Search

CN-122013589-A - High-gloss coating for coated paper and preparation method thereof

CN122013589ACN 122013589 ACN122013589 ACN 122013589ACN-122013589-A

Abstract

The invention relates to the technical field of coatings, in particular to a high-gloss coating for coated paper and a preparation method thereof. The coating is prepared by coating, drying and calendaring a coating containing modified calcium carbonate slurry, colloidal silicon dioxide, styrene-acrylic emulsion, polyvinyl alcohol and ammonium zirconium carbonate cross-linking agent. The core of the method is that a dynamic network is constructed by in-situ compounding of silicon dioxide, adhesion of polydopamine and adding boric acid and borax, and the calcium carbonate pigment is subjected to multistage modification and is coordinated with terminal zirconium crosslinking, so that the microstructure stability, surface smoothness and gloss uniformity of the coating under process fluctuation are remarkably improved, and a coated paper product with high gloss, low roughness, low water absorption and high strength is obtained.

Inventors

  • CHEN SHUANGPING
  • JIN FUYOU
  • Xiao Xude
  • LIU YONGPING

Assignees

  • 中山汉洲科技实业有限公司

Dates

Publication Date
20260512
Application Date
20260402

Claims (10)

  1. 1. The high-gloss coating for the coated paper is characterized by being formed by drying and calendaring a high-gloss coating for the coated paper, and comprises, by mass, 1400 parts of modified calcium carbonate slurry, 140-180 parts of colloidal silica, 180-240 parts of styrene-acrylic emulsion, 60-90 parts of polyvinyl alcohol aqueous solution and 5-8 parts of ammonium zirconium carbonate cross-linking agent; Wherein, the modified calcium carbonate slurry is prepared by the following steps: (1) Dispersing heavy calcium carbonate powder in water to obtain calcium carbonate dispersion slurry; (2) Adding sodium silicate solution into the calcium carbonate dispersion slurry, introducing carbon dioxide gas to stabilize the pH of the system at 8.1-8.5, and aging after stopping ventilation to obtain silicon dioxide composite calcium carbonate slurry; (3) Adding dopamine hydrochloride into the silicon dioxide composite calcium carbonate slurry, and forming a polydopamine adhesive layer under alkaline conditions to obtain calcium carbonate slurry containing catechol-amine sites; (4) Adding a polyvinyl alcohol aqueous solution, boric acid and sodium tetraborate decahydrate into the calcium carbonate slurry containing catechol-amine sites to form a dynamic borate network, and carrying out vacuum dehydration to obtain a modified calcium carbonate slurry with the solid content of 69-71 wt%; Wherein the addition sequence of boric acid in the step (4) is earlier than the addition sequence of sodium tetraborate decahydrate.
  2. 2. The high-gloss coating for coated paper according to claim 1, wherein the median particle diameter of the heavy calcium carbonate powder is 0.5 to 1 μm.
  3. 3. The high-gloss coating for coated paper according to claim 1, wherein the sodium silicate solution in step (2) is added in an amount of 30 to 60 parts by weight based on 1000 parts by weight of the calcium carbonate powder, and the sodium silicate solution has a Na 2 O content of 10 to 12wt% and a SiO 2 content of 25 to 28wt%.
  4. 4. The high gloss coating for coated paper according to claim 1, wherein the dopamine hydrochloride in the step (3) is added in an amount of 0.6 to 1.2 parts based on 1000 parts by weight of the heavy calcium carbonate powder.
  5. 5. The high-gloss coating for coated paper according to claim 1, wherein the amount of the aqueous solution of polyvinyl alcohol added in the step (4) is 10 to 20 parts, the amount of boric acid added is 0.8 to 1.2 parts, and the amount of sodium tetraborate decahydrate added is 1.6 to 2.4 parts.
  6. 6. The high gloss coating for coated paper according to claim 1, further comprising 2 parts of dispersant, 3 parts of sodium carboxymethyl cellulose, 5 parts of calcium stearate, 2 parts of defoamer and 5 parts of ammonia water.
  7. 7. The high-gloss coating for coated paper according to claim 1, wherein the concentration of the aqueous solution of polyvinyl alcohol is 20wt%, the solid content of the colloidal silica is 25wt% to 35wt%, the solid content of the styrene-acrylic emulsion is 45wt% to 55wt%, and the type of the ammonium zirconium carbonate cross-linking agent is Bacote 20.
  8. 8. A method for preparing a high-gloss coating for coated paper according to any one of claims 1 to 7, comprising the steps of adding modified calcium carbonate slurry into a dispersing kettle, stirring and adjusting to 1200rpm, adding a dispersing agent, stirring for 5min, adding colloidal silica, continuing to disperse for 10min, scattering sodium carboxymethyl cellulose at 1500rpm, continuing to disperse for 30min, adding calcium stearate, dispersing for 10min, reducing the rotation speed to 800rpm, sequentially adding styrene emulsion, polyvinyl alcohol aqueous solution, defoaming agent, stirring for 10min, adding ammonia water with the concentration of 25wt%, finally adding ammonium zirconium carbonate cross-linking agent, stirring for 5min at 500rpm, then vacuum-defoaming at 200mbar to obtain a high-gloss coating for coated paper, coating at least one side of the base paper with the high-gloss coating for coated paper, drying the coated base paper, and calendaring the dried paper to obtain coated paper.
  9. 9. The method for preparing a high-gloss coating for coated paper according to claim 8, wherein the base paper is uncoated base paper with a basis weight of 70g/m 2 and is balanced for 24 hours in a 23 ℃ and 50% RH environment, doctor blade coating is adopted for coating, the wet coating weight is 18-22g/m 2 , and the coating linear speed is 80-150m/min.
  10. 10. The method for preparing a high-gloss coating for coated paper according to claim 8, wherein the drying is performed by three stages of hot air, the first stage of hot air is at 105-115 ℃, the second stage of hot air is at 115-125 ℃, the third stage of hot air is at 120-130 ℃, the total residence time is 25-35s, and the calendering is performed under conditions of roller temperature of 55-70 ℃, line pressure of 8-12MPa and number of calender channels of 1-3 channels.

Description

High-gloss coating for coated paper and preparation method thereof Technical Field The invention relates to the technical field of coatings, in particular to a high-gloss coating for coated paper and a preparation method thereof. Background In the production of high-grade coated papers such as coated papers, high glossiness is one of the key quality indexes of the coated papers, and directly influences the color saturation and visual performance of printed matters. In order to pursue high gloss, the conventional technology generally adopts fine-particle-size heavy calcium carbonate or precipitated calcium carbonate as a main pigment, and is supplemented with a high-usage amount of latex binder. This method relies on the smoothness of the pigment itself, and achieves gloss enhancement by applying high pressure during calendering to densify the pigment particles. However, this concept essentially treats the pigment build-up process and the binder film-forming process as two relatively independent stages. The separation treatment mode can be controlled on a high-precision and stable production line, but in actual production, the limitation of the separation treatment mode is not revealed especially when the separation treatment mode faces common process fluctuation of a medium-sized and small-sized production line. First, although fine particle size pigments are advantageous for forming smooth surfaces, if the interfacial effect between the pigment and the binder is not strong during the drying and curing process of the coating, the pigment particles are difficult to achieve high orientation and close packing, and microscopic pores are easily formed and surface roughness is amplified. These microscopic defects act as scattering points for light, directly causing the specular reflection to be reduced, manifesting as reduced or unstable gloss. Second, process flexibility is particularly problematic. Fluctuations in coating line speed, small changes in drying zone temperature gradients, and disturbances in calender roll gap are common variables in mass production. Under conventional formulation systems, these disturbances can exacerbate coating structure non-uniformity. For example, drying temperature gradients may cause binder migration, resulting in localized compositional non-uniformity of the coating, and calendering pressure fluctuations may cause localized collapse or rearrangement of the otherwise insufficiently stable pigment build-up structure. The final result is dark spots and streaks with uneven brightness on the surface of the coating, and the printing effect is seriously affected as well as large fluctuation of the glossiness value (namely poor glossiness uniformity). Therefore, the core contradiction in the prior art is that by simply relying on the physical fine particle size pigment and Gao Guangya light, an effective synergistic mechanism cannot be established between the stacking arrangement of the pigment and the film-forming consolidation of the binder. The stability of the microstructure of the coating is highly dependent on extremely stable process conditions, the capability of resisting inherent disturbance in mass production is lacking, the high gloss performance is difficult to be compatible with the process robustness and the consistency between batches of production, and the application of the technology under wider line production conditions is limited. Disclosure of Invention In view of the above, the invention aims to provide a high-gloss coating for coated paper and a preparation method thereof, so as to solve the problems of uneven gloss and poor stability caused by the fact that a coating microstructure is easy to generate pores and enlarged roughness under the fluctuation of a mass production process due to insufficient synergy of pigment accumulation and binder film formation in the existing coated paper high-gloss coating technology. Based on the above purposes, the invention provides a high-gloss coating for coated paper, which is formed by drying and calendaring a high-gloss coating for coated paper, wherein the high-gloss coating for coated paper comprises, by mass, 1400 parts of modified calcium carbonate slurry, 140-180 parts of colloidal silica, 180-240 parts of styrene-acrylic emulsion, 60-90 parts of polyvinyl alcohol aqueous solution and 5-8 parts of ammonium zirconium carbonate cross-linking agent; Wherein, the modified calcium carbonate slurry is prepared by the following steps: (1) Dispersing heavy calcium carbonate powder in water to obtain calcium carbonate dispersion slurry; (2) Adding sodium silicate solution into the calcium carbonate dispersion slurry, introducing carbon dioxide gas to stabilize the pH of the system at 8.1-8.5, and aging after stopping ventilation to obtain silicon dioxide composite calcium carbonate slurry; (3) Adding dopamine hydrochloride into the silicon dioxide composite calcium carbonate slurry, and forming a polydopamine adhesive layer