A papermaking felt for reconstituted tobacco in papermaking and its preparation method

Abstract

This invention provides a papermaking felt for reconstituted tobacco using a papermaking process and its preparation method. The preparation method includes the following steps: a) pulverizing pulp and mixing it with water to obtain a slurry, then adding an oxidant, a catalyst, and an oxidizing aid to carry out an oxidation reaction to obtain a reaction mixture; then sequentially subjecting the reaction mixture to pH adjustment, ultrasonication, and centrifugation to obtain nanocellulose filaments; b) using the nanocellulose filaments obtained in step a) and activated carbon particles as 3D printing materials, adding a crosslinking agent, and 3D printing according to a pre-designed model, followed by drying to obtain a papermaking felt for reconstituted tobacco using a papermaking process. Compared with the prior art, the preparation method provided by this invention uses specific raw materials combined with specific process steps to achieve better overall interaction, which can improve the dewatering efficiency of wet paper sheets of reconstituted tobacco under low linear pressure conditions, maintain a high bulk of reconstituted tobacco, and thus improve the smoking taste of reconstituted tobacco.

Description

Technical Field

[0001] This invention relates to the field of papermaking felt technology, and more specifically, to a papermaking felt for reconstituted tobacco leaves by papermaking and a method for preparing the same. Background Technology

[0002] Papermaking reconstituted tobacco is an advanced tobacco production process that uses papermaking technology to process tobacco leaf fragments, dust, and stems, thereby improving tobacco utilization. In the production process, the raw materials are mainly uncured or partially cured waste tobacco leaves. First, extraction and pulping are performed. The raw materials are fed into an extraction tank with water for extraction. The extracted tobacco leaf fragments are dehydrated and pressed, and then combined with the stems (after dehydration, pressing, and initial grinding in a disc mill), along with added fibers processed by a refiner, to form a pulp. The pulp is then sent to a paper machine for papermaking, consisting of a headbox, wire section, press section, and drying section (including coating), to form paper sheets. The paper sheets are then broken into flakes, flavored, dried, packaged, and stored. During the pressing process, to improve the dryness of the wet paper sheets, the press line pressure is often increased. However, this reduces the bulk of the reconstituted tobacco leaves, decreases the absorption of the coating liquor, and affects the smoking experience.

[0003] Chinese Patent Application No. CN201520081301.1 discloses a pre-pressing device for improving the dewatering efficiency of wet paper sheets in a reconstituted tobacco papermaking machine. It mainly includes an upper felt conveying device and a lower felt conveying device. The upper felt conveying device mainly includes an upper felt, an upper conveying roller group for conveying the upper felt, an upper felt tensioning device for tensioning the upper felt, a suction and transfer device cooperating with the upper felt, and a pre-pressing upper roller located on the inner side of the upper felt. The pre-pressing upper roller is connected to a pressurizing device and a transmission system. The lower felt conveying device mainly includes a lower felt, a lower conveying roller group for conveying the lower felt, a lower felt tensioning device for tensioning the lower felt, and a pre-pressing lower roller located on the inner side of the lower felt. The pre-pressing lower roller is connected to the transmission system, and a vacuum chamber is provided inside the pre-pressing lower roller.

[0004] Reconstituted tobacco has the characteristics of high filling value, good combustion performance and reduced tar release. It is usually used in traditional cigarettes to replace or partially replace traditional tobacco. The main traditional methods for preparing reconstituted tobacco are papermaking, rolling, and slurry. The slurry method requires a large investment and the technical indicators of the product are significantly lower than those of papermaking reconstituted tobacco. The reconstituted tobacco produced by the rolling process has the disadvantages of poor moisture retention, low flexibility, brittleness, poor color, insufficient aroma, small smoke volume, unsatisfactory taste and low effective utilization rate, which affect the effective use of reconstituted tobacco. Therefore, compared with the other two preparation methods, papermaking reconstituted tobacco is the most widely used in my country. In the pressing process, in order to improve the dehydration efficiency, the current technology is to add a pre-pressing device. Adding a pre-pressing device to the papermaking reconstituted tobacco production line has certain disadvantages, mainly in the following aspects: (1) High cost. The cost of new equipment is usually higher than that of old equipment, which may put pressure on the company's finances. (2) Technological risk. The new equipment may employ some new technologies that may not be mature or have not been proven reliable; this may lead to equipment malfunctions during operation, thereby affecting the company's production efficiency. (3) Employee training. The new equipment may require employee training to use it proficiently; this may require a certain amount of time and resources to familiarize employees with the operation and maintenance of the new equipment. (4) Compatibility with existing systems. The new equipment may not be fully compatible with existing systems and may require additional adjustments and modifications. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a papermaking felt for reconstituted tobacco leaves and a method for preparing the same. The preparation method provided by the present invention can improve the dewatering efficiency of wet paper sheets of reconstituted tobacco leaves under low linear pressure conditions, maintain a high bulk of reconstituted tobacco leaves, and improve the smoking taste of reconstituted tobacco leaves.

[0006] This invention provides a method for preparing papermaking felt for reconstituted tobacco leaves using a papermaking process, comprising the following steps:

[0007] a) The pulp is crushed and mixed with water to obtain a slurry. Then, an oxidant, a catalyst and an oxidizing aid are added to carry out an oxidation reaction to obtain a reaction mixture. The reaction mixture is then subjected to pH adjustment, sonication and centrifugation in sequence to obtain nanocellulose filaments.

[0008] b) The nanocellulose filaments and activated carbon particles obtained in step a) are used as 3D printing materials, and a crosslinking agent is added. The materials are 3D printed according to a pre-designed model. After drying, a papermaking blanket for reconstituted tobacco leaves is obtained.

[0009] Preferably, the pulp in step a) is softwood pulp; the mesh size of the pulverized pulp is 40 to 60 mesh; and the mass ratio of pulp to water is 1:(40 to 50).

[0010] Preferably, the oxidant in step a) is 2,2,6,6-tetramethylpiperidine oxide, and the amount added is 0.02% to 0.03% of the slurry mass;

[0011] The catalyst is NaBr and / or KBr, and the amount added is 0.02% to 0.03% of the slurry mass;

[0012] The oxidizing agent is NaClO and / or KClO, and the amount added is 8% to 10% of the slurry mass.

[0013] Preferably, the oxidation reaction in step a) is carried out at a temperature of 20°C to 50°C for a time of 30 min to 60 min.

[0014] Preferably, in step a), the pH is adjusted to neutral; the sonication time is 100 min to 120 min; the centrifugation speed is 5000 r / min to 8000 r / min, and the time is 5 min to 10 min.

[0015] Preferably, the diameter of the nanocellulose filaments in step a) is 50nm to 100nm and the length is 1500nm to 2000nm.

[0016] Preferably, the method for preparing the activated carbon particles in step b) is as follows:

[0017] After drying the biomass raw material, it is pulverized to 40-60 mesh and then thermally decomposed to 600-800℃ under N2 atmosphere at a heating rate of 20℃ / s-30℃ / s. The resulting carbon is then ground to 400-600 mesh to obtain activated carbon particles.

[0018] Preferably, in step b), the mass ratio of the nanocellulose filaments to the activated carbon particles is (100-300):1; and the amount of the crosslinking agent added is 1%-2% of the total mass of the 3D printing material.

[0019] Preferably, the 3D printing temperature in step b) is 180℃~230℃ and the speed is 300mm / s~500mm / s.

[0020] The present invention also provides a papermaking felt for reconstituted tobacco leaves using a papermaking process, which is prepared by the preparation method described in the above technical solution.

[0021] This invention provides a papermaking felt for reconstituted tobacco using a papermaking process and its preparation method. The preparation method includes the following steps: a) pulverizing pulp and mixing it with water to obtain a slurry, then adding an oxidant, a catalyst, and an oxidizing aid to carry out an oxidation reaction to obtain a reaction mixture; then sequentially subjecting the reaction mixture to pH adjustment, ultrasonication, and centrifugation to obtain nanocellulose filaments; b) using the nanocellulose filaments obtained in step a) and activated carbon particles as 3D printing materials, adding a crosslinking agent, and 3D printing according to a pre-designed model, followed by drying to obtain a papermaking felt for reconstituted tobacco using a papermaking process. Compared with the prior art, the preparation method provided by this invention uses specific raw materials combined with specific process steps to achieve better overall interaction, which can improve the dewatering efficiency of wet paper sheets of reconstituted tobacco under low linear pressure conditions, maintain a high bulk of reconstituted tobacco, and thus improve the smoking taste of reconstituted tobacco. Detailed Implementation

[0022] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0023] This invention provides a method for preparing papermaking felt for reconstituted tobacco leaves using a papermaking process, comprising the following steps:

[0024] a) The pulp is crushed and mixed with water to obtain a slurry. Then, an oxidant, a catalyst and an oxidizing aid are added to carry out an oxidation reaction to obtain a reaction mixture. The reaction mixture is then subjected to pH adjustment, sonication and centrifugation in sequence to obtain nanocellulose filaments.

[0025] b) The nanocellulose filaments and activated carbon particles obtained in step a) are used as 3D printing materials, and a crosslinking agent is added. The materials are 3D printed according to a pre-designed model. After drying, a papermaking blanket for reconstituted tobacco leaves is obtained.

[0026] In recent years, products made from waste tobacco stems, dust, and sticks discarded during the cigarette-making process using papermaking methods have been termed reconstituted tobacco. Reconstituted tobacco possesses physical properties such as looseness and porosity, good combustibility, softness and folding resistance, good machinability, and high filling value. It also has unique chemical properties; for example, its tar content is only 50% of that of natural tobacco leaves, and the nicotine and aroma content can be artificially controlled during production. Therefore, adding an appropriate amount of reconstituted tobacco to cigarettes can, on the one hand, maximize the conservation of raw materials and effectively reduce production costs; on the other hand, it can effectively improve the use value of low-grade tobacco leaves, producing diversified products that meet market demands. Absorption performance is an important criterion for evaluating the quality of papermaking reconstituted tobacco. Like paper, papermaking reconstituted tobacco has a porous structure, and its absorption performance is closely related to both the porosity (air permeability) and the liquid absorption capacity of the reconstituted tobacco. The high absorbency of reconstituted tobacco leaves means that the fibers are loose and porous with a high filler value. This not only improves the fullness of cigarettes and reduces the amount of tobacco used, but also ensures complete combustion of the tobacco, reducing the amount of harmful substances. Furthermore, it allows the tobacco sheet to fully absorb the coating liquid during the coating process, guaranteeing a good coating effect. Therefore, how to improve the bulk and absorbency of reconstituted tobacco leaves is a topic of common concern in academic research and the reconstituted tobacco manufacturing industry.

[0027] In summary, since reconstituted tobacco leaves produced by papermaking differ significantly from ordinary paper in terms of physical structure and fiber characteristics, and given the fiber characteristics and performance requirements of reconstituted tobacco leaves, papermaking reconstituted tobacco leaves need to have a certain bulk. Therefore, the purpose of this invention is to provide a papermaking felt for papermaking reconstituted tobacco leaves and its preparation method, which increases the water absorption rate of the papermaking felt without increasing the pressure of the press line, thereby significantly improving the dewatering efficiency of papermaking reconstituted tobacco leaves.

[0028] The present invention first pulverizes paper pulp and mixes it with water to obtain a slurry, then adds an oxidant, a catalyst and an oxidizing aid to carry out an oxidation reaction to obtain a reaction mixture; then the reaction mixture is subjected to pH adjustment, sonication and centrifugation in sequence to obtain nanocellulose filaments.

[0029] In this invention, the pulp is preferably softwood pulp; the source of the softwood pulp is not particularly limited and commercially available products known to those skilled in the art can be used.

[0030] In this invention, the pulverizing device can be a pulverizer well known to those skilled in the art; the preferred mesh size of the pulverized material is 40 mesh to 60 mesh.

[0031] In this invention, the preferred mass ratio of pulp (oven-dry) to water is 1:(40-50).

[0032] In this invention, the oxidant is preferably 2,2,6,6-tetramethylpiperidine oxide (TEMPO), and the amount added is preferably 0.02% to 0.03% of the slurry mass; the catalyst is preferably NaBr and / or KBr, more preferably NaBr, and the amount added is preferably 0.02% to 0.03% of the slurry mass; the oxidation aid is preferably NaClO and / or KClO, more preferably NaClO, and the amount added is preferably 8% to 10% of the slurry mass. This invention does not impose any special restrictions on the source of the oxidant, catalyst, and oxidation aid; commercially available products well known to those skilled in the art can be used.

[0033] In this invention, the temperature of the oxidation reaction is preferably 20°C to 50°C, and the time is preferably 30 min to 60 min.

[0034] In this invention, the pH adjustment is preferably to neutral, and can be performed using hydrochloric acid solution and / or sodium hydroxide solution well known to those skilled in the art; the purpose of the ultrasonication is to clean and disperse, and the ultrasonication time is preferably 100 min to 120 min; the purpose of the centrifugation is to separate the fibers, and the centrifugation speed is preferably 5000 r / min to 8000 r / min, and the centrifugation time is preferably 5 min to 10 min.

[0035] In this invention, the nanocellulose filaments are TEMPO-oxidized nanocellulose filaments, with a preferred diameter of 50 nm to 100 nm and a preferred length of 1500 nm to 2000 nm.

[0036] In this invention, nanocellulose has the following structural characteristics: (1) Nanocellulose has a highly ordered lattice structure, in which cellulose chains are closely arranged in the lattice and exhibit a regular parallel arrangement. (2) The fiber diameter of nanocellulose is usually at the nanometer level. Cellulose fibers in this size range have a large specific surface area and good mechanical properties, and therefore have broad application prospects in many fields. (3) Nanocellulose has good chemical stability and can maintain stability under conditions such as strong acid, strong alkali or high temperature. (4) Nanocellulose can be processed into fibers of various shapes and sizes, such as films, microspheres, nanotubes, etc.; these changes in shape and size can be achieved by changing the preparation process and conditions. (5) Nanocellulose has good biocompatibility and can be used to prepare biomedical materials and drug carriers, etc.; at the same time, nanocellulose also has good biodegradability, which is beneficial to environmental protection.

[0037] After obtaining the nanocellulose filaments, the present invention uses the obtained nanocellulose filaments and activated carbon particles as 3D printing materials, adds a crosslinking agent, performs 3D printing according to a pre-designed model, and obtains papermaking blankets for papermaking reconstituted tobacco leaves after drying.

[0038] In this invention, the preferred method for preparing the activated carbon particles is as follows:

[0039] After drying the biomass raw material, it is pulverized to 40-60 mesh and then thermally decomposed to 600-800℃ under N2 atmosphere at a heating rate of 20℃ / s-30℃ / s. The resulting carbon is then ground to 400-600 mesh to obtain activated carbon particles.

[0040] In this invention, the preferred mass ratio of the nanocellulose filaments to the activated carbon particles is (100-300):1; the preferred amount of the crosslinking agent is 1%-2% of the total mass of the 3D printing material.

[0041] In this invention, the crosslinking agent promotes the crosslinking of nanocellulose and is preferably selected from one or more of calcium salts, aluminum salts, and silicates, more preferably calcium chloride, aluminum chloride, or calcium silicate. This invention does not impose any particular limitation on the source of the crosslinking agent; commercially available products well known to those skilled in the art can be used.

[0042] In this invention, the pre-designed model is preferably digitally designed: a 3D model is created using computer-aided design, and all subsequent operations will be performed based on this model.

[0043] In this invention, the thickness of the model is preferably 5.0mm to 10.0mm, the width is preferably 2.5m to 3.0m, and the length is preferably 25m to 30m, wherein the length and width are specifically determined according to the paper machine model.

[0044] In this invention, the preferred temperature for 3D printing is 180℃~230℃, and the preferred speed is 300mm / s~500mm / s; 3D printing is started to prepare papermaking blankets.

[0045] In this invention, the drying temperature is preferably 30°C to 50°C.

[0046] This invention first prepares nanocellulose, and then uses 3D printing to obtain a papermaking felt for reconstituted tobacco leaves using a papermaking process; the structural characteristics of the nanocellulose are as follows:

[0047] Highly ordered: Nanocellulose has a highly ordered crystal lattice structure, in which cellulose chains are closely arranged in the lattice and exhibit a regular parallel arrangement.

[0048] Microfibers: The diameter of nanocellulose fibers is usually in the nanometer range. Cellulose fibers in this size range have a large specific surface area and good mechanical properties, so they have broad application prospects in many fields.

[0049] Chemical stability: Nanocellulose has good chemical stability and can maintain its stability under conditions such as strong acids, strong alkalis or high temperatures; this makes nanocellulose a great potential material for the preparation of functional materials and composite materials.

[0050] Plasticity: Nanocellulose can be processed into fibers of various shapes and sizes, such as films, microspheres, and nanotubes; these changes in shape and size can be achieved by changing the preparation process and conditions.

[0051] Biocompatibility: Nanocellulose has good biocompatibility and can be used to prepare biomedical materials and drug carriers; at the same time, nanocellulose also has good biodegradability, which is beneficial to environmental protection.

[0052] 3D printing of nanocellulose is a method for preparing nanocellulose materials using 3D printing technology. Through 3D printing, nanocellulose materials can be printed according to a preset shape and size, achieving rapid and precise preparation of materials. 3D printed nanocellulose materials usually use biocompatible and biodegradable nanocellulose as raw materials. By adjusting the printing parameters and material formulation, nanocellulose materials with different shapes and properties can be printed.

[0053] This invention also provides a papermaking felt for reconstituted tobacco using a papermaking process, prepared using the method described above. In this invention, the papermaking felt is prepared from 3D-printed nanocellulose. Nanocellulose has a high specific surface area, effectively absorbing moisture from the wet paper of reconstituted tobacco. Activated carbon is added during the 3D printing process to filter contaminants from the reconstituted tobacco production process. Therefore, the dehydration efficiency of the wet paper of reconstituted tobacco can be improved without increasing the linear pressure, maintaining the bulk of the reconstituted tobacco, which is beneficial for smoking (for every 1% increase in bulk, the filling value can increase by 0.54%; this means that increasing the bulk of reconstituted tobacco can increase its filling value, thereby affecting the smoking experience; in addition, the bulk of reconstituted tobacco also affects the quality of the reconstituted tobacco, thus affecting the smoking quality of cigarettes; for example, when the bulk of reconstituted tobacco is higher, its woody aroma is lighter and its irritation is less, which helps to improve the smoking experience). This invention is highly innovative. There are currently no reports on its application to papermaking for reconstituted tobacco blankets. Furthermore, the product has excellent overall performance and can effectively improve the dehydration efficiency and smoking taste of reconstituted tobacco.

[0054] This invention provides a papermaking felt for reconstituted tobacco using a papermaking process and its preparation method. The preparation method includes the following steps: a) pulverizing pulp and mixing it with water to obtain a slurry, then adding an oxidant, a catalyst, and an oxidizing aid to carry out an oxidation reaction to obtain a reaction mixture; then sequentially subjecting the reaction mixture to pH adjustment, ultrasonication, and centrifugation to obtain nanocellulose filaments; b) using the nanocellulose filaments obtained in step a) and activated carbon particles as 3D printing materials, adding a crosslinking agent, and 3D printing according to a pre-designed model, followed by drying to obtain a papermaking felt for reconstituted tobacco using a papermaking process. Compared with the prior art, the preparation method provided by this invention uses specific raw materials combined with specific process steps to achieve better overall interaction, which can improve the dewatering efficiency of wet paper sheets of reconstituted tobacco under low linear pressure conditions, maintain a high bulk of reconstituted tobacco, and thus improve the smoking taste of reconstituted tobacco.

[0055] To further illustrate the present invention, the following embodiments are provided for detailed description. All raw materials used in the following embodiments of the present invention are commercially available.

[0056] Example 1

[0057] (1) Preparation of nanocellulose. ① Pulp of softwood was pulverized to 40 mesh using a pulverizer; ② Water was added to the pulverized softwood pulp, with a dry pulp to water mass ratio of 1:40. 0.02 wt.% TEMPO oxidant and 0.02 wt.% NaBr catalyst were added and dissolved in the pulp; ③ The oxidation reaction was accelerated by NaClO (8 wt.%, 150 mmol / ml), the reaction temperature was 20℃, and the time was 30 min; ④ The pH was adjusted to neutral using 0.2 mmol / ml HCl and NaOH; ⑤ The mixture was sonicated for 100 min; ⑥ The mixture was centrifuged at 5000 r / min for 5 min to obtain CNF (nanocellulose filaments) oxidized by TEMPO, with a diameter of 50 nm to 100 nm and a length of 1500 nm to 2000 nm.

[0058] (2) Preparation of activated carbon particles. ① The biomass raw materials (coniferous wood, broad-leaved wood, grass, etc.) are dried and pulverized to 40 mesh; ② Thermal pyrolysis is carried out in N2 atmosphere at 600℃ with a heating rate of 20℃ / s; ③ The carbon obtained by thermal pyrolysis is ground to 400 mesh to obtain activated carbon particles.

[0059] (3) 3D printing. ① Digital design: Use computer-aided design to create a 3D model. All subsequent operations will be based on this model. The thickness is 5.0 mm, the width is 2.5 m to 3.0 m, and the length is 25 m to 30 m (the length and width are determined according to the paper machine model); ② Selection of printing materials: The mass ratio of CNF and activated carbon particles prepared in the above steps is 100:1, and 1.0 wt.% calcium chloride is added to promote the cross-linking of nanocellulose; ③ 3D printing parameters: temperature is 180℃, and speed is 300 mm / s; ④ Start 3D printing to prepare papermaking felt; ⑤ Dry at 30℃ to obtain papermaking felt for reconstituted tobacco leaves using the papermaking method.

[0060] Example 2

[0061] (1) Preparation of nanocellulose. ① Pulp of softwood was pulverized to 50 mesh using a pulverizer; ② Water was added to the pulverized softwood pulp, with a dry pulp to water mass ratio of 1:45. 0.025 wt.% TEMPO oxidant and 0.025 wt.% NaBr catalyst were added and dissolved in the pulp; ③ The oxidation reaction was accelerated by NaClO (9 wt.%, 150 mmol / ml), the reaction temperature was 35℃, and the time was 45 min; ④ The pH was adjusted to neutral using 0.25 mmol / ml HCl and NaOH; ⑤ The mixture was sonicated for 110 min; ⑥ The mixture was centrifuged at 6500 r / min for 8 min to obtain CNF (nanocellulose filaments) oxidized by TEMPO, with a diameter of 50 nm to 100 nm and a length of 1500 nm to 2000 nm.

[0062] (2) Preparation of activated carbon particles. ① The biomass raw materials (coniferous wood, broad-leaved wood, grass, etc.) are dried and pulverized to 50 mesh; ② Thermal pyrolysis is carried out in a N2 atmosphere at 700℃ with a heating rate of 25℃ / s; ③ The carbon obtained from thermal pyrolysis is ground to 500 mesh to obtain activated carbon particles.

[0063] (3) 3D printing. ① Digital design: Use computer-aided design to create a 3D model. All subsequent operations will be based on this model. The thickness is 8.0 mm, the width is 2.5 m to 3.0 m, and the length is 25 m to 30 m (the length and width are determined according to the paper machine model); ② Selection of printing materials: The mass ratio of CNF and activated carbon particles prepared in the above steps is 200:1, and 1.5 wt.% aluminum chloride is added to promote the cross-linking of nanocellulose; ③ 3D printing parameters: temperature is 200℃, and speed is 400 mm / s; ④ Start 3D printing to prepare papermaking felt; ⑤ Dry at 40℃ to obtain papermaking felt for reconstituted tobacco leaves using the papermaking method.

[0064] Example 3

[0065] (1) Preparation of nanocellulose. ① Pulp of softwood was pulverized to 60 mesh using a pulverizer; ② Water was added to the pulverized softwood pulp, with a dry pulp to water mass ratio of 1:50. 0.03 wt.% TEMPO oxidant and 0.03 wt.% NaBr catalyst were added and dissolved in the pulp; ③ The oxidation reaction was accelerated by NaClO (10 wt.%, 150 mmol / ml), the reaction temperature was 50℃, and the time was 60 min; ④ The pH was adjusted to neutral using 0.3 mmol / ml HCl and NaOH; ⑤ The mixture was sonicated for 120 min; ⑥ The mixture was centrifuged at 8000 r / min for 10 min to obtain CNF (nanocellulose filaments) oxidized by TEMPO, with a diameter of 50 nm to 100 nm and a length of 1500 nm to 2000 nm.

[0066] (2) Preparation of activated carbon particles. ① The biomass raw materials (coniferous wood, broad-leaved wood, grass, etc.) are dried and pulverized to 60 mesh; ② Thermal pyrolysis is carried out in N2 atmosphere at 800℃ with a heating rate of 30℃ / s; ③ The carbon obtained by thermal pyrolysis is ground to 600 mesh to obtain activated carbon particles.

[0067] (3) 3D printing. ① Digital design: Use computer-aided design to create a 3D model. All subsequent operations will be based on this model. The thickness is 10.0 mm, the width is 2.5 m to 3.0 m, and the length is 25 m to 30 m (the length and width are determined according to the paper machine model); ② Selection of printing materials: The mass ratio of CNF and activated carbon particles prepared in the above steps is 300:1, and 2.0 wt.% calcium silicate is added to promote the cross-linking of nanocellulose; ③ 3D printing parameters: temperature is 230℃, and speed is 500 mm / s; ④ Start 3D printing to prepare papermaking felt; ⑤ Dry at 50℃ to obtain papermaking felt for reconstituted tobacco leaves using the papermaking method.

[0068] Comparative Example

[0069] (1) Wool, bamboo fiber and flax fiber are mixed to make plush yarn and placed on the yarn frame of the warp knitting machine; polyester is used as the base yarn for warping, with a warping length of 12000m and a warping speed of 600m / min; the warped base yarn and plush yarn are woven into a greige fabric; the knitting speed is 500r / min.

[0070] (2) Cut the fabric obtained in step (1) into two widths from the middle, and pre-shape the fabric at high temperature. The temperature is set to 165℃ and the fabric speed is set to 20m / min. After pre-shaping, brushing and ironing are performed. The brushing direction is the same as the fabric direction and the fabric speed is 6m / min. During the ironing operation, the temperature is 210℃ and the fabric speed is 8m / min.

[0071] (3) The fabric treated in step (2) is subjected to anti-mildew treatment. The anti-mildew liquid contains 5g / L of anti-mildew agent and 2.5g / L of soda ash. The bath ratio of the fabric to the anti-mildew liquid is 1:25. The anti-mildew treatment temperature is 55℃ and the anti-mildew treatment time is 3 hours to obtain an absorbent layer.

[0072] (4) Place the absorbent layer between the two base fabric layers, heat treat at 120°C for 4 hours, and then cure at 150°C for 50 minutes; immerse in deionized water at 35°C for 3.5 hours, and then heat treat at 150°C for 50 minutes to obtain a moisture-absorbing and breathable papermaking blanket.

[0073] The papermaking felts prepared by the preparation methods provided in Examples 1-3 and the comparative examples were subjected to performance tests, and the results are shown in Table 1 below.

[0074] Table 1

[0075] Dehydration rate / % <![CDATA[Reconstituted tobacco bulk density / (cm 3 / g)]]> Example 1 35.17 2.12 Example 2 37.86 2.23 Example 3 39.14 2.29 Comparative Example 31.35 1.99

[0076] Dehydration rate determination: Under a pressing force of 3.0 MPa, the dehydration rate was determined for samples with a quantitative content of 100 g / m³. 2 A pressing and dewatering experiment was conducted on reconstituted tobacco leaf substrate using a papermaking method. The specific experimental procedure was as follows: Before pressing and dewatering, the mass of the substrate was weighed. After pressing and dewatering, the mass of the substrate was weighed again, and the dewatering rate was calculated using the following formula:

[0077]

[0078] In the formula: η—dehydration rate, %;

[0079] a1—Substrate mass before pressing, g;

[0080] a2—Mass of the substrate after pressing, in grams;

[0081] Looseness determination: The bulkness of reconstituted tobacco leaves produced by papermaking was determined according to the national standard GB / T451.3-2002. The specific test procedures are as follows:

[0082] (1) Turn on the power switch of the thickness gauge and preheat for 30 minutes;

[0083] (2) Press any key except the "Reset" key to put the instrument into standby mode;

[0084] (3) Zeroing: When the probe is in contact with the measuring surface, press the "Stop" button, then press the "Zero" button to clear the display screen;

[0085] (4) Insert the sample and measure the amount (automatic calculation of tightness);

[0086] (5) Press the “Test” button, and when the probe rises, place the sample in for testing;

[0087] (6) Replace the sample and conduct the next test.

[0088] The bulk density can be calculated from the sample's quantification and thickness.

[0089]

[0090] In the formula; v—the bulk of the sample, in cm 3 / g;

[0091] g—Quantitative value of sample, g / m 2 ;

[0092] δ—Sample thickness, mm;

[0093] The result is accurate to two decimal places.

[0094] In summary, this invention provides a method for preparing a papermaking blanket for reconstituted tobacco using a papermaking process. The papermaking blanket is prepared by 3D printing nanocellulose. Nanocellulose has a high specific surface area and can effectively absorb moisture from the wet paper sheets of reconstituted tobacco. Activated carbon is added during the 3D printing process to filter pollutants in the reconstituted tobacco production process. Therefore, the dehydration efficiency of the wet paper sheets of reconstituted tobacco can be improved without increasing the linear pressure, maintaining the bulk of the reconstituted tobacco, which is beneficial to the smoking experience and reduces the energy consumption of the drying section.

[0095] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing papermaking felt for reconstituted tobacco leaves using a papermaking process, comprising the following steps: a) The pulp is crushed and mixed with water to obtain a slurry. Then, an oxidant, a catalyst and an oxidizing aid are added to carry out an oxidation reaction to obtain a reaction mixture. The reaction mixture is then subjected to pH adjustment, sonication and centrifugation in sequence to obtain nanocellulose filaments. The nanocellulose filaments have a diameter of 50nm~100nm and a length of 1500nm~2000nm. b) The nanocellulose filaments obtained in step a) and 400-600 mesh activated carbon particles are used as 3D printing materials, and a crosslinking agent is added. 3D printing is carried out according to the pre-designed model. After drying, papermaking blankets for papermaking reconstituted tobacco leaves are obtained. The mass ratio of the nanocellulose filaments to the activated carbon particles is (100~300):1; the amount of the crosslinking agent added is 1%~2% of the total mass of the 3D printing material. The 3D printing temperature is 180℃~230℃, and the speed is 300mm / s~500mm / s.

2. The preparation method according to claim 1, characterized in that, The pulp mentioned in step a) is softwood pulp; the mesh size of the pulverized pulp is 40-60 mesh; and the mass ratio of pulp to water is 1:(40-50).

3. The preparation method according to claim 1, characterized in that, The oxidant mentioned in step a) is 2,2,6,6-tetramethylpiperidine oxide, and the amount added is 0.02%~0.03% of the slurry mass; The catalyst is NaBr and / or KBr, and the amount added is 0.02%~0.03% of the slurry mass; The oxidizing agent is NaClO and / or KClO, and the amount added is 8% to 10% of the slurry mass.

4. The preparation method according to claim 1, characterized in that, The oxidation reaction in step a) is carried out at a temperature of 20℃~50℃ for a time of 30min~60min.

5. The preparation method according to claim 1, characterized in that, In step a), the pH is adjusted to neutral; the sonication time is 100 min to 120 min; the centrifugation speed is 5000 r / min to 8000 r / min, and the time is 5 min to 10 min.

6. The preparation method according to claim 1, characterized in that, The specific method for preparing the activated carbon particles described in step b) is as follows: After drying the biomass raw material, it is pulverized to 40-60 mesh and then thermally decomposed to 600-800℃ under N2 atmosphere at a heating rate of 20℃ / s-30℃ / s. The resulting carbon is then ground to obtain activated carbon particles.

7. A papermaking felt for reconstituted tobacco leaves using a papermaking process, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 6.

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