Coated cardboard and preparation method thereof

Abstract

The present invention belongs to the technical field of papermaking, and discloses a coated cardboard and a preparation method thereof. The coated cardboard comprises a paper base paper layer and a coating layer, wherein the paper base paper layer comprises a base slurry layer, a core slurry layer and a surface slurry layer in sequence, and the coating layer comprises a base coating layer, a core coating layer and a surface coating layer in sequence; the base coating layer comprises 50-grade calcium carbonate, light calcium carbonate, styrene-acrylic latex, styrene-butadiene latex and polyamide modified resin; the core coating layer comprises 50-grade calcium carbonate, light calcium carbonate, styrene-acrylic latex and polyamide modified resin; the surface coating layer comprises 98-grade calcium carbonate, porcelain clay, calcined clay, styrene-acrylic latex and polyamide modified resin. The coated cardboard provided in this embodiment forms a coating layer with a special structure by optimizing the composition of the surface slurry layer and the three-layer coating layer, thereby enhancing the absorbency and compatibility of the coating layer, so that it can match and be compatible with a variety of glues and composite methods.

Description

Technical Field

[0001] The invention belongs to the technical field of papermaking, and in particular relates to a coated cardboard and a preparation method thereof. Background Art

[0002] Coated white cardboard is a kind of paper that is coated on the basis of base paper (multi-layer composite paperboard with wood pulp fiber as the main body and no surface coating). Coating means applying one or more layers of coating on the surface of base paper to improve the surface properties of paper.

[0003] With the progress of society and the improvement of public aesthetics, the printing requirements for finished paper are getting higher and higher based on the requirements of beauty and anti-counterfeiting. At present, paper is mostly made of paper-aluminum composite in subsequent processing. This material has excellent moisture-proof and anti-oxidation properties, taking into account performance, anti-counterfeiting and aesthetic requirements. It is widely used in food, medicine, skin care products and other industries. Paper-aluminum composite materials include laser gold and silver cards, aluminum spray transfer paper, transfer PET, etc. Due to the various types of glue used for transfer, including styrene-butadiene latex, styrene-acrylic latex, polyurethane and acrylate, as well as various types of compounding, the finished paper coating faces more challenges. In order to match and be compatible with the above different glues and composite methods, the coating needs more compatibility. However, the compatibility of the current coated cardboard is poor, and it cannot meet the above composite methods and glue types well. For different glues and processing methods, it is necessary to develop a variety of different coated cardboards, which not only increases the R&D cost, but also brings many inconveniences to actual production.

[0004] Therefore, there is an urgent need to provide a coated cardboard with strong compatibility that can match and be compatible with a variety of glues and composite methods. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention provides a coated cardboard and a preparation method thereof. The coated cardboard provided by the present invention has excellent compatibility and can match and be compatible with a variety of glues and composite methods.

[0006] The invention provides a coated card paper.

[0007] Specifically, a coated cardboard comprises a paper base layer and a coating layer, wherein the paper base layer comprises a base slurry layer, a core slurry layer and a surface slurry layer in sequence, and the coating layer comprises a base coating layer, a core coating layer and a surface coating layer in sequence;

[0008] The surface pulp layer comprises, by weight, 25 to 45 parts of bleached kraft needlewood chemical wood pulp and 55 to 75 parts of bleached kraft broadleaf chemical wood pulp;

[0009] The primer coating layer includes, by weight, 75 to 95 parts of 50-grade calcium carbonate, 5 to 25 parts of light calcium carbonate, 2 to 6 parts of styrene-acrylic latex, 8 to 12 parts of styrene-butadiene latex and 0.3 to 1.5 parts of polyamide modified resin; the coating amount of the primer coating layer is 10 to 15 g / m 2 ;

[0010] The core coating layer comprises, by weight, 80 to 95 parts of 50-grade calcium carbonate, 5 to 20 parts of light calcium carbonate, 8 to 15 parts of styrene-acrylic latex and 0.3 to 1.5 parts of polyamide modified resin; the coating amount of the core coating layer is 5 to 10 g / m 2 ;

[0011] The top coating layer includes, by weight, 65 to 80 parts of 98 grade calcium carbonate, 5 to 25 parts of china clay, 5 to 25 parts of calcined clay, 10 to 20 parts of styrene acrylic latex and 0.3 to 1.5 parts of polyamide modified resin; the coating amount of the top coating layer is 8 to 12 g / m 2 .

[0012] Preferably, the primer coating layer comprises, by weight, 80 to 92 parts of 50-grade calcium carbonate, 8 to 20 parts of light calcium carbonate, 3 to 5 parts of styrene-acrylic latex, 8 to 12 parts of styrene-butadiene latex and 0.4 to 0.8 parts of polyamide modified resin; the coating amount of the primer coating layer is 11 to 15 g / m 2 .

[0013] Preferably, the core coating layer comprises, by weight, 90-95 parts of 50-grade calcium carbonate, 5-10 parts of light calcium carbonate, 8-15 parts of styrene-acrylic latex and 0.4-0.8 parts of polyamide modified resin; the coating amount of the core coating layer is 5-9 g / m 2 .

[0014] Preferably, the top coating layer comprises, by weight, 70 to 80 parts of grade 98 calcium carbonate, 10 to 20 parts of china clay, 5 to 15 parts of calcined clay, 12 to 16 parts of styrene acrylic latex and 0.5 to 1.0 parts of polyamide modified resin; the coating amount of the top coating layer is 9 to 12 g / m 2 .

[0015] Preferably, in the primer coating and the core coating, the particle size of the 50-grade calcium carbonate is ≤2 μm, accounting for 50% to 55%, and the solid content is 75% to 76%; the particle size of the light calcium carbonate is ≤1 μm, accounting for ≥86%, the particle size is ≤2 μm, accounting for ≥96%, and the solid content is ≥73%. In the primer coating and the core coating, adding open-type pigment 50-grade calcium carbonate and light calcium carbonate, and controlling the particle size of the pigment, is conducive to further improving the surface particle size uniformity, ensuring the coating strength and paper surface flatness.

[0016] Preferably, in the topcoat coating, the 98-grade calcium carbonate has a particle size of ≤1 μm accounting for ≥78%, a particle size of ≤2 μm accounting for ≥96%, and a solid content of ≥75%.

[0017] Preferably, the primer coating layer further comprises, by weight, 0.05-0.3 parts of a dispersant, 0.5-1.5 parts of a rheological agent, and 0.1-0.5 parts of a lubricant. Further preferably, the dispersant is sodium polyacrylate, the rheological agent is sodium carboxymethyl cellulose, and the lubricant is oxidized polyethylene emulsion.

[0018] Preferably, the core coating layer further comprises, by weight, 0.05-0.3 parts of a dispersant, 0.5-1.5 parts of a rheological agent and 0.1-0.5 parts of a lubricant. Further preferably, the dispersant is sodium polyacrylate, the rheological agent is carboxymethyl cellulose, and the lubricant is oxidized polyethylene emulsion.

[0019] Preferably, the topcoat coating further comprises, by weight, 0.05-0.3 parts of a dispersant, 0.5-1.5 parts of a rheological agent, and 0.1-0.5 parts of a lubricant. Further preferably, the dispersant is sodium polyacrylate, the rheological agent is sodium carboxymethyl cellulose, and the lubricant is oxidized polyethylene emulsion.

[0020] Preferably, in the facing layer, the beating degree of the bleached kraft softwood pulp is 26-29°SR, and the beating degree of the bleached kraft hardwood pulp is 32-34°SR.

[0021] Preferably, the batter layer further comprises 0.05 to 0.08 parts of rosin by weight.

[0022] The coated cardboard provided in the present invention has no special requirements for the base stock layer and the core stock layer in the base paper layer, but the base paper layer adopts a three-layer fiber structure of the base stock layer, the core stock layer and the surface stock layer, which is conducive to controlling and improving the interlayer bonding strength. In some embodiments of the present invention, the composition of the base stock layer can be the same as the surface stock layer.

[0023] Preferably, the basis weight of the dough layer is 25 to 35 g / m 2 By increasing the slurry layer weight, the surface slurry layer flatness is improved; and by reducing the base slurry layer weight, the base slurry layer weight is controlled at 20-30g / m 2 , which facilitates the moisture flow of the paper after lamination, reduces the risk of deterioration of composite fastness caused by moisture retention inside the paper due to poor moisture discharge, and thus improves the compatibility of coated cardboard with glue and lamination methods.

[0024] Preferably, the coated cardboard includes, from bottom to top, a first sizing layer, a paper base paper layer, a second sizing layer and a coating layer in sequence; the paper base paper layer includes, from bottom to top, a base sizing layer, a core sizing layer and a surface sizing layer in sequence; the coating layer includes, from bottom to top, a base coating layer, a core coating layer and a surface coating layer in sequence.

[0025] The invention also provides a method for preparing the coated card paper.

[0026] A method for preparing coated cardboard, comprising the following steps:

[0027] A primer coating, a core coating coating and a top coating coating are prepared respectively, sizing is applied on the base slurry layer of a paper base layer to obtain a first sizing layer, and sizing is applied on the top slurry layer of the paper base layer to obtain a second sizing layer; then, a primer coating, a core coating and a top coating coating are sequentially applied on the second sizing layer to obtain coated cardboard.

[0028] The base paper layer of the paper of the present invention is composed of a base slurry layer, a core slurry layer and a surface slurry layer, which is conducive to controlling and improving the interlayer bonding strength. The coated cardboard provided by the present invention mainly achieves the compatibility of the coated cardboard with glue and compounding methods by optimizing the surface slurry layer and the structure and composition of the three-layer coating. Specifically, starting from the composite process, the present invention enhances the absorbency, air permeability and uniformity of the coating in a targeted manner by selecting the composition of the base coating, the core coating and the surface coating, and controlling the amount of each component, thereby improving the compatibility of the coated cardboard. It has strong absorbency and better water and glue absorption performance compared to other packaging papers. During the paper-aluminum composite, the glue can be better combined with the paper, and the bonding strength between the coating and the aluminum layer is improved; and improving the uniformity of the coating and the leveling wettability of the glue can make the glue spread better into a film; it has better air permeability, and the coating porosity and absorbency are better, which is conducive to the retention of various types of glue. In addition, the present invention can improve the flatness, strength and absorbency of paper by optimizing the composition of the size layer and increasing the size layer quantity, so that more glue stays in the size layer and the coating layer, and the bonding performance of the glue is improved to the greatest extent.

[0029] More specifically, in the coated cardboard provided by the present invention, the primer coating and the core coating use open pigments (50 grade calcium carbonate and light calcium carbonate), with a combination of coarse and fine particle sizes, and are combined with latex and polyamide modified resins, which are beneficial to coating and enhancing the absorbency and wet strength of the coating, and provide better flatness for the surface coating so that the surface coating effect is smoother and flatter, which is beneficial to the spreading and uniform penetration of the glue during compounding, and improves the bonding between the coating and the aluminum layer; and the top coating uses 98 grade calcium carbonate, porcelain clay and calcined clay as pigments, combined with the use of styrene acrylic latex and amide modified resin, and by controlling the dosage of 98 grade calcium carbonate, porcelain clay and calcined clay, the coating porosity can be optimized, while improving the permeability of the glue and the composite performance of the aluminum layer, balancing the absorption of the ink and the printing effect, thereby improving the overall compatibility of the composite and printing. The study found that when the ratio of porcelain clay and 98-grade calcium carbonate is too high, the structure of the coating is relatively closed, which is not conducive to the penetration of glue and the composite of the aluminum layer; when the ratio of calcined clay is too high, the paper surface will be too rough (large PPS) and the porosity will be large, which is not conducive to the spreading of glue and interface retention. In addition, adding polyamide modified resin to the coating can improve the wet strength of paper, making the surface of the paper coating less likely to be damaged after contact with glue, having better water resistance, and being compatible with a variety of glues.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) The coated cardboard provided in this embodiment optimizes the composition of the face stock layer and the three-layer coating layer to form a coating layer with a special structure, thereby enhancing the absorbency and compatibility of the coating layer, so that it can match and be compatible with a variety of glues and composite methods.

[0032] (2) The coated cardboard provided in this embodiment has good compatibility with glues such as styrene-butadiene, styrene-acrylic, acrylic and polyurethane, as well as two composite methods: composite aluminum foil and composite transfer. The paper-aluminum composite material prepared using it has excellent composite fastness. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A schematic diagram of the structure of coated white cardboard provided by an embodiment of the present invention;

[0034] Figure 2 A schematic diagram of the structure of a coating layer of coated white cardboard provided in an embodiment of the present invention;

[0035] Description of Figure Numbers:

[0036] The first sizing layer-100, the paper base paper layer-200, the base sizing layer-210, the core sizing layer-220, the surface sizing layer-230, the second sizing layer-300, the coating layer-400, the base coating layer-410, the core coating layer-420, and the surface coating layer-430. DETAILED DESCRIPTION

[0037] In order to make the technical scheme of the present invention more clearly understood by those skilled in the art, the following embodiments are listed for illustration. It should be pointed out that the following embodiments do not limit the protection scope of the present invention.

[0038] Unless otherwise specified, the raw materials, reagents or devices used in the following examples and comparative examples can be obtained from conventional commercial sources or by existing known methods.

[0039] Example 1

[0040] A coated cardboard, such as Figure 1 As shown, it includes a first sizing layer 100, a paper base layer 200, a second sizing layer 300 and a coating layer 400 in sequence, the paper base layer 200 includes a base sizing layer 210, a core sizing layer 220 and a surface sizing layer 230 in sequence, and the coating layer 400 includes a base coating layer 410, a core coating layer 420 and a surface coating layer 430 in sequence;

[0041] The surface pulp layer includes 70 parts by weight of bleached kraft broadleaf chemical wood pulp, 30 parts by weight of bleached kraft coniferous chemical wood pulp and 0.06 parts by weight of rosin; the beating degree of bleached kraft coniferous chemical wood pulp is 28°SR, and the beating degree of bleached kraft broadleaf chemical wood pulp is 33°SR; the basis weight of the surface pulp layer is 32g / m 2 ;

[0042] The core pulp layer includes, by weight, 10 parts of bleached coniferous chemical wood pulp, 30 parts of bleached broadleaf chemical wood pulp and 60 parts of bleached chemical thermomechanical pulp; the beating degree of bleached coniferous chemical wood pulp is 28°SR, the beating degree of bleached broadleaf chemical wood pulp is 33°SR, and the beating degree of bleached chemical thermomechanical pulp is 25°SR; the basis weight of the core pulp layer is 135g / m 2 ;

[0043] The bottom pulp layer includes 70 parts by weight of bleached kraft broadleaf chemical wood pulp, 30 parts by weight of bleached kraft coniferous chemical wood pulp and 0.8 parts by weight of rosin; the beating degree of bleached kraft coniferous chemical wood pulp is 28°SR, and the beating degree of bleached kraft broadleaf chemical wood pulp is 33°SR; the basis weight of the bottom pulp layer is 30g / m 2 ;

[0044] The primer coating layer includes, by weight, 90 parts of grade 50 calcium carbonate (55% of particles ≤2μm and 75% of solid content), 10 parts of light calcium carbonate (≥86% of particles ≤1μm and ≥96% of particles ≤2μm and 75% of solid content), 3 parts of styrene-acrylic latex, 10 parts of styrene-butadiene latex, 0.8 parts of polyamide modified resin, 0.1 parts of sodium polyacrylate, 1.0 parts of carboxymethyl cellulose and 0.3 parts of oxidized polyethylene emulsion; the coating amount of the primer coating layer is 11g / m 2 ;

[0045] The core coating layer includes, by weight, 95 parts of 50-grade calcium carbonate (50% to 55% of particles ≤2μm, 75% solid content), 5 parts of light calcium carbonate (≥86% of particles ≤1μm, ≥96% of particles ≤2μm, 75% solid content), 10 parts of styrene-acrylic latex, 0.8 parts of polyamide modified resin, 0.1 parts of sodium polyacrylate, 1.0 parts of carboxymethyl cellulose and 0.3 parts of oxidized polyethylene emulsion; the coating amount of the core coating layer is 7g / m 2 ;

[0046] The top coating layer includes, by weight, 75 parts of 98-grade calcium carbonate (particle size -1 μm ≥ 78%, particle size ≤ 2 μm ≥ 96%, solid content ≥ 75%), 15 parts of china clay, 10 parts of calcined clay, 15 parts of styrene acrylic latex, 0.8 parts of polyamide modified resin, 0.15 parts of sodium polyacrylate, 1.0 parts of carboxymethyl cellulose and 0.3 parts of oxidized polyethylene emulsion; the coating amount of the top coating layer is 10 g / m 2 .

[0047] A method for preparing coated cardboard, comprising the following steps:

[0048] Prepare the base slurry layer, core slurry layer and surface slurry layer slurry respectively.

[0049] Prepare a primer coating, a core coating and a top coating respectively, each coating has a viscosity of 1600 cps, a solid content of 66.5%, and a pH of 9.0;

[0050] Apply sizing (starch, sizing amount is 1.8g / m 2 ) to prepare the first sizing layer, and apply sizing (starch, sizing amount is 2.0g / m 2 ) to obtain a second sizing layer; and then sequentially coating a primer coating, a core coating coating and a top coating coating on the second sizing layer to obtain a coated cardboard.

[0051] Test the general performance of coated cardboard and its compatibility with glue and lamination methods, and evaluate its composite fastness. The evaluation method of composite fastness in the compatibility experiment is as follows:

[0052] Direct lamination of aluminum foil: use adhesive (glue, 6g / m 2 ), under a composite pressure of 5Kg, the front side (coating layer) of the coated cardboard is adhered to the aluminum foil, and the aluminum foil is bonded with the adhesive and tightly adhered to the front side of the base paper.

[0053] Composite transfer paper composite transfer: the aluminum film transfer layer aluminum layer through the glue (7g / m 2 ), under a composite pressure of 3Kg, it adheres to the front side (coating layer) of the coated cardboard, and then peels off the PE layer to obtain the aluminum film coated cardboard composite layer.

[0054] The composite fastness test method is as follows:

[0055] Prepare materials: cold laminator, three A4 paper samples to be tested, different types of glue, alcohol, cut aluminum layer, oven, timer, and 3M tape.

[0056] Steps:

[0057] 1. Place the paper and aluminum layer on top of each other at the entrance of the cold laminator. Put a 15mm wide and 230mm long paper strip (pressing paper strip) on the top of the overlap to fix the paper and the aluminum layer to avoid lamination failure due to static electricity or the aluminum layer being too thin to be adsorbed by the rubber roller of the cold laminator.

[0058] 2. Use a syringe to extract a certain amount of glue, lift up the aluminum layer, apply the glue on the paper to form an even horizontal stripe, then put down the aluminum layer and turn on the cold laminator;

[0059] 3. When the 15mm*230mm long (pressing paper strip) and the aluminum layer pass through the head end of the cold laminator, remove the pressing paper strip;

[0060] 4. When there is 20mm left of the paper-aluminum composite sample, press the reverse key to send the composite sample out through the inlet end;

[0061] 5. Dry the composite paper sample according to the client's drying conditions, which are 120℃, 5S.

[0062] Evaluation: 1. Take the dried paper sample out of the oven and place it in a constant temperature and humidity chamber ((23±1)℃, (50±2)%rh) for 5 minutes to balance, and wait for the paper temperature to return to room temperature; after the composite paper sample returns to stability (the paper temperature is normal and there is no warping), tear off the PET film on the surface (composite transfer), and use 3M tape to pull 3 strips horizontally and vertically (stick the 3M tape on the aluminum surface, press it flat with your fingers, and then pull it up);

[0063] Place the 3M tape pull position on the light box to observe the drop point situation. The evaluation criteria are:

[0064] Excellent: Almost no drop, only a few drop;

[0065] Good: a small amount of dropped points;

[0066] Poor: large pieces dropped, a lot of dots dropped, intensive dots dropped;

[0067] The results are shown in Tables 1 and 2.

[0068] Table 1

[0069]

[0070]

[0071] Table 2

[0072]

[0073] As can be seen from Table 1 and Table 2, the coated cardboard provided in this embodiment can form a coating layer with a special structure by optimizing the composition of the face stock layer and the three-layer coating layer, especially the selection and dosage control of the pigment in the three-layer coating layer (see Figure 2 The coating structure diagram is shown in the figure), and it has good compatibility with glues such as butadiene-styrene, styrene-acrylic, acrylic acid and polyurethane, as well as two composite methods: composite aluminum foil and composite transfer. The prepared paper-aluminum composite material has excellent composite fastness.

[0074] Example 2

[0075] The difference between this embodiment and embodiment 1 lies in the composition of the primer coating, the core coating and the top coating. The remaining layers and preparation methods are the same as those in embodiment 1.

[0076] The primer coating layer includes, by weight, 85 parts of 50-grade calcium carbonate (particle size -1μm to -2μm 50% to 55%, solid content 75% to 76%), 15 parts of light calcium carbonate (particle size -1μm to -2μm ≥ 86%, solid content ≥ 73%), 5 parts of styrene-acrylic latex, 8 parts of styrene-butadiene latex, 0.8 parts of polyamide modified resin, 0.2 parts of sodium polyacrylate, 1.0 parts of carboxymethyl cellulose and 0.3 parts of oxidized polyethylene emulsion; the coating amount of the primer coating layer is 12g / m 2 ;

[0077] The core coating layer includes, by weight, 90 parts of grade 50 calcium carbonate (50% to 55% of particles ≤-2μm, 75% to 76% of solid content), 10 parts of light calcium carbonate (≥86% of particles ≤1μm, ≥96% of particles ≤2μm, ≥73% of solid content), 12 parts of styrene acrylic latex, 0.5 parts of polyamide modified resin, 0.1 parts of sodium polyacrylate, 1.0 parts of carboxymethyl cellulose and 0.3 parts of oxidized polyethylene emulsion; the coating amount of the core coating layer is 9g / m2 ;

[0078] The top coating layer comprises, by weight, 80 parts of 98-grade calcium carbonate (particle size -1 μm ≥ 78%, particle size -2 μm ≥ 96%, solid content ≥ 75%), 12 parts of china clay, 8 parts of calcined clay, 11 parts of styrene acrylic latex, 0.8 parts of polyamide modified resin, 0.15 parts of sodium polyacrylate, 1.0 parts of carboxymethyl cellulose and 0.3 parts of oxidized polyethylene emulsion; the coating amount of the top coating layer is 9 g / m 2 .

[0079] The general performance of the coated cardboard and its compatibility with glue and lamination methods were tested. The test results are shown in Tables 3 and 4.

[0080] Table 3

[0081]

[0082]

[0083] Table 4

[0084]

[0085] It can be seen from Tables 3 and 4 that the coated cardboard provided in this embodiment has good compatibility with glues such as styrene-butadiene, styrene-acrylic, acrylic and polyurethane, as well as two composite methods of composite aluminum foil and composite transfer, and the prepared paper-aluminum composite material has excellent composite fastness.

[0086] Example 3

[0087] The difference between this embodiment and embodiment 1 lies in the composition of the core slurry layer and the bottom slurry layer, and the remaining layers and preparation methods are the same as those in embodiment 1.

[0088] The core pulp layer includes 15 parts of bleached coniferous chemical wood pulp, 35 parts of bleached broadleaf chemical wood pulp and 50 parts of bleached chemical thermomechanical pulp by weight; the beating degree of bleached coniferous chemical wood pulp is 30°SR, the beating degree of bleached broadleaf chemical wood pulp is 32°SR, and the beating degree of bleached chemical thermomechanical pulp is 23°SR; the basis weight of the core pulp layer is 135g / m 2 ;

[0089] The bottom pulp layer, by weight, includes 75 parts of bleached kraft softwood pulp, 25 parts of bleached kraft hardwood pulp and 1.2 parts of rosin; the beating degree of bleached kraft softwood pulp is 28°SR, and the beating degree of bleached kraft hardwood pulp is 33°SR; the basis weight of the bottom pulp layer is 36g / m 2 .

[0090] The general performance of the coated cardboard and its compatibility with glue and lamination methods were tested. The test results are shown in Tables 5 and 6.

[0091] Table 5

[0092]

[0093] Table 6

[0094]

[0095]

[0096] It can be seen from Tables 5 and 6 that the different compositions of the core slurry layer and the base slurry layer will affect the conventional performance of the coated cardboard to a certain extent, but will not significantly affect the compatibility of the coated cardboard with glue and the laminating method. The coated cardboard prepared in this embodiment has excellent compatibility similar to that of the embodiment. The increase in the base slurry quantity and the amount of rosin mainly affects the circulation of water vapor after lamination, resulting in the storage of water inside the paper after lamination, so the water content after lamination will increase.

[0097] Comparative Example 1

[0098] The difference between this comparative example and Example 1 lies in the composition of the primer coating layer, and the remaining layers and preparation methods are the same as those in Example 1.

[0099] Specifically, the primer coating layer includes, by weight, 65 parts of 50-grade calcium carbonate (particle size ≤2μm 50%-55%, solid content 75%-76%), 35 parts of light calcium carbonate (≤1μm ≥86%, ≤2μm particle size ≥96%, solid content ≥73%), 3 parts of styrene-acrylic latex, 10 parts of styrene-butadiene latex, 0.8 parts of polyamide modified resin, 0.1 parts of sodium polyacrylate, 1.0 parts of carboxymethyl cellulose and 0.3 parts of oxidized polyethylene emulsion; the coating amount of the primer coating layer is 11g / m 2 .

[0100] The general performance of the coated cardboard and its compatibility with glue and lamination methods were tested. The test results are shown in Tables 7 and 8.

[0101] Table 7

[0102]

[0103]

[0104] Table 8

[0105]

[0106] It can be seen from Tables 7 and 8 that the coated cardboard provided in this comparative example has more pigments with finer particle sizes added to the primer than in Example 1, which will enhance the sealing property of the primer coating. For glue with poor permeability, the glue cannot be effectively absorbed and retained, and the glue will remain in the topcoat and the corecoat, or form a thick glue film on the surface of the coating, causing the aluminum layer to be falsely adhered to the paper (when the 3M tape is used to pull it up, the aluminum layer is pulled up as a whole, and large pieces fall off).

[0107] Comparative Example 2

[0108] The difference between this comparative example and Example 1 lies in the composition of the primer coating layer and the core coating coating layer, and the remaining layers and preparation methods are the same as those in Example 1.

[0109] Specifically, the primer coating layer includes, by weight, 75 parts of 50-grade calcium carbonate (particle size ≤2μm accounts for 50% to 55%, solid content 75% to 76%), 25 parts of light calcium carbonate (≤1μm accounts for ≥86%, ≤2μm particle size accounts for ≥96%, solid content ≥73%), 13 parts of styrene-acrylic latex, 0.8 parts of polyamide modified resin, 0.1 parts of sodium polyacrylate, 1.0 parts of carboxymethyl cellulose and 0.3 parts of oxidized polyethylene emulsion; the coating amount of the primer coating layer is 11g / m 2 ;

[0110] The core coating layer includes, by weight, 75 parts of 50-grade calcium carbonate (50% to 55% of particles ≤2μm, 75% to 76% of solid content), 25 parts of light calcium carbonate (≥86% of particles ≤1μm, ≥96% of particles ≤2μm, ≥73% of solid content), 10 parts of styrene-acrylic latex, 0.8 parts of polyamide modified resin, 0.1 parts of sodium polyacrylate, 1.0 parts of carboxymethyl cellulose and 0.3 parts of oxidized polyethylene emulsion; the coating amount of the core coating layer is 7g / m 2 .

[0111] The general performance of the coated cardboard and its compatibility with glue and lamination methods were tested. The test results are shown in Tables 9 and 10.

[0112] Table 9

[0113]

[0114] Table 10

[0115]

[0116] As shown in Tables 9 and 10, the coated cardboard provided in this comparative example has more pigments with finer particle sizes added to the base and core coating than in Example 1, and the latex of the base coating is changed to full styrene acrylic latex. The paper coating is dense after two coats of the pigment particle size of the base coating and the core coating, and the base coating, the core coating, and the top coating all use styrene acrylic latex, and the coating strength is not good. The solid content of the composite glue is generally between 15% and 45%, which will cause the coating surface of the paper to be eroded and damaged after contact with the glue, and the strength is reduced, resulting in poor composite conditions. This results in the situation where the composite aluminum drops densely and there are many drop points (the coating at the drop point of the base paper is obviously damaged when the 3M tape is used to pull it up).

[0117] Comparative Example 3

[0118] The difference between this comparative example and Example 1 lies in the composition of the top coating layer, and the remaining layers and preparation methods are the same as those in Example 1.

[0119] Specifically, the topcoat coating includes, by weight, 75 parts of 50-grade calcium carbonate (particle size ≤ 2 μm, accounting for 50% to 55%, solid content 75% to 76%), 15 parts of china clay, 10 parts of calcined clay, 15 parts of styrene-acrylic latex, 0.8 parts of polyamide modified resin, 0.15 parts of sodium polyacrylate, 1.0 parts of carboxymethyl cellulose and 0.3 parts of oxidized polyethylene emulsion; the coating amount of the topcoat coating is 10 g / m 2 .

[0120] The general performance of the coated cardboard and its compatibility with glue and lamination methods were tested. The test results are shown in Tables 11 and 12.

[0121] Table 11

[0122]

[0123]

[0124] Table 12

[0125]

[0126] It can be seen from Tables 11 and 12 that because the topcoat is too rough, the glue penetrates more into the paper and less contact surface with the aluminum layer is retained, resulting in the inability to bond the coating and the aluminum layer, thus causing poor composite fastness and poor paper surface.

[0127] Comparative Example 4

[0128] The difference between this comparative example and Example 1 lies in the composition of the top coating layer, and the remaining layers and preparation methods are the same as those in Example 1.

[0129] Specifically, the topcoat coating layer includes, by weight, 60 parts of 98-grade calcium carbonate (particle size 1 μm accounts for ≥78%, particle size 2 μm accounts for ≥96%, solid content ≥75%), 5 parts of china clay, 35 parts of calcined clay, 15 parts of styrene-acrylic latex, 0.8 parts of polyamide modified resin, 0.15 parts of sodium polyacrylate, 1.0 parts of carboxymethyl cellulose and 0.3 parts of oxidized polyethylene emulsion; the coating amount of the topcoat coating is 10 g / m 2 .

[0130] The general performance of the coated cardboard and its compatibility with glue and lamination methods were tested. The test results are shown in Tables 13 and 14.

[0131] Table 13

[0132]

[0133] Table 14

[0134]

[0135] It can be seen from Tables 13 and 14 that adding too much calcined clay will lead to increased porosity of the coating as a whole, more glue will penetrate into the primer coating and core coating and less will be retained in the top coating, resulting in decreased coating strength and large PPS index. Large PPS and poor paper surface also do not meet the composite requirements, because poor paper surface coating will not result in good composite effect, and excessive addition of calcined clay will also lead to abnormal operation during production.

[0136] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A coated cardboard, characterized in that: The paper base paper layer comprises a base paper layer and a coating layer, wherein the base paper layer comprises a base slurry layer, a core slurry layer and a surface slurry layer in sequence, and the coating layer comprises a base coating layer, a core coating layer and a surface coating layer in sequence; The surface pulp layer comprises, by weight, 25 to 45 parts of bleached kraft needlewood chemical wood pulp and 55 to 75 parts of bleached kraft broadleaf chemical wood pulp; The primer coating layer includes, by weight, 75 to 95 parts of 50-grade calcium carbonate, 5 to 25 parts of light calcium carbonate, 2 to 6 parts of styrene-acrylic latex, 8 to 12 parts of styrene-butadiene latex and 0.3 to 1.5 parts of polyamide modified resin; the coating amount of the primer coating layer is 10 to 15 g / m 2 ; The core coating layer comprises, by weight, 80 to 95 parts of 50-grade calcium carbonate, 5 to 20 parts of light calcium carbonate, 8 to 15 parts of styrene-acrylic latex and 0.3 to 1.5 parts of polyamide modified resin; the coating amount of the core coating layer is 5 to 10 g / m 2 ; The top coating layer includes, by weight, 65 to 80 parts of 98 grade calcium carbonate, 5 to 25 parts of china clay, 5 to 25 parts of calcined clay, 10 to 20 parts of styrene acrylic latex and 0.3 to 1.5 parts of polyamide modified resin; the coating amount of the top coating layer is 8 to 12 g / m 2 .

2. The coated cardboard according to claim 1, characterized in that: The primer coating layer comprises, by weight, 80 to 92 parts of 50-grade calcium carbonate, 8 to 20 parts of light calcium carbonate, 3 to 5 parts of styrene-acrylic latex, 8 to 12 parts of styrene-butadiene latex and 0.4 to 0.8 parts of polyamide modified resin; the coating amount of the primer coating layer is 11 to 15 g / m 2 .

3. The coated cardboard according to claim 1, characterized in that: The core coating layer comprises, by weight, 90 to 95 parts of 50-grade calcium carbonate, 5 to 10 parts of light calcium carbonate, 8 to 15 parts of styrene-acrylic latex and 0.4 to 0.8 parts of polyamide modified resin; the coating amount of the core coating layer is 5 to 9 g / m 2 .

4. The coated cardboard according to claim 1, characterized in that: The top coating layer includes, by weight, 70 to 80 parts of 98 grade calcium carbonate, 10 to 20 parts of china clay, 5 to 15 parts of calcined clay, 12 to 16 parts of styrene acrylic latex and 0.5 to 1.0 parts of polyamide modified resin; the coating amount of the top coating layer is 9 to 12 g / m 2 .

5. The coated card paper according to any one of claims 1 to 4, characterized in that: In the primer coating and the core coating, the particle size of the 50-grade calcium carbonate ≤2 μm accounts for 50% to 55%, and the solid content is 75% to 76%; the particle size of the light calcium carbonate ≤1 μm accounts for ≥86%, the particle size ≤2 μm accounts for ≥96%, and the solid content is ≥73%.

6. The coated card paper according to any one of claims 1 to 4, characterized in that: In the topcoat coating, the particle size of the 98-grade calcium carbonate ≤1 μm accounts for ≥78%, the particle size ≤2 μm accounts for ≥96%, and the solid content is ≥75%.

7. The coated card paper according to any one of claims 1 to 4, characterized in that: The primer coating, the core coating and the top coating also independently include 0.05 to 0.3 parts of a dispersant, 0.5 to 1.5 parts of a rheological agent and 0.1 to 0.5 parts of a lubricant, respectively, by weight.

8. The coated cardboard according to claim 7, characterized in that: The dispersant is sodium polyacrylate, the rheological agent is sodium carboxymethyl cellulose anion, and the lubricant is oxidized polyethylene emulsion.

9. The coated cardboard according to claim 1, characterized in that: In the face pulp layer, the beating degree of the bleached kraft needlewood chemical wood pulp is 26-29°SR, and the beating degree of the bleached kraft broadleaf chemical wood pulp is 32-34°SR.

10. The method for preparing coated cardboard according to any one of claims 1 to 9, characterized in that: The following steps are involved: A primer coating, a core coating coating and a top coating coating are prepared respectively, sizing is applied on the base slurry layer of a paper base layer to obtain a first sizing layer, and sizing is applied on the top slurry layer of the paper base layer to obtain a second sizing layer; then, a primer coating, a core coating and a top coating coating are sequentially applied on the second sizing layer to obtain coated cardboard.

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