Matt coated paper and preparation method thereof

Abstract

The present application provides a matte coated paper and a preparation method thereof, the preparation method comprising: base paper making; slurry comprising pulp, filler and chemical additives; applying a pre-coating layer, the coating of the pre-coating layer comprising ground heavy calcium carbonate and a pre-coating adhesive; applying a topcoating layer, the coating of the topcoating layer comprising a pigment and a topcoating adhesive, wherein the weight ratio of each component in the pigment is as follows: heavy calcium carbonate: light calcium carbonate: china clay = (80-100): (0-20): (0-20). The present application embodiment provides a preparation method, and the matte coated paper obtained has the following main advantages: 1) improving the thickness and stiffness of the paper, so that the matte coated paper has a significant lightweight characteristic, and the bulk is significantly higher than that of conventional coated paper, close to micro-coated paper / lightly coated paper; 2) improving the printing effect of the paper, which is different from micro-coated paper and lightly coated paper. Under the condition that the paper has lightweight characteristics, the printing effect of the paper is improved, and the printing effect of the conventional copper is better.

Description

Technical Field

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

[0002] Matte coated paper, also known as matte pink paper, currently holds a significant market share in the international market (for example, in Europe, matte paper accounts for 40% to 50% of high-end coated paper sales). However, in China, matte paper usage is primarily concentrated in southern China, with Shenzhen, Zhuhai, and the Pearl River Delta leading the way, while usage in northern China is relatively low. Double-sided matte coated paper is primarily used for printed materials such as high-end books and periodicals, commercials, signage, brochures, children's books, travel guides, atlases, and covers. The main reasons for its growing popularity are: 1) Matte coated paper has a higher thickness and stiffness, providing a superior tactile feel, which appeals to consumers' preference for a premium, high-quality finish. 2) Matt coated paper has good printability, and the gloss contrast between the printed product and the paper is large, which can reflect the high-end quality of the printed product. The graphics and text are full of color, and the printed product has a strong three-dimensional sense. The text part also has good reading comfort and is not dazzling when reading. High-quality matt coated paper needs to have excellent gloss contrast (the difference between the printing gloss and the paper surface gloss). To this end, a special process formula needs to be designed. Generally, the paper gloss is reduced by increasing the micro-roughness of the paper surface so that it cannot form a mirror reflection. This is also the principle of not dazzling when reading. To achieve this goal, the conventional solution is to use a different coating formula from that of high-gloss coated paper, and adopt a different surface finishing process. The micro-roughness of the paper surface needs to be adjusted to achieve the requirements of not affecting the ink transfer during offset printing and reducing the printing gloss, while also reducing the paper gloss. Among them, 1) in terms of coating formula selection, the current papermaking industry often uses pigments with low specular reflectivity. The main pigment is ground calcium carbonate with coarse particles (GCC, ≤2μm part, less than 65%). At the same time, in order to improve the ink absorption performance of the paper, a certain amount of precipitated calcium carbonate (PCC, PSD50 0.10~1.0μm) is also added. And porcelain clay is used to improve the post-printing gloss. 2) In terms of surface finishing process selection, high-end coated paper is mainly printed by offset printing. In order to obtain good ink transfer and dot reproduction performance, the paper surface must achieve a certain degree of smoothness. Therefore, in production, the required smoothness is often achieved by controlling the smoothness of the base paper and the finishing process after coating. In order to balance the relationship between the degree of finishing and the low gloss of the paper surface, a light calendering treatment is usually adopted. After collecting paper samples for testing, analysis and investigation, the current quality of matte coated paper produced domestically is as follows: the bulk range is 0.85~0.90cm 3 / g, paper pps 2.5 ~ 3.0μm, Bekk smoothness 200 ~ 300s, paper gloss 25 ~ 35 °, after printing gloss 55 ~ 70 °, contrast 30 ~ 35 °, ink drying rate 0.20 ~ 0.25%. Although the bulk of matte coated paper is higher than that of double copper (0.75 ~ 0.80cm 3 / g), but compared with lightweight coated paper, there is still a big gap (its bulk thickness is 1.00~1.30cm 3 Currently available lightweight coated papers on the market, such as lightly coated and micro-coated papers, are popular for use in books and albums. However, these papers are limited by their low coating weight and lack sufficient coverage, resulting in printing results far inferior to those of copper-coated papers. This restricts the application of lightweight papers in high-end, fine-print products. Market research indicates that high-bulk paper is particularly popular for primary and secondary school teaching aids, social media albums, recipes, and books, and they also place high demands on printing quality. With this in mind, we plan to conduct technical research and improvements in both bulk and printing performance to develop a new, lightweight, high-end matte coated paper.

[0003] Furthermore, with the development of information technology and the widespread use of portable smart devices, the medium for graphic and textual information has shifted significantly. This has reduced demand for printed magazines, advertisements, and books, significantly impacting printing and publishing paper. In an increasingly competitive market, the development of lightweight, matte coated paper with excellent printing properties is more in line with current consumer preferences and can enhance corporate competitiveness. Summary of the Invention

[0004] A first aspect of the embodiments of the present application provides a method for preparing matte coated paper, the method comprising:

[0005] Base paper making; slurry includes pulp, filler and chemical additives;

[0006] Applying a pre-coat, the pre-coat coating comprises ground heavy calcium carbonate and a pre-coating adhesive;

[0007] Apply a topcoat, the coating of the topcoat includes a pigment and a topcoat adhesive, wherein the weight ratio of each component in the pigment is as follows: heavy calcium carbonate: light calcium carbonate: china clay = (80-100): (0-20): (0-20); the topcoat adhesive includes any one of styrene-butadiene latex, carboxylated styrene-butadiene latex, polyvinyl acetate, styrene latex, and polyvinyl alcohol, or a mixture of multiple thereof.

[0008] Among them, in the step of making base paper, the pulp includes chemical mechanical pulp, softwood chemical pulp, hardwood chemical pulp and recycled paper loss pulp; calculated by weight percentage, chemical mechanical pulp: softwood chemical pulp: hardwood chemical pulp: recycled paper loss pulp = (25~35): (10~20): (30~65): (5~20).

[0009] Wherein, the chemical mechanical pulp is an alkaline hydrogen peroxide bleached chemical mechanical pulp with high bulk.

[0010] The weight ratio of the filler to the pulp is (15-25):100; the weight ratio of the chemical additive to the pulp is (0.02-1.2):100.

[0011] The filler comprises a mixture of any one or more of light calcium carbonate, heavy calcium carbonate, porous calcium silicate, talc powder, and titanium dioxide.

[0012] Wherein, in the step of applying the pre-coating layer, the weight ratio of the ground heavy calcium carbonate to the pre-coating adhesive is: 100: (12-30).

[0013] Wherein, in the step of applying the top coating layer, the top coating adhesive includes any one of styrene-butadiene latex, carboxylated styrene-butadiene latex, polyvinyl acetate, styrene latex, and polyvinyl alcohol, or a mixture of multiple thereof.

[0014] Wherein, the coating material of the top coating layer comprises carboxyl styrene butadiene latex, and the weight ratio of the pigment to the carboxyl styrene butadiene latex is 100:(8-12).

[0015] Among them, in the 110g lightweight matte coated paper, the proportions of each material are as follows: the base paper weight is 62-64g / m2, the single-sided coating amount of the pre-coat layer is 8-12g / m2, and the single-sided coating amount of the topcoat layer is 10-12g / m2.

[0016] In a second aspect, an embodiment of the present application provides a matte coated paper, which is prepared using the preparation method described in the above embodiment.

[0017] The preparation method of the matte coated paper provided in the embodiments of the present application has the following main advantages over conventional matte coated paper and lightly coated paper / lightly coated paper: 1) improving the thickness and stiffness of the paper, so that the matte coated paper has a significantly lightweight characteristic, and the bulk is significantly higher than that of conventional coated paper and is close to that of lightly coated paper / lightly coated paper; 2) improving the printing effect of the paper. Unlike lightly coated paper and lightly coated paper, the printing effect of the paper is improved under the condition that the paper has the lightweight characteristic, and the printing effect is better than that of conventional matte coated paper. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0019] Figure 1 This is a flow chart of an embodiment of a method for preparing matte coated paper of the present application. DETAILED DESCRIPTION

[0020] The present application will be further described in detail below in conjunction with the accompanying drawings and examples. It is particularly noted that the following examples are only intended to illustrate the present application and are not intended to limit the scope of the present application. Similarly, the following examples are only some examples of the present application and are not intended to be complete. All other examples obtained by those of ordinary skill in the art without creative work are intended to fall within the scope of protection of the present application.

[0021] The terms "first", "second" and "third" in the embodiments of the present application are used only for descriptive purposes and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first", "second" and "third" may explicitly or implicitly include at least one of such features. In the description of the present application, "multiple" means at least two, for example, two, three, etc., unless otherwise clearly and specifically defined. All directional indications in the embodiments of the present application (such as up, down, left, right, front, back...) are only used to explain the relative positional relationship, movement, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication also changes accordingly. The terms "including" and "having" in the embodiments of the present application and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally also includes steps or units that are not listed, or optionally also includes other steps or components inherent to these processes, methods, products or devices.

[0022] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0023] See also Figure 1 , Figure 11 is a flow chart of an embodiment of a method for preparing matte coated paper of the present application, and the preparation method includes but is not limited to the following steps.

[0024] Step S100: base paper making.

[0025] In this step, the pulp part adopts chemical mechanical pulp (PRC-APMP-alkaline hydrogen peroxide bleached chemical mechanical pulp, BCTMP-bleached thermo-refined chemical mechanical pulp, CTMP-thermo-refined chemical mechanical pulp, etc.), softwood chemical pulp, hardwood chemical pulp, waste pulp (coated waste pulp), and is mixed with fillers and chemical additives to make base paper. Calculated by weight percentage (the same below), the pulp part in the base paper is chemical mechanical pulp: softwood chemical pulp: hardwood chemical pulp: waste pulp = (25-35): (10-20): (30-65): (5-20); filler: pulp = (15-25): 100; chemical additive: pulp = (0.02-1.2): 100. In one embodiment, the mechanical pulp is PRC-APMP pulp with high bulk, with a bulk of 2.60-3.00 cm. 3 / g, tensile index 25-30N.m / g, ISO whiteness 75-80%.

[0026] The filler is a mixture of one or more of light calcium carbonate (PCC), heavy calcium carbonate (GCC), porous calcium silicate (FACS), talc (Talc), titanium dioxide (TiO2), etc. In one embodiment, the filler is porous calcium silicate (FACS) or porous calcium silicate combined with a certain amount of light calcium carbonate (PCC). The amount of APMP (Alkaline peroxide mechanical pulp) and the filler ratio are adjusted according to the actual thickness requirements. The physical properties of porous calcium silicate (FACS) are: average particle size of 15 to 22 μm, ISO whiteness of 91.0 to 93.0%, and bulk density of 1.30 g / cm 3 , with a specific surface area of ​​121.0m 2 / g; the physical properties of light calcium carbonate (PCC) are: average particle size 2.4-3.0 μm, particle size distribution ISO whiteness 92-94.0%.

[0027] Optionally, the chemical additive is a dye, a dry strength agent, an internal sizing agent, a dual or ternary retention / drainage aid (cationic polyacrylamide + microparticle silica sol + anionic polyacrylamide).

[0028] Please continue reading Figure 1 The preparation method further includes step S200, applying a pre-coating layer.

[0029] In step S200, the pigments in the coating composition of the pre-coat layer are all ground calcium carbonate, that is, the proportion of ground calcium carbonate (GCC) is 100%, and the proportion of the ground calcium carbonate particles with a diameter of less than or equal to 2 μm is 65-95%. The pre-coat adhesive includes any one of starch-based biomass latex, styrene-butadiene latex, carboxylated styrene-butadiene latex, polyvinyl acetate, and styrene latex, or a mixture of multiple thereof. The pigment: adhesive ratio is 100: (12-30). To ensure that the base coat layer and the base paper, and the base coat layer and the top coat layer achieve high bonding strength at an appropriate adhesive dosage, in one embodiment, starch-based biomass latex and carboxylated styrene-butadiene latex made from corn / cassava as raw materials are mainly used as adhesives, wherein the starch-based biomass latex is a homemade corn-modified cross-linked bio-latex; the carboxylated styrene-butadiene latex is a carboxylated styrene-butadiene latex with a glass transition temperature of -5-0°C and a particle size of 140-160 nm (laser scattering method). The ratio of pigment: starch-based biomass latex: styrene-butadiene latex is 100: (8-12): (6-10); pigment: dye: dispersant: defoamer: tackifier is 100: (0.003-0.01): (0.05-0.15): (0.05-0.10): (0.2-0.6); water is added to prepare a coating with a solid content of 60-68%, and alkali is added to adjust the pH to 9.0±0.5.

[0030] Please continue reading Figure 1 The preparation method further includes step S300, applying a top coating.

[0031] In this step, the topcoat coating includes pigment and topcoat adhesive. The pigment ratio is: heavy calcium carbonate: light calcium carbonate: china clay = (80-100): (0-20): (0-20); the heavy calcium carbonate used has a particle size of 2 μm or less, accounting for 95-100%; the light calcium carbonate used has a particle size of 2 μm or less, accounting for 80-90%; and the china clay used has a particle size of 2 μm or less, accounting for 90-95%.

[0032] Optionally, the topcoat adhesive includes a mixture of one or more of styrene butadiene latex, carboxylated styrene butadiene latex, polyvinyl acetate, styrene latex, and polyvinyl alcohol. In one embodiment, to ensure the topcoat has a certain white gloss, good ink absorbency, and ink drying properties (printing ink density), the topcoat pigment is primarily fine, narrow-particle heavy calcium carbonate, with a certain amount of light calcium carbonate, wherein the narrow-particle calcium carbonate has a particle size of 2 μm or less, accounting for 99-100%. The adhesive is carboxylated styrene butadiene latex, which is a high-Tg carboxylated styrene butadiene latex with a glass transition temperature of 5-15°C and a particle size of 140-160 nm (laser scattering method).

[0033] Optionally, in one embodiment, pigment (narrow particle size heavy calcium carbonate): pigment (light calcium carbonate) = (80-100): (0-20); pigment: carboxyl styrene butadiene latex = 100: (8-12); pigment: dye: dispersant: defoaming agent: water-resistant agent: lubricant: rheological agent = 100: (0.003-0.01): (0.05-0.15): (0.05-0.10): (0.2-0.6): (0-0.4): (0.03-0.06); water is added to prepare a coating with a solid content of 65-70%, and alkali is added to adjust the pH to 9.0±0.5.

[0034] The coating method is: the pre-coating layer adopts film transfer coating or doctor blade coating; the top coating layer adopts doctor blade coating. The parameters of coating amount are as follows: taking 110g lightweight matte coated paper as an example, the pre-coating layer single-side coating amount is 8-12g / m 2 The coating amount on one side of the topcoat is 10-12g / m 2 , the base paper weight is 62~64g / m 2 .

[0035] In addition, after the coating process, the preparation method can also adopt a light pressure coating method or a non-calendering coating method, which can be selected and adjusted according to the requirements of paper bulk and smoothness. The detailed features of this part are within the scope of understanding of technicians in this field and will not be repeated here.

[0036] Several specific embodiments will be introduced below.

[0037] 1. Base paper making process:

[0038] 1.1 The pulp composition is: high bulk PRC-APMP ratio is 25-35%, the pulp freeness is controlled at 250-300ml, the bulk thickness is 2.60-3.00cm 3 / g, tensile index 25-30N.m / g, ISO brightness 75-80%; NBKP (softwood chemical pulp) ratio is controlled at 10-20%, and refining freeness is controlled at 350-400ml; LBKP hardwood chemical pulp ratio is controlled at 30-65%, and refining freeness is controlled at 350-400ml; coating broke pulp ratio is controlled at 5-20%.

[0039] 1.2 Filler: The slurry ratio is controlled at 15-25%, with porous calcium silicate (FACS) and light calcium carbonate (PCC); according to the actual thickness requirements, the amount of PRC-APMP and the filler ratio are adjusted. The physical properties of porous calcium silicate (FACS) are: average particle size 15-22μm, ISO whiteness 91.0-93.0%, and bulk density 1.30g / cm 3 , with a specific surface area of ​​121.0m 2 / g; the physical properties of light calcium carbonate (PCC) are: average particle size 2.4-3.0 μm, particle size distribution ISO whiteness 92-94.0%).

[0040] 1.3 Other chemical additives in paper include cationic starch (dry strength agent), dual or ternary retention / drainage aids (cationic polyacrylamide + micro-silica sol + anionic polyacrylamide), fluorescent brighteners, dyes, charge control agents, etc.; all of which are chemical additives used in general coated paper base paper. 2 For example, the minimum weight of papermaking is 62-64g / m 2 The moisture content of the base paper is controlled at 3.0-4.5%.

[0041] 2. Coating preparation, coating plan, and post-coating calendering process:

[0042] 2.1 Pre-coat coating: The pigment is ground ground calcium carbonate (GCC) at a ratio of 100%, with a particle size of 65-95% of the material being 2 μm or less. The coating adhesive is made of corn / cassava-based starch-based biomass latex and carboxylated styrene-butadiene latex, with a glass transition temperature of -5-0°C and a particle size of 140-160 nm. The ratio of pigment: starch-based biomass latex: styrene-butadiene latex is 100: (8-12): (6-10). The ratio of pigment: dye: dispersant: defoamer: tackifier is 100: (0.003-0.01): (0.05-0.15): (0.05-0.10): (0.2-0.6). Water is added to achieve a coating solids content of 60-68%, and alkali is added to adjust the pH to 9.0±0.5.

[0043] 2.2 For the topcoat, the pigment is primarily fine, narrow-particle ground calcium carbonate (GCC), supplemented with a certain amount of light calcium carbonate (PCC). The narrow-particle ground calcium carbonate should have a particle size of 2 μm or less, accounting for 99-100%. The adhesive is carboxylated styrene butadiene latex (CSB) with a high Tg (glass transition temperature) of 5-15°C and a particle size of 140-160 nm (laser scattering method).

[0044] Pigment (narrow particle size heavy calcium carbonate): pigment (light calcium carbonate) = (80-100): (0-20); pigment: carboxyl styrene butadiene latex = 100: (8-12); pigment: dye: dispersant: defoamer: water-resistant agent: lubricant: rheological agent = 100: (0.003-0.01): (0.05-0.15): (0.05-0.10): (0.2-0.6): (0-0.4): (0.03-0.06); add water to prepare a coating with a solid content of 65-70%, and add alkali to adjust the pH to 9.0±0.5.

[0045] 2.3 Coating is performed on the base paper. The pre-coating layer is coated by film transfer coating or doctor blade coating. The top coating layer is coated by doctor blade coating. In the coating amount setting part, taking 110g lightweight matte coated paper as an example, the base paper basis weight is 62-64g / m 2 The pre-coating single-sided coating amount is 8 to 12 g / m 2 The coating amount on one side of the topcoat is 10-12g / m 2 After coating, the moisture content is controlled at 3.5-4.0%.

[0046] 2.4 After the coating process, the lightweight matte coated paper is calendered with light pressure or without calendering, and is selected and adjusted according to the requirements of paper bulk and smoothness.

[0047] The lightweight matte coated paper prepared in this embodiment can achieve the following indicators: bulk thickness reaches 1.0-1.25 cm 3 / g(conventional cuprous 0.85~0.90cm 3 / g); roughness 2.50-3.50 μm (conventional cuprous 2.50-3.00 μm); Bekk smoothness 150-300 s / 100 ml (conventional cuprous 200-300 s / 100 ml); white sample gloss 30-40% (conventional cuprous 25-35%), printed gloss 60-85% (conventional cuprous 55-70%), gloss contrast 30-40% (30-35%); KN ink absorbency 18-20 (conventional cuprous 15-16), ink drying rate 0.15-0.18% (conventional cuprous 0.20-0.25%); printing anti-floating grade 3.0 (conventional cuprous 3.0), printability (interpretation gloss) 230-240 cm / s (conventional 220 cm / s).

[0048] Blank Example

[0049] The base paper is made from alkaline hydrogen peroxide bleached chemimechanical pulp (PRC-APMP) with a refining freeness of 250ml; softwood chemical pulp (NBKP) with a refining freeness of 350ml; and hardwood chemical pulp (LBKP) with a refining freeness of 350ml. Coated waste pulp is also recycled. A mixed pulp of 15% PRC-APMP: NBKP: LBKP: coated waste pulp is prepared, with 15% (relative to the weight of the pulp) of light calcium carbonate as a filler. Chemical additives include 1.0% cationic starch, 350ppm of cationic polyacrylamide retention aid, and 7000ppm of silica gel anion retention aid. The paper is then formed, pressed, and dried to control the moisture content between 3.0-4.0%. For example, the base paper has a basis weight of 62g / m², using 110g matte coated paper as an example. 2 .

[0050] For the pre-coating paint, the pigment uses ground heavy calcium carbonate (GCC) at a ratio of 100%, and the part with a particle size of less than or equal to 2μm accounts for 65%; the coating adhesive uses purchased coating starch and conventional styrene-butadiene latex as adhesives, pigment: purchased starch: styrene-butadiene latex = 100: 6: 10; pigment: dye: dispersant: defoamer: thickener = 100: (0.003~0.01): (0.05~0.15): (0.05~0.10): (0.2~0.6); water is added to prepare a coating with a solid content of 65%, and alkali is added to adjust the pH to 9.0±0.5.

[0051] For the topcoat paint, the pigments used are ground heavy calcium carbonate (GCC) and porcelain clay (Clay), with the GCC ratio being 80%, the part with a particle size of less than or equal to 2 μm accounting for 65%, the Clay ratio being 20%, and the part with a particle size of less than or equal to 2 μm accounting for 92%; the adhesive is conventional styrene-butadiene latex, and the ratio of pigment to carboxyl styrene-butadiene latex is 100:10; pigment: dye: dispersant: defoaming agent: water-resistance agent: lubricant: rheological agent is 100:(0.003-0.01):(0.05-0.15):(0.05-0.10):(0.2-0.6):(0-0.4):(0.03-0.06); water is added to prepare a coating with a solid content of 68%, and alkali is added to adjust the pH to 9.0±0.5.

[0052] Coating is carried out on the base paper. The pre-coating layer is coated by film transfer coating or doctor blade coating. The top coating layer is coated by doctor blade coating. In the coating amount setting part, taking 110g matte coated paper as an example, the base paper basis weight is 62g / m 2 , the pre-coating single-sided coating amount is 10g / m 2 The single-sided coating amount of the top coating is 12g / m 2 After coating, the moisture content is controlled at 3.5-4.0%.

[0053] After the coating process, the paper surface is finished by light calendering.

[0054] Comparative Example 1

[0055] For base paper making, the pulp material is high bulk PRC-APMP, the pulping freeness is controlled at 250ml, and the bulk is 2.60-3.00cm 3 / g; NBKP (softwood chemical pulp), refining freeness controlled at 400ml; LBKP hardwood chemical pulp, refining freeness controlled at 400ml; coated broke recovered pulp. A mixed pulp of PRC-APMP:NBKP:LBKP:coated broke pulp = 25%:10%:50%:15% was prepared, and 15% (relative to the weight of the pulp) of porous calcium silicate (FACS) was added as a filler. The physical properties of the porous calcium silicate (FACS) were: average particle size 15-22μm, ISO brightness 91.0-93.0%, and bulk density 1.30g / cm 3 , with a specific surface area of ​​121.0m 2 / g.

[0056] Then add chemical additives, cationic starch 1.0%, cationic polyacrylamide retention aid 350ppm, silica gel anion retention aid 7000ppm, after papermaking and forming, after pressing and drying, control the moisture content at 3.0-4.0%. Taking 110g matte coated paper as an example, the base weight of the paper is 62g / m 2 .

[0057] The pre-coat paint uses ground calcium carbonate (GCC) as the pigment at a ratio of 100%, with 65% of the pigment having a particle size of 2 μm or less. The coating adhesive uses corn starch-based biomass latex and carboxylated styrene butadiene latex (CSB) with a glass transition temperature of -5 to 0°C and a particle size of 140 to 160 nm. The pigment: starch-based biomass latex: styrene butadiene latex ratio is 100:8.0:9.0. The pigment: dye: dispersant: defoamer: tackifier ratio is 100:(0.003 to 0.01):(0.05 to 0.15):(0.05 to 0.10):(0.2 to 0.6). Water is added to achieve a solids content of 67.0%, and alkali is added to adjust the pH to 9.0 ± 0.5.

[0058] For the topcoat, the pigment is a combination of fine, narrow-particle ground calcium carbonate (GCC) and a certain amount of light calcium carbonate (PCC). The narrow-particle GCC has a particle size of 2 μm or less, accounting for 99-100%. The adhesive is a high-Tg carboxylated styrene butadiene latex with a glass transition temperature of 5-15°C and a particle size of 140-160 nm (laser scattering method).

[0059] Pigment (narrow particle size heavy calcium carbonate): pigment (light calcium carbonate) = 80:20; pigment: carboxylated styrene butadiene latex = 100:10; pigment: dye: dispersant: defoamer: water-resistant agent: lubricant: rheological agent = 100: (0.003-0.01): (0.05-0.15): (0.05-0.10): (0.2-0.6): (0-0.4): (0.03-0.06); add water to prepare a coating with a solid content of 65-70%, and add alkali to adjust the pH to 9.0±0.5.

[0060] Coating is carried out on the base paper. The pre-coating layer is coated by film transfer coating or doctor blade coating. The top coating layer is coated by doctor blade coating. In the coating amount setting part, taking 110g matte coated paper as an example, the base paper basis weight is 62g / m 2 , the pre-coating single-sided coating amount is 10g / m 2 The single-sided coating amount of the top coating is 12g / m 2 After coating, the moisture content is controlled at 3.5-4.0%.

[0061] This lightweight matt coated paper is not calendered after the coating process.

[0062] Comparative Example 2

[0063] For base paper making, the pulp material is high bulk PRC-APMP, the pulping freeness is controlled at 250ml, and the bulk is 2.60-3.00cm 3 / g; NBKP (softwood chemical pulp), refining freeness controlled at 400ml; LBKP hardwood chemical pulp, refining freeness controlled at 400ml; coated broke recovered pulp. A mixed pulp of PRC-APMP: NBKP: LBKP: coated broke pulp = 30%: 12%: 43%: 15% was prepared, and 20% (relative to the weight of the pulp) of porous calcium silicate (FACS) was added as a filler. The physical properties of the porous calcium silicate (FACS) were: average particle size 15-22μm, ISO brightness 91.0-93.0%, and bulk density 1.30g / cm 3 , with a specific surface area of ​​121.0m 2 / g.

[0064] Then add chemical additives, cationic starch 1.0%, cationic polyacrylamide retention aid 350ppm, silica gel anion retention aid 7000ppm, after papermaking and forming, after pressing and drying, control the moisture content at 3.0-4.0%. Taking 110g matte coated paper as an example, the base weight of the paper is 62g / m 2 .

[0065] The pre-coat paint uses ground calcium carbonate (GCC) as the pigment at a ratio of 100%, with 65% of the pigment having a particle size of 2 μm or less. The coating adhesive uses corn starch-based biomass latex and carboxylated styrene butadiene latex (CSB) with a glass transition temperature of -5 to 0°C and a particle size of 140 to 160 nm. The pigment: starch-based biomass latex: styrene butadiene latex ratio is 100:8.0:10.0. The pigment: dye: dispersant: defoamer: tackifier ratio is 100:(0.003 to 0.01):(0.05 to 0.15):(0.05 to 0.10):(0.2 to 0.6). Water is added to achieve a solids content of 67.0%, and alkali is added to adjust the pH to 9.0 ± 0.5.

[0066] For the topcoat, the pigment is a combination of fine, narrow-particle ground calcium carbonate (GCC) and a certain amount of light calcium carbonate (PCC). The narrow-particle GCC has a particle size of 2 μm or less, accounting for 99-100%. The adhesive is a high-Tg carboxylated styrene butadiene latex with a glass transition temperature of 5-15°C and a particle size of 140-160 nm (laser scattering method).

[0067] Pigment (narrow particle size heavy calcium carbonate): pigment (light calcium carbonate) = 80:20; pigment: carboxylated styrene butadiene latex = 100:10; pigment: dye: dispersant: defoamer: water-resistant agent: lubricant: rheological agent = 100: (0.003-0.01): (0.05-0.15): (0.05-0.10): (0.2-0.6): (0-0.4): (0.03-0.06); add water to prepare a coating with a solid content of 65-70%, and add alkali to adjust the pH to 9.0±0.5.

[0068] Coating is carried out on the base paper. The pre-coating layer is coated by film transfer coating or doctor blade coating. The top coating layer is coated by doctor blade coating. In the coating amount setting part, taking 110g matte coated paper as an example, the base paper basis weight is 62g / m 2 , the pre-coating single-sided coating amount is 10g / m 2 The single-sided coating amount of the top coating is 12g / m 2 After coating, the moisture content is controlled at 3.5-4.0%.

[0069] This lightweight matt coated paper is not calendered after the coating process.

[0070] Comparative Example 3

[0071] For base paper making, the pulp material is high bulk PRC-APMP, the pulping freeness is controlled at 250ml, and the bulk is 2.60-3.00cm 3 / g; NBKP (softwood chemical pulp), refining freeness controlled at 400ml; LBKP hardwood chemical pulp, refining freeness controlled at 400ml; coated broke recovered pulp. A mixed pulp of PRC-APMP: NBKP: LBKP: coated broke pulp = 35%: 15%: 35%: 15% was prepared, and 20% (relative to the weight of the pulp) of porous calcium silicate (FACS) was added as a filler. The physical properties of the porous calcium silicate (FACS) were: average particle size 15-22μm, ISO brightness 91.0-93.0%, and bulk density 1.30g / cm 3 , with a specific surface area of ​​121.0m 2 / g.

[0072] Then add chemical additives, cationic starch 1.0%, cationic polyacrylamide retention aid 350ppm, silica gel anion retention aid 7000ppm, after papermaking and forming, and then through pressing and drying, control the moisture content at 3.0-4.0%. Taking 110g matte coated paper as an example, the base weight of the paper is 62g / m 2 .

[0073] The pre-coat paint uses ground calcium carbonate (GCC) as the pigment at a ratio of 100%, with 65% of the pigment having a particle size of 2 μm or less. The coating adhesive uses corn starch-based biomass latex and carboxylated styrene butadiene latex (CSB) with a glass transition temperature of -5 to 0°C and a particle size of 140 to 160 nm. The pigment: starch-based biomass latex: styrene butadiene latex ratio is 100:8.0:11.0. The pigment: dye: dispersant: defoamer: tackifier ratio is 100:(0.003 to 0.01):(0.05 to 0.15):(0.05 to 0.10):(0.2 to 0.6). Water is added to achieve a solids content of 67.0%, and alkali is added to adjust the pH to 9.0 ± 0.5.

[0074] For the topcoat, the pigment is a combination of fine, narrow-particle ground calcium carbonate (GCC) and a certain amount of light calcium carbonate (PCC). The narrow-particle GCC has a particle size of 2 μm or less, accounting for 99-100%. The adhesive is a high-Tg carboxylated styrene butadiene latex with a glass transition temperature of 5-15°C and a particle size of 140-160 nm (laser scattering method).

[0075] Pigment (narrow particle size heavy calcium carbonate): pigment (light calcium carbonate) = 80:20; pigment: carboxylated styrene butadiene latex = 100:10; pigment: dye: dispersant: defoamer: water-resistant agent: lubricant: rheological agent = 100: (0.003-0.01): (0.05-0.15): (0.05-0.10): (0.2-0.6): (0-0.4): (0.03-0.06); add water to prepare a coating with a solid content of 65-70%, and add alkali to adjust the pH to 9.0±0.5.

[0076] Coating is carried out on the base paper. The pre-coating layer is coated by film transfer coating or doctor blade coating. The top coating layer is coated by doctor blade coating. In the coating amount setting part, taking 110g matte coated paper as an example, the base paper basis weight is 62g / m 2 , the pre-coating single-sided coating amount is 10g / m 2 The single-sided coating amount of the top coating is 12g / m 2 After coating, the moisture content is controlled at 3.5-4.0%.

[0077] This lightweight matt coated paper is not calendered after the coating process.

[0078] The experimental data of different embodiments are compared in the following table.

[0079]

[0080]

[0081] In the technical solutions in the embodiments of this application:

[0082] 1. Key parameters for base papermaking include: selection of high bulk PRC-APMP pulp, bulk thickness 2.60-3.00 cm 3 / g, its pulp freeness is controlled at 250-300ml, and 25-35% high content is selected for use; 2) porous calcium silicate (FACS) and light calcium carbonate (PCC) are used as fillers. The physical properties of porous calcium silicate (FACS) are: average particle size 15-22μm, ISO whiteness 91.0-93.0%, and bulk density 1.30g / cm 3 , with a specific surface area of ​​121.0m 2 / g; physical properties of light calcium carbonate (PCC) are: average particle size 2.4-3.0 μm, particle size distribution ISO whiteness 92-94.0%).

[0083] 2. Key parameters of the coating formulation include: 1) For pre-coat coatings, corn starch-based biomass latex and carboxylated styrene butadiene latex (CSB) are used as adhesives. The CSB latex has a glass transition temperature (GTT) of -5°C to 0°C and a particle size of 140 to 160 nm. For topcoat coatings, the pigment is fine, narrow-particle ground calcium carbonate (GCC) combined with a certain amount of light calcium carbonate (PCC). The narrow-particle GCC has a particle size of 2 μm or less, accounting for 99 to 100%. The adhesive is carboxylated styrene butadiene latex (CSB), with a high Tg (GTT) of 5 to 15°C and a particle size of 140 to 160 nm (laser scattering method).

[0084] 3. Key parameters for coating and finishing include: 1) The pre-coating layer is applied by film transfer coating or scraper coating; the top coating layer is applied by scraper coating, and the pre-coating layer is applied on one side with a coating weight of 8 to 12 g / m 2 The coating amount on one side of the topcoat is 10-12g / m 2 , after coating, the moisture content is controlled at 3.5-4.0%. 2) The lightweight matte coated paper is not calendered after the coating process.

[0085] The preparation method in the examples of this application, through innovation in papermaking process, improves and enhances the bulk and printing performance of existing matte coated paper, and develops a new lightweight high-grade matte coated paper with the following advantages:

[0086] First, the bulk of the matte coated paper prepared in this embodiment of the present invention is 0.89 cm 3 / g increased to 1.10cm 3 / g or more, an increase of 23.5%. The purpose of improving the bulk of base paper and finished paper is achieved through adjustments to the base paper process, coating formula, and post-coating finishing process, including: selecting high-bulk PRC-APMP and increasing its usage ratio; making special selection of fillers, using high-bulk porous calcium silicate (FACS); using non-calendering post-coating process conditions (to improve the bulk of the finished paper), screening coating pigments and adhesive formulas with better ink absorption capacity and ink absorption uniformity, ensuring that the paper surface can achieve high printing gloss, excellent ink drying properties, and printing anti-floating properties.

[0087] The matte coated paper prepared in the examples of this application has improved comprehensive printing performance and effects, with KN ink absorbency increased by 23.8%, ink drying rate increased by 18%, pre-press / post-press gloss contrast increased by 4-5%, printing anti-blooming performance increased by 0.5 levels, and printability (surface strength) is also better than conventional matte coated paper. The main improvement measures include: optimizing the pre-coating adhesive, selecting biomass latex, and combining it with low-Tg carboxylated styrene butadiene latex to ensure close bonding between the pre-coating layer and the base paper layer, and the pre-coating layer and the topcoat layer; selecting fine and narrow-particle GCC pigments for the topcoat layer, combined with PCC pigments, and selecting high-Tg carboxylated styrene butadiene latex for the adhesive, to achieve a comprehensive improvement in printing performance.

[0088] The preparation method of the matte coated paper provided in the embodiments of the present application has the following main advantages over conventional matte coated paper and lightly coated paper / lightly coated paper: 1) improving the thickness and stiffness of the paper, so that the matte coated paper has a significantly lightweight characteristic, and the bulk is significantly higher than that of conventional coated paper and is close to that of lightly coated paper / lightly coated paper; 2) improving the printing effect of the paper. Unlike lightly coated paper and lightly coated paper, the printing effect of the paper is improved under the condition that the paper has the lightweight characteristic, and the printing effect is better than that of conventional matte coated paper.

[0089] The above descriptions are only some embodiments of the present application and do not limit the scope of protection of the present application. Any equivalent device or equivalent process transformation made using the contents of the description and drawings of this application, or directly or indirectly applied in other related technical fields, are also included in the scope of patent protection of this application.

Claims

1. A method for preparing matt coated paper, characterized in that: The preparation method comprises: Base papermaking; the slurry includes pulp, filler and chemical additives, the weight ratio of the filler to the pulp is (15-25):100, the filler includes porous calcium silicate, the average particle size of the porous calcium silicate is 15-22 μm, and the ISO brightness is 91.0-93.0%; Applying a pre-coat layer, wherein the pre-coat layer comprises ground heavy calcium carbonate and a pre-coat adhesive, wherein the pre-coat adhesive comprises starch-based biomass latex and carboxylated styrene-butadiene latex as adhesives, wherein the starch-based biomass latex is corn-modified cross-linked bio-latex, the carboxylated styrene-butadiene latex has a glass transition temperature of -5 to 0°C, and the weight ratio of the ground heavy calcium carbonate to the pre-coat adhesive is 100:(12 to 30); A topcoat is applied, wherein the coating of the topcoat includes a pigment and a topcoat adhesive, wherein the weight ratio of each component in the pigment is as follows: heavy calcium carbonate: light calcium carbonate: china clay = (80-100): (0-20): (0-20); the proportion of particles of heavy calcium carbonate less than or equal to 2 μm is 95-100%; the topcoat adhesive includes carboxylated styrene-butadiene latex, the glass transition temperature of the carboxylated styrene-butadiene latex is 5-15° C., and the weight ratio of the pigment to the carboxylated styrene-butadiene latex is 100: (8-12).

2. The preparation method according to claim 1, characterized in that In the step of making base paper, the paper pulp includes chemical mechanical pulp, softwood chemical pulp, hardwood chemical pulp and recycled waste pulp; calculated by weight percentage, chemical mechanical pulp: softwood chemical pulp: hardwood chemical pulp: recycled waste pulp = (25-35): (10-20): (30-65): (5-20).

3. The preparation method according to claim 2, characterized in that The chemical mechanical pulp is an alkaline hydrogen peroxide bleached chemical mechanical pulp with high bulk.

4. The preparation method according to claim 1, characterized in that The weight ratio of the chemical additive to the pulp is (0.02-1.2):

100.

5. The preparation method according to claim 4, characterized in that The filler further comprises a mixture of any one or more of light calcium carbonate, heavy calcium carbonate, talc, and titanium dioxide.

6. The preparation method according to claim 1, characterized in that In the step of applying the top coating layer, the top coating adhesive further comprises any one of styrene-butadiene latex, polyvinyl acetate, styrene latex, and polyvinyl alcohol, or a mixture of multiple thereof.

7. The preparation method according to claim 1, characterized in that In 110g lightweight matte coated paper, the proportion of each material is as follows: the base paper weight is 62-64g / m 2 The pre-coating single-sided coating amount is 8 to 12 g / m 2 The coating amount on one side of the topcoat is 10-12g / m 2 .

8. A matte coated paper, characterized in that: The matte coated paper is prepared by the preparation method according to any one of claims 1 to 7.

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