Matt coated paper, modified calcium carbonate and preparation method

Abstract

The invention provides matte coated paper, modified calcium carbonate and a preparation method. The preparation method of the modified calcium carbonate comprises the following steps: drying a certain amount of light calcium carbonate raw material in a drying oven; carrying out dry pre-modification on the dried light calcium carbonate by utilizing a silane coupling agent; carrying out wet deep modification on the light calcium carbonate subjected to dry pre-modification by using stearic acid; filtering the modified suspension, washing a filter cake, and drying; and carrying out superfine grinding on the dried blocky material to obtain the modified calcium carbonate powder. According to the preparation method of the modified calcium carbonate provided by the embodiment of the invention, the prepared modified calcium carbonate powder can improve the absorptivity and retentivity of calcium carbonate to ink, so that matte coated paper has better ink absorptivity and good ink drying performance, and the printing efficiency is further improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of papermaking, in particular to a matte art paper, modified calcium carbonate and a preparation method. BACKGROUND

[0002] The matte art paper is generally used for the inner page printing of books such as literary works, academic works and teaching materials. Its surface is not reflective, which can allow readers to read comfortably under different lighting conditions, reduce eye fatigue, and ensure that the text and images are clearly and delicately presented. In the aspect of magazines, especially humanistic, artistic and lifestyle magazines, the matte art paper can create a high-quality and simple texture, which can well display the details of photos and illustrations, and is in harmony with the style of the magazine.

[0003] Due to the low gloss of the matte art paper, the color brightness and saturation are slightly poor compared with the bright art paper. Some high-saturation colors that need strong gloss to reflect the texture (such as metallic color and fluorescent color) may not achieve ideal printing effects on the matte art paper, which can easily make the colors look less bright. The ink absorption of the matte art paper is relatively strong, which although helps the ink to adhere, but will cause the ink drying speed to slow down. In the process of high-speed printing, if the drying is not timely, the just printed images and texts are easily stained when they are in contact with other papers or parts of the printing equipment. Therefore, it is necessary to produce a matte art paper with fast ink drying speed and good color reproduction. There are still many technical problems to be solved in terms of quality and cost.

[0004] Compared with imported high-grade matte art paper, the currently produced matte art paper in China has the following defects: 1. High price: the production process of matte art paper is complex, and the requirements for raw materials and production equipment are high, which leads to high cost and high price, limiting its application in some cost-sensitive printing projects. 2. Low cost performance: in some scenarios where the printing quality requirements are not particularly high, the high price of matte art paper does not match the effect improvement, so some users will choose ordinary art paper or other paper with lower price. 3. Limited color performance: the matte art paper has large micro roughness on the surface, low gloss after ink adhesion, and lower color saturation than bright art paper. For printing products that require high brightness and high saturation color performance, such as some fashion magazines and advertising posters, matte art paper is not the best choice. 4. Slow drying speed: the matte art paper has strong ink absorption, and the ink drying time is long, which may affect the production efficiency and increase the risk of printing product sticking and staining in large-scale printing or fast printing production line. 5. Bulkiness needs to be improved: the bulkiness of domestic matte art paper is not as good as that of lightweight coated paper, which is not ideal for some printing products that pursue lightness and certain stiffness, such as some portable books and brochures. SUMMARY

[0005] The first aspect of the embodiments of the present application provides a preparation method of modified calcium carbonate, and the preparation method comprises the following steps: A certain amount of light calcium carbonate raw material is placed in an oven for drying; The dried light calcium carbonate is pre-modified by a dry method using a silane coupling agent; The pre-modified light calcium carbonate is further modified by a wet method using stearic acid; The modified suspension is filtered, the filter cake is washed and dried; The dried block material is ultra-finely pulverized to obtain modified calcium carbonate powder.

[0006] In some optional embodiments, in the step of placing a certain amount of light calcium carbonate raw material in an oven for drying, the particle size of the light calcium carbonate raw material is D50=1.0-1.5 μm, and the whiteness is ≥95%, and the light calcium carbonate raw material powder is placed in an oven at 105±5°C for drying for 2-4 hours.

[0007] In some optional embodiments, the step of pre-modifying the dried light calcium carbonate by a dry method using a silane coupling agent comprises the following steps: the dried light calcium carbonate is placed in a high-speed mixer for stirring while spraying the silane coupling agent in a spraying manner; and the addition amount of the silane coupling agent is 1.5%-3% of the mass of the light calcium carbonate.

[0008] In some optional embodiments, the step of further modifying the pre-modified light calcium carbonate by a wet method using stearic acid comprises the following steps: the pre-modified light calcium carbonate powder is dispersed in deionized water to prepare a suspension with a solid content of 15%-20%; the pH value of the suspension is adjusted to 9-10 by using a dilute sodium hydroxide solution; stearic acid is dissolved in an appropriate amount of hot water to prepare a sodium stearate saponification solution; and the sodium stearate saponification solution is added dropwise to the pre-modified light calcium carbonate suspension.

[0009] In some optional embodiments, in the step of dissolving stearic acid in an appropriate amount of hot water to prepare a sodium stearate saponification solution, the addition amount of the stearic acid is 1%-2% of the mass of the light calcium carbonate; and the step of adding the sodium stearate saponification solution dropwise to the pre-modified light calcium carbonate suspension is followed by the steps of: maintaining the temperature of the system at 70-80°C, and reacting for 1.5-2.0 hours.

[0010] In some optional embodiments, in the step of ultra-finely pulverizing the dried block material to obtain modified calcium carbonate powder, the particle size distribution D97 of the obtained modified calcium carbonate powder is ≤5 μm.

[0011] The second aspect of the embodiments of the present application provides a modified calcium carbonate, which is prepared by the preparation method described in the above embodiments.

[0012] In a third aspect, the embodiments of the present application provide a preparation method of the matte art paper, and the preparation method comprises the following steps: pulping a base paper; applying a base coating on one side surface of the base paper; wherein the pigments of the base coating material comprise heavy calcium carbonate and the modified calcium carbonate as described in the above embodiments, and the mass ratio between the heavy calcium carbonate and the modified calcium carbonate is 30-70:30-70.

[0013] applying a surface coating on the other side surface of the base paper; wherein the pigments of the surface coating material comprise heavy calcium carbonate and kaolin, and the mass ratio between the heavy calcium carbonate and the kaolin is 50-80:20-50.

[0014] In some optional embodiments, in the step of pulping the base paper, the pulp of the base paper comprises paper pulp and fillers, wherein the paper pulp comprises chemi-mechanical pulp, softwood chemical pulp and hardwood chemical pulp, and the weight percentage of the chemi-mechanical pulp, the softwood chemical pulp and the hardwood chemical pulp is (20-30):(20-30):(40-60); and the weight percentage of the fillers and the paper pulp is (20-25):(80-75).

[0015] In a fourth aspect, the embodiments of the present application provide a matte art paper, which is prepared by the preparation method as described in the above embodiments.

[0016] The preparation method of the modified calcium carbonate provided by the embodiments of the present application can improve the ink absorption and retention of the calcium carbonate, so that the matte art paper has better ink absorption and good ink drying performance, thereby improving the printing efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0018] Figure 1 is a flowchart of an embodiment of the preparation method of the modified calcium carbonate of the present application; Figure 2 is a specific flowchart of the step of wet deep modification of the dry pre-modified light calcium carbonate of the present application by using stearic acid; Figure 3 is a flowchart of an embodiment of the preparation method of the matte art paper of the present application; Figure 4 is a schematic diagram of the layer structure of an embodiment of the matte art paper of the present application. DETAILED DESCRIPTION

[0019] The application will be described in further detail below with reference to the drawings and embodiments. It is to be particularly pointed out that the following embodiments are only for the purpose of illustrating the application, but not for limiting the scope of the application. Similarly, the following embodiments are only part of the embodiments of the application, and all other embodiments obtained by those skilled in the art without creative efforts fall within the scope of the application.

[0020] The terms "first", "second", "third" in the embodiments of the application are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first", "second", "third" can explicitly or implicitly include at least one of the features. In the description of the application, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise explicitly and specifically limited. All directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the application are only for explaining the relative position relationship, movement condition, etc. between components in a certain posture (as shown in the drawings), and if the certain posture changes, the directional indications also change accordingly. The terms "include" and "have" and any variations thereof in the embodiments of the application are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device including a series of steps or units is not limited to the listed steps or units, but can optionally include steps or units not listed, or can optionally include other steps or components inherent to the process, method, product or device.

[0021] Reference to "embodiments" herein means that the specific features, structures or properties described in connection with the embodiments can be included in at least one embodiment of the application. The phrase appears at various places in the specification does not necessarily all refer to the same embodiments, nor is it necessarily independent or alternative embodiments to other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0022] First, the application provides a preparation method of modified calcium carbonate, please refer to Figure 1 , Figure 1 is a flowchart of an embodiment of the preparation method of modified calcium carbonate of the application, and the preparation method includes but is not limited to the following steps.

[0023] Step S100, a certain amount of light calcium carbonate raw material is placed in an oven for drying.

[0024] In step S100, a certain amount of light calcium carbonate (PCC) powder is taken as the core raw material. Optionally, the particle size of the light calcium carbonate raw material in this embodiment is D50=1.0~1.5μm, and the whiteness is ≥95%. The PCC powder is dried in an oven at 105±5°C for 2~4 hours to remove the surface physical adsorption water, so as to ensure that the subsequent modifier can efficiently act on the surface of the calcium carbonate.

[0025] In step S200, the dried light calcium carbonate is pre-modified by a dry method using a silane coupling agent.

[0026] In this step, the dried PCC (light calcium carbonate raw material) powder is put into a high-speed mixer, and stirring is started at a temperature of 60~80°C and a speed of 800~1200rpm. The silane coupling agent (in an embodiment, it can be γ-methacryloxypropyltrimethoxysilane, KH-570) accounts for 1.5%~3% of the mass of the PCC (light calcium carbonate), which is slowly and uniformly sprayed into the high-speed rotating PCC (light calcium carbonate raw material) powder, and the reaction is continued for 15~30 minutes, so that the silane coupling agent is initially coated on the surface of the PCC. Specifically, the amount of the silane coupling agent added can be 1.5%, 1.6%, 1.65%, 1.8%, 2.0%, 2.3%, 2.6%, 2.8%, 2.9%, 3% or the like of the mass of the PCC (light calcium carbonate raw material).

[0027] In step S300, the light calcium carbonate pre-modified by the dry method is deeply modified by a wet method using stearic acid.

[0028] Among them, please refer to Figure 2 , Figure 2 is the specific process diagram of the step of deeply modifying the light calcium carbonate pre-modified by the dry method using stearic acid in this application, wherein the process includes but is not limited to the following steps.

[0029] In step S310, the light calcium carbonate pre-modified by the dry method is dispersed in deionized water to prepare a suspension with a solid content of 15%~20%.

[0030] Specifically, the PCC powder pre-modified by the dry method is dispersed in hot deionized water at 60~70°C to prepare a suspension with a solid content of 15%~20%. A high-speed disperser is used to pre-disperse at a speed of 1500~2000rpm for 20~30 minutes.

[0031] In step S320, the pH value of the suspension is adjusted to 9~10 with a dilute sodium hydroxide solution.

[0032] In step S330, stearic acid is dissolved in an appropriate amount of hot water to prepare a stearic acid sodium saponification solution.

[0033] In step S330, specifically, stearic acid accounting for 1.0% to 2.0% of the mass of PCC can be dissolved in a proper amount of hot water at 75 to 85°C to prepare a stearic acid sodium saponification solution. The amount of stearic acid added can be specifically 1.0%, 1.2%, 1.25%, 1.3%, 1.5%, 1.6%, 1.8%, 2.0%, etc. of the mass of PCC (light calcium carbonate raw material).

[0034] In step S340, the stearic acid sodium saponification solution is added dropwise to the light calcium carbonate suspension after dry pre-modification.

[0035] Specifically, the stearic acid sodium saponification solution can be slowly added dropwise to the PCC suspension at 65 to 75°C under continuous stirring (500 to 800 rpm).

[0036] In addition, after step S340, the system temperature can be maintained at 70 to 80°C, and the reaction can be performed for 1.5 to 2.0 hours to ensure that the stearic acid is chemically adsorbed and deposited on the surface of the PCC.

[0037] Please continue to refer to Figure 1 The preparation method of the modified calcium carbonate in the embodiment further includes: in step S400, the modified suspension is filtered, the filter cake is washed and dried.

[0038] In this step, the modified suspension can be suction filtered or pressure filtered, and the filter cake can be washed with hot water at 60 to 70°C for 2 to 3 times to remove excess ions and unreacted modifiers. Then, the filter cake is placed in an oven at 100 to 110°C for drying to constant weight (specifically, for 6 to 8 hours).

[0039] Please continue to refer to Figure 1 The preparation method of the modified calcium carbonate in the embodiment further includes: in step S500, the blocky dried material is subjected to ultrafine grinding to obtain modified calcium carbonate powder.

[0040] In step S500, the blocky dried material can be put into an air jet pulverizer for ultrafine grinding, and finally, the modified calcium carbonate powder with uniform particle size distribution is obtained, which is sealed and packaged for use. The particle size distribution of the obtained modified calcium carbonate powder is D97≤5μm.

[0041] The preparation method of the modified calcium carbonate provided in the embodiment can improve the oil ink absorption and retention of the calcium carbonate, so that the matte art paper has better ink absorption and good ink drying performance, thereby improving the printing efficiency.

[0042] In addition, the embodiment of the present application further provides a preparation method of matte art paper, please refer to Figure 3 , Figure 3is a flowchart of an embodiment of a method for preparing a matte art paper according to the present application. The method for preparing the matte art paper includes, but is not limited to, the following steps.

[0043] Step S1000, papermaking of a base paper.

[0044] In this step, the pulp for papermaking of the base paper includes paper pulp and fillers, wherein the paper pulp includes chemical mechanical pulp (including any one or a mixture of more than one of BCTMP-bleached hot ground chemical mechanical pulp, APMP-alkaline hydrogen peroxide bleaching mechanical pulp, CTMP-hot ground chemical mechanical pulp, etc.), coniferous wood chemical pulp, and broad-leaved wood chemical pulp, and the mass percentage of the chemical mechanical pulp:coniferous wood chemical pulp:broad-leaved wood chemical pulp is (20-30):(20-30):(40-60); the mass percentage of the fillers:paper pulp is (20-25):(80-75). The fillers can be a mixture of one or more of light calcium carbonate (PCC), heavy calcium carbonate (GCC), talc (Talc), titanium dioxide (TiO2), etc. The chemical additives can include one or a mixture of dyes, dry strength agents, internal sizing agents, binary or ternary retention / drainage aids (cationic polyacrylamide + fine particle silica sol / bentonite + anionic polyacrylamide), etc. The detailed features of this part are within the understanding of those skilled in the art, and will not be described here.

[0045] The method for preparing the matte art paper in this embodiment adopts a high-usage chemical mechanical pulp: base paper papermaking scheme of “chemical mechanical pulp + chemical pulp”. The proportion of chemical mechanical pulp is increased to save raw materials, reduce energy consumption, and optimize production costs. Increasing the usage of APMP (chemical mechanical pulp) pulp can increase the porosity and roughness of the paper surface, improve the bulk of the paper, make the ink absorption and penetration of the paper more uniform, thereby improving the printing quality, making the ink dry faster, and reducing smearing and other problems.

[0046] Step S2000, base coating on one side surface of the base paper.

[0047] The pigments of the base coating include ordinary heavy calcium carbonate and modified calcium carbonate (prepared according to the preparation methods of the foregoing embodiments), and the mass ratio of the heavy calcium carbonate to the modified calcium carbonate is 30-70:30-70. The adhesive includes starch and SB latex. The modified PCC is used to build a high-strength porous skeleton to ensure the structural properties and water absorption of the coating, and the inexpensive GCC is used to fill the gaps to optimize the coverage and smoothness, thereby achieving excellent base layer performance (high strength, high porosity, and high flatness) while significantly reducing the overall cost, and achieving a perfect balance between function and economy.

[0048] Step S3000, top coating on the other side surface of the base paper.

[0049] Optionally, the pigments in the top coating paint include heavy calcium carbonate and kaolin, and the mass ratio of the heavy calcium carbonate and the kaolin is 50-80:20-50. The pigments in the top coating paint use kaolin as the main pigment, which provides excellent sheet structure to achieve extremely high surface smoothness, uniform gloss and ink covering property. Ordinary GCC (heavy calcium carbonate) is a hydrophilic inorganic substance, and its presence increases the porosity and specific surface area of the coating. More importantly, the accumulation of GCC and sheet kaolin forms a more uniform and controllable microporous structure. The adhesive can be carboxyl styrene butadiene latex, and calcium stearate lubricant is added to improve the lubricity of the coating surface.

[0050] Please refer to Figure 4 , Figure 4 is a schematic diagram of the layer structure of an embodiment of the matte art paper of the present application, wherein 101 represents the base paper layer, 102 represents the top coating layer, and 103 represents the bottom coating layer. The matte art paper is prepared by the preparation method in the foregoing embodiment, and the specific preparation parameters can be referred to the related description of the foregoing embodiment.

[0051] Several specific embodiments will be introduced below to compare the experimental parameters.

[0052] Blank control group Base paper process: fiber ratio N / L / APMP = 21 / 60 / 19, internal filler 20%, basis weight 82g.

[0053] Coating formula and coating amount: Bottom coating formula: C65-100 parts, S (starch) / SB (latex) = 8.5 / 7, solid content 67%; bottom coating amount: 11g Top coating formula: C65 / C95 / PCC-20 / 70 / 10, SB (latex) = 9, solid content 68%; top coating amount: 11g; Embodiment 1 of the present application Base paper process: fiber ratio N / L / APMP = 21 / 57 / 22, internal filler 20%, basis weight 82g.

[0054] Coating formula and coating amount: Bottom coating formula: C65 / PCC (modified) -70 / 30, S (starch) / SB (latex) = 8.5 / 7, solid content 67%; bottom coating amount: 11g Top coating formula: Clay / C65-80 / 20, SB (latex) = 9, lubricant 0.4, solid content 68%; top coating amount: 11g; Embodiment 2 of the present application Base paper process: fiber ratio N / L / APMP = 21 / 57 / 22, internal filler 20%, basis weight 82g.

[0055] Coating formulation and coating weight: Base coat formulation: C65 / PCC (modified) -- 50 / 50, S (starch) / SB (latex) = 6 / 11, solid content 67%; base coat coating weight: 11g Top coat formulation: Clay / C65 -- 80 / 20, SB (latex) = 9, lubricant 0.4, solid content 68%; top coat coating weight: 11g; Example 3 of the present application Base paper process: fiber ratio N / L / APMP = 21 / 57 / 22, internal filler 20%, basis weight 82g.

[0056] Coating formulation and coating weight: Base coat formulation: C65 / PCC (modified) -- 30 / 70, S (starch) / SB (latex) = 6 / 11, solid content 67%; base coat coating weight: 11g Top coat formulation: Clay / C65 -- 80 / 20, SB (latex) = 9, lubricant 0.4, solid content 68%; top coat coating weight: 11g; The experimental data comparison is shown in the following table.

[0057]

[0058] The preparation method of the matte art paper in the example of the present application, through the unique "high mechanical pulp content base paper + functional base coat + simple top coat" systematic design, not only successfully realizes the high performance and low cost of the product, but also creatively solves the industry problem of realizing top coating effect on high mechanical pulp content substrate. The present application ingeniously unifies environmental protection, economy and excellent performance, and provides a matte art paper solution with comprehensive performance far superior to existing products, which has outstanding substantial features and significant progress.

[0059] In the base coat of the matte art paper, modified calcium carbonate is used: in the top coat of the matte art paper, the pigment is surface-modified calcium carbonate (one or a mixture of inorganic surface treatment, organic surface treatment, polymer surface treatment, mechanical force chemical modification, high-energy surface modification), surface modification can make the particle dispersion of calcium carbonate better, and form a more uniform and fine void structure in the paper. When the ink is transferred to the paper, these suitable voids formed by the modified calcium carbonate can make the connecting material in the ink penetrate into the paper faster, thereby accelerating the drying speed of the ink.

[0060] The above merely describes some embodiments of the present application, and does not limit the protection scope of the present application, and any equivalent device or equivalent process transformation using the content of the present application specification and drawings, or direct or indirect application in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for producing a modified calcium carbonate, characterized in that The preparation method comprises: a certain amount of light calcium carbonate raw material is placed in an oven for drying; the dried light calcium carbonate is pre-modified by dry method using silane coupling agent; the pre-modified light calcium carbonate is deeply modified by wet method using stearic acid; the modified suspension is filtered, the filter cake is washed and dried; the dried block material is ultra-finely pulverized to obtain modified calcium carbonate powder.

2. The production method according to claim 1, characterized by, In the step of placing a certain amount of light calcium carbonate raw material in an oven for drying, the particle size of the light calcium carbonate raw material is D50=1.0-1.5 μm, and the whiteness is ≥95%, and the light calcium carbonate raw material powder is placed in an oven at 105±5°C for drying for 2-4 hours.

3. The preparation method according to claim 1, characterized in that, The step of pre-modifying the dried light calcium carbonate by dry method using silane coupling agent comprises: placing the dried light calcium carbonate in a high-speed mixer for stirring while spraying the silane coupling agent by spraying; the addition amount of the silane coupling agent is 1.5%-3% of the mass of the light calcium carbonate.

4. The method of claim 1, wherein, The step of deeply modifying the pre-modified light calcium carbonate by wet method using stearic acid comprises: dispersing the pre-modified light calcium carbonate powder in deionized water to prepare a suspension with a solid content of 15%-20%; adjusting the pH value of the suspension to 9-10 with dilute sodium hydroxide solution; dissolving stearic acid in an appropriate amount of hot water to prepare a stearic acid sodium saponification solution; and adding the stearic acid sodium saponification solution dropwise into the pre-modified light calcium carbonate suspension.

5. The production method according to claim 4, characterized by, In the step of dissolving stearic acid in an appropriate amount of hot water to prepare a stearic acid sodium saponification solution, the addition amount of the stearic acid is 1%-2% of the mass of the light calcium carbonate; and after the step of adding the stearic acid sodium saponification solution into the pre-modified light calcium carbonate suspension, the system temperature is maintained at 70-80°C, and the reaction is carried out for 1.5-2.0 hours.

6. The method of claim 1, wherein, In the step of ultra-finely pulverizing the dried block material to obtain modified calcium carbonate powder, the particle size distribution D97 of the obtained modified calcium carbonate powder is ≤5 μm.

7. A modified calcium carbonate, characterized in that, The modified calcium carbonate is prepared by the preparation method of any one of claims 1-6.

8. A method of producing a matte art paper, characterized by, The preparation method comprises: making base paper; applying a base coating on one side surface of the base paper; wherein the pigments of the base coating coating material comprise heavy calcium carbonate and the modified calcium carbonate of claim 7, and the mass ratio between the heavy calcium carbonate and the modified calcium carbonate is 30-70:30-70. applying a top coating on the other side surface of the base paper; wherein the pigments of the top coating coating material comprise heavy calcium carbonate and kaolin, and the mass ratio between the heavy calcium carbonate and the kaolin is 50-80:20-50.

9. The production method according to claim 8, characterized by, In the step of making base paper, the pulp of the base paper comprises paper pulp and fillers, wherein the paper pulp comprises chemi-mechanical pulp, softwood chemical pulp and hardwood chemical pulp, and the weight percentage of the chemi-mechanical pulp:softwood chemical pulp:hardwood chemical pulp is (20-30):(20-30):(40-60); and the weight percentage of the fillers:paper pulp is (20-25):(80-75).

10. A matte art paper, characterized by, The matte copperplate paper is prepared by the preparation method of claim 8 or 9. The matte copperplate paper is prepared by the preparation method of claim 8 or 9.

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