Method for preparing high-bulk finished paper

Abstract

The invention provides a method for preparing high-bulk finished paper, which comprises the following steps: by taking coniferous wood chemical pulp, broadleaf wood chemical pulp and bleached chemithermomechanical pulp as fiber raw materials, carrying out pulp preparation according to a ratio; chemical auxiliaries added in the pulp preparing process comprise porous calcium silicate, paper machine filler, cationic acrylic resin, spherical anionic polyacrylamide, cationic starch, alkyl ketene dimer and cationic polyacrylamide. The use amount of the porous calcium silicate is 30-60 kg per ton of finished paper; the prepared pulp is subjected to sizing and net part dehydration forming, and wet page paper is formed; the wet page paper is subjected to squeezing, pre-drying, surface sizing and post-drying, and finished paper is obtained. By applying the porous calcium silicate, the bulkiness of the paper can be greatly improved while the retention rate of the finished paper is improved, the stiffness and opacity of the paper can be improved, the requirements of customers on the bulkiness of the finished paper can be met, and the use amount of plant fibers can be reduced, so that the production cost is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of papermaking, and in particular relates to a method for preparing high-bulk paper. Background Art

[0002] Bulk is a very important performance indicator for paper and paperboard. High bulk means that at the same basis weight, the paper or paperboard has a higher thickness, higher stiffness, and higher opacity. Under the same thickness, the basis weight of the paper can be effectively reduced, making the paper lighter, thereby reducing fiber consumption, saving pulp costs, and reducing the consumption of fiber raw material resources such as forests. Lightweight paper can also reduce the cost of commercial paper for customers; for student paper such as textbook and supplementary paper, notebook paper, etc., it can reduce the weight and burden for students. For some paper products with high stiffness requirements, such as electrostatic copy paper, boxboard, etc., lightweighting can effectively improve the stiffness performance, improve the machine performance of copy paper and other products, and optimize the stiffness of cartons.

[0003] At present, the technologies for improving the bulk of paper mainly include: adding high-yield pulp; shoe pressing; metal belt calendering; using bulking agents; reducing paper smoothness, etc. Among them, improving the bulk of paper by adding bulking agents is a hot research direction at present.

[0004] In order to increase the bulk of paper during the production process, one method is to add substances with low density and the other is to increase the porosity of paper. The density of traditional bulk additives is generally greater than that of wood fiber, but less than that of inorganic fillers (such as calcium carbonate); when used, they can only increase the bulk when replacing inorganic fillers, but cannot be used directly to replace wood fiber. Since the price of these bulk additives is much higher than that of inorganic fillers and they cannot effectively reduce the proportion of wood fiber, the cost has increased significantly. Summary of the invention

[0005] In view of the problems existing in the above-mentioned prior art, the object of the present invention is to provide a method for preparing paper with high bulk. The paper product prepared by the present invention has high bulk and the like, and is low in cost. The method and process of the present invention can be widely applied to various papers that require improved paper bulk.

[0006] The present invention provides a method for preparing high bulk paper, comprising the following steps:

[0007] The invention relates to a method for preparing pulp by using coniferous wood chemical pulp, hardwood chemical pulp and bleached chemimechanical pulp as fiber raw materials in proportion. The chemical additives added in the pulping process include porous calcium silicate, paper machine filler, cationic acrylic resin, spherical anionic polyacrylamide, cationic starch, alkyl ketene dimer and cationic polyacrylamide. The amount of the porous calcium silicate is 30-60 kg / ton of finished paper.

[0008] The prepared slurry is sizing, dewatering and forming on a wire to form wet paper.

[0009] The wet paper is subjected to pressing, pre-drying, surface sizing and post-drying to obtain finished paper; the sizing agent used in the surface sizing is enzyme-converted starch glue, and the sizing amount of the surface sizing is 40-60kg per ton of finished paper.

[0010] In an embodiment of the present invention, the coniferous wood chemical pulp and the hardwood chemical pulp are both bleached pulp boards; the bleached chemimechanical pulp is bleached hardwood and miscellaneous wood chemimechanical pulp; the mass ratio of the coniferous wood chemical pulp, the hardwood chemical pulp and the bleached chemimechanical pulp is 8-25:0-65:15-92.

[0011] In an embodiment of the present invention, the beating concentration of the coniferous wood chemical pulp is 4.0-4.5%, and the beating degree is 38-40°SR; the beating concentration of the hardwood chemical pulp is 4.0-4.5%, and the beating degree is 40-42°SR; the pulp concentration of the bleached chemimechanical pulp is 4.0-4.5%, and the beating degree is 52-56°SR.

[0012] In the embodiment of the present invention, the porous calcium silicate crystal is elliptical and honeycomb-shaped, with a median particle size of 4.8-6.2 microns and a density of 0.15-0.2 g / cm 3 , ISO whiteness is 94-96%.

[0013] In an embodiment of the present invention, the porous calcium silicate is added after the paper machine filler is added; and the paper machine filler is calcium carbonate.

[0014] In an embodiment of the present invention, the prepared pulp is sized after being screened, seasoned, flushed, desanded and deaerated, and then finely screened and dehydrated in a mesh to form wet paper.

[0015] In an embodiment of the present invention, the amount of the cationic starch is 8-10 kg / ton of paper; the amount of the alkyl ketene dimer is 15-20 kg / ton of paper.

[0016] In the embodiment of the present invention, the alkyl ketene dimer is added at the pulping inlet to control the Cobb value of the finished paper to be 25-30 g / m 2 ; Add cationic polyacrylamide at the pulping outlet at a dosage of 0.2-0.4 kg per ton of paper.

[0017] In the embodiment of the present invention, the basis weight of the paper is 65-80 g / m 2 , which is light paper, copy paper or notebook paper.

[0018] In an embodiment of the present invention, the bulk thickness of the finished paper is 1.4-2.0 cm2 / g.

[0019] Compared with the prior art, the present invention uses coniferous wood chemical pulp, hardwood chemical pulp and bleached chemical mechanical pulp as fiber raw materials, and adopts a certain amount of inorganic bulking agent in the pulping system. The inorganic bulking agent is a porous calcium silicate obtained by chemical modification, which has the characteristics of light weight, low density, strong adsorption, good dispersibility, etc. It replaces part of the filler in the pulp and is added to the pulp system. After papermaking, a high-bulky paper product is produced. By applying the porous calcium silicate, the present invention can improve the paper retention rate and greatly improve the paper bulk, and can also improve the paper stiffness and opacity, meet the customer's requirements for the bulk of the paper, and can reduce the amount of plant fiber, thereby reducing production costs. The paper produced by this method increases the paper bulk by 5-12% while maintaining the original performance, thereby reducing production costs and maximizing paper profits. DETAILED DESCRIPTION

[0020] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the technical scheme of the present invention is now described in detail below in conjunction with specific embodiments. The described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0021] The present invention provides a method for preparing high bulk paper, comprising the following steps:

[0022] The invention relates to a method for preparing pulp by using coniferous wood chemical pulp, hardwood chemical pulp and bleached chemimechanical pulp as fiber raw materials in proportion. The chemical additives added in the pulping process include porous calcium silicate, paper machine filler, cationic acrylic resin, spherical anionic polyacrylamide, cationic starch, alkyl ketene dimer and cationic polyacrylamide. The amount of the porous calcium silicate is 30-60 kg / ton of finished paper.

[0023] The prepared slurry is sizing, dewatering and forming on a wire to form wet paper.

[0024] The wet paper is subjected to pressing, pre-drying, surface sizing and post-drying to obtain finished paper; the sizing agent used in the surface sizing is enzyme-converted starch glue, and the sizing amount of the surface sizing is 40-60kg per ton of finished paper.

[0025] The paper product prepared by the present invention has higher bulk and the like, and has lower cost. The method and process of the present invention can be widely applied to various papers requiring improved paper bulk.

[0026] To achieve the above purpose, the technical solution adopted in the embodiment of the present invention specifically includes the following process: coniferous chemical pulp, hardwood chemical pulp and bleached chemical mechanical pulp are used as fiber raw materials and are blended according to demand. The blended pulp samples are subjected to thick pulp screening, seasoning, pulping, sand removal and degassing, sizing, fine screening, wire dehydration and forming, pressing, pre-drying, surface sizing, post-drying, calendering, winding and packaging to obtain the desired paper products.

[0027] Specifically, the embodiment of the present invention first performs pulp treatment on the fiber raw materials: the coniferous wood market pulp board and the hardwood market pulp board are respectively sent to the hydraulic pulping for crushing, and then sent to the pre-beating tank; the bleached chemical mechanical pulp is the self-produced bleached chemical mechanical pulp, which is pumped from the pulping workshop to the pre-beating pulp tank.

[0028] Furthermore, the fiber raw materials used in the pulp treatment step are commercial bleached coniferous chemical pulp boards, commercial bleached hardwood chemical pulp boards, and bleached hardwood chemical mechanical pulp produced by the applicant company itself. Specifically, the specifications of the coniferous chemical pulp include: whiteness of 88±2% ISO, fiber length of 1.8-3.2mm, fiber width of 24.1-30.0μm; the specifications of hardwood chemical pulp include: whiteness of 90±2% ISO, fiber length of 0.8-1.1mm, fiber width of 14.0-20.0μm; the whiteness of bleached chemical mechanical pulp can be 74-76% ISO, fiber length of 0.5-0.6mm, fiber width of 15-24μm. The mass ratio of the softwood chemical pulp, the hardwood chemical pulp and the bleached chemimechanical pulp is 8-25:0-65:15-92; in some embodiments, the pulping is carried out with the mass ratio of softwood chemical pulp: bleached chemimechanical pulp being 8-10:90-92, that is, hardwood chemical pulp may not be used, in order to maximize the use of chemimechanical pulp to increase the bulk of the finished paper while ensuring the strength of the finished paper (among the three pulps, chemimechanical pulp contributes the most to the bulk, and softwood chemical pulp contributes the most to the strength).

[0029] The embodiment of the present invention performs pulping: the debonded pulp is pumped from the pre-beating tank into the mill, and pulping is performed according to production needs. Preferably, the pulping concentration is 4.0-4.5%, and the pulp beating degree requirements include: coniferous wood chemical pulp: 38-40°SR, hardwood chemical pulp 40-42°SR, bleached chemical mechanical pulp 52-56°SR; the beaten pulp is sent to the post-beating pulp tank, diluted with paper machine white water and sent to the stock preparation box.

[0030] The embodiment of the present invention also prepares porous calcium silicate: clean water can be added to the material preparation tank, the stirrer is turned on, and then the porous calcium silicate is added to prepare a concentration preferably of 10-15wt%, and the transfer pump is turned on to pump the stirred porous calcium silicate mixture into the storage tank; during production, in order to ensure the stability of the amount of porous calcium silicate added, the liquid level in the storage tank is kept stable as much as possible.

[0031] The porous calcium silicate described in the embodiment of the present invention is characterized by light weight, low density, strong adsorption and good dispersibility; the specific indicators are: the crystal shape is elliptical, honeycomb-shaped, the median particle size is 4.8-6.2 microns, and the density is 0.15-0.2g / cm 3 , ISO brightness 94-96%, and can be a commercially available product.

[0032] In a specific embodiment of the present invention, the porous calcium silicate, other chemicals (including paper machine fillers, starch in pulp, alkyl ketene dimer (AKD), cationic polyacrylamide retention aid, etc.) and auxiliary materials are added including: using a porous calcium silicate addition system to add the porous calcium silicate in an amount of 30-60 kg / t of paper; in addition to adding porous calcium silicate, cationic acrylic resin is also added (the addition amount is 0.5-1.5 kg / t of paper), and the addition point is the pulp preparation tank, and at the same time, a certain amount of spherical anionic polyacrylamide is added in the paper machine tank, and the addition amount is 0.1-0.5 kg / t of paper. In addition, a paper machine filler (preferably calcium carbonate, with a filler dosage of 230-300 kg / t paper) is added to the stock preparation box, and the addition point is before the porous calcium silicate addition point; cationic starch is added to the high-position box outlet, preferably 15-20 kg / t paper AKD is added to the pulp pump inlet, and a cationic polyacrylamide retention aid (GPAM retention aid, the dosage can be 0.3-0.6 kg / t paper) is added to the pulp pump outlet.

[0033] Furthermore, the dosage of the cationic starch can be 8-10 kg / ton of finished paper; the dosage of the AKD is preferably 15-20 kg / ton of finished paper. The AKD is added at the pulping inlet to control the Cobb value of the finished paper to be 25-30 g / m 2 ; Preferably, cationic polyacrylamide is added at the pulping outlet at a dosage of 0.2-0.4 kg per ton of paper. The specifications of the cationic acrylic resin include: solid content of 33-36%, pH value of 5-7, anion requirement of 125-200ueq / L; the specifications of the spherical anionic polyacrylamide include: solid content of 2%, polymerization degree of 150,000-300,000.

[0034] In the pulp described in the embodiment of the present invention, the lower the ratio of chemical mechanical pulp, the more significant the effect of using porous calcium silicate, mainly because the bulk of chemical mechanical pulp is higher than that of chemical pulp. The principle of the porous calcium silicate involved in the process of the embodiment of the present invention to increase the bulk of the finished paper includes: the cationic acrylic resin can first wrap the porous calcium silicate to form particles with a positive charge, and then electrostatically adsorb with the negatively charged spherical polyacrylamide. Since the spherical polyacrylamide has a large number of cationic tentacles, it can effectively capture calcium silicate and cationic acrylic resin, thereby increasing the retention rate of calcium silicate and retaining it in the paper as much as possible. Therefore, if the amount of cationic acrylic resin and spherical polyacrylamide is too low, it is easy to cause incomplete wrapping of calcium silicate and reduce the retention rate, which ultimately leads to a decrease in the effect of calcium silicate on improving bulk.

[0035] After the sizing is completed, the slurry in the embodiment of the present invention is put on the screen by the sizing system, and then the wet paper sheet is made, formed, dried before, sizing on the surface, dried after, and rolled up. The surface sizing process includes: the mass concentration of the enzyme-converted starch glue can be 10%-15% (the viscosity at room temperature can be 5-20mpa·s), the sizing amount is 40-60kg / ton of paper (the sizing amount is 5-6g / m 2 control).

[0036] The embodiments of the present invention have no special restrictions on other process conditions. For example, the pulp concentration on the net can be 0.75-1.03%, the pH value is 7.0-8.5; the pulp-to-net speed ratio is 1.02-1.03. The dehydration involved is a pressing method, double shoe pressing, the first pressing pressure is 700N / m, the second pressing pressure is 900N / m, and the water content after pressing can be 48-52%. The mass concentration of the surface sizing material is 10-15%, and the sizing amount is 5-6g / m 2 Control; the front and rear drying temperatures are usually 50-110°C, there are 5 groups of drying cylinders, and the speed difference of each group can be 0-4m / min; the moisture content before drying is preferably 5-7%, and the moisture content after drying is preferably 6-8%.

[0037] The paper produced by the above process according to the embodiment of the present invention can have a basis weight of 65-80g / m 2 The performance meets the basic requirements of light paper, copy paper or notebook paper, especially the bulkiness has been significantly improved. For example, the bulkiness of the finished paper ranges from 1.4 to 2.0 cm. 2 In some specific embodiments, the amount of chemical mechanical pulp in the copy paper ratio is small, generally only 0-15%; while in other embodiments, the amount of chemical mechanical pulp in the book paper ratio is larger, generally reaching 20-92%, and other papermaking processes are roughly the same.

[0038] In order to further understand the present invention, the method and process for preparing paper provided by the present invention are described in detail below in conjunction with the examples, and the protection scope of the present invention is not limited by the following examples. In the examples, all raw reagents and materials can be obtained commercially, and the experimental methods without specifying specific experimental conditions are conventional methods and conditions well known in the art.

[0039] The pulp used is commercial bleached coniferous chemical pulp, commercial bleached hardwood chemical pulp and the company's own bleached hardwood chemical mechanical pulp, and the specific parameters are as described above. The specific indicators of the porous calcium silicate involved are: the crystal shape is elliptical, honeycomb-shaped, the median particle size is 4.8-6.2 microns, the density is 0.15-0.2g / cm3, and the ISO whiteness is 94-96%; the configuration is as follows: add clean water to the material preparation tank, turn on the stirrer, and then add inorganic bulking agent porous calcium silicate to prepare a concentration of 10-15%, turn on the transfer pump, and pump the stirred porous calcium silicate mixture into the storage tank.

[0040] The specifications of the cationic acrylic resin include: solid content of 33-36%, pH value of 5-7, anion demand of 125-200ueq / L; the specifications of the spherical anionic polyacrylamide include: solid content of 2%, polymerization degree of 150,000-300,000.

[0041] Embodiment 1:

[0042] First, the softwood chemical pulp board is sent to the hydraulic pulping for disintegration, and then sent to the pre-beating pool. The bleached chemical mechanical pulp is pumped from the self-produced bleached chemical mechanical pulp workshop to the chemical mechanical pulp pre-beating pool. Then it is pumped from the pre-beating pool to the corresponding mill for beating. The pulping concentration of softwood chemical pulp is controlled at 4.0-4.5%, and the beating degree is beaten to 38-40°SR; the pulp concentration of bleached chemical mechanical pulp is controlled at 4.0-4.5%, and the beating degree is controlled at 52-56°SR. The beaten pulp is sent to the post-beating pool.

[0043] Then the pulp is diluted with white water and sent to the pulping tank, and the pulp is prepared according to the ratio of softwood chemical pulp: chemical mechanical pulp = 8:92. In the pulping tank, 285kg / t of calcium carbonate filler and 65kg / t of porous calcium silicate are added, as well as 1.0kg / t of cationic acrylic resin; at the same time, 0.3kg / t of spherical anionic polyacrylamide is added to the paper machine tank, 10kg / t of cationic starch is added to the outlet of the high-level box, and 15kg / t of AKD is added to the inlet of the pulping pump to control the Cobb value of the finished paper at 25-30g / m 2 The slurry is sent to the cleaner by the slurry pump and then to the sizing system by the sizing pump, and 0.3kg / t paper cationic polyacrylamide retention aid (GPAM retention aid) is added at the outlet of the sizing pump.

[0044] The slurry is then put on the sizing system for papermaking, forming, and surface sizing (sizing amount is 5-6g / m 2 The mass concentration of the enzyme-converted starch glue is 15% (the viscosity at room temperature can be 15-20mpa·s).

[0045] The paper produced by the above process is light paper, and its main indicators include: basis weight 76.1g / m 2 , thickness 152.3μm, bulk thickness 2.00cm 3 / g, Cobb value 21.5g / m 2 , longitudinal tear length 3.58km, transverse tear length 2.28km, longitudinal stiffness 111.0mN, transverse stiffness 73.1mN, whiteness 77.9%ISO, moisture 6.6%, surface fuzzing coefficient 4.7, smoothness controlled at 7-10s, no paper hair.

[0046] In addition, the finished paper is compared with the paper without porous calcium silicate, see Table 1. The first pass retention of the embodiment of the present invention is increased by 8.8%, the paper sample bulk is increased by 5.3%, the longitudinal stiffness is increased by 6.7%, and the ash content of the finished paper is increased by 6.9%. Other indicators have little change, and can meet the basic requirements of existing light paper.

[0047] Embodiment 2:

[0048] First, the softwood chemical pulp board and the hardwood chemical pulp board are sent to the hydraulic pulping for disintegration, and then sent to their respective pre-beating pools. The bleached chemical-mechanical pulp is pumped from the self-produced bleached chemical-mechanical pulp workshop to the chemical-mechanical pulp pre-beating pool. Then, the pulp is pumped from the pre-beating pool to the corresponding mill for beating. The beating concentration of softwood chemical pulp is controlled at 4.0-4.2%, and the beating degree is beaten to 38°SR; the beating concentration of hardwood chemical pulp is controlled at 4.0-4.3%, and the beating degree is beaten to 41°SR. The pulp concentration of chemical-mechanical pulp is controlled at 4.1%, and the beating degree is controlled at 53°SR. The beaten pulp is sent to the post-beating pool.

[0049] Then, pulp is prepared in the ratio of coniferous wood chemical pulp: hardwood chemical pulp: chemical mechanical pulp = 20:65:15, and 300kg / t of calcium carbonate filler and 50kg / t of porous calcium silicate are added to the pulping tank, as well as 0.8kg / t of cationic acrylic resin; at the same time, 0.4kg / t of spherical anionic polyacrylamide is added to the paper machine tank, 9kg / t of cationic starch is added to the outlet of the high-level box, and 20kg / t of AKD is added to the inlet of the pulping pump to control the Cobb value of the finished paper at 25-30g / m 2 The slurry is sent to the cleaner by the slurry pump and then to the sizing system by the sizing pump, and 0.3kg / t paper cationic polyacrylamide retention aid (GPAM retention aid) is added at the outlet of the sizing pump.

[0050] The slurry is then put on the sizing system for papermaking, forming, and surface sizing (sizing amount is 5-6g / m 2 The mass concentration of the enzyme-converted starch glue is 12%.

[0051] The finished paper produced according to the above process is copy paper, and its main indicators include: basis weight 80g / m 2 , thickness 116μm, bulk thickness 1.45cm 3 / g, Cobb value 25.6g / m 2 , longitudinal tear length 4.68km, transverse tear length 2.51km, longitudinal stiffness 138mN, transverse stiffness 68.2mN, whiteness 105.9%ISO, moisture 6.6%, surface fuzzing coefficient 5.5, smoothness 36s, no paper hair.

[0052] And, compared with the paper without porous calcium silicate, see Table 1. The first pass retention of the embodiment of the present invention is increased by 8.5%, the paper sample bulk is increased by 7.4%, the longitudinal stiffness is increased by 9.5%, and the ash content of the paper is increased by 4.4%, which can meet the basic requirements of all-in-one copy paper.

[0053] Embodiment 3:

[0054] First, the softwood chemical pulp board and the hardwood chemical pulp board are sent to the hydraulic pulping for disintegration, and then sent to their respective pre-beating pools. The bleached chemical mechanical pulp is pumped from the self-produced bleached chemical mechanical pulp workshop to the chemical mechanical pulp pre-beating pool. Then, the pulp is pumped from the pre-beating pool to the corresponding mill for beating. The beating concentration of softwood chemical pulp is controlled at 4.0-4.5%, and the beating degree is beaten to 38-40°SR; the beating concentration of hardwood chemical pulp is controlled at 4.2%, and the beating degree is beaten to 40-42°SR. The pulp concentration of chemical mechanical pulp is controlled at 4.0-4.5%, and the beating degree is controlled at 54°SR. The beaten pulp is sent to the post-beating pool.

[0055] The pulp is diluted with white water and sent to the pulping tank, and the pulp is prepared in the ratio of softwood chemical pulp: hardwood chemical pulp: chemical mechanical pulp = 24:33:43. In the pulping tank, 300kg / t of calcium carbonate filler and 50kg / t of porous calcium silicate are added, as well as 1.0kg / t of cationic acrylic resin; at the same time, 0.4kg / t of spherical anionic polyacrylamide is added to the paper machine tank, 10kg / t of cationic starch is added to the outlet of the high-level box, and 20kg / t of AKD is added to the inlet of the pulping pump to control the Cobb value of the finished paper at 25-30g / m 2 The slurry is sent to the cleaner by the slurry pump and then to the sizing system by the sizing pump, and 0.3kg / t paper cationic polyacrylamide retention aid (GPAM retention aid) is added at the outlet of the sizing pump.

[0056] The slurry is then put on the sizing system for papermaking, forming, and surface sizing (sizing amount is 5-6g / m 2 Control), drying, and winding to obtain paper. Among them, the mass concentration of enzyme-converted starch glue is 12%. In addition, in Examples 1-3, the pulp concentration on the net is 0.75-1.03%, the pH value is 7.0-8.5; the pulp-to-net speed ratio is 1.02-1.03. The dehydration involved is a pressing method, double-shoe pressing, the first pressing pressure is 700N / m, the second pressing pressure is 900N / m, and the pressing moisture is 48-52%. The front and rear drying temperatures are usually 50-110°C, there are 5 groups of drying cylinders, and the speed difference of each group is 0-4m / min; the drying moisture before output is 5-7%, and the drying moisture after output is 6-8%.

[0057] The paper produced according to the process of the above embodiment 3 is a book paper, and its main indicators include: basis weight 65.8g / m 2 , thickness 112.8μm, bulk thickness 1.71cm 3 / g, Cobb value 24.1g / m 2 , longitudinal tear length 3.60km, transverse tear length 1.72km, longitudinal stiffness 60mN, transverse stiffness 27mN, whiteness 76.9%ISO, moisture 6.5%, surface fuzzing coefficient front side 2.2, back side 1.8, smoothness control 20s, no paper hair. And compared with the finished paper without adding porous calcium silicate, see Table 1. The first-pass retention of the embodiment of the present invention is increased by 8.8%; the paper sample bulk is increased by 11.8%, the longitudinal stiffness is increased by 9.1%, and the ash content of the finished paper is increased by 6.7%. Other indicators do not change much, and can meet the basic requirements of existing high-bulk thin paper.

[0058] Table 1 Paper quality test results when different amounts of porous calcium silicate are added

[0059]

[0060] As can be seen from the above examples, the embodiments of the present invention use a specific chemically modified porous calcium silicate, which can improve the paper retention rate and significantly increase the paper bulk, and can also improve the paper stiffness and opacity, meet the customer's requirements for the paper bulk, and can reduce the amount of plant fiber (the amount of fiber is reduced and the ash content of the paper is increased), thereby reducing production costs. The paper produced by this method increases the paper bulk by 5-12% while maintaining the original performance, and the production cost is low.

[0061] The above examples are only used to illustrate the technical features and implementation process of the present invention, rather than to limit the technical solution of the present invention. It should be pointed out that for ordinary technicians in this field, the present invention can still be modified or replaced by equivalents, and modifications or replacements that do not deviate from the principles of the present invention are all covered by the protection of the present invention.

Claims

1. A method for preparing high bulk paper, characterized in that: The following steps are involved: The invention relates to a method for preparing pulp by using coniferous wood chemical pulp, hardwood chemical pulp and bleached chemimechanical pulp as fiber raw materials in proportion. The chemical additives added in the pulping process include porous calcium silicate, paper machine filler, cationic acrylic resin, spherical anionic polyacrylamide, cationic starch, alkyl ketene dimer and cationic polyacrylamide. The amount of the porous calcium silicate is 30-60 kg / ton of finished paper. The prepared slurry is sizing, dewatering and forming on a wire to form wet paper. The wet paper is subjected to pressing, pre-drying, surface sizing and post-drying to obtain finished paper; the sizing agent used in the surface sizing is enzyme-converted starch glue, and the sizing amount of the surface sizing is 40-60kg per ton of finished paper.

2. The method according to claim 1, characterized in that The softwood chemical pulp and hardwood chemical pulp are both bleached pulp boards; the bleached chemimechanical pulp is bleached hardwood chemimechanical pulp; the mass ratio of the softwood chemical pulp, hardwood chemical pulp and bleached chemimechanical pulp is 8-25:0-65:15-92.

3. The method according to claim 2, characterized in that The beating concentration of the softwood chemical pulp is 4.0-4.5%, and the beating degree is 38-40°SR; the beating concentration of the hardwood chemical pulp is 4.0-4.5%, and the beating degree is 40-42°SR; the pulp concentration of the bleached chemimechanical pulp is 4.0-4.5%, and the beating degree is 52-56°SR.

4. The method according to any one of claims 1 to 3, characterized in that: The porous calcium silicate crystal is elliptical and honeycomb-shaped, with a median particle size of 4.8-6.2 microns and a density of 0.15-0.2 g / cm 3 , ISO whiteness is 94-96%.

5. The method according to any one of claims 1 to 3, characterized in that: The porous calcium silicate is added after the paper machine filler is added; the paper machine filler is calcium carbonate.

6. The method according to any one of claims 1 to 3, characterized in that: The prepared slurry is sized after screening, seasoning, flushing, sand removal and degassing, and then finely screened and dehydrated on a wire to form wet paper.

7. The method according to claim 6, characterized in that The dosage of the cationic starch is 8-10 kg / ton of finished paper; the dosage of the alkyl ketene dimer is 15-20 kg / ton of finished paper.

8. The method according to claim 7, characterized in that The alkyl ketene dimer is added at the pulping inlet to control the Cobb value of the finished paper to be 25-30 g / m 2 ; Add cationic polyacrylamide at the pulping outlet at a dosage of 0.2-0.4 kg per ton of paper.

9. The method according to any one of claims 1 to 3, characterized in that: The basis weight of the finished paper is 65-80 g / m 2 , which is light paper, copy paper or notebook paper.

10. The method according to claim 9, characterized in that The bulk thickness of the finished paper is 1.4-2.0 cm 2 / g.

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