application of the method according to any one of claims 1 to 4 or the hollow sodium alginate gel spheres according to claim 5 in loading tobacco flavorings.
7. The application according to claim 6, characterized in that, The flavoring used in tobacco products is one or more of the following: peppermint flavoring, orange flavoring, or rose flavoring.
8. A method for loading tobacco flavoring onto hollow sodium alginate gel spheres as described in claim 5, characterized in that, Includes the following steps: (i) The hollow sodium alginate gel spheres are subjected to a medium exchange with ethanol; (ii) The hollow sodium alginate gel balls after medium exchange are immersed in tobacco flavoring for loading.
9. The method according to claim 8, characterized in that, The specific operation of step (i) is as follows: the hollow sodium alginate gel balls are immersed in ethanol of 90% or more at a volume ratio of 1:2 to 4, stirred and separated, and the operation is repeated at least twice to obtain sodium alginate gel particles.
10. The method according to claim 9, characterized in that, The specific operation of step (ii) is as follows: the sodium alginate gel particles are immersed in tobacco flavoring at a mass ratio of 1:0.5~1.5 for 20~40 minutes, and centrifuged after immersion.