Preparation method of forming paper for cigarette filter stick

Abstract

The invention discloses a preparation method of forming paper for a cigarette filter stick. The preparation method comprises the following steps: preparing mixed fiber slurry from a fiber raw material; diatomite and attapulgite are adopted to prepare a filler, and the mixed fiber slurry is mixed with the filler, a reinforcing agent and a retention aid to obtain sizing slurry; carrying out papermaking treatment on the sizing slurry by adopting a paper sheet former to obtain a wet paper web; sequentially carrying out squeezing treatment and drying treatment on the wet paper web to obtain raw paper of the forming paper; the forming paper is obtained by sequentially extruding and drying raw paper of forming paper after the raw paper of the forming paper is soaked in the reinforcer. The fibers of the mixed fiber slurry form a skeleton structure, and the diatomite and the attapulgite are adopted to prepare the filler, so that the retention rate of a slurry system is increased, and the strength of a micro-system formed by the skeleton structure and the filler can also be improved. By combining the synergistic effect of the reinforcing agent, the retention aid and the reinforcing agent, the strength, firmness, wear resistance and the like of the finally obtained wrap paper are greatly improved, and the conditions of linting and dusting of the wrap paper are effectively prevented or reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of papermaking, and more specifically, to a method for preparing forming paper for cigarette filter rods. Background Art

[0002] A cigarette mainly consists of tobacco, cigarette paper, and a filter tip. The filter tip is located at the mouth end of the cigarette and can reduce the inhaled smoke and suspended particulate matter through physical interception, chemical adsorption, etc., which plays an important role in reducing tar and harmful substances.

[0003] The filter tip (or filter rod) is composed of forming paper wrapped with a filler material and is compounded with the cigarette rod through tipping paper. Among them, the properties of the forming paper such as basis weight, strength, air permeability, etc. will affect the gas flow rate, smoking taste, gas components, processing performance, etc. Therefore, the preparation of the forming paper is very important.

[0004] A Chinese patent application document (application number: 201110153658.1, application date: June 9, 2011) discloses a pulp, a method for preparing pulp, base paper, and a papermaking method. Among them, a filler and a retention aid are added to the filtrate of the short fiber pulp after concentration to form a short fiber pulp; after mixing the short fiber pulp with the filtered long fiber pulp, a strengthening agent and a retention aid are also added to the mixed pulp. The filler is light calcium carbonate, heavy calcium carbonate, talcum powder, or a mixture of any combination thereof. That is to say, in the prior art, it has been disclosed that fiber pulp, filler, strengthening agent, and retention aid are mixed to obtain pulp for manufacturing base paper, and calcium carbonate is selected as the filler.

[0005] Currently, most commercially available ordinary forming papers use inorganic calcium carbonate filler. During the use and processing, the forming paper using inorganic calcium carbonate filler is prone to hair loss and powdering during conduction traction and cutting, which affects the appearance and other physical indicators of the processed filter rod, resulting in an increase in the shutdown frequency and a decrease in the product qualification rate, affecting production efficiency and product quality.

[0006] Therefore, the present invention provides a method for preparing forming paper for cigarette filter rods to improve the problem of hair loss and powdering of the forming paper in the prior art. Summary of the Invention

[0007] In view of this, the present invention provides a method for preparing forming paper for cigarette filter rods, including:

[0008] Making a mixed fiber pulp using fiber raw materials, the fiber raw materials including bleached kraft softwood pulp, bleached kraft hardwood pulp, and carboxymethylated jute pulp;

[0009] Making a filler using diatomaceous earth and attapulgite, and mixing the mixed fiber pulp with the filler, a strengthening agent, and a retention aid to obtain a sizing pulp;

[0010] Use a paper former to sheet the sized slurry to obtain a wet paper web;

[0011] Perform pressing treatment and drying treatment on the wet paper web in sequence to obtain a formed base paper;

[0012] After impregnating the formed base paper with a strengthening agent, perform extrusion treatment and drying treatment on the formed base paper in sequence to obtain a formed paper.

[0013] Optionally, making the mixed fiber slurry with the fiber raw materials includes:

[0014] Mix the bleached softwood kraft pulp and the bleached hardwood kraft pulp and then beat them to obtain an initial mixed slurry, and the beating degree range of the initial mixed slurry is 50°SR - 80°SR;

[0015] Beat the carboxymethylated jute pulp to obtain a single slurry, and the beating degree range of the single slurry is 40°SR - 80°SR;

[0016] Mix the initial mixed slurry and the single slurry to obtain the mixed fiber slurry.

[0017] Optionally, the mass ratio of the bleached softwood kraft pulp in the fiber raw materials is 15% - 60%, the mass ratio of the bleached hardwood kraft pulp in the fiber raw materials is 15% - 60%, and the mass ratio of the carboxymethylated jute pulp in the fiber raw materials is 5% - 40%.

[0018] Optionally, making the filler with the diatomite and the attapulgite includes:

[0019] Perform grinding treatment and calcination treatment on the diatomite in sequence to obtain the treated diatomite;

[0020] Mix the treated diatomite with the attapulgite to obtain the filler, the average particle size range of the attapulgite is 1μm - 5μm, and the mass ratio range of the treated diatomite to the attapulgite is 1:2 - 2:1.

[0021] Optionally, the grinding treatment includes: mixing the diatomite, zirconia beads and water to obtain a mixture, and the mass ratio range of the diatomite, the zirconia beads and water is 1:1:2 - 4:1:1; put the mixture into a sand mill for grinding to obtain the ground diatomite, and the average particle size range of the ground diatomite is 2μm - 10μm;

[0022] The calcination treatment includes: freeze-drying the ground diatomaceous earth and then placing it in a high-temperature furnace for burning to obtain the treated diatomaceous earth. The temperature range of the high-temperature furnace is 300°C - 500°C, and the burning time range is 60 min - 150 min.

[0023] Optionally, the mass ratio of the mixed fiber slurry in the sizing slurry is 80.6% - 94.8%, the mass ratio of the filler in the absolutely dry fiber mass of the sizing slurry is 5% - 20%, the mass ratio of the strengthening agent in the absolutely dry fiber mass of the sizing slurry is 0.5% - 4.0%, and the mass ratio of the retention aid in the absolutely dry fiber mass of the sizing slurry is 0.02% - 0.05%.

[0024] Optionally, the strengthening agent includes hydroxypropyl methylcellulose and hydroxyethyl cellulose, and the mixing ratio range of the hydroxypropyl methylcellulose to the hydroxyethyl cellulose is 1:2 - 2:1.

[0025] Optionally, the retention aid is cationic polyacrylamide.

[0026] Optionally, the strengthening agent is a mixture of chitosan and acrylic latex, or the strengthening agent is a mixture of chitosan and ethylene-vinyl acetate copolymer resin.

[0027] Optionally, the mass concentration range of chitosan in the strengthening agent is 0.5% - 3%;

[0028] The mass concentration range of the acrylic latex in the strengthening agent is 0.5% - 6%, or the mass concentration range of the ethylene-vinyl acetate copolymer resin in the strengthening agent is 0.5% - 6%.

[0029] Compared with the prior art, the preparation method of a forming paper for a cigarette filter rod provided by the present invention achieves at least the following beneficial effects:

[0030] A preparation method of forming paper for cigarette filter rods provided by the present invention includes: making a mixed fiber slurry with fiber raw materials; making a filler with diatomaceous earth and attapulgite, and mixing the mixed fiber slurry with the filler, a strengthening agent and a retention aid to obtain a sizing slurry; using a sheet former to perform papermaking on the sizing slurry to obtain a wet paper web; sequentially performing pressing treatment and drying treatment on the wet paper web to obtain a base paper of the forming paper; impregnating the base paper of the forming paper with a strengthening agent, and then sequentially performing extrusion treatment and drying treatment on the base paper of the forming paper to obtain the forming paper. The fibers of the mixed fiber slurry form a framework structure. Since the filler is made of diatomaceous earth and attapulgite, the irregular diatomaceous earth and rod-shaped attapulgite in the filler are mixed and deposited between the fibers of the mixed fiber slurry, generating a hybrid effect, so that the chance of contact between the filler particles is more than that of a filler with a single form, thereby increasing the retention rate of the slurry system and also increasing the strength of the micro-system composed of the framework structure and the filler. On this basis, combined with the synergistic effects of the strengthening agent, the retention aid and the strengthening agent, the strength, firmness and wear resistance of the finally obtained forming paper are greatly improved, thereby effectively preventing or reducing the situation of linting and powdering of the forming paper. And the increased chance of contact between the filler particles will form more microporous channels. When the forming paper prepared by the method of the present invention is used to make a filter rod, it can also make the filter rod conducive to the adsorption, interception and export of cigarette smoke.

[0031] Of course, it is not necessary for any product implementing the present invention to simultaneously achieve all the above-mentioned technical effects.

[0032] Other features and advantages of the present invention will become clear from the following detailed description of the exemplary embodiments of the present invention with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The drawings incorporated in the specification and constituting a part of the specification illustrate embodiments of the present invention and, together with the description, are used to explain the principles of the present invention.

[0034] Figure 1 is a schematic flow chart of a preparation method of forming paper for cigarette filter rods provided by the present invention.

[0035] Figure 2 is a schematic flow chart of making a mixed fiber slurry with fiber raw materials.

[0036] Figure 3 is a flow chart of making a filler with diatomaceous earth and attapulgite. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] Now, various exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that: unless otherwise specifically stated, the relative arrangements of components and steps, numerical expressions and values set forth in these embodiments do not limit the scope of the present invention.

[0038] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way a limitation on the present invention, its application, or its use.

[0039] Technologies, methods, and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, such technologies, methods, and devices should be regarded as part of the specification.

[0040] In all the examples shown and discussed herein, any specific values should be construed as merely exemplary and not as a limitation. Thus, other examples of the exemplary embodiments may have different values.

[0041] It should be noted that like reference numerals and letters denote like items in the following figures, and thus, once an item is defined in one figure, further discussion thereof is not required in subsequent figures. In connection with Figure 1 , Figure 1 is a schematic flow diagram of a method for preparing forming paper for a cigarette filter rod provided by the present invention, which specifically includes the following steps:

[0042] S101: Prepare a mixed fiber slurry using fiber raw materials, where the fiber raw materials include bleached sulfate softwood pulp, bleached sulfate hardwood pulp, and carboxymethylated jute pulp;

[0043] S102: Prepare a filler using diatomaceous earth and attapulgite, and mix the mixed fiber slurry with the filler, strengthening agent, and retention aid to obtain a sizing slurry;

[0044] S103: Use a paper former to perform papermaking on the sizing slurry to obtain a wet paper web;

[0045] S104: Perform pressing treatment and drying treatment on the wet paper web in sequence to obtain a base paper of the forming paper;

[0046] S105: Immerse the base paper of the forming paper in a strengthening agent, and then perform extrusion treatment and drying treatment on the base paper of the forming paper in sequence to obtain the forming paper.

[0047] It should be noted that the carboxymethylated jute pulp contains carboxymethylated jute fibers. The average length of the carboxymethylated jute fibers in water ranges from 1.2 mm to 2.5 mm, and the average width ranges from 25 μm to 40 μm. The structure of the carboxymethylated jute fibers is rich in hydroxyl and carboxyl groups, which is beneficial to the formation of more hydrogen bonds with the hydroxyl groups on the surface of other plant fibers, significantly increasing the binding force between fibers and making the framework structure formed by the interweaving of fibers more firm. Moreover, this framework structure can also attach fillers between the fiber surfaces and among the fibers through electrostatic adsorption and bridging effects, thereby reducing the linting and dusting of paper. After beating, part of the carboxymethylated jute pulp is fibrous and part is dissolved. Therefore, in this embodiment, the carboxymethyl substitution degree of the carboxymethylated jute pulp is set to 0.1 - 0.5 to avoid excessive dissolution of most carboxymethylated jute fibers due to too large a carboxymethyl substitution degree. Attapulgite has a high aspect ratio and good retention effect, and the oriented arrangement of attapulgite among the fibers helps its combination with the fibers, thereby enhancing the strength of the micro-system composed of fibers and fillers. The irregular diatomite and rod-shaped attapulgite are mixed to prepare the filler, making the contact between filler particles closer, improving the retention of the pulp system, further enhancing the strength of the micro-system composed of fibers and fillers, and also enhancing the overall adsorption of the micro-system, etc. After multiple strengthening effects of the intensifier, retention aid, and strengthening agent on the micro-system, the combination between the filler and the fibers becomes closer, improving the internal bonding strength of the formed paper and achieving the avoidance or reduction of linting and dusting of the formed paper.

[0048] It can be understood that by mixing the fibers of the fiber pulp to form a framework structure, since the filler is made of diatomite and attapulgite, the irregular diatomite and rod-shaped attapulgite in the filler are mixed and deposited between the fibers of the mixed fiber pulp, generating a hybrid effect, making the opportunity for the filler particles to contact each other more than that of a single-shaped filler, having a higher retention rate in the pulp system, and the close combination between the rod-shaped filler and the fibers can increase the strength of the micro-system composed of the framework structure and the filler. On this basis, combined with the synergistic effects of the intensifier, retention aid, and strengthening agent, the strength, firmness, wear resistance, etc. of the finally obtained formed paper are greatly improved, thereby effectively preventing or reducing the linting and dusting of the formed paper. And the increased opportunity for the filler particles to contact each other will form more microporous channels. When using the formed paper prepared by the method of the present invention to make a filter rod, it can also make the filter rod conducive to the adsorption, interception, and export of cigarette smoke.

[0049] Optionally, referring to Figure 2 , Figure 2 is a schematic process diagram of using fiber raw materials to make mixed fiber pulp. In step S101, using fiber raw materials to make mixed fiber pulp includes:

[0050] S1011: Mix bleached softwood kraft pulp and bleached hardwood kraft pulp and then beat them to obtain an initial mixed pulp, where the beating degree of the initial mixed pulp ranges from 50°SR to 80°SR;

[0051] S1012: Beat carboxymethylated jute pulp to obtain a single pulp, where the beating degree of the single pulp ranges from 40°SR to 80°SR;

[0052] S1013: Mix the initial mixed pulp and the single pulp to obtain a mixed fiber pulp.

[0053] It can be understood that the beating degree of the initial mixed pulp can be 50°SR, 55°SR, 60°SR, 65°SR, 70°SR, 75°SR, 80°SR, or any beating degree between 50°SR and 80°SR. The beating degree of the single pulp can be 40°SR, 45°SR, 50°SR, 55°SR, 60°SR, 65°SR, 70°SR, 75°SR, 80°SR, or any beating degree between 40°SR and 80°SR. Defining the beating degree ranges of the initial mixed pulp and the single pulp can not only avoid too high a beating degree, which affects the water filtration performance during subsequent papermaking of the sized pulp, but also avoid too low a beating degree, which may cause the surface of the formed paper to be rough and affect the appearance of the formed paper, and can also avoid too low a beating degree, resulting in a poor improvement effect on the strength of the formed paper.

[0054] Optionally, the mass ratio of bleached softwood kraft pulp in the fiber raw material is 15% - 60%, the mass ratio of bleached hardwood kraft pulp in the fiber raw material is 15% - 60%, and the mass ratio of carboxymethylated jute pulp in the fiber raw material is 5% - 40%.

[0055] Specifically, the mass ratio of bleached softwood kraft pulp in the fiber raw material can be 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, or any value between 15% and 60%. The mass ratio of bleached hardwood kraft pulp in the fiber raw material can be 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, or any value between 15% and 60%. The mass ratio of carboxymethylated jute pulp in the fiber raw material can be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, or any value between 5% and 40%.

[0056] Optionally, refer to Figure 3 , Figure 3It is a flow chart for making a filler using diatomaceous earth and attapulgite. In step S102, making the filler using diatomaceous earth and attapulgite includes:

[0057] S1021: The diatomaceous earth is successively subjected to grinding treatment and calcination treatment to obtain the treated diatomaceous earth. Among them, the grinding treatment includes: mixing the diatomaceous earth, zirconia beads and water to obtain a mixture, and the mass ratio range of the diatomaceous earth, zirconia beads and water is 1:1:2 - 4:1:1; putting the mixture into a grinding machine for grinding to obtain the ground diatomaceous earth, and the average particle size range of the ground diatomaceous earth is 2μm - 10μm; the calcination treatment includes: after freeze-drying the ground diatomaceous earth, placing it in a high-temperature furnace for burning to obtain the treated diatomaceous earth, the temperature range of the high-temperature furnace is 300°C - 500°C, and the burning time range is 60min - 150min.

[0058] S1022: Mix the treated diatomaceous earth with attapulgite to obtain the filler. The average particle size range of attapulgite is 1μm - 5μm, and the mass ratio range of the treated diatomaceous earth to attapulgite is 1:2 - 2:1.

[0059] It can be understood that the diameter range of the zirconia beads is 0.6mm - 3mm, and the grinding time for putting the mixture into the grinding machine is in the range of 30min - 10min, ensuring that the average particle size range of the ground diatomaceous earth is 2μm - 10μm. This particle size range can facilitate the filler to uniformly fill the pores between the fibers and adhere to the fiber surface, making the filler not easy to fall off. By adjusting the mass ratio range of the diatomaceous earth, zirconia beads and water to 1:1:2 - 4:1:1 and the grinding time, the present invention can control the ball milling efficiency and the refinement degree of the diatomaceous earth particles. Of course, when the quality of the diatomaceous earth is relatively high, the amount of zirconia beads can be appropriately reduced, thereby reducing the processing cost.

[0060] Optionally, the mass of the filler accounts for 5% - 20% of the absolute dry fiber mass of the sizing slurry, the mass of the strengthening agent accounts for 0.5% - 4.0% of the absolute dry fiber mass of the sizing slurry, and the mass of the retention aid accounts for 0.02% - 0.05% of the absolute dry fiber mass of the sizing slurry.

[0061] Specifically, the mass ratio of the filler in the absolute dry fiber mass of the sizing slurry can be 5%, 10%, 15%, 20%, or any value between 5% and 20%. The mass ratio of the intensifier in the absolute dry fiber mass of the sizing slurry can be 0.5%, 1%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, or any value between 0.5% and 4.0%. The mass ratio of the retention aid in the absolute dry fiber mass of the sizing slurry can be 0.02%, 0.03%, 0.04%, 0.05%, or any value between 0.02% and 0.05%. In this embodiment, when the mass concentration of the intensifier is 2% and the viscosity of the intensifier is 800 - 3000 cP, the mass ratio of the intensifier in the absolute dry fiber mass of the sizing slurry is 0.5% - 4.0%. Such a setting facilitates the preparation of the intensifier and the control of its usage amount. Otherwise, if the viscosity of the intensifier is too high, it is not easy to prepare and dissolve; if the viscosity of the intensifier is too low, the strengthening effect on the forming paper is not strong. The retention aid helps to retain the filler. The mass ratio of the retention aid in the absolute dry fiber mass of the sizing slurry is set to be 0.02% - 0.05% because if the dosage of the retention aid is too low, the retention effect is poor and the filler is likely to be lost; if the dosage of the retention aid is too high, it will cause obvious flocculation of the pulp, and large flocs are likely to result in poor formation of the paper, ultimately affecting the strength.

[0062] Optionally, the intensifier includes hydroxypropyl methylcellulose and hydroxyethyl cellulose, and the mixing ratio range of hydroxypropyl methylcellulose to hydroxyethyl cellulose is 1:2 - 2:1.

[0063] It can be understood that the dissolved carboxymethylated jute fibers, hydroxypropyl methylcellulose, and hydroxyethyl cellulose will increase the viscosity of the micro - system composed of the skeleton structure and the filler, which is beneficial to the uniform distribution and retention of the filler. Hydroxypropyl methylcellulose and hydroxyethyl cellulose are closely arranged on the fiber surface to form a network structure, which can also increase the dry strength and wet strength of the paper.

[0064] Optionally, the retention aid is cationic polyacrylamide.

[0065] Optionally, the strengthening agent is a mixture of chitosan and acrylic latex, or the strengthening agent is a mixture of chitosan and ethylene - vinyl acetate copolymer resin.

[0066] It can be understood that the impregnated strengthening agent penetrates into the interior of the paper. The amino group of chitosan in the strengthening agent interacts with the carboxyl group in the carboxymethylated modified fiber to form a cross - linked complex, further enhancing the internal bonding strength of the paper. The polymer latex in the strengthening agent covers the surface of the paper fibers and the filler, which can firmly bind the fibers and the filler, and improve the friction resistance of the surface of the forming paper, and can prevent or reduce linting and powdering during the use of the forming paper.

[0067] Optionally, the mass concentration of chitosan in the strengthening agent ranges from 0.5% to 3%; the mass concentration of acrylic latex in the strengthening agent ranges from 0.5% to 6%, or the mass concentration of ethylene-vinyl acetate copolymer resin in the strengthening agent ranges from 0.5% to 6%.

[0068] Specifically, the mass concentration of chitosan in the strengthening agent can be 0.5%, 1%, 1.5%, 2.0%, 2.5%, 3.0%, or any value between 0.5% and 3.0%. The mass concentration of acrylic latex in the strengthening agent can be 0.5%, 1%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, 6.0%, or any value between 0.5% and 6.0%. The mass concentration of ethylene-vinyl acetate copolymer resin in the strengthening agent can be 0.5%, 1%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, 6.0%, or any value between 0.5% and 6.0%. Setting the usage amount of chitosan and acrylic latex, or setting the usage amount of chitosan and ethylene-vinyl acetate copolymer resin, can avoid the situation that the concentration of the strengthening agent is too low to achieve the effect of increasing the surface and internal strength, while too high a concentration of chitosan will lead to too high viscosity of the impregnating solution, which is not conducive to impregnation and the penetration of the impregnating solution into the paper, ultimately affecting the strengthening effect. Of course, the specific addition amounts of the above components can be adjusted according to the actual situation, and this embodiment does not make specific limitations on this.

[0069] Optionally, in step S104, the pressing pressure for pressing treatment is 300 kPa, and the drying treatment is carried out using a vacuum dryer with a drying temperature of 95°C. Of course, this embodiment does not make specific limitations on this and can be adjusted according to the actual situation. In step S105, a two-roll extruder can be used for extrusion treatment to extrude the excess strengthening agent, and the drying temperature for drying treatment is 100°C. Of course, this embodiment does not make specific limitations on this and can be adjusted according to the actual situation.

[0070] The basis weight, density, tensile strength, tensile energy absorption, and internal bond strength of the formed paper are measured according to GB / T451.2—2023, GB / T451.3—2002, GB / T12914—2018, and GB / T26203—2023. After testing, for the formed paper prepared by the above method, its basis weight ranges from 25 g / m 2 - 40 g / m 2 , the density ranges from 0.4 g / cm 3 - 0.7 g / cm 3 , the tensile strength ranges from 22 N to 40 N, and the tensile energy absorption ranges from 20 J / m 2 - 50 J / m2 , the internal bond strength ranges from 500 J / m 2 -1500 J / m 2 , proving that the formed paper prepared by the above method has been greatly improved in terms of strength, firmness, wear resistance, etc., and can effectively prevent or reduce the linting and dusting of the formed paper.

[0071] The present invention provides several specific embodiments as follows:

[0072] Example 1

[0073] Fiber raw materials, including: bleached kraft softwood pulp, bleached kraft hardwood pulp, and carboxymethylated jute pulp. The mass ratios of the three fiber slurries to the fiber raw materials are 20%, 65%, and 15% respectively. The bleached kraft softwood pulp and the bleached kraft hardwood pulp are mixed together in proportion and then beaten. The beating degree after beating treatment is 65°SR; the carboxymethyl substitution degree of the carboxymethylated jute pulp is 0.25, the average length after being dispersed in water is 1.45 mm, and the average width is 30.2 μm. It is beaten alone, and the beating degree is 58°SR. The two beaten slurries are mixed evenly to obtain a mixed fiber slurry.

[0074] Sizing agents, including: fillers, strengthening agents, and retention aids. The filler is made from diatomaceous earth and attapulgite. The original average particle size of the diatomaceous earth is 24 μm. Before adding it to the slurry, the original diatomaceous earth needs to be ground and calcined. The diatomaceous earth is mixed with zirconia beads and water, and ground using a sand mill. The diameter of the zirconia beads is 1 mm, and the mass ratio of zirconia beads, diatomaceous earth, and water is 3:1:1. The grinding time is 60 min. After grinding, the average particle size of the diatomaceous earth is 3.2 μm. The ground diatomaceous earth is freeze-dried and then placed in a high-temperature furnace at 450°C and burned for 60 min. The average particle size of attapulgite is 2.1 μm. The mass ratio of the ground and calcined diatomaceous earth to attapulgite is 1:1. The addition amount of the filler in the slurry is 15% of the absolute dry fiber mass of the sizing slurry. The strengthening agents are hydroxypropyl methylcellulose and hydroxyethyl cellulose, and their mixing ratio is 1:1. The viscosity of the mixed solution of the strengthening agents at a mass concentration of 2% is 2339 cP, and the dosage of the strengthening agents is 1.0% of the absolute dry fiber mass of the sizing slurry. The retention aid is cationic polyacrylamide, and the dosage is 0.03% of the absolute dry fiber mass of the sizing slurry. The mixed filler composed of diatomaceous earth and attapulgite, strengthening agents, and retention aids are added to the mixed fiber slurry. After mixing evenly, the sizing slurry is obtained. The wet paper web is formed by using a rapid sheet former, and the formed paper base paper is obtained after pressing and drying, where the pressing pressure is 300 kPa, vacuum drying is used, and the drying temperature is 95°C.

[0075] Impregnating strengthening agent: The strengthening agent is a mixed solution of chitosan and ethylene-vinyl acetate copolymer resin. The mass concentration of chitosan in the strengthening agent is 1.0%, and the mass concentration of ethylene-vinyl acetate copolymer resin in the strengthening agent is 2.0%. The base paper of the formed paper is impregnated with the strengthening agent, and after extruding the excess strengthening agent through a two-roll extruder, it is dried to obtain the formed paper. The drying temperature is 100 °C, and the mass percentage of the strengthening agent (dry weight) in the formed paper is 6%.

[0076] Example 2

[0077] Fiber raw materials, including: The fiber raw materials are bleached kraft softwood pulp, bleached kraft hardwood pulp, and carboxymethylated jute pulp. The mass ratios of the three fiber slurries to the fiber raw materials are 32%, 48%, and 20% respectively. The bleached kraft softwood pulp and the bleached kraft hardwood pulp are mixed in proportion and then beaten together. The beating degree after beating is 55°SR; the carboxymethyl substitution degree of the carboxymethylated jute pulp is 0.3, and it is beaten alone with a beating degree of 66°SR. The two beaten slurries are mixed evenly to obtain a mixed fiber slurry.

[0078] Sizing aids, including: fillers, strengthening agents, and retention aids. The filler is made from diatomaceous earth and attapulgite. The original average particle size of the diatomaceous earth is 24 μm. Before adding it to the slurry, the original diatomaceous earth needs to be ground and calcined. The diatomaceous earth is mixed with zirconia beads and water, and ground using a sand mill. The diameter of the zirconia beads is 3 mm, and the mass ratio of zirconia beads, diatomaceous earth, and water is 3:1:1. The grinding time is 40 min. After grinding, the average particle size of the diatomaceous earth is 4.1 μm. The ground diatomaceous earth is freeze-dried and then placed in a high-temperature furnace at 400 °C for 80 min of calcination. The average particle size of attapulgite is 2.1 μm. The mass ratio of the ground and calcined diatomaceous earth to attapulgite is 1:1. The addition amount of the filler in the slurry is 20% of the dry fiber mass of the sizing slurry. The strengthening agents are hydroxypropyl methylcellulose and hydroxyethyl cellulose, and their mixing ratio is 1:1. The viscosity of the mixed solution at a mass concentration of 2% is 1679 cP. The dosage of the strengthening agent is 0.7% of the dry fiber mass of the sizing slurry. The retention aid is cationic polyacrylamide, and the dosage is 0.02% of the dry fiber mass of the sizing slurry. The mixed filler composed of diatomaceous earth and attapulgite, strengthening agent, and retention aid are added to the mixed fiber slurry. After mixing evenly, the sizing slurry is obtained. The wet paper web is formed by using a rapid sheet former, and after pressing and drying, the base paper of the formed paper is obtained. Among them, the pressing pressure is 300 kPa, and it is dried using a vacuum dryer with a drying temperature of 95 °C.

[0079] Impregnating strengthening agent: The strengthening agent is a mixed solution of chitosan and ethylene-vinyl acetate copolymer resin. The mass concentration of chitosan in the strengthening agent is 1.5%, and the mass concentration of ethylene-vinyl acetate copolymer resin in the strengthening agent is 2.5%. The base paper of the formed paper is impregnated with the strengthening agent and dried after impregnation to obtain the formed paper. The drying temperature is 100 °C, and the mass percentage of the strengthening agent (dry weight) in the formed paper is 8%.

[0080] Example 3

[0081] Fiber raw materials, including: bleached kraft softwood pulp, bleached kraft hardwood pulp, and carboxymethylated jute pulp. The mass ratios of the three fiber slurries to the fiber raw materials are 30%, 60%, and 10% respectively. The bleached kraft softwood pulp and the bleached kraft hardwood pulp are mixed in proportion and beaten together. The beating degree after beating is 60 °SR; the carboxymethyl substitution degree of the carboxymethylated jute pulp is 0.4, the average length after being dispersed in water is 1.32 mm, and the average width is 30.8 μm. It is beaten alone, and the beating degree is 75 °SR. The two beaten slurries are mixed evenly to obtain a mixed fiber slurry.

[0082] Sizing aids, including: fillers, strengthening agents, and retention aids. The filler is made from diatomite and attapulgite. The original average particle size of the diatomite is 19 μm. Before adding it to the slurry, the original diatomite needs to be ground and calcined. The diatomite is mixed with zirconia beads and water and ground using a sand mill. The diameter of the zirconia beads is 2 mm, and the mass ratio of zirconia beads, diatomite, and water is 3:1:1. The grinding time is 100 min. After grinding, the average particle size of the diatomite is 2.8 μm. The ground diatomite is freeze-dried and then placed in a high-temperature furnace at 350 °C for calcination for 100 min. The average particle size of attapulgite is 2.9 μm. The mass ratio of the calcined diatomite and attapulgite after grinding is 1:1. The addition amount of the filler in the slurry is 10% of the dry fiber mass of the sizing slurry. The strengthening agent is hydroxypropyl methylcellulose and hydroxyethyl cellulose, and their mixing ratio is 1:1. The viscosity of the mixed solution at a mass concentration of 2% is 1009 cP. The dosage of the strengthening agent is 1.5% of the dry fiber mass of the sizing slurry. The retention aid is cationic polyacrylamide, and the dosage is 0.03% of the dry fiber mass of the sizing slurry. The mixed filler composed of diatomite and attapulgite, the strengthening agent, and the retention aid are added to the mixed fiber slurry. After mixing evenly, the sizing slurry is obtained. The wet paper web is formed by using a rapid sheet former, and after pressing and drying, the base paper of the formed paper is obtained. Among them, the pressing pressure is 300 kPa, and it is dried by a vacuum dryer at a drying temperature of 95 °C.

[0083] Impregnating strengthening agent: The strengthening agent is a mixed solution of chitosan and acrylic resin. The mass concentration of chitosan in the strengthening agent is 0.5%, and the mass concentration of acrylic resin in the strengthening agent is 4.0%. The base paper of the formed paper is impregnated with the strengthening agent, and after extruding the excess strengthening agent by a two-roll extruder, it is dried to obtain the formed paper. The drying temperature is 100 °C, and the mass percentage of the strengthening agent (dry mass) in the formed paper is 7%.

[0084] Example 4

[0085] Fiber raw materials, including: bleached kraft softwood pulp, bleached kraft hardwood pulp, and carboxymethylated jute pulp. The mass ratios of the three fiber slurries to the fiber raw materials are 20%, 50%, and 30% respectively. The bleached kraft softwood pulp and the bleached kraft hardwood pulp are mixed in proportion and then beaten together. The beating degree after the beating treatment is 58 °SR; the carboxymethyl substitution degree of the carboxymethylated jute pulp is 0.3, the average length after being dispersed in water is 1.4 mm, and the average width is 30.5 μm. It is beaten alone, and the beating degree is 60 °SR. The two slurries after beating are mixed evenly to obtain a mixed fiber slurry.

[0086] Sizing aids, including: fillers, strengthening agents, and retention aids. The filler is made from diatomaceous earth and attapulgite. The original average particle size of the diatomaceous earth is 19 μm. Before adding it to the slurry, the original diatomaceous earth needs to be ground and calcined. The diatomaceous earth is mixed with zirconia beads and water, and ground using a sand mill. The diameter of the zirconia beads is 2 mm, and the mass ratio of zirconia beads, diatomaceous earth, and water is 3:1:1. The grinding time is 100 min. After grinding, the average particle size of the diatomaceous earth is 2.8 μm. The ground diatomaceous earth is freeze-dried and then placed in a high-temperature furnace at 400 °C and burned for 80 min. The average particle size of attapulgite is 2.9 μm. The mass ratio of the ground and calcined diatomaceous earth to attapulgite is 1:1. The addition amount of the filler in the slurry is 20% of the dry fiber mass of the sizing slurry. The strengthening agent is hydroxypropyl methylcellulose and hydroxyethyl cellulose, and their mixing ratio is 1:1. The viscosity of the mixed solution at a mass concentration of 2% is 1679 cP. The dosage of the strengthening agent is 0.5% of the dry fiber mass of the sizing slurry. The retention aid is cationic polyacrylamide, and the dosage is 0.02% of the dry fiber mass of the sizing slurry. A mixed filler composed of diatomaceous earth and attapulgite, a strengthening agent, and a retention aid are added to the mixed fiber slurry. After mixing evenly, the sizing slurry is obtained. The wet paper web is formed by using a rapid sheet former, and after pressing and drying, the base paper of the formed paper is obtained. Among them, the pressing pressure is 300 kPa, and it is dried by a vacuum dryer. The drying temperature is 95 °C.

[0087] Impregnating strengthening agent: The strengthening agent is a mixed solution of chitosan and ethylene-vinyl acetate copolymer. The mass concentration of chitosan in the strengthening agent is 0.5%, and the mass concentration of ethylene-vinyl acetate copolymer in the strengthening agent is 3.5%. The base paper of the formed paper is impregnated with the strengthening agent, and after extruding the excess strengthening agent by a two-roll extruder, it is dried to obtain the formed paper. The drying temperature is 100°C, and the mass percentage of the strengthening agent (dry weight) in the formed paper is 5%.

[0088] Example 5

[0089] Fiber raw materials, including: bleached kraft softwood pulp, bleached kraft hardwood pulp and carboxymethylated jute pulp. The mass ratios of the three fiber slurries to the fiber raw materials are 20%, 65% and 15% respectively. The bleached kraft softwood pulp and the bleached kraft hardwood pulp are mixed in proportion and beaten together. The beating degree after beating treatment is 49°SR; the carboxymethyl substitution degree of the carboxymethylated jute pulp is 0.3, the average length after being dispersed in water is 1.4 mm, and the average width is 30.5 μm. It is beaten alone, and the beating degree is 66°SR. The two beaten slurries are mixed evenly to obtain a mixed fiber slurry.

[0090] Sizing aids, including: fillers, strengthening agents and retention aids. The filler is made of diatomite and attapulgite. The original average particle size of the diatomite is 19 μm. Before adding it to the slurry, the original diatomite needs to be ground and calcined. The diatomite is mixed with zirconia beads and water, and ground by a sand mill. The diameter of the zirconia beads is 2 mm, and the mass ratio of zirconia beads, diatomite and water is 3:1:1. The grinding time is 100 min. The average particle size of the diatomite after grinding is 2.8 μm. The ground diatomite is freeze-dried and then placed in a high-temperature furnace at 400°C and calcined for 80 min. The average particle size of attapulgite is 2.9 μm. The mass ratio of the ground and calcined diatomite to attapulgite is 1:1. The addition amount of the filler in the slurry is 20% of the dry fiber mass of the sizing slurry. The strengthening agent is hydroxypropyl methylcellulose and hydroxyethyl cellulose, and their mixing ratio is 1:1. The viscosity of the mixed solution at a mass concentration of 2% is 2339 cP. The dosage of the strengthening agent is 0.5% of the dry fiber mass of the sizing slurry. The retention aid is cationic polyacrylamide, and the dosage is 0.03% of the dry fiber mass of the sizing slurry. The mixed filler composed of diatomite and attapulgite, the strengthening agent and the retention aid are added to the mixed fiber slurry, and after mixing evenly, the sizing slurry is obtained. The wet paper web is formed by using a rapid sheet former, and after pressing and drying, the base paper of the formed paper is obtained. Among them, the pressing pressure is 300 kPa, and it is dried by a vacuum dryer, and the drying temperature is 95°C.

[0091] Impregnating strengthening agent: The strengthening agent is a mixed solution of chitosan and ethylene-vinyl acetate copolymer. The mass concentration of chitosan in the strengthening agent is 1.5%, and the mass concentration of ethylene-vinyl acetate copolymer in the strengthening agent is 5.0%. The base paper of the formed paper is impregnated with the strengthening agent, and after extruding the excess strengthening agent with a two-roll extruder, it is dried to obtain the formed paper. The drying temperature is 100 °C, and the mass percentage of the strengthening agent (dry mass) in the formed paper is 12%.

[0092] Example 6

[0093] Fiber raw materials, including: bleached kraft softwood pulp, bleached kraft hardwood pulp and carboxymethylated jute pulp. The mass ratios of the three fiber slurries to the fiber raw materials are 30%, 50% and 20% respectively. The bleached kraft softwood pulp and the bleached kraft hardwood pulp are mixed in proportion and then beaten together. The beating degree after beating treatment is 60°SR; the carboxymethyl substitution degree of the carboxymethylated jute pulp is 0.3, the average length after being dispersed in water is 1.49 mm, and the average width is 29.8 μm. It is beaten alone, and the beating degree is 54°SR. The two beaten slurries are mixed evenly to obtain a mixed fiber slurry.

[0094] Sizing aids, including: fillers, strengthening agents and retention aids. The filler is made of diatomite and attapulgite. The original average particle size of diatomite is 24 μm. Before adding it to the slurry, the original diatomite needs to be ground and calcined. The diatomite is mixed with zirconia beads and water, and ground with a sand mill. The diameter of the zirconia beads is 1 mm, and the mass ratio of zirconia beads, diatomite and water is 3:1:1. The grinding time is 60 min. The average particle size of the ground diatomite is 3.2 μm. The ground diatomite is freeze-dried and then placed in a high-temperature furnace at 450 °C for 60 min of calcination. The average particle size of attapulgite is 2.1 μm. The mass ratio of the ground and calcined diatomite to attapulgite is 1:1. The addition amount of the filler in the slurry is 8% of the dry fiber mass of the sizing slurry. The strengthening agent is hydroxypropyl methylcellulose and hydroxyethyl cellulose, and their mixing ratio is 1:1. The viscosity of the mixed solution at a mass concentration of 2% is 1459 cP. The dosage of the strengthening agent is 1.0% of the dry fiber mass of the sizing slurry. The retention aid is cationic polyacrylamide, and the dosage is 0.02% of the dry fiber mass of the sizing slurry. The mixed filler composed of diatomite and attapulgite, the strengthening agent and the retention aid are added to the mixed fiber slurry. After mixing evenly, the sizing slurry is obtained. The wet paper web is formed by using a rapid sheet former, and after pressing and drying, the base paper of the formed paper is obtained. Among them, the pressing pressure is 300 kPa, and it is dried with a vacuum dryer. The drying temperature is 95 °C.

[0095] Impregnating strengthening agent: The strengthening agent is a mixed solution of chitosan and ethylene-vinyl acetate copolymer resin. The mass concentration of chitosan in the strengthening agent is 1.5%, and the mass concentration of ethylene-vinyl acetate copolymer resin in the strengthening agent is 6.0%. The base paper of the formed paper is impregnated with the strengthening agent, and after extruding the excess strengthening agent through a two-roll extruder, it is dried to obtain the formed paper. The drying temperature is 100 °C, and the mass percentage of the strengthening agent (dry mass) in the formed paper is 15%.

[0096] Comparative Example 1

[0097] Fiber raw materials, including: bleached kraft softwood pulp and bleached kraft hardwood pulp. The mass ratios of the two pulps are 24% and 76% respectively. After mixing, they are beaten together, and the beating degree after beating treatment is 65 °SR.

[0098] Sizing aids, including: fillers, strengthening agents, and retention aids. The filler is made from diatomaceous earth and attapulgite. The original average particle size of diatomaceous earth is 24 μm. Before adding it to the pulp, the original diatomaceous earth needs to be ground and calcined. The diatomaceous earth is mixed with zirconia beads and water, and ground using a sand mill. The diameter of the zirconia beads is 1 mm, and the mass ratio of zirconia beads, diatomaceous earth, and water is 3:1:1. The grinding time is 60 min. After grinding, the average particle size of diatomaceous earth is 3.2 μm. The ground diatomaceous earth is freeze-dried and then placed in a high-temperature furnace at 450 °C and calcined for 60 min. The average particle size of attapulgite is 2.1 μm. The mass ratio of the calcined diatomaceous earth and attapulgite is 1:1. The addition amount of the filler in the pulp is 15% of the dry fiber mass of the sizing pulp. The strengthening agent is hydroxypropyl methylcellulose and hydroxyethyl cellulose, and their mixing ratio is 1:1. The viscosity of the mixed solution of the strengthening agent at a mass concentration of 2% is 2339 cP. The dosage of the strengthening agent is 1.0% of the dry fiber mass of the sizing pulp. The retention aid is cationic polyacrylamide, and the dosage is 0.03% of the dry fiber mass of the sizing pulp. The mixed filler composed of diatomaceous earth and attapulgite, strengthening agent, and retention aid are added to the mixed fiber pulp, and after mixing evenly, the sizing pulp is obtained. The wet paper web is formed by using a rapid sheet former, and after pressing and drying, the base paper of the formed paper is obtained. Among them, the pressing pressure is 300 kPa, dried by a vacuum dryer, and the drying temperature is 95 °C.

[0099] Comparative Example 2

[0100] Fiber raw materials, including: bleached kraft softwood pulp and bleached kraft hardwood pulp. The mass ratios of the two pulps are 24% and 76% respectively. After mixing, they are beaten together, and the beating degree after beating treatment is 65 °SR.

[0101] Sizing aids, including: fillers, strengthening agents, and retention aids. The filler is prepared from diatomaceous earth and attapulgite. The original average particle size of the diatomaceous earth is 24 μm. Before adding it to the pulp, the original diatomaceous earth needs to be ground and calcined. The diatomaceous earth is mixed with zirconia beads and water, and ground using a sand mill. The diameter of the zirconia beads is 1 mm, and the mass ratio of zirconia beads, diatomaceous earth, and water is 3:1:1. The grinding time is 60 min. After grinding, the average particle size of the diatomaceous earth is 3.2 μm. The ground diatomaceous earth is freeze-dried and then placed in a high-temperature furnace at 450 °C and calcined for 60 min. The average particle size of the attapulgite is 2.1 μm. The mass ratio of the ground and calcined diatomaceous earth to attapulgite is 1:1. The addition amount of the filler in the pulp is 15% of the absolute dry fiber mass of the sizing pulp. The strengthening agents are hydroxypropyl methylcellulose and hydroxyethyl cellulose, and their mixing ratio is 1:1. The viscosity of the mixed solution of the strengthening agents at a mass concentration of 2% is 2339 cP. The dosage of the strengthening agents is 1.0% of the absolute dry fiber mass of the final pulp. The retention aid is cationic polyacrylamide, and its dosage is 0.03% of the absolute dry fiber mass of the final pulp. A mixed filler composed of diatomaceous earth and attapulgite, strengthening agents, and a retention aid are added to the mixed fiber pulp. After mixing evenly, the sizing pulp is obtained. The sizing pulp is used to form a wet paper web using a rapid sheet former, and then formed into a base paper through pressing and drying. Among them, the pressing pressure is 300 kPa, dried using a vacuum dryer, and the drying temperature is 95 °C.

[0102] Impregnation strengthening agent: The strengthening agent is a mixed solution of chitosan and ethylene-vinyl acetate copolymer resin. The mass concentration of chitosan in the strengthening agent is 1.0%, and the mass concentration of ethylene-vinyl acetate copolymer resin in the strengthening agent is 2.0%. The base paper of the formed paper is impregnated with the strengthening agent, and after extruding the excess strengthening agent using a two-roll extruder, it is dried to obtain the formed paper. The drying temperature is 100 °C, and the mass percentage of the strengthening agent (absolute dry mass) in the formed paper is 6%.

[0103] Comparative Example 3

[0104] Fiber raw materials, including: bleached kraft softwood pulp, bleached kraft hardwood pulp, and carboxymethylated jute pulp. The mass ratios of the three fiber pulps to the fiber raw materials are 20%, 65%, and 15% respectively. The bleached kraft softwood pulp and the bleached kraft hardwood pulp are mixed in proportion and beaten together. The beating degree after the beating treatment is 65 °SR; the carboxymethyl substitution degree of the carboxymethylated jute pulp is 0.25, the average length after being dispersed in water is 1.45 mm, and the average width is 30.2 μm. It is beaten alone, and the beating degree is 58 °SR. The two beaten pulps are mixed evenly to obtain the mixed fiber pulp.

[0105] Internal sizing aids, including: fillers, strengthening agents, and retention aids. The filler is prepared from diatomaceous earth and attapulgite. The original average particle size of the diatomaceous earth is 24 μm. Before adding it to the pulp, the original diatomaceous earth needs to be ground and calcined. The diatomaceous earth is mixed with zirconia beads and water, and ground using a sand mill. The diameter of the zirconia beads is 1 mm, and the mass ratio of zirconia beads, diatomaceous earth, and water is 3:1:1. The grinding time is 60 min. After grinding, the average particle size of the diatomaceous earth is 3.2 μm. The ground diatomaceous earth is freeze-dried and then placed in a high-temperature furnace at 450 °C and calcined for 60 min. The average particle size of the attapulgite is 2.1 μm. The mass ratio of the ground and calcined diatomaceous earth to the attapulgite is 1:1. The addition amount of the filler in the pulp is 15% of the dry fiber mass of the sizing pulp. The strengthening agents are hydroxypropyl methylcellulose and hydroxyethyl cellulose, and their mixing ratio is 1:1. The viscosity of the mixed solution at a mass concentration of 2% is 2339 cP. The dosage of the strengthening agent is 1.0% of the dry fiber mass of the sizing pulp. The retention aid is cationic polyacrylamide, and its dosage is 0.03% of the dry fiber mass of the sizing pulp. A mixed filler composed of diatomaceous earth and attapulgite, strengthening agents, and retention aids are added to the mixed fiber pulp. After mixing evenly, the sizing pulp is obtained. A wet paper web is formed by papermaking using a rapid sheet former, and then the formed paper base paper is obtained after pressing and drying, where the pressing pressure is 300 kPa and vacuum drying is used, and the drying temperature is 95 °C.

[0106] Comparative Example 4

[0107] Fiber raw materials, including: bleached kraft softwood pulp, bleached kraft hardwood pulp, and carboxymethylated jute pulp. The mass ratios of the three fiber pulps to the fiber raw materials are 20%, 65%, and 15% respectively. The bleached kraft softwood pulp and the bleached kraft hardwood pulp are mixed in proportion and then beaten together. The beating degree after beating is 65°SR; the carboxymethyl substitution degree of the carboxymethylated jute pulp is 0.25, the average length after being dispersed in water is 1.45 mm, and the average width is 30.2 μm. It is beaten separately, and the beating degree is 58°SR. The two beaten pulps are mixed evenly to obtain the mixed fiber pulp.

[0108] Sizing aids, including: fillers, strengthening agents, and retention aids. The filler is diatomaceous earth, with an original average particle size of 24 μm. Before adding it to the pulp, the original diatomaceous earth needs to be ground and calcined. Mix the diatomaceous earth with zirconia beads and water, and grind it using a sand mill. The diameter of the zirconia beads is 1 mm, and the mass ratio of zirconia beads, diatomaceous earth, and water is 3:1:1. The grinding time is 60 min. After grinding, the average particle size of the diatomaceous earth is 3.2 μm. Freeze-dry the ground diatomaceous earth, and then place it in a high-temperature furnace at 450 °C and burn it for 60 min. The addition amount of the filler in the pulp is 15% of the dry fiber mass of the sized pulp. The strengthening agents are hydroxypropyl methylcellulose and hydroxyethyl cellulose, and their mixing ratio is 1:1. The viscosity of the mixed solution of the strengthening agents at a mass concentration of 2% is 2339 cP. The dosage of the strengthening agents is 1.0% of the dry fiber mass of the sized pulp. The retention aid is cationic polyacrylamide, and its dosage is 0.03% of the dry fiber mass of the sized pulp. Add the diatomaceous earth filler, strengthening agents, and retention aid to the mixed fiber pulp, mix evenly to obtain the sized pulp, use a rapid sheet former to form a wet paper web, and then obtain the formed paper base paper after pressing and drying. The pressing pressure is 300 kPa, and it is dried using a vacuum dryer at a drying temperature of 95 °C.

[0109] Impregnation strengthening agent: The strengthening agent is a mixed solution of chitosan and ethylene-vinyl acetate copolymer resin. The mass concentration of chitosan in the strengthening agent is 1.0%, and the mass concentration of ethylene-vinyl acetate copolymer resin in the strengthening agent is 2.0%. Impregnate the formed paper base paper with the strengthening agent, extrude the excess strengthening agent using a two-roll extruder, and then dry it to obtain the formed paper. The drying temperature is 100 °C, and the mass percentage of the strengthening agent (dry mass) in the formed paper is 6%.

[0110] Test the formed papers obtained from Example 1 to Example 6 and Comparative Example 1 to Comparative Example 4 respectively, and obtain Table 1 as follows:

[0111] Table 1. Test Results Table of Formed Papers

[0112]

[0113] Table 1. Test Results Table of Formed Papers

[0114]

[0115] Analyze in combination with Table 1. Compare Comparative Example 1, Comparative Example 2, Comparative Example 3, and Example 1. Comparative Example 1 does not contain carboxymethylated jute pulp and is not impregnated with a strengthening agent. Comparative Example 2 does not contain carboxymethylated jute pulp but is impregnated with a strengthening agent. Comparative Example 3 contains carboxymethylated jute pulp and is not impregnated with a strengthening agent. Example 1 uses the method provided by the present invention, contains carboxymethylated jute pulp and is impregnated with a strengthening agent. The other materials and conditions of Comparative Example 1, Comparative Example 2, Comparative Example 3, and Example 1 are the same.

[0116] Compared with Comparative Example 1, the carboxymethylated jute pulp combined with the impregnation enhancer can increase the tensile strength by 57.6% and the internal bond strength by 196.0%. Referring to Comparative Example 3, using a single carboxymethylated jute pulp, or referring to Comparative Example 2, using a single impregnation enhancer, it can be seen that although the tensile strength also increases, the increase amplitude is lower than 30%.

[0117] Comparing Comparative Example 4 with Example 1, Comparative Example 4 uses 100% diatomite as the filler without rod-shaped attapulgite. The tensile strength of the forming paper is 7.4% lower than that of Example 1, and the air permeability is 15 CU lower than that of Example 1, indicating that the mixed application of diatomite and attapulgite is beneficial to the strength and air permeability of the forming paper.

[0118] In this case, diatomite and attapulgite are used to make the filler, and then the filler, fiber raw material, strengthening agent, retention aid and enhancer are used to make the forming paper. The applicant submitted a case "Preparation Method of Filter Rod Filling Paper" on the same day, which uses carboxymethylated modified fiber pulp, regenerated cellulose fiber pulp, basil leaves, wet strength agent and basil essence to make the filling paper. It has different technical problems to be solved, different technical solutions adopted, different technical effects achieved, and different contents and scopes to be protected from this case.

[0119] In summary, the preparation method of a forming paper for a cigarette filter rod provided by the present invention can effectively improve the strength, firmness and wear resistance of the forming paper, and effectively prevent or reduce the situation of linting and powdering of the forming paper. When the forming paper prepared by the method of the present invention is used to make a filter rod, it can also make the filter rod conducive to the adsorption, interception and derivation of cigarette smoke.

[0120] From the above embodiments, it can be seen that the preparation method of a forming paper for a cigarette filter rod provided by the present invention has at least achieved the following beneficial effects:

[0121] A preparation method of a forming paper for a cigarette filter rod provided by the present invention includes: making a mixed fiber slurry with fiber raw materials; making a filler with diatomite and attapulgite, and mixing the mixed fiber slurry with the filler, a strengthening agent and a retention aid to obtain a sizing slurry; performing papermaking on the sizing slurry by using a paper former to obtain a wet paper web; sequentially performing pressing treatment and drying treatment on the wet paper web to obtain a forming paper base paper; impregnating the forming paper base paper with a strengthening agent, and then sequentially performing extrusion treatment and drying treatment on the forming paper base paper to obtain a forming paper. The fibers of the mixed fiber slurry form a skeleton structure. Since the filler is made of diatomite and attapulgite, the irregular diatomite and rod-shaped attapulgite in the filler are mixed and deposited between the fibers of the mixed fiber slurry, generating a hybrid effect, so that the chance of contact between the filler particles is more than that of a filler with a single form, thereby increasing the retention rate of the slurry system and increasing the strength of the micro-system composed of the skeleton structure and the filler. On this basis, combined with the synergistic effects of the strengthening agent, the retention aid and the strengthening agent, the strength, firmness and wear resistance of the finally obtained forming paper are greatly improved, thereby effectively preventing or reducing the situation of linting and powdering of the forming paper. And the increased chance of contact between the filler particles will form more microporous channels. When the filter rod is made of the forming paper prepared by the method of the present invention, it can also make the filter rod conducive to the adsorption, interception and derivation of cigarette smoke.

[0122] Although some specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are only for illustration and not for limiting the scope of the present invention. Those skilled in the art should understand that the above embodiments can be modified without departing from the scope and spirit of the present invention. The scope of the present invention is defined by the appended claims.

Claims

1. A method for preparing a forming paper for a cigarette filter rod, characterized in that: include: The mixed fiber pulp is prepared by using fiber raw materials, wherein the fiber raw materials include bleached kraft softwood pulp, bleached kraft hardwood pulp and carboxymethylated jute pulp; Using diatomite and attapulgite to make fillers, mixing the mixed fiber slurry with the filler, reinforcing agent and retention aid to obtain sizing slurry; Using a paper sheet former to carry out papermaking treatment on the sizing slurry to obtain a wet paper web; The wet paper web is subjected to pressing and drying treatments in sequence to obtain a forming paper base paper; After the shaping paper base paper is impregnated with a reinforcing agent, the shaping paper base paper is sequentially subjected to extrusion treatment and drying treatment to obtain shaping paper.

2. The method for preparing a forming paper for a cigarette filter rod according to claim 1, characterized in that: The mixed fiber slurry is prepared by using the fiber raw material, comprising: The bleached kraft softwood pulp and the bleached kraft hardwood pulp are mixed and then beaten to obtain an initial mixed pulp, wherein the beating degree of the initial mixed pulp ranges from 50°SR to 80°SR; Beating the carboxymethylated jute pulp to obtain a single pulp, wherein the beating degree of the single pulp is in the range of 40°SR-80°SR; The initial mixed slurry and the single slurry are mixed to obtain the mixed fiber slurry.

3. The method for preparing a shaping paper for a cigarette filter rod according to claim 1 or 2, characterized in that: The mass of the bleached kraft coniferous wood pulp accounts for 15%-60% of the mass of the fiber raw material, the mass of the bleached kraft hardwood pulp accounts for 15%-60% of the mass of the fiber raw material, and the mass of the carboxymethylated jute pulp accounts for 5%-40% of the mass of the fiber raw material.

4. The method for preparing a forming paper for a cigarette filter rod according to claim 1, characterized in that: The filler is prepared by using the diatomite and the attapulgite, comprising: The diatomaceous earth is subjected to grinding treatment and calcination treatment in sequence to obtain the treated diatomaceous earth; The treated diatomaceous earth is mixed with the attapulgite to obtain the filler, the average particle size of the attapulgite is in the range of 1 μm-5 μm, and the mass ratio of the treated diatomaceous earth to the attapulgite is in the range of 1:2-2:

1.

5. The method for preparing a shaping paper for a cigarette filter rod according to claim 4, characterized in that: The grinding process comprises: mixing the diatomaceous earth, zirconia beads and water to obtain a mixture, wherein the mass ratio of the diatomaceous earth, the zirconia beads and the water is in the range of 1:1:2-4:1:1; putting the mixture into a sander for grinding to obtain the ground diatomaceous earth, wherein the average particle size of the ground diatomaceous earth is in the range of 2 μm-10 μm; The calcination treatment comprises: freeze-drying the ground diatomite and then burning it in a high-temperature furnace to obtain the treated diatomite. The temperature range of the high-temperature furnace is 300° C.-500° C., and the burning time range is 60 min-150 min.

6. The method for preparing a forming paper for a cigarette filter rod according to claim 1, characterized in that: The mass of the filler accounts for 5%-20% of the absolute dry fiber mass of the sizing slurry, the mass of the reinforcing agent accounts for 0.5%-4.0% of the absolute dry fiber mass of the sizing slurry, and the mass of the retention agent accounts for 0.02%-0.05% of the absolute dry fiber mass of the sizing slurry.

7. The method for preparing a forming paper for a cigarette filter rod according to claim 1, characterized in that: The enhancer comprises hydroxypropyl methylcellulose and hydroxyethyl cellulose, and the mixing ratio of the hydroxypropyl methylcellulose to the hydroxyethyl cellulose is in the range of 1:2-2:

1.

8. The method for preparing a forming paper for a cigarette filter rod according to claim 1, characterized in that: The retention aid is cationic polyacrylamide.

9. The method for preparing a shaping paper for a cigarette filter rod according to claim 1, characterized in that: The reinforcing agent is a mixture of chitosan and acrylic latex, or the reinforcing agent is a mixture of chitosan and ethylene-vinyl acetate copolymer resin.

10. The method for preparing a shaping paper for a cigarette filter rod according to claim 9, characterized in that: The mass concentration of chitosan in the enhancer is in the range of 0.5% to 3%; The mass concentration of the acrylic latex in the reinforcing agent is in the range of 0.5%-6%, or the mass concentration of the ethylene-vinyl acetate copolymer resin in the reinforcing agent is in the range of 0.5%-6%.

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