Preparation method for microcellular foamed composite material, and microcellular foamed silica GEL filter rod prepared from the composite material
Patent Information
- Application Number
- AE202603026
- Authority / Receiving Office
- AE · AE
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2024-03-15
- Filing Date
- 2025-01-20
Abstract
Description
DESCRIPTION PREPARATION METHOD FOR MICROCELLULAR FOAMED COMPOSITE MATERIAL, AND MICROCELLULAR FOAMED SILICA GEL FILTER ROD PREPARED FROM THE COMPOSITE MATERIAL Technical FieldThe present invention relates to the technical field of cigarette filter rods, and in particular, to a microcellular foamed composite material usable for preparing filter rods, and to a microcellular foamed silica gel filter rod obtained from the microcellular foamed composite material.Background ArtTraditional cigarette filter rods extensively use cellulose diacetate fiber tow as a filter rod material. However, using cellulose acetate to manufacture filter rods having hollowed-out structures suffers from technical defects. This is because cellulose acetate fiber tow is a high-density tow; when constructing a hollowed-out structure through compression molding in a filter rod machine equipped with a mold, the amount of tow used is 2 to 4 times that for producing a conventional cellulose acetate filter rod with a non-hollowed-out structure, leading to a very high manufacturing cost for the hollowed-out cellulose acetate filter rod. On the other hand, since a cellulose acetate filter rod is obtained by molding and compressing tow, its strength is relatively low. Therefore, it is impossible to manufacture hollowed-out patterns with refined and complex structures, thus making it difficult to improve the cooling effect of the filter rod on smoke by designing reasonably shaped smoke pathways.Summary of the InventionAn object of the present invention is to overcome the defects in the prior art, provide a novel microcellular foamed composite material, and enable the preparation of a microcellular foamed silica gel cigarette filter rod using the microcellular foamed composite material, so as to achieve a better smoke cooling effect, while the filter rod shall also possess the physical properties that a cigarette filter rod is supposed to have.Based on this, a preparation method for a microcellular foamed composite material includes the following steps:(1) preparing a porous skeleton foaming agent, which includes:(1.1) taking a porous skeleton material having a particle size of 58 μm to 180 μm, wherein the porous skeleton material is selected from porous hydroxyapatite, perlite, and / or porous silicon;(1.2) wetting the porous skeleton material obtained in step (1.1) with a silicone oil spray to obtain a wetted material;(1.3) weighing the wetted material and a food-grade foaming agent in a mass ratio of 50-100:6-15, mixing them uniformly, and then passing the mixture through a 200-mesh sieve to remove excess foaming agent on the surface of the material, thereby obtaining the porous skeleton foaming agent, wherein the food-grade foaming agent is sodium carbonate and / or sodium bicarbonate;(2) preparing internally-mixed silica gel, which includes:weighing silica gel, white carbon black, and calcium carbonate in a mass ratio of 50-100:10-30:10-30, and mixing them in an internal mixer to obtain the internally-mixed silica gel;(3) preparing the microcellular foamed composite material, which includes:weighing the porous skeleton foaming agent, the internally-mixed silica gel, and a vulcanizing agent in a mass ratio of 1-10:100-900:1-5, and mixing them in an internal mixer to obtain the microcellular foamed composite material.In step (1.1) of the above preparation method, the porous skeleton material is passed through an 80-mesh sieve to collect the undersize, and the obtained product is further passed through a 200-mesh sieve to collect the oversize, thereby obtaining a powdered material having a particle size of 58 μm to 180 μm.The porous skeleton material may be pre-dried, for example, by drying at a temperature of 100 °C to 150 °C for 2 h to 8 h, or by using other conventional drying means. Drying enables the silicone oil to better wet the porous skeleton material in the subsequent step, but it is generally not necessary to define the water content of the porous skeleton material after drying.According to a preferred embodiment, the specific surface area of the porous hydroxyapatite, perlite, or porous silicon in step (1.1) is 20-1000 m² / g, which is measured by a gas adsorption BET method. The porous hydroxyapatite, perlite, and porous silicon are commercially available materials. These materials all have a porous structure, and their specific surface area is generally 20-1000 m² / g, which can meet the requirements of the present invention.As porous materials, the porous hydroxyapatite, perlite, and porous silicon can be used alone or in combination. When they are used in combination, their ratio is generally arbitrary and has little effect on the performance of the final product.Generally, the mass ratio of the porous skeleton material to the silicone oil in step (1.2) is 5-20:100. Wetting the porous skeleton material with the silicone oil enables the foaming agent in the subsequent step to uniformly adhere to the porous skeleton material. Therefore, commercially available silicone oil generally satisfies the requirements of the present invention; for example, a food-grade silicone oil 350 cs product produced and sold by Foshan Guirunbao Biotechnology Co., Ltd. may be used. To achieve the effect of wetting the porous skeleton material, if the amount of silicone oil is too low (less than 5% of the mass of the porous skeleton material), the porous skeleton material cannot be completely wetted, resulting in uneven adhesion of the foaming agent; if the amount exceeds 20%, the porous skeleton material becomes excessively damp, and the porous skeleton foaming agent may suffer from severe caking, which is inconvenient for the implementation of subsequent steps.According to a particularly preferred embodiment, the food-grade foaming agent in step (1.3) is a mixture of sodium carbonate and sodium bicarbonate, and the mass ratio of the wetted material, sodium carbonate, and sodium bicarbonate is 50-100:1-5:5-10, so as to achieve a better foaming effect and better suit the physical property requirements of the filter rod product.In the present invention, the silica gel in step (2) may be a commercially available food-grade silica gel. The density of such products is generally 1.0-1.5 g / cm³, the hardness is 60-80 Shore A, and the tensile strength is greater than 7 MPa; all of which can achieve the technical solution of the present invention. For example, a food-grade silica gel RBB-2030-80 produced and sold by Nanjing Luoen Silicon Material Co., Ltd.According to an alternative embodiment, step (3) further comprises adding a food-grade pigment. The amount of the food-grade pigment added may refer to the colorants recorded in the National Food Safety Standard – Standard for the Use of Food Additives (GB 2760-2014). For example, Brilliant Blue, Tartrazine (Lemon Yellow), Sunset Yellow, and Allura Red are all commonly used edible colorants, which may be used alone or in combination. Generally, the amount of Brilliant Blue is not greater than 0.025‰ of the total weight, while the amounts of Tartrazine, Sunset Yellow, or Allura Red are generally not greater than 0.1‰ of the total weight. By controlling the addition ratio and timing of the pigment, a person skilled in the art can obtain a microcellular foamed composite material having different colors or patterns.In the present invention, the vulcanizing agent is generally a platinum vulcanizing agent.Further, the present invention also provides the use of the microcellular foamed composite material obtained by the above preparation method in a filter rod.In the present invention, the term "filter rod" may refer to a filter rod used in heated non-combustion cigarettes or combustion-type cigarettes.Based on this, the present invention further provides a method for preparing a microcellular foamed silica gel filter rod, said preparation method comprising the following steps:(1) feeding a microcellular foamed composite material into a silica gel extruder having a rotating inner mold, and rotationally extruding a rod-shaped material therefrom, wherein the microcellular foamed composite material is the microcellular foamed composite material obtained by the aforementioned preparation method;(2) heating the obtained rod-shaped material at 160 °C to 250 °C for 10 s to 20 s for vulcanization;(3) naturally cooling the material obtained in step (2), and then cutting the same to obtain the microcellular foamed silica gel filter rod.In the present invention, the silica gel extruder having a rotating inner mold may be, for example, an 80 silica gel tube extrusion equipment product produced and sold by Hebei Xulang Machinery Equipment Manufacturing Co., Ltd. During use, by adjusting the operating parameters of the extruder, the extrusion stroke per revolution of the inner mold can be controlled to 10-50 mm, so as to obtain smoke pathways of different shapes. By replacing the inner mold head having different material flow channel distributions (for example, referring to the extrusion molding die head disclosed in CN 215750663 U), filter rods having different shapes or structures of smoke pathways can be obtained. These smoke pathways can have different cross-section hollowed-out shapes, so as to enrich the options for the appearance and shape of the filter rod end. These cross-section hollowed-out shapes may be symmetrical geometric shapes, such as triangles, regular pentagrams, etc., or may be prepared into asymmetrical pattern shapes, such as cloud shapes, flame shapes, etc.Specifically, in step (2), the duration of heating for vulcanization generally depends on the heating temperature; the higher the heating temperature, the more appropriately the heating time can be shortened, whereas if the heating temperature is relatively low, the time should be appropriately extended, so as to ensure that the heated microcellular foamed silica gel filter rod is sufficiently vulcanized without deformation. The control of heating temperature and time is a technical means that a person skilled in the art can adjust according to actual conditions, and will not be described in detail herein.In the present invention, the porosity of the obtained microcellular foamed silica gel filter rod is 10% to 40%, which can be measured using a porosity tester.Compared with hollowed-out filter rods made of cellulose acetate fiber tow, the microcellular foamed silica gel filter rod of the present invention has good stiffness and rebound rate, and thus has better deformation resistance, and can adapt to more refined and more complex hollowed-out patterns, so as to meet the requirements for the shape and structure design of smoke pathways. Functionally, it further enhances the effects of cooling smoke and adsorbing harmful substances; and aesthetically, it enables filter rod designers to adopt more industrial aesthetic designs.On the other hand, by adding the porous skeleton foaming agent to improve the formulation and preparation method of the microcellular foamed composite material, the present invention makes the outer wall friction force of the microcellular foamed silica gel filter rod more stable, and therefore the blade wear in the subsequent cutting step is reduced, which is manifested as the product being less prone to sticking to blades and material jamming being less likely to occur, thereby extending the blade replacement cycle of the cutting devices, improving the durability of the devices, and lowering the maintenance requirement of the cutting devices.EMBODIMENTSThe following embodiments are used to explain the technical solution of the present invention in a non-limiting manner.In the present invention, unless otherwise specified, the "%" used to express product concentration represents a mass ratio, the ":" denotes a mass ratio, and the term "part(s)" refers to parts by mass.Example 1: Preparation of a microcellular foamed silica gel filter rod having an inner spiral structure(1) Preparing a microcellular foamed composite materialPorous hydroxyapatite having a specific surface area of 26 m² / g was taken and dried at 100 °C for 8 h. After drying, the material was passed through an 80-mesh sieve to collect the undersize, and then passed through a 200-mesh sieve to collect the oversize. The sieved porous hydroxyapatite was wetted with a silicone oil spray, the spraying amount of the silicone oil being 5% of the weight of the porous hydroxyapatite. After wetting, it was sealed and allowed to equilibrate for 24 h. After equilibration, the equilibrated porous hydroxyapatite, food-grade sodium carbonate, and food-grade sodium bicarbonate were taken in a mass ratio of 100:5:10, mixed thoroughly until uniform, and then passed through a 200-mesh sieve to remove excess foaming agent powder, thereby obtaining the porous skeleton foaming agent.Silica gel, white carbon black, and calcium carbonate were weighed in a mass ratio of 100:30:30 as raw materials, and mixed in an internal mixer to obtain a white internally-mixed silica gel.Then, the porous skeleton foaming agent, the internally-mixed silica gel, and a platinum vulcanizing agent were weighed in a mass ratio of 10:900:5, and mixed in an internal mixer to obtain a white microcellular foamed composite material.(2) Preparing the microcellular foamed silica gel filter rodA regular triangular mold head was selected for the inner mold head of the silica gel extruder. The white microcellular foamed composite material was fed into the extruder, and the extrusion speed was set so that the extrusion stroke per revolution of the inner mold was 50 mm. The extruded material was heated at 250 °C to obtain a filter rod having a circumference of 22 mm. Due to the heating, the composite material was vulcanized, and at the same time, the foaming agent in the porous material was fully pyrolyzed, thereby obtaining a uniform porous structure.The filter rod was thoroughly cooled until the material was shaped, thereby obtaining a white cylinder having elasticity and certain strength. It was cut into 100 mm lengths using a filter rod cutting machine, and was designated as Sample 1.Example 2: Preparation of a microcellular foamed silica gel filter rod having an inner spiral structure(1) Preparing a microcellular foamed composite materialPorous hydroxyapatite having a specific surface area of 30 m² / g was taken and dried at 120 °C for 4 h. After drying, the material was passed through an 80-mesh sieve to collect the undersize, and then passed through a 200-mesh sieve to collect the oversize. The sieved porous hydroxyapatite was wetted with a silicone oil spray, the spraying amount of the silicone oil being 7% of the weight of the porous hydroxyapatite. After wetting, it was sealed and allowed to equilibrate for 24 h. After equilibration, the equilibrated porous hydroxyapatite, food-grade sodium carbonate, and food-grade sodium bicarbonate were taken in a mass ratio of 90:4:8, mixed thoroughly until uniform, and then passed through a 200-mesh sieve to remove excess foaming agent powder, thereby obtaining the porous skeleton foaming agent.Silica gel, white carbon black, and calcium carbonate were weighed in a mass ratio of 90:25:20 as raw materials, and mixed in an internal mixer to obtain a white internally-mixed silica gel.Then, the porous skeleton foaming agent, the internally-mixed silica gel, and a platinum vulcanizing agent were weighed in a mass ratio of 9:800:3, and mixed in an internal mixer to obtain a white microcellular foamed composite material.(2) Preparing the microcellular foamed silica gel filter rodA regular triangular mold head was selected for the inner mold head of the silica gel extruder. The white microcellular foamed composite material was fed into the extruder, and the extrusion speed was set so that the extrusion stroke per revolution of the inner mold was 40 mm. The extruded material was heated at 230 °C to obtain a filter rod having a circumference of 22 mm. After cooling and shaping, it was cut into 100 mm lengths and designated as Sample 2.Example 3: Preparation of a microcellular foamed silica gel filter rod having an inner spiral structure(1) Preparing a microcellular foamed composite materialPorous hydroxyapatite having a specific surface area of 28 m² / g was taken and dried at 110 °C for 3 h. After drying, the material was passed through an 80-mesh sieve to collect the undersize, and then passed through a 200-mesh sieve to collect the oversize. The sieved porous hydroxyapatite was wetted with a silicone oil spray, the spraying amount of the silicone oil being 10% of the weight of the porous hydroxyapatite. After wetting, it was sealed and allowed to equilibrate for 18 h. After equilibration, the equilibrated porous hydroxyapatite, food-grade sodium carbonate, and food-grade sodium bicarbonate were taken in a mass ratio of 80:3:7, mixed thoroughly until uniform, and then passed through a 200-mesh sieve to remove excess foaming agent powder, thereby obtaining the porous skeleton foaming agent.Silica gel, white carbon black, and calcium carbonate were weighed in a mass ratio of 80:20:15 as raw materials, and mixed in an internal mixer to obtain a white internally-mixed silica gel.Then, the porous skeleton foaming agent, the internally-mixed silica gel, and a platinum vulcanizing agent were weighed in a mass ratio of 7:750:2, and mixed in an internal mixer to obtain a white microcellular foamed composite material.(2) Preparing the microcellular foamed silica gel filter rodA regular triangular mold head was selected for the inner mold head of the silica gel extruder. The white microcellular foamed composite material was fed into the extruder, and the extrusion speed was set so that the extrusion stroke per revolution of the inner mold was 30 mm. The extruded material was heated at 200 °C to obtain a filter rod having a circumference of 22 mm.After cooling and shaping, it was cut into 100 mm lengths and designated as Sample 3.Example 4: Preparation of a microcellular foamed silica gel filter rod having an inner spiral structure(1) Preparing a microcellular foamed composite materialPorous hydroxyapatite having a specific surface area of 35 m² / g was taken and dried at 105 °C for 2.5 h. After drying, the material was passed through an 80-mesh sieve to collect the undersize, and then passed through a 200-mesh sieve to collect the oversize. The sieved porous hydroxyapatite was wetted with a silicone oil spray, the spraying amount of the silicone oil being 15% of the weight of the porous hydroxyapatite. After wetting, it was sealed and allowed to equilibrate for 6 h. After equilibration, the equilibrated porous hydroxyapatite, food-grade sodium carbonate, and food-grade sodium bicarbonate were taken in a mass ratio of 60:2:6, mixed thoroughly until uniform, and then passed through a 200-mesh sieve to remove excess foaming agent powder, thereby obtaining the porous skeleton foaming agent.Silica gel, white carbon black, and calcium carbonate were weighed in a mass ratio of 60:15:15 as raw materials, and mixed in an internal mixer to obtain a white internally-mixed silica gel.Then, the porous skeleton foaming agent, the internally-mixed silica gel, and a platinum vulcanizing agent were weighed in a mass ratio of 3:200:1, and mixed in an internal mixer to obtain a white microcellular foamed composite material.(2) Preparing the microcellular foamed silica gel filter rodA regular triangular mold head was selected for the inner mold head of the silica gel extruder. The white microcellular foamed composite material was fed into the extruder, and the extrusion speed was set so that the extrusion stroke per revolution of the inner mold was 20 mm. The extruded material was heated at 180 °C to obtain a filter rod having a circumference of 22 mm.After cooling and shaping, it was cut into 100 mm lengths and designated as Sample 4.Example 5: Preparation of a microcellular foamed silica gel filter rod having an inner spiral structure(1) Preparing a microcellular foamed composite materialPorous hydroxyapatite having a specific surface area of 26 m² / g was taken and dried at 100 °C for 2 h. After drying, the material was passed through an 80-mesh sieve to collect the undersize, and then passed through a 200-mesh sieve to collect the oversize. The sieved porous hydroxyapatite was wetted with a silicone oil spray, the spraying amount of the silicone oil being 17% of the weight of the porous hydroxyapatite. After wetting, it was sealed and allowed to equilibrate for 2 h. After equilibration, the equilibrated porous hydroxyapatite, food-grade sodium carbonate, and food-grade sodium bicarbonate were taken in a mass ratio of 50:1:5, mixed thoroughly until uniform, and then passed through a 200-mesh sieve to remove excess foaming agent powder, thereby obtaining the porous skeleton foaming agent.Silica gel, white carbon black, and calcium carbonate were weighed in a mass ratio of 50:10:10 as raw materials, and mixed in an internal mixer to obtain a white internally-mixed silica gel.Then, the porous skeleton foaming agent, the internally-mixed silica gel, and a platinum vulcanizing agent were weighed in a mass ratio of 1:100:1, and mixed in an internal mixer to obtain a white microcellular foamed composite material.(2) Preparing the microcellular foamed silica gel filter rodA regular triangular mold head was selected for the inner mold head of the silica gel extruder. The white microcellular foamed composite material was fed into the extruder, and the extrusion speed was set so that the extrusion stroke per revolution of the inner mold was 10 mm. The extruded material was heated at 260 °C to obtain a filter rod having a circumference of 22 mm.After cooling and shaping, it was cut into 100 mm lengths and designated as Sample 5.Example 6The effect of using an insufficient amount of the porous skeleton foaming agent was investigated.The same procedure as in Example 1 was followed, except that the amount of the porous skeleton foaming agent was reduced: in the preparation of the microcellular foamed composite material, the porous skeleton foaming agent, the internally-mixed silica gel, and a platinum vulcanizing agent were weighed in a mass ratio of 0.5:900:5, and mixed in an internal mixer to obtain a white microcellular foamed composite material.The remaining steps, operations, and parameters were the same as those in Example 1, and the resulting product was designated as Sample 6.Example 7The effect of using an excessive amount of the porous skeleton foaming agent was investigated.The same procedure as in Example 1 was followed, except that the amount of the porous skeleton foaming agent was increased: in the preparation of the microcellular foamed composite material, the porous skeleton foaming agent, the internally-mixed silica gel, and a platinum vulcanizing agent were weighed in a mass ratio of 15:900:5, and mixed in an internal mixer to obtain a white microcellular foamed composite material.The remaining steps, operations, and parameters were the same as those in Example 1, and the resulting product was designated as Sample 7.In addition, the following comparative examples respectively investigate the effects of the porous skeleton foaming agent, the porous skeleton material, and the composite foaming agent on the final filter rod.Comparative Example 1: Preparation of a microcellular foamed silica gel filter rod without a porous skeleton foaming agent(1) Preparing a foamed composite material without a porous skeleton foaming agentThe procedure was carried out in a similar manner to Example 1, with the same steps, operations, and parameters, except that the porous skeleton foaming agent was not used (corresponding to a conventional silica gel filter rod). Specifically:Silica gel, white carbon black, and calcium carbonate were weighed in a mass ratio of 100:30:30 as raw materials, and mixed in an internal mixer to obtain a white internally-mixed silica gel.Then, the internally-mixed silica gel and a platinum vulcanizing agent were weighed in a mass ratio of 900:5, and mixed in an internal mixer to obtain a white microcellular foamed composite material.(2) Preparing the microcellular foamed silica gel filter rodThe same procedure as in Example 1 was followed, specifically: a regular triangular mold head was selected for the inner mold head of the silica gel extruder. The composite material was fed into the extruder, and the extrusion speed was set so that the extrusion stroke per revolution of the inner mold was 50 mm. The extruded material was heated at 250 °C to obtain a filter rod having a circumference of 22 mm.The filter rod was thoroughly cooled until the material was shaped, thereby obtaining a white cylinder having elasticity and certain strength. It was cut into 100 mm lengths using a filter rod cutting machine, and was designated as Sample 8.Comparative Example 2: Preparation of a microcellular foamed silica gel filter rod without food-grade foaming agents(1) Preparing a composite material without food-grade foaming agentsThe procedure was carried out in a similar manner to Example 1, with the same steps, operations, and parameters, except that the food-grade foaming agents were not used. Specifically:Porous hydroxyapatite having a specific surface area of 26 m² / g was taken and dried at 100 °C for 8 h. After drying, the material was passed through an 80-mesh sieve to collect the undersize, and then passed through a 200-mesh sieve to collect the oversize. The sieved porous hydroxyapatite was wetted with a silicone oil spray, the spraying amount of the silicone oil being 5% of the weight of the porous hydroxyapatite. After wetting, it was sealed and allowed to equilibrate for 24 h, thereby obtaining the porous skeleton material.Silica gel, white carbon black, and calcium carbonate were weighed in a mass ratio of 100:30:30 as raw materials, and mixed in an internal mixer to obtain a white internally-mixed silica gel.Then, the porous skeleton material, the internally-mixed silica gel, and a platinum vulcanizing agent were weighed in a mass ratio of 10:900:5, and mixed in an internal mixer to obtain a white microcellular foamed composite material.(2) Preparing the microcellular foamed silica gel filter rodThe same procedure as in Example 1 was followed, specifically: a regular triangular mold head was selected for the inner mold head of the silica gel extruder. The composite material was fed into the extruder, and the extrusion speed was set so that the extrusion stroke per revolution of the inner mold was 50 mm. The extruded material was heated at 250 °C to obtain a filter rod having a circumference of 22 mm.The filter rod was thoroughly cooled until the material was shaped, thereby obtaining a white cylinder having elasticity and certain strength. It was cut into 100 mm lengths using a filter rod cutting machine, and was designated as Sample 9.Comparative Example 3: Preparation of a microcellular foamed silica gel filter rod without a porous skeleton material(1) Preparing a composite material without a porous skeleton materialThe procedure was carried out in a similar manner to Example 1, with the same steps, operations, and parameters, except that the porous skeleton material was not used. Specifically:Food-grade sodium carbonate and food-grade sodium bicarbonate were weighed in a mass ratio of 5:10, and mixed thoroughly to obtain a composite foaming agent.Silica gel, white carbon black, and calcium carbonate were weighed in a mass ratio of 100:30:30 as raw materials, and mixed in an internal mixer to obtain a white internally-mixed silica gel.Then, the composite foaming agent, the internally-mixed silica gel, and a platinum vulcanizing agent were weighed in a mass ratio of 10:900:5, and mixed in an internal mixer to obtain a white microcellular foamed composite material.(2) Preparing the microcellular foamed silica gel filter rodThe same procedure as in Example 1 was followed, specifically: a regular triangular mold head was selected for the inner mold head of the silica gel extruder. The composite material was fed into the extruder, and the extrusion speed was set so that the extrusion stroke per revolution of the inner mold was 50 mm. The extruded material was heated at 250 °C to obtain a filter rod having a circumference of 22 mm.The filter rod was thoroughly cooled until the material was shaped, thereby obtaining a white cylinder having elasticity and certain strength. It was cut into 100 mm lengths using a filter rod cutting machine, and was designated as Sample 10.Table 1: Main Material Ratios in Examples 1-7 and Comparative Examples 1-3 Porous Hydroxyapatite : Sodium Carbonate : Sodium BicarbonateSilica Gel : White Carbon Black : Calcium CarbonatePorous Skeleton Foaming Agent : Internally-mixed Silica Gel : Platinum Vulcanizing AgentExample 1100:5:10100:30:3010:900:5Example 290:4:890:25:209:800:3Example 380:3:780:20:157:750:2Example 460:2:660:15:153:200:1Example 550:1:550:10:101:100:1Example 6100:5:10100:30:300.5:900:5Example 7100:5:10100:30:3015:900:5Comparative Example10:0:0100:30:300:900:5Comparative Example21:0:0100:30:3010:900:5Comparative Example 30:5:10100:30:3010:900:5The appearance characteristics of the above 10 samples were investigated, using a conventional cellulose acetate tow filter rod as a control, as shown in Table 2. Table 2: Appearance Comparison of the Samples from Examples 1-7, Comparative Examples 1-3, and the Control Surface AppearanceLength (mm)Length Tolerance (mm)Cross-section Hollowed-out PatternSensory Evaluation of Cross-section AppearanceControl (Cellulose acetate filter rod)White and matte100±2Regular triangleThe edges of the regular triangle were not sharp enough, approaching an irregular rounded triangle, with slight burrs and protruding fibers.Example 1White and matte100±2Regular triangleThe edges of the regular triangle were sharp, the shape was uniform, and the edges were smooth.Example 2White and matte100±2Regular triangleThe edges of the regular triangle were sharp, the shape was uniform, and the edges were smooth.Example 3White and matte100±2Regular triangleThe edges of the regular triangle were sharp, the shape was uniform, and the edges were smooth.Example 4White and matte100±2Regular triangleThe edges of the regular triangle were sharp, the shape was uniform, and the edges were smooth.Example 5White and matte100±2Regular triangleThe edges of the regular triangle were sharp, the shape was uniform, and the edges were smooth.Example 6White and matte100±2Regular triangleThe edges of the regular triangle were relatively sharp, the shape was uniform, and the edges were smooth.Example 7White and matte100±2Regular triangleThe edges of the regular triangle were relatively sharp, the shape was deformed, and the edges had burrs.Comparative Example 1White and matte100±2Regular triangleThe edges of the regular triangle were sharp, the shape was uniform, and the edges were smooth.Comparative Example 2White and matte100±2Regular triangleThe edges of the regular triangle were relatively sharp, the shape was uniform, and the edges were relatively smooth.Comparative Example 3White and matte100±2Regular triangleThe edges of the regular triangle were relatively sharp, the shape was uniform, and the edges had burrs.The results in Table 2 show that, compared with the existing conventional cellulose acetate filter rod, all silica gel filter rods exhibit sharp edges of the regular triangle. Even when the amount of the porous skeleton foaming agent in Examples 6 and 7 was beyond the designed range, their edges were still relatively sharp, whereas the edges of the cellulose acetate filter rod were not sharp enough. This difference is a product characteristic resulting from the different main materials (i.e., cellulose acetate and silica gel). In Example 7, an excessive amount of the porous skeleton foaming agent also caused product shape deformation and burrs on the product edges, leading to poor hand feel and aesthetics.It can be seen from Comparative Examples 1-3 that the microcellular foamed silica gel filter rod without a porous skeleton foaming agent (Comparative Example 1) still maintained good product appearance, which was consistent with the performance of Examples 1-5. This indicates that the use of the porous skeleton foaming agent is not intended to improve product appearance. However, the porous skeleton foaming agent should be understood as a material composition intended for combined use. If only the porous skeleton material was used alone, or only the composite foaming agent was used (Comparative Example 2 or 3), the product appearance was adversely affected, manifesting as insufficiently smooth edges or burrs. This demonstrates that the porous skeleton material should not be used alone.Therefore, from the perspective of product appearance alone, both the microcellular foamed silica gel filter rod of the present invention and the silica gel filter rod without a porous skeleton foaming agent exhibit good appearance, which is significantly superior to that of the conventional cellulose acetate tow filter rod.Further, the properties of the above 10 samples were tested, and the results are shown in Table 3, including:Porosity: According to the test method of GB / T 34709-2017 "General test methods for silica gel — Determination of pore volume", the test is conducted using a BSD-TD fully automatic true density and porosity analyzer manufactured by Beishide Instrument Technology Co., Ltd.Blade replacement frequency: The blade replacement frequency is defined as the number of filter rods that can be cut with one new blade during cutting using a conventional cutting device after the filter rods are shaped. The average value is taken from 10 statistical measurements. As common general knowledge in the art, the blade of the cutting device wears with normal use, and the blade should be replaced when the cut surface of the filter rod is uneven or burrs appear on the edges after cutting, so as to ensure good product appearance.Smoke temperature: The smoke temperature refers to the lip-end smoke temperature. Under the HCI smoking regime, a single-channel smoking machine is used for the puffing test, with a puff volume of 55 mL, a puff duration of 3 s, a puff interval of 30 s, and a total of 10 puffs. After the puffing starts, a UT3208+ multi-channel temperature tester sold by Uni-Trend Technology (China) Co., Ltd. is used to measure the gas-phase temperature at the center point of the smoke outlet near the lip end of the heated cigarette, until the average smoke temperature per puff upon completion of the puffing is obtained.Filter rod hardness: According to the test method of GB / T 22838.6-2009 "Determination of physical characteristics of cigarettes and filter rods — Part 6: Hardness", the test is conducted using an SHG-E cigarette and filter rod hardness tester manufactured by Chengdu Ruituo Technology Co., Ltd.Rebound resilience: According to the test method of GB / T 1681-2009 "Determination of rebound resilience of vulcanized rubber", the test is conducted using a ZY-1011C touch-screen rubber impact rebound testing machine manufactured by Yangzhou Zhengyi Testing Machinery Co., Ltd.Coefficient of sliding friction: According to the test method of GB / T 10006-2021 "Plastics — Film and sheeting — Determination of the coefficients of friction", the test is conducted using an MXD-02 coefficient of friction tester manufactured by Jinan Saicheng Electronic Technology Co., Ltd.Table 3: Performance Comparison of Filter Rods from Examples 1-7, Comparative Examples 1-3, and the Control Hardness (%)Rebound Rate (%)Smoke Temperature (°C)Porosity (%)Coefficient of Sliding FrictionBlade Replacement Frequency (10,000 rods / time)Control (Cellulose Acetate Filter Rod)90.2975.2342.5830.840.31750Example 188.5283.6733.5638.860.26730Example 289.8985.3834.2834.210.29670Example 392.6187.0434.9426.290.33590Example 495.0891.9635.6629.110.38530Example 596.3694.5336.5324.640.43520Example 697.9595.7937.168.850.45420Example 780.1670.1536.8848.470.2740Comparative Example 197.4897.2837.697.370.48400Comparative Example 298.7996.1538.3613.680.47440Comparative Example 388.4785.7935.1817.160.35590 The results in Table 3 show that:1. Compared with the existing conventional cellulose acetate filter rod, all silica gel filter rods except that of Example 7 exhibited good hardness and rebound rate, had good deformation resistance, and could better maintain their appearance quality, meeting the physical property requirements for cigarettes and filter rods. However, the sample of Example 7 contained an excessive amount of the porous skeleton foaming agent, resulting in a higher foaming degree and more pores formed in the filter rod, which led to decreases in both hardness and rebound rate, making it unsuitable as a tobacco filter rod.2. Compared with the existing conventional cellulose acetate filter rod, all silica gel filter rods exhibited a better cooling effect, which might be related to the increased smoke pathway space inside the filter rod and the improved shape and structure of the smoke pathway.3. Compared with the existing conventional silica gel filter rod (Comparative Example 1), the microcellular foamed silica gel filter rods of Examples 1-5, which had an appropriate amount of porous skeleton foaming agent added, all had a smaller coefficient of sliding friction. A smaller coefficient of sliding friction is beneficial for the direct use of filter rods on traditional cigarette making machines, preventing silica gel products from getting stuck in cigarette combining equipment due to their inherent stickiness or high coefficient of sliding friction. This property facilitates the compatibility of silica gel filter rods with conventional cigarette equipment. However, the sample of Example 6 contained too little porous skeleton foaming agent, resulting in a coefficient of sliding friction that was too large. Similar to conventional filter rods, this easily caused the silica gel filter rods to get stuck at the material inlet of the equipment, rendering it unsuitable.4. Compared with the existing conventional cellulose acetate filter rod, silica gel materials have certain stickiness, which leads to higher wear on the blades of cutting equipment, manifested as generally poor blade durability and a smaller number of products that can be cut with each new blade. Compared with the silica gel filter rod without a porous skeleton foaming agent (Comparative Example 1), the present invention finds that adding an appropriate proportion of porous skeleton foaming agent helps to improve the blade durability of the cutting equipment and overcome the defect of poor blade durability caused by silica gel filter rods. For example, in Example 1, which is the optimal embodiment, the blade durability was close to that of the conventional cellulose acetate filter rod.5. Compared with the existing conventional silica gel filter rod (i.e., the product without a porous skeleton foaming agent in Comparative Example 1), although the use of the porous skeleton foaming agent causes a slight decrease in hardness and rebound rate, these properties still meet the physical performance requirements for cigarettes and filter rods. Moreover, its porosity is higher, and the cooling performance for mainstream smoke is further improved, which is of great significance for enhancing the smoking comfort of cigarettes.In summary, the microcellular foamed composite material of the present invention can be used to prepare a microcellular foamed silica gel filter rod having an inner spiral structure. By adding an appropriate amount of porous skeleton foaming agent, the physical properties of the filter rod material are improved, thereby enriching the appearance options and facilitating the obtainment of filter rods with more complex cross-section hollowed-out patterns. While further improving the smoke cooling effect, the present invention finds that the proper use of the porous skeleton foaming agent can also reduce the blade wear during the subsequent cutting of the filter rod using cutting equipment, thereby reducing the blade replacement frequency and improving equipment durability, indicating a good application prospect.
Claims
1. A method for preparing a microcellular foamed composite material, comprising the following steps:(1) preparing a porous skeleton foaming agent, comprising:(1.1) taking a porous skeleton material having a particle size of 58 μm to 180 μm, wherein the porous skeleton material is selected from porous hydroxyapatite, perlite, and / or porous silicon;(1.2) wetting the porous skeleton material obtained in step (1.1) with a silicone oil spray to obtain a wetted material;(1.3) weighing the wetted material and a food-grade foaming agent in a mass ratio of 50-100:6-15, mixing them uniformly, and then passing the mixture through a 200-mesh sieve to remove excess foaming agent on the surface of the material, thereby obtaining the porous skeleton foaming agent, wherein the food-grade foaming agent is sodium carbonate and / or sodium bicarbonate;(2) preparing internally-mixed silica gel, comprising:weighing silica gel, white carbon black, and calcium carbonate in a mass ratio of 50-100:10-30:10-30, and mixing them in an internal mixer to obtain the internally-mixed silica gel;(3) preparing the microcellular foamed composite material, comprising:weighing the porous skeleton foaming agent, the internally-mixed silica gel, and a vulcanizing agent in a mass ratio of 1-10:100-900:1-5, and mixing them in an internal mixer to obtain the microcellular foamed composite material. 2. The method according to claim 1, characterized in that the porous skeleton material in step (1.1) is obtained by drying at a temperature of 100 °C to 150 °C for 2 h to 8 h, and wherein the porous hydroxyapatite, perlite, and / or porous silicon in step (1.1) has a specific surface area of 20 m² / g to 1000 m² / g. 3. The method according to claim 1, characterized in that a mass ratio of the silicone oil to the porous skeleton material in step (1.2) is 5-20:100. 4. The method according to claim 1, characterized in that in step (1.3), the wetted material, sodium carbonate, and sodium bicarbonate are weighed in a mass ratio of 50-100:1-5:5-10 and mixed uniformly. 5. The method according to claim 1, characterized in that step (3) further comprises adding a food-grade pigment. 6. The method according to claim 1, characterized in that the vulcanizing agent in step (3) is a platinum vulcanizing agent. 7. Use of a microcellular foamed composite material prepared by the method according to any one of claims 1 to 6, in a filter rod. 8. The use according to claim 7, characterized in that the filter rod is a heated non-combustion cigarette filter rod or a combustion-type cigarette filter rod. 9. A method for preparing a microcellular foamed silica gel filter rod, comprising the following steps:(1) feeding a microcellular foamed composite material into a silica gel extruder having a rotating inner mold, and rotationally extruding a rod-shaped material therefrom, wherein the microcellular foamed composite material is the microcellular foamed composite material prepared by the method according to any one of claims 1 to 5;(2) heating the rod-shaped material obtained in step (1) at 160 °C to 250 °C for 10 s to 20 s for vulcanization;(3) naturally cooling the material obtained in step (2), and then cutting the same to obtain the microcellular foamed silica gel filter rod. 10. The method according to claim 9, characterized in that a porosity of the microcellular foamed silica gel filter rod is 10% to 40%.