Coatings for Improving Doctor Blade Marks on Coated White Cardboard and Their Preparation Method

Abstract

This invention belongs to the field of papermaking technology, specifically relating to a coating for improving doctor blade marks on coated white cardboard and its preparation method. The coating for improving doctor blade marks on coated white cardboard includes the following raw materials: calcium carbonate grade 95 slurry, kaolin slurry, latex, CMC slurry, dispersant, lubricant, water-resistant agent, bactericide, defoamer, and alkaline solution. The preparation method of the CMC slurry is as follows: water and CMC are added to a reaction vessel, the temperature is raised, and the mixture is stirred, controlling the solid content of the CMC slurry at 10-12% and the viscosity at 2500-3000 cps. This invention controls the static water retention value of the coating to 120-130 g / m³ by controlling the solid content and viscosity of the CMC slurry during preparation. 2 This improved the problem of scraper marks caused by coating during the production of white cardboard; by controlling the order of raw material feeding, coating viscosity and water retention value, the dispersibility of the coating was improved, further improving the problem of scraper marks caused by coating during the production of white cardboard.

Description

Technical Field

[0001] This invention belongs to the field of papermaking technology, specifically relating to a coating for improving doctor blade marks on coated white cardboard and its preparation method. Background Technology

[0002] The coatings used in blade coating exhibit a pseudoplastic flow pattern. If the coating formulation is improperly handled, the base paper comes into contact with the coating first during the coating process. The doctor blade exerts significant pressure and shear force on both the coating and the base paper, resulting in substantial pressure migration and capillary migration. Currently, to reduce production costs, most white cardboard manufacturers use high-viscosity sodium carboxymethyl cellulose (CMC) (12% solids content, viscosity 3000-4000 cps) to minimize CMC usage. However, if the CMC content in the formulation is inappropriate, the coating's static water retention value will be high, resulting in a large amount of water in the coating. This causes excessive migration of adhesives and additives into the base paper, leading to their loss. More seriously, the coating's internal structure undergoes significant changes, resulting in poor flow properties and potentially exhibiting dilatational flow rheological characteristics. In dilatational flow, the coating viscosity increases sharply with increasing shear rate, ultimately producing numerous doctor blade streaks and uneven coating, which can lead to paper breaks in severe cases. Meanwhile, existing coatings suffer from poor dispersion, leading to the agglomeration of pigment particles such as calcium carbonate and kaolin during the coating process, resulting in scraper marks.

[0003] Therefore, the problems of scraper marks and poor dispersibility that easily occur in the blade coating process urgently need to be solved. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to provide a coating that improves the removal of scraper marks on coated white cardboard, effectively mitigating the problem of scraper marks during the coating process and exhibiting good dispersibility.

[0005] The present invention also provides a preparation method that is simple, easy to implement, and suitable for large-scale production.

[0006] The coating for improving doctor blade marks on coated white cardboard according to the present invention comprises the following raw materials in parts by weight:

[0007]

[0008]

[0009] The preparation method of the CMC slurry is as follows: add water and CMC to the reaction vessel, heat to 60°C, stir evenly, and control the solid content of the CMC slurry to be 10-12% and the viscosity to be 2500-3000cps.

[0010] The solid content of the calcium carbonate grade 95 slurry is 74.5%.

[0011] The solid content of the kaolin slurry is 70%.

[0012] The latex is styrene-butadiene latex with a solid content of 49-51%.

[0013] The dispersant is a mixture of ZH-250, XDFS-406 and APAM in a mass ratio of 1:(0.3-0.4):(0.1-0.2).

[0014] The lubricant is polyethylene wax, and the water-resistant agent is potassium zirconium carbonate.

[0015] The bactericide is 1,4-bis(bromoethyloneoxy)-2-butene.

[0016] The concentration of the alkaline solution is 28 wt.%.

[0017] The method for preparing the coating that improves doctor blade marks on coated white cardboard according to the present invention includes the following steps:

[0018] Add calcium carbonate grade 95 slurry to the reaction vessel, start stirring, add kaolin slurry and dispersant in sequence, stir evenly, then add defoamer, CMC slurry, latex, lubricant, bactericide, water-resistant agent and alkaline solution, mix evenly, and you will get a coating that improves the squeegee marks on coated white cardboard.

[0019] The coating used to improve doctor blade marks on coated white cardboard has a viscosity of 1200-1300 cps and a water retention value of 120-130 g / m³. 2 .

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] (1) This invention controls the static water retention value of the coating to 120-130 g / m³ by controlling the solid content and viscosity of the CMC slurry during preparation. 2 This improved the problem of scraper marks caused by coating during the production of white cardboard.

[0022] (2) By controlling the order of feeding raw materials, the present invention controls the viscosity and water retention value of the coating, thereby improving the dispersibility of the coating and further improving the problem of scraper marks caused by coating during the production of white cardboard.

[0023] (3) The present invention improves the dispersion performance of the coating by using a combination of dispersants ZH-250, XDFS-406 and APAM, which makes the subsequent functional additives more uniformly dispersed and improves the dispersion effect of the coating while ensuring the water retention value. Detailed Implementation

[0024] The present invention will be further described below with reference to the embodiments, but the scope of protection of the present invention is not limited thereto.

[0025] Unless otherwise specified, all raw materials used in the examples were commercially available.

[0026] Dispersant: XDFS-406 produced by Qingzhou Xindi Chemical Co., Ltd.;

[0027] Dispersant: ZH-250 produced by Changshu Juhe Chemical Co., Ltd.;

[0028] Dispersant: APAM, molecular weight 1500;

[0029] Kaolin slurry: KAOFINE90;

[0030] Latex: Styrene-butadiene latex, solid content 50±1%;

[0031] CMC: NX-10 manufactured by Jiangyin Hengda New Material Technology Co., Ltd.

[0032] Lubricant: MS268 manufactured by Jiuzhou Biomedical Technology Group Co., Ltd.

[0033] Water-resistant agent: potassium zirconium carbonate; the bactericide is 1,4-bis(bromoethyloneoxy)-2-butene.

[0034] Defoamer: AmiDefoam 5873 manufactured by Shanghai Emerson Chemicals Co., Ltd.

[0035] Example 1

[0036] The coating for improving doctor blade marks on coated white cardboard comprises the following raw materials in parts by weight:

[0037]

[0038] The preparation method of the CMC slurry is as follows: add water and CMC to the reaction vessel, heat to 60°C, stir evenly at 1500 rpm, and control the solid content of the CMC slurry to be 10% and the viscosity to be 2600 cps.

[0039] The solid content of the calcium carbonate grade 95 slurry is 74.5%.

[0040] The solid content of the kaolin slurry is 70%.

[0041] The dispersant is a mixture of ZH-250, XDFS-406 and APAM in a mass ratio of 1:0.3:0.1.

[0042] The alkaline solution is a sodium hydroxide solution with a concentration of 28 wt.%.

[0043] The method for preparing the coating that improves doctor blade marks on coated white cardboard includes the following steps:

[0044] Add calcium carbonate grade 95 slurry to the reaction vessel, start stirring at 1500 rpm, add kaolin slurry and dispersant in sequence, stir evenly, then add defoamer, CMC slurry, latex, lubricant, bactericide, water-resistant agent and alkaline solution in sequence, mix evenly, and you will get a coating that improves the scratches on coated white cardboard.

[0045] The coating described above for improving doctor blade marks on coated white cardboard has a viscosity of 1250 cps and a water retention value of 123 g / m³. 2 The coating has a solids content of 66%.

[0046] Example 2

[0047] The coating for improving doctor blade marks on coated white cardboard comprises the following raw materials in parts by weight:

[0048]

[0049] The preparation method of the CMC slurry is as follows: add water and CMC to the reaction vessel, heat to 60°C, stir evenly at 1500 rpm, and control the solid content of the CMC slurry to be 10% and the viscosity to be 2600 cps.

[0050] The solid content of the calcium carbonate grade 95 slurry is 74.5%.

[0051] The solid content of the kaolin slurry is 70%.

[0052] The dispersant is a mixture of ZH-250, XDFS-406 and APAM in a mass ratio of 1:0.4:0.2.

[0053] The alkaline solution is a sodium hydroxide solution with a concentration of 28 wt.%.

[0054] The method for preparing the coating that improves doctor blade marks on coated white cardboard includes the following steps:

[0055] Add calcium carbonate grade 95 slurry to the reaction vessel, start stirring at 1500 rpm, add kaolin slurry and dispersant in sequence, stir evenly, then add defoamer, CMC slurry, latex, lubricant, bactericide, water-resistant agent and alkaline solution in sequence, mix evenly, and you will get a coating that improves the scratches on coated white cardboard.

[0056] The coating described above for improving doctor blade marks on coated white cardboard has a viscosity of 1250 cps and a water retention value of 125 g / m³. 2 The coating has a solids content of 65.9%. No scraper marks were generated during the coating process.

[0057] Example 3

[0058] The coating for improving doctor blade marks on coated white cardboard comprises the following raw materials in parts by weight:

[0059]

[0060] The preparation method of the CMC slurry is as follows: add water and CMC to the reaction vessel, heat to 60°C, stir evenly at 1500 rpm, and control the solid content of the CMC slurry to be 10% and the viscosity to be 2600 cps.

[0061] The solid content of the calcium carbonate grade 95 slurry is 74.5%.

[0062] The solid content of the kaolin slurry is 70%.

[0063] The dispersant is a mixture of ZH-250, XDFS-406 and APAM in a mass ratio of 1:0.35:0.15.

[0064] The alkaline solution is a sodium hydroxide solution with a concentration of 28 wt.%.

[0065] The method for preparing the coating that improves doctor blade marks on coated white cardboard includes the following steps:

[0066] Add calcium carbonate grade 95 slurry to the reaction vessel, start stirring at 1500 rpm, add kaolin slurry and dispersant in sequence, stir evenly, then add defoamer, CMC slurry, latex, lubricant, bactericide, water-resistant agent and alkaline solution in sequence, mix evenly, and you will get a coating that improves the scratches on coated white cardboard.

[0067] The coating described above for improving doctor blade marks on coated white cardboard has a viscosity of 1230 cps and a water retention value of 120 g / m³. 2 The coating has a solids content of 66.2%. No scraper marks were generated during the coating process.

[0068] Comparative Example 1

[0069] The coating for improving doctor blade marks on coated white cardboard comprises the following raw materials in parts by weight:

[0070]

[0071]

[0072] The preparation method of the CMC slurry is as follows: add water and CMC to the reaction vessel, heat to 60°C, stir evenly at 1500 rpm, and control the solid content of the CMC slurry to be 12% and the viscosity to be 5000 cps.

[0073] The solid content of the calcium carbonate grade 95 slurry is 74.5%.

[0074] The solid content of the kaolin slurry is 70%.

[0075] The dispersant is a mixture of ZH-250, XDFS-406 and APAM in a mass ratio of 1:0.3:0.1.

[0076] The alkaline solution is a sodium hydroxide solution with a concentration of 28 wt.%.

[0077] The method for preparing the coating that improves doctor blade marks on coated white cardboard includes the following steps:

[0078] Add calcium carbonate grade 95 slurry to the reaction vessel, start stirring at 1500 rpm, add kaolin slurry and dispersant in sequence, stir evenly, then add defoamer, CMC slurry, latex, lubricant, bactericide, water-resistant agent and alkaline solution in sequence, mix evenly, and you will get a coating that improves the scratches on coated white cardboard.

[0079] The coating described above for improving doctor blade marks on coated white cardboard has a viscosity of 1230 cps and a water retention value of 140 g / m³. 2 The coating has a solids content of 66.2%. Obvious scraper marks and paper breaks occurred during the coating process.

[0080] Comparative Example 2

[0081] The coating for improving doctor blade marks on coated white cardboard comprises the following raw materials in parts by weight:

[0082]

[0083]

[0084] The preparation method of the CMC slurry is as follows: add water and CMC to the reaction vessel, heat to 60°C, stir evenly at 1500 rpm, and control the solid content of the CMC slurry to be 10% and the viscosity to be 2600 cps.

[0085] The solid content of the calcium carbonate grade 95 slurry is 74.5%.

[0086] The solid content of the kaolin slurry is 70%.

[0087] The dispersant is ZH-250.

[0088] The alkaline solution is a sodium hydroxide solution with a concentration of 28 wt.%.

[0089] The method for preparing the coating that improves doctor blade marks on coated white cardboard includes the following steps:

[0090] Add calcium carbonate grade 95 slurry to the reaction vessel, start stirring at 1500 rpm, add kaolin slurry and dispersant in sequence, stir evenly, then add defoamer, CMC slurry, latex, lubricant, bactericide, water-resistant agent and alkaline solution in sequence, mix evenly, and you will get a coating that improves the scratches on coated white cardboard.

[0091] The coating described above for improving doctor blade marks on coated white cardboard has a viscosity of 1260 cps and a water retention value of 120 g / m³. 2 The paint has a solids content of 66%. Fine scraper marks are produced during the coating process.

[0092] The standard for determining the water retention value of the coatings prepared in the above embodiments and comparative examples is GB / T 29286-2012.

Claims

1. A coating for improving knife marks on coated white card, characterized in that, The raw materials include the following quality parts: Calcium carbonate 95 level slurry 80-85 parts; Porcelain clay slurry 15-20 parts; Latex 11-13 parts; CMC slurry 0.1-0.4 parts; Dispersant 0.12-0.15 parts; Lubricant 0.2-0.25 parts; Water repellent 0.3-0.5 parts; Bactericide 0.01-0.012 parts; Defoaming agent 0.08-0.01 parts; Alkali solution 0.12-0.14 parts; The preparation method of the CMC slurry is as follows: water and CMC are added into a reaction container, heated to 60℃, stirred uniformly, and the solid content of the CMC slurry is controlled at 10-12%, and the viscosity is controlled at 2500-3000cps; The dispersant is a mixture of ZH-250, XDFS-406 and APAM with a mass ratio of 1:(0.3-0.4):(0.1-0.2).

2. The coating for improving the doctor blade mark of coated white board paper according to claim 1, characterized in that, The solid content of the calcium carbonate 95 level slurry is 74.5%.

3. The coating to improve the doctor blade mark of coated white board paper according to claim 1, characterized in that, The solid content of the porcelain clay slurry is 70%.

4. The coating to improve the doctor blade mark of coated white board paper according to claim 1, characterized in that, The latex is butadiene-styrene latex with a solid content of 49-51%.

5. The coating to improve the doctor blade mark of coated white board paper according to claim 1, characterized in that, The lubricant is polyethylene wax, and the water repellent is potassium zirconium carbonate.

6. The coating to improve the doctor blade mark of coated white board paper according to claim 1, characterized in that, The bactericide is 1,4-bis(bromoacetoneoxy)-2-butene.

7. A method of preparing a coating for improving the doctor blade marks of a coated white card according to any one of claims 1 to 6, characterized in that, The method includes the following steps: The calcium carbonate 95 level slurry is added into a reaction container, stirring is started, the porcelain clay slurry and the dispersant are added in sequence, stirred uniformly, then the defoaming agent, the CMC slurry, the latex, the lubricant, the bactericide, the water repellent and the alkali solution are added, mixed uniformly, and the coating for improving the doctor blade mark of coated white cardboard is obtained.

8. The method of preparing a coating to improve doctor blade marks on coated white card according to claim 7, characterised in that, The viscosity of the coating for improving the doctor blade mark of the coated white card paper is 1200-1300cps, and the water retention value is 120-130g / m 2 .

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