Coated white card and method of making and use thereof

Abstract

The application belongs to the technical field of papermaking, and provides a coated white cardboard, a preparation method and application thereof.The coated white cardboard provided by the application comprises a coating layer and a paper base layer, and the paper base layer comprises a surface layer, a core layer and a bottom layer from the front side to the back side in sequence.The surface of the surface layer comprises a surface sizing layer, a primer layer and a top coating layer from inside to outside in sequence, the top coating layer contains a first inorganic filler, sizing of the surface layer adopts high concentration sizing, raw materials of the core layer adopt coniferous wood bleached chemical thermomechanical pulp and bleached kraft broadleaf wood pulp, and raw materials of the bottom layer adopt a specific ratio of bleached kraft coniferous wood pulp and bleached kraft broadleaf wood pulp.The primer layer contains a second inorganic filler and latex, and the second sizing on the back side is not needed, so that the ink penetration and absorption capacity is improved, the ink penetration effect is good when printing on the back side, the dyeing effect is good, the printing performance of the front side is considered at the same time, and the practical application performance of the coated white cardboard is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of papermaking, more particularly, to a coated white cardboard, a preparation method and application thereof. BACKGROUND

[0002] As a common printing substrate, the coated white cardboard belongs to high-grade products in the cultural printing paper category. The coated white cardboard is white and can have the required color for printing or packaging materials by dyeing. The dyeing of the coated white cardboard in production is usually divided into two types. One is to add fillers to the slurry during the production process for simple and direct dyeing, which can usually achieve good uniform dyeing effect. However, due to the large use of dyes, wastewater and production environment pollution are easily caused, and the cost of manpower and material resources is obviously increased. Moreover, it brings great trouble to subsequent production change. The other is to dye the finished coated white cardboard, i.e. secondary processing, which is the most common way for dyeing the coated white cardboard in the market. Generally, the coated white cardboard is usually composed of a paper base layer and a coating layer. The paper base layer includes a top layer, a core layer and a bottom layer in turn from the front to the back (i.e. the coated white cardboard includes a coating layer, a top layer, a core layer and a bottom layer in turn from the front to the back). The capillary structure of the paper base layer and the coating layer is quite different. The paper base layer is composed of a network structure of cellulose fibers and voids. Compared with the coating layer, the capillary pore size of the paper base layer is larger. When the back of the coated white cardboard is used for printing, the ink vehicle and the pigment particles carried thereby are transferred to the paper. Due to the capillary effect, the ink diffuses to the fibers. However, due to the limitation of the base paper, the uniformity and depth of ink penetration are often unsatisfactory. The ink either cannot penetrate the core layer to uniformly dye the paper base layer or penetrates too deeply, with the ink reaching the coating layer and dirtying the front, which affects the subsequent printing quality. Both results lead to poor dyeing effect of the coated white cardboard.

[0003] In the traditional process of the coated white cardboard, two sizing operations are usually performed on the back. The purpose of the second sizing operation is to further optimize the flatness of the back of the coated white cardboard, to make the dyeing uniform and to improve the strength of the back paper surface. However, the problem brought by this is that the water resistance of the back is improved and the ink absorption capacity is greatly reduced, which further affects the dyeing effect of the back.

[0004] Therefore, it is urgent to develop a coated white cardboard which does not need the second sizing operation on the back, improves the ink penetration and absorption of the coated white cardboard, ensures excellent dyeing effect of the back and at the same time takes into account the printing performance of the front. SUMMARY

[0005] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application provides a coated white card paper and a preparation method and application thereof. The coated white card paper provided by the present application improves the ink absorption of the back surface of the paper without performing second sizing on the back surface by reasonably controlling the use ratio of fibers and the particle size of fillers and the amount of adhesive, and has good ink penetration effect and dyeing effect when printing on the back surface, while taking into account the printing performance of the front surface of the paper, and ensuring the basic practical application performance of the coated white card paper.

[0006] The first aspect of the present application provides a coated white card paper.

[0007] Specifically, a coated white card paper comprises a coating layer and a paper base layer, the paper base layer comprises a surface layer, a core layer and a bottom layer from front to back, the surface of the surface layer comprises a surface sizing layer, a primer layer and a topcoat layer from inside to outside, the coating layer comprises a primer layer and a topcoat layer; the single-side sizing amount of the surface layer is 8-10 g / m 2 ;

[0008] The topcoat layer is coated by using a topcoat coating material, and the raw material components of the topcoat coating material comprise a first inorganic filler, and the content of particles with a particle size of less than or equal to 2 μm in the first inorganic filler is greater than or equal to 95%;

[0009] The primer layer is coated by using a primer coating material, and the raw material components of the primer coating material comprise 100 parts of a second inorganic filler and 40-48 parts of an adhesive according to weight, and the content of particles with a particle size of less than or equal to 2 μm in the second inorganic filler is greater than 50%;

[0010] The raw materials of the core layer comprise softwood bleached chemi-thermal mechanical pulp (BCTMP pulp) and bleached kraft broadleaf wood pulp (LBKP pulp);

[0011] The raw material components of the bottom layer comprise bleached kraft softwood pulp (NBKP pulp) and bleached kraft broadleaf wood pulp (LBKP pulp) at a weight ratio of 1:(7-9).

[0012] The coated white card paper comprises a topcoat layer, a primer layer, a surface sizing layer, a surface layer, a core layer and a bottom layer from front to back. The surface layer is provided with a primer layer on its surface, and a large-particle-size inorganic filler is added, which has loose porosity, is arranged in a group form in the coating layer, makes the coating layer structure have a large porosity, produces a relatively open coating surface, thus the smoothness of the primer layer surface is reduced, the roughness is increased, and it is beneficial to the uniform diffusion of ink. The surface layer is also provided with a topcoat layer, and a small-particle-size inorganic filler is added to the topcoat layer, which is spindle-shaped, and the orderliness of the arrangement of calcium carbonate is greatly improved after adding porcelain clay, the pore size of the coating layer is controlled, the coating layer obtains a good pore volume, maintains the smoothness and optical performance of the coating layer, and at the same time can match the particle size distribution of ink particles to achieve uniform dyeing effect.

[0013] The core layer is the main part of the coated white card, and mainly functions to provide bulkiness and bearing force for the paperboard, so the high bulkiness BCTMP pulp is adopted. The BCTMP pulp used in the core layer has high freeness and high bulkiness, can greatly improve the ink absorption capacity of the fiber, and at the same time, gives the paper a soft and fluffy feeling. However, the anion content on the BCTMP pulp fiber is high, and the surface charge of the ink particles is negative, which will repel the ink particles to a certain extent, and the BCTMP pulp fiber contains more lignin and other hydrophobic wood components, so it has a certain water resistance. Therefore, the present application also adds LBKP pulp in the core layer, which is short fiber, does not contain lignin and other hydrophobic components, has a large specific surface area, and is beneficial to ink absorption. The matching of the BCTMP pulp and the LBKP pulp can greatly optimize the ink permeability while ensuring the physical indicators such as the bulkiness of the paper to be qualified.

[0014] The fiber raw material of the bottom layer adopts bleached kraft softwood pulp (NBKP pulp) and bleached kraft hardwood pulp (LBKP pulp). The bleached kraft softwood pulp (NBKP pulp) contains relatively long fibers (the length is generally 2.0-2.8mm), and the bleached kraft hardwood pulp (LBKP pulp) contains relatively short fibers (the length is generally 0.7-1.1mm). The short fibers have the characteristics of not easy to flocculate and easy to disperse in the pulp, and the present application adopts a large proportion of bleached kraft hardwood pulp (LBKP pulp) short fibers in the bottom layer to optimize the flatness of the paper surface and reduce the roughness of the paper surface. The roughness of the paper surface will affect the printing effect of the formed paper, and if the roughness is too high, the printing will appear the problem of missing points or blurring. At the same time, the present application adds a small proportion of bleached kraft softwood pulp (NBKP pulp) long fibers in the bottom layer, which can improve the paper surface strength. The combination of long and short fibers in a specific ratio can give the bottom layer flatness and high strength, and at the same time optimize the uniformity and depth of ink penetration, without the need for the traditional second sizing operation of the bottom layer (i.e. back sizing), avoiding the increase of the water resistance of the coated white card after the second sizing, which is not conducive to the uniform penetration and absorption of the ink, and further affects the dyeing effect.

[0015] The surface sizing layer can increase the water resistance of the base paper, and in the subsequent coating, not only can reduce the migration of the adhesive into the paper layer, improve the gloss of the finished product and the strength of the coating layer, but also can hinder the penetration of the ink particles to the coating layer to stain the surface layer. The viscosity of the sizing solution can affect the surface sizing amount and the surface strength. The higher the viscosity, the better the film forming property, and the less the sizing solution penetrates into the base paper, which can improve the surface smoothness, reduce the air permeability, hinder the migration of the adhesive in the coating to the inside of the base paper, improve the film forming property of the coating surface, and at the same time hinder the penetration of the ink to the coating layer, providing conditions for the uniform adhesion of the ink particles on the paper machine layer.

[0016] Preferably, the first inorganic filler is a 95 grade inorganic filler and / or a 98 grade inorganic filler.

[0017] Preferably, the second inorganic filler has a particle size less than or equal to 2 μιη with a particle content of greater than or equal to 60%.

[0018] Further preferably, the second inorganic filler is a 60 grade inorganic filler.

[0019] Preferably, the inorganic filler is calcium carbonate and / or china clay.

[0020] Preferably, the calcium carbonate is ground calcium carbonate.

[0021] In industrial production, the particle content of ground calcium carbonate with a particle size less than 2 microns is 94.5-95.5%, i.e. 95 grade calcium carbonate. The particle content of ground calcium carbonate with a particle size less than 2 microns is 59.5-60.5%, i.e. 60 grade calcium carbonate. And so on.

[0022] Further preferably, the raw material components of the base layer include bleached kraft softwood pulp (NBKP pulp) and bleached kraft hardwood pulp (LBKP pulp) in a weight ratio of 1 : (8-9).

[0023] Preferably, the raw material of the core layer includes bleached chemi-thermo mechanical pulp of softwood (BCTMP pulp) and bleached kraft hardwood pulp (LBKP pulp) in a weight ratio of (60-90) : (10-40).

[0024] Preferably, the BCTMP pulp has a freeness of 300-400 mL CSF.

[0025] Preferably, the raw material of the top layer includes bleached kraft softwood pulp (NBKP pulp) and bleached kraft hardwood pulp (LBKP pulp).

[0026] Further preferably, the raw material of the top layer includes bleached kraft softwood pulp (NBKP pulp) and bleached kraft hardwood pulp (LBKP pulp) in a weight ratio of (9-13) : (80-95).

[0027] More preferably, the raw material of the top layer includes bleached kraft softwood pulp (NBKP pulp) and bleached kraft hardwood pulp (LBKP pulp) in a weight ratio of (11-13) : (89-95).

[0028] Preferably, the weight of the paper base layer accounts for 88-90% of the total weight of the coated white card, and / or the weight of the coating layer accounts for 10-12% of the total weight of the coated white card.

[0029] Preferably, the bottom surface further comprises a bottom surface sizing layer, and the coated white card comprises, from front to back, a top coating layer, a bottom coating layer, a surface sizing layer, a top layer, a core layer, a bottom layer, and a bottom surface sizing layer.

[0030] Preferably, the surface sizing layer and the bottom surface sizing layer are obtained by coating a sizing liquid.

[0031] Preferably, the sizing liquid comprises cassava oxidized starch as a raw material component.

[0032] Preferably, the sizing liquid has a solid content of 4-6%.

[0033] Preferably, the single-side sizing amount of the bottom layer is 1-2 g / m 2 .

[0034] The bottom layer sizing adopts a lower single-side sizing amount, reduces the influence of sizing on the porosity and water resistance of the bottom layer, improves the ink absorption of the bottom layer, and through controlling a reasonable sizing amount, improves the strength of the paper while reducing the influence on the ink penetration.

[0035] Preferably, the top coating material further comprises the following raw material components: a binder, a dispersant, a water repellent, a lubricant, and water; and / or the bottom coating material further comprises the following raw material components: a dispersant, a water repellent, a lubricant, and water.

[0036] Further preferably, the top coating material further comprises the following raw material components in parts by weight: 100 parts of a first inorganic filler, 10-18 parts of a binder, 0.05-0.2 parts of carboxymethyl cellulose (CMC), 0.05-0.12 parts of a dispersant, 0.5-1 parts of a water repellent, 1-2 parts of a lubricant, and 0.001-0.01 parts of water.

[0037] More preferably, the first inorganic filler is calcium carbonate and porcelain clay, and the top coating material comprises the following raw material components in parts by weight: 88 parts of 95-grade calcium carbonate, 12 parts of porcelain clay, 14 parts of a binder, 0.05-0.2 parts of carboxymethyl cellulose, 0.05-0.12 parts of a dispersant, 0.5-1 parts of a water repellent, 1.5 parts of a lubricant, and 0.005 parts of water.

[0038] Preferably, the bottom coating material further comprises the following raw material components in parts by weight: 100 parts of a second inorganic filler, 40-48 parts of a binder, 0.05-0.2 parts of carboxymethyl cellulose, 0.05-0.12 parts of a dispersant, 2-3 parts of a water repellent, 1-2 parts of a lubricant, and 0.001-0.005 parts of water.

[0039] Further preferably, the second inorganic filler is calcium carbonate, and the base coat paint comprises the following raw material components by weight parts: 100 parts of 60 grade ground calcium carbonate, 45 parts of adhesive, 0.05-0.2 parts of carboxymethyl cellulose, 0.05-0.12 parts of dispersant, 2.0 parts of water resistance agent, 1.5 parts of lubricant, and 0.003 parts of water.

[0040] Preferably, the adhesive is a styrene-butadiene latex.

[0041] For the styrene-butadiene latex, its glass transition temperature (Tg, Tg of the styrene-butadiene latex is 5.0℃) has a great influence on the structure of the coated white cardboard. Generally, the styrene-butadiene latex with high Tg has small shrinkage of the latex film and low roughness of the coating surface. The styrene-butadiene latex with large particle size (above 200 nm) and high Tg is beneficial to keep the coating structure open and considerate of positive printing performance, and in the drying process, the latex particles no longer fill the pores between the pigments, but form a thin film on the surface of the pigments to improve the strength of the coating. The high content of styrene-butadiene latex in the base layer is to improve the strength of the coating while greatly hindering the excessive penetration of ink particles by the superior film-forming property of the styrene-butadiene latex.

[0042] Preferably, the solid content of the top coat paint is 65-70%, and / or the solid content of the base coat paint is 65-68%. Controlling the reasonable solid content is beneficial to reduce the migration degree of the styrene-butadiene latex to the surface of the paper and the inside of the base paper, and the adhesive is more evenly distributed in the coating, so that the ink absorption is also more uniform.

[0043] Preferably, the coated white cardboard comprises, in order from the front side to the back side, a top coat layer, a base coat layer, a top layer, a core layer, and a base layer, and the base layer is not back-coated.

[0044] The second aspect of the present application provides a preparation method of a coated white cardboard.

[0045] A preparation method of a coated white cardboard comprises the following steps:

[0046] (1) mixing raw material components of the top layer, crushing and refining to obtain top layer pulp, and forming to obtain top layer base paper;

[0047] (2) mixing raw material components of the core layer, crushing and refining to obtain core layer pulp, and forming to obtain core layer base paper;

[0048] (3) mixing raw material components of the base layer, crushing and refining to obtain base layer pulp, and forming to obtain base layer base paper;

[0049] (4) sequentially bonding the top layer base paper, the core layer base paper and the base layer base paper in order from the front side to the back side to obtain paper base layer base paper;

[0050] (5) after the paper base layer raw paper is dried, surface sizing is carried out on the surface layer and the bottom layer respectively, and after drying, a pre-coated raw paper is obtained;

[0051] (6) the bottom coating paint is coated on the front surface of the pre-coated raw paper, dried, and a bottom coating layer is obtained, so that a first coated white cardboard is prepared;

[0052] (7) the top coating paint is further coated on the front surface of the first coated white cardboard, a top coating layer is obtained, and a second coated white cardboard is prepared, and the coated white cardboard is prepared after calendering.

[0053] In the papermaking process, long fibers and short fibers are mixed in a specific ratio, and after the refining, the length of the long fibers does not change significantly, but the ratio of the short fibers is greatly increased (for example, from 17% to 21%), which greatly optimizes the flatness of the paper surface and improves the strength of the bottom layer paper surface.

[0054] Preferably, the preparation method of the top coating paint comprises the following steps: mixing ground calcium carbonate, a dispersing agent and water, adding china clay, then adding carboxymethyl cellulose and butadiene-styrene latex, and finally adding a water repellent and a lubricant, and adjusting the pH value to 8.5-9.5 by using an alkaline solution to prepare the top coating paint.

[0055] Preferably, the preparation method of the bottom coating paint comprises the following steps: adding water in the second inorganic filler, adding butadiene-styrene latex under high-speed stirring, then sequentially adding a dispersing agent, carboxymethyl cellulose, and finally adding a lubricant and a water repellent, and adjusting the pH value to 8.5-9.5 by using an alkaline solution to prepare the bottom coating paint.

[0056] Preferably, the alkaline solution is a NaOH solution. In the process of preparing the paint, the control of the pH value is particularly important, and the water retention of the paint is improved when the pH value is increased, and the water retention is best when the pH value is close to 8.5-9.5 (close to 9.0). With the increase of the pH value of the paint, the ink absorption of the coated white cardboard decreases. If the pH value of the coating layer of the coated white cardboard is too low, that is, the paper is slightly acidic, the drying of the ink is greatly affected, and under the condition of relatively high relative humidity, the drying process of the ink is not obviously slowed down, and even the drying stagnation phenomenon occurs. When the pH value is too high, the contact between the coating layer and the ink affects the ink transfer, destroys the water-ink balance, and it is difficult to achieve the purpose of uniform dyeing.

[0057] Compared with the prior art, the present application has the following beneficial effects:

[0058] The coated white cardboard provided by the present application comprises a paint layer and a paper base layer, and the paper base layer comprises a surface layer, a core layer and a bottom layer from front to back, the surface of the surface layer comprises a surface sizing layer, a bottom coating layer and a top coating layer from inside to outside, the top coating layer contains a first inorganic filler with a relatively small particle size, the sizing of the surface layer adopts high-concentration sizing, the single-side sizing amount of the surface layer is 8-10 g / m 2The raw material of the core layer adopts bleached chemical thermomechanical pulp of coniferous wood and bleached kraft pulp of broad-leaved wood, the raw material of the bottom layer adopts bleached kraft pulp of coniferous wood and bleached kraft pulp of broad-leaved wood in a specific ratio, the second inorganic filler with a larger particle size in the primer layer and the proportion of the latex with a high content, the application adjusts the fiber composition of the coated white card paper, the filler particle size of the coating layer and the proportion of the adhesive, does not need to perform the second sizing on the back, improves the ink penetration and absorption capacity, the ink penetration effect is good when printing on the back, the dyeing effect is good, meanwhile, the printing performance of the front of the paper is considered, and the practical application performance of the coated white card paper is ensured. DETAILED DESCRIPTION

[0059] In order to make the skilled in the art more clearly understand the technical solutions described in the application, the following examples are listed for illustration. It should be pointed out that the following examples do not constitute a limitation on the scope of protection required by the application.

[0060] The raw materials, reagents or devices used in the following examples are commercially available or can be obtained by known methods unless otherwise specified.

[0061] The raw materials used in the application are as follows:

[0062] NBKP pulp: Finland Qianhu brand.

[0063] LBKP pulp: Brazil Fenya brand.

[0064] BCTMP pulp: Russia IP poplar.

[0065] Water repellent agent: zirconium potassium carbonate type water repellent agent.

[0066] Dispersant: polyacrylic acid sodium type dispersant.

[0067] Lubricant: calcium stearate type lubricant.

[0068] Example 1

[0069] A coated white card paper, comprising a paper base layer and a coating layer;

[0070] The paper base layer comprises a surface layer, a core layer and a bottom layer from front to back;

[0071] In the fiber raw material of the surface layer, the weight ratio of NBKP pulp to LBKP pulp is 11:89;

[0072] In the fiber raw material of the core layer, the weight ratio of BCTMP pulp to LBKP pulp is 80:20;

[0073] In the fiber raw material of the bottom layer, the weight ratio of NBKP pulp to LBKP pulp is 11:89;

[0074] The surface sizing agent for the surface sizing of the surface layer and the bottom layer is cassava oxidized starch prepared on site, and the solid content is 5%, the single-sided sizing amount of the surface layer is 9 g / m 2 , and the single-sided sizing amount of the bottom layer is 1.5 g / m 2 ;

[0075] The surface coating layer is coated by using a surface coating material, and the surface coating material comprises the following components by weight: 88 parts of 98-grade calcium carbonate, 12 parts of porcelain clay, 0.05 parts of a dispersing agent, 14 parts of butadiene-styrene latex, 0.15 parts of a lubricant, 0.1 parts of CMC, and 0.1 parts of a water repellent agent. The solid content of the surface coating material is 63%, and the pH is adjusted to 9.7-10.2 by using sodium hydroxide.

[0076] The bottom coating layer is coated by using a bottom coating material, and the bottom coating material comprises the following components by weight: 100 parts of 60-grade calcium carbonate, 45 parts of butadiene-styrene latex, 0.05 parts of a dispersing agent, 0.15 parts of a lubricant, 0.1 parts of CMC, and 2.0 parts of a water repellent agent. The solid content of the bottom coating material is 63%, and the pH is adjusted to 9.7-10.2 by using sodium hydroxide.

[0077] The preparation method of the coated white cardboard comprises the following steps:

[0078] (1) The raw material components of the surface layer are mixed, crushed and ground to obtain surface layer pulp, and the surface layer raw paper is obtained by forming;

[0079] (2) The raw material components of the core layer are mixed, crushed and ground to obtain core layer pulp, and the core layer raw paper is obtained by forming;

[0080] (3) The raw material components of the bottom layer are mixed, crushed and ground to obtain bottom layer pulp, and the bottom layer raw paper is obtained by forming;

[0081] (4) The surface layer raw paper, the core layer raw paper and the bottom layer raw paper are sequentially bonded to obtain the paper base layer raw paper;

[0082] (5) After drying the paper base layer raw paper, surface sizing is performed on the surface layer and the bottom layer respectively, and the pre-coated raw paper is obtained after drying;

[0083] (6) The inorganic filler is added with water, the butadiene-styrene latex is added under high-speed stirring, and then the dispersing agent, the carboxymethyl cellulose, the lubricant and the water repellent agent are sequentially added. The pH value is adjusted to 8.5-9.5 by using a NaOH solution to prepare the bottom coating material. The bottom coating material is coated on the front surface of the raw paper, and the first coated white cardboard is obtained after drying.

[0084] (7) mixing 98 grade ground calcium carbonate, dispersant and water, adding porcelain clay, then adding carboxymethyl cellulose and styrene-butadiene latex, finally adding water repellent and lubricant, adjusting pH value to 8.5-9.5 by NaOH solution, to obtain a top coating material; coating the top coating material on the top surface of the base paper, drying to obtain a second coated white cardboard, further compacting the coating by calendering to obtain a coated white cardboard, which comprises, from top surface to back surface, a top coating layer, a base coating layer, a surface sizing layer, a top layer, a core layer, a bottom layer and a bottom surface sizing layer.

[0085] Example 2

[0086] Example 2 differs from Example 1 in that the proportion of BCTMP pulp and LBKP pulp in the core layer is different.

[0087] A coated white cardboard comprising a paper base layer and a coating layer;

[0088] The paper base layer comprises, from top surface to back surface, a top layer, a core layer and a bottom layer;

[0089] In the fiber raw material of the top layer, the weight ratio of NBKP pulp and LBKP pulp is 11:89;

[0090] In the fiber raw material of the core layer, the weight ratio of BCTMP pulp and LBKP pulp is 90:10;

[0091] In the fiber raw material of the bottom layer, the weight ratio of NBKP pulp and LBKP pulp is 11:89;

[0092] The top layer and the bottom layer are respectively surface sized in the drying section, the sizing agent for surface sizing is on-site prepared cassava oxidized starch, the solid content is 5%, the single-sided sizing amount of the top layer is 9 g / m 2 , and the single-sided sizing amount of the bottom layer is 1.5 g / m 2 ;

[0093] The top coating layer is obtained by coating a top coating material, the top coating material comprises the following raw material components in parts by weight: 98 grade calcium carbonate 88 parts, porcelain clay 12 parts, dispersant 0.05 parts, styrene-butadiene latex 14 parts, lubricant 0.15 parts, CMC 0.1 parts, water repellent 0.1 parts. The solid content of the top coating material is 63%, and the pH is adjusted to 9.7-10.2 by sodium hydroxide;

[0094] The base coating layer is obtained by coating a base coating material, the base coating material comprises the following raw material components in parts by weight: 60 grade calcium carbonate 100 parts, styrene-butadiene latex 45 parts, dispersant 0.05 parts, lubricant 0.15 parts, CMC 0.1 parts, water repellent 2 parts. The solid content of the base coating material is 63%, and the pH is adjusted to 9.7-10.2 by sodium hydroxide.

[0095] The preparation method of the above coated white cardboard comprises the following steps:

[0096] (1) mixing raw material components of the surface layer, crushing, and refining to obtain surface layer pulp, and then forming to obtain surface layer base paper;

[0097] (2) mixing raw material components of the core layer, crushing, and refining to obtain core layer pulp, and then forming to obtain core layer base paper;

[0098] (3) mixing raw material components of the bottom layer, crushing, and refining to obtain bottom layer pulp, and then forming to obtain bottom layer base paper;

[0099] (4) sequentially bonding the surface layer base paper, the core layer base paper, and the bottom layer base paper to obtain paper base layer base paper;

[0100] (5) after drying the paper base layer base paper, performing surface sizing on the surface layer and the bottom layer respectively, and then drying to obtain pre-coated base paper;

[0101] (6) adding water to the inorganic filler, adding styrene-butadiene latex under high-speed stirring, and then sequentially adding a dispersing agent, carboxymethyl cellulose, and finally adding a lubricant and a water-resistant agent, and adjusting the pH value to 8.5-9.5 by using a NaOH solution to prepare a primer coating. The primer coating is applied to the front surface of the base paper, and after drying, a first coated white card paper is obtained;

[0102] (7) mixing 98-grade ground calcium carbonate, a dispersing agent, and water, adding porcelain clay, and then adding carboxymethyl cellulose and styrene-butadiene latex, and finally adding a water-resistant agent and a lubricant, and adjusting the pH value to 8.5-9.5 by using a NaOH solution to prepare a top coating. The top coating is applied to the front surface of the base paper, and after drying, a second coated white card paper is obtained, and the coating is further compressed by calendering to obtain a coated white card paper.

[0103] Example 3

[0104] The difference between Example 3 and Example 1 is that the proportions of BCTMP pulp and LBKP pulp in the core layer are different.

[0105] A coated white card paper comprises a paper base layer and a coating layer;

[0106] The paper base layer comprises, in order from the front surface to the back surface, a surface layer, a core layer, and a bottom layer;

[0107] In the fiber raw material of the surface layer, the weight ratio of NBKP pulp to LBKP pulp is 11:89;

[0108] In the fiber raw material of the core layer, the weight ratio of BCTMP pulp to LBKP pulp is 70:30;

[0109] In the fiber raw material of the bottom layer, the weight ratio of NBKP pulp to LBKP pulp is 11:89;

[0110] The surface sizing agent for the surface sizing of the surface layer and the bottom layer is cassava oxidized starch prepared on site, with a solid content of 5%, and the surface sizing amount of the surface layer is 9 g / m 2 , and the surface sizing amount of the bottom layer is 1.5 g / m 2 ;

[0111] The surface coating layer is coated by using a surface coating material, which comprises the following components by weight: 88 parts of 98-grade calcium carbonate, 12 parts of porcelain clay, 0.05 parts of a dispersing agent, 14 parts of butadiene-styrene latex, 0.15 parts of a lubricant, 0.1 parts of CMC, and 0.1 parts of a water repellent agent. The solid content of the surface coating material is 63%, and the pH value is adjusted to 9.7-10.2 by using sodium hydroxide;

[0112] The bottom coating layer is coated by using a bottom coating material, which comprises the following components by weight: 100 parts of 60-grade calcium carbonate, 45 parts of butadiene-styrene latex, 0.05 parts of a dispersing agent, 0.15 parts of a lubricant, 0.1 parts of CMC, and 2 parts of a water repellent agent. The solid content of the bottom coating material is 63%, and the pH value is adjusted to 9.7-10.2 by using sodium hydroxide.

[0113] The preparation method of the coated white paper comprises the following steps:

[0114] (1) The raw material components of the surface layer are mixed, crushed and ground to obtain surface layer pulp, which is formed into a shape to obtain surface layer raw paper;

[0115] (2) The raw material components of the core layer are mixed, crushed and ground to obtain core layer pulp, which is formed into a shape to obtain core layer raw paper;

[0116] (3) The raw material components of the bottom layer are mixed, crushed and ground to obtain bottom layer pulp, which is formed into a shape to obtain bottom layer raw paper;

[0117] (4) The surface layer raw paper, the core layer raw paper and the bottom layer raw paper are sequentially bonded to obtain paper base layer raw paper;

[0118] (5) After drying the paper base layer raw paper, surface sizing is performed on the surface layer and the bottom layer, and after drying, pre-coated raw paper is obtained;

[0119] (6) Water is added to the inorganic filler, butadiene-styrene latex is added under high-speed stirring, and then a dispersing agent, carboxymethyl cellulose, a lubricant and a water repellent agent are sequentially added. The pH value is adjusted to 8.5-9.5 by using a NaOH solution to prepare a bottom coating material. The bottom coating material is coated on the front surface of the raw paper, and after drying, a first coated white paper is obtained;

[0120] (7) mixing 98 grade ground calcium carbonate, dispersant and water, adding porcelain clay, then adding carboxymethyl cellulose and styrene-butadiene latex, finally adding water repellent and lubricant, adjusting pH value to 8.5-9.5 by NaOH solution to obtain a top coating material. The top coating material is coated on the top surface of the base paper, dried to obtain a second coated white cardboard, and the coating layer is further compacted by calendering to obtain the coated white cardboard.

[0121] Example 4

[0122] Example 4 is different from Example 1 in that the proportions of BCTMP pulp and LBKP pulp in the core layer are different, and 98 grade calcium carbonate is used in the top coating layer.

[0123] A coated white cardboard comprises a paper base layer and a coating layer.

[0124] The paper base layer comprises a top layer, a core layer and a bottom layer in sequence from the top surface to the back surface.

[0125] In the fiber raw material of the top layer, the weight ratio of NBKP pulp to LBKP pulp is 11:89.

[0126] In the fiber raw material of the core layer, the weight ratio of BCTMP pulp to LBKP pulp is 60:40.

[0127] In the fiber raw material of the bottom layer, the weight ratio of NBKP pulp to LBKP pulp is 11:89.

[0128] The top layer and the bottom layer are respectively surface sized in the drying section, and the surface sizing agent is on-site prepared cassava oxidized starch with a solid content of 5%, the single-sided sizing amount of the top layer is 9 g / m 2 , and the single-sided sizing amount of the bottom layer is 1.5 g / m 2 .

[0129] The top coating layer is obtained by coating a top coating material, and the top coating material comprises the following raw material components in parts by weight: 98 grade calcium carbonate 88 parts, porcelain clay 12 parts, dispersant 0.05 parts, styrene-butadiene latex 14 parts, lubricant 0.15 parts, CMC 0.1 parts, and water repellent 0.1 parts. The solid content of the first top coating material is 63%, and the pH value is adjusted to 9.7-10.2 by sodium hydroxide.

[0130] The bottom coating layer is obtained by coating a bottom coating material, and the bottom coating material comprises the following raw material components in parts by weight: 60 grade calcium carbonate 100 parts, styrene-butadiene latex 45 parts, dispersant 0.05 parts, lubricant 0.15 parts, CMC 0.1 parts, and water repellent 2 parts. The solid content of the bottom coating material is 63%, and the pH value is adjusted to 9.7-10.2 by sodium hydroxide.

[0131] The preparation method of the above coated white cardboard comprises the following steps:

[0132] (1) mixing raw material components of the surface layer, crushing, and refining to obtain surface layer pulp, and then forming to obtain surface layer base paper;

[0133] (2) mixing raw material components of the core layer, crushing, and refining to obtain core layer pulp, and then forming to obtain core layer base paper;

[0134] (3) mixing raw material components of the bottom layer, crushing, and refining to obtain bottom layer pulp, and then forming to obtain bottom layer base paper;

[0135] (4) sequentially bonding the surface layer base paper, the core layer base paper, and the bottom layer base paper to obtain paper base layer base paper;

[0136] (5) after drying the paper base layer base paper, performing surface sizing on the surface layer and the bottom layer respectively, and then drying to obtain pre-coated base paper;

[0137] (6) adding water to the inorganic filler, adding styrene-butadiene latex under high-speed stirring, and then sequentially adding a dispersing agent, carboxymethyl cellulose, a lubricant, and a water-resistant agent, and adjusting the pH value to 8.5-9.5 by using a NaOH solution to prepare a primer coating. The primer coating is applied to the front surface of the base paper, and then dried to obtain a first coated white card;

[0138] (7) mixing 98-grade ground calcium carbonate, a dispersing agent, and water, adding china clay, and then adding carboxymethyl cellulose and styrene-butadiene latex, and finally adding a water-resistant agent and a lubricant, and adjusting the pH value to 8.5-9.5 by using a NaOH solution to prepare a top coating. The top coating is applied to the front surface of the base paper, and then dried to obtain a second coated white card, and the coating is further compacted by calendering to obtain a coated white card.

[0139] Comparative Example 1

[0140] The difference between Comparative Example 1 and Example 1 is that the core layer pulp does not contain LBKP pulp (short fibers) and only contains BCTMP pulp.

[0141] A coated white card comprises a paper base layer and a coating layer;

[0142] The paper base layer comprises, in order from the front surface to the back surface, a surface layer, a core layer, and a bottom layer;

[0143] In the fiber raw material of the surface layer, the weight ratio of the NBKP pulp to the LBKP pulp is 11:89;

[0144] In the fiber raw material of the core layer, the content of the BCTMP pulp is 100%;

[0145] In the fiber raw material of the bottom layer, the weight ratio of the NBKP pulp to the LBKP pulp is 20:80;

[0146] The surface sizing of the surface layer and the bottom layer is respectively carried out in a drying section, the sizing agent for the surface sizing is on-site prepared cassava oxidized starch with a solid content of 5%, the single-sided sizing amount of the surface layer is 9 g / m 2 , and the single-sided sizing amount of the bottom layer is 1.5 g / m 2 .

[0147] The coating used for the surface coating layer comprises the following components in parts by weight: 88 parts of 98-grade calcium carbonate, 12 parts of porcelain clay, 0.05 parts of dispersing agent, 14 parts of butadiene-styrene latex, 0.15 parts of lubricant, 0.1 parts of CMC, and 0.1 parts of water repellent agent. The solid content of the first surface coating is 63%, and the pH is adjusted to 9.7-10.2 by sodium hydroxide;

[0148] The coating used for the bottom coating layer comprises the following components in parts by weight: 100 parts of 60-grade calcium carbonate, 45 parts of butadiene-styrene latex, 0.05 parts of dispersing agent, 0.15 parts of lubricant, 0.1 parts of CMC, and 2 parts of water repellent agent. The solid content of the bottom coating is 63%, and the pH is adjusted to 9.7-10.2 by sodium hydroxide.

[0149] The preparation method of the coated white card paper, comprising the following steps:

[0150] (1) mixing the raw material components of the surface layer, crushing and pulp refining to obtain the surface layer pulp, and forming the surface layer raw paper by papermaking;

[0151] (2) mixing the raw material components of the core layer, crushing and pulp refining to obtain the core layer pulp, and forming the core layer raw paper by papermaking;

[0152] (3) mixing the raw material components of the bottom layer, crushing and pulp refining to obtain the bottom layer pulp, and forming the bottom layer raw paper by papermaking;

[0153] (4) sequentially bonding the surface layer raw paper, the core layer raw paper and the bottom layer raw paper to obtain the paper base layer raw paper;

[0154] (5) after drying the paper base layer raw paper, respectively performing surface sizing on the surface layer and the bottom layer, and obtaining the pre-coated raw paper after drying;

[0155] (6) coating the bottom coating to the front side of the raw paper, and obtaining the first coated white card paper after drying;

[0156] (7) coating the surface coating to the front side of the raw paper, and obtaining the second coated white card paper after drying, and further compacting the coating layer by calendering to obtain the coated white card paper.

[0157] Comparative Example 2

[0158] The difference between Comparative Example 2 and Example 1 is that the bottom layer pulp is only added with LBKP pulp (short fiber) without NBKP pulp.

[0159] A coated white card paper comprises a paper base layer and a coating layer;

[0160] The paper base layer comprises successively from the front side to the back side a top layer, a core layer and a bottom layer;

[0161] In the fiber raw material of the top layer, the weight ratio of the NBKP pulp and the LBKP pulp is 11:89;

[0162] In the fiber raw material of the core layer, the weight ratio of the BCTMP pulp and the LBKP pulp is 80:20;

[0163] In the fiber raw material of the bottom layer, the content of the LBKP pulp is 100%;

[0164] The top layer and the bottom layer are respectively surface sized in the drying section, the sizing agent for surface sizing is on-site prepared cassava oxidized starch with a solid content of 5%, the single side sizing amount of the top layer is 9 g / m 2 , and the single side sizing amount of the bottom layer is 1.5 g / m 2 ;

[0165] The coating used for the top coating layer comprises the following components in parts by weight: 88 parts of 98-grade calcium carbonate, 12 parts of porcelain clay, 0.05 parts of dispersing agent, 14 parts of butadiene-styrene latex, 0.15 parts of lubricant, 0.1 parts of CMC and 0.1 parts of water repellent agent. The solid content of the first top coating is 63%, and the pH is adjusted to 9.7-10.2 by sodium hydroxide;

[0166] The coating used for the bottom coating layer comprises the following components in parts by weight: 100 parts of 60-grade calcium carbonate, 14 parts of butadiene-styrene latex, 0.05 parts of dispersing agent, 0.15 parts of lubricant, 0.1 parts of CMC and 0.1 parts of water repellent agent. The solid content of the bottom coating is 63%, and the pH is adjusted to 9.7-10.2 by sodium hydroxide.

[0167] The preparation method of the coated white card paper comprises the following steps:

[0168] (1) mixing the raw material components of the top layer, crushing and refining to obtain the top layer pulp, and then forming the top layer raw paper;

[0169] (2) mixing the raw material components of the core layer, crushing and refining to obtain the core layer pulp, and then forming the core layer raw paper;

[0170] (3) mixing the raw material components of the bottom layer, crushing and refining to obtain the bottom layer pulp, and then forming the bottom layer raw paper;

[0171] (4) sequentially bonding the top layer raw paper, the core layer raw paper and the bottom layer raw paper to obtain the paper base layer raw paper;

[0172] (5) after drying the paper base layer raw paper, performing surface sizing on the top layer and the bottom layer respectively, and then drying to obtain the pre-coated raw paper;

[0173] (6) applying a base coating to the front side of the base paper, drying to obtain a first coated white card paper;

[0174] (7) applying a top coating to the front side of the base paper, drying to obtain a second coated white card paper, further compacting the coating by calendering to obtain the coated white card paper;

[0175] Comparative Example 3

[0176] Comparative Example 3 differs from Example 1 in that the proportions of the base layer pulp are different.

[0177] A coated white card paper comprises a paper base layer and a coating layer;

[0178] The paper base layer comprises, in order from the front side to the back side, a top layer, a core layer and a base layer;

[0179] In the fiber raw material of the top layer, the weight ratio of the NBKP pulp and the LBKP pulp is 11:89;

[0180] In the fiber raw material of the core layer, the weight ratio of the BCTMP pulp and the LBKP pulp is 80:20;

[0181] In the fiber raw material of the base layer, the weight ratio of the NBKP pulp and the LBKP pulp is 25:75;

[0182] The top layer and the base layer are respectively surface sized in the drying section, the sizing agent for surface sizing is on-site prepared cassava oxidized starch, the solid content is 5%, the single-sided sizing amount of the top layer is 9 g / m 2 , and the single-sided sizing amount of the base layer is 1.5 g / m 2 ;

[0183] The coating used for the top coating layer comprises the following components in parts by weight: 88 parts of 98-grade calcium carbonate, 12 parts of porcelain clay, 0.05 parts of dispersant, 14 parts of butadiene-styrene latex, 0.15 parts of lubricant, 0.1 parts of CMC, and 0.1 parts of water repellent agent. The solid content of the first top coating is 63%, and the pH is adjusted to 9.7-10.2 by sodium hydroxide;

[0184] The coating used for the base coating layer comprises the following components in parts by weight: 100 parts of 60-grade calcium carbonate, 14 parts of butadiene-styrene latex, 0.05 parts of dispersant, 0.15 parts of lubricant, 0.1 parts of CMC, and 0.1 parts of water repellent agent. The solid content of the base coating is 63%, and the pH is adjusted to 9.7-10.2 by sodium hydroxide.

[0185] The preparation method of the above coated white card paper comprises the following steps:

[0186] (1) mixing the raw material components of the top layer, crushing and refining to obtain the top layer pulp, and forming into a top layer base paper;

[0187] (2) mixing raw material components of the core layer, crushing, and refining to obtain the core layer pulp, and then forming to obtain the core layer base paper;

[0188] (3) mixing raw material components of the bottom layer, crushing, and refining to obtain the bottom layer pulp, and then forming to obtain the bottom layer base paper;

[0189] (4) sequentially bonding the surface layer base paper, the core layer base paper, and the bottom layer base paper to obtain the paper-based layer base paper;

[0190] (5) after drying the paper-based layer base paper, performing surface sizing on the surface layer and the bottom layer respectively, and then drying to obtain the pre-coated base paper;

[0191] (5) applying the bottom coating paint to the front surface of the base paper, and then drying to obtain the first coated white cardboard;

[0192] (6) applying the surface coating paint to the front surface of the base paper, and then drying to obtain the second coated white cardboard, and further compacting the coating layer by calendering to obtain the coated white cardboard;

[0193] Comparative Example 4

[0194] The difference between Comparative Example 4 and Example 1 is that the content of the styrene-butadiene latex in the bottom coating layer is reduced.

[0195] A coated white cardboard comprises a paper-based layer and a coating layer;

[0196] The paper-based layer comprises, in sequence from the front surface to the back surface, a surface layer, a core layer, and a bottom layer;

[0197] In the fiber raw material of the surface layer, the weight ratio of the NBKP pulp to the LBKP pulp is 11:89;

[0198] In the fiber raw material of the core layer, the weight ratio of the BCTMP pulp to the LBKP pulp is 80:20;

[0199] In the fiber raw material of the bottom layer, the weight ratio of the NBKP pulp to the LBKP pulp is 11:89;

[0200] The surface layer and the bottom layer are respectively subjected to surface sizing in the drying section, and the sizing agent for surface sizing is on-site prepared cassava oxidized starch with a solid content of 5%, and the single-sided sizing amount of the surface layer is 9 g / m 2 , and the single-sided sizing amount of the bottom layer is 1.5 g / m 2 ;

[0201] The surface coating layer is obtained by applying the surface coating paint, and the surface coating paint comprises the following raw material components in parts by weight: 88 parts of 98-grade calcium carbonate, 12 parts of porcelain clay, 0.05 parts of a dispersing agent, 14 parts of styrene-butadiene latex, 0.15 parts of a lubricant, 0.1 parts of CMC, and 0.1 parts of a water-resistant agent. The solid content of the surface coating paint is 63%, and the pH is adjusted to 9.7-10.2 by sodium hydroxide.

[0202] The base coat is obtained by coating a base coat paint, which comprises the following components by weight: 100 parts of 60-grade calcium carbonate, 15 parts of butadiene-styrene latex, 0.05 parts of dispersant, 0.15 parts of lubricant, 0.1 parts of CMC, and 2.0 parts of water repellent. The solid content of the base coat paint is 63%, and the pH is adjusted to 9.7-10.2 by sodium hydroxide.

[0203] The preparation method of the coated white cardboard comprises the following steps:

[0204] (1) mixing the raw material components of the surface layer, crushing and pulp refining to obtain surface layer pulp, and forming the surface layer pulp into a shape to obtain surface layer raw paper;

[0205] (2) mixing the raw material components of the core layer, crushing and pulp refining to obtain core layer pulp, and forming the core layer pulp into a shape to obtain core layer raw paper;

[0206] (3) mixing the raw material components of the base layer, crushing and pulp refining to obtain base layer pulp, and forming the base layer pulp into a shape to obtain base layer raw paper;

[0207] (4) sequentially bonding the surface layer raw paper, the core layer raw paper, and the base layer raw paper to obtain paper base layer raw paper;

[0208] (5) after drying the paper base layer raw paper, performing surface sizing on the surface layer and the base layer respectively, and drying to obtain pre-coated raw paper;

[0209] (6) adding water to the inorganic filler, adding butadiene-styrene latex under high-speed stirring, and then sequentially adding dispersant, carboxymethyl cellulose, and finally adding lubricant and water repellent, and adjusting the pH value to 8.5-9.5 by NaOH solution to prepare the base coat paint. The base coat paint is coated on the front surface of the raw paper, and dried to obtain the first coated white cardboard;

[0210] (7) mixing 98-grade ground calcium carbonate, dispersant, and water, adding porcelain clay, and then adding carboxymethyl cellulose and butadiene-styrene latex, and finally adding water repellent and lubricant, and adjusting the pH value to 8.5-9.5 by NaOH solution to prepare the surface coat paint. The surface coat paint is coated on the front surface of the raw paper, and dried to obtain the second coated white cardboard, and the coating is further compacted by calendering to obtain the coated white cardboard.

[0211] Comparative Example 5

[0212] The difference between Comparative Example 5 and Example 1 is that the amount of surface layer single-side sizing is reduced to 1.5 g / m 2 .

[0213] A coated white cardboard comprises a paper base layer and a coating layer;

[0214] The paper base layer comprises, in order from the front surface to the back surface, a surface layer, a core layer, and a base layer;

[0215] The weight ratio of the NBKP pulp and the LBKP pulp in the fiber raw material of the surface layer is 11:89;

[0216] The weight ratio of the BCTMP pulp and the LBKP pulp in the fiber raw material of the core layer is 80:20;

[0217] The weight ratio of the NBKP pulp and the LBKP pulp in the fiber raw material of the bottom layer is 11:89;

[0218] The surface sizing is respectively performed on the surface layer and the bottom layer in the drying section, the sizing agent for the surface sizing is the on-site prepared cassava oxidized starch, the solid content is 5%, the single-side sizing amount of the surface layer is 1.5 g / m 2 , and the single-side sizing amount of the bottom layer is 1.5 g / m 2 ;

[0219] The surface coating layer is coated by using a surface coating paint, according to weight parts, the surface coating paint comprises the following raw material components: 98-grade calcium carbonate 88 parts, porcelain clay 12 parts, dispersing agent 0.05 parts, butyl styrene latex 14 parts, lubricant 0.15 parts, CMC 0.1 part, water repellent 0.1 part. The solid content of the surface coating paint is 63%, and the pH is adjusted to 9.7-10.2 by using sodium hydroxide.

[0220] The bottom coating layer is coated by using a bottom coating paint, according to weight parts, the bottom coating paint comprises the following raw material components: 60-grade calcium carbonate 100 parts, butyl styrene latex 45 parts, dispersing agent 0.05 parts, lubricant 0.15 parts, CMC 0.1 part, water repellent 2.0 parts. The solid content of the bottom coating paint is 63%, and the pH is adjusted to 9.7-10.2 by using sodium hydroxide.

[0221] The preparation method of the coated white cardboard, comprising the following steps:

[0222] (1) mixing the raw material components of the surface layer, crushing and refining to obtain the surface layer pulp, and then forming the surface layer raw paper;

[0223] (2) mixing the raw material components of the core layer, crushing and refining to obtain the core layer pulp, and then forming the core layer raw paper;

[0224] (3) mixing the raw material components of the bottom layer, crushing and refining to obtain the bottom layer pulp, and then forming the bottom layer raw paper;

[0225] (4) sequentially bonding the surface layer raw paper, the core layer raw paper and the bottom layer raw paper to obtain the paper base layer raw paper;

[0226] (5) after drying the paper base layer raw paper, performing the surface sizing on the surface layer and the bottom layer respectively, and then drying to obtain the pre-coated raw paper;

[0227] (6) In the inorganic filler, add water, add styrene-butadiene latex under high speed stirring, then add dispersant, carboxymethyl cellulose mixture, finally add lubricant and water repellent, using NaOH solution to adjust pH value to 8.5-9.5, to prepare the primer coating. The primer coating is coated to the front side of the base paper, dried to obtain the first coated white card paper;

[0228] (7) Mix 98 grade ground calcium carbonate, dispersant and water, add porcelain clay, then add carboxymethyl cellulose and styrene-butadiene latex, finally add water repellent and lubricant, using NaOH solution to adjust pH value to 8.5-9.5, to prepare the top coating. The top coating is coated to the front side of the base paper, dried to obtain the second coated white card paper, and further compacted by calendering to obtain the coated white card paper.

[0229] Comparative Example 6

[0230] The difference between Comparative Example 6 and Example 1 is that the particle size of the ground calcium carbonate in the top coating is larger.

[0231] A coated white card paper, comprising a paper base layer and a coating layer;

[0232] The paper base layer comprises, in order from the front side to the back side, a top layer, a core layer and a bottom layer;

[0233] In the fiber raw material of the top layer, the weight ratio of NBKP pulp and LBKP pulp is 11:89;

[0234] In the fiber raw material of the core layer, the weight ratio of BCTMP pulp and LBKP pulp is 80:20;

[0235] In the fiber raw material of the bottom layer, the weight ratio of NBKP pulp and LBKP pulp is 11:89;

[0236] The top layer and the bottom layer are respectively surface sized in the drying section, and the surface sizing agent is on-site prepared cassava oxidized starch with a solid content of 5%, and the single-sided sizing amount of the top layer is 9.0 g / m 2 , and the single-sided sizing amount of the bottom layer is 1.5 g / m 2 ;

[0237] The top coating is obtained by coating the top coating material, and the top coating material comprises the following raw material components in parts by weight: 98 grade calcium carbonate 88 parts, porcelain clay 12 parts, dispersant 0.05 parts, styrene-butadiene latex 14 parts, lubricant 0.15 parts, CMC 0.1 parts, and water repellent 0.1 parts. The solid content of the top coating material is 63%, and the pH is adjusted to 9.7-10.2 by sodium hydroxide.

[0238] The primer layer is obtained by coating a primer coating material. The primer coating material comprises the following components by weight: 100 parts of 60-grade calcium carbonate, 45 parts of butadiene-styrene latex, 0.05 parts of dispersant, 0.15 parts of lubricant, 0.1 parts of CMC, and 2.0 parts of water repellent. The solid content of the primer coating material is 63%, and the pH is adjusted to 9.7-10.2 by sodium hydroxide.

[0239] The method for preparing the coated white cardboard comprises the following steps:

[0240] (1) mixing the raw material components of the surface layer, crushing and refining to obtain surface layer pulp, and forming the surface layer pulp into a shape to obtain surface layer raw paper;

[0241] (2) mixing the raw material components of the core layer, crushing and refining to obtain core layer pulp, and forming the core layer pulp into a shape to obtain core layer raw paper;

[0242] (3) mixing the raw material components of the bottom layer, crushing and refining to obtain bottom layer pulp, and forming the bottom layer pulp into a shape to obtain bottom layer raw paper;

[0243] (4) sequentially bonding the surface layer raw paper, the core layer raw paper, and the bottom layer raw paper to obtain paper base layer raw paper;

[0244] (5) after drying the paper base layer raw paper, performing surface sizing on the surface layer and the bottom layer respectively, and drying to obtain pre-coated raw paper;

[0245] (6) adding water to the inorganic filler, adding butadiene-styrene latex under high-speed stirring, and then sequentially adding dispersant, carboxymethyl cellulose, and finally adding lubricant and water repellent, and adjusting the pH value to 8.5-9.5 by NaOH solution to prepare a primer coating material. The primer coating material is coated on the front surface of the raw paper, and dried to obtain the first coated white cardboard;

[0246] (7) mixing 98-grade ground calcium carbonate, dispersant, and water, adding porcelain clay, and then adding carboxymethyl cellulose and butadiene-styrene latex, and finally adding water repellent and lubricant, and adjusting the pH value to 8.5-9.5 by NaOH solution to prepare a top coating material. The top coating material is coated on the front surface of the raw paper, and dried to obtain the second coated white cardboard, and the coating is further compacted by calendering to obtain the coated white cardboard.

[0247] Comparative Example 7

[0248] The difference between Comparative Example 7 and Example 1 is that the particle size of the ground calcium carbonate in the primer layer is larger.

[0249] A coated white cardboard comprises a paper base layer and a coating layer;

[0250] The paper base layer comprises, in order from the front surface to the back surface, a surface layer, a core layer, and a bottom layer;

[0251] The weight ratio of the NBKP pulp and the LBKP pulp in the fiber raw material of the surface layer is 11:89;

[0252] The weight ratio of the BCTMP pulp and the LBKP pulp in the fiber raw material of the core layer is 80:20;

[0253] The weight ratio of the NBKP pulp and the LBKP pulp in the fiber raw material of the bottom layer is 11:89;

[0254] The surface sizing is respectively performed on the surface layer and the bottom layer in the drying section, the sizing agent for the surface sizing is the on-site prepared cassava oxidized starch, the solid content is 5%, the single-side sizing amount of the surface layer is 9.0 g / m 2 , and the single-side sizing amount of the bottom layer is 1.5 g / m 2 ;

[0255] The surface coating layer is coated by using a surface coating paint, according to weight parts, the surface coating paint comprises the following raw material components: 98-grade calcium carbonate 88 parts, porcelain clay 12 parts, dispersing agent 0.05 parts, butyl styrene latex 14 parts, lubricant 0.15 parts, CMC 0.1 part, water repellent 0.1 part. The solid content of the surface coating paint is 63%, and the pH is adjusted to 9.7-10.2 by using sodium hydroxide.

[0256] The bottom coating layer is coated by using a bottom coating paint, according to weight parts, the bottom coating paint comprises the following raw material components: 50-grade calcium carbonate 100 parts, butyl styrene latex 45 parts, dispersing agent 0.05 parts, lubricant 0.15 parts, CMC 0.1 part, water repellent 2.0 parts. The solid content of the bottom coating paint is 63%, and the pH is adjusted to 9.7-10.2 by using sodium hydroxide.

[0257] The preparation method of the coated white cardboard, comprising the following steps:

[0258] (1) mixing the raw material components of the surface layer, crushing and refining to obtain the surface layer pulp, and then forming the surface layer paper;

[0259] (2) mixing the raw material components of the core layer, crushing and refining to obtain the core layer pulp, and then forming the core layer paper;

[0260] (3) mixing the raw material components of the bottom layer, crushing and refining to obtain the bottom layer pulp, and then forming the bottom layer paper;

[0261] (4) sequentially bonding the surface layer paper, the core layer paper and the bottom layer paper to obtain the paper base layer paper;

[0262] (5) after drying the paper base layer paper, performing the surface sizing on the surface layer and the bottom layer respectively, and then drying to obtain the pre-coated paper;

[0263] (6) Inorganic filler is added with water, and styrene-butadiene latex is added under high-speed stirring, and then dispersant, carboxymethyl cellulose are added in sequence, and finally lubricant and water repellent are added, and the pH value is adjusted to 8.5-9.5 by using NaOH solution to prepare the primer coating. The primer coating is coated on the front side of the base paper, and dried to obtain the first coated white card paper;

[0264] (7) 98-grade ground calcium carbonate, dispersant and water are mixed, and then porcelain clay is added, and then carboxymethyl cellulose and styrene-butadiene latex are added, and finally water repellent and lubricant are added, and the pH value is adjusted to 8.5-9.5 by using NaOH solution to prepare the top coating. The top coating is coated on the front side of the base paper, and dried to obtain the second coated white card paper, and the coating is further compacted by calendering to obtain the coated white card paper.

[0265] Product effect test

[0266] Whiteness (brightness) is tested according to GB / T7974. Bulkiness is tested according to the standard of GB / T541.3-2002. Print surface roughness (PPS) is tested according to the provisions of GB / T22363 with 1000kPa pressure hard pad. Air permeability is tested according to GB / T458-2008. Front ink absorption value is tested according to GB / T12911 standard. Breaking degree is tested according to GB / T1935-2007. Ink penetration depth test method is as follows: 50mL rubber bulb dropper is used to suck appropriate amount of dye, and then the dye is dropped on the back of the paper along the longitudinal direction of the paper at a uniform speed, and five drops are continuously dropped. The paper is cut into appropriate size, embedded in epoxy resin, and then the dyed part is cut to obtain the cross section of the dyed paper, and then the cross section is observed under an electron microscope at 80-100 times magnification to obtain the penetration depth of the ink in the coating. Then the ink penetration ratio is calculated according to the following formula (1), and the average value of five groups of data is obtained, which is the ink penetration depth of the paper.

[0267] Ink penetration ratio = penetration depth / paper thickness*100% Formula (1)

[0268] Table 1 Performance test results of each example and comparative example

[0269]

[0270]

[0271] As shown in the table above, the coated white cardboard prepared in Examples 1-4 of the present invention has high whiteness and bulk, a front surface roughness in the range of 0.83-0.87 μm, a back surface roughness in the range of 8.22-8.49 μm, a front air permeability in the range of 0.38-0.56, a back air permeability in the range of 6.88-8.48, and high ink absorption and ink penetration depth, indicating that the coated white cardboard of the present invention has excellent ink penetration and absorption performance, thereby improving the dyeing effect.

[0272] Comparative Example 1: The core layer material only contains BCTMP pulp and no LBKP pulp, which leads to a decrease in the whiteness of the coated white cardboard, a rougher surface, and a decrease in the ratio of ink absorption and ink penetration depth.

[0273] Comparative Example 2: The bottom layer material only contains LBKP pulp and no NBKP. It has little impact on ink penetration and the paper surface is smooth, but the burst strength drops to 426 kPa, which seriously affects the back strength.

[0274] Comparative Example 3 showed that reducing the proportion of LBKP paste and increasing the proportion of NBKP paste in the bottom layer resulted in a rougher back surface and affected ink penetration.

[0275] Comparative Example 4 reduced the styrene-butadiene latex content in the base coating, resulting in excessive ink penetration and easy smudging of the front side of the paper.

[0276] Comparative Example 5: Reducing the amount of sizing applied to one side of the front layer resulted in excessive ink penetration, which easily smudged the front of the paper.

[0277] The grinding calcium carbonate used in the comparative example 6 coatings was replaced with grade 90 calcium carbonate, which has a larger particle size and a rougher surface, affecting the printing quality.

[0278] In Comparative Example 7, the ground calcium carbonate in the base coating was replaced with Grade 50 calcium carbonate, which has a larger particle size and a rougher surface. The ink had already seeped into the coating layer, affecting printing.

Claims

1. A coated white card, characterized in that, The paper base layer comprises a surface layer, a core layer and a bottom layer from front to back, the surface of the surface layer comprises a surface sizing layer, a primer layer and a top coating layer from inside to outside, and the coating layer comprises a primer layer and a top coating layer; the bottom layer is not back-coated; the single-side sizing amount of the surface layer is 8-10 g / m 2 ; The top coat is obtained by coating a top coat paint, raw material components of which include a first inorganic filler, content of particles with particle size less than or equal to 2 μm in the first inorganic filler being greater than or equal to 95%; The base coat is obtained by coating with a base coat paint, the raw material components of which include 100 parts by weight of a second inorganic filler and 40-48 parts by weight of a binder, the second inorganic filler being ground calcium carbonate, the content of particles of the ground calcium carbonate having a particle size of less than 2 microns being 59.5 60.5%; Raw material of the core layer is composed of bleached chemical thermo-mechanical pulp of coniferous wood and bleached kraft pulp of broad-leaved wood with weight ratio of (60-90):(10-40); Raw material components of the bottom layer include bleached kraft pulp of coniferous wood and bleached kraft pulp of broad-leaved wood with weight ratio of 1:(7-9).

2. The coated white card according to claim 1, characterized in that, Raw material of the top layer includes bleached kraft pulp of coniferous wood and bleached kraft pulp of broad-leaved wood.

3. The coated white paper according to claim 2, characterized in that, Raw material of the top layer includes bleached kraft pulp of coniferous wood and bleached kraft pulp of broad-leaved wood with weight ratio of (9-13):(80-95).

4. The coated white paper according to claim 1, characterized in that, The top coat paint further includes the following raw material components: adhesive, dispersant, water repellent, lubricant and water; and / or the bottom coat paint further includes the following raw material components: dispersant, water repellent, lubricant and water.

5. The coated white paper according to claim 4, characterized in that, According to weight parts, the first inorganic filler is 100 parts, the adhesive is 10-18 parts, the carboxymethyl cellulose is 0.05-0.2 parts, the dispersant is 0.05-0.12 parts, the water repellent is 0.5-1 part, the lubricant is 1-2 parts, and the water is 0.001-0.01 part.

6. The coated white paper according to claim 4, characterized in that, According to weight parts, the bottom coat paint further includes the following raw material components: the second inorganic filler is 100 parts, the adhesive is 40-48 parts, the carboxymethyl cellulose is 0.05-0.2 parts, the dispersant is 0.05-0.12 parts, the water repellent is 2-3 parts, the lubricant is 1-2 parts, and the water is 0.001-0.005 part.

7. The coated white paper according to claim 1, characterized in that, The weight of the paper base layer accounts for 88-90% of the total weight of the coated white cardboard, and / or the weight of the coating layer accounts for 10-12% of the total weight of the coated white cardboard.

8. A process for the production of a coated white card according to any one of claims 1 to 7, characterised in that, The method comprises the following steps: (1) mixing raw material components of the top layer, crushing and pulp refining to obtain top layer pulp, and forming to obtain top layer raw paper; (2) mixing raw material components of the core layer, crushing and pulp refining to obtain core layer pulp, and forming to obtain core layer raw paper; (3) mixing raw material components of the bottom layer, crushing and pulp refining to obtain bottom layer pulp, and forming to obtain bottom layer raw paper; (4) sequentially bonding the top layer raw paper, the core layer raw paper and the bottom layer raw paper in the order from the front side to the back side to obtain paper base layer raw paper; (5) after drying the paper base layer raw paper, performing surface sizing on the top layer and the bottom layer respectively, and drying to obtain pre-coated raw paper; (6) coating the bottom coat paint on the front side of the pre-coated raw paper, and drying to obtain the bottom coat layer, thereby preparing the first coated white cardboard; (7) coating the top coat paint on the front side of the first coated white cardboard to obtain the top coat layer, thereby preparing the second coated white cardboard, and calendering to obtain the coated white cardboard.

9. The coated white cardboard according to any one of claims 1-7 is applied in printing materials or packaging materials.

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