Kraft paper and preparation method thereof

Abstract

The invention relates to craft paper and a preparation method thereof. The preparation method comprises the following steps: adding an attapulgite clay water suspension dispersed by adopting a high-speed stirring method into OCC waste paper pulp, uniformly mixing, and carrying out papermaking; the addition amount of the attapulgite clay is 10-40kg / t finished paper. Compared with the prior art, the method has the advantages that the original compact aggregate and crystal bundles of the attapulgite clay are disassembled through high-speed stirring, a new loose slender crystal bundle and rod crystal structure which can be easily combined with fine paper fibers is formed, Si-OH groups on the surface of the attapulgite clay are also increased, and thus better hydration and adsorption effects are achieved. The attapulgite crystal clay fibers and fine fibers of the OCC waste paper pulp are wound and adsorbed and are effectively retained in paper webs of the craft paper in the papermaking process, meanwhile, the retention rate of the OCC waste paper pulp fibers is increased, the ash content of finished paper is increased, and the retention rate is effectively increased.

Description

Technical Field

[0001] The present invention relates to the field of papermaking, in particular to kraft paper and a preparation method thereof. Background Art

[0002] In the papermaking industry, filling refers to the addition of inorganic fillers such as calcium carbonate, talc, and kaolin to the paper pulp during the paper production process. Filling is a well-established papermaking process, primarily designed to replace expensive papermaking fiber raw materials with lower-cost fillers. Traditional papermaking fillers like calcium carbonate, talc, and kaolin, which fill the interwoven network of paper fibers, negatively impact and hinder fiber bonding. This significantly reduces the paper's tensile strength, bursting strength, and folding resistance.

[0003] Kraft paperboard must strictly meet the required tensile strength, bursting strength, folding strength and other strengths to meet the requirements of manufacturing strong cartons, so conventional filling processes are not applicable. Summary of the Invention

[0004] Therefore, it is necessary to provide a kraft paperboard and a preparation method thereof that uses attapulgite clay filler to replace part of the pulp. This method also increases the ash content of the finished kraft paperboard, effectively improves the retention rate, and reduces the amount of pulp and various additives used in the kraft paperboard.

[0005] The present invention first provides a method for preparing kraft paper, comprising the following steps: adding an attapulgite clay aqueous suspension dispersed by a high-speed stirring method to OCC waste paper pulp, mixing them uniformly, and then making paper, wherein the attapulgite clay is added in an amount of 10 to 40 kg / t of paper.

[0006] High-speed stirring, through hydration and intense shearing of the attapulgite clay, breaks up the original crystal bundles and aggregates, forming fine crystal bundles and rods. These rods are less susceptible to breakage even at high water concentrations. The structure of the attapulgite clay in the aqueous suspension after high-speed stirring undergoes significant changes: first, the crystal bundles become slender, loosely interlaced, and form numerous open pores. This also gives the attapulgite clay crystal bundles a high specific surface area, enhancing their adsorption and increasing the number of Si-OH groups on their surface, resulting in better hydration.

[0007] The attapulgite fibers in the attapulgite clay water suspension have a high binding force with the OCC waste paper pulp because:

[0008] (1) The high aspect ratio of attapulgite fiber makes it easy to form a entanglement effect: attapulgite has a unique rod-shaped and fibrous crystal structure (its diameter is 20-50 nm, length is 0.5-1 μm, and aspect ratio is 20-50). It is a natural nano-scale mineral fiber material. Its high aspect ratio makes it easy to entangle with pulp fibers and form a three-dimensional network entanglement structure with the fibers.

[0009] (2) The large specific surface area of attapulgite clay and the surface roughness matching the fiber make it easy to adsorb with OCC fiber: attapulgite clay is nano-sized particles. When dispersed by high-speed stirring method, the dispersed particle size is about 46 μmq, and the specific surface area is measured to be 1876 m 2 / kg, has a large specific surface area, and its surface concave-convex structure can increase the contact area with the fiber, showing strong mutual adsorption with OCC fiber.

[0010] (3) Hydrogen bonding: The abundant silicon hydroxyl groups (Si-OH) on the surface of attapulgite clay form a hydrogen bonding network with the hydroxyl groups (-OH) on the fiber surface, which enhances the bonding force between fiber-attapulgite-fiber.

[0011] (4) Electrostatic interaction: Under the pH value (6-8) of the papermaking wet end, the fiber surface is negatively charged (zeta potential is about -15mV), and the attapulgite clay is weakly negatively charged (zeta potential is about -5mV). The electrostatic interaction causes them to adsorb each other. In addition, there are divalent cations (Ca) from the papermaking white water in the papermaking wet end. 2+ Mg 2+ ), can be combined with divalent cations (Ca 2+ Mg 2+ ) to achieve electrical adsorption. Furthermore, the addition amount of the attapulgite clay is 30-40 kg / t of paper.

[0012] Furthermore, the attapulgite clay aqueous suspension has a solid content of 10-20%, a pH value of 8-10, and a viscosity of 20-250 mPa.s.

[0013] Furthermore, the attapulgite clay water suspension is added to the mixed pulp tanks of the surface, core and bottom layers of the paper machine, and is stirred with the OCC waste paper pulp in the mixed pulp tank for 10 to 30 minutes before papermaking.

[0014] Furthermore, the attapulgite clay has a dynamic viscosity of 20-500 mPa.s and a particle size of less than 200 mesh. Furthermore, the CaO content in the attapulgite clay is less than 7.0 wt%, and the oxides further include MgO 1.5-10 wt%, and Si2O4 50-65 wt%.

[0015] Furthermore, the preparation of the attapulgite clay aqueous suspension comprises the following steps: mixing attapulgite clay with water, and stirring the mixture with a high-speed stirrer at 1000 to 1500 rpm for 10 to 90 minutes to obtain the attapulgite clay aqueous suspension.

[0016] Furthermore, the preparation of the attapulgite clay aqueous suspension includes the following steps: mixing attapulgite clay with water, stirring with a high-speed stirrer at 1000-1500 rpm for 10-90 minutes, and then filtering through a 60-mesh sieve to remove impurities to obtain the attapulgite clay aqueous suspension.

[0017] Furthermore, in the slurry preparation step, the attapulgite clay water suspension is diluted to a solid content of 5 to 10% and then added to the OCC waste paper pulp for slurry preparation.

[0018] The present invention further provides a kraft paper, which is prepared by the above-mentioned preparation method.

[0019] Unlike existing technologies, high-speed stirring breaks up the dense aggregates and crystal bundles of attapulgite clay, forming new, loose, elongated crystal bundles and rods that easily bind to fine paper fibers. This also increases the number of Si-OH groups on the surface, resulting in better hydration and adsorption. The attapulgite crystal clay fibers entangle and adsorb with the fine fibers of OCC waste pulp, effectively retaining them in the kraft paper web during the papermaking process. This also improves the retention rate of the OCC waste pulp fibers, increases the ash content of the finished paper, and effectively increases the retention rate. DETAILED DESCRIPTION

[0020] In order to explain the technical content, structural features, achieved objectives and effects of the technical solution in detail, the following is a detailed description in conjunction with specific embodiments.

[0021] In order to explain in detail the possible application scenarios, technical principles, specific solutions that can be implemented, and the purpose and effects achieved by this application, the following is a detailed description of the specific embodiments listed. The embodiments described herein are only used to more clearly illustrate the technical solutions of this application and are therefore only examples and are not intended to limit the scope of protection of this application.

[0022] References to "embodiments" herein mean that the specific features, structures, or characteristics described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the word "embodiment" in various places in the specification does not necessarily refer to the same embodiment, nor does it particularly limit its independence or relevance to other embodiments. In principle, in this application, as long as there are no technical contradictions or conflicts, the various technical features mentioned in the embodiments can be combined in any manner to form a corresponding implementable technical solution.

[0023] Unless otherwise defined, the technical terms used herein have the same meanings as those generally understood by those skilled in the art to which this application belongs; the use of relevant terms herein is only for describing specific embodiments and is not intended to limit this application.

[0024] In the description of this application, the term "and / or" is used to describe a logical relationship between objects, indicating that three relationships can exist. For example, A and / or B means: A exists, B exists, and both A and B exist. In addition, the character " / " in this document generally indicates that the objects before and after are in a logical "or" relationship.

[0025] In this application, terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual quantity, priority or sequence relationship between these entities or operations.

[0026] Without further limitations, in this application, the words "include", "comprise", "have" or other similar expressions used in the sentences are intended to cover non-exclusive inclusion. These expressions do not exclude the presence of additional elements in the process, method or product including the elements, so that the process, method or product including a series of elements may include not only those defined elements, but also other elements not explicitly listed, or elements inherent to such process, method or product.

[0027] Consistent with the understanding in the Examination Guidelines, in this application, expressions such as "greater than," "less than," and "exceed" are understood to exclude the number itself; expressions such as "above," "below," and "within" are understood to include the number itself. Furthermore, in the description of the embodiments of this application, "multiple" means more than two (including two), and similar expressions related to "multiple" are also understood in this manner, such as "multiple groups," "multiple times," etc., unless otherwise specifically defined.

[0028] 1. Testing of properties of attapulgite clay, specific grade of attapulgite clay.

[0029] Attapulgite clay is a clay mineral with attapulgite as its main component. In addition to attapulgite, it often contains minerals such as dolomite, montmorillonite, illite, hydromica, sepiolite, quartz, opal, and carbonates.

[0030] GB / T 41741-2022 Attapulgite clay classification and testing method was used to classify the attapulgite clay.

[0031] Classification and expression of dynamic viscosity of attapulgite clay:

[0032]

[0033] According to the dynamic viscosity of attapulgite, it is classified into:

[0034] The attapulgite clay with a dynamic viscosity of grade 4 (the dynamic viscosity of attapulgite clay is 20-500 mPa.s) and a particle size of less than 200 mesh is used.

[0035] Dynamic viscosity level 4 attapulgite clay is cost-effective and has a particle size of less than 200 mesh. After high-speed dispersion, the fiber lattice structure becomes more slender and has a larger specific surface area. After addition, it is effectively retained in the paper, effectively increasing the strength of the finished paper and effectively reducing the unit consumption of waste paper raw materials.

[0036] The oxides include MgO 1.5-10wt%, Si2O4 50-65wt%, of which CaO <7.0wt%. CaO <7.0wt% is to prevent excessive content of Ca-containing hard impurities (quartz sand, calcium carbonate, etc.) to avoid abnormal wear of paper machine equipment and process spare parts.

[0037] 2. Factors affecting the dispersion effect of attapulgite clay:

[0038] Attapulgite clay has a good dispersing effect, which is beneficial to paper uniformity, strength, and paper machine wire retention. Under laboratory conditions, attapulgite clay dispersion preparation tests were conducted at different concentrations, stirring speeds, and stirring times. The results are as follows:

[0039] 1. Test of dispersion preparation of attapulgite clay at different concentrations. The results are shown in Table 1

[0040] Table 1

[0041] concentration% Stirring speed rpm Stirring time min Viscosity mPa·s 10 8000 25 80 15 8000 25 420 20 8000 25 830

[0042] Experimental results show that the preparation concentration affects the dispersion of attapulgite clay. Under the same stirring speed and time, higher preparation concentrations result in higher viscosity and better dispersion. At a stirring concentration of 20%, strong hydraulic shear partially exfoliates the attapulgite layered structure, exposing more active edge sites and improving performance. However, too high a stirring concentration can damage the attapulgite structure, affecting performance; too low a concentration can prevent effective exfoliation, also impacting performance.

[0043] 2. Test of dispersion preparation of attapulgite clay at different stirring speeds. The results are shown in Table 2

[0044] Table 2

[0045] concentration% Stirring speed rpm Stirring time min Viscosity mPa·s 20 1000 30 240 20 1500 30 460 20 8000 30 840

[0046] The experimental results show that the stirring speed of the stirrer will affect the dispersion effect of attapulgite clay. Under the conditions of the same preparation concentration and stirring time, the higher the stirring speed, the higher the viscosity of the attapulgite clay and the better the dispersion effect.

[0047] 3. Test of dispersion preparation of attapulgite clay under different stirring times. The results are shown in Table 3

[0048] Table 3

[0049] concentration% Stirring speed rpm Stirring time min Viscosity mPa·s 20 1000 30 130 20 1000 45 200 20 1000 60 265

[0050] The experimental results show that the stirring time of the stirrer affects the dispersion effect of attapulgite clay. Under the conditions of the same preparation concentration and stirring speed, the longer the stirring time, the higher the viscosity of the attapulgite clay and the better the dispersion effect.

[0051] 4. Orthogonal test:

[0052] The more fully dispersed the fibers are in the suspension, the smaller the equivalent diameter of the fibers will be, and the longer the settling time will be in the medium. Therefore, the dispersion quality of attapulgite can be examined through settling experiments of attapulgite slurries.

[0053] In order to explore the dispersion preparation process of attapulgite clay for large-scale industrial production, the following three-factor three-level orthogonal test was conducted. The results are shown in Table 4:

[0054] Table 4

[0055]

[0056] 5. Orthogonal test range analysis:

[0057] a. Solution concentration (10%, 15%, 20%)

[0058] 10%: x1=(40+47+87) / 3=58

[0059] 15%: x2=(38+55+90) / 3=61

[0060] 20%: x3=(57+58+92) / 3=69

[0061] Range R1 = x3 - x1 = 69 - 58 = 11

[0062] b. Stirring speed (1000rpm, 1500rpm, 3000rpm)

[0063] 1000rpm: y1=(40+38+57) / 3=45

[0064] 1500rpm: y2=(47+55+58) / 3=53.3

[0065] 3000rpm: y3=(87+90+92) / 3=89.7

[0066] Range R2 = y3 - y1 = 89.7 - 45 = 44.7

[0067] c. Stirring time (30min, 45min, 60min)

[0068] 30min: z1=(40+90+58) / 3=62.7

[0069] 45min: z2=(47+38+92) / 3=59

[0070] 60min: z3=(87+55+57) / 3=66.3

[0071] Range R3 = z3 - z1 = 66.3 - 59 = 7.3

[0072] The maximum range of stirring speed is 44.7%, followed by solution concentration at 11%, and stirring time at 7.3%. Therefore, the factors affecting the dispersion of attapulgite clay are: stirring speed is the main factor, followed by solution concentration, and stirring time has the least influence.

[0073] At the same time, high-speed stirring at speeds exceeding 1000 rpm hydrates the attapulgite clay and exerts strong shearing action, breaking up the original crystal bundles and aggregates into fine crystal bundles and rods. These rods are less susceptible to breakage at high water concentrations. The structure of the attapulgite clay in the aqueous suspension after high-speed stirring also undergoes significant changes: first, the crystal bundles become slender, loosely interlaced, and form numerous open pores. This also gives the attapulgite clay bundles a high specific surface area, enhancing their adsorption and increasing the number of Si-OH groups on their surface, resulting in better hydration.

[0074] 3. Adjustment of industrial production parameters:

[0075] According to the existing production practice and equipment power, the stirring speed is set to 1000-15000 rpm, the dispersion concentration is 10-20%, and the stirring time is 10-90 minutes.

[0076] 4. Copy test:

[0077] 1. Use a grade 4 dynamic viscosity (20-500 MPa.s for attapulgite clay) with a particle size less than 200 mesh. Mix attapulgite clay containing 1.5-10 wt% MgO, 50-65 wt% SiO, and <7.0 wt% CaO with water. Stir the mixture at 1000 rpm in a high-speed blender for 45 minutes to achieve a good dispersion. The resulting attapulgite clay suspension has a solids content of 20% and a dynamic viscosity of 200 MPa.s.

[0078] 2. The prepared attapulgite clay suspension was mixed with OCC waste paper pulp and a sheeting test was performed. The results are shown in Table 5. The retention and enhancement results were analyzed and evaluated:

[0079] Table 5

[0080]

[0081] From the results in Table 5 we can see that

[0082] (1) When the addition amount is 2%, the quantitative increase of the blank sample is 10.8%; when the addition amount is 3%, the quantitative increase of the blank sample is 13.8%. The quantitative increase of attapulgite clay is significantly higher than the addition ratio, indicating that the attapulgite clay has a positive effect on retention.

[0083] (2) The tear resistance and ring pressure of the sheet do not change much.

[0084] (3) The ash content of the sheets is increased.

[0085] 3. The above-mentioned attapulgite clay slurry was mixed with OCC waste paper pulp and a sheet making test was carried out. The results are shown in Table 6, which analyzes the feasibility of adding attapulgite clay to kraft paperboard:

[0086] Table 6

[0087]

[0088] From the results in Table 6 we can see that

[0089] (1) When attapulgite clay was added at 10-30 kg / t, the bursting strength, ring crush strength and breaking length of the kraft paperboard were higher than those of the blank sample, indicating that the addition of attapulgite clay was feasible.

[0090] (2) When attapulgite clay is added at 50 kg / t, the bursting strength, ring crush strength and breaking length of kraft paperboard are lower than those of the blank sample, indicating that there is an inflection point when the addition amount is between 30 and 50 kg / t. In actual production, the papermaking process should be adjusted according to the required indicators.

[0091] In this embodiment, the attapulgite clay used is the attapulgite clay of model XHY and dynamic viscosity level 4, which is produced by Xuyi Huixinyuan Attapulgite New Materials Co., Ltd.

[0092] The attapulgite clay aqueous suspension in this embodiment is prepared in the following manner:

[0093] The attapulgite clay was mixed with water, stirred with a high-speed stirrer at 1000 rpm for 45 minutes, and then passed through a 60-mesh sieve to remove impurities, thereby obtaining an attapulgite clay aqueous suspension with a solid content of 20% and a dynamic viscosity of 200 mPa.s.

[0094] Examples 1-5

[0095] 1. Pulping: 100% OCC waste paper raw materials are graded and processed on the OCC waste paper pulping line to produce OCC long fiber, OCC medium fiber and OCC short fiber pulp. The pulp characteristics are as follows:

[0096] OCC long fiber pulp beating degree 20-30. SR, fiber wet weight 5.0-8.0g

[0097] The fiber pulp in OCC has a beating degree of 25-35. The fiber wet weight of SR is 4.5-6.0g.

[0098] OCC short fiber pulp beating degree 30-45. SR, fiber wet weight 3.5-5.0g

[0099] 2. Slurry preparation:

[0100] The attapulgite clay water suspension is added to the mixed pulp tanks of the surface, core and bottom layers of the paper machine, and is stirred with the OCC waste paper pulp in the mixed pulp tank for 10 to 30 minutes before papermaking.

[0101] Surface layer: medium fiber 92-99.7wt%, attapulgite clay 0.3-10wt%;

[0102] Core layer: long fiber 40-47wt%, short fiber 45-59.7wt%, attapulgite clay 0.3-10wt%.

[0103] Bottom layer: 40-47 wt% of long fibers, 45-59.7 wt% of short fibers, and 0.3-10 wt% of attapulgite clay.

[0104] 3. Copying:

[0105] After mixing and preparing the pulp, the paper feeder's short circulation system dilutes, screens, and purifies the pulp, and then the paper feeder's wire section begins papermaking. The papermaking process includes flow and distribution of the pulp, dewatering and forming in the wire section, pressing and dewatering in the press section, pre-drying in the paper machine, sizing in the surface sizing press, drying in the post-drying section, and calendering.

[0106] According to the operation status of each part of the paper machine and the paper production indicators, adjust the papermaking process and raw material and auxiliary material process of each part of the paper machine to ensure that the operating speed and output of the paper machine are normal and the paper quality indicators are qualified.

[0107] 4. Parameters and result analysis:

[0108] The process conditions, wire retention rates, and finished paper quality indicators of the blank examples and Examples 1-5 with different attapulgite clay addition amounts are shown in Table 7:

[0109] Table 7 Process parameters and performance indexes of kraft paper of Examples 1-5

[0110]

[0111]

[0112] When the addition amount of attapulgite clay is 10-50kg / t paper, the paper machine operates normally, the speed and output are normal, and the quality indicators of the finished paper such as bursting strength, folding strength, and ring crush strength are qualified.

[0113] 1) After adding attapulgite clay, the consumption of waste paper pulp decreases:

[0114] After adding attapulgite clay, the white water concentration below the wire did not increase but instead decreased, and the retention rate at all paper machine layers increased. This indicates that the addition of attapulgite clay retained the majority of the clay in the paper, and also improved the retention of fine fibers and other fillers on the paper machine. An increase in the ash content of the finished paper was detected, and the number of points of ash increase coincided with the amount of attapulgite clay added, indicating that the attapulgite clay was effectively retained in the paper, increasing the ash content of the finished paper.

[0115] Adding 10-50 kg / t of attapulgite clay reduces waste paper consumption per ton of paper. In actual production, the white water concentration below the wire end of the paper machine decreased from 0.7-0.8% to 0.4-0.5%, and the first-pass retention rate on the wire section increased from 50-52% to 60-64%. This demonstrates that the attapulgite clay effectively retains the paper while also effectively improving the retention of fine fibers and fillers, replacing waste paper raw material fibers and reducing waste paper raw material consumption per ton. Taking into account paper machine operating efficiency, output, and raw material cost-effectiveness, the optimized process was determined: adding 30-40 kg / t of attapulgite clay reduces OCC waste paper consumption by 30-40 kg / t.

[0116] 2) Adding attapulgite clay increases the retention rate and reduces the retention and filtration aids:

[0117] After adding attapulgite clay, the white water concentration under the paper machine wire decreased and the wire retention rate increased (the white water concentration under the wire decreased from 0.6-0.8% to 0.4-0.5%, and the white water concentration decreased by 30-40%. The first-pass retention rate of the wire increased from 50-55% to 65-70%, and the first-pass retention rate increased by 30-40%).

[0118] Therefore, based on the operation of different grammage kraft paperboard machines and paper quality requirements, the dosage of papermaking retention aid (cationic polyacrylamide, molecular weight 8 million, dosage 0.4-0.6 kg / t paper) and papermaking filter aid (cationic polyacrylamide, molecular weight 5 million, dosage 0.4-0.6 kg / t paper) can be appropriately reduced. After adjustment, the papermaking retention aid dosage is 0.25-0.45 kg / t paper, a decrease of 25-40%. The papermaking filter aid dosage (0-0.2 kg / paper) is a decrease of 50-100%, indicating that attapulgite clay can still play a partial role in papermaking retention and filtration.

[0119] 3) After adding attapulgite clay, the amount of defoamer used is reduced: because the concentration of white water under the screen is effectively reduced, the air content of white water and the slurry on the screen is reduced, and the amount of defoamer used is reduced from 0.5-0.7 kg / t paper to 0.3-0.4 kg / t paper, and the defoamer amount is reduced by 30-40%.

[0120] 4) After adding attapulgite clay, the dye amount does not change much: After adding attapulgite clay, the amount of papermaking dye does not change much and remains the original process amount.

[0121] 5) After adding attapulgite clay, the water absorption of the finished paper does not change much. Sizing agent (AKD) and surface sizing agent: After adding attapulgite clay, the water absorption of the finished paper does not change much. The dosage of AKD and surface sizing agent remains at the original process.

[0122] 6) Paper Strength: Adding 10-40 kg / t of attapulgite clay increases the bursting strength of kraft paperboard and reduces the amount of dry strength agents and surface sizing starch used for paper reinforcement. Under the same process conditions, the dry strength agent decreases by 5-20%, and the surface sizing starch decreases by 5-20%. However, at an addition of 50 kg / t, paper strength decreases.

[0123] 7) The addition of attapulgite clay improves whitewater system cleanliness and reduces the use of papermaking process additives such as papermaking detergents and papermaking sterilizers: With the continued addition of attapulgite clay, the cleanliness of the papermaking wet-end flow system and whitewater system is effectively improved, sticky deposits are reduced, and the bacterial content of the pulp and whitewater is reduced. Based on actual production inspections and test results, the dosage of papermaking detergents and papermaking sterilizers is appropriately reduced to maintain normal cleanliness of the paper machine flow system and whitewater system.

[0124] 5. Determination of the optimal embodiment:

[0125] Taking into account the paper machine's operating efficiency, output, and raw material cost-effectiveness, the optimal addition parameters were determined to be 30-40 kg / t of attapulgite clay per ton of paper (Examples 3 and 4). When the optimal parameters were used, the paper quality and changes in major chemical auxiliary materials compared to the blank were shown in Table 8:

[0126] Table 8

[0127]

[0128]

[0129] 7. Benefit evaluation:

[0130] Under the same paper quality requirements, if a paper machine produces 450,000 tons of high-grade kraft paper annually and adds 30kg / t of attapulgite clay, the corresponding output is:

[0131] Reduction in waste paper consumption: 450,000 × 0.03 = 13,500 tons / year.

[0132] Increase in attapulgite clay consumption: 450,000×0.03=13,500 tons / year Reduced electricity consumption: 13,500×110=1,485,000 kwh / year, equivalent to about 180 tons / year of standard coal Reduced steam consumption: 13,500×0.20=2,700 tons / year, equivalent to about 240 tons / year of standard coal Reduced paper retention aid: 450,000×0.15 / 1000=67.5 tons / year Reduced paper filter aid: 450,000×0.50 / 1000=225 tons / year Reduced defoaming agent: 450,000×0.2 / 1000=90 tons / year Reduced dry strength agent: 450,000×0.005=2,250 tons / year

[0133] Corn starch reduction: 450,000 × 0.002 = 900 tons / year

[0134] The new process of producing kraft paper by adding attapulgite clay has been successfully applied in actual production, with good energy-saving and emission-reduction benefits.

[0135] Finally, it should be noted that although the above embodiments have been described in the specification of this application, this does not limit the scope of patent protection of this application. All technical solutions generated by replacing or modifying equivalent structures or equivalent processes based on the essential concepts of this application using the contents recorded in the specification of this application, as well as directly or indirectly implementing the technical solutions of the above embodiments in other related technical fields, are included in the scope of patent protection of this application.

Claims

1. A method for preparing kraft paper, characterized in that: The following steps are involved: The attapulgite clay water suspension dispersed by high-speed stirring is added to the OCC waste paper pulp and mixed evenly before papermaking; the addition amount of the attapulgite clay is 10 to 40 kg / t of paper.

2. The preparation method according to claim 1, characterized in that The addition amount of the attapulgite clay is 30-40 kg / t of paper.

3. The preparation method according to claim 1, characterized in that The attapulgite clay water suspension has a solid content of 10-20%, a pH value of 8-10, and a viscosity of 20-250 MPa.s.

4. The preparation method according to claim 1, characterized in that The attapulgite clay water suspension is added to the mixed pulp tanks of the surface, core and bottom layers of the paper machine, and is stirred with the OCC waste paper pulp in the mixed pulp tank for 10 to 30 minutes before papermaking.

5. The preparation method according to claim 1, characterized in that The attapulgite clay has a dynamic viscosity of 20 to 500 MPa.s and a particle size of less than 200 meshes.

6. The preparation method according to claim 1, characterized in that The CaO content in the attapulgite clay is less than 7.0 wt%.

7. The preparation method according to claim 1, characterized in that The preparation of the attapulgite clay aqueous suspension comprises the following steps: mixing attapulgite clay with water, and stirring the mixture with a high-speed stirrer at 1000 to 1500 rpm for 10 to 90 minutes to obtain the attapulgite clay aqueous suspension.

8. The preparation method according to claim 7, characterized in that: The preparation of the attapulgite clay aqueous suspension comprises the following steps: mixing attapulgite clay with water, stirring with a high-speed stirrer at 1000-1500 rpm for 10-90 minutes, and filtering through a 60-mesh sieve to remove impurities, thereby obtaining the attapulgite clay aqueous suspension.

9. The preparation method according to claim 1, characterized in that In the slurry preparation step, the attapulgite clay water suspension is diluted to a solid content of 5 to 10% and then added to the OCC waste paper pulp for slurry preparation.

10. A kraft paperboard, characterized in that: The kraft paper is prepared by the preparation method according to any one of claims 1 to 9.

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