Method for the production of soft household paper

Abstract

The embodiment of the present application provides a kind of soft living paper preparation method, it is characterized in that, including the following steps: S1: providing fiber raw material, and the fiber raw material is scattered pulp and forms first pulp, and add cellulase when scattering pulp, cellulase addition amount 0.2 ~ 0.3 kg / T;S2: first pulp is ground pulp and forms second pulp, add fiber swelling protein in second pulp and obtain third pulp after reaction, wherein, the beating degree of second pulp is 20 ~ 30 °SR, the concentration of first pulp is 3 ~ 6% when grinding pulp, the addition amount of fiber swelling protein is 0.5 ~ 2 kg / T;S3: third pulp is formed by being copied into shape, drying, and wrinkle forms soft living paper, by cellulase and fiber swelling protein combined application, can reduce the restriction of temperature condition in beating process and fiber swelling protein application process, in addition, by cellulase, fiber swelling protein and the combined application of small fiber can improve the use efficiency of softening agent, greatly reduce the use amount of softening agent.

Description

Technical Field

[0001] This invention relates to a method for preparing soft household paper. Background Technology

[0002] Facial tissues, toilet paper, napkins, kitchen paper towels, and hand towels are essential consumer goods for modern consumers. As living standards improve, people have increasingly higher requirements for the softness of household paper products, especially those that come into contact with human skin.

[0003] Currently, the main method to improve the softness of tissue paper is by adding softeners. However, adding softeners usually affects the strength of the paper. Therefore, some new solutions to reduce the amount of softener used have been proposed. For example, CN103142176A proposes to use softeners and nanocrystalline cellulose at the same time, and CN109577066A proposes to soften the pulp and add pulping enzymes during the pulping process. However, these solutions are costly and require strict control conditions. For example, the pulping enzymes proposed in CN109577066A need to be strictly controlled at a reaction temperature of 52℃~58℃, making it difficult to promote their widespread use.

[0004] Therefore, a new technical solution needs to be developed to solve the above-mentioned technical problems. Summary of the Invention

[0005] Therefore, the present invention provides a method for preparing soft household paper to solve the above-mentioned technical problems.

[0006] A method for preparing soft household paper, characterized by comprising the following steps: S1: Provide fiber raw materials and slurry the fiber raw materials to form the first slurry, and add cellulase during slurrying, with a cellulase addition amount of 0.2-0.3 kg / T; S2: The first pulp is milled to form the second pulp. Fiber swelling protein is added to the second pulp and reacted to obtain the third pulp. The freeness of the second pulp is 20-30°SR, the concentration of the first pulp during milling is 3-6%, and the amount of fiber swelling protein added is 0.5-2 kg / T. S3: The third pulp is formed, dried, and creased to create soft household paper.

[0007] In the process of paper forming, white water is filtered out, the proportion of fine fibers in the white water is adjusted, and it is added to the third sizing agent so that the fine fiber content in the third sizing agent is 4-6%. Softener is added to the white water so that the content of softener in the third sizing agent is 0.05-0.1 kg / T.

[0008] In this process, the white water filtered out during the papermaking process is filtered a second time through a filtration device to form clear white water, fine fibers, and ordinary fibers, so that the content of fine fibers in the clear white water is less than 2%. Softener is added to the clear white water, and then fine fibers are added to the clear white water before it is added to the third slurry. The papermaking process is carried out through the third slurry.

[0009] The softener is a cationic quaternary ammonium salt, and its content in the third slurry is 0.1 kg / T.

[0010] The fiber raw material is a mixture of 20% to 40% coniferous wood fiber and 60% to 80% broadleaf wood fiber.

[0011] In this process, after adding softener to the bleaching water, fine fibers are added to the bleaching water after 5 minutes, and then added to the third sizing agent. After 30 minutes, the paper is formed using the third sizing agent.

[0012] The forming process involves using a crescent forming machine for forming, a Yankee drying cylinder for drying, and a wrinkling scraper with a 10° to 20° angle for wrinkling, resulting in a wrinkling rate of 15 to 25%. The machine speed is 1200 to 1800 meters per minute, and the wrinkling scraper is an alloy scraper.

[0013] The cellulase mentioned is a cellulase produced through deep fermentation of a fungus-specific humic mold.

[0014] Beneficial Effects: This invention provides a method for preparing soft household paper, characterized by the following steps: S1: Providing fiber raw materials and pulping the fiber raw materials to form a first pulp, and adding cellulase during pulping, with a cellulase addition amount of 0.2-0.3 kg / T; S2: Refining the first pulp to form a second pulp, adding fiber swelling protein to the second pulp and reacting to obtain a third pulp, wherein the freeness of the second pulp is 20-30°SR, the concentration of the first pulp during refining is 3-6%, and the addition amount of fiber swelling protein is 0.5-2 kg / T; S3: Forming, drying, and creping the third pulp to form soft household paper. By combining cellulase and fiber swelling protein, the limitations of temperature conditions during pulping and fiber swelling protein application can be reduced. In addition, the combined application of cellulase, fiber swelling protein, and fine fibers can improve the efficiency of softener use and significantly reduce the amount of softener used. Detailed Implementation

[0015] This invention provides a method for preparing soft household paper, which will be further described below.

[0016] S1: Provide fiber raw materials and slurry the fiber raw materials to form the first slurry, and add cellulase or hemicellulase during slurrying, with the amount of cellulase or hemicellulase added being 0.2 to 0.3 kg / T.

[0017] The fiber raw material can be cellulose fiber (generally known as wood pulp fiber) or cellulose-derived fiber (including, for example, rayon and viscose filament). Preferably, the cellulose fiber can be wood pulp fiber, such as softwood fiber or hardwood fiber. The wood pulp fiber can be prepared from natural trees by chemical or mechanical pulping methods. The chemical pulping methods can be sulfite process, sulfate process or caustic soda process. The mechanical pulping methods can be mechanical milling wood pulp, etc. In addition, various semi-chemical and chemimechanical methods can be used, and bleached and unbleached fibers can also be considered.

[0018] In this embodiment, the fiber raw material can be a mixture of 20% to 40% coniferous wood fiber and 60% to 80% hardwood fiber. In a specific embodiment, the fiber raw material is provided in the form of pulp boards. The coniferous wood fiber pulp boards and hardwood fiber pulp boards are fed into a pulping device in a predetermined ratio. The pulping device disperses the fiber raw material into water through mechanical action during the pulping process to form a fiber suspension. The pulping device can be a hydraulic pulper.

[0019] Understandably, the cellulase is added to the hydrapulper, and the amount of cellulase added is 0.2-0.3 kg / T, which is based on oven-dry pulp.

[0020] The cellulases mentioned are enzymes that degrade cellulose into smaller fragments (mainly glucose), including endonucleases and exonucleases. Endonucleases can randomly hydrolyze β (1-4) bonds along the cellulose chain, while exonucleases can cleave glucose molecules from one end of the cellulose chain.

[0021] In one specific embodiment, the cellulase is a cellulase produced by deep fermentation of a fungus-specific humic mold, and the main active substances of the cellulase are endoglucanase, cellobiase, cellobiase, xylanase and hemicellulase.

[0022] S2: The first pulp is milled to form the second pulp. Fiber swelling protein is added to the second pulp and reacted to obtain the third pulp. The freeness of the second pulp is 20-30°SR, the concentration of the first pulp during milling is 3-6%, and the amount of fiber swelling protein added is 0.5-0.2 kg / T.

[0023] Pulping is a process that causes fiber raw materials to absorb water, swell, and become finer fibers. This greatly increases the external surface area of ​​the fibers and exposes more hydroxyl groups in the cellulose molecular chains, promoting hydrogen bonding. This increases the uniformity and strength of the paper, reduces the rigidity of the fiber raw materials, weakens their elasticity, increases their plasticity, and makes the fibers soft and malleable.

[0024] In this embodiment, the pulp concentration is controlled within a range of 3-6%, for example: 3%, 3.5%, 4.5%, 5%, 6%, etc. The pulping equipment for pulping the first pulp can be a double disc pulper. In the double disc pulper, a rotating disc and a fixed disc act on the bamboo pulp fibers between the two discs, causing the bamboo pulp fibers to receive friction, impact, kneading, torsion, and shearing forces, thereby completing the pulping in a short time. Furthermore, the pulping power of the double disc pulper of this invention can be set to be greater than 90 kWh / t, more preferably greater than or equal to 100 kWh / t.

[0025] The freeness of the second pulp after refining is 20-30°SR, specifically 20°SR, 22°SR, 24°SR, 26°SR, 28°SR, 30°SR, etc.

[0026] The aforementioned fibrous expanding proteins refer to protein / peptide compounds that can cause the fibrous structure of natural substrates such as crystalline cellulose and hemicellulose to expand and loosen. These proteins do not have a catalytic function for cellulose degradation, but they can enhance the hydrolytic ability of cellulase on microcrystalline cellulose. Also known as fibrous expanding factors, these fibrous expanding proteins are a class of plant cell wall expanding proteins, possessing the typical structural domain composition of cellulase (including the cellulose-binding domain (CBD)) and are non-hydrolyzed active proteins. Plant-derived fibrous expanding proteins are mainly of two types, named α-expansin and β-expansin, respectively. These two types of fibrous expanding proteins have high homology in structure and function: α-expansin has a molecular weight of approximately 25 kDa, with a highly conserved amino acid sequence and 70%–90% homology; β-expansin has a molecular weight of approximately 29 kDa, but its amino acid sequence varies considerably. Expansin mainly has two structural domains: the N-terminus is a catalytic domain, whose sequence has high homology with glycosyl hydrolases of family 45; the C-terminus is a substrate-binding domain, with 50% homology with pollen allergen group-II. Enzymatic analysis showed that plant fiber expansin lacked cellulase activity; however, it could induce acid-dependent cell wall extension and stress relaxation by breaking hydrogen bonds between cell wall polymers, thus promoting plant cell wall stretching and expansion. During the enzymatic hydrolysis of microcrystalline cellulose, it had a synergistic effect with cellulase, significantly improving the hydrolysis efficiency of microcrystalline cellulose.

[0027] The amino acid sequence of fibrous swelling proteins is described in detail in the literature (McQueen-Masone et al. (1992) Plant Cell 4:1425-33). Like expansin, the bacterial fibrous swelling protein sweatrenin, while not hydrolyzing cellulose, can dissociate polysaccharide chains from the cellulose surface. This breaks the cross-linking between fibers, making the crystalline regions in the cellulose structure more disordered, thus promoting fiber swelling. As a result, fungal cellulases can more easily enter the fiber interior and access more substrates, while the dextran on the microfibril surface becomes more sensitive to cellulase attack, thereby increasing the hydrolytic activity of cellulases on natural substrates. Compared to expansin, sweatrenin has many unique properties; for example, it is a larger protein and contains a cellulose binding domain (CBD). Furthermore, sweatrenin has the advantage of being heterologously expressed and molecularly modified in microbial hosts.

[0028] S3: The third pulp is formed, dried, and creased to create soft household paper.

[0029] The forming process involves using a crescent forming machine for forming, a Yankee drying cylinder for drying, and a wrinkling scraper with a 10° to 20° angle for wrinkling, resulting in a wrinkling rate of 15 to 25% and a machine speed of 1200 to 1800 meters per minute. Preferably, the wrinkling scraper is an alloy scraper.

[0030] Furthermore, the following steps are included after step S3: S4: During the paper forming process, filter out the white water, adjust the proportion of fine fibers in the white water, and add it to the third sizing agent so that the fine fiber content in the third sizing agent is 4-6%. Add softener to the white water so that the softener content in the third sizing agent is 0.05-0.1 kg / T.

[0031] The softener can be a quaternary ammonium salt. In other embodiments, fatty acid esters, paraffin waxes, polyethylene, silicone resins, etc., can also be used.

[0032] The fine fibers referred to are fibers with a length of less than 0.3 mm.

[0033] Specifically, in step S4, the white water filtered out during the paper forming process is filtered a second time through a filtration device to form clear white water, fine fibers and ordinary fibers, and the content of fine fibers in the clear white water is less than 2%. Softener is added to the clear white water, and then fine fibers are added to the clear white water and added to the third slurry. The paper forming is carried out through the third slurry.

[0034] Understandably, the amount of softener and fine fibers added should be such that the softener content in the third sizing is 0.05-0.1 kg / T and the fine fiber content is 4-6%.

[0035] Further research revealed: I. By combining cellulase and fiber swelling protein, the temperature restrictions during pulping and fiber swelling protein application can be reduced in practice. Fiber swelling protein can be used at temperatures ranging from 0 to 80°C, thus significantly improving the flexibility of its application.

[0036] II. By controlling the fine fiber content in the third pulp to be between 4% and 6%, the following effects can be further achieved: (1) Combining cellulase and fiber swelling protein, the efficiency of softener use is greatly improved. In this embodiment, 0.05 to 0.1 kg / T of softener is used, which is more than 95% less than the conventional softener usage of 2 kg / T. While greatly reducing the amount of softener used, the paper softness is almost the same.

[0037] (2) On the one hand, fine fibers have a larger specific surface area. When the softener is added into the fine fibers, it is adsorbed by the fine fibers. At the same time, the adsorption of the softener by the fiber swelling protein makes the softener play a more obvious role on the paper, that is, improve the use efficiency of the softener. On the other hand, when the proportion of fine fibers is in the range of 4 to 6%, the detachment / falling off of fine fibers during the forming process will not affect the forming, that is, the paper can still have good forming performance.

[0038] Furthermore, after adding softener to the bleaching water, after 5 minutes, fine fibers are added to the bleaching water and then added to the third sizing agent. After 30 minutes, the paper is formed using the third sizing agent.

[0039] The method for preparing high-permeability bamboo pulp liner paper of this application will be described below with reference to specific embodiments.

[0040] Example 1: S11: Provide fiber raw materials and pulp the fiber raw materials to form the first pulp, and add cellulase during pulping. The amount of cellulase added is 0.2 kg / T. The fiber raw materials are NBKP (bleached sulfate softwood pulp):LBKP (bleached sulfate hardwood pulp) = 20:80.

[0041] S12: The first pulp is milled to form a second pulp. Fiber swelling protein is added to the second pulp and reacted to obtain a third pulp. The freeness of the second pulp is 22°SR, the concentration of the first pulp during milling is 4%, and the amount of fiber swelling protein added is 0.5 kg / T.

[0042] S13: The second pulp is formed into soft tissue paper through papermaking, drying, and creping. The papermaking process uses a crescent forming machine, the drying process uses a Yankee drying cylinder, and the creping process uses a 15° creping doctor blade with a creping rate of 20% and a machine speed of 1500 meters per minute.

[0043] Example 2: During the paper forming process, the white water is filtered out, the proportion of fine fibers in the white water is adjusted, and it is added to the third sizing agent so that the fine fiber content in the third sizing agent is 5%. A softener is added to the white water so that the softener content in the third sizing agent is 0.1 kg / T. The softener is a cationic quaternary ammonium salt.

[0044] The remaining steps are the same as in Example 1.

[0045] Comparative Example 1: No cellulase is added during pulping, and no fiber swelling protein is added after the second pulp is formed.

[0046] The remaining steps are the same as in Example 1.

[0047] Comparative Example 2: No cellulase was added during pulping. After the second pulp was formed, fiber swelling protein was added only to the second pulp, and the amount added was the same as in Example 1.

[0048] The remaining steps are the same as in Example 1.

[0049] Comparative Example 3: When the fiber swelling protein is added to the second slurry and reacted to obtain the third slurry, 0.1 kg / T of softener is added at the same time.

[0050] The remaining steps are the same as in Example 1.

[0051] Comparative Example 4: Based on Comparative Example 1, 3 kg / T of softener, which is a cationic quaternary ammonium salt, was added to the second slurry.

[0052] The remaining steps are the same as in Example 1.

[0053] The paper sheets prepared in Examples 1-2 and Comparative Examples 1-4 were tested, and the test results are as follows: Quantitative g / ㎡ 31.8 32.1 31.5 32.0 31.9 32.4 MDT gf / 1'' 583 562 701 601 551 544 CDT gf / 1'' 308 295 342 320 299 281 thickness μm 234 231 229 239 222 224 elongation % 20.0 21.3 22.2 20.2 21.2 22.3 Softness mN 69 55 97 83 74 57 Lateral water absorption mm 59 54 66 59 55 63 The above items were tested according to the following testing methods.

[0054] Basis weight: Tested according to GB / T 451.2-2002 "Determination of basis weight of paper and paperboard".

[0055] MDT: 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", with a sample width of 1 inch.

[0056] MDT: 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", with a sample width of 1 inch.

[0057] 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".

[0058] Thickness: Tested according to GB / T 451.3-2002 "Determination of thickness of paper and paperboard".

[0059] Softness: Tested according to the test method in GB / T 20808-2022 "Paper Facial" 5.9.

[0060] Lateral water absorption: Tested according to GB / T 461.1-2002 "Determination of capillary liquid absorption height of paper and paperboard (Klem method)". Based on the above test results, compared with the prior art, the method of the present invention, in Example 1 using cellulase + fiber swelling protein, shows a significant reduction in softness compared to Comparative Example 1 without cellulase + fiber swelling protein, Comparative Example 2 with only fiber swelling protein, and Comparative Example 3 with 0.1 kg / T added to Comparative Example 2. This indicates that cellulase and fiber swelling protein exhibit a synergistic effect, further reducing softness when used together. In Example 2, which uses fine fibers + a small amount of softener based on Example 1, an effect comparable to using 3 kg / T softener can be achieved. Simultaneously, its strength and thickness are superior to Comparative Example 4 using 3 kg / T softener. Therefore, the combined use of cellulase + fiber swelling protein + fine fibers + softener improves the efficiency of the softener and enhances the strength properties of tissue paper. The above descriptions are merely embodiments of the present invention and do not limit the scope of the patent. Any equivalent structural or procedural transformations made based on the content of this specification, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of this invention.

Claims

1. A method for preparing soft household paper, characterized in that, Includes the following steps: S1: Provide fiber raw materials and slurry the fiber raw materials to form the first slurry, and add cellulase during slurrying, with a cellulase addition amount of 0.2-0.3 kg / T; S2: The first pulp is milled to form the second pulp. Fiber swelling protein is added to the second pulp and reacted to obtain the third pulp. The freeness of the second pulp is 20-30°SR, the concentration of the first pulp during milling is 3-6%, and the amount of fiber swelling protein added is 0.5-2 kg / T. S3: The third pulp is formed, dried, and creped to form soft household paper; during the forming process, white water is filtered out, the proportion of fine fibers in the white water is adjusted, and added to the third pulp so that the content of fine fibers in the third pulp is 4-6%, and a softener is added to the white water so that the content of softener in the third pulp is 0.05-0.1 kg / T. The fine fibers refer to fibers with a fiber length of less than 0.3 mm.

2. The preparation method according to claim 1, characterized in that, The white water filtered out during the paper forming process is filtered a second time through a filtration device to form clear white water, fine fibers and ordinary fibers, so that the content of fine fibers in the clear white water is less than 2%. Softener is added to the clear white water, and then fine fibers are added to the clear white water. The mixture is then added to the third slurry and paper forming is carried out through the third slurry.

3. The preparation method according to claim 2, characterized in that, The softener is a cationic quaternary ammonium salt, and the softener content in the third slurry is 0.1 kg / T.

4. The preparation method according to claim 2, characterized in that, The fiber raw material is a mixture of 20% to 40% coniferous wood fiber and 60% to 80% broadleaf wood fiber.

5. The preparation method according to claim 2, characterized in that, Add softener to the bleaching water, and after 5 minutes, add fine fibers to the bleaching water and add it to the third sizing agent. After 30 minutes, form the paper using the third sizing agent.

6. The preparation method according to claim 2, characterized in that, The forming process is carried out using a crescent forming machine, drying is performed using a Yankee drying cylinder, and wrinkling is performed using a wrinkling scraper with a 10° to 20° angle, resulting in a wrinkling rate of 15 to 25%. The machine speed is 1200 to 1800 meters per minute, and the wrinkling scraper is an alloy scraper.

7. The preparation method according to claim 2, characterized in that, The cellulase mentioned is a cellulase produced through deep fermentation of a fungus-specific humic mold.