Papermaking filler treatment method and paper product obtained by same

Abstract

The invention relates to a papermaking method. The method comprises the following steps: treating a filler with starch and a dry powder retention aid to form a filler composition with a controllable particle size; the filler composition is mixed with cellulosic fibers and formed into paper wherein the dry powder retention aid is used in an amount of 0.25 to 2.5 kg / ton relative to absolute dry filler and the starch is used in an amount of 2 to 64 kg / ton relative to absolute dry filler, therefore, the median particle size of the filler composition obtained after the filler is treated by the starch and the dry powder retention aid is in a range of 10 microns to 200 microns. The filler composition prepared by the method is controllable in particle size, the paper strength is improved, the starch and the dry powder retention aid used in the method are widely applied to the papermaking industry, and the field operation process of the method is simplified.

Description

Technical Field

[0001] This invention relates to, but is not limited to, methods for treating paper filling materials and paper products obtained by such methods. Background Technology

[0002] Fillers have a long history of use in the papermaking industry. The addition of fillers improves paper whiteness and opacity, enhances paper uniformity, and promotes improved printability. Since fillers are typically much cheaper than paper fibers, replacing fibers with fillers usually yields better economic benefits. Therefore, the industry tries to use as many fillers as possible in the papermaking process. However, because fillers have small particle sizes and do not bind to fibers, using fillers to replace fibers can bring many negative problems to the papermaking process and the paper itself, such as decreased retention, reduced chemical efficiency, and decreased paper strength.

[0003] Fillers are typically added to the thick or thin pulp of the papermaking pulp system, and retention aids are used to help them remain on the paper. To increase the ash content of paper, the usual practice is to increase the amount of retention aid to improve the initial retention of the pulp. However, increasing the amount of retention aid can easily lead to larger pulp clumps, thus affecting paper uniformity and, in extreme cases, reducing paper strength, impacting continuous paper machine operation and paper quality.

[0004] One method to mitigate these negative impacts from increased filler content is to pre-flocculate the filler before adding it to the wet end processing system of the paper machine. Flocculation refers to the process of adding one or more flocculants to the filler to form filler flocs with a controllable particle size distribution under a certain shear force. The choice of flocculant and the flocculation process determine the size, distribution, and stability of the filler flocs. To prevent pseudo-flocculation—where some filler particles do not fully contact the flocculant and a large amount of unflocculated filler re-enters the pulp system after shearing—medium- to low-molecular-weight chemicals are typically used as flocculants. Filler flocs treated by the flocculation process reduce filler coverage on fibers, thereby increasing fiber-fiber bonding probability, improving paper strength, and reducing the adsorption of other wet end chemicals by the filler, thus improving the efficiency of wet end chemicals. Furthermore, the flocculation process must be economically feasible.

[0005] CN107407054 discloses a papermaking method to increase the ash content of paper products. This method uses a flocculant with a molecular weight of 1,200,000 to 7,500,000 Daltons to treat fillers, forming filler flocs with particle sizes of 10 to 150 micrometers. This method has been consistently and stably used on hundreds of paper machines both domestically and internationally, helping to increase the ash content of paper by 1-3% while maintaining paper quality and paper machine operation. However, the method has areas for improvement. First, the filler flocs formed by this method cannot form bonds with the fibers, limiting the improvement in paper strength. Second, the method uses medium-to-low molecular weight flocculants to ensure sufficient contact between the filler and the flocculant; to maintain a certain floc size in the paper machine headbox filler flocs, the dosage of the flocculant must be high. Furthermore, this method requires the introduction of one or more additional flocculants to complete the flocculation technology, posing challenges to the layout of the wet end of the paper mill, chemical quality control, and production safety management.

[0006] WO03087472 discloses a filler treatment method comprising preparing an expanded starch-emulsion composition with or without co-additives, and adding the composition to a filler suspension. Using the treated filler in the papermaking process improves filler retention and produces paper with a higher filler content, wherein the addition of filler has only a minimal negative impact on strength properties. The expanded starch-emulsion composition can be prepared in a batch or jet cooker, or by mixing with hot water under controlled conditions (i.e., temperature, pH, mixing, and mixing time) using a mixing device to allow the starch granules to fully expand to improve their performance as a filler additive, while avoiding over-expansion that could cause them to break. Subsequently, the expanded starch-emulsion composition is rapidly mixed with the filler (preferably in a static mixer) and added before the papermaking raw material enters the headbox of the paper machine. The treated filler is easily retained in the paper web during the papermaking process, improving drainage performance and producing paper with good formability. Paper made using the treated filler has higher adhesive strength and tensile strength than paper made using only expanded starch or only emulsion-treated filler. The proposed solution uses a filler treated with an emulsion polymer-expanded starch composition, which can partially bond with fibers, thereby improving paper strength. However, the emulsion polymer has a small molecular weight and low effective content. To avoid high-speed shearing on the paper machine, a higher dosage of the chemical is required, or the filler treatment material needs to be added as close as possible to the paper machine headbox to maintain a certain size of the flocculated filler in the headbox. This solution is costly and difficult to implement on-site.

[0007] With the shortage of waste paper raw materials and the increasing environmental protection requirements, using sludge generated from papermaking wastewater treatment as a substitute for fiber has become an option for many paperboard companies. Sludge from papermaking wastewater treatment contains a large amount of filler and fine fibers. Papermaking sludge used as filler shares the same advantages and disadvantages as general fossil fillers. For paper mills, sludge has almost no cost, and the economic benefits of replacing fibers are significant. However, the filler particles in the sludge are small, making it difficult to retain them when recycled to the paper machine. Even with a significant increase in retention aids, provided the paper uniformity is acceptable, the system's retention is still worse than without sludge. As sludge accumulates in the system, both system adhesives and paper quality are challenged.

[0008] Pre-flocculation of papermaking sludge is considered a feasible method to help paper mills utilize more sludge. For example, patent CN116497621 discloses a papermaking sludge recycling conditioner, its preparation method, and its application. The use of a combination of low-molecular-weight cationic cellulose JR-400, high-molecular-weight cationic flocculant JR-3000, and amphoteric organic flocculant can effectively promote the retention of fillers and fine particles. However, the use of expensive cationic cellulose increases the overall cost of the solution. Furthermore, the amphoteric flocculant, limited by its molecular weight, requires a relatively high quantity to achieve the desired treatment effect, further increasing the cost.

[0009] In summary, the chemical environment and high fluid shear rates present in modern high-speed papermaking necessitate stable and shear-resistant filler flocs. To maintain a certain particle size in the filler flocs before the pulp is fed into the wire, current technologies introduce one or more flocculants to flocculate the filler. However, the dosage of these flocculants is relatively high, impacting the economic viability of the process. Furthermore, the introduction of new flocculants presents challenges to wet-end management in paper mills. Therefore, continuous improvement of filler flocculation technology is necessary. Summary of the Invention

[0010] This invention relates to a papermaking method, comprising: treating filler with starch and a dry powder retention aid to form a filler composition with controllable particle size; mixing the filler composition with cellulose fibers to form paper, wherein the amount of the dry powder retention aid is 0.25 to 2.5 kg / ton relative to the oven-dry filler, and the amount of starch is 2 to 64 kg / ton relative to the oven-dry filler, thereby resulting in a median particle size of the filler composition obtained after treatment with the starch and dry powder retention aid being in the range of 10 micrometers to 200 micrometers. This method increases the particle size of the filler composition, improves paper strength, and the starch and dry powder retention aid used in this method are widely used in the papermaking industry. The filler treatment method also simplifies the operation process.

[0011] In one embodiment, this disclosure relates to a method of papermaking in which a filler is treated with a combination of starch and a dry powder retention aid to form a filler composition. The filler composition is then mixed with a cellulose fiber raw material, and the mixture from the filler composition and the cellulose fiber raw material forms paper. In some embodiments, the starch and the dry powder retention aid are premixed together prior to the filler treatment. In some embodiments, the starch and the dry powder retention aid are added to the filler simultaneously.

[0012] In other embodiments, this disclosure relates to a method of papermaking in which a charge regulator is added to the filler before it is formed into a filler composition using starch and a dry powder retention aid, followed by mixing the filler composition with a cellulose fiber raw material and forming paper from the mixture of the filler composition and the cellulose fiber raw material. In some embodiments, starch and a flocculant are premixed together before processing the filler. In some embodiments, starch and a dry powder retention aid are added to the filler simultaneously.

[0013] In one embodiment, this disclosure relates to a papermaking method in which papermaking sludge is treated with a combination of starch and a dry powder retention aid to form a filler composition. The filler composition is then mixed with a cellulose fiber raw material, and the mixture from the filler composition and the cellulose fiber raw material forms paper. Attached Figure Description

[0015] Figure 1 This is a graph showing the relationship between the tensile strength of paper and the ash content of paper under different filler treatment methods.

[0016] Figure 2 This is a graph showing the relationship between paper tensile strength and paper ash content under the method of treating sludge with a starch / dry powder retention aid composition. Specific implementation methods

[0017] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be particularly noted that the following embodiments are for illustrative purposes only and do not limit the scope of the application. Similarly, the following embodiments are only some, not all, embodiments of the present application, and all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of the present application.

[0018] In some embodiments, this disclosure relates to a filler treatment method comprising premixing starch with a dry powder retention aid, and then treating filler particles in a papermaking process with the premixed starch / dry powder retention aid composition. It has been found that adding the starch and dry powder retention aid composition to the filler causes an increase in filler particle size. The method for increasing filler particle size disclosed herein is considered to have several advantages. First, the filler composition particle size is significantly increased. Second, the specific surface area of ​​the filler is reduced, resulting in less interference with cellulose-cellulose hydrogen bonding after the filler composition and cellulose are mixed, allowing for more opportunities for fiber-to-fiber bonding, leading to increased paper strength. Third, the protruding starch molecules on the surface of the filler composition can form bonds with fibers or wet-end chemicals, improving filler retention and paper strength. Fourth, the reduced specific surface area of ​​the filler also reduces the adsorption of other wet-end chemicals by the filler, increasing the efficiency of wet-end chemicals. Fifth, the overall solution requires low chemical dosage. Sixth, the overall solution requires minimal modification to the paper machine's wet-end system.

[0019] In some embodiments, this disclosure relates to a method for treating fillers in a papermaking process, wherein starch and a dry powder retention aid are added to the filler simultaneously. This process results in an increase in filler particle size, improved cellulose-cellulose bonding, and stronger paper, especially compared to the case where starch and the dry powder retention aid are added sequentially.

[0020] In some embodiments, this disclosure relates to a method for treating fillers in a papermaking process by premixing starch with a dry powder retention aid and subsequently combining the premixed starch / dry powder retention aid composition with a filler. Exemplary combinations of starch and dry powder retention aids include: cationic starch and dry powder retention aid; anionic starch and dry powder retention aid; nonionic starch and dry powder retention aid; and zwitterionic or amphoteric starch and dry powder retention aid may also be used.

[0021] The mixture of starch and dry powder retention aid can be prepared in a batch or continuous manner, or it can be prepared directly using existing starch and dry powder retention aid solutions from the wet end of papermaking. Starch preparation requires strict control of concentration, temperature, pH, stirring method, and stirring time. The mixture of starch, dry powder retention aid, and filler is then mixed with cellulose fibers to finally form paper.

[0022] Studies have found that treating filler particles with water-soluble cationic polymers (including cooked cationic starch, polyethyleneimine, polymethyl dimethacrylate, or polyethyleneamine) can induce flocculation. However, the improvement in the strength of filled paper achieved by this treatment method is still far less significant than the improvement achieved by the starch-dry powder retention aid composition of this invention.

[0023] It is worth noting that starch and dry powder retention aids are routine chemicals in modern papermaking, and this treatment method reduces the investment in special chemical equipment and the daily maintenance burden on paper machine operators.

[0024] filler

[0025] Exemplary fillers include any inorganic or organic particles or pigments used to increase opacity or brightness, increase smoothness, or reduce the cost of paper or paperboard. Exemplary fillers include: calcium carbonate, bleaching clay, kaolin, talc, and combinations thereof.

[0026] The exemplary filler also includes papermaking sludge. Papermaking sludge is a solid waste generated during the wastewater treatment process in the papermaking industry. Traditionally, sludge is treated through methods such as landfill and incineration. With the shortage of waste paper fiber raw materials and increasing environmental pressure, using wastewater-treated sludge as a substitute for fiber as a papermaking raw material has become an option for many companies. Papermaking sludge generally contains 40% to 50% inorganic particles and a large number of fine fibers. Reusing sludge can not only save the cost of traditional treatment methods, but also partially replace paperboard pulp, greatly reducing production costs. However, sludge contains a large number of inorganic particles and fine fibers, and its reuse can bring many negative problems to papermaking production, such as low retention, difficulty in dewatering, and low paper strength. Reusing sludge needs to overcome the problem of difficulty in retention due to its small particle size and its impact on paper strength.

[0027] In some embodiments, the filler is selected from calcium carbonate, talc, and combinations thereof. In some embodiments, the filler is 100% calcium carbonate, 100% talc, 100% sludge, or a mixture of calcium carbonate and other fillers.

[0028] starch

[0029] The starch raw materials applicable to this invention include, but are not limited to, corn, waxy corn, potato, wheat, cassava, sorghum, waxy sorghum, and rice. These starches can be raw starch, cationic (positively charged), anionic (negatively charged), or amphoteric (possessing both positive and negative charges), and can be modified or retained in their original state. The average particle size of the starch granules is typically between 5 and 150 μm. In some embodiments, the starch is cationic starch.

[0030] Starch and its derivatives are important chemicals in the papermaking industry, ranking third among paper consumables after fiber raw materials and fillers. Starch and its derivatives play a role in multiple stages of papermaking. Their effects include: starch added to the wet end improves the retention of fine fibers and fillers, increasing paper ash content; it forms new chemical bonds with plant fibers, making the adhesion between fibers tighter, thus significantly improving paper strength and durability; through surface sizing (such as sizing press or coating), it improves paper surface smoothness, integrity, and printability, reduces paper fuzzing, and enhances surface strength. Furthermore, starch is a natural, renewable, and biodegradable environmentally friendly additive that can partially replace synthetic chemicals.

[0031] Starch preparation can be accomplished using either batch cooking or continuous cooking. In batch cooking, the starch slurry, preferably with fresh steam, is heated to a desired temperature (e.g., 95°C) with continuous agitation. The starch must be held at this temperature for at least 5, 10, 20, or 30 minutes to ensure complete dissolution of the starch granules. In continuous cooking, dry starch is first metered into a slurry tank, where it is mixed with cold water. The slurry is then pumped out via a venturi jet pump, which is similar in principle to a hydrodynamic vacuum pump, and after being mixed with fresh steam, it is passed through a cooking spiral tube, where the starch is held at a temperature (e.g., 120 to 130°C) for a time sufficient to ensure complete cooking of the granules.

[0032] In some embodiments, the starch dosage is 2 to 64 kg / ton of untreated filler, preferably 4 to 32 kg / ton of untreated filler, where kg / ton refers to the number of kilograms of active starch corresponding to 1 ton of dried filler.

[0033] Dry powder retention aid

[0034] Paper retention aids are key chemicals used in the papermaking process to improve fiber and filler retention and enhance water filtration performance. Their core function is to reduce the loss of fine fibers and fillers through charge adsorption or bridging, thereby lowering costs, improving paper quality, and reducing the burden on wastewater treatment.

[0035] With the continuous increase in paper machine speed and the growing demands for paper quality, dry powder retention aids are widely used in the papermaking industry due to their high molecular weight, high effective content, and ease of transportation and storage. The dry powder retention aids are selected from (but not limited to) cationic polyacrylamide, anionic polyacrylamide, polyethyleneimine, polyaminoamide, and polyethylene oxide; unlike the dry powder cationic polyacrylamide used in other parts of papermaking, the molecular weight range of dry powder retention aids used for wet-end retention is between 8 million and 15 million. A suitable dosage is 0.25 kg / ton to 2.5 kg / ton of oven-dry untreated filler, with a preferred dosage of 0.5 kg / ton to 1.5 kg / ton of untreated filler.

[0036] Starch-dry powder retention aid composition

[0037] After the dry powder retention aid solution and the starch solution are mixed, they interact through electrostatic adsorption and physical entanglement. This composition typically contains 40–99% starch and 60–1% dry powder retention aid (based on the solid content of starch and dry powder retention aid), totaling 100%. The ratio of starch to dry powder retention aid depends on the type of filler and the performance requirements of the target paper type.

[0038] The starch-dry powder retention aid composition is used at a rate of 0.5–100 kg / ton of untreated filler relative to oven-dried filler.

[0039] After the starch-dry powder retention aid composition is formed, it can be mixed with the target filler immediately, or it can be left in the pipeline or storage equipment for 0 to 2 hours before being mixed with the target filler.

[0040] Charge regulator

[0041] The starch-dry powder retention aid composition of the present invention can optionally include a charge modifier in the filler before being added. This charge modifier alters the charge of the target filler, improving the performance of the filler after treatment with starch and the dry powder retention aid. The charge modifier can be selected from (but is not limited to) cationic types, such as alum, polyaluminum chloride, cationic polyacrylamide, polyethyleneimine, cationic starch, cationic guar gum, and polyamide polyamine; or anionic types such as carboxymethyl cellulose, polyacrylic acid, alginate, colloidal silica, bentonite polyacrylamide, and soluble soap bases.

[0042] The amount of charge control agent used depends primarily on the type of filler. In some embodiments, the amount of charge control agent used is 0.25 to 5 kg / ton of untreated filler.

[0043] packing treatment

[0044] When preparing a starch-dry powder retention aid composition, the selection of preferred starch, dry powder retention aid, and optional charge regulator, and their addition to the filler slurry, requires comprehensive consideration of the ionic charge characteristics of the starch, dry powder retention aid, and charge regulator used, as well as the surface charge properties of the filler to be treated. For example, if the filler to be treated is neutral or slightly cationic, an anionic charge regulator can be added before adding the starch-dry powder retention aid composition to the filler to promote bridging and flocculation between the starch-dry powder retention aid composition and the filler. If the untreated filler is strongly anionic, to prevent over-flocculation after adding the starch-dry powder retention aid composition to the filler, a cationic charge regulator can be added before adding the starch-dry powder retention aid composition to the filler, thereby weakening the bridging effect between filler particles.

[0045] The starch-dry powder retention aid composition can be prepared by separately preparing the starch and dry powder retention aid preferred for a specific filler, or by directly using pre-prepared starch and dry powder retention aids already available in the paper mill. The starch solution and dry powder retention aid solution are added to the filler after passing through a mixing device (e.g., a static mixer). Typically, the filler concentration is controlled between 5% and 40%, preferably 10% to 20%.

[0046] Efficient mixing is crucial for the preparation of starch-dry powder retention aid compositions and for their mixing with fillers. The mixing of the starch-dry powder retention aid composition and fillers leads to filler flocculation, necessitating the introduction of appropriate charge modifiers before the composition for some fillers. Filler flocculation is controllable; the particle size after flocculation can be adjusted by varying the amount of starch-dry powder retention aid composition and regulating the shear strength of the system.

[0047] The filler treated in this invention is used in an amount where the dry solids constitute 5% to 60% of the dry weight of the pulp. Studies have found that, under the same filler addition conditions, the tensile strength of paper using the treated filler is significantly improved, far exceeding that of paper without the treated filler.

[0048] Papermaking process

[0049] The treated filler is fed into and mixed with the fiber pulp. After the treated filler is combined with the fiber pulp, other paper additives may be present or added to the fiber pulp. The mixture of filler and fiber (with other optional additives) is then pumped through a moving screen to filter out water, producing a wet paper web. The wet paper web is fed into a press to mechanically squeeze out more water. The paper web exiting the press is fed into a dryer where the remaining water is removed by heating. The resulting dried paper is used to measure paper strength properties.

[0050] If the above definitions or descriptions set forth elsewhere in this application are inconsistent with their common meanings (clear or ambiguous) as stated in a dictionary or in the original document incorporated herein by reference, then the terms in this application, in particular the claims, should be understood to be interpreted according to the definitions or descriptions in this application, rather than according to the common definitions, dictionary definitions, or definitions incorporated by reference.

[0051] The present invention will be further described below with reference to embodiments. Unless otherwise specified, all reagents and raw materials used in the embodiments of the present invention are commercially available products. In different embodiments, the same reagents are from the same source.

[0052] Example

[0053] Example 1

[0054] Example 1 illustrates the treatment of heavy calcium carbonate using starch alone. The starch used was CCS-03, available from Hangzhou Zhiyou Technology Co., Ltd. The calcium carbonate used was from Jintong Paper Industry Co., Ltd., Zhenjiang City, Jiangsu Province, China.

[0055] Preparation of 2% starch solution: Add 6g of starch powder to 294g of cold tap water while stirring at 250rpm to prepare a starch solution. Heat the solution to 95℃, increase the stirring speed to 500rpm, and cook the starch solution for 15 minutes before stopping heating.

[0056] To treat the packing material, it was diluted to a 10% concentration with tap water. 300 ml of the diluted packing material was taken, and the stirring speed was initially set to 800 rpm. An appropriate amount of starch was added to the diluted packing material using a syringe. After adding the chemical, the stirring speed was increased to 1500 rpm to shear the packing material for 2 minutes. The particle size distribution of the obtained packing material was measured using a Malvern particle size analyzer, available from Malvern Instruments Ltd., Worcestershire, UK. The distribution and particle size (D(0.1), D(0.5), D(0.9)) were recorded for each solution.

[0057] The results are shown in Table 1, which shows that starch alone can flocculate calcium carbonate, resulting in small particle sizes after flocculation, and that the adsorption of starch by the filler is limited.

[0058] Example 2

[0059] Example 2 illustrates the treatment of heavy calcium carbonate using a dry powder retention aid alone. The dry powder retention aid A (RSV: 15 dL / g, with a 9% cationic charge) used was available from Jiangsu Fumiao Technology Co., Ltd., China.

[0060] Preparation of 0.25% dry powder retention aid solution: 0.75g of dry powder retention aid was added to 299.25g of tap water under stirring at 400rpm, and stirred for 30 minutes before use.

[0061] The method of Example 1 is used, except that a 0.25% dry powder retention aid solution is used instead of a 2% starch solution.

[0062] The results are shown in Table 1, which shows that treating calcium carbonate with dry powder retention aid alone resulted in over-flocculation, and the method is not feasible as a filler treatment.

[0063] Example 3

[0064] Example 3 involves treating heavy calcium carbonate using starch / dry powder retention aid compositions in different proportions. The starch, dry powder retention aid, and filler used are the same as in Examples 1 and 2. The method of Example 1 is employed, except that a 2% starch solution is replaced with a pre-mixed starch-dry powder retention aid composition in different proportions and amounts.

[0065] The results are shown in Table 1, demonstrating that the starch / dry powder retention aid composition effectively treats calcium carbonate, resulting in a significantly larger particle size compared to calcium carbonate treated with starch alone. The particle size of the treated filler composition was influenced by both the amount of starch and the amount of dry powder retention aid; both promoted an increase in particle size. However, under the same treatment conditions, the high molecular weight dry powder retention aid had a greater impact on the final particle size than starch, while the low molecular weight starch had a greater impact on the final particle size distribution. Based on the particle size and distribution of the treated filler, the results showed that a starch dosage between 2 and 64 kg / ton of oven-dry filler, and a dry powder retention aid dosage between 0.25 and 2.5 kg / ton of oven-dry filler, yielded filler compositions with controllable particle sizes. A starch dosage between 4 and 32 kg / ton of oven-dry filler, and a dry powder retention aid dosage between 0.5 and 1.5 kg / ton of oven-dry filler, resulted in higher efficiency for both starch and the dry powder retention aid.

[0066] Example 4

[0067] Example 4 is similar to Example 3, using a starch / dry powder retention aid composition to treat heavy calcium carbonate. The difference is that dry powder retention aid B (RSV: 16 dL / g, with 15% cationic charge, available from Jiangsu Fumiao Technology Co., Ltd., China), dry powder retention aid C (RSV: 8 dL / g, with 18% cationic charge, available from Jiangsu Fumiao Technology Co., Ltd., China), and dry powder retention aid D (RSV: 14 dL / g, with 17% cationic charge, available from Jiangsu Fumiao Technology Co., Ltd., China) are used instead of dry powder retention aid A. The ratio of starch to dry powder retention aid is 4:1, and the total dosage is 5 kg / ton of filler.

[0068] The results are shown in Table 1, which demonstrates that starch / dry powder retention aid compositions formed using multiple retention aids can effectively treat calcium carbonate.

[0069] Example 5

[0070] Example 5 is the same as Example 3, using a starch / dry powder retention aid composition to treat heavy calcium carbonate, the difference being that the starch is natural potato starch (available from China National Pharmaceutical Group Chemical Reagent Co., Ltd., code 69023736). The ratio of natural potato starch to dry powder retention aid is 4:1, and the total dosage is 5 kg / ton of filler.

[0071] The results are shown in Table 1, which shows that the natural potato starch / dry powder retention aid composition can effectively treat calcium carbonate, but the flocculation efficiency is slightly lower than that of cationic starch.

[0072] Table 1

[0073] Example 6

[0074] Example 6 is similar to Example 3, using a starch / dry powder retention aid composition to treat heavy calcium carbonate, the difference being the simultaneous addition of starch and dry powder retention aid. The starch dosage was 4 kg / ton of filler, and the dry powder retention aid dosage was 1 kg / ton of filler. The results are shown in Table 1, indicating that the simultaneous addition of starch and dry powder retention aid can effectively treat calcium carbonate, but the filler distribution is slightly worse.

[0075] Example 7

[0076] Example 7 is similar to Example 5, except that it treats 100% talc (from Ningbo Asia Pulp & Paper Co., Ltd., Zhejiang Province, China). First, it is treated with charge regulator A (acrylamide polymer with 50% anionic charge, available from Nalco Company, Naperville, Illinois, USA), followed by a starch / dry powder retention aid A composition. The ratio of starch to dry powder retention aid is 4:1, and the dosage of the composition is 5 kg / ton of filler. The results are shown in Table 2, demonstrating that using the anionic charge regulator first, followed by the starch / dry powder retention aid composition, effectively treats non-dispersed filler (talc).

[0077] Example 8

[0078] Example 8 is similar to Example 5, except that it treats a mixed filler consisting of 90% heavy calcium carbonate (from Asia Pulp & Paper Co., Ltd., Ningbo, Zhejiang Province, China) and 10% shale calcium carbonate (from Specialty Minerals, Inc., USA). First, the filler was treated with charge modifier B (polyepoxychloropropaneamine, with a 50% cationic charge, available from Nalco Company, Naperville, Illinois, USA), followed by a starch / dry powder retention aid A composition at a ratio of 4:1. The composition was applied at a rate of 5 kg / ton of talc. The results are shown in Table 3, demonstrating that the initial application of the cationic charge modifier, followed by the starch / dry powder retention aid composition, increased the particle size of the dispersed mixed filler (containing heavy calcium carbonate and shale).

[0079] Table 2

[0080] Table 3

[0081] Example 9

[0082] Example 9 is the same as Example 5, except that it treats papermaking sludge (from Huanan Shanying Paper Industry Co., Ltd., Zhangzhou City, Fujian Province). The results are shown in Table 4, demonstrating that the starch / dry powder retention aid composition can effectively treat papermaking sludge.

[0083] Table 4

[0084] Test Example 1

[0085] The purpose of this test case is to evaluate the effect of starch / dry powder retention aid composition on the tensile strength of hand-made sheet paper treated with heavy calcium carbonate as a function of paper ash content. The tensile strength of the paper was measured according to Tappi T494.

[0086] The fillers used in the test examples were heavy calcium carbonate treated with Example 1 (16 kg starch / ton of heavy calcium carbonate) and Example 3 (a blend of 16 kg starch / ton of heavy calcium carbonate and 1 kg dry powder retention aid / ton of heavy calcium carbonate), with untreated heavy calcium carbonate as the control group, to compare the effect of the starch / dry powder retention aid composition on paper strength.

[0087] Different proportions of fillers were added to a pulp with a solid content of approximately 0.7%, consisting of 60% hardwood bleached chemical pulp, 20% softwood bleached chemical pulp, and 20% bleached thermomechanical pulp. A certain weight of the filler-containing pulp was weighed and stirred at 800 rpm. Cationic starch, dry powder retention aid A (200 ppm), and bentonite (1 kg / ton of paper) were added every 15 seconds. When the filler was treated with single starch or a starch / dry powder retention aid combination, the amount of starch added was 10 kg / ton of paper. When using untreated filler, the amount of starch used was the sum of the amount of starch in the treated filler in the test example and the 10 kg / ton of paper added later, to maintain a consistent total amount of starch used in hand-made sheets under the same filler addition. The resulting paper samples were placed under constant temperature and humidity (23 degrees Celsius, 50% humidity) for overnight drying.

[0088] The results of analyzing the obtained paper samples, including untreated filler, starch-treated filler, and filler treated with a starch / dry powder retention aid composition, are shown in the table below. Figure 1 middle. Figure 1 This is a graph showing the relationship between the tensile strength of paper and the ash content of paper under different filler treatment methods.

[0089] from Figure 1 It can be seen that the tensile index of paper treated with the starch / dry powder retention aid composition is significantly improved.

[0090] Test Example 2

[0091] This test case uses sludge as the filler and aims to evaluate the effect of treating sludge with a starch / dry powder retention aid composition on the tensile strength of hand-made sheet paper as a function of paper ash content.

[0092] The filler used in the test example was the sludge treated with Example 9 (a blend of 8 kg starch / ton sludge and 1 kg dry powder retention aid / ton sludge), with untreated sludge as the control group, to compare the effect of the starch / dry powder retention aid composition on paper strength.

[0093] Different proportions of sludge were added to 100% waste paper pulp with a solid content of approximately 0.7%. A certain weight of the sludge-containing pulp was weighed and stirred at 800 rpm. Cationic starch, dry powder retention aid A (200 ppm), and bentonite (1 kg / ton of paper) were added every 15 seconds. When the filler was treated with the starch / dry powder retention aid composition, the amount of starch added was 10 kg / ton of paper. When using untreated sludge, the amount of starch used was the sum of the amount of starch in the treated sludge in the test example and the 10 kg / ton of paper added later, to maintain a consistent total amount of starch used in hand-made sheets under the same sludge addition. The resulting paper samples were placed under constant temperature and humidity (23 degrees Celsius, 50% humidity) for overnight drying.

[0094] Analysis of the obtained paper samples showed that the results of treating the sludge with untreated sludge and a starch / dry powder retention aid composition were displayed. Figure 2 middle. Figure 2 This is a graph showing the relationship between paper tensile strength and paper ash content under the method of treating sludge with a starch / dry powder retention aid composition.

[0095] from Figure 2 It can be seen that after the sludge is treated with the starch / dry powder retention aid composition, the retention of fine sludge ash is significantly improved at the same sludge addition amount, and the tensile index of paper is also improved.

Claims

1. A papermaking method, comprising: a. Treat the filler with starch and dry powder retention aid; b, The treated filler and cellulose fiber raw material are combined; and, c, Paper is formed from processed fillers and cellulose fiber raw materials; The amount of the dry powder retention aid is 0.25 to 2.5 kg / ton relative to the oven-dry filler, and the amount of starch is 2 to 64 kg / ton relative to the oven-dry filler. The median particle size of the filler after treatment is 15 micrometers to about 200 micrometers.

2. The method according to claim 1, wherein the starch and the dry powder retention aid have been mixed together before processing the filler.

3. The method according to claim 1, wherein the starch and the dry powder retention aid are added simultaneously to the filler.

4. The method according to claim 1, wherein the filler is selected from one or more of calcium carbonate, sludge, kaolin, and talc.

5. The method according to claim 1, wherein the starch is selected from one or more of raw starch, nonionic starch, anionic starch, cationic starch, and amphoteric starch.

6. The method according to claim 5, wherein the starch is cationic starch.

7. The method according to claim 1, wherein the dry powder retention aid is selected from cationic polyacrylamide, polyethyleneamine, polyethyleneimine, or mixtures, block copolymers, grafts, or other derivatives of the above substances.

8. The method according to claim 7, wherein the dry powder retention aid is cationic polyacrylamide.

9. The method according to claim 1, wherein the amount of the dry powder retention aid is 0.5 to 1.5 kg / ton relative to the oven-dry filler, and the amount of starch is 4 to 32 kg / ton relative to the oven-dry filler.

10. The method according to any one of claims 1-9, further comprising: Add a charge regulator before adding the starch / dry powder retention aid composition; The charge regulator is one or more materials selected from the group consisting of: alum, polyaluminum chloride, cationic polyacrylamide, polyethyleneimine, polyamide polyamine, polyepoxychloropropaneamine, and anionic acrylamide and sodium acrylate copolymer.

11. A paper article, said paper article being prepared by the method according to any one of claims 1-10.

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