Paper product, paper pulp and preparation method thereof

Abstract

The invention provides a paper product, paper pulp and a preparation method thereof. The preparation method comprises the following steps: adding microfibrillated cellulose into a broke pulping line, mixing the microfibrillated cellulose with broke pulp, and pulping; mixing the ground paper pulp with mechanical pulp and hardwood pulp; and adding a medicine into the mixed paper pulp. According to the paper pulp preparation method provided by the embodiment of the invention, the MFC (microfibrillated cellulose) is added before a broken paper disc mill, the MFC and the broken paper are ground together, are firstly combined with the broken paper fibers, and are then combined with the chemical pulp and the mechanical pulp along with the broken paper fibers, so that the strength of a paperboard core layer paper sheet and the ash retention rate of the broken paper can be improved; the problems that when microfibrillated cellulose is applied to a large paper machine, the microfibrillated cellulose is not matched with a paper machine wet part system, the dehydration efficiency of the paper machine is affected, and the enhancement effect is not obvious are solved.

Description

Technical Field

[0001] The present application relates to the technical field of papermaking, and in particular to a paper product, pulp and a preparation method thereof. Background Art

[0002] Microfibrillated cellulose (MFC) is a one-dimensional nanoscale cellulose material made from plant fibers through mechanical defibrination. Its width is less than 100nm, but its length can reach 2-200um. MFC has a very high aspect ratio, high specific surface area and abundant surface hydroxyl groups. The scientific community has conducted extensive research on the preparation of MFC and its application in the food, medicine, papermaking, cosmetics and coating industries.

[0003] Since MFC has a large specific surface area and abundant surface hydroxyl groups, it can increase the electrostatic repulsion between fibers after being added to the pulp, which is beneficial to the dispersion of fibers and fillers in the papermaking process. When the pulp is dehydrated and formed, the high hydroxyl content on the surface of MFC can improve the ability of hydrogen bonding between fibers and enhance the strength of paper sheets. Studies on the effect of MFC on the drainage performance and strength of bleached softwood kraft pulp show that the application of MFC will reduce the drainage performance of the pulp, but will significantly enhance the tensile strength of the paper.

[0004] During the pulping and bleaching process, a large number of carboxyl and carbonyl groups will be generated on the fiber surface, making the fiber surface negatively charged, which will not only cause electrostatic repulsion between long fibers and fine fibers, but also hinder the formation of larger flocs, affecting the water filtration performance of pulp and the retention rate of fillers. Generally, the method of adding cationic retention and drainage aids is used to improve the water filtration performance of pulp, improve the retention of fine components and fillers, and improve the strength of paper sheets. Therefore, a large number of studies have shown that by introducing positive charges into the fiber surface through chemical modification to make the fiber have a certain positive charge, the problems of salt accumulation and charge reversal caused by general cationic additives can be eliminated, and it has the advantages of high retention rate of fine fibers and fillers, good water filtration performance, etc., and can also significantly improve the strength of paper.

[0005] Microfibrillated cellulose can be cationized to improve the retention of microfibrillated cellulose and the strength of paper sheets by using the charge effect. However, in industrial applications, especially in large-scale high-speed paper machines, there are still problems such as low retention rate of MFC, affecting paper machine dehydration, and the inability to reflect the enhancement efficiency. Therefore, it is necessary to select the appropriate MFC in combination with the system conditions of the paper machine, and develop application processes to make MFC have good compatibility with the papermaking wet system and give full play to its enhancement effect. Summary of the invention

[0006] A first aspect of an embodiment of the present application provides a method for preparing pulp, the method comprising:

[0007] The microfibrillated cellulose is added to the broke pulping line and mixed with the broke pulp for refining;

[0008] Mixing refined pulp with mechanical pulp and hardwood pulp;

[0009] Add chemicals to the mixed pulp.

[0010] In some optional embodiments, before the step of adding the microfibrillated cellulose to the broke paper refining line and mixing it with the broke paper pulp for refining, the step also includes: subjecting the microfibrillated cellulose to a cation modification treatment, so that the PCD of the microfibrillated cellulose after cation modification is: +100000 to +300000ueq / L.

[0011] In some optional embodiments, the aspect ratio of the microfibrillated cellulose is greater than 5000.

[0012] In some optional embodiments, the microfibrillated cellulose has a solid content of 6-10% and a viscosity of 400-1000 cps.

[0013] In some optional embodiments, in the step of adding the microfibrillated cellulose to the broke refining line and mixing it with broke pulp for refining, the ratio of the added amount of the microfibrillated cellulose to the broke is 1-5%.

[0014] In some optional embodiments, in the step of mixing the refined pulp with the mechanical pulp and the broadleaf pulp, the concentration of the mixed pulp is 3.5-4.5%; the step of adding chemicals to the mixed pulp includes: adding 0.3-0.5% strong cationic PAC to the mixing tank, diluting the pulp to a concentration of 1.0-1.5% with white water, and adding a sizing agent, a calcium carbonate filler and a cationic retention aid in sequence before the pressure screen pump.

[0015] In a second aspect, an embodiment of the present application provides a pulp, which is prepared by the preparation method described in the above embodiment.

[0016] In a third aspect, an embodiment of the present application provides a paper product, which is prepared using the pulp described in the above embodiment.

[0017] In some optional embodiments, the paper product comprises a surface layer, a surface lining layer, a core layer and a bottom layer stacked in sequence, wherein the core layer is prepared using the pulp according to claim 7.

[0018] In some optional embodiments, the surface layer and the surface lining layer include 20-30% coniferous wood pulp and 70-80% broadleaf wood pulp; the core layer includes 40%-60% mechanical pulp, 10%-30% broadleaf wood pulp, 20%-30% damaged paper pulp and 0.2-1% MFC; the bottom layer includes 20-30% coniferous wood pulp and 70-80% broadleaf wood pulp.

[0019] The pulp preparation method provided in the embodiment of the present application adds MFC (microfibrillated cellulose) before the broken paper disc grinding, and allows the MFC to be ground together with the broken paper, first combining with the broken paper fibers, and then combining with the chemical pulp and mechanical pulp. This can improve the strength of the core layer paper sheets of the paperboard and the ash retention rate of the broken paper, and solves the problem that the microfibrillated cellulose is not matched with the wet end system of the paper machine when used on a large paper machine, affects the dehydration efficiency of the paper machine, and has an insignificant strengthening effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0021] Figure 1 It is a schematic flow chart of an embodiment of a method for preparing pulp of the present application;

[0022] Figure 2 It is a schematic flow chart of another embodiment of the method for preparing pulp of the present application;

[0023] Figure 3 It is a schematic diagram of the stacking structure of an embodiment of the paper product of the present application. DETAILED DESCRIPTION

[0024] The present application is further described in detail below in conjunction with the accompanying drawings and examples. It is particularly noted that the following examples are only used to illustrate the present application, but are not intended to limit the scope of the present application. Similarly, the following examples are only some embodiments of the present application rather than all embodiments, and all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application.

[0025] The terms "first", "second", and "third" in the embodiments of the present application are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Thus, the features defined as "first", "second", and "third" can expressly 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 clearly and specifically defined. In the embodiments of the present application, all directional indications (such as up, down, left, right, front, back...) are only used to explain the relative position relationship, movement, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication also changes accordingly. The terms "including" and "having" in the embodiments of the present application and any of their variations are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but optionally also includes steps or units that are not listed, or optionally also includes other steps or components inherent to these processes, methods, products, or devices.

[0026] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0027] The preparation method in this embodiment specifically comprises refining microfibrillated cellulose and broke paper together to obtain broke pulp containing microfibrillated cellulose. The broke pulp containing MFC is then pumped to the mixing pipe of the paper machine, and the pulps are mixed by the static mixer of the mixing pipe and then flowed to the pulp pool of the paper machine. During the flow of the pulp, chemicals from the wet end of papermaking are added, and the MFC is dispersed again through the flow system.

[0028] The present application example first provides a method for preparing pulp. Figure 1 , Figure 1 The figure is a schematic flow chart of an embodiment of a method for preparing pulp of the present application. The method for preparing pulp includes but is not limited to the following steps.

[0029] Step S100, adding the microfibrillated cellulose to the broke paper refining line and mixing it with the broke paper pulp for refining.

[0030] In this step, the MFC is added at the inlet of the disc refiner pump of the broke paper refining line. The MFC is mixed with the broke paper pulp by the suction of the pump and then the broken paper pulp containing MFC is obtained after the broken paper is refined by the disc refiner. The amount of MFC added is 1-5% of the broken paper, and can be 1%, 1.2%, 1.5%, 2%, 2.4%, 3%, 4.5%, 5% and the like. The solid content of the microfibrillated cellulose is 6-10%, the viscosity is 400-1000cps, and the aspect ratio of the microfibrillated cellulose is greater than 5000.

[0031] The process parameters of the broken paper line are set as follows: the broken paper is diluted to a concentration of 3-5% by a horizontal pulper, mechanically stirred for 10 minutes, and becomes broken paper pulp with a size of 0.5-4 cm, which enters the broken paper tower. The pulp in the 3-5% broken paper tower is pumped to the deflaker, and the broken paper fragment pulp is dispersed into broken paper fiber pulp, which passes through a high-concentration cleaner to remove impurities with a large specific gravity, and then passes through a 0.35mm pressure screen to remove unbroken broken paper pieces to obtain broken paper pulp. The damaged paper pulp is pumped by a centrifugal pump through two parallel and one series disc refiners. The power of the two parallel disc refiners is set to 314kw / 244kw respectively, and the specific energy is 20-30kwh / T; the series disc refiner has a power of 700-800kw and a specific energy of 20-30kwh / T. MFC is added to the pump inlet of the centrifugal pump, and the damaged paper pulp and MFC are evenly mixed through the centrifuge. The fibers are squeezed and ground by the grinding disc of the disc refiner. Physical grinding can reduce the distance between MFC and the fiber, allowing MFC to form hydrogen bonds with the papermaking fiber first and occupy the binding sites of the fiber.

[0032] Please continue reading Figure 1 The preparation method in this embodiment further includes step S200 of mixing the refined pulp with the mechanical pulp and the broadleaf pulp.

[0033] In this step, the mixed pulp (including broken pulp and MFC) after refining is mixed with mechanical pulp and hardwood pulp in the pulp mixing pipe of the paper machine core layer, and the concentration of the mixed pulp is 3.5-4.5%. It is pumped to the mixing tank through a static mixer and then mixed.

[0034] Please continue reading Figure 1 The preparation method in this embodiment further includes step S300 of adding chemicals to the mixed pulp.

[0035] In step S300, after entering the mixing tank, 0.3-0.5% strong cationic PAC (polyaluminium chloride) is added, 10-20kg of cationic amphoteric dry strength agent or cationic starch is added at the outlet of the mixing tank, and 4-7kg of glyoxal-modified polyacrylamide is added at the outlet of the paper machine pulp tank. The slurry is diluted to a concentration of 1.0-1.5% with white water, and 500-2000ppm of ASA sizing agent, 50-150kg of calcium carbonate filler, and 200-300ppm of cationic retention aid are added before the pressure screen pump.

[0036] The pulp preparation method provided in the embodiment of the present application adds MFC (microfibrillated cellulose) before the broken paper disc grinding, and allows the MFC to be ground together with the broken paper, first combining with the broken paper fibers, and then combining with the chemical pulp and mechanical pulp. This can improve the strength of the core layer paper sheets of the paperboard and the ash retention rate of the broken paper, and solves the problem that the microfibrillated cellulose is not matched with the wet end system of the paper machine when used on a large paper machine, affects the dehydration efficiency of the paper machine, and has an insignificant strengthening effect.

[0037] See also Figure 2 , Figure 2 2 is a flow chart of another embodiment of the method for preparing pulp of the present application. Different from the above-mentioned embodiment, the preparation method in this embodiment further includes step S400 of subjecting the microfibrillated cellulose to cationic modification.

[0038] The PCD of the cationic-modified microfibrillated cellulose is: +100000 to +300000ueq / L, the solid content of the microfibrillated cellulose is 6-10%, the viscosity is 400-1000cps, and the aspect ratio is greater than 5000.

[0039] Please continue reading Figure 2 The preparation method in this embodiment further includes step S100, adding the microfibrillated cellulose to the broke paper refining line and mixing it with the broke paper pulp and then refining it.

[0040] In this step, the MFC is added at the inlet of the disc refiner pump of the broke paper refining line. The MFC is mixed with the broke paper pulp by the suction of the pump and then the broke paper pulp is refined by the disc refiner to obtain the broke paper pulp containing MFC. The amount of MFC added is 1-5% of the broke paper, and can be 1%, 1.2%, 1.5%, 2%, 2.4%, 3%, 4.5%, 5% and other values.

[0041] The process parameters of the broken paper line are set as follows: the broken paper is diluted to a concentration of 3-5% by a horizontal pulper, mechanically stirred for 10 minutes, and becomes broken paper pulp with a size of 0.5-4 cm, which enters the broken paper tower. The pulp in the 3-5% broken paper tower is pumped to the deflaker, and the broken paper fragment pulp is dispersed into broken paper fiber pulp, which passes through a high-concentration cleaner to remove impurities with a large specific gravity, and then passes through a 0.35mm pressure screen to remove unbroken broken paper pieces to obtain broken paper pulp. The damaged paper pulp is pumped by a centrifugal pump through two parallel and one series disc refiners. The power of the two parallel disc refiners is set to 314kw / 244kw respectively, and the specific energy is 20-30kwh / T; the series disc refiner has a power of 700-800kw and a specific energy of 20-30kwh / T. MFC is added to the pump inlet of the centrifugal pump, and the damaged paper pulp and MFC are evenly mixed through the centrifuge. The fibers are squeezed and ground by the grinding disc of the disc refiner. Physical grinding can reduce the distance between MFC and the fiber, allowing MFC to form hydrogen bonds with the papermaking fiber first and occupy the binding sites of the fiber.

[0042] Please continue reading Figure 2 The preparation method in this embodiment further includes step S200 of mixing the refined pulp with the mechanical pulp and the broadleaf pulp.

[0043] In this step, the mixed pulp (including broken pulp and MFC) after refining is mixed with mechanical pulp and hardwood pulp in the pulp mixing pipe of the paper machine core layer, and the concentration of the mixed pulp is 3.5-4.5%. It is pumped to the mixing tank through a static mixer and then mixed.

[0044] Please continue reading Figure 2 The preparation method in this embodiment further includes step S300 of adding chemicals to the mixed pulp.

[0045] In step S300, after entering the mixing tank, 0.3-0.5% strong cationic PAC (polyaluminium chloride) is added, 10-20kg of cationic amphoteric dry strength agent or cationic starch is added at the outlet of the mixing tank, and 4-7kg of glyoxal-modified polyacrylamide is added at the outlet of the paper machine pulp tank. The slurry is diluted to a concentration of 1.0-1.5% with white water, and 500-2000ppm of ASA sizing agent, 50-150kg of calcium carbonate filler, and 200-300ppm of cationic retention aid are added before the pressure screen pump.

[0046] Among them, the pulp data after adding MFC to the broken paper pulp is as follows.

[0047]

[0048] After adding MFC, cationic MFC can combine with the fibers in the broken paper pulp, acting as a bridge between fibers and connecting the broken paper fibers. The high aspect ratio entanglement and strength toughness can improve the tensile strength of the fibers, and the hydrogen bonding with the fibers can enhance the internal binding force between the fibers. The formed micro-flocs are also beneficial to the retention of fillers in the broken paper.

[0049] Among them, after 20% of damaged pulp with MFC added was added to the core layer pulp of the paper product, the data of the mixed pulp were as shown in the following table.

[0050]

[0051] In addition, the present application also provides a paper product, see Figure 3 , Figure 3 1 is a schematic diagram of the stacked structure of an embodiment of the paper product of the present application, wherein the paper product in this embodiment may include a surface layer 101, a surface lining layer 102, a core layer 103 and a bottom layer 104 stacked in sequence. Optionally, the core layer 103 in this embodiment may be prepared using the pulp in the aforementioned embodiment.

[0052] Among them, the surface layer 101 and the surface lining layer 102 may include 20-30% of coniferous wood pulp and 70-80% of hardwood pulp; the core layer 103 includes 40%-60% of mechanical pulp, 10%-30% of hardwood pulp, 20%-30% of damaged paper pulp and 0.2-1% of MFC; the bottom layer 104 may include 20-30% of coniferous wood pulp and 70-80% of hardwood pulp. The wet paper sheets of the surface layer 101, the surface lining layer 102, the core layer 103 and the bottom layer 104 are compounded through multiple layers after being dehydrated after being put on the screen. Other parameter characteristics of the paper product can be conventionally selected, which is within the scope of understanding of those skilled in the art and will not be repeated here.

[0053] It should also be noted that this embodiment only illustrates a four-layer stacked paper product solution. In some other embodiments, the paper product may also have other stacked numbers, which will not be listed and described in detail here.

[0054] Among them, the strength parameters of the paper products after the various paper layers are compounded are shown in the following table.

[0055] MFC dosage in broke pulp 0％ 0.2％ 0.5％ 0.8％ <![CDATA[Interlayer bonding strength. J / m 2 > 186 198 208 219 Ash content, % 33.87 33.95 34.75 35.62 Number of blistering of cardboard TV-16, front side 3 3.5 4 4.5 Number of blistering of cardboard TV-16, back side 3 3.5 4 4.5

[0056] During the preparation process of the paper products in the examples of the present application, the application of MFC in the papermaking industry was studied, and the dispersing and retaining effects of the addition point of MFC on the application of MFC in the papermaking industry were demonstrated. The high aspect ratio, high specific surface area and rich hydroxyl characteristics of microfibrillated cellulose were fully utilized for enhancement. The pulping application together with papermaking broken paper solved the difficulties of dispersion, low retention rate and influence on paper dehydration of microfibrillated cellulose in papermaking, and at the same time, the retention rate of fillers and fine fibers in broken paper pulp was improved, and the ash content and strength of paper sheets were increased, thereby realizing industrial enhanced application.

[0057] The above descriptions are only some embodiments of the present application, and do not limit the protection scope of the present application. Any equivalent device or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly used in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for preparing pulp, characterized in that: The preparation method comprises: The microfibrillated cellulose is added to the broke pulping line and mixed with the broke pulp for refining; Mixing refined pulp with mechanical pulp and hardwood pulp; Add chemicals to the mixed pulp.

2. The preparation method according to claim 1, characterized in that: Before the step of adding the microfibrillated cellulose to the broke paper refining line and mixing it with the broke paper pulp for refining, the method further comprises: subjecting the microfibrillated cellulose to a cation modification treatment, so that the PCD of the microfibrillated cellulose after the cation modification is: +100000 to +300000ueq / L.

3. The preparation method according to claim 2, characterized in that: The aspect ratio of the microfibrillated cellulose is greater than 5000.

4. The preparation method according to claim 2, characterized in that: The microfibrillated cellulose has a solid content of 6-10% and a viscosity of 400-1000 cps.

5. The preparation method according to claim 1, characterized in that: In the step of adding the microfibrillated cellulose to the broke pulping line and mixing it with the broke pulp before refining, the ratio of the added amount of the microfibrillated cellulose to the broke pulp is 1-5%.

6. The preparation method according to claim 1, characterized in that: In the step of mixing the refined pulp with the mechanical pulp and the hardwood pulp, the concentration of the mixed pulp is 3.5-4.5%; the step of adding chemicals to the mixed pulp includes: adding 0.3-0.5% of strong cationic PAC to the mixing tank, diluting the pulp to a concentration of 1.0-1.5% with white water, and adding a sizing agent, a calcium carbonate filler and a cationic retention aid in sequence before the pressure screen pump.

7. A pulp, characterized in that: The pulp is prepared by the preparation method according to any one of claims 1 to 6.

8. A paper product, characterized in that: The paper product is prepared by using the pulp described in claim 7.

9. The paper product according to claim 8, characterized in that: The paper product comprises a surface layer, a surface lining layer, a core layer and a bottom layer which are stacked in sequence, wherein the core layer is prepared by using the pulp according to claim 7.

10. The paper product according to claim 9, characterized in that: The surface layer and the surface lining layer include 20-30% of coniferous wood pulp and 70-80% of broadleaf wood pulp; the core layer includes 40%-60% of mechanical pulp, 10%-30% of broadleaf wood pulp, 20%-30% of damaged paper pulp and 0.2-1% of MFC; the bottom layer includes 20-30% of coniferous wood pulp and 70-80% of broadleaf wood pulp.

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