Preparation method of high-air-permeability bamboo pulp lining paper

Abstract

The embodiment of the invention provides a preparation method of high-air-permeability bamboo pulp lining paper, which comprises the following steps: S1, a fiber raw material is dispersed to form first pulp, the concentration of the dispersed pulp is 4-6%, the proportion of bamboo pulp fibers in the fiber raw material is greater than or equal to 95%, the average length of the bamboo pulp fibers is greater than or equal to 1.6 mm, and the content of fine components in the bamboo pulp fibers is less than or equal to 1%; the bamboo pulp fiber with the length of 1-1.5 mm accounts for 6-15%, then pulping, papermaking forming, drying and wrinkling are performed to form the high-air-permeability bamboo pulp lining paper, the formed high-air-permeability bamboo pulp lining paper has high strength and high air permeability, and compared with the prior art, the air permeability is improved by more than 17%.

Description

Technical Field

[0001] The invention relates to a method for preparing high-air-permeability bamboo pulp lining paper. Background Art

[0002] In disposable absorbent products, backing paper is widely used as a covering layer for the absorbent core. The covering of the backing paper can prevent the fluff pulp and SAP from falling off during the manufacturing process of the disposable absorbent product, thereby maintaining the shape of the absorbent core.

[0003] For disposable absorbent products, people hope that they have good absorption performance to quickly absorb body fluids, and also hope that they have good breathability to provide better comfort. Therefore, it is hoped that the lining paper wrapped around the absorbent core also has good breathability.

[0004] To this end, documents such as CN112575610A have proposed some processes for preparing lining paper with high air permeability, using coniferous wood pulp + hardwood pulp, and adopting wet forming and light dry corrugation process to form the lining paper. However, due to the large difference between bamboo pulp fiber and wood pulp fiber, more specifically, bamboo pulp fiber has a larger aspect ratio and finer fibers. If the lining paper formed by the conventional wood pulp preparation process is formed, the structure is denser, resulting in its air permeability being greatly reduced compared with wood pulp.

[0005] In addition, document CN106149452A also proposes to use wood pulp but no stripping agent to obtain a higher air permeability effect (the air permeability is 3 times that of the existing technology). However, for the papermaking of bamboo pulp, based on the process of bamboo pulp papermaking, in practice, because bamboo pulp fibers are stiffer and contain more fine fibers, stripping agents must be used in production to improve the paper stripping performance on the one hand, reduce dust on the other hand, and improve the smoothness of the paper surface and protect the drying cylinder.

[0006] Therefore, it is necessary to develop a method for preparing a high-permeability lining paper based on bamboo pulp to solve the above technical problems. Summary of the invention

[0007] To this end, the present invention provides a method for preparing a high-permeability bamboo pulp lining paper to solve the above technical problems.

[0008] A method for preparing high-permeability bamboo pulp lining paper, characterized by comprising: S1: Provide fiber raw materials, and slurry the fiber raw materials to form a first slurry, the slurry concentration is 4-6%, the proportion of bamboo pulp fibers in the fiber raw materials is greater than or equal to 95%, and the average length of the bamboo pulp fibers is greater than or equal to 1.6 mm, the content of fine components in the bamboo pulp fibers is less than or equal to 1%, and the proportion of bamboo pulp fibers with a length of 1-1.5 mm is 6-15%.

[0009] S2: The first slurry is refined to form a second slurry, with a refining concentration of 3-6% and a beating degree of 30-35°SR.

[0010] S3: The second pulp is subjected to papermaking, forming, drying and corrugating to form a bamboo pulp lining paper with high air permeability, wherein the papermaking and forming is performed by a crescent former, the drying is performed by a Yankee dryer, the corrugating is performed by a corrugating scraper with an angle of 10° to 20°, the corrugating rate is 15 to 25%, and the machine speed is 1200 to 1800 m / min.

[0011] Wherein, the fiber raw materials are all bamboo pulp fibers.

[0012] The length of the bamboo pulp fiber is 1.7-2.5 mm, and the wall-to-cavity ratio of the bamboo pulp fiber is 1.2-6.5.

[0013] Among them, the fiber raw material is provided in the form of pulp board, the bamboo pulp fiber forms bamboo pulp board, and the bamboo pulp board has the following technical indicators: tensile strength is greater than or equal to 58N·m / g, burst resistance index is greater than or equal to 4KPa·㎡ / g, tear index is greater than or equal to 8.5mN·㎡ / g, ash content is less than or equal to 1%, and viscosity is greater than or equal to 700ml / g.

[0014] Among them, bamboo pulp fibers with a length of 1 to 1.5 mm account for 7 to 10%.

[0015] Wherein, step S1 also includes a step of adjusting the proportion of bamboo pulp fibers of different lengths in the fiber raw material by screening and compounding.

[0016] After the wet paper sheets are formed, a high-permeability felt is used to transfer the wet paper sheets, and the wet paper sheets are dehydrated through a vacuum water suction box. The air permeability of the high-permeability felt is 22-24 CFM, and the vacuum degree of the vacuum water suction box is -28kpa.

[0017] Among them, after the fiber raw material is dispersed to form a first slurry, the first slurry is screened by a first screening device to form a primary screened slurry, and then the primary screened slurry is screened for a second time, and bamboo pulp fibers with a length of 1 to 1.5 mm are separated to obtain a second screened slurry, and then the separated bamboo pulp fibers with a length of 1 to 1.5 mm are added into the second screened slurry in a predetermined proportion to obtain a mixed slurry, and the mixed slurry is refined in step S2, and the predetermined proportion refers to the proportion of bamboo pulp fibers with a length of 1 to 1.5 mm being 6 to 15%, and the proportion is the proportion of bamboo pulp fibers with a length of 1 to 1.5 mm in the mixed slurry.

[0018] Wherein, the high air permeability bamboo pulp lining paper has a basis weight of 13 to 16 g / ㎡.

[0019] Beneficial effect: The embodiment of the present invention provides a method for preparing a high-permeability bamboo pulp lining paper, comprising: S1: pulping a fiber raw material to form a first slurry, the pulp concentration is 4-6%, the proportion of bamboo pulp fibers in the fiber raw material is greater than or equal to 95%, and the average length of the bamboo pulp fibers is greater than or equal to 1.6 mm, the content of fine components in the bamboo pulp fibers is less than or equal to 1%, and the proportion of bamboo pulp fibers with a length of 1-1.5 mm is 6-15%, and then pulping, forming, drying, and wrinkling are performed to form a high-permeability bamboo pulp lining paper. The high-permeability bamboo pulp lining paper formed by the above method has high strength and high permeability, and the air permeability is increased by more than 17% compared with the prior art. DETAILED DESCRIPTION

[0020] The embodiment of the present invention provides a method for preparing a bamboo pulp lining paper with high air permeability, and the present application is further described below.

[0021] S1: Provide fiber raw materials, and slurry the fiber raw materials to form a first slurry, the slurry concentration is 4-6%, the proportion of bamboo pulp fibers in the fiber raw materials is greater than or equal to 95%, and the average length of the bamboo pulp fibers is greater than or equal to 1.6 mm, the content of fine components in the bamboo pulp fibers is less than or equal to 1%, and the proportion of bamboo pulp fibers with a length of 1-1.5 mm is 6-15%.

[0022] In this embodiment, the fiber raw material is provided in the form of a pulp board, and the pulp board formed by bamboo pulp fiber is called a bamboo pulp board, and the bamboo pulp board has the following technical indicators: tensile strength greater than or equal to 58N·m / g, burst index greater than or equal to 4KPa·㎡ / g, tear index greater than or equal to 8.5mN·㎡ / g, ash content less than or equal to 1%, and viscosity greater than or equal to 700ml / g. Further, the fiber raw material is all bamboo pulp fiber, that is, the fiber raw material does not contain other fibers such as wood pulp fiber.

[0023] Furthermore, the bamboo pulp fiber has a length greater than or equal to 1.6 mm, and an aspect ratio of 80 to 160, and a wall-to-cavity ratio greater than or equal to 1. Specifically, the bamboo pulp fiber can be selected from fibers formed by a sulfate or caustic soda method such as those obtained by using bamboo shoots, moso bamboo, wood bamboo, green bamboo, and nan bamboo. Preferably, the bamboo pulp fiber has a length of 1.7 to 2.5 mm, for example: 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm, etc. In addition, preferably, the wall-to-cavity ratio of the bamboo pulp fiber is 1.2 to 6.5, and more preferably, it is 1.6 to 5.0.

[0024] Furthermore, the bamboo pulp fibers with a length of 1 to 1.5 mm account for 7 to 10%, and the fine components refer to the components that can be removed by screening with a sieve hole with a pore size of 0.4 mm.

[0025] Furthermore, step S1 also includes a step of adjusting the proportion of bamboo pulp fibers of different lengths in the fiber raw material. Specifically, the proportion of bamboo pulp fibers of different lengths can be adjusted by screening-compounding. The screening-compounding refers to separating fibers of different lengths in the bamboo pulp by a screening device, and then mixing the fibers of different lengths to form a compounded first slurry.

[0026] In a specific embodiment, after the fiber raw material is pulped to form a first slurry, the first slurry is screened by a first screening device to remove fine components to form a primary screened slurry, and then the primary screened slurry is screened for a second time to separate bamboo pulp fibers with a length of 1 to 1.5 mm and obtain a second screened slurry, and then the separated bamboo pulp fibers with a length of 1 to 1.5 mm are added into the second screened slurry in a predetermined proportion to obtain a mixed slurry, and the mixed slurry is refined in step S2. It can be understood that the predetermined proportion means that the proportion of bamboo pulp fibers with a length of 1 to 1.5 mm is 6 to 15%, and the proportion is the proportion of bamboo pulp fibers with a length of 1 to 1.5 mm in the mixed slurry.

[0027] In addition, the bamboo pulp fiber is a mixture of at least two types of bamboo pulp fibers, and the length-width ratio of the mixed bamboo pulp fiber is 80-100, and the wall-to-cavity ratio is 1-3.

[0028] It can be understood that the lengths in the description are all average lengths, the aspect ratios are average aspect ratios, the wall-to-cavity ratios are average wall-to-cavity ratios, and the fine components include fine fibers and miscellaneous cells.

[0029] It can be understood that the fiber raw material is pulped by pulping equipment, and during the pulping process, the fiber raw material is dispersed in water by mechanical action to form a fiber suspension. The pulping equipment can be a hydraulic pulper.

[0030] In addition, the pulping equipment also includes a pulping tank. Before pulping, carboxymethyl cellulose (CMC) can also be added to the pulping tank. Carboxymethyl cellulose is an important cellulose ether, which is a polyanion product with good water solubility obtained after chemical modification of plant fibers. It is easily soluble in cold water and has unusual physical and chemical properties such as dispersibility, non-corruptibility and bio-harmlessness. In this embodiment, CMC is used as a wet strength aid to improve the efficiency of the wet strength agent in the later stage. It is added in the front-stage pulping process of the daily paper preparation method, which increases the action time of CMC and bamboo pulp fibers, and helps CMC to maximize its effectiveness. Among them, the amount of CMC added to each ton of bamboo pulp relative to the absolute dry pulp can be 1 to 4 kg, for example: 1 kg, 2 kg, 3 kg, 4 kg, etc.

[0031] S2: The first slurry is refined to form a second slurry, with a refining concentration of 3-6% and a beating degree of 30-35°SR.

[0032] Pulping is a process that makes the fiber raw materials absorb water, swell and fibrillate, thereby greatly increasing the external specific surface area of ​​the fiber, exposing more hydroxyl groups in the cellulose molecular chain, promoting the combination of hydrogen bonds, increasing the uniformity and strength of the finished paper, and reducing the rigidity of the fiber raw materials, weakening the elasticity, increasing the plasticity, and making the fiber soft and plastic.

[0033] In this embodiment, the concentration range of the refined pulping concentration is controlled to be 3-6%, for example: 3%, 3.5%, 4.5%, 5%, 6%, etc. The refining equipment for refining bamboo pulp can be a double-disc refiner. In the double-disc refiner, a rotating disk and a fixed disk act on the bamboo pulp fibers between the two disks, so that the bamboo pulp fibers receive friction, impact, rubbing, twisting and shearing forces, thereby completing the refining in a short time. In addition, the refining power of the double-disc refiner of the present invention can be set to be greater than 90kwh / t, more preferably greater than or equal to 100kwh / t. When the pulp is 100% bamboo pulp, the refining power is preferably 105-125kwh / t. Of course, the refining can also be carried out at other powers, and the present invention is not further limited.

[0034] The beating degree of the bamboo pulp after pulping is 30-35°SR, specifically, it can be: 30°SR, 31°SR, 32°SR, 33°SR, 34°SR, 35°SR, etc.

[0035] Furthermore, a wet strength agent is added to the second slurry, and the amount of the wet strength agent added is 5 to 25 kg / t based on the absolute dry slurry.

[0036] S3: The second pulp is subjected to papermaking, forming, drying and corrugating to form a bamboo pulp lining paper with high air permeability, wherein the papermaking and forming is performed by a crescent former, the drying is performed by a Yankee dryer, the corrugating is performed by a corrugating scraper with an angle of 10° to 20°, the corrugating rate is 15 to 25%, and the machine speed is 1200 to 1800 m / min.

[0037] Preferably, the wrinkling scraper is an alloy scraper, and the replacement time is 2 to 5 hours.

[0038] Furthermore, after the wet paper sheets are formed, a high-permeability felt is used to transfer the wet paper sheets, and the wet paper sheets are dehydrated by a vacuum water suction box, wherein the high-permeability felt has an air permeability of 22 to 24 CFM, and the vacuum degree of the vacuum water suction box is -28 kpa. Compared with the 20 to 21 CFM felt and the vacuum water suction box with a vacuum degree of -34 to -32 kpa commonly used in the prior art, the air permeability can be further improved by more than 8%. In particular, due to the high aspect ratio of bamboo pulp fibers, a good dehydration effect can still be achieved when a lower vacuum degree is used for water absorption.

[0039] The felt used in the production of backing paper has an air permeability of 23CFM and a vacuum suction box negative pressure of -28kpa It can be understood that before step S3, a bonding agent and a peeling agent are sprayed on the Yankee dryer so that the formed paper sheet can be easily bonded to the Yankee dryer and then peeled off by a creping scraper.

[0040] Furthermore, the high-permeability bamboo pulp lining paper has a basis weight of 13 to 16 g / m2. Studies have shown that when the basis weight is too low, the strength of the lining paper is insufficient, and when the basis weight is too high, the air permeability of the lining paper decreases.

[0041] The applicant has found that when all bamboo pulp is used to prepare backing paper, due to the slenderness of bamboo pulp fibers and the characteristics of having more fine components, ordinary bamboo pulp contains more than or equal to 25% of fine components. After the backing paper is formed, these fine components are interspersed between the fibers so that the pores between the formed three-dimensional structure are filled, thereby causing the air permeability to decrease. The fine components also affect the strength and other properties of the backing paper. At the same time, the fine components also increase the dust of the backing paper. However, after the fine components are removed as much as possible in the conventional way, due to the small thickness of the bamboo pulp fibers and the slenderness of the bamboo pulp fibers, the structure of the formed backing paper is still dense, so the air permeability is still insufficient. The study found that if the proportion of 1.0-1.5mm between fine components and longer fibers is controlled and adjusted, the air permeability can be increased while ensuring the strength performance indicators. This is because the 1.0-1.5mm long bamboo pulp fibers can, on the one hand, be entangled with other fibers to form a three-dimensional network structure, and on the other hand, they are not too long to form more twisted shapes. At the same time, their relatively stiff structure is interspersed between the fibers, so that the three-dimensional network structure forms more pores, so that the formed lining paper has good strength and excellent air permeability, and can even exceed the lining paper made of wood pulp.

[0042] The method for preparing high air permeability bamboo pulp lining paper of the present application is described below with reference to specific embodiments.

[0043] Embodiment 1: S11: providing fiber raw materials, and slurrying the fiber raw materials to form a first slurry, wherein the slurry concentration is 4.5%, bamboo pulp fibers account for 100% of the fiber raw materials, the average length of the bamboo pulp fibers is 1.75 mm, the content of fine components in the bamboo pulp fibers is less than or equal to 1%, and the bamboo pulp fibers with a length of 1 to 1.5 mm account for 9.7%.

[0044] S12: The first slurry is refined to form a second slurry, with a refining concentration of 4.1% and a beating degree of 32°SR.

[0045] S13: The second pulp is subjected to sheet forming, drying and corrugation to form a bamboo pulp lining paper with high air permeability, wherein the sheet forming is performed by a crescent former, the sheet is dried by a Yankee dryer, the sheet is corrugated by a 15° corrugating scraper, the corrugation rate is 20%, and the machine speed is 1500 m / min.

[0046] Embodiment 2: In step S11, the average length of the bamboo pulp fibers is 1.93 mm, the bamboo pulp fibers with a length of 1 to 1.5 mm account for 8.6%, and the remaining steps are the same as in Example 1.

[0047] Comparative Example 1: The preparation method is as described in Example 1 of CN112575610A.

[0048] Comparative Example 2: The preparation method of Example 1 is adopted, wherein in step S11, the fine components are not controlled, and the bamboo pulp fibers with a length of 1 to 1.5 mm account for 12.9%, and the remaining steps are the same as those of Example 1. The paper sheets prepared in Example 1, Example 2, Comparative Example 1, and Comparative Example 2 are tested, and the test results are as follows: project unit Example 1 Example 2 Comparative Example 1 Comparative Example 2 Quantification g / ㎡ 13.6 14.2 14.2 13.8 Tensile index-MD Nm / g 13.39 14.10 15.5 11.01 Tensile index-CD Nm / g 2.86 3.33 3.8 2.11 Wet-MDT N / m 20.8 21.8 51.3 17.1 Elongation % 20.8 20.1 19.1 19.5 Breathability L / ㎡ / s 1211 1255 1035 1001 Among them, the above items are tested according to the following test methods.

[0049] Basis weight: Tested according to GB / T 451.2-2002 Determination of Basis Weight of Paper and Paperboard.

[0050] Tensile index-MD: tested according to "GB / T 24328.3-2020 Toilet paper and its products Part 3: Determination of tensile strength, elongation at maximum force and tensile energy absorption".

[0051] Tensile index-CD: tested according to "GB / T 24328.3-2020 Toilet paper and its products Part 3: Determination of tensile strength, elongation at maximum force and tensile energy absorption".

[0052] Wet-MDT: Tested according to method 7.8 in GB / T 20808-2022 Paper Towels.

[0053] Elongation: Tested according to GB / T 24328.3-2020 Toilet paper and its products Part 3: Determination of tensile strength, elongation at maximum force and tensile energy absorption.

[0054] Air permeability: Tested according to GB / T 22819-2008 Determination of air permeability of highly air permeable paper. The pressure during the air permeability test is 125Pa.

[0055] From the above test results, the air permeability of the method of the present invention is improved by more than 17% compared with the prior art. At the same time, the strength is basically the same as that of the prior art, and only the wet strength is relatively low. However, the backing paper does not need to have better wet strength. Therefore, the reduction in wet strength will not have a significant impact on the product. At the same time, compared with the untreated bamboo pulp, not only the strength is improved, but also the air permeability is improved by more than 20%. The above is only an embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the content of the present invention specification, or directly or indirectly used in other related technical fields, is also included in the patent protection scope of the present invention.

Claims

1. A method for preparing high air permeability bamboo pulp lining paper, characterized in that: include: S1: providing a fiber raw material, and slurrying the fiber raw material to form a first slurry, wherein the slurry concentration is 4-6%, bamboo pulp fibers account for greater than or equal to 95% of the fiber raw material, and the average length of the bamboo pulp fibers is greater than or equal to 1.6 mm, the content of fine components in the bamboo pulp fibers is less than or equal to 1%, and bamboo pulp fibers with a length of 1-1.5 mm account for 6-15%; S2: The first slurry is refined to form a second slurry, with a refining concentration of 3-6% and a beating degree of 30-35°SR; S3: The second pulp is subjected to papermaking, forming, drying and corrugating to form a bamboo pulp lining paper with high air permeability, wherein the papermaking and forming is performed by a crescent former, the drying is performed by a Yankee dryer, the corrugating is performed by a corrugating scraper with an angle of 10° to 20°, the corrugating rate is 15 to 25%, and the machine speed is 1200 to 1800 m / min.

2. The preparation method according to claim 1, characterized in that The fiber raw materials are all bamboo pulp fibers.

3. The preparation method according to claim 1, characterized in that: The length of the bamboo pulp fiber is 1.7-2.5 mm, and the wall-to-cavity ratio of the bamboo pulp fiber is 1.2-6.

5.

4. The preparation method according to claim 1, characterized in that: The fiber raw material is provided in the form of pulp board, and the bamboo pulp fiber forms bamboo pulp board, and the bamboo pulp board has the following technical indicators: tensile strength is greater than or equal to 58N·m / g, burst resistance index is greater than or equal to 4KPa·㎡ / g, tear index is greater than or equal to 8.5mN·㎡ / g, ash content is less than or equal to 1%, and viscosity is greater than or equal to 700ml / g.

5. The preparation method according to claim 1, characterized in that: Bamboo pulp fibers with a length of 1 to 1.5 mm account for 7 to 10%.

6. The preparation method according to claim 1, characterized in that: Step S1 also includes a step of adjusting the proportion of bamboo pulp fibers of different lengths in the fiber raw material by screening and compounding.

7. The preparation method according to claim 6, characterized in that: After pulping the fiber raw material to form a first slurry, the first slurry is screened by a first screening device to form a primary screened slurry, and then the primary screened slurry is screened for a second time to separate bamboo pulp fibers with a length of 1 to 1.5 mm and obtain a second screened slurry, and then the separated bamboo pulp fibers with a length of 1 to 1.5 mm are added into the second screened slurry in a predetermined proportion to obtain a mixed slurry, and the mixed slurry is refined in step S2, wherein the predetermined proportion refers to the proportion of bamboo pulp fibers with a length of 1 to 1.5 mm being 6 to 15%, and the proportion is the proportion of bamboo pulp fibers with a length of 1 to 1.5 mm in the mixed slurry.

8. The preparation method according to claim 1, characterized in that: The high-air-permeability bamboo pulp lining paper has a basis weight of 13 to 16 g / ㎡.

9. The preparation method according to claim 1, characterized in that: After the wet paper sheet is formed, a high-permeability felt is used to transfer the wet paper sheet, and the wet paper sheet is dehydrated by a vacuum water suction box, wherein the air permeability of the high-permeability felt is 22-24 CFM, and the vacuum degree of the vacuum water suction box is -28kpa.