A method for removing water from conductive paste

Abstract

This invention belongs to the field of conductive paste technology and relates to a method for dewatering conductive paste, comprising the steps of: soaking and drying a porous absorbent material, filling it into a filter, connecting it to a circulation pipeline system, and passing the conductive paste through the circulation pipeline system until the moisture content reaches the standard. The conductive paste dewatering method of this invention is simple and easy to implement, with a fast dewatering speed, reducing the moisture content of the conductive paste from 1169 ppm to 324 ppm in only 10 minutes. The solid content and solvent loss of the paste are low, and the conductivity of the paste is not affected. It is suitable for continuous production, eliminating the need for stringent control of raw material moisture content and production environment humidity, and stably achieving the production of low-moisture conductive paste, making the conductive paste meet the needs of high-end application scenarios.

Description

Technical Field

[0001] This invention relates to a method for dewatering conductive slurry, belonging to the field of conductive slurry technology. Background Technology

[0002] Conductive pastes are key functional materials for electronic components such as lithium-ion batteries, solar cells, and touch screens, and their performance stability directly affects the quality and reliability of the end products. Moisture content is one of the key indicators affecting the performance of conductive pastes. Excessive moisture can lead to paste agglomeration and reduced dispersibility, thereby affecting coating uniformity and the electrochemical performance of the final product.

[0003] The traditional methods for controlling the moisture content of conductive pastes in the industry mainly include the following.

[0004] (1) Raw material moisture control method. By strictly detecting and controlling the moisture content of raw materials such as conductive fillers (e.g., carbon black, graphene, carbon nanotubes), binders, and solvents, the introduction of moisture can be reduced from the source. However, this method has extremely high requirements for the quality control of raw material suppliers and cannot completely eliminate the problem of moisture adsorption during the production process.

[0005] (2) Process environmental control method. This method involves controlling the humidity of the environment during processes such as feeding, mixing, and filling, and using facilities such as drying rooms and dehumidification equipment to reduce the moisture content in the air. This method requires complex equipment support and high-energy-consuming operating environment maintenance, resulting in higher production costs.

[0006] Currently, the average moisture content of NMP-based conductive pastes in the industry is generally maintained within the range of 1000 ppm, with some high-end applications having even more stringent moisture requirements. Traditional dehydration methods are complex, difficult to control, and struggle to consistently achieve low moisture content while ensuring other properties of the paste are maintained.

[0007] Therefore, there is an urgent need to develop a method for dewatering conductive slurry that is easy to operate, has a significant dewatering effect, does not degrade the performance of conductive slurry, and is suitable for continuous production. Summary of the Invention Technical issues

[0008] Traditional methods for dewatering slurries struggle to consistently achieve low moisture content while preserving other slurry properties. There is an urgent need to develop a simple, effective, and continuous dewatering method for conductive slurries that does not degrade their properties. Technical solution

[0009] This invention provides a method for dewatering conductive slurry, comprising the steps of: filling a filter with a porous absorbent material, passing the conductive slurry through the filter until the moisture content of the conductive slurry is below 300 ppm; wherein the mass of the porous absorbent material is 5-10% of the mass of the conductive slurry; the porous absorbent material is selected from one of aluminosilicate, aluminosilicate phosphate, and aluminosilicate, with a diameter of 1.5-2.5 mm, a pore size of 0.25-0.55 nm, and a bulk density of 0.7-0.8 g / mL; the viscosity of the conductive slurry is 1000-3000 cp; the circulation flow rate is 500-1000 L / h, and the permeation flux of the porous absorbent material is 200-400 L / (m³). 2 ·h).

[0010] In a preferred embodiment of the present invention, the porous absorbent material has a pore size of 0.25~0.35 nm.

[0011] In one embodiment of the present invention, the conductive paste is an NMP-based conductive paste.

[0012] As one embodiment of the present invention, the filter is selected from one or more of basket filters, bag filters, cartridge filters, candle filters, Y-type filters, and T-type filters.

[0013] As one embodiment of the present invention, the porous absorbent material is first pretreated and then filled into the filter; the pretreatment method is to soak the porous absorbent material in water for 12~36 h, dry it, and cool it to ≤40℃.

[0014] In one embodiment of the present invention, a dewatering device is used for dewatering. The dewatering device includes a raw slurry storage tank, a dewatering storage tank, a filter, and a pump. The raw slurry storage tank is connected to the filter inlet, and the dewatering storage tank is connected to the filter inlet. During operation, the conductive slurry to be dewatered is loaded into the raw slurry storage tank, the filter is filled with porous absorbent material, and the dewatering storage tank is used to receive the dewatered conductive slurry. The pump pumps the conductive slurry in the raw slurry storage tank through the filter for dewatering and stores it in the dewatering storage tank. The conductive slurry is repeatedly dewatered through the filter until the moisture content is below 300 ppm.

[0015] In one embodiment of the present invention, a circulating dewatering device is used for dewatering. The circulating dewatering device includes a group A storage tank, a group B storage tank, a filter, and a circulating pump. The outlets of both group A and group B storage tanks are connected to the inlet of the filter, and the dewatering storage tank is connected to the inlet of the filter. During operation, the circulating pump pumps the conductive slurry in the storage tank through the filter and back to the storage tank. While one group of storage tanks is dewatering, the other group of storage tanks is filled with undewatered conductive slurry. The two groups of storage tanks alternately feed and dewater, achieving continuous production. A schematic diagram of the circulating dewatering device is shown below. Figure 2 .

[0016] As one embodiment of the present invention, water is removed under conditions of 20~30℃ and 95~105 kPa.

[0017] As one embodiment of the present invention, the used porous absorbent material can be reused after regeneration and performance verification.

[0018] As one embodiment of the present invention, the regeneration process includes the following steps: (1) Rinse the porous absorbent material with NMP solvent at a flow rate of 1000~2000 L / h and a rinsing time of 10~40 min; (2) Place the porous water-absorbing material in NMP solution, heat to 150~200℃, and stir for 1~2 h; (3) Dry the porous absorbent material.

[0019] As one embodiment of the present invention, the performance verification is to conduct a small-scale test of conductive slurry dewatering using recycled porous absorbent material, and confirm that the recycled porous absorbent material has recovered to more than 95% of the original water absorption performance of the porous absorbent material before it can continue to be used.

[0020] The conductive slurry dehydration method of the present invention is simple and easy to implement, and the dehydration speed is fast. It only takes 10 minutes to reduce the water content of the conductive slurry from 1169 ppm to 324 ppm. The solid content and solvent loss of the slurry are low, and the conductivity of the slurry is not affected.

[0021] The conductive paste dehydration method of the present invention is suitable for continuous production, without the need for strict control of the moisture content of raw materials and the humidity of the production environment, and can stably achieve the production of conductive paste with low moisture content, so that the conductive paste meets the needs of high-end application scenarios. Attached Figure Description

[0022] Figure 1 This is a flowchart of a method for removing water from conductive slurry.

[0023] Figure 2 This is a schematic diagram of a circulating water removal device. Detailed Implementation Test methods

[0024] Moisture content: The moisture content of conductive paste was tested according to the "General Method for Determination of Moisture in Chemical Reagents - Karl Fischer Method" (GB / T 606-2003).

[0025] Dewatering effect: The water content of the conductive slurry before and 4 hours after dewatering was tested, and the dewatering effect was calculated as follows: Dewatering effect = 100% × (Water content of conductive slurry before dewatering - Water content of conductive slurry after dewatering) / Water content of conductive slurry before dewatering.

[0026] Solid content: Weigh the slurry and record the mass of the slurry before drying as M. Dry the slurry solvent in an oven and record the mass of the slurry after drying as m. Then the solid content = 100% × m ÷ M. Comparative Example 1

[0027] A commercially available NMP-based lithium-ion conductive paste (viscosity 1000 cP) is composed of graphene, carbon nanotubes, dispersant, and NMP solvent.

[0028] The conductive paste was left to stand, and its moisture content was tested. The results are shown in Table 1. Example 1

[0029] The commercially available NMP-based lithium-ion conductive slurry of Comparative Example 1 was dehydrated using the following steps.

[0030] (1) Pretreatment of porous water-absorbing material: Take porous water-absorbing material (aluminosilicate, diameter 2 mm, pore size 0.3 nm, bulk density 0.7 g / mL), soak it in deionized water for 24 hours to remove impurities and adsorbed substances that may exist on the surface of the porous water-absorbing material; then place the porous water-absorbing material in a vacuum drying oven and dry it at ≥200℃, take it out and cool it to room temperature for later use.

[0031] (2) Filling the dewatering device: The porous absorbent material treated in step (1) is loaded into the filter of the dewatering device. The amount of porous absorbent material added is 10% of the mass of the conductive slurry to be dewatered. After checking the sealing of the device and ensuring that there is no leakage, it is connected to the circulation pipeline system. The dewatering device includes a raw slurry storage tank, a dewatering storage tank, a filter, and a pump; the raw slurry storage tank is connected to the filter inlet, and the dewatering storage tank is connected to the filter inlet.

[0032] (3) Injecting the slurry to be treated: The NMP-based lithium-ion conductive slurry described in Comparative Example 1 is injected into the slurry storage tank, with a total slurry volume of 1000 kg.

[0033] (4) Circulating water removal: The circulating water removal system is started at 25℃ and 100 kPa. The slurry is pumped to the water removal device and returned to the storage tank after passing through the porous absorbent material. The circulation flow rate is controlled at 1000 L / h, and the permeation flux of the porous absorbent material is 400 L / (m²). 2 ·h).

[0034] During the circulating dewatering process, the moisture content of the slurry was measured using a Karl Fischer moisture analyzer, and the results are shown in Table 1. The moisture content gradually decreased with increasing circulation frequency. Offline sampling was performed every 30 minutes. Dewatering was considered complete when three consecutive sampling measurements showed a moisture content below 300 ppm, and the circulation pump could be stopped. The solids content and mass of the slurry after dewatering were tested, and the results are shown in Table 2. Comparative Example 2

[0035] The only difference from Example 1 is that a porous absorbent material (aluminosilicate, 2 mm in diameter, 0.4 nm in pore size, and 0.68 g / mL in bulk density) is used. Comparative Example 3

[0036] The only difference from Example 1 is that a porous water-absorbing material (aluminosilicate, 2 mm in diameter, 0.5 nm in pore size, and 0.66 g / mL in bulk density) is used. Comparative Example 4

[0037] The commercially available NMP-based lithium-ion conductive slurry of Comparative Example 1 was dehydrated using the following steps.

[0038] (1) The porous water-absorbing material (aluminosilicate, diameter 2 mm, pore size 0.3 nm, bulk density 0.7 g / mL) was soaked in deionized water for 24 hours to remove impurities and adsorbed substances that may exist on the surface of the porous water-absorbing material; then the porous water-absorbing material was placed in a vacuum drying oven and dried at ≥200℃, and then taken out and cooled to room temperature for later use.

[0039] (2) Mix the porous absorbent material with the conductive slurry, let it stand, take a sample every 30 minutes, and determine the moisture content of the slurry using a Karl Fischer moisture analyzer.

[0040] Table 1. Moisture content of Example 1 and Comparative Examples 1-3

[0041] Table 1 shows the moisture content during the settling process of Comparative Example 1 and the dehydration processes of Examples 1 and 2-3. In Comparative Example 1, the moisture content did not decrease significantly during the 4-hour settling period, and even increased slightly. Example 1 showed the best dehydration effect, reducing the moisture content from 1169 ppm to 324 ppm in 10 minutes and to 54 ppm in 4 hours. Example 2 showed the second best dehydration effect, reducing the moisture content to 121 ppm in 4 hours. Comparative Example 3 showed the worst dehydration effect, reducing the moisture content to 198 ppm in 4 hours. Comparative Example 4 used settling for dehydration, and after 4 hours, the moisture content only decreased slightly, indicating an insignificant dehydration effect.

[0042] Table 2 Solid content and mass loss of dewatering slurry

[0043] Table 2 shows the solid content and slurry mass loss after standing in Comparative Example 1 and after dehydration in Examples 1 and 2-3. Example 1 showed low solid content and slurry mass loss. This may be because the porous absorbent material used had higher selectivity for water molecules. The high solid content and slurry mass loss after dehydration in Comparative Examples 2 and 3 indicate that the porous absorbent material used adsorbed NMP molecules and conductive agents, resulting in raw material waste and deterioration of the slurry's conductivity. Example 2

[0044] The amount of porous water-absorbing material added in step (2) of Example 1 was replaced with 2.5%, 5%, 10% and 15% of the mass of conductive slurry, and the remaining steps were the same as in Example 1. A series of dewatering slurries were prepared and the dewatering effect was tested. The results are shown in Table 3. Comparative Example 5

[0045] The amount of porous absorbent material added in step (2) of Comparative Example 2 was replaced with 2.5%, 5%, 10% and 15% of the mass of conductive slurry, and the remaining steps were the same as those in Comparative Example 2. A series of dewatering slurries were prepared and the dewatering effect was tested. The results are shown in Table 3.

[0046] Table 3. Effect of Porous Absorbent Material Addition Amount on Water Removal Efficiency

[0047] Table 3 shows that the water removal effect increases with the increase of the amount of porous absorbent material added. When the amount added reaches 10%, the increase in water removal effect slows down significantly. To balance cost and water removal effect, the preferred addition range is 5%~10%. Comparative Example 6

[0048] The only difference from Example 1 is that the conductive paste with a different viscosity is replaced, and the circulation flow rate and the permeation flux of the porous absorbent material in step (4) are adjusted. The time taken to reduce the moisture content to 300 ppm is recorded, as shown in Table 4.

[0049] Table 4. Time consumption and raw material loss of the dehydration process

[0050] High-viscosity slurries have poor fluidity and require lower circulation rates to ensure sufficient contact time; low-viscosity slurries have good fluidity and can use higher circulation rates to improve treatment efficiency. To balance dewatering efficiency, capacity requirements, and raw material loss, conductive slurries with a viscosity of 1000–3000 cP are suitable for a circulation flow rate of 500–1000 L / h, and porous absorbent materials for a permeation flux of 200–400 L / (m²). 2 ·h).

[0051] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A method for dewatering conductive paste, characterized in that, The process includes the following steps: filling a filter with a porous absorbent material, passing a conductive slurry through the filter until the moisture content of the conductive slurry is below 300 ppm; wherein the mass of the porous absorbent material is 5-10% of the mass of the conductive slurry; the porous absorbent material is selected from one of aluminosilicate, aluminosilicate phosphate, or aluminosilicate, with a diameter of 1.5-2.5 mm, a pore size of 0.25-0.55 nm, and a bulk density of 0.7-0.8 g / mL; the viscosity of the conductive slurry is 1000-3000 cp; the circulation flow rate is 500-1000 L / h, and the permeation flux of the porous absorbent material is 200-400 L / (m²·h).

2. The method for dewatering conductive paste according to claim 1, characterized in that, The porous absorbent material has a pore size of 0.25~0.35 nm.

3. The method for dewatering conductive paste according to claim 1, characterized in that, The conductive paste is an NMP-based conductive paste.

4. The method for dewatering conductive paste according to claim 1, characterized in that, The filter is selected from one or more of the following: basket filter, bag filter, cartridge filter, candle filter, Y-type filter, and T-type filter.

5. The method for dewatering conductive paste according to claim 1, characterized in that, First, pre-treat the porous absorbent material, and then fill the filter. The pre-treatment method is to soak the porous absorbent material in water for 12~36 hours, dry it, and cool it to ≤40℃.

6. The method for dewatering conductive paste according to claim 1, characterized in that, A dewatering device is used to remove water. The dewatering device includes a raw pulp storage tank, a dewatering storage tank, a filter, and a pump. The raw pulp storage tank is connected to the filter inlet, and the dewatering storage tank is connected to the filter inlet.

7. The method for dewatering conductive paste according to claim 1, characterized in that, A circulating dewatering device is used for dewatering. The circulating dewatering device includes a group A storage tank, a group B storage tank, a filter, and a circulating pump. The outlets of the group A storage tank and the group B storage tank are both connected to the inlet of the filter, and the dewatering storage tank is connected to the inlet of the filter.

8. The method for dewatering conductive paste according to claim 1, characterized in that, Used porous absorbent materials can be reused after regeneration and performance verification.

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