Modified kaolin with high viscosity concentration as well as preparation method and application thereof

Abstract

The invention relates to the technical field of kaolin modification, in particular to modified kaolin with high viscosity concentration and a preparation method and application thereof. The preparation method of the modified kaolin with high viscosity concentration comprises the following steps: mixing kaolin and sulfamide, ball-milling, drying and modifying to obtain the modified kaolin. The invention provides a process for modifying the kaolin by combining dry ball milling and dry modification technologies and using sulfamide, so that the viscosity concentration of the kaolin can be improved, the structure of the kaolin is not changed, the original whiteness of the kaolin is maintained, the viscosity of a kaolin product is effectively reduced, and the comprehensive quality of the kaolin product is improved; and subsequent papermaking coating and other process applications are not influenced, so that the requirements of the papermaking industry are better met.

Description

Technical Field

[0001] This invention relates to the field of kaolin modification technology, and in particular to a modified kaolin with high viscosity concentration, its preparation method, and its application. Background Technology

[0002] Kaolin, a high-quality clay mineral with a layered crystal structure, occupies a key position in papermaking, coatings, ceramics, and other fields due to its excellent hydrophilicity, high whiteness, good plasticity, and chemical inertness. Especially in the field of high-grade paper coating, it is the core white pigment for preparing high-performance coated paper. The papermaking industry has stringent requirements for the physical properties of coating-grade kaolin, requiring it to be within 500 mPa. Achieving a viscosity concentration of ≥70% under s viscosity conditions—this indicator directly determines the fluidity of kaolin slurry, thereby affecting the operating efficiency of high-speed coating machines, as well as the printability, smoothness, and gloss of paper.

[0003] The domestic paper industry has widely adopted imported coating machines with higher line speeds and larger capacities, significantly increasing the requirements for the fluidity, purity, and industrial stability of kaolin. The paper industry requires a viscosity concentration of ≥65%, while coating-grade kaolin typically needs a viscosity concentration of 66%-70% to meet rheological requirements. However, controlling the viscosity concentration of kaolin for high-grade paper coating has long been a bottleneck in China: even with improvements in whiteness and fineness through advanced bleaching and centrifugal grading technologies, the high viscosity and poor fluidity of the pulp make it difficult to match the production demands of high-speed coating machines. This has led to a reliance on imported kaolin for high-grade coated paper production, hindering the high-end development of the domestic paper industry.

[0004] Patent CN201310055276 focuses on the research and development of compound viscosity reducers. The effective components of this viscosity reducer consist of sodium hexametaphosphate (preferably 20-30%), sodium polyacrylate, borax, sodium hydroxide, and methylene blue. It is prepared by dissolving and mixing these components in a specific order: sodium hexametaphosphate → sodium polyacrylate → borax. Water is added to adjust the total solids content to 8-20%, and then sodium hydroxide and methylene blue are added dropwise. This viscosity reducer is added to bleached kaolin concentrate slurry (0.5-2.0%). Through the dispersing effect of sodium hexametaphosphate and sodium polyacrylate, the viscosity-reducing effect of borax, and the lubricating effect of sodium hydroxide, it alters the Zeta potential of the kaolin particles, allowing the product to maintain a viscosity within 500 mPa. The viscosity concentration under certain conditions was increased to over 70.2%. However, this technology relies on the precise synergistic ratio of multiple agents, and the amount of agents added is easily affected by batch fluctuations in raw materials, so its stability needs to be improved.

[0005] Patent CN1315601A reduces viscosity by kneading and extruding a kaolin mixture with a solid content of 60-85% for 10-60 minutes. Although this can achieve a viscosity concentration of over 68%, it easily damages the kaolin crystal structure and cannot guarantee whiteness, resulting in insufficient overall product quality and interfering with subsequent paper coating processes. Another solution relies on selecting natural flaky kaolin raw materials, which can naturally reduce viscosity, but its applicability is limited by resource distribution and is difficult to promote industrially. Summary of the Invention

[0006] The purpose of this invention is to address the aforementioned shortcomings of the prior art by proposing a method for preparing modified kaolin with high viscosity concentration.

[0007] The first objective of this invention is to provide a method for preparing modified kaolin with high viscosity concentration, comprising the following steps: mixing and ball milling kaolin and sulfuramide, followed by drying and modification to obtain modified kaolin.

[0008] Furthermore, the mass ratio of kaolin to thioamide is 100:6-8.

[0009] Furthermore, the ball mill is rotated at 300-600 r / min for 10-20 minutes in a planetary ball mill, with a ball-to-material ratio of 0.5-0.8:1.

[0010] Furthermore, the drying modification was carried out in a forced-air drying oven.

[0011] Furthermore, the drying modification temperature is 80-105℃.

[0012] Furthermore, the drying modification temperature is 95℃.

[0013] Furthermore, the drying modification time is 3-5 hours.

[0014] Furthermore, the drying modification time is 4 hours.

[0015] This invention proposes a process combining dry ball milling and dry modification techniques, using sulfuramide to modify kaolin. This process can increase the viscosity concentration of kaolin to 71.97%, representing a viscosity concentration increase of 5.07%, without altering the kaolin's structure or maintaining its original whiteness. It effectively reduces the viscosity of kaolin products, improves their overall quality, and does not affect subsequent paper coating and other processes, thus better meeting the needs of the paper industry. This process is simple to operate, widely applicable, environmentally friendly and safe, and easy to scale up for industrial production, demonstrating significant industrialization potential. Attached Figure Description

[0016] Figure 1 XRD patterns of the modified kaolin prepared in the examples and comparative examples; Figure 2Fourier transform infrared spectra of the modified kaolin prepared for the examples and comparative examples. Detailed Implementation

[0017] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings to further illustrate the technical solutions of the present invention. However, the present invention is not limited to these embodiments.

[0018] The kaolin used in this embodiment of the invention is kaolin TL04 and kaolin ZT-01A from China-Africa Maoming New Materials Co., Ltd. The viscosity concentration of TL04 is 68.5%; the viscosity concentration of kaolin ZT-01A is 70.15%.

[0019] Example 1: 1) Prepare a ball mill jar, weigh 250g of kaolin (TL04) and 17.5g of thioamide, and rotate them in a planetary ball mill at 600r / min for 15min to obtain a mixed sample; 2) The mixed sample from step 1) was sealed and placed in a forced-air drying oven at 95°C for 4 hours to obtain modified kaolin with a tested viscosity concentration of 71.5%.

[0020] Example 2: 1) Prepare two ball mill jars, weigh 150g of kaolin (TL04) and 10.5g of thioamide, and rotate them in a planetary ball mill at 600r / min for 15min to obtain a mixed sample; 2) The mixed sample from step 1) was sealed and placed in a forced-air drying oven at 95°C for 4 hours to obtain modified kaolin with a tested viscosity concentration of 71.6%.

[0021] Example 3: 1) Prepare two ball mill jars, weigh 150g of kaolin (TL04) and 10.5g of thioamide, and rotate them in a planetary ball mill at 300r / min for 15min to obtain a mixed sample; 2) The mixed sample from step 1) was sealed and placed in a forced-air drying oven at 95°C for 4 hours to obtain modified kaolin with a viscosity concentration of 71.97%.

[0022] Example 4: 1) Prepare two ball mill jars, weigh 150g of kaolin (TL04) and 10.5g of thioamide, and rotate them in a planetary ball mill at 450r / min for 15min to obtain a mixed sample; 2) The mixed sample from step 1) was sealed and placed in a forced-air drying oven at 95°C for 4 hours to obtain modified kaolin with a tested viscosity concentration of 71.64%.

[0023] Example 5: 1) Prepare 4 ball mill jars, weigh 180g of kaolin (ZT-01A) and 12.6g of thioamide, and rotate them in a planetary ball mill at 600r / min for 15min to obtain a mixed sample; 2) The mixed sample from step 1) was sealed and placed in a forced-air drying oven at 95°C for 4 hours to obtain modified kaolin with a viscosity concentration of 72.29%.

[0024] Example 6: 1) Prepare 4 ball mill jars, weigh 180g of kaolin (ZT-01A) and 12.6g of thioamide, and rotate them in a planetary ball mill at 300r / min for 15min to obtain a mixed sample; 2) The mixed sample from step 1) was sealed and placed in a forced-air drying oven at 95°C for 4 hours to obtain modified kaolin with a tested viscosity concentration of 71.50%.

[0025] Comparative Example 1: 1) Prepare a ball mill jar, weigh 250g of kaolin (TL04) and 17.5g of urea, and rotate it in a planetary ball mill at 600r / min for 15min to obtain a mixed sample; 2) The mixed sample from step 1) was sealed and placed in a forced-air drying oven at 95°C for 4 hours to obtain modified kaolin with a viscosity concentration of 69.1%.

[0026] Comparative Example 2: 1) Prepare a ball mill jar, weigh 250g of kaolin (TL04) and 17.5g of o-aminobenzamide, and rotate it in a planetary ball mill at 600r / min for 15min to obtain a mixed sample; 2) The mixed sample from step 1) was sealed and placed in a forced-air drying oven at 95°C for 4 hours to obtain modified kaolin with a tested viscosity concentration of 64.2%.

[0027] Comparative Example 3: 1) Prepare a ball mill jar, weigh 250g of kaolin (TL04) and 17.5g of 2-thiouracil, and rotate it in a planetary ball mill at 600r / min for 15min to obtain a mixed sample; 2) The mixed sample from step 1) was sealed and placed in a forced-air drying oven at 95°C for 4 hours to obtain modified kaolin with a viscosity concentration of 69.1%.

[0028] Comparative Example 4: 1) Prepare a ball mill jar, weigh 250g of kaolin (TL04) and 17.5g of N-methylthiourea, and rotate it in a planetary ball mill at 600r / min for 15min to obtain a mixed sample; 2) The mixed sample from step 1) was sealed and placed in a forced-air drying oven at 95°C for 4 hours to obtain modified kaolin with a viscosity concentration of 70.1%.

[0029] Comparative Example 5: 1) Prepare a ball mill jar, weigh 250g of kaolin (TL04) and 17.5g of methylurea, and rotate them in a planetary ball mill at 600r / min for 15min to obtain a mixed sample; 2) The mixed sample from step 1) was sealed and placed in a forced-air drying oven at 95°C for 4 hours to obtain modified kaolin with a tested viscosity concentration of 69.6%.

[0030] Comparative Example 6: 1) Prepare a ball mill jar, weigh 250g of kaolin (TL04) and 17.5g of biuret, and rotate it in a planetary ball mill at 600r / min for 15min to obtain a mixed sample; 2) The mixed sample from step 1) was sealed and placed in a forced-air drying oven at 95°C for 4 hours to obtain modified kaolin with a tested viscosity concentration of 67.6%.

[0031] Comparative Example 7: 1) Prepare a ball mill jar, weigh 250g of kaolin (TL04) and 17.5g of formamide, and rotate it in a planetary ball mill at 600r / min for 15min to obtain a mixed sample; 2) The mixed sample from step 1) was sealed and placed in a forced-air drying oven at 95°C for 4 hours to obtain modified kaolin with a tested viscosity concentration of 64.5%.

[0032] Comparative Example 8: 1) Prepare a ball mill jar, weigh 250g of kaolin (TL04) and 17.5g of urethane, and rotate it in a planetary ball mill at 600r / min for 15min to obtain a mixed sample; 2) The mixed sample from step 1) was sealed and placed in a forced-air drying oven at 95°C for 4 hours to obtain modified kaolin with a tested viscosity concentration of 66.7%.

[0033] Phase analysis: The phase structure of the material was studied using XRD technology. The test results are as follows: Figure 1As shown, TL04 exhibits very strong and sharp diffraction peaks at 12.5° and 24.9°, which correspond to the typical layered silicate structure (001) and (002) crystal planes of kaolin. Formamide, urea, and o-aminobenzamide all showed varying degrees of peak shift, successfully inserting into the interlayer. In contrast, the XRD pattern of kaolin after thioamide modification did not change, indicating that its crystal structure was not destroyed, preserving the uniqueness of kaolin and having no impact on subsequent actual papermaking production. Furthermore, the viscosity concentration of kaolin was further improved, which is of great significance in practical production applications.

[0034] Infrared spectroscopy analysis: Fourier transform infrared spectroscopy (FTIR) was used to detect and analyze the chemical functional groups and molecular structure in the samples. The test results are as follows: Figure 2 As shown, taking TL04 / thioamide as an example, at 3500-3100cm -1 The NH stretching vibration peak of the amino group appeared at 1480 cm⁻¹. -1 The stretching vibration peak at C=S indicates that thioamide has successfully compounded with kaolin, and the peak at 1001 cm⁻¹ proves this. -1 The peak corresponds to the asymmetric stretching vibration of Si-O-Si at 3500-4000 cm⁻¹, and the peak is located at 3500-4000 cm⁻¹. -1 The presence of characteristic peaks of kaolinite, such as the Al-OH stretching vibration peak, indicates that the structure of kaolinite has not changed, which is consistent with the results of the XRD pattern. This further proves that the material can increase the viscosity concentration of kaolinite without changing its structure. Other modifiers also showed their corresponding stretching vibration peaks, such as TL04 / formamide at 3500-3100 cm⁻¹. -1 The NH stretching vibration peak appeared at 1500-1600 cm⁻¹. -1 The peak of C=O stretching vibration at the point is observed, but it has a small effect on increasing the viscosity of kaolin and changes the crystal structure of kaolin, which may affect the practical application of kaolin.

[0035] Analysis of viscosity concentration test results: Table 1 shows the process parameters and viscosity concentrations for the comparative examples and embodiments. Table 1

[0036] The viscosity concentration of kaolin was optimized by various modifiers through viscosity concentration tests on the finished products, as shown in Table 1. The TL04 / thioamide combination showed the best improvement, reaching a maximum of 71.97%, a significant increase of 5.07% compared to TL04's 68.5%. The ZT-01A / thioamide combination achieved a maximum viscosity concentration of 72.29%, still showing a significant improvement of 3.05% compared to ZT-01A's 70.15%. This invention achieves the goal of reducing kaolin viscosity and increasing its viscosity concentration without altering the kaolin structure, playing a crucial role in practical papermaking applications.

[0037] For any points not covered above, existing technologies shall apply.

[0038] Although specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the direction of the invention or exceeding the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc., made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing modified kaolin with high viscosity concentration, characterized in that, The process includes the following steps: mixing kaolin and sulfuramide, ball milling, drying and modifying to obtain modified kaolin.

2. The method for preparing modified kaolin with high viscosity concentration as described in claim 1, characterized in that, The mass ratio of kaolin to sulfuramide is 100:6-8.

3. The method for preparing modified kaolin with high viscosity concentration as described in claim 1, characterized in that, The ball mill is operated in a planetary ball mill at 300-600 r / min for 10-20 minutes, with a ball-to-material ratio of 0.5-0.8:

1.

4. The method for preparing modified kaolin with high viscosity concentration as described in claim 1, characterized in that, The drying modification was carried out in a forced-air drying oven.

5. The method for preparing modified kaolin with high viscosity concentration as described in claim 1, characterized in that, The drying modification temperature is 80-105℃.

6. The method for preparing modified kaolin with high viscosity concentration as described in claim 1, characterized in that, The drying modification temperature is 95℃.

7. The method for preparing modified kaolin with high viscosity concentration as described in claim 1, characterized in that, The drying and modification time is 3-5 hours.

8. The method for preparing modified kaolin with high viscosity concentration as described in claim 1, characterized in that, The drying modification time is 4 hours.

9. A modified kaolin with high viscosity concentration prepared by the preparation method according to any one of claims 1-8.

10. An application of modified kaolin with high viscosity concentration as described in claim 9, characterized in that, Used for papermaking.

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