White card and base paper therefor

Abstract

The application provides a white card paper and a base paper thereof, the base paper comprising: a surface layer, a core layer and a bottom layer which are sequentially stacked; wherein the pulp of the core layer comprises wood pulp, ground calcium carbonate and white mud light calcium carbonate; wherein the wood pulp comprises 50-95% by mass of mechanical pulp and 5-50% by mass of chemical pulp; the mass fraction of the ground calcium carbonate is 10-50%, and the mass fraction of the white mud light calcium carbonate is 10-50%. The base paper of the white card paper provided in the application can improve bulk, improve sizing efficiency, improve ash retention, reduce abrasion and has great market application value by mixing a certain amount of white mud light calcium carbonate which can be obtained at low cost into the pulp.

Description

Technical Field

[0001] This application relates to the technical field of papermaking, specifically to a white cardboard and its base paper. Background Technology

[0002] Light calcium carbonate from bleached mud (referred to as bleached mud calcium carbonate) is a type of light calcium carbonate recovered from bleached mud for papermaking. During the formation of bleached mud, numerous ions and silicates, among other impurities, result in precipitated calcium carbonate with a loose structure and varying shapes and sizes, making it difficult to directly apply to paper machine production. A specific process (for which there is extensive literature) is required to produce qualified bleached mud calcium carbonate. How to reuse the light calcium carbonate recovered from bleached mud in the papermaking process has become a pressing issue. Summary of the Invention

[0003] The first aspect of this application provides a base paper for white cardboard, the base paper comprising: a face layer, a core layer, and a bottom layer stacked sequentially; wherein the pulp of the core layer comprises wood pulp, ground calcium carbonate, and bleached light calcium carbonate; wherein the wood pulp comprises 50-95% by weight of mechanical pulp and 5-50% by weight of chemical pulp; the ground calcium carbonate comprises 10-50% by weight, and the bleached light calcium carbonate comprises 10-50% by weight.

[0004] In some embodiments, the particle size D50 of the white clay light calcium carbonate is between 2 and 8 μm.

[0005] In some embodiments, the particle size D50 of the white clay light calcium carbonate is between 4 and 6 μm.

[0006] In some embodiments, the solid content of the white clay light calcium carbonate is 10%-35%.

[0007] In some embodiments, the pulp of the core layer further includes starch, sizing agent, cationic additive, and silica.

[0008] In some embodiments, the starch is used at a rate of 5-7 kg / ton of slurry, the sizing agent is an alkyl ketene dimer used at a rate of 1-8 kg / ton of slurry, or the sizing agent is an alkenyl succinic anhydride used at a rate of 0.1-1 kg / ton of slurry, the cationic additive is 100-200 ppm, and the silica is 1-3 kg / ton of slurry.

[0009] In some embodiments, the pulp of the surface layer comprises wood pulp, starch, and additives, wherein the wood pulp comprises 10-30% by weight of softwood bleached pulp and 70-90% by weight of hardwood bleached pulp; the amount of starch is 0-5% by weight, and the amount of additives is 0-0.3% by weight.

[0010] In some embodiments, the underlying pulp comprises wood pulp, starch, and additives, wherein the wood pulp comprises 10-20% by weight of softwood bleached pulp and 80-90% by weight of hardwood bleached pulp; the amount of starch is 0-5% by weight, and the amount of additives is 0-0.3% by weight.

[0011] Secondly, this application provides a white cardboard, which includes a coating layer and the base paper described in the above embodiments, wherein the coating layer is coated on the surface of the base paper.

[0012] In some embodiments, the coating layer includes a pre-coating layer, a back coating layer, a middle coating layer, and a top coating layer; wherein the pigments of the pre-coating layer, the back coating layer, and the middle coating layer are all 100% ground calcium carbonate; and the pigments of the top coating layer are 0-30% kaolin and 70-100% ground calcium carbonate.

[0013] The white cardboard base paper provided in this application embodiment can improve bulk, increase sizing efficiency, improve ash retention, and reduce abrasion by adding a certain amount of low-cost white clay light calcium carbonate to the pulp, thus having great market application value. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a schematic diagram of the laminated structure of an embodiment of the base paper of the white cardboard of this application;

[0016] Figure 2 This is a schematic diagram of the laminated structure of a white cardstock according to an embodiment of this application;

[0017] Figure 3 This is a schematic diagram of the stacked structure of another embodiment of the white cardboard of this application. Detailed Implementation

[0018] 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.

[0019] The terms "first," "second," and "third" used in the embodiments of this application are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first," "second," or "third" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified. All directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationships and movement of components in a specific posture (as shown in the figures). If the specific posture changes, the directional indication will also change accordingly. The terms "comprising" and "having," and any variations thereof, in the embodiments of this application are intended to cover non-exclusive inclusion. 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 may optionally include steps or units not listed, or may optionally include other steps or components inherent to these processes, methods, products, or devices.

[0020] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0021] It is well known that GCC (heavy calcium carbonate) is inexpensive, while PCC (light calcium carbonate, also known as precipitated calcium carbonate) is expensive. White clay light calcium carbonate, however, possesses the excellent properties of PCC and is also cheaper than traditional PCC. Currently, white clay light calcium carbonate is used in cultural paper to replace ordinary GCC and improve bulk. Because cultural paper generally has a low proportion of mechanical pulp and high requirements for whiteness, the amount of GCC used is very small, so white clay light calcium carbonate can be used to replace ordinary GCC.

[0022] However, there is no precedent in the industry for using bleached lime to replace ordinary GCC in white cardboard. Because white cardboard is generally multi-layered, and the core layer has a high proportion of mechanical pulp (low whiteness), applying bleached lime to the core layer of white cardboard is advantageous because bleached lime is a recycled waste material, cheaper than GCC, and can also increase bulk, improve sizing efficiency, increase ash retention, and reduce abrasion.

[0023] The process for treating white clay with light calcium carbonate is as follows:

[0024] White mud pulping → Pretreatment (screening, washing) → Carbonation reaction (+CO2) → Solid-liquid separation → Washing → Drying → Crushing and grading → Packaging → Finished product PCC.

[0025] The specific processing parameters are within the understanding of those skilled in the art and there is a large body of existing literature available for reference, so they will not be elaborated here.

[0026] The chemically treated slurry white mud is processed into light calcium carbonate white mud. The basic physical properties before and after processing are shown in the table below.

[0027] White clay White clay light calcium-1 White clay light calcium-2 White clay light calcium-3 Particle size μm, PSD50 15.78 2.1 4.1 6 <![CDATA[Specific surface area m 2 / g]]> 1.99 4.4 3.6 3.1 ISO whiteness % 85.42 89.9 88.2 88 wear mg - 10.1 10.5 21.2 pH 12.85 8.6 8.1 8 Solid content % 74.35 30.6 30.1 30.1 Conductivity ms / cm 9.75 1.48 1.28 1.15

[0028] In view of this, the present application first provides a base paper for white cardstock. Please refer to... Figure 1 , Figure 1 This is a schematic diagram of the laminated structure of a base paper of the white cardboard of this application. The base paper 100 includes a surface layer 110, a core layer 120 and a bottom layer 130 stacked sequentially.

[0029] Specifically, the pulp of the core layer 120 includes wood pulp, ground calcium carbonate, and bleached light calcium carbonate; wherein the wood pulp includes 50-95% by weight mechanical pulp and 5-50% by weight chemical pulp; the ground calcium carbonate is 10-50% by weight, and the bleached light calcium carbonate is 10-50% by weight.

[0030] Optionally, in this embodiment, the particle size D50 of the bleached clay lightweight calcium carbonate is between 2 and 8 μm, preferably between 4 and 6 μm. Specifically, the particle size D50 can be 4 μm, 4.5 μm, 4.6 μm, 5 μm, 5.2 μm, 5.8 μm, 6 μm, 6.1 μm, etc. A larger D50 particle size of 4-6 μm is beneficial for improving bulk thickness, ash content, and sizing degree. The solid content of the bleached clay lightweight calcium carbonate is 10%-35%.

[0031] Optionally, the pulp of the core layer 120 in this embodiment further includes starch, sizing agent (such as alkylketene dimer), cationic additive (such as cationic polyacrylamide), and silica. The amount of starch used is 5-7 kg / ton of pulp, specifically 5 kg / ton, 5.2 kg / ton, 5.5 kg / ton, 6 kg / ton, 6.8 kg / ton, 7 kg / ton, etc. The sizing agent can be alkylketene dimer (AKD) or alkenyl succinic anhydride (ASA); when the sizing agent is alkylketene dimer, the amount used is 1-8 kg / ton of pulp, specifically 1 kg / ton, 4 kg / ton, 6 kg / ton, 8 kg / ton, etc. When the sizing agent is alkenyl succinic anhydride, the dosage is 0.1-1 kg / ton of pulp, specifically 0.1 kg / ton of pulp, 0.2 kg / ton of pulp, 0.25 kg / ton of pulp, 0.45 kg / ton of pulp, 0.5 kg / ton of pulp, 0.8 kg / ton of pulp, and 1 kg / ton of pulp.

[0032] The cationic additive is 100-200 ppm, specifically 100 ppm, 120 ppm, 150 ppm, 180 ppm, 185 ppm, 190 ppm, and 200 ppm. Silica is 1-3 kg / ton of slurry, specifically 1 kg / ton of slurry, 1.3 kg / ton of slurry, 1.5 kg / ton of slurry, 2 kg / ton of slurry, 2.5 kg / ton of slurry, and 3 kg / ton of slurry.

[0033] Pulp preparation and sheet making: Mix mechanical pulp, chemical pulp, GCC, and white clay light calcium carbonate in the proportions mentioned above to form a thin slurry, and then add chemicals: In one embodiment, the chemicals can be: starch 6 kg / ton slurry, AKD (sizing agent, alkyl ketone dimer) 6 kg / ton slurry, CPAM (cationic additive, cationic polyacrylamide) 150 ppm, and silica (silica) 2 kg / ton slurry. After the above materials are mixed evenly, they are made into hand-made sheets.

[0034] The table below compares the parameters of several specific embodiments.

[0035]

[0036]

[0037] The results of the physical property testing of the handwritten sheet are shown in the table below.

[0038]

[0039] As can be seen from Examples 1-3 and the control group, after replacing GCC with an equal amount of white clay light calcium carbonate, the bulk thickness of the hand-made sheets increased, the strength was maintained, the abrasion was reduced, and the sizing degree was better. In Example 4, compared with the control group, GCC was replaced with an equal amount of white clay light calcium carbonate-3, while the amount of APMP was increased by 5% and the amount of NBKP was decreased by 5%. The bulk thickness, strength and other indicators were maintained, and the abrasion was reduced.

[0040] White cardboard core layers typically use GCC as filler because the core pulp is primarily mechanical pulp, resulting in high bulk, and GCC filler is inexpensive. This invention innovatively applies bleached clay (light calcium carbonate) to the white cardboard core layer. Bleached clay is a recycled waste material, cheaper than GCC, and simultaneously increases bulk, improves sizing efficiency, enhances ash retention, and reduces abrasion.

[0041] Optionally, in this embodiment, the pulp of the surface layer 110 of the base paper 100 includes wood pulp, starch, additives, and silica. The wood pulp includes 10-30% by weight of bleached softwood pulp and 70-90% by weight of bleached hardwood pulp; the amount of starch is 0-5% by weight, the amount of additives is 0-0.3% by weight, and the amount of silica is 0-0.3% by weight. The basis weight of the surface layer 110 is 30-40g, and the coating weight is 30-40g.

[0042] Optionally, in this embodiment, the pulp of the bottom layer 130 of the base paper 100 includes wood pulp, starch, additives, and silica. The wood pulp includes 10-20% by weight of bleached softwood pulp and 80-90% by weight of bleached hardwood pulp. The amount of starch is 0-5% by weight, the amount of additives is 0-0.3% by weight, and the amount of silica is 0-0.3% by weight. The basis weight of the bottom layer 130 is 20-30g, and the coating weight is 10-20g.

[0043] The changes in paper properties after replacing GCC with white clay light calcium carbonate are mainly based on the following technical principles:

[0044] 1. Increased Looseness: White calcium carbonate granules have a regular shape and uniform particle size distribution, which fills the gaps between fibers, increasing paper porosity and improving bulk. GCC granules, on the other hand, are irregular and have a poorer filling effect. 2. Reduced Abrasion: The fine and uniformly distributed white calcium carbonate granules reduce the roughness of the paper surface and lower abrasion. GCC granules are coarser, which can easily lead to uneven surfaces and increase abrasion. 3. Better Sizing: The high specific surface area and active surface of white calcium carbonate allow for better adsorption of sizing agents, improving sizing effect. GCC has weaker adsorption capacity and a poorer sizing effect.

[0045] The white cardboard base paper provided in this application embodiment can improve bulk, increase sizing efficiency, improve ash retention, and reduce abrasion by adding a certain amount of low-cost white clay light calcium carbonate to the pulp, thus having great market application value.

[0046] In addition, this application also provides a white cardstock, please refer to [link / reference]. Figure 2 , Figure 2 This is a schematic diagram of the laminated structure of a white cardboard according to an embodiment of this application. In this embodiment, the white cardboard 10 includes a coating layer 200 and a base paper 100. The coating layer 200 is coated on at least one surface of the base paper 100; in this embodiment, the coating layer 200 is coated on opposite sides of the base paper 100. Detailed structural and parametric features of the base paper 100 can be found in the descriptions of the foregoing embodiments and will not be repeated here.

[0047] Please see Figure 3 , Figure 3 This is a schematic diagram of the laminated structure of another embodiment of the white cardboard of this application, wherein the white cardboard 10 in this embodiment includes a coating layer 200 and a base paper 100. Unlike the previous embodiments, the coating layer 200 in this embodiment includes a pre-coating layer 210, a back coating layer 240, a middle coating layer 220, and a top coating layer 230. The pigments in the pre-coating layer 210, back coating layer 240, and middle coating layer 220 are all 100% ground calcium carbonate, and may also include 0.1-0.3% by weight of dispersant, 0.1-0.3% by weight of lubricant, and 5-10% by weight of latex, etc. The pigments in the top coating layer 230 are 0-30% kaolin and 70-100% ground calcium carbonate, and may also include 0.1-0.3% by weight of dispersant, 0.1-0.3% by weight of lubricant, and 5-10% by weight of latex, etc. Detailed parameters and characteristics of the coating layer 200 of the white cardboard 10 are within the understanding of those skilled in the art and will not be listed or described in detail here.

[0048] The white cardboard in this embodiment of the application has a base paper that incorporates a certain amount of low-cost white clay light calcium carbonate into the pulp, which can increase bulk, improve sizing efficiency, increase ash retention, and reduce abrasion, thus having great market application value.

[0049] The above description is only a part of the embodiments of this application and does not limit the scope of protection of this application. Any equivalent device or equivalent process transformation made based on the content of this application specification and drawings, or direct or indirect application in other related technical fields, are similarly included in the patent protection scope of this application.

Claims

1. A base paper for white cardstock, characterized in that, The base paper comprises: a top layer, a core layer, and a bottom layer stacked sequentially; wherein the pulp of the core layer comprises wood pulp, ground calcium carbonate, and bleached light calcium carbonate; wherein the wood pulp comprises 50-95% by weight mechanical pulp and 5-50% by weight chemical pulp; the ground calcium carbonate comprises 10-50% by weight, and the bleached light calcium carbonate comprises 10-50% by weight.

2. The base paper according to claim 1, characterized in that, The particle size D50 of the white clay light calcium carbonate is between 2 and 8 μm.

3. The base paper according to claim 2, characterized in that, The particle size D50 of the white clay light calcium carbonate is between 4 and 6 μm.

4. The base paper according to claim 1, characterized in that, The solid content of the white clay light calcium carbonate is 10%-35%.

5. The base paper according to claim 1, characterized in that, The pulp of the core layer also includes starch, sizing agent, cationic additive, and silica.

6. The base paper according to claim 4, characterized in that, The starch is used at a rate of 5-7 kg / ton of slurry, the sizing agent is an alkyl ketene dimer used at a rate of 1-8 kg / ton of slurry, or the sizing agent is an alkenyl succinic anhydride used at a rate of 0.1-1 kg / ton of slurry, the cationic additive is 100-200 ppm, and the silica is 1-3 kg / ton of slurry.

7. The base paper according to claim 1, characterized in that, The pulp of the surface layer includes wood pulp, starch, and additives, wherein the wood pulp includes 10-30% by weight of softwood bleached pulp and 70-90% by weight of hardwood bleached pulp; the amount of starch is 0-5% by weight, and the amount of additives is 0-0.3% by weight.

8. The base paper according to claim 7, characterized in that, The underlying pulp comprises wood pulp, starch, and additives, wherein the wood pulp comprises 10-20% by weight of softwood bleached pulp and 80-90% by weight of hardwood bleached pulp; the amount of starch is 0-5% by weight, and the amount of additives is 0-0.3% by weight.

9. A type of white cardstock, characterized in that, The white cardboard includes a coating layer and a base paper as described in any one of claims 1-8, wherein the coating layer is applied to the surface of the base paper.

10. The white cardboard according to claim 9, characterized in that, The coating layer includes a pre-coating layer, a back coating layer, a middle coating layer, and a top coating layer; wherein the pigments of the pre-coating layer, the back coating layer, and the middle coating layer are all 100% ground calcium carbonate; and the pigments of the top coating layer are 0-30% kaolin and 70-100% ground calcium carbonate.

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