A method for preparing fluffy base paper

Abstract

The present invention relates to the field of papermaking technology, and specifically to a method for preparing fluffy base paper. The preparation method includes the following parts: 1. After the pulp board raw material is crushed and refined, the long fiber and short fiber pulp are mixed, and the upper and lower headboxes spray the pulp onto the forming net under a certain stable pressure to evenly divide it into wet paper sheets, and perform preliminary water filtration; 2. The wet paper sheets are transferred from the forming net to the felt cloth for further dehydration; 3. The paper sheets are then transferred to a small drying cylinder through a shoe press, and the paper sheet fibers are still arranged in a conventional structure; 4. The paper sheets are stacked into the structural net through speed difference control, and the fibers are plastically treated by a double drying cylinder + a three-dimensional structure shaping net, and the thickness of the paper sheets will increase significantly during this process; 5. Finally, the paper sheets are transferred from the structural net to the drying cylinder for final drying. By means of the above technical scheme, the new base paper prepared by the present invention has a better fluffy feeling, which not only improves the production capacity but also reduces the production cost on the basis of ensuring the performance of the paper.

Description

Technical Field

[0001] The invention relates to the technical field of household paper production, and in particular to a method for preparing fluffy base paper. Background Art

[0002] As people's living standards improve, the demand for facial tissues used in daily life is also growing. It can not only be used to wipe the moisture and oil on the hands, but also to clean the home. Someone once conducted an experiment. After washing hands, the hands were dried with facial tissues, hand towels, and dryers, and then the bacterial residues on the hands were detected. The results showed that facial tissues had the least bacterial residues. In the process of use, it is hoped that it has a thick feel while being ultra-soft, cotton-soft, and fluffy. It also has high dry and wet strength and good water absorption. Papermaking raw materials are mainly divided into two categories: plant fibers and non-plant fibers. Non-plant fibers mainly include inorganic fibers, chemical fibers, metal fibers, etc. At present, my country's papermaking raw materials mainly use plant fibers, and there are many varieties of plant fiber raw materials. my country's forestry resources are limited, and there are many industries that need wood, which cannot meet the growing demand for raw materials in the papermaking industry. At the same time, due to the increase in environmental protection requirements, the proportion of non-wood pulp has declined rapidly year by year. Imported raw materials have become the main support for the development of my country's papermaking industry. However, in recent years, the price of imported wood pulp has continued to rise, and for enterprises, there is an urgent need to save costs. The existing plant fiber toilet paper with good softness has low dry and wet strength, while the plant fiber toilet paper with high dry and wet strength has poor softness. Therefore, it is necessary to develop a plant fiber toilet paper with both softness and dry and wet strength. Summary of the invention

[0003] The present invention aims to solve the current problems of high paper production cost and low output, and proposes a new method for producing base paper with good fluffiness. The production method proposed by the present invention can achieve that the thickness of paper can be almost doubled under the same raw material conditions, and the paper prepared by the improved production method has obvious improvements in liquid absorption height, powder loss rate, microbial value, softness, dustiness, holes, etc.

[0004] A method for preparing fluffy base paper of the present invention, the specific process is as follows:

[0005] 1. Pulping: 100% of the original long fibers are crushed and then refined to make long fiber pulp with a concentration of 4-5% and a beating degree of 18-22; the original short fibers are crushed and concentrated to a concentration of 16-20% and then refined to make short fiber pulp with a beating degree of 22-26; the long fiber pulp and the short fiber pulp are mixed in a mass ratio of 1:1.

[0006] 2. Forming paper sheets: The slurry is sprayed onto the forming net under a certain pressure and evenly distributed to form wet paper sheets, and then initially filtered. The wet paper sheets are then transferred from the forming net to the felt cloth for further dehydration. The slurry spraying pressure is maintained at 120-200 kpa so that the slurry can be sprayed smoothly, and the ratio of slurry speed to wire speed is maintained at 0.98-1.1.

[0007] 3. Preliminary drying: The wet paper sheets are transferred to the small drying cylinder with the felt cloth for drying, reducing the humidity of the paper sheets to 50-55wt% in preparation for entering the structural network for shaping. At this time, the paper sheet fibers are still in a conventional arrangement structure, and the temperature in the cylinder is controlled at 120-135℃. When the paper sheets are lifted out of the small drying cylinder, the moisture content of the paper sheets is reduced to achieve the purpose of energy saving and consumption reduction.

[0008] 4. Shaping treatment:

[0009] The wet paper sheets are stacked from the small drying cylinders into the three-dimensional structure shaping net through speed difference control. The moving speed of the three-dimensional structure shaping net is lower than that of the small drying cylinders, and the difference between the moving speeds of the small drying cylinders and the three-dimensional structure shaping net is 8% to 20% of the moving speed of the small drying cylinders. This process makes the fibers form a three-dimensional arrangement, and in this process, the thickness of the paper sheets will increase significantly. At this time, the wet paper sheets have entered the speed difference zone to increase the thickness of the paper sheets.

[0010] 5. Final drying:

[0011] The paper is sent from the three-dimensional structure shaping net to the large drying cylinder for final drying. After high temperature baking in the large drying cylinder and drying by the hot air hood, the fiber ends are further stretched and the paper is more fluffy. The temperature in the cylinder is 130℃-160℃, the hot air temperature is 300-400℃, and the moisture content of the paper out of the drying cylinder is 3%-8wt%.

[0012] The present invention adopts double drying cylinders + forming net + felt cloth + three-dimensional structure shaping net to carry out plastic treatment on the fiber.

[0013] Compared with the prior art, the technical solution of the present invention has the following advantages and beneficial effects:

[0014] 1. The technical solution of the present invention can distribute and arrange the paper fibers on the Z axis through a three-dimensional structure shaping net, so that the paper fibers can expand the longitudinal space of the paper while maintaining the interweaving force and bonding force, making the paper more fluffy and thick, and making the paper more cottony and tough in experience.

[0015] 2. The thickness of the paper prepared by this method is increased without consuming more pulp, which saves more raw materials, reduces production costs and improves economic benefits.

[0016] 3. The paper prepared by this method has stronger lateral liquid absorption height, higher softness, lower drop rate and better performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a plane SEM image of the improved paper of Example 1. It can be seen from this image that the improved paper is distributed in the Z-axis direction, and the fibers are distributed perpendicular to the plane of the paper;

[0018] Figure 2 This is a plane SEM image of the original paper of comparative example 1. It can be seen from this image that the original paper has no distribution in the Z-axis direction, and the fibers are distributed on the plane, that is, only the X-axis and Y-axis are distributed;

[0019] contrast Figure 1 and Figure 2 It was found that the improved technical means made the fibers distributed in the Z-axis direction in addition to the plane distribution. This is also the fundamental reason why the paper becomes thicker;

[0020] Figure 3 This is a cross-sectional SEM image of the improved paper of Example 1. It can be seen from this image that the improved paper cross-section is thicker, with a thickness of 150 um;

[0021] Figure 4 This is a cross-sectional SEM image of the original paper of Comparative Example 1. It can be seen from this image that the original paper is relatively thin, with a thickness of 70 um;

[0022] Figure 5 This is a schematic diagram of the structure of double drying cylinders + forming net + felt cloth + structural shaping net in Example 1. DETAILED DESCRIPTION

[0023] To make the purpose, technical scheme and advantages of the present invention clearer, the present invention will be further described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] First, the terms designed by the present invention are explained as follows:

[0025] Refining refers to the continuous treatment of pulp suspension by using refining and beating equipment such as disc grinding to give the pulp the characteristics required for papermaking. This operation process is different from beating. Refining is a continuous operation, and the fibers are parallel to the blades (or grinding teeth) when passing through the refining mechanism. Beating is an intermittent operation, and the fibers are arranged perpendicular to the blades when passing through the beating mechanism. Refining (beating) pulping subjects the pulp fibers to shear force. In addition to kneading and decomposing the pulp to decompose the fiber bundles into single fibers, the fiber cell wall first displaces and deforms, the P layer and S layer of the cell wall are partially broken and fiber fragments are produced, and the fibers are cut and twisted, curled, compressed and stretched. At the same time, the fibers absorb water, swell and become fine fibers, and the fiber surface is separated into many fine fibers. The ends of the fibers are broomed, and many hydroxyl groups are released. The specific surface area of ​​the fibers increases, the surface becomes rough, and the cohesion between the layers decreases. The fibers become softer and more plastic, and the water filtration performance of the overall paper material decreases. Through refining, the water filtration performance of the paper material on the screen is controlled, the paper web is well formed, and the uniformity and strength of the paper sheet are improved.

[0026] The softness test refers to the measurement of the sample into a gap of a certain depth by a plate-shaped probe that moves up and down under a certain test gap width, and the vector sum of the sample's own bending resistance and the friction between the sample and the gap is measured. This value represents the softness of the paper. When measuring the longitudinal softness, the longitudinal direction of the sample is perpendicular to the direction of the gap; when measuring the transverse softness, the longitudinal direction of the sample is parallel to the direction of the gap.

[0027] Longitudinal Y axis / cross direction X axis, since most of the fiber arrangement is in the direction of the paper machine, and in this direction, the paper is subjected to greater traction, this is the so-called longitudinal direction (Machine direction). The cross direction of the paper is perpendicular to the running direction of the paper machine.

[0028] Spherical bursting resistance refers to the situation where a sample of toilet paper and its products is firmly clamped by two concentric rings, and a highly polished stainless steel ball penetrates the sample in the vertical direction at a constant rate. The maximum force that the surface of the sample can withstand in the vertical direction is the spherical bursting resistance.

[0029] The ratio of pulp speed to wire speed, the height of the water level in the headbox corresponds to the pulp speed according to the formula, and the ratio of pulp speed to the running speed of the copper mesh is the ratio of pulp speed to mesh speed. When the pulp speed is equal to the mesh speed, the degree of turbulence is small, there is no directional force, so that the dispersed fibers may re-flocculate on the net, and the paper uniformity is poor. When the pulp speed is greater than the mesh speed, the pulp flow will flow on the mesh surface, and the number of fibers arranged horizontally on the net is large. If it is a free pulp, due to the fast water filtration speed, it is easy to produce fiber curling or fiber arrangement perpendicular to the mesh surface, resulting in wavy paper defects. When the pulp speed is slightly less than the mesh speed, the acceleration of the mesh reduces the possibility of fiber re-flocculation and improves the uniformity of the paper.

[0030] The transverse liquid absorption height is to immerse the lower end of a vertically suspended sample in water and measure the capillary liquid absorption height after a certain period of time. The height of the transverse liquid absorption height directly reflects the water absorption effect. The transverse liquid absorption height mainly depends on the capillary effect between the transverse fibers of the paper sheet. The stronger the capillary effect, the better the water absorption. The main factors affecting the transverse liquid absorption height are the type of pulp and the control of the production process. Generally speaking, pure wood pulp, free pulping, and low density paper have better water absorption.

[0031] Example 1: A method for preparing fluffy base paper, in which double drying cylinders + forming net + felt cloth + structural shaping net are used to shape the fibers. The specific steps are as follows:

[0032] (1) 100% of the original long fiber is crushed by a hydraulic pulper and then enters a low-concentration pulper to produce long-fiber pulp with a concentration of 4-5% and a beating degree of 18-22, and enters a pulp storage tower; the original short fiber is crushed by a hydraulic pulper and then enters a high-concentration concentrator to increase the concentration to 16-20%, and then is ground by a high-concentration pulper to produce short-fiber pulp with a beating degree of 22-26, and enters a pulp storage tower; the long-fiber pulp and the short-fiber pulp are mixed in a mass ratio of 1:1 to form a slurry and enter the paper machine. The slurry is sprayed at a pressure of 150k The wet paper is sprayed onto the forming net 1 at pa and evenly distributed to form a wet paper sheet, and preliminary water filtering is performed. At this time, the pulp speed and the net speed ratio is 1:1. Subsequently, the wet paper sheet is transferred from the forming net 1 to the felt cloth 2 for further dehydration. The felt cloth 2 moves cyclically under the drive of the guide roller. The felt cloth 2 transfers the wet paper sheet to the small drying cylinder 4 under the action of the upper paper roller 3. The wet paper sheet is pressed and dried, and the temperature in the small drying cylinder 4 is controlled to be 120°C. The humidity of the paper sheet is reduced to 55wt% when the paper sheet exits the small drying cylinder 4, so as to achieve the purpose of energy saving and consumption reduction. At this time, the paper sheet fibers are still in a conventional arrangement structure.

[0033] (2) The wet paper sheet is transferred from the small drying cylinder 4 to the three-dimensional structure shaping net 5 by controlling the speed difference. The moving speed of the three-dimensional structure shaping net 5 is less than the linear speed of the small drying cylinder 4, and the difference between the moving speeds of the small drying cylinder 4 and the three-dimensional structure shaping net 5 is 20% of the linear speed of the small drying cylinder 4. At this time, when the wet paper sheet is transferred from the small drying cylinder 4 to the three-dimensional structure shaping net, stacking occurs at the contact point between the small drying cylinder 4 and the three-dimensional structure shaping net 5. The wet paper sheet achieves a wrinkling effect under the squeezing action of the small drying cylinder 4 and the three-dimensional structure shaping net 5, so that some fibers are distributed and arranged in a certain manner in the longitudinal direction. In this process, the thickness of the paper sheet will increase significantly.

[0034] (3) Finally, the paper sheet on the three-dimensional structure shaping net 5 is transferred to the large drying cylinder 6 for final drying. The paper sheet is baked at a high temperature of 140°C in the large drying cylinder 6 and dried at a temperature of 300°C in the hot air hood to further stretch the fiber ends and make the paper sheet more fluffy, ensuring that the moisture content of the paper is controlled at 8wt% when it leaves the large drying cylinder. The paper prepared by this method is subjected to quality inspection, and its properties are shown in Table 1 below.

[0035] Table 1

[0036]

[0037] Example 2: A method for preparing fluffy base paper, in which double drying cylinders + forming net + felt cloth + structural shaping net are used to shape the fibers. The specific steps are as follows:

[0038] (1) 100% of the original long fiber is crushed by a hydraulic pulper and then enters a low-concentration pulper to produce long-fiber pulp with a concentration of 4-5% and a beating degree of 18-22, and enters a pulp storage tower; the original short fiber is crushed by a hydraulic pulper and then enters a high-concentration concentrator to increase the concentration to 16-20%, and then is ground by a high-concentration pulper to produce short-fiber pulp with a beating degree of 22-26, and enters a pulp storage tower; the long-fiber pulp and the short-fiber pulp are mixed in a mass ratio of 1:3 to form a slurry and enter the paper machine. The slurry is sprayed at a spray pressure of 1 At 60kpa, the liquid is sprayed onto the forming net and evenly distributed to form a wet paper sheet, which is then initially filtered. At this time, the ratio of pulp speed to net speed is 1:1. The wet paper sheet is then transferred from the forming net to a felt cloth for further dehydration. The felt cloth moves in a cycle driven by the guide roller. The felt cloth 2 transfers the wet paper sheet to a small drying cylinder 4 under the action of the upper paper roller 3. The wet paper sheet is squeezed and dried, and the temperature in the small drying cylinder is controlled to be 125°C. The humidity of the paper sheet is reduced to 50wt% when the paper sheet leaves the small drying cylinder, achieving the purpose of energy saving and consumption reduction. At this time, the paper sheet fibers are still in a conventional arrangement structure.

[0039] (2) The wet paper sheet is transferred from the small drying cylinder 4 to the three-dimensional structure shaping net 5 by controlling the speed difference. The moving speed of the three-dimensional structure shaping net 5 is less than the linear speed of the small drying cylinder 4, and the difference between the moving speeds of the small drying cylinder 4 and the three-dimensional structure shaping net 5 is 15% of the linear speed of the small drying cylinder 4. At this time, when the wet paper sheet is transferred from the small drying cylinder 4 to the three-dimensional structure shaping net, stacking occurs at the contact point between the felt cloth and the three-dimensional structure shaping net. The wet paper sheet achieves a wrinkling effect under the squeezing action of the felt cloth and the three-dimensional structure shaping net, so that some fibers have a certain distribution and arrangement in the longitudinal direction. In this process, the thickness of the paper sheet will increase significantly.

[0040] (3) Finally, the paper sheet on the three-dimensional structure shaping net contacts the large drying cylinder for final drying. The paper sheet is baked at a high temperature of 150°C in the large drying cylinder and dried at a temperature of 320°C in the hot air hood to further stretch the fiber ends and make the paper sheet more fluffy, ensuring that the moisture content of the paper is controlled at 7wt% when it leaves the drying cylinder. The paper prepared by this method was subjected to quality inspection, and its properties were measured and shown in Table 2 below.

[0041] Table 2

[0042]

[0043] Comparative Example 1 The base paper before improvement was prepared by the following method:

[0044] Comparative Example 1: A method for preparing base paper, the specific steps are as follows:

[0045] (1) 100% of the original long fibers are crushed by a hydraulic pulper and then sent to a low-concentration pulper to form long-fiber pulp with a concentration of 4-5% and a beating degree of 18-22, which then enters a pulp storage tower; the original short fibers are crushed by a hydraulic pulper and then sent to a high-concentration concentrator to increase the concentration to 16-20%, and then ground by a high-concentration pulper to form short-fiber pulp with a beating degree of 22-26, which then enters a pulp storage tower; the long-fiber pulp and the short-fiber pulp are mixed in a mass ratio of 1:3 to form a slurry that enters a paper machine. The slurry is sprayed onto the forming net at a spraying pressure of 160 kpa and evenly distributed to form wet paper sheets. At this time, the ratio of pulp speed to net speed is 1:1, followed by preliminary water filtration, and then transferred to a felt cloth for further dehydration. The dehydrated wet paper sheets are transferred to a small drying cylinder, and the temperature in the cylinder is controlled to be 145°C. Figure 2 As shown, at this time the paper sheet fibers are still in a conventional arrangement structure.

[0046] This embodiment uses a single drying cylinder + forming net + ordinary felt cloth to shape the fibers. Figure 4 As shown, the thickness of the paper sheet has not increased.

[0047] The paper prepared by this method was subjected to quality inspection, and its properties were measured and shown in Table 3 below.

[0048] Table 3

[0049]

[0050] Comparative Example 2 is a method for preparing base paper. This solution uses double drying cylinders + forming nets + felt cloth + structural shaping nets to shape the fibers. The specific steps are as follows:

[0051] (1) 100% of the original long fiber is crushed by a hydraulic pulper and then enters a low-concentration pulper to produce long-fiber wood pulp with a concentration of 4-5% and a beating degree of 18-22, and enters a pulp storage tower; the original short fiber is crushed by a hydraulic pulper and then enters a high-concentration concentrator to increase the concentration to 16-20%, and then is ground by a high-concentration pulper to produce short-fiber wood pulp with a beating degree of 22-26, and enters a pulp storage tower; the long-fiber wood pulp and the short-fiber wood pulp are mixed in a mass ratio of 1:3 to form a slurry and enter the paper machine. The slurry is sprayed on the paper machine. The wet paper is sprayed onto the forming net at a pressure of 160 kPa and evenly distributed to form a wet paper sheet, which is then initially filtered. At this time, the ratio of pulp speed to net speed is 1:1. The wet paper sheet is then transferred from the forming net to a felt cloth for further dehydration. The felt cloth moves in a cycle driven by the guide roller. The felt cloth 2 is transferred to a small drying cylinder 4 under the action of the upper paper roller 3. The wet paper sheet is squeezed and dried, and the temperature in the small drying cylinder is controlled to be 140°C. The humidity of the paper sheet is reduced to 42wt% when it leaves the small drying cylinder. At this time, the paper sheet fibers are still in a conventional arrangement structure.

[0052] (2) The wet paper sheet is transferred from the small drying cylinder 4 to the three-dimensional structure shaping net 5 by controlling the speed difference. The moving speed of the three-dimensional structure shaping net 5 is less than the linear speed of the small drying cylinder 4, and the difference between the moving speeds of the small drying cylinder 4 and the three-dimensional structure shaping net 5 is 20% of the linear speed of the small drying cylinder 4. At this time, when the wet paper sheet is transferred from the small drying cylinder 4 to the three-dimensional structure shaping net, stacking occurs at the contact point between the felt cloth and the three-dimensional structure shaping net. The wet paper sheet achieves a wrinkling effect under the squeezing action of the felt cloth and the three-dimensional structure shaping net, so that some fibers are distributed and arranged in a certain manner in the longitudinal direction. In this process, the thickness of the paper sheet will increase significantly.

[0053] (3) Finally, the paper sheet on the three-dimensional structure shaping net contacts the large drying cylinder for final drying. The paper sheet is baked at a high temperature of 150°C in the large drying cylinder and dried at a temperature of 320°C in the hot air hood to further stretch the fiber ends and make the paper sheet more fluffy, ensuring that the moisture content of the paper is controlled at 7wt% when it leaves the drying cylinder. The paper prepared by this method was subjected to quality inspection, and its properties were measured and shown in Table 4 below.

[0054] Table 4

[0055]

[0056] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Therefore, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing fluffy base paper, the specific process is as follows: S1. Pulping: 100% of the original long fiber is crushed and then refined to prepare long fiber pulp with a concentration of 4-5% and a beating degree of 18-22°SR; the original short fiber is crushed and concentrated to a concentration of 16-20%, and then refined to prepare short fiber pulp with a beating degree of 22-26°SR; the long fiber pulp and the short fiber pulp are mixed at a mass ratio of 1:1; S2. Forming paper sheets: The slurry is sprayed onto the forming net under a certain pressure and evenly distributed to form wet paper sheets, and the water is initially filtered. The wet paper sheets are then transferred from the forming net to the felt cloth for further dehydration. The slurry spraying pressure is maintained at 120-200 kPa so that the slurry can be sprayed smoothly, and the ratio of slurry speed to wire speed is maintained at 0.98-1.1; S3, preliminary drying: the wet paper is transferred to a small drying cylinder with the felt cloth for drying, reducing the humidity of the paper to 50-55wt% to prepare for shaping into the structural net. At this time, the paper fiber is still in a conventional arrangement structure, and the temperature in the cylinder is controlled at 120-135℃. When the paper leaves the small drying cylinder, the moisture content of the paper is increased to achieve energy saving and consumption reduction. S4, shaping treatment: The wet paper sheets are stacked from the small drying cylinder to the three-dimensional structure shaping net through speed difference control. The moving speed of the three-dimensional structure shaping net is lower than that of the small drying cylinder, and the difference between the moving speed of the small drying cylinder and the three-dimensional structure shaping net is 8% to 20% of the moving speed of the small drying cylinder. This process makes the fibers form a three-dimensional arrangement. In this process, the thickness of the paper sheets will increase significantly. At this time, the wet paper sheets enter the speed difference zone to increase the thickness of the paper sheets. S5. Final drying: The paper sheets are sent from the three-dimensional structure shaping net to the large drying cylinder for final drying. After high-temperature baking in the large drying cylinder and drying by the hot air hood, the fiber ends are further stretched and the paper sheets are made more fluffy. The temperature in the cylinder is 130℃-160℃, the hot air temperature is 300-400℃, and the moisture content of the paper sheets leaving the drying cylinder is 3%-8wt%.

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