Paper, papermaking filler and method for modifying the same

Abstract

The application provides a paper product, a papermaking filler and a modification method of the papermaking filler, the modification method comprising: adding polyaluminum chloride into a calcium carbonate filler solution and stirring to form a first mixed solution; adding pregelatinized phosphate ester starch into the first mixed solution and stirring to form a second mixed solution; adding a 2-sodium acrylate homopolymer solution into the second mixed solution and stirring to form a third mixed solution; adding a cationic polyacrylamide solution into the third mixed solution and stirring to obtain filler flocculation with a coating material. The modification method first performs coating modification on the filler, and then performs pre-flocculation modification, and the modified filler is added into paper pulp for papermaking, in the case of increasing the filler addition amount, the pulp filtration performance, the retention property are not deteriorated, and the paper physical property strength and the surface strength are maintained. Under the premise of ensuring the paper machine running performance, the papermaking raw material cost is reduced when the same paper quality is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of papermaking filler, in particular to a paper product, a papermaking filler and a modification method thereof. BACKGROUND

[0002] Papermaking filler is the largest proportion of paper pulp fiber removed from the material, which can account for 5% to 40% of the paper material components. The benefits of adding filler include reducing the cost of papermaking raw materials, and giving the paper some beneficial properties, such as better uniformity, high opacity and whiteness, etc. Adding filler can also improve the printing suitability of the paper product and increase its economic value. The types of fillers currently used are diverse, among which the commonly used mineral fillers in papermaking are calcium carbonate (CaCO3), talc and kaolin, etc. From a global perspective, the most widely used papermaking filler is kaolin, but the consumption of calcium carbonate filler is increasing, and the use of calcium carbonate will become more and more widespread. First, the papermaking process has shifted from acidic papermaking to neutral / alkaline papermaking; second, the production process and quality of calcium carbonate are more suitable for papermaking filling. According to different production methods, calcium carbonate is divided into ground calcium carbonate (GCC) and precipitated calcium carbonate (PCC). GCC filler can be obtained by mechanical grinding of natural limestone, etc., while PCC is processed by chemical methods. The settling volume of PCC (>2.5 mL / g) is larger than that of GCC (1.2-1.9 mL / g), PCC is called light calcium carbonate, and GCC is called heavy calcium carbonate. According to the traditional filling process, the filler will affect the bonding between the fibers, causing a significant decrease in paper strength. Excessive filling amount will also cause a decrease in filler retention rate, paper linting / doffing and other problems.

[0003] Based on the deficiencies of traditional filler addition, the industry has done a lot of work on the modification of fillers. So far, the technologies that have achieved some success include two categories: filler pre-flocculation technology and filler coating technology. Pre-flocculation is to mix fillers with flocculants, functional additives, etc. in advance to form flocculation bodies, and then add the flocculation bodies to the pulp for papermaking. Pre-flocculation technology can provide better filler retention and reduce the impact of fillers on fiber bonding strength. The disadvantage of pre-flocculation technology is also obvious. Before the paper is formed, the modified fillers need to maintain the flocculation body form to play a role, but under the action of shear force, the filler flocculation body is easy to be dispersed, reducing the effect of filler modification. For modern high-speed paper machines, the high fluid shear rate in the flow delivery system poses a great challenge to the stability of the filler flocculation body. In addition, the contact surface between the filler pre-flocculation body and the fiber is essentially the contact between the filler and the fiber, and there is no hydrogen bond binding force, so there is still room for improvement in paper strength. The coating modification of fillers is to use special substances to coat inorganic fillers to form a core-shell composite structure with fillers as the core and coating materials as the shell. The selected coating material can have good bonding with cellulose fibers, avoiding direct contact between fillers and fibers, thereby improving the impact of filled fillers on fiber bonding strength, or improving the filling amount of fillers under the condition of maintaining certain paper strength performance. It has been proved that the coating modification of fillers with sugar compounds and their derivatives can improve the strength performance of filled paper, and to some extent, improve the retention of fillers and reduce the impact of fillers on fiber bonding strength. However, in general, the filler coating modification technology has too many parameters to control, the condition control is relatively strict, or it needs subsequent processing such as vacuum drying and grinding (such as dry starch coating filler technology), so it is difficult to realize on-site modification processing in paper mills. In addition, after the fillers are coated with sugar compounds and their derivatives and added to the pulp, they generally have some adverse effects on the drainage of the pulp, which is generally unacceptable for high-speed paper machines. In summary, pre-flocculation technology and coating technology each have their own advantages and disadvantages. SUMMARY

[0004] The first aspect of the embodiments of the present application provides a modification method of papermaking fillers, the modification method comprising:

[0005] adding polyaluminum chloride to the calcium carbonate filler solution and stirring to form a first mixed solution;

[0006] adding pre-gelatinized phosphate starch to the first mixed solution and stirring to form a second mixed solution;

[0007] adding a 2-sodium acrylate homopolymer solution to the second mixed solution and stirring to form a third mixed solution;

[0008] adding a cationic polyacrylamide solution to the third mixed solution and stirring to obtain filler flocculation with coating material.

[0009] In the step of adding polyaluminum chloride to the calcium carbonate filler solution and stirring to form a first mixed solution, the solid content of the calcium carbonate filler is 10-30%; the addition amount of the polyaluminum chloride is 0.02%-0.30% of the absolute dry mass of the calcium carbonate filler.

[0010] In the polyaluminum chloride, the content of aluminum trioxide is greater than 10.0%, and the salt base B(%) is 40.0-90.0.

[0011] In the first mixed solution, the PSD50 particle size control range of the micro-flocculation is 5-20 μm, and the micro-particle charge control range is +10 μeq / L to +200 μeq / L.

[0012] In the step of adding pregelatinized phosphate ester starch to the first mixed solution and stirring to form a second mixed solution, the addition amount of the pregelatinized phosphate ester starch is 0.1-3.0% of the absolute dry mass of the calcium carbonate filler, and the substitution degree is 0.03-0.05%.

[0013] In the step of adding a 2-sodium acrylate homopolymer solution to the second mixed solution and stirring to form a third mixed solution, the addition amount of the 2-sodium acrylate homopolymer is 2.0-5.0% of the absolute dry amount of the phosphate ester starch.

[0014] In the step of adding a cationic polyacrylamide solution to the third mixed solution and stirring to obtain filler flocculation with coating material, the solid content of the cationic polyacrylamide solution is 0.05-0.30%, and the addition amount of the cationic polyacrylamide is 0.05-0.50% of the absolute dry amount of the calcium carbonate filler.

[0015] In the obtained filler flocculation with coating material, the PSD50 is 22-60 μm, and the micro-particle charge is +10 μeq / L to +100 μeq / L.

[0016] In a second aspect, the embodiments of the present application provide a papermaking filler prepared by the modification method described in the above embodiments.

[0017] In a third aspect, the embodiments of the present application provide a paper product prepared by the papermaking filler described in the above embodiments.

[0018] The papermaking filler modification method provided in the embodiments of the present application first performs coating modification on the filler, and then performs pre-flocculation modification, and the modified filler is added into paper pulp for papermaking, so that the pulp drainage performance and retention characteristics are not deteriorated, and the paper physical strength and surface strength are maintained under the condition of increasing the filler addition amount. The papermaking raw material cost is reduced under the premise of ensuring the paper machine running performance and achieving the same paper quality. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and all other drawings obtained by those skilled in the art without creative effort are within the protection scope of the present application.

[0020] Figure 1 is a flowchart of an embodiment of the papermaking filler modification method of the present application. DETAILED DESCRIPTION

[0021] The present application will be further described in detail below with reference to the drawings and embodiments. It is particularly pointed out that the following embodiments are only used to illustrate the present application, but do not limit the scope of the present application. Similarly, the following embodiments are only some embodiments of the present application, and all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present application.

[0022] The terms "first", "second", "third" in the embodiments of the present application are only used for description purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first", "second", "third" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise specifically limited. All directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present application are only used to explain the relative positional relationship, movement condition, etc. between the components in a certain posture (as shown in the drawings), and if the certain posture changes, the directional indications also change accordingly. The terms "include" and "have" and any variations thereof in the embodiments of the present application are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device including a series of steps or units is not limited to the listed steps or units, but can optionally include steps or units not listed, or can optionally include other steps or components inherent to the process, method, product or device.

[0023] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of one another. As will be apparent to those of ordinary skill in the art, embodiments described herein can be combinable with other embodiments.

[0024] The application provides a modification method of papermaking filler, please refer to Figure 1 , Figure 1 is a flowchart of an embodiment of the modification method of papermaking filler of the application, which comprises but is not limited to the following steps.

[0025] S100, adding polyaluminum chloride in the calcium carbonate filler solution and stirring to form a first mixed solution.

[0026] In this step, first, the calcium carbonate filler to be modified can be prepared, wherein the type of calcium carbonate filler includes single component of light calcium carbonate PCC, heavy calcium carbonate GCC, or mixture of light calcium carbonate PCC and heavy calcium carbonate GCC. The solid content of the calcium carbonate filler is 10-30%, and the calcium carbonate dispersion is uniformly dispersed by pre-stirring. Under the condition of maintaining slow stirring, 0.02%-0.30% of polyaluminum chloride based on the absolute dry mass of the calcium carbonate filler is added to the calcium carbonate dispersion, and the moderate stirring is maintained to promote the calcium carbonate filler to form a micro-flocculation particle system and make the surface of the micro-flocculation filler have a certain positive charge. The polyaluminum chloride can be high-purity iron-free polyaluminum chloride solution, the content of aluminum oxide is 10.0%, the base degree B(%) is 40.0-90.0, and the amount of polyaluminum chloride used for the calcium carbonate filler is determined according to the composition difference between PCC(light calcium carbonate) and GCC(heavy calcium carbonate) in the filler. The untreated filler PCC dispersion generally has weak negative charge or weak positive charge or is neutral, the untreated filler GCC dispersion generally has higher negative charge, and when the proportion of GCC in the filler composition is high, the amount of polyaluminum chloride used is adjusted and increased. The actual amount is determined according to the particle size and charge control range of the filler micro-flocculation, the PSD50 particle size of the micro-flocculation in the first mixed solution is controlled in the range of 5-20 μm(X-ray sedimentation method), and the particle charge is controlled in the range of +10 μeq / L to +200 μeq / L.

[0027] Please continue to refer to Figure 1 The modification method of papermaking filler in the embodiment of the application further comprises the step S200 of adding pregelatinized phosphate starch to the first mixed solution and stirring to form a second mixed solution.

[0028] The first mixed solution is kept stirring, and the pregelatinized phosphate ester starch is added, so that the pregelatinized phosphate ester starch is uniformly mixed with the first mixed solution. The phosphate ester starch can be selected from phosphate ester starch with a degree of substitution of 0.03-0.05%, a viscosity of 4% paste viscosity of 0.05 Pa·S (25°C), and a pH value of 6. The absolute dry amount of the phosphate ester starch to the absolute dry amount of the calcium carbonate filler is 0.1-3.0%.

[0029] Please continue to refer to Figure 1 The modification method of the papermaking filler in the embodiment of the application further includes step S300 of adding a 2-sodium acrylate homopolymer solution to the second mixed solution and stirring to form a third mixed solution.

[0030] In step S300, the 2-sodium acrylate homopolymer solution is added to the second mixed solution, and stirring is kept, so that the 2-sodium acrylate homopolymer is uniformly mixed with the second mixed solution. The absolute dry amount of the 2-sodium acrylate homopolymer to the absolute dry amount of the phosphate ester starch is 3.0-4.0%.

[0031] Please continue to refer to Figure 1 The modification method of the papermaking filler in the embodiment of the application further includes step S400 of adding a cationic polyacrylamide solution to the third mixed solution and stirring to obtain filler flocculation with a coating material.

[0032] In this step, the cationic polyacrylamide solution with a solid content of 0.05-0.30% is added to the third mixed solution, and stirring is kept, so that the cationic polyacrylamide is uniformly mixed with the third mixed solution. The filler flocculation with a coating material on the surface is obtained. The polyacrylamide has a molecular weight of 8-12 million and a cationization degree of 5-8%, and the absolute dry amount of the cationic polyacrylamide to the absolute dry amount of the calcium carbonate filler is 0.10-0.30%. According to test detection, the particle size PSD50 of the filler flocculation with a coating material on the surface is 22-60 μm (X-ray sedimentation method detection), and the particle charge is +10 μeq / L to +100 μeq / L (PCD particle charge detector detection).

[0033] The specific application of the papermaking filler obtained by the above method in papermaking will be introduced below.

[0034] The treatment process of the calcium carbonate filler is as follows:

[0035] The first step, the calcium carbonate filler to be modified is prepared with a solid content of 10-30%, and is pre-stirred to obtain a uniformly dispersed calcium carbonate dispersion. While maintaining slow stirring, 0.02%-0.30% of polyaluminum chloride based on the absolute dry mass of the filler is added to the calcium carbonate dispersion, and the stirring is maintained to promote the formation of a micro-flocculated particle system of the calcium carbonate filler, and to impart a certain positive charge to the surface of the micro-flocculated filler. Test detection shows that the PSD50 particle size of the micro-flocculated filler is 6-15 μm (X-ray sedimentation method), and the particle charge is +20-+150 μeq / L (PCD particle charge detector).

[0036] In a specific embodiment, the polyaluminum chloride is selected from a high-purity iron-free polyaluminum chloride solution with Al203≥10.0%, and a basicity B (%) of 40.0-60.0. The amount of polyaluminum chloride used for the filler is determined according to the composition difference between PCC and GCC in the filler. The untreated filler PCC dispersion generally has weak negative charge or weak positive charge or is neutral. The untreated filler GCC dispersion generally has a higher negative charge. When the proportion of GCC in the filler composition is high, the amount of polyaluminum chloride used is adjusted and increased. The actual amount is determined according to the particle size and charge control range of the micro-flocculated filler. The PSD50 particle size control range of the micro-flocculated filler is 6-10 μm (X-ray sedimentation method), and the particle charge control range is +20-+50 μeq / L.

[0037] The second step, 1.0-8.0% of pre-gelatinized phosphate ester starch is added to the filler system under stirring after the first step, and the absolute dry amount of the phosphate ester starch to the absolute dry amount of the calcium carbonate filler is 0.10%-3.0%. The stirring is maintained to uniformly mix the starch and the filler. In an embodiment, the phosphate ester starch is selected from a medium-substituted phosphate ester starch with a substitution degree of 0.03-0.05%, a viscosity of 4% paste viscosity value of 0.05 Pa·S (25°C), and a pH value of 6. The absolute dry amount of the phosphate ester starch to the absolute dry amount of the filler is 1.0-3.0%.

[0038] The third step, 5.0%-15% of 2-sodium acrylate homopolymer solution is added to the filler system under stirring after the second step, and the absolute dry amount of the 2-sodium acrylate homopolymer to the absolute dry amount of the phosphate ester starch is 2.0%-5.0%. The stirring is maintained to uniformly mix the 2-sodium acrylate homopolymer, the phosphate ester starch, and the filler. In an embodiment, the solid content of the 2-sodium acrylate homopolymer solution is 10%, and the absolute dry amount of the 2-sodium acrylate homopolymer to the absolute dry amount of the phosphate ester starch is 3.0-4.0%.

[0039] After the above first, second and third steps, the negative charge of the phosphate starch enables it to combine with the partial positive charge on the surface of the filler flocculate, depositing and coating on the surface of the filler flocculate particles to form an effective deposition film. The sodium 2-acrylate homopolymer enables the starch molecules to form a stable combination structure with the filler flocculate, and the deposition film is difficult to dissolve or insoluble in the aqueous system, so that the modified filler has good stability. In this way, the purpose of completely coating or partially coating the filler is achieved. The phosphate starch has a hydroxyl structure and can form hydrogen bonds with fibers, thereby improving the combination between the filler and the fibers and improving the strength of the paper.

[0040] In the fourth step, a cationic polyacrylamide solution with a solid content of 0.05-0.30% is added to the filler system in a stirred state after the third step, and the absolute dry weight of the cationic polyacrylamide to the absolute dry weight of the calcium carbonate filler is 0.05-0.50%. The stirring is maintained to enable the cationic polyacrylamide to mix uniformly with the filler system treated in the third step. In the optimized process, the sodium polyacrylate has a molecular weight of 8-12 million and a cationization degree of 5-8%, and the absolute dry weight of the cationic polyacrylamide to the absolute dry weight of the filler is 0.10-0.30%. According to test detection, the particle size PSD50 of the filler flocculate with the coating substance on the surface is 22-60 μm (X-ray sedimentation method detection), and the particle charge is +10 to +100 μeq / L (PCD particle charge detector detection).

[0041] After the above four steps, the filler flocculate with the coating substance on the surface is obtained, and the filler flocculate is added to the paper stock for filling and papermaking, and compared with the filler filling without treatment. Under the condition that other conditions remain unchanged, the filler addition amount is increased by 2.0-4.0%, the pulp drainage performance is maintained or slightly higher, the total retention is increased by 1.9-2.7%, the ash retention is increased by 3.0-4.1%, the pulp is formed into a shape by papermaking, and the paper strength is detected. Under the condition that the ash content of the paper is increased by 1.8-3.7%, the tensile strength of the paper is equivalent, the interlayer bonding strength is equivalent and is increased by 5-6%, the folding and tearing strength is equivalent, and the opacity is increased by 1.2-1.6%.

[0042] Blank Example 1

[0043] Filler is 100% ground calcium carbonate GCC, pulp is alkaline peroxide bleached chemi-mechanical pulp (PRC-APMP) with 250 ml freeness, softwood chemical pulp (NBKP) with 350 ml freeness, hardwood chemical pulp (LBKP) with 350 ml freeness, and broke pulp. Prepare a mixed pulp of PRC-APMP: NBKP: LBKP: broke pulp = 15%: 15%: 55%: 15%, add 16% (relative to the weight of the pulp) of the aforementioned ground calcium carbonate GCC as filler (GCC filler PSD50 particle size of 2.5-3.0 μm, X-ray sedimentation method; GCC filler charge of -850-1200 μeq / L, 20% solid content), then add chemical additives, cationic starch 1.0% (absolute dry to pulp), cationic polyacrylamide retention aid 350 ppm (absolute dry to pulp), silica-based anionic retention aid 7000 ppm (absolute dry to pulp), measure the drainage performance and retention performance of the pulp, and then go through papermaking forming, then go through pressing and drying, control the moisture content at 3.5-4.0%, and the base weight of the paper made is 80 g / m2.

[0044] Blank Example 2

[0045] Filler is 50% ground calcium carbonate GCC and 50% light calcium carbonate PCC mixture, pulp is alkaline peroxide bleached chemi-mechanical pulp (PRC-APMP) with 250 ml freeness, softwood chemical pulp (NBKP) with 350 ml freeness, hardwood chemical pulp (LBKP) with 350 ml freeness, and broke pulp. Prepare a mixed pulp of PRC-APMP: NBKP: LBKP: broke pulp = 15%: 15%: 55%: 15%, add 16% (relative to the weight of the pulp) of the aforementioned mixed calcium carbonate as filler (mixed filler PSD50 particle size of 2.5-3.0 μm, X-ray sedimentation method; mixed filler charge of -300-550 μeq / L, 20% solid content), then add chemical additives, cationic starch 1.0% (absolute dry to pulp), cationic polyacrylamide retention aid 350 ppm (absolute dry to pulp), silica-based anionic retention aid 7000 ppm (absolute dry to pulp), measure the drainage performance and retention performance of the pulp, and then go through papermaking forming, then go through pressing and drying, control the moisture content at 3.5-4.0%, and the base weight of the paper made is 80 g / m2.

[0046] Blank Example 3

[0047] Filler is 100% light calcium carbonate PCC mixture, pulp is alkaline hydrogen peroxide bleaching chemi-mechanical pulp (PRC-APMP) with freeness 250 ml, softwood chemical pulp (NBKP) with freeness 350 ml, hardwood chemical pulp (LBKP) with freeness 350 ml, and coated broke pulp. The mixed pulp is prepared with PRC-APMP: NBKP: LBKP: coated broke pulp = 15%: 15%: 55%: 15%, and 16% (relative to the weight of the pulp) of the aforementioned light calcium carbonate PCC is added as filler (PCC filler PSD50 particle size is 2.5-3.0 μm, X-ray sedimentation method; PCC filler charge is -80-+120 μeq / L, 20% solid content), and then chemical additives are added, cationic starch 1.0% (absolute dry to pulp), cationic polyacrylamide retention aid 350 ppm (absolute dry to pulp), silica-based anionic retention aid 7000 ppm (absolute dry to pulp), the drainage performance and retention performance of the pulp are measured, and then the pulp is formed into paper, pressed, dried, and the moisture content is controlled at 3.5-4.0%, and the base weight of the paper produced is 80 g / m2.

[0048] Example 1 of the present application

[0049] Filler pretreatment: the filler before treatment is 100% heavy calcium carbonate GCC with a solid content of 20%, and a uniform calcium carbonate dispersion is obtained by pre-stirring. While maintaining slow stirring, 0.30% of polyaluminum chloride based on the absolute dry mass of the filler is added to the calcium carbonate dispersion, and the stirring is maintained to promote the formation of micro-flocculated particles of the calcium carbonate filler and to give the micro-flocculated filler surface a certain positive charge. The PSD50 particle size of the micro-flocculated filler is controlled to be in the range of 6.9 μm (X-ray sedimentation method), and the particle charge is controlled to be +36 μeq / L. In the filler system under the above stirring conditions, 4.0% of a pregelatinized phosphate ester starch with a solid content is added, and the absolute dry amount of the phosphate ester starch to the absolute dry amount of the filler is 3.0%. The stirring is maintained to uniformly mix the starch and the filler. In the filler system under the above stirring conditions, 5% of a 2-acrylic acid sodium homopolymer solution with a solid content is added, and the absolute dry amount of the 2-acrylic acid sodium homopolymer to the absolute dry amount of the phosphate ester starch is 4.0%. The stirring is maintained to uniformly mix the 2-acrylic acid sodium homopolymer, the phosphate ester starch, and the filler. In the filler system under the above stirring conditions, 0.20% of a cationic polyacrylamide solution with a solid content is added, and the absolute dry amount of the cationic polyacrylamide to the absolute dry amount of the filler is 0.30%. The stirring is maintained to uniformly mix the cationic polyacrylamide and the filler system treated in the third step. A filler flocculate with a coating on the surface is obtained. Test detection shows that the particle size PSD50 of the filler flocculate with a coating on the surface is 38 μm (X-ray sedimentation method), and the particle charge is +56 μeq / L (PCD particle charge detector).

[0050] The pulp is PRC-APMP bleached by alkaline hydrogen peroxide, the refining freeness is 250ml; NBKP, the refining freeness is 350ml; LBKP, the refining freeness is 350ml; coated broke pulp. The mixed pulp of PRC-APMP: NBKP: LBKP: coated broke pulp = 15%: 15%: 55%: 15% is prepared, 18% (relative to the weight of the pulp) of the aforementioned pretreated heavy calcium carbonate GCC is added as filler, and chemical additives are added, cationic starch 1.0% (dry to the pulp), cationic polyacrylamide retention aid 350ppm (dry to the pulp), silica-based anionic retention aid 7000ppm (dry to the pulp), the drainage performance and retention performance of the pulp are measured, and the pulp is formed into paper by papermaking, then pressed, dried, and the moisture content is controlled at 3.5-4.0%, and the basis weight of the paper made is 80g / m2.

[0051] Embodiment 2 of the present application

[0052] Pretreatment of the filler: the filler before treatment is a mixture of 50% heavy calcium carbonate GCC and 50% light calcium carbonate, with a solid content of 20%, and a uniform calcium carbonate dispersion is obtained by pre-stirring. Under the condition of maintaining slow stirring, 0.20% of polyaluminum chloride (dry to the filler) is added to the calcium carbonate dispersion, the stirring is maintained, the calcium carbonate filler forms a micro-flocculation particle system, and the surface of the micro-flocculation filler has a certain positive charge, the PSD50 particle size of the micro-flocculation filler is controlled in the range of 4.9μm (X-ray sedimentation method), and the particle charge is controlled at +41μeq / L. In the filler system under the above stirring condition, 4.0% of pre-gelatinized phosphate ester starch with a solid content is added, the dry amount of the phosphate ester starch to the dry amount of the filler is 2.5%, and the stirring is maintained to uniformly mix the starch and the filler. In the filler system under the above stirring condition, 5% of 2-acrylic acid sodium homopolymer solution with a solid content is added, the dry amount of the 2-acrylic acid sodium homopolymer to the dry amount of the phosphate ester starch is 3.0%, and the stirring is maintained to uniformly mix the 2-acrylic acid sodium homopolymer, the phosphate ester starch and the filler. In the filler system under the above stirring condition, 0.20% of cationic polyacrylamide solution with a solid content is added, the dry amount of the cationic polyacrylamide to the dry amount of the filler is 0.20%, and the stirring is maintained to uniformly mix the cationic polyacrylamide and the filler system treated in the third step. The filler flocculation with a coating material on the surface is obtained. It is detected by test that the particle size PSD50 of the filler flocculation with a coating material on the surface is 42μm (X-ray sedimentation method), and the particle charge is +68μeq / L (PCD particle charge detector).

[0053] The pulp is PRC-APMP bleached by alkaline hydrogen peroxide, the beating freeness is 250 ml; NBKP, the beating freeness is 350 ml; LBKP, the beating freeness is 350 ml; coated broke pulp. The mixed pulp of PRC-APMP: NBKP: LBKP: coated broke pulp = 15%: 15%: 55%: 15% is prepared, 19% (relative to the weight of the pulp) of the aforementioned pretreated mixed calcium carbonate is added as filler, chemical additives are added, cationic starch 1.0% (dry to the pulp), cationic polyacrylamide retention aid 350 ppm (dry to the pulp), silica-based anionic retention aid 7000 ppm (dry to the pulp), the drainage performance and retention performance of the pulp are measured, and the pulp is formed into paper, then pressed, dried, the moisture content is controlled at 3.5-4.0%, and the base weight of the paper made is 80 g / m2.

[0054] Embodiment 3 of the present application

[0055] Pretreatment of the filler: the filler before treatment is 100% light calcium carbonate PCC, the solid content is 20%, and a uniform calcium carbonate dispersion is obtained by pre-stirring. Under the condition of maintaining slow stirring, 0.10% of polyaluminum chloride (dry to the filler) is added to the calcium carbonate dispersion, the stirring is maintained, the calcium carbonate filler forms a micro-flocculated particle system, and the surface of the micro-flocculated filler has a certain positive charge, the PSD50 particle size of the micro-flocculated filler is controlled in the range of 8.2 μm (X-ray sedimentation method), and the particle charge is controlled at +63 μeq / L. In the filler system under the above stirring condition, 4.0% of pre-gelatinized phosphate ester starch with a solid content is added, the dry amount of the phosphate ester starch to the dry amount of the filler is 2.0%, and the stirring is maintained to uniformly mix the starch and the filler. In the filler system under the above stirring condition, 5% of a 2-acrylic acid sodium homopolymer solution with a solid content is added, the dry amount of the 2-acrylic acid sodium homopolymer to the dry amount of the phosphate ester starch is 2.0%, and the stirring is maintained to uniformly mix the 2-acrylic acid sodium homopolymer, the phosphate ester starch, and the filler. In the filler system under the above stirring condition, 0.20% of a cationic polyacrylamide solution with a solid content is added, the dry amount of the cationic polyacrylamide to the dry amount of the filler is 0.15%, and the stirring is maintained to uniformly mix the cationic polyacrylamide and the filler system treated in the third step. The filler flocculated with the coating material on the surface is obtained. The particle size PSD50 of the filler flocculated with the coating material on the surface is 56 μm (X-ray sedimentation method), and the particle charge is +87 μeq / L (PCD particle charge detector).

[0056] The pulp is PRC-APMP bleached by alkaline hydrogen peroxide, the refining freeness is 250ml; NBKP, the refining freeness is 350ml; LBKP, the refining freeness is 350ml; coated broke pulp. The mixed pulp of PRC-APMP: NBKP: LBKP: coated broke pulp = 15%: 15%: 55%: 15% is prepared, 20% (relative to the weight of the pulp) of the aforementioned pretreated mixed calcium carbonate is added as filler, chemical additives are added, cationic starch 1.0% (dry to pulp), cationic polyacrylamide retention aid 350ppm (dry to pulp), silica-based anionic retention aid 7000ppm (dry to pulp), the drainage performance and retention performance of the pulp are measured, and the pulp is formed into paper by papermaking, then is pressed and dried, the moisture content is controlled at 3.5-4.0%, and the base weight of the paper made is 80g / m2.

[0057] The comparison table of experimental data is as follows.

[0058]

[0059]

[0060]

[0061] The papermaking filler modification technology provided by the embodiments of the present application combines the filler coating technology and the filler pre-flocculation technology to modify the calcium carbonate filler, so that the filler loading of the paper is further improved, the negative impact of the filler on the strength performance of the paper is reduced under the condition that the drainage and retention of the pulp are not affected, and the running performance of the paper machine is not affected. The specific beneficial effects are as follows.

[0062] 1) Compared with the unmodified calcium carbonate filler (GCC, PCC, or a mixture of GCC and PCC), the modified filler flocculation (GCC, PCC, or a mixture of GCC and PCC) has an increased loading of 2.0%-4.0%, the pulp is prepared and other conditions remain unchanged, the pulp drainage is equivalent or slightly better (increased by 7-8ml / 10s), the ash retention is increased by 3.0-4.1%, and the total retention is increased by 1.9-2.7%.

[0063] 2) compared with unmodified calcium carbonate filler (GCC, PCC, or GCC and PCC mixture), the modified filler flocculation (GCC, PCC, or GCC and PCC mixture), the filling amount is increased by 2.0%~4.0%, the slurry is prepared and other conditions are maintained and is formed into a shape, the paper ash is increased by 1.80~3.70%, the interlayer bonding strength is increased by 5~6%, the tensile strength and folding resistance are maintained, the thickness of the paper is decreased by about 1.5~2.0μm due to the increase of ash, which is within the acceptable control range (according to the thickness of the blank example 73μm, according to the national standard hanging upper and lower limit 4%, the thickness fluctuation range is 3μm).

[0064] 3) according to the increase of 1.80~3.70% of ash, the price difference of 4000 yuan / ton of modified filler and fiber is calculated, the raw material cost of ton of paper can be reduced by 72~148 yuan / ton of paper.

[0065] The modification method of the papermaking filler provided by the embodiment of the application is to coat and modify the filler first, and then pre-flocculate and modify the filler, and the modified filler is added into the paper pulp for papermaking, in the case of increasing the filling amount, the pulp filtration performance and retention characteristics are not deteriorated, and the paper physical strength and surface strength are maintained. Under the premise of ensuring the paper machine running performance, the raw material cost of papermaking is reduced to achieve the same paper quality.

[0066] The above only describes some embodiments of the application, and does not limit the protection scope of the application, and any equivalent device or equivalent process transformation using the content of the specification and drawings, or direct or indirect application in other related technical fields, are also included in the patent protection scope of the application.

Claims

1. A method for modifying paper filling materials, characterized in that, The modification method includes: Adding polyaluminum chloride to the calcium carbonate filler solution and stirring to form a first mixed solution promotes the formation of micro-flocculent particles from the calcium carbonate filler, and makes the surface of the micro-flocculent particles positively charged. Pregelatinized phosphate starch is added to the first mixed solution and stirred to form a second mixed solution; wherein the amount of pregelatinized phosphate starch added is 0.1~3.0% of the oven-dry mass of the calcium carbonate filler, and the degree of substitution is 0.03~0.05%; A sodium 2-acrylate homopolymer solution is added to the second mixed solution and stirred to form a third mixed solution; wherein the amount of sodium 2-acrylate homopolymer added is 2.0~5.0% of the oven-dry weight of the phosphate starch; A cationic polyacrylamide solution is added to the third mixed solution and stirred to obtain a filler flocculant with a coating material.

2. The modification method according to claim 1, characterized in that, In the step of adding polyaluminum chloride to the calcium carbonate filler solution and stirring to form a first mixed solution, the solid content of the calcium carbonate filler is 10-30%; the amount of polyaluminum chloride added is 0.02%-0.30% of the oven-dry mass of the calcium carbonate filler.

3. The modification method according to claim 2, characterized in that, The polyaluminum chloride contains more than 10.0% aluminum oxide and has a basicity B of 40.0% to 90.0%.

4. The modification method according to claim 3, characterized in that, The PSD50 particle size of the micro-flocculent particles in the first mixed solution is controlled within the range of 5~20μm, and the particle charge is controlled within the range of +10μeq / L to +200μeq / L.

5. The modification method according to claim 1, characterized in that, In the step of adding cationic polyacrylamide solution to the third mixed solution and stirring to obtain filler flocs with coating material, the solid content of the cationic polyacrylamide solution is 0.05~0.30%, and the amount of cationic polyacrylamide added is 0.05~0.50% of the oven-dry weight of the calcium carbonate filler.

6. The modification method according to claim 5, characterized in that, The obtained filler flocs with coating material have a PSD50 particle size of 22~60μm and a particle charge of +10μeq / L to +100μeq / L.

7. A papermaking filler, characterized in that, The papermaking filler is prepared using the modification method described in any one of claims 1-6.

8. A paper product, characterized in that, The paper product is prepared using the papermaking filler described in claim 7.

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