Reconstituted tobacco and preparation method thereof

Abstract

The invention discloses reconstituted tobacco and a preparation method thereof. The method for preparing the reconstituted tobacco comprises the following steps: performing secondary countercurrent extraction on the tobacco, and adjusting the concentration to form leaf pulp; the leaf pulp, the stem pulp and wood pulp are subjected to pulp mixing and low-concentration pulp grinding; wherein the stem pulp is prepared by adopting a method comprising the following steps: performing fiber decomposition, high-concentration pulp grinding and pulp washing on tobacco stems to form the stem pulp; the wood pulp is prepared by a method comprising the following steps: hydraulically disintegrating additional fibers, and adjusting the concentration to form the wood pulp. When the method is used for preparing the reconstituted tobacco, the film base composition control precision is improved, the physical performance of the film base is improved, the combustion performance of a finished product is improved, and the tar content in smoke of the finished product is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of papermaking-based reconstituted tobacco production, and in particular to reconstituted tobacco and a preparation method thereof. Background Art

[0002] Reconstituted tobacco papermaking utilizes a wet papermaking process to extract solids from tobacco raw materials (such as stems, shredded tobacco, tobacco dust, and ash sticks), mechanically pulp them, and form them into paper sheets. During this process, the liquid phase is concentrated and flavored before being coated onto a sheet base, ultimately creating the reconstituted tobacco product. However, most reconstituted tobacco companies currently use mechanical pulping, without pre-treatment by homogenization and screening. The added fiber is primarily coniferous pulp, resulting in the presence of fiber bundles, raw material particles, and fine components in the slurry, leading to poor slurry uniformity. These issues result in the reconstituted tobacco sheet base exhibiting defects such as stiffness, roughness, and poor absorbency. Furthermore, the sheet can shed dust and hair during production and processing, resulting in poor processing resistance.

[0003] Therefore, in view of the current status and shortcomings of reconstituted tobacco, it is of great significance to study and develop a high-performance reconstituted tobacco and its preparation method to achieve the goals of high load-bearing capacity, suitable physical properties, process resistance and excellent sensory quality. Summary of the Invention

[0004] Based on this, the present application at least provides a method for preparing reconstituted tobacco and its application.

[0005] In one aspect of the present application, a method for preparing reconstituted tobacco is provided, the method comprising the following steps:

[0006] The tobacco leaves are subjected to secondary countercurrent extraction and the concentration is adjusted to form leaf pulp;

[0007] Mixing the leaf pulp, stem pulp and wood pulp;

[0008] The stem pulp is prepared by a method comprising the following steps: defibrillating, high-consistency refining, and washing the tobacco stems to form the stem pulp;

[0009] The wood pulp is prepared by a method comprising the following steps: hydraulically crushing the added fibers and adjusting the concentration to form the wood pulp.

[0010] In some embodiments, the wood pulp is beated at least once.

[0011] In some embodiments, the conditions for beating include:

[0012] The wood pulp concentration was adjusted to 10 wt%~15 wt% and the pulp was hydropulverized for 30 min~60 min.

[0013] In some embodiments, the secondary countercurrent extraction is performed at a temperature of 55° C. to 75° C. and a solid-to-liquid ratio of 1:(5-8).

[0014] In some embodiments, the concentration of the slurry is 3 wt% to 5 wt%.

[0015] In some embodiments, the defibration comprises:

[0016] The tobacco stems are extracted 1-2 times and subjected to solid-liquid separation at a temperature of 55-75°C and a solid-liquid ratio of 1:(5-8), and then defibrated and squeezed to form a stem fiber pulp with a beating degree of 5-15°SR and a dryness of 25%-35%.

[0017] In some embodiments, high-consistency refining includes subjecting the stem fiber pulp having a dryness of 25% to 35% to high-consistency refining to form a 10-25° SR stem pulp.

[0018] In some embodiments, pulp washing includes subjecting the 10-25° SR stem pulp to secondary countercurrent washing to obtain a stem pulp with a concentration of 3 wt% to 5 wt%.

[0019] In some embodiments, the hydraulic disintegration includes: adjusting the concentration of the added fiber to 10 wt% to 15 wt% and hydraulically disintegrating for 30 min to 60 min.

[0020] In some embodiments, the concentration of the formed wood pulp is 3 wt% to 5 wt%.

[0021] In some embodiments, in the step of mixing the leaf pulp, the stem pulp and the wood pulp, the weight ratio of the leaf pulp, the stem pulp and the wood pulp is (30-50): (40-60): (10-20).

[0022] In some embodiments, the types of the added fiber include one or more of broadleaf, coniferous, and bamboo pulp.

[0023] Another aspect of the present application provides reconstituted tobacco leaves prepared using the method for preparing reconstituted tobacco leaves as described above.

[0024] In some embodiments, the reconstituted tobacco leaf meets one or more of the following items (1) to (11):

[0025] (1) The coefficient of variation of the total nitrogen content of the reconstituted tobacco leaf is 4% to 6%;

[0026] (2) The porosity of the reconstituted tobacco leaf base is 55% to 75%;

[0027] (3) The total pore volume of the reconstituted tobacco leaf base is 0.9 mL / g to 1.8 mL / g;

[0028] (4) The water absorption rate of the reconstituted tobacco leaf base is 15 mm / 10 min to 22 mm / 10 min;

[0029] (5) The maximum burning rate of the reconstituted tobacco is 25% / min to 30% / min;

[0030] (6) The comprehensive combustion characteristic index of the reconstituted tobacco leaf is (14-17)×10 -7 / (% 2 min -2 ℃ -3 );

[0031] (7) The longitudinal tensile strength of the reconstituted tobacco leaf base is 0.2 KN / m to 0.6 KN / m;

[0032] (8) The filling value of the reconstituted tobacco leaf is 4 cm³ / g to 6 cm³ / g;

[0033] (9) The bulk thickness of the reconstituted tobacco leaf is 3 cm 3 / g~4cm 3 / g;

[0034] (10) The true density of the reconstituted tobacco leaf is 1 g / mL to 2 g / mL;

[0035] (11) The apparent density of the reconstituted tobacco leaf is 1 g / mL to 2 g / mL.

[0036] The method provided by this application has at least the following advantages:

[0037] A complete pulping process was developed and put into operation based on the principle of "separately defibring stems and leaves, minimizing the physical differences between stems, leaf ends, and outer fibers, and then precisely blending and mixing the pulp." Specifically, stems undergo extraction, defibration, high-consistency refining, and pulp washing to form separate stem pulp. Leaves undergo secondary countercurrent extraction and concentration adjustment to form leaf pulp. Outer fibers undergo hydraulic disintegration and concentration adjustment to form wood pulp. The three pulps are blended according to the designed process ratio and then pulped through low-consistency grinding.

[0038] The fiber structure improved after the process was applied: the weight-average length and aspect ratio of the mixed pulped fibers were higher than those of the individually pulped fibers, increasing by an average of 18.68% and 21.76%, respectively. Meanwhile, the fiber coarseness and bristle ratio were lower than those of the individually pulped fibers, decreasing by an average of 17.98% and 29.81%, respectively. The fibers of the individually pulped samples exhibited stiffness and a crisscross pattern, with a curled cross-section. The fibers of the mixed pulped samples exhibited softness and intertwined fibers, with larger interfiber spaces and a flat cross-section.

[0039] 3. After the process was implemented, the control accuracy of the film base composition was improved: The coefficient of variation of the total nitrogen in the film base was used to represent the control accuracy of the film base composition. Compared with the before and after improvements, the coefficient of variation of the total nitrogen in the film base was reduced from 8.3% to 5%, which significantly improved the control accuracy of the film base composition.

[0040] 4. Improved sheet base physical properties after application of the process: The process was applied to Products 1 and 2. Compared with separate pulping, mixed pulping reduced the sheet base's longitudinal and transverse tensile strength, filling value, true density, and internal pore volume. However, the sheet base's porosity, total pore volume, and water absorption increased by an average of 14.27%, 50.61%, and 28.40%, respectively. Bulk and apparent density also saw slight increases.

[0041] 5. The combustion performance of the finished product is improved after the process is applied: The process was applied to Products 1 and 2. The maximum combustion rate and comprehensive combustion characteristic index of the same raw and auxiliary materials after mixed pulping were higher than those of the products pulped separately, with improvements of 19.11% and 19.61%, respectively.

[0042] 6. Tar content in finished product flue gas decreased after the process was applied: The process was applied to Products 1 and 2. The tar and CO contents in the flue gas of Product 1 decreased by 13.09% and 11.92%, respectively; the tar and CO contents in the flue gas of Product 2 remained basically the same. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions in the implementation methods and examples of this application and to more completely understand the application and its beneficial effects, the following briefly introduces the drawings required for the description of the implementation methods or examples. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work. It should also be noted that the drawings are all drawn in a simplified form and are only used to conveniently and clearly assist in explaining the present application.

[0044] Figure 1 The weight-average length distribution of four reconstituted tobacco leaf samples in one embodiment of the present application is shown.

[0045] Figure 2 The fiber plane microstructures of four reconstituted tobacco samples according to one embodiment of the present application are shown; the scale is 50 μm.

[0046] Figure 3 The fiber cross-sectional microstructures of four reconstituted tobacco leaf samples according to one embodiment of the present application are shown; the scale is 50 μm.

[0047] Figure 4 The combustion characteristic curve of sample 1# in one embodiment of the present application at a heating rate of 15°C / min is shown.

[0048] Figure 5 The TG curves of four samples in one embodiment of the present application at a heating rate of 15°C / min are shown.

[0049] Figure 6 The DTG curves of four samples in one embodiment of the present application at a heating rate of 15° C. / min are shown. DETAILED DESCRIPTION

[0050] To facilitate understanding of the present application, a more comprehensive description of the present application will be provided below with reference to the accompanying drawings. The accompanying drawings illustrate preferred embodiments of the present application. However, the present application may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the disclosure of the present application.

[0051] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0052] In this application, unless otherwise specified, "one or more" refers to any one of the listed items or any combination of the listed items. Similarly, "one or more" and other similar expressions that refer to "one or more" are also understood in the same way unless otherwise specified.

[0053] The terms "combination thereof", "any combination thereof", "any combination thereof" and the like used in this application include all suitable combinations of any two or more of the listed items.

[0054] In this application, the word "suitable" in "suitable combination", "suitable method", "any suitable method", etc. shall be based on the ability to implement the technical solution of this application, solve the technical problems of this application, and achieve the expected technical effects of this application.

[0055] In this application, the terms "further," "further," "particularly," "for example," "such as," "example," and "for example" are used for descriptive purposes to indicate that the preceding and following technical solutions are related in terms of the content covered, but should not be construed as limiting the preceding technical solution or the scope of protection of this application. In this application, unless otherwise specified, A (such as B) means that B is a non-limiting example of A, and it is understood that A is not limited to B.

[0056] In this application, the terms "optionally," "optional," and "optional" mean optional, that is, they refer to either option selected from the two parallel options of "yes" or "no." If multiple "options" appear in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "optional" is independent. Unless otherwise specified, the descriptions "optionally include," "optionally include," etc. in this application, taking "optionally include" as an example, mean "may include or not include."

[0057] As used herein, the terms "comprising," "including," and "include" are synonymous and are inclusive or open-ended, not excluding additional, unrecited members or features. Examples of members or features include materials or components, structures, elements, and instruments. Non-limiting examples of members or features include actions, conditions for the occurrence of actions, timing, and states.

[0058] In this application, the technical features or technical solutions described in open language include closed technical features or technical solutions composed of the listed contents, and also include open technical features or technical solutions containing the listed contents.

[0059] In this application, exemplary descriptions such as "in some embodiments (or examples)" and "in one embodiment (or example)" may include but are not limited to the following meanings: these solutions can be combined with other solutions in a suitable manner to form new technical solutions.

[0060] In this application, the terms "first," "second," "third," "fourth," etc. in "the first aspect," "the second aspect," "the third aspect," "the fourth aspect," etc. are used for descriptive purposes only and should not be understood as indicating or implying relative importance or quantity, nor should they be understood as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc. serve only for the purpose of non-exhaustive enumeration and description, and should be understood not to constitute a closed-ended limitation on quantity.

[0061] In this application, when referring to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values ​​in the numerical interval is considered to be continuous and includes the two numerical endpoints (i.e., the minimum and maximum values) of the numerical interval, and each numerical value between the two numerical endpoints. Unless otherwise specified, when a numerical interval only refers to an integer in the numerical interval, including the two endpoint integers of the numerical range and each integer between the two endpoints, is equivalent to directly enumerating each integer. When multiple numerical ranges are provided to describe a feature or characteristic, these numerical ranges can be merged. In other words, unless otherwise specified, the numerical range disclosed herein should be understood to include any and all subranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. "Numerical interval" allows broadly including numerical interval types such as percentage intervals, ratio intervals, and ratio intervals.

[0062] In this application, if a method flow involves multiple steps, unless otherwise specified herein, there is no strict order restriction on the execution of these steps, and they can be executed in an order other than the order described. Moreover, any step can include multiple sub-steps or multiple stages, and these sub-steps or stages do not necessarily need to be completed at the same time, but can be executed at different times, and their execution order is not necessarily sequential, but can be executed in turn, alternating, or simultaneously with other steps or parts of sub-steps or stages of other steps.

[0063] With "improving the control accuracy of stem and leaf ratio and improving pulping effect" as the core, we focus on solving problems such as low stem and leaf ratio accuracy, high residue content in stem liquid, large loss of leaf powder during pulping, low pulping stability, high pulping energy consumption, and poor absorbency of the sheet base. We plan to implement the process research of "separately defibring the stems and leaves, reducing the physical morphology differences between the tobacco stems, leaf powder and outer fibers, and then conducting precise pulping and mixed pulping". We will change the previous tank-to-tank pulping of stem raw materials and leaf raw materials, and instead use absolute dry pulping according to concentration and flow rate to improve pulping accuracy, develop a new pulping process, and effectively improve the quality of high-absorption and high-load sheet base required for reconstituted tobacco leaves.

[0064] In a first aspect of the present application, a method for preparing reconstituted tobacco is provided, the method comprising the following steps:

[0065] The tobacco leaves are subjected to secondary countercurrent extraction and the concentration is adjusted to form leaf pulp;

[0066] Mixing leaf pulp, stem pulp and wood pulp;

[0067] The stem pulp is prepared by a method comprising the following steps: defibrillating, high-consistency refining, and washing the tobacco stems to form the stem pulp;

[0068] The wood pulp is prepared by a method comprising the following steps: hydraulically crushing the added fibers and adjusting the concentration to form the wood pulp.

[0069] In some embodiments, the method comprises the steps of:

[0070] The tobacco leaves are subjected to secondary countercurrent extraction and the concentration is adjusted to form leaf pulp;

[0071] Mixing leaf pulp, stem pulp and wood pulp and refining at low consistency;

[0072] The stem pulp is prepared by a method comprising the following steps: defibrillating, high-consistency refining, and washing the tobacco stems to form the stem pulp;

[0073] The wood pulp is prepared by a method comprising the following steps: hydraulically crushing the added fibers and adjusting the concentration to form the wood pulp.

[0074] In some embodiments, recycled water may be used to adjust the concentration of the slurry during preparation.

[0075] In some embodiments, during the preparation of wood pulp, clean water may be used to adjust the concentration.

[0076] In some embodiments, the wood pulp is beated at least once.

[0077] The conditions for knocking include illustratively:

[0078] The wood pulp concentration was adjusted to 10 wt%~15 wt% and the pulp was hydropulverized for 30 min~60 min.

[0079] In some embodiments, the wood pulp concentration is adjusted to 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, or a range or value between any two values; the hydraulic disintegration time can be illustratively 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, or a range or value between any two values.

[0080] In some embodiments, performing secondary countercurrent extraction includes: a temperature of 55°C to 75°C, and a solid-to-liquid ratio of 1:(5-8). Exemplarily, the temperature is 55°C, 60°C, 65°C, 70°C, 75°C, or a range or value between any two values.

[0081] In some embodiments, the solid-to-liquid ratio may be, for example, 1:5, 1:6, 1:7, 1:8, or a range or value between any two values.

[0082] In some embodiments, the concentration of the slurry is 3 wt% to 5 wt%.

[0083] In some embodiments, the defibration comprises:

[0084] The tobacco stems are extracted 1-2 times and subjected to solid-liquid separation at a temperature of 55-75°C and a solid-liquid ratio of 1:(5-8), and then defibrated and squeezed to form a stem fiber pulp with a beating degree of 5-15°SR and a dryness of 25%-35%.

[0085] In some embodiments, during the extraction step, the temperature is 55°C, 60°C, 65°C, 70°C, 75°C, or a range or value between any two values.

[0086] In some embodiments, in the extraction step, the solid-liquid ratio is 1:5, 1:6, 1:7, 1:8, or a range or value between any two values.

[0087] In some embodiments, in the defibration step, the stem fiber slurry formed has a beating degree of 5°SR, 6°SR, 7°SR, 8°SR, 9°SR, 10°SR, 11°SR, 12°SR, 13°SR, 14°SR, 15°SR, or a range or value between any two values.

[0088] In some embodiments, during the defibration step, the stem fiber slurry formed has a dryness of 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35% or a range or value between any two values.

[0089] In this application, the terms "beating degree" and "freezing degree" are used interchangeably to refer to the degree of fiber cutting, splitting, swelling, and hydration after pulping. In this application, the beating degree of pulp is determined according to ISO 05267-1.

[0090] In some embodiments, high-consistency refining includes subjecting the stem fiber pulp having a dryness of 25% to 35% to high-consistency refining to form a 10-25° SR stem pulp.

[0091] In some embodiments, pulp washing includes subjecting the 10-25° SR stem pulp to secondary countercurrent washing to obtain a stem pulp with a concentration of 3 wt% to 5 wt%.

[0092] In some embodiments, during the preparation of wood pulp, the hydraulic disintegration includes: adjusting the concentration of the added fiber to 10 wt% to 15 wt% and hydraulically disintegrating for 30 min to 60 min.

[0093] In some embodiments, the concentration of the added fiber is adjusted to 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, or a range or value between any two values; the hydraulic disintegration time can be illustratively 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, or a range or value between any two values.

[0094] In some embodiments, during the process of preparing wood pulp, the concentration of the formed wood pulp is 3 wt% to 5 wt%.

[0095] In some embodiments, in the step of mixing the leaf pulp, the stem pulp and the wood pulp, the weight ratio of the leaf pulp, the stem pulp and the wood pulp is (30-50): (40-60): (10-20).

[0096] In some embodiments, the types of the added fiber include one or more of broadleaf, coniferous, and bamboo pulp.

[0097] Another aspect of the present application provides reconstituted tobacco leaves prepared using the method for preparing reconstituted tobacco leaves as described above.

[0098] In some embodiments, the reconstituted tobacco leaf meets one or more of the following items (1) to (11):

[0099] (1) The coefficient of variation of the total nitrogen content of the reconstituted tobacco leaf is 4% to 6%;

[0100] (2) The porosity of the reconstituted tobacco leaf base is 55% to 75%;

[0101] (3) The total pore volume of the reconstituted tobacco leaf base is 0.9 mL / g to 1.8 mL / g;

[0102] (4) The water absorption rate of the reconstituted tobacco leaf base is 15 mm / 10 min to 22 mm / 10 min;

[0103] (5) The maximum burning rate of the reconstituted tobacco is 25% / min to 30% / min;

[0104] (6) The comprehensive combustion characteristic index of the reconstituted tobacco leaf is (14-17)×10 -7 / (% 2 min -2 ℃ -3 );

[0105] (7) The longitudinal tensile strength of the reconstituted tobacco leaf base is 0.2 KN / m to 0.6 KN / m;

[0106] (8) The filling value of the reconstituted tobacco leaf is 4 cm³ / g to 6 cm³ / g;

[0107] (9) The bulk thickness of the reconstituted tobacco leaf is 3 cm 3 / g~4 cm 3 / g;

[0108] (10) The true density of the reconstituted tobacco leaf is 1 g / mL to 2 g / mL;

[0109] (11) The apparent density of the reconstituted tobacco leaf is 1 g / mL to 2 g / mL.

[0110] Unless otherwise specified, the term "coefficient of variation of total nitrogen in the film base" in this application refers to the ratio of the standard deviation of the total nitrogen content in the film base (on a dry basis) to the average value, usually expressed as a percentage.

[0111] Unless otherwise specified, the term "substrate porosity" in this application refers to the percentage of pore volume in the substrate to the total volume, which can be measured by mercury intrusion testing.

[0112] Unless otherwise specified, the term "total pore volume of the substrate" in this application refers to the total volume of all pores in the substrate per unit mass (usually measured by mercury porosimetry or gas adsorption method), and the unit is usually cm³ / g (or mL / g).

[0113] Unless otherwise specified, the term "water absorption rate of the film base" in this application refers to the percentage of the increased mass of the film base after absorbing water within a specified time to the initial mass.

[0114] Unless otherwise specified, the term "maximum burning rate" in this application refers to the maximum mass loss rate of the substrate during combustion per unit time, which is determined by thermogravimetric analysis or combustion experiments.

[0115] Unless otherwise specified, the term "comprehensive combustion characteristic index" in this application refers to a dimensionless index that combines parameters such as combustion rate, burnout temperature, and heat release. The calculation formula varies depending on the standard.

[0116] Unless otherwise specified, the term "longitudinal tensile strength of the film base" in this application refers to the maximum tensile force per unit area that the film base can withstand when it breaks along the longitudinal direction (manufacturing direction), in units of kN / m or MPa.

[0117] Unless otherwise specified, the term "filling value" in this application refers to the volume occupied by a certain mass of substrate under standard pressure, unit: cm³ / g.

[0118] Unless otherwise specified, bulk is an important indicator to measure its physical properties. It refers to the volume occupied by unit mass of reconstituted tobacco leaves, usually in cm³ / g.

[0119] Unless otherwise specified, the term "true density" in this application refers to the actual density of the base material after excluding all pores (usually measured by helium pycnometer method), unit: g / cm³ (or g / L).

[0120] Unless otherwise specified, the term "apparent density" in this application refers to the mass per unit volume of the substrate including pores, and the unit is g / cm³ (or g / L).

[0121] Some examples are provided below.

[0122] The embodiments of the present application will be described in detail below with reference to the examples. It should be understood that these examples are intended to illustrate the present application only and are not intended to limit the scope of the present application. The experimental methods for which the conditions are not specified in the following examples are preferably referred to the guidance provided in the present application, and may also be based on the experimental manuals or conventional conditions in this area, or on the conditions recommended by the manufacturer, or with reference to experimental methods known in the art.

[0123] Example 1

[0124] 1 Materials and Methods

[0125] 1.1 Materials and Instruments

[0126] Domestic papermaking reconstituted tobacco samples are marked 1#, 2#, 3# and 4#. Among them, 1# and 3# samples are papermaking reconstituted tobacco leaves formed by pulping tobacco pulp and added fibers separately in a certain proportion, mixing pulp and papermaking. 2# and 4# samples are papermaking reconstituted tobacco leaves formed by mixing tobacco pulp and added fibers in a certain proportion, mixing pulp and papermaking. The raw materials of 1# and 2#, 3# and 4# samples are the same. The details are as follows:

[0127] Sample Processing for Samples 1# and 3#: Tobacco leaves undergo a secondary countercurrent extraction at a temperature of 55-75°C and a solid-liquid ratio of 1:5-8, followed by solid-liquid separation and concentration adjustment to produce a leaf pulp with a concentration of 5%-10%. Tobacco stems undergo one or two extractions at a temperature of 55-75°C and a solid-liquid ratio of 1:5-8, followed by solid-liquid separation to produce an extracted stem material with a dryness of 10-20%. The two are then mixed, defibrated, and squeezed to produce a mixed pulp with a beating degree of 5-15°SR and a dryness of 25-35%. The mixed pulp undergoes secondary countercurrent washing and concentration adjustment within a concentration range of 3%-5%, resulting in a mixed pulp with a concentration range of 5%-10%. The mixed pulp is then subjected to high-consistency and low-consistency refining to produce a pulp with a wet weight of 3g-4g. Wood pulp (two to three types of broadleaf, coniferous, and wood pulp in varying proportions) is hydraulically crushed at a consistency of 10% to 15% for 30 to 60 minutes, adjusting the consistency to 3% to 5%. This pulp is then refined at low consistency to a pulp with a beating degree of 40 to 60° and a wet weight of 1g to 6g. The resulting stem and leaf pulp is then mixed with wood pulp in a ratio of 80 to 90:10 to 20 to form a 3% to 4% consistency pulp. This pulp is then processed through a paper machine, coated, and dried to produce reconstituted tobacco products.

[0128] Sample 2# and 4# processing: Tobacco leaf material undergoes secondary countercurrent extraction at a temperature of 55°C to 75°C and a solid-liquid ratio of 1:(5-8). After solid-liquid separation and concentration adjustment, a leaf pulp with a consistency of 3% to 5% is obtained. Tobacco stems undergo one or two extractions at a temperature of 55°C to 75°C and a solid-liquid ratio of 1:(5-8). Solid-liquid separation, defibration, and squeezing are performed to produce a stem fiber pulp with a beating degree of 10-15°SR and a dryness of 25% to 35%. The 25% to 35% dryness stem fiber pulp is further refined at high consistency to produce a stem pulp with a 10-25°SR. The stem pulp is then subjected to secondary countercurrent washing and concentration adjustment within a 3% to 5% consistency range to produce a stem pulp with a 3% to 5% consistency range. Wood pulp (two or three of broadleaf, conifer, and wood pulp in varying proportions) is hydraulically crushed within a 10% to 15% consistency range for 30-60 minutes and concentrated to a wood pulp with a 3% to 5% consistency. The resulting leaf pulp, stem pulp, and wood pulp are mixed in a ratio of 30-50:40-60:10-20 to create a mixed pulp with a consistency ranging from 3% to 5%. The mixed pulp is then subjected to low-consistency refining to a pulp with a beating degree (SR) of 20-40° and a wet weight of 2-4g. The pulp is then processed on a paper machine, coated, and dried to produce reconstituted tobacco products.

[0129] Fiber analyzer (BTG); ZLDW 30A tensile tester (Changchun Yueming Small Testing Machine Co., Ltd.); YTH-4C thickness gauge (Hangzhou Yante Technology Co., Ltd.); ZXK-200 water absorption tester (Changchun Yueming Small Testing Machine Co., Ltd.); YDZ430 filling value tester (Zhengzhou Tobacco Research Institute of China National Tobacco Corporation); true density meter (Quantavi 1200e, USA); thermogravimetric analyzer (Waters, USA); U-1015 scanning electron microscope (Hitachi, Japan); RM20H smoking machine (BORGWALDT).

[0130] 1.2 Methods

[0131] Fiber morphology analysis: The moisture content of four samples was detected, and the samples were dissociated by adding water to prepare a fiber slurry with a concentration of 1 wt%. The fiber morphology was analyzed using a fiber analyzer.

[0132] Sample cross-section preparation and scanning electron microscopy observation: The reconstituted tobacco leaf sample was fixed to the sample stage with conductive tape, vacuum dried and gold-sprayed on an ion sputtering instrument, and then observed by scanning electron microscopy at an operating voltage of 10 kV.

[0133] Physical Property Measurement: The tensile strength, filling value, thickness, true density, and apparent density of reconstituted tobacco leaves were measured according to GB / T 12914-2018, YC / T 152-2001, GBT 451.3, and YC / T 473-2013, respectively. Water absorption was measured by cutting a fixed length of sheet and inserting the sample into the water tank of the tester 10 mm deep. The water absorption height was measured for 10 minutes. The average of five test results was calculated in mm / 10 minutes. Bulk was calculated using the following formula: v = δ × 1,000 / g.

[0134] Where: v is the bulk thickness (cm 3 / g), δ is thickness (mm), g is basis weight (g / m 2 ).

[0135] Thermogravimetric analysis: The combustion process of four samples was tested in a simulated atmospheric pressure atmosphere at a heating rate of 15°C / min, ranging from room temperature to 900°C. The thermogravimetric (TG) system records the change in sample mass with temperature, thereby obtaining the sample's combustion characteristic curve.

[0136] The comprehensive combustion characteristic index P used in the prior art reflects the combustion characteristics of tobacco biomass. The larger the P value, the better the combustion characteristics of the biomass. P is expressed as follows:

[0137]

[0138] Where: (dw / dt)max is the maximum burning rate, % / min; (dw / dt)mean is the average burning rate, % / min; Ti is the ignition temperature, °C; Th is the burnout temperature, °C.

[0139] Flue gas analysis: Nicotine, moisture, total particulate matter, tar, and carbon monoxide in flue gas were tested in accordance with the standard methods of YC / T 156, YC / T 157, GB / T 19609-2004, and GB / T 23356-2009, respectively.

[0140] 2 Results and Discussion

[0141] 2.1 Fiber morphology analysis

[0142] Table 1 shows the results of fiber weight-average length, width, coarseness, and brooming rate measurements for four reconstituted tobacco samples. As shown in Table 1, for reconstituted tobacco prepared using the same raw materials and auxiliary materials, the weight-average length and aspect ratio of fibers pulped from a mixture of tobacco pulp and added fibers were higher than those pulped from tobacco pulp and added fibers alone, increasing by an average of 18.68% and 21.76%, respectively. However, the coarseness and brooming rate of fibers were lower than those pulped from tobacco pulp and added fibers alone, decreasing by an average of 17.98% and 29.81%, respectively. This suggests that mixed pulping can improve fiber threadability by enhancing the interaction between tobacco pulp and added fibers. The weight-average length, width, coarseness, and brooming rate of fibers from different reconstituted tobacco samples prepared using the same process varied significantly. The weight-average length, width, coarseness, and brooming rate of fibers from samples 3# and 4# were all lower than those from samples 1# and 2#. This is primarily due to the difference in raw materials used between the two samples, with samples 1# and 2# using a greater amount of long fibers than samples 3# and 4#.

[0143] Figure 1Figure 2 shows the weight-average length distribution of four reconstituted tobacco samples. The proportion of fibers in the 200-585 μm range was higher in single-pulping than in mixed-pulping, while the proportion of fibers longer than 1710 μm was lower. Length distribution characteristics also vary between single-pulping and mixed-pulping methods. In samples 1# and 2#, which contain a higher proportion of long fibers, the proportion of single-pulping fibers in the 585-836 μm and 1196-1710 μm ranges was higher than in mixed-pulping methods. However, in samples 3# and 4#, which contain a higher proportion of short fibers, the proportions showed the opposite pattern. The proportion of fibers in the 836-1196 μm range remained essentially unchanged in samples 1# and 2#, while sample 4# showed a significant increase in this proportion compared to sample 3#. Overall, mixed-pulping reduces the proportion of short fibers and increases the proportion of long fibers. The starting point for this increase in long fiber proportion varies among different raw materials and auxiliary materials. The mixed pulp products with a larger proportion of long fiber application have a larger increase in the length ratio of 1710~2445μm, while the mixed pulp products with a larger proportion of short fiber application have a larger increase in the length ratio of 585~1196μm.

[0144] The weight-average fiber length is closely related to the physical properties of paper, while the aspect ratio is closely related to the interweaving ability of the fibers and represents the strength of the finished paper. Fiber coarseness is generally determined by the thickness of the fiber cell wall, the diameter of the fiber cell cavity, and the density of the various components within the fiber. Generally speaking, pulp with a smaller fiber coarseness produces a finer, smoother paper, while a larger fiber coarseness results in a rougher sheet. The fiber bristle rate, which indicates the occurrence of fuzzing, tearing, and splitting in the fiber cell wall, is particularly important in production because it can improve the physical properties of the pulp, such as strength.

[0145] Table 1: Fiber morphology analysis of four reconstituted tobacco samples

[0146]

[0147] 2.2 Fiber microstructure

[0148] Figure 2 、 Figure 3 The plane microstructure and cross-sectional microstructure of 4 reconstituted tobacco samples are shown respectively. Figure 2 and Figure 3 The instrument used for the structure shown in the figure is a U-1015 scanning electron microscope (Hitachi, Japan). The process includes: sample cross-section preparation and scanning electron microscope observation: the reconstituted tobacco leaf sample is fixed to the sample stage with conductive tape, vacuum dried and gold-sprayed on an ion sputtering instrument, and then subjected to scanning electron microscope observation with an operating voltage of 10 kV.

[0149] The microstructures of the plane and cross sections reveal that the fibers of the individually pulped samples exhibit stiff, horizontally and vertically interlaced fibers, with a curled cross-section. The fibers of the mixed pulp samples exhibit soft, intertwined fibers, with larger interfiber spaces, which facilitate the absorption of the subsequent coating solution. Their cross-sections show a flat arrangement. Research by Li Youming et al. found that, compared with a horizontally and vertically interlaced arrangement, intertwined fibers are more conducive to increasing product bulk and reducing tensile strength. This intertwined fiber arrangement is one of the key factors contributing to the superior quality of reconstituted tobacco.

[0150] 2.3 Physical indicators

[0151] Table 2 shows the physical performance of four reconstituted tobacco leaf samples. The table shows that mixed pulping reduces the longitudinal and transverse tensile strength and fill value of the sheet compared to single pulping, significantly increases water absorption, reaching an average of 28.40%, and slightly improves bulk. Combining fiber morphology and microstructure analysis, compared to the same raw materials but different processes, when the fibers are long, have a high aspect ratio, are low in coarseness, have a low brooming rate, and have a tangled microstructure, the longitudinal and transverse tensile strength of the sheet is low, the fill value of the finished product is low, and the sheet absorbency is significantly improved. Compared to different raw materials and different processes, the fiber aspect ratio is inversely proportional to the sheet tensile strength, and the fiber brooming rate is inversely proportional to the sheet water absorption rate.

[0152] Table 3 shows the porosity indicators of the sheet base and finished products of four types of reconstituted tobacco. In terms of sheet base porosity distribution, the highest proportion of porosity for all four samples lies within the macropore range (>50 nm), exceeding 98.88%. The proportion of porosity within the micropore range (<2 nm) is zero for all four samples. Compared to single pulping, mixed pulping increased the sheet base porosity and total pore volume by an average of 14.27% and 50.61%, respectively. The increases in porosity and total pore volume for samples 3# and 4# were two times and 4.6 times those for samples 1# and 2#, respectively. This indicates that mixed pulping increases the sheet base porosity, facilitating the penetration and absorption of the coating liquid, further confirming the conclusion that the sheet base's water absorption rate is improved. The apparent density, true density, and internal pore volume of the tobacco cuts produced by mixed pulping show an increase in apparent density, while the true density and internal pore volume decrease. This indicates that after the sheet base is coated, the coating liquid fully penetrates the sheet base pores, resulting in a decrease in the internal pore volume.

[0153] Table 2: Physical indicators of four reconstituted tobacco samples

[0154]

[0155] Table 3: Porosity indexes of four reconstituted tobacco leaf samples

[0156]

[0157] 2.4 Combustion performance

[0158] 2.4.1 Determination of ignition and burnout temperatures

[0159] Figure 4 The combustion characteristic curve of 1# reconstituted tobacco sample at a heating rate of 15℃ / min is shown in Figure 1. The ignition temperature is determined by the TG-DTG tangent method. Figure 4 On the DTG curve, a vertical line is drawn through the first peak point A and intersects the TG curve at point B. A tangent line is drawn through this point and the tangent line intersects the baseline of the initial weight loss at point C. The temperature corresponding to point C is the ignition temperature of the volatile matter, T. i，1 The same method is used to draw a vertical line and a tangent line through the second peak, and the point F is defined as the ignition temperature T of the fixed carbon. i，2 The corresponding ignition temperatures of the other three samples were obtained by analyzing them using the TG-DTG tangent method.

[0160] Depend on Figure 4 It can be seen that when the temperature rises to point C, the volatile matter begins to ignite. As the volatile matter ignition temperature rises rapidly in the initial stage, the volatile matter precipitates rapidly and the weight loss rate increases; when the temperature rises to point A, the volatile matter precipitates gradually decreases and the weight loss rate begins to decrease; when the temperature reaches point F, the fixed carbon begins to burn and the weight begins to drop sharply again until the fixed carbon is burned out at point E.

[0161] 2.4.2 Comparison of combustion characteristic parameters

[0162] Table 4 shows the volatile matter combustion temperature, fixed carbon combustion temperature, burnout temperature, maximum burning rate, average burning rate, and comprehensive combustion characteristic index of the four samples. As can be seen from the table, there is no significant difference in the volatile matter combustion temperature, fixed carbon combustion temperature, burnout temperature, and average burning rate of the four samples, with average values ​​of 240.5°C, 421.1°C, 432.9°C, and 1.50% / min, respectively. For the same raw and auxiliary materials, the maximum burning rate and comprehensive combustion characteristic index of the mixed pulping products are higher than those of the single pulping products, with increases of 19.11% and 19.61%, respectively. This is mainly related to the sheet structure after mixed pulping. After mixed pulping, the fiber brooming rate of the sample is low, the fibers are intertwined, the bonding force between the fibers is small, the heat transfer resistance is small, and it is conducive to combustion.

[0163] Table 4: Combustion characteristics of four reconstituted tobacco samples

[0164]

[0165] 2.4.3 Combustion characteristic curve analysis

[0166] The combustion process of the samples was tested using a thermogravimetric analyzer (Waters, USA) in a simulated atmospheric pressure atmosphere at a heating rate of 15°C / min. The test temperature range was from room temperature to 900°C. The thermogravimetric (TG) system records the change in sample mass with temperature, thereby obtaining the sample's combustion characteristic curve (see Figure 5 and Figure 6 ). From the TG and DTG curves of the four samples shown in the figure, it can be seen that the thermal weight loss trends of the four samples are basically the same, and can be divided into four typical weight loss peaks. The first stage is below 130 ° C. This stage is mainly caused by the loss of volatile substances such as water, and loses about 10% of the weight; the second stage is 130~400 ° C. In this stage, as the temperature rises, low molecular weight substances first decompose and gasify. When the ignition temperature is reached, gas phase combustion occurs, which accelerates the decomposition of substances such as hemicellulose and cellulose, produces a large amount of volatile substances, and the first maximum weight loss peak appears. In this stage, about 46% of the weight is lost; the third stage is 400~550 ° C. This stage is mainly caused by the oxidation and combustion of carbon produced by decomposition, and the second The maximum weight loss peak is greater than the first maximum weight loss peak, indicating that the combustion rate of fixed carbon in the reconstituted tobacco leaf sample is greater than the combustion temperature of volatile matter, and the weight is lost at this stage by about 29%; the fourth stage above 550℃ is mainly the thermal decomposition of inorganic salts, and the weight is lost at this stage by about 6%. The final remaining proportions of the four samples at 900℃ are 10.81%, 10.73%, 8.66% and 8.09%, respectively. The content of inorganic salts such as calcium carbonate in samples 1# and 2# is higher than that in samples 3# and 4#, mainly because the content of inorganic salts such as calcium carbonate in samples 1# and 2# is higher than that in samples 3# and 4#.

[0167] 2.5 Flue gas analysis

[0168] Table 5 shows the flue gas analysis results for the four samples. As can be seen, the flue gas tar and CO levels in the mixed pulp samples were reduced by an average of 13.09% and 11.92%, respectively, compared to the single pulp samples. This is primarily because the mixed pulp samples are softer and looser, resulting in lower mass and heat transfer resistance during combustion and better combustion performance, which helps reduce the tar content in the flue gas.

[0169] Table 5: Four types of flue gas samples

[0170]

[0171] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0172] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the patent in this application shall be determined by the appended claims, and the specification and drawings shall serve to interpret the claims.

Claims

1. A method for preparing reconstituted tobacco, characterized in that: The method comprises the following steps: The tobacco leaves are subjected to secondary countercurrent extraction and the concentration is adjusted to form leaf pulp; Mixing the leaf pulp, stem pulp and wood pulp; The stem pulp is prepared by a method comprising the following steps: defibrillating, high-consistency refining, and washing the tobacco stems to form the stem pulp; The wood pulp is prepared by a method comprising the following steps: hydraulically crushing the added fibers and adjusting the concentration to form the wood pulp.

2. The method according to claim 1, characterized in that The wood pulp is subjected to at least one beating; Optionally, the conditions for knocking include: The wood pulp concentration was adjusted to 10 wt%~15 wt% and the pulp was hydropulverized for 30 min~60 min.

3. The method according to claim 1 or 2, wherein: Two-stage countercurrent extraction was performed at a temperature of 55°C to 75°C and a solid-liquid ratio of 1:(5-8); And / or, the concentration of the leaf pulp is 3 wt%~5 wt%.

4. The method according to any one of claims 1 to 3, wherein The defibrination comprises: The tobacco stems are extracted 1-2 times at a temperature of 55-75°C and a solid-liquid ratio of 1:(5-8), and then subjected to solid-liquid separation, followed by defibration and squeezing to form a stem fiber slurry with a beating degree of 5-15°SR and a dryness of 25%-35%. Optionally, the high-consistency refining comprises refining the stem fiber pulp with a dryness of 25% to 35% to form a 10-25° SR stem pulp; Further optionally, the pulp washing includes performing a secondary countercurrent washing on the 10-25° SR stem pulp to obtain a stem pulp with a concentration of 3 wt% to 5 wt%.

5. The method according to any one of claims 1 to 4, wherein The hydraulic disintegration comprises: adjusting the concentration of the added fiber to 10 wt% to 15 wt% and hydraulically disintegrating for 30 min to 60 min.

6. The method according to claim 5, wherein The concentration of the formed wood pulp is 3 wt%~5 wt%.

7. The method according to any one of claims 1 to 6, wherein In the step of mixing leaf pulp, stem pulp and wood pulp, the weight ratio of the leaf pulp, the stem pulp and the wood pulp is (30-50): (40-60): (10-20).

8. The method according to any one of claims 1 to 7, wherein The types of the added fibers include one or more of broadleaf, needleleaf and bamboo pulp.

9. Reconstituted tobacco prepared by the method for preparing reconstituted tobacco according to any one of claims 1 to 8.

10. The reconstituted tobacco leaf according to claim 9, wherein The reconstituted tobacco leaves meet one or more of the following items (1) to (11): (1) The coefficient of variation of the total nitrogen content of the reconstituted tobacco leaf is 4% to 6%; (2) The porosity of the reconstituted tobacco leaf base is 55% to 75%; (3) The total pore volume of the reconstituted tobacco leaf base is 0.9 mL / g to 1.8 mL / g; (4) The water absorption rate of the reconstituted tobacco leaf base is 15 mm / 10 min to 22 mm / 10 min; (5) The maximum burning rate of the reconstituted tobacco is 25% / min to 30% / min; (6) The comprehensive combustion characteristic index of the reconstituted tobacco leaf is (14-17)×10 -7 / (% 2 min -2 ℃ -3 ); (7) The longitudinal tensile strength of the reconstituted tobacco leaf base is 0.2 KN / m to 0.6 KN / m; (8) The filling value of the reconstituted tobacco leaf is 4 cm³ / g to 6 cm³ / g; (9) The bulk thickness of the reconstituted tobacco leaf is 3 cm 3 / g~4 cm 3 / g; (10) The true density of the reconstituted tobacco leaf is 1 g / mL to 2 g / mL; (11) The apparent density of the reconstituted tobacco leaf is 1 g / mL to 2 g / mL.

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