[0017] The technical solutions in the embodiments of the present application will be described clearly and completely in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of this application.
[0018] An embodiment of the present application provides a core layer slurry for packaging paperboard. The core layer slurry includes bleached chemical thermomechanical pulp (BCTMP), and the bleached chemical thermomechanical pulp includes softwood mechanical pulp, and softwood mechanical pulp accounts for bleaching. The percentage of the absolute dry mass of the chemical thermomechanical pulp is 25%-30%.
[0019] The core layer slurry of the present application is added to the softwood mechanical pulp. The softwood mechanical pulp has a longer fiber length and good tensile strength. Therefore, the softwood mechanical pulp is characterized by high bulk and high stiffness, and 25% is added. -30% of the bleached chemical thermomechanical pulp of softwood mechanical pulp has both high bulk and strength, and the core slurry containing the bleached chemical thermomechanical pulp improves the interweaving ability of core fibers and enhances the core layer Z-direction (thickness direction) strength, the prepared paperboard has the characteristics of high bulk, high strength, and stiffness, so the core layer slurry can be used to make the core layer of white cardboard, food cardboard and other packaging cardboard , Especially suitable for the field of medium and high-grade food packaging cardboard. In one embodiment, the percentage of softwood mechanical pulp to the absolute dry mass of the bleached chemical thermomechanical pulp is 25%-30%, for example, 25%, 26%, 27%, 28%, 29% or 30%, etc., There is no restriction here.
[0020] In one embodiment, the bulk of the softwood mechanical pulp is 2.7-3cm 3 /g, for example, 2.7cm 3 /g、2.8cm 3 /g、2.9cm 3 /g or 3cm 3 /g etc. The tensile strength is 24-28N·m/g, such as 24N·m/g, 25N·m/g, 26N·m/g, 27N·m/g or 28N·m/g. The main raw materials of bleached chemical thermomechanical pulp are eucalyptus and poplar. The thickness of eucalyptus pine is generally 3.0-3.5cm 3 /g, the tensile strength is 9-14N·m/g, the thickness of poplar pine is generally 2.5-2.8cm 3 /g, the tensile strength is 11-14N·m/g. The corresponding coniferous mechanical pulp can be selected according to the characteristics of other mechanical pulps in the bleached chemi-thermomechanical pulp to fine-tune the bleached chemi-thermomechanical pulp to obtain the optimization of the fiber ratio structure, thereby obtaining the core layer pulp Cardboards with high bulk, high stiffness and good tensile strength can be prepared according to requirements.
[0021] In one embodiment, the whiteness of the softwood mechanical pulp is above 74%. When the core layer slurry of the present application is used to prepare white cardboard, the color requirements are relatively high. The whiteness of the softwood mechanical pulp is 74%. Above, the prepared core layer has high whiteness, which meets the requirements of the use of white cardboard.
[0022] In one embodiment, the freeness of softwood mechanical pulp is 300-410ml. Canadian Standard Freeness (CSF) is one of the methods for measuring the filtration performance of the slurry. Generally speaking, the greater the freeness of the slurry, The faster the filtration rate. In this embodiment, the freeness of the softwood mechanical pulp is controlled between 300ml and 410ml, such as 300ml, 320ml, 350ml, 380ml, 400ml, 410ml, etc., which reflects the degree of fiber splitting. If the freeness is too low, the splitting will be better, the air permeability will be worse, and the fibers will be cut more. Therefore, in order to maintain the fiber length, the freeness of the selected coniferous mechanical pulp is more in the range of 300ml-410ml. For appropriate.
[0023] In an embodiment, the core layer slurry further includes a positive starch and a dry strength agent, wherein the amount of the positive starch is 0.6-1% of the absolute dry mass percentage of the bleached chemi-thermomechanical pulp, such as 0.6%, 0.7%, 0.8 %, 0.9%, or 1%, etc., there is no limitation here; the amount of dry strength agent is 2.1-3.1% of the absolute dry mass percentage of the bleached chemical thermomechanical pulp, such as 2.1%, 2.5% or 3.1%, etc. limit. Positive starches include starches formed by introducing tertiary ammonium groups, quaternary ammonium groups, primary amine groups or quaternary amine groups into starch macromolecules. By adjusting the ratio of positive starch to further improve the interlayer bonding force of the prepared core layer. The positive starch has a high retention rate. It is added to the core slurry and is absorbed by the fibers in the slurry. In the process of manufacturing base paper, the positive starch flocculates the anionic fibers together and makes the fine fiber retention rate. Increase, thereby helping to form a fiber-fiber bond, thereby improving the interlayer bonding force of the prepared base paper. Dry strength agents are used to compensate for the decrease in paperboard strength caused by the addition of fillers or low-grade fibers (such as recycled fibers). By adjusting the amount of positive starch and dry strength agent used, the strength of the core slurry can be fine-tuned. Compared with the prior art, the positive starch and dry strength agent of the present application are reduced. Reducing the positive starch and dry strength agent helps to improve the flexibility of the paperboard. Too much positive starch and dry strength agent make the paper brittle. Poor folding resistance.
[0024] In an embodiment, the percentage of the bleached chemical thermomechanical pulp to the absolute dry mass of the core slurry is 50%-70%, such as 50%, 60%, or 70%. The core layer slurry also includes waste paper deinked pulp (DIP), bleached sulphate hardwood pulp (LBKP) and broken paper, wherein the waste paper deinked pulp accounts for 5% of the absolute dry mass of the core layer slurry -15%, such as 5%, 8%, 12% or 15%, etc.; bleached sulphate hardwood pulp accounts for 5%-15% of the absolute dry mass of the core layer pulp; broken paper accounts for the core layer The percentage of the absolute dry mass of the slurry is 5%-25%, such as 5%, 10%, 15%, 20%, or 25%.
[0025] Another embodiment of the present application provides a packaging paperboard, including a bottom layer, a core layer and a surface layer, and the core layer is prepared by using the core layer slurry in any of the above embodiments. The packaging cardboard of the present application has the characteristics of high bulk, high strength, and stiffness, and can be used for white cardboard, food cardboard, etc., especially suitable for the field of medium and high-grade food packaging cardboard.
[0026] Further, the core layer slurry of the present application is prepared without refining treatment in the process of preparing the core layer. Through a large number of experiments, it is found that the bulk loss of the cardboard prepared after refining the core layer slurry is large, but the strength is improved It is not obvious, so the core layer slurry of the present application does not undergo refining treatment during the process of preparing the core layer, and the finally obtained cardboard has the characteristics of high bulk, high strength, and stiffness.
[0027] The following description is combined with a specific embodiment:
[0028] Table 1: The core layer slurry ratio of comparative example and example 1
[0029]
[0030] Table 2: Pulp data of eucalyptus and softwood mechanical pulp used in Table 1:
[0031]
[0032] Table 3: Comparison of the quality of the core layer copy of the comparative example and the example:
[0033]
[0034] Table 4: Comparison of the quality of the packaging paperboards of the comparative examples and the examples:
[0035]
[0036] Please refer to Table 1 to Table 4. Table 1 is the core layer slurry ratio of Comparative Example and Example 1. The ratio unit of each component is percentage, which means that each component accounts for the absolute dry mass of core layer slurry Table 2 is the slurry data of the eucalyptus and softwood mechanical pulp used in Table 1; Table 3 is the comparison of the quality of the core layer of the comparative example and the embodiment; Table 4 is the comparative example and the embodiment packaging paperboard Quality comparison. It can be seen from Table 1 and Table 2 that the ratio and data of each component are within the aforementioned range. From Table 3 and Table 4, it can be seen that the packaging board prepared by the core slurry of the present application has a high bulk , High strength, and both stiffness characteristics, so the core layer slurry can be used to manufacture white cardboard, food cardboard and other packaging paperboard core layer, especially suitable for the field of high-grade food packaging paperboard.
[0037] See figure 1 , figure 1 It is a schematic flow diagram of an embodiment of the method for preparing packaging paperboard of the present application.
[0038] Another embodiment of the present application provides a method for preparing packaging cardboard, which specifically includes:
[0039] S101: preparing the bottom layer slurry, the core layer slurry and the surface layer slurry described in any of the above embodiments.
[0040] Among them, the bottom slurry includes bleached broad-leaved kraft pulp and bleached softwood kraft pulp, wherein the bleached broad-leaved kraft pulp accounts for 60%-80% of the absolute dry mass of the bottom slurry, for example, 60%, 70%, 80%, etc., the percentage of bleached softwood kraft pulp to the absolute dry mass of the bottom slurry is 20%-40%, such as 20%, 30%, 40%, etc.
[0041] The core layer slurry adopts the core layer slurry described in any of the above embodiments.
[0042] The surface layer slurry includes bleached hardwood kraft pulp and bleached softwood kraft pulp, wherein the bleached hardwood kraft pulp accounts for 60%-80% of the absolute dry mass of the surface layer slurry, for example, 60%, 70%, 80%, etc., the percentage of bleached softwood kraft pulp to the absolute dry mass of the surface slurry is 20%-40%, such as 20%, 30%, 40%, etc.
[0043] S102: Use the bottom layer slurry, the core layer slurry and the surface layer slurry to prepare the bottom layer, the core layer and the surface layer of the base paper respectively.
[0044] Among them, the core layer slurry is prepared without refining treatment in the process of preparing the core layer.
[0045] S103: Laminating the bottom layer, the core layer and the surface layer together in sequence, and performing post-processing to form a base paper.
[0046] Specifically, the post-treatment may include the steps of pressing, drying, sizing, drying, calendering, and coiling.
[0047] The packaging paperboard produced by the preparation method of this embodiment has the characteristics of high bulk, high strength, and stiffness.
[0048] The above are only examples of this application, and do not limit the scope of this application. Any equivalent structure or equivalent process transformation made by using the description and drawings of this application, or directly or indirectly applied to other related technologies In the same way, all fields are included in the scope of patent protection of this application.
