Manufacturing method of high-stiffness high-air-permeability large-basis-weight punching-free forming paper

Abstract

The invention provides a manufacturing method of high-stiffness high-air-permeability large-weight punching-free forming paper. The manufacturing method comprises the following steps: taking softwood pulp fibers, sisal pulp and chemical fibers with specific raw material performance indexes as raw materials; performing defibering treatment on the softwood pulp fibers, the sisal pulp and the chemical fibers respectively; mixing the defibered softwood pulp fibers, the defibered sisal pulp and the defibered chemical fibers according to the mass percent of 50-100%, 0-50% and 0-50% respectively, adding polyamide epichlorohydrin resin, diluting, further adding a polyoxyethylene solution, mixing, simultaneously controlling the net concentration of the mixed pulp to be 0.05-0.3 wt%, carrying out net papermaking molding, and then sequentially carrying out squeezing and drying treatment; the paper sheet is dip-coated with a sizing agent, then drying treatment is conducted again, and the paper sheet is obtained through coiling. The forming paper has high stiffness, high air permeability and large quantitative performance, and compared with an existing forming paper preparation process and on-sale forming paper, the forming paper has obvious technical advantages and performance advantages.

Description

Technical Field

[0001] This invention relates to the field of papermaking technology, specifically to a method for manufacturing high-stiffness, high-permeability, high-basis-weight, non-perforated forming paper. Background Technology

[0002] In tobacco product manufacturing, countersunk filter rods have specific requirements for the forming paper. Due to the unique design of countersunk filter rods, their good appearance depends on the forming paper having high stiffness. Currently used rigid forming paper does meet the stiffness requirements, satisfying the need for countersunk filter rods to have a crisp appearance and be resistant to deformation. However, to minimize the harm caused by smoking, the filter rod needs to be perforated to allow outside air to enter, thereby diluting the smoke and reducing its concentration and tar content, thus reducing the smoker's inhalation of harmful substances. However, existing perforation processes are costly, increasing production costs and putting pressure on market prices.

[0003] On the other hand, high-permeability filter rod forming paper has significant advantages in reducing tar and harm due to its own characteristics, and can effectively improve the impact of smoking on human health. However, in order to achieve the high air permeability requirement, this type of high-permeability filter rod forming paper generally has a low basis weight, around 25 grams. The low basis weight inevitably leads to poor stiffness, which cannot meet the strict requirement of a stiff appearance for countersunk filter rods. Therefore, it cannot be used in countersunk filter rods for the time being.

[0004] Furthermore, existing patents also disclose methods for producing forming paper using countersunk filter rods, but these methods generally cannot simultaneously meet the dual requirements of high stiffness and high air permeability. For example, CN201910767042.0 – a method for producing forming paper using countersunk filter rods – produces forming paper with a maximum longitudinal stiffness of over 980 mN and a maximum transverse stiffness of over 700 mN, but the reported air permeability is only over 15 CU. Another example is CN201810006280.5 – a method for preparing oleophobic, seepage-proof, high-permeability filter rod forming paper, which produces forming paper with a maximum air permeability of 12358 CU, but the longitudinal tensile strength is approximately 2 kN / m, and the transverse tensile strength is approximately 0.2 kN / m. Summary of the Invention

[0005] In order to simultaneously achieve the high stiffness and high air permeability of countersunk filter rod forming paper, the present invention provides a method for manufacturing high stiffness, high air permeability, high basis weight non-drilling forming paper.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] In a first aspect, the present invention provides a method for manufacturing high-stiffness, high-air-permeability, high-basis-weight, non-perforated forming paper, comprising the following steps:

[0008] Step 1: Using softwood pulp fiber, sisal pulp, and chemical fibers as raw materials; wherein, the softwood pulp fiber has a length ≥ 2.0 mm, a fiber thickness ≥ 0.12 mg / m, a fiber width of 20–35 μm, and a fiber twist ≥ 10%; the sisal pulp fiber has a length ≥ 1.8 mm, a fiber thickness ≥ 0.12 mg / m, a fiber width of 10–30 μm, and a fiber twist ≥ 15%; the chemical fibers are viscose fiber and / or Tencel fiber, with a length ≥ 3.0 mm, a fiber thickness ≥ 0.15 mg / m, a fiber width of 20–35 μm, and a fiber twist ≥ 8%;

[0009] Step 2: The softwood pulp fiber, sisal pulp and chemical fiber are debonded separately. The process control of the debonding treatment of softwood pulp fiber and sisal pulp is to ensure that the fiber length, fiber width and fiber twist of the softwood pulp fiber and sisal pulp are not damaged.

[0010] Step 3: Mix the defragmented softwood pulp fiber, sisal pulp and chemical fiber at a mass percentage of 50-100%, 0-50% and 0-50% respectively, add polyamide epichlorohydrin resin and dilute, then add polyethylene oxide solution and mix, while controlling the online concentration of the mixed pulp to 0.05-0.3wt%, and then conduct online paper forming, followed by pressing and drying treatment to obtain a paper sheet with a moisture content of 5-7%.

[0011] Step 4: Dip the paper sheet into the sizing agent, then dry it again, and finally roll it to obtain the formed paper.

[0012] Preferably, in step 2, a disc mill is used to decompose the softwood pulp fiber, sisal pulp and chemical fiber, and the decomposition power is controlled to be below 120kw or the decomposition current is controlled to be below 120A.

[0013] Preferably, in step 3, the mixed pulp is diluted to a mass concentration of 2-4%; and / or, the amount of polyamide epichlorohydrin resin added is 15-30 kg / ton of oven-dry pulp; and / or, the mass concentration of polyethylene oxide solution is 0.01-0.05 wt%, and the amount added is 8-12 kg / ton of oven-dry pulp; and / or, the paper forming is done using a cylinder paper machine; and / or, the drying temperature is 90-120°C.

[0014] Preferably, in step 4, the sizing agent is an oxidized starch solution and / or a polyvinyl alcohol solution.

[0015] Furthermore, when using a compound solution of oxidized starch and polyvinyl alcohol as a sizing agent, the mass ratio of oxidized starch to polyvinyl alcohol can be adjusted as needed, such as 1:1, 2:1, 1:2, etc.

[0016] More preferably, the mass concentration of the sizing agent is 8-12%.

[0017] More preferably, the amount of sizing agent used is 60-150 kg / ton of paper.

[0018] Preferably, in step 4, the drying temperature is 85-120℃.

[0019] In a second aspect, the present invention provides a shaped paper obtained by the manufacturing method described in the first aspect.

[0020] Preferably, the formed paper has at least the following performance indicators: basis weight of 60-150 g / m³. 2 Air permeability is 1000-15000Cu, bending stiffness (longitudinal) (bending moment 5mm) ≥100mN, D65 brightness ≥70%, D65 fluorescence brightness ≤1.0%, longitudinal tensile energy absorption ≥20J / m 2 .

[0021] More preferably, the formed paper has the following performance indicators: basis weight of 60-120 g / m³. 2 Air permeability is 5000-15000Cu, bending stiffness (longitudinal) (bending moment 5mm) ≥400mN, D65 brightness ≥80%, D65 fluorescence brightness = 0, longitudinal tensile energy absorption ≥90J / m 2 .

[0022] Compared with the prior art, the technical advantages of the present invention are as follows:

[0023] This invention successfully prepared formed paper with high stiffness, high air permeability, and high basis weight by optimizing the fiber ratio (wood pulp + hemp pulp + chemical fiber), controlling the defragmentation process, and using specific additives (PAE + PEO) and sizing agents. The actual performance of this formed paper far exceeds the minimum technical standard: basis weight of 60-150 g / m³. 2 Air permeability is 1000-15000Cu, bending stiffness (longitudinal) (bending moment 5mm) ≥200mN, D65 brightness ≥70%, D65 fluorescence brightness ≤1.0%, longitudinal tensile energy absorption ≥20J / m 2 Compared with existing paper forming processes and commercially available paper forming products, this method has significant technological and performance advantages, making it worthy of wider promotion. Attached Figure Description

[0024] Figure 1 The image shows a physical drawing of the formed paper of the present invention, wherein 1 is the formed paper obtained in Example 1 of the present invention, and 2 is a common high-permeability formed paper. Detailed Implementation

[0025] This invention, through the rational selection of performance indicators for wood pulp fiber, hemp pulp fiber, and chemical fiber raw materials, and the adjustment of their mass percentages, combined with the optimization of polyamide epichlorohydrin resin, polyethylene oxide additives, and sizing agents, and the fabrication of the formed paper using a cylinder paper machine, ultimately yields a perforation-free formed paper with excellent comprehensive properties such as high stiffness, high air permeability, and high basis weight. This formed paper is mainly used for countersunk filter rods.

[0026] Furthermore, the performance indicators of the raw materials, excipients, and additives used in the embodiments of the present invention are as follows:

[0027] 1) Softwood pulp fiber: Fiber length: ≥2.0mm, fiber thickness: ≥0.12mg / m, fiber width: 20~35μm, fiber twist: ≥10%;

[0028] 2) Sisal pulp fiber: fiber length: ≥1.8mm, fiber thickness: ≥0.12mg / m, fiber width: 10~30μm, fiber twist: ≥15%;

[0029] 3) Chemical fibers: fiber length: ≥3.0mm, fiber thickness: ≥0.15mg / m, fiber width: 20~35μm, fiber twist: ≥8%;

[0030] 4) Polyethylene oxide: relative molecular weight of 1 million;

[0031] 5) Oxidized starch: Viscosity: 5-50 cP (Temperature: 50℃, Concentration: 5-15%);

[0032] 6) Polyvinyl alcohol: degree of alcoholysis: 98-100 mol / mol, viscosity: 18-30 cP (temperature: 50℃, concentration: 5-15%).

[0033] In the description of this invention, it should be noted that unless specific conditions are specified in the examples, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0034] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. However, the following embodiments are limited to a part of the research of the present invention and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on this, other embodiments obtained by those skilled in the art without creative effort are all within the protection scope of the present invention.

[0035] Example 1

[0036] This embodiment provides a method for producing high-stiffness, high-basis-weight, and high-air-permeability formed paper, including the following steps:

[0037] (1) Using the softwood pulp fibers with the technical specifications described above as raw materials, the softwood pulp fibers are dispersed and then subjected to a disc milling process to loosen them. The loosening power is controlled below 120 kW (or the loosening current is controlled below 120 A). This loosening power (or current) will not damage the fiber length, fiber width, and fiber twist of the softwood pulp fibers and sisal pulp. If the fiber length, fiber width, and fiber twist of the softwood pulp fibers and sisal pulp are damaged, it will affect the air permeability and basis weight of the formed paper, as shown in Comparative Example 2.

[0038] (2) After the decomposition is completed, polyamide epichlorohydrin resin is added to 100% softwood pulp fiber at a rate of 20 kg / ton of oven-dry pulp. The mixed pulp is diluted to a mass concentration of 3.0%, and then fed into the wire box after rinsing. Polyoxyethylene solution with a mass concentration of 0.03% is added to the wire box at a rate of 10.0 kg / ton of oven-dry pulp. The pulp is fed into the wire box in the form of spraying or scooping, and the pulp concentration on the wire is controlled at 0.1%. The paper is formed using a rotary paper machine, and then pressed and dried in sequence. The pressing pressure is 3.2 / 3.2 MPa (referring to the pressure on the operating side and the transmission side, respectively), and the drying temperature is 90-120℃ to obtain a paper sheet with a moisture content of 6.5%.

[0039] (3) The paper sheet is dipped and coated with a sizing agent, which is a 10% (w / w) oxidized starch solution, at a sizing rate of 100 kg / ton of paper. It is then dried again at a temperature of 85–120°C, and finally wound to obtain the formed paper. The performance indicators of the formed paper are shown in Table 2. The results of the following examples and comparative examples are the same.

[0040] Example 2

[0041] The difference between this embodiment and Embodiment 1 is that it uses 50% by weight of softwood pulp fiber and 50% by weight of viscose fiber as raw materials.

[0042] Example 3

[0043] The difference between this embodiment and Embodiment 1 is that it uses 70% by weight of softwood pulp fiber and 30% by weight of viscose fiber as raw materials.

[0044] Example 4

[0045] The difference between this embodiment and Embodiment 1 is that it uses 90% softwood pulp fiber and 10% viscose fiber as raw materials by weight.

[0046] Example 5

[0047] The difference between this embodiment and Embodiment 1 is that it uses 50% by weight of softwood pulp fiber and 50% by weight of sisal pulp fiber as raw materials.

[0048] Example 6

[0049] The difference between this embodiment and Embodiment 1 is that it uses 70% by weight of softwood pulp fiber and 30% by weight of sisal pulp fiber as raw materials.

[0050] Example 7

[0051] The difference between this embodiment and Embodiment 1 is that it uses 90% by weight of softwood pulp fiber and 10% by weight of sisal pulp fiber as raw materials.

[0052] Example 8

[0053] The difference between this embodiment and Embodiment 1 is that it uses 50% by weight of softwood pulp fiber, 40% by weight of sisal pulp fiber and 10% by weight of viscose fiber as raw materials.

[0054] Example 9

[0055] The difference between this embodiment and Embodiment 1 is that it uses 70% by weight of softwood pulp fiber, 20% by weight of sisal pulp fiber and 10% by weight of viscose fiber as raw materials.

[0056] Example 10

[0057] The difference between this embodiment and Embodiment 1 is that it uses 90% by weight of softwood pulp fiber, 5% by weight of sisal pulp fiber and 5% by weight of viscose fiber as raw materials.

[0058] Example 11

[0059] The difference between this embodiment and Embodiment 1 is that it uses 50% by weight of softwood pulp fiber, 20% by weight of sisal pulp fiber and 30% by weight of viscose fiber as raw materials.

[0060] Example 12

[0061] The difference between this embodiment and embodiment 8 is that viscose fiber is replaced with Tencel fiber.

[0062] Example 13

[0063] The difference between this embodiment and embodiment 9 is that viscose fiber is replaced with Tencel fiber.

[0064] Example 14

[0065] The difference between this embodiment and embodiment 10 is that viscose fiber is replaced with Tencel fiber.

[0066] Example 15

[0067] The difference between this embodiment and embodiment 11 is that viscose fiber is replaced with Tencel fiber.

[0068] Example 16

[0069] The difference between this embodiment and Embodiment 10 is that the sizing agent is a 10% polyvinyl alcohol solution by mass.

[0070] Example 17

[0071] The difference between this embodiment and Embodiment 16 is that the sizing agent is a 10% mass concentration solution of oxidized starch and polyvinyl alcohol, wherein the oxidized starch and polyvinyl alcohol are compounded in a mass ratio of 1:1.

[0072] Example 18

[0073] The difference between this embodiment and Embodiment 17 is that the sizing agent is a 10% mass concentration solution of oxidized starch and polyvinyl alcohol, wherein the oxidized starch and polyvinyl alcohol are compounded in a mass ratio of 2:1.

[0074] Example 19

[0075] The difference between this embodiment and Embodiment 17 is that the sizing agent is a 10% mass concentration solution of oxidized starch and polyvinyl alcohol, wherein the mass ratio of oxidized starch and polyvinyl alcohol is 1:2.

[0076] Comparative Example 1

[0077] This comparative example provides a large-scale production process for conventional rigid forming paper, using softwood pulp and hardwood pulp as raw materials, with an air permeability of around 20 CU and a basis weight of 60-130 g. The specific process is as follows:

[0078] (1) Softwood pulp and hardwood pulp are dispersed using a hydraulic pulper and then beating is performed separately. The wood pulp fibers are beating with 2-5 disc mills. The disc milling is mainly for cutting and buffing. The freeness is 20-60 (30 in this example). The wet weight of softwood is 6-15g (11g in this example) and the wet weight of hardwood is 0.5-2.0g (0.7g in this example). The beating concentration is controlled between 4.0-5.0.

[0079] (2) After mixing softwood pulp and hardwood pulp at a mass percentage ratio of 50%:50%, cationic starch is added at a rate of 15-40 kg per ton of paper (30 kg in this example). Then, alkyl ketene dimer 5-15 kg / ton of paper (10 kg / ton of paper in this example), polyamide epichlorohydrin resin 10 kg / ton of paper, and finally calcium carbonate 150 kg / ton of paper are added. The pulp concentration on the wire is 0.8-1.0%. After being formed by the wire section of the wire paper machine, the paper enters the press section. The press section undergoes first press / second press / third press, with control parameters of 60-120 KN / m. After physical dehydration by pressing, the paper enters the pre-drying section. The drying cylinder temperature is 90-120℃, and the moisture content of the pre-drying paper is about 5-7% (6.3% in this example).

[0080] (3) Before the paper is dried, it is dipped in an oxidized starch solution with a solution concentration of 4-6% (5% in this example) and the sizing amount is 100 kg / ton of paper. After that, it is dried and then subjected to a post-drying treatment at a temperature of 85-130°C. After being finished by a second calender, it is rolled into a hard paper.

[0081] Comparative Example 2

[0082] This comparative example provides a preparation process for high-permeability forming paper. The basis weight of the high-permeability forming paper is generally 21-30 g / m², and the air permeability is 3000-26000 CU. The specific process is as follows:

[0083] (1) Selected: Fiber length: ≥2.0mm, fiber thickness: ≥0.12mg / m, fiber width: 20~35μm, fiber twist: ≥10% softwood pulp fiber;

[0084] Fiber length: ≥0.60mm eucalyptus pulp fiber;

[0085] Sisal pulp fiber with fiber length ≥1.8mm, fiber coarseness ≥0.12mg / m, fiber width 10~30μm, and fiber twist ≥15%;

[0086] Viscose fiber with fiber length ≥3.0mm, fiber thickness ≥0.10mg / m, fiber width 15~30μm, and fiber twist ≥8%.

[0087] (2) The wood pulp fibers (softwood pulp fiber and eucalyptus pulp fiber), sisal pulp fiber, and viscose fiber are dispersed using a hydraulic pulper and then pulped separately. During pulping, 40 kg / ton of polyamide epichlorohydrin resin is added. Wood pulp fibers and sisal pulp are pulped using 1-3 disc mills, primarily for disintegration. Viscose fiber is disintegrated using 1-2 disc mills, with a disintegration time of approximately 10 minutes. The pulping concentration is controlled between 3.0 and 5.0. The ratio of the four fibers is: softwood 58%, sisal pulp 10%, viscose 22%, and eucalyptus pulp 10%.

[0088] (3) After diluting the mixed pulp to a mass concentration of 2.0%, it enters the wire section after being flushed. The pulp concentration on the wire is 0.05-0.1%. A polyethylene oxide solution with a mass concentration of 0.02% is added to the wire box / flushing tank at a rate of 1-3 kg / ton of paper. After the paper is formed on the wire section of the rotary paper machine (or a slanted paper machine), it enters the press section along with the felt. After the paper is physically dehydrated in the press section, it enters the pre-drying section. The drying cylinder temperature is 90-120℃, and the moisture content of the pre-drying paper is about 5-7%.

[0089] (4) Before the paper is dried, it is dipped or coated with an oxidized starch solution by an applicator or a film transfer agent. The solution concentration is 7% and the sizing amount is 100 kg / ton of paper. After that, it is dried at a temperature of 85-130℃ and then rolled to obtain a high-permeability formed paper.

[0090] Examples 1-19 and Comparative Examples 1-2 were tested for relevant performance indicators. The technical standards for the forming paper established in this invention are shown in Table 1.

[0091] Table 1. Technical standards and testing methods for the formed paper established in this invention.

[0092]

[0093]

[0094] Table 2. Performance test results of the forming paper in the embodiments and comparative examples of the present invention, as well as commercially available products.

[0095]

[0096]

[0097] Note: Commercially available 1 is ordinary forming paper sold by the applicant; commercially available 2 is high-transparency forming paper sold by a company in Shanghai; and commercially available 3 is rigid forming paper sold by a company in Yunnan.

[0098] As can be seen from the data in Table 2, all embodiments of the present invention meet the forming paper technical standards set in Table 2, obtaining forming paper with high stiffness, high tensile strength, moderate air permeability, good brightness, and no fluorescence. In contrast, the forming paper of Comparative Example 1 has low air permeability and poor stiffness; the forming paper of Comparative Example 2 has high air permeability but low basis weight, poor stiffness, low tensile energy, and insufficient mechanical properties; commercially available products have some cases of high air permeability or high basis weight, and cannot balance stiffness, air permeability, and strength in terms of performance. Therefore, these forming papers have failed to balance the performance parameters such as basis weight, mechanical strength, stiffness, and air permeability, and do not meet the forming paper technical standards in Table 1. The present invention, through continuous optimization of various links and details of the process, such as fiber ratio (wood pulp + hemp pulp + chemical fiber), control of the delamination process, use of specific additives (PAE + PEO), and optimization of sizing agents, has successfully prepared forming paper with high stiffness, high air permeability, and high basis weight, breaking through the process bottleneck that stiffness and air permeability cannot be achieved simultaneously.

[0099] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for manufacturing a high-stiffness, high-air-permeability, high-basis-weight, perforation-free forming paper, characterized in that, Includes the following steps: Step 1: Using softwood pulp fiber, sisal pulp, and chemical fibers as raw materials; wherein, the softwood pulp fiber has a length ≥ 2.0 mm, a fiber thickness ≥ 0.12 mg / m, a fiber width of 20–35 μm, and a fiber twist ≥ 10%; the sisal pulp fiber has a length ≥ 1.8 mm, a fiber thickness ≥ 0.12 mg / m, a fiber width of 10–30 μm, and a fiber twist ≥ 15%; the chemical fibers are viscose fiber and / or Tencel fiber, with a length ≥ 3.0 mm, a fiber thickness ≥ 0.15 mg / m, a fiber width of 20–35 μm, and a fiber twist ≥ 8%; Step 2: The softwood pulp fiber, sisal pulp and chemical fiber are debonded separately. The process control of the debonding treatment of softwood pulp fiber and sisal pulp is to ensure that the fiber length, fiber width and fiber twist of the softwood pulp fiber and sisal pulp are not damaged. Step 3: Mix the defragmented softwood pulp fiber, sisal pulp and chemical fiber at a mass percentage of 50-100%, 0-50% and 0-50% respectively, add polyamide epichlorohydrin resin and dilute, then add polyethylene oxide solution and mix, while controlling the online concentration of the mixed pulp to 0.05-0.3wt%, and then conduct online paper forming, followed by pressing and drying treatment to obtain a paper sheet with a moisture content of 5-7%. Step 4: Dip the paper sheet into the sizing agent, then dry it again, and finally roll it to obtain the formed paper.

2. The manufacturing method according to claim 1, characterized in that, In step 2, a disc mill is used to decompose the softwood pulp fiber, sisal pulp and chemical fiber, and the decomposition power is controlled to be below 120kw or the decomposition current is controlled to be below 120A.

3. The manufacturing method according to claim 1, characterized in that, In step 3, the mixed pulp is diluted to a mass concentration of 2-4%; and / or, the amount of polyamide epichlorohydrin resin added is 15-30 kg / ton of oven-dry pulp; and / or, the mass concentration of polyethylene oxide solution is 0.01-0.05 wt%, and the amount added is 8-12 kg / ton of oven-dry pulp; and / or, the paper forming is done using a cylinder paper machine; and / or, the drying temperature is 90-120℃.

4. The manufacturing method according to claim 1, characterized in that, In step 4, the sizing agent is an oxidized starch solution and / or a polyvinyl alcohol solution.

5. The manufacturing method according to claim 4, characterized in that, The mass concentration of the sizing agent is 8-12%.

6. The manufacturing method according to claim 5, characterized in that, The amount of sizing agent used is 60-150 kg / ton of paper.

7. The manufacturing method according to claim 1, characterized in that, In step 4, the drying temperature is 85-120℃.

8. The shaped paper obtained by the manufacturing method according to any one of claims 1 to 7.

9. The formed paper according to claim 8, characterized in that, The formed paper has at least the following performance indicators: basis weight of 60-150 g / m³ 2 Air permeability is 1000-15000Cu, bending stiffness (longitudinal) (bending moment 5mm) ≥100mN, D65 brightness ≥70%, D65 fluorescence brightness ≤1.0%, longitudinal tensile energy absorption ≥20J / m 2 .

10. The paper according to claim 9, characterized in that, The formed paper has the following performance indicators: basis weight of 60-120 g / m³ 2 Air permeability is 5000-15000Cu, bending stiffness (longitudinal) (bending moment 5mm) ≥400mN, D65 brightness ≥80%, D65 fluorescence brightness = 0, longitudinal tensile energy absorption ≥90J / m 2 .

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