Silicon dioxide microsphere with core-shell structure and hierarchical pores as well as preparation method and application of silicon dioxide microsphere

Abstract

The invention relates to the technical field of cigarette materials, in particular to a silica microsphere with a core-shell structure and hierarchical pores as well as a preparation method and application of the silica microsphere. The preparation method of the silicon dioxide microspheres with the core-shell structure and the hierarchical pores comprises the following steps: 1) mixing a polyvinyl alcohol aqueous solution with nano silicon dioxide particles, and stirring to form floccules; (2) preparing the floccule obtained in the step (1) into a sphere, namely a core structure of the silicon dioxide microsphere; (3) wrapping the surface of the core structure prepared in the step (2) with a pre-mixed mixture of mesoporous silica particles and a pore-foaming agent to serve as a shell structure of the silica microsphere, so as to obtain the silica microsphere with the core-shell structure; and 4) performing heat treatment to form hierarchical pores in the core-shell structure of the silicon dioxide microsphere, thereby obtaining the silicon dioxide microsphere with the core-shell structure and the hierarchical pores. The silicon dioxide microsphere with the core-shell structure and the hierarchical pores has the hierarchical pores with different sizes, so that the fragrance carrying amount can be increased, and the slow release performance can be improved.

Description

Technical Field

[0001] This invention relates to the field of tobacco materials technology, and in particular to a silica microsphere with a core-shell structure and hierarchical pores, its preparation method and uses. Background Technology

[0002] As people's living standards continue to improve, cigarette consumers have higher requirements for cigarette quality, which not only concerns the basic taste but also aroma and health aspects. During cigarette manufacturing, to enhance aroma and improve taste, natural porous materials, plant starch, or supramolecular gels are typically added to the filter rod to achieve flavor enhancement and moisture retention. However, these traditional materials have some drawbacks in practical applications, particularly in high-temperature resistance. In high-temperature environments, the structural stability of the materials is affected, consequently impacting the overall quality and safety of the cigarette. Furthermore, some materials may generate micro- or nano-sized particles during the molding process; if these particles are inhaled, they may pose health risks.

[0003] Traditional flavoring materials also face other problems, such as low mechanical strength, limited flavor carrying capacity, and poor sustained-release properties. These problems limit the improvement of cigarette quality and flavor profile. For example, flavoring materials with insufficient mechanical strength are prone to breakage during processing, which will affect their uniform distribution in cigarettes and thus the flavoring effect. Flavoring materials with limited flavor carrying capacity and poor sustained-release properties will lead to unstable aroma release during combustion, resulting in fluctuating aroma intensity for smokers and affecting the overall smoking experience. Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a silica microsphere with a core-shell structure and hierarchical pores, as well as its preparation method and uses, to solve the problems in the prior art.

[0005] To achieve the above and other related objectives, the present invention first provides a method for preparing silica microspheres with a core-shell structure and hierarchical pores, the preparation method comprising the following steps:

[0006] 1) Mix the polyvinyl alcohol aqueous solution with nano-silica particles and stir to form a flocculent substance;

[0007] 2) The flocculent material obtained in step 1) is prepared into spheres, which is the core structure of silica microspheres;

[0008] 3) The pre-mixed mixture of mesoporous silica particles and pore-forming agent is wrapped around the core structure surface prepared in step 2) as the shell structure of silica microspheres to obtain silica microspheres with a core-shell structure.

[0009] 4) After heat treatment, hierarchical pores are formed on the core-shell structure of the silica microspheres, thus obtaining silica microspheres with a core-shell structure and hierarchical pores.

[0010] This invention also provides silica microspheres with a core-shell structure and hierarchical pores obtained by the above preparation method.

[0011] The present invention also provides the application of the above-mentioned silica microspheres with core-shell structure and hierarchical pores in cigarette flavoring.

[0012] The present invention also provides a cigarette comprising the aforementioned silica microspheres having a core-shell structure and hierarchical pores.

[0013] As described above, the silica microspheres with a core-shell structure and hierarchical pores of the present invention, their preparation method, and their uses have the following beneficial effects:

[0014] 1) The silica microspheres with core-shell structure and multi-level pores provided by the present invention have a core-shell structure with nano-silica as the core and mesoporous silica as the shell, and have ultra-high temperature resistance.

[0015] 2) The shell structure of the microspheres can prevent nanoparticles from entering the body during the suction process, while improving the mechanical strength of the material;

[0016] 3) The microspheres have multi-level channels of different sizes and a high specific surface area, which makes it easier for the fragrance carrier material to enter the interior of the sphere. The fragrance carrier material is easily adsorbed by the mesoporous channels inside the material, which can increase the fragrance loading and improve the sustained release performance.

[0017] 4) The microsphere uses mesoporous silica nanoparticles as the shell, which have a macroporous structure to ensure that fragrance molecules can enter the core load. Attached Figure Description

[0018] Figure 1 The diagram shows a schematic representation of the silica microspheres with a core-shell structure and hierarchical pores of the present invention.

[0019] Figure 2 The image shows the surface morphology of silica microspheres with a core-shell structure and hierarchical pores prepared according to Example 1 of the present invention.

[0020] Figure 3 The image shows the surface morphology of silica microspheres with a core-shell structure and hierarchical pores prepared according to Example 1 of the present invention.

[0021] Figure 4 The attached diagram shows the nitrogen adsorption-desorption process of the silica microspheres with a core-shell structure and hierarchical pores prepared in Example 1.

[0022] Figure 5The diagram shows the pore size distribution of silica microspheres with a core-shell structure and hierarchical pores prepared in Example 1. Detailed Implementation

[0023] This invention first provides a method for preparing silica microspheres with a core-shell structure and hierarchical pores, the preparation method comprising the following steps:

[0024] 1) Mix the polyvinyl alcohol aqueous solution with nano-silica particles and stir to form a flocculent substance;

[0025] 2) The flocculent material obtained in step 1) is prepared into spheres, which is the core structure of silica microspheres;

[0026] 3) The pre-mixed mixture of mesoporous silica particles and pore-forming agent is wrapped around the core structure surface prepared in step 2) as the shell structure of silica microspheres to obtain silica microspheres with a core-shell structure.

[0027] 4) After heat treatment, hierarchical pores are formed on the core-shell structure of the silica microspheres, thus obtaining silica microspheres with a core-shell structure and hierarchical pores.

[0028] In some embodiments of the present invention, the nano-silica particles in step 1) are nano-sized particles composed of silicon dioxide.

[0029] Furthermore, the nano-silica particles are porous nano-silica particles or other non-porous nano-silica particles with high specific surface area.

[0030] Furthermore, the porous nano-silica particles are one or more of mesoporous nano-silica particles, porous nano-silica particles, and dendritic nano-silica particles.

[0031] In some embodiments of the present invention, if there are multiple types of porous silica nanoparticles, the multiple porous silica nanoparticles can be mixed in any proportion.

[0032] In some embodiments of the present invention, in step 1), the polyvinyl alcohol aqueous solution is obtained by mixing polyvinyl alcohol with water. Preferably, the water is deionized water.

[0033] In some embodiments of the present invention, in step 1), the stirring device is a magnetic stirrer.

[0034] In some embodiments of the present invention, in step 1), the stirring speed is 400 to 800 rpm.

[0035] In some embodiments of the present invention, in step 1), the stirring time is 10 to 20 hours. The stirring time is selected from any of the following ranges: 10 to 12 hours, 12 to 14 hours, 14 to 16 hours, 16 to 18 hours, and 18 to 20 hours.

[0036] In some embodiments of the present invention, in step 1), the mass concentration of the polyvinyl alcohol aqueous solution is 8% to 15%. The concentration of the polyvinyl alcohol aqueous solution is selected from any of the following ranges: 8% to 10%, 10% to 12%, 12% to 14%, and 14% to 15%. Preferably, the concentration of the polyvinyl alcohol aqueous solution is 10% to 12%. More preferably, the concentration of the polyvinyl alcohol aqueous solution is 10%.

[0037] In some embodiments of the present invention, the polyvinyl alcohol is one or more of polyvinyl alcohol type 1788, polyvinyl alcohol type 1799, polyvinyl alcohol type 2488, and polyvinyl alcohol type 2699.

[0038] In some embodiments of the present invention, in step 1), an aqueous solution of polyvinyl alcohol is used as an adhesive.

[0039] In some embodiments of the present invention, in step 1), the mixing mass ratio of the nano-silica particles to the polyvinyl alcohol aqueous solution is 1:(1.5-2). The mixing mass ratio of the nano-silica particles to the polyvinyl alcohol aqueous solution is selected from any of the following ranges: 1:(1.5-1.7), 1:(1.7-1.9), 1:(1.9-2).

[0040] In some embodiments of the present invention, in step 2), the particle size of the spheres is 0.3 to 0.5 mm.

[0041] In some embodiments of the present invention, step 2) further includes forming strip-shaped particles by extrusion granulation of the flocculent material before preparing it into spheres.

[0042] Furthermore, the length of the strip-shaped particles is 0.5 to 2 centimeters.

[0043] In some embodiments of the present invention, in step 2), the equipment used to prepare the spheres is a shot blasting machine.

[0044] Furthermore, in step 2), the rotation speed of the shot blasting machine is 200-400 rpm.

[0045] In some embodiments of the present invention, in step 3), the mesoporous silica particles refer to silica particles with a mesoporous structure and a pore size between 2 and 50 nm. The mesoporous silica particles are mesoporous silica particles with a particle size on the micrometer and / or nanometer scale.

[0046] In some embodiments of the present invention, in step 3), the mixing mass ratio of the mesoporous silica to the porogen is 1:(0.1 to 10). The mixing mass ratio of the mesoporous silica to the porogen is selected from any of the following ranges: 1:(0.1 to 0.5), 1:(0.5 to 1), 1:(1 to 5), 1:(5 to 10).

[0047] In some embodiments of the present invention, in step 3), the mesoporous silica particles are one or more of the following types: SBA-15, SBA-16, SBA-8, and SBA-11.

[0048] Furthermore, when using multiple types of mesoporous silica particles, the multiple types of mesoporous silica particles can be mixed in any proportion.

[0049] In some embodiments of the present invention, in step 3), the pore-forming agent is one or more of polyvinyl alcohol, polypropylene, or polystyrene.

[0050] Furthermore, the polyvinyl alcohol, polypropylene, or polystyrene is polyvinyl alcohol, polypropylene, or polystyrene with a micron-level size.

[0051] Furthermore, the polyvinyl alcohol, polypropylene, or polystyrene is polyvinyl alcohol, polypropylene, or polystyrene with a size of 100 micrometers.

[0052] In some embodiments of the present invention, when there are multiple porogens, the multiple porogens can be mixed in any proportion.

[0053] In some embodiments of the present invention, in step 3), a mixture of pre-mixed mesoporous silica particles and a pore-forming agent is wrapped around the core structure surface prepared in step 2) in a shot blasting machine.

[0054] Furthermore, in step 3), the rotation speed of the shot blasting machine is 100-200 rpm.

[0055] In some embodiments of the present invention, step 3) further includes verifying the particle size of the silica microspheres containing the core-shell structure.

[0056] In some embodiments of the present invention, the particle size of silica microspheres containing a core-shell structure is verified by sorting sieves.

[0057] In some embodiments of the present invention, in step 3), if the silica microspheres containing the core-shell structure meet the predetermined size, then step 4) is directly performed; if the particle size of the silica microspheres containing the core-shell structure does not reach the predetermined size, the process further includes adding polyvinyl alcohol aqueous solution and pre-mixed mesoporous silica particles and pore-forming agent mixture multiple times until the predetermined size is reached, then step 4) is performed.

[0058] In some embodiments of the present invention, in step 4), the heat treatment is drying followed by calcination.

[0059] In some embodiments of the present invention, the drying temperature is 50–100°C.

[0060] Furthermore, the calcination equipment is a muffle furnace.

[0061] In some embodiments of the present invention, the calcination temperature is 500–600°C. The calcination temperature is selected from any of the following ranges: 500–520°C, 520–540°C, 540–560°C, 560–580°C, and 580–600°C.

[0062] In some embodiments of the present invention, the calcination time is 4 to 8 hours. The calcination time is selected from any of the following ranges: 4 to 5 hours, 5 to 6 hours, 6 to 7 hours, and 7 to 8 hours.

[0063] In some embodiments of the present invention, in step 4), the particle size of the silica microspheres having a core-shell structure and hierarchical pores is 1 to 2 mm.

[0064] In some embodiments of the present invention, in step 4), the mechanical strength of the silica microspheres having a core-shell structure and hierarchical pores is 2.0 to 15.0 N.

[0065] In some embodiments of the present invention, in step 4), the silica microspheres having a core-shell structure and hierarchical pores are microspheres with a shell structure including mesopore-sized channels and / or micropore-sized channels.

[0066] The term "microsphere with micropore size" refers to a microsphere whose pores are at the micrometer level.

[0067] The present invention also provides silica microspheres with a core-shell structure and hierarchical pores obtained by the above preparation method.

[0068] The present invention also provides the application of the above-mentioned silica microspheres with core-shell structure and hierarchical pores in cigarette flavoring.

[0069] The present invention also provides a cigarette comprising the aforementioned silica microspheres having a core-shell structure and hierarchical pores.

[0070] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0071] Before further describing specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terminology used in the embodiments of the present invention is for describing specific embodiments and not for limiting the scope of protection of the present invention; in the specification and claims of the present invention, unless otherwise expressly stated in the text, the singular forms "a", "an" and "this" include the plural forms.

[0072] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. In addition to the specific methods, apparatus, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description of this invention, any prior art methods, apparatus, and materials similar to or equivalent to those described, apparatus, and materials in the embodiments of this invention may be used to implement the present invention.

[0073] Example 1: Preparation of core-shell structured hierarchical porous silica microspheres

[0074] 1) Add 100g of polyvinyl alcohol to 900ml of deionized water and stir for 10 hours to obtain a polyvinyl alcohol aqueous solution adhesive;

[0075] 2) Take 400g of nano-silica particles and mix them with 800g of polyvinyl alcohol aqueous solution binder obtained in step 1), and stir them into flocculent material;

[0076] 3) The nano-silica flocculent obtained in step 2) is extruded into long strips in extrusion granulation, and then placed in a shot blasting machine at a speed of 300 rpm to blast into 0.3 mm small balls, thus obtaining the core structure of silica microspheres;

[0077] 4) Add 500g of SBA-15 mesoporous silica and 50g of polyvinyl alcohol with a size of 100μm to the shot blasting machine in step 3), and adjust the speed of the shot blasting machine to 100 rpm. Collect the obtained silica microspheres with core-shell structure and screen them through a sorting sieve. Since the particle size of the obtained silica microspheres with core-shell structure did not reach the predetermined size of 2mm, spray the polyvinyl alcohol aqueous solution binder obtained in step 1) from above the shot blasting machine again to form spheres until the particle size of the silica microspheres with core-shell structure reaches 2mm.

[0078] 5) The silica microspheres with core-shell structure obtained in step 4) are dried at 50°C and placed in a muffle furnace for high-temperature calcination at a heating rate of 10°C / min and a termination temperature of 600°C for 8 hours to obtain silica microspheres with core-shell structure and hierarchical pores.

[0079] Example 2 Characterization of core-shell structured hierarchical porous silica microspheres

[0080] 1) The calcined silica microspheres with core-shell structure and hierarchical pores from step 1 were examined using a scanning electron microscope, such as... Figure 2 and Figure 3 As shown, the microspheres are spherical and their surfaces are covered with multi-level pores.

[0081] 2) The calcined silica microspheres with a core-shell structure and hierarchical pores were subjected to a BET nitrogen adsorption-desorption test, such as... Figure 4 and Figure 5 As shown, the specific surface area of ​​the prepared microspheres is 439.51 m2 / g, the pore volume is 1.269 cm3 / g, and the pore size is 36.38 nm.

[0082] Example 3: Performance Verification of Core-Shell Structured Hierarchical Porous Silica Microspheres

[0083] 1) Take 10g of the silica microspheres with core-shell structure and hierarchical pores prepared in step 1, immerse them in 50mL of ethyl vanillin fragrance solution, let stand for 24h, and then dry them to obtain fragrance-loaded silica microspheres.

[0084] 2) Take 40 hollow cigarettes;

[0085] 3) Add 50 mg of flavor-loaded silica microspheres obtained in step 1) to 20 hollow cigarettes to obtain flavor-loaded cigarettes;

[0086] 4) The mainstream flue gas was captured by the standard ISO suction method, extracted with ethanol, and analyzed by GC / MS.

[0087] Table 1 shows a comparison of the aroma component content in the smoke of the hollow cigarette (step 2) and the flavored cigarette (step 3). The addition of flavor-loaded silica microspheres significantly increased the content of ethyl vanillin, a flavoring component, in the smoke of the flavored cigarette to 75.6 times that of the hollow cigarette, and the vanillin content to 2.3 times that of the hollow cigarette.

[0088] Table 1. Data on flavoring components in the smoke of hollow-type and flavored cigarettes.

[0089]

[0090]

[0091] The above embodiments are for illustrating the implementation schemes disclosed in this invention and should not be construed as limiting the invention. Furthermore, various modifications and variations of the methods listed herein will be apparent to those skilled in the art without departing from the scope and spirit of the invention. Although the invention has been specifically described in conjunction with various specific preferred embodiments, it should be understood that the invention should not be limited to these specific embodiments. In fact, various modifications as described above that are obvious to those skilled in the art to obtain the invention should be included within the scope of this invention.

Claims

1. A method for preparing silica microspheres with a core-shell structure and hierarchical pores, characterized in that, The preparation method includes the following steps: 1) Mix the polyvinyl alcohol aqueous solution with nano-silica particles and stir to form a flocculent substance; 2) The flocculent material obtained in step 1) is prepared into spheres, which is the core structure of silica microspheres; 3) The pre-mixed mixture of mesoporous silica particles and pore-forming agent is wrapped around the core structure surface prepared in step 2) as the shell structure of silica microspheres to obtain silica microspheres with a core-shell structure. 4) After heat treatment, hierarchical pores are formed on the core-shell structure of the silica microspheres, thus obtaining silica microspheres with a core-shell structure and hierarchical pores.

2. The method for preparing microspheres according to claim 1, characterized in that, Step 1) includes one or more of the following conditions: 12) The stirring speed is 400-800 rpm; 13) The stirring time is 10 to 20 hours; 14) The mass concentration of polyvinyl alcohol in the polyvinyl alcohol aqueous solution is 8% to 15%; 15) Polyvinyl alcohol is selected from one or more of polyvinyl alcohol type 1788, polyvinyl alcohol type 1799, polyvinyl alcohol type 2488, and polyvinyl alcohol type 2699; 16) The mass ratio of the nano-silica particles to the polyvinyl alcohol aqueous solution is 1:1.5 to 2.

3. The method for preparing microspheres according to claim 1, characterized in that, Step 2) includes one or more of the following conditions: 21) The particle size of the spheres is 0.3–0.5 mm; 22) Before being prepared into spheres, the process also includes extruding and granulating the flocculent material into strip-shaped particles; 23) The equipment for preparing spheres is a shot blasting machine, and the rotation speed of the shot blasting machine is 200 to 400 rpm.

4. The method for preparing microspheres according to claim 1, characterized in that, Step 3) includes one or more of the following conditions: 31) The mass ratio of the mesoporous silica to the pore-forming agent is 1:0.1 to 10; 32) The type of mesoporous silica particles is selected from one or more of SBA-15, SBA-16, SBA-8, and SBA-11; 33) The pore-forming agent is one or more of polyvinyl alcohol, polypropylene, or polystyrene; 34) The pre-mixed mixture of mesoporous silica particles and pore-forming agent is coated onto the surface of the core structure prepared in step 2) in a shot blasting machine. Preferably, the rotation speed of the shot blasting machine is 100 to 200 rpm.

5. The method for preparing microspheres according to claim 1, characterized in that, Step 3) also includes verifying the particle size of the silica microspheres containing the core-shell structure; preferably, the particle size of the silica microspheres containing the core-shell structure is 1 to 2 mm.

6. The method for preparing microspheres according to claim 5, characterized in that, If the particle size of the silica microspheres containing the core-shell structure meets the predetermined size, then proceed directly to step 4); if the particle size of the silica microspheres containing the core-shell structure does not meet the predetermined size, proceed to step 4 again until the particle size of the silica microspheres containing the core-shell structure meets the predetermined size.

7. The method for preparing microspheres according to claim 1, characterized in that, Step 4) includes one or more of the following conditions: 41) The heat treatment is drying followed by calcination; preferably, the drying temperature is 50-100℃; preferably, the calcination temperature is 500-600℃; preferably, the calcination time is 4-8 hours; 42) The particle size of the silica microspheres with core-shell structure and hierarchical pores is 1-2 mm; 43) The mechanical strength of the silica microspheres with core-shell structure and hierarchical pores is 2.0 to 15.0 N; 44) The silica microspheres with core-shell structure and hierarchical pores are microspheres with shell structure including mesopore-sized channels and / or micropore-sized channels.

8. A silica microsphere having a core-shell structure and hierarchical pores, characterized in that, The silica microspheres with core-shell structure and hierarchical pores are prepared by the preparation method according to any one of claims 1 to 7.

9. The application of silica microspheres with core-shell structure and hierarchical pores as described in claim 8 in cigarette flavoring.

10. A cigarette, characterized in that, The cigarette comprises the silica microspheres with a core-shell structure and hierarchical pores as described in claim 8.

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